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The Coatings ExpertISSUE 4 | MARCH 2018
CAPACITY EXPANSION FOR SPECIALTY COPOLYESTERSin Witten (Germany) starts upPage 6
WATERBORNE EPOXY CURING AGENTS AND RESIN DISPERSIONS Page 10
DURABLE YET FLEXIBLE SOLUTIONS for coating metal objects in multilayer structures Page 12
A cloak of invisibility for ships
Evonik already has effective solutions for antifouling coatings in its portfolio.
The Group’s researchers are now working on new raw materials for coatings for effective protection of ship hulls against biofouling that use fewer biocides, or even dispense with these altogether.
shutterstock/John de la Basti
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The Coatings Expert | Issue 4 | March 2018
Editorial
Dear Readers,
New market trends, the shift to digital technologies, and increasing demands on products and applications – We are constantly facing up to the ambitious new challenges which are demanded by the coatings market and which we, as Evonik, gladly accept.
We have the knowledge! Innovative and effective solutions are in the foreground for us.
Issues such as durability and flexibility in the coating of metal objects, preserving resources, long lasting protection against biological growth and new binders for heat seal applications are just a few things to mention.
Our self-image includes making the resulting investments in the expansion of production and capacity in order to support further growth in the market.
We offer numerous solutions for new silicone resins with excellent weathering resistance, additional adhesion in can coatings with TEGO® AddBond LTW, VISIOMER® Methacrylates for cross-linking solutions and Direct-to-Metal (DTM) coatings for metals.
In this issue you will learn more about these and many other exciting topics for the global challenges of our time.
We hope you enjoy reading the new journal!
Yours,
Dr. Claus Rettig Chairman of the Board of Management Evonik Resource Efficiency GmbH
Figure 2: Combining the benefits - Using a curing catalyst, scientists bind hydrophobic silicone to a hydrophilic polymer.
+ Si
Si
OR
OR
-OR
-OR
OR
OR RO
RO-
RO
Polymer
Hydrophobic silicone Hydrophilic polymer with silane groups
Ship’s hullSilicone hybrid
Maritime transport is the first preference for cargo; nearly 90 percent of all goods transported worldwide are carried by more than 50,000 ships plying the world’s oceans. The commercial viability of the glob-al merchant fleet depends heavily on the shell of the vessels. Biofouling, caused by plant and animal growth on the hull under the waterline is a particular con-cern. Proteins, carbohydrates and other micronutri-ents from the ocean attach themselves to the hull only seconds after its first contact with sea water. As nutri-ents, they attract marine organisms that then settle on the shell.
The biofilms thus formed are highly complex hab-itats in which several hundred species interact with one another positively or negatively, hindering the movement of ships on the world’s oceans (Fig. 1). The significant roughening of the hull’s surface due to biofouling leads to a drastic increase in frictional resistance during movement. The result is a vicious circle in which, to maintain the same speed of travel, the ship needs more energy and fuel, with an associat-ed rise in CO2 emission. Current studies indicate that even slight encrustation raises fuel consumption by up to 30 percent. In addition, the maneuverability of the ships is reduced and the risk of corrosion increases. Hence, ships need more frequent stays in the dry dock for cleaning and repairs. Short maintenance cycles and increased fuel consumption result in high costs for shipping companies. And the climate is also affected: Even a thin biofilm gives rise to CO2 emissions of more than 270 million metric tons every year.
Demand is therefore high for coatings that protect ships’ hulls from biofouling. These antifouling coatings prevent the settling of marine organisms and counter-act the negative effects of biofouling. But the search for the right coating is a challenge. The most effective method known so far for protecting the hull is a bio-cide-containing coating. Its functioning is based on a leaching process in which active toxic substances are dissolved out of the coating matrix and arrive at the surface of the ship’s hull. Here they form a kind of bio-cide cloud around the ship and damage microorganisms before these can settle on the hull.
Among the best known of the biocides is tributyltin hydride (TBT), an organometallic complex of tin. But there’s a problem here: Investigations have revealed that the toxicity of the biocides is not confined to organisms at the hull’s surface but extends also to oth-er species in the sea. Even a low TBT concentration, for example, interferes with shell growth in Pacific rock oysters. In snails and other species TBT induces imposex, a condition in which female animals develop male sex organs and vice versa, so that reproduction is no longer possible and the species is in danger of extinction.
To protect marine organisms, therefore, the use of TBT-based underwater paints is banned worldwide and no biocides based on toxic tin, arsenic, or mercury compounds may be used any longer. This has spurred the search for alternatives that are equally effective but also eco-friendly. But despite considerable efforts an entirely satisfactory solution to the problem has not yet been found. In the absence of suitable alternatives, bio-cides are still used in antifouling coatings. The active agent of choice today is copper oxide, which is regard-ed as more eco-friendly than TBT and acts on the same leaching principle. But it too is a heavy metal oxide and the copper ions dissolving out from the coating can be toxic in high concentrations. And so the search contin-ues for a new and better antifouling solution.
COATINGS WITHOUT BIOCIDES
This is where Evonik comes into the picture. The Coat-ing Additives Business Line is in the process of estab-lishing a Smart Surface Solutions Competence Center to resolve open questions in coating technology. The team also plans to develop an eco-friendly alternative to the current antifouling solutions, entirely without biocides. The researchers are putting their existing expertise in the area of silicones to good use. Evonik has a sili-cone-epoxy hybrid resin system, called SILIKOPON® EF in its portfolio, whose anti-adhesive action makes it dif-ficult right from the start for organisms to settle.
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This is due to the very low surface tension and extreme-ly smooth surface of the hybrid. Organisms like algae, bivalves, and barnacles have difficulty adhering to this surface. Even if they do initially succeed, the smooth surface is easily cleared because the organ-isms become detached by the water stream once the ship starts to move, even at slow speeds. As an added plus, SILIKOPON® EF has high mechanical and chemical resistance which prevents long-term corrosion damage.
The researchers want to exploit these advantages and add another property: The new coating binder should prevent organisms from adhering to the hull because they cannot recognize the surface as such. For this purpose the scientists are combining the hydro-phobic silicone with a hydrophilic polymer (Fig. 2) to produce what is known as amphiphilic polymers, in which hydrophilic and hydrophobic areas alternate. The hydrophilic areas form a film of water around the polymer that masks the surface to the organisms. These can no longer identify the surface, unambig-uously, and prefer not to settle on it (Fig. 3). The researchers are exploiting a natural principle here: Living beings always seek out the most favorable hab-itat for reproduction.
DECREASING COSTS
The researchers are well on the way to finding a solu-tion. They have been able to show in tests that the novel coatings raw materials are non-toxic, and have an effi-cacy comparable to that of binder systems already used on the market. In close cooperation with customers, the aim is to develop durable and protective coatings based on these polymers. The researchers are optimistic that they will soon be able to increase the intervals between re-coating the ships. In this way, shipping companies would be able to reduce maintenance costs for ships as well as overcoming the other disadvantages of fouling. To achieve this, the researchers are using various test methods to further optimize the binder systems. In col-laboration with the University of Münster, new screen-ing tests have been developed that allow prediction of the antifouling performance of the coatings after only six weeks. If a tested substance already shows undesir-able toxic properties in the initial laboratory test, it is rejected or the formulation is revised. If, on the other hand, it is promising, it is tested in the sea. Every year between March and October the experts suspend var-iously coated test panels to the sea. In this period with
high “growth pressure”, the tendency for biofouling is at its peak and the rate at which growth will develop under real conditions becomes clear. Only then is it pos-sible for the researchers to reliably assess the efficacy of new formulations. This is why Evonik is not only devel-oping a completely new solution but is concurrently working on improving existing antifouling coatings.
Researchers of the Coating Additives Business Line have developed a hydrophilic structurally modified AEROSIL® that significantly improves the efficacy and service life of antifouling coatings. Coatings manufac-turers can formulate the product, marketed as VP 4200, in combination with copper oxide to enhance the action of the latter. VP 4200 interacts with the copper oxide, fixing it in the film, which becomes tougher and more resistant. Thus, the copper oxide is available over a longer period of time. If the liquid coating contains ten percent VP 4200, effective protection against biofoul-ing can be achieved with a significantly lower copper oxide content of about six percent. This is 80% less than in conventional formulations, which normally contain 30 percent or more copper oxide.
Figure 1: How biofilms form - Just seconds after contact with water, microorganisms settle on the ship’s hull. These serve as nourishment for other organisms, and a biofilm is formed.
non-adhering bacteria
adhering bacteria
bacterialfilm
bacteria, diatoms,microalgal spores,
macroalgae, larvae of invertebratemarine animals, other invertebrates
(seconds) (hours-days) (days-months)
substrate developingfilm
(seconds-minutes)
Figure 3: Protection against biofouling - In the new system, hydrophobic and hydrophilic domains alternate. Organisms can no longer unambiguously identify the surface.
