DE102022003374A1 - coating process - Google Patents

Abstract

In a process for the production of matt and scratch-resistant coatings on multidimensional substrates with a radiation-curing lacquer that is applied manually or with automatic systems, the applied coating is irradiated under a first UV radiation with a wavelength between 360 nm and 420 nm and pre-gelled After pre-gelling, the coating is photochemically folded using excimer irradiation technology in the wavelength range between 150 nm and 225 nm in an inert atmosphere and the coating is then finally cured under a second UV irradiation with UV medium-pressure lamps.

Description

The invention relates to a method for producing highly matt surface coatings by means of spray application on multidimensional objects with radiation-curing paints and after curing with electromagnetic radiation

The invention relates to a method for producing matt and scratch-resistant surfaces on multi-dimensional workpieces. A radiation-curing paint is applied to the object using an atomization process for spraying (spray application). After optional forced drying, the paint is pre-gelled by a combination of electromagnetic radiation, then folded on the surface by short-wave monochromatic UV radiation and finally hardened again by electromagnetic radiation. Thanks to specially coordinated parameters, all four narrow surfaces (edges), the surface and other profiles located in the surface are created with just one coat of paint in the desired matt gloss level.

The production of matt surfaces is a common process in the coatings industry. The effect can be achieved on the one hand by physical processes (drying of a paint with solids < 100% by weight) or by chemical composition (matting agents, waxes, inorganic fillers). Furthermore, there is the possibility of photochemically folding the surface using high-energy radiation in the wavelength range ≥ 150 nm to ≤ 225 nm, preferably at 172 nm, and thus creating deep matt and highly scratch-resistant coatings. The latter method, also known as excimer technology, is described in various patent specifications and is already being used in surface coating

However, the field of application of this technology is limited to use with flat substrates of different compositions (MDF, paper, plastic). In order to achieve a comparable effect on narrow surfaces (edges), specially manufactured and coated edging strips must be attached to the edge.

Furthermore, the excimer technology is limited in its previous application to rolling and casting applications.D

The task of the present method is to offer a coating system that, using the well-known excimer technology, produces a homogeneous, deep-matt and highly scratch-resistant coating on all visible surfaces when sprayed on multi-dimensional objects with a single application.

• Strahlenhärtender Lack (Festkörper wasserverdünnt ≥ 35 Gew.-% bis ≤55 Gew.-%; Festkörper nicht wasserverdünnt ≥80 Gew.-%) Lackauftrag mittels manueller und automatischer Anlagen (Handspritzstand, Spritzautomat, Spritzroboter) durch Sprühverfahren (pneumatisch und hydraulisch) mit oder ohne forcierte Trocknung

The present method is characterized by the following profile:

• Radiation-curing paint (solids, water-diluted ≥ 35 wt.% to ≤55 wt.%; solids, not water-diluted ≥80 wt.%) Paint application using manual and automatic systems (manual spray stand, spray gun, spray robot) by spraying processes (pneumatic and hydraulic) with or without forced drying

The coating produced in step 1 is exposed to UV light with a wavelength of ≥ 360 nm to ≤ 420 nm; preferably irradiated at 395nm and pre-gelled.

After pre-gelling, the coating is photochemically folded in an inert atmosphere using excimer irradiation technology in the wavelength range ≧150 nm to ≦225 nm, preferably at 172 nm.

The final curing of the coating then takes place with classic UV medium-pressure lamps to achieve the final properties such as high scratch resistance and high chemical resistance.

• Ein oder mehrere UV-strahlenhärtende Bindemittel:
  • Bindemittel I: Mit Acryl/Methacrylsäure veresterte aliphatische Urethanacrylat, die zum Teil wasserverdünnbar sind
  • Bindemittel II: UV-härtbare Aliphatische Polyuerthandispersionen, mit Wasser verdünnt mit einem Festkörper von 30-70 Gew.-%
  • Bindemittel III: Mit Acryl/Methacrylsäure veresterte Polyetheracrylate
  • Bindemittel IV: Mit Acryl/Methacrylsäure veresterte Polyethylene Glykole

The amount of paint applied to the substrate in step (2) is 60-120 g/m ² .
According to the invention, the radiation-curing lacquer used contains:

• One or more UV radiation curing binders:
  • Binder I: Aliphatic urethane acrylate esterified with acrylic/methacrylic acid, some of which are water-dilutable
  • Binder II: UV-curable aliphatic polyurethane dispersions, diluted with water to a solids content of 30-70% by weight
  • Binder III: Polyether acrylates esterified with acrylic/methacrylic acid
  • Binder IV: Polyethylene glycols esterified with acrylic/methacrylic acid

One or more reactive diluent monomers, if required. These are a variety of ethylene/propylene glycols esterified with acrylic acid/methacrylic acid and polyfunctional aliphatic/aromatic alcohols

