Low density oriented polymer composition with inert inorganic filler

Abstract

An oriented polymer composition containing thirty to 95 weight-percent inert inorganic filler and a continuous phase of at least one orientable polymer contains void spaces due to cavitation and has a density of less than 0.8 grams per cubic centimeter, a flexural modulus of 1.4 gigapascals or more, cross section dimensions all greater than 1.5 millimeters, a delamination force value of 44.5 Newtons (ten pounds force) or more and little or no blowing agent.

Description

[0001]This application claims benefit of U.S. Provisional Application No. 60 / 930,145, filed on May 14, 2007.BACKGROUND OF THE INVENTION[0002]1. Field of the Invention[0003]The present invention relates to solid state drawing processes and oriented polymer compositions produced by solid state drawing processes.[0004]2. Description of Related Art[0005]Oriented polymer compositions are desirable for having higher strength and stiffness over non-oriented polymer compositions. Historically, polymeric films and fibers have enjoyed the benefits of orientation through drawing processes. However, when a polymer cross section becomes larger than that of a film or fiber, drawing to a controlled and consistent shape becomes more complex and new drawing processes are necessary.[0006]Great Britain (GB) patent 1311885 discloses a solid state die drawing process to address the challenges of orienting larger cross section polymer compositions, which the patent identifies as compositions having a cro...

AI Technical Summary

Benefits of technology

[0014]Experimentation leading to the present invention surprisingly revealed that solid state drawing a polymer composition containing thirty weight-percent or more (based on polymer composition weight) of inert inorganic filler can result in cavitation within the polymer composition sufficient to achieve an oriented polymer composition having a density comparable to or less than wood (that is, less than 0.8 grams per cubic centimeter) and a modulus sufficient to meet building codes without requiring a blowing agent or a linear draw ratio of eleven. As a result, articles of the present invention surprisingly enjoy combined benefits of high concentrations of filler (30 wt % or more by weight of polymer), low density (less than 0.8 g / cm3), high flexural modulus (1.4 gigapascals or more) and high delamination force values (44.5 Newtons (N) or more; 10 pounds force or more) typically absent from compositions having a linear draw ratio greater than eleven while also being virtually, even completely free of blowing agent.

Problems solved by technology

However, when a polymer cross section becomes larger than that of a film or fiber, drawing to a controlled and consistent shape becomes more complex and new drawing processes are necessary.

Organic fillers, however, are subject to handicaps including color bleaching when exposed to the sun, and to decomposition, mold and mildew when exposed to humidity even within a polymer composition.

Additionally, reactive inorganic fillers such as Portland cement and gypsum are reactive with water (see, for example, PCT publication WO 2004 / 009334), which can result in an unstable polymer composition density in humid environments.

However, free drawn oriented compositions having such a large linear draw ratio (greater than eleven) tend to suffer from a low delamination force.

Moreover, a free draw process offers little control over the dimension of a final drawn article as compared to die drawn processes.