Curable Coated Abrasive Make Layer Resists Oxygen Inhibition
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Solution Overview
Problem
Existing coated abrasive articles face challenges with oxygen inhibition during free-radical polymerization, leading to undercured surfaces and degraded abrading performance.
Innovation Solution
A curable composition comprising 45-55% epoxy resin, 6-12% trifunctional (meth)acrylate, 35-45% polythiol, 0-10% dicyandiamide, 0.1-2% free-radical photoinitiator, 0.5-1% 2-alkylimidazole, and 0-5% phenolic resin is used to create a make layer in coated abrasive articles, which is then partially cured and embedded with abrasive particles before a size layer is applied.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If free-radical polymerization is used to cure the make layer precursor, then the make layer can be cured quickly, but oxygen inhibition occurs leading to undercured surface and degraded abrading performance
Solution Approach 1:
The patent uses a composite curing system combining cationic photopolymerization (epoxy resin + photoinitiator) and free-radical polymerization ((meth)acrylate + photoinitiator). The cationic system is not inhibited by oxygen and provides reliable bulk curing, while the free-radical system contributes to surface curing and crosslinking. This composite approach resolves the contradiction by leveraging the strengths of both polymerization mechanisms.
Solution Approach 2:
The patent modifies the chemical composition parameters of the make layer precursor by incorporating specific ratios of epoxy resin (45-55 wt%), (meth)acrylate (6-12 wt%), and photoinitiators (0.1-2 wt%). These parameter changes enable the dual polymerization mechanism to function effectively, allowing fast curing while maintaining surface quality and abrading performance despite oxygen presence.
2Manufacturing precision
If UV irradiation is applied to the make layer precursor before abrasive particle coating, then mineral penetration is well controlled and abrasive particle orientation is improved, but oxygen inhibition causes undercured surface
Solution Approach 1:
The dual polymerization system allows the make layer to achieve proper crosslinking and surface cure completeness (reliability) while still enabling controlled mineral penetration and abrasive particle orientation (precision). The cationic photopolymerization provides the structural framework that supports particle orientation, while the free-radical component ensures surface curing despite oxygen inhibition.
Solution Approach 2:
The patent creates different curing characteristics in different regions of the make layer. The bulk undergoes cationic polymerization that is not oxygen-inhibited and provides structural integrity for particle orientation, while the surface benefits from free-radical polymerization that contributes to crosslinking. This local differentiation of curing mechanisms resolves the contradiction between precision and reliability.
3Reliability
If phenolic resin is used as thermal cured make layer precursor, then oxygen inhibition is avoided, but abrasive particle orientation control is degraded
Solution Approach 1:
The patent replaces pure thermal-cured phenolic resin with a composite photopolymerizable system containing epoxy resin, (meth)acrylate, and dual photoinitiators. This composite system maintains resistance to oxygen inhibition through the cationic polymerization mechanism while enabling UV irradiation to control abrasive particle orientation during the coating process, thus resolving both reliability and precision requirements.
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
This approach improves the orientation of abrasive particles and provides good resistance to surface oxygen inhibition, resulting in enhanced abrading performance.
Implementation Method 1
UV irradiation of the make layer precursor prior to abrasive particle coating can result in a make layer precursor that is partially gelled
Implementation Method 2
Abrasive particles are then at least partially embedded into the make layer precursor (e.g., via electrostatic coating)
Data Source
AI summary
A curable composition comprises from 45 to 55 percent by weight of epoxy resin preparable by reaction of epichlorohydrin with at least one of bisphenol A or bisphenol F, from 6 to 12 percent by weight of an at least trifunctional (meth)acrylate, from 35 to 45 percent by weight of a polythiol, 0 to 10 percent by weight of dicyandiamide, 0.1 to 2 percent free-radical photoinitiator, 0.5 to 1 percent by weight of a 2-alkylimidazole, and 0 to 5 percent of phenolic resin, based on the total weight of components a) to g). The curable composition is useful as make layer precursor for preparing coated abrasive articles. Methods of making and using the coated abrasive articles are also disclosed.