NON-FLAMMABLE PILE FABRIC

This invention relates to non-flammable pile fabrics, and to methods for making same.

There are various applications for fabrics which can withstand intense heat and which have a strong insulating effect. Of particular relevance are fabrics used in clothing intended to be worn in very hot surroundings. For example, firemen and some military personnel are often exposed to the intense heat of fires and explosions, and they rely on their clothing for protection. Similarly, in some industri¬ al environments such as foundries and open furnaces, personnel need protective clothing for their safety. Since the wearers of such clothing would likely need ease of movement, it would be very desirable that the clothing be made from a fabric of low mass.

Over the years, efforts have been made to develop fabrics having high resistance to intense heat and having a high insulating effect in hot environ¬ ments. It is known to treat textiles with various chemicals to retard flammability, as disclosed for example in U.S. Patent Nos. 2,032,605, 3,480,582, 4,053,673, 3,87-4,155 and 3,874,157. U.S. Patent No. 3,874,155 proposed fireproo ing mixtures of cellu- lostic fibers such as rayon with polyester, and further mentions a fire retardant blend of rayon and a cotton. U.S. Patent No. 3,925,823 discloses a multi¬ layer construction including absorbent material for firemen's garments which may be saturated with water; the layers consist of an external wick of wool and asbestos, an absorbing rayon layer, and a 5056 wool-505? rayon reservoir layer all bonded to a neoprene or nylon vapor barrier layer. U.S. Patent No. 4,257,221

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describes a textile prepared from separately carded slivers containing 6 55-8555 of an inherently fire resistant matrix, preferably Vinal and Vinyon fibers, and 35%-155 of a staple fiber such as cotton, flax, linen polyester rayon or nylon.

There are no known pile-type flame resistant materials incorporating natural fibers. Nor are multi-component, flame resistant fabrics known which comprise a pile face fabric, a backing yarn and a back coating.

A disadvantage of some prior art fabrics, particularly those with synthetic fibers, is their tendency to melt when intense heat is applied. This melting can be dangerous, since the hot melt may persist for a period of time after the source of the heat is removed and can therefore burn the wearer of the fabric.

Another disadvantage of some prior art fabrics is what is called afterglow. Fabrics made of cotton, wool or cellulostic fibers treated for flame resistance, can have an expanding ring of burning material when ignited even though no flames are pre¬ sent. This ring or afterglow is usually hotter than the actual flame, and can burn the wearer of the fabric.

Fabrics made of materials such as Nomex (a Jr>du. t of DuPont Corporation, Wilmington, Delaware) are known which have limited usefulness in hot envi- frfroonnmmeenntt:s because of their tendency ^" to shrink when heated.

Some prior art fabrics, particularly chemically-treated fabrics, generate large amounts of toxic gases when combusted. This characteristic is

referred to as "off gassing". It is desirable to minimize off gassing.

Some prior art fabrics are not moisture- absorbent (that is, they are hydrophobic) and this contributes to the discomfort of the wearer, and creates a dangerous potential for moisture in contact with the wearer's body to freeze in sub-freezing weather which can be a life-threatening situation in cold climates. It is desirable that fabrics be washable, while retaining both their texture and dimension after washing. However, at least some known fabrics tend to lose their bulk and texture after washing, and mat after washing. This has an adverse effect on their insulation capability. In the case of flame retardant and fire resistant fabrics, at least some known fab¬ rics tend to lose these qualities upon washing.

It is thus desirable to have a fabric that provides good insulation against heat and cold, has high thickness and low mass, and which further avoids the disadvantages of known fabrics.

The non-flammable pile fabric according to this invention resists melting when heated. The fabric is non-flammable, even when In direct contact with the flame of a blowtorch; the fabric may carbon¬ ize, but it still stays intact. Since the fabric does not burn, it has no afterglow. It features low off gassing. It Is a good insulator, with high thickness and low mass. Moreover, it is moisture absorbent, ^• thereby reducing the likelihood of discomfort of the wearer and injury to the wearer in very cold tempera¬ tures. It may be washed without substantially affect¬ ing its texture and dimensions. Also, it resists shrinkage when exposed to high heat.

In its preferred embodiment, the non¬ flammable pile fabric according to this invention features a face of pile fabric, a backing attached to the face fabric and a back coating applied to the backing. More preferably the face fabric is composed of 655? permanently flame retarded ("PFR") rayon and 35% wool treated for shrinkage resistance and wash- ability. The backing comprises PFR rayon for giving the fabric bulk and for supporting the pile, and a textile fiber which strengthens the fabric while not contributing to fabric flammability. Most preferably the backing is a 16/2 ply cotton count, spun yarn made of 80/6 PFR rayon and 2056 Nomex ara id. The back coating stabilizes the back of the fabric and provides support for the face fabric. Most preferably the back coating is made of an acrylic polymer which does not contribute to fabric flammability and which has been reinforced with thermosetting resins; the back coating can comprise a flame retarded acrylic polymer. The preferred method for making the non¬ flammable pile fabric according to the invention Involves the following steps: the raw fibers of PFR rayon and treated wool are blended together; the blended fibers are run through a carding machine to form a sliver; the sliver is fed into the base of a silver knit machine while backing yarn is fed into the top 'of the machine; and the resulting tube is slit to form a griege fabric. The griege fabric is sheared to yiefd a fabric with generally uniform*pile height. The fabric is next stretched to the desired width, coated with the back coating and dried. The coated fabric is tumbled to impart a curl to the fabric's pile should such a curl be desired.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Preferably, the non-flammable pile fabric according to this invention has three basic com¬ ponents. First, there is a face of pile fabric. Most preferably this face fabric Is composed of 655? Durvil and 3556 treated wool. Durvil is a product of Avtex Corp., Front Royal, Virginia, and Is a permanently flame retarded ("PFR"), high modulus rayon. The wool is treated by an appropriate process such as the

Superwash process (a process of the Wool Bureau Inc., Woodbury, New York) to provide it with shrink resis¬ tance and to render It washable.

