NO125853B - - Google Patents

Description

Method and bath for coating electrically conductive objects.

The present invention relates to a method of the type specified in patent claim 1's general term for coating electrically conductive objects, and the method is characterized by the features specified in claim 1's characterizing part." The invention also relates to a coating bath of the type specified in patent claim 7's general term for implementation of the method, and the coating bath is characterized by what is stated in patent claim 7's characterizing part.

In the present method, a coating material which is ionizable in an aqueous solution of a water ionizable amino compound and which consists of an alkenic a,p-unsaturated carboxylic acid resin is dispersed in an aqueous solution of the amino compound, and the resulting ionized resin is electrodeposited on an electrically conductive workpiece which is moved through the bath, by producing an electrical voltage difference between the workpiece and another electrode in contact with the bath, whereupon the coated workpiece obtained is transferred to a gaseous medium, and the newly deposited coating is polymerized on the surface of the workpiece, forming a non - adhesive, durable surface coating using a beam of polymerization-promoting electrodes.

The immediate nature and connection between the electrical, chemical, physical and electrochemical mechanisms of deposition, reaction and dehydration in connection with electrically induced deposition of a polycarboxylic acid resin is not yet fully understood, although phenomena such as electrophoresis, electroendosmosis, electrochemical turnover etc. has been put forward as an explanation. However, such an understanding is not required to recognize the excellent advantages that durable, strong, continuous coatings with a high quality surface, which can be obtained by electron-induced polymerization of a fresh electrodeposited coating, exhibit.

The resins in question here have a relatively high molecular weight and can be composed so that they are deposited as a continuous film with high specific resistance and essentially uniform thickness. Such films are essentially electrically irreversible under the coating conditions, i.e. when current is reversed. However, little is known about the resulting orientation of an electrodeposited resin or resin and monomer and the physicochemical state thereof in a freshly deposited film. Thus, a full explanation of the special suitability of such a film for electron-induced polymerization cannot immediately be given. Apart from the observable effects and qualities of the present method, other advantages derive from the complementary nature of the method steps, as each step interacts with the properties of the other step that distinguish this from other methods for deposition and polymerization. An electron-induced polymerization takes place e.g. very fast in that it takes a few seconds as opposed to several minutes in the case of conventional oven curing, and although this leads to great savings in terms of time and space, this feature of the method also causes problems in producing curing without leaving areas that are under- or over-hardened. If the film is of uniform thickness, the possibility of uneven curing is reduced. The electrically induced deposition in the present method is characterized by the fact that it is self-levelling as a result of the growing resistance as the film deposition takes place. Furthermore, volatile solvents are generally used in connection with conventional methods for applying paint.

In slow curing processes, the evaporation of such solvents does not present any particular problem. With electron-induced polymerization, it can result in remnants of broken gas bubbles solidifying in place, resulting in an unattractive surface. The water-dispersible, electrodepositable paints used in the present method can be, and should preferably be, free of solvents which evaporate in significant quantities or at a considerable rate during the polymerization step. Moreover, the energy supplied to an overcoat by electron-induced polymerization can be controlled within extremely narrow limits, and polymerization can be accomplished without increasing the temperature. This expands the scope of electrically induced overcoating. in that electrically conductive products which are thermally degradable can be coated, and furthermore the possible compositions of electrodepositable coating materials which would be unsuitable for use by slower curing at a higher temperature are expanded.

Radiation-induced polymerization, including also the use of

an electron beam as a source of radiant energy, is known from U.S. Patent Nos. 32>+.7012, 3188229,3188228,3188165", 3170892, 31^-6l<>>+6, 313767^, 3131139, 3107206, 3088791, 3077^20, 3077^19, 3077^18, 3077^17, 307590^,- 3013895, 2999056, 296^56, 295690^, 2955953, 2921006, 290M+81 and 2900277.

Oxygen has a tendency to have an inhibitory effect on such polymerization, and the method can be carried out more effectively in a gaseous medium which offers significantly lower resistance to electron bombardment than air. If the intermediate medium is air, the average radiation energy falls rapidly, e.g. with a loss response-end to a reduction of the voltage of up to 10,000 volts or more per cm of intervening air, and a rising part of the beam is completely attenuated before it reaches the workpiece.

A particularly effective embodiment of the present method is therefore characterized by the fact that a closed polymerization zone filled with an essentially inert gaseous medium is placed in contact with the aqueous dispersion, the dispersion acting as a liquid seal for part of the polymerization zone and constituting

an entry device through which the object can pass from it

aqueous dispersion and into the polymerization zone. A particularly advantageous sealing of the polymerization zone is achieved by feeding the obtained object with the polymerized film from the polymerization zone into a liquid bath which forms a liquid sealing device for part of the polymerization zone.

With respect to the coating material, "paint" by means of electrically induced deposition in this description shall include deposition of finely divided pigment or filler in the binder, i.e. the ionizable resin or mixtures of the ionizable resin and vinyl monomer, deposition of the binder without pigment or filler or very small amounts of this, but possibly coloured, and deposition of other water-dispersible coating compositions containing the binder which can largely be considered analogous to enamel, varnish or lacquer base materials, and the coating material for such a deposition is referred to in this description as a "paint" . Thus, the binder which is converted into a water-resistant film by electrodeposition and finally converted into a durable film which is resistant to normal conditions of use and which is induced by electron polymerization, can be all or practically all that must be deposited to form the film, or the can be a binder for a pigment, a mineral filler, other resins or several of these materials on which, beyond the desired effect for depositing the film.

According to a preferred embodiment of the present invention, a polycarboxylic acid resin with alkyl α,(3-unsaturation and vinyl monomers is used as a binder. It is preferred to use a percentage content of vinyl monomers of 1-15.5, preferably 7-1^.5, and especially 9 -1^-% by weight of the organic binder.

The carboxylic acid resin is distinctive in that it has a molecular weight of over 1,000, preferably between 2,000 and 20,000, if it is of the polyester type. With acrylic or other vinyl polymers, the molecular weight should preferably be approx. 15,000, e.g. within the range of 5,000-50,000, or more. The polymer is further characterized by'

that it has 0.5 - 3.0, preferably 0.8 - 2.0, units of alkenic α,P unsaturation per 1000 molecular weight units, an acid number of 30-300, as a rule <>>+0-120, and an electrical equivalent weight of 1,000-20,000, preferably 1,000-3,000. The polymers or resins used here are characterized in terms of their deposition ability in that the deposition is mainly directly proportional to the direct current that passes

through the bathroom. This is because a film with a high specific resistance is built up during the deposition. The polymers used in the present method are deposited as a film of (1) substantially uniform thickness, provided that the workpiece has such a design that an essentially uniform electrical induction for coating can be achieved at all surfaces of the workpiece for a considerable period of time during over -the drawing process, (2) practical insolubility in water, (3) a high specific resistance, (h) a finite maximum pieceIse for a given voltage and (5) rapid polymerizability to a non-tacky state by means of an electron beam. Electrically induced deposition of a polycarboxylic acid resin exhibiting the first four of these aforementioned properties is described in U.S. Pat. patent no. 3230162. As far as is known, the binder resins used so far for electrically induced deposition from an aqueous bath have not been suitable for rapid curing by electron-induced polymerization.

