EP2007529A2

EP2007529A2 - Repairing small coating defects

Info

Publication number: EP2007529A2
Application number: EP07775407A
Authority: EP
Inventors: Samuel Joseph Kincaid; Patrick Henry Corcoran; Carl L. Kishbaugh; James A. Schultz
Original assignee: EI Du Pont de Nemours and Co
Current assignee: EIDP Inc
Priority date: 2006-04-18
Filing date: 2007-04-13
Publication date: 2008-12-31
Also published as: WO2007123854A2; WO2007123854A3

Abstract

This invention is directed to a method for repairing coating defects on a coated substrate, such as autobody. The method includes mixing Part A and Part B of a coating composition to form a pot mix; applying an overlay of the pot mix over an affected area having the coating defect; partially drying the overlay; removing the excess of partially dried pot mix from the affected area by rubbing the affected area with a rubbing solvent mix wherein the rubbing solvent mix includes one or more hydrocarbon aliphatic solvents; and curing the partially dried overlay to produce a defect free area on the coated substrate. Part A of the coating composition includes one or more crosslinkable components and Part B of the coating composition includes one or more crosslinking components. If desired, the coating composition can include Part C containing pigments or dyes that match the color of the coated substrate.

Description

Repairing Small Coating Defects

Cross-Reference to Related Application

This application claims the benefit of U. S. Provisional Application Serial No. 60/792,826 filed on April 18, 2006 which is hereby incorporated by reference in its entirety.

FIELD OF INVENTION

This invention is directed to a method for repairing small coating defects on a coated substrate. This invention is further directed to a method for repairing small coating defects on a vehicle.

BACKGROUND OF THE INVENTION

Small coating defects of a vehicle are non-structural and visible defects or flaws in small coating areas of the vehicle that are caused by mechanical or chemical actions or by atmospheric conditions. Such small defects include small paint chipping (chip defects), scratches, small blemishes or other coating deteriorations in small areas. Currently, these defects can be repaired by sending the vehicle to a full service automotive body shop, or using off-the-shelf "Do-lt-Yourself" (DIY) repair products by a vehicle owner or a person who is permitted to repair the vehicle. The defects can also be left un-repaired.

Currently, if the vehicle is sent to a full service automotive body shop, the vehicle generally must be left at the facility for several days to complete the repair and refinish. For vehicles with small coating defects without major structural body damage, it is desirable to have a quick service to repair the defects in a short period of time without having the vehicle in a repair facility for several days. Since full service automotive body shops are designed to repair large areas of coating damages using technologies such as spray coating, repairs of small coating defects are not suited to regular repairing workflows and methods in these full service automotive body shops for cost effective operation and therefore not desired. In situations where a vehicle is damaged in an accident, coating defects caused by the accident is usually repaired by a full service automotive body shop and paid for by an insurance company under an insurance policy covering the vehicle. Small coating defects occurring independent of the accident is normally not covered by the insurance policy therefore need to be paid for by the vehicle owner. If the regular repairing workflow and methods are used, the repair is usually of high cost therefore rejected by the vehicle owner. That results in loss of business opportunity for the automotive body shop. The vehicle owner still needs to find a cost effective way to repair the small defects. The full service automotive body shop is in need of a cost effective method for repairing the small coating defects of the vehicle. Off-the-shelf "Do-lt-Yourself" (DIY) products, such as touch-up paints, can be used to repair some of the defects, however, the quality of repair is usually limited. Most of the touch-up paints produce repaired coatings with unsatisfactory solvent resistance and generally lack long term durability. Color matching for metallic colors with metallic pigments such as metallic flakes is especially difficult to achieve with currently available touch-up products.

Many small coating defects, such as chipped areas and scratches on paint finishes, can cause further deterioration of the vehicle if left unrepaired for a extended period of time. It is to the vehicle owner's best interest to have these small coating defects repaired before they develop into major damages. For sale or re-sale of a vehicle, market value of the vehicle will be significantly reduced if small coating defects are not repaired.

Recently, some "Do-lt-For-You" (DIFY) type of services began to emerge. These DIFY services provide professional repairs on small damages on vehicles including small coating defects that are not suited for full service automotive body shops. These services usually use similar methods and materials as the full service automotive body shops that require mixing relatively large amounts of materials resulting in waste of materials. The DIFY services also use the touch-up products therefore bearing same limitation as described above.

Therefore a need still exists for a method to cost effectively repair small coating defects with a satisfactory coating quality, color match and within a short period of time. SUMMARY OF THE INVENTION

This invention is directed to a method for repairing an affected area having at least one coating defect disposed on a coated substrate into defect free area, said method comprising the steps of: a) mixing a Part A and a Part B of a coating composition to form a pot mix, wherein said Part A comprises 33 percent to 99 percent by weight percent based on the total weight of said Part A of one or more crosslinkable components, said crosslinkable components having at least two crosslinkable groups per molecule or polymer chain; and wherein said Part B comprises one or more crosslinking components having one or more crosslinking groups per molecule or polymer chain; b) applying an overlay of the pot mix over the affected area; c) partial drying the overlay; d) removing excess of partially dried pot mix from the affected area by rubbing the affected area with a rubbing solvent mix wherein the rubbing solvent mix comprises one or more hydrocarbon aliphatic solvents; and e) curing said partially dried overlay to produce said defect free area on said coated substrate.

