Ulrich Meier-Westhues

Karsten Danielmeier

Peter Kruppa

Edward P. Squiller

Polyurethanes

Coatings, Adhesives and Sealants

2^nd Revised Edition

Cover: Onionastudio, Adobe Stock

Ulrich Meier-Westhues, Karsten Danielmeier, Peter Kruppa, Edward P. Squiller

Polyurethanes: Coatings, Adhesives and Sealants, 2^nd Revised Edition

Hanover: Vincentz Network 2019

European Coatings Library

ISBN 978-3-86630-788-9

ISBN 978-3-86630-782-7

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European Coatings Library

Ulrich Meier-Westhues

Karsten Danielmeier

Peter Kruppa

Edward P. Squiller

Polyurethanes

Coatings, Adhesives and Sealants

2^nd Revised Edition

Foreword

A world without polyurethanes is hard to imagine these days. Polyurethane chemistry has become an established technology worldwide in various industrial applications. For innovative coatings, adhesives and sealants, it plays a significant role and has been in many cases the key to new technology implementation. Polyurethanes enable innovation and technological advancement and help to develop products that meet market needs, devising efficient and environmentally friendly manufacturing processes and asserting a position in the global competitive environment.

In 2007 the first edition of the textbook Polyurethanes for Coatings, Adhesives and Sealants was published with the purpose to give a comprehensive overview of the potential offered by polyurethane chemistry. It was a time, when the significance of solvent-free, water-borne or UV-cured systems had steadily increased and reached a considerable importance. While solvent-borne formulations occupied center stage for many years before, polyurethane chemistry suddenly demonstrated that environmental improvements, better quality and economy were not mutually exclusive, but could be synergistic.

The book became an established standard work for professionals and students in technical and commercial areas, who desired the know-how and background of polyurethane related topics for coatings, adhesives and sealants.

Now, 11 years later, we once more deal with this topic and analyze the current role of polyurethane chemistry for coatings, adhesives and sealants, taking the development within the past decade into account. Based on our findings we updated the book, added new technical developments, extended the global view and included increasingly important topics such as sustainability and digitalization. Additionally, we refreshed citations and reduced content in areas deemed to be less relevant as they had been eleven years ago.

Polyurethane chemistry appears to have become even more established in the last decade and has continued to develop. Some of the trends foreseen in the previous edition have come to fruition, e.g., the trend towards water-borne systems. Furthermore, new, even more specialized systems and application technologies have been developed. This widened the applications fields and pushed the performance of the PU technology even further. Examples include the first bio-based PU raw materials which are entering the market, new catalyst systems which have been developed, or the digital printing process as new application technology that makes its way into the market place. Due to the adaptability of polyurethanes, modern systems are able to address the more stringent market, legislation and sustainability demands of today, and it is anticipated that polyurethanes will be able to do this in the future. The enormous diversity and possible combinations of polyurethane raw materials result in an impressive breadth of properties enabling the development of specific, customized solutions. The potential of further development is by no means exhausted.

Although the book has been revised, we took care to maintain the original intent of providing a comprehensive overview that allows newcomers to the industry an understanding of the principles and the potential of the polyurethane chemistry in the applications of coatings, adhesives and sealants, as well as, give the experienced specialist the option to refresh their knowledge and inspire the interested reader to think about how new innovations in polyurethanes can solve the problems of the future. The book opens with an introduction to polyurethane chemistry and technology, followed by a discussion of the many different applications, their current significance and their future prospects. Like the first edition of the book, the second one was also created in a global team approach involving experts in their respective fields for each chapter including experts of the Covestro group of companies, as well as, partners from universities and institutes. We would like to thank all of them for their contribution and patience. The book would not have been possible without their commitment and dedication to the PU technology.

The following authors contributed to the respective chapters in alphabetical order:

Most notably we like to thank James W. Rawlins, Wolfgang Fischer and Michael Hilt for their contribution in the respective chapters and Piet Driest, Christoph Eggert, Veronika Eilermann, Lennart Gehrenkemper, Silke Köster, Birgit Schäfer, Tina Stockhausen as well as Jan Sütterlin for their support in managing diverse challenges with regard to the writing of the book.

