Bleaching and dyeing; fluid treatment and chemical modification – Bleaching – Chemical
Reexamination Certificate
2001-09-17
2003-12-16
Einsmann, Margaret (Department: 1751)
Bleaching and dyeing; fluid treatment and chemical modification
Bleaching
Chemical
C008S101000, C008S109000, C008S102000, C008S107000, C008S128300, C008S918000
Reexamination Certificate
active
06663677
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to improved methods for use both in wool whitening and garment washing. More particularly, methods of the present invention employ a stripping composition comprising a first reducing agent, preferably a borohydride material, and a second reducing agent, preferably a bisulfite material to increase the brightness (whiteness) of wool and to reduce color components in certain fabrics, particularly denim. Methods of the present invention are particularly useful in the garment and piece goods industries.
2. Background
Raw (unprocessed) wool is typically quite crude. Cleansing of the wool is achieved using conventional procedures generally known as pre-scouring and scouring. Such procedures remove a variety of materials including dirt, oil, hair and feces from the raw stock. Once cleansed, it is desirable that the wool be further processed in order to achieve a particular level of brightness (whiteness).
Certain early processes achieved brightening by bleaching (oxidizing) the wool. Such processes typically employed highly alkaline reagents such as hydrogen peroxide and were carried out at relatively high temperatures, e.g., in excess of 120° C. However, the harsh reagents and high pH caused significant damage to the proteinaceous fibers of the wool. Further, though some brightening was achieved, such processes also produced unlevel substrate backgrounds. It is well established that a level background is essential in producing high quality, evenly dyed wool.
Various other reagents also were evaluated for brightening wool. For instance, U.S. Pat. No. 3,250,587 reports a process which employs a combination of alkali solutions for bleaching wool to a high brightness. According to that process, the wool is saturated with a first aqueous solution containing an alkali bisulfite, then immersed in a second aqueous solution containing an alkali borohydride. The borohydride is removed from the wool by washing the treated wool with water or by heating it to a temperature in excess of 110° C.
Notable disadvantages were observed using the afore-mentioned procedure. For example, the '587 process calls for the combination of bisulfite-soaked wool with a borohydride bath. This reaction is exothermic and potentially highly explosive. Also, air becomes trapped inside the wool during the process leading to unlevel dyeing. Further, as with the earlier bleaching processes, the high pH of the reagents causes degradation of the fibers which make up the wool. Still further, this process is suitable only for use in a continuous system; it cannot be performed in batch runs. As is generally known in the art, batch operations are particularly desirable in that they accommodate process variations easily.
Other processes for brightening wool employed one or more traditional textile reducing agents, such as sodium hydrosulfite (Hydro), thiourea dioxide (TUDO), formamidine sulfinic acid (FAS), zinc formaldehyde sulfoxylate (ZFS), and sodium formaldehyde sulfoxylate (SFS). Such processes also were problematic in that each of the reagents loses strength through oxidation during even minimal storage time. Additionally, processes which utilize ZFS, SFS and Hydro often produce an undesirable odor during the reaction process. Further, environmentally hazardous by-products are generated using certain of those procedures. For example, the zinc by-product which results in the case of ZFS is highly undesirable, as are the carcinogens associated with processes employing TUDO.
Various other processes have been developed in the piece goods and garment industries for reducing color components, e.g., dyes, in fabrics. For example, processes for reduction of indigo dye in denim goods are highly desirable in order to achieve a “pre-washed” appearance. A conventional process known generally as “stone-washing” is often used for this purpose. However, stone-washing requires that the denim goods be combined not only with stones but with caustic chemicals. Such chemicals are highly damaging to many fabrics including cotton. Additionally, an extended period of time, e.g., six hours, is required to achieve desirable results using such a process. Further, re-deposit of the indigo dye can occur during the procedure.
Thus, it would be highly desirable to develop improved processes for wool brightening and garment washing suitable for use in industries such as the garment and piece goods industries. Specifically, it would be highly desirable to develop new methods for brightening wool which do not require alkali bleaching solutions, that do not cause degradation of the wool's fibers, that provide level backgrounds for dyeing, that are safe to operate, and that do not produce environmentally harmful by-products. It also would be particularly desirable to develop new processes for garment washing that would be effective in reducing color components, e.g., dyes, without causing damage to the fabric. Such methods would be particularly useful for application to denim goods, and could replace the lengthy “stone-washing” procedures which employ caustic reagents and which are highly damaging to many substrates. It also would be desirable if such methods employed non-flammable, shelf-stable reagents. It would be further desirable for such processes to also offer improved economics, e.g., savings in terms of materials, overall cost and time. Such processes would present significant commercial value to the garment and piece goods industries.
SUMMARY OF THE INVENTION
We have now discovered new processes for brightening wool and other polyamides which may be safely and effectively carried out at a substantially neutral pH in relatively short cycle times. Such methods also are suitable for use in garment washing, particularly in reducing color components, e.g., dyes, present in a variety of fabrics including dyed denim goods and other cotton-based materials. Methods of the invention utilize a stripping or washing composition comprising a first reducing agent, preferably a borohydride material, and a second reducing agent, preferably a bisulfite material.
Wool treated with stripping compositions of the invention provide notably high brightness measurements with little or no fiber degradation. Reducing fiber degradation is particularly important when working with more delicate wools and wool blends, including sports wools (wool/polyester blends) such as COLONA (manufactured by Brush Fabrics, Victoria, Australia) and hercosett-treated wool. Further, using methods of the invention, denim and other fabrics may be treated to achieve a pre-washed appearance without the use of stones or caustic chemical reagents. Methods of the invention also are beneficial in that they do not produce environmentally hazardous by-products or noxious fumes. Further, such methods offer reduced cycle times relative to the conventional processes and provide significant savings in terms of materials, cost and time.
While not wishing to be bound by theory, it is believed that the addition of the second reducing agent, e.g., bisulfite, enhances the effectiveness of the first reducing agent, e.g., borohydride. It is believed that bisulfite is regenerated in-situ during the reaction and that it acts as both a co-reducing agent and a catalyst in the reaction scheme. Likewise, the borohydride is believed to catalyze the bisulfite reduction at least to some extent, thereby further increasing the efficiency of the reaction. Conventional reducing agents, e.g., Hydro and FAS, do not exhibit similar efficiency and/or effects when combined.
In a first aspect of the invention, methods of the invention are employed for whitening and/or brightening wool. Raw wool, e.g., that which is obtained from the animal, typically is first cleansed by conventional pre-scouring and scouring procedures in order to remove impurities such as dirt, oil, hair and feces.
In accordance with the invention, the cleansed wool is preferably wetted, e.g., using a surfactant or other wetting agent, and treated in a single bath procedure wit
Schoots Harrie Peter
Stevens, Jr. Lester Franklin
Crimaldi Kenneth
Einsmann Margaret
Rohm and Haas Company
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