Presentation on theme: "The Manufacture of Fine Papers Spring Semester 1999 TEC 4562 Ink & Paper Substrates."— Presentation transcript:
The Manufacture of Fine Papers Spring Semester 1999 TEC 4562 Ink & Paper Substrates
Introduction n“The ability of humans to supplement their speech with the written word is an indication of a high degree of civilization.” nFrom carvings on slabs of rock to paper, humans have been able to devise a form of communication that goes beyond speech.
The History of Paper nWhat civilization invented paper? –Ancient Egyptians? –Moors or Arabs –Persians? –Aztecs? –Japanese? –Chinese?
Pre-Paper Media nThe following is a list of pre-paper media developed by early humans: –Wood –Metal –Stone –Leaves –Ceramics –Bark –Papyrus –Parchment –Cloth
Egyptians and Papyrus nThe papyrus developed before 2,200 B.C. by the Egyptians was not considered true paper. nThe reason papyrus and the other materials did not qualify as paper was due to the way it is formed from a liquid suspension of individual fibers into a mat or sheet. nIt was made by slicking the plant’s stalk from end-to-end into very thin blades and then laminating them into something of a weave. nIt appears similar to cloth.
The History of Paper nAlthough papyrus is not structured like the writing or printing surfaces in use today—it became the Latin word for paper. nNearly 2,000 years later, the Chinese created the first true or practical form of paper. nThey did this by reducing raw material into individual fibers and then forming them into a mat or sheet.
The Inventor of Paper nIt is widely accepted that Ts’ai Lun, a Chinese court official, invented paper in 105 AD.
Ts’ai Lun’s Paper Ts’ai Lun’s Paper nMulberry Bark nHemp Waste nOld Rags nFish Nets
The Wove Mold Process The Wove Mold Process nThis process was devised by the Chinese –Pulp was made by beating bark (Pulp Friction), which had been washed and boiled –During the washing and boiling process, the pulp fibers were separated using smooth-edged stones and sticks.
The Laid Mold nConsisted of a flexible cover made of thin strips of bamboo held together with silk or some other similar thread nIt was placed on a wooden frame. nThe papermaker would hold the two together and dip them in a vat of water and fibers.
The Laid Mold (continued) nThe papermaker would lift the mold and let the water drain away. nThis formed the sheet. nThe layer of wet paper and light bamboo were lifted from the wooden frame and placed on a smooth stone with the wet fiber mat facing down. nThe light bamboo matting was then rolled from the paper leaving a wrinkle-free sheet to be dried. nThe mold was reusable.
Therefore, nthe Laid Mold was considered better than the Wove Mold
Historical significance of paper... nEarly use as a symbol for money to burn over graves of the dead n175 A.D. - Paper replaced silk as a medium for writing. n610 A.D. the Japanese began to make paper n750 A.D. the battle fought between Muslims and Chinese at Samarkand in Turkestan (now part of Uzbekistan at formerly part of the Soviet Union) spurred the development of paper outside China’s domain.
n875 A.D. - First known use of toilet paper. nLate 900’s - Playing cards invented. nMid 15th century - Johannes Gutenburg’s invention of movable type spurred the production for paper necessary for the production of books.
The “Paper Renaissance”- 17th to 19th Century Europe nFrance was the center of paper production... –Exported papers to all of Europe –It possessed the best papermakers and the finest equipment in the world. nFrance also experienced internal struggle and unrest during the 17th century... –This caused their papermakers to flee to England, Holland and America. –The skilled French papermakers contributed to the English and Dutch paper manufacturers, thus, transforming them into the “foremost paper manufacturers in Europe.”
America’s First Paper Mill nBuilt in 1690 by William Rittenhouse nLocation: Philadelphia nSince that time, America has become the world’s largest producer of paper and pulp products
Fibers for Papermaking nFibers are defined as “...tough threadlike substances capable of being spun or woven, whether they be natural (vegetable, mineral, animal) or man-made.” nIn papermaking, animal fibers are not used at all, and mineral fibers are used only occasionally. nVegetable fibers (cellulose) wet easily in a water medium and will form a strong bond to each other when dried in contact.
Four Types of Cellulose Fibers nSeed Hair Fibers –Cotton fibers nBast Fibers –Flax plant –Only 5% of the flax plant is usable for paper manufacturing nGrass Fibers –Wheat straw –Bagasse fiber (extracted from sugar cane stalks) –Esparto grass –Kenaf plant nWood Fibers
Seed Hair Fibers—Cotton Plant nCotton fibers are very expensive. nUsed primarily for bank notes, high grade writing papers, maps— anything that requires exceptional strength and durability.
Bast Fibers nObtained from the flax plant. nLocated inside the stem. nOnly 5% usable for papermaking. nHemp and jute are other forms of bast fibers. nHemp has been used for cigarette and Bible papers.
