Lesson 1 The history of papermaking
Paper derives its name from the reedy plant, papyrus. The ancient Egyptians produced the world’s 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 suspension of bamboo or mulberry fibers. The Chine subquently developed papermaking into a highly skilled art. After a period of veral 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 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 Robert, 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 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.
qq邮箱怎么改密码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 to 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 patented in 1854. A later patent in 1865 covered the incineration of the spent soda liquor to recover most of he alkali ud in the process.
The inventions and pioneering prototypes provided the basis for the modern paper industry. The twentieth century has been the rapid refinement and modification 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 Expressions
Paper 纸，纸张papyrus纸莎草
川剧变脸的原理揭秘
beating 打浆pressing 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 双网成形蓬莱仙洞在哪里
compute process control 计算机过程控制
Lesson 2 Fibrous materials of papermaking
Theoretically, 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 ud to make paper each year world wide is from non-wood plant, including straws (wheat, rye, rice and barley)，grass（bamboo，esparto and papyrus)，canes and reeds (bagas, corn stalks and kenaf), bast (flax, hemp, jute, ramie and
mulberry), and ed hairs (cotton). Non vegetable fibers such as polyethylene and glass fibers are also ud. In recent years, condary 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 compod almost entirely of long, tapping cells called tracheids. The wall of a typical trachied or fiber is compod of veral layers. The middle lamella with very high lignin content parates two contiguous trachieds. Each trachied has primary wall and a three-layered condary wall with specific alignments of microfibrils. Microfibrils are bundles of cellulo molecules, and their orientation can influence the characteristics of a pulp fiber.
The principal vertical structure of hardwood is compod of both relatively long, narrow cells, called libriform fibers, and much shorter, wide cells, called vesls. Hardwoods also 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 vesls. Softwood fibers are more than twice as long as hardwood fibers.
Technically, wood is xylem tissue, which consists of cellulo, hemicellulo, 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 earlywood, 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 composition, wood species, chip dimensions, and length of storage.
Words and expressions
straws 稻麦草wheat 小麦
rye 黑麦rice 稻谷
barly 大麦grass 草类
bamboo 竹子esparto 西班牙草创投圈
canes and reeds 蔗苇类bagas 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
ed hairs 种毛类polyethylene 聚乙烯
glass fibers 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condary wall 次生壁
microfibril 微纤丝cellulo 纤维素
libriform fiber 韧皮纤维vesls 导管
parenchyma system 薄壁组织系统hemicellulo 半纤维素
extractive 抽提物sapwood 边材
heartwood 心材earlywood 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 materials
Chemical composition of the candidate plant gives an idea of how feasible the plant is as raw material for papermaking. The fibrous constituent is the 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. Cellulo is the principal component in cell walls and in fibres. The none-cellulo components of the cell was include hemicellulos, pectins, lignin and proteins, and in the epidermal cells also certain minerals. The amount and composition of the cell wall compounds differ among pla
nt species and even among plant parts, and they affect the pulping properties of the plant material. Some of non-woody fibre plants contain more pentosans (over 20%), holocellulo (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 grass and annuals lowers the requirement of chemicals for cooking and bleaching. Except for the fibrous material, plants also consist of other cellular elements, including mineral compounds. While the inorganic compounds are esntial for plant growth and development, they are undesirable in pulping and papermaking.
Cellulo
Cellulo is the principal component of plant fibres ud 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. Cellulo always has the same primary structure, it is α-1,4 linked polymer of D-glucans. It occurs in the form of long, linear, ribbon-like chains, which are aggregated into structural fibrils. Each fibril contains from 30 to veral hundred polymeric chains that run parallel with the laterally expod hydroxyl groups. The hydroxyl groups take part in hydrogen bonding, with linkages both within the polymeric molecules and between them. This arrangement of the hydroxyl groups in cellul
o makes them relatively unavailable to solvents, such as water, and gives cellulo its unusual resistance to chemical attack, as well as its high tensile strength.
The first layer of cellulo are formed in the primary cell walls during the extension stage of the cell, but most cellulo is deposited in the condary walls. The proportion of cellulo in primary cell walls is 20 to 30% of DM and in condary cell walls 45 to 90%. The cellulo content of a plant depends on the cell wall content, which can vary between plant species and varieties. The age of the plant and plant part also affect the cellulo content. Annual plants generally have about the same cellulo content as woody species, but their higher content of hemicellulo increas the level of pulp yield more than the expected level on the basis of cellulo content alone. The cellulo and alpha-cellulo contents can be correlated with the yields of unbleached and bleached pulps, respectively.
