As we all know, wood pulp is the most common pulp around the world. In the international pulp market, the most of pulp is bleached softwood KP pulp and bleached hardwood kraft pulp. The market pulp mainly comes from China, Canada, America, Russia, Finland, Sweden, Indonesia, Brazil, and other countries. The bleached kraft wood pulp can be divided into five types, including NBSK pulp, NBHK pulp, SBSK pulp, SBHK pulp, and BEK pulp.
NBSK pulp
NBSK pulp is an acronym for Northern bleached softwood kraft pulp, the paper industry’s benchmark grade of pulp. Market NBSK is produced mainly in Canada and the Nordic countries, Russia.
Nordic countries
Nordic countries only produce two kinds of softwood: pine and spruce. Generally, the length of fiber is 3.1-3.33mm, and diameter is 30-32μ m, and it’s thinner and shorter than the same type of Canada. This kind of fiber has similar specification and cell wall and spread evenly in the paper pulp. The NBSK pulpmade in this region has less tension stress, foldability and tear resistance than SBSK pulp, but higher bursting strength. Due to the long fiber and short diameter, the NBSK pulp from Nordic countries applies for manufacture coated offset paper, two text paper, one-side coated paper, intaglio printing paper, release paper, etc.
Russia
Russian NBSK pulp is mainly made from red pine, white pine, and larch. Red pine and white pine is very similar to spruce and fir of Canada, low latewood percentage, thin cell wall. The softwood made in Russia mix with larch can produce synergistic, so mixing pulping is more common to see. The NBSK pulp of Russian Far East and NBSK pulp of Nordic countries can be classified as the same type.
Canada
Canada is so vast, and NBSK pulp types are various. The paper pulp mill is generally built near the forest, Canadian forest can be divided into six areas.
- West coast of BC: native hemlock and secondary hemlock are main types, in the Vancouver Island and along the coastline; there are large numbers of Douglas fir and cedar. The softwood on the west coast of BC has long fiber, the length might over 4mm, and apply for paper with light weight, which requires wet tension stress and largest felting.
- Mackenzie of BC: this region has many kinds of softwood, such as engelmann’s spruce, lodgepole pine, western yellow pine, bracted fir, white spruce, and hemlock. Besides, Douglas fir and cedar barely born in this region. The NBSK of this region is a multipurpose pulp but without outstanding physical property. Even though, this kind of paper pulp is also popular among paper pulp manufacturers.
- Eastern foot of the Rocky Mountains: the environment of this region is most harsh in Canada. Engelmann’s spruce, lodgepole pine, and rocky mountain fir are three typical types of softwood in this region. The electrical paper and masking tape of Canada are all made from softwood fiber of this region.
- Plain and western Ontario: just like Mackenzie of BC, the NBSK pulp is also universal in this region. Picea mariana of this region perfect apply for facial tissue manufacture.
- Quebec: Picea mariana is common in this region.
- Eastern coastal provinces: most complete types of wood, including red spruce, Picea mariana, red pine, white pine, hemlock and balsam fir. Compared to other regions of Canada, the fiber is shorter and thinner.
NBHK pulp
NBHK pulp is short for northern bleached hardwood kraft. The northern hardwood mainly includes birch, maple, beech, and poplar, aspen. Most of NBHK pulp are mixed hardwood, which is made in Northeast of North America, Nordic countries, Russia. Because the big difference between various kinds of hardwood, the hardwood pulp made from single fibers becomes hot in the market, such as birch pulp of Nordic, beech pulp of America, poplar pulp of Canada, birch and poplar pulp of Russia.
SBSK pulp
SBSK pulp is also called southern bleached softwood kraft pulp, it is mainly made from seven kinds of softwood, which all belongs to pine. Four of them are southern pine, including slash pine, longleaf pine, loblolly pine, jack pine, they are advantageous. Slash pine and longleaf pine are commonly born in the south-east of America, very suitable for fluff pulp. The significant attribute of SBSK pulp is the tearability, which is better than NBSK pulp.
SBHK pulp
SBHK pulp stands for southern bleached hardwood Kraft pulp. Southern hardwood has various types, for example, there are more than 80 kinds of hardwood, so they are generally called hardwood. Most of the southern hardwood can be applied to chemical pulping, but not suitable for mechanical wood pulping. Because the short length and low strength of hardwood fibers, it is applicable for cultural and toilet paper.
Recently, acacia of Indonesia becomes one of popular material for SBHK manufacture, with the advantages of single type and stable quality, high light-scattering coefficient, good opaqueness, it is widely used to manufacture cultural paper.
In the USA, SBHK pulp from Kentucky include 55% white oak, and it usually applies for copy paper, computer printout paper, envelope paper, note paper. SBHK pulp from Alabama and Mississippi include 43% maple and 35% red oak, rest fibers include poplar, sweet pecan, platanus, etc. it is suitable to manufacture vellum paper, text paper and cover paper.
The SBHK pulp of China is similar to America’s, due to the limitation, the northern hardwood is not yet planted in large areas.
BEK pulp
BEK pulp (bleached eucalyptus Kraft pulp) actually belongs to SBHK, but most of eucalyptus is planted solely in large areas. In the virgin time, the commercial growing of eucalyptus begins in the 1950s, until 1970s, it is sold as market pulp. The BEK pulp has features of opaqueness, smoothness, formability, print gloss, and it is accepted by many paper and pulp mills gradually. BEK pulp is considered as the ideal fiber materials for manufacture tissue paper.
The eucalyptus has a lot of kinds, such as eucalyptus grandis, eucalyptus urophylla, blue gum, eucalyptus citriodora, lauan, eucalyptus exserta, and etc. some kinds of eucalyptus with high specific gravity are not suitable for paper making, the proper value is lower than 0.7. Different kinds of eucalyptus decide different quality of paper pulp. In general, Brazilian BEK pulp is made from eucalyptus grandis; BEK pulp of Chile and Spanish are made from blue gum; while the BEK pulp of China is made from eucalyptus urophylla and eucalyptus citriodora.
Beside these five bleached chemical pulp, there are various kinds of pulp, including sulfate pulp, CTMP pulp, wastepaper pulp, etc.
