E-Book, Englisch, 396 Seiten, Format (B × H): 160 mm x 230 mm, Gewicht: 918 g
ISBN: 978-3-7486-0484-6
Verlag: Vincentz Network
Format: EPUB
Kopierschutz: Kein
With the slow change from solvent-borne resins and coatings to water-borne coatings "Resins for waterborne coatings" is a must-read for any formulator wanting to expand their knowledge.
The authors discuss important aspects of the "solvent-to-water-transition" of the past 40 to 50 years, take a deep dive into the key aspects and theories behind the production, properties and applications of these resins as well as providing an overview of how they are currently used in water-borne coatings.
Autoren/Hrsg.
Weitere Infos & Material
2Water-borne resins and coatings: history, markets and definitions
Jaap Akkerman and Dirk Mestach This chapter deals with the history of water-borne resins and its coatings. In order to understand water-borne resins that are used in the water-borne coating formulations, not only the history is important, but also the markets and application areas in these markets. In order to use the same language, the definitions used in Europe and the deviating ones used elsewhere are discussed. 2.1History of water-borne coatings
and resins
2.1.1The past
Paint made its earliest appearance about 40,000 years ago. It was one of the earliest inventions of mankind as it truly can be traced to the dawn of history, to artefacts from pre-historic humans, and all cultures. Tribes in Europe, Australia, and Indonesia painted images of hunters and herders on cave walls and had expanded their colour palette to include many colours. Some cave paintings drawn with red or yellow ochre, hematite, manganese oxide, and charcoal were made by early Homo sapiens as long as 40,000 years ago [1]. They used eggs, blood, milk or tree sap as “resins” in order to improve the adhesion and durability. Water was the only solvent available at that time. They then applied the paint with fingers, brushes, or by blowing them through hollow bones, very much like today’s airbrushes. Ancient coloured walls at Dendera, one of the best-preserved temple complexes in Egypt, which were exposed for years to the elements, still possess their brilliant colour, as vivid as when they were painted more than 2,300 years ago. The Egyptians mixed their colours with a binding substance, such as casein, egg whites, bees wax and vegetable gums such as Gum Arabic, the hardened sap of various species of the acacia tree and applied them separately from each other without any blending or mixing them. They appear to have used only six basic colours: white, black, blue, red, yellow, and green. First the area was covered entirely with white, then the design was traced in black, leaving out the lights of the ground colour. The Egyptians continued the advancements and began painting on fresh lime plaster, where the pigments became fixed by carbonization and drying of the lime. Greeks and Romans expanded upon these techniques, to create a painting style not matched till the Renaissance – when Italian artists made paint with plant oils to create works of astonishing colour and depth that still captivate viewers today. The Greeks also developed lead white paint, which was the most popular white paint in use until titanium dioxide replaced it in the nineteenth century. White lead is the basic lead carbonate, 2PbCO3·Pb(OH)2 [2] and occurs naturally as a mineral. Lead-based paint has been the source of health issues for painters and others for centuries. Before the industrial revolution “whitewash” also known as calcimine, kalsomine, calsomine, or just lime paint, a type of paint made from slaked lime (calcium hydroxide, Ca(OH)2 or chalk calcium carbonate, (CaCO3), was one of the main paint types used. Whitewash cures through a reaction with carbon dioxide in the atmosphere to form calcium carbonate in the form of calcite, a reaction known as carbonization. It was usually used for exterior applications, however, it has been also applied for interior applications, for example in kitchens. Whitewash could be tinted for decorative use however it can rub off to a small degree [3]. Various materials were added to the lime to improve the quality of the coating. Portland cement was added to improve the durability in harsh environments. Casein, a protein extracted from milk, was added to improve adhesion and durability. Actually, the origins of modern water-borne paints begin with these casein paints. At the onset of the industrial revolution, in the mid-18th century, paint was being ground in steam-powered mills, and an alternative to lead-based pigments had been found in a white derivative of zinc oxide. Interior house painting increasingly became the norm as the 19th century progressed, both for decorative reasons and because the paint was effective in preventing the walls being