Hyperbranched Aliphatic Polyesters and Reactive Diluents in Thermally Cured Coil Coatings

Abstract

Two hydroxy-functional hyperbranched aliphatic polyesters based on 2,2-dimethylolpropionic acid (bis-MPA) and a partially aromatic conventional polyester have been studied as thermoset resins for solvent-borne thermally cured polyester cross-linked with melamine coatings for precoated sheet metal, i.e., coil coatings. The hyperbranched polyesters differ with respect to the ratio of the end groups, being either hydroxyls or alkyl esters. The rheological properties of formulations with different polyester resin composition and reactive diluent, i.e., rape seed methyl ester, content have been evaluated with viscosity measurements. Films cured either under industrial cure conditions to obtain a peak metal temperature of 232-241 degrees C or at a lower temperature, i.e., 130 degrees C, on untreated or organic primer-coated hot-dipped-galvanized steel substrates have been prepared. The film properties have been evaluated with differential scanning calorimetry and conventional film characterization techniques, i.e., adhesion, impact, Erichsen cupping, pencil hardness, microhardness, and scratch and chemical resistance tests. Formulations possessing high drying ability with maintained suitable film application viscosity were obtained using a hyperbranched polyester resin and a reactive diluent. It is proposed that a solvent-free polyester/melamine formulation with sufficient film properties to withstand the rough forming procedures associated with coil coatings can be obtained by further modification of the resin and greater amounts of reactive diluent.

Alkyd resins based on hyperbranched polyesters and PET waste for coating applications

“…The application of hyperbranched polyesters, the most studied class of hyperbranched polymers, in different coating technologies such as UV curable coatings, powder coatings and in blends with epoxy resins have been presented [22,25,26].…”

Measurements of mass-fraction activity coefficient at infinite dilution of aliphatic and aromatic hydrocarbons, thiophene, alcohols, water, ethers, and ketones in hyperbranched polymer, Boltorn H2004, using inverse gas chromatography

“…It has a highly branched polymer backbone based on second-generation hydroxy-functional hyperbranched polyester in which 62.5% of the hydroxy-functional end groups have been modified with 8-carbon-long alkyl acid [38]. The B-H2004 was modified to a greater extent than the previous generation, giving a higher molar mass and a lower amount of remaining hydroxyls as shown in figure 1 [38].…”

Measurements of the density and viscosity of binary mixtures of (hyper-branched polymer, B-H2004+1-butanol, or 1-hexanol, or 1-octanol, or methyl tert-butyl ether)

“…Water content was analyzed by using the Karl-Fisher titration technique (method TitroLine KF). Samples of polymer or solvents were dissolved in methanol and titrated with steps 0.0025 cm 3 . The analysis showed that the water content in the solvents and the mixtures with the polymer was <230 Á 10 À6 .…”

“…It has highly branched polymer backbone based on second-generation hydroxy-functional hyper-branched polyester in which 62.5% of the hydroxy-functional end groups have been modified with 8-carbon-long alkyl acid [3]. The B-H2004 was modified to a greater extent than the previous generation, giving a higher molar mass and a lower amount of remaining hydroxyl groups.…”