Speciality Sequestering Agents
This family covers the conditions a single-base sequestering agent does not: binding iron in strong caustic, stabilising peroxide without silicate, and concentrated use. Four products.
Why is heptonate needed in strong caustic?
The binding strength of a chelating agent depends on pH. Phosphonates work over a wide range, but their capacity to hold iron weakens as the caustic concentration rises. Heptonate and similar sugar acid salts are strong exactly there: at high alkalinity they hold iron as a soluble complex.
That matters on steps carrying high alkali, such as bleaching and the mercerising wash boxes. Pinholes and spot-wise strength loss from iron mostly originate at those steps.
What does a peroxide stabiliser do?
In a bleach bath, hydrogen peroxide is meant to decompose in a controlled way; uncontrolled decomposition costs whiteness and oxidises the fibre. The stabiliser regulates that rate, and the largest part of the job is binding the iron and manganese that trigger it.
The classical answer is sodium silicate. It is cheap and it works, but it leaves deposits on the machine and the cloth: the residue stiffens the handle, scales the pipework and becomes a source of unlevelness in the next dyeing. Organic stabilisers remove that deposit and make the dosage adjustable against the water quality.
What is in this family?
|
Product type |
Strength |
|---|---|
|
Polymeric concentrate |
Broad effect at low dosage, dispersion |
|
Heptonate-based |
Iron binding at high caustic concentration |
|
Acrylate-heptonate combination |
Combines hardness control with stabilisation |
|
Concentrated blend |
Cuts the number of items on the recipe |
The family is made up of items formulated for conditions a single-base product does not cover. The selection follows the bath rather than the chemistry: pH, temperature, caustic concentration and the iron content of the water.
How is the dosage set?
It starts with a water analysis: total hardness, iron and manganese. Then the liquor ratio and the peroxide concentration in the bleach recipe come in. Without those three, a dosage is either short or needlessly high.
Overdosing has a price too. Strong chelating agents can strip metal from metal-complex dyes and shift the shade, and colour yield falls on some reactive dyes. The sound approach is to build a dosage curve on the mill's own water: pending from the client.
Product comparison
Comparison
| Product | Description | Chemical base | Working pH range | Temperature | Dosage |
|---|---|---|---|---|---|
| DK PML K | Concentrated polymeric sequestering agent | Polymeric | awaiting data | awaiting data | awaiting data |
| DK SEQUA 1624 | Heptonate based sequestering agent | Heptonate | awaiting data | awaiting data | awaiting data |
| DK SEQUA ACS | Acrylate and heptonate sequestering agent and stabiliser | Polyacrylate + heptonate | awaiting data | awaiting data | awaiting data |
| DK SEQUA PS PLUS | Concentrated sequestering agent blend | awaiting data | awaiting data | awaiting data | awaiting data |
Products
- DK PML K
Concentrated polymeric sequestering agent giving hardness control and dispersion at low dosage, with less storage.
- DK SEQUA 1624
Heptonate based sequestering agent that holds iron as a soluble complex at high caustic concentration.
- DK SEQUA ACS
Acrylate and heptonate sequestering agent and stabiliser that holds peroxide steady without using silicate.
- DK SEQUA PS PLUS
Concentrated sequestering blend that brings hardness, heavy metals and peroxide stabilising onto one dosing line.
Common questions
Is it possible to drop silicate entirely?
With organic stabilisers it is, and many mills have made the change. The gain is no scale in the machine, no stiffened handle and one less source of unlevelness. In return the unit cost rises and the dosage has to be set against the water quality.
How do you confirm the source of pinhole damage?
Measure iron and manganese in the water and on fabric samples taken before and after bleaching. If the damage is local and spot-wise, the source is usually undissolved metal particles, and the rust in the water line and the machine interior should be checked too.
Is there a difference between a concentrate and a standard grade?
At the correct dosage the result is the same; the difference is freight, storage volume and dosing accuracy. A dosing error weighs more with a concentrate, so concentrates suit mills with automatic dosing.
Other families in this category
Related applications
Guides on these products
Not finding what you need?
We develop custom formulations. Tell us your process, machine type and the result you are after, and the lab will set up a trial and send a sample.