Denim Desizing
Zahirul Islam BUTEX
Latest posts by Zahirul Islam BUTEX (see all)
- Denim Wet Process | Bleach Wash | Acid Wash - June 14, 2020
- Acid Wash / Random Wash - May 8, 2020
- Denim Wet Process | Enzyme Wash - April 15, 2020
Denim Washing | Denim Desizing
Desizing
Desizing is the process of removing the size material from the warp yarns after the textile fabric is woven. This is the most important part of denim washing.
During sizing, the warp yarn threads are treated with auxiliary chemicals known as sizing chemicals which impart the strength, friction resistance during weaving. The purpose of sizing is to protect the thread by coating. Different types of sizing chemicals are used like Starch, Modified starch, polyester, polyacrylates, polyvinyl alcohol, polyvinyl acetate, CMC etc. During washing, those chemicals must be removed to bring desired look on the fabric.
Its main objectives are given below:
- removing the impurities which came from fibre or different manufacturing processes like oil, acedic or alkaline chemicals, dirts, dusts etc.
- removing the sizing chemicals used in weaving
- decreasing the crease risk on the garment etc.
Types of Desizing Agents
Different types of desizing agents are applied in denim washing considering it’s compatibility, price, advantages, disadvantages, availability etc.
Types are given below:
- Detergents
- Enzymes
- High alkalines
- High acids
- Oxidative chemicals
1 . Detergent
Generally, detergents are used to promote the removal of soil from fabric and also disperse as well as stabilize oil droplets from materials. Those abilities depend on the composition of detergent and the nature of the substance.
The major components of laundry detergents are anionic surfactants, alkaline builders, water softening agents and anti re deposition agents. Higher end detergents contain enzymes and optical brighteners. Some liquid detergents contain nonionic surfactants.
Laundry detergents are formulated to provide general cleaning, which includes removal of soils and stains as well as the ability to maintain whiteness and brightness. In addition, many premium laundry detergents offer additional benefits like fabric softening, dye lock, fiber protection, and disinfectancy.
2 . Enzymes
Enzyme is a kind of protein, that is obtained by extraction method from naturally existing bacteria and fungi. The structure of enzyme is a biologic polymer and it can be found every cell. Enzymes help the chemical reactions in living cells by breaking the large molecules to smaller ones or vice versa.
Enzymes are called as biological catalyst because of it’s initiation and speed of reaction. The starting molecule in a reaction is called “substrate” and the yield molecule is called “substate”. Enzymes incorporate the reaction for yielding the “substate” but they may be recovered unchanged at the end of the reaction. Therefore, the reaction can continue over and over again while the enzyme is active.
The relationship between the enzyme and substrate can be explained like lock-key model. So, there is only one substrate that the enzyme is active on. Different types of enzymes are used for desizing fabric in washing like:
- Alpha amylase enzyme – removes starch
- Cellulase enzyme – breaks and removes fibre
- Laccase enzyme – attack the cellulose within a very short time
- Catalase enzyme – breaks peroxides but don’t effect cellulose fibres
3 . High alkaline
High alkaline means the PH level must be higher like 8-14. High alkalinefa acts as a high-performance cleaner by reacting with the acids found in organic soils. The acids in the soil reacts with the alkali and it neutralizes as well as cleans the substrate. This higher PH helps in neutralizing higher reactive acids and the high alkalinity has no affect in cleaning quality except the removal of impurities.
High alkaline washing agent are like Soda ash (Na2CO3), Sodium Hydroxide (NaOH), Ammonia (NH3) etc. They are mostly used for high quality cleaning and their PH level are given below:
Table 1 List of alkali with PH level
|
Alkali |
PH |
Soils |
|
Mild Alkali |
8-10 |
Light oils, small particles |
|
Ammonia |
10-11 |
Oils, particulates, film |
|
Soda Ash |
11-12 |
Oils, fats, proteins |
|
Sodium Hydroxide |
13-14 |
Heavy grease/soils |
4 . High Acids
High acid means the range of PH in between 1-6. They are particularly used for cleaning mineral soils by their strong acidity. Strong acid like sulfuric, phosphoric, acetic acid and citric acids are good while removing mineral oils. As most soils are acidic so they are less used for desizing in textiles, they are helpful while removing the dirt, clays, salts, rust and oxides.
5 . Oxidative Chemicals
Oxidative chemicals like hydrogen peroxide (H2O2) is used to clean stains from textile fabric. Dilute hydrogen peroxide (H2O2) is a good way to remove bloodstains and also used in washing for removing sizing chemical by oxidation. In this process, H2O2 oxidizes and decomposes sizing chemicals by chemical reaction.
H2O2 —- ½ O2 + H2O
Available Chemicals Used in Washing Factories in Bangladesh
Chemicals used in washing factories are given below:
- Detergents: Surf Excel, Sultafan DI, Lava sperse SPC, Ecozyme 15-L,etc.
- Enzymes: Eco-zyme ulta, G-zyme ultra, InvaGymes Cel, Lavacell NHC Cold, Novozymes – Denillite 2 S, largezyme 330 etc.
- Anti backstainer: RM, Fortress eco-2, Fortress GSL, Partix GSL, Seyco Sperse SPW – 801, Lava Sperse Kds etc.
- Anti Creasing agent: Imacol C2G Th LIG, Lava Lupe M-CF etc.
- High Alkalines: Caustic soda, soda ash etc.
- Acids: Acetic acid.
- Oxidative chemicals: Hydrogen peroxide (H2O2), Potasium permanganet (KmnO4), Bleaching powder (Ca(Ocl)Cl), bleach etc.
- Bleach Activator: GT-clor-plus, soad ash etc.
- Softener: Resoft A090, Alam BC, Resilk MES, Alam GRM, UCS, Jingen 60, Alam Rp MSS13, Ricofin GWE, Velveton-H, Si- Nyce, Si-oil, DenimKol SPD etc.
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Zahirul Islam BUTEX
Latest posts by Zahirul Islam BUTEX (see all)
- Denim Wet Process | Bleach Wash | Acid Wash - June 14, 2020
- Acid Wash / Random Wash - May 8, 2020
- Denim Wet Process | Enzyme Wash - April 15, 2020