Leverkusen, Germany, January 2019

Ulrich Meier-Westhues

Karsten Danielmeier

Peter Kruppa

Edward P. Squiller

Contents

1 Introduction

1.1 Historical aspects

1.2 Definition of scope

1.3 References

2 Economic aspects and market analysis

2.1 Introduction and definitions

2.2 Coatings

2.2.1 Fields of application

2.2.2 Chemistries and regions

2.2.3 Market forecasts

2.3 Adhesives and sealants

2.3.1 Fields of application

2.3.2 Chemistries and regions

2.3.3 Market forecasts

3 Chemical principles

3.1 Diisocyanates

3.2 Isocyanate reactions

3.3 Polyisocyanates

3.3.1 Derivatization

3.3.2 Monomer separation

3.4 Prepolymers

3.4.1 Water content of the raw materials

3.4.2 Stability of NCO prepolymers

3.5 Thermally activated polyurethane crosslinkers

3.6 Hydrophilically-modified polyisocyanates

3.7 Co-reactants for polyisocyanates

3.7.1 Solvent-borne polyacrylate polyols

3.7.2 Polyester polyols

3.7.3 Polyether polyols

3.7.4 Polycarbonate polyols

3.7.5 Polycaprolactone polyols

3.7.6 Solvent-based polyurethane polyols

3.7.7 Polyamines

3.8 Aqueous dispersions

3.8.1 Polyurethane dispersions

3.8.2 Polyacrylate dispersions

3.8.3 Hybrid polyurethane/polyacrylate dispersions

3.8.4 Polyester polyol dispersions

3.9 Urethane acrylates

3.9.1 Chemistry of urethane acrylates

4 Coating technology principles

4.1 Formulation basics of polyurethane coatings

4.1.1 Basics

4.1.2 Selection of polyurethane raw materials

4.2 Aspects of one- and two-component coating technology

4.2.1 Physical drying

4.2.2 Chemical curing

4.2.3 Air-drying coatings

4.2.4 Dual-cure technology

4.2.5 Silyl-modified polyurethanes

4.2.6 Application

4.2.7 Catalysis in polyurethane coatings

4.3 Solvent-borne and solvent-free systems

4.3.1 Classification

4.3.2 Applications

4.3.3 Quality characteristics of two component polyurethane coatings

4.4 Water-borne systems

4.4.1 Water-borne one-component polyurethane systems

4.4.2 Water-borne two-component polyurethane systems

4.5 Process technology

4.5.1 Processing of one-component polyurethane coatings

4.5.2 Processing of two-component polyurethane coatings

4.6 Crosslinking technologies based on the polyaddition reactions of polyisocyanates

4.7 Powder coatings

4.7.1 Overview of powder coating technology

4.7.2 Application methods

4.7.3 Application efficiency

4.7.4 Uses

4.7.5 Polyurethane powder coatings

4.7.6 Properties

4.7.7 Uses of polyurethane powder coatings

4.8 DirectCoatin”/DirectSkinning

4.8.1 Outlook

4.9 Digital printing as disruptive application technology for coatings and adhesives

4.10 Radiation curing

4.10.1 Technology and coating formulation

4.10.2 Binders for radiation curing

4.10.3 Urethane acrylates for UV (mono-cure) and electron beam curing applications

4.10.4 Water-borne UV-curing polyurethane coatings

4.10.5 Urethane acrylates for UV powder applications

4.10.6 Dual-cure technology

4.10.7 Outlook

5 Polyurethane Coatings

5.1 Wood coating

5.1.1 Industry needs: requirements of wood and furniture coatings

5.1.2 Urethane-modified oil and alkyd resin coatings

5.1.3 Two-component polyurethane coatings

5.1.4 Water-borne polyurethane coatings

5.1.5 Radiation-curing PU-based technologies

5.1.6 Outlook

5.2 Metal coating

5.2.1 General industrial coating

5.2.2 Coil coating

5.2.3 Can coating

5.2.4 Protective and marine coatings

5.2.5 Wire coating

5.3 Automotive OEM finishing

5.3.1 Automotive OEM finishing process

5.3.2 Cathodic electrodeposition coating

5.3.3 Seam sealing, underbody protection and sound insulation

5.3.4 Primer surfacer

5.3.5 Base coat and clear coat

5.3.6 Outlook

5.4 Automotive refinish and transportation coating

5.4.1 Automotive refinish

5.4.2 Transportation coating

5.4.3 Application and characteristic data of 2K PU coatings for automotive refinish and transportation coatings

