EP3180134B1 - Method for the production of a coated substrate - Google Patents

Description

Technical area

The present invention relates to a method for producing a coated substrate by applying to the substrate at least one coating agent which comprises a plastic selected from a group consisting of polyethylene (PE), polypropylene (PP), thermoplastic polyolefins (TPO) or mixtures from it, as well as a corresponding plastic component.

State of the art

In the automotive industry, plastics now account for between 15 and 20 percent by weight and the trend is increasing. These are often exterior and interior parts that receive their corresponding visual, haptic and functional properties through a coating. The increasing demands on quality and economy as well as resource efficiency, but also the global competitive pressure, require ever more economical, sustainable and flexible painting processes.

The trend towards fewer painting steps, for example through filler-free paint systems, is also enjoying success Plastic attachments are very popular. The elimination of intermediate drying reduces energy consumption and, at the same time, material consumption and solvent emissions decrease. In addition, less production space is required for the paint shop.

Corresponding paint solutions are available for glossy, injection-molded interior parts, for example trim strips, made from an ABS-PC blend (ABS: acrylonitrile butadiene styrene, PC: polycarbonate). With a single-layer lacquer structure, the lacquer ensures an elegant, high-gloss surface.

In the automotive industry, mostly solvent-based and water-based paints have been used to date for the coating of plastics. Solvent-based UV dual cure systems have also been used for a number of years. They enable good matting properties as well as metallic colors. However, not all metallic colors can be produced with UV lacquers. High-gloss surfaces are created with solvent-based UV dual cure clear coats in a structure with base coats. Recently, both 100% UV clear lacquers with a piano lacquer look and 2K dual cure systems have been increasingly used for plastic lacquering, with the former having significantly higher chemical resistance properties. Good adhesion values are achieved on many common plastic substrates such as ABS, SAN (styrene-acrylonitrile), PS (polystyrene) and ABS / PC (polycarbonate) without pretreatment. Otherwise, the adhesive properties can usually be optimized by activating the surface by flame treatment, plasma treatment or gas phase fluorination.

Dual-Cure describes the combined curing by heat and actinic radiation. Dual-cure coating materials and processes and devices for curing them with actinic radiation, in particular UV radiation, are from the German patent applications DE 198 18 735 A1 , DE 42 15 070 A1 , DE 199 30 665 A1 , DE 199 30 067 A1 , DE 199 30 664 A1 , DE 199 24 674 A1 or DE 199 20 799 A1 known. They are used to produce coatings, in particular clearcoats and multicoat color and / or effect paint systems. Curing with actinic radiation is mainly carried out with UV radiation.

The binder components contained usually have different functional groups which, under suitable conditions, usually network independently of each other. Customary dual cure systems belonging to the prior art have radiation-curable and thermally curable groups, with particularly advantageous properties being achieved when isocyanate and hydroxyl groups are used as thermally crosslinking functions.

EP 1 419 015 discloses a process for producing coatings from coating materials curable thermally and with actinic radiation, in which A) the coating materials are applied to primed or unprimed substrates or to uncured, partially cured and / or fully cured paint layers located thereon, and B) the resulting layers are applied the coating materials alone or together with the uncured and / or partially cured paint layers cures thermally and with actinic radiation, the Curing with actinic radiation is carried out under an oxygen-depleted atmosphere.

DE 199 45 291 A1 discloses a painting system for painting plastic objects with a pretreatment zone in which the surfaces are prepared for painting, in particular cleaned and rinsed. The objects pretreated in this way are then brought through a drying zone into a painting zone. In a first pass through this painting zone, the objects are pre-painted in a first painting station with a modified basecoat with primer properties and then sprayed with normal basecoat, then evaporated and dried and, in a second pass through this painting zone in a second painting station, sprayed with clearcoat and then finally dried.

Description of the invention

The object of the present invention is therefore to provide a simplified method for producing a plastic part containing coated polyethylene (PE), polypropylene (PP), or thermoplastic polyolefins (TPO), in which the number of painting steps and the costs for the painting plant are reduced and at the same time, the quality requirements for the paintwork are met.

