Understanding Data color

Understanding Datacolor

Datacolor is an instrument which works by emitting a single or multiple wavelengths on to substrate (target) and then records the reflectance values. Afterwards uses these values to create a skeleton or graph which shows how substrate has behaved with varying wavelength.  Typical wavelength used here is of visible region that is of 400nm to 700nm. For example let say we are trying to read values of a black fabric through data color. As, we know black color absorb every wavelength which fall on to it. That’s why it appears black,

Behavior of Black fabric

Same happens with data color graph and it shows zero or near to no reflectance value. We will be getting results reverse we try to repeat this experiment with white fabric and we will be having maximum reflectance value.

Behavior of White Fabric

Visible region of Electromagnetic waves covers from 400 to 700nm and colors vary on different wavelength as we move from 400 to 700nm we see Yellow toRed .

%Reflectance value for green color and graph will be like

Behavior of Green fabric

Comparison of Hydrogen peroxide bleaching and conventional sodium chlorite bleaching

 

Hydrogen peroxide Bleaching.

Hydrogen peroxide is most widely used bleaching agent. Beside the good removal of the seeds, there peroxide bleach delivers a high degree of whiteness, the white effects are stable and do not tend to yellow during storage.

Results expected from hydrogen peroxide bleaching

Degree of whiteness: High degree of whiteness for white goods and pastel shades.

Seed removal :  Complete removal of seeds coats.

Criteria	Hydrogen peroxide	Sodium Chlorite
Accelerated Continuous process	Yes	No
Applicability by all possible methods, e.g. cold bleach	Yes	No
Suitability for natural fiber	Yes	Yes
Efficient removal of husks	Yes	Limited
High water absorbing power	Yes	NO
Odor Irritation	No	YES
Corrosion problems(Vessel of resistant material required)	No	Yes
Suitability for combination processes (Boiling off/Bleaching)	Yes	No
One bath application with brighteners for cellulosic fiber	Yes	Limited
Deposits on fabrics and machines	Limited	No

On the whole, there are so many points in favor of hydrogen peroxide bleaching that it is easy to understand why it so widely used.

Utilizing Bifunctional reactive dyes for reactive printing.

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Utilizing Bi functional reactive dyes for reactive printing.

Chemistry of dyes which are used in reactive printing is different from other classes. Among them one is MCT (Mono chlor Triazine), A dye having single chlorine attached to functional Triazine.

This Chemistry of dyes (MCT) provided better fastnesses, Specially washing fastness ISO 105 CO3, Dipping fastness. 

A common practice is to use other family of reactive dyes in printing although this fulfills the task and advantages associated with this phenomena are 
1) cheap/Economical dyes. 
2) Bulk amount available 
3)Nearly same shade depth and tone 

But, disadvantages are poor fastnesses. Commonly in use dyes for reactive dyeing includes bi functional dyes including new generation high built dyes. These dyes have high fixation values and percentage of hydrolyze dye in dye bath is quite low but these dyes can not stand on with alkaline medium for longer period of time. 

Stock paste used for printing include alginate, mild oxidizing agent, urea and above all quite huge quantity of soda ash (25g/Kg), which is recommended for fixation of reactive dyes in printing. As, already mentioned these dyes are not quite good with alkaline medium when left for longer period of time. So, when these dyes are mixed with stock paste and not printed soon or after immediate addition. These start to hydrolyze and lose up its strength and tone. Temperature work as catalyst here. Temperature effect inversely to the hydrolyzation. More the temperature more quickly dye is going to hydrolyze. As, major areas of Pakistan are hot and quite hardly hit in summer. So, for this experiment 50°C is chosen to check the hydrolyzation rate of bi functional and Purely MCT dyes.

For a clear Preview, Right click on image and open in new Tab or in new Window

How reactive dye works?

