Polyethyleneimine Storage — PEI Tank Selection for Paper, Water Treatment, CO2 Capture

Polyethyleneimine Storage — PEI Tank Selection for Paper Wet-Strength, Water Treatment Flocculation, Adhesion Promoter, and CO₂ Capture Service

Polyethyleneimine (([CH₂CH₂NH]_n) PEI, CAS 9002-98-6) is a branched cationic polyamine with the highest amino-group density of any commercial polyamine (nitrogen-to-carbon ratio 1:2). It is supplied across a wide molecular-weight range from 800 g/mol low-molecular-weight grade to 10⁶ g/mol high-molecular-weight grade, with two physical-form options: water-free anhydrous viscous liquid (typical 99.5% active, viscosity 5,000-50,000 cP at 25°C depending on MW) and aqueous solution at 30-50 wt% (typical 1,000-10,000 cP at 25°C). Aqueous PEI solutions are alkaline (pH 10-11.5 due to amine basicity) and present moderate corrosion risk to copper, zinc, and aluminum; HDPE and 316L stainless are the standard tank materials. The polymer's signature property — high cationic charge density at all pH below 9 — drives its commercial dominance in paper wet-strength chemistry, water-treatment flocculation, and adhesion-promoter applications.

The six sections below cite BASF (Ludwigshafen Germany; Lupasol P, FG, FT WF, G 20, water-free + waterborne grades from 800 to 10⁶ g/mol — the dominant global PEI producer), Nippon Shokubai (Osaka Japan; Epomin brand), Wuhan Qianglong Chemical (China-domestic supply), and ChemPoint distribution for North American Lupasol service. Regulatory citations point to OSHA 29 CFR 1910.1200 hazard communication, NFPA 704 Health 2 / Flammability 1 / Instability 0, DOT UN 2735 (polyamines, liquid, corrosive, n.o.s.) Hazard Class 8 PG II for the higher-concentration grades, EPA TSCA inventory grandfathered listing, and FDA 21 CFR 176.170 food-contact paper-coating clearance for specific Lupasol grades.

1. Material Compatibility Matrix

PEI solution is moderately alkaline (pH 10-11.5) and chelates copper, zinc, and several other transition metals via the amine functional groups. Material selection avoids these metals in direct-contact service; HDPE, FRP, and 316L stainless are standard.

For paper-mill wet-strength resin storage and water-treatment flocculation use, FRP vinyl ester or HDPE rotomolded tanks with PP fittings and EPDM gaskets are the industry standard. For gas-treating CO₂-capture amine service requiring high-temperature resistance and amine-thermal-degradation control, 316L stainless construction with PFA / PTFE elastomer specification is required. NEVER use copper, brass, zinc, or aluminum in PEI service — the amine-complex chemistry will degrade both the metal and the polymer activity.

2. Real-World Industrial Use Cases

Paper Machine Wet-Strength and Dry-Strength Resin (Dominant Use, 30-40% of Global Demand). PEI is added at the paper-machine wet-end at 0.1-1.0% on dry-fiber weight to improve wet-strength (the strength of paper after re-wetting, critical for tissue, paper towels, and food-packaging-paper applications) and dry-strength of the finished sheet. Typical mill-scale dose is 5-15 lb of active PEI per ton of paper produced. Mill storage is typically 5,000-30,000 gallon HDPE or FRP bulk tanks of 50% solution Lupasol, with metering through diaphragm pumps to the wet-end thick-stock or thin-stock injection points. Kuraray, BASF Lupasol, and Solenis Kymene grades dominate the food-grade tissue and towel specification with FDA 21 CFR 176.170 clearance.

Water Treatment Flocculation and Sludge Dewatering. PEI is a primary cationic flocculant for raw-water clarification at municipal water-treatment plants (alongside polyaluminum chloride and aluminum sulfate as primary coagulants) and for sludge dewatering at municipal wastewater-treatment plants. Dosing is typically 5-30 mg/L on raw-water flow or 20-150 mg/L on dewatering-feed sludge. Plant-scale storage is 200-5,000 gallon HDPE day-tanks with diaphragm metering pump dosing. NSF/ANSI 60 certification is required for drinking-water-treatment use; specific Lupasol grades carry NSF 60 listing.

Adhesion Promoter on PET Film and PE Films. Biaxially-oriented polyethylene-terephthalate (PET) film for food-packaging, photographic, and electronic-display applications is in-line coated with 1-3% PEI solution at the film-line tenter exit to provide a primer surface for downstream adhesive lamination, ink printing, or vacuum-deposited metallization. Film-converter use is at 50-500 gallon batch-mix tank scale with continuous metering to the in-line coating bar.

