NL8320409A - IMPROVED METHOD. - Google Patents

Description

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Coating method.

The invention relates to the drying of coatings, films and the like. The invention provides an improved method (and a resultant product) in which drying is more effective than for these.

In one general aspect, the invention provides a method of forming a dried coating layer on a suitable substrate, comprising applying a vehicle to that substrate and subjecting the applied vehicle to a treatment with a drying active agent. agent is electrostatically deposited on the applied vehicle.

The invention also has other aspects which will be shown below.

The invention finds application in the drying of paints, lacquers, varnishes, binders of printing inks and printing inks, liquid adhesives, surface coating materials, compositions for paint applications and the like. The above description is to be understood as follows: 1. With regard to the coating, film or the like - to be subjected or subjected to the method according to the invention - the term "drying-acting" should be used (i) as well as including "curing" and (ii) indicating that the coating is either tack-free, insoluble in solvent or possesses a high degree of consistency or is capable of a reasonable abrasion or withstand pressure without damage. It will be understood that under some circumstances a dry coat layer can demonstrate all of the above properties. The term "cladding layer" when used as a noun is to be understood as synonymous with "film" (or the like) for the purpose of the invention.

2. The term "substrate" is to be interpreted in the broadest possible sense, as encompassing any surface on which the vehicle can be adhered 8320409-2- * and on which it will remain while the treatment with the (drying agent) is carried out . For example, widely varying materials such as cardboard, metal foil, steel sheet, plastic material, heat-sensitive material etc. (depending on the circumstances) can be used).

3. The term "vehicle" includes paints as well as everything specifically mentioned above.

4. The term "agent" means the at least one chemical compound that induces the curing or drying of the vehicle 10. It may also sometimes be referred to in this specification as a catalytic agent or simply as a catalyst.

In one form of the invention, the vehicle may be of the type containing free isocyanate groups. The term "free isocyanate groups" also includes such groups that are potentially free, the meaning to be conveyed is that the prepolymer has isocyanate groups that can be released, or are available, for reaction with any other active hydrogen compounds place both (for the purpose of polymer enlargement and / or film formation). The compounds comprising free isocyanate groups enclose all such compounds. This therefore includes not only isocyanates with a urethane structure and polyisocyanates, but also isocyanates with a polyisocyanate, biuret and allophanate structure.

The drying (or catalytically acting) agent which can exert its action in the vapor phase can be ammonia, or an amine or any other possible compounds such as organometallic compounds or inorganic metal salts capable of accelerating the desired reaction path. The term "amine" includes not only the amine with a simple primary aliphatic monofunctional structure, but also amines characterized by (i) polyfunctionality and (ii) a further degree of hydrogen substitution. The term "vapor phase" means that the agent - namely, ammonia, an amine, etc. - is in the gas phase, vapor phase, or other air-dispersed form (for example, dispersion, mist, or aerosol) in which it is available for 8320409-3 - reaction.

Many examples of the amine itself can be given. Typical examples are, for example, mono-compounds such as methylamine, ethylamine, propylamine, isopropyl-5 amine and the many isomers of butylamine and polyfunctional amines such as hydrazine, ethylenediamine, propylenediamine and diethylene triamine. Further examples are diethylamine, triethylamine and dimethylethanolamine (DMEA) and ditertiary amines such as NNN ', N-tetra-methyl ethylenediamine TMEDA) and NNN'N'.2-pentamethyl-1.2-10 propanediamine (PMT) - and all possible combinations of such amines, in proportions as required, taking advantage of the synergistic effect of such combination.

Many examples of the OrgaQ & metal compounds can also be given. Typical examples are, for example, dibutyltin dilaurate, lead tetraethyl, titanium acetyl acetonate, dimethyl tin dichloride, and stannous and zinc octoates. Among the inorganic salts that have been found effective can be mentioned bismuth nitrate and ferric chloride. Likewise, the synergistic effect of these compounds can be taken advantage of in association with each other and with the above-mentioned amine (s).