 

Polyester (PES) Discharge/Disperse Discharge through Alkali (Soda Ash, Na2CO3)

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Polyester (PES) Discharge/Disperse Discharge through Alkali (Soda Ash, Na2CO3)

Chemicals:

Synthetic Thickener (Polysacchride), Soda Ash, Sodium Hydro sulfite and Caustic for Reduction Cleaning (although not necessary, it is done to have shin and glorious effect), Disperse Dyes

1. Stable to Alkali

2. Not Stable to Alkali.

Bit Discussion:

Polyester dyed or printed fabric can also be discharged but discharging requires more severe conditions like chemicals and parameters to obtain good results. Discharge of Polyester is more crucial and every dye cannot be discharged.

Normally there are two ways to Discharge a polyester fabric printed through Disperse dyes. First, utilization of simple alkali like soda ash which provides alkaline medium required to carry out discharge and other is done through utilization of Ragolit C and Tin Chloride.

Here in this post we are going to utilize former method in which we will be discharging though alkali soda ash. There are two kind of disperse dyes. One, Which are not stable to Alkaline medium at all and Second, Those disperse dyes which can bit stand with alkaline medium. So, this is basic principle which we are going to utilize in our both discharges, white and color Discharge.

Process:

Dyeing Recipe:

Padding Liquor{Continuous Process}

Disperse Dye (Not stable to Alkali)    30  g/Kg

Acetic Acid                              To Adjust Ph between 5-6

Water                                                     Balance

Total                                                      1     Kg

Pad at pressure 2bar with pick up 70 to 80.

Dry at 110C° for 1Min.

After Dyeing, Not fixed Yet and remember, we need not to fix it here.

Pigment Printing

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Pigment Printing

Pigment Printing:

For me design/Pattern is printing for others combination of thickener (Paste) and Screen (Design) is called printing. Dyeing can hold single color where as printing can handle 12 to 20 colors in single go. Printing can simply be classified according to Technique, Fiber type and Dye Class.

Note: On graph Bigger the pie {portion of circle} bigger the percentage of that part have. For example Rotary screen on first have more than 50% portion of the circle meaning internationally more than 50% printing is done through rotary printing.

As, Chart Describes major portion of textile printing is covered by Pigment Printing so it becomes an important topic to discuss.To print on different substrates different chemistry is required for example printing on natural cellulose is majorly done with reactive dyes. Polyester is printed with disperse dyes, Cotton is printed with sulfur dyes, but, Pigment printing can be applied to various type of fibers like Cotton, Polyester, Blend PC, Polyamide and many more. Isnt that great enough that one learns a technique of printing and now can apply on every type of substrate. This is really big advantage in the court of pigment printing that makes it more ecological, eco-friendly, efficient and safe.

Pigment Printed on 100% Cotton, Unmercerized

Pigment printing can be taken as wall painting, literally wall painting{Distemper}. If we look at the major constituents involved in wall paint are Binder, COLOR{Pigment}, Thickener, Drying Oil, Drying Agent, Fillers etc. Ok, Lets now see the composition of pigment printing paste its Binder, COLOR{Pigment},  Urea {for controlling formaldehyde}, Thickener, Ammonia{for adjustment of pH}. So, Closely looking the constituents will evaluate that around 65 to 80% components are same in pigment printing and Wall painting Distemper. In simple same constituents same chemistry that wholly relays on the working of Binder and of course we will love it to discuss with you.

Pigment Printed

Understanding Binder:

Nor Pigment printing neither Wall painting is possible without Binder. Binders plays key role in both former and later fields. Binder are mononers which on heating get converted into polymers. Yes I said by simple heating, no pressure , no steaming , no electricity.

Binders{Monomer}------Heat----------> Plasticizer/Plastic{Polymer}

Yeah, binders form plastic but, its too soft and transparent that its difficult to see it but we can feel its harshness on the fabric. That’s why pigment printed fabric have more harshness when compared to other printing techniques. Binder actually hold the pigment color and sandwich it between fabric surface and plastic coating and this coating help color to stick there and stand with high and severe conditions.

