Aqueous Polymer Composition for High Elongation and Blocking Resistance
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Solution Overview
Problem
Existing aqueous polymer compositions for coatings, particularly on wooden substrates, face challenges in achieving high elongation at break and impact resistance while maintaining blocking properties, especially when pigmented, due to the trade-off between toughness and tackiness, and are limited by the use of pure vinyl systems or urethane-vinyl combinations.
Innovation Solution
An aqueous polymer composition comprising 5 to 30 wt.% polyurethane and 70 to 95 wt.% vinyl polymer, with specific weight ratios and molecular weights, including a blend of soft and hard vinyl polymers, is used to achieve high elongation at break and toughness without losing blocking properties, suitable for both clear and pigmented applications.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a polymer with low Tg is used to achieve high elongation at break, then elongation at break is improved, but blocking resistance deteriorates due to tacky film formation
Solution Approach 1:
The invention changes the chemical composition parameters of the polymer system by incorporating acid functional groups and controlling the ratio of soft to hard vinyl polymers, which modifies the film's surface properties to reduce tackiness while preserving bulk elasticity for high elongation
Solution Approach 2:
The invention creates a composite polymer system combining soft vinyl polymer (for elasticity), hard vinyl polymer (for structure), and acid functional groups (for surface properties), achieving both high elongation at break and good blocking resistance through synergistic material combination
2Reliability
If the Tg is increased to improve blocking resistance and reduce tackiness, then blocking resistance is improved, but toughness and elongation are reduced
Solution Approach 1:
The invention applies local quality by differentiating between surface properties and bulk properties: acid functional groups modify the surface to reduce tackiness and improve blocking, while the soft vinyl polymer matrix maintains bulk elasticity and toughness for high elongation
3Ease of manufacture
If pure vinyl systems are used to maintain simplicity, then ease of manufacture is improved, but impact resistance and elongation at break are insufficient especially when pigmented
Solution Approach 1:
The invention creates a composite binder system combining multiple vinyl polymers with different Tg values and acid functional groups, achieving superior impact resistance and elongation at break while maintaining compatibility with pigments and aqueous formulation
Data Source
AI summary
An aqueous polymer composition which when in the form of a film shows excellent elongation at break comprising (i) 5 to 30 wt. % of polyurethane where the acid value of the polyurethane is between 3 to 40 mg KOH/g; (ii) 70 to 95 wt. % of vinyl polymer comprising 20 to 90 wt. % of vinyl polymer with Tg<20° C.; 10 to 80 wt. % of vinyl polymer with Tg≥20° C.; where at least one of the vinyl polymers contains acid functional groups with acid value in the range of from 15 and 240 mg KOH/g.