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Home , Gift wrapping, Greaseproof paper, Paperboard, Printing, Wet strength, Wrapping tissue

686 PACKAGING, AND / Packaging Grades

H C OH 3 Cl

O N H C CH N 3 3

NH

HN

N H C 3 CH3 N O

Cl HO CH3

Pigment Yellow 13 Figure 11 Structure of pigment yellow 13.

See also: : Grades; The History of O H Paper and Papermaking; World Paper Overview.

H3C C N Further

Adams JM and Dolin PA (2002) Printing Technology. N C CH3 Clifton Park, NY: Delmar. H O DeJidas LP and Destree TM (1999) Sheetfed Offset Press Operating. Pittsburgh: GATF Press. Figure 12 Structure of quinacridone pigment. Dennis EA, Odesina O, and Wilson DG (1997) Litho- graphic Technology. Albany, NY: Delmar. Eldred NR and Scarlett T (2001) What the Should Know about . Pittsburgh: GATF Press. CH3 FFTA (1999) : Principles and Practices, 5th edn. Ronkonkoma, NY: FTA/FFTA. Gray T (ed.) (2003) Gravure Process and Technology. Rochester, NY: GEF/GAA. Kipphan H (ed.) (2001) Handbook of Print Media. Berlin, : Springer-Verlag. Levy U and Biscoe G (1998) Nonimpact Electronic − Printing. Charlottesville, VA: Interquest. SO 3 Thompson B (1998) Printing Materials. Leatherhead, UK: PIRA. + Wilson LA (1998) What the Printer Should know about Ca2 N Paper. Pittsburgh: GATF Press. N

OH Packaging Grades G J F Ring, University of Wisconsin–Stevens Point, Stevens Point, WI, USA − CO 2 & 2004, Elsevier Ltd. All Rights Reserved.

Pigment Red 57:1 Figure 13 Structure of pigment red 57. Introduction obtained by varying the pH, temperature, and time Nasiri Khosrau of Persia (now Iran) recorded the first of heating during oxidation. These were used by use of paper as a packaging material in 1035 AD printers for all printing through the mid nine- when he observed vendors in Cairo () wrapping teenth century, before the discovery of synthetic vegetables, spices, and dry goods in paper. Today, organic dyes. paper continues to be an important material used to PACKAGING, RECYCLING AND PRINTING / Packaging Grades 687 transport, distribute, and market virtually every together to a block bottom that is ideal for commodity and manufactured item. Paper competes packaging flour, rice, sugar, and other dry food items. very successfully with metals, , , , The satchel-bottom , when filled, can stand and , because it has many desirable properties upright. Finally, self-opening bags have gussets to including being biodegradable, recyclable, and re- form square bags and specially folded bottoms that newable. Paper functions in many diverse packaging form flat-bottom squares or rectangles. These bags applications from heavyweight shipping are folded flat but are designed to open with a snap to lightweight wrapping . This article will of the wrist and stand by themselves for filling. concentrate on lightweight specialty papers such as Grocery bags and sandwich lunch bags are examples paper bags, food wrapping, , of self-opening bags. spiral-wound paper tubes, stock, and other is an important paper additive for specialty items. The cut sheet size for wrapping retail bags. Grocery bags in particular must be able papers is 24 in. by 36 in., giving a total ream area of to maintain a substantial portion of their strength 3000 ft2. Types of paper used to manufacture when brought into contact with wet food and other and containers are discussed elsewhere (see Paper- products. making: Grades).

