造纸专业英语教材.doc

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1、Lesson 1 The history of papermakingPaper derives its name from the reedy plant, papyrus. The ancient Egyptians produced the worlds first writing material by beating and pressing together thin layers of plant stem. The first authentic papermaking originated in China as early as 100 AD, utilizing a su

2、spension of bamboo or mulberry fibers. The Chinese subsequently developed papermaking into a highly skilled art. After a period of several centuries, the art of papermaking extended into the Middle East and later reached Europe, where cotton and linen rags became the main materials. Paper was first

3、made in England in 1496. by he end of the 15th century, a number of paper mills existed in Spain, Italy, Germany and France. The first paper mill in North America was established near Philadelphia in 1690.The development of the paper machine is the most important milestone of the industry. Louis Rob

4、ert, working at the paper mill owned by Ledger Didot, made his first model of the continuous paper machine in 1796 near Paris and received a French patent for his machine in 1799 at the age of 37. In 1803, a patent was issued to Fourdrinier brothers for the improved continuous paper machine designed

5、 by Bryan Donkin. At about the same time, John Dickson, a colleague and friend of Donkin, was working his cylinder machine, which was refined by 1809.In 1840, groundwood pulping method was developed in Germany. The first manufacture of pulp from wood using soda process was patented on July 1, 1854 t

6、o an England inventor named Hugh Burgess. In 1867, a Philadelphia chemist, Benjamin Tilgham, was awarded the U. S. patent for the sulfite pulping process; the first commercial sulfite pulp was produced in Sweden in 1874. C. F. Dahl is credited with the development of the kraft process was originally

7、 patented in 1854. A later patent in 1865 covered the incineration of the spent soda liquor to recover most of he alkali used in the process.These inventions and pioneering prototypes provided the basis for the modern paper industry. The twentieth century has been the rapid refinement and modificati

8、on of the early and rather crude technology, along with the development of techniques as refiner mechanical pulping, continuous cooking, continuous multistage bleaching, on-machine paper coating, twin-wire forming, and computer process control.Words and ExpressionsPaper 纸，纸张 papyrus纸莎草beating 打浆 pre

9、ssing 压榨，压合papermaking 抄纸，造纸 fiber 纤维paper machine 纸机 groundwood pulping 磨木法制浆soda process 烧碱法制浆 sulfite pulping process亚硫酸盐法制浆kraft（sulfate） process 硫酸盐法制浆 refiner mechanical pulping 盘磨机械法制浆continuous cooking 连续蒸煮 continuous multistage bleaching连续多段漂白on-machine paper coating 机内涂布 twin-wire forming

10、双网成形compute process control 计算机过程控制Lesson 2 Fibrous materials of papermakingTheoretically, pulp fiber can be extracted from almost any vascular plant found in nature. So far, wood is still the most abundant source of papermaking fibers. Besides, about 10% of the fiber used to make paper each year wo

11、rld wide is from non-wood plant, including straws (wheat, rye, rice and barley)，grasses（bamboo，esparto and papyrus)，canes and reeds (bagasse, corn stalks and kenaf), bast (flax, hemp, jute, ramie and mulberry), and seed hairs (cotton). Non vegetable fibers such as polyethylene and glass fibers are a

12、lso used. In recent years, secondary fiber utilization is increasing at a rapid pace.Botanically, woods are classified into two major groups: softwoods or conifers and hardwoods or broad-leafed-trees, either deciduous or evergreen.The vertical structure of conifers is composed almost entirely of lon

13、g, tapping cells called tracheids. The wall of a typical trachied or fiber is composed of several layers. The middle lamella with very high lignin content separates two contiguous trachieds. Each trachied has primary wall and a three-layered secondary wall with specific alignments of microfibrils. M

14、icrofibrils are bundles of cellulose molecules, and their orientation can influence the characteristics of a pulp fiber.The principal vertical structure of hardwood is composed of both relatively long, narrow cells, called libriform fibers, and much shorter, wide cells, called vessels. Hardwoods als

15、o have a vertical parenchyma system and a horizontal or ray parenchyma system.Generally, softwood has higher amount of fibers while hardwood has higher percentage of vessels. Softwood fibers are more than twice as long as hardwood fibers.Technically, wood is xylem tissue, which consists of cellulose

16、, hemicellulose, lignin and extractives, hence a lignocellulosic material. Sapwood is the outer part of the trunk and contains some living cells. Heartwood is found in the centre of older trees, containing only dead cells, and is generally drier than sapwood. Each annual growth ring contains earlywo

