KR100863830B1 - Methods for removal of polymeric coating layers from coated substrates - Google Patents

Abstract

The present invention provides a method of at least partially removing one or more polymer coating layers from a coated substrate having at least one coated surface. The method of the present invention comprises generating at least one reactive species in an ionized air stream discharged at atmospheric pressure; And positioning a coated surface within said ionized air stream. At least one reactive species reacts with the one or more polymeric coating layers such that the one or more coating layers are at least partially removed from the coated surface of the substrate at atmospheric pressure.

Description

METHODS FOR REMOVAL OF POLYMERIC COATING LAYERS FROM COATED SUBSTRATES

The present invention generally relates to a method for removing a polymer coating layer, and in particular, the present invention relates to a method for removing a polymer coating layer from a coated substrate using an atmospheric pressure plasma discharge.

The term "plasma" generally describes a partially ionized gas consisting of ions, electrons and neutral species. Plasma can be generated, for example, by means of energy input by chemical means, extremely high temperatures, strong constant electric fields and in particular by radio frequency (RF) electromagnetic fields.

Plasma has been widely used in a wide range of industrial and high-tech fields, including, for example, semiconductor manufacturing, various surface modifications and coating of reflective films for window panels and compact discs. Plasma in the high vacuum (<0.1 mTorr) to several Torr pressure range is common and has been used for film deposition, reactive ion etching, sputtering and various other forms of surface modification. For example, gas plasma is known to treat plastics and molding substrates (eg, thermoplastic olefinic substrates used as bumpers and instrument panels in the automotive industry) to improve the adhesion of continuously applied coating layers. Typically, by improving to several molecular layer depths, the bulk properties of the polymer substrate are not affected. The main advantage of using plasma for this purpose is that it generates little or no waste, requires no harmful conditions such as high pressure, and can be applied to a variety of vacuum-compatible materials, in particular silicon, metals, glass and ceramics. To cause an "all dry" process.

Typically, it is known to use plasma, typically O ₂ plasma, as a means for removing hydrocarbons and other organic surface contaminants from various substrates. However, due to the short lifespan of their reactants and their line-of-sight reactivity on the surface, such highly activated reactants are irregular surfaces, unpolished or rough metal surfaces or surfaces of surfaces with three-dimensional topography. Not particularly suitable for cleaning.

In addition, the use of a plasma at reduced pressure has several disadvantages that require the substrate to be treated or cleaned to be vacuumed and able to withstand under such reduced pressure conditions. The use of plasma at or above atmospheric pressure can avoid such drawbacks. One problem associated with conventional atmospheric discharges was the rapid recombination of O ₂ + with atomic oxygen at that pressure. However, metastable oxygen (1 Δg O ₂ ) formed in the plasma has a lifetime in the range of 0.1 seconds (at atmospheric pressure) to 45 minutes (at zero pressure) and also has an internal energy of 1 eV. Brought and promotes its chemical reactivity. The production of metastable oxygen in the plasma increases at high pressure. It is known to use metastable materials including metastable O ₂ to clean the surface, and both vacuum affinity and vacuum non affinity materials can be plasma treated with reduced cost and complexity.

Atmospheric pressure plasma torches and sparks typically rely on high power DC or RF discharges and thermal ionization and generally operate at high temperatures resulting in substantial ionization. As a result, such plasma can destroy most substrate surfaces.

In the automotive surface refinish industry, at least partially remove a portion of the coating layer from the vehicle body, for example in a crash damage zone, sometimes before applying a refinish coating on the repair zone. It may be necessary to remove or to completely remove one or more coating layers. Depending on the extent of damage to the coating, it may be necessary to remove part of the clear coat layer of the color-plus-clear finish, or to remove one of the colored coat layer and the transparent coat layer. It may be necessary to do this, or it may be necessary to remove both. Similarly, it may be necessary to remove all coating layers, including top coats, primer-surfacers, and / or electrocoat primer layers to expose substrates that may be metallic or nonmetallic. Similarly, a coating layer removal step may be necessary in an automotive assembly plant for repairing the "end of the line" of the original equipment coating. Typically, such coating layer removal can be accomplished by sanding or abrading through the coating layer (s). As can be expected, it is very difficult to control the amount of one or more coating layer thicknesses to be removed by sanding. Moreover, the sanding process is undesirable for removing the coating layer from sensitive substrates. For example, when "sanding through" all coating layers to a substrate, in particular to an elastomeric substrate, the primer-surfacer may be applied to the extent to which the part needs to be discarded or at least before subsequent application of a refinish or repair coating. The substrate may be scratched or damaged to the extent that recoating may be necessary. In addition, the manufactured articles, such as automobile bodies and various coating parts and accessories thereof, are three-dimensional terrain that is not easy to sand uniformly in addition to substantially flat horizontal and vertical surfaces (e.g. hoods, roofs and main door surfaces). Or have a profile.