Multiwall Paper Sacks Retail Paper Bags Multiwall paper sacks are designed to be exception- Retail bags are closed-bottom, flexible-walled con- ally strong and carry heavy and bulky materials for tainers that are capable of carrying many types of dry the building, food, and chemical industries. In goods within them. Paper bags are manufactured essence, multiwall sacks are two or more separate from due to the requirement for high sacks nested together to form a stronger and tougher À strength. The paper may be bleached or unbleached sack. Five or six total plies of paper (60–110 g m 2) depending upon the use. The range for may be necessary. For paper sacks, kraft paper is À lightweight bags is 40–60 g m 2. For heavier weight used; however, stretch and porosity as well as bags such as grocery bags that are required to carry strength are critical performance criteria. as much as 12 kg the grammage range extends to Stretch or extensibility is important because multi- À 110 g m 2. wall sacks are required to withstand numerous Historically, bags were fabricated from textiles or impacts during shipping and warehousing without animal skins with sewn bottoms. During the early rupturing and spilling their contents. Sack paper’s nineteenth century, powdered goods such as flour or ability to absorb shock during impact is measured by medicines were sold in hand-rolled paper sacks called tensile energy absorption (TEA), which is a paper ‘pokes.’ These early paper bags were actually property that combines both strength and stretch. inverted cones that required only folding to close TEA can be thought of as a measure of ‘work to the bottom. By 1877, paper bags were produced by burst.’ Special extensible sack paper that has been machines that cut, folded, and either glued or sewed produced through the ‘clupak’ process greatly the sides from rolls of paper. Today, paper bags come enhances TEA and permits the use of lower À in four basic shapes: flat, square, satchel-bottom, and grammage ranges (50–100 g m 2) thus saving about self-opening. 20% fiber by weight. The clupak process, invented Flat paper bags are made from kraft paper that has by Sanford Cluett, produces extensible paper that is been glued with a -based to form a difficult to tear by passing wet paper through a steel with its bottom folded and glued. This type of and rubber nip that causes fiber crimping in the is commonly used for candy, greeting cards and machine direction. Additional extensibility in the many retail items that are small and lightweight. The machine direction is produced on the square-bottom bag is similar to the flat bag except through using slack draws in the dryer section. Slack that the paper tube is first folded inwards along the draws prevent the sheet from developing dried-in sides to form an expanding gusset before the bottom drains leading to limited stretch. is folded. When the square bag is opened or filled, the Porosity is important for multiwall paper sacks bag has a square or rectangular cross section. In this because air needs to escape through the wall of the manner, the square bag can hold thicker and heavier bag to permit rapid filling. Sack filling machines are items such as and . The satchel- able to fill a 25–50 kg sack in 1 second at bottom bag also forms a square shape when opened temperatures that can exceed 1001C. Sewn-bottom but the bottom is folded into triangles and glued and pasted bottom open-mouthed sacks are used for 688 PACKAGING, RECYCLING AND PRINTING / Packaging Grades low gravity-filling systems. Valve sacks function of the roughness of the paper. Rough paper are required when materials must be filled under surfaces produce matte or dull appearing metal pressure. layers, while smooth paper surfaces produce glossy Multilayer sacks may be constructed with metal layers. High-gloss metal layers are manufac- liners to prevent moisture contamination. Plastic tured via indirect or transfer metallizing. In transfer linings are important for foods and chemicals where metallizing a web is metallized. the ingredients have to maintain a certain moisture Because the metal does not bond to the polypropy- level. Wet-strength are also used to control lene, the entire metal layer can be transferred to the moisture penetration through the paper. surface of an adhesive- sheet. The transferred metal layer has the surface smoothness of the polypropylene sheet. Thus, a high gloss Food Wrapping Paper metallized sheet is produced regardless of the original Paper intended for the wrapping and serving of surface of the paper. Before printing, metallized food must be manufactured from ingredients paper is coated with a special primer layer to that do not adulterate food. This requirement enhance adherence of the printing inks. Metallized necessitates the use of virgin chemically processed paper is used as packaging materials for a number of pulps along with paper additives and that food products that include chocolate bars, oily snack are recognized as safe to human consumption. These foods, candies, and chewing gums. papers must have some form of wet strength Foil-backed paper is produced by laminating and grease resistance as well as have reasonable aluminum foil to paper with an aqueous adhesive. printing properties. The basis weight range for The resultant sheet is attractive, easily printed upon, À food wrapping paper is 28–65 g m 2. General and has similar barrier properties to metallized categories of food wrapping paper include: grease- paper. However, additional properties such as proof, metallized, and foil-backed papers. Special dead fold and heat retention capabilities that make fruit wrapping papers impregnated with preserva- it ideal for wrapping fast-food items such as tives can also be found. hamburgers and other hot sandwiches. Dead fold is Greaseproof papers are papers that resist the a direct property of the aluminum foil. Aluminum penetration of grease and oils, and are also called metal is very malleable and can be greatly deformed moisture resistant papers. Vegetable is a without cracking or losing its barrier capability. nonporous, homogeneous sheet of formed When fully annealed, aluminum maintains no from sulfuric acid treating . This material is the ‘temper’ and retains its shape when deformed. Thus, traditional form of but is very dead fold gives foil-backed paper an ability to expensive by present standards. Surface or wrap around and temporarily seal a fast-food sizingwithwaxorsyntheticmaterialsisnowamore product from the time of purchase to the time of common method of greaseproof consumption. paper from standard, bleached kraft paper. Food- Twisting paper is a food wrapping paper that safe paraffin wax is lightly applied to one side of is used primarily for personal-sized confections and the sheet. Thicker coatings of wax are also applied cough drops. It has a high machine direction fiber À when a shiny surface is desirable. Synthetic surface orientation and a grammage range of 25–40 g m 2. treatments include silicone or polyvinyl alcohol Some twisting papers may be metallized with based materials. Highly refined and supercalendered aluminum to improve product attractiveness. Furnish , coated or uncoated, may also serve in this additives include: for enhanced category. Grease or moisture resistance refers to opacity, and wet strength agents. Twisting papers are surface treatments that have intermediate grease slit into very narrow widths to match the size of the resistance between uncoated paper and greaseproof confection. A heavier weight, non-food twisting paper. paper is sometimes found making up the handles of Metallized paper is an excellent packaging materi- paper bags used for shopping though it is now al for foods that are sensitive to moisture and light. virtually obsolete. The metal, usually aluminum, is applied in a very An interesting paper grade that is frequently thin layer (0.02–0.05 mm) onto the paper sheet excluded as a packaging or wrapping grade is tea through vacuum deposition that involves vaporizing bag paper. Tea bag paper is a lightweight (grammage À high purity metal. Due to the high surface free energy range 12–17 g m 2) made from very of paper, the vaporized metal bonds to the paper durable and long-fibered pulp such as abaca (banana surface forming a moisture and gas impenetrable leaf). This paper has to be porous yet hold the fine- layer. The gloss of a metallized paper sheet is a sized tea leaves within the fabricated product. PACKAGING, RECYCLING AND PRINTING / Packaging Grades 689

