Reductive Bleaching For Denim Garments - Less Rejections & Excellant Softness

A large part of denim garments are subjected to processes that make them aged or old or worn out. This aged effect is generally obtained by a hypochlorite or peroxide bleaching of the garment or by stone washing or by an enzymatic bleaching treatment with the help of cellulase enzymes. In all the above cases the garment processors land up with the following problems:

• No uniformity in ageing or fading of shades; generally out of 100 garment pieces about 10 to 15 may got over bleached or under bleached due to the aggressive nature of the bleaching agents used.
• Generally the bleached garments become very harsh to feel. Every time a a softening treatment is required.
• If enzymes such as cellulase are used, they have to be deactivated to stop the process at the required stage.

But all the above said problems can be over come by your own home made Reductive Bleaching Agent.

How to make an effective Reductive Bleaching Agent?

What are the chemicals or ingrediant required for making this?

Its very simple.

Ingredients and 2  formulas:

For Making 100 kgs of Reductive Bleaching Agent -1.

• Liquid Glucose = 850 grams
• Non-ionic Detergent =  40 grams (100% Ethoxylate Based fatty alcohol poly glycolic ethers)
• Ammonium Sulphate = 110 grams (You can use Ammonium Chloride, acetate, citrate)

All mixed together  gives 1kg of Type-1 Reductive Bleaching Agent.


For Making 100 kgs of Reductive Bleaching Agent -2.

• Liquid Glucose = 830 grams
• Non-ionic Detergent =  70 grams (100% Lauric Acid Based n-methy glucomide)
  
• Sodium Citrate = 80 grams 
• Sodium Perborate = 20 grams

Bleaching Treatment:

Treat the  the materials to be bleached with sufficient quantity of caustic soda lye so that the pH of the bath is 13 to 14 at 90°C for 15 minutes. To this bath add 0.15% to 0.2% of the above Reductive Bleaching formulation. Continue treatment at 90°C for 80 minutes.

Drain the bath. Do 1 cycle cold wash followed by mineral acid neutralization. (About 3 to 5 gpl of HCl (35%) may be used for neutralization. Go Cold wash thoroughly to ensure complete removal of mineral acid.Hydro Extract and tumble dry.

You will get uniformly aged/worn out denim garments with good soft feel.

(Try these experiments for a very small batch and adjust the recipes according to your actual requirements).

Heat Sensitive Thermochromic dyes on Garments - a special effect!

Thermochromic colors:

Color changing inks were introduced during the 1970s with novelty items such as cups that change color when not liquids such as coffee or tea are poured in to them.

Color changes of thermo chromic pigments are induced by a temperature change. When temperature rises to a specific temperature, the color changes. The color starts fading back to the original color as the pigment is cooled down. 

Application of thermo chromic color on garment:

There are fifteen thermo chromic colors like Americos Red, Magenta, Vermilion, Orange, Yellow, Yellow Green, Charm Green, Sky Blue, Turq Blue, Dark Blue, Violet, and Black. The temperature interval available from 0^OC to 70^OC. Specific demand can be set up for different temperature intervals from 2^OC to 10^OC.

By using the above colors another color can be obtained but use different colors of thermo chromic pigments with the same temperature range to create more colors. Regular pigments can also be mixed with thermo chromic pigment so that the color can be changed from one to another. At lower temperature, the color reveals matched shade. When the temperature is increased, the thermo chromic pigments start fading to colorless. It only shows color of the regular pigments. By mixing the thermo chromic pigments with different temperature ranges, the color can be varied for more than two colors like temperature ranges for 3 color variation.

These t-shirts and other garments can change color by wearing or touching them. The heat from your body, hand or the environment makes this clothing change color. Once cooled the fabric changes back to the original color.

Sun Fading dyes and special effect garments

SUN FADING  - Photochrmic dyes on garments

Photo chromic color changes from clear when indoors to color when taken out-doors. The phenomenon produced in Photo chromic materials is called photochromism, where the change in color is due to incident light. Specifically, they exhibit color in response to exposure to sunlight or other source of UV radiation. UV light changes the chemical structure of the photo chromic material and makes it absorb color like a dye. It then reverts to a clear state when the UV source is removed.

