Water-Based Printing Inks for PU Paper
Converters printing leather-look book covers, folders and wall panels need a PU paper printing ink supplier whose chemistry bonds to a polyurethane coating, not to raw paper fiber. chemlinkai formulates water-based inks for PU paper that wet the coated surface, stay flexible through creasing and embossing, and run clean on gravure or flexo lines.
How the system works
PU paper is a coated substrate: a paper core carries a polyurethane surface layer that supplies the grain, softness and wear resistance. The ink has to do what paper inks never face — adhere to a polymer film while staying flexible enough to crease without cracking.
The system starts with a binder package chosen for the PU surface chemistry and surface energy of your coating, not a generic paper-ink resin. Wetting, drying and rewind blocking are set together: the ink must level on a low-absorbency surface, dry within your oven budget, and not block when the printed web is rewound warm.
- Adhesion screening on your actual PU-coated paper, including the grain direction
- Flexibility tuning for creasing, folding and embossing steps downstream
- Blocking control matched to rewind temperature and stack conditions
- Formulation and color development supported by in-house resin synthesis
Why does ink pull off PU paper after folding or in storage — and how is it prevented?
Two failure modes dominate on PU paper. The first is weak anchorage: the PU coating is a film with low surface energy and little porosity, so a binder built for cellulose fibers cannot establish grip; ink lifts in crosshatch or crease tests. The second is blocking: because the surface does not absorb solvent, the film stays soft longer, and warm rewind or stacked sheets stick together, pulling print from one sheet onto the next.
Both are solved at the formulation level before the trial. We screen candidate binders on your PU surface, tune the dry-film hardness and slip against your creasing and stacking conditions, and set the drying profile to the oven capacity on your line. As a PU paper printing ink supplier, we deliver the chemistry and the process window together, so the trial result transfers to production.
Representative system parameters
Guidance ranges for water-based inks on PU-coated paper before a print trial. Final targets are confirmed on your material.
| Parameter | Representative range | Remark |
|---|---|---|
| Solids content | 30 – 45 % | Set by coverage and drying budget |
| Viscosity (DIN 4 cup, 25 °C) | 15 – 30 s | Window for gravure or flexo transfer |
| pH | 7.5 – 9.0 | Neutral-to-mildly-alkaline window protecting the PU coating |
| Fineness of grind | ≤ 5 μm | Checked per production batch |
| Surface wetting | Method-specific — set by trial | Drawdown rating on your PU paper |
| Blocking resistance | Method-specific — set by trial | Tested at your rewind and stack conditions |
| Storage stability | 6 months sealed, 5 – 35 °C | Re-dispersion procedure provided with supply |
Representative ranges for system selection — typical values — batch TDS on request.
Where the ink sits on the PU paper stack
The ink bonds to the PU coating on top of the paper core; the printed sheet then faces creasing, embossing or lamination depending on the product.
Verified data on PU-surface adhesion, flexibility and blocking tests is published after customer and company approval. Request current test results via the form.
PU paper printing — common questions
Direct answers for converters, purchasers and QC engineers.
Can you print both gravure and flexo on PU paper with the same system?
The binder and color systems carry over, but viscosity and drying are re-set per process. We recommend confirming the primary process in the trial and keeping the second as a documented variant.
How do you handle PU papers from different coating suppliers?
PU coatings differ in polymer type, surface energy and additives. We qualify each coated paper separately — adhesion and blocking results on one supplier do not transfer automatically.
What is the minimum order quantity for a first order?
MOQ is agreed per color and per paper qualification. Trial ink for the first print test is supplied under the trial agreement before any production commitment.
Which documents come with the ink for export orders?
TDS, SDS, COA and compliance statements for the agreed application and destination. Scope is confirmed at inquiry; documents are released after verification and supplied with the shipment.
Why does the printed roll block even when the ink looks dry at the reel?
Apparent dryness is not film hardness. If blocking appears, we rebalance the drying profile and the dry-film slip package against your rewind temperature rather than only extending drying time.
Documentation
Documents are released per application and destination after final verification.
Documents marked “pending” are released after final verification — request the current version through the form and we will send it with the applicable scope.
Book a print trial on your coated paper.
Send the PU paper you run, a print sample or target color, and your line conditions. We match the ink system and set up the trial within a confirmed schedule.