Synthetic fibers such as polypropylene are frequently 48 inches and wall thicknesses as much as 1/2 inch. mixed into the furnish to produce a heat sealable bag. Depending upon the final dimensions, the tube can be referred to as a tube, a can, or a . After gluing, the tubes are first rough cut, then cleaned, and Wrapping Papers precisely cut. Inside and outside layers can incorpo- rate separate specialty papers that are optimized for Wrapping papers are produced for a variety of barrier and printing properties. When tubes are used purposes. Three major types include kraft wrapping as cans or closed packages, the tube ends can be paper, tissue paper, and gift-wrap paper. Kraft sealed by a variety of methods. In general, a paper top wrapping paper is sold in roll widths from 400 to À 2 can be glued over the ends, the ends can be sealed by 1200 mm with a grammage range of 50–90 g m .It crimping and gluing, or a metal or plastic cap can be is produced from either unbleached or bleached pulp inserted. and is similar to kraft sack paper. When recycled pulp is used, it is sometimes called ‘imitation’ kraft paper and is dyed brown. Kraft wrapping paper is Paper Cups frequently used in retail transactions involving items that are not prepackaged or as an outer wrapping for Paper cups are essentially single-wrap paper tubes food items that have flimsy, easily damaged food- with only one end sealed. The cup is sealed down the grade packages. side similar to paper bags. The cup bottom may be Tissue wrapping paper is a lightweight paper sheet sealed by either gluing a separate paper end cap or À having a grammage range of 14–40 g m 2. The rolling the cup into a cone or convolute tube. standard tissue wrapping paper has a machine glazed Bleached, food-grade quality kraft paper similar to finish due to the use of a high-temperature Yankee milk stock is required. The paper needs to dryer that produces high gloss on the bottom side of have a high tensile strength, a low cross-machine the sheet. Unglazed tissue may also be produced stretch, and a low ash content. The top edge of a using lower drier temperatures. Tissue wrapping is rolled under to provide a smooth edge. paper is used to protect fragile or expensive gift items This cup feature requires that paper cup stock have such as glass trinkets, ornaments, and jewelry. the ability to delaminate internally and hold the is made in colors running the rolled edge. spectrum from white to . White wrapping Paper cup stock also needs to have a high moisture tissue may have a brightness as high as 80. Special resistance for cold drinks. Wax coatings provide acid-free tissue is available to wrap items that are adequate moisture resistance as well as provide good prone to tarnish, such as silver metal. sealing on the seam. However, wax coatings are Gift-wrap paper is produced in above likely to melt with hot drinks such as coffee and À 36 g m 2, and is coated and calendered to maximize permit liquid leakage. Polymer or the attractiveness of the printed pattern. The paper’s extruded coatings are used on cups intended for gloss is improved through the of metal hot beverages. The polymer coating is used only on foil or the extrusion of a polymer coating. Rolls of one side to provide the moisture barrier and a gift-wrap are sold in widths of 500–800 mm and sealable seam, while the outside of the cup is usually lengths of 1–5 m. uncoated to provide better heat insulation. Clay coatings are frequently applied to increase print- ability and opacity. Miscellaneous paperboard items Paper Tubes related to the use of paper cups in restaurants are insulating sleeves made from unbleached or recycled Spirally wound paper tubes are used in a myriad of fiber and carrier trays. Many paper cups intended packaging products. Some examples include: mailing for hot drinks have paperboard handles glued to tubes, snack food cans, and cores for paper roll their sides. products. The paper used is made from either virgin kraft or recycled fiber and has a grammage range of À 2 35–95 g m . Label Papers The process of producing a paper tube begins with slitting paper into narrow (minimally 2 inch) strips Paper is an important method of labeling packages from a 50-inch roll. The strips of paper are then and containers that are nonprintable such as metal coated with a glue and several layers are wrapped tins or cans and . Paper is also an important into a spiral having an angle of approximately 451. method of labeling items in the office and at home The final tubes can have typical diameters as great as with pressure sensitive . Paper designed for 690 PACKAGING, RECYCLING AND PRINTING / Packaging Grades labels has one surface optimized for printing and the oven techniques. Solvent silicone systems are still other optimized for the application of an adhesive. used but