The hydrophilic properties of the polymer mask the surface by producing a hydrate layer
Aquatic organisms
Amphiphilic hybrid system
Ship’s hull
Hydrophobic domain
Aquatic organisms leave the surface
CONTACT
Dr. Katrin Roland [email protected]
Dr. Michael Fiedel [email protected]
Dr. Günther Michael [email protected]
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The Coatings Expert | Issue 4 | March 2018
The solvent based binders for heat sealing applications sold by Evonik Resource Efficiency GmbH under the brand name DEGALAN® offer unique options for for-mulating high performance heat sealing lacquers. They are primarily used for sealing dairy packaging such as yogurt cups or pharmaceutical blister packs. The requirements for heat sealing lacquers keep becoming more demanding. Among other factors, this is reflected by a wide range of materials to be sealed. The lids of yogurt cups, for example, can be made of aluminum, plastics such as polyethylene terephthalate (PET), or paper-PET composite systems, while cup materials con-sists of polypropylene (PP), polystyrene (PS) or PET. Here, DEGALAN® binders ensure a reliable and strong seal and at the same time are convenient and easy to open.
Evonik Heat Sealing is now offering a full range of upgraded DEGALAN® binders called the 42-Series. The new 42-Series is based on ethylidene norbornene free olefin copolymers (OCP) and are characterized by a nar-rower molecular weight distribution as well as a lower viscosity. As a result, the new DEGALAN® 42-Series has no restrictions for any filling good and shows less tendency causing rub-off deposits on customer rollers during coating and handling processes. This leads to less cleaning and conversion costs and thus contributes to a higher output. Another advantage of the DEGALAN® 42 series is the universal sealability: Whether lidding materials made of aluminum or PET or cups made of PP, PS, PET, PVC, PBT or PLA - consistently high sealing strength and smooth opening is achieved. Besides, most of the new products have a higher solid content.
DEGALAN® VP 4220 E is the modified version of DEGALAN® PM 555 and achieves comparable sealing strength at a layer thickness between 5 to 8 g/m2. DEGALAN® VP 4220 E requires the addition of a prim-er such as VINNOL® H 30 / 48 M. It can be conveniently added into the formulation or pre-applied as part of a two-step coating process.
DEGALAN® VP 4221 E is the successor product of DEGALAN® PM 666 and provides its best heat sealing properties with a coating weight of 5 to 8 g/m2 as well.
DEGALAN® VP 4221 E can be easily formulated and applied in a one-step coating process – an additional adhesion promoter is not required and the coating is free of PVC.
DEGALAN® VP 4250 E has a higher solid content than its predecessor DEGALAN® 4150 E which results in similar sealing strength values while less material is needed during coating process.
DEGALAN® VP 4251 E is the modified version of DEGALAN® 4151 E. With a related polymer composi-tion, a solid content of 45% is achieved. This represents an increase of 12.5% compared to the predecessor product. This has no influence on the viscosity. The advantages of a direct adhesion and therefore PVC-free formulation remain with DEGALAN® VP 4251 E.
The most universal applicable product is the new DEGALAN® VP 4294 E which is unique in its polymeric structure. The organic dispersion consists of copoly-mers of methacrylic esters grafted on OCP and polyes-ters. DEGALAN® VP 4294 E adheres directly to alumi-num and PET. The new composition of its polymers and solvents achieves a solid content of 52%.
The trend towards transparent packaging becomes increasingly evident in retail refrigeration cases. With the newly developed DEGALAN® VP 4322 E, Evonik
Resource Efficiency GmbH offers another innova-tive heat sealing binder that is specifically designed for fully transparent packaging applicat ions. DEGALAN® VP 4322 E can be applied in a single coat-ing process, which does not require or contain any PVC. The product can be sealed against the most common plastic materials such as PET, PS, PVC, PVdC and PLA. A pure PET-PET-sealing offers additional benefits such as high recyclability, and therefore represents a true and cost-effective alternative to PET-PE-composites, which are still primarily used in transparent packaging. At the same time, DEGALAN® VP 4322 E also offers the advantage of a high sealing strength of more than 8 N/15 mm. Its haze value is below 10%, measured on a PET film with a dry coating weight of 5 g/m2, to allow consumers a clear view of the packaged items. All DEGALAN® heat seal binders fulfill the requirements according to FDA 21 CFR § 175.300.
INNOVATIVE DEGALAN® BINDERS FOR HEAT SEAL APPLICATIONS
CONTACT
Jürgen Hartmann [email protected]
Solid content comparison of DEGALAN® 42-Series products
DEGALAN® SOLID CONTENT [%] DEGALAN® 42-SERIES SOLID CONTENT [%]
DEGALAN® PM 555 45 DEGALAN® VP 4220 E 45
DEGALAN® PM 666 45 DEGALAN® VP 4221 E 45
DEGALAN® 4150 E 43 DEGALAN® VP 4250 E 45
DEGALAN® 4151 E 40 DEGALAN® VP 4251 E 45
DEGALAN® 4174 E 47 – –
– – DEGALAN® VP 4294 E 52
Technical properties of DEGALAN® VP 4322 E
Heat Seal Strength HSS > 6 N/15mm
Lid Materials Transparent PET and Paper/PET-laminates
Substrates PET, PS, PVC, PVdC, PLA, PBT
FDA §175.300 V
Solid Content 40%
Viscosity < 8.000 mPas
Haze at 5.0 gsm Bare Film: 4 / Reference: 25 / DEGALAN® VP 4322 E: < 10
Blocking Temperature > 60 °C
Cover lid
CupSealing substrates: PET, PS, PVC, PVdC, PLA, PBT
Label print
Transparent PET,Paper /metPET or Aluminum
heat seal lacquer based onDEGALAN® VP 4322 E
One step direct adhesive
PET-film, 36μm, uncoated PET-film, 36μm, 5.0 gsm coated with standard heat seal lacquer
PET-film, 36μm, 5.0 gsm coated with heat seal lacquer including DEGALAN® VP 4322 E
PET 36 μm vs. APET and PS, both sealed with DEGALAN® VP 4322 E
240 220 200 180 160 140 120 100
1086420
N/1
5mm
Sealing Temperature in °C
PS APET
Conditions: One-step lacquering 5.0 gsmSolvent: Ethyl acetateSealing conditions: 0.5 s, 3 barHeat Sealing Strength Test, α = 180 °
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In a recent study, we tackled one of the more difficult challenges in terms of pigment stabilization in water-borne inkjet inks: TiO2. The challenge: TiO2 has a ten-dency to settle over time due to the high density of this inorganic pigment.
For this study, we tested several reference dis-persants and compared them to ZETASPERSE® 3800 and a mixture of TEGO® Dispers 750 W and TEGO® Dispers 760 W (Figure 1). ZETASPERSE® 3800 and TEGO® Dispers 750 W are both sophisticated dispersants with numerous anchor groups that can attach to the surface of all classifications of pigments. TEGO® Dispers 760 W works as a co-dispersant to fur-ther stabilize the system.
The direct grinds, with 40% pigment loading of TiO2, were then stored for 6 weeks. As seen in Figure 2, we
were able to stabilize 40% TiO2 at viscosities at or lower than 10 cps and maintain these values over 6 weeks of stability. The tested reference formulations displayed good initial viscosity reduction but failed to keep the viscosity at the low base level over time, which is man-datory for use in inkjet inks. With ZETASPERSE® 3800 and the mixture of TEGO® Dispers 750 W and TEGO® Dispers 760 W, greater stabilization was achieved. The reason for the enhanced storage stability seems to be the combination of electrostatic repulsion and steric hindrance made possible by the unique structures of the ZETASPERSE® and TEGO® Dispers technology. It is important to note that both systems also showed the best overall sedimentation behavior, yielding in only a minor amount of very soft settlement which could easily be reincorporated or dispersed.
Furthermore, both dispersant systems delivered very favorable particle sizes at a d50 between 300-400 nm, which would enable their use in a modern print head.
For further information on the study please contact:
TEGO® DISPERS & ZETASPERSE®: Dispersant power for the most difficult tasks
Figure 1: Guiding formulation for TiO2
RAW MATERIAL CONTENT
Water Rest
Dispersing agent (10% - 25% ASOP) x
TEGO® Humectant 7000 5%
TEGO® Foamex 3062 0.5%
TiO2 (Sachtleben RDIS) 40%
Total 100
PREPARATION & MEASUREMENT
12 h grinding with beads (0.2-0.3mm)Determination of viscosity before and after storageParticle size measurements before and after storage
CONTACT
Dr. Christian Maus [email protected]
Viscosity stability after 6 weeks storage
0.0
5.0
10.0
15.0
20.0
25.0
30.0
35.0
40.0
45.0
Ref. A (10%AsoP)
ZETASPERSE® 3800 (10%AsoP)
Ref. B (10%AsoP)
TEGO® Dispers 750 W/TEGO® Dispers 760 W
(25%AsoP)
Ref. C (10%AsoP)
Ref. C ( 20%AsoP)
visosity 10/s (cps) visosity 10/s (cps)aer 6 Weeks
visosity 100/s (cps) visosity 100/s (cps)aer 6 Weeks
visosity 1000/s (cps) visosity 1000/s (cps)aer 6 Weeks
The printing industry continues to shift towards digital technologies, in particular inkjet printing. What began as a niche market for prototyping has developed into a well-recognized industrial printing technology. With current single-pass printing processes, the print speed of industrial inkjet applications can be increased signifi-cantly to a range of 75 lin. meters per minute [1].