DETAILED DESCRIPTION OF THE INVENTION The use of numerical values in the various ranges specified in this application, unless expressly indicated otherwise, are stated as approximations as though the minimum and maximum values within the stated ranges were both proceeded by the word "about." In this manner, slight variations above and below the stated ranges can be used to achieve substantially the same results as values within the ranges. Also, the disclosure of these ranges is intended as a continuous range including every value between the minimum and maximum values.

"Two-pack coating composition" means a thermoset coating composition having two components stored in separate containers. The containers containing the two components are typically sealed to increase the shelf life of the components of the coating composition during storage. The components are mixed just prior to use to form a pot mix, which has a limited pot life, typically ranging from a few minutes (15 minutes to 45 minutes) to a few hours (4 hours to 8 hours). A pot life is a time period between the time when components of a coating composition are mixed to form a pot mix, referred to as time zero, and to the time when the pot mix becomes too thick or too hard for practical application. A pot life of a specific coating composition is a characteristic of that coating composition and is typically determined empirically.

The pot mix is then applied as a layer of a desired thickness on a substrate surface, such as an automobile body. After application, the layer dries and cures at ambient or at elevated temperatures to form a coating on the substrate surface having desired coating properties, such as, high gloss, mar-resistance and resistance to environmental etching.

A "coated substrate" refers to a substrate covered with a coating, or multiple coatings. A coating or coatings can be a primer, a pigmented basecoat, a clear topcoat, or an un-colored clearcoat. The substrate can be covered by multiple layers of two different coatings, such as one or more layers of primers and one or more layers of pigmented basecoats as topcoats. The substrate can also be covered by multiple layers of at least three different coatings, such as one or more layers of primers, one or more layers of pigmented basecoats, and one or more layers of un- colored clearcoats. Examples of coated substrates can be a vehicle body or body parts coated with one or more monocolor paints, a vehicle body or body parts coated with one or more metallic paints, a bicycle body or body parts coated with one or more paints, a boat or boat parts coated with one or more paints, furniture or furniture parts coated with one or more paints, an aiφlane coated with one or more paints. The substrate can be made of metal, wood, plastic or other natural or synthetic materials.

As used herein, terms "small coating defects" or "coating defects" or "defects" refer to chips, scratches, cracks, small blemishes or other deterioration of a coating that breaks one or more layers of the coating on the coated substrate resulting in small spaces void of one or more layers of the coating in shapes such as small dots, thin lines or small patches. The small coating defects are non-structural defects visible to human eye on the coating, such as key scratches and chips caused by stone. The small coating defects can break through only one or two layers of the coating leaving other layers intact. The small coating defects can break through all layers of the coating to expose the underlying substrate. The small coating defects are usually too small in size to be repaired with a spray coating method.

As used herein "vehicle" includes an automobile, such as car, bus, truck, semi truck, pickup truck, SUV (Sports Utility Vehicle); tractor; motorcycle; trailer; ATV (all terrain vehicle); heavy duty mover, such as, bulldozer, mobile crane and earth mover; airplanes; boats; ships; and other modes of transport that are coated with coating compositions. "Crosslinkable component" includes a compound, oligomer, polymer or copolymer having functional crosslinkable groups positioned in each molecule of the compound, oligomer, the backbone of the polymer, pendant from the backbone of the polymer, terminally positioned on the backbone of the polymer, or a combination thereof. One of ordinary skill in the art would recognize that certain crosslinkable group combinations would be excluded from the crosslinkable component of the present invention, since, if present, these combinations would crosslink among themselves (self-crosslink), thereby destroying their ability to crosslink with the crosslinking groups in the crosslinking components defined below.

Typical crosslinkable component can have on an average 2 to 25, preferably 2 to 15, more preferably 2 to 5, even more preferably 2 to 3, crosslinkable groups selected from hydroxyl, acetoacetoxy, carboxyl, primary amine, secondary amine, epoxy, anhydride, ketimine, aldimine, or a combination thereof.

The hydroxyl and secondary amine functional groups are preferred, secondary amine functional groups are further preferred, and hindered secondary amines such as aspartic amines are even further preferred functional crosslinkable groups of this invention. A crosslinkable component with hindered secondary amine functional groups, such as aspartic amines, provides an optimum and tunable balance of pot life and curing time and form finishes useful for vehicle coatings. Suitable crosslinkable components having hydroxyl functional groups are described and can be produced by processes described in a commonly assigned U.S. Patent No. 6,221 ,494, which is incorporated herein by reference. Suitable crosslinkable component having secondary amine functional groups can be produced by processes described in a commonly assigned U.S. Patent Application Serial No. 11/303083, filed on Dec. 14, 2005, ifs entirety is herein incorporated by reference. Hindered secondary amine under the trademark Desmophen® NH-1420 sold by Bayer Corporation of Pittsburgh, Pennsylvania, is also suitable. Desmophen® is registered a trademark of Bayer, Leverkusen, Germany. As use herein "Part A" of a coating composition refers to one part of a two-pack coating composition that comprises the crosslinkable component. The Part A can further include a carrier. The carrier is used to mix all components and to modulate physical properties, such as viscosity or density of Part A as determined by one of ordinary skill in the art. The carrier can include one or more common organic or inorganic solvents known to one of ordinary skill in the art.