• a- Nassreinigen des unbehandelten Substrats;
• b- Auftragen eines ersten Beschichtungsmittels;
• c- Zwischentrocknung oder Nass/Nass-Behandlung des mit dem ersten Beschichtungsmittel beschichteten Substrats;
• d- Auftragen eines zweiten Beschichtungsmittels, welches thermisch und durch aktinische Strahlung (Dual-Cure) härtbar ist;
• e- Erwärmen oder Trocknen des beschichteten Substrats, wobei eine Polyaddition erfolgt;
• f- Bestrahlen des beschichteten Substrats mit aktinischer Strahlung, wobei eine Polymerisation ausgelöst wird.

According to the invention, this object is achieved in terms of the method by the following steps:

• a- wet cleaning the untreated substrate;
• b- applying a first coating agent;
• c- intermediate drying or wet / wet treatment of the substrate coated with the first coating agent;
• d- applying a second coating agent which is curable thermally and by actinic radiation (dual-cure);
• e- heating or drying the coated substrate, a polyaddition taking place;
• f- irradiating the coated substrate with actinic radiation, with polymerization being initiated.

In view of the prior art, it was surprising and not foreseeable for the person skilled in the art that the object on which the present invention was based could be achieved with the aid of the method according to the invention. A particular advantage of the invention is that in the proposed method the step of activating the substrate is completely dispensed with.

This not only eliminates investment costs for the activation units when converting or upgrading existing painting systems, but also the fire protection measures and operating costs associated with the activation units (flame, plasma). The plastic substrate made of polyethylene (PE), polypropylene (PP), or thermoplastic polyolefins (TPO) can be filled or unfilled.

On the plastic substrates made of polyethylene (PE), polypropylene (PP), or thermoplastic polyolefins (TPO), one, two and three-layer structures made of dual-cure, 2K or 1K systems that meet the requirements of the automobile manufacturer can be provided without activation , for example for painted interior plastic components made of polypropylene, are sufficient.

The first coating agent in step b preferably contains at least one 1K or 2K hydroprimer or a solvent primer and / or UV 2K dual-cure primer.

According to the invention, the second coating agent contains at least one UV-2K dual-cure hydro lacquer.

The process combination of 1K or 2K solvent and / or hydroprimer and / or UV / 2K dualcure primer with UV / 2K dualcure hydro paint systems on substrates made of PP and TPO can be combined with ABS, ABS mod. PC, PC ABS, PC, PMMA for painted interior components. An activation unit, e.g. with flame or plasma is not required.

The process using UV / 2K-Dualcure hydro lacquers advantageously enables the production of matt and highly scratch-resistant lacquer systems with decor, soft and comfort haptics for lacquered interior components.

Another advantage of such a coated plastic component is, inter alia in its perfume resistance, e.g. against essential oils and in its soft feel.

The process combination of UV / 2K-Hydro-Dualcure clear coats with 1K or 2K solvent and hydroprimers and / or 2K basecoats and / or UV / 2K-Dualcure hydro paint systems also enables the generation of a wide range of products with matt, semi-gloss or high-gloss surfaces.

According to the invention, the surface of the substrate or plastic is not activated before the first coating agent is applied.

The conventional activation of plastic substrates by means of flame, plasma processes, which are differentiated into low-pressure and atmospheric pressure plasmas, and gas-phase fluorination can be used primarily for cleaning off thin organic contaminants while simultaneously activating the surface. This dual function is based on a physical and chemical reaction in the process. As a result, in addition to a clean surface, an increase in surface tension or surface energy is achieved in order to create optimal conditions for the subsequent painting process.

In view of the method according to the invention, however, the simultaneous weakening of the plastic surface by the energy input during activation seems to be just as decisive for the adhesive strength on the plastic substrates mentioned and has so far hardly been taken into account. Analytical investigations of the activation effects mostly aim at the type and the proportion of the polar functional groups generated and the polarity achieved thereby, but disregard disadvantageous degradation effects.

In the case of PE, PP or TPO materials that are susceptible to polymer degradation, for example, it seems to be the case that activation can be dispensed with in order to enable reliable adhesion of water-based paint systems without the adverse effect of a potential polymer degradation occurs due to activation.

