Multilayer Flexible Packaging

John R. Wagner Jr., John R. Wagner, Jr.

• Publisher: William Andrew
• Year: 2016
• Print ISBN: 9780323371001
• eBook ISBN: 9780323477185
• Edition: 2
• Topic: Technology & Engineering
• Subtopic: Materials Science
• Index: Technology & Engineering

Multilayer Flexible Packaging, Second Edition, provides a thorough introduction to the manufacturing and applications of flexible plastic films, covering materials, hardware and processes, and multilayer film designs and applications. The book gives engineers and technicians a better understanding of the capability and limitations of multilayer flexible films and how to use them to make effective packaging.It includes contributions from world renowned experts and is fully updated to reflect the rapid advances made in the field since 2009, also including an entirely new chapter on the use of bio-based polymers in flexible packaging. The result is a practical, but detailed reference for polymeric flexible packaging professionals, including product developers, process engineers, and technical service representatives.The materials coverage includes detailed sections on polyethylene, polypropylene, and additives. The dies used to produce multilayer films are explored in the hardware section, and the process engineering of film manufacture is explained, with a particular focus on meeting specifications and targets. In addition, a new chapter has been added on regulations for food packaging – including both FDA and EU regulations.- Provides a complete introduction to multilayer flexible packaging, assisting plastics practitioners with the development, design, and manufacture of flexible packaging for food, cosmetics, pharmaceuticals, and more- Presents thorough, well-written, and up-to-date reviews of the current technology by experts in the field, making this an essential reference for any engineer or manager- Includes discussion and analysis of the latest rules and regulations governing food packaging

Part I

Introduction

Outline

1 Introduction

1

Introduction

John R. Wagner Jr.¹ and Scott B. Marks², ¹Crescent Associates, Inc., Rochester, NY, United States, ²E.I. du Pont de Nemours & Co., Wilmington, DE, United States

Abstract

Multilayer films have their history of development steeped in the depths of the development of plastic films and resins. From the early concept of a desire for a non-staining table cloth arose the thought processes that lead to cellulosic films such as cellophane, and onward into the world of many polymers such as polyethylene, polypropylene, polystyrene, and nylon. Many other polymers followed suit, leading to a revolution in the world of plastics and their many downstream uses.

This chapter gives a historical perspective of plastic films, presents some data on the global economy and looks at materials, the processes used, requirements, barrier and sealability.

Keywords

Polyethylene; polypropylene; polyester; polystyrene; coextrusion; tie resins; EVOH; Nylon; barrier films; multilayer films

1.1 Materials: A Historical Perspective

Today we have many clear plastic packaging films. Jacques E. Brandenberger invented the first common clear film, “cellophane” in 1908. He was a Swiss textile engineer whom first thought of the idea for a clear, protective, packaging layer in 1900. He was seated at a restaurant when a customer spilled wine onto the tablecloth. As the waiter replaced the cloth, Brandenberger decided that he would invent a clear flexible film that could be applied to cloth, making it waterproof.

Brandenberger experimented with different materials and tried applying liquid viscose (a cellulose product known as rayon) to cloth, but the viscose made the cloth too stiff. His idea failed but he noted that the coating peeled off in a transparent film. Like so many inventions, the original use was abandoned and new and better uses were found. By 1908 he developed the first machine to manufacture transparent sheets of regenerated cellulose. By 1912 he was making a saleable thin flexible film used in gas masks. He obtained patents to cover the machinery and the essential process ideas [1]. The rights to produce cellophane were then obtained by E.I. du Pont de Nemours & Co, who began to produce and further refine the process for producing cellophane. Breakthrough improvements included adding a moisture barrier layer to the cellophane, in the form of a nitrocellulose coating. This allowed for better stiffness retention in the cellophane and facilitated using the film as a food overwrap film. This coating was then refined to make it heat sealable as well, creating the first readily sealable packaging film. Later on, other coatings were applied to cellophane including PVDC (polyvinylidene chloride), which added oxygen barrier and moisture barrier to the cellophane, resulting in the original nonmetal barrier film for food packaging.

Today we have many polymers such as PE (polyethylene), PP (polypropylene), PET (polyester), and PS (polystyrene) that are used to produce clear films for packaging. While these aforementioned polymers are commonly used in monolayer format, they are also used in multilayer films produced by coextrusion and/or lamination processes. There also exist many specialty polymers and compounds, which sometimes are used monolithic, but are more commonly used in coextrusions.

Polyethylene was first synthesized by the German chemist Hans von Pechmann who prepared it by accident in 1898 while heating diazomethane. When his colleagues Eugen Bamberger and Friedrich Tschirner characterized the white, waxy, substance that he had created, they recognized that it contained long –CH₂– chains and termed it “polymethylene” [2].

The first industrially practical polyethylene synthesis was discovered (again by accident) in 1933 by Eric Fawcett and Reginald Gibson at the ICI works in Northwich, England. Upon applying extremely high pressure (several hundred atmospheres) to an ethylene and benzaldehyde mixture, they again produced a white, waxy, material. Because the reaction had been initiated by trace oxygen contamination in their apparatus, the experiment was, at first, difficult to reproduce. It was not until 1935 that another ICI chemist, Michael Perrin, developed this accident into a reproducible high-pressure synthesis for polyethylene that became the basis for industrial low-density polyethylene (LDPE) production beginning in 1939 [2].

Subsequent landmarks in polyethylene synthesis have revolved around developing several catalysts that promote ethylene polymerization at more mild temperatures and pressures. The first was a chromium trioxide–based catalyst discovered in 1951 by Robert Banks and J. Paul Hogan at Phillips Petroleum. In 1953 the German chemist Karl Ziegler developed a catalytic system based on titanium halides and organoaluminum compounds that worked at even milder conditions than the Phillips catalyst. The Phillips catalyst is less expensive and easier to work with; however, both methods are used in industrial practice.

By the end of the 1950s, both the Phillips- and Ziegler-type catalysts were being used to produce high-density polyethylene (HDPE). Phillips initially had difficulties producing a uniform quality HDPE product and filled warehouses with off-specification plastic. However, financial ruin was unexpectedly averted in 1957, when the hula hoop, a toy consisting of a circular polyethylene tube, became a fad among youth in the United States.

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Table of contents

• Cover image
• Title page
• Table of Contents
• Copyright
• Preface to the First Edition
• Preface to the Second Edition
• Acknowledgments
• List of Contributors
• Contributors
• Part I: Introduction
• Part II: Resins
• Part III: Technologies
• Part IV: Multilayer Films – Descriptions, Performance Characteristics, Uses, Considerations, Properties
• Appendix. Writing Guide for Packaging Films and Other Multilayer Structures
• Index