The materials described in the above-mentioned group of patents, and other materials which have so far been polymerized by radiation energy, have not, as far as is known, been used or effectively used in the form of water-dispersible, electro-depositable coating materials.

The new binders used according to the invention are distinctive in that they are both electrodepositable in the same way as the resins according to the above-mentioned U.S. patent no. 3230162, and electron-polymerizable by the methods described in the other patents cited above.

Particularly advantageous binders for use in the present method have a molecular structure in which silicon components derived from cyclic or acyclic siloxanes are incorporated, which give the obtained coating excellent weather resistance.

Although such binders can be mixed with a common solvent and applied using a common paint application technique, they are particularly suitable for intimate dispersion in aqueous solutions of amino compounds, and particularly suitable for use in the coating of electrically conductive objects by means of electrically induced provision.

The term "siloxane" is used here for a compound containing a

the other valences being occupied by a hydrocarbon group, an oxyhydrocarbon group, hydrogen, a hydroxyl group or an oxygen atom which connects the silicon atom with this valence to another silicon atom. For incorporation, suitable siloxanes have a molecular structure with at least 2 reactive groups, e.g. hydroxyl or oxyhydrocarbon groups. Acyclic siloxane molecules for use in the production of the resins used according to the present method should preferably contain at least three silicon atoms per molecule with corresponding oxygen bonds. It is preferred to use acyclic siloxanes with the following general formula: where n is at least 1 and X is (a) a monovalent hydrocarbon group with 1-8 carbon atoms, preferably an alkyl group with carbon atoms, (b) ai a monovalent oxyhydrocarbon group with 1-8 carbon atoms, preferably an alkoxy group with 1-h carbon atoms, (c) a hydroxyl group or (d) hydrogen, with at least two of the groups X separated by a

is either (b) or Ce).

Suitable cyclic siloxane molecules contain at least 35 preferably* • show 6-12, and as a rule no more than 18, silicon atoms per molecule with corresponding oxygen bonds. The cyclic siloxanes can have one of the following formulas:

The following formula is used as an example:

The following formula is used as an example:

As an example, the following formula is given: or a condensation dimer, -trimer, etc. formed therefrom by loss of water or alcohol.

The following formula is given as an example:

where m is 0 or an integer.

The following formula is given as an example:

where n is an integer.

A wide range of methods for producing siloxanes are known. These include controlled hydrolysis of siloxanes, polymerization of lower molecular weight siloxane in the presence of an alkoxysilane, reaction of silicon tetrachloride with. an alcohol etc. Siloxanes,

their preparation and their incorporation into organic resins are described in U.S. Pat. Patents Nos. 315^597, 307^90)+, 3CM-980, 30^979, 3015637, 2996^79, 2973298, 2937230, 29095^9 and 2877202.

The silicone-modified resins used in the present process contain at least 10, preferably 15-50, and especially 20-^-0, by weight of silicones, i.e. structures derived from siloxanes.

Functionally, the silicone-modified resins used according to the present method differ from the previously known binder resins in that they are both electrodepositable with vinyl monomers from an aqueous dispersion thereof and polymerizable with such vinyl monomers by means of relatively low-energy electrons, i.e. at least 50,000 and up to e.g. 500,000 eV, when such a film has become

deposited.

With regard to the coating bath, the aqueous dispersion must contain between 0.5 and 35% by weight of the dispersed binder material, preferably 3 - 12%. The water-soluble amino compound used as dispersing aid is used in a greater amount than is necessary to induce intimate dispersion of the resin and make it act as an anionic polyelectrolyte. The optimum amount of amino compounds will vary with the acid number of the resin or polymer. If the resulting pH value is sufficiently high, the bath will absorb CO2 from the atmosphere unless a controlled atmosphere is used. The concentration of the amino compound or amino compounds will also affect the electrical resistance of the bath, and the concentration is considered to be too high if the bath resistance drops significantly below approx. 500 ohms. An amount of amine is used that is greater than the minimum amount necessary to make the exposed binder resin or the exposed resin mixture in the bath act as an anionic polyelectrolyte. It is preferred to use concentrations of 1.5 - 5.3 times this minimum concentration. The specific resistance of the bath should preferably be 700 - 1000

ohm cm. A higher bath resistance will give a thinner overcurrent at a given voltage difference, and vice versa. A bath with a pH as low as approx. 5 and as hby as approx. 10 can be used. A pH of 6.5 - 8.5, preferably 7.0 - 7.5, is preferably used in the bath.

The bath's viscosity bbr is preferably kept lower than approx. 30 times the viscosity of water. Bath temperatures in the range of 15-50°C facilitate the maintenance of bath stability and prevent polymerization in the bath.

The term "water-soluble amino compound" is intended in this description to include ammonia and water-soluble amines. It is less advantageous to use ammonia in the present method for partial neutralization of the acid resin or resin mixture because it is highly volatile at the working temperatures used, and small additions of ammonia can cause relatively large changes in the pH of the bath. The amines used must be water-soluble at 20°C to an extent of at least approx. 1 wt% of the solution, and the amines include hydroxylamines, polyamines and monoamines, e.g. monoethanolamine, diethanolamine, triethanolamine, N-methyl-rethanol-amine, N-aminoethyl-ethanolamine, N-methyl-diethanolamine, monoisopropanolamine, diisopropanolamine, triisopropanolamine, "poly-glycolamines", such as HOCC^H^O^C^HgNH ^, hydroxylamine, butanolamine, hexanolamine, methyldiethanolamine, butanolamine, hexanolamine, methyldiethanolamine, octanolamine and alkylene oxide reaction products of mono- and polyamines, such as the reaction product of ethylenediamine with ethylene oxide or propylene oxide, laurylamine with ethylene oxide, etc.', ethylenediamine, diethylenetriamine, triethylenetetramine , hexamethylenetetramine, tetraethylenepentaain,

propylenediamine, 1,3-diaminopropane, imino-bis-propylamine and the like, and mono-, di- and trialkyl (C-^-C8)-amines such as mono-, di- and tri-ethylamine.

To supplement the carboxylic acid resin in the bath as the process progresses, further binder concentrate is added continuously or in stages. This concentrate may possibly contain pigment. With regard to easy dispersion, a concentrate is advantageously used in the form of a concentrated aqueous dispersion containing, on a pigment- and filler-free basis, 50 - 95% by weight of polycarboxylic acid resin (alone or with stretching agents) and 1 - 10% by weight of water-soluble amino compound, calculated on the weight of the polycarboxylic acid resin , the rest being made up of water.