In the XPS analysis (photoelectron spectroscopy), untreated PP shows pure -CC proportions of 91.25%, no -COOH proportions. With flame and with ADP processes (Atmospheric pressure plasma process via nozzle), in particular, the carboxyl group proportions (-COOH) rise very sharply. With 2K systems, known isocyanate secondary reactions in the direction of bi ureth and urea groups occur through curing.

With ToF-SIMS (secondary ion mass spectrometry), such surface species can be detected, which then shows differences to the untreated PP. Characterization and verification are therefore carried out with coupled analyzes of XPS and ToF-SIMS.

The first coating agent and / or the second coating agent preferably contains at least one UV adsorbent, as a result of which the cured coating agent is effectively protected from UV radiation, in particular from sunlight. Paint exposed to sunlight therefore becomes brittle more slowly and has a longer shelf life.

The first coating agent and / or the second coating agent preferably contains at least one adhesive additive or a binder in order to improve the adhesion of the lacquer to the substrate. The adhesive additive or the binder contain, for example, pigments and resins.

The plastic component with coated substrate obtained by a method described above has the first coating agent a layer thickness of 10-30 μm, preferably 15 μm and / or the second coating agent a layer thickness of 3-20 μm, preferably 15-40 μm, particularly preferably 25 μm. 30 µm. The second coating agent preferably has a layer thickness of 3 to 20 μm Coating of transparent substrates, especially in connection with polycarbonate.

A device for producing a coated substrate by applying at least one coating agent to the substrate, which comprises a plastic which is selected from a group consisting of polyethylene (PE), polypropylene (PP), thermoplastic polyolefins (TPO) or mixtures thereof
a washing device for alkaline wet cleaning of the non-activated substrate;
a downstream adhesive water dryer with cooling zone;
a first painting device with an area for applying a first coating agent and a downstream second painting device with an area for applying a second coating agent, which has at least one hydropack that cures by heat and actinic radiation (dual-cure), wherein
an intermediate drying and / or cooling zone is arranged between the first painting device and the second painting device; and
an irradiation unit with actinic radiation downstream of the first and second coating devices.

The first painting device is preferably suitable for applying a first coating agent which contains at least one 1K or 2K hydroprimer or solvent primer and / or UV-2K dual-cure hydro primer.

The second painting device is preferably suitable for applying a second coating agent which contains at least one UV-2K dual-cure hydro paint.

The intermediate drying and / or cooling zone is preferably designed for drying temperatures of 20-90 ° C.

Examples Example paint structure:

The following examples show in tabular form various paint systems consisting of a hydro-primer as the first coating agent and a basecoat or protective varnish as the second coating agent on flamed and non-flamed substrates. The coatings generally have a 1K primer with UV Dualcure top coat or a 1K primer with 2K top coat or UV Hydro Dualcure top coat.

This is followed by a paint test for scratch resistance and the effects of cream.

Untreated PP as a substrate shows inadequate substrate adhesion when 1K, 2K, etc. hydro paints are used alone, whereby the coatings can be completely removed from the substrate. Solvent-based paints also adhere poorly without pretreatment. The cross-cut tests result in characteristic values> GT 3 - GT 5 (very poor adhesive strength) for hydro paints on PP without activation. The paint systems according to the invention, on the other hand, show characteristic values - GT 1-GT 0 (very good adhesive strength) in the cross-cut tests.

Furthermore, analysis methods such as DSC (differential scanning calorimetry) and tests of scratch resistance (e.g. Vickers penetration hardness), use of general surface analysis such as IR spectroscopy, XPS and ToF-SIMS, as described above, can be used to characterize the paint adhesion.

The effects achieved for UV / 2K Dualcure top coats are for decor, soft, comfort, any color tones for interior, exterior, such as black, beige, red, silver, chrome, contrast anthracite, titanium, etc., matt, silk matt and piano black, Pianowhite and high gloss.

The optical effects for UV / 2K clear lacquers are high gloss, silk matt and matt, common colors are possible.

