EP0566958A1 - Verfahren zum Reparieren von defekten Beschichtungen auf einem metallischen Substrat - Google Patents

Verfahren zum Reparieren von defekten Beschichtungen auf einem metallischen Substrat Download PDF

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Publication number
EP0566958A1
EP0566958A1 EP93105974A EP93105974A EP0566958A1 EP 0566958 A1 EP0566958 A1 EP 0566958A1 EP 93105974 A EP93105974 A EP 93105974A EP 93105974 A EP93105974 A EP 93105974A EP 0566958 A1 EP0566958 A1 EP 0566958A1
Authority
EP
European Patent Office
Prior art keywords
coating
defect
article
repairing
existing
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Withdrawn
Application number
EP93105974A
Other languages
English (en)
French (fr)
Inventor
Donald L. Brownewell
Dwight B. Raddatz
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Ball Corp
Original Assignee
Ball Corp
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Ball Corp filed Critical Ball Corp
Publication of EP0566958A1 publication Critical patent/EP0566958A1/de
Withdrawn legal-status Critical Current

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Classifications

    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B05—SPRAYING OR ATOMISING IN GENERAL; APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
    • B05D—PROCESSES FOR APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
    • B05D5/00—Processes for applying liquids or other fluent materials to surfaces to obtain special surface effects, finishes or structures
    • B05D5/005—Repairing damaged coatings
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B05—SPRAYING OR ATOMISING IN GENERAL; APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
    • B05D—PROCESSES FOR APPLYING FLUENT MATERIALS TO SURFACES, IN GENERAL
    • B05D3/00—Pretreatment of surfaces to which liquids or other fluent materials are to be applied; After-treatment of applied coatings, e.g. intermediate treating of an applied coating preparatory to subsequent applications of liquids or other fluent materials
    • B05D3/02—Pretreatment of surfaces to which liquids or other fluent materials are to be applied; After-treatment of applied coatings, e.g. intermediate treating of an applied coating preparatory to subsequent applications of liquids or other fluent materials by baking
    • B05D3/0254—After-treatment
    • B05D3/0281—After-treatment with induction heating