The terms "radiation", "ionizing radiation" and "radiation energy" are used here to mean radiation with a minimum energy corresponding to 50,000 eV. In the following preferred methods for curing films of the paint binders referred to here on the substrates on which they have been applied, the films are exposed to a polymerization-inducing electron beam which, at the point where it is emitted, i.e. at the exit from the electron window, has electrons with a energy of 100,000-<>>+50,000 eV, preferably 200,000-350,000 eV.

By varying the distance between the electron source and the film in relation to the beam's voltage, the difference in polymerization rate with thickness can be reduced. Within the above voltage range, it is preferred to use a minimum voltage of approx. 10,000 V per cm. distance between the radiating body and the film to be cured. In accordance with the present method, the distance between the radiating member and the film on the workpiece can vary from approx. 61 cm to the smallest distance compatible with the contour of the workpiece.

A distance of 5 - ^5 cm will generally be most effective. The importance of correlating the distance in relation to the radiation voltage increases with increasing either the distance or the thickness of the film. In connection with the smaller distances, voltages within the lower part of the range can be successfully used. Higher voltages in this area

in

are necessary in connection with the greater distances in order to achieve the desired uniform polymerization rate with the thickness. When using energies within the range 200,000-3000J300 eV, it is preferred to use distances of 5 - 30 cm.

Although the tolerable limit of forward irradiation will vary somewhat with the composition of the film, the time required to induce substantially complete polymerization of the film where it is at its greatest thickness should generally not be longer than twice that time which is necessary to polymerize the most easily polymerizable part of the film. This time is preferably less than 1.5 times the time required to achieve the first polymerization. The temperature of the film must not be so high that before or during the polymerisation any significant evaporation of the most volatile component in the film will occur. To comply with these conditions, doses within the range 0.01 - 15 megarad/s, preferably 0.1 - 10 megarad/s, have proven to be well suited.

The term "rad" here means the radiation d'Ose which causes absorption of an energy of 100 erg per g absorbent, i.e. cover film.

The term "acrylic monomer" is used here in the sense of an α,8-monounsaturated monocarboxylic acid or an ester thereof, and includes e.g. acrylic acid, alkacrylic acids, e.g. methacrylic acids, monovalent alcohol esters of acrylic acids and alkacrylic acids, e.g. glycidyl methacrylate, 2-hydroxyethyl methacrylate, etc.

The acid number of resins without significant amounts of anhydride groups can be determined with KOH by ASTM Standard Method 555 - 5^. If significant amounts of anhydride groups are present, the acid number can be determined by boiling a sample of 1.5 - 2 g of the amount of resin under reflux for 1 hour with 50 ml of 0.5 N aqueous K0H and 25 ml of pyridine, then back titrating with 0, 5 N HC1 until covering with phenol-phthalein is obtained.

A given resin or a resin mixture's electrical equivalent weight is defined here as the amount of resin or resin mixture that will be deposited per Faraday electrical energy supply at the following working conditions. For this purpose, 1 Faraday is considered here as 96<*>+93 coulomb, or 1 Faraday will deposit 107.88 g of solv (the gram atomic weight of solvate), i.e. 1 coulomb will deposit 0.001118 g of solv from a solv nitrate solution. If thus 0.015 g of coating, of which the polycarboxylic acid resin binder makes up 90% by weight and the rest is an amino compound used to disperse this in the bath, is transferred to and deposited on the anode per added coulomb by the present method, the electrical equivalent weight of the resin is 0.015 x 0.9 x 107.80, i.e. approx. 1303.

To further illustrate the above, the electrical equivalent weight of a particular polycarboxylic acid resin or a particular resin mixture can be easily and satisfactorily determined for typical working conditions as follows: A polycarboxylic acid resin concentrate is prepared at 65.56°C by thoroughly mixing 50 g of polycarboxylic acid resin, 8 g of distilled water and diisopropanolamine in a sufficient quantity for the resin dispersion to have a pH of 7.8 or somewhat lower after a subsequent dilution of the concentrate. The concentrate is then diluted to 1 liter with additional distilled water until a resin concentration of 5% by weight is obtained in the resulting dispersion. (If a somewhat too small amount of amine is used and the pH of the dispersion is below 7.8, the pH is brought up to 7.8 by adding further diisopropanolamine). The dispersion is poured into a metal tank whose widest side walls are substantially parallel to and located at a distance of 2.5*+ cm from the surface of a thin metal plate anode. The tank is connected as a DC cathode, and the DC anode is a 0.953 mm thick, 10.17 cm wide, tared steel plate immersed in the bath to a depth of 7.62 cm. At a bath temperature of 26.7°C, it is then sent

a direct current from the anode to the cathode at 100 Vil minute from an external current source, the current being measured by means of a coulomb meter, after which the current is switched off. The anode plate is immediately taken up, rinsed with distilled water, heated for 20 minutes at 176.7°C and weighed. Volatile material, such as water and amine, is assumed to have been sufficiently removed from the film by heating. The difference between the initial tare weight of the plate and the final weight of the heated plate divided by the amount of current applied in coulombs multiplied by 107.88 and divided by 0.001118 gives the electrical equivalent weight of the resin.

According to the second embodiment of the present method, mainly polymers which are homopolymerizable are used as the polymerizable part of the binder. In this embodiment, the vinyl monomer component of the composition can thus be omitted, and the binder polymer has a molecular weight of over 250, at least 1 and preferably 2 dissociable carboxyl groups per molecule and at least 2 alkenic a,B-unsaturations per molecule. These unsaturations can preferably be located at the ends of the polymer if it is mainly linear and there are approx. 2 - 1+ such units per 1000 molecular weight units.

These polymers can form the only component in a paint binder or they can be used in combination with other poly-

mers or monomers with which they are copolymerizable by ionizing radiation. Depending on the intended end use and the presence or absence of other unsaturated components in the coating composition, the molecular weight of such polymers may be from the above minimum and upwards to an average molecular weight of

weight of several thousand.' When dispersing certain embodiments of these polymers in an aqueous bath and during the electrodeposition thereof on a conductor, it is advantageous to use a compatible organic solvent with the polymer which, depending on the desired end product, can either be removed by evaporation for curing or retained as a plasticizer in the cured film. Such solvents will facilitate the formation of a continuous and adherent film by electrodeposition.

The aforementioned polymers are produced by reacting a base polymer with at least two functional groups per molecule, i.e. hydroxyl, amino, carboxyl, anhydride, mercapto or ethoxide groups, with an organic compound containing alkenic α,B unsaturation, preferably di- or polycarboxylic acids or anhydride. When the polymer is to be electrodeposited, the resulting polymer product must contain a sufficient amount of ionizable functional groups in its molecular structure to enable dispersion in an aqueous bath and subsequent electrodeposition, e.g. dissociable carboxyl groups if anodic deposition is carried out. These ionizable functional groups may originally be present in the above-mentioned base polymer or in the organic compound with which it is reacted.

