Different shrinkage composite yarn and its preparation method

A different shrinkage composite yarn, comprising a modified polyester, and the modified polyester is composed of a terephthalic acid chain, an ethylene glycol chain and a diol chain containing a branched diol;

• a size of the different shrinkage composite yarn is 100-150 dtex;
• a breaking strength is ≥1.9 CN/dtex, an elongation at break is 30.0±5.0;
• at a temperature of 80° C.-130° C., a space gap between molecular chains in the modified polyester increases by 10-30 v/v %;
• a deviation rate of fiber density of the different shrinkage composite yarn is ≤2.0%;
• a CV value of breaking strength is ≤4.0%, and a CV value of elongation at break is ≤8.0%, and a CV value of crimp shrinkage coefficient of variation is ≤8.0%, and crimp shrinkage is 3.50±2.0%, and an oil content is 1.0±0.2%, network degree is 20±5 units/m;
• wherein, the increase of the space gap between the molecular chains refers to a comparison of the spatial gaps between molecular chains at a same temperature between the modified polyester and a polyester without the branched diol;
• the branched diol is one or more items selected from the group consisting of a 2-pentyl-1,3 propanediol, a 2-hexyl-1,3 propanediol, a 2-heptyl-1,3 propanediol, a 2-octyl-1,3 propanediol, a 2-pentyl-1,4 butanediol, a 2-hexyl-1,4 butanediol, a 2-heptyl-1,4 butanediol, a 2-octyl-1,4 butanediol, a 2-pentyl-1,5 pentanediol, a 2-hexyl-1,5-pentanediol, a 2-heptyl-1,5-pentanediol, a 2-octyl-1,5-pentanediol, a 2-pentyl-1,6 hexanediol segment, a 2-hexyl-1,6 hexanediol, and a 2-heptyl-1,6-hexanediol, a 2-octyl-1,6-hexanediol.