affected by moisture. Linseed oil was also increasingly used as an inexpensive “resin”. The paint and coatings industry, however, had to wait for the industrial revolution before it became a recognized element of the economy. The first US paint patent dating from 1865 to Flinn (US 50,068), covers a composition based on zinc oxide, potassium hydroxide, resin, milk and linseed oil. In 1867, Averill of Ohio patented the first prepared or “ready mixed” paints in the United States. In the mid-1880s, paint factories began springing up in populated and industrial centres across the nation. In 1866, Sherwin-Williams in the United States started as a large paint-maker and invented a paint that could be used directly from the tin without additional preparation. The casein paints were continually improved. By the 1930s they contained pigments with a high refractive index (high covering power), similar to those used in oil paints. The casein paints were traded as a powder or in the form of a paste. In order to trade the paste form, it was necessary to protect the paint against hydrolysis and infestation by micro-organisms. A major advantage of casein binders was their low cost. The paints were easy to apply and provided covering in one layer. A disadvantage of the casein paints was, that they are porous and therefore easily fouled. Adding drying oils resulted in a more compact film and improved durability as well. A drawback was that the drying process became slower. When the amount of oil in the paint was increased, the casein paint evolved into an “emulsion paint”. In the 1920s, however, alkyd resins were first developed [4] [5]. In many cases, the drying oil was partially or completely replaced by an alkyd to accelerate the drying of the paint film. The role of the casein in the paint shifted from “resin” to emulsion stabilizer and thickener. The drying oil and the alkyd became the real binders. 2.1.2The present: from polymer science to resins
The development of modern paint is closely associated with the event of polymer science. However, as early as the 1830s people like Braconnot and Schönbein developed derivatives of the natural polymer cellulose such as celluloid and cellulose acetate. In 1844, Goodyear, amongst others, discovered that adding sulphur to natural rubber, polyisoprene, transformed the material from a flexible, non-sticky material to a hard solid (“ebonite”) [6], depending on the amount of sulphur used. In 1907 Baekeland invented the first synthetic polymers: phenol-formaldehyde condensation resins called Bakelite [7] and Novolac [8]. Despite advances made, the molecular nature of polymers was not well understood until the work of Staudinger in 1922[9]. He was the first to propose that polymers consisted of long chains of atoms held together by covalent linkages. He presented this at a meeting of the Swiss Chemical Society, coining the term “macro-molecules” [10]. He was awarded the Nobel Prize for this in 1953. Meanwhile, also the very first inventions were made that would eventually lead to the development of water-borne paints. In 1912 Gottlob patented the dispersion polymerization of isoprene (German patents 254 & 255), using egg albumin or starch as emulsifier. Polyvinyl acetate was patented by Klatte and Rollet in Germany in 1914. Rather than using naturally occurring stabilizers, the first synthetic surfactants developed in Germany during World War I(WWI) were used. These were short-chain alkyl naphthalene sulfonates, similar to the materials are still used today. It was not until the end of the World War I, when a lot of paint raw materials such as linseed oil were in short supply, that artificial resins became available on the market. In 1920 Kienle of General Electric develops unsaturated alkyds [11] that were commercialized under the name “Glyptal” resins (from glycerol phthalate). A patent is applied for, but the patent is ruled invalid in 1935 due to existing prior art, which enables other companies to produce and sell alkyds (after 1935). Kienle was probably responsible for the combination of the word alkyd – from the condensation of alcohols and acids. Alkyd modified oil paints and then alkyd paints were eventually used on cars and household appliances. In 1929 Carothers (DuPont) publishes papers on linear polyesters [12], He is generally credited with formalizing the concept of functionality, although Kienle had almost certainly been thinking along the same lines. By 1930 Flory [13] starts work on molecular weight distributions (experimentally and theoretically) and shows that step-growth polymerizations follow the Gaussian distribution for molecular weight. In the years leading up to the second World War, a range of additional synthetic resins was appearing. In 1933 Schlak patents the first epoxy resins: diglycidyl ethers made from epichlorhydrin...