CO₂ Post-Combustion Capture Solvent. PEI is one of the leading sterically-hindered amine candidates for CO₂ post-combustion capture from coal-fired and natural-gas-fired power-plant flue gas, both as a liquid-phase amine scrubber solvent and as a solid-supported amine sorbent (impregnated on porous silica, alumina, or polymer support). Pilot and demonstration-scale plants at 1-25 MW thermal capacity equivalent operate at multiple US, EU, and Asia sites using Lupasol or Nippon Shokubai Epomin chemistry. Commercial-scale deployment is anticipated as carbon-capture economics become viable; storage at the demonstration plant is typically 1,000-5,000 gallons of 30% solution in 316L stainless tanks.

Tire Cord Adhesion in Automotive and Truck Tires. PEI is added to RFL (resorcinol-formaldehyde-latex) dip baths used to coat polyester and nylon tire-cord fabric for promoting adhesion to the rubber compound at the tire-build stage. Tire-plant dip-tank scale is 500-2,000 gallons of compounded RFL at the cord-treatment line; PEI delivery is typically as 50% solution in 55-gallon drums or IBC totes.

Pigment Manufacturing and Plastic-Modification Compatibilizer. PEI is used as a wetting agent and dispersant in pigment manufacturing (titanium dioxide, iron oxide, organic pigments) and as a compatibilizer in PA / PE / PP polymer-blend modification. Use volumes are modest relative to paper-mill and water-treatment applications.

3. Regulatory Hazard Communication

OSHA and GHS Classification. PEI 50% aqueous solution carries GHS classifications H290 (may be corrosive to metals), H314 (causes severe skin burns and eye damage), H317 (may cause an allergic skin reaction), H361 (suspected of damaging fertility or the unborn child), H400 (very toxic to aquatic life), H410 (very toxic to aquatic life with long-lasting effects). The H317 sensitization classification is the chronic occupational driver: repeated dermal exposure to PEI can sensitize workers, after which subsequent exposures produce contact dermatitis at low concentration. Glove and PPE specification is mandatory at all PEI-handling stations.

NFPA 704 Diamond. PEI 50% rates NFPA Health 2, Flammability 1, Instability 0, no special hazard. Anhydrous PEI rates Health 2, Flammability 2, Instability 0 because the higher organic content of the water-free product produces low-temperature flash characteristics on heating.

DOT and Shipping. PEI 50% solution ships as UN 2735 (polyamines, liquid, corrosive, n.o.s.), Hazard Class 8 (corrosive), Packing Group II. Anhydrous PEI ships as UN 2735, Class 8, Packing Group III. Dilute solutions below 10% may ship as non-hazardous. IBC totes, 55-gallon drums, and tank-truck delivery are all standard shipping modes; the Class 8 designation requires hazmat-trained carriers and shipping-papers documentation.

FDA Food-Contact and NSF/ANSI 60. Specific BASF Lupasol grades (Lupasol P, Lupasol FG, Lupasol FC) are FDA-approved for food-contact paper-coating use under 21 CFR 175.105 and 21 CFR 176.170. Specific lower-MW Lupasol grades carry NSF/ANSI 60 certification for drinking-water-treatment chemical use. Procurement files for food-contact paper or drinking-water chemical purchases should include the FDA citation and NSF 60 certificate as standard line items.

EPA TSCA Inventory. PEI is grandfathered on the TSCA inventory under CAS 9002-98-6. Modified PEI grades (ethoxylated, propoxylated, quaternized, sulfonated) carry separate CAS numbers and may require Premanufacture Notice per their specific modification chemistry.

EPCRA SARA 313. PEI is not on the SARA 313 Toxic Release Inventory list. Ethyleneimine (the monomer, CAS 151-56-4) IS SARA 313 listed and is a separate regulated chemical — do not confuse the polymer (CAS 9002-98-6) with the monomer.

4. Storage System Specification

Bulk Liquid Storage. Paper mills consuming bulk PEI typically maintain 30-60 days of inventory in 5,000-30,000 gallon HDPE rotomolded or FRP vinyl ester tanks. Storage requires: temperature control to keep solution viscosity in the pumpable range (typically 50-70°F for 50% solution; below 40°F the viscosity rises sharply), nitrogen blanket on high-purity gas-treating-amine grades to prevent CO₂ uptake from atmosphere (which converts amine to carbamate and reduces flocculation activity), and segregation from acid storage and copper / zinc / aluminum hardware. Tank fittings: 2-inch top fill, 2-inch bottom outlet to feed pump suction, 4-inch top vent, 18-inch top manway, level + temperature indicators.

Day-Tank for Continuous Dosing. Pump-feed operations often use 200-500 gallon day-tanks decoupled from the bulk storage for steady metering pump suction. Day-tank is replenished from bulk on level-controlled fill. Material: HDPE rotomolded with PP fittings.