Hemicellulo
Hemicellulo consist of a heterogeneous group of branched polysaccharides. The specific constitution of the hemicellulo polymer depends on the particular plant species and on the tissue. Gluco, xylo and manno often predominate in the structure of the hemicellulos, and are gen
erally termed glucans, xylans, xyloglucans and mannans. Xylans are the most abundant non-cellulo polysaccharides in the majority of angiosperms, where they account for 20 to 30% of the dry weight of woody tissues. They are mainly condary cell wall components, but in monocotyledons they are found also in the primary cell walls, reprenting about 20% of both the primary and condary walls. In dicots they amount to 20% of the condary walls, but to only 5% of the primary cell walls. Xlans are also different in monocots and in dicots. In gymnosperms, where galactoglucomannans and glucomannans reprent the major hemicellulos, xylans are less abundant (8%). The hemicellulos in condary cell walls are associated with the aromatic polymer, lignin.
Pectins
动态说说Pectins, 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 condary walls the proportion of hemicellulo polysaccharides greatly exceeds the amounts of pectic polysaccharides. The pectic substances are characterid 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 ar
e 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.
公司缴纳社保流程Lignin
Lignin is the most abundant organic substance in plant cell walls after polysaccharides. Lignins are highly branched phenolic polymers 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 chemically dissolved becau of the paration 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 precursors may form veral 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 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 both syringyl units (S-units), polymerized from sinapyl alcohol, and G-units with a small proportion of H-units. Syringyl lignin increas in proportion relative to guaiacyl and p-hydroxylphenyl lignin during maturation of some grass. In grass species the total lignin content varies from 15 to 26%. For reed canary grass Burrit et all found only 1.2%. in grass 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 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 complex three-dimensional network. This clo connection between phenolic polymers and plant cell wall carbohydrates makes the effective paration and utilization of the fibres more complicated. In woody plants relatively few covalent bonds exist between carbohydrates and lignin compared with tho in forage legumes and grass
where the lignin component is also covalently linked to phenolic acids, notably 4-hydroxycinnamic acids, p-coumaric acid and ferulic acid. Lignin and hemicellulos fill the spaces between the cellulo chains in the cell wall and between the cells themlves. This combined structure gives the plant cell wall and the bulk tissue itlf structural strength, and improves stiffness and toughness properties.
Minerals
There are 19 minerals that are esntial or uful for plant growth and development. The macro nutrients, such as N, P, S, K(Potassium), Mg and Ca are integral 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 esntial only in some plant species. The
amount of silicon uptakes by plants is described by silica (SiO2) concentration. The highest silica concentrations (10-5%) are found in Equitum ()-species and in grass plants growing in water, such as rice. Other monocotyledons, including cereals, forage grass and sugarcane contain SiO2 at 1-3
% of DM. Si in epidermis cells is assumed to protect the plant against herbivores and in xylem walls, to strengthen the plant as lignin. The concentration of a particular mineral substance in a plant varies depending on plant age or a stage of development, plant species and the concentration of other minerals as well as the plant part.
In the pulping process the minerals of the raw materials are considered to be impurities and should be removed during pulping or bleaching. The same elements are found both in non-woody and in woody species, but the concentrations are lower in woody plants. Si is the most deleterious element in the raw material for pulping, becau it complicates the recovery of chemicals and energy in pulp mills. Si wears out the installations of paper factories and can lower the paper quality. Other harmful elements for the pulping process include K, Cl, Al, Fe, Mn, Mg, Na, S, Ca and N. Choosing a suitable plant species as the raw material for pulping can minimi the amount of undesirable minerals in process. Moreover, using only the plant parts that contain low amounts of minerals such as Si reprents an improvement.
Reading material:biosynthesis of the lignin polymer：
Lignification, in analogy with other polymerization process, is the means by which lignin macromol
ecules grow. Thus the primary reactions of concern are tho in which the macromolecule is extended by the coupling of a new monomer to the growing polymer. Branching reactions are also important. They can occur when two quential reactions are possible at the growing end, i.e. the phenolic end, of the polymer.
The primary monomers for lignification are the three p-hydroxycinnamyl alcohols: p-coumaryl alcohol, coniferyl alcohol, and sinapyl alcohol. The monolignols differ in their degree of methoxylation. In the lignin polymer, the monolignols produce p-hydroxyphenyl, guaiacyl, and syringyl units. Due to the capability of electron-delocalized radicals to couple at various sites, a variety of structural units are found in the resulting polymer. Erdtman was the first to recognize that major lignin structural features were consistent with a process of radical coupling of phenols. Simple chemical dehydrodimerization reactions of coniferyl alcohol, using either the peroxida-H2O2 system that is implicated in vivo, or other chemical single-electron oxidants including various Fe, Mn, Cu, and Ag salts, produce three dehydrodimeric coupling products incomparable amounts. Most reviews and texts also include other coupling modes for the mono lignols, but the are in fact not obrved; 5–5- and 4–O–5- coupled structures in lignins do not ari from monolignol-monolignol coupling reactions. The products involve at least one of the monolignols coupling at its favored β-pos
ition. Evidence for further coupling reactions between the monolignol and the initially formed dimmer became available from well-characterized oligomers. The notion that lignification was a process involving “uncontrolled” radical coupling reactions was therefore born, although Erdtman suspected that lignification might be found to be more highly controlled.