Definitions

  • This invention relates to a method for repairing a defective coating on a coated ferromagnetic substrate and in particular to a method of repairing a defect in an existing coating which has been previously applied to discrete metallic articles such as cans and can ends manufactured from ferromagnetic materials.
  • Sheet metal which is to be utilized for producing various products, such as metal cans and ends and decorative metal pieces, usually has a coating applied to the metal for protective and/or decorative purposes.
  • the metal may be in coil form or in the form of individual sheets.
  • the protective coating is usually applied to the metal in liquid form by various techniques, such as a roller coaters, dipping, spraying, electrostatic application and the like, as the metal substrate is passed through the coater.
  • Various coatings and inks can be applied which are well known to those skilled in the art, including for example, vinyls, epoxys, alkyds and phenolics. These coatings include various resins and pigments dissolved in a solvent.
  • the solvent may be either a volatile organic solvent or may be an inorganic solvent, such as a water based solvent.
  • flaws in the coating are not detected until after the discrete article, such as a can or end, is cut and fabricated from a precoated sheet or strip.
  • Various types of defective coatings may be encountered.
  • the coating may not properly adhere to the substrate or during the fabrication process a score line may be formed in the metal such as when an easy open can end is formed and the coating does not cover the score line, but is is desirable to have the score line coated to avoid oxidation of the metal.
  • a further defect may arise out of a failure to have all of the solvent vaporized or a failure to have meat release products contained in the coating come to the surface where they are usable for releasing product from the can. Other defects may also be encountered.
  • the metal substrate may not have been properly etched.
  • the chemical balance of the etching, washing and rinsing solutions may not have been properly maintained or the solution temperature may have been inadequate, contributing to an unclean surface for which the coating is intended to adhere.
  • the final rinse was not made properly, leaving mill oil on the substrate or too many lubricants and rust inhibitors are applied to the metal which can cause adhesion problems when the coating is applied to the metal substrate.
  • Coating chemistry can also cause adhesion problems.
  • curing inhibitors are added to prevent the cross-linking of the coating surface particles prior to release of the coating solvents. Sometimes these inhibitors prevent the coating from becoming properly cured which causes adhesion problems between the coating and the substrate.
  • coating problems are related to the bake or curing cycle. Insufficient cure of the coating may occur because the oven temperature is too high or too low or there is a lack of air flow to provide proper solvent release. From time to time the metal or coating is either too hot or too cold to provide the proper bond between the coating and the substrate.
  • the article is a formed article, such as a metal can or end, it may be appropriate to utilize either a spray application or an electrostatic device for applying additional coating.
  • a spray application or an electrostatic device for applying additional coating.
  • Other methods and techniques of applying additional coating will be apparent to those skilled in the art.
  • the additional coating to be applied must be chemically and physically compatible with the existing coating.
  • the articles are passed through an electromagnetic induction coil.
  • the induction coil produces eddy currents in the metal substrate causing the metal substrate to rise in temperature, thereby heating the coating from the inside towards the outer surface.
  • a skin is not formed over the surface of the coating so that solvents contained within the coating can be released to atmosphere.
  • the existing coating is softened by the heat generated and, because it is heated from the inside out, the coating does not skin over as would be the case if a convection oven were used and with the present invention the coating becomes sufficiently fluid so that any solvents which may have remained in the existing coating due to incomplete curing in the prior manufacturing process will be released or volatilized.
  • solvents contained in the newly applied coating, if any, will be released to thereby dry and cure the coating.
  • Solvents which may be released to atmosphere must be collected in a suitable collection device. If there are adequate solvents to be volatilized, means may be provided for condensing the volatilized solvents and collection of the same.
  • the article Following the heating and curing of the coating on the article, the article must be cooled for further handling.
  • the principle object of this invention to provide a method for repairing a defect in an existing coating on a metal article.
  • a method of repairing a defect in an existing coating which has previously been applied to a discrete metallic article comprising the steps of analyzing the defective coating to determine whether it is required to apply additional coating to repair observed defects in the existing coating; if required following the preceding step, applying additional coating compatible with the original coating; heating the article and the coating to a temperature sufficient to cause the existing coating to become sufficiently fluid to repair the defect and cure the existing coating after it has become fluid and to volatilize substantially all of the solvents which are contained in the additional coating which may have been applied to the article and to cure such additional coating and the existing coating; and cooling the article.
  • the coating is soft, has good adhesion to the substrate, but does not pass the hardness test required by the customer specifications.
  • the present invention it has been discovered that if the defective article is passed through an electromagnetic induction coil to provide additional heat compared to that originally used to attempt to cure the coating, the proper molecular cross-linking occurs resulting in a substantial cure so that the proper coating hardness is obtained. There is usually no reason to add additional coating or thinners to the defective part.
  • the coating is underbaked, i.e., the coating contains solvents which have not been released. As a result, the coating has not flowed properly to cover the scarf marks.
  • the coating and the entrapped solvent in some instances will become sufficiently fluid to flow into the scarf mark.
  • the coating which has become fluid and flows into the uncovered area is then cured by the heat induced as the metal substrate by the induction coil, thereby making the article usable.
  • additional coating must be applied through a suitable applicator, such as a spray nozzle or coated roller, to apply solvent to the scarf area prior to subjecting the article to induction heating in the electromagnetic induction coil.
  • a suitable applicator such as a spray nozzle or coated roller
  • the substrate is heated first so that the coating next to the substrate becomes hotter than the coating on the surface to which the solvent has been previously applied.
  • the solvent has time to react with the existing coating causing the newly applied surface coating and solvent mixture to flow into the scarf marks completely covering the metal substrate before all of the solvent has evaporated or been volatilized by the heat.
  • the newly applied coating and the softened existing coating cross link and are bonded together to form an uninterrupted coating on the surface of the metal article after cure.
  • a third condition is when the coating has cured properly and has sufficient molecular cross-linking, but for some unknown reason, it did not cover the scarf mark completely.
  • Applying induction heating to the article to heat the coating or applying additional solvent does not effect any change in the coating structure.
