DE102009020264B4 - Process for painting and using a polymeric material to mask a surface of a component - Google Patents

Abstract

A method of painting a surface of a component, wherein the surface has at least one painting area to be painted and at least one masking area not to be painted, characterized by the steps of: a) applying the masking area with a polymeric material having thixotropic properties in discrete or separable form in the form of droplets and / or solid particles to form a coherent polymer film, altering the cohesive and / or adhesive properties of the polymer film by energization, the cohesive forces upon application being less than the adhesive forces; b) painting the painting area; c) crosslinking the polymer film and / or curing the polymer film, wherein the cohesive forces of the polymer film are greater than the adhesion forces between the polymer film and the masking region; and d) removing the polymer film.

Description

The invention relates to a method for painting a surface of a component according to the preamble of claim 1 and a use of a polymeric material in such a method.

Such a method is known from DE 197 37 065 A1 or the US 2006/0194905 A1 known.

The Lackierbereich is referred to as such because intended paint is applied there. The masking area is referred to as such because, as intended, a masking or no varnish is applied there during the application.

Certain functional surfaces of the surface of components, in particular of plastic components, must be covered in conventional methods by applying a Maskierbands, usually in the form of a special adhesive film. Background is the necessary coverage or masking of these surfaces during a painting process, so that later in these areas or on these surfaces no paint film or spray is. Following the painting process, the masking tape, which is preferably in the form of the adhesive film, is usually removed. Subsequently, the further processing of these affected surfaces is carried out by various confectioning operations (eg welding or gluing with other parts). The protection of these surfaces or areas is imperative to ensure the function of subsequent operations.

This known masking method requires, in particular with regard to the coating of a large number of components, such as in particular of plastic bumpers for motor vehicles, a high personnel costs or high initial costs for suitable automation solutions. Further, due to the geometry of the component or component dependent contours to be masked, such as in the form of narrow radii, usually the need for denomination of the masking tape to be applied, along with the disadvantageous fact that in the areas of the denomination a desired overlap effect fails to peel off and requires additional effort.

The invention is therefore based on the object of specifying a method for painting a surface of at least one component, with which precise masking of the masking of the surface of a component in a practical manner and without much effort is possible compared to known solutions.

• a) Beaufschlagen des Maskierbereichs mit einem polymeren Material, das thixotrophe Eigenschaften aufweist, in diskreter oder trennbarer Form, in der Form von Tröpfchen und/oder Feststoffpartikeln, um einen zusammenhängenden Polymerfilm zu bilden das Verändern der kohäsiven und/oder der adhäsiven Eigenschaften des Polymerfilms durch Energiebeaufschlagung, wobei die Kohäsionskräfte beim Beaufschlagen kleiner als die Adhäsionskräfte sind;
• b) Lackieren des Lackierbereichs;
• c) Vernetzen des Polymerfilms und/oder Härten des Polymerfilms, wobei die Kohäsionskräfte des Polymerfilms größer als die Adhäsionskräfte zwischen dem Polymerfilm und dem Maskierbereich sind; und
• d) Entfernen des Polymerfilms.

To achieve this object, the method for painting a surface of a component according to claim 1 is provided. The method according to the invention for coating a surface of a component which has at least one painting area to be coated and at least one masking area which is not to be painted comprises the steps:

• a) subjecting the masking region with a polymeric material having thixotropic properties, in discrete or separable form, in the form of droplets and / or solid particles to form a continuous polymer film, the changing of the cohesive and / or adhesive properties of the polymer film Energization, the cohesive forces being less than the adhesion forces when applied;
• b) painting the painting area;
• c) crosslinking the polymer film and / or curing the polymer film, wherein the cohesive forces of the polymer film are greater than the adhesion forces between the polymer film and the masking region; and
• d) removing the polymer film.

The step d) is preferably carried out only after complete curing of the paint.

The phrase "masking area not to be painted" is set to the state after masking. Nevertheless, the component in the masking region can already have a pre-coating or contrasting finish before the masking is applied, so that the masking protects a previously painted surface, for example against overcoating or against the thermal stress of a paint drying oven. By the phrase "coating the masking region with a cohesive, polymeric material in finely divided" is meant an application of the polymeric material in discrete or separable form, whether solid or liquid, whether in the form of droplets, solid particles or the like, whether by knife coating, painting, spraying or the like. The polymeric material may be applied to the masking area by hand or by an automated applicator. In contrast to a masking tape, the application of the polymeric material in a fine distribution permits contour-appropriate masking. Due to the cohesive properties, the finely divided polymeric material can combine to form a coherent, integral and opaque polymer film, preferably to form chemical bonds, to mask the masking area and prevent paint application in the masking area. The polymer film is preferably designed to be removed without residue from the surface of the component. The polymer film can then be residue-free and in the essentially in a single piece from the surface of the component, preferably manually, removed or withdrawn. According to the invention, the surface may preferably have a plurality of painting areas, which are painted one after the other or simultaneously.