In view of the foregoing, it is desirable to provide a method for at least partially and selectively removing one or more polymer coating layers from various coated substrates, including coated substrates having various topography and profiles, which are different from sanding.

Summary of the Invention

In one embodiment, the invention is a method of at least partially removing one or more polymer coating layers from a coated substrate having at least one coated surface, the method comprising: at least one in an ionized air stream discharged at atmospheric pressure Generating a reactive species; And positioning a coated surface in the ionized airflow, wherein the at least one reactive species reacts with at least one polymeric coating layer such that at least one coating layer is at least partially removed from the coated surface of the substrate at atmospheric pressure. .

The invention also relates to a method for at least partially removing one or more polymer coating layers from a substrate having at least one coated surface coated with a multi-layer composite coating comprising two or more polymer coating layers. will be.

Except where otherwise indicated in the examples or otherwise indicated, all values indicative of the amount of components, reaction conditions, etc. used in the specification and claims are to be understood as being modified in all instances by the term "about." Accordingly, unless indicated to the contrary, the numerical parameters set forth in the following specification and appended claims are approximations that may vary depending upon the desired properties obtained by the present invention. In any case, no attempt is made to limit the application of the doctrine of equivalents to the claims, but each numerical parameter should at least be construed in light of the number of significant figures reported, applying conventional peripheral techniques.

Although the numerical ranges and parameters setting forth the broad scope of the invention are approximations, the numerical values set forth in the specific examples are reported as precisely as possible. However, certain numerical values inherently contain certain errors which inevitably arise from the standard deviation found in their respective experimental measurements.

In addition, certain numerical ranges referred to herein are to be understood to include all sub-ranges subsumed therein. For example, the range "1 to 10" means all subranges between (and including) the minimum value 1 mentioned and the maximum value 10 mentioned, that is, the minimum value 1 or more and the maximum value 10 or less. It is considered to include all subranges that it has.

As mentioned above, the present invention relates to a method for at least partially removing one or more polymer coating layers from a coated substrate having at least one coated surface. Such a method comprises generating at least one reactive species in an ionized air stream discharged at atmospheric pressure; And positioning a coated surface within said ionized air stream. At least one reactive species is reacted with at least one polymeric coating to remove one or more coatings at least partially from the coated surface of the substrate at atmospheric pressure.

The process of the present invention is a substrate that can accommodate a polymer coating, such as, for example, wood, metal, glass, fabric, plastic, fiberglass and fiberglass reinforced composites, foams, as well as elastomeric substrates, and the like. It can be used to substantially remove one or more polymer coating layers from the. In certain embodiments, the methods of the present invention may generally be used to remove one or more polymeric coating layers from a substrate suitable for use in making an article of manufacture.

In one embodiment of the present invention, the substrate may comprise a metal substrate. Examples of suitable metal substrates may include ferrous metals and nonferrous metals. Suitable iron-based metals include iron, steel and their alloys. As non-limiting examples of useful steel materials are cold-rolled steel, the vulcanized (galvanized) steel, electro galvanized Steel, Stainless steel, bleaching steel (pickled steel), steel onto a galvanic coating to carbonyl ^R (GALVANNEAL ^R), going Baru methoxy ^R (GALVALUME ^R ) and Galvan ^{R R} zinc-aluminum alloys and combinations thereof. Useful nonferrous metals include aluminum, zinc, titanium, magnesium and their alloys. Combinations or complexes of ferrous and nonferrous metals, or combinations or complexes of metals and nonmetals may also be used. The substrate may or may not be cleaned and / or pretreated with certain cleaner compositions and pretreatment compositions known in the art.