The vehicle may be a one or two component paint or the like containing free isocyanate groups (as defined above). A typical example for such a paint - which can be applied electrostatically or otherwise to a substrate to be coated and quickly dried by means of a vapor phase drying agent as further demonstrated below - is a two component formulation. composed of a hydroxyl group-bearing synthetic resinous first component and a prepolymer with isocyanate-terminated terminal groups as the second component. It will be clear that many examples of these components themselves can be given.

A suitable paint of this type is a two component white polyurethane composition in which a pigment is dispersed and formulated using a coconut oil alkyd resin which is then mixed with a prepolymer having 8320409-4-terminal isocyanate groups based on XDI (xylene diisocyanate) ).

In other compositions, the XDI-terminated isocyanate groups prepolymer may be replaced by one or more MDI-TDI-HDI-H based prepolymers. "MDI, IPDI and H XDI (to use 12 6 5 standard abbreviations) - or the reaction products of these diisocyanate monomers with suitable polyols, polycarboxy or polyamine intermediates. Likewise, the first component can also be selected from acrylic, epoxy, polyether, polyester, and silicone resins, among others (to use general terms).

A further model example of a vehicle which can be electrostatically or otherwise applied to the substrate and which can be dried quickly according to the invention is a two-part vehicle, the first part of which contains a hydrojypyp-containing polyepoxide resin and the second 15 part comprises a free polyamide group containing resin.

Electrostatic deposition of the drying or catalytic agent can be carried out by subjecting the evaporated agent to an generated electrostatic field. In one embodiment of the invention, the electrostatic field can be created in an orthodox manner, typically by means of an electrostatic gun of the type conventionally known for that purpose.

In one embodiment of the invention, electrostatic deposition of the drying agent (catalyst) may follow a previous step in which the vehicle is applied to the substrate. However, co-deposition, including electrostatic co-deposition, i.e., simultaneous application of both coating agent and drying agent by the action of an electrostatic field, is also within the scope of the invention. According to a further method aspect, the invention therefore also relates to a method as generally described above, which is further characterized in that the steps of applying the vehicle to the substrate and electrostatically depositing the drying agent are carried out simultaneously. In a related aspect, the invention relates to a device as described below for performing this method.

As an introduction to the description of the device just mentioned, reference is made to the manner in which the vehicle is applied to the substrate. In this regard, the vehicle, typically a paint, can be applied by hand painting (using a brush), dipping, spraying, or by using a device to electrostatically apply the paint to the substrate itself. This electrostatic deposition of paint can be accomplished by means of an electrostatic paint gun.

The device for performing the co-deposition of vehicle and drying agent can do this (as indicated above) through the action of an electro-15 field. Followers; this related aspect of the invention provides the invention for a device which, in combination, comprises means for directing an electrostatically charged vehicle, eg a paint, to the substrate to be coated and means for simultaneously directing an electrostatically charged drying agent agent, which is typically vapor phase, to the substrate with the first and second mentioned agents arranged concentrically with respect to each other. This device, which can also serve to supply only a drying active agent to the substrate, will be described in more detail below.

The vapor phase drying agent can be generated in various ways, including evaporation techniques or injection techniques. A device which effectively produces a vapor phase drying agent is another aspect of the invention. According to this aspect, the invention provides an apparatus which, in combination, comprises means for vaporizing a liquid drying active agent, means for controlling the evaporating agent to a desired location - for example, to said second means of the device described above, and means located in the 8320409-6 (along which the evaporated agent is passed) for determining (the concentration of said agent) which effectively ensures that the concentration of the supplied evaporated agent is kept within predetermined limits. When the vaporized agent is fed to said second agents, the vapor phase-developing components and the co-deposition (triggering components) function together as a single device.

The invention will now be described successively with reference to the accompanying drawings and a number of specific examples. It will be understood that the following description is intended to illustrate operating features of the invention - and should not be construed as limiting.

