Close-up of the dyed fabric surface
Knitted fabric leaves the dyeing machine and enters the soaping bath. The scum on the surface is not thick, but it is sticky: after the fabric travels one round, loose dye settles back onto it, shade variation between dye lots and colour spots appear one by one on the inspection table, and the rework tickets line up behind them.
Chemi Tech supplies defoamers for the low-alkali washing and soaping stages run by textile dyeing and printing plants, drawn from the KM-902 series; the dosage is set by the soaping temperature, the detergent concentration and the fabric speed. This grade is low-foaming and alkali-resistant — temperature is not the main obstacle here, so a line that only needs the mechanical foam pushed down runs it at lower cost; the on-site measurement of the overflow-outlet foam height and the foam marks on the fabric is the direct basis for setting the KM-902 dosage.
Advantages of Chemi Tech Defoamers
Chemi Tech KM-902 series defoamer is low-foaming and alkali-resistant, and breaks foam quickly in the soaping liquor; besides which, its foam suppression holds, so mechanical foam no longer piles up under the repeated agitation of the detergent; on top of that, it is compatible in the same bath as the soaping agent and does not cling to the fabric, so loose dye is not carried back onto it by the foam; and in addition the dosage is economical — the dosing cost in a cool, low-alkali stage sits one step below a high-temperature grade, the washing bath does not overflow, and control stays good.
Industry Pain Points and Solutions
Foam in a low-alkali washing stage mostly comes from the surfactant in the detergent and the mechanical air entrainment of the running fabric, and the consequences land in two places: loose dye back-staining and an unbalanced overflow.
The path by which loose dye is carried back onto the fabric is built by the foam; KM-902 cuts that path inside the bath, and the foam marks no longer drop onto the cloth.
The foam surface is driven round again and again by the fabric speed and piles up first at the overflow outlet, so the liquid carry-over swings up and down with it. The KM-902 dosage is set by the detergent concentration, and the liquid level falls back with it.
At the other end, on the inspection table, the thickness of the rework pile depends on how much foam marking there is. Once the soaping temperature, the detergent concentration and the fabric speed have been compared, the dosage range settles, and the rework rate returns to its normal level.
Typical Operating Conditions and Verification
Customer: a knitted-fabric dyeing and printing enterprise in Hubei, for the soaping and washing stage after reactive-dye dyeing.
The inspector reported that after dark shade lots came off the machine the foam marks were scattered as points, reading under the lamp as rings of faint haloes; on site, the scum at the soaping bath overflow outlet was being lifted repeatedly by the running fabric. After comparison, Chemi Tech set the KM-902 dosage for the plant, with the concentration adjusted to the detergent concentration. The foam surface at the overflow outlet came down first; the foam marks on the fabric disappeared lot by lot; the rework rate returned to its normal level, and the inspection hours came down with it.
Frequently Asked Questions
If the soaping temperature is not high, is a dedicated defoamer still needed?
As long as mechanical foam is still carried round by the fabric, loose dye has a path back onto it. KM-902 has completed defoaming comparisons under both normal-temperature and low-alkali soaping conditions, and within the recommended dosage range the foam marks no longer land on the cloth. The soaping temperature, the detergent concentration and the fabric speed need to be set together; Chemi Tech pins the dosage down through a parallel comparison of the overflow-outlet foam height and the foam marks on the fabric.
Only with clean fabric can dye lots be compared with one another.