Packaging Technology and Engineering. Dipak Kumar Sarker

2 Chemical Engineering of Packaging Materials

      CHAPTER MENU

       Introduction

       Building Blocks, Extraction, and Raw Materials

       Industrial Processes, Wood‐Pulping, Processing, and Smelting

       Making Glass

      Abstract

      In this chapter packaging materials are considered from a chemical engineering perspective, that is, processes involving the building blocks of certain raw materials, such as ores, and methods of extraction and exploitation. The use of rigorous extraction in industrial processes and its influence on material quality and waste production including scrappage (slag and clinker) follows. Processes including wood‐pulp manufacture and ore‐smelting are core contributory stages in the fabrication of modern packaging materials. The description of these processes is accompanied by an outline of the manufacture of glass and its use according to its starting materials. The raw materials are used combinatorially in numerous grades and forms of complex and composite‐type materials.

      Keywords life cycle; extraction; materials; commodities; smelting; haematite; Kraft paper;

2.1 Introduction

Raw materials united through a combination of the processes indicated in Figure 2.1a following on from refining, purification, or gradation are able to produce a suitable ‘working material’ for packaging use. The working material may require further adaptation, such as polyethylene (PE) lamination to create better gas or moisture impermeability. Needless to say, such chemistry then creates further waste. The testing that takes place aligns the steps of chemical modification to produce both the working material and various types of waste. Testing has to ensure the correct degree of purity (as befitting the final end use) as well as optimal functionality and performance. Smelting of metals, fractionation and cracking of crude oil and natural gas sources for plastics, silicate mining for glass, and wood‐pulp generation for paper are the usual sources of raw materials. These materials are then moulded and shaped into forms suitable for carrying and retaining a commercial product.

Figure 2.1a shows a range of unit operations in the form of an organogram associated with the life cycle of commercial packaging materials. Following adequate screening and refining or purification (particularly when recycled materials are being used), the raw materials are converted into the working material and shaped into the final product. For example, this can be cullet, sand, soda, and lime for glass manufacture. However, as part of the refining process natural waste materials are generated [1]. Some working material may also require chemical modification, such as the embedding of nano‐materials [2], the hydroxypropyl derivatisation of cellulose to create polymer for use in biopolymer film packaging [3], or the corona discharge treatment of polypropylene to form carbonyl, carboxylate or amide groups on the surface [4] that aid printing. Working material in the form of assorted designations of various packaging materials produces stock such as multi‐lamellar laminate films for a range of adaptations. At this point materials can pass on to manufacturing processes for various applications, such as bottled product or vacuum‐packed modified‐atmosphere trays [5]. These formed packaging products then pass on to the distribution chain and, either as a result of this distribution and poor storage or as a result of transit damage and natural loss of materials during manufacture, on to accrued waste. Importantly, at all steps of the process from sourcing materials to finished distributed product, assessment of quality and performance is essential.