In another embodiment of the present invention, the substrate may comprise an elastomeric substrate. Suitable elastomeric substrates may include certain thermoplastic or thermoset synthetic materials that are well known in the art, including fiber reinforced thermoset and thermoplastic materials. As used herein, "thermosetting material" or "thermosetting composition" refers to a material that is irreversibly "cured" upon curing or upon crosslinking, wherein the polymer chains of the polymer component are linked together by covalent bonds. . This property is generally sometimes associated with crosslinking reactions of compositional components, e.g., induced by heat or radiation. Hawley, Gessner G., The Condensed Chemical Dictionary, 9th Edition, page 856; Surface Coatings, vol. 2, Oil and Color Chemists' Association, Australia, TAFE Educational Books (1974). As soon as it is cured or crosslinked, the thermosetting material or composition will not melt upon application of heat and is insoluble in the solvent. In contrast, a “thermoplastic material” or “thermoplastic composition” includes a polymeric component that is soluble in a solvent that can form a liquid flow upon heating by being not covalently linked [Saunders, KJ, Organic] Polymer Chemistry, pp. 41-42, Chapman and Hall, London (1973).

Non-limiting examples of suitable elastomeric base materials include polyethylene, polypropylene, thermoplastic polyolefins ("TPO"), injection molded polyurethanes ("RIM"), and thermoplastic polyurethanes ("TPU").

Non-limiting examples of thermoset materials useful as substrates associated with the present invention include polyesters, epoxides, phenols, polyurethanes such as "RIM" thermosets, and mixtures of certain of them. Non-limiting examples of suitable thermoplastics include polyethylene, thermoplastic polyolefins such as polypropylene, polyamides such as nylon, thermoplastic polyurethanes, thermoplastic polyesters, acrylic polymers, vinyl polymers, polycarbonates, acrylonitrile-butadiene-styrene ( "ABS") copolymers, ethylene propylene diene terpolymer ("EPDM") rubbers, copolymers, and mixtures of certain of the foregoing.

In some cases, the polymer substrates described above may have adhesion promoters present on the surface of the substrate on which many coating compositions (including the coating compositions described below) may be applied. In order to promote adhesion of the organic coating to the polymeric substrate, the substrate is pretreated using an adhesion promoter layer or a tie coat, for example a thin layer of 0.25 mil (6.35 microns) thick, or It can be pretreated by flame, corona or atmospheric plasma treatment.

Non-limiting examples of adhesion promoters suitable for use on polymeric substrates include chlorinated polyolefin adhesion promoters, saturated polyhydroxylated polydiene polymers, and blends thereof.

For the purposes of the present invention, the terms " polymeric coating layer " and " polymeric layer " are intended to exclude layers of mill oil, lubricating oil and / or mechanical oil, and oils, for example from fingerprints and the like. As used herein, a polymer layer or composition formed over “at least a portion of” a substrate is applied to at least a portion of the substrate as well as a polymer layer or composition formed directly on at least a portion of the substrate surface. It refers to a polymer layer or composition formed on a particular coating layer (s) or adhesion promoter material or pretreatment material applied in advance.

That is, a “substrate” having a first polymeric layer formed thereon may include a metallic or elastomeric substrate to which one or more coating layers have been previously applied. For example, a “substrate” can include a primer coating on a metallic substrate and at least a portion of the substrate surface, and the first polymer layer can include an electrodepositable primer coating. Similarly, a “substrate” can include a (optionally pretreated) metallic substrate having an electrodepositable primer formed on at least a portion thereof, and a primer-surfacer coating on at least a portion of the electrodepositable primer. The first polymer layer may comprise, for example, a colored base coat on at least a portion of such multilayer “substrate”, and the second polymer layer may be substantially pigment free formed on at least a portion of the colored base coat. It may include a top coat (top coat).

