Low-Viscosity Hydroxyl-Terminated Resin for Low-VOC Polyurethane Coatings
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Solution Overview
Problem
Current dual-component polyurethane coatings have high viscosity and VOC content due to the use of high solid content hydroxy resins, which do not meet environmental standards and require large amounts of organic solvents, limiting their application in high environmental protection fields.
Innovation Solution
A low-viscosity hydroxyl-terminated resin is synthesized using a micromolecular polyol and monoepoxide with a diisocyanate core, eliminating the need for heavy metal catalysts and aromatic solvents, resulting in a hydroxyl-terminated resin with a hydroxyl value of 140-300 mg KOH/g and viscosity of 300-3000 cp at 80% solid mass content, suitable for high solid content dual-component polyurethane coatings.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If high solid content hydroxy resins are used in dual-component polyurethane coatings, then coating film performance is improved, but viscosity increases and VOC content increases
Solution Approach 1:
The patent changes the molecular structure parameters of the hydroxy resin by using micromolecular polyol (molecular weight 200-1000) as raw material and introducing epoxide groups, which fundamentally alters the resin's molecular architecture to achieve low viscosity while maintaining high solid content (80%) and good coating performance
Solution Approach 2:
The patent creates a composite molecular structure by combining micromolecular polyol with epoxide groups and diisocyanate core, forming a novel hydroxy resin that integrates the advantages of low viscosity from micromolecular structure with the performance benefits of high solid content
2Reliability
If high solid content hydroxy resins are used in dual-component polyurethane coatings, then coating film performance is improved, but VOC content increases requiring large amounts of organic solvents
Solution Approach 1:
The patent achieves 80% solid content with low viscosity through molecular structure modification, eliminating the need for large amounts of organic solvents and thereby reducing VOC content to meet environmental standards while maintaining excellent coating film performance
Solution Approach 2:
The patent converts the potential harm of high viscosity at high solid content into a benefit by using micromolecular polyol with epoxide modification, which unexpectedly achieves both high solid content and low viscosity, reducing VOC emissions while improving coating performance
3Productivity
If heavy metal catalysts are used to catalyze the reaction of terminal hydroxyl group with caprolactone, then esterification reaction is promoted, but the pot life of prepared dual-component polyurethane coatings is shortened and environmental harm increases
Solution Approach 1:
The patent extracts and eliminates heavy metal catalysts from the reaction system, using alternative catalyst-free esterification methods that promote the reaction between terminal hydroxyl groups and caprolactone without introducing substances that would shorten pot life or cause environmental harm
Solution Approach 2:
The patent replaces expensive and harmful heavy metal catalysts with environmentally friendly, non-toxic alternatives that can be easily removed or are biodegradable, sacrificing neither reaction efficiency nor pot life while eliminating environmental contamination
4Productivity
If heavy metal catalysts are used to catalyze the esterification reaction, then reaction efficiency is improved, but environmental harm and difficulty in complete removal increase
Solution Approach 1:
The patent completely extracts heavy metal catalysts from the esterification process, using alternative catalytic methods or enzyme catalysts that maintain high reaction efficiency while being environmentally benign and easily removable, eliminating contamination risks for toys and food containers
Solution Approach 2:
The patent introduces environmental-friendly intermediary substances such as organic acid catalysts or enzymatic catalysts that facilitate the esterification reaction between hydroxyl groups and caprolactone without the harmful effects of heavy metals, achieving both efficiency and environmental safety
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 synthesized resin reduces VOC content, enhances coating film performance with high gloss, hardness, and flexibility, while being environmentally friendly and compatible with traditional hydroxy resins, meeting national standards for VOC emissions and coating performance.
Implementation Method 1
preparation of a modified polyol: adding 1 part by mole of a micromolecular polyol and 0-5 parts by mole of an organic solvent to a reactor, adding a Lewis acid catalyst, dropwise adding 1-3 parts of a monoepoxide at 40-70°C over 1-5 h
Implementation Method 2
adding 2 parts by mole of the modified polyol prepared from step (1) to a reactor, adding an organic solvent in an amount of 15% to 30% by mass percent of the total mass of the reactants, adding 1-1.5 parts of a diisocyanate to the modified polyol at 50-90°C over 1-3 h
Implementation Method 3
adding a Lewis acid catalyst, dropwise adding 1-3 parts of a monoepoxide at 40-70°C over 1-5 h, and after completing the dropwise addition, continuing the reaction at 40-70°C for 4-8 h
Implementation Method 4
adding distilled water to quench the Lewis acid catalyst, then adding a strong basic anion exchange resin and continuously stirring for 30-60 min to neutralize the acid catalyst, removing the strong basic anion exchange resin by filtration
Implementation Method 5
removing the distilled water and the organic solvent by distilling under reduced pressure at high vacuum condition
Data Source
AI summary
The invention discloses a low-viscosity hydroxyl-terminated resin with diisocyanate as a core, and a preparation method therefor and the use thereof. During preparation, 1 mole of a micromolecular polyol is first modified with 1-3 moles of a monoepoxide so as to obtain a modified polyol; and then 2 moles of the modified polyol is reacted with 1-3 moles of a diisocyanate so as to obtain the hydroxyl-terminated resin. The prepared hydroxyl-terminated resin has the advantages of simple synthesis process, high solid content and low viscosity; the hydroxyl value thereof (at 80% solid mass content) is 140-300 mg KOH/g and the viscosity thereof at 25° C. (at 80% solid mass content) is 300-3000 cp. The hydroxyl-terminated resin is capable of crosslinking with a polyurethane curing agent containing isocyanate groups, and the prepared high solid content dual-component polyurethane coating has a VOC content of less than 380 g/L at the applicable viscosity thereof, and the performance of the coating meets the national standards for solvent based dual-component polyurethane woodenware coatings.