17、od, which is characterized by large cells with thin cell walls, and latewood, which is characterized by small cells and thick walls.Some of the important pulping variables of wood and wood chips are: moisture content, specific gravity, tension and compression strength, bark content, chemical composi

18、tion, wood species, chip dimensions, and length of storage.Words and expressionsstraws 稻麦草 wheat 小麦rye 黑麦 rice 稻谷barly 大麦 grasses 草类bamboo 竹子 esparto 西班牙草canes and reeds 蔗苇类 bagasse 蔗渣corn stalks 玉米茎秆 kenaf 洋麻bast 韧皮类 flax 亚麻hemp 大麻 jute黄麻ramie 苎麻 mulberry 桑树seed hairs 种毛类 polyethylene 聚乙烯glass fibe

19、rs 玻璃纤维 softwood 软木，针叶木conifer 针叶树，针叶木 hardwood 硬木，阔叶木broad-leafed-tree 阔叶树 tracheid 管胞middle lammela 胞间层 lignin 木素primary wall 初生壁 secondary wall 次生壁microfibril 微纤丝 cellulose 纤维素libriform fiber 韧皮纤维 vessels 导管parenchyma system 薄壁组织系统 hemicellulose 半纤维素extractive 抽提物 sapwood 边材heartwood 心材 earlywood

20、 早材latewood 晚材 moisture content 水分含量specific gravity 比重 tension and compression strength 抗张与抗压强度Reading material: Chemical composition of raw materialsChemical composition of the candidate plant gives an idea of how feasible the plant is as raw material for papermaking. The fibrous constituent is th

21、e most important part of the plant. Since plant fibres consist of cell walls, the composition and amount of fibres is reflected in the properties of cell walls. Cellulose is the principal component in cell walls and in fibres. The none-cellulose components of the cell was include hemicelluloses, pec

22、tins, lignin and proteins, and in the epidermal cells also certain minerals. The amount and composition of the cell wall compounds differ among plant species and even among plant parts, and they affect the pulping properties of the plant material. Some of non-woody fibre plants contain more pentosan

23、s (over 20%), holocellulose (over 70%) and less lignin (about 15%) compared with hardwoods. They have also higher hot water solubility, which is apparent from the easy accessibility of cooking liquors. The low lignin content in grasses and annuals lowers the requirement of chemicals for cooking and

24、bleaching. Except for the fibrous material, plants also consist of other cellular elements, including mineral compounds. While the inorganic compounds are essential for plant growth and development, they are undesirable in pulping and papermaking.CelluloseCellulose is the principal component of plan

25、t fibres used in pulping. It forms the basic structural material of cell walls in all higher terrestrial plants being largely responsible for the strength of the plant cells. Cellulose always has the same primary structure, it is -1,4 linked polymer of D-glucans. It occurs in the form of long, linea

26、r, ribbon-like chains, which are aggregated into structural fibrils. Each fibril contains from 30 to several hundred polymeric chains that run parallel with the laterally exposed hydroxyl groups. The hydroxyl groups take part in hydrogen bonding, with linkages both within the polymeric molecules and

27、 between them. This arrangement of the hydroxyl groups in cellulose makes them relatively unavailable to solvents, such as water, and gives cellulose its unusual resistance to chemical attack, as well as its high tensile strength.The first layer of cellulose are formed in the primary cell walls duri

28、ng the extension stage of the cell, but most cellulose is deposited in the secondary walls. The proportion of cellulose in primary cell walls is 20 to 30% of DM and in secondary cell walls 45 to 90%. The cellulose content of a plant depends on the cell wall content, which can vary between plant spec

29、ies and varieties. The age of the plant and plant part also affect the cellulose content. Annual plants generally have about the same cellulose content as woody species, but their higher content of hemicellulose increases the level of pulp yield more than the expected level on the basis of cellulose

30、 content alone. The cellulose and alpha-cellulose contents can be correlated with the yields of unbleached and bleached pulps, respectively.HemicelluloseHemicellulose consist of a heterogeneous group of branched polysaccharides. The specific constitution of the hemicellulose polymer depends on the p

31、articular plant species and on the tissue. Glucose, xylose and mannose often predominate in the structure of the hemicelluloses, and are generally termed glucans, xylans, xyloglucans and mannans. Xylans are the most abundant non-cellulose polysaccharides in the majority of angiosperms, where they ac