As mentioned above, the present invention also relates to a method for at least partially removing one or more polymer coating layers from a substrate having at least one coated surface coated with a multilayer composite coating. The multilayer composite coating comprises two or more polymer coating layers, where one or more coating layers are formed on one or more pre-coated coating layers. Such multilayer composite coating may comprise only two polymer coating layers, wherein the first polymer coating layer is formed on at least a portion of the substrate and the second polymer coating layer is formed on at least a portion of the first polymer coating layer. Alternatively, if there is at least one continuous polymer layer formed on at least a portion of the second polymer layer, or having at least one polymer layer applied to the substrate prior to applying the first polymer coating layer, the multilayer composite coating of the present invention A first polymer coating layer on at least a portion of the silver substrate, and a second polymer coating layer formed on at least a portion of the first polymer layer.

For example, the first polymer layer may comprise a primer-surfacer coating and the second polymer layer may comprise a color-enhancing base coating to which a transparent top coat is applied successively. In addition, the first polymer coating layer may comprise an electrodepositable primer coating layer, and the second polymer coating layer comprises an appearance-enhancing monocoat or colored basecoat layer and a substantially pigment free topcoat layer. The color + transparent coating system may comprise a primer-surfacer coating layer applied successively. Incidentally, the first polymer layer may comprise a transparent top coat (as a transparent coating of the color + transparent coating system) and the second polymer layer may comprise a repair top coat.

In an embodiment of the invention, the coated substrate has a three dimensional topography. When the substrate is used as a component for manufacturing the article of manufacture, such an article may have a particular shape and topography and may consist of any of the substrates described above.

In the process of the present invention, certain coated substrates as described above by generating at least one reactive species in an ionized air stream (ie, plasma) discharged at atmospheric pressure primarily and then placing the coated surface in the ionized air stream. One or more polymer coating layers are removed from the. The reactive species reacts with at least one polymeric coating to at least partially remove the at least one coating. Reactive species include, for example, photons, metastable atoms, atomic species, free radicals, molecular segments, monomers, electrons and ions. While certain species of these species may be present in the ionized air stream, the reactive species are sufficiently chemically reactive to remove the coating layer (s) to be removed. For example, the oxygen plasma can include O, O ₂ ^*, and O ₃ . This method is carried out at atmospheric pressure, thereby eliminating the need to vacuum the substrate, as is required by many conventional plasma techniques performed at reduced pressure.

Although certain plasma sources can be used in the method of the present invention, this method can be carried out under atmospheric pressure (ambient pressure). Those skilled in the art will know that "atmospheric pressure" (or "ambient pressure") changes in proportion to sea level, and therefore will vary with terrain location. For the purposes of the present invention, it should be understood that the specific temperature of the ionized airflow from which the coating layer is removed is selected based on the type of polymer coating (s) removed from the coated substrate and, in some circumstances, the type of substrate itself.

Certain suitable atmospheric plasma sources can be used in the method of the present invention. Suitable plasma sources include atmospheric plasma jets described in US Pat. No. 5,961,772, column 3, line 66 to column 7, column 7, and US Pat. No. 6,262,523 B1, column 4, line 29 to column 7, line 7. pressure plasma jet); And 1 atmosphere of uniform glow discharge plasma apparatus described in column 66 of column 2 to column 28 of column 5 of US Pat. No. 5,414,324.

In certain embodiments of the invention, at least one reactive species is generated in the ionized airflow in the electromagnetic field. In another embodiment of the present invention, reactive species may be generated, for example, in ionized airflows in RF, DC, pulsed DC or optionally generated asymmetric wave electromagnetic fields.

For the present invention, the plasma source may be held by hand during use, or may be used as a stationary "in-line" plasma source, or such plasma source may be, for example, a coil line. May be removed using a robot or other mechanical means to remove one or more coating layers from the coiled metal substrate. Similarly, the method of the present invention can be used in finishing parts and is particularly suitable for removing coating layers from coated substrates with three-dimensional topography.

In the process of the invention, at least one reactive species is generated in an ionized air stream derived from a feed gas comprising a certain number of gases or combinations thereof. In an embodiment of the invention, the ionized gas may be derived from a feed gas selected from helium, argon, neon, krypton, oxygen, carbon dioxide, nitrogen, hydrogen, methane, acetylene, propane, ammonia and / or air.

