The patent's assignee for patent application serial number 583255 is
News editors obtained the following quote from the background information supplied by the inventors: "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.
"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. by roller, trowel, spray, etc.), and 5) infusion (e.g. for porous structure consolidation, preforms for composites, etc.).
"Lower molecular weight, lower viscosity compounds, termed 'diluents,' are commonly added to epoxy formulations, commonly on the epoxy resin side of two-part formulations, for viscosity reduction. Diluents that polymerize into the system, known as reactive diluents, are preferred over the use of non-reactive diluents, since mechanical and thermal property reductions in the cured resin are less severe for reactive diluents. Property reductions become greater as diluent levels are increased, thus there is often a trade-off between achieving the desired low viscosity and maintaining the required properties in the cured resin. For this reason, decreasing viscosity while minimizing the level of diluent used is an ongoing goal as formulators simultaneously search for diluents having either greater efficiency or show lower property reduction.
"One relatively simple viscosity reduction method is heating the epoxy resin and hardener. 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. Thus, ways of decreasing the peak exotherm temperature of epoxy formulations are of benefit in may circumstances.
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