According to the invention, the polymeric material has thixotropic properties. The term thixotropy refers to the property of a non-Newtonian fluid to reduce viscosity at a constant shear over a time axis. After exposure to the shear stress, the initial viscosity is rebuilt. Thus, the polymeric material can be adjusted to solidify due to its thixotropic properties after application to the masking region. Thus, a contour-compatible application of the polymeric material is possible without the applied polymeric material deliquesces after application.

The method of the invention comprises adjusting the cohesive and / or adhesive properties of the polymer film so that the cohesive forces of the polymer film are greater than the adhesion forces between the polymer film and the masking region. Thus, the formation of the polymer film according to the invention, with which residue-free removal from the surface of the component is possible, can be provided. In step (a), the smallest possible cohesive forces of the polymeric material are preferred, so that the polymeric material can be applied as finely as possible in a fine distribution. The adhesion forces should be so great that the applied polymeric material adheres to the masking area and does not flow off. Prior to or during step (b), cohesive forces and adhesion forces are preferred, such that the polymer film is e.g. B. during a washing process of the component ("power-wash"), in which the component is subjected to a water pressure of about 80 bar, is not damaged and does not peel off. After step (b), the adhesion forces should be correspondingly small, so that the polymer film can be detached in one piece without residue and without much effort.

According to the invention, the cohesive and / or adhesive properties of the polymer film are adjusted by applying energy to the polymer film. The cohesive and / or the adhesive properties of the polymer film are u. a. influenced by the chemical bonds. The chemical bonds of the polymer film, in turn, for example, via the power supply, z. As irradiation can be influenced. For example, the temperature has an influence on the chemical bonds of the polymer film, for. B. in the networking.

According to the invention, the polymer film is cured. Curing of the polymer film is understood in this context to be an increase in the viscosity of the polymer film. The cohesive forces of the polymer film and the adhesion forces between the polymer film and the masking region change. As a result of the curing of the polymer film, the cohesive forces of the polymer film increase and the adhesion forces between the polymer film and the masking region decrease. By energizing the polymer film, the curing cycle can be tuned to the painting cycle.

According to the invention, the polymer film is chemically crosslinked. The crosslinking makes it possible to contrast the cohesive forces of the polymer film and the adhesion forces between the polymer film and the masking region. As the degree of crosslinking increases, the cohesive forces of the polymer film increase and the adhesive forces between the polymer film and the masking region decrease. Upon crosslinking, the polymeric material solidifies and shrinks slightly.

It may prove helpful if the polymeric material is applied in the liquid state to the masking area. The liquid state of matter is characterized by a high volume resistance and low dimensional stability, so that the shape of the polymeric material, in contrast to solids by small forces, which can be applied in particular manually changeable. In this respect, the term "liquid" in particular also includes a viscous, z. B. gel-like consistency of the polymeric material. According to the invention, the liquid polymeric material can therefore be applied to the masking area in a practical manner, such as by knife coating, painting, coating or the like, preferably manually or preferably automated, depending on the location of the painting or the number of components to be painted can be done. In this case, the polymeric material preferably has a dynamic viscosity which, at the same temperature, is greater than the viscosity of water (water has a dynamic viscosity of about 1 mPa.s at normal pressure and a temperature of 20 ° C.), in order to flow off to avoid the already applied to the masking polymeric material. Preferably, at a temperature of 20 ° C, and preferably at normal pressure, the polymeric material has a dynamic viscosity which is greater than 100 mPa · s, preferably 10000 mPa · s. At a dynamic viscosity above 10000 mPa · s, which corresponds approximately to the dynamic viscosity of honey at a temperature of 20 ° C, the already applied polymeric material flows only very slowly due to possible inclinations formed on the surface of the component, so that while usual Lackierzeiten practically a constant form of the surface applied to the polymeric material is provided according to the invention. Particularly preferred is a polymeric material which, when mixed, ie under shear, has a viscosity lower than 20 Pa · s, preferably even lower than 10 Pa · s. With the release of the shear forces, the material forms a very high viscosity, so that overall the behavior can be described as thixotropic and it does not expire on vertical surfaces and remains stable in the applied form.

