DD217644A5 - AN IMPROVED METHOD FOR DRYING FILMS AND THE SIMILAR - Google Patents

Abstract

The invention is intended to ensure rapid drying of the films, cost savings with regard to combustible materials and electricity, wherein the drying substance is successively electrostatically sprayed onto the surface to be dried or juxtaposed with the actual surface coating and the drying substance of the product is applied without applying the spray to the coating Need to become. According to the invention, this is achieved by coating a medium on the substrate surface and subjecting the coated medium to a desiccant treatment, wherein the desiccant is electrostatically deposited on the coated medium, wherein the apparatus for carrying out the process is designed to be combined Form elements for guiding the electrostatically charged medium, such. B. color, are provided on the substrate surface to be coated and elements for the simultaneous management of an electrostatically charged drying agent in vapor form on the Substratflaeche, wherein the first and the second-mentioned elements are mounted concentrically to each other. Fig. 1

Description

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Berlin, 25.07.1984 AP G 03 D / 259 052/7 '63 385/23/20 ,,

Method and apparatus for drying films and the like

Field of application of the invention:

The invention relates to a method for forming a dried coating on a suitable substrate surface, and a .. Apparatus for carrying out the method.

The invention is particularly applicable to the drying of paints, lacquers, clearcoats, dyeing binders and printing inks, liquid adhesives, coating agents, sealants and the like. "

Characteristic of the known technical solution

Known drying processes, such as B, described in AU-ES 476 431, relate to the processes for effecting the rapid drying of the prepolymer of the polyisocyanate. The most important step in these processes is the use of a catalyst in surface coatings comprising paints, varnishes, varnishes, printing inks and printing inks, liquid adhesives, sealing compounds and other suitable surface coatings.

Other prior art cases, such as AU patent application 36214/78, also relate to the rapid drying of specific poyc and polyurethane paints and inks by use of a catalyst. However, these processes were such that the catalysts were not were deposited electrostatically,

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Object of the invention

Ea is. the object of the invention is rapid drying of the treated; To ensure films, coverings and the like, as well as a cost saving with regard to combustible materials such as gas and oil as well as electricity.

Essence of the invention

The invention is based on the object of providing a process for forming a dried coating on a suitable substrate surface, as well as an apparatus for performing dea method in which the drying substance is successively electrostatically sprayed on the surface to be dried or the actual surface coating side by side and .Daß- the drying substance of the product to be dried achieved without sprays for coating the front and back must be applied, with a hardening of the zu.r drying product is guaranteed ».

According to the invention, this object is achieved in that a medium is coated on the substrate surface and the coated medium is subjected to a treatment with a drying agent, wherein the drying agent is electrostatically deposited on the coated medium.

Advantageously, the steps of coating the medium on the substrate surface, and electrostatic deposition of the desiccant, are carried out either sequentially or simultaneously.

It is convenient if the drying agent performs the trociation treatment in the vapor phase.

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According to the invention, the medium is a one- or two-part medium containing free isocyanate groups. ; '.

Preferably, the drying agent is selected from ammonia, an amine, an organic metal catalyst, or any combination thereof. . \

Conveniently, the drying agent is an alkanolamine

Bs is of particular advantage when the desiccant produced in the vapor phase by controlled atomization of a preliminary liquid desiccant

the invention provides that the steps of coating a medium on a substrate surface and treating the medium with a drying agent are to be carried out in the vapor phase, wherein the drying agent is electrostatically deposited on the medium and the step of coating the medium on the substrate surface prior to the step of electrostatically depositing the drying agent in the vapor phase, or the step of coating the medium on the substrate surface and the step of electrostatically depositing the drying agent in the vapor phase simultaneously.

Advantageously, the medium is a one- or two-part medium containing free isocyanate groups. .

Preferably, the medium is electrostatically coated on the substrate surface,

The device for carrying out the method according to the invention is characterized in that in combined form elements for guiding the electrostatically charged

Medium, such as ζ, B. Color, on the '.beschichtende substrate surface and elements for the simultaneous guidance of an electrostatically charged drying agent in vapor form on the substrate surface are present, the first and the second-mentioned elements are mounted concentrically to each other.

Preferably, in combined form elements for the evaporation of a liquid desiccant. Elements for controllably supplying the gaseous agent to a device and sensor elements mounted in the delivery path which maintain the concentration of the supplied gaseous agent within predetermined limits.

It is of particular importance in this case that the gaseous agent is supplied controllably to the feed element.