The mentioned products are linear copolymers with alkenic α,B unsaturations at their ends.

The invention is explained in more detail below

with the drawings, where

fig. 1 schematically shows an embodiment of an apparatus for carrying out the present method,

fig. 2 schematically and partially cut through shows an embodiment

form of one of the two electron radiation units shown in fig. 1,

fig. 3 shows a metal foil sheet which serves as an electron window in the one in fig. 2 displayed device,

fig. h shows in perspective an embodiment of a combined window-supporting grid and a heat dissipation device which forms part of it in fig. 2 displayed device,

fig. 5 shows in perspective a window holder device provided with an opening which frames the electron window in fig. 2 and 3 and keeps this in contact with the window-supporting grid and the heat dissipation device according to fig. 3,

fig. 6 shows a section along the line VI-VI in fig. 1, and

Fig. 7 schematically shows another embodiment of an apparatus, parts of which are shown in section.

In fig. 1, a drum holder 11 carries a drum 13. The drum 13 is made of a suitable non-conductive material, e.g. wood, plastic and the like, and is rotatably mounted on the holder 11 and carries a metal sheet material* 15. As it is unwound from the drum 13, the sheet material 15 passes over an intermediate wheel 17 which may have the same or a different design than the intermediate wheel according to fig. 6 which will be described later. The intermediate wheel 17 is rotatably mounted on an axle 19 which is in turn carried by an upright support member 21. The axle 19 consists of a non-conductive material, and the intermediate wheel 17 is electrically isolated from earth. The Atek material 15 passes under a brush or roller contact 23. The contact 23 is carried by and is in electrical connection with a metal shaft 25. In the first embodiment, the contact 23 is rotatably mounted on the shaft 25. According to another embodiment, the contact 23 is fixed to the shaft 25. This is carried by a horizontal support member 27. The support member 25 consists of a non-conductive material and is supported by the original support member. 21. In a first embodiment, the shaft 27 is hollow, and part of the shaft 25 extends into the shaft 27 and is rotatably arranged therein. According to the second embodiment, the shaft 25 is attached to the end of the shaft 27.

After passing in electrical connection with contact 23, the sheet material 15 is immersed in an aqueous bath 29 consisting of a dispersion of alkenic or olefinic α,8-unsaturated carboxylic acid resin and amino compound as previously described. The bath 29 is held in a coating tank 31 which serves as the grounded cathode in an electrodeposition cell. The tank 31 is in electrical connection with the line 33, which in turn is in electrical connection with an electric direct current source 35. The line 37 is also in electrical connection with the current source 35, and the line 37 is also in electrical connection with the metal shaft 25 via the switch 39 and the line hl. An electrical circuit is thus obtained which includes the sheet material 15, the contact 23, the bath 29, the grounded tank 31, the line 33, the current source 35, the line 37, the switch 39, the line hl and the shaft 25.

Between the sheet material 15 and the tank 31, an electrical voltage difference is maintained which is higher than the threshold deposition voltage for the resin used. The term "threshold deposition voltage" or "threshold voltage" is intended herein to denote the minimum voltage at which deposition of an electrically resistive film of the base resin is initiated. This will vary somewhat with the resin used and/or the composition of the resin-amino compound that makes up the dispersion. A high threshold deposition voltage is typical for a more stable dispersion. This minimum voltage will generally be above approx. 5 volts and below approx. 20 volts. However, for practical residence times in most industrial coating operations, a voltage of over approx. 50 volts. As a rule, the voltage will be between 100 and 250 volts. The upper limit for this voltage difference will depend on the voltage at which the deposited film will break if it is kept during the entire residence time in the bath. This will also vary with the resin or molding material used, but it will generally be below approx. 500 volts. According to the preferred embodiments of the present method, at least the majority of the film is electrically irreversible under overcoating conditions.

The AJk material 15 emerges from the bath 29 with a continuous, resinous coating of practically uniform thickness. At this point in the process, the resinous coating has not been hardened and is relatively easily destroyed by mechanical stress. This coating should be handled as little as possible for the polymerization.

However, in connection with certain embodiments, it will prove to be advantageous to rinse the covering or coating after it has emerged from the bath in order to remove loosely connected or adhered coating materials from the coating's surface. If there is a need for this, the newly coated sheet material can be led through a cleaning or rinsing zone where the coated or coated surface is sprayed or showered with water.

In accordance with the present method, the electrodeposited film is exposed to polymerization-inducing radiation energy immediately after it has been formed, i.e. before any substantial dehydration has occurred after deposition. The polymerization must generally be carried out within a period of a few seconds to a few minutes, preferably in the course of less than 10 minutes, and especially less than 1 minute.

After the coated sheet material 15 has left the coating or coating bath 29, it passes over an intermediate roller M-3, an embodiment of which is reproduced in more detail in fig. 6.

The intermediate roller ^3 is rotatably mounted via lower k5 and k-7 inside and on the support stand M-9 for the intermediate roller. This consists of a central shaft

*+3-l which extends through and rotates on bearings ^5 and h7, a rudder-shaped support device ^3-2 fixedly placed on..the shaft *+3-l and through which the shaft 1+3~1 guides, and circular support devices ^3-3 and h2>- h which are fixedly connected to the opposite ends of the support device

•+3-2. The circular support devices 1+3~3 and 1+3_1+ have inclined surfaces ^3-5 and<*>+3-6 against which the edges of the sheet material 15 rest when

it is pulled over the intermediate roller<>>+3 and thereby causes it to rotate. The circular support devices 1+3-3 and 1+3-1+ can also have the form of cylindrical projections, but as the coating or coating on the sheet material 15 has not been hardened at this stage and can therefore be easily damaged, these support devices must be tight as possible. The intermediate roller ^3 consists of a non-conductive material and isolates the sheet material 15 from ground contact. The intermediate roller stand<*>+9 can be moved along the longitudinal axis of the sheet material 15 as it is fixed in slots U-9-1 and M?-2 in the bottom plate 50.

After passing over the intermediate roller<*>+3

passes the coated sheet material 15 between a pair of electron irradiation units arranged in a housing 51 and which induces polymerization of the coating to a non-sticky state. An electron irradiation unit which is suitable for this purpose and representative of the electron irradiation units in the housing 51 is shown in fig. 2 - 5 and described in detail in connection with the following description of these figures.

After passing between the above-mentioned electron irradiation units, the sheet material 15 with the coating polymerized to a non-sticky state is turned around a receiving roller 73 - This is made of a non-conductive material that isolates the sheet material 15 from soil. The roller 73 is rotatably mounted on a roller support 75. The roller 73 has a central shaft 73-1 which is in connection with an electric motor 77. This is in electrical connection with the current source 35 via the line 79, the switch 8l and the line 83. The motor 77 is also grounded.

