1. Inorganic Salt Builders

Inorganic salts form the baseline matrix of heavy-duty powdered and liquid detergent formulations. They act as alkalinity sources, electrolyte boosters, saponification agents, and mineral water softeners.

A. Phosphate Builders

• Sodium Tripolyphosphate (STPP): Exceptional builder for heavy grease removal. Exhibits strong chelating power for Ca²⁺ and Mg²⁺ ions, excellent dispersion and emulsification capacities, and balanced corrosion performance (inhibits steel corrosion while displaying slight reactivity toward copper components).
• Sodium Hexametaphosphate (SHMP): High-solubility polyphosphate effective as a threshold agent and builder for light-to-medium oil soilings, preventing scale precipitation in circulating aqueous systems.
• Tetrapotassium / Tetrasodium Pyrophosphate (TKPP / TSPP): Premium builder options for heavy industrial grease and oil. TKPP offers superior water solubility, making it ideal for highly concentrated liquid detergent systems.

B. Silicate, Carbonate & Alkaline Builders

Alkaline builders hydrolyze in water to yield hydroxyl ions (OH⁻), essential for saponifying animal and vegetable oils into soluble soaps.

C. Auxiliary Inorganic Salts

• Sodium Chloride (NaCl): Serves as an inorganic inorganic electrolyte and viscosity modifier. Effectively reduces micellar critical concentration (CMC) and thickens ionic surfactant systems.
• Sodium Sulfate (Na₂SO₄): Standard processing aid and filler in detergent powders. Enhances ionic strength, improving surfactant micellar activity on fabric surfaces.
• Borax (Sodium Tetraborate): Moderately soluble in water and highly soluble in glycerol. Acts as a pH buffer, mild disinfectant, enzyme stabilizer, and corrosion inhibitor.

2. Organic Salt Additives & Chelating Agents

When phosphate restrictions apply or targeted metal-ion sequestration is required, organic salts provide high-performance sequestration, anti-redeposition, and hydrotropic action.

A. Aminopolycarboxylate & Organophosphonate Salts

EDTA Salts (Disodium, Trisodium, Tetrasodium EDTA): Disodium EDTA (slightly acidic) and Tetrasodium EDTA (alkaline) are industry standards for sequestering divalent and trivalent metal ions (Ca²⁺, Mg²⁺, Fe³⁺). They prevent insoluble soap precipitation, lower micella concentration requirement, and act as synergetic hydrotropes and temporary rust preventatives.

HEDP-4Na (Etidronate Tetrasodium): An organophosphonate salt displaying outstanding chelation for Ca²⁺, Mg²⁺, Fe²⁺/³⁺, Al³⁺, and Zn²⁺ ions under extreme alkaline conditions (pH > 12) and elevated temperatures. Note: Shows mild reactivity toward copper alloys.

B. Organic Acid Salts & Hydrotropes

• Sodium & Ammonium Citrates: Environmentally friendly, non-toxic Builders. Sequester iron (Fe²⁺/Fe³⁺) and hardness ions (Ca²⁺/Mg²⁺), serving as sustainable alternatives to phosphates in green detergent formulations.
• Sodium Gluconate: Outstanding chelating agent for iron and heavy metals in strong hot alkaline solutions. Outperforms Disodium EDTA in aggressive rust-removal and bottle-washing formulations.
• Sodium Benzoate: Dual-function additive operating as a preservative and hydrotropic solubilizer in liquid systems.
• Sodium Xylenesulfonate (SXS): Powerful hydrotrope used to couple incompatible surfactants and inorganic builders into stable, single-phase liquid concentrates without adding detersive drag.
• Sodium Polyacrylate: High-efficiency sequestering and anti-redeposition polymer. Neutralizes water hardness and prevents suspended particulate dirt from redepositing onto substrate surfaces.
• Triethanolamine Oleate: Excellent emulsifier capable of dispersing mineral oils, synthetic lubricants, and animal/vegetable fats in industrial degreasing baths.
• Citric Acid: Primary organic acidulant used to adjust solution pH, neutralize residual alkalinity, chelate transition metal ions, and prevent redeposition on washed textiles.

3. Solvent Builders & Alkanolamines

Solvents increase the solubility of hydrophobic soils, optimize formulation cloud points, and penetrate dried, polymerized grease films.

A. Monohydric & Polyhydric Alcohols

Ethanol, Isopropanol (IPA), Ethylene Glycol, Glycerol: Short-chain alcohols (Ethanol, IPA) lower formulation viscosity and enhance wetting penetration into non-polar grease layers. Polyols (Ethylene Glycol, Glycerol) act as freeze-thaw stabilizers, coupling solvents, and enzyme carriers.

B. Glycol Ethers

Ethylene Glycol Ethers (E-series) & Propylene Glycol Ethers (P-series): Powerful mutual solvents bridging water and hydrocarbon phases. Significantly improve organic grease removal, elevate liquid formulation cloud points, and enhance surface wetting speed.

C. Alkanolamines

Alkanolamines deliver reserve alkalinity, greasy soil solubilization, and cloud-point elevation in liquid formulations:

• Monoethanolamine (MEA): Base pH ~11.5. Rapidly saponifies acidic soils and boosts cloud points in heavy-duty liquid cleaners.
• Diethanolamine (DEA): Base pH ~11.9. Strong alkaline builder and grease-cutting additive for hard surface cleaners.
• Triethanolamine (TEA): Base pH ~10.7. Most widely used alkanolamine. Delivers superior detergency, mild chelating capacity for metal ions, and temporary corrosion protection for ferrous metals.

4. Performance Comparison Matrix

Select the optimal functional builder based on system parameters and targets:

5. Formulation Key Takeaways

• Primary Hardness Sequestration: EDTA remains the most universally effective chelating agent for binding hard water calcium and magnesium ions under standard operating conditions.
• ABS / LAS Surfactant Synergy: Combining Linear Alkylbenzene Sulfonic Acid (LABSA/ABS) formulations with Sodium Polyacrylate drastically improves detergency performance, soil suspension, and hard water tolerance.
• Ferrous Rust Prevention: For cleaning formulations requiring temporary anti-corrosion and anti-rust properties on steel substrates, Sodium Benzoate and Triethanolamine are top-tier choices.

6. Frequently Asked Questions (Q&A)