However, to date, photochromism is most important for optical switching data and imaging systems, rather than in textile applications.

Application of photo chromic colors on garment:
Now  photo chromic colors are plastisol based ready to use off-white liquid are available in the market. When exposed to UV radiation, color appears. These colors are available in various hues.

Photo chromic colors can be applied on garment by three methods:
•    Spray
•    Brush
•    Screen Print
In all the above methods, photo chromic colors are directly applied on garment and cured at 1500C for 30-90 seconds.

These t-shirts and other garments can change color by wearing or touching them. The heat from your body, hand or the environment makes this clothing change color. Once cooled the fabric changes back to the original color.

The ghost printed  t-shirts have color changing screen prints when exposed to sunlight. The screen print appears as a black and white image with color highlights when indoors but once you go outside into the sun it appears in full color.

Teflon Treated Garments - stain resistant

Denim Treated with Teflon

Cotton is the most highly demanded fiber on the planet and is prized for its absorbent qualities, comfort, ease of wear, and versatility. Although a popular choice for many differing articles of clothing, there is one problem with the versatile fabric, it is extremely prone to soiling. Everything from chocolate to oil to red wine instantly stains the fabrics made from this fiber and are sometimes tricky to remove. This is where Teflon comes in to save the day. Teflon is part of advanced stain repellent technology that provides excellent protection against liquid spills and stains.

Teflon, also known as Polytetrafluoroethyhlene, was discovered in 1938 by the DuPont Company in their Jackson laboratory and is at the forefront of stain resistant innovations. The technology of Teflon is simple. The molecular make-up of chemicals binds around the individual cotton fibers instantly repelling oil and water based stains and releasing ground in dirt and natural stains during the laundering process. The molecules that make up Teflon are hydrophilic or water loving and they attract water and detergent into the fabric, liberating the stains into the wash leaving the fabric looking bright and clean. This new technology for repelling stains uses "nano-whiskers" that are adhered to the individual fibers and cause liquids to bead or roll off of the surface of the fabric. The stain does not adhere with the fibers and therefore soiling is minimal (Kadolph, 369). It is quite remarkable and clearly the best stain repellent out there.

Teflon creates a completely stain-resistant fabric that still has the natural drape, color, or breathability of similar untreated fabrics and that is something that people are willing to pay for. Denim is the perfect fabric for Teflon treatment because of its diverse market of consumers, versatile end uses, and the wide range of environmental factors that it is exposed to every day. It needs to be wearable, functional, and long lasting; all characteristics that are enhanced by Teflon treatments. Denim may be used for a tablecloth, a pair of jeans, or even a backpack and although each of these products requires different things from a fabric; they all need to be stain resistant. Cotton and Teflon are a perfect blend of style and function for daily life due to their combined ease of wear, soft hand, versatility, stain resistance, and breathability.

Sanded Finish of Denim Garment

Sanded Denim - fashion of the day!

A sanded finish for denim is achieved through a combination of pumice stones, enzymes and sand; used to create the illusion of aged denim jeans. Although the purpose of this is generally for aesthetics, this process also loosens the fibers in the denim, making the denim fit more comfortably and move more easily. Sanding jeans creates an uneven, worn look, which is ideal for daily casual wear, and also for pairing with solid colors or denim jackets . However, it is very labor intensive to sand finish denim, therefore a pair of jeans that has been sand finished will usually be slightly more expensive than one that has not . It is a necessity to finish denim in order to get a final soft touch. 

Most denims are enzyme washed or stonewashed for an overall softness, however, it is essential to sand-wash, or sandblast, for a more strategically placed worn and frayed finish . The picture on the next page displays what a sand-finished pair of jeans looks like. 

There are many types of finishes for jeans, and sand finishing is just one of the many ways to make denim more aesthetically pleasing the eye. This type of finish became popular around the 1980's, and is still a huge trend today because of it's ability to make jeans look and feel more versatile. Although there are many ways to go about finishing jeans, sanded finishes continue to prove to be a popular choice among consumers throughout the years

Garment Enzyme Washing Procedure

CELLULASE ENZYME
Stones are not only  abrasive to garments but also to the equipment.

