PKG Lecture 9 Notes
PKG Lecture 9 Notes PKG 101
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This 5 page Class Notes was uploaded by Samantha Shea on Tuesday October 4, 2016. The Class Notes belongs to PKG 101 at Michigan State University taught by p. koning in Fall 2016. Since its upload, it has received 5 views. For similar materials see Principles of Packaging in Packaging Science at Michigan State University.
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Date Created: 10/04/16
Paper and Paperboard Tuesday, October 4, 210:25 AM Early Papermaking • Single sheet manufacturing ○ Rags and cloth Process Development • Two new continuous processes developed for faster production ○ Fourdrinier process Cylinder Process ○ U.S Paper Today • Paper mostly made from wood • Rags are added to make high quality stationary and other specialty papers. 1. Fourdrinier Machine 2. Cylinder Machine 3. Twin-‐Wire Machines The Nature of Paper • Paper is composed of matted cellulose fibers • Cellulose fiber quality is the prime determinant of properties North American Fiber Sources • Hardwoods ○ Short fibers ○ Smooth, good formation ○ Even, good printing but poor physical strength • Softwoods ○ Long fibers ○ Good tensile, puncture, tear, and fold strength ○ But poor formation & printing Other Papermaking Fiber Sources • Recycled paper and packaging • Ranges from low quality newsprint to high quality corrugated board Wood Consists of… • 50% cellulose (the desired product) • Lignin (undesired) • Carbohydrates (undesired) Fiber Extraction • There are 3 main types of pulping processes • 50% cellulose (the desired product) • Lignin (undesired) • Carbohydrates (undesired) Fiber Extraction • There are 3 main types of pulping processes ○ Mechanical ○ semi-‐chemical ○ Chemical Fiber Extraction (pulping) • Semi-‐chemical Major pulping process for corrugating medium, the wavy fluted layer in ○ corrugated board. • Chemical extraction with sulfate (kraft process) ○ Costly ○ Low fiber degradation ○ Dissolves away lignin ○ Strongest wood pulp, strongest paper products ○ Environmentally stable • The kraft process is by far the most widely used process for making pulp for packaging paper and paperboard. Defintition • Paper ○ A matted or felted sheet usually composed of plant fiber. ○ Paper caliper is 0.012" or less • Paperboard ○ Heavier paper stock ○ Paperboard caliper is more than 0.012" Paper and Paperboard terms • Gauge/caliper -‐ thickness of the sheet expressed in thousands of inch, or points (0.001" = 1pt) ○ Paper is 0.012" or less (up to and including 12 pts) Paperboard is > 0.012" (12ps or greater) ○ • Basis weight-‐ weight of known area • Brightness-‐total reflectance of the white light • Structure-‐composition of sheet • Machine direction-‐ long direction of web Brightness • A measure of the total reflectance of white light • Vales expressed on a scale of 1 to 100 • The value is not a percentage • Not to be confused with 'whiteness', a color description • Most papers range from 78 and 84 bright Types of Paper • Vales expressed on a scale of 1 to 100 • The value is not a percentage • Not to be confused with 'whiteness', a color description • Most papers range from 78 and 84 bright Types of Paper • Kraft Paper ○ Noted for its strength ○ Bleached and unbleached (strongest) ○ Grocery bags, envelopes, gummed sealing tape, and multiwall bags • Glassine Paper (waxed) • Tissue Paper • Vegetable parchment • Cellophane • Containerboards (linerboard and medium) ○ Linerboard (facings) ○ Medium (fluting) Types of Paperboard • Chipboard-‐low quality paperboard, 100% recycled fiber • Bending chipboard-‐slightly better grade, still primarily recycled fiber • Liner chipboard-‐white face-‐liner applied • Single white-‐lined (SWL) • Clay-‐Coated Newsback (CCNB) • Double White-‐Lined (DWL) • Solid Bleached Sulfate (SBS) -‐100% bleached Kraft paperboard. Strong, premium, white throughout. Consistent manufacturing performance. • Solid Unbleached Sulfate (SUS) -‐unbleached Kraft paperboard, provides maximum strength • Food Board Common Paperboards • Clay Coated Newsback-‐(CCNB) SWL with a gray newsback liner • Solid Unbleached sulfate-‐(SUS) 100% chemical pulp • Solid Bleached sulfate-‐(SBS) 100% bleached chemical pulp 1. The Fourdrinier Machine Paper(board) Manufacturing • "Wet End" ○ Headbox ○ Water removal section • "Dry End" ○ Dryer section ○ Calendering Stack ○ Wind-‐Up Furnish • Furnish for making paper-‐mixture of water, pulp and additives (about 98% water) is fed into the Headbox ○ Dryer section ○ Calendering Stack ○ Wind-‐Up Furnish • Furnish for making paper-‐mixture of water, pulp and additives (about 98% water) is fed into the Headbox Drier Section Calendar Stack Water Removal • Gravity • Suction • Pressing • Drying Rolls • Paper dries to 5 -‐10% moisture content The number of rollers, the pressure, and optional heating of the calendar rolls all affect the characteristics of the paper. …continuous length of paper on a roll is also called a "Web" 2. The Cylinder Machine The Cylinder Machine • No Headbox • Screen Covered Cylinders pick up pulp from vats • Each vat can contain a different types of pulp • Each cylinder adds another layer • Makes heavy grades (Paperboard > 12 points) 3. Twin-‐Wire Machines Cylinder and Fourdrinier • Generally, papers are made on Fourdrinie-iire formers, whereas heavier paperboard products are made on Cylinder machines • Cylinder board is always multi-‐ply (has multiple layers), while Fourdrinier paper is most often eply (only one layer). Paper Directionality • Paper is an Anisotropic material (not isotropic), which means their properties do depend on direction. Molded Pulp(Fibre) Containers & Forms • Three dimensional structures • Screen mesh covered mold • Furnish is poured or dipped • Vacuum assist • Multiple cycles to achieve needed caliper • Drying oven • Low grade or recycled stock • Advanced, precision, slower method of pressing between molds ○ Higher grade pulp • Vacuum assist • Multiple cycles to achieve needed caliper • Drying oven • Low grade or recycled stock • Advanced, precision, slower method of pressing between molds ○ Higher grade pulp
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