The success of inkjet technologies can be attributed to the high degree of freedom they allow. Nearly every image possible can be printed with no changeover costs or time.
However, customers are not willing to forego the well-known image quality they are used to from con-ventional printing processes such as f lexographic printing. Here the Inkjet Inks suffer from a drawback. In order to use the inkjet process, the viscosity of the
ink must be significantly lower than those used in con-ventional printing inks. The limitations for viscosity are determined by the inkjet print heads, which eject picoliter-size droplets of ink onto the substrate. Typical viscosities of waterborne inkjet inks are below 10 cps; this limits the use of solids (e.g. pigment) and binders to create the image. In addition, a typical print head, with its hundreds of nozzles, can only process inks with very small and narrow particle sizes and distributions of the containing pigments. Pigments with large particle sizes could clog the nozzle, which can ultimately lead to malfunction of the expensive print head.
To maintain the ink’s performance requirements – such as low viscosity, small and narrow particle sizes, and storage stability – only high-performance disper-sants can be used.
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The Coatings Expert | Issue 4 | March 2018
Since the invention of the food can in the year 1810 there has been little change in the way it works: Its interior is hermetically sealed against light and oxygen so that it can preserve food for considerably longer. More than 200 years later the focus is still on the inside of the can, and specifically on modernizing the coating to ensure perfect preservation of the contents.
In past decades interior surfaces have been coated with technically proven coatings based on epoxy resins con-taining the component bisphenol A (BPA). However, over the past years the market trend away from BPA in materials for food contact uses has gained momentum.
Polyester based coatings are regarded as good alter-natives to standard epoxy resin based coating systems.
Evonik spotted this trend early, expanded its product portfolio accordingly, and developed appropriate pat-ent-protected technology*. As a leading global supplier of polyesters to the coatings industry for the applica-tions of metal coating and reactive hot melt adhesives, Evonik offers under the brand name DYNAPOL® suit-able alternatives to the current BPA-containing sys-tems. These are excellently suited for the formulation of high-performance coatings for food cans.
By the end of 2015 Evonik had already decided to invest in additional capacity in response to continuing growth in this market. This decision was implemented with the extension of a production plant for specialty copolyesters at the Witten site in Germany and a mid double digit million euro sum was invested. The exten-sion has an annual production capacity of several thou-sand metric tons and went on stream in the first quarter of 2018.
* EP 1498461B1
CAPACITY EXPANSION FOR SPECIALTY COPOLYESTERS IN WITTEN (GERMANY) STARTS UP
CONTACT
Dr. Thorsten Brand [email protected]
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HIGH WATER VAPOR DIFFUSION, LOW WATER ABSORPTION
Facade paints must promote good diffusion of water vapor so that moisture coming from the interior does not accumulate in the brickwork. Under some circum-stances, this moisture may lead to a build-up of pressure that can cause coatings that are not permeable to water vapor to burst. High water vapor diffusion is achieved by the supercritical pigment volume concentration at which the binder, due to its low quantity, does not fill all the interstitial spaces of the filler and pigment particles, thus allowing a network of micropores to be formed.
These pores create a surface prone to attack by pen-etrating water, such as rain. Hydrophilic pores absorb water strongly. This absorption strength can be illus-trated by modeling a pore as a vertical cylindrical cap-illary. The capillary rise h of the water is given by the capillary equation:
h= 2σ cosθ ρgr
where σ is the surface tension and ρ is the density of the water, θ is the contact angle of the water on the
capillary surface, g is the gravitational constant, and r is the pore radius. For a hydrophilic pore with a con-tact angle of 0 ° and a radius of 100 nm, the capillary rise is 157 meters, so the water column would be taller than Cologne Cathedral. This effect needs to be mini-mized, and this is most effectively achieved through the surface chemistry of the capillary. When the contact angle θ > 90 °, the water sinks instead of rising: Under the same conditions (but with a contact angle of 140 °), the water sinks by as much as 100 meters. The pore surfaces must therefore be made hydrophobic — with-out heavily impacting the microporous structure that makes water vapor diffusion possible. In practice, this is achieved by the addition of silicone resin emulsions.
Evonik’s researchers have conducted trials to quan-tify the hydrophobic effect of the new silicone resin. They painted mineral substrates with a paint previous-ly treated with TEGO® Phobe 1659 and immersed the substrates in water for 24 hours. The water absorption during this period was found to be significantly low-er than for formulations using commercially available reference products. The water absorption coefficient w24 was below 0.1 kg/(m2*h½) and 60-80% lower at a silicone resin concentration of 4.8%. Even at a concen-tration of only 2.0%, TEGO® Phobe 1659 retains this excellent w24 value — something never before achieved. (Graphic 1)
The w24 value of a coating generally decreases upon additional exposure to water because the surface-active components that enable penetration of water into the pore network are washed out of the coating. In practice, it is best if the lowest possible w24 value is obtained after only a few exposures to water. This property is termed “early water resistance”. TEGO® Phobe 1659 achieves its optimum w24 after the second exposure to water. For the reference products, the results after the first two passes were inadequate and comparable performance was not achieved until further exposure to water was had. For users, this means that paints formulated with TEGO® Phobe 1659 show good water resistance directly after drying – not only after a few heavy showers.
TRANSMISSION ELECTRON MICROSCOPY
To further investigate the distribution of the silicone resin in the paint, the developers obtained electron micrographs. By means of spatially resolved energy dispersive x-ray spectroscopy (EDX), they also deter-mined the local distribution of the elements. To allow for identification of the silicone resin, no silicone-con-taining fillers or pigments (such as quartz or silica) were used; calcium carbonate and titanium dioxide were used exclusively. A commercially available styrene-acrylate dispersion was used as primary binder.
Paint layers with 2.0% and 4.8% silicone resin — based on TEGO® Phobe 1659 and on a commercially available standard — were removed from the substrate and embedded in an epoxy resin under vacuum. The researchers then prepared 180 nm thick sections and investigated these. Figure 1 shows a representative result.
The paint contains 2.0% TEGO® Phobe 1659 and, as expected, has a porous, non-homogeneous structure. Micrographs of paint layers with another silicone res-in at a higher concentration are almost identical at first glance. Three regions can be distinguished, which are denoted in the image by I, II, and III. Region I is pale in color, amorphous, and homogeneous. EDX shows almost exclusively carbon (C) and oxygen (O), and this appears to be pure binder. Region II consists of dark, homoge-neous structures of high electron density. EDX shows here titanium (Ti) and calcium (Ca) as well as other ele-ments, therefore this must be pigment or filler. Finally, for the non-homogeneous region III, also with fairly high electron density, EDX shows silicone (Si) in addition to carbon (C) and oxygen (O). This appears to be silicone resin.
A NEW SILICONE RESIN TECHNOLOGY RAISES THE BAR FOR FACADE PAINTS AND PLASTERS
Graphic 1: Water absorption of a silicone resin paint with various silicone resins
0.00
0.10
0.20
0.30
0.40
0.50
0.60
0.70
TEGO® Phobe 1659 Standard resin 1 Standard resin 2 Standard resin 3
w24
val
ue
1st exposure to water 2nd exposure to water 3rd exposure to water 4th exposure to water
For decades, facade paints have had two important functions: They lend an attractive appearance and offer protection from the effects of weathering. Therefore, producers of premium facade paints have worked hard to optimize these two properties in their products. Silicone resin paints are now state-of-the-art options for exterior applications. These paints contain emulsified silicone resins in addition to a primary binder, which is generally a styrene-acrylate dispersion. Such paints have excellent weathering resistance and a long service life.
Over the last few years, however, customer requirements have increased. The color selection needs to be larger. The facade needs to be slower to soil than before and all these performance characteristics need to be achieved by environmentally compatible means. Researchers at Evonik have now developed a new silicone resin that meets these increased requirements: TEGO® Phobe 1659. As an added bonus, it can be used in significantly lower concentrations than the established alternatives, thus saving costs.
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The Coatings Expert | Issue 4 | March 2018
The distribution of silicone resin in the film is of crucial importance for its effectiveness. Upon more detailed examination, striking differences are seen here between TEGO® Phobe 1659 and the market standard. Figures 2A and 2B show higher resolution micrographs; silicone resin can be seen in addition to the primary binder.
