Aqueous Polymer Composition Yellowing Reduction
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Aqueous polymer compositions containing acetoacetyl group-containing acrylic polymers used in coatings tend to discolor over time when exposed to sunlight, leading to yellowing issues despite efforts to reduce this problem in existing methods.
Innovation Solution
A method for producing a stable aqueous polymer composition through emulsion polymerization of a monomer composition comprising acetoacetyl functional monomers, ethylenically unsaturated monomers with functional groups, and optional ethylenically unsaturated acid monomers, with pH adjustment using ammonia or primary amines to achieve a stable pH range, resulting in reduced yellowing of dry films.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If ammonia or organic amine is added to neutralize acrylic polymers to pH 8.0-10.0, then the desired coating properties (high gloss, block resistance, durability, adhesion) are achieved, but discoloration (yellowness) occurs over time when exposed to sunlight
Solution Approach 1:
The patent changes the pH parameter from the conventional 8.0-10.0 range to a lower range of 5.0-7.0, and modifies the amine structure by selecting cyclic secondary amines with specific ring sizes (5-7 membered rings). This parameter change resolves the contradiction by maintaining coating durability while significantly reducing yellowing, as the lower pH and specific amine structure prevent the discoloration that occurs with conventional high pH neutralization
Solution Approach 2:
The patent applies local quality by selecting specific types of amines (cyclic secondary amines with particular structural characteristics) rather than using any amine. The specific local structural features of these amines (ring size, substitution patterns) provide the desired neutralization function while minimizing yellowing, creating a localized solution that addresses both requirements simultaneously
2Stability of the object's composition
If conventional aqueous polymer compositions are used to maintain storage stability, then the composition remains stable during storage, but yellowing occurs after heat aging and sunlight exposure
Solution Approach 1:
The patent changes the pH parameter to 5.0-7.0 and selects specific cyclic secondary amines, which maintains storage stability while preventing yellowing after heat aging. The lower pH and specific amine structure create a more stable system that resists both hydrolysis during storage and discoloration during heat aging, resolving the contradiction between storage stability and resistance to yellowing
Solution Approach 2:
The patent uses cyclic secondary amines as intermediary substances that mediate between the acrylic polymer and the environment. These amines provide the necessary neutralization function while their specific structural properties act as a protective intermediary that prevents yellowing during storage and heat aging, rather than allowing direct interaction that would cause discoloration
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 method provides a storage-stable aqueous polymer composition with less than 12% hydrolysis of acetoacetyl groups and dry films with Δb value less than 1.0 after heat aging, effectively reducing yellowing and maintaining film properties.
Implementation Method 1
ammonia or an organic amine is typically added to neutralize the acrylic polymers to a pH of about 8.0-10.0
Implementation Method 2
emulsion polymerization of a monomer composition, optionally in the presence of ammonia, a primary amine, or mixtures thereof, to give an emulsion polymer
Implementation Method 3
the aqueous polymer composition is storage stable, which shows a hydrolysis ratio of acetoacetyl groups less than 12% after heatage at 50° C. for 2 weeks
Data Source
AI summary
A method of producing an aqueous polymer composition and a method of reducing yellowing of an aqueous polymer composition and a coating made therefrom.