What is PU thinner composition

Polyurethane paint: paint in top form

According to the manufacturer, a new water-based 1K polyurethane paint should result in particularly hard-wearing and mechanically highly resilient surfaces. The special 3-D structure of the binder matrix not only prevents the writing effect; The extremely smooth surface is also scratch and impact resistant and resistant to dirt and hand perspiration. The Malerblatt took a close look at the polyurethane paint.

Author: Susanne Sachsenmaier-Wahl | Photos: CD-Color

Particularly high demands are placed on lacquers on particularly stressed components in public or commercial areas, but also in privately used hallways or in children's rooms. In addition to being insensitive to impact and scratching, resistance to grease and hand perspiration is desirable. It is also often required that the surface is easy to clean and that the undesirable “writing or polishing effect” is largely absent. All of this should a paint layer only a few micrometers thick be able to achieve?

Very good results have already been achieved in recent years with water-based polyurethane paints. However, these highly resistant paints usually consist of two components. And this is where problems arise again and again. Because the handling of a 2K paint is often not suitable for the construction site: First, the material must be mixed exactly according to the manufacturer's instructions (which can be complicated, especially with partial quantities), then the pot life must be taken into account, which can create time pressure for the processor. For some craftsmen this is too uncomfortable.

Since September 2017, a water-thinnable polyurethane special colored lacquer has been promising all these properties in just one component - and therefore ready to use out of the pot. Christopher Jahn, Product Manager at CD-Color in Herdecke, where the lacquer was developed and produced, remembers: "We wanted and want to expand the area of ​​water-thinnable lacquers in the future." They worked on developing a "generalist", with which all employees of a painting company can be reached - even those who have no technical training, but are very often to be found on construction sites. Jahn is satisfied with the result: “In terms of mechanical resilience, with the new 1K paint we are pretty close to what we know from the 2K range.” The Malerblatt wanted to know exactly and so I got this new one A closer look at the paint generation.

No polishing or writing effect

One thing is immediately noticeable when looking at it and feeling it: the new material impresses with its very smooth surface. The fact that this is also extremely hard and shock-resistant becomes clear in the "mechanical endurance test": fingernails, even rings, keys or coins that are rubbed with pressure over the paint surface leave almost no traces - whatever remains visible, it is the metal abrasion of the scratched object. The mechanical robustness is of great importance, especially with intensive colors: Here the coating scores - so I learn from the graduate engineer Elfriede Gartz, who played a key role in the development of the new paint - with its 3-D structure, which is the case with mechanical Prevents the so-called polishing or writing effect. As a reminder: When subjected to mechanical loads, matt coating materials often leave behind whitish, glossy marks that can no longer be removed - the dreaded writing or polishing effect.

3-D structure as a protective shield

And what is special about the 3D structure? Elfriede Gartz, technical director of development at CD-Color, explains: “With a conventional acrylic paint, the binding agent matrix is ​​compressed by mechanical action. The 3-D structure withstands the mechanical impact. “Of course, that is still a bit too succinct for me and I would like to know why that is the case. Elfriede Gartz is not at a loss for an answer and she takes me into the depths of dispersion film formation. While a standard dispersion binder forms a linear structure without side chains, the 3-D dispersion film formers produce a branched structure with side chains. Terms like “electronegativity differences between the atoms” and “dipole-dipole interaction” come up and I quickly notice that my chemical background is now exhausted. But that's not so bad at all, because what Elfriede Gartz then tells me, even a painter without a chemistry degree can easily understand: The physical effects of the new 1K polyurethane paint create a three-dimensional network from the side chains, and this network is in it the pigments embedded. During the drying process, the polymer particles melt together and, with the increased proportion of high-quality polyurethane binders, form a stable 3-D structure that can hardly be compressed under mechanical action. This almost completely prevents the unwanted writing effect, dirt cannot penetrate the pores and the surface's cleanability is significantly increased. The paint is also resistant to dirt, grease and hand sweat.