In the drawings:

Fig. 1 is a perspective view of an apparatus 15 for vaporizing (generating) the drying agent.

Fig. 2 is a perspective view of an apparatus for effecting a deposition of drying agent - or / for co-depositing vehicle and agent.

The device of FIG. 1 (which is generally indicated by reference numeral 1). consists of a box-shaped outer structure 2 containing a tank 3 for the liquid catalyst. The catalyst is atomized into an inner chamber 4 located below the tank 3 by means of atomizing nozzles 5 which are fed the catalyst from the tank 3 under the influence of gravity. Air is admitted into the chamber 4 through an air inlet filter 7 in a side wall 8 of the structure. A turbulent air flow is generated in the chamber 4 to facilitate mixing and atomization therein.

This is accomplished by a turbulence inducing fan 6 in the lower part of the chamber.

The atomizing nozzles 5, while catalyst is supplied therefrom from the tank 3, are supplied with compressed air through a hose 9, which air 1 is used to form a finely dispersed mist at the nozzles 5.

8320409 -7-

To deliver the vapor phase (in the) catalyst from the chamber 4, a variable speed turbulence induced fan 10, the operation of which is controlled by a mechanism 16, is mounted in a side wall 11 of the structure opposite the side wall 8 in which the air filter 7 is located. The fan 10 carries the vapor-phase catalyst to a desired location - in a particular case to the co-deposition device 10 described above and described below with reference to Fig. 2 via a flexible pipe 12. In a hood 13 which placed around the fan 10, means for detecting (the presence of) a catalyst (sensor) 14 is placed.

This sensor measures the concentration of vapor phase catalyst passing through the line and gives a concentration reading that is returned to and displayed by a pointer with dial: 15.

By adjusting the atomization and evaporation of the liquid catalyst stored in the tank 3, which can be controlled by means of the dial 15 within predetermined limits, the concentration of the catalyst in the vapor phase released by the device can be adjusted, be followed if necessary. As indicated above, the rate at which the catalyst is released is also controlled by adjusting the. variable speed fan 10. In this way, preset concentrations of catalyst can be accurately maintained.

In the case of a molecular solution of the vapor phase catalyst in air, the concentrations will naturally vary between zero and the saturation concentration for the particular catalyst used at the temperature under consideration. In the case of an aerosol-shaped mist, this limitation does not exist.

As indicated above, the device of Figure 1 may utilize a flexible conduit 12 to supply vapor phase catalyst 35 to the device illustrated 8320409-8 in Figure 2 (and which is generally indicated by reference numeral 20 ). This device can be used for the electrostatic deposition of catalyst alone, or for the electrostatic co-deposition of catalyst and of a vehicle - typically a paint.

The device 20 comprises a standard electrostatic gun 21 with a barrel 22 from which the electrostatic charge is emitted. A supply line 23, which opens at the rear of the gun 21, delivers the paint to the barrel 22 of the gun, from which this paint is also delivered with an electrostatic charge. An electrical conductor 24 supplies the energy for generating the electrostatic charge in the gun 21. To that extent, the gun is conventional and well known in the art.

As indicated above, the flexible conduit 15 12 can connect the device of Fig. 1 to the gun 21. The vapor phase catalyst is sprayed against the barrel of the electrostatic gun by the differential pressure generated by the fan 10 from FIG. 1. In the apparatus of FIG. 2, a barrel casing 25 disposed concentrically around the barrel 22 ensures that the vapor phase catalyst is not released from the gun 21 before the front end of the barrel is reached. In this way, the catalyst is also charged by the electrostatic field generated at the leading edge of the barrel 22 and this catalyst is charged sufficiently to cause the evaporated and now charged catalyst to settle on a grounded substrate where the gun is is directed towards it.

