WorléePol 1181 – special polyester polyols for the modification of versatile reactive coating systems

For particularly high-quality solvent-based, solvent-free and also water-based coating systems, reactive 1 K and 2 K systems are usually used. These are, for example, isocyanate or melamine-crosslinking systems. These coating systems are often based on polyacrylates, polyurethane dispersions, polyesters and also other binder systems.

Depending on the different applications, it may be necessary to modify the developed coating systems with regard to certain properties. In order to avoid a completely new development, specially formulated polyester polyols of the WorléePol 1181 series, among others, are suitable here.

Polyester polyols are produced by esterifying polyhydric alcohols with polyhydric carboxylic acids.

The structure of the starting materials (aliphatic, cycloaliphatic, aromatic), their mixing ratio and the type and number of functional groups (e.g. hydroxyl or acid groups) determine the properties of the polyester resin. Polyester polyols for modification are mostly linear or only slightly branched and have a high proportion of reactive hydroxyl groups. The very broad selection of aromatic, aliphatic and cycloaliphatic monomers enables the targeted control of a wide range of properties.

The special composition of the polyester polyols of the WorléePol 1181 series makes it possible to optimise the following properties, for example, even with small additions:

• ?Elasticity
• Scratch and abrasion resistance
• Shine and fullness
• Processing and flow properties
• UV and weather resistance
• Chemical resistance
• VOC content

The two available products cover a wide range of applications

?Both WorléePol 1181/03 and WorléePol 1181/09 are characterised by a very low viscosity and a very high hydroxyl content. The compatibility of both products is given in different paint systems. It is therefore suitable for use in solvent-based, solvent-free but also water-based paint systems.

The products of the WorléePol 1181 series improve the mechanical properties in the coating systems to a similar extent. WorléePol 1181/09 does not contain any aromatic components and is therefore more suitable for systems that must have particularly good UV resistance.

Both products are available almost worldwide. However, the WorléePol 1181/03 is easier to use from a regulatory point of view in applications involving direct or indirect food contact.

WorléePol 1181/09 improves the properties of high-solids two-component polyurethane coatings

High-solid acrylates are produced by lowering the average molecular weight while maintaining the same viscosity. In doing so, an attempt is made to reduce the higher molecular weight portion, as this has a particular influence on viscosity. On the other hand, this high molecular content also ensures a certain viscoplasticity of the corresponding binders. In addition, high-solid acrylates should also dry quickly and have a high level of hardness. The corresponding composition of the monomers and modification is essentially responsible for this. Thus, it is possible today to produce acrylates that dry very well and are rich in solids, which can, however, be modified with regard to some of their properties.

Smaller additions of WorléePol 1181/09 are suitable to round off the properties of such coating systems.

For example, replacing only 5% of the main binder with WorléePol 1181/09 can significantly optimise the properties of, for example, a high-quality clearcoat [Table 2].

The first differences become apparent after the isocyanate-added coating has been adjusted to the desired processing viscosity [Table 2]. The coating modified with WorléePol 1181/09 has a measurably higher non-volatile content and thus a lower VOC content at the same viscosity.

The modification with WorléePol 1181/09 leads to a noticeably higher hardness with forced drying. The initial slightly lower hardness during drying at room temperature equalises completely in the course of the drying time [Table 3].

The clearcoat examined is certainly suitable for painting cars, for example. Scratch resistance is an important criterion when painting such objects. The lacquer is permanently exposed to brushes, fingernails, stones and dust. To assess scratch resistance, the clearcoats were painted on a blue basecoat and left to dry for a fortnight at room temperature. After the drying time, the surface was scratched with a Scotch-Brite sponge and a Crockmeter with 20 double strokes. The gloss level was determined before and after exposure. Likewise, such paint systems are subject to a certain recovery. The gloss levels sometimes recover somewhat over time, as the binders are subject to a slight reflow effect. This recovery was considered at room temperature and at 60°C. Such temperatures can be reached when a car is parked in the sun, for example.

The addition of WorléePol 1181/09 reduces the loss of gloss due to scratching and also improves recovery at room temperature. In contrast, there is no advantage when stored at 60°C. The polyacrylate used alone shows a good recovery effect here [Table 4].

Due to its composition, WorléePol 1181/09 is very UV resistant. This property is of course important for all varnishes used outdoors. The two clearcoats were compared in an alternating climate test with UV-B radiation (QUV B 313 rapid weathering). This rapid test includes an alternation of irradiation with UV-B radiation and a condensation phase without radiation. Even without light stabiliser, the base binder used achieves good resistance. The small addition of WorléePol 1181/09 improves this even further [Table 4].