  • additional coating and solvent must be applied by using an applicator.
  • the applicator will be a simple spray device or for more complex requirements an electrostatic deposition device can be used.
  • the electrostatic deposition device tends to deposit most of the coating on the bare metal substrate, in this case the bare scarf marks, thereby increasing coating application efficiency.
  • the end is subjected to induction heating which causes the coating-solvent mixture to flow in the uncoated areas and scarf marks prior to solvent evaporation or volatilization. Once cooled, the article is salvaged and can be utilized for its intended purpose.
  • the coating on the metal was originally cured in a conventional convection oven, the coating cures from the outside surface down to the metal substrate.
  • This inward cure cycle is usually an eight minute bake at a temperature sufficient to drive off the solvents. Since the coated article is heated from the outside inwardly, the outer coating surface hardens first. This condition causes a skinning-over effect which traps the solvents, meat release products and internal lubrication products in the coating.
  • the ferrous substrate By subjecting the defective coated part to induction coil heating, the ferrous substrate is rapidly heated. Once hot, the substrate causes the existing coating to become sufficiently fluid to permit solvents, internal lubricants and meat release products to volatilize at the metal substrate/ coating interface to be released allowing for a better bond and better adhesion to take place between the coating and the metal substrate.
  • the meat release and internal lubricant products are driven to the coating surface where they are needed to complete the manufacturing process.
  • the meat release product is an additive blended into the coating to better facilitate emptying the container after it has been opened. With the present invention, these meat release products are no longer trapped beneath the surface of the dried coating, but are now located at the surface where they can perform their intended function.
  • the apparatus includes a source 1 of articles, such as cans or can ends, which have a defective coating.
  • the article is illustrated in the form of a can end 2.
  • the particular article to be covered is not intended to be a limiting factor of the present invention.
  • An important criteria is that the article should have a metal (preferably ferromagnetic) substrate which is coated with a heat cured coating such as resins contained in a solvent.
  • a conveyor belt 5 is provided for transporting the article having the defective coating through the various apparatus required for carrying the process of the present invention.
  • the defective parts are placed in an orderly fashion on the insulated conveyor belt 5.
  • a suitable feeder device (not shown) may be utilized for distributing the articles from the source 1 onto the belt 5. The particular feeder device required will be dependent upon the quantity of articles to be treated, the type of article to be treated and other factors which will be apparent to those having ordinary skill in the art.
  • a vacuum hold down system In order to keep the article from sliding off the insulated conveyor belt, a vacuum hold down system generally indicated at 10 is provided. Since the parts will be heated in an electromagnetic induction coil, it is necessary to use an insulated conveyor belt to prevent arcing between the conveyor and the part.
  • the vacuum hold down system 10 may include a vacuum pump 11 and suitable vacuum lines 12 leading to a plenum chamber 13 for applying a vacuum through the porous conveyor belt 14 which forms parts of the conveyor 5.
  • the coated article to be repaired is conveyed through a coating application apparatus generally indicated at 20.
  • this application apparatus while illustrated as a spray system may take the form of an electrostatic coating applicator of the type known to those skilled in the art, a bath or other suitable means for applying additional coating to the defective article.
  • the particular apparatus may either have the coater 20 deactivated or removed entirely.
  • the next step in the process is to rapidly heat the defective article by means of an electromagnetic induction coil generally indicated at 25.
  • This induction coil may include an induction generator 26, power lines 27 and water cooled induction coil 28.
  • the induction coil 28 produces an oscillating magnetic flux which induces eddy currents in the ferromagnetic metal substrate that heats the outside surface of the metal substrate. Ferrous metal as thin as 0.0035 inches can be accommodated without becoming saturated by the magnetic field flux.
  • the induction generator contains suitable transformers and capacitors to match the electrical load to the induction coil 28 to achieve maximum power transfer to the defective part 2. Details of the control system are disclosed in the aforementioned U.S. Patent Application Serial No. 07/686,961, filed April 18, 1991.
  • the conveyor 5 conveys the parts 2 through the induction coil where they are subjected to the rapid alternating of the flux field produced in the coil 28 to produce eddy currents in the articles 2, thereby producing rapid heating of the metal substrate to heat the coating from the inside out to drive off the unwanted materials, provide increased adhesion and a more homogeneous protective covering to the metal substrate.
  • the heating of the metal substrate causes the existing coating to soften and become sufficiently fluid so that any solvents which remain in the existing coating are volatilized and solvents in any newly applied coatings are volatilized.
  • the softened coating flows into uncovered areas of the metal substrate.
  • the heat generated by the induction coil will result in better adhesion of the coating to the substrate.
  • Solvents in the existing coating which are volatilized and solvents in the newly applied coating which are volatilized will be discharged to atmosphere where they are collected in a hood 30 and conveyed through suitable ducting 31 to an air pollution control device (not shown).
  • the rapid heating of the metal substrate results in a drying and curing of the coating as well as the repair of the defective coating.
  • a cooling hood 35 has also been illustrated in Fig. 1 and is used to distribute cooling air supplied through a duct 36 to cool the article to a temperature suitable further handling.
  • another cooling method or apparatus may be used or the cooling hood could be eliminated and the part allowed to cool by exposure to ambient temperature.
  • Repaired articles are conveyed by conveyor 5 to a collection point 40 to complete the process.
  • the coated articles 2 may be conveyed through the electromagnetic induction coil in a manner similar to that illustrated in U.S. Patent Application Serial No. 07/686,961, filed April 18, 1991.
  • Induction coil power input of 35KHz to 300KHz is usable depending on the thickness of the metal substrate. A lower frequency gives greater metal penetration and a higher frequency results in more of a skin effect.
  • the process of the present invention can then be set up to either apply additional coating or operate without the necessity of additional coating.
  • the temperature at which the particular article needs to be heated to correct the defect in the existing coating can be determined and based on this temperature, the power which needs to be applied to the electromagnetic induction coil and the speed at which the conveyor used to move the articles through the induction coil can be determined.
  • the temperature selected must be sufficiently high to cause the existing coating to become at least partially fluid to flow into voids and cracks and allow unvaporized solvents to escape, but not exceed a temperature which will cause the coating to burn. These temperature extremes will normally be available from the coating manufacturer.
  • the coating to be applied would be the same as that originally applied, although it may be possible to select a physically and chemically compatible but not identical coating in order to effect the cure.
  • the invention may be summarized as follows:

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  • Application Of Or Painting With Fluid Materials (AREA)
EP93105974A 1992-04-22 1993-04-13 Verfahren zum Reparieren von defekten Beschichtungen auf einem metallischen Substrat Withdrawn EP0566958A1 (de)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
US87225492A 1992-04-22 1992-04-22
US872254 1992-04-22

Publications (1)

Publication Number Publication Date
EP0566958A1 true EP0566958A1 (de) 1993-10-27

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EP93105974A Withdrawn EP0566958A1 (de) 1992-04-22 1993-04-13 Verfahren zum Reparieren von defekten Beschichtungen auf einem metallischen Substrat

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Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB2305376A (en) * 1995-09-19 1997-04-09 Honda Motor Co Ltd Repairing a coating defect
WO2000054894A1 (de) * 1999-03-17 2000-09-21 Basf Coatings Ag Verfahren zur herstellung und ausbesserung von lackierungen
CN114394368A (zh) * 2020-01-03 2022-04-26 河源轩朗光电科技有限公司 裁切机、输送机构、输送带及其制造方法

Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
BE453738A (de) *
BE440862A (de) *

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
BE453738A (de) *
BE440862A (de) *

Cited By (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB2305376A (en) * 1995-09-19 1997-04-09 Honda Motor Co Ltd Repairing a coating defect
GB2305376B (en) * 1995-09-19 1998-08-12 Honda Motor Co Ltd Coating line system and method of repairing coating defect
US5922399A (en) * 1995-09-19 1999-07-13 Honda Giken Kogyo Kabushiki Kaisha Coating line system and method of repairing coating defect
WO2000054894A1 (de) * 1999-03-17 2000-09-21 Basf Coatings Ag Verfahren zur herstellung und ausbesserung von lackierungen
CN114394368A (zh) * 2020-01-03 2022-04-26 河源轩朗光电科技有限公司 裁切机、输送机构、输送带及其制造方法
CN114394368B (zh) * 2020-01-03 2024-01-19 河源轩朗光电科技有限公司 裁切机、输送机构、输送带及其制造方法

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