When the desired amount of coated sheet material has been taken up on the roller 73, the current to all circuits is interrupted, the sheet material 15 is cut off between the housing 51 and the roller 73, the roller 73 is removed from the support 75, a new receiving roller is installed on the support 75, the sheet material is fixed to the new roller and the process is started again.

Although only two electron irradiation units are indicated in FIG. 1, the person skilled in the art will understand that the speed at which the sheet material is moved through the polymerization zone can be reduced by increasing the number of electron irradiation units used for polymerization of the coating. Likewise, the length of the overdraft bath can be increased to allow an increased linear velocity through it.

The housing 51 can be moved along a line perpendicular to the longitudinal axis of the sheet material 15 by means of slots 51-1 and 51-2 in the support plate 51-3.

A control unit 53 is mounted on the housing 51. The control unit 53 stands

in electrical connection with earth, with the current source 35 via the line 55 and with the cathodes in the electron irradiation units in the housing 51 via the line '55-1. The housing 51 and the anodes in the electron irradiation units in the housing 51 are electrically connected to earth via the line 55-2. The control unit 53 is also electrically connected to a superior control unit (not shown) which may comprise electrically or electronically activated programming devices, via the lines 57 and 59. The control unit 53 is also electrically connected to the switch 39 via the lines 61 and 63 and to the contact 8l via wires 65 and 67.

On the side of the housing 51 that comes after the coating bath and the polymerization zone, a control unit 69 is mounted and arranged for constant control of the surface of the sheet material 15. The control unit 69 is in electrical connection with the control unit 53 via the line 71. It is also in electrical connection with the housing 51 and thereby with earth. The control unit 69 comprises foils, e.g. photoelectric devices, for constant control of the condition of the film coated on the sheet material 15 as the sheet material passes from the polymerization zone, e.g. by measuring the light reflection from there, and devices for transmitting a constant determination thereof to the control unit 53. It will be understood that other control devices or differently arranged control devices can also be used, e.g. contact friction measuring devices, thickness measuring devices, etc.

The control unit 53 comprises common electrical and/or electronic components which are operatively connected, including contact devices for activating and deactivating the electron irradiation units in the housing 51, voltage regulation devices for varying the voltage of the electron beams used for polymerization of the coating, transfer devices for setting the distance between the electron irradiation units in the housing 51 and the sheet material 15, devices for receiving and effecting programmed control signals from a superior control unit for controlling the polymerization process, and devices for receiving signals from the control unit 69 and interrupting the current in all circuits when incomplete coating is detected and/or for transferring such signals to a superior control unit, etc.

Fig. 7 shows another embodiment of an apparatus. A support 11 carries a drum 13 for the sheet material. The drum or roller 13 which is made of a suitable non-conductive material, e.g. wood, plastic and the like, is rotatably mounted on the support 11 and carries a metal sheet material 15, which, when located on the roller 13, is isolated from soil. After being unwound from the roller 13, the sheet material 15 passes under a bed or roller contact 19. The contact 19 is electrically connected to a metal shaft 21 which in turn via the wire 23 is electrically connected to the positive pole of an electric direct current source 25 and is carried by the support arm 27 mounted on the support 11. The support arm 27 is, according to a first embodiment, made of a non-conductive material. If it is made of a conductive material,

it is isolated from the contact 19 by means of insulating materials not shown. Thus, both the sheet material on the roller 13 and the contact 19 are isolated from earth. After passing under the contact 19, the sheet material 15 enters an aqueous coating bath 29 in the coating tank

31. The coating tank 31 is grounded and electrically connected to the power source 25 via the line 37. The sheet material then passes under the intermediate roller 33 and the intermediate roller 35 before it comes out of the bath 29

into the controlled atmosphere of a polymerization chamber ^0 in a housing ^1. The intermediate roller 35 is electrically isolated from and supported by the housing<*>+1 by means of the support member M-3. The intermediate roller 33 is isolated from and supported by the tank 31 by means of non-conductive support means 33 -1. Alternatively, the intermediate roller 33 is carried by not shown suspension

devices placed above the tank.

The sheet material 15 comes out of the bath. 29 into the controlled atmosphere in the polymer icing chamber ^-0 carrying a continuous resinous coating or coating of substantially uniform thickness. At this point in the process, the resinous coating has not been cured, and it will therefore be easily mechanically damaged. This coating must be handled as little as possible for the polymerization. The housing hl, which essentially encloses the polymerization chamber *f0, extends down into the bath 29, forming a liquid trap for the gas in the chamber ho at the surface 29-1 of the bath 29. Upon entry into the chamber ho through this liquid trap, the transfer of the coated sheet material is produced from the aqueous medium in..badei; 29 into the gaseous medium in the chamber hO without contact with a solid object. The intermediate rollers mentioned above and in the following are designed and arranged in such a way that they provide the least possible contact with the sheet material 15, e.g. as shown in fig. 6 which is described in detail below. The coated sheet material 1"5 passes after it has entered

in the polymerization chamber ho above the intermediate roller<>>+5 which is electrically isolated from and supported by a support h7 which is again supported by the floor hl-1 in the housing hl which extends over the bottom of the polymerization chamber ho. After passing over the intermediate roller h5, the sheet material 15 passes through a rinsing zone hO-1 in the polymerization chamber ho where the water-resistant coating is rinsed with water to remove loosely adhered material from the coating material by means of showers 51 and 53 arranged on each side of the sheet material. Showers 51 and 53 are mounted on and supplied with water from lines 51-1 and 53-1 respectively. The water flow through these lines is regulated using valves, respectively 51-? and 53-2. The rinse water flows out of the chamber ^0 via a drain 55. The sheet material 15 then passes between screens 57 and 59 which keep the rinse water in place in the rinse zone ^-0-1 and directs it towards the drain 55.

The coated sheet material 15 then passes between oppositely arranged electron irradiation units 61 and 63 which are described in detail below and each of which individually directs electron beams towards the coated surface and induces polymerization thereof. The units 61 and 63 are electrically connected to the negative pole of the current source 25 via lines 61-1 and 63-I, respectively. The positive electrodes in these units are grounded. The irradiated sheet material then passes over an intermediate roller 65 which is isolated from and supported by a support 67 which is in turn supported by the floor<>>+l-l in the house *fl. This also extends down into a water bath 69 in a tank 71 which forms a liquid lock with the bath 69's surface 69-1. According to another embodiment, the liquid lock is omitted by means of the bath 69, and the sheet material 15 exits into the surrounding air through an opening in the housing<*>+l which is slightly larger and has the same cross-sectional shape as the end of the exiting workpiece. As the coating at this stage is preferably polymerized to a non-sticky state, it is not necessary to prevent contact with a solid object, although this is still preferred. In the embodiment shown, the sheet material passes 15

over an intermediate roll 65 and emerges from the gaseous medium in the polymerization chamber ^fO and into the water bath 69. After entering the bath 69, the coated sheet material is guided under a roller roll 73 which is insulated from and carried by a carrier device 75 attached to the house i+1. After passing under the intermediate roller 73, the coated sheet material is led under an intermediate roller 77 which is carried by and electrically isolated from the tank 71 by means of carrying devices 77-1. After passing under the intermediate roller 77, the coated sheet material is taken up on a roller 79 which is electrically isolated from and supported by a support 71. The take-up roller 79 is driven by an electric motor 83 which gets the roller

79 to rotate counterclockwise whereupon the roller pulls the sheet material l5 from the roller 13 and through the above-mentioned baths 29 and 69 and the polymerization chamber ho. The electric motor 83 is grounded via the line 85

and is connected to the direct current source 25 via line 87, switch 89 and line 91.

