Articles Including High Modulus Fibrous Material

Abstract

A composite sheet material including substantially randomly oriented high modulus fibrous material and a nonwoven web of thermoplastic fibrous material is disclosed. The composite sheet material can further include a substantially fluid impervious layer. The resultant composite sheet material can exhibit isotropic physical properties. The isotropic nature of the product can in turn improve the dimensional stability of the product, which can be useful for applications subject to multidirectional stresses, such as roofing membranes exposed to temperature variances.

Description

BACKGROUND OF THE INVENTION[0001]The present invention relates to textile products useful as supporting substrates.[0002]Synthetic nonwoven sheet materials have been used as components in a wide variety of products, including supporting substrates for roofing membranes, floor coverings, and the like. Many applications require a supporting substrate that exhibits good mechanical properties. In addition, in many applications, the nonwoven sheet materials can be exposed to varying temperature conditions during installation and subsequent use. Accordingly, such applications can require a substrate having good dimensional stability to minimize distortion of the product.[0003]U.S. Pat. No. 5,118,550 to Baravian et al. is directed to a substrate stated to exhibit good dimensional stability, even under conditions of production and subsequent treatments and use, such as bituminous impregnation. The substrate can include a synthetic nonwoven material in combination with high modulus threads a...

AI Technical Summary

Benefits of technology

[0007]Incorporating substantially randomly oriented high modulus fibrous material into the composite sheet materials of the invention can result in a substantially isotropic product, that is, a product exhibiting substantially similar machine direction and cross direction properties. The isotropic nature of the product can in turn result in improved dimensional stability as compared to a similar product including high modulus fibrous materials arranged parallel to one another. As a result, it is currently believed that the isotropic nature of the product can provide advantages for products subject to stresses in multiple directions. The resultant composite sheet materials can be particularly useful as a roofing membrane because the product can exhibit minimal distortion when subject to multidirectional stresses resulting from temperature variances.

[0009]In another aspect of the invention, the composite sheet material includes substantially randomly oriented high modulus fibrous material and a nonwoven web of substantially continuous thermoplastic filaments, such as a nonwoven web of spunbonded filaments. In various embodiments of this aspect of the invention, the composite sheet material can include at least one additional layer, for example, an additional web of substantially continuous thermoplastic filaments positioned to sandwich the high modulus fibrous material between the nonwoven webs. The nonwoven web of substantially continuous thermoplastic fibrous materials can impart additional advantageous properties to the resultant product, such as improved strength, stability and abrasion resistance.

Problems solved by technology

In addition, in many applications, the nonwoven sheet materials can be exposed to varying temperature conditions during installation and subsequent use.

Such products can, however, suffer various drawbacks.

Further, many products, such as roofing membranes, are subject to stresses in all directions of the product, and not just in the machine direction.

This in turn can result in failure of the roofing product.

Even products including high modulus nets with intersecting longitudinal and transverse threads may not withstand the force of multidirectional stresses, thereby resulting in failure of this type of product as well.

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