Figure A shows that the commercially available silicone resin is encapsulated to a large extent by the primary binder, undoubtedly to the detriment of its efficacy. On the other hand, Figure B shows that with TEGO® Phobe 1659, there is almost complete separa-tion between silicone resin and binder, so the silicone resin is fully effective. This microscopic phase separa-tion is likely due to the molecular structure of the sili-cone resin and the choice of emulsifiers used.
A second difference between the two silicone res-ins is observed in the EDX spectra of the pigments. (Graphic 2)
The EDX spectrum of the commercially available standard shows some calcium and titanium but no sili-cone. Alternatively, the EDX spectrum of TEGO® Phobe 1659 shows both titanium and silicone, indicating that the pigment particles have been coated with a silicone resin film. The high affinity of TEGO® Phobe 1659 for pigments and fillers — in addition to the aforementioned phase separation — explains its particularly high effica-cy at low concentrations.
LOWER DIRT PICK-UP
In an accelerated soiling test in the laboratory that simu-lates outdoor weathering, the researchers also found that facades with formulations based on TEGO® Phobe 1659 pick up dirt only half as much as the market standard. (Figure 3)
For this test, Evonik used a special machine. Water is treated with a dirt mixture consisting of tar, carbon black, and Japanese Norm Dirt. Test plates coated with silicone resin paints are soiled with this water in the machine. The machine then heats the plates to 50 °C and
Graphic 2: EDX of pigment particles. When TEGO® Phobe 1659 is used, silicone (Si) is found in addition to titanium (Ti), which is not the case for the commercially available standard.
0
10
20
30
40
50
C O Si Ca Ti
Wt%
Phobe 1659 Standard
Figure 1: Electron transmission micrograph of a silicone resin paint containing 2.0% TEGO® Phobe 1659. Magnification: x 2000. Three areas can be dis-tinguished, denoted in the image by I, II, and III.
Figure 2B: Electron transmission micrograph of a silicone resin paint containing 4.8% TEGO® Phobe 1659. Magnification: x 4000. Primary binder (light) and silicone resin (dark) are spatially separated from each other.
Figure 3: Tendency to soiling. Formulations based on TEGO® Phobe 1659 show L values that are lower by up to 30% in the soiling test.
Figure 2A: Electron transmission micrograph of a silicone resin paint with 4.8% of a commercially available standard. Magnification: x 4000. The silicone resin (dark colored) is partly encapsulated by the primary binder.
Graphic 3: Tendency to soiling in the accelerated laboratory test
0
4
8
12
16
20
24
Del
ta L
val
ue
Standard resin 2Standard resin 1 Standard resin 3TEGO® Phobe 1659
9
washes them with clean water. This cycle is repeated several times over a defined period. After the simulat-ed soiling, the formulation with the new silicone resin structure showed L values (which indicate the degree of soiling) up to 30% lower than formulations with other silicone resins. (Graphic 3)
FORMULATION WITH ORGANIC PIGMENTS
The high pigment affinity of the new silicone resin is also important for pigment concentrate uptake. Tests have shown that color paste uptake for paints formulat-ed with silicone resin is better than pigment concentrate uptake for paints without silicone resin. This means that formulators can save on pigment concentrate while still obtaining the same tinting strength.
The particular strength of TEGO® Phobe 1659 lies in its versatility: It can also be used with pigment concen-trates based on organic pigments and therefore allows a far wider choice of colors than what has been previously possible with most silicone resins. (Graphic 4)
ADVANTAGES IN PROCESSING AND STORAGE
TEGO® Phobe 1659 is suitable for liquid plasters as well as facade paints. It offers additional advantages in pro-cessability because the usual flow limit on the market is currently significantly higher. Tests have shown that, particularly after storage, the flow limit of plasters for-mulated with the new silicone resin is only about one-third of that for plasters using the reference products, regardless of storage time.
Formulations with the new silicone resin structure have a very favorable rheological profile, which simplifies application for the processor. Moreover, the homoge-neous distribution of the silicone resin results in a more uniform structure in the plaster. (Figure 4)
This enhances its visual appearance and also pre-vents the formation of fairly large grooves, which would strongly promote water absorption. The viscos-ity remains significantly lower than for other commer-cially available products, even if the paint is exposed to
a temperature of 50 °C over a fairly long period. This facilitates application after storage. Tests showed no effect on viscosity even after 256 days of storage — in contrast to reference products and to paints without additive, where the viscosity increased by a factor of 50.
Analyses of the storage modulus G‘ support this observation: After only one week of storage, this value was significantly lower than that of the reference prod-uct and of the formulation without hydrophobing agent. After 256 days of storage, the storage modulus G‘ for TEGO® Phobe 1659 had doubled, while the standard product and the formulation without additive showed an 8-fold increase. (Graphic 5)
While this data doesn’t indicate that the standard product compromises the formulation’s stability, it does confirm that TEGO® Phobe 1659 provides a more stable product over time. This can be attribut-ed to TEGO® Phobe 1659’s high affinity for pigments and fillers and it ultimately why formulations contain-ing TEGO® Phobe 1659 have a signification longer service life.
ENVIRONMENTALLY COMPATIBLE FOR BROAD MARKET ACCESS
Because all these functions are obtained with even thin paint layers, the user’s material requirements are reduced. And the environment also benefits because, since the beginning, the developers have chosen the raw materials so that the finished formulation can sat-isfy high certification demands and easily surmount the regulatory obstacles in various countries. Possible cer-tificates include Blue Angel, the Nordic Ecolabel, and the EU Ecolabel.
Graphic 4: Rub-out values after addition of 5% pigment concentrate
TEGO® Phobe 1659Control Standard resin 1 Standard resin 2 Standard resin 3
Del
ta E
val
ue
0.0
0.2
0.4
0.6
0.8
1.0
1.2
1.4
1.6
Inorganic pigment Organic pigment Carbon black
Figure 4: Surface structure of plasters. Formulations based on TEGO® Phobe 1659 show a more uniform surface structure with the same filler package.
10
The Coatings Expert | Issue 4 | March 2018
TECHNOLOGY STANDARD RAISED
To sum up, Evonik has launched TEGO® Phobe 1659 – a silicone resin that shows improved technical properties even at reduced concentrations. For the end customer, it offers a wider selection of colors and reduces main-tenance costs. These benefits are combined with high environmental compatibility, so that the product sets a new technology standard on the market for hydropho-bing agents for facade paints and plasters.
Graphic 5: Storage modulus G‘ as a function of time. With TEGO® Phobe 1659, G‘ is lower by one third at the onset and increases only slightly over time. Without silicone resin, or with the market standard, G‘ increases strongly over time.
101 100
Time (days)
1000
G`/
Pa
100
1000
10000
without TEGO® Phobe 1659 standard
CONTACT
Markus Vogel [email protected]
WATERBORNE EPOXY CURING AGENTS AND RESIN DISPERSIONS
Figure 1 Comparison of conventional epoxy resin dispersion with ANCAREZ® AR 555.
0
30
20
10
40
50
60
Wei
ght %
Molecular Weight
SelfCoalescing Fast Dry
ANCAREZ® AR 555
ANCAREZ® AR 555
Two-component epoxy systems are well known for their excellent chemical resistance, mechanical proper-ties and superior adhesion to a wide range of substrates. They have, as a result, been widely used in concrete floor coatings and protective metal coatings. Driven by environmental regulations, and safety and health con-cerns, waterborne epoxy systems have become a com-mercially important technology and have gained wide acceptance in the coating industry. Important advantag-es of waterborne systems are low VOC, low emissions, low f lammability, low toxicity, excellent adhesion, even to poorly prepared substrate, and easy clean up with water.
There are two main types of waterborne epoxy sys-tems. Type I is based on low molecular weight liquid epoxy resin (LER), and a curing agent that is designed to serve as an emulsifier for the resin and is amphiphilic in nature. Type II is based on higher molecular weight solid epoxy resin dispersion (SER). Each system has its own advantages and the proper choice is dictated by the required application properties and final coatings
11
performance. The Type I system, in general, has short pot-life but longer drying time than Type II. It also offers good final hardness and chemical resistance, however with low flexibility and low impact resistance. Type II systems have longer pot-life, very fast lacquer dry time and improved flexibility and impact resistance.
Evonik offers a wide portfolio of waterborne epoxy curing agents and solid resin dispersions. Our curing agents can be used with liquid epoxy resin (Type I) or solid resin dispersion (Type II), therefore providing for-mulators with a range of application latitude and final product performance properties. Curing agents for the Type I system are often designed with built-in reactive emulsifier technology to provide good stability in water, and excellent capability to emulsify liquid epoxy resins. We also offer unique solid epoxy resin (SER) disper-sions. Commonly available SER has single modal molec-ular weight distribution with high molecular weight solid resin that requires a coalescing solvent. As shown in Figure 1, Evonik’s proprietary technology offers dis-persions with bimodal molecular weight distribution that combine the best properties of Type I and Type II systems: extremely fast drying, and good chemical
and mechanical properties. Furthermore, since Evon-ik’s resin dispersions have the low molecular weight for self-coalescing, they are truly zero VOC. Our waterborne curing agents and resin dispersions are used in a wide range of applications including pro-tective and concrete coatings, self-leveling and mortar floors, tile grouts, and anti-corrosion primer for OEM and light duty applications. Waterborne epoxy systems can be applied at temperatures between 40 °F to 95 °F and at relative humidity up to 85%, with pot-life rang-ing from 1-6 hours, thus providing end-users an exten-sive option of working environments and conditions. The major properties of our waterborne curing agents are provided in Table 1. The product selection guide is presented in Table 2.
