Definition The word "paper" is etymologically derived from papyros, Ancient Greek for the Cyperus papyrus plant. Noun: Material manufactured in thin sheets from the pulp of wood or other fibrous substances, used for writing, drawing, or printing on, or as wrapping material. A thin material mainly used for writing upon, printing upon, drawing or for packaging. It is produced by pressing together moist fibers, typically cellulose pulp derived from wood, rags, or grasses, and drying them into flexible sheets.
History of Paper Paper was invented by the Chinese by 105 AD during the Han Dynasty and spread slowly to the west via Samarkand and Baghdad. Papyrus is a thick, paper-like material produced from the pith of the Cyperus papyrus plant which was used in ancient Egypt and other Mediterranean cultures for writing long before the development of paper in China.
TREES USEDFOR PAPER-MAKING
HARDWOOD OAK TREE MAPLES TREE
SOFTWOOD PINE TREE SPRUCE TREE
PROCESSES Wood Preparation - Debarking - Chipping + Mechanical Pulp + Chemical Pulp - Pulp Digester - Blow Tank - Screening and Cleaning of Wood Pulp - Bleaching Stock Preparation - Preparation of the furnish - Beating and Refining Paper-Making Process -Fourdrinier Machine
Generally done with a friction-type machine called a drum barker.
The stripped bark is then used for fuel or as soil enrichment.
Bark is stripped from the logs by knife, drum, abrasion, or hydraulic barker.
CHIPPING Major objective is to liberate the fibers of the wood. Chip size is not uniform and screens are necessary to separate the oversize chips.
MECHANICAL PULP Mechanical pulp yields over 90% of the wood as fiber is produced by forcing debarked logs, about two meters long, and hot water between enormous rotating steel discs with teeth that literally tear the wood apart. Trees contain up to 30% lignin, a material which is sensitive to light and degrades, and turns brown in sunlight, which explains why papers made from mechanical pulp will discolor. The special advantages of mechanical pulp are that it makes the paper opaque and bulky.
CHEMICAL PULP Chips from the storage bins are fed into a digester to which chemicals have been added. The woodchips are then 'cooked' to remove lignin. These processes’ aim is to dissolve the lignin so that the wood will be completely reduced to fibers.
PULP DIGESTER Huge pressurized vessels where wood chips are cooked. By the process of pressure cooking, it will separate the wood fibers from unwanted ingredients, pricipallylignin
BLOW TANK From the digester, the fibre goes into a blow tank, where a rapid change in pressure causes the wood to separate into individual fibres. A large cylindrical vessel which functions as intermediate storage of the cooked pulp, from which the pulp is now called “brown stock” is discharged in a even flow of washing process.
BLEACHING The purpose of bleaching operations is to impart the desired final physical and chemical properties to the pulp, showing its whiteness or brightness. Bleaching removes lignin and is necessary for paper products requiring whiteness, brightness, softness, and printability.
SCREENING AND CLEANING It is done to remove oversized debris from the pulp to allow the latter states of screening, cleaning and improving to work efficiently. Likewise, an undersize or sawdust fraction is also removed which is enriched in bark fragments. The pulp is also washed thoroughly to remove chemicals and dissolved lignin. The pulp, now a brown-coloured combination of individual wood fibres and water, is then stored to await bleaching.
STOCK PREPARATION Includes all intermediate operations between preparation of the pulp and fabrication of the paper.
PREPARATION OF THE FURNISH Furnish is prepared to give desired characteristics to the finished paper. Furnish – water slurry of fiber and chemicals which ultimately goes to the paper machine for fabrication into paper.
BEATING AND REFINING Beating and refining is necessary for strength development. Refining increases the degree of interfiber bonding in the paper sheet.
FOURDRINIER PAPER MACHINE To receive a mixture of the prepared pulp which is 99% water and 1% fibre, and to intermesh the fibres. Then to remove the water stage by stage, that results to a dry, compact, solid, continuous web.
HEADBOX Ensures that the stuff (slurry) flows on to the wire evenly and in a controlled quantity, and at the same time keeps the fibres and water uniformly mixed.
FOURDRINIER WIRE Forms an endless belt having welded and almost invisible joint; soldered or sewn seams tend to mark the paper.
DANDY ROLL An open metal cylinder covered with a wire mesh and have journals at each end which run on bearings fixed to the frame of the forming table. It is supported so that it rests lightly on the web, which it compresses while itself being driven by the web. It is located above the suction boxes.
WET PRESSES Its function is to remove more water and to consolidate the sheet according to the ultimate bulk required. After the press the slurry is now 1/3 fibre and 2/3 water, water is not completely removed from the mixture because the remaining water must be removed by heat at the dry end so that the flatness of the final paper will be ensured.
Dry End When the paper sheet enters the paper machine Dryer Section, it is about 50% water. It must be dried to less than 10% water for a finished product.
Calendering Process of smoothing and compressing paper during production by passing a continuous sheet through a number of pairs of heated rolls.
REELING Reeling operations generally involve a driven reel drum, and a winding reel, or reel spool, which is driven by engagement with the paper sheet passing in contact with the reel drum. The winding reel usually is supported on rails during the reeling operation.