Can we stop sodium alginate from getting hard and choking the printing machines?

Name: Radhika

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Alginate

Country or region: India

Message: I import sodium alginate (textile grade) used in cloth printing. Recently, someclients have told me that, with the use of sodium alginate in printing, the cloth becomes very hard and also the printing machine is getting choked up. What's the solution to this problem?

Although my area of expertise is small-scale hand dyeing, I may be able to make some useful suggestions.

Alginate forms a gel in the presence of calcium ions, which are extremely common, and which are always found in hard water. Unless you and your clients have exceptionally soft water supplies, lacking in the usual amount of calcium ions, this is likely to be your problem. Unlike gels formed from agarose or gelatin, an alginate-calcium gel will not dissolve in hot water, making it very difficult to remove.

Although using distilled water is effective, it is inconvenient. A more convenient solution is to add a water softener that works by sequestering calcium and magnesium ions, such as sodium hexametaphosphate, to your print paste mixtures. Water that has been softened by replacing its calcium and magnesium ions with salt will also work well. Not all water softeners are suitable for this purpose; the polycarboxylates that are popular in in grocery-store water softeners can interfere with dyeing.

It may be difficult or impossible to require your customers to use only softened water. If you add sodium hexametaphosphate or another calcium sequestering agent to your print paste mixtures, you can be sure that your customers will have it when they need it.

Sodium alginate also tends to produce gels if the pH is too low or too high. You should avoid using sodium alginate at a pH that is below 3.5 or above 11.5. If this is your problem, you may need to use a chemical buffer system to keep your pH in the desired range. Reactive dyes are often used at a pH around 11, while acid dyes are usually used at a pH between 4 and 7, depending on the class of acid dye being used.

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Posted: Thursday - December 23, 2010 at 12:20 PM

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Can we stop sodium alginate from getting hard and choking the printing machines?

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