We continuously strive to meet market trends and drivers, such as minimizing downtime to improve cost and productivity, and improving coating robustness and better aesthetics over the service life. Evonik’s new waterborne product development is focused on the next generation of waterborne epoxy curing agents that will provide excellent fast cure speed even under adverse conditions, such as low temperatures, down to 10oC
and high humidity, up to 80%; superior adhesion to sub-strate when used as a concrete primer, particularly on damp concrete, and excellent aesthetics as a topcoat.
As such, our latest waterborne curing agent, ANQUAMINE® 728, launched in 2018, can be used as both a primer and topcoat -- applied on the same day -- enabling formulators to design new floor systems that can be installed in just 1-day, with walk-on readiness the next morning. The product is a low color aqueous solution at 55% solid, with moderate viscosity of 6,000-9,000 cPs, and an HEW of 250. In addition to a very fast cure speed, ANQUAMINE® 728 also provides good chemical and UV yellowing resistance.
CONTACT
Dr. Shiying Zheng [email protected]
Table 1 Basic properties of waterborne curing agents and resin dispersions
ANQUAMINE® ANCAREZ® 550/555PROPERTIES 100 287 360 401 419 701 721 731 735
Viscosity cP@ 77F 200 0.4-1k 30-50k 25-40k 8-14k 5-10k 35-45k 50k 5-15k 200
Color (Gardner)
milky white dispersion 12 14 12 8 milky yellow
emulsion 5 5 5 milky white dispersion
Amine Value (mg/KOH/g) 90-110 155-175 150-190 240-260 150-190 130-165 150-190 175 240
AHEW 350 240 240 166 284 300 300 200 200 1300 (EEW)
PHR1 (as supplied) 180 125 100-150 60-9013-162
45-553 20-323 145 140-180 100 100
Solids 55% 50% 50% 70% 60% 55% 50% 55% 55% 55%
Solvents 2% 0% 0% 0% 25% 0% 0% 0% 0% 0%
TFST (hr)1 2.5 2 11 3 2.5 2.5 5.5 N/A 5.5 <0.5
Pot Life (hr) 6-8 1+ 1-2 1-4 6 2-5 1-2 0.5-0.75 0.5-0.75 3+
1 with liquid epoxy resin, EEW=190 2 with solid epoxy resin dispersion, EEW=1000 3 with solid epoxy resin dispersion, EEW=530.
Table 2 Waterborne curing agent selection chart
CURING AGENT USE WITH LER ANCAREZ® 555
ANQUAMINE®
701 360 401 100 287 721 731 735 401 100 419
PrimerStandard Primer + + + +++ + +
Penetrating Primer +++
CE Thin Film
Standard Concrete Paint + + + +++ + +
Transparent Topcoat +++ +++
DIY Garage Floor +++ +
Institutional +++ +++
CE Thick Film
Self Leveling + +++ +++
Tile Grout/Adhesive + +++ +++
Thermal shock flooring +++
MetalOEM Primer + +++ +++ +++
PC/Marine + +++ +++
+++ Primary recommendation + Alternative recommendation.
12
The Coatings Expert | Issue 4 | March 2018
A bridge railing is installed or upgraded. It looks won-derful at first, but over time, daily wear and tear pro-duces scratches and spalling — damage that ultimately devalues the painted object. Along with these types of damage, other equally important concerns include sustained protection from mechanical abrasion and the ability to maintain the visual appearance of the object over an extended period of time. To introduce a possi-ble solution to these challenges, this analysis will focus on non-isocyanate (NISO) crosslinking, 2K coating systems that contain minimal solvent, last a long time, and are durable enough for multilayer coatings on metal objects. NISO crosslinking, 2K coating systems are specifically valued for these applications, as they can be used for protecting infrastructural elements – both new and repaired – from corrosion.
The α-Ω-alkoxysilane-terminated polyurethane technology underlying ALBIDUR® 1223 is responsible for improving the flexibility of aliphatic silicone epoxy hybrid resins (SILIKOPON® EF). The resins involved are solvent-free and offer several advantages: They are easy to handle, can be readily incorporated by mixing, and are suitable for a broad range of applications. With these properties, it is entirely possible to maintain a consistent level of durability in the coating.
HOW DOES THE NISO CURING MECHANISM WORK IN SILIKOPON® EF?
The NISO curing mechanism occurs in two stages: SILIKOPON® EF (an aliphatic silicone epoxy hybrid res-in) is crosslinked with a bifunctional curing agent, such as DYNASYLAN® AMEO. One stage of this process is an addition-curing step, during which the amino group of DYNASYLAN® AMEO crosslinks with the oxirane group of SILIKOPON® EF. The other stage is a conden-sation reaction, during which the alkoxysilane group of DYNASYLAN® AMEO reacts with the alkoxy group of SILIKOPON® EF to release a short-chain alcohol.
When crosslinked in this way, the resin is highly resistant to weathering and exhibits excellent anti-cor-rosion properties. In terms of drying — both of the sur-faces and of the resin as a whole — the curing time is comparable to that of traditional high-solid, 2K-PUR or 2K-EP materials. The presence of humidity has a posi-tive effect on curing rates. Heating the coating film in
an oven or by some other method, however, tends to be counter-productive and extends the drying time. In oth-er words, this resin matrix was developed with consid-eration for applications that cure at room temperature, such as bridges, steps, or support structures.
MECHANISM UNDERLYING ALBIDUR® 1223
Because the glass transit ion temperature of ALBIDUR® 1223 is relatively low, the SILIKOPON® EF matrix is more flexible and can crosslink in two ways:
1. In the presence of ambient humidity, it crosslinks with itself to release a low-molecular-weight alcohol (hydrolysis-condensation reaction).
2. Through the reaction of the alkoxy groups of both resins involved, a low-molecular-weight alcohol is released (also a hydrolysis-condensation reaction).
In either case, the binder matrix cures to lend long-term flexibility to the coating film. Chemical crosslink-
ing also prevents the kind of migration observed when flexibility enhancers (such as plasticizers) bleed.
SAMPLE PREPARATION
The materials were applied by spraying them onto a uniformly primed sheet of metal, to a dry film thickness of 80–90 µm. Researchers selected a flexible epoxy resin primer that met the requirements of mechanical tests such as the mandrel bend test and Erichsen cup-ping test.
The top coat was cured in the laboratory at room temperature in order to simulate crosslinking as it would typically proceed on large pieces of infrastruc-ture. The first test was performed after 14 days, with additional tests after one, three and six months. Posi-tive results were obtained from the adhesion test, which involves pulling a piece of tape off of a section of coat-ing into which a crosshatch pattern has been cut. All of the coated substrates were rated GT 0, regardless of the concentration of ALBIDUR® 1223 or the amount of time involved.
DURABLE YET FLEXIBLE: Solutions for coating metal objects in multilayer structures
Erichsen cupping test
1 m0.5 m 3 m 6 m
Cup
ping
[m
m]
0
1
2
3
4
5
6
poor
good
time [month]
Guiding Formulation (incl. 5% ALBIDUR® 1223)Reference Formulation
13
No negative side effects were noted during process-ing; drying – both of the surfaces and of the coating as a whole (as measured by a drying recorder) – was improved by adding the product at concentrations of 5 and 10%.
VOC OBSERVATIONS: THE NON- VOLATILE CONTENT REMAINS LOW
Reducing the solvent content of paints is becoming increasingly important throughout the world.
Innovative α-Ω-alkoxysilane-terminated polyure-thane technology allows researchers to formulate long-lasting, highly resistant anti-corrosion coatings. At the same time, the solids content of the resulting paint formulation remains quite high. In conclusion, the solid
content of test formulations is very high, coming in at about 95%, which corresponds to an ultra-high-solids coating material.
RESISTANCE TO CHEMICALS
Another critical test criteria is resistance to aggres-sive chemicals. To test this property, a coated surface was treated with 20% sodium hydroxide, hydrau-lic fluid, and 50% sulfuric acid. Constant exposure to these chemicals can cause the coating film to soften or delaminate.
After 14 days, three months and six months, the effect of the chemicals on the samples was found to be extremely uniform: The films only tended to soften on surfaces exposed to 50% sulfuric acid. Crosslinked
ALBIDUR® 1223, in other words, has no negative impact on the ability of SILIKOPON® EF to resist common aggressive chemicals.
