UV-Curable Coating Agent with Segmented Photoinitiators

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Solution Overview

Problem

Existing UV-curable coating systems face challenges in achieving both sufficient curing and long-term UV resistance due to the competition between UV polymerization and UV protection, leading to issues like incomplete hardening and reduced weathering stability.

Innovation Solution

A radiation-curable coating agent containing polymerizable unsaturated compounds and organic UV absorbers with maximum absorption below 390 nm, allowing for effective UV protection without interfering with the curing process, and optionally including photoinitiators and other components for enhanced polymerization and stability.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If UV absorbers are added to UV-curable coating systems to improve UV resistance, then the UV protection of the layer is enhanced, but the curing of the printed layer becomes insufficient due to UV radiation absorption

Engineering Contradiction:

ImproveUV resistanceVSAvoidcuring completeness

Core Design Contradiction:

ReliabilityVSStability of the object's composition

Solution Approach 1:

The UV spectrum is segmented into different wavelength ranges with dedicated photoinitiators for each range. The coating composition includes photoinitiators for UV-A (315-400 nm), UV-B (280-315 nm), and UV-C (200-280 nm) ranges, allowing different portions of UV radiation to initiate polymerization at different depths and times, thereby overcoming the blocking effect of UV absorbers

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The invention changes the spectral parameters of the photoinitiators to match different UV wavelength ranges. By selecting photoinitiators with specific absorption characteristics for different UV bands, the system achieves complete curing even in the presence of UV absorbers that block certain wavelengths

Inventive Principle:

Principle #35Parameter changes

2Reliability

If inorganic pigments are used to replace organic pigments for improved light resistance, then the light resistance is significantly increased, but the imageable color space is reduced and UV absorption increases

Engineering Contradiction:

Improvelight resistanceVSAvoidimageable color space

Core Design Contradiction:

ReliabilityVSAdaptability or versatility

Solution Approach 1:

The invention creates a composite system combining organic pigments with multi-spectrum photoinitiators and UV absorbers. This composite approach allows the use of vibrant organic pigments while compensating for their UV sensitivity through the synergistic action of multiple photoinitiators and UV protection agents

Inventive Principle:

Principle #40Composite materials

Solution Approach 2:

The invention converts the harmful UV absorption by pigments into a beneficial effect by using the absorbed UV energy to initiate and enhance polymerization. The UV absorbers and multi-range photoinitiators system captures UV radiation that would otherwise degrade the organic pigments and converts it into useful polymerization energy

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

3Reliability

If UV absorbers are used in classic UV-curing systems, then UV protection is provided, but the UV radiation penetration required for complete polymerization is blocked

Engineering Contradiction:

ImproveUV protectionVSAvoidUV radiation penetration

Core Design Contradiction:

ReliabilityVSUse of energy by moving object

Solution Approach 1:

The UV radiation source is segmented into multiple wavelength bands, each targeted by specific photoinitiators. This segmentation allows different UV bands to penetrate to different depths and initiate polymerization at various levels, ensuring complete curing even when UV absorbers block certain wavelengths

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The curing process uses periodic or sequential activation of different photoinitiator systems. By cycling through different UV wavelength ranges, the system ensures that all layers of the coating receive sufficient energy for complete polymerization, overcoming the periodic blocking effect of UV absorbers

Inventive Principle:

Principle #19Periodic action

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 coating agent achieves good to very good UV light resistance while ensuring complete curing, maintaining the balance between hardness and flexibility, and providing long-term protection against UV degradation.

Implementation Method 1

the UV absorbers have their maximum degree of absorption in a wavelength range of

Methodology Applied

Scientific EffectUV absorption: Absorption (EM radiation)

Implementation Method 2

UV-curable coating agent containing polymerizable unsaturated compounds

Methodology Applied

Scientific EffectPhotopolymerization: Photopolymerisation

Data Source

PatentEP3174940B1Ultraviolet-curable coating agent with improved sunlight resistance

Publication Date: 2019.02.06 TIGERWERK LACK & FARBENFAB

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AI summary

What is described is a radiation-curable coating composition comprising polymerizable unsaturated compounds such as (meth)acrylates, vinyl compounds or the like in a concentration range of 15-98% by weight, with an addition of 5-35% by weight, preferably 5-20% by weight, of organic UV absorbers, where the UV absorber(s) have their maximum absorption level within a wavelength range of < 390 nm, preferably < 350 nm, where the coating composition optionally comprises further components in an amount of the residue to 100% by weight, and a method for curing such a coating composition. Also described is a coating composition of this kind, wherein the organic UV absorber is free-radically polymerizable.