Silicone Antifoams

Silicone antifoams are products in which silicone oil and hydrophobic silica particles work together. They enter the bubble wall and tear it open; the knock-down is fast and lasts as long as the product stays in the bath. The Derin Kimya range covers two products.

Where does the foam come from?

What makes foam in a dyebath is the surfactant. Wetting agent, washing agent, levelling agent and dispersant molecules gather at the water-air boundary and hold the bubble wall up. As the machine runs, air is drawn into the liquor; in jet and overflow machines that is unavoidable.

The cost in production is easy to see. Bath volume runs out of control, the pump draws air, circulation falls and the cloth stops meeting the dye evenly. What follows is unlevel dyeing, and at times cloth jamming in the machine.

How does a silicone antifoam work?

A silicone antifoam has two parts doing two jobs. The silicone oil has a lower surface tension than the bath, so it enters the bubble wall and spreads it sideways. The hydrophobic silica particles carried in it then bridge the two faces of that wall and tear the bubble open.

That is why the effect is both fast and long-lived. It knocks existing foam down quickly and, for as long as it stays in the bath, makes it harder for new foam to build.

Which step suffers most from foam?

In pre-treatment, scouring and bleaching baths carry a heavy wetting agent load and are open to foaming. In dyeing the real trouble is in jet and overflow machines, where cloth and liquor move together and air is drawn in continuously. In washing, the source is the soap and the oil stain remover.

On the padder the problem looks different. Foam formed in the trough transfers to the cloth as air bubbles, the finish never touches the fabric at those points, and the result is unfinished areas that read as stains. That is why an antifoam is usually added to the pad liquor.

How is the spotting risk managed?

The known drawback of a silicone antifoam is that the same silicone can stain the cloth. Spotting becomes more likely as the dosage rises, as the product is fed neat, and as shear in the bath increases.

Four habits keep the job on the safe side:

1. Dilute the product in warm water and dose it under agitation rather than pouring it into the machine.
2. Feed small doses as they are needed instead of one large charge.
3. On whites, pale shades and sensitive finishing recipes, consider an oil-based grade instead.
4. Rinse the machine after the dyebath is dropped; silicone left in the sump carries into the next lot.

Setting dosage and feed

An antifoam is not a one-shot product. The initial dose is consumed over time, because surfactant re-covers the surface. On long processes, feeding small doses beats a single large charge on both effectiveness and safety.

The control is visual: the foam level in the sight glass and any swing in pump pressure are the quickest indicators. Dosage and feed figures for Derin Kimya products are given on the product pages: pending from the client.

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