flammability and environmental concerns Flexographic, gravure, and are the are making newer aqueous systems more preferable. most important commercial processes used for Modern machines that produce pressure sensitive labeling retail products; however, blank labels used labels coat and cure the backing paper and then in the office and in the home must be receptive to pen apply the pressure sensitive adhesive directly to the inks and ink-jet printing. Paper label stock may also silicone treated side. Simultaneously, the face stock is be clay coated, extrusion coated with plastic or coated with an adhesive-receptive primer that is then laminated with metal. dried. Both sheets are then laminated together to Label stock intended for bottles and other liquid form the final product. packages needs to be resistant so that the label Face stocks can come in a variety of grades from À neither washes off the nor losses its printing lightweight (65 g m 2) supercalendered paper to À during normal usage. The label must also have relatively heavy tag-grade paperboard (230 g m 2). wet strength sufficient to keep it intact if it is Face stocks may be either bleached or unbleached intended for use in recycled bottles where the label depending upon the application. Recycled fiber must be washed off with strong cleansing alkali. percentages as high as 100% may occur with Paper used for these applications is white with ISO consumer waste percentages reaching as high as brightness above 80%, a gloss above 80%, and a 50%. Face stocks are printed using a variety of high smoothness. The paper also needs to be stiff, methods including flexographic, letterpress and on- dimensionally stable, and absorbent to . demand printing methods, such as direct thermal, The paper furnish is derived from and thermal transfer, and /ink jet technologies. chemical pulps with a grammage range of À 70–75 g m 2. See also: Packaging, Recycling and Printing: Paper Pressure sensitive labels are produced by laminat- Recycling Science and Technology. Papermaking: Over- ing a printable face sheet on top of a ‘release’ liner view; Paper Grades; Paper Raw Materials and Techno- using a suitable adhesive that completely peels away logy; Paperboard Grades; Tissue Grades; World Paper with the label allowing the label to be applied and Industry Overview. Pulping: Bleaching of Pulp; Physical Properties. adhered to another surface. Also known as ‘peel and stick,’ pressure sensitive labels come in either preprinted or blank forms that are -cut to form Further Reading individual labels on a roll or sheet. Pressure sensitive labels are used for: packages, , mailing labels, Attwood B and Morre G (1995) An Introduction to the computer disks, office labeling, and even postage Theory and Practice of Multiply Forming. Leatherhead, stamps. UK: Pira International. The , also known as backing paper, is Biermann CJ (1993) Essentials of Pulping and Papermak- frequently silicone coated to create a smooth, ing. New York: Academic Press. pinhole-free surface that will not permanently bond Cakebread D (1993) Paper-Based Packaging. Leatherhead, with the adhesive of the face stock. The release liner UK: Pira International. Hunter D (1947) Papermaking: The History and Techni- can be either glassine or bleached kraft. Glassine is que of an Ancient Craft. New York: Knopf. inferior to bleached kraft in regards to curl and ISO (1998) ISO Standards Handbook: Paper, Board and dimensional stability, but its transparency makes it Pulps. Geneva: International Organization for Standar- suitable where machine scanners are used to bring dization. die-cut labels into position for printing and auto- Kouris M (ed.) (1990) Pulp and Paper Manufacture: matic labeling of packages. Glassine used for release Coating, Converting, and Specialty Processes. Atlanta, À liners has a grammage range of 30–80 g m 2 and GA: Joint Committee of the Paper Industry. a caliper of up to 65 mm. Release liners made Paulapuro H (ed.) (1998) Papermaking Science and from bleached kraft have a grammage range of Technology: Paper and Board Grades. Helsinki: À 30–130 g m 2 with maximum caliper of 100 mm. Fapet Oy. The extra stiffness, dimensional stability, and bulk of Paulapuro H (ed.) (2000) Papermaking Science and Technology: Papermaking, Part 1, Stock Preparation the bleached kraft liners are required for high quality and Wet End. Helsinki: Fapet Oy. printing requirements. The need for high smoothness Savolainen A (ed.) (1998) Papermaking Science and often necessitates supercalendering at about 20% Technology: Paper and Paperboard Converting. Helsin- moisture content. Silicone in the form of silicone ki: Fapet Oy. acrylate is off-machine coated using a roll coater and Smook GA (1992) Handbook for Pulp and Paper then cured using either electron , or Technologists. Vancouver, BC: Angus Wilde.