Logo weiterlesen.de
Fillers for Paints

European Coatings Library

Detlef Gysau

Fillers for Paints

Fundamentals and Applications

3rd Revised Edition

For Jacqueline and Gian-Flurin and Mica-Ladina and also Rambo and Fuchur

There is no debt more pressing than the expression of gratitude.

Marcus Tullius Cicero

Foreword

The topic of fillers for use in paints and varnishes is an old one, so one might ask why there has been no comprehensive book on the subject to date. Could it be something to do with the earlier prevailing perception of fillers as cheap materials for bulking up profits? Are fillers even worth writing about? Certainly! The sheer number of mineral end-products, the frequently underestimated effort that goes into their manufacture, the testing done to characterise their diverse properties, their wide-ranging applications – that is an awful lot of information to pack into a single work without diluting its focus.

Simply to consider the spectrum of professions involved in producing and using fillers – geologists, mineralogists, mechanical engineers, machine operators, chemists, paint and varnish specialists – highlights the extent of hidden technical activity. Fillers are instrumental in many properties of coating materials and films: their rheology, content of volatile organic compounds, solids content, brightness, opacity, reflectivity, adhesion, anti-corrosion characteristics, mechanical and chemical resistance… the list goes on. The bottom line is, proper use of fillers calls for a great deal of knowledge.

The present book sets out to convey that knowledge in a straightforward and understandable manner, without compromising scientific objectivity and rigour. Special attention has been given to clear topical division and structuring, to facilitate finding pertinent information, fast. That having been said, the gamut of available fillers is so vast that there would be insufficient space to cover all the materials out there, some of them quite exotic. Instead, this book concentrates on fillers in regular current use, with numerous figures and tables to illustrate their properties and applications. All the same, this book cannot claim to be exhaustive in scope. Readers wishing to obtain further information and details will be served by the extensive bibliographic references provided.

This book is intended for anyone who is in any way professionally involved with fillers used in coating materials. Beginners and students will gain a comprehensive overview of the field, while experienced developers will find practical details of immediate relevance to solving their everyday problems.

In 2016 I was notified that also the second edition of “Fillers for Paints” is going to be sold out soon as well. I am more than delighted to learn that also the second edition found so many new readers. The continued interest in my book is also judged by manifold feedbacks which I received since 2006. All of them expressed to me their thanks and congratulations by filling a knowledge gap in raw materials for paints.

In particular, I appreciate that the book supports training for all different kind of groups, either in industry or science. The third edition allowed me to place small corrections, update market and filler data and add more sub chapters about new fillers and nevertheless an outlook about the future, for example sustainability and light weight fillers.

