Alkali-Soluble Acrylate in Aqueous Coating Composition
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Solution Overview
Problem
Existing water-borne coating compositions based on oxidatively drying polymers, such as alkyd-acrylic hybrids, face challenges in achieving fast drying times and meeting performance standards for solvent-based coatings, particularly in terms of drying speed, open time, flow, and substrate wetting.
Innovation Solution
Incorporating alkali-soluble acrylates with an acid number of at least 15 mg/KOH and a weight average molecular weight of 200,000 g/mole or lower into the coating composition, which are non-crosslinking and used in amounts of 1.5% or more by total weight, enhances the performance by improving open time, flow, and substrate wetting, allowing for the formulation of high-solid aqueous paints with low VOC content.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If water-borne coating compositions are used to reduce VOC content, then health and safety benefits are achieved, but drying times become unacceptably long
Solution Approach 1:
The invention uses a composite binder system combining water-borne alkyd resin with emulsified acrylic polymer. The alkyd provides oxidatively drying properties for reduced VOC content, while the acrylic component contributes to film formation and performance. This composite approach allows the coating to achieve both low VOC content and acceptable drying times by leveraging the complementary properties of each polymer system.
2Loss of time
If high molecular weight acrylic polymers are added to reduce drying time, then drying speed improves, but open time and flow properties deteriorate
Solution Approach 1:
The invention carefully controls the molecular weight of the acrylic polymer (20,000-500,000 g/mol) and its composition in the hybrid system. By optimizing these parameters, the coating achieves a balance where the acrylic contributes to faster drying through coalescence assistance, while the overall formulation maintains sufficient open time and flow properties for proper application and defect correction.
3Ease of operation
If alkali-soluble acrylates are used to improve open time and flow, then substrate wetting and gloss potential improve, but the formulation complexity increases
Solution Approach 1:
The invention specifies alkali-soluble acrylates with acid numbers of at least 15 mg/KOH and molecular weights of 200,000 g/mol or lower. These parameter specifications allow the acrylate to provide improved open time, flow, and substrate wetting while maintaining compatibility with the oxidatively drying resin system. The controlled parameters ensure predictable performance without requiring overly complex formulation adjustments.
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 use of alkali-soluble acrylates results in improved gloss potential, hiding power, and reduced VOC content, achieving drying times comparable to solvent-borne systems while maintaining high solid content and preventing defects like de-wetting and cratering.
Implementation Method 1
improved open time, flow and substrate wetting
Implementation Method 2
crosslink on exposure to oxygen from air by virtue of containing unsaturated fatty acid residues. Alkyds are typical examples of such polymers. Alkyd paints cure under the influence of oxygen, via oxidative crosslinking of unsaturated fatty acid building blocks.
Implementation Method 3
The acrylate can be obtained by the free radical addition polymerisation of at least one olefinically unsaturated monomer selected from esters of acrylic acid and methacrylic acid
Data Source
AI summary
Aqueous coating composition comprising an oxidatively drying resin and an alkali-soluble acrylate having an acid number of at least 15 mg KOH/g in a content of at least 1.5 wt. %. Optionally a second acrylate can also be used, such as a polyurethane acrylate.