Solvent-Free Polyurethane Coating Sag Resistance
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Solution Overview
Problem
Conventional polyurethane waterproof coatings face issues with high viscosity, slow drying, and sagging on inclined surfaces due to the use of solvents, which complicates construction in special environments and increases costs.
Innovation Solution
A solvent-free, quick-drying sag-resistant polyurethane waterproof coating is developed using a polyurethane prepolymer, plasticizer, dispersing agent, filler, dehydrating agent, catalyst, and defoaming agent, with an oxazolidine reactive diluent, and a specific catalyst composition to reduce viscosity and enhance thixotropic properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If solvents are added to reduce viscosity, then the coating becomes easier to apply, but the drying time increases and environmental pollution occurs
Solution Approach 1:
The patent removes solvents from the coating formulation entirely, extracting the harmful component that caused slow drying and pollution while maintaining coating applicability through alternative means (prepolymer structure and catalyst system)
Solution Approach 2:
The patent changes the chemical parameters of the system by using specific prepolymer structures and catalyst combinations to achieve low viscosity without solvents, fundamentally altering how the coating achieves its application properties
2Ease of operation
If solvents are added to reduce viscosity, then the coating becomes easier to apply, but air pollution and unpleasant smell occur
Solution Approach 1:
The patent extracts and eliminates solvents from the formulation, removing the source of air pollution and unpleasant smell while preserving the coating's applicability through prepolymer and catalyst optimization
3Reliability
If conventional polyurethane coating is used on facades or slope surfaces, then the coating provides waterproofing, but the coating flows and creates uneven thickness
Solution Approach 1:
The patent changes the rheological parameters of the coating through catalyst selection and prepolymer structure, achieving sag resistance that prevents flowing on inclined surfaces while maintaining uniform thickness and waterproofing function
Solution Approach 2:
The patent creates a dynamic viscosity profile where the coating remains workable during application but quickly develops sag resistance to prevent flowing, achieving both applicability and thickness uniformity
4Reliability
If multiple coating layers are applied to achieve required thickness, then the coating provides adequate waterproofing, but construction efficiency decreases and cost increases
Solution Approach 1:
The patent changes the coating's rheological and drying parameters to enable single-layer application at required thickness, eliminating the need for multiple coats and thereby improving construction efficiency while maintaining waterproofing reliability
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 coating achieves faster film formation, improved sag resistance, and excellent physical and mechanical properties, making it suitable for construction in rainy conditions and on slopes without the drawbacks of solvent-based systems.
Implementation Method 1
an oxazolidine reactive diluent that accounts for 1-10% by mass of the raw materials
Implementation Method 2
a catalyst and a defoaming agent, the raw materials further comprise an oxazolidine reactive diluent that accounts for 1-10% by mass of the raw materials, the catalyst is composed of pentamethyl dipropylidene triamine, tetramethylethylenediamine, and 1,8-diazacyclo[5,4,0]undecene
Implementation Method 3
enhance thixotropic properties
Data Source
AI summary
A quick-drying solvent-free sag-resistant polyurethane waterproof coating and preparation method therefor, raw materials therefor comprising a polyurethane prepolymer, a plasticizer, a dispersant, a filler, a dehydrant, a catalyst, a defoamant, and an oxazolidine reactive diluent. The catalyst is composed of pentamethyl dipropylene triamine, tetramethylethylenediamine, and 1,8-diazabicyclo[5.4.0]undecene. Raw materials of the polyurethane prepolymer comprise a polyether diol, a polyether triol, an isocyanate, and a chain extender. The prepolymer is prepared by means of the following method: 1) measuring out the raw materials for the polyurethane prepolymer, and reacting the polyether diol with the isocyanate until reaction is complete; 2) then adding the polyether triol for reaction until reaction is complete; 3) then adding the chain extender for reaction, completing preparation. The waterproof coating preparation method is: i) preparing the polyurethane prepolymer; ii) mixing the prepared polyurethane prepolymer with the rest of the raw materials for the waterproof coating to obtain the final product. The present waterproof coating features such advantages as exceptional film-forming speed and sag resistance, and low viscosity.