Second, there is a backing yarn attached to the face fabric. Most preferably this is a 16/2 ply cotton count spun yarn made of 8056 PFR rayon and 2056 material having high strength, and good heat resistant and flame retardant qualities. Nomex is appropriate as the latter material, a limitation being its ten- dency to shrink when exposed to high heat. Nomex has been found to work satisfactorily when It forms 2056 of the backing yarn.

Third, there is a back coating which provides dimensional stability to the back of the fabric and provides support for the face fabric by locking the pile in place. Most preferably the back coating is a latex type coating such as an acrylic polymer (such as Rhoplex acrylic resin made by Rohm and Haas Company) or vinyl chloride polymer (such as Geon made by Goodyear Corporation) which do not contribute to fabric flammability. Flame retarded acrylic polymers which have been reinforced with thermosetting resins can be the back coating, although such polymers tend

to have a short shelf life which can impede the manu¬ facturing process. Appropriate thermosetting resins may be found in the glyoxyl and melamine families. It is noteworthy that in addition to the bulk and pile support features of the rayon in the backing, the rayon further is penetratable by the thermosetting resins which adds to the stability of the fabric. The preferred method for making the non¬ flammable pile fabric according to the invention involves the following steps:

Blending — The raw fibers of PFR rayon and treated wool are blended together in a coarse manner. Emulsifiable mineral oil compounds are added for the purpose of assisting future processing by inhibiting static and increasing sliver strength by improving fiber-to-fiber cohesion in such quantities as not to contribute to fabric flammability.

Carding — Clumps of the blended fibers are run through a carding machine where the fibers are oriented in a generally parallel relationship and further blended together. The output of the carding machine is a web which is twisted into a rope-like form and commonly referred to as a sliver or a roving. Knitting — The sliver is introduced into the base of a sliver knit machine while backing yarn is introduced into the top of the machine. The sliver is initially broken up into .fibers. Knitting needles pick .up _. these fibers and the yarn in rapid sequence. The needles knit these materials into a sliver knit fabric in the form of a tube with the pile on the inside of the tube and the backing on the outside. The tube is dimensioned to compensate for subsequent dimensional changes so that the final product will have the desired width. The tube is slit to form an

unfinished piece of fabric commonly called a griege fabric. The pile of the griege fabric is soft, un¬ kempt, and its fibers are loosely held by the yarn of the backing. Shearing — The pile of the griege fabric is sheared to produce a generally uniform pile height. A vacuum is applied to remove loose fibers.

Stretching, coating and drying — The sheared fabric is treated in a pin tenter machine. The web of the fabric is attached to a pair of spaced, parallel continuous chains which form part of the tenter frame. On this frame the fabric is stretched to the desired width. As the chains move continuously, a latex compound of acrylic and thermosetting resins selected so as not to contribute to fabric flammability is sprayed onto the back of the fabric, and the fabric is transported through an oven where the coated fabric is dried and the coating cured. As the fabric leaves the oven, it does not shrink and the pile is locked in place. It is believed that the shrink resistance is the result of several factors. The rayon is cross linked internally by at least one of the thermosetting resins. Also, the acrylic coating forms a film on the back of the fabric (thereby stabilizing the fabric), and the thermosetting resin cross links the acrylic to enhance its shrink resistance, even during laundering.

Tumbling — The coated fabric is introduced into a large laundry tumbler where curl Is imparted to the pile via the use of heat, moisture and mechanical action in a manner known in the art. The final tum¬ bling of the fabric helps to relax the fabric (I.e., relieve internal stresses), thereby contributing to the resistance of the fabric to shrinkage during laundering.

It should be understood that the principles of the invention can be utilized in connection with other pile fabrics, such as woven pile, tufted pile, napped pile, brushed pile, flocked pile, double woven and double-knit fabrics. Furthermore, the pile of such fabrics can have any configuration such as curled or erect (upright). The invention applies to fabrics which are both bulky and lightweight, that is, fabrics which are of pile-like construction. It has been explained that the wool of the fabric is treated for shrink resistance. Shrinkage in untreated wool is attributed to scales on the wool fibers which tend to interlock. Processes such as the Superwash process coat the fibers and cover the scales to reduce or eliminate the interlocking effect.

Alternatively, shrink resistance could be achieved by removing the scales, such as by a chlorinating process which is known in the art. Such processes also render the fabric washable, by eliminating the tendency of wool to lose bulk and mat after washing.

The fabric according to the invention can be used in many ways. For example, it can be incorporat¬ ed into a garment, in which case the face of pile fabric is worn on the inside next to the wearer with the free ends of the pile (i.e., the portion not connected to the support, such as the part of looped fibers extending from a support) extending toward the wearer. Also, fabric according to ,the invention can be combined with a reflective metallic backing to add resistance to radiant heat in addition to the con¬ ductive and convective heat resistance of the fabric. A non-flammable pile fabric according to the foregoing resists melting, does not suffer from after¬ glow, exhibits low off gassing, acts as a good Insula-

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tor having high bulk and low mass, has a moisture- absorbent face, can be washed without losing its texture or non-flammable features, and it resists shrinking.

The Invention has been described in detail with particular emphasis on the preferred embodiments, but it should be understood that there are variations and modifications within the scope and spirit of the invention.