"Crosslinking component" is a component that includes a compound, oligomer, polymer or copolymer having crosslinking functional groups positioned in each molecule of the compound, oligomer, the backbone of the polymer, pendant from the backbone of the polymer, terminally positioned on the backbone of the polymer, or a combination thereof, wherein these functional groups are capable of crosslinking with the crosslinkable functional groups on the crosslinkable component (during the curing step) to produce a coating in the form of crosslinked structures. One of ordinary skill in the art would recognize that certain crosslinking group/crosslinkable group combinations would be excluded from the present invention, since they would fail to crosslink and produce the film forming crosslinked structures. Typical crosslinking component can be selected from a compound, oligomer, polymer or copolymer having crosslinking functional groups selected from the group consisting of isocyanate, amine, ketimine, melamine, epoxy, polyacid, anhydride, and a combination thereof. It would be clear to one of ordinary skill in the art that generally certain combinations of crosslinking groups from crosslinking components crosslink with certain crosslinkable groups from the crosslinkable components. Some of those paired combinations include: (1 ) ketimine crosslinking groups generally crosslink with acetoacetoxy, epoxy, or anhydride crosslinkable groups; (2) isocyanate and melamine crosslinking groups generally crosslink with hydroxyl, primary and secondary amine, ketimine, or aldimine crosslinkable groups; (3) epoxy crosslinking groups generally crosslink with carboxyl, primary and secondary amine, ketimine, or anhydride crosslinkable groups; (4) amine crosslinking groups generally crosslink with acetoacetoxy crosslinkable groups; (5) polyacid crosslinking groups generally crosslink with epoxy crosslinkable groups; and (6) anhydride crosslinking groups generally crosslink with epoxy and ketimine crosslinkable groups. Isocyanate crosslinking groups are preferred crosslinking groups of this invention.

Polyisocyanates are compounds or oligomers having multiple isocyanate crosslinking groups, also known as crosslinking isocyanate functionalities. Typically, the polyisocyanates are provided within the range of 2 to 10, preferably 2 to 8, more preferably 2 to 5 crosslinking isocyanate functionalities. Some suitable polyisocyanates include aromatic, aliphatic, or cycloaliphatic polyisocyanates, trifunctional polyisocyanates and isocyanate functional adducts of a polyol and difunctional isocyanates. Some of the particular polyisocyanates include diisocyanates, such as 1 ,6- hexamethylene diisocyanate, isophorone diisocyanate, 4,4'-biphenylene diisocyanate, toluene diisocyanate, biscyclohexyl diisocyanate, tetramethyl-m-xylylene diisocyanate, ethyl ethylene diisocyanate, 1- methyltrimethylene diisocyanate, 1 ,3-phenylene diisocyanate, 1,5- napthalene diisocyanate, bis-(4-isocyanatocyclohexyl)-methane and 4,4'- diisocyanatodiphenyl ether.

Some of the suitable trifunctional polyisocyanates include triphenylmethane triisocyanate, 1 ,3,5-benzene triisocyanate, and 2,4,6- toluene triisocyanate. Trimers of diisocyanate, such as the trimer of hexamethylene diisocyanate sold under the trademark Desmodur® N3300A Polyisocyanate by Bayer Material Science LLC, of Pittsburgh, Pa. and the trimer of isophorone diisocyanate are also suitable. Furthermore, trifunctional adducts of triols and diisocyanates are also suitable. Trimers of diisocyanates are preferred and trimers of isophorone and hexamethylene diisocyanates are more preferred.

As used herein "Part B" of a coating composition refers to a second part of the two-pack coating composition that includes the aforedescribed crosslinking component. The Part B can further include a modifier. The modifier is used to mix all the crosslinking component or to modulate physical properties, such as viscosity or density of the crosslinking component to fit specific coating needs as determined by one of ordinary skill in the art. The modifier can include organic or inorganic solvents as determined appropriate by one of ordinary skill in the art.

The term "pigment" or "pigments" used herein refers to a colorant or colorants that produces color or colors. A pigment can be from natural and synthetic sources and made of organic or inorganic constituents. A pigment also includes metallic particles or flakes with specific or mixed shapes and dimensions. A pigment is usually not soluble in a coating composition.

The term "dye" means a colorant or colorants that produce color or colors. Dye is usually soluble in a coating composition.

Tints are formulated color concentrates comprising pigments, dyes or a combination thereof that can provide color to a paint. Multiple tints can be further mixed to generate a different color.

The term "curing catalyst" refers to a compound that can catalyze crosslinking reactions between the crosslinkable components and the crosslinking components, during the curing step, to produce a coating in the form of crosslinked structures. Addition of the curing catalyst is optional in this invention. Generally, in the range of about 0.001 percent to about 5 percent, preferably in the range of from 0.005 percent to 2 percent, more preferably in the range of from 0.01 percent to 1 percent of the curing catalyst is utilized, all in weight percent based on the total weight of Part A. A wide variety of curing catalysts can be used, such as, carboxylic acids, tertiary amines, water, and organic tin compounds, including dibutyl tin dilaurate and dibutyl tin diacetate. In one embodiment of this invention, a small amount of water, in a range of 0.01 percent to 1 percent, in weight percent based on the total weight of Part A, is included in Part A as a curing catalyst. Addition of water as a curing catalyst is optional for this invention. Under normal conditions, moisture in the air can be effectively functioning as a curing catalyst once the pot mix is applied to the coating substrate and exposed to the air.

The term "additives" means diluents, stabilizers, rheology control agents, defoamer, leveling agent, flow agents, toughening agents, UV protection agents, and fillers that can be added to the coating composition. Such additives will, of course, depend on the intended use of the coating composition as determined by one of ordinary skill in the art. The foregoing additives can be added to either Part A or Part B, or both of the coating composition, depending upon the intended use of the coating composition. These additives are preferably added to Part A of the coating composition. Small coating defects such as chipped paint areas of a vehicle are first evaluated to determine the extent of the damage. A small area of the vehicle where the defects are located, herein referred to as an affected area, is then cleaned by conventional methods^' known to one of ordinary skill in the art such as by using water, detergent, common solvent or solvents, or a combination thereof.

