From wood to pulp, to pulp, paper, and paper products

2. Classification of bleached broadleaf pulp

Bleached pulp, in contrast to bleached needle pulp, is generally no longer differentiated by several types of pulp, and the tree species and supply quantity are more influential factors.

Bleached eucalyptus pulp, wood pulp made of eucalyptus as the main raw material, mainly produced in South America Brazil, Chile, Uruguay and Europe, a small amount from Southeast Asia, in a wide variety of eucalyptus, coupled with regional climate differences, all kinds of eucalyptus pulp quality prices are also different, generally considered to be the best quality of Brazilian eucalyptus, Southeast Asia's worst, but also depending on the specific use.

Bleached Acacia Pulp: The main origin is Indonesia, Acacia wood (also known as whole acacia) as a specially developed pulping wood, has no less than the rapid growth of tropical eucalyptus river production effect, especially suitable for artificial cultivation of Southeast Asian climate, in recent years, with the rapid growth of production, has gradually become an important option in the market, in terms of pricing, Its representative brand of lovesickness has been matched with Brazilian eucalyptus wood.

Poplar and other single tree pulp: It mainly refers to the broadleaf pulp of Aspen, Birch and Maple tree species. Broadleaf pulp of a single tree species generally reflects some characteristics in some aspects. Like eucalyptus and acacia wood, it is necessary to find a "selling point", otherwise it will reflect a reasonable value. If it is difficult to sell and just to dump in the market, the general price will be slightly lower.

Hardwood: mainly produced in Indonesia and parts of North America: Hardwood, hardwood, natural broad-leaved forest, of which there are many species, very one by one, in most of the pulp are first cut down hard mixed forest after planting plantation, hard mixed forest will not recover by itself, so a future trend is that the number of natural hard mixed forest will gradually reduce, at the same time, the cutting of hard mixed forest will seriously damage natural ecology, Most of the pulp felling hard mixed forest has a bad reputation and is under increasing environmental pressure. In the long term, the supply of hard mixed wood pulp will gradually decrease and eventually disappear.

Second, pulping

Pulping: The process of dispersing papermaking raw materials into a single fiber is called pulping, and the product obtained is called pulp.

Purpose of pulping: Dissolve the lignin in the raw material, separate the raw material into a single fiber, and increase the specific surface area of the fiber (surface area per unit weight of the fiber).

Lignin is a complex phenolic polymer formed from three alcohol monomers (p-coumarol, coniferol, sinapol). Lignin is one of the components of plant cell wall, which has the function of connecting cells. Lignin is a kind of polycyclic polymer organic matter containing many negative electric groups, and has a strong affinity for high price metal ions in soil.

Chemical pulping principle: Use chemical liquid to cook the material sheet, and react with the lignin in the material sheet at high temperature to form a water soluble substance, so that the fiber is separated and dispersed into a slurry. At the same time, as much as possible to retain cellulose, and varying degrees of retention of hemicellulose.

Chemical pulping is mainly divided into acid pulping and alkali pulping. Alkali pulping process mainly through SH-, OH- plasma and lignin nucleophilic reaction, the ether bond of macromolecules of lignin is broken, the macromolecules become small molecules, and the lyophilic phenolic hydroxyl group is increased, the lyophilic lignin is enhanced, and the lignin is dissolved from the wood chips. The acid pulping process is mainly through S032- or HS03- and lignin nucleophilic reaction, lignin sulfonic acid, lignin sulfonic acid combined with the salt base in the solution, the formation of lignin sulfonate, dissolved from the wood chips.

Three, making paper

Papermaking is the dispersion of the resulting pulp to obtain evenly interwoven sheets. Paper products are usually divided into cultural paper, wrapping paper, household paper, and special paper according to the use of finished products: (1) Cultural paper covers all printing and writing paper, including newsprint, uncoated cultural paper (double-adhesive paper, writing paper, lightweight paper, electrostatic copy paper, etc.) and coated cultural paper (mainly coated paper); (2) Packaging paper covers all paper packaging raw materials, including cardboard (white board paper, white cardboard, corrugated paper, box board paper, kraft paper, etc.); (3) Household paper (toilet paper, diapers, etc.); (4) Special paper.

Cultural paper refers to the writing and printing paper used for disseminating cultural knowledge, which is mostly used for information transmission and cultural inheritance, mainly including uncoated printing paper, coated printing paper and newsprint. Typical uncoated printing paper includes duplex paper, writing paper, lightweight paper, SC paper, xerographic paper and printer paper. Coated printing paper mainly includes light-weight coated paper and coated paper, among which coated paper consumption accounts for more than 90% of coated cultural paper.