pulp n paper

• CLAY TABLETS

  Cuneiform characters were imprinted on a wet clay tablet with a stylus often made of reed (reed pen)
• PAPYRUS PAPER

  Papyrus was developed in Egypt as early as 3,000 BCE. It was made by slicing the papyrus plant lengthwise, and then laying the strips side-by-side. A second layer of strips was placed on top, perpendicular to the first layer. The two layers were then pounded together into a laminate
• PARCHMENT PAPER


  Parchment, named for the Greek city of Pergamum, was invented in the second century BCE. Parchment use was widespread in Europe for centuries, and the United Kingdom continued to use parchment to record new laws into the twenty-first century. The skin of the sheep or cow was scraped, stretched, and lime rubbed into the skin to stabilize it as it dried. The skin would then be cut into smaller pieces for documents
• PALM LEAVES


  In south-east Asia, palm leaves were used as a writing surface as long ago as the fifth century BCE. The leaves were cut into a long, rectangular shape. A sharp tool was used to scratch text onto the leaf, and rubbing soot into the marks revealed the writing. Books were made from palm leaves by cutting two holes in each leaf and holding them together with either metal prongs or twine. Lacquered and elaborately painted palm leaves were made into covers to protect the book contents
• TAPA


  Tapa, used widely in tropical civilizations, is a pre-paper cloth like material. Tapa is made by beating, but not breaking down, the bark of the mulberry tree into thin sheets. A 2-inch strip of bark can be beaten into a 10 inch sheet. The bark of other trees such as the fig and breadfruit can also be used to make tapa cloth. Tapa is used for many purposes beyond writing, including clothing, bedding, and other household purposes. Tapa degrades easily in its native environment and only fragments remain from its earliest use
• PULP MAKING PROCESS

  Pulp and paper are made from cellulosic fibers (i.e., fibers from trees) and other plant materials, although some synthetic materials may be used to impart special qualities to the finished product. Most paper is made from wood fibers, but rags, flax, cotton linters, and bagasse (sugar cane residues) are also used in some papers
• WOOD


  The principal strengthening and nutrient-conducting tissue of trees and other plants and one of the most abundant and versatile natural materials
• WOOD PARTS

  • CELLULOSE
  • LIGNIN
  • HEMICELLULOSE
  • EXTRACTIVES
• CELLULOSE


  The fibers of primary interest in papermaking, comprises about 50 percent of wood by ovendry weight
• LIGNIN


  Cements the wood fibers together, is a complex organic chemical the structure and properties of which are not fully understood
• HEMICELLULOSE


  A group of heterogeneous polysaccharides representing around 30% of wood where the dominating types are xylans, glucomannans and xyloglucans
• HARDWOOD


  Generally have shorter fibers and therefore produce a weaker paper, but one that is smoother, more opaque, and better suited for printing
• PULP AND PAPER MILL

  1. Raw material preparation (e.g., debarking and chipping)

  2. Mechanical and/or chemical separation of the wood fibers [i.e., grinding, refining, or digestion (cooking)] to dissolve the lignin and extractives

  3. Removal of coloring agents (primarily residual lignin) by bleaching
• Pulp grades

  • Chemical pulps: sulfite pulp, Kraft sulfate pulp, Dissolving pulp

  Semichemical pulps: Cold-caustic process, Neutral sulfite process
• Mechanical pulps


  • Stone groundwood, Refiner mechanical (RMP), Thermomechanical (TMP)
• Raw material preparation: Sustainably managed forests, Raw material to sawmills and paper mills
• FIBER SEPARATION (KRAFT CHEMICAL PULPING)


  Wood received at a pulp mill may be in several different forms

  Chips are fed into a large pressure cooker (digester), into which is added the appropriate chemicals (NaOH, Na2S, Na2SO4, Na2CO3) - white liquor

  After digestion, the cooked pulp (brown stock) is discharged into a pressure vessel (blow tank) where the steam and volatile materials are siphoned off

  The cooking liquor, that by this time has turned dark brown from the dissolved lignin (black liquor), is returned to the chemical recovery cycle
• FIBER SEPARATION (KRAFT CHEMICAL PULPING)