32、count for 20 to 30% of the dry weight of woody tissues. They are mainly secondary cell wall components, but in monocotyledons they are found also in the primary cell walls, representing about 20% of both the primary and secondary walls. In dicots they amount to 20% of the secondary walls, but to onl

33、y 5% of the primary cell walls. Xlans are also different in monocots and in dicots. In gymnosperms, where galactoglucomannans and glucomannans represent the major hemicelluloses, xylans are less abundant (8%). The hemicelluloses in secondary cell walls are associated with the aromatic polymer, ligni

34、n.PectinsPectins, i.e. pectic polysaccharides, are the polymers of the middle lamella and primary cell wall of dicotyledons, where they may constitute up to 50% of the cell wall. In monocotyledons, the proportion of pectic polysaccharides in normally less than this and in secondary walls the proport

35、ion of hemicellulose polysaccharides greatly exceeds the amounts of pectic polysaccharides. The pectic substances are characterised by their high content of D-galacturonic acid and methylgalacturonic acid residues. Pectins are more important in growing than in non-growing cell walls, and thus they a

36、re not a significant constituent in commercial fibres except in flax fibre, where pectins are found in lamellae between the fibres and account for 1.8% of dry weight.LigninLignin is the most abundant organic substance in plant cell walls after polysaccharides. Lignins are highly branched phenolic po

37、lymers and constitute an integral cell wall component of all vascular plants. The structure and biosynthesis of lignin has been widely studied. The reason for the great interest is the abundance of lignin in nature, as well as its economical importance for mankind. For papermaking, lignin is chemica

38、lly dissolved because of the separation of the fibres in the raw material. In cattle feeds, lignin markedly lowers the digestibility.Lignins are traditionally considered to be polymers, which are formed from monolignols: p-coumaryl alcohol, coniferyl alcohol, and sinapyl alcohol. Each of the precurs

39、ors may form several types of bonds with other precursors in constructing the lignin polymer. A great variation in lignin structure and amount exists among the major plant groups and among species. Great variation in lignin structure and amount exists also among cell types of different age within a

40、single plant and even between different parts of the wall of a single cell. Gymnosperm lignin contains guaiacyl units (G-units), which are polymerized from coniferyl alcohol, and a small proportion of p-hydroxylphenyl units (H-units) formed from p-coumaryl alcohol. Angiosperm lignins are formed from

41、 both syringyl units (S-units), polymerized from sinapyl alcohol, and G-units with a small proportion of H-units. Syringyl lignin increases in proportion relative to guaiacyl and p-hydroxylphenyl lignin during maturation of some grasses. In grass species the total lignin content varies from 15 to 26

42、%. For reed canary grass Burrit et all found only 1.2%. in grasses and legumes lignins are predominantly formed from coniferyl and sinapyl alcohols with only small amounts of p-coumaryl alcohol.Lignins are considered to contribute to the compressive strength of plant tissue and water impermeability

43、of the cell wall. Lignins aid cells in resistance to microbial attack, but they do not influence the tensile properties of the cell wall. Monolignols can also form bonds with other cell wall polymers in addition to lignin. Cross-linking with polysaccharides and proteins usually results in a very com

44、plex three-dimensional network. This close connection between phenolic polymers and plant cell wall carbohydrates makes the effective separation and utilization of the fibres more complicated. In woody plants relatively few covalent bonds exist between carbohydrates and lignin compared with those in

45、 forage legumes and grasses where the lignin component is also covalently linked to phenolic acids, notably 4-hydroxycinnamic acids, p-coumaric acid and ferulic acid. Lignin and hemicelluloses fill the spaces between the cellulose chains in the cell wall and between the cells themselves. This combin

46、ed structure gives the plant cell wall and the bulk tissue itself structural strength, and improves stiffness and toughness properties.MineralsThere are 19 minerals that are essential or useful for plant growth and development. The macro nutrients, such as N, P, S, K(Potassium), Mg and Ca are integr

47、al to organic substances such as proteins and nucleic acids and maintain osmotic pressure. Their concentrations in plants vary from 0.1 to 1.5% of DM. The micro nutrients, such as Fe, Mn, Zn, Cu, B, Mo (molybdenum), Cl, and Ni, contribute mainly to enzyme production or activation and their concentrations in plants are low. Silicon (Si) is essential only i