Unbleached Softwood Kraft Pulp

Unbleached softwood kraft pulp is produced by the kraft (sulphate) chemical process from softwood and is not carried through a bleaching sequence, so it retains residual lignin and its characteristic brown colour. Because the fibre is neither brightened nor exposed to the additional chemical stages that bleaching requires, buyers choose it where mechanical performance and cost per tonne of strength are the deciding factors. The commercial conversation is about strength delivery — tear, tensile and burst at a defined refining level — plus cleanliness, runnability and consistency between shipments. Those values differ by mill and grade and are confirmed against supplier documentation, never assumed from the grade name.

This product is asked for as UKP, unbleached kraft pulp, virgin unbleached kraft pulp, natural kraft pulp and brown softwood kraft. All of those point to the same canonical product and are covered here. What the terminology does not establish is interchangeability: two pulps sold under the same broad description can differ materially in kappa number, strength profile, freeness and cleanliness. Grade and specification must be confirmed at quotation for the particular lot on offer.

Bleached softwood kraft — NBSK being the reference grade — is chosen where brightness, brightness stability and cleanliness are part of the product requirement, typically in tissue, printing and writing and white board furnishes. Unbleached softwood kraft is chosen where the finished product is brown or where the sheet is not seen. Both are long-fibre reinforcement pulps, but they are separate purchases with separate specifications; if you are comparing them, state the finished product so the comparison is made on the properties your machine actually needs.

Normally specified on kappa number or residual lignin level, strength properties at a defined refining energy, freeness, cleanliness/dirt count, moisture on an air-dry basis and bale presentation. Allzone publishes no values for these parameters: they vary by mill and grade and are confirmed against supplier documentation at quotation.

Unbleached softwood kraft is produced in the northern softwood regions, including Canada, as well as in other producing regions worldwide. Canadian mills have an established softwood kraft production and export base, but neither Canadian nor any other origin is implied for a given offer. Origin, mill, availability, certification and specification are confirmed at quotation against the lot actually offered. Origin is a supply attribute, never an assumed property of the product, and no fibre source is implied by this page.

Traded on an air-dry tonne basis; confirm the weight and moisture settlement basis in the contract · Quoted FOB, CFR or CIF, container or breakbulk · State whether certified fibre is required so chain of custody can be contracted rather than added later · Bale integrity matters commercially: broken bales are a pulper problem, so agree unitisation and wire specification in advance.

Commonly relevant documentation: mill quality certificate / certificate of analysis, packing list, certificate of origin, bill of lading, and — where contracted in advance — chain-of-custody documentation. Availability of each document is confirmed per order, per mill and per destination.

Useful in a first enquiry: the exact pulp type and grade, the end use, quantity in metric tonnes or containers, destination port, the fibre or specification you must match, and your Incoterm. For unbleached softwood kraft also state: the finished paper or board grade, the strength properties that govern acceptance, your refining capability, any kappa or freeness requirement, moisture basis, certification requirement and required bale presentation.

Unbleached coniferous chemical wood pulp of the sulphate (kraft) type, other than dissolving grades, falls within HS 4703.11. The tariff line applied to a specific shipment is verified against the material actually offered and the destination's classification practice.