5.4.4 Raw material selection for conventional solids automotive refinish and transportation coatings

5.4.5 Low emission polyurethane coatings

5.4.6 Radiation curing coatings

5.4.7 Outlook

5.5 Plastics coating

5.5.1 Market evaluation

5.5.2 Coating process

5.5.3 Raw material selection

5.5.4 Coating concepts for automotive add-on components

5.5.5 Soft-feel coatings

5.5.6 Industrial plastics coating

5.5.7 UV technology in plastics coating

5.5.8 In-mold coating

5.5.9 Polyurethane gelcoats

5.5.10 Outlook

5.6 Application on glass

5.6.1 Coatings for glass containers

5.6.2 Glass fiber sizing

5.7 Use on textiles and leather

5.7.1 Textile coating

5.7.2 Polyurethane synthetics and microporous coatings

5.7.3 Screen Printing

5.7.4 Micro-fiber dipping

5.7.5 Supported glove dipping

5.7.6 Leather coating

5.7.7 Outlook

5.8 Coating and finishing of paper and films

5.8.1 Papermaking

5.8.2 Paper coating

5.8.3 Production of decorative films for furniture and interior design

5.8.4 Finishing of technical papers and films

5.8.5 Outlook

5.9 Construction applications

5.9.1 Floor coatings

5.9.2 Architectural wall coatings

5.9.3 Waterproofing and Roofing

5.9.4 Outlook

5.10 Light-stable, thick film coatings

5.10.1 Spray-applied, aromatic polyurethane elastomeric coatings

5.10.2 Spray-applied, aliphatic polyurethane elastomeric coatings

5.10.3 Spray application technology

5.10.4 Outlook

6 Polyurethane adhesives

6.1 Introduction

6.2 Classification

6.3 Polyurethane reactive adhesives

6.3.1 Raw materials

6.3.2 Two-component polyurethane reactive adhesives

6.3.3 Moisture-curing one-component reactive adhesives

6.4 Solvent-borne adhesives based on hydroxyl polyurethanes

6.4.1 Hydroxyl polyurethanes

6.4.2 Isocyanate crosslinkers for solvent-borne adhesives

6.5 Water-borne polyurethane adhesives

6.5.1 Products

6.5.2 Formulation

6.5.3 Crosslinkers for water-borne polyurethane adhesives

6.5.4 Drying

6.5.5 The principle of heat-activated adhesive bonding

6.5.6 Applications and application technology

6.5.7 Latent reactive polyurethane dispersion adhesives

6.6 Hot melt adhesives

6.6.1 Non-reactive hydroxyl polyurethane hot melt adhesives

6.6.2 Reactive polyurethane hot melt adhesives

6.7 Outlook

7 Polyurethane sealants

7.1 Terms and definitions

7.2 Chemical structure

7.2.1 Polyisocyanate crosslinking systems

7.2.2 Silane-modified polymers

7.3 Formulation

7.3.1 NCO-reactive one-component polyurethane sealants

7.3.2 Silane-terminated polyurethanes

7.4 Processing

7.5 Outlook

8 New areas of application for polyurethanes

8.1 Polyurethanes for medical application

8.1.1 Polyurethanes for wound care

8.1.2 Polyurethane as latex substitute

8.1.3 Outlook

8.2 Polyurethanes in cosmetic applications

8.2.1 Hair styling

8.2.2 Skin care

8.2.3 Outlook

8.3 Polyurethanes for light guiding applications

8.3.1 Photopolymers

8.3.2 Polyurethane photopolymers

8.3.3 Manufacturing process

8.3.4 Holographic recording

9 From combinatorial chemistry to lab automation and data sciences

9.1 Introduction and history

9.2 Use cases in polyurethane coatings and adhesives

9.3 Data-driven coatings development

9.4 Outlook

10 Occupational hygiene in the manufacture and processing of PU systems

10.1 Occupational health and safety

10.1.1 Monomeric and polymeric isocyanates

10.1.2 Co-reactants for polyurethane hardeners

10.1.3 Processing of polyurethane coating, adhesive and sealant systems

10.1.4 Spill response, handling containers and waste disposal

10.2 Consumer protection aspects

10.2.1 Polyurethane coatings, adhesives and sealants – indoor air quality

10.2.2 Do-it-yourself and polyurethanes

10.2.3 Relevant legal provisions covering raw materials for coatings and adhesives in contact with foodstuffs

10.2.4 Polyurethane coatings and drinking water