In another embodiment of the invention, the feed gas comprises a mixture of helium and oxygen. In such helium / oxygen gas mixtures, based on the total volume of the mixture, helium is typically present in the mixture in an amount ranging from 99.5 to 75 volume percent, or in the range from 95 to 80 volume percent, or in the range from 90 to 85 volume percent; Oxygen is present in the mixture in an amount ranging from 0.5 to 25% by volume, or in the range from 5 to 20% by volume, or in the range from 10 to 15% by volume.

In another embodiment of the invention, the feed gas comprises a mixture of nitrogen and oxygen. In such nitrogen / oxygen gas mixtures, based on the total volume of the mixture, nitrogen is typically present in the mixture in an amount ranging from 99.5 to 75% by volume, or in the range from 95 to 80% by volume, or in the range from 90 to 85% by volume; Oxygen is present in the mixture in an amount ranging from 0.5 to 25% by volume, or in the range from 5 to 20% by volume, or in the range from 10 to 15% by volume.

In certain embodiments of the present invention, at least one reactive species is generated in an ionized air stream derived from ambient air which may include water vapor and / or various other gases.

For the purposes of the present invention, the fact that a particular feed gas or mixture of these feed gases, and the mixing ratio of these gases, will be selected based on the type of polymer coating (s) to be removed from the coated substrate and, in some cases, the substrate itself. Should know.

In the method (s) of the invention, the effective feed gas flow rates can vary widely, for example, the feed gas flow rate is from 1 to 100 standards ft ³ / hr (scfh, standard cubic feet per hour), e.g. 5 to 75 scfh, or 10 to 50 scfh, or 10 to 35 scfh. Also, as an example, when an atmospheric glow discharge plasma source is used, a negative pressure applied in an air stream induced by conveying the coated substrate through a gap between the plates, or in a region where the treated substrate is discharged from the ionized air stream. It may not be necessary to use anything other than airflow induced by negative pressure. It has also been found that the separation distance between the plasma source and the coated substrate surface can adversely affect the removal of the polymer coating layer. The effective separation distance may vary and typically may range from 0.1 to 50 mm, for example 0.1 to 35 mm, or 0.1 to 25 mm, or 1 to 10 mm. Similarly, the effective power density (power per unit volume) for the plasma (i.e. ionized airflow) can range from 0.1 watts / cm 3 (W / cm 3), for example, from 0.5 to 150 W / cm 3. have. It should also be noted that the dwell time (ie, the residence time of the coated substrate surface in the ionized airflow) can range widely depending on the type of polymer coating to be removed and the type of substrate itself, as well as other method parameters. do. For example, residence times ranging from 0.01 to 1 second have been found to be effective in removing layer-by-layer thermosetting polyurethane coating systems from glass fiber composite substrates.

Those skilled in the art will appreciate that certain aforementioned parameters, such as separation distance, power density, feed gas flow rate and residence time, required to at least partially remove the polymer coating layer from the coated substrate, depend on which plasma source was used. It will be appreciated that it can vary widely. For example, an atmospheric glow discharge plasma source will typically generate a plasma that diffuses much more than that generated by an atmospheric plasma torch-type plasma source. Thus, glow discharge plasma sources are believed to have much lower power densities than atmospheric plasma torch-type plasma sources. Similarly, atmospheric glow discharge plasma sources may require longer residence times to remove the polymer coating layer than would be required when using atmospheric plasma torch-type plasma sources.

With appropriate selection of the relevant process parameters such as plasma source and / or amount of power, feed gas (s), flow rate of feed gas (s), temperature, residence time, etc., the method of the present invention results in a coating layer applied before the layer is removed ( Is particularly useful for controlling and / or selectively removing one or more polymer coating layers while maintaining the original appearance of the s), or the original appearance of the substrate itself, or both. That is, for example, some layers of one coating layer (for example, a monocoat layer or a transparent topcoat layer) may be applied by applying a controlled removal parameter while keeping the base coat applied before the topcoat intact. It can be removed or all topcoat layers can be controlled and / or selectively removed. Similarly, this method can remove all top coats (eg, base coat / transparent coat system, or monocoat) while keeping the primer-surfacer coating applied before the top coat removed. Can be done in any way. Moreover, it is possible to maintain the original appearance of the substrate by removing all coating layers from the sensitive substrate without the use of aggressive solvents or sanding.

