Cotton is a very popular textile fibre with some excellent properties, such as : comfort during wear, ease of dye ability, soft handle and with good tensile properties. However, cotton fabric has a great tendency to retain creases acquired in laundering and in use. Due to the poor crease recovery properties cotton fibre have been facing considerable competition from synthetic fibres.
In 1930, The Tootal Broadhurst Lee Co. Ltd. first disclosed details of a procedure for producing easy care finishing (crease resistant finishing) for cotton. The demands on cotton fabrics for high levels of easy care finishing have become more important in recent years and the research to improve the process is still continuing.
Easy care finishing can be expressed as a chemical modification of fibrous cellulose resulting from a heterogeneous reaction with a di-functional or poly-functional reagent which generates resilience in cotton containing fabrics by a “modus operandi” (called cross linking) which occurs in accessible regions of the fibre between hydroxyl groups on two different molecules of cellulose in unspecified locations in the microstructure.
Easy care finishes are expected to impart the following desirable properties to the fabric :
Minimum wrinkling when dry or wet
No ironing necessary
Good soil-repellency and easy removal of soil by washing
Full retention of all creases and pleats
Good retention of dimensions and shape
Wearer comfort in different climates
Adequate resistance to wear and tear.
Formaldehyde in the presence of an acid catalyst is the oldest, cheapest but most destructive reagent (reduces strength) for obtaining crease resistance effects on cotton. Formaldehyde behaves as a bi-functional reagent and forms covalent cross-linkage with cellulose.
Two types of cross-linkage many be formed:
1Though formaldehyde is a cheap, efficient, cross linker, it has not found commercial success as a cross-linking agent. There are three reasons for the restricted use of formaldehyde in easy care finishing:
-The odor and toxicity of the reagent
-The variability of results
-The excessive loss of fabric strength.
Later the cyclic urea of two methyl group has developed to impart to the cotton a high degree of resistance to dry and wet creasing, good chlorine fastness, and good stability towards hydrolysis. The simplest derivatives of this groups is 1, 3-dimethylol-2-imidazolidone, commonly known as dimethylolethyleneurea (DMEU). This bi-functional product is water soluble and forms cross links with the hydroxyl groups of cellulose through N-methylol groups.