Method of producing flame retardant textile fabric
A high performance flame retardant textile fabric is provided which is suitable for use in producing close-fitting garments, such as undergarments, that come into direct contact with the skin of the wearer and provide a protective function, as well as in non-apparel applications. The fabric is formed of yarns of rayon continuous filaments, the yarns having outer filaments along the periphery of the yarn and inner filaments in the interior of the yarn. A cured phosphorus-based flame retardant compound is durably affixed to the filaments and imparts flame retardant properties to the fabric. The outer filaments of the yarns have a phosphorus content at least 25% greater than the inner filaments of the yarn.
1. A method of treating a textile product to impart flame retardant properties, said method comprising the steps of: providing a fabric formed of comprising yarns comprised of rayon continuous filaments, the yarns having outer rayon continuous filaments along the periphery of the yarn and inner rayon continuous filaments in the interior of the yarn, directing the fabric into and through a pad bath containing a phosphorus-based flame retardant compound, compressing the fabric with a first set of cooperating rolls to force the flame retardant compound into the fabric and to impregnate the yarns of the fabric, subsequently compressing the fabric with a second set of cooperating rolls to effect a second forcing of the flame retardant compound into the fabric and to impart an additional impregnation of the yarns of the fabric by the flame retardant compound so that the outer filaments of the yarns have a phosphorus content at least 25% by weight greater than the inner filaments; and curing the flame retardant compound on the fabric to render it insoluble and durably affixed to the fabric.
2. A method according to claim 1 wherein the phosphorus-based flame retardant compound is a hydroxymethyl phosphonium compound and wherein the curing step produces an insoluble polymer that is present on the fabric at an add-on level of at least 20% by weight of the fabric.
3. A method according to claim 1 wherein the curing step comprises passing the fabric through a gaseous ammonia chamber and exposing the impregnated fabric to gaseous ammonia.
4. A method according to claim 1 wherein the curing step comprises heating the fabric.
5. A method according to claim 1 wherein the rayon continuous filaments comprise viscose rayon.