The small coating defects are repaired by using the following steps. In Step a) of the present method, effective amounts of Part A and Part B of the coating composition are mixed to form a pot mix. The effective amounts are amounts necessary for repairing the small coating defects typically in the range of from 0.5 grams to about 500 grams, preferably in the range of from 0.5 gram to 100 grams, more preferably in the range of from 0.5 gram to 50 grams, most preferably in the range of from 1 gram to 20 grams. Pot life of the pot mix is usually specific to the coating composition and can be determined empirically.

In Step b) of the present method, an overlay of the pot mix is applied over the affected area of the small coating defects. The overlay can be applied by conventional techniques, such as using a putting knife, a spatula, a scraper, or a wooden stirrer, to effectively fill the coating defects with the pot mix within a time period of less than 50 percent of the pot life of the pot mix from the time zero. For example, an overlay should be applied within 10 minutes, preferably within 1 to 3 minutes after the time zero for a pot mix with a pot life of about 20 minutes. Excess pot mix over the affected area can be removed with wiping, such as wiping with a squeegee or a plastic trowel. The overlay should fill the coating defect to approximately to the same level as the area adjacent to the affected area.

In Step c) of the present method, the overlay is then allowed to partial dry. The time period needed for partial drying is dependent on the pot life of the pot mix. The partial dry time can be in the range of from 5 percent to 110 percent of the pot life of the pot mix after the time zero. The partial dry time is in the range of from 10 percent to 80 percent, preferably in the range of from 20 percent to 70 percent, of the pot life of the pot mix after the time zero. In one embodiment, the pot life of a first pot mix is about 30 minutes. An overlay from the first pot mix is applied within 2 minutes after the time zero, and allowed to dry for a period of time in the range of from 10 minutes to 25 minutes after the time zero, corresponding to about 40 percent to 90 percent of the pot life of the first pot mix. In another embodiment, the pot life of a second pot mix is about 45 minutes. An overlay from the second pot mix is applied within 3 minutes after time zero, and allowed to dry for a period of time in a range of from 10 minutes to 25 minutes after time zero, corresponding to about 28 percent to 62 percent of the pot life of the second pot mix. In Step d) of the present method, the affected area covered by the partially dried overlay is rubbed with a rubbing solvent mix to further remove excess coating composition outside the filled coating defect area to produce a repaired defect free area preferably leveled with adjacent areas on the coated substrate. The affected area can be rubbed with a cloth wetted with the rubbing solvent mix. Preferably, the cloth is inert to the rubbing solvent mix. A synthetic cloth, such as Sontara SPS™ Final- Tack Cloth E4141 from E.I. du Pont de Nemours and Company, Wilmington. Delaware, is suitable. The cloth wrapped on an flat object, such as a spatula with a flat end or a sanding block, such as 3M™ Stikitt^M Soft Hand Block catalog #05442 available from 3M, St. Paul, Minnesota, can be used as a flat rubbing surface. To avoid over-wetting the partially dried overlay, only minimum amount of the rubbing solvent mix should be used to wet the cloth during rubbing. Applicants have unexpectedly discovered that if the affected area is over wetted, the appearance of the affected area as well as the area adjacent to the affected area can adversely affected, such as loss of flop of a metallic paint coat on automate body. Selection of the rubbing solvent mix is important to the quality of the repair, especially for maintaining color match. The rubbing solvent mix should not affect the color or color effects, especially those with metallic paints, of the overlay filled in the defect. Inventors of this invention discovered that the best rubbing solvent mix is the one comprising mostly non-oxygenated hydrocarbon aliphatic solvents. The term "non- oxygenated hydrocarbon aliphatic solvents", or "hydrocarbon aliphatic solvents", or "aliphatic hydrocarbon solvents", or "hydrocarbon solvents", or "aliphatic solvents" used herein refers to aliphatic solvents having essentially hydrogen and carbon atoms and no oxygen atoms. The inventors discovered that oxygenated aliphatic solvent can cause some color change if used in rubbing solvent mix. These oxygenated aliphatic solvents, such as acetone, are not suitable when color match between the defect free area and the adjacent area on the substrate is desired. If color match is not desired, oxygenated aliphatic solvents can be used. It is preferred that the rubbing solvent mix comprises in the range from 70 percent to 100 percent and more preferably in the range from 75 percent to 100 percent of non-oxygenated hydrocarbon aliphatic solvents, based on total weight of the rubbing solvent mix. In one embodiment, a rubbing solvent mix comprises 75 percent of non-oxygenated aliphatic solvents and 25 percent of aromatic solvents, based on total weight of the rubbing solvent mix. In another embodiment, a rubbing solvent mix comprises 100 percent of non-oxygenated aliphatic solvents. Suitable hydrocarbon aliphatic solvents can include aliphatic alkane, such as n-pentane, n-hexane, hexane, heptane, octane, nonane, trimethylpentane, dimethylhexane; or cycloalkane, such as cycloheptane, dimethylcyclohexane, ethylcyclohexane, methylcyclohexane; or a mixture of aliphatic hydrocarbon solvents such as petroleum naphtha, VM&P naphtha, or mineral spirits. In one embodiment, a rubbing solvent mix comprises hydrocarbon aliphatic solvents selected from heptane, mineral spirits, or a combination thereof. A mixture of solvents such as the one sold under the commercial name cleaner 3901 S comprising heptane, VM&P naphtha, toluene, hexane, methylcyclohexane, and isopropanol, from E.I. du Pont de Nemours and Company, Wilmington, Delaware, is also suitable.

