Process for desizing and color fading garments

A process for desizing an/or color fading of fabrics and garments utilizing a reducing agent. The process is particularly for pretreating fabrics which are subsequently decolorized with oxidizing agents.

FIELD OF THE INVENTION 
The present invention relates to a process for desizing and/or the color 
fading of fabrics and garments. More particularly, there is provided a 
process for the simultaneous desizing and decolorizing of dyed fabrics and 
garments utilizing a reducing agent. 
BACKGROUND OF THE INVENTION 
Garment and fabric processing today includes dyeing and desizing. Sizing is 
important in the fabric weaving process. The size is usually removed in a 
finishing operation after the fabric is woven. In some fabrics e.g. denim, 
the size is left in to give desirable properties to the denim garment so 
as to improve the wear properties of the fabrics or garments. However, if 
the garments or fabrics are further processed, for example, treated with a 
crosslinking agent and/or decolorized or finished in garment form, it is 
necessary to first remove the sizing. 
The removal of sizing is today performed in most textile plants by one or 
more of the following methods. The primary method of desizing is 
enzymatically, for example utilizing amylolytic enzymes. In garment 
finishing this process is more costly. Mechanical action is another method 
of desizing. In this method, abrasive drum linings in extractors and/or 
pumice stones are utilized to improve the garment softness, give the 
garment special features, etc. Alkaline and acidic hydrolysis have also 
been employed but such techniques also cause chemical attack of the fabric 
so as to result in a loss of the abrasive strength of the fabric. 
Oxidative desizing is generally employed using large amounts of sodium 
hypochlorite in solution. The use of hypochlorite creates environmental 
problem and further can significantly degrade the fabric. Desizing is 
required where the fabrics or garments are to undergo further processing 
such as dyeing, printing, decolorization, treatment with a crosslinker, 
ozone treatments and the like. 
Garment dyeing technology, particularly with denim jeans, to achieve a 
differential color appearance has focused on treatments in which the dyer 
starts with a dyed garment and achieves a differential color effect by 
partial color removal. Removal of color is achieved by use of porous 
stones soaked in oxidizing agents, such as strong bleach or permanganates, 
and more recently, by treatment with cellulase enzymes to remove fiber and 
thereby also remove some sizing. 
The desizing and removal of color of denim garments generally requires two 
independent operations wherein the sizing is first removed and then the 
garment is treated chemically or physically to obtain removal of the 
color. It would be more economical and less time consuming if the two 
operations could be accomplished simultaneously. Such a procedure would be 
advantageous in garment treating processes wherein the garment undergoes a 
color fading procedure such as treatment with a bleaching agent or an 
oxidizing agent such as ozone, permanganates, sodium hypochlorite and the 
like. 
SUMMARY OF THE INVENTION 
The present invention provides a process for the simultaneous desizing 
and/or decolorizing of fabrics and garments utilizing a reducing agent. 
More particularly, the invention provides a means for removing sizing 
and/or dyes from garments and fabrics which are to be subsequently 
oxidized or bleached. 
Advantageously, the fabrics or garments are treated with a reducing agent 
while in an aqueous bath at elevated temperatures. Temperatures of the 
bath between about 120.degree. to 180.degree. F. are suitable for the 
simultaneous desizing and dye removal of fabrics. 
Accordingly, the fabric with a portion of the dye removed requires less 
time and bleaching agent or oxidizing agent in order to produce a garment 
having the appearance of being "stone washed" or "acid washed". 
It is therefore a general object of the invention to provide a means for 
simultaneously desizing and decolorizing a fabric or garment. 
It is another object of the invention to desize a garment more efficiently 
and in a shorter time than with enzymes. 
It is yet another object of the invention to prepare a fabric or garment 
for further treatment by removal of a sizing agent. 
It is yet still further object of the invention to selectively and/or 
evenly decolorize or fade dyed garments to produce fashion garments. 
It is another object of the invention to provide garments with different 
degrees of color by use of dyes of varying sensitivity to reducing agents 
and/or to provide different levels of colorization throughout the garment. 
DESCRIPTION OF THE PREFERRED EMBODIMENTS 
Although specific terms are used in the following description for the sake 
of clarity, these terms are intended to refer only to the particular 
feature of the invention selected for illustration and are not intended to 
define or limit the scope of the invention. 
