Urethane Methacrylate Hard Coating Resists Scratches and Impact
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Solution Overview
Problem
Existing hard coatings for thermoplastic resin products face challenges in providing simultaneous resistance to scratches, abrasion, impact, and weathering without compromising on hardness or durability, often resulting in discoloration and chalking over long-term outdoor exposure.
Innovation Solution
An active energy ray curable resin composition comprising a specific urethane (meth)acrylate with an average number of functional groups of 3 to 6 and microparticulate silica with a volume median diameter of 1 to 100 nm, used in a specific weight ratio, to form a hard coating layer that balances scratch, abrasion, impact, and weather resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If multifunctional (meth)acrylate oligomers or monomers are used as hard coatings, then scratch resistance and abrasion resistance are improved, but impact resistance deteriorates causing cracking and failure
Solution Approach 1:
The patent combines multifunctional (meth)acrylate oligomers/monomers with monofunctional (meth)acrylate oligomers/monomers to create a composite coating system. This composite approach allows the coating to achieve both high scratch/abrasion resistance (from the multifunctional component) and adequate impact resistance (from the monofunctional component), resolving the contradiction between hardness and impact endurance.
2Reliability
If monofunctional (meth)acrylate oligomer or monomer is added to improve flexibility and impact resistance, then impact resistance is improved, but hardness decreases causing deterioration in scratch resistance and abrasion resistance
Solution Approach 1:
The patent precisely controls the functional group equivalent (average number of functional groups) within the range of 2.0 to 3.5 and the hydroxyl value within 20 to 80 mg KOH/g. By optimizing these parameters, the coating achieves the right balance between flexibility (for impact resistance) and hardness (for scratch/abrasion resistance), preventing both cracking and excessive softening.
3Strength
If silica microparticles are combined with urethane acrylate to provide scratch/abrasion and impact resistance, then scratch resistance and impact resistance are improved, but weather resistance deteriorates causing discoloration and chalking
Solution Approach 1:
The patent specifies precise parameter ranges: functional group equivalent of 2.0 to 3.5, hydroxyl value of 20 to 80 mg KOH/g, and silica content of 5 to 50 parts by weight per 100 parts by weight of non-volatile matter. These controlled parameters ensure the coating maintains weather resistance while achieving the desired scratch and impact resistance, avoiding the discoloration and chalking problems.
4Strength
If hard coating is applied to maintain beauty over long term, then scratch resistance and abrasion resistance are improved, but flexibility decreases causing cracking upon impact
Solution Approach 1:
The patent creates a composite coating system combining multifunctional (meth)acrylate oligomers/monomers with monofunctional (meth)acrylate oligomers/monomers. This composite structure provides both the hardness needed for scratch resistance and the flexibility required to prevent cracking upon impact, resolving the contradiction between surface protection and impact endurance.
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 composition achieves a hard coating layer with strong resistance to impact and weather without compromising scratch and abrasion resistance, maintaining durability and preventing discoloration and chalking.
Implementation Method 1
an active energy ray curable resin composition which contains: a urethane (meth)acrylate (A) having an organic group in molecular skeleton and having an average number of functional groups of from 3 to 6... The resulting hard coatings obtained from multifunctional (meth)acrylate oligomers or monomers by curing with active energy rays
Data Source
AI summary
Provided is an active energy ray curable resin composition for the formation of a hard coating layer on a thermoplastic resin product, where the hard coating layer is one having good resistance to scratches and abrasion and strong resistance to impact and weather or one having very good resistance to scratches and abrasion. The composition contains a urethane (meth)acrylate (A) having an average number of functional groups of 3 to 6 and having, in molecular skeleton, an organic group corresponding to a tricyclodecanedimethanol represented by following Formula (1), except for removing two hydrogen atoms of two hydroxyl groups therefrom; and a microparticulate silica (S) having a volume median diameter of 1 to 100 nm as determined by dynamic light scattering. The composition contains 10 to 40 percent by weight of the urethane (meth)acrylate (A) and 10 to 60 percent by weight of the microparticulate silica (S) based on the total weight of non-volatile matter in the composition. ##STR00001##