10.2.5 Behavior of polyurethane coatings, adhesives and sealants in the event of fire

11 Sustainable development

11.1 The global context of sustainable development

11.2 Reducing the negative impact/fostering positive impact

11.3 Decoupling economic growth from linear use of resources

11.4 Sustainable development in the coating, adhesive and sealants industry

11.5 Outlook

12 Outlook

Authors

Index

1 Introduction

1.1 Historical aspects

Coating, bonding and sealing are techniques that humankind has used for many centuries. For a long time, only natural resins, oils and fats were used for these purposes.

Shellac, a natural resin secreted by the scaly lac insect, has been used in India as a weather-resistant coating for surfaces. The word lacquer in English is derived from the Sanskrit word laksha, which means one hundred thousand and describes the unimaginably large number of insects required to produce shellac lacquers. Later it was learned that lacquer resins could also be obtained from other sources, e.g. by boiling down wood oil.

Animal tissue, especially bones and hide, were the basis for glues and adhesives in many applications for a long time. The makers of high-quality glues were called Kellepsos in ancient Greece. During the Middle Ages development was largely static. The invention of the printing press by Johannes Gutenberg then led to a new and rapidly growing need for adhesives in the emerging bookbinding industry.

The development of synthetic resins began in the early 20th century driven by the oil industry and the emerging downstream industry with their related products. This laid the foundation for the production of coatings, adhesives and sealants of vastly improved quality and in volumes. Polyurethanes were discovered in 1937 when Heinrich Rinke produced 1,6-hexamethylene diisocyanate (HDI) and Otto Bayer developed the diisocyanate polyaddition process^[1–3]. Initial research in this new field of polymer chemistry in the 1940s focused on polyurethane fibers, while the first polyurethane foams were produced a little later.

Fifty years ago, the first polyurethane coatings were developed. Otto Bayer and his team discovered that the technical properties of alkyd resins could be improved through modification with diisocyanates. However, the real conquest of the coatings sector by polyurethanes only began with the development and industrial use of low-monomer polyisocyanates. The first products were based on toluene diisocyanate. Due to the aromatic nature of the base isocyanate, these tend to yellow on exposure to light and can therefore only be used for interior applications or in primers.

The range of applications was broadened later with the introduction of products based on aliphatic diisocyanates, initially hexamethylene diisocyanate. “Desmodur” N was the first product of this type and was launched in the early 1960s by Bayer AG. Gradually, the two-component (DD) coatings prepared by combining polyisocyanates (“Desmodur“) with polyols (“Desmophen”) replaced the traditional alkyd coatings, first in the coating of large vehicles. The driving force was the quality of the coatings which, even when dried under mild conditions, matched the performance of coatings which had been baked. This is important when coating large vehicles (airplanes, rail wagons and buses) as their size makes baking impossible.

In the 1970s, it was found that the quality of automotive refinish coatings could be substantially improved with the help of polyurethane chemistry. By adding polyisocyanates based on isophorone diisocyanate (IPDI) to the medium oil-based alkyd resins mainly used at that time, the hardness, overcoatability and gasoline resistance of the resulting coatings could be improved significantly. Today, two-component polyurethane coatings have almost completely replaced alkyd resin chemistry in this segment.

