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



The paper industry is a typical long-chain, asset-heavy, long-cycle industry with diverse needs: the typical papermaking industry chain is "forest-pulp-papermaking - all kinds of downstream paper". Among them, the cultivation of rapid growth forest for pulping requires reserve forest land and cultivation, and the maturity cycle of trees is longer, requiring at least 5 years to be harvested for production. The production of pulp and machine-made paper needs to purchase large paper making equipment and supporting production capacity, the cycle is about 2-3 years; The growth rate of all types of downstream demand has slowed down after experiencing China's high-speed growth stage, and cyclicality is gradually replacing growth.

According to the national economic industry classification standard, the paper industry mainly refers to the paper and paper products manufacturing industry, including pulp manufacturing industry, paper industry, paper products manufacturing industry three links; Therefore, the paper industry is highly related to some basic industries, such as forestry, agriculture, printing, packaging, machinery manufacturing, chemical industry, environmental protection and so on. In general, the paper industry has the characteristics of intensive technology capital, significant economies of scale, high resource dependence and consumption, and relatively dispersed industry concentration.

I. Wood

According to plant classification, wood can be divided into two categories, gymnosperms commonly referred to as cork or coniferous trees. Angiosperms are called hardwoods or broad-leaved trees, or deciduous trees or evergreen trees.

Coniferous wood has tight tissue structure, high lignin content, and most of it is distributed in the cell wall, and it is difficult to cook. The structure of broadleaf wood is more compact than that of coniferous wood, and it is difficult to penetrate, but compared with coniferous wood, the content of lignin is lower, and the cell wall is less, so it is easier to cook than coniferous wood.

The same is coniferous wood or broadleaf wood, due to different species, its organizational structure, physical properties and chemical composition are different, cooking conditions and pulp properties are also different. Even if it is the same tree, due to sapwood, heartwood ratio, late wood rate and different species of origin, it is inevitable to differ. Hardwoods typically contain more cellulose and less lignin than softwood, with higher extract content.

Common softwood pulp types are: Scandinavian pine, Radiata pine, Southern pine, red ceder, lodgepole pine, cedar (ceder), hemlock (hemlock) white pine is white spruce (white spruce), black spruce (black spruce), douglas pine (also known as douglas fir), larch (larch), balsam fir (balsam fir), Alpine fir (Alpine fir) and so on.

Radiata Pine and Southern pine are commonly used for pulping in American pulp, Chilean pulp and New Zealand pulp, Scandinavian pine is commonly used for pulping in Northern European countries, and several other species are common in Canada. In North American tree species, the extract content of absolute dry wood is mostly less than 1%, and the extract content of southern pine is slightly higher.

Commonly used broad-leaved wood pulp species are: eucalyptus, acacia wood, poplar, birch, maple and so on.

Eucalyptus (Eucalyptus) itself has many varieties, such as eucalyptus macrophylla, eucalyptus urophylla, eucalyptus macrophylla, eucalyptus blue, eucalyptus lemon, eucalyptus salix, eucalyptus fornix, eucalyptus red. Some eucalyptus (such as hole edge eucalyptus) is not suitable for papermaking, too high proportion of eucalyptus is not suitable for papermaking, generally less than 0.7 is appropriate. There are certain differences in the quality of various types of eucalyptus BEK, so it is necessary to understand what kind of eucalyptus BEK is made of. Generally, Brazil's BEK is mainly made of eucalyptus grandis, Chile and Spain are mainly made of eucalyptus bleu, and China's Guangxi Liujiang Paper Factory and paper Company produces a certain amount of commercial BEK, and the raw materials are mainly lemon eucalyptus and eucalyptus grandis. Due to the wide variety of eucalyptus, coupled with regional climate differences, the quality and price of various types of eucalyptus pulp are also different, it is generally believed that the quality of Brazilian eucalyptus is the best, and the worst in Southeast Asia, but it also depends on the specific use.

acacia (also known as acacia, sweet acacia or golden acacia), as a specially developed pulping wood, has no less rapid growth and high yield effect than tropical eucalyptus, especially suitable for artificial cultivation in 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 Lovesickness has been on a par with Brazilian eucalyptus.

Broad-leaved wood of Aspen, Birch and Maple species. Hard miscella, that is, mixed hardwood miscella, that is, natural broadleaf forest, of which there are many species, it is difficult to list one by one, because most pulp mills are first cut down hard miscella forest after planting plantation, hard miscella forest will not recover by itself, so a future trend is that the number of natural hard miscella forest will gradually reduce, at the same time, because the logging of hard miscella forest will seriously damage the natural ecology, In the long term, the supply of hardwood pulp will gradually decrease and eventually disappear, as most of the pulp mills that cut hardwood pulp have a poor reputation and are under increasing environmental pressure.

Two, pulp

Pulp is a fibrous substance made from plant fibers by different processing methods. It can be divided into many subdivisions according to the source of raw materials, processing methods, processing degrees, etc., and can be widely used in papermaking, artificial fibers, plastics, chemical and other fields.

Pulp is mainly divided into wood pulp, waste pulp and non-wood pulp according to the source of raw materials. Wood pulp is divided into two categories, are coniferous pulp (including masson pine, larch, red pine, spruce and other species of wood pulp) and broad-leaf pulp (including birch, poplar, linwood, eucalyptus, maple and other species of wood pulp), generally coniferous pulp has stronger toughness and stretchability than broad-leaf pulp, Therefore, in the use of wood pulp is usually mixed with a certain proportion of coniferous pulp to enhance the toughness of paper; Waste pulp is the paper pulp which is sorted and screened after the waste paper is recycled, soaked with warm water, and then repulped for reuse. There are three main types of non-wood pulp: grass fiber pulp (such as straw, wheatgrass, reed, bamboo, bagasse, etc.), bast fiber pulp (such as hemp, kenaf, flax, mulberry bark, cotton stalk bark, etc.) and seed wool fiber pulp (such as cotton fiber, etc.).