According to the present invention, sized and/or dyed fabrics and garments 
which are required to be desized before undergoing further processing can 
be treated with a reducing agent so as to remove the sizing. If desired, 
such as in the case of denim jeans, where the present fashion requirement 
is a bleached or washed appearance, the garment can be simultaneously 
decolorized. Typically, blue jeans which would normally undergo only 
desizing in a washer-extractor, can now undergo simultaneous desizing and 
decolorization by treatment with a reducing agent. 
The denim jeans are normally placed in a drum type washer-extractor and 
covered with water at an elevated temperature, preferably at a temperature 
range between about 120.degree. to 180.degree. F. A reducing agent is 
added and the mixture is agitated for a period of about 20 minutes, 
depending upon the reducing agent and type of sizing utilized. 
Advantageously, a dye complexing agent such as polyvinyl pyrrolidone is 
added to prevent redeposit of the degradated dye. 
Typical reducing agents which are useful for desizing starch type sizing 
and decolorizing denim jeans include alkali metal hydrosulfites, for 
example, sodium hydrosulfite, alkali metal sulfoxylate formaldehyde, for 
example NaHSO.sub.2 --CH.sub.2 --2H.sub.2 O, thiourea dioxide, and the 
like. 
Reducing agents which are primarily useful for decolorization of the 
fabrics include the alkali metal hydrogen sulfites, sulfides, 
thiosulfates, oxalates, hydrosulfites and sulfides. 
The compounds which are especially useful for reducing sulfur dyes include 
sodium hydrosulfite, sodium hydrosulfide and sodium sulfide. 
Other suitable reducing agents include arsenious oxide and titaneous 
sulfate, which is useful for reducing reactive dyes. 
Advantageously, sodium or zinc sulfoxylate formaldehyde is used under 
either acidic or basic conditions and sodium hydrosulfite is used under 
basic conditions. 
The garments or fabrics to which the present may be applied comprise both 
natural and/or synthetic fibers including cotton, linen, other bast 
fibers, rayon, wool, polyester, rayon, alone or in combination with other 
natural or synthetic fibers. 
Preferably, the garment or fabric is desized and/or decolorized without 
causing degradation of the fabric. 
The type of dye used on the garment is not critical. It is only important 
that the dye is reactive with the reducing agent where intended. Cellulose 
substantive dyes, such as vat dyes, which are common in the garment 
industry, are preferably used. Exemplary of the dyes which are or can be 
made to be substantive to cellulose that can be used include Acid Light 
Scarlet GL, and acid leveling dye, Sevron Brilliant Red 2B, indigo vat 
dye, a cationic dye, Sulfonine Brilliant Red B, and anionic dye, Brilliant 
Milling Red B, C. I. Disperse Blue, pyrazolone azomethine dye, hydroxy azo 
dyes, or the like. Other suitable dyes that can be used are identified in 
the paper of Charles B. Sweeney entitled, "Identifying a Dye can be Simple 
or it can Involve Hours of Laboratory Analysis", Textile Chemist and 
Colorist, Vol. 2, No. 1, January 1980, pp 26/11, which is incorporated 
herein by reference. 
The garments may be colored (dyed) with one or more dyes. Utilizing dyes of 
differing degrees of reactivities provides the garment with zones of 
different appearances or effects. For example, faded, stone washed, 
ice-washed, sand blasted or mottled effects may be obtained. The same 
effect can be achieved by utilizing blocking agents. The blocking agents 
may comprise organic materials such as hydrocarbon oils, greases or waxes 
or inorganic materials such as clay which are not reduced. Masking tape, 
or other coverings may be used. 
The blocking agent can also be any chemical agent which itself is reduced 
with the reducing agent but prevents or blocks a dye or portion of a dye 
on the fabric from becoming decolorized. 
In a preferred operation of the process of the invention the garments or 
fabrics are placed in a washer-extractor which is similar to the type that 
would have been utilized in a conventional desizing operation utilizing an 
enzyme. The washer-extractor is then filled with water having an elevated 
temperature, that is, about 120.degree. to 185.degree. F. The higher the 
temperature the greater the discoloration. It is understood that at the 
higher temperatures the reducing agent selected must have a requiste 
temperature stability. The pH of the bath is adjusted according to the 
type of reducing agent utilized. The reducing agent is then added to the 
bath. The bath is normally agitated for about 0.3 to 1.0 hour and then the 
water is extracted and the garments or fabrics are rinsed with water. The 
garments or fabrics can then be further processed if desired. 