The broad range of applications for polyurethanes in coatings was quickly recognized. Other examples of applications include wood finishing, corrosion protection and construction, as well as textile coating. Another advance has been the development of two-component metering technology. The breakthrough in automotive OEM finishing occurred in the mid-1980s, and since this time, plastic coatings have become a further domain for polyurethanes.

Polyurethane adhesives came onto the market in the 1950s with the development of the hydroxyl polyurethanes and the first trifunctional isocyanate crosslinker, “Desmodur” R. The early 1960s also saw the development of plasticizer-resistant hydroxyl polyurethanes, which laid the foundation for the success of these products in shoe manufacture.

Solvent-free polyurethane reactive adhesives have been used since the 1970s, first in automotive production, and then in the manufacture of laminated films and sandwich elements. They were later joined by reactive sealants. Since the 1990s, polyurethane-based reactive and waterborne adhesives have gained significant market share in automotive, construction, furniture and shoe production.

The process of substituting traditional technologies in coatings, adhesives and sealants with polyurethane is ongoing, and can be observed occurring around the world. Against a background of increasingly demanding quality requirements, ever more stringent environmental legislation, and cost optimization of the end-product manufacturing processes, there has been growth in the use of low-solvent, solvent-free, waterborne and radiation-curing formulations of one- and two-component polyurethane systems^[5–9]. Bearing in mind current concomitant developments, polyurethanes will continue to gain further importance. Their spectrum of use will thus expand beyond the established applications into other new areas.

1.2 Definition of scope

This book describes the use of polyurethane raw materials for coatings, adhesives and sealants in selected application areas. Topics covered include applications in the wood and furniture industry, the automotive sector, construction, the broad area of metal coatings including corrosion protection, the shoe industry, and plastic coating and bonding. Also discussed are the manufacture of laminated films and the coating of textiles, leather, glass and paper. In addition to describing the chemical and technical principles involved, the issues of occupational hygiene and sustainability associated with the handling of polyurethane coatings, adhesives and sealants are covered. The broad spectrum of applications is evidence of one key property of polyurethanes: the versatility resulting from their chemistry which is also exploited in segments other than coatings, adhesives and sealants.

For example, polyurethane raw materials are used in the manufacture of foams: rigid foams for insulation (construction industry, refrigerators) or energy-absorbing components in automobile interiors (instrument panels); integral skin foams, e.g. for furniture and medical applications; flexible foams for upholstery, mattresses and packaging materials. Other applications for polyurethanes are found in the manufacture of versatile elastomers for the footwear and electrical industries, thermoplastic urethanes, e.g. for sports and leisure equipment, and polyurethane elastic fibers for stretch fabrics.

This book does not intend to address all these applications. Detailed information can be found in other sources^[10–12].

1.3 References

[1] DRP 728 981 (1937) I.G. Farben

[2] O. Bayer, Angew. Chem. 59 (1947) 257

[3] D. Dieterich, Chemie in unserer Zeit, 24 (1990) 135

[4] Archiv Bayer AG, Leverkusen

[5] Brock, Groteklaes, Mischke, European Coatings Handbook, 2nd editon (2010) Vincentz Network ISBN: 978-3-86630849-7

[6] Goldschmidt, Streitberger, BASF Handbook on Basics of Coating Technology, 3rd edition, BASF Coatings AG, Münster, Vincentz Network, Hannover, 2018, ISBN 978-3-86630-336-2

[7] W. Brockmann, P. L. Geiss, J. Klingen, B. Schroeder et al., Adhesive bonding: materials, applications and technology, Wiley-VCH, Weinheim 2009

[8] R. M. Evens, Polyurethane Sealants, CRS Press Inc. Lancaster 1993

[9] K. L. Mittal, A. Pizzi, Handbook of Sealant Technology, CRS Press 2009

[10] G. Avar, U. Meier-Westhues, H. Casselmann, D. Achten in K. Matjaszewski, M. Möller (eds.), Polymer Science: Vol 10, 411–441, Elsevier BV, 2012

[11] H.-W. Engels, H.-G. Pirkl, R. Albers, R. W. Albach, J. Krause, A. Hoffmann, H. Casselmann, J. Dormish, Angew. Chem., 125, 9596–9616, 2013