Pump Selection. Diaphragm metering pumps are the standard for PEI dosing. Verify diaphragm material (PTFE diaphragm preferred over EPDM at extended service), check valves (PTFE ball + EPDM seat), and head materials (PVC or PVDF). LMI, Pulsafeeder, ProMinent, and Grundfos brands have PEI-service-rated configurations. For bulk transfer at 5,000-50,000 gallon tank scale, progressive-cavity or lobe pumps handle the high-viscosity fluid better than centrifugal pumps.

Temperature Conditioning. 50% PEI solution viscosity ranges from 1,000 cP at 25°C to 5,000 cP at 5°C. Cold-climate storage (Northern US, Canada, Northern Europe) typically uses electric trace-heating on storage-tank piping plus heated-tank dome covers to keep solution temperature above 50°F for reliable pumping. Insulation thickness is typically 2-4 inches polyurethane foam with weather-jacketing.

Secondary Containment. Per IFC Chapter 50 and most state EPA hazardous-waste rules, PEI 50% solution storage tanks above 55 gallons require secondary containment sized to 110% of the largest tank capacity. HDPE pans, FRP curbs, or epoxy-coated concrete dikes are standard. Containment must capture full tank failure for a Class 8 corrosive without breaching.

5. Field Handling Reality

The Viscosity Reality. 50% PEI solution at room temperature is approximately the consistency of motor oil; high-MW Lupasol G 35 grades approach the consistency of honey at refrigerator temperature. Pump suction-line sizing must be larger than for a comparable water-strength alkaline-chemistry solution — typically 1.5-2x diameter at the same flow rate. NPSH-available calculations must use the actual solution viscosity at minimum-storage-temperature, not the 25°C published value. Pumping problems with PEI in cold-climate operations are nearly always traceable to undersized suction-side hydraulics rather than to pump-end issues.

The Foaming Reality. PEI solution at 30-50% concentration is moderately surface-active and foams aggressively when agitated, splashed, or air-entrained. Storage-tank fill operations should use submerged-fill pipes (eduction to within 6 inches of tank bottom) to prevent splash-fill foaming that can fill tank vapor space with stable foam in 5-15 minutes. Day-tank fill-and-recirculate cycles should run with low-rpm slow agitator settings to prevent vortex foaming.

The Carbamate-Drift Reality. Open-vent PEI tanks slowly absorb atmospheric CO₂ via the amine groups, forming carbamate species that reduce the polymer's cationic charge density and flocculation activity. For paper-mill use the activity loss is acceptable up to 5-10% over 30-60 day inventory turnover; for high-purity gas-treating CO₂-capture amine use, the activity loss is unacceptable and nitrogen-blanket on the storage tank is mandatory. NSF/ANSI 60 drinking-water grade has the same activity-loss concern; specific Lupasol grade selection plus storage-time control are the management tools.

Spill Response Chemistry. PEI spills are absorbed with sand, vermiculite, or universal-spill absorbent. Acid neutralization with dilute (5-10%) sulfuric or hydrochloric acid is recommended for spills greater than 5 gallons to convert the amine to amine-salt form that is much less environmentally damaging on subsequent water entry. Spill waste is disposed as RCRA listed hazardous waste under D002 (corrosive). NEVER flush PEI spills to storm water — PEI is highly toxic to aquatic life (LC₅₀ daphnia 1-5 mg/L) and creates persistent water-column toxicity in any receiving stream.

Glove and Skin Sensitization Reality. Repeated PEI dermal exposure produces sensitization in 10-30% of regularly-handling workers within 1-3 years. Once sensitized, an exposed worker can no longer handle PEI even with conventional PPE because trace residue on glove exteriors or work-station surfaces produces dermatitis at sub-1-mg exposure. Mandatory glove + arm-sleeve PPE for all PEI handling, with weekly glove-integrity replacement schedule, prevents sensitization. Sensitized workers must transition to non-PEI handling roles — documented sensitization is generally permanent.

Related Chemistries in the Water-Treatment Coagulant Cluster

Related chemistries in the water-treatment coagulant + polymer-flocculant cluster (municipal + industrial + paper-mill coagulation + flocculation):

• polyDADMAC — Cationic polymer flocculant sister chemistry
• Polyvinyl Alcohol (PVOH) — Water-soluble polymer flocculant companion
• Sodium Polyacrylate — Anionic polymer flocculant counterpart
• Polyaluminum Chloride (PAC) — Inorganic primary coagulant companion
• Ferric Chloride (FeCl3) — Iron-based primary coagulant pair

Related Hub Pillars

For broader chemistry context, see the OneSource Plastics high-traffic chemical-compatibility hub pillars:

• Ferric Chloride (FeCl₃)
• Sodium Hydroxide (NaOH / caustic soda)
• Hydrochloric Acid (HCl / muriatic)