Bast Fibers (continued) nJute obtained from new burlap cuttings or other sources… –It is used for heavy duty shipping tags and heavy pattern boards.
Grass Fibers nWheat Straw –Absorbs water readily. –Was used during World War II in England due to a severe shortage of pulpwood. nBagasse fiber –Made from crushed stalks of sugar cane. –Used as a source of fuel for Sugar Mills. nEsparto Plant –Has very little strength and does not split into fibrils easily. –Impractical for use in the United States because of the distance from the source of supply.
Grass Fibers (continued) nKenaf plant –Shows great potential for papermaking. –May produce 5 to 7 times more pulp/acre than pine. –Grows to maturity in 120 days compared to 20 years for most trees.
Wood Fibers n95% of all paper is made from wood fibers. nDeciduous hardwood trees, e.g., Oak, Gum, Maple, Aspen, etc. nConiferous softwood trees, e.g., Pine, Spruce, Fir, etc. (the softwoods produce a stronger pulp).
Wood Procurement n39% of the available forests in the United States are in the South. nPrivate citizens own 3 quarters of land. nPaper industry uses specially designed equipment to harvest & prepare crops of trees: –Power chain saws –Skidders-forest tractors are used for opening sections of land. –Specially designed combines. –Mechanized tree shears. –Cranes, clamp trucks, truck dumpers. –Slashers saws. –Debarking drums.
Pulping nThe objective of pulping is to separate the wood into individual fibers. nThree broad classifications of pulping methods: –Mechanical (groundwood) –Chemical –Combination (chemi-mechanical)
Mechnical Pulping Processes nStone Groundwood –Mechanical process used to rip fibers from the logs –Slurry of pulp formed from the grounded mix. –Can be made from either hardwood or softwood. nRefiner-Mechanical Pulping –Wood chips are pumped into rotating disks causing internal friction that generates heat. –The heat from the refiner softens lignin. nThermo-Mechanical Pulping nChemi-Mechanical Pulp
To Make Groundwood Pulp... nThe bark is removed from the logs. nThen, the cut logs are forced by hydraulic or steam pressure against a revolving grinding stone in the presence of water. nThis treatment converts the wood into a pulp consisting of minute particles of both fibrous and nonfibrous portions of wood. nThe nonfibrous materials deteriorate when left for some time in contact with air. nTherefore, paper made from this kind of pulp lacks permanency.
Groundwood Pulp nThis type of pulp is not as strong as chemical pulp. nGroundwood pulp has to be mixed with other pulps, e.g., Newsprint—contains 80% groundwood pulp and 20% chemical pulp. nIt is highly suitable for products such as wallpaper, paper towels, or lightweight catalog papers. nIt is unexcelled in its ability to produce papers with high opacity, smoothness and ink receptivity.
Thermo-Mechanical Pulp nTo make TMP, wood chips or sawdust are first softened by steam and then subjected, under pressure, to the defibering action of a a disk-type refiner. nThis causes the fibers to completely separate from each other and suffer less damage than those produced by the conventional groundwood pulp process. nTMP is cleaner and stronger when compared with groundwood pulp.
Chemical Pulp nChemicals are used to reduce wood chips into fibers. nThis process separates each fiber from its bonding material—lignin. –The adhesive qualities of lignin holds cellulose fibers together.
Bleaching nThe purpose of bleaching is to remove stains caused by lignin. nMajor bleaching agents –chlorine, sodium hypochlorite, hydrogen peroxide, chlorine-dioxide, and oxygen. nChlorine gas is one of the different bleaching systems that are used to remove lignin that remains in the pulp. –Chlorine gas is passed into the pulp-water mixture. –The gas reacts with whatever lignin that is left and becomes chlorinated. –The chlorinated lignin is then removed when treated with the caustic soda NaOH (Sodium Hypochlorite)
Fourdrinier Paper Making Machine nNicolas Louis Robert invented the papermaking machine in 1798. nSealy Fourdrinier and Robert improved the original design of the papermaking machine to produce paper with a felt side and a wire side. nThe paper is formed at the wet end of the machine—after the pulp-water mixture has been refined. –Fillers –Coloring material –Sizing
The Headbox nThe headbox spreads pulp and water mix evenly over the moving wire. –The pulp-water mixture containing the added fibers, coloring material and size is diluted with water to make “slurry” containing ½ % to 1 % of cellulose fibers. –The headbox must maintain the uniform delivery of dispersion of fibers across the width of the machine.
The Fourdrinier Wire nThe fourdrinier wire causes the forming of paper at the wet end of the machine. –It is the section of the papermaking machine made up of a fine woven screen to let water drain away causing the pulp to remain to form a thin mat. –Suction boxes remove water as the mat moves along the wire. –Synthetic plastic fiber wires are used in modern papermaking machines. nWhen the mat had left this stage of production it contains 75% water.