Stones can create sludge in waste treatment systems.

Cellulase enzyme is a particular strain of enzyme derived from microorganisms  selective to cotton form of  cellulose and not to starch.  They attack 1  - 4 beta glucoside linkages resulting in reduced molecular weight and therefore removal of surface fiber.

Main factors  that control enzyme washing:
1  -  pH
2- temperature
3- time
4 -  concentration
5 - mechanical action

Once the reaction takes place, the mechanical action between garments and
equipment as well as between garments femoves weaker fibers resulting a cleaner,
smoother surface.  Stones may be added to enhance the abrasion.

TYPICAL PROCEDURE FOR CELLULASE ENZYME WASHDOWN (TWO STEP PROCEDURE)

Load garments (addition of  stones optional)
Desize for starch
-  alpha-amalase enzyme or
-  oxidative desize

Rinse

Adjust pH to 4.5 - 5.0 with
-  acetic acid or  a buffer system

Heat to 50 to 60 C ( 122  - 140  F)

Add cellulase enzyme
Tumble for 30 - 60 minutes

*Deactivation step   -  rinse hot  >  65° C

Rinse cold

Soften and/or optically brighten

Tumble dry

*Deactivation of  the cellulase enzyme to prevent further weight reduction
can be done by temperatures in excess of  60 C (140 F)  and/or at a pH
higher than 5.0.

Cellulase enzymes may be used as an aftertreatment to clean up surfaces of garments which have become fuzzy during garment dyeing.  The shade of  the dyed garments may change which requires preliminary lab work to determine if this will be a problem or not.

Acid Washing of Denim Garments - an over view!

ACID WASH

Acid wash is also considered to produce an worn-out effect that is harsher than stone wash. This treatment is mainly being carried out on denim and coarser varieties of garments.

• Acid wash is also known as  Ice wash, Snow Wash and White wash.

• In acid wash a complete discharge or removal of  color possible

• Uses pumice rocks,  bleaching agents and dyestuffs that are sensitive to the bleaching agents.

• Porous rocks that have a medium to high dusting capability are soaked in solutions of bleaching agents such as sodium hypochlorite or  potassium permanganate.  The chemical is absorbed and is transferred by  the cutting action of the rocks and deposited with the dust onto the garment surfaces.

Some more points a garment washer should take care of during acid wash:

-  Rocks must have ability to

• absorb chemistry in less  than 2 hours
• dust easily
• apply dust evenly on smooth surfaces and on high peaks of garment such
• around cuffs, waist band, fly, side seams, etc. and not in recessed spaces
• in those same areas.

-  Load size in pounds of garments should only be 25 -  33% of  rated capacity to allow for free  tumbling of  the garments and stones and for proper drop distance. 

-  Ratio of  the weight of  the stones to the garments should be
                                    0.5 : 1  for a light wash out
                                      3  : 1 for a complete white out

Procedure for Acid Washing:
1) Load  (25 - 33% rated capacity)
2)  Desize for starch with alpha-amalase enzyme or oxidative desize
3)  Rinse
4)  Extract to a certain uniform moisture
                 60 - 70% light frost
                 70 - 90% medium frost
                 90 - 100%  heavy frost (white-out)
5) Add presoaked stones (machine should be dry)  with ratio dependent 

6) Tumble  for 10  - 30 minutes
7)  Remove garments
8) Neutralize
9)  Soften and/or brighten upon desired effect (0.5-3.0 :  1,  stones to garments)
10) Tumble dry 

Some more points about Acid Washing:

• Stones should be allowed to drip or blotted with waste fabric  to remove
  excess solution to prevent spotting.  Stones can be used up to three times
  in some cases before resoaking is necessary.
• Neutralization usually takes place in another machine and the exact proced
  ure is dependent on the discharge agent used.
  Potassium permanganate (KMnO  and  purple in  solution )  converts
  to manganese dioxide (MnO  which is orange-brown in color)
  which must be neutralized with sodium bisulfite or  hydroxylamine
  sulfate ((NH  OH)  H SO  ).