The Addition Amount of the Dyeing Auxiliary HPMA

The addition amount of Hydrolyzed Polymaleic Anhydride (HPMA) as a dyeing auxiliary varies significantly depending on the specific stage of the textile process (scouring, bleaching, or dyeing) and the hardness of the water being used.

As a high-performance phosphorus-free chelating and dispersing agent, HPMA is generally used in the following concentrations:

1. Typical Dosage by Application

Application Stage Recommended Dosage (g/L) Primary Function

Scouring & Boiling 1.0 – 3.0 g/L Disperses wax, pectin, and impurities; prevents calcium/magnesium soap precipitation.

Oxygen Bleaching 0.5 – 2.0 g/L Stabilizes the bleach bath by chelating Fe³⁺ and Cu²⁺ ions, preventing fabric "pinholes."

Dyeing (Leveling) 0.5 – 1.5 g/L Prevents dye aggregation and metal-ion interference with reactive or direct dyes.

After-Washing (Soaping) 1.0 – 2.0 g/L Prevents unfixed dye from redepositing on the fabric; improves color fastness.

2. Factors Affecting the Addition Amount

Water Hardness: In areas with extremely hard water (high calcium and magnesium content), the dosage should be increased toward the upper limit (e.g., 2.0–3.0 g/L) to ensure effective sequestration.

Bath Ratio: For processes with a low liquor-to-goods ratio (e.g., 1:5 or 1:8), the concentration (g/L) may need to be higher compared to high liquor ratio processes (1:20) to maintain the same chemical efficiency per kilogram of fabric.

Dye Type: Reactive dyes are particularly sensitive to metal ions; using 1.0 g/L of HPMA can help maintain shade consistency and brightness.

3. Usage Advantages of HPMA

High Temperature Stability: Unlike traditional polyphosphates, HPMA remains effective at temperatures up to 300°C, making it ideal for high-temperature and high-pressure (HTHP) dyeing.

Alkaline Resistance: It maintains h3 chelating power in high pH environments (pH 8–12), which is common in scouring and reactive dyeing.

Low Toxicity: It is an environmentally friendly, biodegradable auxiliary that meets modern "Green" textile standards.

4. Technical Note on Compounding

In many industrial settings, HPMA is not used alone but as part of a blended auxiliary. If you are using a pre-formulated "Chelating Dispersant," the manufacturer's suggested dosage (often 1–2 g/L) usually accounts for the synergistic effects of HPMA mixed with other polymers like PAAS or organic phosphonates.