Grade selection and in-polymer guidance
Most TiO₂ problems are solved before the first bag is opened — at the selection stage. This page collects the guidance we give customers every week, so you can narrow the field before we talk.
Which grade for which process?
A starting point only — final selection always accounts for your polymer, lustre target and filtration limits.
| Fibre / polymer system | Start with | Why |
|---|---|---|
| Polyester (PET) filament & staple — semi-dull | HK-700 / HK-600 | Balanced dispersibility and filterability at standard semi-dull addition levels. |
| Polyester — full-dull | HK-800 | Full-dull runs at a much higher loading, so ultra-low sieve residue protects spin packs. |
| Acrylic fibre | HK-800 | Inorganic aluminium coating gives superior dispersion stability in wet-spinning systems. |
| Viscose / rayon | HK-800 | Low residue and stable whiteness through the spinning bath. |
| Nylon 6 / Nylon 66 polymerisation | HK-900 | Si-Al coating withstands polymerisation temperature without agglomerating or yellowing. |
| White / TiO₂ masterbatch | HK-600 / HK-900 | High purity and consistent tinting strength reduce screen changes during long runs. |
| Plastics, coatings, paint, paper, rubber, ink | HK-200 | General-purpose anatase with high whiteness and broad compatibility. |
| Food contact & pharmaceutical colouring | HK-400 | High-purity anatase with controlled heavy metals: arsenic ≤ 3 ppm and lead ≤ 10 ppm. |
| Cellulose acetate fibre | HK-500 | Food-grade anatase with single-aluminium inorganic treatment — excellent dispersibility and filterability for acetate spinning. |
Semi-dull and full-dull reference levels
TiO₂ on polymer — enough to remove the glossy, translucent look of undelustered filament while keeping tenacity and dye behaviour close to baseline.
TiO₂ on polymer — a deep matt appearance. At this loading, dispersion quality and sieve residue matter far more than at semi-dull levels.
Powder dosing is simple and low-cost; slurry dosing gives tighter metering and less dust, but needs a grade engineered for aqueous dispersion and stable suspension. Tell us which route you use — the grade is not interchangeable.
Why anatase, and why filterability decides everything
Polymer molecules in a synthetic filament pack in a regular lattice, so the fibre surface is smooth and partly transparent and reflects light as a hard sheen. Delustering works by scattering that light at the pigment–polymer interface — and the pigment you choose determines whether your line runs or fights you.
Anatase is the fibre standard
Anatase is the crystal form normally chosen for melt-spun fibre: it is less abrasive than rutile, so it is kinder to spinnerets, metering pumps and filtration media, and it gives the clean, bright white that fibre producers specify. Rutile scatters more strongly per unit weight and is generally reserved for coatings, plastics and paper.
Residue on the 45 µm sieve
This single number predicts spin-pack behaviour better than any other. Coarse particles and agglomerates raise pack pressure, shorten spinneret life and show up as broken filaments or visible specks in the yarn. Our fibre grades are specified at ≤ 0.03 %, and for the most demanding lines ≤ 0.01 %.
Dispersion is a system property
Surface treatment, particle-size distribution and your own shear all contribute. A grade that performs well on one line can underperform on another with different mixing intensity — which is why we always ask about your process before recommending.
Batch-to-batch consistency
In fibre, a small drift in whiteness or residue changes the shade of a whole production run. Every lot ships with a Certificate of Analysis, and lot numbering is traceable back to its production record.
What a TDS and a COA actually tell you
A datasheet is a set of promises; the certificate of analysis is the evidence for the specific bags you received. You want both, and you want them to agree.
TiO₂ content
Purity of the pigment itself. Higher content means less inert coating per kilogram of white, so tinting strength per unit cost improves.
Where it bites: dosage economics.
Particle size & spread
Scattering peaks at roughly half the wavelength of visible light. A tight distribution around 0.26–0.28 µm gives predictable opacity and a consistent shade.
Where it bites: brightness repeatability.
Fe₂O₃ and colour L*b*
Iron is the usual cause of a yellow or grey cast in white fibre. Trace iron plus the L* and b* figures tell you whether the tone will match your reference.
Where it bites: shade claims, rejects.
Oil absorption, pH, resistivity
These three describe the surface coating and how the pigment behaves in a water slurry — relevant to dosing route, and to how fast a filter pack will load.
Where it bites: slurry stability, filter life.
What we recommend testing before you commit
Do
- Run a sample trial on your own line, not a lab simulation.
- Log filter differential pressure at fixed intervals.
- Compare against your current reference at equal TiO₂ loading.
- Ask for the COA of the exact lot, not a typical sheet.
- Check slurry stability if you dose as a water slurry.
Avoid
- Judging a grade on tinting strength alone.
- Switching rutile for anatase without re-checking wear parts.
- Raising loading to fix a dispersion problem — it usually compounds it.
- Ignoring packaging and pallet configuration until the shipment arrives.
- Skipping the RSL or food-contact question on export orders.
Questions we are asked most
Which grade should I use for semi-dull polyester staple fibre?
Start with HK-700; if your line is sensitive to pack pressure or you run at the higher end of semi-dull loading, HK-800 gives a wider safety margin thanks to its lower sieve residue. Send us your denier, lustre target and current grade and we will confirm.
Do you supply powder and slurry-compatible grades?
Yes. Slurry dosing needs a grade whose surface treatment keeps a stable aqueous suspension, so the two routes are not interchangeable. Tell us your addition form when you request a quote and we will recommend accordingly.
Can we get a sample before ordering?
Yes — samples are arranged for trial runs. Give us the grade, your delivery address and the quantity you need for a line trial, and we will confirm lead time together with the quotation.
What documentation ships with an order?
Certificate of Analysis with tested values for the lot, packing list, invoice and certificate of origin. TDS and GHS-format SDS are provided for every grade, and drafts can be pre-approved before dispatch to keep customs moving.
Can you work against a brand restricted-substances list (RSL)?
Tell us which standard applies — ZDHC, OEKO-TEX or a specific brand RSL — and we will confirm compliance status and the supporting documentation before quotation.
Why anatase rather than rutile for fibre?
Anatase is less abrasive than rutile, which matters when pigment passes through spinnerets and metering pumps every hour of a production run. It also gives the bright, neutral white fibre buyers expect. Rutile scatters light more strongly and is normally used in coatings, plastics and paper instead.
Technical documents we provide
Sent the same business day on request — no account needed.
TDS
Full technical data sheet per grade.
COA
Lot-by-lot certificate of analysis.
SDS
GHS safety data sheet, English.
Certificates
ISO, REACH and compliance status.