Adduct and thermosetting surfacing film and method of forming the same

Abstract

In various embodiments, the invention provides an in-situ adduct formed by reacting liquid, solid, and / or semi-solid epoxy resins with a di-carboxylic acid functionalized polymer. The adducting process at least doubles the viscosity of the mixture. A hot melt thermosetting surfacing film and composite formed using the adduct are also disclosed. Methods of preparing and using are also disclosed.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS[0001]This application claims priority to U.S. Provisional Patent Application No. 61 / 409,692, filed on Nov. 3, 2010, the disclosure of which is incorporated herein in its entirety for all purposes.BACKGROUND OF THE INVENTION[0002]1. Field of the Invention[0003]This invention relates, in general, to an adduct of one or more resins and a functionalized polymer and in various aspects to a hot melt thermosetting surfacing film and methods for their preparation and use.[0004]2. Description of Background Art[0005]Conventional painting processes for cured composite parts require undesirable, repeated sand-fill-sand steps to prepare the surface before applying the paint primer. The process is time-consuming and leads to high labor costs. A surfacing film, which applied at the time of layup and molding of the composite part, provides a ready-to-prime, smooth, and porosity or pinhole-free protecting surface (either with light scuff sanding or without san...

AI Technical Summary

Benefits of technology

The invention provides a hot melt thermosetting surfacing film composition that includes an adduct formed by reacting liquid, solid, or semi-solid epoxy resins with a carboxylic acid functionalized polymer. This adduct increases the viscosity of the resin and can be used in applications that require fast cure times, such as rapid cure, large composite parts manufacturing, or fast cure surfacing films. The formulation includes different curing agents and catalysts that can be adjusted to achieve the desired cured surface quality and cosmetics, while also reducing part production costs through higher throughput rates.

Problems solved by technology

Conventional painting processes for cured composite parts require undesirable, repeated sand-fill-sand steps to prepare the surface before applying the paint primer.

The process is time-consuming and leads to high labor costs.

However, existing techniques for increasing viscosity also have significant negative impact on the resin mixing and film coating processes.

For example, it is difficult to make light-weight or thin film with a high viscosity resin especially in a hot melt process.

One of the concerns arising when using high molecular weight materials or high loading of fillers to raise the viscosity of the resin is that the resulting film might be too dry.

The material likely will not have ideal tack at room temperature, thus making layup difficult if the film will not adhere to other layers during the layup process.

Furthermore, such a material will have inadequate drapability.

Both of these features make the material less desirable from a processability standpoint.

For some commercial products it is difficult or nearly impossible to process such high molecular weight materials using the hot melt method due to ultra high viscosity of these materials.

Besides inducing high viscosity that causes poor processability, high filler loading also negatively affects mixing of and coating with the resin.

High molecular weight and high filler loading also tend to have significant negative impact on the cured film physical properties, e.g., toughness and adhesion strength.

In many cases, however, a hot melt process is preferred over the solvent process due to the material costs and environmental concerns associated with using a volatile solvent.

Since the residual solvent is volatile, it can cause problems such as porosity / fish eye (craters), orange peel, sag, and the like.

Attempts to remove residual solvent by application of higher temperatures or longer heating times can lead to over drying and negatively affect film properties such as tack and drape.

In addition, a solvent process-derived product tends to have residual solvent(s) in the product, which can outgas during cure and form cosmetic defects requiring additional rework / repair.

It is difficult to adjust the raw input materials for easier hot melt processing while still achieving a resulting product with desirable performance.