If the gun is to be used, in one embodiment, for electrostatic deposition of drying agent only (after prior dyeing of the substrate) operating the trigger mechanism 27 more will accomplish the intended purpose. If, in another embodiment, co-deposition is desired, the gun 20, controlled by actuation of the trigger mechanism 27, will simultaneously receive paint supplied through line 35 23 and vapor phase catalyst through line 12 (and electrostatic 8320409 -Si- charge via conductor 24). When trigger 27 is depressed in that embodiment, paint from barrel 20 and catalyst from shell 25 will be charged electrostatically simultaneously. Both the flow of paint and the flow and concentration of catalyst can be controlled so that a desired ratio is achieved in the co-deposition of paint and catalyst. It will be appreciated that when the components of Figure 1 supply the vapor phase drying agent to the components of Figure 2 through the flexible conduit 12, the components so associated function as a single device.

The method of applying electrostatically charged catalyst to pre-painted objects (on all surfaces thereof) or effecting co-deposition of electrostatically charged catalyst and paint (on all those surfaces) leads to a significant acceleration of the curing of the paint layer or film that achieves drying times that are clearly of commercial importance. The manner in which deposition or co-deposition is accomplished on all surfaces will be clearly shown in Fig. 2 - wherein the divergent 2Q is away from drying agent from vehicle once that agent and 1 vehicle leave the device.

The invention is now further described by means of five examples. The following should be noted with regard to these examples.

The paint used in these examples is a two-component white polyurethane composition as noted above.

As far as it is of known construction, the electrostatic gun corresponds to (one of) three basic types - which, for convenience, are hereinafter referred to as Types I, II and III, respectively. Briefly, type I gun accomplishes the electrostatic deposition of paint (or other vehicle) by means of a rotating disc that sprays the paint in an electrostatic field generated at the end of a filament filament present for that purpose. (and the thus loaded paint is delivered to the substrate which is coated 8320409-10-. The Type II gun generates an electrostatic field through a filament placed at the end of a barrel through which the paint is fed through the electrostatic charge must be carried away (the 5 paint being delivered to and transported through the barrel, using air) The Type III gun works in much the same way as the Type II gun, the paint to be electrostatic loaded, however, is supplied hydraulically to the barrel.

10 Example 1 (switch off successively).

A properly grounded metal sheet is coated on both surfaces with a paint as previously described using a Type I electrostatic hand-held spray gun. Air containing approximately 2000 parts per million of dimethylethanolamine 15 in vapor form and which was developed with the apparatus of Fig. 1. Aimed at right angles to the painted plate - and within a two minute period, the vapor phase catalyst is charged using an electrostatic spray gun type III with no paint being supplied to that gun 20 and only one charge being generated. The gun is positioned opposite the plate so that the charged field can cross the catalyst flow. The transport of vapor phase catalyst in the electrostatic field from the Type III gun continues continuously for about two minutes after which time both the catalyst (flow) and the (flow of) electrostatic charge are interrupted. After a further eight minutes post-curing time in slightly turbulent air, the film appears to have accelerated drying on both sides of the plate and a satisfactory dried film has been obtained.

30 Example 2 (sequential turn off)

Evaporated dimethylethanolamine (hereinafter referred to as DMEA) from the device of Figure 1 is supplied through a flexible tube 12 to the plastic casing of the barrel 25 located around the barrel 22 of an electrostatic gun. This is the device of Fig. 2, the gun in this case being an electro-8320409-11 static gun type II. Painted plates prepared in the same manner as described in Example 1 were exposed to a flow of the vapor phase catalyst from the gun as illustrated in Fig. 2. The vapor phase catalyst 5 is loaded into a concentration of about 2500 parts per million, for about sixty seconds after painting. This catalyst flow is maintained for about two minutes, after which it is stopped and the plate is exposed to gently flowing air for about 10 eight minutes. After this post-curing period, drying of the painted film appears to have noticeably accelerated on both sides of the plate.