Although hydrocarbon aliphatic solvents are preferred in this invention as the rubbing solvent mix, presence of small amounts of aromatic solvents (less than 25% of total weight of the rubbing solvent mix) can be desirable to reduce the fire hazards. Aromatic solvents are those organic solvents having one or more aromatic rings in the molecule. Examples of aromatic solvents include xylene, toluene, benzene, and mesitylene, etc.

In Step e) of the present method, the repaired defect free area is allowed to dry and cure. Time needed for dry and cure can range from a few minutes (10 to 20 minutes) to a few hours (0.5 to 8 hours) depending on the type and amounts of the crosslinkable and the crosslinking components and solvents used in the coating composition. The repaired defect free area is generally indistinguishable from adjacent undamaged areas of the coating substrate from a certain distance, such as 1.5 meters (5 feet) away, by naked human eyes from at least one viewing angles as accepted by current industry convention. The defect free area can be then coated with a spray wax and polished dry with conventional methods known in the industry, such as with a Sontara® Polish/Detail Cloth available from E.I. du Pont de Nemours and Company, Wilmington, Delaware.

When it is desired to match a color of the coating of a vehicle, an additional Part C of the coating composition can be prepared and mixed together with Part A and Part B to form a pigmented pot mix, wherein Part C comprises one or more pigments, one or more dyes, or a combination thereof. The Part C can be prepared on the basis of a color formulation that matches the color of the coating. Such color formulations can be readily obtained from color formulas available from refinish automotive paint suppliers. For example, the color of the coating on the vehicle and the color formulation to match the color of the coating can be determined by a number of ways such as: (1 ) visual comparison of the vehicle color against a set of color reference cards as those described in a commonly assigned U.S. Patent No. 6,914,613, herein incorporated in by reference; (2) using a color code or a vehicle identification number (VIN) associated with the vehicle as described in U.S. Patent No. 6,522,977, and in a commonly owned U.S. Application Serial No. 11/353914, filed February 14, 2006, all of which are incorporated in by reference, or (3) using instrumental measurements as described in a commonly owned U.S. Patent No. 6,891 ,617 and U.S. Provisional Application Serial No. 60/678310, filed on May 5, 2005, all herein incorporated in by reference. For determining and matching coatings with metallic flakes, methods and device described in a commonly owned U.S. Patent No. 6,952,265, herein incorporate in by reference, can be used. To find the best color formulation to match a color of a vehicle, VINdicator™ system supplied by E.I. du Pont de Nemours and Company, Wilmington, Delaware, can be used. A match color mixture can be prepared according to the color formulation and conventional color mixing methods know to one of ordinary skill in the art to best match the color of the vehicle. In one embodiment, a pigmented pot mix can be prepared by mixing 1. 5 gram of Part A, 1.0 gram of Part B and 1.0 gram of Part C. The coating composition can contain additional additives such as rheology agent, defoamer, leveling agent, one or more solvents, curing catalyst, diluents, stabilizers, flow agents, toughening agents, UV protection agents, fillers or a combination thereof. The additives can be added to either Part A or Part B before mixing. It would be clear to one of ordinary skill in the art that generally certain additives can react with the crosslinking groups or the crosslinkable groups and therefore should not be added into Part A or Part B during storage. One such example is that the curing catalyst should not be added to Part B comprising the crosslinking component during storage. In this invention, it is preferred that the above mentioned additives be added to Part A of the coating composition during storage.

Repairing the small coating defects only needs small amounts of Part A and Part B, or Part C₁ such as in the range from 1 gram to 10 gram. Since each of Part A, B and C comprise several materials, preparing small amounts of Part A, B or C requires weighing these materials in sub-gram amounts, which is possible only by using special weighing equipment otherwise substantial weighing errors can occur thereby affecting the quality and appearance of the defect area produced by such coating compositions. To reduce the risk of weighing errors, to reduce cost and to improve productivity, it is preferable to prepare suitable amounts of Part A, Part B separately and package and store these separate small quantities of Part A and Part B typically needed to form a pot mix for a single repair. The packaged Part A and Part B can be stored separately under suitable storage conditions, such as in sealed small containers. Just before use, Part A and Part B can be mixed directly without weighing again. In one embodiment, 1.5 gram of Part A and 1.0 gram of Part B are stored separately under seal and mixed just before use to form a pot mix. In another embodiment, 1.0 gram of Part A and 1.2 gram of Part B are stored separately and mixed just before use to form another pot mix. One container with two separate compartments or two separate containers can be used to store Part A Part B. Prior to use, the stored Part A and part B can be mixed in the to form the pot mix without the need to weigh. The features and advantages of the present invention will be more readily understood, by one of ordinary skill in the art, from reading the following detailed description. It is to be appreciated that certain features of the invention, which are, for clarity, described above and below in the context of separate embodiments, may also be provided in combination in a single embodiment. Conversely, various features of the invention that are, for brevity, described in the context of a single embodiment, may also be provided separately or in any sub-combination. In addition, references in the singular may also include the plural (for example, "a" and "an" may refer to one, or one or more) unless the context specifically states otherwise.