It may prove useful to apply the polymeric material as a spray to the masking area. The application as a spray allows a very close-contour application in hard to reach, curved masking areas. The polymeric material is preferably sprayed onto the masking area by means of an automated spraying device. The automated spraying device is preferably mounted on an industrial robot and preferably has an automated metering device. By means of this practical development, in which an application of the polymeric material takes place by spraying, an automation solution can be provided according to the invention, which enables the incorporation of the method according to the invention into an automated painting process.

Overall, it may prove convenient to apply the polymeric material as a powder to the masking area. This can be helpful if the component is charged electrostatically. This can prevent the polymeric material from deliquescing after application.

It may be helpful if the polymeric material in a thickness of 50 to 500 microns, preferably 100 to 300 microns, preferably 200 microns, is applied. In this thickness or thickness, the polymeric material or the polymer film formed therefrom can withstand the stresses acting during the painting process. In addition, the internal strength of the polymer film is sufficiently high, so that the polymer film can be removed or removed without residue. The required thickness of the polymer film may vary depending on the chosen polymeric material.

It may be advantageous if the polymeric material is adhesive on plastic, preferably on polypropylene. As a result, plastic injection molded components, in particular polypropylene, can be easily and efficiently masked.

It may prove helpful if a degree of crosslinking of the polymer film at the end of the painting process is over 75%, preferably over 90%. In this degree of crosslinking, the adhesion forces are correspondingly small, so that the polymer film can be detached in one piece residue-free and without much effort.

It may be useful if the crosslinking rate is controlled by energizing the polymer film. As a result, the crosslinking cycle can be matched to the painting cycle.

A preferred aspect of the invention relates to the use of a polymeric material for masking a surface of a component in a method according to any one of the preceding embodiments, wherein the polymeric material is a preferably liquid adhesive, preferably containing polyol and isocyanate. The material used preferably uses components of general polyurethane chemistry wherein at least one component, polyol or isocyanate, is formed with a filler which imparts thixotropic properties to the polymeric material as a whole. The preferred properties are achieved particularly well with a two-component polyurethane adhesive.

In a preferred embodiment, the polymeric material for masking a surface of the component is a material available under the trade name Araldit 2027. Araldite 2027 comprises components XD 4712 (A) and XD 4713 (B), wherein XD 4712 (A) is the isocyanate component and XD 4713 (B) is the polyol component. The components XD 4712 (A) and XD 4713 (B) are preferably mixed in a ratio of 9.7 to 10 and are present as pastes with thixotropic properties. The viscosity is between 19,000 and 35,000 mPa · s.

Component A, containing isocyanate (XD 4712), preferably comprises about 55 to 65 wt .-% of modified diphenylmethane diisocyanate (MDI), about 33 to 44 wt .-% of inorganic fillers such as carbonates, wollastonite or silica, and about 0 , 5 to 2 wt .-% of water-absorbing additives.

Component B, containing polyol (XD 4713), preferably comprises a total of about 30 to 35 wt .-% castor oil, about 9 to 13 wt .-% of polyols such as polyether or aliphatic polyols, about 48 to 61 wt. % inorganic fillers such as carbonates, wollastonite or silica, about 2 to 4 wt .-% water-absorbing additives, about 0.2 to 1 wt .-% adhesion promoter (based on silane), about 0.01 to 0.03 wt .-% catalysts such. As stannates or lithium chloride (LiCl), and lower components (about 0.1 to 0.2 wt .-%) of other additives.

The inventive method is particularly suitable for painting large-volume plastic components, such as spoilers, bumpers or Radlaufblenden. It is characterized by the fact that, in particular by application, doctoring or brushing of the polymeric material, a virtually completely contour-independent masking of masking regions is possible, wherein, in particular, even narrow radii can be easily masked on the plastic component. Therefore, the formation of a continuous, one-piece polymer film in highly curved areas is possible. This results in advantages when peeling off after painting, since the polymer film can be removed in one piece. The technical and personnel effort in applying is reduced. Since the masking tape previously used is offered only in small rolls with short run lengths, resulting from the inventive method advantages, including the elimination of material residues on the rollers, the elimination of disruption or fallow times for role change and the elimination of any dependencies for recycling material.