In addition to binder an other component is also added to the textile pigment printing paste and that is called fixer. Fixers are mostly formaldehyde based. Have you ever heard word UREA-FORMALDEHYDE,  haana? Actually this is a plastic and used to make plastic plates and dishes with two component Urea {NH2}2CO and Formaldehyde {HCHO} as name suggests. So, Here in our paste formaldehyde work in same manner and form plastic which helps in strengthening of binder to hold on pigment

Studying all possible Fixation Modes of Reactive Printing. Evaluating CMC and Strength Report through Data Color

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Studying all possible Fixation Modes of Reactive Printing. Evaluating CMC and Strength Report through Data Color

Chemicals:

Dye, Stock paste.

Purpose:

Purpose is to propose different fixation modes other than recommended (Steaming) with little or no compromise on yield and tone of shade.

Recipe:

Stock paste:

Mild. Oxidizing agent                  10  g/Kg

Urea                                          100g/Kg

Sodium Bicarbonate                   25  g/Kg

Alginate Thickener                      25 g/Kg

Water                                       Balance

Total                                       1 Kg

Dye Glass:

Dye                                         50  g/Kg

Stock paste                              Balance

Total                                       1 Kg

Options:

Options which are being tried are as follow.

Fixation through Curing/Heating only at strenter (Oven) without Air Flow Control.

Fixation through Curing/Heating only at strenter with Air Flow Control.

Fixation through Steaming by utilizing Saturated Steam.

In addition to these modes different other parameters like time was also varied to see the behavior of the dyes on varying fixation Modes.

Jeans/Denim pents/trousers seem first resistance to Snake bites

Narrated and Coated  "When I was a medical student, I served a summer externship in 1975 with the Indian Health Service at Fort Belknap in Harlem, Montana. On some hot summer evenings, I went fishing at a place the locals called "Snake Lake," which was loaded with cutthroat trout, and surrounded by rocky outcroppings that were home to scores of rattlesnakes. I was advised to stay away from the rocks, and to always wear long pants.

In the December, 2009 issue of the Annals of Emergency Medicine (Ann Emerg Med 2009;54:830-836), there appeared an article reporting a study by Shelton Herbert, PhD and William Hayes, PhD entitled "Denim Clothing Reduces Venom Expenditure by Rattlesnakes Striking Defensively at Model Human Limbs." The purpose of the study was to determine whether ordinary clothing (denim material from blue jeans) interferes with the kinematics of venom delivery, thereby reducing the amount of venom injected by a typical snake into a (model) human limb.

Discharge is like ABC...

Self Explanatory Video

Color Discharge on Reactive Printed/Dyed fabric through Sulfur Dyes.

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Color Discharge on Reactive Printed/Dyed fabric through Sulfur Dyes.

Chemicals:

Urea, Sodium Bicrarbonater, Sulfur Dyes, Reactive Dyes, Rangolit C (Sodium formaldehyde Sulfoxylate HOCH2SO2Na). Sodium perborate, Textile Washing off agent.

Discharge:

Discharge is not a new term for a textile Person. Discharge is classified into white and Color Discharge. Term Discharge may be mixed up or used instead of stripping which is not right as stripping is to lower the depth of shade (usual dyers term) where as during discharge screens are used to create patterns by removing partial or full color of the fabric (Textile Printers term).

Printing is now done on variety of fabrics consequently with variety of dyes. In this post we are just focusing on discharging cotton fabric printed/Dyed with Reactive dyes. Suitable discharging agent for reactive dyes or printed fabric is Rangolit C (Sodium formaldehyde Sulfoxylate HOCH2SO2Na). It is prepared by chemically reacting dilute solution of formaldehyde with Sodium Hydrosulfite. So, like Hydrosulfite it is also strong reducing agents. That why no dye can stand with Rangolit and get reduced consequently ending up by losing their colors. Therefore discharging reactive with reactive is not frequently heard process.

Black Ground Discharged with Yellow Sulfur Dye.

As, discussed Earlier discharge can be of two types White or color Discharge. White is done with rangolic C and later one is majorly carried out with Pigment and Binder system, Such binders are considered which are stable with rangolit C. so Rangolit C (Sodium formaldehyde Sulfoxylate HOCH2SO2Na) discharges ground dyed/Printed Fabric and resultantly pigment take over the white ground produced by rangolit C. The only drawback in this process is that pigment printed fabrics have very poor rubbing and washing fastnesses. So, One has to compromise at this end. So, why not to propose some other method rather than a typical pigment binder color discharge.