[12] G. Oertel, Polyurethane Handbook, Hanser Gardner Publications, 1994, ISBN-13: 978-156990-157-1

2 Economic aspects and market analysis

2.1 Introduction and definitions

When looking at the economic importance of coatings, adhesives, and sealants, there is a significant market of formulated products with 64 million tons or 170 billion € globally in 2017 (see Figure 2.1). The formulated product always describes the ready to use material as it will be applied to the end product – being it a wall, car or industrial good. The formulated product contains the so called resin, binder or film forming component and further additives, pigments, fillers and organic solvents or water. This market is split roughly 75:25 for coatings versus adhesives and sealants with 49 versus 15 million tons of material (see Figure 2.1).

With regard to the resin within the formulated product, several market studies and also the authors of this book refer to the resin supply form. This includes not only the monomeric, oligomeric or polymeric resin material itself, but also a certain share of organic solvent or water that is usually included in the commercially available products.

Other market data sources use the term of dry resin to describe only the active resin material without any solvents that will eventually evaporate in the final film forming process during application of the formulated product.

Within this book the term polyurethane (PU) chemistry is used to describe markets, which comprise all resin materials that are crosslinked by urethane or urea groups. In addition, the term also covers all materials that are indirectly based on isocyanates or the reaction products thereof. This means, that the isocyanate is not necessarily reacted in the last crosslinking step, but might be used as a precursor (see Chapter 3). In general, polyurethane resins consist of aliphatic polyisocyanates, aromatic polyisocyanates, prepolymers, polyurethane dispersions (PUDs), polyols and specific diamines.

Based on these definitions, polyurethane based resins have a market size of 2.4 million tons or 6.7 billion €. This represents a 12 % share of the overall resins market in supply form. Therefore, polyurethane chemistry is usually recognized as a specialty market where the final application demands for increased performance, e.g. durability or quality of appearance.^[1]

2.2 Coatings

The world consumption of coatings for industrial and architectural applications (i.e. the total production of formulated coating products sold) amounted to 49,000 kilotons in 2017 (see Figure 2.2). This represented global consumption of 16 million tons of coating resins in supply form, corresponding to a value of 44 billion €. Polyurethane resins account for 1.6 million tons representing roughly 10 % of the overall resins market in supply form.^[2]

2.2.1 Fields of application

There are two general fields of application for coatings in the world: The architectural applications account for approximately 66 % by volume, including dispersions for architectural coatings, whereas the general industrial coatings make up approximately 34 % (see Figure 2.3).

The architectural market is dominated by interior wall applications, i.e. wall emulsions/dispersions with 51 %. This segment is followed by exterior wall coatings with 24 %. After wood coatings with 15 %, floor coatings (8 %) and roof coatings (2 %) hold the smallest share (see Figure 2.3). Within this market, polyurethane technology only holds a very small share and thus the architectural applications are not further considered within this book with regard to market data.

The industrial market accounts for 34 % of the coating market and can be divided into seven different fields (see Figure 2.4, see page 25) with the largest, named metal, representing roughly 40 % of the market share. This application is followed by protective and marine with 22 %. Industrial wood and automotive account for 14 % and 13 %, respectively. They are followed by agricultural, construction, earthmoving equipment (ACE) and plastics with 4 % each. The smallest segment is transportation with 3 %.^[4] Other markets include textile, leather, glass and paper coating. The market size for textile and leather coating sums up to approximately 5,100 kilotons of resins in supply form, of which 50 % is based on polyurethane technology.^[5] This market is not reflected in the following graphs but will be discussed in detail in the respective chapter.

The weighting is different if one compares polyurethane coatings to the total formulated industrial coatings market (i.e. the sum of all coatings types) in terms of share of technologies (see Table 2.1): Industrial wood, automotive, plastics, and ACE have a higher or even significantly higher market share in the polyurethane market compared to the total formulated industrial coatings market. This clearly shows that high-quality polyurethane resins are preferred for applications with more demanding requirements in terms of quality and durability – and these are found accordingly in a higher price segment.

