Bleaches & Laundry Aids

Liquid chlorine bleach employs sodium hypochlorite (NaOCl, CAS 7681-52-9) as its active species, with the hypochlorite anion (OCl⁻) acting as the primary oxidant at alkaline pH.

Formulation Card FC-12.1-M: Liquid Chlorine Bleach

Sodium hypochlorite stability is governed by two competing decomposition pathways. The dominant route at elevated temperature is chlorate-forming disproportionation: 3 NaOCl → 2 NaCl + NaClO₃ . The alternative oxygen-producing pathway (2 OCl⁻ → 2 Cl⁻ + O₂) becomes significant in the presence of transition metal catalysts (Cu²⁺, Ni²⁺, Fe³⁺, Co²⁺) . Both reactions exhibit second-order kinetics, with activation energy for a 15.89% NaOCl solution reported at 96.43 kJ/mol . The decomposition rate increases by a factor of ~3.5 for every 10 °C rise in temperature ; storage at 15 °C versus 25 °C extends shelf life 3.5-fold.

The HOCl/OCl⁻ equilibrium has pKₐ ≈ 7.5, so at pH 11.5–13.0 the equilibrium lies overwhelmingly toward the stable hypochlorite anion . Below pH 10.8, decomposition accelerates sharply . Excess NaOH at 0.025–0.35% by weight achieves the target pH, with sodium silicate chelating trace metal ions. Fabric safety requires that available chlorine in the wash liquor remain below 0.5%; higher concentrations cause oxidative cellulose chain scission. The product must never be mixed with acids (toxic Cl₂ gas), ammonia (chloramine formation), or hydrogen peroxide.

Liquid oxygen bleach uses hydrogen peroxide (H₂O₂, CAS 7722-84-1) as a color-safe oxidant. Formulated at acidic pH for storage stability, the active perhydroxyl anion (HOO⁻) generates only upon dilution into alkaline wash liquor.

Formulation Card FC-12.2-M: Oxygen Bleach Liquid

Hydrogen peroxide has pKₐ = 11.6; at formulation pH 3–5 it exists as stable undissociated HOOH . Dilution into wash liquor at pH 9–11 generates HOO⁻, the active bleaching species. Storage stability requires a dual-component system: amino polyphosphonates such as HEDP chelate dissolved metal cations (Fe³⁺, Cu²⁺, Mn²⁺), while hindered phenols such as BHT scavenge free radicals. Accelerated aging at 37.8 °C for 8 weeks showed formulations with HEDP (0.12%) + BHT (0.01%) retained >95% of initial H₂O₂ versus <78% for unstabilized controls . Nonionic alcohol ethoxylates provide wetting and mild detergency. Performance on heavily stained whites is inferior to chlorine bleach, but the product is safe for all colorfast fabrics at 25–50 mL per 4.5 kg load at 40–60 °C.

Powdered oxygen bleach delivers hydrogen peroxide in solid form through sodium percarbonate (2Na₂CO₃·3H₂O₂, CAS 15630-89-4), with tetraacetylethylenediamine (TAED, CAS 10543-57-4) as a bleach activator for low-temperature performance at 30–60 °C.

Formulation Card FC-12.3-M: Oxygen Bleach Powder

The percarbonate-TAED system proceeds through perhydrolysis: under alkaline conditions (pH 10–11), one mole of TAED reacts with two moles of perhydroxide anion to generate two moles of peracetic acid (PAA) and biodegradable diacetylethylenediamine (DAED) :

PAA is a substantially more potent oxidant than H₂O₂ below 60 °C. Each gram of TAED releases 0.67 g PAA (0.14 g active oxygen) . Optimal perhydrolysis requires pH 10–11, while optimal PAA bleaching occurs near its pKₐ of 8.2 . In practice, the initial high pH from sodium carbonate ensures rapid TAED activation, then pH drifts downward as acetic acid byproduct forms. TAED at 2–4% of product weight (0.04–0.12 g/L in wash liquor) combined with percarbonate at 5–10% delivers ~10–20 ppm available oxygen as PAA . Concentrations below 50 mg/L produce negligible bleaching; up to 500 mg/L yield progressively higher whiteness indices . The system has been the dominant European bleach activator since the 1980s with annual consumption of ~75 kt ; both TAED and DAED are readily biodegradable.