The amount of reducing agent utilized is determined by the type of reducing 
agent utilized and the effect desired. For example, in a commercial size 
washer-extractor in which about 180 denim jeans are to be desized, when 
thiourea dioxide is the reducing agent, about 0.75 lbs is used in a bath 
containing 260 gal. of water to achieve a light blue effect. While 1.5 lbs 
gives a pale blue effect. With sodium hydrosulfite as the reducing agent, 
about 1.75 lbs is utilized to achieve a similar result. It is understood 
that compounds such as polyvinylpyrrolidone can be added to the system to 
prevent redeposition of the dye removed from the garments during 
reduction. 
The invention is particularly useful in preparing fashion garments such as 
faded denim blue jeans, and the like, without the use of harsh chemical 
bleaches or the abrasive effects of stones, pumice, sand or the like. 
The reducing agents are particularly effective where the sizing comprises a 
starch, starch derivative or a modified starch. 
Denim blue jeans and jackets which have been faded, "stone-washed", ice 
washed, and/or sand blasted to produce a particular appearance are very 
popular. However, to produce the desired effect it has been necessary to 
utilize processes which cause substantial deterioration or degradation of 
the fabric. Bleaching solutions containing chlorine or actual pelleting of 
the garment with sand or stones to produce a fashion effect causes damage 
to the fabric which affects its wear life. 
Special effects can also be achieved by selectively treating the garment 
with dyes having different degrees of reactivity. The non-reactive or 
lesser reactive dyes may be applied by spraying, brushing, dipping, or the 
like. In a similar manner reducing agents can then be applied. 
The application of reducing agents to garments by stones soaked in these 
reagents also provides a means of modifying the color of the garments and 
of modifying the texture of the garment. The stones, such as pumice 
stones, that are ordinarily used in stone washing, can be soaked in a 
suitable reducing solution and then tumbled with the garment. The areas 
which are touched by the stones would undergo greater decolorization so 
that a color differential would occur on the garment. The pattern and the 
decolorization differential may be varied by utilizing stones which have 
been treated with different types of reducing agents.

The following examples are illustrative of the practice of the method of 
the present invention. It will be understood, however, that is not to be 
construed in any way limitative of the full scope of the invention since 
various changes can be made without departing from the spirit of the 
teachings contained herein in light of the guiding principles which have 
been set forth above. All percentages stated herein are based on weight 
except wherein otherwise noted. 
EXAMPLE 1 
Into a 500 gal. capacity rotary drum washer-extractor was placed 180 blue 
dyed denim jeans containing a starch sizing. 350 gal. of water at a 
temperature of 175.degree. F. is added to the washer-extractor. The drum 
is rotated and 0.75 lbs of thiourea dioxide together with 2.0 lbs of 50% 
sodium hydroxide is added. The drum was rotated for about 20 minutes and 
the water was extracted. The garments were then rinsed twice with 220 gal. 
of cold water and spun to extract the water. 
The resulting garments were all desized and decolorized to a very light 
blue. When 1.5 lbs thiourea and 4 lbs 50% NaOH is added a pale blue color 
was obtained. If an even lighter color is desired the process can be 
repeated for 10 minutes prior to rinsing since concurrent desizing is not 
necessary. 
The garments can be further decolorized by subjecting them to a standard 
bleaching operation or by treatment with ozone. 
EXAMPLE 2 
The procedure of Example 1 was followed except that in lieu of 0.75 lbs of 
thiourea dioxide and the sodium hydroxide there was utilized 3.0 lbs of 
sodium sulfoxylate formaldehyde and sufficient citric acid to give a pH of 
4.0-4.5 (buffered with sodium citrate) or acetic acid (56%) buffered with 
sodium acetate at a temperature of 180.degree.-185.degree. F. 
The resulting garments were all desized and decolorized to a pale blue. 
EXAMPLE 3 
A concentrated solution of sodium hydrosulfite was prepared and 
approximately two pounds of pumice stones were soaked in the solution for 
one hour. Two enzyme desized denim jeans which were wetted in a 2% sodium 
hydroxide bath were inserted into a Unimac sample garment dyeing machine. 
The stones were removed from the solution and inserted into the machine 
which was rotated at the speed of forty cycles per minute for 7 minutes. 
The garments were then washed in a standard home type washer and dried. 
The garments were lightened and had a soft hand. The garments gave the 
appearance of being acid washed. 
EXAMPLE 4 
The procedure of Example 1 was followed except that 5 lbs sodium 
hydrosulfite and 10 lbs of 50% NaOH were employed along with 7 lbs of a 
40% solution of polyvinylpyrrolidone. The mixture was heated and rotated 
to 130.degree. F. for 25 minutes. 
The resulting garments were all desized and decolorized to a pale blue.