2.2.2 Chemistries and regions

The world consumption for industrial coatings is distributed unequally (see Figure 2.5). More than half of the industrial coating demand is consumed in the Asia-Pacific (APAC) region, while slightly more than one quarter is used in EMEA, namely Europe (21 %) and the Middle East and Africa (4 %), and just under one quarter is going to the Americas (NAFTA and LATAM) with 23 %. It should be emphasized here that APAC’s share of global industrial coatings consumption has grown in the last five years (2012 to 2017) to more than 50 % and is expected to continue to rise.

The volume of formulated solvent-borne coating products summed up to 65 % over all technology classes (see Figure 2.6), whereas water-borne coatings, including electrocoats for cathodic electrodeposition (CED), make up 17 % of the formulated coatings market. The remaining share is distributed among powder coatings (14 %), UV coatings (3 %), and others (1 %).

The volume distribution by chemistry type shows that the traditional systems, such as alkyd resins, acrylics, and polyesters, including others, are still of great importance (see Figure 2.7). In 2017, these product groups accounted for just over 51 % of world consumption. Polyurethane coatings have a market share of 20 %.

The main components of polyurethane coating resins are polyisocyanates, polyurethane dispersions, and other polyurethane materials, such as prepolymers and polyols based on polyacrylates, polyesters, polyethers as well as specific diamines. The 1.6 million tons of polyurethane coating resins used worldwide are distributed as shown in Table 2.2 (see page 26):

The key isocyanates used in coatings resins are polyisocyanates, prepolymers and further derivatives. Aliphatic materials are based on hexamethylene diisocyanate (HDI), isophorone diisocyanate (IPDI) or dicyclohexylmethane diisocyanate (H₁₂MDI). Aromatic isocyanates are based on toluene diisocyanate (TDI) or diphenylmethane diisocyanate (MDI).

2.2.3 Market forecasts

For the coming years (2017 to 2021), annual market growth of 3.1 % is forecasted for formulated industrial coatings, which represents a higher growth rate than the 2.1 % observed from 2012 to 2017. It is expected that growth in APAC will be above global average at 4.1 %, whereas the European and American markets are expected to grow at around 1.8 % and 2.1 % respectively.

The market growth of formulated industrial coatings for different coating technologies reveals that water-borne coatings and electrocoats grew above regional market average in the past five years (2012 to 2017). This trend is expected to continue for APAC and Americas. For Europe, electrocoats should continue to grow above average, while water-borne coatings will grow at average market rates.

Polyurethanes are expected to experience an increasing annual growth of approximately 2.7 % in the upcoming years (2017 to 2021) compared to the past (2012 to 2017), which grew at 2.2 %. This is driven by APAC and Middle East and Africa with roughly 4 % annual growth. For polyurethanes, the market growth was driven by different technologies, depending on the region. Most of the growth was accounted for by solvent-borne and powder coatings in APAC, while in Europe water-borne and UV coatings posted stronger growth. In the Americas, UV and solvent-borne coatings grew above average.^[4]

2.3 Adhesives and sealants

In 2007, the world adhesives and sealants industry had a volume of approximately 11.8 million tons and was worth some 30 billion €.^[8] After a decrease of about 4 % during the financial crisis in 2008/2009 and the subsequent economic recovery in the following years the volume and value growth in this industry sector averaged around 3 %. In 2017, world demand of formulated adhesives and sealants reached approximately 15 million tons, which according to the latest estimates represent a value of approximately 40 billion € (see Figure 2.8).^[9] This total volume of formulated adhesives and sealants corresponds to a global consumption of approximately 3.8 million tons of resins in supply form in 2017. The total world market of all polyurethane resins in supply form for adhesives and sealants amounts to approximately 800,000 tons.^[10]

2.3.1 Fields of application

The main field of application for adhesives and sealants is the packaging segment (approximately 37 %), followed by the construction industry (24 %), assembly (13 %), woodworking (10 %) and transportation (8 %). Consumer/do-it-yourself (DIY) applications and footwear have a share of 5 % and 3 % respectively (see Figure 2.9).