Example 3 (co-deposition)

A deposition gun, as described in Example 2 and illustrated in Fig. 2, is set up and connected to the device of Fig. 1. Paint, as described above, is then passed through the gun and - simultaneously, the vapor phase catalyst is (DMEA) at a concentration of about 4000 parts per million DMEA supplied as a molecular solution in air. Well-grounded plates were painted by simultaneously applying paint and catalyst. Under these conditions, the painted plates reached a touch-dry state just as quickly as a general commercial dry one; status.

25 Example 4

This example is similar to that described in Example 3, i.e. the same procedure was repeated, but in this case the vapor phase catalyst used was PMT (while all other parameters were the same).

The rate of accelerated drying was even more apparent than with DMEA and an even faster commercial dryness was achieved.

Example 5

In this example, the vapor phase catalyst was lead tetraethyl. All other conditions were identical to the circumstances described in detail in Example 3. Again an equally marked acceleration of the curing of the paint was achieved.

Finally, it is repeated that the foregoing detailed description is only intended to illustrate the invention. As long as the basic criteria are observed, matters that fall within this and which are not critical in themselves can be varied according to the requirements depending on the situation.

8320409

Claims (15)

1. A method of forming a dried coating layer on a suitable substrate, characterized in that a vehicle is applied to that substrate and the applied vehicle is subjected to a treatment with a drying active agent, which agent is electrostatic. is deposited on the applied vehicle. 2. A method according to claim 1, characterized in that the application of the vehicle to the substrate and the electrostatic deposition of the drying agent are carried out either consecutively or simultaneously. A method according to claim 1 or 2, characterized in that the drying acting agent exerts its drying action in the vapor phase. 4. A method according to any one of claims 1 to 3, characterized in that the vehicle is a one or two part vehicle containing free isocyanate groups. Method according to claim 3 or 4, characterized in that the drying agent is selected from ammonia, an amine, an organometallic catalyst or some combination thereof. Process according to claim 5, characterized in that the drying agent is an alkanolamine. A method according to claim 3 or any one of claims 4 to 6, insofar as dependent on it, characterized in that the drying active agent is brought into the vapor phase by controlled atomization of a liquid precursor of the drying active agent. 8. A method of forming a dried coating on a suitable substrate, characterized in that a vehicle is applied to the substrate and the vehicle is subjected to treatment with a drying active agent in the vapor phase, the drying active agent becoming electrostatic deposited on the vehicle and (i), the step of applying the vehicle to the substrate precedes the step of electrostatically depositing the drying agent in the vapor phase, or (iii the step of applying the vehicle 35 8320409-14) to the substrate. application of the vehicle to the substrate and the step of electrostatically depositing the drying agent in the vapor phase are carried out simultaneously. The method according to claim 8, characterized in that the vehicle is a one-piece or two-piece vehicle containing free isocyanate groups. Method according to claim 8 or 9, characterized in that the vehicle is applied electrostatically to the substrate. A method according to claim 1 or 8, substantially as described herein by "one or more of the preceding examples and / or the accompanying drawings. Device for use in carrying out the method according to claim 1 or 8, characterized by, in combination, means for directing an electrostatically charged vehicle, such as a paint, to the substrate to be coated and means for simultaneously directing an electrostatically charged vapor phase drying agent to the substrate, said first and second agents being placed concentrically with respect to each other. 13. Device for use in carrying out the method according to claim 1 or 8, characterized by, in combination means for evaporating a liquid drying active agent, means for controlled delivery of the evaporated agent at a desired location and means for determining (the presence of evaporated agent) applied in the delivery path and operating to ensure that the concentration of delivered evaporated agent is maintained within predetermined limits. 14. Device according to claim 13, characterized in that the required place is the device according to claim 12 and that the evaporated agent is delivered in a controlled manner to said second means of the latter device. 8320409 -15- k 15. Device as claimed in any of the claims 12 to 14, substantially as described previously with reference to Figures 1 and 2 of the accompanying drawings. 8320409