Detlef Gysau

Oftringen/Switzerland, January 2017

Contents

Introduction

1.1 Historical overview

1.2 Filler market

1.3 Definition of fillers and pigments

1.4 Classification of fillers

1.5 References

Mineralogy

2.1 Carbonates

2.1.1 Calcium carbonate

2.1.2 Dolomite

2.2 Silicas

2.2.1 Quartz

2.2.2 Cristobalite

2.2.3 Kieselguhr

2.3 Silicates

2.3.1 Talcum

2.3.2 Kaolin

2.3.3 Mica

2.3.4 Feldspar

2.4 Barium sulphate

2.5 References

Production of fillers

3.1 Production of natural fillers

3.1.1 Prospecting

3.1.2 Mining

3.1.3 Processing

3.2 Synthetic fillers

3.2.1 Precipitated calcium carbonate

3.2.2 Precipitated barium sulphate

3.2.3 Modified calcium carbonate

3.2.4 Synthetic silicic acids

3.2.5 Precipitated aluminium silicate

3.3 Surface treatment of fillers

3.4 References

Characterisation of fillers

4.1 Filler testing

4.1.1 Optical properties

4.1.2 Morphology

4.1.3 Physical properties

4.1.4 Chemical properties

4.2 Filler analytics

4.2.1 Scanning electron microscopy

4.2.2 Spectroscopy

4.2.3 Chromatography

4.2.4 Further methods

4.3 References

Properties of fillers

5.1 Carbonates

5.1.1 Natural calcium carbonate

5.1.2 Precipitated calcium carbonate

5.1.3 Modified calcium carbonate

5.1.4 Dolomite

5.2 Silicates

5.2.1 Talcum

5.2.2 Kaolin

5.2.3 Mica

5.2.4 Feldspar

5.2.5 Precipitated aluminium silicate

5.3 Silicas

5.3.1 Quartz

5.3.2 Cristobalite

5.3.3 Diatomaceous earth

5.3.4 Pyrogenous silicic acid

5.3.5 Precipitated silicic acid

5.4 Barium sulphate

5.4.1 Natural barium sulphate

5.4.2 Precipitated barium sulphate

5.5 Aluminium hydroxide and other mineral fillers

5.6 Organic fillers

5.7 References

Applications of fillers

6.1 Importance of fillers in paints and coatings

6.2 Important formulation parameters

6.2.1 Non-volatile matter

6.2.2 Spreading rate

6.2.3 Pigment volume concentration

6.2.4 Critical pigment volume concentration

6.2.5 Pigment/filler loading

6.2.6 Packing density

6.3 Filler influences on coating materials

6.3.1 Dispersibility

6.3.2 Rheology

6.3.3 Wet hiding power

6.3.4 Storage stability

6.4 Filler influences on coatings

6.4.1 Hiding power

6.4.2 Colour properties

6.4.3 Reflectivity

6.4.4 Mechanical properties

6.4.5 Chemical resistance

6.4.6 Outdoor durability

6.5 References

Trends

7.1 Nanotechnology

7.2 Forms of delivery

7.3 Sustainability

7.4 Light weight fillers

7.5 References

Examples for guide formulations

List of filler examples

Author

Index

Introduction

1.1 Historical overview

Paints and varnishes have a history that goes back around 100,000 years, to the time when stone age peoples applied red body-paint as part of their cultish rituals[1]. The first paintings on cave walls date back to the late Stone Age, their origins still somewhat shrouded in mystery. Many thousands of years later, in the 4th century B.C., the intermingling of ancient Egyptian and Greek civilisations brought remarkable developmental advances through “Hagia Techné” or “Alchimia” – hallowed arts practiced by the high priests of the day. Their discoveries about the secrets of paint making remained influential well beyond the 16th century A.D. As the industrial revolution started in the 18th century, paints and varnishes came into widespread use for many different applications. Early 20th century triumphs of chemistry and technology in particular signified a clear departure from empiricism, to science.

The history of fillers can be traced back almost as far as paints and varnishes. Pigment analysis has revealed the presence of filler materials in early cave paintings[2, 3], the oldest identifiable specimens dating from 20,000 to 30,000 years ago, see Table 1.1 p.14.

However, the first people to systematically use fillers for their cave paintings were the ancient Egyptians, and the Mediterranean cultures that succeeded them. The most frequent materials were chalk and gypsum, both white mineral fillers. Clays, or crushed mollusc shells, were also used on occasion. As history progressed, the ancient Greeks began using a mineral that was whiter still: white lead. Because of its rare occurrence in nature, they developed an intricate process to obtain the pigment synthetically. Contemporary demand for greater opacity and brightness evidently made the effort worthwhile. The Roman historians Pliny and Vitruvius respectively reported eight and five white pigments then in use, although only three were of real significance: the minerals melinum, paraetonium and cerussa (white lead).

During the period of the Roman Empire, there was a marked increase in the consumption of fillers, which were used in paints for murals, panels and frescoes. But filler production collapsed along with the Roman Empire, and artists subsequently resorted to local minerals. There were large chalk deposits in England, France, the Netherlands and Germany. Even in Spain, chalk grew prevalent under the name of Spanish white. In Italy, though, gypsum predominated. That was the situation until the 19th century, when the industrial revolution came into full swing.

The enormous increase in consumption of raw materials during the industrial revolution also brought a sustained rise in demand for fillers. Semi- and fully-automatic dressing processes were developed to address this demand, as well as to meet the steadily advancing requirements of industry. High-power machinery like crushers, grinding drums and classifiers came into use. The end of the Second World War brought even greater demand for fillers, which was a motor for further modernisation by the filler industry. The resulting technical developments led to ever-finer natural fillers and tailor-made synthetic fillers, some with surface coatings, see Figure 1.1 p.14.

Table 1.1: Natural and synthetic white minerals used by the ancients

Ancient name

Modern name

Mineral composition

Cerussa(1,2)

White lead, Krems White, etc.

Basic lead carbonate, made from metallic lead and vinegar

Creta anularia(1,2)

Crete white

Chalk mixed with powdered glass

Cimolia creta(1)

Kimolos chalk

Chalk or clay-like material

Creta eretria(1)

 

Probably a white talc, named after a place on the southwest coast of Euboa

Creta selinusia(1,2)

Selinus chalk

Chalk or chalk clay, named after a place on Sicily

Melinum(1,2)

Melian white

Bianca San Giovannini or white clay

Paraetonium(1,2)

White sepiolite

Limestone chalk with some magnesium phosphate, silicic acid and clay, named after a place in Libya

Creta argentaria(1)

Argentiferous chalk

Chalk

(1) Pliny, Natural History, XXXV (2) Vitruvius, Ten Books on Architecture, VII