Purpose:

Purpose is to propose an other method else than pigment binder for color discharge on reactive Printed/Dyed Fabric.

Sulfur Dye Suitability:

Sulfur dyes are reduced before dyeing or Printing.Normally this is done with reducing agent like Sodium Hydrosulfite Na2S2O4. As, we have discussed earlier  Rangolit C (Sodium formaldehyde Sulfoxylate HOCH2SO2Na) is a reducing agent which can replace Hydro sulfite but, Here need of Rangolit will be much greater as it has to perform two tasks one, Iit has to reduce the dye and secondly it has to discharge the ground color.

Studying effect of Viscosity on Shade Depth (Strength), CMC (Change of Shade) and Staining on White Ground.

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Studying effect of Viscosity on Shade Depth (Strength), CMC (Change of Shade) and Staining on White Ground.

Chemicals:

Dye, Stock paste with varying Viscosity. Viscosity can be obtained with high concentration of Thickener. For example Viscosity chosen for this experiment was 50,000 and 15,000 for Brookfield Viscometer spindle 6 and RPM 10.

Alginate Thickener at 40g/Kg approx gives Viscosity 15,000 at 6/10.

Alginate Thickener at 80g/Kg approx gives Viscosity 50,000 at 6/10.

Note: These concentrations are for general idea. You can test at your end to adjust viscosities.

Purpose:

Purpose is to studying effect of Viscosity on Shade Depth (Strength), CMC (Change of Shade) and Staining on White Ground while using same Mercerized Fabric and controlling all external parameters which can interfere with the result like (Time & Temperature during Drying, Steaming and washing.

Back preview of low and high viscous stock paste.

Recipe:

Stock paste:

Mild. Oxidizing agent             10  g/Kg

Urea                                        100g/Kg

Sodium Bicarbonate               25g/Kg

Alginate Thickener               Xg/Kg

Water                                      Balance

Total                                       1 Kg

Xg/Kg can be

Alginate Thickener at 40g/Kg approx gives Viscosity 15,000 at 6/10.

Alginate Thickener at 80g/Kg approx gives Viscosity 50,000 at 6/10

Resist Printing

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Resist Printing

Chemicals:

Dye (1. MCT Range Dye for ground print, 2. VS Range Dye for Over print), Urea, Sodium Bicarbonate, Sodium Sulfite, Alginate Thickener.

Purpose:

Resist printing is a special effect like Discharge printing. As name suggests resist mean TO STOP. Background of fabric in this technique is colored with a dye having MCT (Mono chloro Triazine) Chemistry. Dyes having this chemistry is more stable to reducing agents like Sodium sulfite which is main player in resist printing. So, Ground printing paste has dye, thickener, mild oxidizing agent, Sodium sulfite. While Over print(Full Bloch) dyes are chosen from VS (Vinyl Sulfone) Range. These dyes are unstable to reducing agents like Sodium sulfite

Consequntly a Ground printed portion (usually design/pattern)have sulfite and will eat up all Over color (Full Bloch) on that region. So, over print will only survive those regions which don’t have ground printed. Through this mechanism we can achieve versatile designs and patterns.

Difference Between Discharge and Resist Printing:

Sometime People may confuse Discharge and Resist Printing. Both are two different methods and have versatile useage in textile industry. Results are amazing and adimreable with very low economy (No extra screens, No high class machinery, No special chemicals).

Discharge:

Ground color is eaten up/Destroyed chemically with Sodium formaldehyde sulfoxylate normally called Rangolit C.

Resist:

Over color is eaten up/Destroyed chemically through Soium Sulfite.

Industry News.

4 banks join hands to boost textile industry

The four international as well as local banks have provided trade finance coverage of 110 million euros to Ibrahim Fibers Limited to import modern German machinery for production of polyester staple fiber and polyester chips. Due to this trade finance the Ibrahim Fiber’s polyester production capacity will further be increased by 650 tons per day to 1,250 tons to make it more than double.

