Dyes for synthetic polymer fibres

1 CA and CTfibres. Fully acetylated cellulose contains three acetyl groups per hexose unit. Controlled hydrolysis gives a secondary cellulose 

PES fibres are hydrophobic, have a closely packed molecular structure and need disperse dyes of more elaborate structure than those satisfactory for CA. The rate of dyeing is low and hence pressure dyeing, which allows higher temperatures to be used, or a swelling agent (also called a carrier) must be 

The presence in certain positions of NO2 and CN groups in the diazo component gives a strong bathochromic effect and blues of good quality can be produced in this way. In particular they are easily discharged to a clean white in textile printing operations, in contrast to A/Q disperse blues which are not. 

The positive charge is here an integral part of the chromophoric system and the dyes are termed delocalized cationic dyes. 

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