Table 1: Comparison of Bleaching Chemistries

Table 1 highlights the fundamental bleach selection trade-off. Chlorine bleach offers the broadest temperature compatibility and strongest biocidal action at the cost of fabric damage. Hydrogen peroxide liquid provides color safety and long shelf life but requires elevated wash temperatures (>50 °C). The percarbonate-TAED system bridges this gap through in-situ PAA generation at 30–60 °C, though its solid form demands moisture-protected storage.

Figure 12.1 — Relative bleaching performance as a function of wash temperature. Sodium hypochlorite maintains consistent performance across all temperatures with increasing fabric damage risk above 60 °C. H₂O₂ alone requires >60 °C for adequate performance. The percarbonate-TAED system achieves its optimum in the 30–60 °C low-temperature wash zone.

Laundry aids supplement detergent action through enzymatic hydrolysis, surfactant-solvent penetration, quaternary ammonium antimicrobial action, or molecular encapsulation. Each product type is designed for a defined point in the wash process.

Laundry boosters are supplemental powder products added to the main wash to enhance stain removal on heavily soiled loads, combining the percarbonate-TAED system with targeted enzymatic activity.

Formulation Card FC-12.4-M: Laundry Booster / Stain Remover Powder

The enzymatic component targets specific stain categories: protease cleaves peptide bonds in protein soils (blood, egg, milk, grass); amylase hydrolyzes starch soils (rice, pasta, potato); and lipase cleaves triglyceride esters in fatty soils (cooking oil, body sebum) . Lipase requires temperatures above the substrate melting point (>30 °C) to access insoluble lipids. The 2–4% enzyme blend corresponds to ~0.05–0.12% active enzyme protein in wash liquor at standard dose. The combined action of PAA (from TAED activation) and enzymes produces synergistic stain removal: oxidation degrades chromophores while enzymatic hydrolysis solubilizes the underlying polymer matrix. Citrate (3–5%) moderates the pH profile and assists bleaching positively . Percarbonate must be added last in blending with mix temperature below 35 °C to prevent premature decomposition .

Pre-wash treatments are applied directly to fresh stains before the main wash and must remain localized without running, demanding a gel or high-viscosity vehicle.

Formulation Card FC-12.5-M: Pre-Wash Stain Treatment Gel

The high surfactant content (15–24% total) combined with glycol ether solvents provides strong penetration of hydrophobic stains. DPnB (HLB ~10) displaces oily soils from fibers upon mechanical rubbing. The gel matrix uses xanthan gum for shear-thinning rheology and hydroxyethyl cellulose for surface film formation, preventing wicking beyond the stained area . Target viscosity of 3 000–8 000 mPa·s ensures the product clings to vertical fabric surfaces for the recommended 5–10 minute dwell time. The near-neutral pH (6.5–7.5) maximizes protease activity. Not suitable for wool, silk, or other protein fibers where protease may attack the fabric.

Laundry sanitizers are rinse-cycle additives delivering antimicrobial efficacy, particularly important in cold-water washes where detergent and bleach action may be insufficient.

Formulation Card FC-12.6-M: Laundry Sanitizer

Benzalkonium chloride (BAC) is a cationic surfactant with the general formula [CₙH₂ₙ₊₁N(CH₃)₃]⁺Cl⁻. Its mechanism involves adsorption to negatively charged microbial membrane phospholipids, disrupting membrane fluidity and causing cell lysis . BAC is effective against Gram-positive and Gram-negative bacteria and enveloped viruses. The rinse-cycle addition is deliberate: during the main wash, anionic surfactants in detergent form insoluble complexes with cationic BAC, inactivating both. In the final rinse, after detergent removal, BAC deposits onto fabric surfaces unimpeded. The diluted rinse liquor concentration of ~0.01–0.02% exceeds the MIC for common skin flora including S. aureus and E. coli. Commercial products at 2.0–2.5% BAC claim 99.9% kill against standard test organisms .