The present invention is further defined in the following Examples. It should be understood that these Examples, while indicating preferred embodiments of the invention, are given by way of illustration only. From the above discussion and these Examples, one skilled in the art can ascertain the essential characteristics of this invention, and without departing from the spirit and scope thereof, can make various changes and modifications of the invention to adapt it to various uses and conditions.

EXAMPLES Preparation of Coating Composition 1

Preparation of Part A1 :

Part A1 was prepared based on the weight listed in Table 1. To a quart can containing item I and item Il in Table 1, item III was added slowly while mixing with an air driven mixer and mixed for 2 hours. Then 5.73 gram of item IV was added while mixing and mixed for 30 minutes, wherein the item IV was prepared by mixing 10.4 gram of deionized water and 17.4 gram of acetone. The Part A1 had a hazy and gelatinous appearance. Table 1

I. Desmophen^® NH-1420 Diamine¹ 318.50 gram

II. Airex^® 986 Defoamer² 1.73 gram ill. Crayvallac^® PA4X20 Wax³ 19.30 gram IV. Water/Acetone Mixture 5.73 gram

1 : Available from Bayer Material Science LLC, Pittsburgh,

Pennsylvania. Desmophen is registered a trademark of Bayer, Leverkusen, Germany.

2: Available from D. B. Becker Company, Clinton, New Jersey. 3: Available from Cray Valley, Stallingborough, North East

Lincolnshire, United Kingdom. Preparation of Part B1 :

Part B1 consisted solely of Desmodur^® N3300A Polyisocyanate supplied by Bayer Material Science LLC, Pittsburgh, Pennsylvania. Preparation of Part C1 :

Part C1 , a color concentrate, was prepared based on the formula in Table 2 to generate a B9806 Gold Metallic color that best matched a color specified by General Motors' color code 398E. All Tints were supplied by E.I. du Pont de Nemours and Company, Wilmington, Delaware.

Table 2

Preparation of Coating Composition 2

Preparation of Acrylic Polyol Resin

To a 2-liter flask fitted with an agitator, a water condenser, a thermocouple, a nitrogen inlet, a heating mantle, and addition pumps and ports was added 305.3 gram xylene which was agitated and heated to reflux temperature (137 to 142^CC). A monomer mixture of 106.1 grams styrene, 141.4 grams methyl methacrylate, 318.3 grams isobutyl methacrylate, 141.4 grams hydroxyethyl methacrylate and 10.4 gram xylene was then added to the flask via the addition pumps and ports simultaneously with an initiator mixture of 17.0 grams t-butyl peracetate and 85.2 gram xylene. The monomer mixture was added over 180 minutes and the addition time for the initiator mixture was also 180 minutes. The batch was held at reflux (137°C to 142⁰C) throughout the polymerization process. A second initiator mixture of 4.3 gram t-butyl peracetate and 57.8 gram methyl ethyl ketone was then immediately added to the reaction mixture over 60 minutes and the batch was subsequently held at reflux for 60 minutes. The batch was then cooled to below 90⁰C and 13.0 gram of methyl ethyl ketone were added. The resulting polymer solution has weight solids of 60% and viscosity of 14,400 cps. The number average molecular weight of the acrylic polymer was 5,000 and weight average molecular weight was 11 ,000, as determined by gel permeation chromatography (polystyrene standard). Preparation of Part A2:

Items I, II, III, IV and V listed in Table 3 below were mixed briefly in a pint can. Then 3.6 gram of item Vl was added while mixing and mixed for 15 minutes, wherein item Vl was prepared by mixing 3.0 gram of deionized water and 9.0 gram of isopropanol. Item VII was then added while mixing and mixed for 30 minutes. The Part A2 had a slightly hazy appearance.

Table 3

1 : Available from Bayer Material Science LLC, Pittsburgh, Pennsylvania.

2. Available from Degussa Coatings & Colorants, Parsippany, New Jersey. Vestamin® is a registered trademark of HuIs Aktiengesellschaft Corporation, Marl, Germany.

3. Available from D. B. Becker Company, Clinton, New Jersey

4. Available from BYK-Chemie USA, Wallingford, Connecticut. Preparation of Part B2:

Part B2 consisted solely of Desmodur N3300A Polyisocyanate supplied by Bayer Materials Science LLC, Pittsburgh, Pennsylvania. Preparation of Part C2:

Part C2, a basecoat color concentrate, was prepared based on the formulation in Table 4 below for L8397 Dark Blue Metallic color matching a color specified by a Nissan color code 232. All tints were supplied by E.I. du Pont de Nemours and Company, Wilmington, Delaware.

Table 4

Example 1 Repairing Coating Defects with the Coating Composition 1

To prepare a basecoat/clearcoat paint panel for use as a substrate 1 for a chip repair, a primed 10"x10"steel panel, part number APR-42824 available from ACT Laboratories of Hillsdale, Michigan, was first sanded with 400 grit sandpaper and then coated with a commercial refinish paint system with a color B9806 from E.I. du Pont de Nemours and Company of Wilmington, Delaware, per manufacturer's instructions. The panel was baked at 60⁰C (140⁰F) for 60 minutes. After the panel aged overnight at room temperature, it was baked at 93°C (200⁰F) for 2 hours. A razor blade was used to cut at least 3 sets of small scratches (simulated coating defect) in the clearcoat and basecoat exposing the primer on the substrate 1.

