Building material having a fluorocarbon based capstock layer and process of manufacturing same with less dimensional distortion

Abstract

The present invention provides building materials and methods for the manufacturer which includes an extrudable thermoplastic or thermosetting substrate having a fluorocarbon-based capstock layer applied to the substrate. The fluorocarbon-based capstock layer can further include one or more top coats for providing a variegated, colored or textured pattern. The capstock layer, with or without the top coats, preferably has a thickness less than 4 mil and contains a UV-resistant PVDF resin.

Description

CROSS REFERENCE TO RELATED APPLICATIONS [0001] The present application is related to U.S. Ser. No. 10 / 389,400 filed Mar. 14, 2003, now U.S. Pat. No. 6,752,941 (D0932-00229), which are hereby incorporated by reference in its entirety. The Examiner is directed to inspect the complete files of this earlier application for any material information concerning the instant claims.FIELD OF THE INVENTION [0002] The present invention relates to building materials having a capstock which may contain durable imagery to simulate actual surface textures, colors and appearances, and more particularly, siding, decking, window and fencing components having a wood grain. BACKGROUND OF THE INVENTION [0003] Vinyl siding was introduced in the early 1960's, but did not gain much attention until the 1970's. During the 1980's and 1990's, its use increased dramatically. Siding is the second largest market for polyvinyl chloride (“PVC”) resin, after pipe manufacturing, with approximately one billion pounds o...

AI Technical Summary

Benefits of technology

[0017] The use of special formations and thin inks, paints or coatings can create consistent special effects, such as variegated wood grains. This invention preferably employs direct printing and / or coating operations for providing both the capstock and, optionally, further layers, which are performed independently of the extrusion process, so as to provide extremely thin coatings to substantially eliminate bowing and dimensional distortion of panel siding, window lineals and other building products. The minimization of bowing and dimensional distortion is achieved by thinner cross-sections, more compatible resins from a coefficient of lineal thermal expansion point of view, the elimination of co-extruded ASA capstock processes, or a combination thereof.

[0022] The present invention can also be useful in connection with roofing materials, such as synthetic slates, tiles or shakes, or in multi-shake roofing panel products. For example, the capstock layer of this invention can be applied directly to a roofing substrate so as to present a printed or otherwise aesthetic appearance to synthetic slates, tiles or shakes, to make them more realistic in appearance.

Problems solved by technology

Nevertheless, due to sun exposure, vinyl siding colors can dull and the surface of siding can become chalky.

The manufacturer also claims that Solarkote® PB / PVC blends impart weathering performance in medium dark colors where chalking can be an issue.

Various methods of manufacturing such plastic articles have been used, but very few have succeeded in achieving a realistic wood-grain appearance in which the wood grain is strongly accented against a background layer.

Through its experience in manufacturing PVC siding with ASA capstock, CertainTeed Corporation has observed that existing ASA capstock material has a fairly narrow processing window during extrusion with unfortunate consequences if the processing window is missed.

If the processing temperature is too high during the manufacturing of such products, the melt viscosity of the capstock will become sticky; if the temperature is too low, the melt flow will center around the die.

This can lead to a difference in contraction rates during cooling between the predominantly ASA capstock and the predominantly PVC substrate, which can lead to undesirable bowing or dimensional distortion of the building material.

It has also been noticed that for many variegated products using streaker pigment in acrylic based capstocks, it is inherently difficult to control the melt rheology in the ASA matrix for consistent streak wood grain patterns.

While printing variegated colors and textures such as wood grains could alleviate the above-mentioned consistency problem associated with providing streaked stained wood appearances through a multi-viscosity fusion process, there is no suggestion in Bosler et al. for overcoming the distortion problems caused by differences in the coefficient of liner thermal expansion.

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