raw materials for paper making and the processing procedure involved..pptx

raw materials for paper making and the processing procedure involved

1. raw materials for paper making and the processing procedure involved.

2. Paper has a very interesting history. The ancient Egyptians in 2400 B.C. used the pith of a plant Cyperus papyrus for preparing a paper-like vegetative parchment called 'papyrus' from which the word 'paper' is derived. The Romans are also known to have used the Egyptian papyrus for writing purposes. The first makers of paper were, however, the Chinese. The paper industry spread to India, Persia, and Arabia from China. Later, it spread to Spain and other European countries. In 1690 a paper mill was established in USA. The Chinese made paper from pulp prepared by boiling old rags, silk waste, hemp, rice leaves, and bark of mulberry trees. The invention of a machine by French worker Louis Robert in 1799 for manufacturing paper and the discovery by Frederic Keller in 1845 that ordinary wood could be converted into a paper pulp led to the establishment of the modern paper industry. Origin and History 1

3. Raw Materials 1 The chief raw materials of paper are natural fibrous materials like wood fibers, cotton, and linen. Cellulose in the pure form gives the best quality paper. Wood pulp composed of long and strong cellulose fibers is the most wanted raw material for the paper industry. Spruces ( Picea spp.), pines ( Pinus spp.), aspens ( Populus spp.), and the balsam fir ( Abies balsamea ) are important wood pulp-yielding plants. Some hardwoods like beech ( Fagus grandifolia ), sugar maple (Acer saccharum ), and birch ( Betula lutea ) also furnish wood pulp. Other raw materials of minor importance are textile fibers of jute and hemp, wastes of the textile industry, the esparto grass ( Stipa tenacissima ),paper mulberry, papyrus ( Cyperus papyrus), bamboo ( Bambusa spp.), baobab ( Adansonia digitata ), Dephne cannabina , and Baib -grass ( Eulaliopsis binata ) and a number of other plants and fibrous materials. Low-grade paper, strawboard, cardboard, pasteboard, etc. are produced from the fibrous stems of wheat, rye, barley, rice, oats, and other grasses.

4.  Paper is made from cellulose fibers, which are obtained from trees, recovered papers and annual plant fibers like cereal straws. Today about 97% of the world's paper and board is made from wood-pulp, and about 85% of the wood-pulp used is from hardwoods and softwoods.​   Hardwoods are used as an ideal raw material for corrugated cases as well as printing and writing papers.​   Softwoods offer longer fibers (average 3 mm compared with 1 mm for hardwoods) and continue to be used for papers requiring the highest strength characteristics. ​  Paper is called board when it is heavier than 224 g/m 2 .​  Chemically pure cellulose consists of long, ribbon-like molecules made up of smaller glucose units. ​  Paper and board can be used in contact with food in many different ways, either directly or indirectly, and either singly or laminated with other materials such as plastic or met al foil.  [1,2] 1. Introduction 1

5. 2. Manufacture of Paper  2.1 Pulp manufacturing Manufacturing of pulp starts with raw material preparation by  debarking  (in case of wood),  chipping , and other processes.  Cellulosic pulp is manufactured from the raw materials, using chemical and mechanical means.  [3,4] 2.1.1 Mechanical Pulping   Mechanical pulping separates fibers from each other by mechanical energy applied to the wood matrix causing the gradual break of the bonds between the fibers In the mechanical pulping, the objective is to maintain the main part of the lignin in order to achieve high yield with acceptable strength properties and brightness  casuing  have a low resistance to aging. The main processes are  Groundwood Pulping (GW)   by pressing wood chips against a rotating surface to grind off small pieces,  Thermo-Mechanical Pulping (TMP) , by using high-temperature steaming before refining. [5,6] 2

6. 2.1.2 Chemical Pulping Chemical pulps are made by cooking (digesting) the raw materials, using the  kraft  (sulfate) and sulfite processes. In the  kraft  pulp process the active cooking chemicals (white liquor) are sodium hydroxide (NaOH) and sodium sulfide (Na 2 S). Kraft pulp possesses superior pulp strength properties in comparison to  sulphite  pulp.  Kraft processes produce a variety of pulps used mainly for packaging and high-strength papers and board. In the sulfite process Acid (bi) sulphite ,  Bisulphite , Neutral  sulphite  (NSSC), and Alkaline  sulphite are mainly used to attack and remove lignin. Mechanical pulps are weaker than chemical pulps, but cheaper to produce (about 50% of the costs of chemical pulp) and are generally obtained in the yield range of 85–95%. Chemical pulping yields approximately 50% but offers higher strength properties and the fibers are more easily breached because the mechanical pulping process does not remove lignin.  [5,6] 3

7. 2.2 Pulp washing and screening   To  removes impurities  and recycles any residual cooking liquor via the pulp washing process.  [5,6] 2.3 Bleaching   Bleaching is any process that chemically alters pulp to increase its brightness.  The principal pulp bleaching agents are chlorine, chlorine dioxide, hypochlorite, peroxide, chlorite, oxygen and ozone .  The pulp is prepared for the paper machine including the blending of different pulps, dilution, and the addition of chemicals.  4

8. 2.4 Pressing and Drying As the paper enters the press section , it undergoes compression between two rotating rolls to squeeze out more water. Then it  continues  its way through the steam heated dryers losing moisture each step of the way. About 90% of the cost of removing water from the sheet occurs during the pressing and drying operations. 2.5   Coating/ Calendering Coating is the treatment of the paper surface with clay or other pigments and/or adhesives to enhance printing quality, color, smoothness, opacity, or other surface characteristics. There is a great demand for paper with a very smooth printing surface . 5

9. 2.6 Finishing At the end of the drying process, the sheet is smoothed using an "ironing" method, which consists of hot polished iron rollers mounted in pairs with synthetic material rollers, one above the other. 2.7  Shipping The paper comes off the machine ready for reeling up into large reels, which can be cut or slit into smaller ones , according to customer requirements.  2.8 Quality control to ensure that the paper or board is of a consistently high quality. Moreover, for food contact applications , microbiological and chemical controls have to be carried out. 6

10. Reference [1] Paine, F.A. and Paine, H.Y. 1992. A Hand Book of Food Packaging. Blackie Academic & Professional.  [2] Robertson GL. 1993. Food Packaging Principles and Practice. Marcel Dekker INC. New York  [3]  Smook  GA (1992a) Wood and chip handling. Handbook for Pulp & Paper Technologists, 2nd  edn . Angus Wilde Publications, Vancouver, p 20 [4] Biermann CJ (1996a) Wood and fiber fundamentals. Handbook of Pulping and Papermaking. Academic, San Diego, p 13  [5]  Smook  GA (1992b) Overview of pulping methodology. Handbook for Pulp & Paper Technologists, 2nd  edn . Angus Wilde Publications, Vancouver, p 36 [6] Biermann CJ (1996b) Pulping fundamentals. Handbook of Pulping and Papermaking. Academic, San Diego, p 55  [7]  Smook  GA (1992e) Paper manufacture – wet end operations. Handbook for Pulp & Paper Technologists, 2nd  edn . Angus Wilde Publications, Vancouver, p 228 [8] Biermann CJ (1996f) Paper manufacture. Handbook of Pulping and Papermaking. Academic, San Diego, p 209  [9]  Smook  GA (1992d) Preparation of papermaking stock. Handbook for Pulp & Paper Technologists, 2nd  edn . Angus Wilde Publications, Vancouver, p 194 [10] Biermann CJ (1996e) Stock preparation and additives for papermaking. Handbook of Pulping and Papermaking. Academic, San Diego, p 190