The chamber ^-0 is continuously supplied with gas, preferably helium, via the line h- 2, the valve 1+ 1+, the line MS and gas for sewing the stench

W.

Gas is continuously withdrawn from the chamber ^0 via the line 50, the valve 52 and the line 5^ to a cleaning device 56, e.g. a counter-current gas scrubber, where the gas entering from line 5^ is led upwards through a stream of water or another cleaning liquid which enters at the top of the cleaning device via line 58 and flows out near the bottom via line 60. The cleaned gas stream is withdrawn from the top of the cleaning device 56 and is returned to the tank<!>+8 via the line 62, the valve 6<*>+ and the line 66.

In fig. 2, the lower end of an electron accelerator tube 100 consisting of a main housing 101 containing a cathode assembly 103 is shown partially cut through. The cathode assembly 103 consists of a cathode housing 105 with an elongated opening 107 over most of its underside.

Placed inside the housing 105 are a pair of separate busbars 109 and 111

both of which are electrically connected to a series of tungsten filaments 113 which serve as cathodes. The opening 107 has such a size and design that it will direct a flat electron beam from the filaments 113 towards the window area. In embodiments where a scanned beam is used, an alternating magnetic field is used to direct the electron beam in such a way that the desired distribution of electrons at the window surface is obtained. The busbars 109 and 111 are electrically connected to the conductors 115 and 117, respectively, which during operation are electrically connected to the negative pole of an electric direct current source, e.g. current-. the source 35, via the line 55-1, the control unit 53 and the line 55 as shown in fig. 1. The conductors 115 and 117 are isolated from the housing 101 and the housing 105. The energy which is supplied to the negative conductors 115 and 117 is regulated by means of ordinary electrical regulation devices (not shown) so that a small voltage difference is maintained, e.g. .

5V, between the negative conductors 115 and 117 to thereby produce a current through the filaments 113.

A conductor 119 constitutes the positive conductor and is electrically connected to the housing 101 and to earth, e.g. via line 55-2 in fig. 1.

■A heat sink and a window-supporting grid 121 are attached

to the bottom of the housing 101 by means of suitable fixing devices, e.g. bolts, clamps, screws and the like. The grid 121 is shown in more detail in fig. h. According to this embodiment, the grid 121 consists of copper or aluminum or an alloy thereof and has a central, longitudinal opening 123. A series of transverse bars 125

is fixed in slots 127 and extends across the opening 123. The grid 121 also has a number of threaded holes 129 whose purpose is explained below.

The grid 121 also has a circumferential groove 131 which is designed in this way

that it can accommodate a line 133 arranged to bring a heat exchange fluid, e.g. water, in heat exchange ratio to the grid 121.

A window-forming sheet lhl is placed under the grid 121, and

the sheet consists of a thin metal sheet which may be made of aluminum, an aluminum alloy containing a small amount of lithium, titanium, beryllium, magnesium or thorium, stainless steel, etc., The window-forming sheet 1<*>+1 is in fig. 2 and 3 shown in enlarged thickness to facilitate the location and identification thereof in the drawing. The

is arranged so that it completely covers the opening 123 in the grid 121, and it extends on each side of the opening 123 for a sufficient distance so that it can be fixed over the grid 121 by means of a window holding block 151.

The window-forming sheet 1^1 is electrically connected to the housing 101 and serves as an anode. The window retaining block 15l which is reproduced in more detail in fig. 5 is provided with a central opening 153 of essentially the same size and shape as the opening 123 in the grid 121 and has a number of threaded holes 155. The opening 153 frames the window itself. The threaded holes 155 form the device for fixing the window holding block 151 to the grid 121 in such a way that the window-forming sheet 1<*>+1 is clamped firmly against the grid 121. The window holding block 151, the window-forming sheet 1M-1, the grid 121 and the housing 101 is joined together as described above, possibly using suitable gaskets, sealing rings, etc. (not shown) so that

a vacuum is formed for sealing the lower end of the housing 101. Part of the sheet material 15 in fig. 1 is also shown in fig. 2 as it passes through an electron beam from the electron shaft generator described above.

The polymerization-causing electrons are produced by electrons being accelerated to high energy in an evacuated tube, e.g. the rudder 100, and the accelerated electrons are led out from the rudder through a suitable electron window, e.g. the above-described window-forming sheet 1^1, against the coating to be polymerized. To provide complete coverage, the electrons can be made to come out of the tube in the form of a flat beam, and the object to be irradiated can be moved through the electron beam. The electron radiation unit described above is only representative of a number of such devices which are suitable for this purpose. In such a device, electrons are accelerated as a narrow beam inside an evacuated rudder, and the electron beam is then subjected to a rapid scanning movement as it passes through the electron window and exits the rudder. In another such device, an electron beam is focused into a sheet-like shape inside the rudder by means of a system of cylindrical electron optics. If precise focusing is not required, the electron-emitting cathode or cathodes can simply be partially enclosed in a suitable housing in the rudder which limits and directs the electron beam towards the electron window, as in the irradiation unit described and shown in the drawing.

The main housing 101, the window-forming sheet 1*4-1, the window-supporting grid 121 and the window-holding block 151 with suitable gaskets, fastening devices, etc. enclose and delimit a substantially gas-tight emission chamber which has been made virtually completely gas-free by means of conduits and pumping devices (not shown), e.g. up to an air pressure of approx. 10"^ mmHg. The window-forming sheet 1*4-1 through which the electrons emerge from the acceleration tube is a thin sheet of relatively light metal, and the sheet should be as thin as possible, e.g. 0.0025 mm, so that the electrons can pass: through the sheet with minimal energy loss On the other hand, the window-forming sheet 1*4-1 must have sufficient mechanical strength to withstand a pressure difference of

about. 1 atmosphere, as its inner side will face the evacuated emission chamber and its outer side will usually be exposed to atmospheric pressure.

The amount of radiation that can be released through the electron window is determined by the physical properties of the window and the energy of the beam that hits the electron window. Part of the radiation energy will inevitably be lost in the form of heat when electrons pass through the window. The grid 121 and the window holding block 151 constitute means for heat exchange with the window. The wire 133 enables additional heat transfer via circulation of a suitable cooling agent through the wire. The distance between the grid components 125 represents a compromise between consideration of the desired maximum mechanical support and heat absorption on the one side and consideration of the desired least possible braking of electrons passing between the cathode and the window-forming sheet 1*4-1 which serves as the anode.

