Organophosphonate CAS 37971-36-1

PBTC 50%

ZEELCHEM™ 121

2-Phosphonobutane-1,2,4-Tricarboxylic Acid with superior calcium tolerance up to pH 9.5 and complete 100% resistance to chlorine and oxidizing biocides. Prevents zinc precipitation in all-organic cooling programs.

Official Technical Documents Available

Technical Specification Target

Chemical Formula:C₇H₁₁O₉P
CAS Number:37971-36-1
Active PBTC:50.0% min
Phosphorous Acid:≤ 0.5% max
Phosphoric Acid:≤ 0.2% max
Specific Gravity:1.27 – 1.30 g/cm³
Color (APHA):≤ 20 APHA
Standard Packaging:60kg, 250kg Drum, 1250kg IBC

High-Stress Chlorine Tolerance & Zinc Stabilization

Standard phosphonates degrade into orthophosphate in the presence of free chlorine (>0.5 ppm), causing calcium phosphate scaling. PBTC contains unique carboxylic and phosphonic groups providing total immunity to oxidizing halogens.

In alkaline cooling systems (pH 8.0 to 9.2), PBTC prevents zinc hydroxide precipitation, keeping corrosion inhibitor ions dissolved in active circulation.

Standard Industrial Dosage

ApplicationRecommended Dosing
High Cycles of Concentration Cooling5.0 – 15.0 ppm
Zinc Stabilization Corrosion Formulations3.0 – 8.0 ppm
Closed Chilled Water Loops10.0 – 25.0 ppm
Industrial Detergents & Cleaners0.5 – 2.0%

Packaging, Handling & Storage

  • Packaging Options: 60 kg HDPE carboys, 250 kg virgin HDPE drums, 1,250 kg IBC containers, and bulk tankers.
  • Storage Conditions: Store in tightly closed containers in a dry, ventilated area away from direct sunlight.
  • Shelf Life: 24 months in sealed original packaging.
  • Handling Safety: Mildly acidic. Standard PPE (gloves, safety goggles) required.
High Calcium Tolerance: Unlike ATMP and HEDP, PBTC does not precipitate with calcium ions even when water hardness exceeds 1,200 ppm as CaCO₃.
Technical Knowledgebase

Frequently Asked Questions: PBTC 50%

Expert technical answers on dosing, chemistry, handling, and application performance.

Q1. What is PBTC 50% and why is it superior in alkaline cooling water?

PBTC (2-Phosphonobutane-1,2,4-Tricarboxylic Acid, CAS 37971-36-1) possesses both phosphonic and carboxylic groups, giving it 100% resistance to chlorine and superior scale inhibition at high pH and high hardness.

Q2. What is the standard dosage of PBTC 50% in industrial systems?

In high-cycles open cooling towers, dosing ranges from 5.0 to 15.0 ppm active. In zinc stabilization programs, 3.0 to 8.0 ppm is used to keep zinc in solution.

Q3. How does PBTC compare to HEDP and ATMP?

PBTC has much higher chlorine tolerance than HEDP and ATMP, does not precipitate easily with high calcium concentrations, and operates effectively up to pH 9.5.

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