The one or more coating layer (s) that are at least partially removed in the process of the invention range from 1 kPa to 10,000 microns, such as from 0.001 microns to 5,000 microns, or from 0.001 microns to 1,000 microns, or from 0.01 microns to 500 microns, or from 0.1 microns to It can have a total thickness in the range of 250 microns. The thickness of the coating layer (s) may range between certain values of these values, including the values mentioned above.

In addition, the effects of the process of the present invention may be more sensitive to removal by certain reactive species, such as those well known in the art, which may be sensitive to oxygen ions or oxidation and / or reduction, e. For example, it is contemplated that improvements can be made through the use of a coating applied as a monocoat in a polyester based and / or polyether based coating or as one or more coating layers.

One or more coating layers that can be removed by the method of the present invention include electrodepositable film forming compositions, primer compositions, colored or uncolored monofilm compositions, colored base coating compositions, transparent or substantially pigment free topcoat compositions and It may be selected from other coatings commonly used in coating of substrates. The multilayer composite coating is formed by combining at least two of the aforementioned coating compositions. Non-limiting examples include electrophoretically-applied compositions followed by spray-coated primer compositions, or electrophoretic-coated compositions followed by spray-coated primer compositions and then monocoated compositions, or electrophoresis. -Applied compositions followed by spray-coated primer compositions and then pigmented + transparent composite coating compositions. Alternatively, the first coating composition may optionally be a single composition applied directly to a pretreated substrate or to a substrate previously coated with one or more protective and / or decorative coatings. The second coating composition may be applied directly onto the specific composition mentioned above as the first coating composition.

The coating composition (s) can include any of a variety of thermoplastic and / or thermosetting compositions known in the art. Such coating composition (s) may be an aqueous or solvent-based liquid composition or, alternatively, may be in solid particulate form, ie, powdery coating.

Thermosetting coating compositions typically include, for example, aminoplasts, polyisocyanates including blocked isocyanates, polyepoxides, beta-hydroxyalkylamides, polyacids, anhydrides, organometallic acid) -functional materials, polyamines, polyamides and crosslinkers which may be selected from mixtures of certain of the foregoing.

In addition to or instead of the crosslinker described above, the coating composition typically comprises at least one film-forming resin. Thermosetting or curable coating compositions typically include a deposition polymer having a functional group that reacts with a crosslinking agent. The deposition resin in the first coating composition can be selected from a variety of specific polymers well known in the art. Such film-forming resins may be selected from, for example, acrylic polymers, polyester polymers, polyurethane polymers, polyamide polymers, polyether polymers, polysiloxane polymers, copolymers thereof and mixtures thereof. In general, such polymers may be specific polymers of the type made by certain methods known to those skilled in the art. Such polymers may be solvent based or water dispersible, emulsifiable, or have limited water solubility. The functional group on the film-forming dendrite is selected from a variety of specific reactive functional groups including, for example, carboxylic acid groups, amine groups, amide groups, urea groups, isocyanate groups (including blocked isocyanate groups), mercaptan groups and combinations thereof. Can be.

Suitable mixtures of film forming resins may also be used in the preparation of the coating composition.

If desired, coating compositions used to form certain coating layers include plasticizers, antioxidants, hindered amine light stabilizers, thixotropes such as bentonite clay, pigments, fillers, organic cosolvents, catalysts including phosphoric acid, and other conventional And any other materials well known in the formulated surface coating art, such as adjuvants. Such materials may constitute up to 40% by weight of the total weight of the coating composition.

To form the coating layer, the coating composition may be applied to the substrate using conventional means, including electrodeposition, brushing, dipping, flow coating, spraying, roll coating, and the like. In the electrodeposition process, the electroconductive substrate to be coated and the electroconductive counter electrode, which are provided as electrodes, are placed in contact with the ionic electrodepositable composition. Passing a current between the electrode and the opposite electrode while in contact with the electrodepositable composition will cause an adhesive film of the electrodepositable composition to be deposited on the metal substrate in a substantially continuous manner.

