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Metal Coatings Trends and Innovations

SpecialChem | Ben Leeuwen - Sep 12, 2011

Anti Microbial (AM) Coatings
Self-stratifying Coatings Provide Better Corrosion Protection
Anti Corrosive Pigments
Cradle to Cradle®
Take Back Program
Self-Crosslinking Acrylic-modified Emulsions
Polyaspartic Coating Technology

Anti Microbial (AM) Coatings

Antimicrobial coatings are being used on a generous scale, in many ranges of application, varying from anti-fouling paints, coatings used in hospitals and on medical equipment, to algaecidal and fungicidal coatings in and around the house. Until now, coatings with added toxins are being used for these purposes. A growing problem in our world is that on the one hand, for reasons of health and environment, more and more biocides are being prohibited, while on the other hand bacteria are becoming more resistant. Good example is the growing problems with a.o. MRSA bacteria in hospitals.

With the technology which has been developed by AM Coatings, anti-microbial coatings (i.e. paints with anti-bacterial, anti-algae and/or anti-fungal effects) can be produced without the use of recently used "slow release biocides" (toxics).

The AM coating technology operates completely differently: not chemical or toxic, but mechanical. By using a double polymerization process, an anti-microbial binding agent (medium, the main ingredient of any coating) is fabricated. This binding agent has a very special property, creating a kind of "nanotechnological barbwire" surface, during the curing process. When a microbe (or any micro-organism) gets in touch with this surface, its cell wall will be punctured like a balloon, so the microbe will die.

By analogy with a mouse trap, instead of a mouse poison, the AM Technology works like a kind of microbe trap on a nano scale. Apart from being completely safe for man and environment, this mechanical action has another big advantage: microbes will not become resistant to this kind of control; a phenomenon which appears to become a growing problem, for instance with the notorious MRSA infection in hospitals.

Self-stratifying Coatings Provide Better Corrosion Protection

Paint applied as a single layer and its spontaneous separation to form a primer and a top coat is one of the newest concepts of effective and economical application of two layers in one step. Ewa Langer from the Institute for Polymer Engineering and Dyes, Poland, has investigated the influence of decorative and anti-corrosive pigments on the distribution and protective properties of self-stratifying epoxy/acrylic coating systems. The results of investigations of self-stratifying coatings in a salt spray chamber prove that such systems have comparable or even better corrosion protection properties compared to classical two-layered systems containing the same resins and pigments. The best adhesion to substrate, interlayer cohesion and pigment distribution was obtained in systems containing micaceous iron oxide as anticorrosive pigment. Ewa Langer will talk about self-stratifying coatings at the European Coatings Conference "Anti-corrosive coatings" on the 7th September in Berlin, Germany.

Anti Corrosive Pigments

The future trend in anti corrosive pigments is to obtain chromate free and heavy metal free pigments and to go in the direction of sub-micron and nanotechnology anti corrosive pigments and smart coatings with corrosion-sensing. This type of smart coatings do contain microcapsules containing pH indicator or corrosion inhibitor or/and self healing agents. The shell of the microcapsule breaks down under basic pH conditions. The pH indicator changes color and is released from the microcapsule together with corrosion inhibitor and / or self healing agents.

The future is 'green technology' and also the different government bodies already give direction in the following directives:

  • OSHA PEL proposed 5 µg/m3 for Cr6+ in workplaces Feb 27, 2006.
  • OSHA ordered to promulgate new PEL. (aerospace PEL now 20 µg/m3)
  • EU Directive 2000/53/EC - End-of-Life Vehicle: Cr6+, Pb, Cd, Hg banned from vehicles marketed after July 1, 2003
  • California Air Resources Board (CARB) approved an Airborne Toxic Control Measure (ATCM) for Emissions of Cr6+and Cd from Motor Vehicle and Mobile Equipment Coatings (Automotive Coatings) September 21, 2001.
  • Anti corrosive pigments which do confirm these regulations are e.g.: Calcium Phosphate; Calcium Borosilicate; Calcium silicagel; Magnesium Phosphate.