In connection with. Coating, film or the like - which are or were to be subjected to the process of the invention - the term "drying" includes the process of "curing ¹¹ " and indicates that subsequently the coating is either free or "sticky", insoluble is in solvent, having a high degree of integrity, or able to withstand reasonable abrasion or pressure without damage "It is also acknowledged · that, under certain circumstances, a dry ¹ covering can have all the properties mentioned above""When the term" coating "in When used as a noun, the context of this invention should be considered synonymous with "film" (or the like).

The term "substrate" is to be understood in the widest possible sense and includes any surface. that the binder can be applied adhesively and on which it is held while the treatment with the drying

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medium, so Sa can be used as'different materials such as cardboard, metal foil, steel plates, plastic material, heat sensitive s material asw , (in: depending on other circumstances).

The term "binder" includes in its meaning the colors of paints, varnishes, binders, inks, etc. ",

The drying agent is at least one chemical compound which is the. Curing or drying of the binder, referred to, Sa may alternatively be referred to in this text occasionally as a catalytic agent or simply as a catalyst

In one form of the invention, the binder may be of the type containing free isocyanate groups. The term "free isocyanate groups" includes such meaning in its meaning as "potentially" free groups, the substantive meaning being that the prepolymer has IO-cyanoate groups. which can be released or for the reaction. with another compound having active hydrogen sites, for the purpose of polymer spreading and / or film formation. The term ', compounds having free isocyanate groups should be understood to include all of these compounds. Thus, not only isocyanate with urethane structure and polyisocyanate, but also with polyisocyanurate, biuret and aliophanate structure are meant.

The desiccant or catalytic agent which may affect the vapor phase treatment may be ammonia or an amine or any other. Compound, such as organometallic or inorganic metal salts, which is the

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desired reaction sequence-accelerated. The term "amine" includes not only those having a simple primary aliphatic monofunctional structure but also amines which are characterized by polyfunctionality and

2, a higher degree. Hydrogen substitution, The term "vapor phase" indicates that the desiccant - ie ammonia, an A ^! min., etc. - is in the gas, vapor or other air entrained form (eg B, dispersion, mist or aerosol) in which it is available for reaction.

The amine itself can be very different. "Typical examples are u ,. a, Mono compounds such as methylamine, ethylamine, propylamine, isopropylamine and the numerous isomers of butylamine and polyfunctional amines such as hydrazine, ethylenediamine, propylenediamine and diethylenetriamine Further examples are diethylamine, triethylamine and dimethylethanolamine (DMSA) and ditertiary amines such as Ι, Η, Ι ', Sf-tetramethylethylenediamine (TMBDA) and ίί, Ν, Ι', U'-2-pentamethyl-1,2-propanediamine (PMT) - "and, in fact, any combination of such amines proportioned to the extent necessary to produce it it is possible to take advantage of the synergistic effect of such a combination,.

Examples of typical examples are, in particular, dibutyl indutilaurate, lead tetraethyl, titanium acetylacetonate, dimethylaluminum dichloride, and tin and zinc octoates. "The inorganic metal salts which are active include, among others, vinyl nitrate and iron (III) chloride. It is equally possible to use the synergistic effect of these compounds in conjunction with one or the other and with the abovementioned amines.

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The binder may be a one or two component color, etc. containing free isocyanate groups (as defined above). A typical such color, which may be electrostatically or otherwise applied to the exterior coating substrate and rapidly dried by a desiccant in the vapor phase, as will be discussed further below, is a two-component preparation consisting of a first hydroxyl-bearing Kunstharzkocaponente and a second in one. Iaozyanat; ending prepolymer component. It is obvious that there are many embodiments for these components themselves.

Such suitable paint is a white two-component polyurethane preparation in which the pigment was dispersed using a coconut alkyd base resin, which was then blended with an isocyanate-terminated, XDI-based prepolymer (xylene diisocyanate). In alternative preparations, the isocyanate-terminated, XDI-based prepolymer may be replaced by one or more prepolymers based on MDI, TDI, HDI, H ₁₂ MDI, IPDI and HgXDI (the standard abbreviations were used) or the reaction products thereof Diisocyanate Monomers Containing Polyols, Polycarboxylic or Polyamine Intermediates "Alternatively, the first component may alternatively be selected from, among others, acrylic, epoxy, polyester, polyether, and polysiloxane resins (using the style designations).

