Curable Backing Composition for Flat, Heat-Stable Coated Abrasives
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Solution Overview
Problem
Conventional backing treatments for coated abrasive articles suffer from issues such as separation from the backing due to frictional heating, emission of volatiles like water and formaldehyde, and surface oxygen inhibition during free-radical polymerization, leading to degraded abrading performance and backing curling.
Innovation Solution
A curable composition comprising epoxy resin, trifunctional (meth)acrylate, polythiol, dicyandiamide, free-radical photoinitiator, 2-alkylimidazole, and optional phenolic resin, applied as a backing treatment, providing excellent adhesion and resistance to surface oxygen inhibition.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If conventional backing treatments (resole phenolic, phenolic/latex blends, urea-formaldehyde, melamine formaldehyde resins) are used, then good adhesion to make layers is achieved, but volatiles (water, phenol, formaldehyde) are emitted causing porosity and curing interference
Solution Approach 1:
The patent changes the chemical composition parameters of the backing treatment by using epoxy resin combined with polythiol and (meth)acrylate, replacing conventional resins that emit volatiles. This parameter change eliminates volatile emission while maintaining adhesion strength through the reactive functional groups that form strong chemical bonds with the make layer.
Solution Approach 2:
The patent creates a composite backing treatment system combining epoxy resin, polythiol, and (meth)acrylate components. This composite material provides both excellent adhesion through the epoxy-polythiol reaction and resistance to oxygen inhibition through the (meth)acrylate free-radical polymerization, while avoiding volatile emission inherent in conventional single-resin systems.
2Reliability
If free-radically polymerizable compositions are used in backing treatments, then curing is achieved, but surface oxygen inhibition occurs leading to degraded abrading performance
Solution Approach 1:
The patent uses a composite formulation combining epoxy resin with polythiol and (meth)acrylate. The (meth)acrylate component undergoes free-radical polymerization that is less susceptible to oxygen inhibition compared to conventional free-radically polymerizable compositions, while the epoxy-polythiol reaction provides additional crosslinking that ensures complete curing and eliminates the surface inhibition problem.
Solution Approach 2:
The patent modifies the polymerization mechanism by incorporating (meth)acrylate groups that polymerize via free-radical mechanism initiated by photoinitiators. This parameter change in the curing mechanism provides resistance to oxygen inhibition while maintaining reliable curing, unlike conventional free-radically polymerizable compositions that are highly susceptible to oxygen interference.
3Reliability
If free-radically polymerizable compositions are used in backing treatments, then curing is achieved, but significant shrinkage occurs leading to stress build-up and backing curling
Solution Approach 1:
The patent employs a composite system where epoxy resin reacts with polythiol to form a crosslinked network with minimal shrinkage, complemented by (meth)acrylate polymerization. This composite approach balances the curing requirements with shape stability, as the epoxy-polythiol reaction provides structural integrity with lower shrinkage compared to purely free-radical polymerizing systems.
Solution Approach 2:
The patent changes the polymerization parameters by using epoxy-polythiol crosslinking in combination with (meth)acrylate polymerization. This parameter change reduces the overall shrinkage during curing compared to conventional free-radically polymerizable compositions, thereby preventing stress build-up and backing curling while ensuring complete curing.
4Strength
If conventional backing treatments are used, then adhesion to make layers is achieved, but frictional heating causes abrasive layer separation during use
Solution Approach 1:
The patent changes the chemical composition to epoxy resin with polythiol and (meth)acrylate, which form a more thermally stable crosslinked network. This parameter change increases the bond stability under frictional heating conditions, preventing abrasive layer separation while maintaining strong adhesion to the make layer.
Solution Approach 2:
The patent creates a composite backing treatment that combines epoxy-polythiol crosslinking with (meth)acrylate polymerization. This composite material provides superior thermal stability and bond strength compared to conventional treatments, ensuring the adhesive bond remains stable under the thermal and mechanical stresses of frictional heating during abrasive use.
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 solution ensures excellent backing flatness and adhesion to make layers, preventing separation and curling, while maintaining effective abrading performance.
Implementation Method 1
Free-radically polymerizable compositions have been included in backing treatments, which can be polymerized using electromagnetic radiation (e.g., ultraviolet (UV) and/or visible light)
Implementation Method 2
a curable composition comprising, based on the total weight of components a) through g): a) from 45 to 80 percent by weight of epoxy resin preparable by reaction of epichlorohydrin with at least one of bisphenol A or bisphenol F; c) from 5 to 45 percent by weight of a polythiol
Implementation Method 3
f) 0.5 to 1 percent by weight of 2-alkylimidazole
Data Source
AI summary
A curable composition comprises from 45 to 80 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 5 to 45 percent by weight of a polythiol, from 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 from 0 to 5 percent of phenolic resin. The curable composition is useful for preparing treated backings that can be incorporated in coated abrasive articles and used to abrade a workpiece.