Fire retardant and heat resistant yarns and fabrics treated for increased strength and liquid shedding

Abstract

Fire retardant and heat resistant yarns and fabrics include an inner core comprised of oxidized polyacrylonitrile encapsulated by an outer shell comprised of a liquid-resistant and strengthening polymer material. The liquid-resistant and strengthening polymer material includes one or more types of cured silicone polymer resin. A fluorchemical may be at least partially impregnated into the inner core prior to applying the liquid-resistant and strengthening polymer material in order to further enhance the liquid shedding properties of the yarns or fabric. Because the silicone polymer resin only encapsulates the yarn, but does not form a continuous coating over the whole fabric, the treated fabric is still able to breath through pores and spaces between individual yarn strands that make up the fabric. The liquid-resistant and strengthening polymer material increases the strength, abrasion resistance, durability and liquid and gel shedding capability of the fire retardant heat resistant yarn or fabric.

Description

CROSS-REFERENCE TO RELATED APPLICATION[0001]This application claims the benefit under 35 U.S.C. § 119 of U.S. provisional application Ser. No. 60 / 786,853, filed Mar. 29, 2006, the disclosure of which is incorporated herein in its entirety.BACKGROUND OF THE INVENTION[0002]1. The Field of the Invention[0003]The present invention is in the field of fire retardant and heat resistant yarns and fabrics. More particularly, the present invention is in the field of fire retardant and heat resistant yarns comprised of oxidized polyacrylonitrile fibers and encapsulated with a liquid-shedding and strengthening polymer, as well as fabrics and articles of manufacture made therewith.[0004]2. The Relevant Technology[0005]Fire retardant clothing is widely used to protect persons who are exposed to fire, particularly suddenly occurring and fast burning conflagrations. These include persons in diverse fields, such as race car drivers, military personnel, and fire fighters, each of which may be exposed...

AI Technical Summary

Benefits of technology

[0014]The present invention encompasses novel yarns and fabrics that include a high concentration of oxidized polyacrylonitrile (O-Pan) fibers, which maintain a high level of fire retardance and heat resistance, while also possessing improved tensile strength, abrasion resistance, durability, and the ability to shed liquids and gels. The inventive yarns include O-Pan fibers, typically combined with one or more strengthening fibers, and are encapsulated by a liquid-resistant and strengthening coating, such as a silicone polymer. Encapsulating the fire retardant and heat resistant yarn with a silicone polymer increases the tensile strength, abrasion resistance, durability, and liquid and gel shedding capability of the yarn, as well as fabrics and articles made from such yarn. Encapsulating the yarn, rather than coating the whole fabric, not only seals the individual yarn strands in superior fashion, it also maintains breathability of the fabric as a whole rather than forming an impermeable barrier. This greatly improves performance and comfort when worn against a person's body.

[0015]The present invention combines the tremendous fire retardant and heat resistant characteristics of yarns made from O-Pan fibers with the strengthening and liquid and gel shedding properties imparted by a liquid resistant polymer coating. Simply encapsulating the yarn of a conventional flammable fabric with a silicone polymer coating cannot yield a fabric having a flame retardance and heat resistance that is even remotely similar to the level provided by O-Pan based fabrics. Moreover, encapsulating aramid-based materials with a liquid-resistant and strengthening silicone polymer coating does not alter the inherent tendency of fabrics formed from such materials to char, shrink, and form holes when exposed to direct flame and / or heated to above 600° F. Only by combining the tremendous fire retardant and heat resistant properties of O-Pan based fabrics with the strengthening aspects and liquid and gel shedding capabilities offered by liquid-resistant and strengthening polymer encapsulation can true synergy be obtained (i.e., the ability to provide the highest level of fire retardance and heat resistance to a fabric, while also providing enhanced tensile strength, abrasion resistance, durability, and liquid and gel shedding capabilities, all of which synergistically contribute to the ability of the fabric to protect a wearer from fire and heat).

