Textile finishing may be done using either “wet” or “dry” chemical treatment techniques. Wet finishing commonly uses a “pad and cure” approach, in which the fabric is immersed in, and pulled through a water-based, chemical “soup” containing emulsified oligomers and polymers, as well as various surfactants and other ingredients used to adjust the pH and to help prevent chemical precipitation in the bath. Often, fabric softeners are also added to the bath.
Finishing chemists need to constantly adjust the concentration of the bath components as they are absorbed, or picked-up by the fabric. Impurities on the fabric, or chemicals carried over from prior treatments, may over time contaminate the finishing bath.
The finishing bath needs to be periodically flushed out and replaced with fresh chemicals. Chemical reactions may occur in the bath that lead to precipitation and unwanted chemical by-products. This leads to chemical waste, inefficient use of chemicals and uneven treatment over the length of the roll goods. The chemicals flushed out of the bath may add to water and ground pollution, or require expensive chemical waste management.
The treated wet fabric is then dried in a “tenter frame”, which is a large oven in which the edges of the fabric are held taut to minimize shrinkage during drying. This curing step consumes much energy when water is boiled away.
When cured and dried, the fabric contains the finishing chemicals, including the surfactants and emulsifiers. These additives reduce the laundry durability of the treatment and may also affect the breathability and feel of the fabric. The emulsifiers also become the failure agents that cause laundry-based degradation of the finish.
For reasons described above, “wet” finishing is environmentally-unfriendly, inefficient and wasteful. Yet, it is the dominant approach used today for textile finishing and is also one of the key reasons why the textile industry has long experienced issues with water pollution.
Dry finishing is accomplished without immersing the fabric in water-based chemicals and without the use of surfactants. In various approaches, gases, plasma or even foams may be used. In the ChemStik® approach, a thin coating of the finishing treatment is applied to one or both sides of the fabric. This is infused directly into the yarn for durability and abrasion resistance.
Because there is no chance for the fabric to contaminate the finishing chemicals, and because fresh chemical is continuously applied to the fabric, the finishing treatment results in a higher quality product than is achieved using wet finishing.
There is little or no waste using most dry finishing techniques because there is no water bath that requires periodic replacement or replenishing. Spray application can result in overspray, but this is minimal.
The GTT technology applies the ChemStik® formula directly to the fabric using rollers, non-aqueous padding or carefully guided spray methods, so there is virtually no waste. Either the hydrocarbon or the GTT oleophobic treatment is done this way. The result is a cost-effective, high-performance and laundry-durable treatment that is also environmentally-friendly.
Dry finishing is energy efficient because there is no need to dry wet fabric. The final treatment also ends up being higher quality than wet finishing because there are no emulsifiers or surfactants left in the fabric. The cured finish contains only a high-quality, covalently-bonded polymer. The GTT dry finishing technology uses cross-linkers to permanently bond the polymer to the fabric. Cross-linkers are too reactive to use in wet finishing because they react with water or are immiscible in water. .