Heat-curable eproxy resin composition

Abstract

The invention relates to compositions containing at least one epoxy resin A with on average more than one epoxy group per molecule; at least one epoxy adduct B with on average one epoxy group per molecule; at least one thixotropic agent C, based on a urea derivative in a non-diffusing support material; and at least one curing agent D for epoxy resins, which is activated by an increased temperature. According to preferred embodiments, the invention also relates to compositions containing at least one core-shell polymer E and / or filler F and / or reactive diluent G. The invention also relates to the use of said compositions as a single-component adhesive and to a method for producing the compositions. The invention further relates to the use of the thixotropic agent C, based on a urea derivative in a non-diffusing support material as an agent for increasing the impact resistance.

Description

TECHNICAL FIELD [0001] The invention relates to heat-cured compositions which are distinguished by both high impact strength and a high glass transition temperature at the same time, and which in particular can be used as one-component adhesives. PRIOR ART [0002] High-quality adhesives are increasingly used in manufacture of both vehicles and mounted parts or machinery and equipment, either instead of or in combination with conventional joining methods such as riveting and punching or welding. This results in advantages and new options for manufacturing, for example manufacture of composite and hybrid materials, or greater freedom in designing components. For use in vehicle manufacture, adhesives must have good adhesion to all substrates used, in particular electrogalvanized, hot-dip galvanized, and subsequently phosphatized sheet steel, lubricated sheet steel, as well as various types of aluminum. These good adhesion properties must also be maintained in particular after aging (alt...

AI Technical Summary

Problems solved by technology

When the bond is subjected to impact loading, however, conventional epoxy adhesives are usually too brittle; and so under crash conditions, when both high tensile and high peel stresses occur, they are far from able to meet the requirements of the automobile industry in particular.

They also have insufficient strengths at high temperatures and in particular at low temperatures.

This results in formation of highly elastic domains in the hard brittle epoxy matrix, which increase the impact strength.

A considerable drawback of the prior art is generally that by increasing the impact strength, the glass transition temperature and / or the strength of the adhesive is reduced; or that by raising the glass transition temperature, the strength is indeed increased as a rule but the impact strength, as well as the adhesion and especially the peel strength, is reduced.

This situation severely limits use as a structural bodyshell adhesive, in particular because extremely high demands are made on a crash-resistant adhesive.

Additionally, the use of liquid rubbers is quite disadvantageous, since it means that the extent of phase separation and thus also the improvement of impact strength depends very much on the manufacturing or cure conditions, leading to considerable variations in the properties.