The following tables show examples of various combinations of first and second coating agents on a substrate and their properties: Paint build-up Color 1 Color 2 Color 3 high gloss black Color 4 Color 5 Paint manufacturer Color type UV-2K - Dualcure two-layer UV silver K 2K UV hydrolacquer UV black 2K - UV hydrolack UV black high gloss In addition: contrasting colors, galvano effect, titanium syllable, titanium gray, etc. Quicksilver, Meica, Micra colors, matt silk-gloss, high-gloss matt interleur according to OEM specifications Harder Hardener 1 for UV matt black and silver, electroplated hardener 2 for high-gloss black Batch -No. Decor / Soft / Comfort color: Mixing ratio 100: 10 (vol.) For silver 1405577 1405454 1405635 100: 20 (vol.) For black 100: 5 (vol.)) For black gloss Primer 2K - hydro primer for standard substrates ABS PC modified / PB ABS Tick measured viscosity top coat in sec Temperature in ° C PP components were coated in advance with a 1K solvent primer. In the future, 1K, 2K hydroprimer or UV / 2K dualcure hydroprimer Harder Hardener 1 DIN Primer 4th Yes Education ratio 100: 10 (vol.)) ISO Top coat 6th Yes Specification of layer thickness specifications Viscosity Decor / Soft / Comfort color: Layer thickness 15-20 µm 27 22nd 16 Layer thickness UV / 2K Dualcure 15-25 µm Primer batch no. 2K hydro primer + 2% deionized water viscosity 35

Example high-gloss structures:

Paint build-up primer Top coat Material designation 1 component solvent primer UV hydrolysis paint silver matt Substrate PP GF 30 PP GF 30 Pretreatment Flamed Without flames TL226 Hydrolysis storage 72h at 90 ° C and> 96% rel. Humidity Change in the surface No change in the surface No change in the surface Cross cut according to 3.7.1 <= 1 GT0 GT <1 Scratch resistance according to 3.8 no tearing of the paint surface no tearing of the paint surface Cream testing Change in the surface No change in the surface No change in the surface Cross cut according to 3.7.1 <= 1 GT0 GT <1 Scratch resistance according to 3.8 no tearing of the paint surface no tearing of the paint surface Perfume resistance Standard test hollow / flat glass G1 solution on sprinkled filter medium. After 24 hours of storage at room temperature, the filter medium is removed, wiped off with a damp cloth and the sample is assessed visually. No change in the surface No change in the surface Scratch resistance according to PLN-Kr-1/01 Erichsen test rod 318 test tip 1.00 mm load 5 N no tearing of the paint surface no tearing of the paint surface

Brief description of the figures

Individual embodiments of the painting device of the invention are described in more detail below with reference to the drawings.

Fig. 1a,b

eine schematische Darstellung zweier Lackiervorrichtungen aus dem Stand der Technik für Interieurbauteile im Nass/Nass Prozess (Fig. 1a) oder mit Zwischentrocknung nach Grundierung (Fig. 1b);

Fig. 2

eine schematische Darstellung einer Lackiervorrichtung für Kunststoffbauteile im Nass/Nass-Prozess;

Fig. 3

eine schematische Darstellung einer Lackiervorrichtung für Kunststoffbauteile mit Zwischentrocknung nach Grundierung;

Fig. 4

eine schematische Darstellung einer Lackiervorrichtung für Kunststoffbauteile im Nass/Nass-Prozess für Klarlacke;

Fig. 5

eine schematische Darstellung einer Lackiervorrichtung für Kunststoffbauteile mit Zwischentrocknung nach Grundierung für Klarlacke.

Show in it:

Fig. 1a, b

a schematic representation of two painting devices from the state of the art for interior components in the wet / wet process ( Fig. 1a ) or with intermediate drying after priming ( Figure 1b );

Fig. 2

a schematic representation of a painting device for plastic components in the wet / wet process;

Fig. 3

a schematic representation of a painting device for plastic components with intermediate drying after priming;

Fig. 4

a schematic representation of a painting device for plastic components in the wet / wet process for clear coats;

Fig. 5

a schematic representation of a painting device for plastic components with intermediate drying after priming for clear coats.

