Q. Describe the stripping process of reactive dyed fabric with recipe.
Ans.
Stripping: Stripping becomes necessary when uneven dyeing occurs. By stripping azo groups (- N = N -) brome the dye is removed.
There are two methods of stripping such as –
· Partial stripping method.
· Full stripping method.
Partial stripping method: Partial stripping is obtained by treating the dyed fabric with dilute acetic acid or formic acid. The recommended concentration is between 5 to 10 ml glacial acid or 2.5 – 10 parts of formic acid (85%) per 1000 parts of water.
Recipe:
Glacial acetic acid — 5 – 10 gm/L
Time — 20 – 30 mins.
Temperature — 85ᵒC – 90ᵒC
Full stripping: For complete stripping, the goods are firstly treated with Sodium hydrosulphite (Na2S2O4) at boil. Then washed off and bleached at ordinary atmospheric temperature in liquor containing 1 part per 100 of commercial sodium hypochlorite.
Recipe:
Na2S2O4 — 5 gm/L
Na2CO3 — 2 gm/L
Boiling — 20 – 30 mins.
Time — 20 – 30 mins.
Temperature — Boiling
Q. Mention the function of different chemicals used in reactive dye.
Ans.
Salt: Salt acts as an electrolytic material. It helps to absorb the dye particle.
Soda Ash: Soda Ash acts as an alkali medium and it also acts as a fixing agent.
Urea: It will give deeper shade in dyeing bath. A few amount of urea will give light shade. To soluble the dye stuff properly urea is used.
Sodium alginate: It is a thickening agent. It is collected from sea – weeds. It helps to bind the dye materials in their position. It will also act as a fixing agent
Q. Why Soaping is necessary after dyeing?
Ans. We use different types of dyes in the dye bath. Maximum cases dye stuffs are sedimented (তলানি) on the bottom of the dye bath and deposited on the textile material we use soaping method to increase the brightness and to remove the floated color we use soaping process.
Q. Mention the use of salt & soda ash in reactive dye for different shade.
Ans.
Shade
Salt (g/L)
Soda Ash (g/L)
Light shade
37
12
Medium shade
60
15
Deep shade
80
20
Q. Write down the application of reactive dyes on cotton goods.
Ans. Now – a – days reactive dyes are popularly used for cotton goods. Generally 4 types of cotton goods are used to dye with the reactive dye –
i. Loose fiber form.
ii. Yarn form.
iii. Knit goods
iv. Woven fabric.
Jigger dyeing m/c (Woven fabric), Winch dyeing m/c (Knitted fabric) and Jet dyeing m/c (Knitted + Woven)
Q. Write down the test method of reactive dye.
Ans.
Recipe:
H2SO4 — 1 cc/litre of water
Na2S2O4 — 2 cc/litre of water
M: L — 1:20
Temp. — Up to boiling
Time — 30 mins.
ü When a sample of reactive dyed fabric is treated in a test tube containing H2SO4 of 1 cc per 1 litre water, it results bleaching of reactive color from the dyed fabrics. It is one of the identification tests of reactive color.
ü The reactive color remains fixed on the textile material though it is treated or boiled with pyridine or chloroform. On the other hand, textile material dyed with direct, azoic etc. dye stuffs and treated with above chemicals then color will come out easily. It is one of the identification tests of reactive color.
The second one is one of the most efficient test methods of reactive dye.
Q. Write down the classification of reactive dye with example.
Ans.
1 On the basis of reactive group: Two types;
Halogen added group (Cl 2, F2, Br2,I2)
Example: Pyrimidine.
Vinyl added group (– CH = CH2)
(– D – SO2 – NH – CH = CH2) [– CH = CH2 ……….Reactive group]
Example: Levafix.
2 On the basis of reactivity: Three types;
High reactivity. Ex. Procion – E. {Medium alkali (NaHCO3) used}.
Moderate reactivity. Ex. Livafix – E. {Medium alkali (Na2CO3) used}.
Low reactivity. Ex. Premazine. {Strong alkali (NaOH) used}.
3 On the basis of use: Two types;
Cold brand reactive dyes (High reactivity) – 40ᵒC – 50ᵒC
Hot brand reactive dyes (Low reactivity) – 90ᵒC – 95ᵒC
Use of Hot brand is maximum in our country, Cold brand is used for batik, tye dye etc.
Q. Mention the reactive dyeing methods.
Ans.
Ø Batch dyeing method (Discontinuous method):
· Hot brand Dye.
· Cold brand Dye.
Ø Continuous method:
· Pad system method.
· Pad thermo fixation method.
Ø Semi – continuous method:
· Pad roll method
· Pad – jigger method.
Q. Describe the Cold Brand dyeing with reactive dye.
Ans.
Recipe:
Dye stuff —- 3% (According to the wt of mlts)
Soda Ash —- 15 gm/L
H2O —- 10 times
Temperature —- 40ᵒC
Salt —- 60 gm/L
Time —- 1 Hour
Dyeing scheme:
At first solubulize the dye stuff with a little amount of cold water. Take required water to the dye bath.
Procedure:
At first solubulize the dye stuff with a little amount of cold water. Take required water to the dye bath. Dye liquor and salt is given to the dye bath and stirred (নাড়ানো) throughly. Then the textile material is taken to the dye bath and dyed for 20 – 30 mins. After dyeing the material is rinsed (পরিষ্কার পানি দিয়ে ধোয়া) with cold water. Then treated with 20% soap and 1% soda solution in a bath for 30 minutes, then the material is washed and dried.
Textile Notes24 