Shrink resistant rayon fabrics

Details Shrink resistant rayon fabrics Shrink resistant rayon fabrics

2000-12-08

2003-05-20

Gupta, Yogendra N. (Department: 3749)

Bleaching and dyeing; fluid treatment and chemical modification

Chemical modification of textiles or fibers or products thereof

Cellulose fibers

C008S181000, C008S183000, C008S116100, C442S059000, C442S087000, C442S099000, C442S106000, C442S109000, C442S152000, C442S153000

Reexamination Certificate

active

06565612

ABSTRACT:

TECHNICAL FIELD
This invention relates to rayon fabrics. More particularly, the invention relates to fabrics comprising rayon fibers which have a combination of good durable press properties, good dimensional stability and good water absorption. The invention also relates to fabrics comprising rayon fibers which may be subjected to aqueous laundering.
BACKGROUND OF THE INVENTION
Many fabrics, particularly fabrics comprising natural fibers, do not possess durable press (or “wash and wear” or “smooth-dry”) performance or dimensional stability, i.e., shrinkage resistance. Cellulosic fabrics such as cotton have been treated with aminoplast resins, including N-methylol cross-linking resins such as dimethylol dihydroxyethyleneurea (DMDHEU) or dimethylol propylcarbamate (DMPC), to impart durable press properties, as disclosed, for example, in the Martin et al U.S. Pat. No. 4,520,176. Unfortunately, many reacted aminoplast resins break down during storage, thus releasing formaldehyde. The formaldehyde release may occur not only throughout the preparation of the fabric but also during garment-making. Further, garments or fabrics treated with aminoplast resins may release additional formaldehyde when stored under humid conditions. Aminoplast resins may also hydrolyze during washing procedures, resulting in a loss of the durable press performance, and tend to give fabric a harsher handle, that is, make the fabric feel less soft. The fabric is often treated with additional softeners, for example silicone softeners. Unfortunately, the silicone softeners tend to make fabric hydrophobic although it is often preferred that the fabric have hydrophilic properties.
Cellulosic fibers have also been cross-linked with formaldehyde to impart durable press properties. For example, the Payet U.S. Pat. Nos. 3,960,482, 3,960,483, 4,067,688 and 4,104,022 disclose durable press processes which comprise impregnating a cellulosic fiber-containing fabric with an aqueous solution comprising a catalyst, and, while the fabric has a moisture content of above 20% by weight, exposing the fabric to formaldehyde vapors and curing under conditions at which formaldehyde reacts with the cellulose. The Payet U.S. Pat. No. 4,108,598 discloses a process which comprises treating cellulosic fiber-containing fabrics with an aqueous solution of formaldehyde and a catalyst, heat curing the treated fabric by introducing the fabric into a heating zone, and gradually increasing the temperature of the heating zone, thereby increasing the temperature of the heated fabric to prevent the loss of an amount of formaldehyde which will reduce the overall extent of curing. The Payet U.S. Pat. No. 5,885,303 also discloses a durable press process for cellulosic fiber-containing fabrics. The process comprises treating the fabric with an aqueous solution of formaldehyde, a catalyst capable of catalyzing the cross-linking reaction between formaldehyde and cellulose, and an effective amount of a silicone elastomer to reduce loss in tear strength in the treated fabric. Formaldehyde is generally less expensive than aminoplast resins, and formaldehyde treatment of cellulosic fabrics typically results in durable press properties which are more durable than those obtained by aminoplast resins.
Rayon garments are desirable by consumers for a variety of reasons. However, many durable press treatment processes that have been provided for cotton cellulose fabrics have not been suitable for rayon fabrics. Although rayon and cotton are both cellulose fibers, they react very differently from one another. Particularly, rayon-containing fabrics exhibit significant shrinkage when subjected to aqueous washing or laundering and therefore generally require dry cleaning as opposed to washing in an aqueous environment.
The copending Payet application Ser. No. 09/163,319 discloses processes for providing rayon fabrics with durable press properties wherein a rayon fiber-containing fabric is treated with an aqueous mixture containing a high concentration of formaldehyde and a catalyst capable of catalyzing the cross-linking reaction between formaldehyde and the rayon, and the treated fabric is heat cured. Payet discloses that the fabric may be washed or laundered in an aqueous system and does not shrink substantially on aqueous washing. Additionally, a silicone elastomer may be employed to reduce loss in tear and tensile strength in the treated fabric.
An important feature of cellulose fabrics, both cotton and rayon particularly, is that they are naturally hydrophilic, and therefore absorb moisture. Typically, garments made of fabrics which are hydrophilic are more comfortable for wear and therefore are preferred by consumers over garments which are formed of hydrophobic, non-moisture absorbing fabrics. However, many conventional fabric treatments for improving durable press and/or for reducing shrinkage of cellulose fabrics, and particularly for cotton and rayon fabrics, inhibit the natural water absorbency of the cellulose fibers and render the fabrics hydrophobic. Such fabrics are therefore not preferred for garment use owing to their reduced ability or substantial inability to absorb moisture.
Accordingly, there is a continuing need to further improve individual characteristics of fabrics comprising rayon fibers, and to improve the overall combinations of properties exhibited by such fabrics.
SUMMARY OF THE INVENTION
Accordingly, it is an object of this invention to obviate various problems of the prior art and to provide improved fabrics comprising rayon fibers. It is also an object of this invention to provide for fabrics comprising rayon fibers which have a combination of good durable press properties, good dimensional stability, and good water absorption. It is another object of this invention to provide for rayon fabrics having a durable press property which is maintained after repeated aqueous launderings.
In accordance with one aspect of the invention there are provided fabrics comprising rayon fibers and exhibiting, after the fabric has been aqueous laundered at least one time, changes in dimension in length and in width of less than about 5% each, a durable press value of at least about 2.5, and a water absorbency time of less than about 100 seconds. In accordance with another aspect of the invention there are provided fabrics comprising rayon fibers and exhibiting, after the fabric has been aqueous laundered at least one time, changes in dimension in length and in width of less than about 8% each, a durable press value of at least about 3.5, and a water absorbency time of less than about 100 seconds.
In accordance with one aspect of the invention there are provided methods of laundering a fabric comprising rayon fibers comprising the steps of aqueous laundering and drying. The fabrics exhibit, after at least one cycle of aqueous laundering and drying, changes in dimension in length and in width of less than about 5% each.
In accordance with one aspect of the invention there are provided treated fabrics comprising rayon fibers which after at least one aqueous laundering exhibits, as compared to untreated fabric having the same fiber composition, changes in dimension in length and in width which are each at least about 25% less than that exhibited by the untreated fabric, a durable press value at least about 0.5 unit greater than that exhibited by the untreated fabric, and a water absorbency time of less than about 100 seconds.
In accordance with one aspect of the invention there are provided fabrics comprising rayon fibers selected from the group consisting of fabrics comprising no less than about 50% rayon fibers and exhibiting, after the fabric has been aqueous laundered at least one time, a total shrinkage of less than about 5% and a durable press value of at least about 3.5; fabrics comprising no less than about 85% rayon fibers and exhibiting, after the fabric has been aqueous laundered at least one time, a total shrinkage of less than about 10% and a durable press value of at least about 3; and fabrics comprising about 100% rayon fibers and exhibi

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