Fig. 1 shows two painting devices from the prior art for interior components made of acrylonitrile-butadiene-styrene (ABS) copolymer, ABS-modified polycarbonate (PC), polycarbonate (PC), polymethyl methacrylate (PMMA) or mixtures thereof, in the wet / wet process, ie without Intermediate drying ( Fig. 1 a) in the dryer 8, or with intermediate drying after priming in the first painting booth 6 (1 b).

In this usual process sequence, according to Fig. 1a the Dekorsoftlack applied wet on wet in two coats. There is no intermediate drying, only a flash-off for 7-10 minutes at 20 ° - 26 ° C and 55 ± 5% relative humidity.

In the first painting booth 6, a primer is applied with or without intermediate drying for priming. In the second painting booth 11, 2K hydro topcoat is applied for interior paints, decor, soft and effect paints such as metallic, silver, chrome, etc.

In both cases, alkaline wet cleaning 1 takes place as an equivalent for two degreasing zones in two rinsing zones as well subsequent rinsing with fully demineralized water. This is followed by a blowing zone 2 with an adhesive water dryer 3. Usually, in the case of plastic components that are not made from acrylonitrile-butadiene-styrene (ABS) copolymer, ABS-modified polycarbonate (PC), polycarbonate (PC), polymethyl methacrylate (PMMA) or mixtures thereof, an activation device (not shown) is provided after the adherent water dryer 3 ) intended. This is followed by a drive-through area 5 in front of the first 6 and second 11 paint booths. A first cooling zone 4 is located in front of the drive-through area 5 to the first painting booth 6.

In the usual two-layer construction process, two soft decorative paints are applied wet-on-wet in the first 6 and second 11 paint booths, with a control zone 10 between the paint booths, in which the flash-off also takes place. The second paint booth has an evaporation zone 12 with the final paint dryer 13, in which the completely coated substrate is dried at 80 ° C. for 30 minutes. After passing through the final cooling zone 14, the now painted component reaches the exit area 15 and continues to the parts acceptance control 17, as well as the parts task 18 and the assembly area 19.

In the process sequence according to Figure 1b the decorative soft paint is dried in two applications in the primer dryer 8, which is preceded by an evaporation zone 7, after priming in the first paint booth 6 (1 b). Here, too, a control zone 10 is arranged between the painting booths, in which the flash-off also takes place. The second paint booth is an evaporation zone 12 with the final one Downstream paint dryer 13, in which the fully coated substrate is dried at 80 ° C. for 30 minutes. After passing through the final cooling zone 14, the now painted component reaches the exit area 15 and continues to the parts acceptance control 17, as well as the parts task 18 and the assembly area 19.

In the prior art, no direct coating without activation is not possible for PP / TPO substrates. Activation is currently also mandatory for the use of aqueous primers. The painting systems described below represent a fixture-side solution to this problem.

Fig. 2 shows a schematic representation of a painting device for plastic components, in particular interior components, containing polyethylene (PE), polypropylene (PP), thermoplastic polyolefins (TPO) or mixtures thereof in the wet / wet process. There is no intermediate drying 8, but only a flash-off for 7-10 minutes at 20 ° -26 ° C. and 55 ± 5% relative humidity.

PP, TPO without activation, possibly in combination with ABS, ABS mod., PC ABS, PC or PMMA are used as substrates. The process combination of 1K or 2K solvent and / or hydroprimer and / or UV / 2K dualcure primer with UV / 2K dualcure hydro lacquer systems on substrates made of PP and TPO can also be used in combination with ABS, ABS mod. PC, PC ABS, PC, PMMA for all painted interior components. A complex and costly activation unit, for example with flame or plasma, is not required. This not only eliminates Investment costs for the activation units when converting or upgrading existing painting systems, but also the fire protection measures and operating costs associated with the activation units (flame, plasma).

In the case of the UV-Hydro Dualcure paint systems according to the invention, too, the painting process can in principle be "wet on wet" ( Fig. 2 ) or with intermediate drying in the primer dryer 8 ( Fig. 3 ) the adhesion-promoting layer take place. In addition, there is a flash-off for 7-10 minutes at 24 ° - 26 ° C and 55 ± 5% relative humidity.