    Cradle to Cradle®

    Cradle to Cradle® becomes more and more also an issue for the paint industry and the paint industry has to be aware of their responsibility for now and in the future for our planet. Cradle to Cradle® design is about creating continuous cycles of both biological and technical 'nutrients'. This means that products are made from pure components that are easy to disassemble, in order to create new products (= up cycling) in both the biological and technical cycles. They will have been produced using manufacturing processes which rely on renewable energy, and which seek to conserve water, and to embrace social responsibility. Customers have to be sure that products are made from environmentally friendly pure materials that are good for human health and are designed so that at the end of their useful lives, they can be biologically or technically recycled.

    The ideal environmental coating should not only perform well during its service life, but should be readily removed, recycled or otherwise degraded at the end of it. In general, paints cannot be separated from their substrates and the emphasis must be on ensuring that they do not interfere with recycling or reuse of the substrate.

    Take Back Program

    Within the Cradle to Cradle® concept, it is vital that every part of products is completely integrated into a technical or biological cycle.

    Under a Cradle to Cradle® commitment, a Take Back Program has to be active, where over complete stocks are collected, thus ensuring that it can be properly reprocessed.

    Every year, millions of liters of paints are thrown away due to over complete stocks. In order to promote this and be able to achieve a complete Cradle to Cradle® production process, a Take Back program has to be developed.

    Together with various partners, an international collection of over complete paints has to be organized. As an innovative and responsible paint manufacturer, a creative closed cycle has to be set up. This can be done by using pure materials which are safe for people and the planet and new production methods, as well as by collecting over complete paints. Participating parties receive a Take Back certificate as a guarantee that the material was recycled according to Cradle to Cradle® principles.

    Self-Crosslinking Acrylic-modified Emulsions

    Many emulsion producers do develop self-crosslinking acrylic-modified emulsions to get a step closer to the replacement of solvent based systems. Nowadays products are available for anti-corrosive primers for metal coatings with excellent anti-corrosive properties. Protection, offering high performance corrosion protection as well as being environmental friendly with lower solvent demand.

    The biggest challenge within the industrial metal coatings industry today is providing environmentally sustainable products which offer the right balance between coating properties and performance.

    A variety of technologies have been developed over the years in order to cope with the diversity of demands. Use of one technology over another is usually due to a number of factors like regional markets, existing application systems, substrate choice and environmental pressures. The previous has led to the EEC VOC legislation directive which has become one of the major driving forces behind the conversion to water-based from solvent-based systems. This, together with health, environmental and safety concerns including the risk of fires and the reduction in manufacturers' insurance costs, is continuing to push the conversion further.

    Polyaspartic Coating Technology

    The chemistry is based on the reaction of an aliphatic polyisocyanate and a polyaspartic ester, which is an aliphatic diamine. This technology was initially used in conventional two-component polyurethane solvent-borne coating formulations because the polyaspartic esters are excellent reactive diluents for high solids polyurethane coatings.

    More recent developments in polyaspartic coating technology have concentrated on achieving low or near-zero VOC coatings where the polyaspartic ester is the main component of the co-reactant for reaction with a polyisocyanate. The unique and adjustable reactivity of the polyaspartic esters allows for the design of fast-curing coatings tailored to the needs of the application. The fast curing feature of these coatings can provide significant, money-saving productivity improvements, along with high-build, low-temperature curing, and abrasion and corrosion resistance.

    The name polyaspartics has recently become popular among formulators in the industry due to the need to differentiate it from polyureas and polyurethanes. By definition, a polyaspartic is an aliphatic polyurea because it is the reaction of an aliphatic polyisocyanate with a polyaspartic ester - which is an aliphatic diamine. However, polyaspartic coatings are very different in both application and coating performance properties from conventional polyureas. For example, polyaspartics allow the formulator to control the rate of reaction and cure, thus, potlife of the two-component mixture can range from five minutes to two hours. While spray application techniques include the use of plural component spray equipment, many applications can be applied with conventional sprayers, making application much less complicated and less prone to error.

    Polyaspartic technology is closer in its applications and performance characteristics to 2-component aliphatic polyurethane coatings. It is often used as a topcoat due to its non-yellowing nature. But, here too, there are noteworthy differences. The polyaspartic coatings, for example, can be formulated to very high solids (70-100% solids) and applied at higher film builds (up to 15 mils WFT in a single coat) than typical two-component aliphatic polyurethanes. Because polyaspartics are much faster drying than typical aliphatic polyurethanes, they are often used in applications where fast cure means improved productivity in the painting operation.










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