Bleaching and Optical Brightening of Silk

This is as per a brochure from CSTRI ( Central Silk Board)

Bleaching Receipe

M:L- 1:30
Soda Ash- 0.5 GPL or 1% on the weight of the material.
Sodium Silicate- 1.5 GPL
Hydrogen Peroxide- 20 MI/Lit
Temperature- 80 deg C, Time- 60 to 90 Min, pH-9

Procedure
-Take required quantity of water.
-Dissolve soda ash and sodium silicate
- Enter the material at 40 deg C
- Work for 5 min.
- Take out the material and add Hydrogen Peroxide
- Raise the temperature to 80 deg C
-Work for 60-90 min followed by cold wash.
- Removal of excess water by using hydro extractor.

Optical Whitening Receipe

M:L- 1:30
Ranipal WHN-3% on the weight of the material
Hydrose- 2 GPL
Temperature- 60-70 Deg C, Time-15 min, pH-9

Procedure

- Take required quantity of water.
- Add Ranipal WHN and hydrose ( Dissolve Ranipal in hot water)
- Enter the material at 40 deg C.
- Raise the temperature to 60-70 deg C
- Work for 15 minutes followed by cold wash.
- Removal of excess water by using hydro extractor.
- Drying under shade.

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Degumming of Silk

This is as per a brochure from CSTRI ( Central Silk Board)

Receipe

M:L- 1:30
Soap- 5 GPL or 15% on the weight of the material.
Soda Ash- 1 GPL or 3% on the weight of the material
Temperature- 90-95 deg C., Time- 30 to 45 minutes, pH- 9.5 to 10.5

Methods/Procedure

- Dissolve soap and soda in the required amount of water.
- Enter the material at 40 deg C
- Raise the temperature to 90-95 deg C
- Work for 30-45 minutes
- Take out the material and hot wash for 10 minutes for 60 to 70 deg C.
- Followed by cold wash.
- Removal of water by using hydroextractor.
- Drying under Shade.

Single Bath Degumming and Bleaching

Receipe

M:L- 1:30
Soap- 5 GPL or 15% on the weight of the material.
Soda Ash- 0.5 GPL or 1% on the weight of the material.
Sodium Silicate- 1.5 GPL
Hydrogen Peroxide- 20 MI/Lit
Temperature - 85-90 deg C, Time- 60 to90 min., pH- 10

Procedure

- Take required quantity of water.
- Dissolve Soap, Soda Ash and Sodium Silicate
- Enter the material at 40 Deg C
- Work for 5 minutes
- Take out the material and add hydrogen peroxide.
- Raise the temperature to 85-90 deg C
- Work for 60 to 90 minutes followed by hot wash and cold wash.
- Removal of excess water by using hydro extractor.
- Drying in Shade

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Dyeing of Silk with Reactive Dyes

This is as per a brochure from CSTRI ( Central Silk Board Bangalore)

Receipe

M:L- 1:30
Dye: X% on the weight of material.
Glauber Salt- 20% of the weight of material ( 1st Stage)
Glauber Salt- 20% of the weight of material (2nd Stage)
Soda Ash- 5% of the weight of material ( 1st Stage)
Soda Ash- 5% on the weight of material (2nd Stage)
Temperature ( Cold Brand)- 50 deg C
Temperature ( Hot Brand) - 60 deg C
pH-9,  Time: 65-75 minutes

 Procedure

Preparation of dye solution:

Dissolve required dye powder in boiling water in a separate beaker/vessel.

Set the dye bath with required quantity of water.
Add dye solution and add 20% Glauber salt and 5% soda ash at 1st stage.
Enter the material and work for 10 minutes.
Add 20% glauber salt and 5% sold ash at 2nd stage and work for 20 minutes.
For Cold brand reactive dyes, work for 45 minutes at 50 deg.
For hot brand reactive dyes, work for 45 minutes at 60 deg.
Take out the material followed by cold wash.
Remove excess water by using hydro extractor.
Dry under shade.


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Chemicals used in Textile Processing-2

1. Bleaching Powder

It is hypochlorite of calcium and sodium. Bleaching powder on treatment with small quantities of dilute acid liberates hyopchlorous acid, whcih can easliy furnish nascent oxygen and thus acts as an oxidizing and bleaching agent. It is used for the following purposes:

1. As an oxidising agent in garment processing
2. For bleaching cotton, linen and wool.
3. In rendering wool unshrinkable.

2. Hydrogen Peroxide, H2O2

Hydrogen peroxide is a colorless, odorless, syrupy liquid in the anhydrous state. It is a powerful oxidizing agent. It destroys the color of some organic compounds and is used in garment and textile industry for bleaching delicate fabrics like wool, straw and silk.

3. Potassium Chlorate KClO3

Potassium chlorate is a white crystalline solid, which is soluble in water. On heating it decomposes to give oxygen. The ease with which it can lose oxygen, it acts as a strong oxidizing agent. It is used for garment printing.

4. Potassium Chromate

Potassium chromate is available in the form of lemon yellow crystals with no water of crystallization. In garment industry it is used as a mordant.

5. Potassium Dichromate

It is available in the form of orange red crystals. It is soluble in water. In neutral or acidic solution, potassium dichromate furnishes nascent oxygen and thus acts as an excellent oxidizing agent. It is used in garment industry as an oxidizing agent and as mordant in dyeing.

6. Potassium Permanganate

It acts as a powerful oxidising agent in neutral, alkaline or acidic solution and hence used in the garment industry as an oxidising agent.

7. Sodium Perborate

Sodium perborate is mainly used as a bleaching agent for a variety of fabrics namely wool, cotton, rayon, linen etc. It is also used as an oxidising agent and dye fixing agent.

8. Sodium Hypochlorite

Sodium hypochlorite liberates hypochlorous acid and thus acts as a powerful oxidizing and bleaching agent. It is used in textile and garment industry for bleaching process.

9. Sodium Bisulfite, NaHSO3

An aqueous solution of sodium bisulfite is obtained when an aqueous solution of sodium carbonate is saturated with sulphurdioxide. It is an important reducing agent and is used as an antichlor after bleaching garments with chlorine.

10. Sodium Hydrosulfite

It is used as reducing and bleaching agent in garment and textile industry.

11. Sodium Metabisulfite

On heating, it decomposes into sodium bisulfite and sulfur dioxide and hence it is an important reducing agent. It is used as an antichlor after bleaching garments with chlorine.

12. Sodium Sulfite

It forms colorless crystals very soluble in water. It is decomposed by dilute mineral acids with the evolution of sulfur dioxide. It is used as mild bleaching agent for silk and woollen fabrics and as an antichlor after chlorine bleach.

13. Sodium Sulfide

Its aqueous solution shows and alkaline reaction due to hydrolysis. It is used for manufacture of sulfur dyes and as reducing agent in garment industry.

14. Sodium Sulfoxylate Formaldehyde

It is also known as Rongalite C. It is a powerful reducing agent and exerts its full reducing action only at high temperatures. It finds extensive application in garment and textile industry for printing and stripping dyed fabric prior to re-dyeing.

15. Sodium Thiosulfate

It is also know as hypo. It is a colorless, crystalline and efflorescent substance. It is used as an antichlor after bleaching garments with chlorine.

16. Stannous Chloride: It is used as mordant in garment dyeing and printing.

17. Dextrin

It is a modified starch prepared by heat treatment of starch in the dry state, with or without the addition of small quantities of chemicals. It is a white powder, and finds extensive use as sizing and finishing agent.

18 Glucose

It acts as a strong and cheap reducing agent in garment industry.


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