After applying the coating layer to the substrate, a film is formed on the surface of the substrate by generally draining (flashing) water and / or organic solvent out of the film by heating or air-drying. When applying one or more coating compositions to a substrate, it may be flashed or, optionally, cured after applying each coating layer.

The coated substrate may be heated to at least partially cure the coating layer. In the curing operation, the solvent is discharged and the film forming material is crosslinked. The heating or curing operation may be carried out at ambient temperature or alternatively at a temperature in the range of 160-350 ° F. (71-177 ° C.). In some cases, lower or higher temperatures may be used than are required to activate the crosslinking mechanism. Again, when applying one or more coating compositions to a substrate, it may be cured after each coating layer has been applied, or multiple layers may be cured simultaneously. Such coating composition (s) may be formulated as a one-component composition in which curing agents such as aminoplast resins and / or blocked isocyanate compounds as described above are mixed with other composition components. It should be mentioned. The one-component composition can be stored stably as a formulated composition. Alternatively, the composition may be formulated as a two-component composition, for example, added to a pre-formed mixture of other composition components just prior to applying the polyisocyanate curing agent as described above. The pre-formed mixture may also comprise a curing agent, such as an aminoplast resin and / or blocked isocyanate compound as described above.

As mentioned above, the coating composition may be a thermoplastic composition. In such cases, the one or more deposition polymers used in the coating composition (s) may or may not include reactive functional groups. Similarly, certain additional polymers or adjuvant materials included in the thermoplastic coating composition may or may not include reactive functional groups. In some cases, the coating composition may further comprise one or more pigments (in addition to the specific components described above). Non-limiting examples of suitable metallic pigments include aluminum flakes, copper bronze flakes, and metal oxide coated mica. In addition to metallic pigments, coating compositions may also include, for example, inorganic pigments such as titanium dioxide, iron oxide, chromium oxide, lead chromate and carbon black; And nonmetallic colored pigments commonly used in surface coatings, such as organic pigments such as phthalocyanine blue and phthalocyanine green.

As will be appreciated by those skilled in the art, the coating film thickness, and curing temperature and conditions may be determined by the type of coating layer formed: electrodeposition coating, primer-surface coating, base coating, monocoating; As well as the coating composition itself, i.e., thermoset or thermoplastic, ambient or thermoset, and, if thermoset, will depend on the type of curing reaction required. The following examples illustrate the invention, but the invention is not limited to these details.

Example A

This embodiment uses an atmospheric plasma gun with the following parameters to fabricate a polyurethane coating system layer (primer and top coat) from two aircraft substrates (ie, a glass fiber composite substrate and a carbon fiber composite substrate). To describe how to remove it.

Supply gas: ambient air

Gas flow rate: 10 to 35 scfh

Separation distance: 3 to 10 mm

Power level: 300 to 500 watts (W)

For each coated substrate type, 1 inch by 1 inch plaques were cut. For each coated substrate sample, plaques were secured to the upper turntables equipped with an atmospheric plasma gun. The atmospheric plasma gun was positioned so that the plasma source was perpendicular to the approximate center of the plaque to be treated. The turntable was rotated for a total of eight revolutions at a speed of 50 rpm under plasma (ionized airflow) such that the plasma was in contact with the coated surface of the substrate (exposure width 5 mm / exposure length 25.4 mm). The coating was removed to expose the substrate (total coating thickness of approximately 70 microns). The area of the coating removed per unit time was measured as follows. If the radius of the rotating sample was measured to be 2.5 ", the circumference was calculated to be 15.71". After 8 revolutions divided by 50 rpm, the total treatment time was found to be 0.16 minutes. The total treatment time divided by the ratio of the treated length to the circumference showed that the treatment time for the sample was 0.01 min. Assuming the 0.07 mm × 5 mm × 25.4 mm volume was exposed for 0.01 min, the time to remove a sample of 1 ft × 1 ft size was calculated. Using a 5 mm exposure width, 5.08 bins were calculated to be contained in the 25.4 mm sample. Subsequently, to remove the 1 in ² sample, 0.01 minutes were multiplied by 5.08 bins and measured to correspond to 0.052 minutes. Multiplying 0.052 minutes × 12 1in bins to calculate the time taken to remove the 1in × 12in coating sample resulted in 0.621 minutes. Finally, 0.621 minutes was multiplied by another 12 1in bins to calculate the time to remove the 1ft ² coating sample, corresponding to 7.451 minutes, ie 8.0ft ² / min.