In contrast to the system according to Fig. 1 a, b the adhesion-promoting UV / 2K dual-cure hydroprimer / primer or a 2K hydroprimer is now applied in the first painting booth 6.

In the second painting booth 11, the UV / 2K Dualcure - hydro base paints for interior paints, decor, soft and effect paints such as metallic, silver, chrome, etc. are applied.

On the device side, devices additionally have a UV emitter unit 16 compared with the prior art, which is preferably arranged in the system area between the closing cooling zone 14 and the extension area 15.

The painting device for producing a coated substrate is thus characterized in particular by the combination of a washing device for alkaline wet cleaning 1 of the non-activated substrate, a downstream adherent water dryer 3 with cooling zone 4, a first painting device 6 for applying a first coating agent and a downstream, second painting device 11 to apply a second Coating agent which has at least one dual-cure curing hydrolack. An intermediate drying and / or evaporation zone 7, 8 is arranged between the first painting device and the second painting device, as well as an irradiation unit 16 with actinic radiation downstream of the second painting device 11.

Fig. 4 shows analogous to Fig. 2 , a schematic representation of a painting device in the wet / wet process for clear coats.

In the case of the UV-Hydro-Dualcure clearcoat systems, the painting process can in principle also be "wet on wet" ( Fig. 4 ) or as a two-layer structure with intermediate drying 8 ( Fig. 5 ) the adhesion-promoting layer take place. With intermediate drying 8, there is also a flash-off for 7-10 minutes at 24 ° - 26 ° C and 55 + 5% relative humidity.

In the first painting booth 6, an adhesion-promoting UV-hydro base paint in black, metallic-aqueous, etc. (interior colors, decor, comfort, soft and effect paints such as metallic, silver, chrome) is applied. Then in the second painting booth 11 the application of the UV hydro clear lacquer, e.g. matt, semi-gloss or high-gloss.

Iron-doped lamps are preferred as UV lamps for UV / 2K dual-cure hydro-base paints (decor, soft, comfort matt with effect and interior colors), and mercury-doped UV lamps for clearcoat systems.

List of reference symbols

1

- wet cleaning

2

- Blow zone

3

- Adhesive water dryer

4th

- Cooling zone 1

5

- Drive-through area before painting

6th

- Painting booth 1

7th

- Evaporation zone 1

8th

- dryer primer

9

- cooling zone 2

10

- control zone

11

- Painting booth 2

12

- Evaporation zone 2

13

- dryer paint

14th

- cooling zone 3

15th

- Exit area

16

- UV lamp unit

17th

- Part acceptance / control

18th

- parts task

19th

- Equipping the slide

20th

- Start end

Claims (5)

1. Method for producing a coated substrate by applying at least one coating composition to the substrate, which comprises a plastic selected from a group consisting of polyethylene (PE), polypropylene (PP), thermoplastic polyolefins (TPO) or mixtures thereof,
   characterized by

   a - wet cleaning of the untreated substrate;

   b - application of a first coating composition, with the surface of the substrate not being activated before the application of the first coating composition;

   c - intermediate drying or wet-on-wet treatment of the substrate coated with the first coating composition;

   d - application of a second coating composition, which is curable thermally and by actinic radiation (dual cure) and comprises at least one UV 2K dual-cure water-based varnish;

   e - heating or drying of the coated substrate, with a polyaddition taking place;

   f - irradiation of the coated substrate with actinic radiation, with a polymerization being triggered.
2. Method according to Claim 1, characterized in that the first coating composition comprises at least one water-based primer or one solvent-based primer.
3. Method according to either of Claims 1 and 2,
   characterized in that
   the first coating composition and/or the second coating composition comprise at least one UV adsorber.
4. Method according to any of Claims 1 to 3, characterized in that
   the first coating composition and/or the second coating composition comprise at least one adhesion additive or one binder.
5. Method according to any of Claims 1 to 4, characterized in that
   the first coating composition has a film thickness of 10-30 µm, preferably 15 µm, and/or the second coating composition has a film thickness of 3-20 µm.

Images