Self-crosslinkable Polyurethane-vinyl Polymer for Coatings
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Solution Overview
Problem
Current polyurethane-based polymers used in coatings face challenges such as high cost, poor weatherability, and poor water and alkali resistance, necessitating an improvement in their properties for broader industrial applications.
Innovation Solution
A self-crosslinkable polymer with a molar equivalent ratio of hydrazide to carbonyl functional groups ranging from 1:2 to 2:1, capable of undergoing self-crosslinking reactions to form a network structure, is developed, which is incorporated into an aqueous dispersion and used in coating compositions for enhanced properties like wear resistance and strength.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If polyurethane polymer is modified with vinyl polymers through free radical polymerization, then the coating properties such as wear resistance and strength are improved, but the manufacturing complexity and cost increase
Solution Approach 1:
The polymer is designed with self-crosslinking capability through incorporating both carbonyl groups (from vinyl monomers like acrylonitrile) and hydrazide groups (from the polyurethane backbone) into the same molecular chain. This allows the polymer to automatically form crosslinked networks during film formation without requiring external crosslinking agents or complex multi-step processes, thereby improving coating strength while simplifying manufacturing
Solution Approach 2:
The invention creates a hybrid polyurethane-vinyl polymer combining the adhesive properties of polyurethane with the mechanical strength and chemical resistance of vinyl polymers. The molecular structure integrates segments from both polymer types, enabling the coating to exhibit enhanced wear resistance and strength while maintaining good adhesion to substrates
2Stability of the object's composition
If conventional polyurethane polymer is used, then good adhesion to substrates is achieved, but weatherability and water resistance are poor
Solution Approach 1:
The polymer structure is modified by changing the chemical composition parameters - incorporating vinyl monomers with nitrile groups (acrylonitrile) and carboxylic acid groups that enhance chemical resistance and weatherability. The self-crosslinking capability further modifies the network structure parameters, creating a more dense and stable coating matrix that resists water and weathering while preserving adhesion
Solution Approach 2:
The self-crosslinking mechanism acts as an intermediary process that connects the polyurethane segments (providing adhesion) with the vinyl segments (providing weatherability). The crosslinks formed between carbonyl and hydrazide groups create a bridging network that integrates the beneficial properties of both polymer types while protecting the adhesive polyurethane segments from environmental degradation
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 self-crosslinkable polymer improves the coating's wear resistance and strength by forming a network structure during or after film formation, addressing the limitations of traditional polyurethane-based polymers and providing improved performance on various substrates.
Implementation Method 1
The self-crosslinkable polymer comprises a polyurethane backbone and at least one pendant group capable of undergoing condensation reaction with an isocyanate group of the polyurethane backbone to introduce a self-crosslinking capability
Implementation Method 2
Conventionally, process for the modification comprises free radical polymerization of vinyl monomers with a urethane prepolymer containing ethylenically unsaturated functionality to form a urethane-vinyl hybrid polymer
Data Source
AI summary
This disclosure is directed to a self-crosslinkable polymer and and an aqueous dispersion comprising particles of the polymer. The self-crosslinkable polymer has a molecular skeleton containing urethane linkages, and a hydrazide functional group and a carbonyl functional group capable of reacting with the hydrazide functional group chemically bonded to the molecular skeleton.