When working with viscous, high-boiling plasticizers — DOP (Dioctyl Phthalate), DINP (Diisononyl Phthalate), DOTP (Dioctyl Terephthalate), or DEHCH — proper cleaning of the IBC container after unloading is essential. These plasticizers leave oily residues on container walls that water alone cannot remove. If the container is not cleaned thoroughly, residual plasticizer can contaminate future batches, reduce product purity, or trigger compatibility issues when the IBC is repurposed for a different chemical.
The procedure below is a proven industrial cleaning sequence that works as a baseline for all common plasticizers, with plasticizer-specific adjustments noted in the final section.
Step 1: Drain and Pre-Treatment
After unloading the plasticizer, drain all remaining liquid completely. Use an absorbent cloth or scraper to remove visible residues from the bottom and inner walls of the IBC.
If a large amount of residue remains, add a small amount of solvent oil and gently heat the container to 50–60 °C, allowing the plasticizer to dissolve before draining.
Step 2: Solvent Cleaning
Use a strong organic solvent to dissolve and wash away the oily film.
Recommended solvents:
- No. 2 Solvent Oil (Naphtha)
- Xylene / Toluene
Procedure:
- Add solvent at 5–15% of the IBC volume (see plasticizer-specific guidance below).
- Seal the lid and shake the container for 5–10 minutes.
- Drain the solvent completely.
- Repeat the process if oil traces remain.
Both Naphtha and Xylene/Toluene show excellent dissolving power for ester-based plasticizers, breaking down the oily film and cleaning the internal surfaces of the IBC.
Step 3: Alkali Washing (Oil Film Removal)
To remove any remaining plasticizer film, prepare an alkaline cleaning solution:
- 5–10 % Sodium Hydroxide (NaOH) in water
- Add a small amount of surfactant or industrial detergent for better results
Instructions:
- Heat the solution to about 50 °C (122 °F).
- Pour into the IBC container and soak or agitate for 15–30 minutes.
- Drain the alkali solution and rinse 3–5 times with clean water until the rinse water reaches neutral pH (~7).
This step removes stubborn residues and ensures the inner surface is completely degreased.
Step 4: Drying
After washing, completely dry the container:
- Leave the IBC open in a well-ventilated area, or
- Use warm air (50–60 °C) for faster drying.
Ensure no odor or oily residue remains before refilling the IBC with any chemical product.
Step 5: Safety and Environmental Precautions
- Perform all cleaning steps in a well-ventilated area away from open flames.
- Wear chemical-resistant gloves, goggles, and a mask when handling solvents or alkali.
- Collect and dispose of waste solvent and alkali water according to local environmental regulations.
Plasticizer-Specific Adjustments
The five-step procedure above is the baseline. The following adjustments reflect viscosity, volatility, and film tenacity differences between plasticizers.
DOP (Dioctyl Phthalate, DEHP)
- Solvent dose: 5–10% of IBC volume is sufficient.
- Pre-treatment: Heat to 50–60 °C if residue is heavy. DOP’s high adhesion responds well to gentle warming before solvent contact.
- Why it matters: DOP is the legacy industry workhorse with the highest viscosity among common phthalates. Its oily film resists short solvent contact times; the alkali step is essential, not optional.
DINP (Diisononyl Phthalate)
- Solvent dose: 10–15% of IBC volume — higher than DOP. DINP’s branched isononyl side chain produces a slightly thicker film that needs more solvent to dissolve.
- Agitation: Shake the sealed container vigorously for 5–10 minutes (more aggressive than DOP).
- Why it matters: DINP’s higher molecular weight makes its film harder to break with passive solvent soaking. Active agitation matters more than for DOP.
DOTP (Dioctyl Terephthalate / DEHT)
- Solvent dose: 5–10% of IBC volume (comparable to DOP).
- Notes: DOTP’s terephthalate backbone has slightly lower polarity than ortho-phthalates, but in practice the cleaning procedure is identical to DOP. If the IBC will be refilled with a phthalate (DOP, DINP), ensure no DOTP traces remain — cross-contamination is a regulatory concern for customers specifying phthalate-free.
DEHCH and DINCH (Cyclohexanoates)
- Solvent dose: 5–10% of IBC volume.
- Alkali step: Extend soak time to 30–45 minutes. Cyclohexanoate plasticizers have lower volatility than phthalates and form a more tenacious surface film.
- Why it matters: DEHCH and DINCH are commonly used in medical and food-contact applications where any residual contamination is unacceptable. Verify rinse water pH and conduct a wipe test before reuse.
DOA (Dioctyl Adipate) and Other Adipates
- Solvent dose: 5% of IBC volume is usually sufficient.
- Alkali step: May be reduced to 15 minutes if the IBC will be refilled with the same DOA grade.
- Why it matters: DOA’s lower viscosity and shorter ester chain make it easier to remove than phthalates. Aggressive cleaning is rarely necessary unless the IBC will switch service to a different plasticizer family.
Cross-Contamination Risk When Switching Plasticizer Service
If an IBC is being repurposed from one plasticizer to another, follow the cleaning procedure for the more demanding of the two plasticizers. Specifically:
- Switching from phthalate (DOP, DINP, DBP) to non-phthalate (DOTP, DINCH, DEHCH, DOA): Treat with the cyclohexanoate or non-phthalate protocol (longer alkali soak, verified rinse pH). Even trace DOP contamination above 50–100 ppm can disqualify the next batch for REACH-compliant or medical-grade customers.
- Switching between phthalates: The baseline procedure is sufficient.
- Switching to a different chemical family entirely: Do not reuse — IBCs that have held plasticizers should not be repurposed for solvents, acids, or aqueous chemicals without a full triple-rinse plus visual inspection of the gasket and dip tube.
Conclusion
Cleaning IBC containers after unloading plasticizers requires both solvent and alkali washing to achieve complete residue removal. The baseline procedure — Naphtha or Xylene/Toluene solvent followed by 5–10% NaOH at 50 °C — works across DOP, DOTP, DINP, DEHCH, DINCH, and DOA, with plasticizer-specific dose and contact-time adjustments captured above.
Properly cleaned IBCs protect product purity, prevent cross-contamination between plasticizer grades, and support consistent quality for downstream PVC compounders.