Considering the polyurethane-based adhesives and sealants, a slightly different picture is observed. Of the total market of approximately 1.4 million tons, around 30 % is attributed to the packaging segment, 19 % to construction, 16 % to transportation and 11 % to footwear. In these market segments, polyurethane-based adhesives and sealants are typically preferred for applications with more demanding requirements in terms of quality and durability.^[12]

2.3.2 Chemistries and regions

The regional distribution of adhesives and sealants consumption is fairly balanced between Europe, Middle East and Africa (EMEA), Americas (North and South), and the Asia-Pacific region (APAC), each accounting for approximately one third of the total market volume (see Figure 2.10). APAC in particular has seen above-average growth in recent years, and this is expected to continue in the upcoming years.

Breaking down the adhesives and sealants market into the underlying material classes shows the broad range of applied chemistries. In addition to the polyurethane-based materials, natural products and a multitude of polymer materials can be used to formulate adhesives and sealants systems (see Figure 2.11).

In recent years, however, the more complex application profiles in adhesives and sealants processes have led to a growing demand for high-quality systems. In particular, polyurethane systems are benefiting due to their outstanding property profile compared with other materials.

Overall the adhesives market is dominated by water-borne systems due to large applications in construction and packaging (see Figure 2.12). Solvent-borne adhesives are still traditionally used in some applications with a volume market share of 14 %. New systems of water-borne materials and formulations have been developed to ensure compliance with VOC (volatile organic compounds) workplace guidelines.

The main components of polyurethane resins for adhesives and sealants are isocyanates, polyisocyanates and prepolymers as well as polyols such as polyesters or polyethers. The most important isocyanates, polyisocyanates and prepolymers for adhesives and sealants resins are based on the aromatic diphenylmethane diisocyanate (MDI) and toluene diisocyanate (TDI), as well as on the aliphatic hexamethylene diisocyanate (HDI), isophorone diisocyanate (IPDI), dicyclohexylmethane diisocyanate (H₁₂MDI), and the corresponding derivatives of these diisocyanates.

Polyesters may have an aliphatic, aromatic or mixed (araliphatic) structure, vary in chain length, and exhibit amorphous or crystalline properties. Polyethers can be varied to yield the desired property profile through the choice of starter or chain-building monomers.

2.3.3 Market forecasts

In the upcoming years (2017 to 2021) the global market for adhesives and sealants resins in supply form is expected to grow at least 4.0 % per year compared to a global growth rate of 3.5 % in the past five years (2012 to 2017). In the APAC region growth is expected to be above global average at up to 4.9 %, whereas Europe and American markets are forecasted at 3.7 % and 3.9 %, respectively.^[9] Polyurethane materials in general are expected to grow at least with the market. Here, besides the construction area, converting and packaging as well as footwear will be the main growth drivers.^[12]

2.4 References

[1] “Irfab” Global Industrial Coatings Markets (GICM) and Global Architectural Coatings Market (GACM) 2015, 2017, 2018 PRA World Ltd, CHEM Research 2018, Orr & Boss 2017, Covestro assumptions

[2] “Irfab” Global Industrial Coatings Markets (GICM) and Global Architectural Coatings Market (GACM) 2015, 2017, 2018 PRA World Ltd, Orr & Boss 2017, and Covestro assumptions

[3] “Irfab” Global Industrial Coatings Markets (GICM) and Global Architectural Coatings Market (GACM) 2015, 2017, 2018 PRA World Ltd

[4] “Irfab” Global Industrial Coatings Markets (GICM) 2017, 2018 PRA World Ltd.

[5] Covestro estimate 2018

[6] “Irfab” Global Industrial Coatings Markets (GICM) 2017, 2018 PRA World Ltd. and Covestro assumptions

[7] Orr & Boss 2017

[8] CHEM Research, Market Review – FEICA Conference Izmir Sept. 13, 2013 and Covestro assumptions

[9] CHEM Research 2018

[10] Orr & Boss 2017. CHEM Research estimates the market to be up to 5.5 million tons of resin in supply form

[11] CHEM Research 2018, Orr & Boss 2017 and Covestro assumptions

[12] Orr & Boss 2017 and Covestro assumptions