Example B

This example describes a method of calculating the rate of removal of a coating by exposure to an atmospheric plasma. The uncolored aircraft polyurethane primer coating composition was spun on a silicon wafer. The coated silicon wafer surface was exposed (plasma treated) to plasma (under the process parameters described above). The coated silicon wafer sample was fixed to the turntable as described above for the coated substrate plaques. The turntable was rotated 10 at a speed of 60 rpm. A step height of 3.69 microns (height from the exposed substrate surface to the untreated coating surface immediately adjacent to the area where the coating was removed by the plasma) was measured. By measuring the radius of the treated / exposed sample and the treated / exposed length, the treatment ratio for the rotating circumference was calculated to be 0.33. This constituted a total exposure / treatment time of 0.055 minutes. The removal rate was measured by dividing the step height of 3.69 microns by the treatment time of 0.055 minutes, and was 67 microns / minute.

While specific embodiments of the present invention have been described above for purposes of illustration, it is to be understood that various modifications may be made to the invention without departing from the scope of the invention as defined in the appended claims to those skilled in the art. Will be self explanatory.

Claims (22)

A method of at least partially removing one or more polymer coating layers from a coated substrate having at least one coated surface, the method comprising: At least one coated surface of the substrate is coated with a multilayer composite coating comprising two or more polymer coating layers, Generating at least one reactive species in an ionized air stream discharged at atmospheric pressure; And positioning the coated surface in the ionized air stream, wherein the ionized air stream comprises an ionized gas derived from a feed gas comprising a mixture of nitrogen and oxygen, Reacting at least one reactive species with at least one polymer coating layer such that the at least one polymer coating layer is at least partially removed from the coated surface of the substrate at atmospheric pressure. The method of claim 1, Wherein said at least one reactive species occurs in an ionized air stream in the electromagnetic field. The method of claim 1, And said at least one reactive species occurs in an ionized air stream in a radiofrequency electromagnetic field. delete delete The method of claim 1, Wherein the nitrogen is present in the mixture in an amount in the range of 99.5 to 75 volume percent and the oxygen is present in the mixture in an amount in the range of 0.5 to 25 volume percent. The method of claim 1, At least one polymer coating layer removed from the at least one coated surface has an overall thickness in the range of from 1 micron to 10,000 microns. delete The method of claim 1, At least one polymer coating layer removed from at least one coated surface comprises at least a portion of a top coat layer in a multilayer composite coating. The method of claim 1, Wherein the at least one polymeric coating layer removed from the at least one coated surface comprises at least a portion of the base coating layer in the multilayer composite coating. The method of claim 1, Wherein the at least one polymeric coating layer removed from the at least one coated surface comprises at least a portion of the base coat layer and at least a portion of the top coat layer in the multilayer composite coating. The method of claim 1, At least one polymer coating layer removed from at least one coated surface comprises at least a portion of a primer coating layer. The method of claim 1, Wherein said coated substrate comprises a coated automotive part. The method of claim 1, Wherein said coated substrate comprises a substrate comprising a metal substrate, an elastomeric substrate, a glass substrate, a glass fiber substrate, a wood substrate, their composites and / or combinations thereof. The method of claim 1, And the coated substrate comprises an ferrous metal substrate, a nonferrous metal substrate, and / or combinations thereof. The method of claim 1, Wherein said coated substrate has a three-dimensional terrain. The method of claim 1, The flow rate of said feed gas is in the range of 1 to 100 standard ft ³ / hr. The method of claim 1, And wherein the coated substrate is maintained in the ionized air stream for 0.01 to 1 second. The method of claim 1, Wherein said at least one reactive species in an ionized airflow has a power density in the range of 0.1 W / cm 3 to 200 W / cm 3. The method of claim 1, The distance between the coated surface and the source of ionized airflow is in the range of 0.1 to 50 mm. The method of claim 1, Wherein said at least one reactive species is generated in an ionized air stream at or near room temperature. The method of claim 1, Wherein said coated substrate is a composite substrate.