Another example of a binder which can be electrostatically or otherwise applied to the substrate and which is rapidly dried according to the invention is a two-part binder, the first part consisting of a polyepoxide resin which forms hydroxyl groups.

and the second part of resinous free polyamide groups,. ,

The electrostatic application of the drying or catalytic agent may be carried out so that the vaporized agent is exposed to a generated electrostatic field. In one embodiment of the invention, the electrostatic precipitate may be prepared in an orthodox manner, typically by an electrostatic gun of the type generally known for this purpose.

, . ' , , ι In one embodiment of the invention, the electrostatic application of the Trocknungsmittela (catalyst) at the previous step of application of the binder onto the substrate may be followed by ": A co-deposition, including electrostatic. However, codeposition d, h ,, the simultaneous application of dea covering and desiccant by the action of an electrostatic field - is also possible within the scope of the invention. Thus, according to another aspect of the invention, the invention provides a process as defined in the general sense above and which is further characterized in that the steps of applying the binder to the substrate and electrostatic application of the desiccant are carried out simultaneously In a related aspect, the invention provides an apparatus for carrying out this method.

In preparation for defining the device, reference is made to the manner in which the binder is applied to the substrate. Thus, the binder, typically a paint, may be applied by painting by hand, using a brush, dipping or spraying, or by using a device

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which the application of the ink to the substrate is electrostatic. This electrostatic application of the paint can be done with an electrostatic spray gun. I '

The device for realizing the code adjustment of binding and desiccant, as stated above, can operate using an electrostatic field. According to this aspect of the invention, the invention provides a device which consists of a combination of elements to which electrostatically charged binder, for example a paint, onto the substrate to be coated, and elements for simultaneously conducting an electrostatically charged tracking agent, typically in a vapor phase, to the substrate, the first and second means being concentric * This device can be used to pass only the desiccant to the substrate «'

The vapor phase desiccant can be produced in a variety of ways, including 'evaporation or sinusoidal injection methods.'

The invention provides a device which consists of a combination of elements for the evaporation of a liquid desiccant} elements for controllably delivering the vaporized desiccant to the necessary location - for example, to the second-mentioned element of the above-defined device - and Meßeiementen in the discharge track is inserted and ensure that the concentration of the delivered quantity of deaerated drying3 is kept within specified limits

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The desiccated desiccant is delivered to the second element, joins the steam generating components and the Kodepositionakomponenten and working as. a single device ·

embodiment

The invention will be explained below with reference to the following with reference to the accompanying drawings and some embodiments. In the accompanying drawings show: '

, Pig .:, 1; a perspective view of the device for 'producing the drying agent in vapor phase}

Pig. 2: a persektivische view of the device for applying the desiccant or for code position of binder and desiccant «. ,

Di, e device 1 of Fig. 1 consists of a box-like outer construction · 2, which contains a tank 3 for the liquid catalyst. The catalyst is atomized in an inner chamber 4, which is located below the tank 3, by atomizing nozzles 5 which receive the catalyst under gravity. Air enters the chamber 4 via an air inlet filter 7 in side 8 of the structure 2. In the chamber 4 a turbulent air flow is generated to facilitate mixing and atomization therein by a turbulence generating fan 6 in the base of the chamber 4 reached.

While the atomizing nozzles 5 catalyst is supplied from the tank 3, they receive via the hose 9 compressed air, which serves to produce a fine atomizing mist on the nozzle 5 au »

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In order to remove the vapor phase catalyst from the chamber 4, located in a side 11 of the structure opposite the side 8 containing the air filter 7 is a variable speed turbulence fan 10, the work of which is controlled by a mechanism 16. The fan 10 directs the vapor phase catalyst to the desired location, in particular pail to the codeposition apparatus as defined above and described below with reference to Pig. Describes 2, 12 via a flexible line in a cover 13 _for the · is arranged around the fan 10, S ₁ is I have a Ka taly sat or sensor 14 · This sensor 14 measures the concentration of the (in steam phase contained catalyst the line 12 passes and produces a concentration indication which is returned to and displayed on a display.

By adjusting the atomization and evaporation of the liquid catalyst stored in the tank 3 ', which can be controlled within defined limits via the display, the concentration of the vapor phase. Catalyst supplied by the device are controlled as required. In addition, as already mentioned, the discharge rate of the catalyst is controlled by the work of the variable displacement blower 10. _(In this way We ise can be accurately maintained almost down concentrations of catalogs "lysators.

Of course, in a molecular solution of the vapor phase catalyst in air, the concentrations will vary between Hull and the saturation concentration for the particular catalyst used at the appropriate temperature. With an aerosol lever this restriction does not apply.