To repair a first set of the scratches on the coated substrate 1 , 1.5 gram of Part A1 , 1.0 gram of Part B1 , and 1.0 gram of Part C1 were mixed thoroughly on the lid of a quart can using a small spatula to form a pot mix 1. Pot life of the pot mix 1 was about 20 min. The spatula was used to apply an overlay of the pot mix 1 to cover the first set of scratches. A plastic trowel, such as the one available from Dynatron with catalog #358 3"x4", was then used to remove excess material and level the coating. It took about 1 to 2 minutes to finish the steps described above in this example. The overlay was allowed to partially dry for 5 to 10 minutes. Then a synthetic cloth, such as Sontara® SPS Final-Tack Cloth E4141 supplied by E.I. du Pont de Nemours and Company, Wilmington, Delaware, folded over a spatula was wetted with a cleaning solvent 3901 S (acting as a rubbing solvent mix) sold by E.I. du Pont de Nemours and Company, Wilmington, Delaware, and used to rub the scratches and adjacent area to completely remove any excess pot mix 1 from the adjacent area. To avoid over-wetting the partially dried overlay, only minimum amount of the cleaning solvent 3901 S was used to wet the cloth during the rubbing. The overlay was cured to produce a repaired defect free area on the substrate 1.

Example 2

Repairing Coating Defects with the Coating Composition 2 To prepare a basecoat/clearcoat paint panel as a substrate 2 for a chip repair, a primed 10"x10"steel panel, part number APR-42824 available from ACT Laboratories of Hillsdale, Michigan, was first sanded with 400 grit sandpaper and then coated with a commercial refinish paint system from E.I. du Pont de Nemours and Company of Wilmington, Delaware. The paint system having URO® 1104S primer-filler, ChromaBase® basecoat in color L8397, and ChromaClear® 7900S clearcoat was spray applied over the panel surface per manufacturer's instructions. The panel was baked at 60⁰C (140⁰F) for 60 minutes. After the panel aged overnight at room temperature, it was baked at 93°C (200°F) for 2 hours. A razor blade was used to cut at least 3 sets of small scratches in the clearcoat and basecoat exposing the primer on the substrate 2.

To repair a first set of small scratches on the coated substrate 2, 2.0 gram of Part A2, 1.0 gram of Part B2, and 1.0 gram of Part C2 were mixed in a small plastic beaker using a wooden stirrer to form a pot mix 2. Pot life of the pot mix 2 was about 20 minutes. The wooden stirrer was used to apply an overlay of the pot mix 2 to cover the chipped area. A plastic trowel was then used to remove most of the excess material and level the pot mix 2 on the chipped area. It took about 1 to 2 minutes to finish the steps described above in this example.

The overlay was allowed to partially dry for 5 to 10 minutes. Then a synthetic cloth folded over a sanding block, such as 3M™ Stikitt^M Soft Hand Block catalog #05442 available from 3M, St. Paul, Minnesota, was wetted with a cleaning solvent 3901 S (acting as the rubbing solvent mix) sold by E.I. du Pont de Nemours and Company, Wilmington, Delaware, and used to rub the chipped area to completely remove any excess pot mix 2. To avoid over-wetting the partially dried overlay, only minimum amount of the cleaning solvent 3901 S was used to wet the cloth during the rubbing. The overlay was allowed to dry and cure completely to produce a repaired defect free area on the substrate 2.

Example 3

Repairing Coating Defects with Additional Clearcoats A second set of the scratches on the coated substrate 1 were first repaired with the same pot mix 1 using the same procedure as described in Example 1. A pot mix 3 was then prepared by mixing 1.5 gram of Part A1 and 1.0 gram of Part B1. However, no Part C1 was not added to the Pot mix 3. An overlay of the pot mix 3 was then applied over the second scratches already repaired with the pot mix 1 to add an additional layer of clearcoat. The overlay was allowed to partially dry for about 5 to 10 minutes, and rubbed with the rubbing solvent mix as described in Example 1 and cured to form a clearcoat on top of the pigmented basecoat providing additional durability. A second set of the scratches on the coated substrate 2 was first repaired with the same pot mix 2 using the same procedure as described in Example 2. A pot mix 4 was then prepared by mixing 2.0 gram of Part A2 and 1.0 gram of Part B2. However, no Part C2 was added to the pot mix 4. An overlay of the pot mix 4 was then applied over the second set of scratches on the substrate 2 already repaired with the pot mix 2 to add an additional layer of clearcoat. The overlay was partially dried for 10 minutes and rubbed with the cleaning solvent 3901 S as a rubbing solvent mix as described in Example 2 and cured to form a clearcoat providing additional durability. Example 4

Repairing Coating Chip Defects on a Vehicle A coated substrate 3 is the front hood cover of a General Motor (GM) car having a GM color code 398E. Through the VINdicator™ system, a color formulation B9806 Gold Metallic is identified as the best match of the vehicle's color. The hood cover has a coating chip defect.

An affected are having the chip defect is first cleaned with detergent and water. The affected area is then polished with conventional polishing compound to remove any oxidized paint. The affected area is then further cleaned according to conventional cleaning method. A pot mix is prepared with Part A1 , Part B1 and Part C1 as described in Example 1. Same procedure as described in Example 1 is used to repair the coating chip defect with a colored matching basecoat.

A clearcoat as described in Example 3 is then applied over the repaired chip area to provide additional durability and better color match of the metallic color.