The masking area can have any geometry. If a polymeric material with thixotropic properties is used, the masking region can also be "overhead" since the polymeric material does not drip due to the thixotropic properties. The masking region may be formed, for example, band-shaped, for example, to provide unpainted surfaces for bonding or welding of the component with other components. Typical widths of the masking region may be between 20 mm and 30 mm. In particular, the surface of the component may have a plurality of masking regions, wherein the masking regions may be arranged relative to each other according to a predetermined pattern. Each masking region of the multiplicity of masking regions can also be designed, for example, as band-shaped, wherein the masking regions can be arranged in a line-like manner one behind the other and can be spaced apart from one another by means of painting regions. The individual masking regions can also be punctiform, circular or oval-shaped, wherein the individual masking regions can be arranged in a straight line or along a curved line one behind the other.

Brief description of the drawings

1 shows a schematic representation of a plastic component in the form of a spoiler for motor vehicles, together with a schematic representation of an attached to an industrial robot applicator for the cohesive, polymeric material, eg. B. in the form of a spray device.

Detailed Description of the Preferred Embodiment

An embodiment of the invention will be explained in more detail with reference to the accompanying drawings.

This in 1 schematically illustrated plastic component in the form of a spoiler 10 for motor vehicles has a masking area in the form of an adhesive surface 12 on. In 1 is also schematically an industrial robot 18 shown, the straight along the longitudinal extent of the spoiler 10 is guided, with the spoiler 10 on a movable goods carrier (not shown) may be located.

At the industrial robot 18 is an automated applicator 16 for the cohesive, polymeric material 14 , z. In the form of a spraying device, which, inter alia, has an automatic or automated metering device (not shown in greater detail), and is arranged to cooperate with the industrial robot 18 predetermined areas of the surface of a plastic component, in this case in particular the adhesive surface 12 , with the cohesive, polymeric material 14 to apply in fine distribution, z. B. to spray them with the cohesive, polymeric material 14 to cover / coat. The spray device comprises a nozzle of appropriate geometry to apply the polymeric material in the desired thickness of preferably 200 μm and width (20-30 mm). To any areas of the surface of a plastic component with the cohesive, polymeric material 14 to cover / coat, has the applicator 16 a control device (not shown in detail), which is adapted to the applicator 16 in cooperation with the industrial robot 18 to control such that predetermined areas with the inventive cohesive, polymeric material 14 can be charged / sprayed. By means of this method according to the invention, a very high accuracy with regard to the attachment of the cohesive, polymeric material can be achieved. The cohesive polymeric material in the described embodiment is a liquid adhesive containing polyol and isocyanate, preferably Araldite 2027.

The process according to the invention initially involves the covering or coating of the adhesive surface 12 with the cohesive, polymeric material in fine distribution through the applicator 16 in cooperation with the industrial robot 18 , After curing of the cohesive, polymeric material 14 the painting of the surface of the spoiler takes place 10 , which also by means of the illustrated industrial robot 18 can take place, on which also a painting device (not shown in detail) can be attached. After painting the surface of the spoiler 10 and after a predetermined drying time for the applied paint, the removal of the cured polymer film, which is preferably carried out manually, takes place 14 from the adhesive surface 12 by suitable manual stripping.

The provided by the method according to the invention, unpainted remaining adhesive surface 12 is according to the invention a functional surface which can be glued in an advantageous manner with surfaces of other components or other plastic components or alternatively also welded, and in particular may have any geometry due to the practical spraying invention.

• • In feiner Verteilung aufgetragen werden und sich aufgrund seiner kohäsiven Eigenschaften zu einem zusammenhängenden, einstückigen Polymerfilm verbinden;
• • Automatisch aufgebracht werden;
• • Jeder Geometrie folgen, wie Rippen, Winkeln, etc;
• • Thixotope Eigenschaften aufweisen;
• • In flüssigem Aggregatszustand vorliegen und z. B. als Spray aufgetragen werden;
• • In festem Aggregatszustand vorliegen und z. B. als Pulver aufgetragen werden;
• • Auf dem Maskierbereich aushärten;
• • Auf dem Maskierbereich vernetzt werden;
• • Einen an den Lackierzyklus angepassten Vernetzungs- bzw. Härtezyklus haben, wobei die zur angestrebten Vernetzung bzw. Aushärtung erforderliche Zeit auf die zur Lackierung erforderliche Zeit abgestimmt ist, was z. B. durch dosierte und gezielte Energiebeaufschlagung erreicht wird; und
• • Auf Oberflächen kleben, selbst auf solchen mit geringer Oberflächenenergie wie Polypropylen.