  Logs are cut to convenient lengths and debarked, then conveyed to the chippers, which are large rotating disks holding four or more heavy knives. These reduce the wood to chips of preselected size

  The chips are screened on either rotating or vibrating screens to separate the oversize chips, the desired product, and the sawdust. The oversize chips and slivers are sent to rechippers to reduce them to the proper size
• After digestion, the cooked pulp (brown stock) is discharged into a pressure vessel (blow tank) where the steam and volatile materials are siphoned off
• The cooking liquor, that by this time has turned dark brown from the dissolved lignin (black liquor), is returned to the chemical recovery cycle
• FIBER SEPARATION (KRAFT CHEMICAL PULPING)


  • Logs are cut to convenient lengths and debarked
  • Logs are conveyed to chippers which reduce the wood to chips of preselected size
  • Chips are screened to separate oversize chips, desired product, and sawdust
  • Oversize chips and slivers are sent to rechippers to reduce them to the proper size
• Bleaching agents

  • chlorine gas
  • chlorine dioxide
  • sodium hypochlorite
  • hydrogen peroxide
  • oxygen
• Between bleaching treatments, a strong alkali (usually sodium hydroxide) is used to extract the dissolved lignin from the surface of the fibers
• The bleaching agents and the sequence in which they are used depend on a number of factors, such as the relative cost of the bleaching chemicals, type and condition of the pulp, desired brightness of the paper to be produced, and sometimes in response to environmental guidelines and regulations
• After bleaching, the pulp is washed and rethickened in preparation for making it into coarse sheets dry enough to fold into a bundle, store, and ship-these are called laps
• The pulp may also be used directly for making paper
• CHEMICAL PULPING


  • Involves treating wood chips with chemicals to remove the lignin and hemicellulose, thus separating and cleaning the fibers
• KRAFT (SULFATE) PULPING


  • Pulping involves treating wood chips and sawdust with a sodium sulfide and sodium hydroxide solution
  • Bleached softwood kraft pulps are often mixed with mechanical pulps to add strength to newsprint and printing papers
  • Bleached hardwood kraft pulps are added to bleached softwood pulp to improve printability for specialty paper products like magazine stock and coated papers
• SULFITE PULPING


  • Lignin can be dissolved by sulfonation with an aqueous solution of sulfur dioxide and calcium, sodium, magnesium, or ammonium bisulfite
  • Four basic sulfite pulping processes: acid sulfite, bisulfite, neutral sulfite, and alkaline sulfite
  • Sulfite pulping processes are suitable only for species with low extractive contents
  • Sulfite pulp is a light color and can sometimes be used without bleaching if high brightness is not required
  • Unbleached sulfite pulp is often blended with groundwood and other high-yield mechanical pulps for strengthening newspaper stock
• MECHANICAL PULPING


  • Generally used with softwoods because of the added strength imparted by the long fiber length of softwood species
  • Some hardwoods require chemical pretreatment (chemical mechanical pulping) to produce a suitable groundwood pulp
  • Fibers separated mechanically are substantially damaged in the process and therefore make weaker paper or paperboard
  • Used principally to manufacture newsprint, printing papers, towelling, tissue, and coated specialty papers that do not require high-strength
• WET PROCESS: PULP STOCK PREPARATION

  • Beating and refining of the pulp increase surface area of fibers so that better contact between fibers will result in higher mechanical properties of the paper
  • Other materials added during the refining process: fillers for smoother surface, more brilliant whiteness, improved smoothness and printability, and improved opacity; sizes to improve resistance of penetration by liquid; dyes for color
• TWO TYPES OF CONVENTIONAL WET PROCESS PAPER MACHINES

  • FOURDRINIER MACHINE: Pulp flows on the screen, water is drained away, thin sheet of fiber mat is formed; moisture content reduced using suction units and drum type dryers
  • CYLINDER MACHINE: employed for the manufacture of heavy paper, cardboard and nonuniform paper
• CALENDERING


  • Process to enhance both physical and mechanical properties of paper as it passes through a specially designed series of drum type rolls as a result of friction
  • Produces coated (matte, semi matte and glossy) or uncoated paper