Voile, Cambric, Terry voile, shiffon, long cloth, classical oxford, pin-point oxford, Chief Value Cotton

Voile

It is a doubled yarn, highly twisted with count range >60s. It has an square and open construction. The fabric made from it is light weight, transparent, crispy and granular feel. It can be either cotton or P/C. Its trade name is 2 x2 Rubia. 72 epi and 72 ppi.

Cambric

It is a single yarn, rest properties are same as voile.

Terry Voile

It is name of voile with 2/81 high twisted fabric in 67:33 blend which is later carborised to get a 100% polyester fabric.

Shiffon

Count is 62s. Here weft is highly twisted (1400-1500 tpm) polyester filamnet and textured and warp is p/c. 67:33

Long Cloth

It is a plain fabric with special kind of finish which remains for some times even after normal washing.

Poplin Broad Cloth
A tightly woven, subtle variation on a plain-weave fabric, characterised by a very high thread count- 100 to 200 tpi- produces a thin, but relatively opaque fabric with a crisp, hard finishing. Also characteristics of the fabric is its fine horizontal ribbing, produced by the lengthwise warp threads being packed more densly than the crossing weft threads. The ribbing is scarcely noticeable but makes any on-grain stripes very clear and appear solid in color, and it also adds a little shine on the fabric. If the cotton fiber itself has any shine, it will enhance the shine of ribbing and produces a very dressy effect. It comes in solid colors, stripes, plaids and checks.

120 *72
Chambray: It looks solid color but is a plain worked with two colors of yarns, usually a white warp and a colored weft or vice-versa. They are woven in all weights. It can be poplin, or twill or dobby chambray

Classical Oxford
It is like chambray, but in contrast to a chambrays plain weave, oxford cloth is woven in a basket weave. It produces the fabric's soft bulkiness.

Warp is Dyed and weft grey
warp --> 2/40s, Weft --> 2/30s

Pin Point Oxford
When worked in a fine weave, oxford cloth is called a pinpoint oxford.

both warp and weft 2/80s, 144 ends/inch in grey and 60-62 ppi.

Chief Value Cotton

60% cotton, 40% polyester

German Finish

Enzyme treatment. Here fabric gets very good lustre and feel. Also we do a process called weight reduction process ( weight is reduced by 4-5%, so bulkiness in the fabric is given.

Chinos

3/1 twill with 2/40s * 2/30s. When single yarn is used it is called Drill.

Gaberdine
2/1 twill
with 2/40s * 2/30s

Notes on Dyeing of sulphur black on Rope Dyeing Range

1. Process of dyeing of sulphur color:

1st Wash tank: mercerisation by taking 22% NaOH ie. 250 gpl
2nd Wash Tank: Hot Wash
3rd Wash Tank: Cold Wash

2. In 1st and 2nd dye bath take sulphur color 6-8% on the weight of the yarn sheet. Temperature 90 deg. cel. The solution contains the following:

1. solubalised sulphur color: 150 gpl
2. Na2S--> reducing agent: It is added to increase its reducing power
3. Caustinc Soda --> 10 gpl--> reducing agent
4. Wetting agent--> 2gpl
5. Antioxident Sulphide ( Glucose paste--> 5gpl). This is added to prevent the oxidation of of Sulphide solution. It will always remain in reduced form
( Alos if the shade is slightly greyish, one can add tiny tinge of sulpher blue--> 20gpl)

in III, IV and V dye bath--> cold wash
in 6th dye bath. We take H2O2(30%)+Acetic Acid(2:1 by weight). H2O2 acts as an oxidising agent. But as it acts on neutral pH (=7) and after cold bath the solution is slightly alkaline, to make it neutral wil add acetic acid. Acs in alkaline pH, oxidising action of H2O2 will be similar to the bleaching action, which may cause tendering in the fabric.

7th and 8th Dye Bath: Cold Wash

Wash Box Number 4: Here washing is done with detergent and soda ash at 60-70 deg.c

5th and 6th Wash Box: Hot Wash

7th wash Box: Here softner is added at 25 gpl. It is cationic softener with pH 4.5 to 6.5. As during oxidation of sulphur, strength is reduced by 10%. On a yarn sulphur is of two types :
1. Free Sulphur
2. Reacted Sulphur.

The free sulphur will react with moisture in the atmosphere to form:
H2O + S --> H2SO4
Which tenders the yarn. Now at acidic pH reaction is much faster. So we add only a small amount of softener (25 gpl) as against that in indigo which is 100gpl.

3rd Point

Over all during sulphur dyeing and storing, the yarn strength is reduced by 15% as compared to Indigo.

4th point

If ball formation takes place of sulphur dyed warp at loom shed, then we can taken in 4th dye bath little Na2S+Caustic to reduce the free sulphur.

Fabric Knowledge

Please refer to the following link for fabric knowledge

Practical Notes on Rope Dyeing for Indigo Dyed Denim

Practical Considerations in Rope Dyeing for Indigo dyed Denim.