Pulp according to the processing technology is divided into mechanical pulping, chemical pulping, semi-chemical pulping. Mechanical pulping refers to the method of making pulp from fiber raw materials (mainly wood) by simply using mechanical grinding, and its products are collectively referred to as mechanical pulp; Chemical pulping refers to the method of making pulp by treating raw materials with chemical agents, and its products are collectively referred to as chemical pulp; Semi-chemical pulping (also known as chemical mechanical pulping) refers to the pulping method using chemical pretreatment and mechanical grinding after treatment, and its products are collectively referred to as chemical pulp (CMP).

In addition, pulp according to the degree of processing is divided into refined pulp, bleached pulp, semi-bleached pulp and this color paste, such a classification standard is mainly the degree of bleaching of pulp, different whiteness of pulp is also used in different paper industry because of its different nature, such as bleached sulfate wood pulp can be used to manufacture advanced printing paper, painting newspaper, offset paper and writing paper. This color paste is mainly used for making medium printing paper, thin wrapping paper, translucent paper and greaseproof paper.

1. Classification of bleached coniferous pulp

There are two major categories of bleached coniferous wood sulfate pulp: Northern bleached coniferous wood sulfate pulp (NBSK) and Southern bleached coniferous wood sulfate pulp (SBSK) :

(1) Northern bleached coniferous wood sulfate pulp (NBSK) :

Scandinavia: The Scandinavian countries produce only two main conifers, pine and spruce. Generally, the total length of the fiber is 3.1-3.3mm, and the diameter is only 30-32μm, which is shorter and thinner than the domestic similar varieties such as Canada. These fibers are uniformly distributed in the pulp and have roughly the same size and similar cell walls. This NBSK does not have particularly high tensile or folding resistance, has a much lower tear than any southern coniferous pulp, but has a higher rupture resistance, and has a higher fiber number per unit weight (fiber number/gram) due to the longer fiber length and smaller diameter. Therefore, it is suitable for the manufacture of low weight coated offset paper, double-sided coated paper, single-side coated paper, gravure printing paper, pressure resistant paper and so on.

Russia: The main species of NBSK in Russia are red, white pine and larch. Red and white pine are similar to spruce and fir in Canada, with low late wood rate and thin cell wall, and can produce better synergistic effect with larch, so mixed pulping is generally adopted. The NBSK of the Russian Far East is roughly in the same category as that of Scandinavia.

Canada: Canada has a vast territory, the production of NBSK because of different materials, the fiber itself has a great inconsistency, and China imports NBSK from Canada is also the most. Canadian forests can be roughly divided into six areas, and pulp mills are generally close to forest areas.

(2) Southern bleached softwood sulfate Pulp (SBSK) :

Although there are seven major different tree species in this category, they all belong to the pine family. The four dominant species are thick-walled pine, long-leaved pine, thin-walled loblolly Pine and short-leaved pine, collectively known as Southern Pine. The first two (wet pine and longleaf pine) are mostly grown in the southeastern United States and are well suited for fluff absorbent products, silky wool (deep caustic soda treatment) products, infiltrated latex products, and chemical fiber derivatives. The end use of this type of pulp makes it more expensive than loblolly pine and shortleaf pine. Thin-walled loblolly pine has better beating performance than thick-walled pine. The remarkable property of SBSK is that its tearing (which decreases with beating) is much better than NBSK. The bleached pulp of Phoenix Paper Company and paper company in Guangxi is made of Masson pine, and the bleached pulp of Yunjinglin Paper Company in Yunnan is made of Simao pine, both of which belong to SBSK.

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.

Packaging paper refers to a class of paper used for packaging purposes, generally used for downstream household appliances, daily chemicals, food and beverage, cigarettes and other industry products packaging. The main types of wrapping paper include corrugated paper, box board paper, whiteboard paper and white cardboard. Among them, box board paper and corrugated paper are mostly used in the fields of home appliance packaging and daily chemical packaging, and white board paper and white cardboard are often used for packaging cigarettes, food, pharmaceuticals and cosmetics.

The industrial chain of wrapping paper is "pulp - paper - all kinds of paper downstream". Looking at the subdivision of the packaging paper industry, according to the production of different raw materials can be roughly divided into two categories. First, corrugated paper and box board paper, the production of raw materials are mainly straw pulp and waste paper. Corrugated paper is mainly made of natural hardwood semi-chemical pulp, cold alkali pulp or natural alkaline straw pulp or with waste pulp, which is sent to the circular screen multi-cylinder paper machine after free beating. The raw materials used for box board paper are sulfate wood pulp, waste hemp pulp, cotton stalk pulp, waste paper pulp and rice straw pulp. The second is white board paper and white cardstock. The raw materials of each layer of white board paper are mostly composed of wood pulp, grass pulp and waste pulp, while the white cardstock uses 100% wood pulp as raw material. The middle reaches are papermaking enterprises, and the downstream paper products are mostly used in the consumer goods market, of which box board paper and corrugated paper are the mainstream. The packaging paper industry is a typical resource-constrained industry, and the supply of raw materials largely affects the profitability and development of enterprises.