UV-Curable Matt Coatings with Epoxy Acrylate
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Solution Overview
Problem
Current radiation-curable coating systems struggle to produce matt surfaces with higher gloss levels and a soft-feel effect, as they typically result in dull, hard surfaces with limited gloss and unsatisfactory tactile experience.
Innovation Solution
A method involving a UV radiation-curable paint formulation with specific ethylenically unsaturated double bonds, oligomers, and aromatic epoxy acrylate content, irradiated in specific wavelength ranges under different atmospheres to achieve partial and full hardening, allowing for adjustable gloss and soft-feel properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If radiation-curable coating systems are used to produce matte surfaces, then the coating can be cured by UV radiation, but the surface becomes hard and cold-feeling instead of soft and velvety
Solution Approach 1:
The patent changes the chemical composition parameters of the coating formulation by incorporating specific ratios of aromatic epoxy acrylate (20-80 wt.%) and aliphatic epoxy acrylate (10-60 wt.%), along with controlled double bond content (3.0-8.0 mol/kg). These parameter changes in the formulation composition enable the coating to achieve both reliable UV curing and desirable soft-feel properties that contradict conventional radiation-curable coating behavior.
2Shape
If conventional matting agents are added to the formulation to create matte surfaces, then the surface appears matte, but the gloss level remains limited and the soft-feel effect is not achieved
Solution Approach 1:
Instead of relying solely on conventional matting agents, the patent changes the fundamental chemical parameters of the coating system by using epoxy acrylate oligomers with specific double bond contents and ratios. This approach produces matte surfaces with higher gloss levels (up to satin finish) and soft-feel effects without depending on traditional matting agents that limit gloss performance.
3Reliability
If the coating formulation contains high amounts of curable components to achieve 100% system, then the coating achieves complete curing, but it becomes difficult to produce matte surfaces with soft-feel effect
Solution Approach 1:
The patent resolves this contradiction by precisely controlling the chemical parameters of the 100% system formulation. By specifying aromatic epoxy acrylate (20-80 wt.%), aliphatic epoxy acrylate (10-60 wt.%), and total double bond content (3.0-8.0 mol/kg), the formulation achieves complete curing while simultaneously enabling matte finish and soft-feel effects that are otherwise difficult to achieve in 100% systems.
Solution Approach 2:
The patent uses a composite coating formulation combining aromatic epoxy acrylate and aliphatic epoxy acrylate in specific ratios, along with other curable components. This composite material approach enables the 100% system to achieve both complete curing and desirable surface properties (matte finish and soft-feel effect) that cannot be obtained with single-component systems.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The method enables the production of matt coatings with higher gloss levels up to silky gloss and a pleasant soft-feel effect, while maintaining mechanical stability and chemical resistance, allowing for gloss adjustment and improved tactile experience.
Implementation Method 1
These coating systems are liquid formulations containing oligomers or polymers with multiple ethylene-unsaturated double bonds, often in the form of acrylic groups (CH2=CH-C(O) groups). To produce the coatings, the liquid coatings are applied to the substrate surface, and the resulting coating layer is then cured by irradiation with actinic radiation, such as UV radiation. This process involves radical polymerization of the ethylene unsaturated double bonds, forming a cross-linked polymer film.
Implementation Method 2
the coating formulation F contains at least one aromatic epoxy acrylate in an amount of at least 20 wt.%, specifically at least 30 wt.%, and most specifically at least 40 wt.%, based on the total weight of the curable components contained in the paint formulation
Data Source
AI summary
The present invention relates to a process for producing matt coatings on sheetlike substrates comprising the following consecutive steps i. - iv., i. providing an uncured lacquer layer of a UV radiation-curable liquid lacquer formulation F on the surface of the substrate to be coated; ii. irradiating the lacquer layer with UV radiation substantially in the wavelength range of 250 to 420 nm with a radiation dose which results in partial curing of the lacquer layer; iii. irradiating the partially cured lacquer layer with UV radiation in the wavelength range of 150 to < 250 nm under inert gas; iv. irradiating the partially cured lacquer layer with UV radiation substantially in the wavelength range of 250 to 420 nm or with electron radiation with a radiation dose which results in end-curing of the lacquer layer; wherein, based on the total weight of the constituents of the lacquer formulation F that form the coating, the lacquer formulation F consists to an extent of at least 80% by weight of one or more curable constituents comprising ethylenically unsaturated double bonds, the lacquer formulation F additionally contains at least one photoinitiator, wherein the lacquer formulation F contains at least one oligomer or polymer which bears on average at least 1.5 ethylenic double bonds per molecule and has a number-average molecular weight Mn of at least 450 Dalton and wherein the lacquer formulation F fulfils at least one of the following features (A), (B), (C) or (D): (A) the number of ethylenically unsaturated double bonds based on the constituents which are present in the lacquer formulation F and form the coating is in the range from 3.0 to 8.0 mol/kg; (B) the lacquer formulation F contains, based on the curable constituents present therein, at least 30% by weight of an oligomer or polymer or a mixture of oligomers and/or polymers where the quotient a/To of calculated network arc length α in g/mol and the onset temperature T0 in Kelvin of the glass transition is at least 1.2; (C) the mass-average quotient a/T0 averaged over the weight fractions of all curable constituents of the lacquer formulation F is at least 1.0; (D) the lacquer formulation F contains at least one aromatic epoxy acrylate in an amount of at least 20% by weight based on the total weight of the curable constituents present in the lacquer formulation F.