As stated above, the device of the Pig. 1 via the flexible conduit 12 in vapor phase catalyst of the in'der Fig ^.; 2 shown device 20 are supplied. This device 20 can be used for the electrostatic application of only the catalyst or for the electrostatic codeposition of the catalyst and the binder, typically a paint.

The device 20 consists of a standard electrostatic gun 21 with a drum 22, from which the electrostatic: Tables charge exits "In the rear of the gun 21, a supply line 23 is introduced which in the ^die.Farbe: brings drum 22 of the gun 21, from which it is also discharged with an electrostatic charge. The power line 24 ensures the supply of energy for the generation of the electrostatic charge in the gun 21, so it is a conventional gun 21, as is well known ».

As stated above, the flexible conduit 12 may comprise the device, 1 the Pig. 1 to the gun 21. The vapor phase catalyst is directed into the orifice of the electrostatic gun 21 by the pressure differential created by the blower 10 of FIG. In the apparatus 20 of Fig. 2, a drum reinforcement flange 25 concentrically disposed about the drum 22 ensures that the vapor phase catalyst does not exit the gun 21 before the tip 26 of the drum 22 is reached, in this manner Likewise, the catalyst is also charged by the electrostatic field generated at the top of the drum 22, and it is charged to a sufficient extent for the vaporized and now charged catalyst itself to deposit on a grounded substrate WEL

chea the gun 21 directed iat.

the Piatole 21 at one. Execution mode for the electrostatic charging and application of only the drying agent (which adjoins daa previous painting of the substrate is used) daa by, actuation of the Aualösemechaniamus 27 is achieved. If the code position is required in another, outer viewing mode, the gun 21, which is controlled by the work of the triggering mechanism 2.7, simultaneously with color 'but the line 23,. vapor phase catalyst via line 12, and an electrostatic charge via line 24. In this embodiment, when the triggering mechanism 27 is printed, ink from the drum 20 and catalyst on the posthardening flange 25 are electrostatically charged at the same time. Both the Parbstrom and the Strom ^v and the concentration of the catalyst can be controlled to achieve the desired ratio in the Kodeposition of color and catalyst. It is of course easy to see that the interconnected components, when the components of Fig .. 1 supply the desiccant in vapor phase to the components of FIG. 2 via the flexible conduit 12, operating as a single device.

• The procedure according to v / elchem the electrostatically charged catalyst on pre-painted products, applied to all surfaces, or after which carried out the code position of the electrostatically charged catalyst and the electrostatically charged paint on all surfaces, is; to substantially speed up the curing of the paint film, thereby achieving drying times of ₍ apparently commercial) importance The manner in which application or co-deposition occurs on all surfaces will be apparent from Fig. 2;

shows the diverging trajectory of the drying agent and the binder when this drying and binding agent leaves the device.

The invention will now be described in detail with reference to five examples. The following should be noted. ^:

The paint used in these examples is a white two component polyurethane preparation.

The electrostatic fuel gun is similar to the known., Models, and it is worked with three types, which are referred to below for simplicity as the types I, II and III. Bei'der gun of the type. electrostatically applying the paint (or other binder) through a rotating disk which atomizes the paint within an electrostatic field generated at the tip of a filament attached for this purpose. The loaded in this way. A color is then applied to the substrate to be coated. The Type II gun generates an electrostatic field by means of a filament placed at the end of the drum through which the paint passes: that is to be conducted by the electrostatic charge. The paint becomes to and through the drum The Type III drum works essentially like Type II, but the electrostatically charged paint is hydraulically applied to the drum »

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Example 1 (sequential application):

Sine metal plate, which is grounded in, suitably, becomes. on both surfaces, as described above, using a Type I electrostatic handgun - air containing approximately 2000 parts / Hill Dim ethyl ethanolamine in vapor form and in the apparatus of Pig is produced is directed at right angles to the painted plate, and within two minutes, the vapor phase catalyst is charged using a type III electrostatic gun, wherein the gun is not supplied Karbe and only the charge is generated ·; The gun is positioned opposite the plate so that the charged field can cut the catalyst stream. The exit of the vapor phase catalyst and the electrostatic field from the Type III gun are continuous for the duration of. for about 2 minutes, the supply of the catalyst and the electrostatic charge are interrupted. After a further 8 minutes post-curing time. in slightly turbulent air, the drying of the film on both sides was sufficiently accelerated to produce a sufficiently dried film.