It is different with conventional water-based acrylate-based paints: Here the polymer chains (which do not have any “side arms”) are randomly assembled. The pigments are also randomly distributed and can therefore sometimes lie on the surface. Due to the exclusively linear arrangement of the polymer chains, the binder matrix is ​​compacted relatively quickly under mechanical stress. The pigments break and the affected areas begin to shine, which affects the appearance of the entire surface. As a result, chemical loads can damage the coating and dirt can be deposited on the surface.

Easy processing

The question still remains as to how the new special paint can be processed. Together with Benedikt Müller-Wortmann, the head of application technology at CD-Color, I go into the workshop and swing the brush or the roller. After professional pre-treatment and a primer with primer, the new 1K PU lacquer can be applied to wood, wooden materials, mineral substrates, metals, non-ferrous metals and hard plastics by brushing and rolling. The manufacturer certifies that the material has high hiding power, good flow and a long open time. And I am positively surprised: After replacing the painting tools with the computer keyboard a number of years ago and consequently being out of practice, I managed to paint by hand with a brush with the new polyurethane paint quite well. That probably indicates that the material is easy to process than on special craftsmanship ... With the roller - even for me - a decent application of varnish is child's play. The prerequisite is of course the right tool, as application engineer Carsten Schmitz, who supports me during the practical test, emphasizes. But natural hair bristles were already obsolete in the first generations of acrylic lacquer and synthetic bristles made way for them. Otherwise, conventional foam rollers are sufficient to apply the new polyurethane paint evenly.

The special 3-D structure always forms, even if the layer thickness is very thin, I find out on request. The opacity of the paint is also impressive. Nevertheless, one should of course pay attention to the prescribed layer thickness. But every practitioner knows that this cannot always be adhered to so precisely under construction site conditions. Only the processing and object temperature should not drop below five degrees Celsius, because then the binder (as with all water-based paints) no longer forms a film.

Polyurethane paint: For indoor and outdoor use

When used indoors, the odor-free polyurethane paint impresses with its minimized VOC content and thus ensures a pleasant room climate during and after processing. The material also meets the requirements of DIN EN 71: 2014 Part 3 on the safety of toys. I can see for myself that the smell remains very bearable even after prolonged exposure. Together with Bernd Thäwel, who works in the development laboratory in Herdecke, I - equipped with protective goggles and the like - produce my own "small batch" of the paint of one liter, which does not differ in any way from large-scale production in terms of ingredients. After about an hour I leave the laboratory again - without clouding my senses, but richer in the knowledge that paints are real high-performance materials.

With its special properties, the new paint surface is recommended as a scratch and impact-resistant protective shield for highly stressed components not only indoors but also outdoors. In the outdoor area, the high UV and weather resistance makes the coating particularly durable. The good blocking resistance also allows it to be used on windows and doors.

The silk-gloss lacquer surface is highly resilient, gloss, color and white stable. Yellowing is not possible, explains Elfriede Gartz - and it becomes chemical again - "because no triple bonds are formed that are responsible for the yellow effect". There is also no embrittlement, as is known from alkyd resin lacquers, since the new lacquer does not dry oxidatively, but rather hardens through a chemical reaction.

Last but not least, the polyurethane paint also has a lot to offer visually. Its extremely smooth, silk-gloss surface looks noble and of high quality. Using tint technology, 2,000 color tones according to RAL, NCS and other collections can be mixed from just two bases (white and transparent), something which the trade in particular should be pleased about: Their warehousing can thus be reduced to a minimum.

More information:
www.cd-color.de


PraxisPlus

For stressed surfaces

In the case of the paint used by
Editor Susanne Sachsenmaier-Wahl tested, it is "Lucite 1K-PU Color Satin" from CD-Color. Additional Information:

www.cd-color.de


Elfriede Gartz, Technical Director Development at CD-Color

“With a conventional acrylic paint, mechanical impact
the binder matrix is ​​compacted.
The 3-D structure can withstand the mechanical impact. "