Low Temperature Heat-Curable Powder Coating Composition
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Solution Overview
Problem
Current powder coating compositions face challenges in curing heat-sensitive substrates without thermal stress, achieving uniform curing on complex shapes, and maintaining flexibility and adhesion, especially when heavily pigmented or used on three-dimensional objects.
Innovation Solution
A heat-curable powder coating composition comprising at least 7.5 wt% crystalline polyester resin, up to 92.5 wt% amorphous polyester resin, and 0.65 parts peroxide per hundred parts of resin, with 2-butenedioic acid ethylenic unsaturations, which can be cured at low temperatures, ensuring flexibility and good adhesion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional powder coating compositions are used, then complete curing is achieved, but thermal stress damages heat-sensitive substrates
Solution Approach 1:
The patent changes the chemical composition parameters of the powder coating by incorporating specific ratios of crystalline polyester resin (7.5-50 wt%), amorphous polyester resin (50-92.5 wt%), and peroxide (0.65-2.0 pph) with controlled decomposition characteristics. This compositional parameter change enables curing at lower temperatures (100-150°C) while maintaining complete cure, thereby reducing thermal stress on heat-sensitive substrates like wood and plastic
Solution Approach 2:
The patent creates a composite powder coating system combining three distinct components: crystalline polyester resin, amorphous polyester resin, and peroxide initiator. This composite material approach allows synergistic effects where each component contributes specific properties - the crystalline resin provides structural integrity, the amorphous resin ensures complete penetration and curing, and the peroxide enables low-temperature activation, collectively solving the thermal stress problem while maintaining curing completeness
2Temperature
If radiation curing is used, then low temperature curing is achieved, but uneven curing occurs on heavily pigmented or complex three-dimensional objects
Solution Approach 1:
The patent replaces radiation-based curing (electromagnetic field) with heat-based curing (thermal field) using peroxide decomposition. Thermal energy penetrates uniformly through pigmented coatings and complex three-dimensional geometries, ensuring consistent curing throughout the coating layer and on all surfaces of complex objects, eliminating the penetration limitations of radiation methods
Solution Approach 2:
The patent modifies the curing mechanism by using peroxide decomposition kinetics that can be controlled through temperature and catalyst selection. This allows gradual, uniform heat generation and chemical reaction throughout the coating, ensuring homogeneous curing even on heavily pigmented or complex-shaped substrates while maintaining relatively low curing temperatures
3Ease of manufacture
If the powder coating is heavily pigmented, then aesthetic requirements are met, but radiation penetration is blocked resulting in uneven curing
Solution Approach 1:
The patent replaces radiation curing with thermal curing through peroxide decomposition. Heat energy penetrates pigmented coatings effectively, and the peroxide-initiated crosslinking reaction proceeds uniformly throughout the coating layer regardless of pigment content, ensuring complete and even curing on heavily pigmented surfaces while maintaining aesthetic quality
4Strength
If high crosslinking density is achieved, then adhesion and strength are improved, but flexibility is reduced
Solution Approach 1:
The patent creates a composite resin system where crystalline polyester resin provides crosslinking density for strong adhesion, while amorphous polyester resin maintains flexibility and elongation. The peroxide-initiated crosslinking creates an optimized network structure that balances strength and flexibility, preventing the brittle behavior that would result from excessive crosslinking density alone
Solution Approach 2:
The patent controls the crosslinking parameters by adjusting peroxide concentration (0.65-2.0 pph) and selecting peroxides with specific decomposition temperatures and rates. This controlled crosslinking achieves sufficient adhesion strength while maintaining flexibility by preventing excessive crosslink density that would cause brittleness
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 allows for effective curing at low temperatures, maintaining flexibility and adhesion, and can be used on both heat-sensitive and non-heat-sensitive substrates, even when highly pigmented, with enhanced performance on complex shapes.
Implementation Method 1
The invention provides a heat-curable powder coating composition comprising a crystalline polyester resin, an amorphous polyester resin and a peroxide
Implementation Method 2
a heat-curable powder coating composition comprising at least 7.5 wt% crystalline polyester resin, up to 92.5 wt% amorphous polyester resin, and 0.65 parts peroxide per hundred parts of resin
Implementation Method 3
the powder coating composition is dispersed in an air stream and passed through a corona discharge field where the particles acquire an electrostatic charge. The charged particles are attracted to and deposited on the grounded article to be coated
Implementation Method 4
the powder coating composition is dispersed in an air stream and passed through a corona discharge field where the particles acquire an electrostatic charge
Data Source
AI summary
Heat-curable powder coating compositions are provided which include i) at least one crystalline polyester resin present in an amount of at least 7.5 wt %; ii) at least one amorphous polyester resin present in an amount of at most 92.5 wt %; and iii) at least one peroxide present in an amount of at least 0.65 parts of peroxide in hundred parts of i)+ii) (pph), wherein the at least one crystalline polyester resin has 2-butenedioic acid ethylenic unsaturations and/or the at least one amorphous polyester resin has 2-butenedioic acid ethylenic unsaturations. The compositions may be cured to an acceptable degree at low temperature, e.g., 130° C. /20 minutes offering powder coatings that may exhibit enhanced flexibility and good adhesion. In addition, the compositions can suitably be used on heat- and/or non heat-sensitive substrates, even if the composition is highly pigmented.