Cycloaliphatic carbonates as reactive diluents in epoxy resins

Abstract

Embodiments of the present invention disclose a method for limiting peak exotherm temperatures in epoxy systems comprising the step of: combining an amine hardener, an epoxy and a diluent to form an epoxy system, wherein the diluent is selected from the group consisting of: ethylene carbonate, propylene carbonate, butylene carbonate, delta-valerolactam, delta-valerolactone, gamma valerolactone, butyrolactam, beta butyrolactone, gamma butyrolactone, and combinations thereof.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS[0001]This application claims priority to U.S. Pat. App. Ser. No. 61 / 312,924, filed Mar. 11, 2010, which is incorporated herein by reference.STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT[0002]Not applicable.BACKGROUND OF THE INVENTION[0003]1. Field of the Invention[0004]The present invention relates generally to methods of producing epoxy resin systems and more particularly to the use of cycloaliphatic carbonates as reactive diluents in epoxy resin systems.[0005]2. Background of the Invention[0006]Formulators of epoxy resin systems have long used various means for reducing the viscosity of formulations in order to effectively utilize the performance benefits ascribable to cured epoxy resins, relative to other available chemistries. For many epoxy resin applications, low viscosities provide desired benefits such as improvements in 1) mixing, 2) wetting (of surfaces, fillers, fibers, etc), 3) crack injection, 4) application (e.g...

AI Technical Summary

Benefits of technology

This patent aims to discover a diluent that can reduce the temperature during the polymerization reaction of epoxy resin. By doing so, it becomes possible to increase the temperature of the reactants before mixing them. This reduces the need for diluents and allows for higher temperatures, which improves the properties of the cured resin system.

Problems solved by technology

This method is of limited utility in some cases since the heat increases the polymerization rate and unacceptably shortens the available processing time.

Also, the higher initial temperatures of the reactants lead to higher exotherm temperatures that may exceed allowable limits.

Too high of an exotherm temperature can lead to a variety of problems.

In such applications where the mass of the reactive epoxy mixtures is great enough that the heat of reaction raises the temperature excessively, problems can arise from a variety of causes such as 1) thermal expansion of the components, 2) expansion of entrained gases, 3) volatilization of lower boiling components, 4) thermal degradation of the material (particularly in the thickest sections which become hottest), 5) sagging, 6) cycle time lengthening (e.g. due to needed cooling to attain rigidity for de-molding), 7) added thermal load in buildings where manufacturing is being done, etc.

For certain applications several of these means of exotherm reduction are unacceptable.

For instance, pre-cooling of components may raise viscosity and prevent good mixing, wetting, mold-filling, etc.

Phase change materials may be expensive, chemically reactive, soluble once liquid, change at non-optimum temperatures, etc.

Direct cooling is poorly effective in the thickest regions and may create additional residual stresses due to thermal expansion mismatches between components.

Components having lower reactivity are also typically slower curing and require additional heat for full polymerization, thus they create a need for longer cycle times or higher bake temperatures.

Additionally, though higher filler levels decrease exotherm temperatures, there are practical upper limits of use level, based on both processing and performance, which cannot be exceeded.

Of these, low molecular weight epoxies and acrylates are known to have adverse health effects on some people exposed to them.

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