FLEXIBLE AND ROBUST
Hardness measurements are a proven method for quantifying the service life of a surface. The degree of flexibility of a cured coating can be gauged very well using not only the König pendulum hardness test (DIN 53157), but also the Erichsen cupping test (DIN 50101) and the conical mandrel bend test (ISO 6860).
At a concentration of 5%, ALBIDUR® 1223 success-fully reduced pendulum hardness by approximately 25% and absorbed 50% of the vibrations at a concentration of 10%. Performance in the Erichsen cupping test could be improved at these concentrations by approx. 400% and 500%, respectively. Results for the conical man-drel bend test were likewise improved, from unmeasur-able to 6 mm. Both tests demonstrate that the top-coat becomes less sensitive to mechanical point stress.
Damage such as chalking or a yellowish-brown dis-coloration are typical of coatings subjected to constant environmental exposure. For this reason, stressing samples in a QUV tester is another important test, as it quickly simulates exposure to the elements. Results after 2,000 hours were uniform, with all samples exhib-iting color difference values (delta E*) of approximately 1.15 — a value this low is considered to be very good.
SUMMARY
SILIKOPON® EF and ALBIDUR® 1223 are non-isocya-nate-curing resins offering an excellent base resin for long-lasting, low-VOC anti-corrosion systems for met-als. When combined in normal relative proportions, this duo allows manufacturers to selectively adjust the hard-ness of a coating with no negative impact on important properties such as chemical resistance, light fastness, or resistance to weathering. These basic components of paints and coatings give manufacturers what they need to meet the demands of the future: durability and flexibility.
Weather resistance
1000 h500 h 1500 h 2000 h
delta
E
time [hours]
0.9
1.1
1.2
1
Guiding Formulation (incl. 5% ALBIDUR® 1223)Reference Formulation
CONTACT
Marco Heuer [email protected] Marion Siemens [email protected] Fabian Eichenberger [email protected]
Chemical test
AGING OF TEST PANELS 14 d 1 m 3 m 6 m
Reference formulation
Guiding formulation (incl. 5% ALBIDUR® 1223)
THE CHEMICAL RESISTANCE IS UNCHANGED WHILE THE OVERALL ROBUSTNESS OF THE COATING IS IMPROVED!
According to DIN EN ISO 2812-4 for 8 hours
= fully resistant against: Sulfuric acid (50%) Sodium hydroxide (20%) Hydraulic oil fluid
Pendulum hardness
10.5 3 6
Swin
gs o
f pen
dulu
m
time [months]
80
60
100
120
140
poor
good
Guiding Formulation (incl. 5% ALBIDUR® 1223)Reference Formulation
14
The Coatings Expert | Issue 4 | March 2018
Evonik Performance Materials has a long-standing his-tory as a supplier of monomers for crosslinking, for example, polyol acrylic resins with diisocyanates, but also offers a broad portfolio of methacrylate cross-linkers for reactive systems, to improve their mechani-cal and chemical properties.
The coatings and adhesives industry has a growing interest in environmentally friendly and non-hazardous systems. One further need is to introduce innovative technologies that can save energy during the curing process. Over recent years Evonik´s Methacrylates Business Line has developed and launched on the mar-ket several innovative products to meet these trends and the desire for advanced solutions.
One response to these needs was the development of VISIOMER® 6976, which contains benzophenone meth-acrylate and enables daylight curing of acrylic resins at room temperature. This monomer is fully commer-cialized and has now not only found its way to coatings producers but is also used in adhesive formulations.
Another trend in the coatings industry is a reduc-tion of hazardous chemicals, which can affect curing without isocyanates. For non-isocyanate coatings the Methacrylates Business Line has developed VISIOMER® GCMA (glycerol carbonate methacrylate), a new prod-uct with a carbonate structure in the side chain that reacts readily with diamines. It thus allows resin formu-lators to build polymers with hydroxyurethane groups. For experts it comes as no surprise that this kind of resin shows outstanding adhesion on all kinds of polar substrates, on top of the typically excellent methacry-late properties.
Broad screening of different carbonate resins with various diamines produced crosslinked resins whose properties (water absorption, pendulum hardness, cross-cut tests) are very similar to those of conventional urethanes from polyol and isocyanate.
VISIOMER® KEMA AS ENVIRONMENTALLY FRIENDLY ALTERNATIVE
A more eco-friendly methacrylate monomer can now be used in place of the harmful component diacetone acrylamide (DAAm) in resins for condensation cross-linking. VISIOMER® KEMA is a new developmental product for formulation of environmentally friendly waterborne coating systems with modifiable proper-ties. Its strong crosslinking capability allows it to easily substitute diacetone acrylamide in ambient temperature crosslinking. VISIOMER® KEMA can alternatively be reacted with diamines or dihydrazides as crosslinking agents and is suitable for water borne systems.
Basic investigations show that the properties of KEMA containing resins that are crosslinked with ADH are superior to those of resins with AAEMA (acetoace-toxyethyl methacrylate) or DAAM with respect to sol-vent absorption, pendulum hardness and gloss.
VISIOMER® METHACRYLATES: A versatile toolbox for crosslinking solutions
Crosslinking is an important technology for many applications, especially for coatings and adhesives. Crosslinking technologies widely applied today by many paint formula-tors are polyurethanes and epoxy systems.
Figure 1: Solvent absorption and mechanical properties as a function of BPMA content of cured systems
0
1
2
3
4
5
6
7
8
9
10
0,3 5 3,2 1,6 0
400
800
1.200
1.600
MEK
abs
oprt
ion
[wt%
]
BPMA [wt%]
tens
ile s
tren
gth
[MPa
]
Figure 2: Pendulum hardness and water uptake of crosslinked films using various diamines (X-linkers A, B, and C)
50
100
150
200
120
curing temperature [°C]
6060 12060120145HEMA+ HDI
GCMA+ X-linker A
GCMA+ X-linker B
GCMA+ X-linker C
0
1
2
3
4
5
6
7
0
pend
ulum
har
dnes
s [s
]
wat
er u
ptak
e [%
]
15
Specialty medium- to high-molecular-weight (MW) polyester resins can be used in food can coating appli-cations. These polyester resins provide good flexibility and substrate adhesion – properties that are important in this particular market.
In some instances, however, additional adhesion is required to pass the stringent sterilization process that canned foods must undergo. During sterilization, the sealed food-filled cans are heated under pressure at 129 °C or more for one hour. Under such conditions, coating delamination can occur.
To overcome this delamination issue, Evonik offers the well-known adhesion promoter TEGO® AddBond LTW: a unique polyester that enhances the adhesion of the high-MW polyester resin to the metal substrate. Its chemical functionalities allow it to create a strong coordinating complex with the substrate for improved adhesion. Image 1 depicts these mechanism of adhesion promotion.
TEGO® AddBond LTW also improves cohesion and adhesion in metallic-finish can coatings, as illustrated in Image 2. It promotes better orientation of aluminum flakes, resulting in a brighter appearance for the metal-lic finish.
It enhances the adhesion and cohesion of the poly-ester coating while also improving its corrosion protec-tion and flexibility. TEGO® AddBond LTW is listed on the A lists of the Swiss Ordinance 817.023.21, Annex 6. Detailed information on the FDA status is available on request.
SET NEW TRENDS
Our aim is to continue as leaders in innovation trends for specialty methacrylates. Therefore, the Business Line had run an Open Innovation program “Next-Gen-eration Cross-Linkers for Acrylic Resins”. Several research institutes around the world contributed in this competition and submitted promising ideas that were evaluated towards the end of 2017.
Figure 3: Solvent absorption and gloss of KEMA/ADH crosslinked films compared with AAEMA and DAAm
100
200
300
400
500
600
700
800
50
100
150
4% AAEMA 4% DAAm 4% KEMA00
MIB
K up
take
[%
]
glos
s at
60°
CONTACT
John Wey [email protected]
TEGO® AddBond – LTW: The Extra Adhesion for Can Coatings
Image 1: TEGO® AddBond – Mechanisms of adhesion promotion
OH
HOOC–O OH
M
OH
Ability to covalently link to binder
Interaction with substrate
Interaction with binder
Coordination to e.g. surface metal atoms
Image 2: Improved Cohesion and Adhesion in Metallic Coatings
substrate
CONTACT
Bob Lin [email protected]
16
The Coatings Expert | Issue 4 | March 2018
ADDRESSING HEALTH CONCERNS FOR TERRAZZO FLOORING APPLICATORS WITH NONYLPHENOL FREE PRODUCT
TableProperties of ANCAMINE® 2814 compared to typical curing agent for Terrazzo application.