[0016]The failure to provide all of these features in a single fabric can greatly undermine the otherwise excellent protection from fire. For example, even though conventional CARBONX fabrics provide superior protection against fire, heat and burns compared to other leading fire resistant fabrics such as the leading aramid “fire retardant” fabrics, such protection can be compromised if the fabric lacks sufficient tensile strength, abrasion resistance and durability for a given application. The fabric will typically only protect the wearer to the extent the fabric is able to maintain its structural integrity when protection is needed most, i.e., a fabric designed to protect the skin advantageously remains positioned between the wearer's body and the heat source to provide maximum protection. An inadvertent hole or tear can provide a conduit through which heat and flame can breach the otherwise continuous protective shield. Because of the generally weaker nature of O-Pan based fabrics compared to conventional fabrics, encapsulating the yarn comprising O-Pan based fabrics with a strengthening polymer provides a much greater incremental benefit with regard to tensile strength, abrasion resistance, and durability compared to conventional fabrics which are stronger to begin with. Encapsulation of the O-Pan based yarn with a liquid-shedding polymer also greatly increases the ability of the O-Pan based fabric to shed liquids and gels, including flammable liquids and gels.

[0017]Thus, encapsulating the yarn of O-Pan based fabrics with a liquid-resistant and strengthening polymer reduces the tendency of such fabrics to form holes or tears while protecting the wearer from flame and heat, and it helps such fabrics to shed liquids and gels, including flammable liquids and gels that can engulf the wearer in flames if absorbed into the fabric. Encapsulation of the O-Pan based yarn with a liquid-resistant and strengthening polymer coating greatly increases the range of situations where O-Pan based fabrics can provide superior protection from heat and flame as intended, even though the liquid-shedding and strengthening polymer may not itself provide any significant incremental heat or flame resistance beyond that which is already provided by the O-Pan based fabric. The high level of heat and flame resistance is provided mainly or exclusively by the O-Pan based fabric. The encapsulation of the O-Pan yarn comprising the fabric with a liquid-resistant and strengthening polymer coating mainly provides the auxiliary benefits of increased tensile strength, abrasion resistance, durability, and liquid and gel shedding capability (e.g., flammable liquids and gels). Nevertheless, the overall protection to the wearer against flame and heat is greatly enhanced by the auxiliary benefits imparted by encapsulating the yarn with a liquid-resistant and strengthening polymer coating, demonstrating the synergistic effect of combining O-Pan based fabrics with polymer encapsulation of the yarn comprising the fabric.

[0019]Exemplary liquid-resistant and strengthening polymer coatings include a wide variety of curable silicone-based polymers and polysiloxanes. Such polymers are typically encapsulated over the individual yarn strands of a tensioned fabric that is drawn through a bath of shear thinned polymer resin. Thereafter, the polymer resin is cured to form the final encapsulated yarn. The process advantageously only encapsulates the yarn strands but leaves spaces between the yarn strands that are woven or knitted together so as to permit the treated fabric to breathe. In this way, the treated fabric still feels and behaves more like an ordinary fabric rather than a laminate sheet or plugged fabric.

[0022]According to one embodiment, the yarn or fabric may be pre-treated with a fluorochemical prior to encapsulation with the shear thinned polymer coating. Pre-treatment with a fluorochemical may assist in helping the polymer encapsulated yarn or fabric repel or shed liquids and gels, such as water and hydrocarbons. The fluorochemical may advantageously be applied as a suspension or solution in combination with a solvent that is driven off by evaporation. Thereafter, the silicone polymer is applied to the yarn or fabric in order to encapsulate the yarn strands. The fluorochemical is at least partially impregnated into the yarn.

Problems solved by technology

Simply encapsulating the yarn of a conventional flammable fabric with a silicone polymer coating cannot yield a fabric having a flame retardance and heat resistance that is even remotely similar to the level provided by O-Pan based fabrics.

The failure to provide all of these features in a single fabric can greatly undermine the otherwise excellent protection from fire.

For example, even though conventional CARBONX fabrics provide superior protection against fire, heat and burns compared to other leading fire resistant fabrics such as the leading aramid “fire retardant” fabrics, such protection can be compromised if the fabric lacks sufficient tensile strength, abrasion resistance and durability for a given application.

Encapsulation of the O-Pan based yarn with a liquid-resistant and strengthening polymer coating greatly increases the range of situations where O-Pan based fabrics can provide superior protection from heat and flame as intended, even though the liquid-shedding and strengthening polymer may not itself provide any significant incremental heat or flame resistance beyond that which is already provided by the O-Pan based fabric.