The passage of yarn in rope dyeing is as follows:

Pre-scouring -->hot wash-->cold wash --> Dye baths--> hot wash-->cold wash--> application of softener

lets discuss these processes one by one:

Pre-scouring

1. The objectives of pre-scouring are the removal of wax content from cotton, removal of trapped air from cotton yarn and Making yarn wet

2. This is done at 90 o C

3. We use the following ingredients at pre-scouring stage:

Caustic Soda: Its quantity depends upon the quality of cotton fibres used in the mixing. Generally we take 2-4% of caustic soda. It removes the wax by the action of soapanification.
Wetting agent: It is anionic in nature
Sequestering Agent: Even with the use of water softening, it is very difficult to find the desired softness in water ( about 2-3 ppm) . So we use the agent to make the water soft.

4. Why Trapped Air should be removed. The reason for this can be understood as follows:
In 1 kg of yarn, there is approximately 2 litres of air. 1 litre of air decomposes 1.8 litres of Sodium Hydrosulphide. It will cause uneven dyeing and more consumption of Sodium Hydrosulphide ( hydro).

5. Absorbency of yarn may be checked after scouring.


Hot wash

As some caustic is carried by the yarn after pre-scouring, so hot water is given at 70-800C. If this is not done, this yarn will go into the dye-bath which will change the pH of the dye-bath.

Cold Wash

After hot wash, yarn temperature is more. To bring it back to its room temperature, cold wash is given to it.

INDIGO DYEING

1. Indigo is not a perfect vat color. It may be called a trash vat color. The constant of substantivity for other colors is 30, for indigo it is only 2.7. So there is a need of 5 to 6 dye baths and make the use of multi-dip and multi-nip facility to increase the penetration.
2. The dyeing is done at room temperature as indigo belongs to Ik class of vat dyes, where dyeing is done at room temperature and oxidation is done by air only and not by chemicals. If oxidizing agents are used, they will cause stripping of colors.

3. Indigo is not soluble in water. So it is reduced with Sodium Hydrosulphide. Then caustic soda is added to make sodium salt of vat colors to make it soluble. To reduce 1 kg of Indigo, 700 gms of sodium hydrosulphide is required. However some extra SHS needs to be taken to avoid some decomposition of SHS.

Practically it is prepared in the following sequence

-Take indigo
-Add caustic
-Then reducing agent

4. When caustic is added to indigo, it is an exothermic reaction. It is allowed to cool down, then before sending it to feeder, sodium hydro-sulphide is added. Reducing agent is not added first as it will be decomposed first, so consumption of it will increase. It is also not advisable to take solubalised vat, as offered by some companies due to the following reasons:

a. If it is used after 6 months, there will be a decomposition of sod. Hydrosulphide. It will become partially soluble. Then to make it soluble again, more SHS has to be added.
b. Transportation is difficult
c. Cost is more

5. Feeding System

Rat of flow of yarn is given by

((No of ropes x no of ends x speed of machine)/ count x 1.693 x 1000)

in kg of yarn / minute

So we can determine the rate of feed of indigo. It is very important that replenishment of indigo is there as any variation will result in the change of shade and also if level is more, there is a problem of over-flow.

6. If total capacity of dye bath for example is 15000 litres, then circulation must be 3 times the volume. If it is less then there are 100% chances of getting a lighter shade.

7. Core and ring dyeing effect
This effect is obtained by multidip-multinip facility

8. pH of the Dye bath should be kept in between 10.5-11.5. At this pH , sodium salt of Indigo is mono phenolic form. At this form, the strike rate of dye is very high. So after washing, there will be a better dye effect. At pH 11.5 to 11.7, at this affinity is less, so dye effect will be less prominent.

pH is controlled by the addition of caustic soda.

9. Testing of Hydro

TOTAL HYDRO
We take 10 ml of indio with SHS in 30-35 ml of water. It is set for one minute and shaken. As air will decompose SHS. So vacuum created will fetch the water from above. If 3 ml of water is required, then concentration of hydro is 3 gpl. As a thumb rule, concentration of total hydro should be min. 1.5 gpl.

REDUCED HYDRO

It is the hydro that is used for the reduction of Indigo. It should be around 0.7 ( 1000 kg of Indigo needs 700 kg of hydro to reduce it). For testing we take 10 ml of dye solution and 30 ml of water and 5-6 drops of 40% formaldehyde and shake it for one minute. The water that goes gives the readings of the reduced hydro.

Total Hydro- Reduced Hydro = free hydro

If Total hydro is min. 1.5 gm/lit. then free hydro must be min. 0.5 gms/ litre which acts as buffer

10. Also hydro reduction capacity is measured by mV meter which measures the Redox Potential.

It should be around 760-800

Through the day, the redox potential should be +- 20 mV of the norm. If it is more then the process control is a failure.

Caustic--> It is around 0.4 to 0.5 times the hydro used.

Washing
Rubbing fastness of indigo is very important. On a scale of (1-4), it is 2. Washing is done to improve the rubbing fastness.

Wash at 60 deg.--> Wash at 60 deg.--> Wash at room temperature--> wash with softener

Why Softener:

1. The rope is going to be opened at Long Chain Beamer. It the softener is not used, opening will be hampered.

2. It is generally 1.2% of the weight of the yarn. It is a cationic softener. It is always having pH in the range of 4 to 55. Softening is done at room temperature. If high temperature is used there is always some chance of tendering of yarn.

3. Concept of Buffer pH is given by Virkler USA, they say by addition of this, there is 40% less consumption of Indigo for same shade depth.

4. Metering Consumption

If solution is of 900 litres
10% Indigo-->90 litres
Hydro--> 90*.7 = 63 kg
Caustic--> 63*0.445= 28 kg.