One or more reactive diluent oligomers, if required. These are different ethylene/propylene glycols esterified with acrylic acid/methacrylic acid and higher molecular weight polyfunctional aliphatic/aromatic alcohols

Water

This is demineralized or normal tap water

photoinitiator

These are photo-induced radical images based on Norrish type I and/or Norrish type II reactions

Organic solvents

These are acetates, glycols, glycol acetates, glycol ethers

matting agent

These are precipitated and modified silicic acids, inorganic fillers and waxes based on polymerized urea, ethylene, propylene, amide compounds

additives

1. a. Benetzungsadditive auf Silikon- und Acrylatbasis
2. b. Entschäumeradditive auf Silikonbasis in Kombination mit gefällten Kieselsäuren
3. c. Amin-Additive auf Basis aliphatischer Amino-alkohol Verbindungen zur Regulierung des pH-Wertes
4. d. Rheologieadditive auf Basis organischer und anorganischer Verbindungen

Tabelle 1: Beispielhafte Zusammensetzung der Lacksysteme Wasserverdünnter Lack [Gew.-%] Nicht wasserverdünnter Lack [Gew.-%] Bindemittel I 15-20% - Bindemittel I 15-20% - Bindemittel I - 15-20% Bindemittel II 5-10% - Bindemittel III - 5-15% Bindemittel IV 5-10% Reaktivverdünner-Monomer - 20-50% Reaktivverdünner-Oligomer 5-10% 10-30% Wasser 20-40% Photoinitiator I 0,5-2% 1-6% Photoinitiator II 0,1-0,5% 0,1-0,5% Organisches Lösemittel 2-5% Mattierungsmittel - 2-6% Benetzungsadditiv 0,1-2% 0,1-1% Entschäumeradditiv 0,1-2% Amin-Additiv 0,5-2% Rheologieadditiv I 0, 5-2% Rheologieadditiv II - 0,1-0,5% Rheologieadditiv III - 0,1-2%

1. a. Silicone and acrylate based wetting additives
2. b. Silicone-based defoamer additives in combination with precipitated silica
3. c. Amine additives based on aliphatic amino-alcohol compounds to regulate the pH value
4. i.e. Rheology additives based on organic and inorganic compounds

Table 1: Exemplary composition of the paint systems Water-diluted paint [% by weight] Non-water-thinned paint [% by weight] Binder I 15-20% - Binder I 15-20% - Binder I - 15-20% binder II 5-10% - binder III - 5-15% Binder IV 5-10% Reactive Diluent Monomer - 20-50% reactive diluent oligomer 5-10% 10-30% Water 20-40% Photoinitiator I 0.5-2% 1-6% Photoinitiator II 0.1-0.5% 0.1-0.5% Organic solvent 2-5% matting agent - 2-6% wetting additive 0.1-2% 0.1-1% defoamer additive 0.1-2% amine additive 0.5-2% Rheology Additive I 0.5-2% Rheology additive II - 0.1-0.5% Rheology additive III - 0.1-2%

Suitable substrates for the method according to the invention are, for example, wood (solid and veneered), wood-based materials (HDF, MDF, etc.), mineral substrates, plastic- and paper-coated wood and composite materials.

Before the transparent paint is applied, the substrate is pre-treated in various ways with spatulas and primers in order to achieve mechanical, chemical and coloring properties.

The raw material formulation of the paint can vary in order to achieve an optimal bond with the next lower paint layer.

1. 1. Strahlenhärtender Lack (Festkörper wasserverdünnt ≥ 35 Gew.-% bis ≤55 Gew.-%; Festkörper nicht wasserverdünnt ≥80 Gew.-%)
2. 2. Lackauftrag mittels manueller und automatischer Anlagen (Handspritzstand, Spritzautomat, Spritzroboter) durch Sprühverfahren (pneumatisch und hydraulisch) mit oder ohne forcierte Trocknung
3. 3. Erzeugte Beschichtung aus Schritt 1 wird mit UV-Licht der Wellenlänge ≥ 360nm bis ≤420nm; vorzugsweise bei 395nm bestrahlt und vorgeliert.
4. 4. Nach der Vorgelierung wird die Beschichtung mittels Excimer-Bestrahlungstechnik im Wellenlängenbereich ≥ 150nm bis ≤225nm, vorzugsweise bei 172nm, unter Inertatmosphäre photochemisch gefaltet.
5. 5. Im Anschluß erfolgt die Endaushärtung der Beschichtung mit klassischen UV-Mitteldruckstrahlern zur Erzielung der Endeigenschaften wie hohe Kratzfestigkeit und hohe chemische Beständigkeit

A process for the production of matt and scratch-resistant surfaces on multi-dimensional surfaces is explained according to the following scheme:

1. 1. Radiation-curing lacquer (solids, water-diluted ≥ 35 wt.% to ≤55 wt.%; solids, not water-diluted ≥80 wt.%)
2. 2. Paint application using manual and automatic systems (manual spray stand, spray machine, spray robot) by spraying methods (pneumatic and hydraulic) with or without forced drying
3. 3. The coating produced in step 1 is exposed to UV light with a wavelength of ≥ 360 nm to ≤ 420 nm; preferably irradiated at 395nm and pre-gelled.
4. 4. After pre-gelling, the coating is folded photochemically in an inert atmosphere using excimer irradiation technology in the wavelength range ≥150 nm to ≤225 nm, preferably at 172 nm.
5. 5. The final curing of the coating then takes place with classic UV medium-pressure lamps to achieve the final properties such as high scratch resistance and high chemical resistance

The amount of paint applied to the substrate in step (2) is 60-120 g/m ² .

The method is further characterized in that under point 1 of the scheme both UV coatings and water-dilutable UV coatings can be used, further that the coating systems mentioned in point 1 of the scheme one or more binders and one or more photoinitiators from the above mentioned groups, further that under point 2 of the scheme a single spray application produces a homogeneous, deep matt and highly scratch-resistant coating on all visible surfaces. The visible surfaces of the object include the narrow surfaces (edges), the surface itself and all other profiles located in the surface.

1. 1. Pneumatische Zerstäubung: 2-5 bar Luftdruck
2. 2. Hydraulische Zerstäubung (Airless): 70-140 bar Materialdruck
3. 3. Pneumatisch unterstützte Hydraulische Zerstäubung: ): 70-140 bar Materialdruck und 0,5-2,5 bar Luftdruck

In this process, the paint is applied indirectly using pneumatic, hydraulic (airless) and pneumatically assisted hydraulic (airmix) atomization processes. The following air or material pressures can be used:

1. 1. Pneumatic atomization: 2-5 bar air pressure
2. 2. Hydraulic atomization (airless): 70-140 bar material pressure
3. 3. Pneumatically assisted hydraulic atomization: ): 70-140 bar material pressure and 0.5-2.5 bar air pressure

In the method under point 3 of the scheme, the energy of the UV light is 50-250mJ/cm ² and is preferably generated by LED lamps.

Ultimately, in the process under point 5 of the scheme, the energy for final curing is generated by UV light using conventional UV high and medium pressure lamps (Hg lamps with variable doping from gallium, iron and indium), at an energy of 100 to 3000mJ/ ^cm2 .

Claims (11)

Process for the production of matt and scratch-resistant coatings on multidimensional substrates with a radiation-curing lacquer applied manually or with automatic systems, characterized in that the applied coating is subjected to a first UV irradiation of a wavelength between 360 nm and 420 nm; preferably at 395 nm, is irradiated and pre-gelled, that after pre-gelling, the coating is photochemically folded using excimer irradiation technology in the wavelength range between 150 nm and 225 nm, preferably at 172 nm, under an inert atmosphere, and that the coating is then finally cured under a second UV irradiation takes place with UV medium-pressure lamps. procedure after claim 1 , characterized in that the application takes place in a spraying process. Method according to one or more of the preceding claims, characterized in that the amount of lacquer applied to the substrate is 60-120 g/m ² . Method according to one or more of the preceding claims, characterized in that the proportion of solids in a water-diluted paint is between 35% by weight and 55% by weight and in a paint that is not water-diluted it is over 80% by weight. Method according to one or more of the preceding claims, characterized in that the paint has at least one binder and at least one photoinitiator. Process according to one or more of the preceding claims, characterized in that a binder which hardens under UV radiation consists of an aliphatic urethane acrylate esterified with acrylic/methacrylic acid, or of a partially water-dilutable binder made of UV-curable aliphatic polyurethane dispersions, diluted with water with a solids content of 30-70% by weight, or of polyether acrylates esterified with acrylic/methacrylic acid, or of polyethylene glycols esterified with acrylic/methacrylic acid. Process according to one or more of the preceding claims, characterized in that photo-induced free-radical formers based on Norrish type I and/or Norrish type II reactions are provided as photoinitiators. Process according to one or more of the preceding claims, characterized in that the paint is applied indirectly by pneumatic, hydraulic or pneumatically assisted hydraulic atomization processes. procedure after claim 8 , characterized by an air pressure of 2 bar to 5 bar in the case of pneumatic atomization, by a material pressure of 70 bar to 140 bar in the case of hydraulic atomization or in the case of pneumatically assisted hydraulic atomization by a material pressure of 70 bar to 140 bar and an air pressure of 0, 5 bars to 2.5 bars. Method according to one or more of the preceding claims, characterized in that the energy of the first UV irradiation is 50-250 mJ/cm ² . Method according to one or more of the preceding claims, characterized in that the energy of the second UV irradiation is 100-3000 mJ/cm ² .