Presses nDuring this stage of production, the mat enters wet rollers carried by felt blankets to reduce the amount of water to 60 - 65%. nIt is during this stage that the thin mat or paper begins to form a web or long ribbon. nThe paper continues through press rolls and felt blankets to remove water.
Dryers nSteam heated cylinders dry paper to 5% moisture.
Size Presses nSize press applies 10 % starch solution to both sides of paper.
Dryers nSecond dryer unit removes moisture applied to sheet in size press.
Calender-Reel nPolished rollers iron and control thickness of sheet. Reel winds paper on mandrel.
Winder nWinder unwinds paper from mandrel, passes sheet across slitter to trim edges and cut paper to final width.
Twin Wire Machines nThis method of papermaking was developed to improve the efficiency of the fourdrinier design. nTwo vertical sides restrain the furnish to permit the extraction of water from both sides of the paper. nIncrease machine speeds and reduction in drying.
Cylinder Machine nThis type of machine is designed for making extremely heavyweight paper and/or multi-ply products used in the manufacture of corrugated containers, folding cartons, and solid fiber boxes. nAll layers for multi-ply products can be manufactured with all layers formed in a single continuous operation. nTwo types of cylinder vats: contraflow and direct flow.
Paper (handout) 1. The Chinese are given credit for inventing the technique of papermaking. 2. To make a continuous supply of wood, the basic raw material for making paper, paper companies operate tree farms. 3. Pulp fibers are obtained from, woody fibrous materials, and reclaimed products are made from these materials. 4. Wood pulp sources are divided between softwood (coniferous) and hardwood (deciduous).
Paper (handout) continued 5. All paper fibers are made of a compound called cellulose. 6. Lignin serves as a binder and support for the cellulose fibers of woody plants. 7. Groundwood pulp process uses almost all of the substance in wood to make paper. 8. The manufacturer of chemical pulp uses chemical action to dissolve some of the wood’s substances to make higher quality paper.
Paper (handout) continued 9. The chemical-mechanical pulp method combines mechanical and cooking separation processes. 10. Opacity refers to the amount of light that can be seen through a sheet of paper. 11. In all three pulping methods, washing is used to remove all traces of chemicals and dirt from wood fibers. 12. True. Groundwood pulp is often referred to as mechnical pulp because it has been reduced to fibers by a mechanical grinding process.
Paper (handout) continued 13. The pulp selected for bleaching is treated with chlorine and similar chemical solutions to whiten the paper fibers. 14. The primary purpose of adding fillers to the pulp is to strengthen its properties. 15. Sizing is used to helpl make paper less absorbent and more water repellent, so it will not allow ink to spread. 16. Dyes and pigments are added to pulp during washing to give paper color.
Paper (handout) continued 17. The forming of paper starts at the wet end of the papermaking machine. Then processed pulp, which is 99% water, flows rapidly over an apron the width of the machine onto a moving mesh wire screen. 18. Where the paper touches the screen, it shows a mesh pattern. This is called the wire side of the paper.
Paper (handout) continued nA. 99.0 - 99.5 % nB. 75% nC. 60 - 65% 19. Identify the water content and machine sections of a typical papermaking machine operation in the mill. nD. 5% nE. 35% nF. 4.7 - 5.5%
Paper Making Machine nG. Headbox nH. Fourdrinier nI. Presses nJ. Dryers nK. Size nL. Dryers nM. Calender-Reel nN. Winder Press
Paper (handout) continued 20. As the paper starts to form, the pulp passes under a dandy roll to produce a surface finish on the paper. The roll is made of mesh wire. 21. The paper begins to form into a web, or long ribbon as it passes through the papermaking machine. 22. The ribbon of paper continues through press rolls and felt blankets, which remove more water.
Paper (handout) continued 23. The side of the paper that is in contact with the felt blanket is called the felt side of the paper. 24. Calender rolls are made of smooth iron to polish the paper and give it a very smooth finish. 25. Sheet-fed offset paper must have more strength than other printer processes because of the tackier ink. 26. The basis weights of paper generally used for web offset range from about 20 - 80 pound.
Paper (handout) continued 27. Joining the ends of two rolls of paper is referred to as splicing. 28. There are eight paper properties which must be considered for each job: 3Grain 3Finish 3Pick Resistance 3Brightness and Basis weight 3Flatness 3Ink setting and sizing 3Moisture absorbency and resistance 3Opacity
29. Fibers tend to align themselves in the paper as it passes through the machine. This alignment of fiber is referred to as the grain of the paper. 30. Tear strength in paper increases with increased fiber strength. 31. The term finish refers to any action performed to the surface of the sheet of printing paper that affects its surface. 32. Coated papers are exceptionally smooth, since they are subjected to an additional smoothing process.