The MCB Bank, Asian Development Bank, International Finance Corporation and Citibank have announced that they have completed a trade transaction that will help boost the textile industry in Pakistan, a sector that accounts for over 60 percent of the country’s industrial activity, said a press release, posted on the website of the ADB.

It is to be noted that last year, ADB’s Trade Finance Program supported over $600 million of cross-border trade in Pakistan. Over the past six months, IFC has provided Pakistani banks with $328 million in trade finance guarantees, a $125 million increase in guarantees compared to the same period last year. The trade financing helps Pakistan increase cross-border trade, and benefits many important business sectors.

READ MORE: Source

Using Commercially available chemicals for the fixation of sulfur dyes in Sulfur Printing (Coating).

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Using Commercially available chemicals for the fixation of sulfur dyes in Sulfur Printing (Coating).

Chemicals:

Sodium Bicarbonate, Sodium perborate, Zinc Oxide, Resist Salt, Borax, Sodium Alginate, Soap (Polyglycolether, Nonionic).

Purpose:

Chemical Industries are offering different products for better fixation (oxidation) of sulfur dyed/Printed or coated fabric to ensure good wash fastness and to meet the requirement of buyer. Many Standards included in ISO used chemicals which are true test of color. So, meeting the need is a goal here.

Oxidation is the last step involve in printing of Sulfur Dyes. Oxidation phenomena actually brought back the dye to its original structure Big complex Molecular structure which is actually responsible for the good washing fastness of sulfur Dyes. Different Oxidation method which can be applied are

Oxidation through Air (atmospheric oxygen)

Oxidation through Chemicals

Acetic Acid

Hydrogen Peroxide

Commercially available Oxidizing agent like One of the famous in market Clariant product Diresul Oxidant BRI.

Sodium Bicarbonate

Sodium boromate
Sodium perborate
Resist Salt

Sulfur Printing (Coating).

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Sulfur Printing (Coating).

Chemicals:

Sodium Sulfide or SSodium Hydrosulfite (Na2s2o4), Acetic Acid (Conc), hydrogen peroxide, Sodium Bicarbonate, Sodium Borate, Levling Agent(If Possible), Dispersing Agent (If Possible)Sodium Alginate, Soap (Polyglycolether, Nonionic).

Purpose:

Major use of Sulfur dyes as for as printing is concerned finds in coating application of Denim and heavy GSM twill fabrics. After coating with sulfur different washing outs are carried out like

Stonewash

 Enzyme Wash

 Hypochlorite Washings.

There are three classes of sulfur dyes, which are available commercially,
1.Conventional water insoluble dyes which have no substantively to cellulosic’s.
2.Solubilised sulfur dyes , which are water soluble and non substantive to cellulosic’s.
3.Pre-reduced sulfur dyes, in the stabilized leuco compound form , which are substantive to cellulosic’s.

These Washings gives very beautiful effects to denim fabric all because of Sulfur Dyes.

Sulfur Dyes:

Sulfur dyes are cheap with good washing fastness. Procedure is also quite simple. Stages Involved are.

1. Reduction of Dye
2. Printing
3. Oxidation of Dye

Reduction

This step is generally carried out in the presence of some reducing agent. Common reducing agent being utilized are Sodium Sulfite and King of reducing agents (HYDROS F) Sodium Hydrosulfite (Na2s2o4). Recipe of Sulfur Printing describes 3% amount of Reducing agent regarding to the concentration of dye is sufficient. Sulfur Molecules are complex and larger in Size So, insoluble in water and also have no substantivity towards the fabric. They are reduced to smaller size in the presence of some suitable reducer this makes the dyes to get solubilize and dye shows substantivity towards fabric too.

Some other parameter which are generally not being practiced while printing with sulfur dyes or coating are involved in reduction of dyes during dyeing are as follow

For Dyeing

Here it is worthy to mention that. During dyeing of sulfur. In addition to reducing agent. Caustic (NaoH) is also added. Ph is normally above 10. Temperature of the reduction bath is kept to 80C.