In summary, the invention has the following advantages: The cohesive, polymeric material can:

• • are applied in a fine distribution and, due to its cohesive properties, combine to form a coherent, one-piece polymer film;
• • applied automatically;
• • Follow any geometry, such as ribs, angles, etc;
• • have thixotopic properties;
• • Are in liquid state and z. B. be applied as a spray;
• • exist in a fixed state of aggregation and z. B. be applied as a powder;
• • cure on the masking area;
• • be networked on the masking area;
• • Have an adapted to the painting cycle curing or curing cycle, wherein the time required for the desired cross-linking or curing is tuned to the time required for painting, which z. B. is achieved by metered and targeted energization; and
• • Stick to surfaces, even those with low surface energy such as polypropylene.

• • in Schritt (a) die Adhäsionskräfte zwischen dem Polymerfilm und dem Maskierbereich ausreichend groß sind, so dass das aufgetragene polymere Material im Maskierbereich haftet und nicht abfließt;
• • Vor bzw. während des Schrittes (b) die Kohäsionskräfte des Polymerfilms und die Adhäsionskräfte zwischen dem Polymerfilm und dem Maskierbereich ausreichend groß sind, so dass der Polymerfilm nicht beschädigt wird und sich während des „gesamten” Lackierprozesses (insbesondere während des sog. „power-wash”) nicht ablöst;
• • In Schritt (c) die Adhäsionskräfte zwischen dem Polymerfilm und dem Maskierbereich möglichst klein sind, insbesondere geringer als eine innere Festigkeit des Bauteils, und die Kohäsionskräfte des Polymerfilms möglichst groß sind, so dass sich der Polymerfilm in einem Stück rückstandsfrei und ohne großen Kraftaufwand ablösen lässt.

The polymeric material or polymer film may have variable properties over time, e.g. B. is achieved by oxidation or by metered and / or targeted energization. The cohesive forces of the polymer film and the adhesion forces between the polymer film and the masking region are adjustable so that

• In step (a), the adhesive forces between the polymer film and the masking region are sufficiently great that the applied polymeric material adheres to the masking region and does not flow off;
• • Before or during step (b), the cohesive forces of the polymer film and the adhesion forces between the polymer film and the masking region are sufficiently great that the polymer film is not damaged and becomes damaged during the "entire" painting process (especially during the so-called "power -wash ") does not replace;
• In step (c), the adhesion forces between the polymer film and the masking region are as small as possible, in particular lower than an internal strength of the component, and the cohesive forces of the polymer film are as large as possible, so that the polymer film is detached in one piece without residue and without great effort leaves.

Depending on the required curing / crosslinking time of the polymer film z. B. be applied by means of a radiant lamp energy to the required area, or the component can be heated prior to the application of the polymeric material, or the component with applied masking can then be heated. The curing / crosslinking is preferably carried out at a temperature of 20 to 80 ° C.

The invention is applicable to packaging, cartons, components in the land transport, aviation, naval industries for all fields of injection molded or laminated or molded parts with very low surface energy where an accurate stencil for painting is required.

Claims (10)

Method for painting a surface of a component, wherein the surface has at least one painting area to be painted and at least one masking area not to be painted, characterized by the steps: a) applying the masking region with a polymeric material having thixotropic properties, in discrete or separable form, in the form of droplets and / or solid particles, to form a coherent polymer film, changing the cohesive and / or adhesive properties of the polymer film by energization, the cohesive forces when applied being less than the adhesive forces; b) painting the painting area; c) crosslinking the polymer film and / or curing the polymer film, wherein the cohesive forces of the polymer film are greater than the adhesion forces between the polymer film and the masking region; and d) removing the polymer film. A method according to claim 1, characterized in that the polymeric material is applied in the liquid state to the masking region. Method according to one of the preceding claims, characterized in that the polymeric material is applied as a spray on the masking region. A method according to claim 1, characterized in that the polymeric material is applied as a powder on the masking region. Method according to one of the preceding claims, characterized in that the polymeric material in a thickness of 50 to 500 .mu.m, preferably 100 to 300 .mu.m, preferably 200 .mu.m, is applied. Method according to one of the preceding claims, characterized in that the polymeric material is adhesively applied to a component made of plastic, preferably polypropylene. Method according to one of the preceding claims, characterized in that a degree of crosslinking of the polymer film at the end of the coating process is over 75%, preferably over 90%. Method according to one of the preceding claims, characterized in that the crosslinking rate is controlled by energization of the polymer film. Use of a polymeric material for masking a surface of a component in a method according to one of the preceding claims 1 to 8, characterized in that an adhesive is used as the polymeric material. Use according to claim 9, characterized in that a polyol and isocyanate-containing adhesive is used.

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