Core-shell polymer dispersion for low VOC coating integrity
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Solution Overview
Problem
Existing aqueous coating compositions face challenges in achieving improved film integrity, particularly at low or no VOC content, and require enhanced scrub resistance while minimizing energy expenditure.
Innovation Solution
An aqueous dispersion of polymeric particles comprising 5-80% of a first polymer and 20-95% of a second polymer, where the second polymer is formed by polymerization at temperatures between 5°C to 65°C, encapsulating the first polymer, and is used to create a coating with improved film formation and integrity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional aqueous coating compositions are used to achieve film formation, then coating coverage is provided, but film integrity and scrub resistance are insufficient, particularly at low VOC levels
Solution Approach 1:
The invention segments the polymer structure into core-shell architecture, where the core polymer provides film formation and the shell polymer provides durability and scrub resistance. This segmentation allows each component to specialize in specific functions, achieving superior film integrity without requiring complex manufacturing processes.
Solution Approach 2:
The invention uses composite polymer materials with distinct core and shell phases, where the core polymer (first polymer) and shell polymer (second polymer) have different Tg ranges and properties. This composite structure combines the advantages of both polymers to achieve both film formation and durability.
2Reliability
If polymer mass is increased to improve film integrity, then coating durability improves, but energy expenditure and material usage increase
Solution Approach 1:
The invention uses a thin shell polymer layer (20-95% by weight of the polymeric particles) that encapsulates the core polymer. This thin shell provides sufficient scrub resistance and film integrity without requiring excessive polymer mass, thereby reducing energy expenditure during film formation and material usage.
Solution Approach 2:
The invention optimizes the Tg parameters of both core and shell polymers, where the shell polymer has Tg of -40°C to 30°C to provide flexibility and adhesion at low temperatures, while the core polymer has higher Tg for structural integrity. This parameter optimization achieves high scrub resistance with minimal polymer mass.
3Productivity
If polymerization temperature is increased to improve polymerization efficiency, then production speed increases, but film formation capability at low temperatures decreases
Solution Approach 1:
The invention applies local quality by creating distinct thermal zones within the polymeric particles - the core polymer is formed at higher temperatures (65-90°C) for efficient polymerization, while the shell polymer is formed at lower temperatures (5-65°C) to ensure proper film formation capabilities. This local temperature differentiation allows both high productivity and good film formation.
Solution Approach 2:
The invention uses dynamic temperature control during the polymerization process, where the temperature is adjusted in stages: initially at 65-90°C for core polymer formation, then reduced to 5-65°C for shell polymer formation. This dynamic temperature adjustment optimizes both polymerization efficiency and film formation properties.
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 solution results in coatings with superior film integrity and scrub resistance, achieving these results while reducing the mass and energy required for film formation, particularly at low VOC levels.
Implementation Method 1
at least 90 weight % of the second polymer is formed by polymerization at a temperature of from 5° C. to 65° C.
Data Source
AI summary
An aqueous dispersion of polymeric particles, the particles including: from 5% to 80% by weight, based on the weight of the polymeric particles, of a first polymer including at least one copolymerized ethylenically unsaturated monomer; and, substantially encapsulating the first polymer, from 20% to 95% by weight, based on the weight of the polymeric particles, of a second polymer including at least one copolymerized ethylenically unsaturated monomer, the second polymer having a Tg of from −40° C. to 30° C., wherein at least 90 weight % of the second polymer is formed by polymerization at a temperature of from 5° C. to 65° C. is provided. The invention also relates to a process for forming the aqueous dispersion of polymeric particles and an aqueous coating composition including the aqueous dispersion of polymer particles, a method for providing a coated substrate, and the coated substrate so provided.