Cold Pad Batch Dosing Pump Ratio Calibration Procedures
Dosing pump ratio calibration in cold pad batch dyeing prevents reactive dye hydrolysis, shade tailing, and costly bulk fabric rejections.
Sodium Hydroxide Dosage
Chemical Allocation
Quantitative chemical feeding protocols dispense calculated quantities of strong alkali reagents to activate, swell and chemically transform cellulosic and synthetic substrates during industrial wet processing. Sodium hydroxide dosage controls the mass or volumetric concentration of caustic soda delivered into scouring, mercerizing, bleaching and reactive dyeing processing baths. The boundary of this chemical additions parameter covers alkaline preparation and wet processing sequences, stopping where acid neutralization and chemical washing stages terminate the active alkaline reaction.
Cellulosic Activation
Caustic soda converts cellulose into alkali cellulose by deprotonating hydroxyl groups along the polymer backbone. Precise sodium hydroxide dosage governs the level of fiber swelling, surface cleaning and chemical reactivity achieved during processing. In scouring operations, alkali saponifies natural cotton waxes, pectins and residual fats into water-soluble soaps.
During reactive dyeing, alkali dosing generates cellulosate anions that react covalently with vinyl sulfone or chlorotriazine reactive groups. Mercerization processes utilize high-concentration caustic additions around twenty to thirty percent by weight to transform crystalline cellulose I into the more accessible cellulose II lattice. Automated chemical dispensing systems pump concentrated liquid caustic soda into continuous mixer heads based on incoming dry fabric weight.
Bath Maintenance
Titration units and conductivity sensors track free hydroxide depletion as fabric passes through continuous saturation troughs. Maintaining accurate sodium hydroxide dosage requires closed-loop replenishment systems that counter caustic consumption, atmospheric carbon dioxide neutralization and wet fabric dilution effects. Overdosing damages cellulosic fibers through macromolecular chain scission, causing tensile strength loss.
Underdosing leaves natural waxes intact, resulting in poor fabric absorbency and uneven dye affinity.
Saturated Excess
Excessive caustic concentrations induce fiber embrittlement, pinhole formation during peroxide bleaching and severe oxycellulose degradation. Laboratory verification measures post-treatment tensile strength, residual wax content and barium activity numbers to audit sodium hydroxide dosage accuracy. Production lots processed outside target alkalinity specifications are rejected before subsequent dyeing operations.