仙草冰Synthetic lignins, so-called dehydrogenation polymers(DHPs), can be prepared in vitro from monolignols oxidized by peroxida-H2O2. Such synthetic lignins are valuable fore xploring and understanding coupling and post-coupling reactions, and as models for spectroscopic and reactivity studies. However, they differ from native or isolated lignins; in particular they have a lower β–O–4-ether content. The primary reason is that dehydrodimerization reactions are over-reprented. Dehydrodimerization of coniferyl alcohol yields three primary products, where as sinapyl alcohol yields two. Coupling at the β-position is favored for coniferyl and even more strongly for sinapyl alcohol; the coupling products always result from coupling of atleast one of the monolignols at its β-position. In coupling reactions, including in a biomimetic
peroxida-H2O2 system, the β-ether dimmer is typically produced in less than one third of the yield in the coniferyl alcohol ca, and at only about the 9% level for sinapyl alcohol. Monolignol radicals prefer entially couple with like monolignol radicals (when available) rather than cross-couple with dim
mers or higher oligomers. Dehydrodimerization reactions are therefore over-reprented in synthetic lignins even when attempts are made to introduce the monolignol slowly. Conquently, the β-ether frequency is low, considerably lower than in typical lignins. Limiting the diffusion rates (and there fore monolignol radical concentrations) to favor cross-coupling reactions reveals that β-ethers are strongly favored in cross coupling reactions.
宋代古币价格Lignin monomers do not have any optical activity–unlike the protein and polysaccharide monomers, they posss no chiral centers. Optical centers are however created in each coupling reaction involving the sidechain β-position, two per event. The result is that the number of isomers of any “randomly” formed lignin structure increas with its degree of polymerization, quickly becoming astronomical. Thus a β-ether dimer, forexample, has 4 optical isomers and half that number (i.e.2 of “real” chemically distinct isomers. A β-ether trimer has 8 chemically distinct isomers, that can be resolved in high-resolution proton NMR spectra. A β-ether tetramer has 32 isomers. And so it progress geometrically. A pure random β-ether 110-mer was noted to have about the same number of isomers as there are atoms in our galaxy.
Lesson 3 Pulp and paper properties and testing
A large number of pulp testing methods are in common to characterize pulps with respect to quality, processability, and suitability for various end us. The most “fundamental” measurements provide the means to predict behavior while “functional” tests are designed to measure specific properties.
The kappa number test is ud in mill control work to indicate the degree of delignification occurring during cooking and the chemical requirement for bleaching. A good indication of cellulo degree of polymerization (DP) can be obtained by measuring viscosity of a cellulo solution of known concentration using cupriathylene diamine hydroxide (CED) as a solvent.
Pulp drainability is an important property with respect to pulp processing and papermaking. Measurement of pulp drainage are known as freeness, slowness, wetness, or drain time according to the instrument or method ud. Freeness and slowness scales have an inver relationship. The Canadian Standard Freeness (CSF) and the Schopper-Riegler (°SR) slowness tester are two principal drainage testing devices ud respectively for the two properties in North America and Europe. To simulate the type of drainage with microturbulence and oriented shear, the Britt dynamic drainage jar (DDJ) was developed for studying stock drainage phenomenon under conditions more cloly approaching tho of the paper machine.
The wide diversity of paper grades with different functional properties necessities a multiplicity of paper test methods. Some basic properties are important for all grades such as basis weight or grammage and caliper. Others are specifically developed to asss the performance attributes of speciality products and their application.
Since paper is a hygroscopic material and will ek equilibrium moisture with the surrounding air, paper samples must be conditioned in a standardized environment to obtain reproducible results. Due to the “two-sidedness”, the wire and top-side’s properties must be taken into account for certain end us. Paper has a definite “grain” caud by the greater orientation of fibers in the machine direction and by the stress/strain impod during pressing and drying. The directionality of paper must be also taken into account in measuring physical properties. The physical tests on paper can be conveniently divided into four groups: mechanical and strength properties( tensile, burst, tear, folding strength, stiffness, softness, etc); surface properties (roughness, pick strength); optical properties (brightness, opacity, gloss, color); and permeability to fluids (sizing degree,
