I. Basic Principle of Enzymatic Desizing
In textile pretreatment before dyeing and finishing, desizing is a critical process for removing sizing agents applied to fabrics. Due to its high specificity, mild operating conditions and minimal fiber damage, enzymatic desizing has gradually become one of the mainstream technologies replacing traditional alkaline desizing.
According to the thermal stability of amylase, commercial desizing enzymes are generally classified into three categories:
Medium & Low Temperature Desizing Enzyme
High Temperature Desizing Enzyme
Wide Temperature Range Desizing Enzyme
Different temperature characteristics make them suitable for different process equipment and fabric types. The following sections explain the technical positioning and application scenarios of these three types.
II. Medium & Low Temperature Desizing Enzyme
Medium & low temperature desizing enzymes exhibit optimum activity within relatively lower temperature ranges. They are suitable for fabrics sensitive to high-temperature processing, including:
Wool, silk and blended fabrics (high temperature may cause yellowing or hand-feel hardening);
Stretch fabrics containing spandex (high temperature may result in elasticity loss);
Certain regenerated cellulose fibers such as Lyocell and Modal, which may experience strength reduction under high-temperature alkaline conditions.
Typical application scenarios include:
Intermittent Desizing Processes
For example, one-bath desizing in jet dyeing machines, which can be combined with scouring processes.
Cold Pad-Batch Desizing
The fabric is stacked at room temperature or low temperature for an extended period, allowing continuous enzymatic action.
Low Energy Consumption Production Lines
No need to heat the working bath to high temperatures, reducing thermal energy consumption.
This type of enzyme is usually compatible with neutral or weakly alkaline conditions and maintains stability within a relatively wide pH range, facilitating its use with other pretreatment auxiliaries.
III. High Temperature Desizing Enzyme
High temperature desizing enzymes are modified for enhanced thermal stability and maintain catalytic activity under elevated temperatures.
They are mainly used in continuous desizing processes, especially combined desizing ranges equipped with steaming systems.
Typical application conditions include:
Continuous pad-steam desizing, where fabrics enter the steaming chamber after padding and complete the desizing reaction under high humidity and temperature conditions;
Desizing of heat-resistant fibers such as cotton and flax without concern for thermal damage;
High-speed production lines requiring satisfactory desizing efficiency within short residence times.
When using high temperature desizing enzymes, attention should be paid to:
Uniformity of padding temperature and stable temperature distribution within steaming chambers;
Proper pH adjustment to ensure operation within the optimum enzyme activity range;
Adequate washing after desizing to remove hydrolyzed low-molecular sizing materials and avoid re-deposition.
IV. Wide Temperature Range Desizing Enzyme
Wide temperature desizing enzymes provide effective activity over a broad temperature range.
They are developed mainly to meet the following production requirements:
Seasonal Temperature Variations
Environmental and process water temperatures vary with seasons. Wide temperature enzymes reduce the need for seasonal process adjustments.
Equipment Differences
Actual operating temperatures may vary among desizing equipment. Wide temperature enzymes have higher tolerance to such variations.
Multi-Product Switching
When frequently changing fabric types with different fiber compositions, one enzyme can cover both heat-sensitive and heat-resistant fabrics, avoiding frequent switching between enzyme products.
Simplified Inventory Management
Universal enzyme products help reduce inventory categories and simplify material management.
Wide temperature adaptability does not mean identical activity at all temperatures, but rather maintaining acceptable desizing efficiency across a wider temperature range. Final selection should still be verified according to the actual process temperature.
V. Process Coordination and Quality Control
The effectiveness of enzymatic desizing depends on several process parameters:
pH Value
Different enzymes have their own optimum pH ranges. Deviation may reduce enzyme activity.
Reaction Time
Adequate contact time is required. Insufficient time may lead to incomplete desizing.
Enzyme Dosage
Insufficient dosage lowers desizing efficiency, while excessive dosage only increases cost unnecessarily.
Washing Conditions
Thorough washing is essential to remove hydrolyzed sizing fragments; otherwise residues may cause fabric stiffness or dyeing defects.
Desizing efficiency can be semi-quantitatively evaluated using the iodine-starch coloration method.
Residual starch reacts with iodine to produce blue or purple coloration. Darker color indicates more residual sizing.
Incomplete desizing before dyeing may cause:
Uneven dyeing
Color spots
Shade variation
Therefore, desizing stability directly affects subsequent processing quality.
VI. Conclusion
Medium & low temperature, high temperature and wide temperature desizing enzymes correspond to different process temperature requirements and fabric conditions.
Selection should be based on:
Equipment capability
Fabric specifications
Process stability
rather than simply pursuing universal applicability or a single performance index.
Taikun Chemical technical documents normally provide recommended process ranges. Before large-scale production, laboratory trials or pilot tests are recommended to verify desizing performance under specific fabric and sizing conditions.
All three desizing enzyme types belong to specific starch-degrading enzyme systems. They effectively decompose starch sizing, cause no chemical damage to cellulose fibers and possess good biodegradability.
They represent an environmentally friendly and precision-oriented solution for modern textile pretreatment.
