Garment dipping

Garment dipping

What is a wrinkle free shirt?

A wrinkle free shirt is a garment that has been treated in such a way that it preserves its shape, smooth appearance and creases after laundering. If the garment is tumble dried, little Ironing or No ironing is required.

Wrinkle free materials can withstand even the roughest of treatment. Even though Wool is much stronger than cotton, this method is mostly done with cotton fabrics. Cellulosic fiber containing fabrics are made resistant to creases by the use of a durable wrinkle- free process which is composed of the treatment of a cellulosic fiber with formaldehyde, a resin with a catalyst, a softener, polywax emulsion and an Optical Brightening agent.

The process is carried out in conditions at which the formaldehyde reacts with the cellulose in the presence of a catalyst and a softener to improve the wrinkle resistance of the fabric and better tear strength after laundering with less treatment.

The most common agents that crosslinks among themselves and results in the wrinkle free finishes are often the derivative of Urea.

Figure 1.0 show the crosslinking between DMDHEU (dimethylol dihydroxyethyleneurea) and DMEU (dimethylol ethylene urea)

"Chemical

Figure 1.0

Nowadays most of the wrinkle free shirts are being composed of cotton and synthetic fibers even if the label states 100% cotton. Due to the loose regulations, a list additional materials is necessary in the fabric if the secondary fibers exceed a certain percentage of the entire garment which affects its quality and may result in shirts that don’t last as long as they should. Some wrinkle free shirts are not meant to be pressed at a professional dry cleaner because the more the temperature is , the more exposed the shirts are to the discoloration of the resins used during manufacturing.

What are the components that the resin is made up of?

1) Catalyst

A catalyst is asubstance that speeds up a chemical reaction, but is not consumed by the reaction; hence a catalyst can be recovered chemically unchanged at the end of thereaction .The rate and speed of the reaction is positively affected by the presence of a catalyst. It speeds up the reaction and allows a better flow

For chemicals to react with the cellulosic fibers, the ingredients involved in the reaction should have a rearrangement of chemical bonds. Energy is needed to form the transition state and it is called the energy of activation. Reactants with lower energy cannot react with high energy ones and this is where the catalyst is used so that it provides a different route for the reaction. The catalyst allows a greater proportion of reactant species so that they gain enough energy to pass through the transition state and complete the reaction. This will result into the perfect distribution of chemicals throughout the shirts.

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2) Softeners

There are normally 2 types of softener that are being used and it depends on the structure, colour and resistance of the fabric being used.

i) An elastomer softener is used and it is an innovative finishing agent, mainly composed of multifunctional polyurethane. It enhances wrinkle recovery and prevents wrinkle of fabric. The softener also gives perfect elasticity to the fabrics and it does not cause yellowing on white fabrics.

It is a clear viscous liquid with a pH of 6.5 , a nonionic substance and it is very soluble in water.

Normally 1-4 % of the weight of the fabric is added with a pickup of 80% maximum. Curing should be performed at 180deg maximum.

ii) A Silicone softener is also used and it a highly concentrated softener normally found in gel form. Silicone normally delivers excellence in softness and smoothness of garments. It gives the garments a durable soft handle and very smooth feel. It also increases crease recovery, shape depth and brilliancy when applied on dyed fabrics.

It is a transparent liquid and is a blend of amino silicones and urethane. It is a non-ionic substance with a pH of 7 and is soluble in water. A pickup of 70-80% should be used and maximum temperature should be around 130 degrees.

3) Optical Brightening Agent

Fibers contain natural or contaminant coloring matters are generally subjected to decolorisation by the different bleaching methods therefore chemical treatments need to be done so that every substance are neutralized and an optical brightening agent is used.

In order to use an optical brightener for textile application, it should have a good solubility, good fastness properties, build up properties, exhaustion properties, effect of water hardness, good leveling and penetrating properties, should not absorb light , compatible with the other chemicals in the concentration and should be stable and fast to the oxidative and reductive bleaching agents.

Types ofWrinkle Free Process of Cotton Shirts:

This concept of non-iron shirts existed since the very roots of cotton shirt making decades ago. Polyester and other fibers were firstly tried but the result was just a failure and it is then that the consumers got to know about the positive properties of the cotton fiber. The ability of cotton fibers to hold moisture and release it controlled makes cotton one of the best fibers among all. It has got a good breathability and gives a feeling of comfort to the user. Since some 15 years back, new methods have been established to use chemicals with the cotton fiber in order to make them almost wrinkle free and there are mainly 4 types of methods that are used:

• Pre- Curing

• Post- Curing

• Dip- Spin

• Vapor – Phase

Pre- Cured fabric:

The fabric used can be a 100% cotton fabric or a cotton blend and as compared to the other processes, this method does not require any further heat treatment as curing has already been done prior to the manufacture of the shirt. The already finished fabric is resistant to wrinkles already.

Post- Cured fabric:

In this system also, 100% cotton fabric or cotton blends can be used and the fabric will be delivered with the curing chemicals found inside. After the shirt had been manufactured, it has to be ironed entirely and hanged inside an oven indicating a temperature of 130°C to 150°C.

Dip- Spin system:

This method is the most commonly used process to manufacture wrinkle free shirts and can be used both for 100% cotton and cotton blends. After the full assembling of the shirt, it will be dipped into a mixture of chemicals which will be absorbed by the cotton fibers. The shirt being moisturized is kept in a closed bucket and will be pressed entirely. After pressing, the shirts will be placed onto a hanger and will be sent to cure in an oven of about 140°C for 5 minutes maximum.

This one belongs to the most popular process for wrinkle free shirts and can be used for 100 % cotton fabrics or cotton blends. After the shirt is manufactured as usually, it will be dipped into a mixture of chemicals, which will be absorbed by the cotton fibres. After the treatment in a tumbler the shirt is still moisturized and has to be pressed entirely.After pressing the shirt will be put on a hanger and can be cured in a curing oven by about 140°C for about 3 -5 min. After the curing process is over, all wrinkles will tay for life. A re-touching by an iron is impossible.
This is the process that I will be emphasizing more in the following pages.

Vapor – Phase:

This method cannot be practiced in many countries as very aggressive chemicals are being used. It follows the same system as the Dip Spin and is manufactured in the same way. After the last pressing, a special curing over is used instead of liquid chemicals, gas chemicals are used to make the shirt wrinkle free. The gas circulating throughout the oven and gradually penetrates the cotton fiber. The gas has to be extracted later on and the products need to be washed in order to remove the excess chemicals left inside.

Garment dipping in Mauritius

I have explained above about the different components and processes towards the production of a Non-Iron shirt on foreign lands. Coming now to Mauritius where this process was implemented only by Laguna Clothing in the year 2012. It was introduced on a pilot project and several testing were conducted before taking any command from their abroad clients. Gradually the different machines like the sprayer, dryer, bulk press and the oven were installed. After 1 year they started to get demands to produce Non iron shirts and at first they produced around 500 shirts per day but with the increase in commands, they had to boost the production and nowadays they produce around 1000-1200 shirts per day according to the client specifications.

Garment dipping

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