Alkyd Coating Molecular Weight Distribution for Low VOC Brushability
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Solution Overview
Problem
Alkyd paints face challenges with high viscosity due to high molecular weight polymers, requiring large amounts of volatile organic solvents for application, leading to environmental pollution and poor drying properties when attempting to reduce VOC content.
Innovation Solution
An autoxidisable coating composition with a specific molecular weight distribution of alkyd resin and autoxidisable material, combined to achieve a shear-thinning viscosity and reduced VOC content, allowing for low brush resistance and improved drying properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If the amount of volatile organic solvent is reduced in alkyd paint, then environmental pollution is reduced and VOC content is lowered, but the viscosity of the paint increases making it difficult to apply by brush
Solution Approach 1:
The patent changes the molecular weight parameter of the alkyd resin from conventional high molecular weight to specifically controlled low molecular weight (Mw < 25,000, preferably < 15,000 gmol-1). This parameter change reduces the intrinsic viscosity of the resin, allowing the paint to maintain low viscosity and good brush applicability even with reduced volatile organic solvent content, thereby resolving the contradiction between low VOC and ease of application
Solution Approach 2:
The patent uses a composite approach by combining low molecular weight alkyd resin with specific pigments and additives to achieve the desired paint performance. The low molecular weight resin serves as the base, and complementary materials are added to provide necessary functional properties while maintaining low viscosity and good application characteristics despite reduced solvent content
2Ease of operation
If the average molecular weight of the alkyd resin is reduced, then the viscosity decreases improving brush applicability, but the drying rate becomes slow at temperatures below 30 °C
Solution Approach 1:
The patent optimizes the molecular weight parameter to a specific range (Mw < 25,000, preferably < 15,000 gmol-1) rather than simply reducing it. This controlled parameter change achieves the right balance where the resin is light enough for good brush applicability but heavy enough to maintain adequate drying rate at ambient temperatures, resolving the contradiction between applicability and drying performance
Solution Approach 2:
The patent applies different functional requirements to different aspects of the paint system. The low molecular weight resin provides good brush applicability, while the specific composition and formulation maintain adequate drying rate. The patent locally optimizes the resin molecular weight to satisfy the more critical applicability requirement while using formulation adjustments to maintain drying performance
3Ease of operation
If reactive diluents are added to lower viscosity, then the paint becomes easier to apply by brush, but the drying time increases and the film hardness is reduced
Solution Approach 1:
Instead of adding reactive diluents to lower viscosity, the patent changes the fundamental parameter of the alkyd resin molecular weight. This approach achieves the desired low viscosity and brush applicability without the negative side effects of reactive diluents, namely extended drying time and reduced film hardness, thereby resolving the contradiction between applicability and drying performance
Solution Approach 2:
The patent extracts and eliminates the need for reactive diluents by using low molecular weight alkyd resin as the base. This removes the harmful effects of reactive diluents (increased drying time, reduced hardness) while maintaining the beneficial effect of low viscosity and good brush applicability through the inherent properties of the low molecular weight resin
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 fast drying, minimal yellowing, and resistance to sagging with a high solids content and reduced VOC levels, meeting legislative requirements while maintaining paint quality.
Implementation Method 1
a binder consisting of components: (i) 20 to 70 wt. % of autoxidisable alkyd resin with an Mz of 80 000 gmol-1; (ii) 30 to 80 wt. % of autoxidisable material with a Mn of 2 000 to 4 000 gmol-1 and a Mw of 4 000 to 8 000 gmol-1
Implementation Method 2
The composition achieves fast drying, minimal yellowing, and resistance to sagging with a high solids content and reduced VOC levels
Data Source
Figure 1A~1B
Figure 2
Figure 3A~3B
AI summary
Autoxidisable coating composition comprising a binder consisting of components: 20 to 70 wt.% of autoxidisable alkyd resin with an Mz of 80 000 gmol -1 or more; and 30 to 80 wt.% of an autoxidisable material with an Mp in the range of 1 700 to 4 000 gmol -1; a polydispersity index (PDI) in the range of 1 to 2; and an oil length of 50 % or more; wherein (a) the molecular weight distribution of components (i) and (ii) in the binder is such that 1) at least 5 wt.% of the components (i) and (ii) taken together has a weight average molecular weight Mw of 100 000 gmol -1 or more; 2) at least 30 wt.% of components (i) and (ii) taken together has a weight average molecular weight Mw in the range of 2 000 to 4 000 gmol -1; and (b) the binder consisting of components (i) and (ii) has an Mp in the range of 1 700 to 4 500 gmol -1, said molecular weights Mw, Mz and Mp being determined by gel permeation chromatography in THF using polystyrene standards.