The clearcoat is dried for about 10 minutes. The affected area is then applied with a spray wax and polished dry with a Sontara® Polish/Detail Cloth available from E.I. du Pont de Nemours and Company, Wilmington, Delaware. Comparative Example 1

This example demonstrates that when acetone is used as a rubbing solvent mix, unsatisfactory color match can result. A third set coating chip on the substrate 1 was repaired according to the process described in Example 1. Instead of using the cleaning solvent 3901 S, a synthetic cloth folded over a flat sanding block was wetted with acetone and used to rub the chipped area to completely remove any excess pot mix 1. After drying and curing, the outline of the chip was still visible, and the pot mix 1 filled interior had the same general color as the adjacent undamaged area of the substrate 1 , but the edge of the filled chip was shiny and metallic looking resulting in unsatisfactory color match and appearance since some of the colorant appears to have been removed during the rubbing with acetone. Comparative Example 2

This example demonstrates that when aromatic solvent, such as toluene is used as a rubbing solvent mix, unsatisfactory color match can result.

A third set coating chip defects on the substrate 2 was repaired according to the process described in Example 2. However, instead of using the cleaning solvent 3901 S, a synthetic cloth folded over a flat sanding block was wetted with toluene and used to rub the chipped area to completely remove any excess pot mix 3. After drying, the outline of the chip was still visible, and the pot mix 3 filled interior had the same general color as the adjacent undamaged area of the substrate 2, but the edge of the filled chip was shiny and metallic looking resulting in unsatisfactory color match since some of the colorant appears to have been removed during the rubbing with toluene.

Claims

CLAIMSWhat is claimed is:

1. A method for repairing an affected area having at least one coating defect disposed on a coated substrate into a defect free area, said method comprising the steps of: a) mixing Part A and Part B of a coating composition to form a pot mix, wherein said Part A comprises 33 percent to 99 percent by weight percent based on the total weight of said Part A of one or more crosslinkable components, said crosslinkable components having at least two crosslinkable groups per molecule or polymer chain; and wherein said Part B comprises one or more crosslinking components having one or more crosslinking groups per molecule or polymer chain; b) applying an overlay of the pot mix over the affected area; c) partial drying the overlay; d) removing excess of partially dried pot mix from the affected area by rubbing the affected area with a rubbing solvent mix wherein the rubbing solvent mix comprises one or more hydrocarbon aliphatic solvents; and e) curing said partially dried overlay to produce said defect free area on said coated substrate.

2. The method of claim 1 , wherein the crosslinking group is ketimine when the crosslinkable groups are selected from the group consisting of acetoacetoxy, epoxy, anhydride, and a combination thereof; wherein the crosslinking groups are selected from the group consisting of isocyanate, melamine, and a combination thereof when the crosslinkable groups are selected from the group consisting of hydroxyl, primary amine, secondary amine, ketimine, aldimine, and a combination thereof; wherein the crosslinking group is epoxy when the crosslinkable groups are selected from the group consisting of carboxyl, primary amine, secondary amine, ketimine, anhydride, and a combination thereof; wherein the crosslinking group is amine when the crosslinkable group is acetoacetoxy; wherein the crosslinking group is polyacid when the crosslinkable group is epoxy; wherein the crosslinking group is anhydride when the crosslinkable groups are selected from the group consisting of epoxy, ketimine, and a combination thereof.

3. The method of claim 2, wherein the crosslinking group is isocyanate.

4. The method of claim 3, wherein the crosslinkable groups are selected from the group consisting of hydroxyl, secondary amine, and a combination thereof.

5. The method of claim 4, wherein the secondary amine is aspartic amine.

6. The method of claim 1 , wherein the Part A or the Part B further comprises one or more additives selected from the group consisting of rheology control agents, defoamers, leveling agents, diluents, stabilizers, flow agents, toughening agents, UV protection agents, fillers, and a combination thereof.

7. The method of claim 1, wherein the Part A further comprises a curing catalyst.

8. The method of claim 7, wherein the curing catalyst is selected from the group consisting of carboxylic acids, tertiary amines, water, organic tin compounds, and a combination thereof.

9. The method of claim 8, wherein the curing catalyst is water.

10. The method of claim 1 , wherein the coating composition further comprises a Part C comprising one or more pigments, one or more dyes, or a combination thereof.

11.The method of claim 1 , wherein the rubbing solvent mix comprises 70 percent to 100 percent by weight percent based on the total weight of the rubbing solvent mix, of hydrocarbon aliphatic solvents.

12. The method of claim 11 , wherein the hydrocarbon aliphatic solvents are selected from the group consisting of aliphatic alkanes, cycloalkanes, naphtha, mineral spirits, and a combination thereof.

13. The method of claim 12, wherein the aliphatic alkanes are selected from the group consisting of n-pentane, n-hexane, hexane, heptane, octane, nonane, trimethylpentane, dimethylhexane; cycloalkane, and a combination thereof.

14. The method of claim 12, wherein the aliphatic cycloalkanes are selected from the group consisting of cycloheptane, dimethylcyclohexane, ethylcyclohexane, methylcyclohexane, and a combination thereof.

15. The method of claim 1 further comprising the step of applying a layer of a clearcoat over said defect free area on said coated substrate.

16. The method of claim 1 , wherein the coating composition comprises said Part A and the Part B stored separately.

17. The method of claim 1 , wherein the coating composition further comprises a Part C comprising one or more pigments, one or more dyes, or a combination thereof and wherein .the Part C is stored separately from the Part A and the Part B.

18. The method of claim 1 or 16 or 17, wherein the coated substrate is a vehicle body, a vehicle body part, or a vehicle.

19.A defect free area on a coated substrate produced by the method of claim 1.

20. A defect free area on a coated substrate produced by the method of claim 1 wherein said coated substrate is a vehicle body, a vehicle body part, or a vehicle.