An alternative active is chloroxylenol (PCMX, 4-chloro-3,5-dimethylphenol, CAS 88-04-0), a halogenated phenol effective against bacteria and fungi . PCMX operates at 0.5–1.0% in liquid formulations and has higher chemical stability than BAC, though its characteristic phenolic odor and low water solubility (0.03 wt%) require co-solvent solubilization .

Laundry odor removers address malodors persisting through normal washing, particularly body odor compounds trapped in synthetic fabrics. Beta-cyclodextrin (β-CD) serves as the primary odor-capture agent, supplemented by enzymes that degrade odor precursors.

Formulation Card FC-12.7-M: Laundry Odor Remover

Beta-cyclodextrin is a cyclic oligosaccharide of seven glucose units forming a toroidal structure with a hydrophobic internal cavity and hydrophilic exterior. Volatile malodor molecules—short-chain fatty acids, volatile amines, thiols—enter the cavity and are physically trapped through non-covalent hydrophobic interactions and van der Waals forces, forming an inclusion complex . While encapsulated, odor molecules cannot volatilize into air and cannot be detected by olfactory receptors. The cavity’s size selectivity (internal diameter ~0.78 nm) provides specificity for body odor compounds rather than non-specific absorption .

Hydroxypropyl-beta-cyclodextrin (HP-β-CD) is preferred over native β-CD for liquid formulations because hydroxypropyl substitution dramatically increases water solubility, enabling clear solutions at up to 50% concentration . Native β-CD has limited cold-water solubility (~1.8 g/100 mL at 25 °C) and is suited to powder applications. The enzymatic component provides complementary action: protease breaks down proteinaceous sweat residues; lipase hydrolyzes sebaceous lipids that serve as bacterial odor precursors . The combination addresses odor through both elimination (enzymatic) and encapsulation (cyclodextrin) pathways.

Table 2: Enzyme Specificity in Laundry Applications

Table 2 shows why multi-enzyme systems are standard in modern laundry boosters. No single enzyme covers the full soil spectrum; the six classes collectively address protein, carbohydrate, lipid, and plant polysaccharide matrices. Lipase requires temperatures above the lipid melting point for substrate access, while cellulase—which cleaves cellulose microfibrils to restore brightness—must be dosed carefully to avoid structural weakening of cellulosic fibers. In powder products containing both enzymes and percarbonate, granulated enzyme forms with protective coatings are essential; modern stabilized enzyme granules exhibit <10% activity loss after 12 weeks at 37 °C in percarbonate-containing matrices.

Table 3: Bleach and Laundry Aid Comparison — Complete Product Overview

Table 3 consolidates all seven formulations and provides a basis for product selection. The choice between chlorine and oxygen bleach technologies determines the overall fabric safety profile. Within oxygen bleach, liquid H₂O₂ offers convenience and long shelf life but requires elevated temperatures, while percarbonate-TAED powder enables low-temperature performance at the cost of requiring dry, moisture-protected storage. The four laundry aid products address specific functional gaps: boosters extend cleaning for heavily soiled loads, pre-wash gels deliver concentrated action to individual stains, sanitizers provide rinse-cycle antimicrobial deposition, and odor removers use cyclodextrin inclusion chemistry to capture volatile malodors. These categories are not mutually exclusive—a heavily soiled, malodorous athletic load might incorporate odor remover spray as pre-treatment, oxygen bleach powder in the main wash, and sanitizer in the rinse cycle. The formulator’s task is to match active chemistry to soil type, fabric substrate, wash temperature, and consumer safety requirements. -e

ewpage