Example 2 (sequential application):

Evaporated dimethylethanolamine (hereinafter referred to as DMSA) from the apparatus of FIG. Line 12 of the drum reinforcement flange 25 made of plastic is fed around the drum 22 of an electrostatic spray gun 21. This is the door direction of Fig. 2, in which case an electrostatic spray gun of type II is used Painted panels prepared in the same manner as in Example 1 are exposed to a stream of the vapor phase catalyst from the spray gun 21, such as

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which is illustrated in FIG. The catalyst, which is in the vapor phase, is supplied at a concentration of about 2500 parts / hill for the duration of about 60 minutes after painting. This catalyst stream is maintained for about 2 minutes, then switched off, and the plate is heated For a period of about 8 minutes, it is exposed to slightly turbulent air. After this period of curing, it can be seen that the drying of the paint film on both sides of the plate has been significantly accelerated.

Example 3 (code position) j:

An application gun 2, as described in example 2 and shown in fig. 2 and then connected to the device of PIg * 1. Color is then passed through the gun 21 as described above and at the same time the vapor phase catalyst (DMSA) is formed. in a concentration of approx. 4000 parts / mill. DMSA introduced as a molecular solution in air. Correspondingly grounded plates were painted by the simultaneous application of paint and / catalyst. Under these conditions, the coated panels achieved equally fast a touch-dry condition and a total commercial dryness. , -. '.

Example 4j

This example corresponds to the case described above in Example-3, d. The same procedure was used, but in this case the vapor phase catalyst was PMT (all other parameters unchanged). The degree of accelerated drying was even greater than with DMEA, and even faster became commercial Dryness achieved.

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Supplement 5:

In this example, the vapor phase was. Catalyst lead tetraethyl ·; All other conditions were identical to those mentioned in Example 3. Also in this Pail, an equally pronounced acceleration of the color hardening was achieved.

 Finally, it is repeated that the above detailed description is only illustrative of the invention *,. By retaining the basic criteria, details which are themselves of no critical importance may be changed in accordance with the needs of the situation «: ''

Claims (13)

1". A method of forming a dried coating on a suitable substrate surface characterized by coating a medium on the substrate surface , 'and the coated medium is subjected to a treatment with a desiccant, wherein the desiccant is electrostatically deposited on the coated medium. 2. Method according to item 1, characterized in that the steps of coating the medium on the substrate surface and the electrostatic deposition of the. Drier be carried out either sequentially or simultaneously * .... 2 59 05 Claim , 3>; Method according to points 1 or 2, characterized by; in that the drying agent carries out the drying treatment in the vapor phase; 4 · Method according to items 1 to 3 », characterized in that - the medium is a one- or two-part medium containing free isocyanate groups. 5 * Procedure according to points 3 or 4, characterized by. in that the desiccant is selected from ammonia, an amine, an organic metal catalyst or any combination thereof, 6, method according to item 5, characterized in that the desiccant is an aikanolamine, ^N 25 9052. 7 7 #, procedure according to item 3 or items 4 to 6 ,; characterized in that the desiccant is prepared in the vapor phase by controlled atomization of a preliminary liquid desiccant. A process for forming a dried coating on a suitable substrate surface, characterized in that the steps of coating a medium. on a substrate surface and the treatment of the medium with a drying agent in the vapor phase, wherein the drying agent is electrostatically deposited on the medium and the step of coating the medium on the substrate surface is carried out before the step of electrostatic deposition of the drying agent in the vapor phase, or the step of coating the medium on the substrate surface and the step of electrostatically depositing the drying agent in the vapor phase are carried out simultaneously: 9. The method according to item 8, characterized in that the medium is a one- or two-part medium containing free isocyanate groups. 10. Method according to items 8 or 9 »characterized« in that the medium is electrostatically coated on the substrate surface « _; , 11 ». Apparatus for carrying out the method according to item 1 or 8j characterized in that; that in combined form elements for guiding the electrostatically charged medium, such. Example, color, are provided on the substrate surface to be coated and elements for the simultaneous guidance '' - an electrostatically charged drying agent in vapor form on the substrate surface, wherein the the first and second elements are concentric with each other «: 12 ·; Apparatus according to item 1 or 8, characterized in that in combined form elements for the evaporation of a liquid drying agent ,: elements for controllable; Supply of the gaseous agent to a. Device and ,, in the supply path -assembled sensor elements, which keeps the concentration of the supplied gaseous means within gate certain limits provided ^ sInd. 13 · device according to item 12, characterized in that; that; .The gaseous agent is supplied to the supply element controllable · is «; - For this purpose, 2 pages Z-eichnungen