Water-clear aliphatic polyurethane pultrusion formulations and processes

Abstract

Clear polyurethane fiber reinforced composites are produced by a pultrusion process with a polyurethane-forming system that includes: (a) a clear, aliphatic polyisocyanate having a viscosity at 25° C. of no more than 1000 centipoise, (b) a colorless polyol component comprising an amine-initiated polyol having a molecular weight of from about 150 to about 400 and an OH functionality greater than or equal to 3, and (c) a catalyst. These fiber-reinforced composites are characterized by both excellent weathering characteristics and excellent physical properties.

Description

FIELD OF THE INVENTION[0001]The present invention relates to aliphatic polyisocyanate formulations useful in pultrusion processes, and more specifically, to water-clear, aliphatic polyurethane formulations and pultrusion processes utilizing such formulations.BACKGROUND OF THE INVENTION[0002]Pultrusion is a manufacturing process for producing continuous lengths of fiber reinforced plastic (“FRP”) structural shapes. Raw materials used in pultrusion processes include a liquid resin mixture (containing resin, fillers and specialized additives) and reinforcing fibers. The process involves pulling these raw materials, rather than pushing as is the case in extrusion, through a heated steel forming die using a continuous pulling device. The reinforcement materials are in continuous forms such as rolls of fiberglass mat or doffs of fiberglass roving. The two ways to impregnate, or “wet out”, the glass are open bath process and resin injection. Typical commercial resins include polyester, vin...

AI Technical Summary

Benefits of technology

The present invention provides a reaction system for the pultrusion process of making fiber reinforced composite materials using an aliphatic polyisocyanate component. These materials have excellent weathering properties and physical properties comparable to those produced with aromatic isocyanate-based systems. The materials are also clear in color and have a high glass transition temperature. This invention also provides a pultrusion process for producing fiber reinforced composite materials that have good weathering, are clear in color, and have a high glass transition temperature. Additionally, this invention provides composite articles that have good weathering characteristics, are clear in color, and have a high glass transition temperature.

Problems solved by technology

However, these aromatic polyisocyanate-based systems do not perform well in unprotected outdoor applications.

Poor weathering characteristics of the resin will result in color change, gloss loss and deterioration of the resin matrix and exposure of bare glass fibers (commonly referred to as “blooming”).

However, substitution of an aliphatic isocyanate for the aromatic isocyanate in known pultrusion systems produces composites with better weathering characteristics but inferior physical properties.