Лако-красочные материалы — производство

The earliest known use of paints dates back to the prehistoric era. Humans, by nature, have a sense of aesthetics and there is con­siderable evidence of human beings using some type of paint for decoration of their dwellings or their bodies. The Greek and Roman civilizations (from ~ 4000 BC) used paints to decorate buildings, statues and other objects. These paints were composed of a variety of natural gums, hide glue, starches, beeswax, charcoal and various clays and minerals. Jumping forward in time, it was around 1000 AD when Rodgerus von Helmershausen, also known as Theophilus, first described coatings and gave detailed recommendations for formu­las in his book Schedula Diversarium Artium. These coatings were primarily based on linseed oil and natural resins (amber), without use of any volatiles due to their unavailability. The art of extracting turpentine oil from plants became known around the 10th century, and it is believed that turpentine was first used as a solvent for red­ucing the viscosity of coating compositions in the early 15th century. This is an important landmark in the history of coatings because on one hand, use of a volatile solvent expanded coating applications rapidly, while on the other hand, it can be considered the beginning of the era of environmental problems due to solvent emissions that the industry is struggling hard to address even today. The develop­ment of coatings by what was known as the paint boiling process (as it required heating natural resin and linseed oil for a long time) continued, and by the 17th century, the art of making different types of coatings using different combinations of natural resins, linseed oil and volatiles was available.

The Industrial Revolution in the 18th century brought about a dra­matic change in coating demand. An increasing number of coatings were now required for protection of iron, which was used in buil­dings and other products. This was the time when coating materials started slowly moving from their role of decoration to protection. Even in the 19th century, with the exception of a few pigments, the raw materials for coatings were all of natural origin. After heavily exploiting petroleum-based synthetic raw materials for more than a century, it is interesting that one of the major initiatives of the coating industry today in the early 21st century, for sustainability reasons, is to go back to natural-based raw materials.

Introduction of the continuous production line by Henry Ford in the early 20th century represented the industrial-scale painting tech­nology, which required quicker drying and more durable coatings and faster coating processes. This led to the development of quick­drying cellulose-based paints and replacement of brush-application processes by spray processes. After the launch of the first entirely synthetic resin — phenol-formaldehyde — in 1907, rapid develop­ment of other synthetic polymers such as vinyl resins, urea resins, alkyds, acrylic resins, polyurethanes, melamine resins and epoxy resins, especially during and after World War II, made available a wide range of binder for coatings. It was in 1919 when titanium dioxide, the key raw material for coatings even today, was commer­cially available for the first time. Many synthetic pigments, both organic and inorganic types, were also commercialized during this time.

With continued industrialization and demand for coatings for a myriad of applications, the industry witnessed a steady increase in demand. It should, however, be noted that up until mid-20th century, all coating materials were almost entirely of the solventbased type. Prior to 1960, there were hardly any regulations that restricted the use of toxic substances or volatile organic compounds (VOCs) in coatings. The increased usage of such coating materials, with high VOC content, resulted in high emissions, and consequently, their harmful effects on safety, health and the environment were reco­gnized. These concerns generated a need for regulation of paints and coatings.

Rising concerns for safety, health and the environment and esta­blishment of agencies and regulations across developed nations heralded a new era for the paint and coating industry. Toxic mate­rials such as lead and chrome were restricted and limits on use of VOCs for paints and coatings were established during the 1960s and later. These limits became increasingly stringent over the years and required coating formulators to think of new ways to offer coatings that satisfied customers’ needs while meeting the needs of regula­tory requirements and cost. To address the issues of VOC reduction, three important approaches emerged:

• high-solid coatings, which are essentially solvent-based systems but formulated using a reduced amount of solvent (made possible by using low-viscosity binders),

• waterborne coatings, by replacing the majority of the solvents (VOCs) with water, and

• powder coatings, by eliminating volatiles and offering coatings in fine powder form.

These approaches required entirely new types of coating raw mate­rials to meet their formulation, application, cure and performance requirements. They also required new crosslinking technologies that provided faster curing. For instance, ultraviolet (UV) radiation curable technology was developed that offered very short curing times to formulations that are ~100 % solid. All the above-mentioned approaches developed into the full-fledged coating technologies of today. Due to highly diverse product offerings based on these technologies, combined with increasingly demanding requirements both by customers and regulators, has resulted in an ever-widening palette of coating raw materials.

Today’s coating raw materials are comprised of a range of organic, inorganic and special-effect pigments, offered both in dry form as well as dispersions in water. Resins and binders are offered as tradi­tional solutions in organic solvents, or as advanced aqueous disper­sions with a variety of particle sizes and morphologies. The above development has also resulted in the availability of a wide range of additives specific for waterbased, powder, or UV-cure coatings for optimum performance.

As with many other fields of material technology, use of nanomate­rials in formulations of advanced paints and coatings has been very promising. Nanoparticle size pigments and fillers, nanopolymer dispersions, and nanoadditives are now commercially available and many more such products are in the development stage. Another important challenge for the coating raw material industry in recent years has been to offer “green” raw materials that reduce the envi­ronmental footprint of coatings. With increasing awareness and consumer interest for using bio-based and greener raw materials, researchers and industries are trying to provide such raw materi­als at affordable costs without compromising their performance. The outlook for future coating raw materials seems to be highly advanced, multifunctional, and with a significantly lower carbon footprint, and hence more sustainable.