Aqueous Polymer Dispersion for Low-Temperature Glossy Coatings
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Solution Overview
Problem
Existing aqueous polymer dispersions used in glossy coatings require solvents and coalescent agents for film formation at low temperatures, compromising eco-friendliness and failing to maintain high scratch, block, and solvent resistance.
Innovation Solution
Aqueous polymer dispersion with a minimum film forming temperature (MFFT) below 5°C, achieved through radically initiated multi-stage emulsion polymerization, comprising two phases with specific monomer compositions and a water-soluble cross-linking component, ensuring high gloss, scratch, and solvent resistance without solvents or coalescent agents.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If traditional binders are used for glossy coatings, then good gloss formation, block resistance, scratch resistance, and solvent resistance are achieved, but solvents and coalescent agents are required which compromise eco-friendliness
Solution Approach 1:
The patent changes the chemical parameters of the polymer dispersion by incorporating specific monomer compositions with different glass transition temperatures and functional groups. The use of monomers with Tg below 0°C combined with carboxyl/carboxamide-containing monomers enables low-temperature film formation without solvents, directly resolving the contradiction between eco-friendliness and solvent content.
Solution Approach 2:
The invention creates a composite polymer system through multi-stage emulsion polymerization, combining soft polymer phases (low Tg) with hard polymer phases (high Tg) and cross-linking components. This composite structure achieves both low MFFT for solvent-free application and maintains the durability properties (scratch, block, solvent resistance) traditionally associated with solvent-based systems.
2Object-affected harmful factors
If aqueous dispersions are formulated without solvents and coalescent agents, then eco-regulations are met, but film formation at low temperatures is compromised
Solution Approach 1:
The patent modifies the thermal parameters of the dispersion system by selecting monomers with specific glass transition temperatures. The inclusion of monomers with Tg below 0°C in controlled amounts (1-30% by weight) directly lowers the MFFT to below 5°C, enabling low-temperature film formation without solvents while meeting emission regulations.
Solution Approach 2:
The invention applies local quality by creating a heterogeneous polymer system with distinct soft and hard phases. The soft polymer regions (low Tg) provide low-temperature film formation capability, while the hard polymer regions (high Tg) maintain film integrity and resistance properties, allowing the system to function at low temperatures without solvents.
3Strength
If multi-stage polymerization is used to improve elasticity, then good block resistance and scratch resistance are achieved, but minimum film forming temperature becomes too high
Solution Approach 1:
The patent optimizes the monomer composition parameters in each polymerization stage. By controlling the ratio of soft monomers (Tg below 0°C) to hard monomers (Tg above 65°C) and incorporating carboxyl/carboxamide-containing monomers (1-30% by weight), the system achieves low MFFT below 5°C while maintaining high scratch and block resistance through the multi-stage process.
Solution Approach 2:
The invention creates a dynamic polymer system where the multi-stage polymerization produces a heterogeneous structure with soft and hard phases that can adapt during film formation. The soft phases enable low-temperature flexibility while the hard phases provide strength, allowing the film to form at low temperatures without sacrificing resistance 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
Enables defect-free film formation at low temperatures while maintaining high gloss, scratch, and solvent resistance, meeting stringent eco-regulations without the need for solvents or coalescent agents.
Implementation Method 1
radically initiated multi-stage emulsion polymerization
Implementation Method 2
radically initiated multi-stage emulsion polymerization
Implementation Method 3
a water-soluble cross-linking component
Data Source
AI summary
An aqueous polymer dispersion is produced by multistage emulsion polymerization, in which a monomer composition I comprising 19 to 29 wt% hard monomers and 64 to 74 wt% soft monomers is polymerized to produce a first polymer phase and then a monomer composition II comprising 65 to 95 wt% hard monomers and 5 to 35 wt% soft monomers is polymerized to produce a second polymer phase. Monomer composition I also comprises from 1 to 5 wt% of at least one monomer selected from ethylenically unsaturated sulfonic acids, phosphonic acids, phosphoric acids, carboxylic acids, carboxylic amides, carboxylic anhydrides and mixtures thereof and 1 to 7.5 wt% of ethylenically unsaturated monomers containing keto groups. The weight ratio of monomer composition I to monomer composition II ranges from 50:50 to 65:35 and the polymer dispersion also contains a water-soluble cross-linking component selected from polyfunctional carboxylic hydrazides and/or polyfunctional amines.