ANCAMINE® 2814 TYPICAL CURING AGENT FOR TERRAZZO
Color (APHA) <1 <1
Gel time (min) > 30 > 30
Mix Viscosity (cP) 1000 1683
Shore D Hardness: 4 hrs 85 70
Shore D Hardness: 24 hrs 85 88
CONTACT
Shafiq Fazel [email protected]
Svetlana Ivanova [email protected]
Terrazzo is a centuries-old flooring option
that provides a huge versatility in design and can be found everywhere, from ancient palaces to current day airports, hospitals, museums, schools, and many other buildings. Terrazzo flooring can be described as a composite material that consists of chips of aggregates, such as marble, quartz, granite or glass, combined within a binder material. When epoxy systems are used as a binder, the resulting terrazzo floor exhibits exceptional durability, beautiful aesthetics, and low maintenance.
A typical epoxy terrazzo binder is 100% solid, two-component epoxy system that includes liquid epoxy resin and amine-based curing agent. Most exist-ing curing agents for terrazzo application contain alkylated phenols, such as nonylphenol, which can pres-ent a significant health concern to flooring applicators
and end-users, due to a classification of these materials as endocrine disrupters.
As a market leader in developing innovative cur-ing agents, Evonik has introduced ANCAMINE® 2814 curing agent, which contains no alkylated phenols, in response to these concerns. In addition to address-
ing health concerns for terrazzo flooring applicators, ANCAMINE® 2814 curing agent also offers a long pot-life with rapid hardness development, low viscosity, and low color. (Table)
17
Developing industrial and commercial floor coatings that are durable and eco-friendly with pleasing aes-thetics is a challenge. Formulators traditionally have had to sacrifice one attribute to gain another. Well, times have changed. Evonik’s polycarbamide amine curing agent technology, in combination with Evonik’s VESTANAT® polyisocyanate resins, offers a one-stop shop for advanced aliphatic polyurea or polyaspartic floor coatings. The benefits of this two-component sys-tem include fast return to service, rapid low tempera-ture cure, UV durability and great chemical resistance.
Evonik offers several polycarbamide curing agents including AMICURE® IC-221, AMICURE® IC-321 and AMICURE® IC-322 curing agents. The properties of the three curing agents are shown in Table 1. AMICURE® IC-221 curing agent provides return to service of only two hours at ambient conditions with rapid property development even at low temperatures. AMICURE® IC-321 curing agent provides return to service of six hours with long open time for applicators to apply during warmer temperatures and high humidity condi-tions. AMICURE® IC-322 curing agent is a new unique
curing agent that retains the UV stability and durabili-ty of the previous curing agents, and also allows sheen to be customized between high gloss and satin. These curing agents are fully compatible with one another and can be combined in various ratios to tailor a coating for-mulation reactivity for specific customer needs.
Polycarbamide curing agents are designed to deliv-er clear and pigmented coatings that can be applied up to 20 mils in a single pass directly over concrete or an epoxy primer when cured with standard polyisocyanate resin. Additionally, Evonik offers a strong portfolio of aliphatic polyisocyanate resins, or crosslinkers, based on isophorone diisocyanate (IPDI) and hexamethylene diisocyanate (HDI) technology for light stable polyure-thane and polyurea coatings. The benefits of using these crosslinkers include high chemical resistance; dura-bility against environmental impacts; high reactivity and compatibility, even at low temperatures, and short curing cycles. Evonik’s recommended crosslinkers for the AMICURE® IC curing agents that are based on HDI trimers are shown in Table 2.
The coating formulation is prepared by mixing AMICURE® curing agent and VESTANAT® polyisocyate resin and is typically applied by squeegee, followed by a single back-roll. The reaction of the two components begins immediately after mixing and the thermoset coating resulting from the mixture cures very rapidly. Both high humidity and higher application temperature will accelerate the cure in these resin systems, which can significantly impact pot-life and cure times. Con-versely, lower temperature and humidity will extend working time. Applicators can easily adjust their sys-tem performance by modifying the ratio of AMICURE® IC curing agents in the final formulation. The low mix viscosity of the AMICURE® IC curing agents and poly-isocyanates formulation makes it easy to use and allows formulation of 100% solids systems for odor-free, low-VOC and low emission coatings, which are preferred by applicators and end users. The fast cure time of polycar-bamide systems provides applicators with the ability to minimize downtime and increase productivity.
The features and benefits of the polycarbamide cur-ing agents combined with VESTANAT® polyiscoayates are highlighted in Table 3. The final aliphatic polyurea or polyaspartic coatings formed by the combination of AMICURE® curing agent and VESTANAT® polyisocy-ate have very high performance properties including superior aesthetics; enhanced UV stability; great chem-ical resistance; high film hardness; impact and abrasion resistance.
CONTACT
Shafiq Fazel [email protected]
Svetlana Ivanova [email protected]
ONE- STOP- SHOP FOR ADVANCED POLYASPARTIC FLOOR COATINGS WITH EVONIK POLYCARBAMIDE TECHNOLOGY AND VESTANAT® ISOCYANATE RESINS
Table 2: Polyisocyanate resins recommended for polycarbamide amine curing agents. VESTANAT® HT Polyisocyanates; HDI-trimer
PHYSICAL FORM NCO CONTENT VISCOSITY AT 23 °C
COMMERCIAL AVAILABILITY
VESTANAT® HT 2500 L 90% in BuAc/Solvesso 100 (1:1) 19.6% 550 mPas 500 mPas (25 °C)
Europe NAFTA
VESTANAT® HT 2500/100 100% (liquid) 21.8% 3.000 mPas 2.500 mPas (25 °C)
Europe NAFTA
VESTANAT® HT 2500 LV 100%, low viscosity (liquid) 23.0% 1.200 mPas 1.100 mPas (25 °C)
Europe NAFTA
Table 3: Features and benefits by product
AMICURE ® IC-221 AMICURE ® IC-321 AMICURE ® IC-322
UV stable + + +
Fast return to service + (<2h) + (6-8h) + (6-8h)
High abrasion resistance + + +
Low temperature cure + + +
Low color, consistent high gloss + + +
Customizable sheen (with flatting agent) – – +
Film thickness up to 20 mils in one pass + + +
High Shore D hardness + + +
High impact resistance + + +
High chemical resistance + + +
Environmentally friendly – 100% solids, 0 VOC + + –
Environmentally friendly – Low VOC + + +
Table 1: Physcial properties of AMICURE® IC curing agents.
CURING AGENT TYPE Col
or1
(Gar
dner
)
Vis
cosi
ty2
(cP
@ 7
7°F)
Spec
ific
Gra
vity
(@
77°
F )
Am
ine
Equi
vale
nt W
eigh
t
Use
Lev
el
(PH
R)4
Vis
cosi
ty B
uild
(m
in @
77°F
, to
12,0
00 c
P)
Thin
Film
Tac
k Fr
ee T
IME
(min
@ 7
7°F)
Thin
Film
Thr
ough
Cur
e
(H, @
77°
F)
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AMICURE® IC-221 Modified Amine < 1 350 1.06 376 185-195 22 45 2.5 118 ambient temp
AMICURE® IC-321 Modified Amine < 1 225 1.05 379 185-195 55 102 6-7 104 ambient temp
AMICURE® IC-322 Modified Amine < 1 105 1.08 379 190 60 75 7 104 ambient temp
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The Coatings Expert | Issue 4 | March 2018
POLYCARBAMIDE TECHNOLOGY – MATERIALS AND PHYSICAL PROPERTIES
A polycarbamide functional group results when two amines are linked together via a carbonyl group1. The key moieties within polymeric cross-linked systems for polycarbamide (left) and polyurethane (right) are given in Figure 1. Polycarbamides have a distinct reactivity with isocyanates and reactivity rates can be customized through structure.
Figure 1Key moieties within the polymeric cross-linked systems
OR R
NH
NH
OR R
NH
O
polycarbamide (left) and polyurethane (right)
Evonik offers two polycarbamide amine curing agents: AMICURE® IC-133 curing agent and AMICURE® IC-166 curing agent. Table 1 shows the reactivity via gel time and pot-life of each, indicating that these products are ideally suited for dual component spray applications.
The polycarbamide amine curing agent properties are summarized in Table 2. These products are specif-
ically designed to be used with polyisocyanate resins. The HDI trimer used in this study had solids of 100% and NCO of 21.8%.
PERFORMANCE PROPERTIES
Pigmented DTM polycarbamide coatings were formu-lated with AMICURE® IC-133, AMICURE® IC-166 and mixtures thereof to meet specific cure requirements. These formulations were benchmarked against a 2K PU. Zinc phosphate anticorrosive pigments were used in all of the DTM coating formulations for this study.
Coating Performance: In Table 3, the performance properties of polycarbamide DTM coatings are com-pared to a commercial 2K PU DTM coating. First, the levels of VOC’s in polycarbamide DTM’s are significant-ly lower than a commercially available 2K PU DTM. This
is significant to the formulator as demand for reduced exposure for workers continues.Next, the data shows that the dry times for the polycar-bamide technology is significantly less than the com-mercially available 2K PU formulations. With contin-ued pressure to decrease job time and labor expense, a product with fast dry times becomes highly beneficial from an economic standpoint.
