Fabric (woven – knitted – or nonwoven textile or cloth – etc.) – Coated or impregnated woven – knit – or nonwoven fabric which... – Coating or impregnation is specified as water proof
Reexamination Certificate
1998-09-30
2003-01-28
Gupta, Yogendra N. (Department: 1751)
Fabric (woven, knitted, or nonwoven textile or cloth, etc.)
Coated or impregnated woven, knit, or nonwoven fabric which...
Coating or impregnation is specified as water proof
C442S059000, C442S099000, C442S106000, C442S109000, C442S152000, C008S115600, C008S116400, C008S127500, C008S127600, C008S128100, C008S128300, C008S181000, C008S183000, C008S185000
Reexamination Certificate
active
06511928
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of Invention
This invention relates to a durable press/wrinkle-free process for cellulosic fiber-containing fabrics and more particularly to a process which permits high treatment level amounts of formaldehyde and catalysts to impart wrinkle resistance to the cellulosic fiber-containing fabrics while reducing the loss in both tensile and tear strength normally associated with such treatment processes. The process of the present invention is particular adopted for the treatment of rayon and rayon blend fabrics.
2. Description of Related Art
There are a number of known processes for treating cellulosic fiber-containing fabrics, such as cotton-containing fabrics, to make them wrinkle-free. These treatment processes include resin or polymer treatment of the fabric, but these are costly and unsatisfactory. Another process for treating cellulosic fiber-containing products relies on formaldehyde to provide durable cross linking of the cellulose molecules and to thereby impart durable crease resistant and smooth drying characteristics to these products. However, problems have been encountered with the known processes, especially when applied to rayon. A simple, reproducible, completely satisfactory low-cost formaldehyde durable press process for rayon has not yet been achieved.
It has long been known to treat cellulosic materials with formaldehyde, as is evidenced by U.S. Pat. No. 2,243,765. This patent describes a process for treating cellulose with an aqueous solution of up to 40% formaldehyde and a small proportion of an acid catalyst under such conditions of time and temperature that the reaction is allowed to approach its equilibrium.
It is further stated that, in carrying out this process, the proportion of the solution of formaldehyde to the cellulose must be at least such that the cellulose is always in a fully swollen state. It is also stated that the time and temperature of the treatment with the solution of formaldehyde and acid catalyst will vary with one another, the time required increasing rapidly as the temperature diminishes. When it is desired, the product may be isolated by washing and drying; preferably at a temperature of about 212° F. The products obtained according to this process are said to show no increase in wet strength and possess a highwater imbibition, no increased resistance to creasing and a slight increase in affinity to some direct dyes. There is no mention of rayon in this patent although it does mention that the cellulose material may be bleached wood pulp.
In recent years additional methods have been devised for treating cellulosic fiber-containing products in order to impart durable crease retention, wrinkle resistance and smooth drying characteristics to these products. As discussed, formaldehyde has been cross linked with cellulose materials to produce these products. It is also known to treat cellulose materials with resins or precondensates of the urea-formaldehyde or substituted urea-formaldehyde type to produce a resin treated durable press product.
Textile fabrics treated with durable press resins require treatment with softening agents to achieve commercially acceptable hand, strength, and wrinkle recovery. U.S. Pat. No. 4,184,004 describes the treatment of a durable press resin treated fabric with a softener which is a silicone compound which may be a hydrophilic organosilicone terpolymer which contains a plurality of reactive epoxy groups. U.S. Pat. No. 4,520,176 also describes the use of silicone softeners for the treatment of aminoplast resin treated fabrics. The silicone softeners are organopolysiloxanes which are capable of being cross-linked.
As noted in U.S. Pat. No. 3,841,832, while formaldehyde has made a significant contribution to the cotton finishing art, it has had virtually no impact with respect to rayon containing fabrics even though rayon and cotton may be considered cellulosic containing fibers. Even with respect to cotton, the result has been far from perfect. For instance, in some cases the formaldehyde crosslinking treatment has tended to lack reproducibility, since control of the formaldehyde cross-linking reaction has been difficult.
U.S. Pat. No. 4,396,390, points out that the lack of reproducibility is especially true on a commercial scale. Moreover, unacceptable loss of fabric strength has also been observed in many of the proposed aqueous formaldehyde treatment processes. When high curing temperatures were used with an acid or potential acid catalyst, excess reaction and degradation of the cotton often happened which considerably impaired its strength. On the other hand, when attempts were made to achieve reproducibility at temperatures of 106° F. or less, much longer reaction or finishing times were usually required, rendering the process economically relatively unattractive. A solution to this is set forth in U.S. Pat. No. 4,108,598, the entire disclosure of which is herein incorporated by reference. This patent specifically states that rayons, e.g. regenerated cellulose (both viscose and cuprammonium) may be treated by the process described therein but there is no exemplification of the treatment of rayon.
Rayon is chemically the same as cotton and for this reason one would expect that systems which are effective in treating cotton would also be effective in treating rayon. Rayon is made from wood pulp (cellulose) in which the original cellulose fibers are changed into a thick, syrupy solution that is pressed through a group of exceedingly fine openings called spinnerets to form long filaments. As these filaments emerge and solidify in an acidic liquid, they are put under tension and formed into strands. The strands are processed into yarns then woven into fabrics. However, rayon is a very amorphous fiber (its molecules are spread out) and rayon does not resemble cotton in the way it reacts, even though it is chemically the same as cotton. In fact, even though some of the prior art includes rayon as a possible cellulosic material to be treated with formaldehyde and acid catalysts, there is no commercially viable formaldehyde rayon treatment process and rayon is treated with resins to improve its properties. None of the above discussed patents contain examples which describe the treatment of rayon containing fabrics even though some of the patents refer to rayon containing fabrics as the type of fabric which may be treated by the process described in the patent.
Shrinkage is a very serious problem when aqueous systems are applied to rayon containing fabrics and because of this shrinkage, rayon containing fabrics generally require dry cleaning as opposed to washing in an aqueous solution, such as water and a detergent. This is a disadvantage for rayon fabrics and it would be a significant advance if rayon containing fabrics could be treated so as to make them washable in water and avoid the inconvenience and added expense of dry cleaning. When the fabric is made from 100% rayon fiber and subjected to aqueous washing, shrinkage may be as high as 18%-20%. The shrinkage problem is also severe with a polyester/rayon fabric, because the rayon shrinks so much, and the polyester shrinks so little, that the fabric becomes completely distorted due to the extreme difference in the rate of shrinkage of the two fibers which make the blended fabric. The fabric will not lay flat on aqueous washing, and manufactures are forced to require dry cleaning of a garment made from this type of fabric.
SUMMARY OF THE INVENTION
In accordance with the present invention it is possible to obtain good durable press properties in a rayon fiber-containing fabric with good strength retention with a process that produces consistent results and which controls shrinkage so that the resulting fabric may be cleaned using normal washing detergents and water and does not require that the fabric be dry cleaned. This invention relates to an aqueous durable press/wrinkle-free process for rayon fiber-containing fabrics and more particularly to a process which utilizes acid catalysts and high concentrations of forma
Dinsmore & Shohl LLP
Gupta Yogendra N.
Mruk Brian P.
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