Although in the embodiment shown a sheet material is used as the workpiece to be coated, it will be understood that a number of different objects can be used as the workpiece which are led through the coating bath suspended in a conveyor above it. In such an embodiment, the location of the electron acceleration units will change in accordance with the shape and size of the workpiece, e.g. by lateral displacement from the direction of movement of the suspended and recently coated workpiece from the conveyor. Furthermore, if the workpiece is a sheet material, the devices for supplying, transporting, charging and collecting the sheet material can be changed in a large number of ways while performing the same functions as the corresponding devices shown.

Example 1

A silicon-modified polycarboxylic acid resin of the polyester type was prepared from the following ingredients:

The polysiloxane used was a commercially available hydroxyl-functional, cyclic polysiloxane with the following properties:

The glycol, polysiloxane and xylene were introduced into a 3-necked 1-liter flask and heated to a temperature of 160-165°C for approx. 2 hours under stirring and under a nitrogen atmosphere. The reaction mixture was cooled to 125-130°C, the maleic anhydride, the tetrahydrophthalic anhydride and the hydroquinone were added, and the temperature was slowly increased to 190-200°C and maintained for approx. 3.5 hours until an acid value of approx.<*>+7.7 was achieved. The heating was stopped, the xylene distilled off and the mixture cooled to approx. 80°C. About. h5 g xylene and approx. k- 5 g of methyl methacrylate was added. The acid number of the binder solution was then determined to be approx. ^B,^. This binder solution is therefore designated binder A.

A ground mixture was prepared from the following ingredients:

The mixture was placed in a ball mold and ground for approx. 38 hours. This paint mixture is referred to below as paint base 1. A resin monomer dispersion was prepared from the following ingredients:

The amine and water were mixed in a mixer at high speed. The paint base and binder were pre-mixed and then kept in the swirling mixture of amine and water. The whole was then mixed for 10 minutes, after which the mixing was stopped for 5 minutes and then continued for 5 minutes. Mixing was then stopped for 20 minutes and then continued for 5 minutes. After 5 minutes, the dispersion was stirred with <*>+00 g of distilled water. The resulting emulsion contained approx. 10% by weight solids.

This emulsion was placed in a tank which served as the cathode in an electrodeposition cell. A steel sheet material was coated using a voltage difference between the cathode and the sheet material (anode) of approx. 100 V for approx. 1 minute.

The sheet material was quickly removed from the bath into a nitrogen atmosphere,

and the substantially uniform and continuous coating or coating was polymerized to a non-tacky state by passing the coated sheet through an electron beam. The irradiation conditions used were as follows:

Example 2

The procedure according to example 1 was repeated, except that the pigment concentration in the bath was increased in separate steps to 15, 20 and 25% by weight of the bath's solids content.

Example

The procedure according to example 1 was repeated, except

that instead of that in example. 1 used polysiloxane was used

a reaction equivalent amount of a commercially available methoxylated partial hydrolyzate of monophenyl- and phenylmethylsilanes consisting essentially of dimethyltriphenyl-trimethoxytrisiloxane with the following typical properties:

Example h

A paint was prepared which was electrolytically deposited from an aqueous bath onto a metal plate and polymerized by means of an electron beam as in Example 1, except for the differences noted below. The following materials were introduced into a reaction vessel:

The xylene was heated to 130°C under a nitrogen atmosphere and continuously stirred. The monomers (a), (b), and (c), the reaction initiator (f), and the hydroquinone (g) were added to the xylene. The monomers (a), (b) and (c) were separated and gradually added over the course of approx. 3 hours. The charge was heated to 130 - 133 C for approx. 3 hours. It was then cooled to approx. 50°C.

The methacrylic acid (d) was added to the charge, and the temperature was gradually raised to 138°C and maintained until an acid number of approx. 60. The xylene was then removed.

The acrylic polymer thus formed was mixed with styrene and methyl methacrylate in the same ratio as in example 1.

The applied voltage in the electrolytic deposition was

about. 170 V. The pH of the bath was approx. 7.3. The amine used was diisopropanolamine.

The following conditions were applied when irradiating the thus obtained coated plates:

Example 5

A polycarboxylic acid resin of the polyester type was prepared from the following ingredients:

The above materials were mixed with 250 ml of xylene and 0.02% hydroquinone. The mixture was heated to 190°C until 130 ml of water had been removed and an acid number of approx. 50 had been achieved. The solvent was removed with a stream of nitrogen gas, and a yield of approx. 2,*f86 g.

Using a conventional mixer, 300 ml of water was mixed with 26 ml of 1 N diisopropanolamine. 30 g of the resin was slowly added and stirring was continued for 30 minutes. The resulting dispersion was diluted with water to a total weight of 390 g. This material contained approx. 0.9 alkenic a,p-unsaturations per 1,000 molecular weight unit.

Steel plates pretreated by a common zinc phosphate process were used as anodes in an electrodeposition cell, in which the above dispersion served as the electrolyte and the coating tank as the cathode. That. submerged area of the anode was 37.*+- cm 2 (5.2 cm x 7.2 cm). The distance between cathode and anode was approx. 5 cm. A voltage difference between anode and cathode of approx. 100 V for 1 minute, and a resin film of substantially uniform thickness was deposited. The initial current between the anode and cathode was approx. 0.82 A, and this fell to approx. 0.07 A with increasing electrical resistance due to the deposited film. This gave a provision of approx. 0.2l8 g of resin on the plate with a consumption of approx. 8.8 coulomb or an electrical equivalent weight of

The anode was taken up from the bath and exposed to an electron beam. The distance between the electron window and the coated plate was approx. 30.5 cm. The atmosphere was air. The electron emission took place at 280,000 eV. The coating was exposed to a total dosage of approx.<*>+-0 me gar ad, op a non-sticky film was obtained.

This procedure was repeated, except that the binder solution was prepared by mixing styrene monomer with the resin for the dispersion in the bath. When irradiated in a similar way, it turned out that a non-sticky film was obtained with a dosage of approx. 10 megarad.

The mixture used contained approx. 12% styrene and approx. 88% resin.

This procedure was repeated, except that half

of the styrene was replaced with methyl methacrylate.

Example 6

The procedure according to example h was repeated several times in succession, with the concentration of the binder in the coating bath being regulated to 0.5, 12 and 35% by weight in separate trials.

Example 7

Procedure according to text example V was repeated, except

that the voltage used for electrolytic deposition of the binder was reduced to 50 V and the residence time for the workpiece in the bath increased to 3 min.

Example 8

The procedure according to example h was repeated, except

that the voltage used for electrolytic deposition of the binder was set to 25p V.