The data also shows that the UV resistance of the polycarbamide formulations is improved compared to the polyurethane. Often PU is chosen for UV stability. Further, the other key properties tested were as good as the 2K PU.
Corrosion Performance: Corrosion resistance prop-erties of the same DTM coatings were tested using salt spray for 500 h. The viscosity of the coatings was reduced to 28 seconds as measured by #2 Zahn cup with MAK solvent and spray applied to iron phosphat-ed steel, zinc phosphated steel, sand blasted steel and cold rolled steel. Pictures of the panels after 500 h are shown in Figure 2.
The pictures show that the polycarbamide DTM and 2K PU coatings had similar performance on cold rolled steel with no corrosion creep or face blisters and that the polycarbamide performed well on other substrates.
Chemical Resistance Performance: Spot tests were performed on DTM formulations in order to under-stand their chemical resistance properties. The coat-ings were applied by drawdowns on steel panels at 3 mil DFT, dried for 7 days at room temperature, and spots of reagents were applied (2-3 cm diameter). The spots were covered to prevent evaporation and rated after 24 h of exposure. The results are shown below in Table 4.
POLYCARBAMIDE RESINS FOR INDUSTRIAL DIRECT TO METAL COATINGS APPLICATIONS
INTRODUCTION
Corrosion protection of metal is often obtained by multi-layer coating systems involving at least a primer and a top coat often of different chemistries. This introduces complexity in the application and drying equipment as well as their respective processes. Direct-to-Metal (DTM) coatings provide both decorative and protective properties to metal while simplifying the coating process.
The current state of technology for DTM coatings for ISO 12944 moderately corrosive (C 3) environments is a 2-part polyurethane (2K PU). 2K PU DTM coatings are formulated using aliphatic polyisocyanates and polyester or acrylic polyols for acceptable outdoor weathering performance. Both tend to be viscous and require solvent which contributes high levels of volatile organic compounds (VOC’s) and results in slower cure, poor flexibility and compromised corrosion protection.
Evonik introduced new polycarbamide technology that provides excellent corrosion protection and enhanced productivity through faster cure rates and reduced formulation complexity. The polycarbamide technology offers excellent adhesion to difficult metal substrates like galvanized, cold and hot rolled steel as well as improved coating flexibility and superior weathering properties – all at very low VOC’s. This article reviews the chemistry and application properties of polycarbamide technology in DTM formulations compared to traditional 2K polyurethane systems.
Table 1Gel time and pot-life for clear coats based on polycarbamide resins with HDI trimer and methyl amyl ketone
POLYCARBAMIDE GEL TIME AT 25 °C, min POT LIFE (TIME TO 2000 cP), min
AMICURE® IC-166 / HDI Trimer / MAK 22 11
AMICURE® IC-133 / HDI Trimer / MAK 64 20
Table 2Typical physical properties of AMICURE® IC-133 and AMICURE® IC-166
PROPERTIES AMICURE® IC-133 AMICURE® IC-166
Amine Equivalent Weight (g/eq) 256 267
Viscosity @ 25 °C (mPa-s) 1734 1500
Density 1.06 1.07
Color (APHA) <50 <50
Tg°C 7 day cure at 25 °C 55 53
19
CONCLUSIONS
AMICURE® IC133 and IC166 therefore provide benefits above industry standard 2K PU technology by meeting the demanding market needs for reduced VOC’s, fast cure and excellent barrier properties without sacrific-ing the other key performance properties tested.
For a copy of the full technical paper that includes the full data set, the formulary, the use of this
technology as a top coat, and performance compared to polyaspartic systems, please contact us at
References:1 Rob Rasing,& Jared Bender Polymer Paint Color Journal PPCJ – May 2013
Table 4Chemical resistance spot tests- DTM coatings
CHEMICAL AMICURE® IC-133 DTM AMICURE® IC-166 DTM COMMERCIAL 2K PU DTM
Xylene Slight swell Slight swell Slight swell
10% NaOH No effect No effect No effect
10% H2SO4 No effect No effect No effect
10% HNO3 Slight stain Slight stain Slight stain
Hydraulic oil No effect No effect No effect
Gasoline No effect No effect No effect
Diesel fuel No effect No effect No effect
Table 3Performance properties of AMICURE® IC-133, AMICURE® IC-166, compared to 2K PU DTM
PROPERTY AMICURE® IC-133 DTM AMICURE® IC-166 DTM 2K PU DTM
VOC at application (g/L) 200 200 317
Admixed viscosity (Zahn #2, s) 28 28 28
Dry times* (STT, TF, DH, TC) (h)ASTM D5895 0.5, 4.0, 5.0, 7.0 0.3, 0.5, 0.8, 1.0 1.0, 2.5, 3.0, >14
Gloss (60o)ASTM D523 86 89.5 90
QUV B, 1000 h-, 60o gloss ret. / ∆EASTM D4587 84 / 0.5 85 / 0.5 80 / 1.5
Water immersion (24 h immersion) Pass Pass Pass
Tape adhesion (dry, wet)ASTM D3359 5A, 5A 5A, 5A 5A, 5A
Direct / reverse impact flex (in-lbs)ASTM D2974 160 / 160 160 / 160 160 / 160
Persoz hardnessASTM D4366 196 191 190
Mandrel bend (in)ASTM D522 Pass 1/8” Pass 1/8” Pass 1/8”
* STT= Set To Touch | TF=Tack Free | DH= Dry Hard | TC= Through Cure
Figure 2
AMICURE® IC-133 / AMICURE® IC-166 2K PU
Iron phosphated steel Zinc phosphated steel Sand blasted steel Cold rolled steel Cold rolled steel
CONTACT
Sudhir Ananthachar [email protected]
As a country with an ever-growing coatings market, China has recently started to focus more on the envi-ronment. This has created a new challenge for the Chi-nese coatings industry: develop more environmentally friendly coatings.
This new focus has impacted the container coatings market in a unique way. In order to reduce the VOCs in container coating formulations, the China Container Industry Associate (CCIA) has decided to change the former solvent-based container coatings to water-based container coatings. This change – implemented on April 1, 2017 – is mandatory.
As a result of the CCIA’s mandate, producers of container coatings are now faced with new challeng-es in the manufacture of their products. When applied via airless spray, these high-build waterborne coatings are prone to more micro-film generation than previ-ous solventborne coatings. The micro-foam and its
consequential pinhole problem negatively impact the anti-corrosion performance of the coatings, which is vital for container coatings.
Fortunately, Evonik offers a solution for this micro-foam challenge: TEGO® Airex 901 W, a deaerator concentrate with 100% active matter based on poly-ether siloxane combined with hydrophobic parti-cles. This additive optimizes the composition of basic components, allowing for excellent elimination of micro-foam.
In order to maintain the anti-corrosion properties needed in this market, waterborne container coatings are developed as a 3-layer system (similar to solvent-borne container coatings): an epoxy zinc-rich primer, a 2-pack epoxy base-coat, and a polyurethane acrylic (PAC) top-coat. TEGO® Airex 901 W is very suitable for both epoxy and PAC systems and can therefore be used in the entire 3-layer coating system.
Photo 1 illustrates the difference in performance of a coating formulated with TEGO® Airex 901 W and a blank, without the additive. The current testing meth-od consists of counting the number of foam bubbles in the surface intersection with a magnifier, after airless application. In this critical test, TEGO® Airex 901 W – a 100% silicone-based concentrate with strong deaerat-ing efficiency – displays the best balance between effi-ciency and compatibility, both in exterior and interior coating systems, and significantly increases the protec-tion effect of the waterborne paint film.
The extended family of TEGO® Airex products for waterborne coatings – such as TEGO® Airex 902 W and TEGO® Airex 904 W – also received positive feed-back from customers. In addition, our non-foaming sub-strate wetting agents – TEGO® Twin 4000/4100 and SURFYNOL® 104 series – also displayed good results in this application.
IMPRINT Layout / Design Liebchen+Liebchen Kommunikation GmbH www.LplusL.de Frankfurt am Main, Germany
Print Knipp Medien und Kommunikation GmbH, Dortmund Printed in Germany
DATES April 10 ‒ 12, 2018 American Coatings Show | USA, Indianapolis
December 4 ‒ 6, 2018 ChinaCoat | China, Guangzhou
Editor Evonik Industries AG Rellinghauser Straße 1 – 11 45128 Essen, Germany [email protected]
The Coatings Expert | Issue 4 | March 2018
FROM SOLVENTBORNE TO WATERBORNE: Deaerator TEGO® Airex promotes technology shift in container coatings
CONTACT
Huibin Zhao [email protected]
View via microscope:
Left: Coating formulated without TEGO® Airex 901 W
Right: Coating formulated with TEGO® Airex 901 W
100 µm 100 µm
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