Example 9

The procedure according to example 1 was repeated, except

that the voltage of the electron beam was reduced to approx. 150 e.kV and the linear speed to 0.6 m/min.

Example 10

A polymer was prepared as follows:

1. The following ingredients were added at room temperature to a flask equipped with a retort, dropping funnel, thermometer, condenser and nitrogen supply device:

Resin A was an epoxy resin with an epoxy equivalent of 185 - 192, and the resin had been prepared by the usual reaction of epichlorohydrin and bisphenol A in the presence of alkali metal hydroxide. The resin product had the following properties:

2. The charge was heated in a nitrogen atmosphere at reflux temperature for h hours. Titration with aqueous NaOH showed that all the anhydride had reacted and that 50% of the anhydride's theoretical carboxyl value had returned. 3. The solvent (dioxane) was removed by distillation followed by vacuum distillation.

<*>f. A light amber colored resin product was isolated as a viscous liquid.

An electrolytic deposition bath was prepared by mixing 100 g of the product thus prepared with 200 ml of water and 26.8 ml of diethyl amine with stirring until a dispersion of the resin was obtained. The dispersion was further diluted with water until a bath volume of 1 liter was obtained. This liquid was then used as a bath in an electrodeposition cell where the metal container of the bath served as the cathode. A metallic workpiece, a zinc phosphate-treated steel plate, was immersed in the bath and used as the anode in the cell. Electrolytic deposition of the dispersed resin on the anode was achieved by applying a voltage difference of approx. 32 V between the anode and the cathode for 1 minute. The average distance between the anode and the cathode was approx. 7.6 cm, and the current at the end of the one minute was approx. 0.2 A. The coated area on each workpiece's two main sides was approx. 39 cm 2. The workpiece was taken out of the bath and immediately rinsed with water.

The coating or coating on the workpiece thus obtained was polymerized to a non-sticky state by passing the workpiece through a beam of polymerizing electrons. The following conditions were used for the irradiation of the coated

Example 11

The procedure according to example 10 was repeated, except that approx. 5 ml of xylene was added to the electrolytic deposition bath and that the electrolytic deposition was carried out at a voltage difference of approx. 15 V for 1 minute.

Example 12

The procedure according to example 10 was repeated, except that the polymer was prepared in the following way: 1. 313 g of resin A from example 10 and 175 g of diethanolamine were introduced into the reaction flask. 2. The solution was kept at 70°C, and 275 ml of dioxane was added over the course of approx. 3 hours. 3. The reaction mixture was heated at reflux temperature for approx. 3 hours.

h. The resin product obtained was isolated from the solvent and named resin B.

5. Resin B was mixed with *+28 g of itaconic anhydride and 500 ml

dioxane under nitrogen. The reaction was exothermic, and the temperature rose to approx. 55°C. The contents of the reaction vessel were kept at a temperature of KO - 50°C overnight, and the polymer thus obtained was separated from the solvent.

An electrodeposition bath as in Example 8 was prepared, except that the polymer prepared above was used together with sufficient added dioxane to achieve a Gardner viscosity of approx. Z3.

The electrolytic deposition and electron-induced polymeri-

sering was carried out as in example 8.

The commonly used term "base polymer" is intended to include dimers, trimers and tetramers as well as higher molecular weight polymers.

The term "dispersion" used here for intimate disperser

ing of polymer with an aqueous coating bath is intended to encompass a broad meaning of this term, i.e. colloidal suspensions, emulsions, solutions, etc.

Claims (12)

1. Procedure for coating electrically conductive objects, where the object is immersed in a coating bath consisting of an aqueous dispersion of an amino compound ionizable in water and a paint binder which, in addition to any pigments and particulate fillers, consists of a film-forming polymerizable organic coating material, and an electric direct current is provided through the dispersion to deposit a film of the coating material on the object by using the object as an anode and creating an electrical voltage difference between the object and a cathode arranged at a distance from the object and in electrical contact with the dispersion, characterized by the use of a coating material consisting of (a) a homopolymerizable alkenic α,6-unsaturated polycarboxylic acid resin with a molecular weight above 250, at least one dissociable carboxyl group per molecule and at least two units of alkenic a,B unsaturation per molecule or (b) an alkenic α,B-unsaturated polycarboxylic acid resin having a acid number between 30 and 300, an electrical equivalent weight between 1,000 and 20,000, a molecular weight above 1,000 and between 0.5 and 3.0 units of alkenic α,§-unsaturation per 1000 molecular weight units and a crosslinking amount of vinyl monomer, and the coated object is transferred from the aqueous dispersion to a gaseous medium in an irradiation zone and the electrodeposited film on the object, because significant dehydration has taken place after the deposition, is exposed to ionizing radiation with an energy of at least 50,000 éV until the film is polymerized. 2. Method according to claim 1, characterized in that the electrodeposited film on the object is exposed to the ionizing radiation and polymerized for 10 minutes, preferably for 1 minute, after it has been removed from the coating bath. 3. Method according to claim 1 or 2, characterized in that a gaseous medium with reduced oxygen content compared to air is used in the irradiation zone. h. Method according to claims 1-3, characterized in that a gaseous medium mainly consisting of an inert gas is used in the irradiation zone. 5. Method according to claim 1- <*> +-, characterized in that the ionizing radiation is provided in the form of an electron beam with an average energy of 100000 - <>> +50000 eV.; 6. Method according to claims 1-5, when coating a metallic plate material, characterized in that the electrodeposition of the coating material is carried out on another part of the plate material at the same time that the polymerization of the deposited film is carried out on a first part thereof.; 7. Coating bath for carrying out the method according to claims 1-6, consisting of an aqueous dispersion of an amino compound ionizable in water and a paint binder which, in addition to any pigments and particulate fillers, consists of a film-forming polymerizable organic coating material, characterized in that the coating material consists of (a) a homopolymerizable, alkenic α,B-unsaturated polycarboxylic acid resin with a molecular weight above 250, at least one dissociable carboxyl group per molecule and at least two units of alkenic a,B unsaturation per molecule or (b) an alkenic a,B-unsaturated polycarboxylic acid resin having an acid number between 30 and 300, an electrical equivalent weight between 1000 and 20,000, a molecular weight above 1000 and between 0.5 and 3.0 units of alkenic a,B unsaturation per . 1000 molecular weight units and a crosslinking amount of vinyl monomer.; 8. Coating bath according to claim 7, characterized in that the organic coating material is of type (b) and contains 1-15.5% vinyl monomer by weight.; 9. Coating bath according to claim 8, characterized in that the vinyl monomers make up 9-1 <*> +- weight$ of the coating material. 10. Coating bath according to claim 9, characterized in that the vinyl monomers are selected from styrene and methyl methacrylate. 11. Coating bath according to claims 7-10, characterized in that the acidic resin contains 10-50% by weight of siloxane radicals. 12. Coating bath according to claim 11, characterized in that the resin contains 15~50% divalent siloxane radicals by weight.