The water-based polyester coatings have gained significant interest during time, indeed they have been considered a valid alternative to the commonly used solvent-borne coating systems due to their safety in application [1]. For this reason, water dispersions are gaining ground in many fields of application where the consumers safety is of utmost importance such as paints, adhesives, inks and the food packaging sector [2]. Besides, due to the current resource depletion, biodegradable polyester have emerged as a promising alternative for the replacement of their fossil-based counterparts [3]. Herein, an effective and innovative methodology for the preparation of water-based dispersions of biodegradable polyesters for coating purposes is presented [4]. The procedure involves two steps: in the first one, an oil-in water emulsion is obtained by mixing a solution of the chosen polyester in the proper organic solvent with a water phase containing surfactant and stabilizer. Different homogenization methods as well as oil/water phase ratio, surfactant and stabilizer combinations were examined. In the second step, the quantitative evaporation of the organic solvent provides stable water dispersions. The organic solvent recovered can be properly recycled to lower the process’s environmental impact. Biodegradable polyester dispersions with polymer contents around 20 % and biobased content higher than 85 % are obtained. Particle size was in the 200 nm or 500 nm range, depending on the chosen substrate and preparation conditions. Furthermore, the film forming ability of formulations developed was studied by identifying the temperature which allows the formation of continuous and homogenous polymeric film. The identified temperatures were observed to be related to the glass transition or melting temperature of the polyester. In order to coat the formulation onto porous-substrate, such as paper, the viscosity of the formulation was increased by the addition of thickeners. Several polysaccharides were tested and suitable rheology control was achieved with xanthan gum [5]: the thickened dispersions were successfully coated on paper. The barrier to liquid water was increased up to 50% with respect to the uncoated paper, the exact effect depending on the coating composition and morphology.
PREPARATION AND APPLICATION FOR COATING PURPOSES OF BIODEGRADABLE POLYESTERS WATER-BASED DISPERSIONS
Giada Belletti;Sara Buoso;Olga Bortolini;Monica Bertoldo
2022
Abstract
The water-based polyester coatings have gained significant interest during time, indeed they have been considered a valid alternative to the commonly used solvent-borne coating systems due to their safety in application [1]. For this reason, water dispersions are gaining ground in many fields of application where the consumers safety is of utmost importance such as paints, adhesives, inks and the food packaging sector [2]. Besides, due to the current resource depletion, biodegradable polyester have emerged as a promising alternative for the replacement of their fossil-based counterparts [3]. Herein, an effective and innovative methodology for the preparation of water-based dispersions of biodegradable polyesters for coating purposes is presented [4]. The procedure involves two steps: in the first one, an oil-in water emulsion is obtained by mixing a solution of the chosen polyester in the proper organic solvent with a water phase containing surfactant and stabilizer. Different homogenization methods as well as oil/water phase ratio, surfactant and stabilizer combinations were examined. In the second step, the quantitative evaporation of the organic solvent provides stable water dispersions. The organic solvent recovered can be properly recycled to lower the process’s environmental impact. Biodegradable polyester dispersions with polymer contents around 20 % and biobased content higher than 85 % are obtained. Particle size was in the 200 nm or 500 nm range, depending on the chosen substrate and preparation conditions. Furthermore, the film forming ability of formulations developed was studied by identifying the temperature which allows the formation of continuous and homogenous polymeric film. The identified temperatures were observed to be related to the glass transition or melting temperature of the polyester. In order to coat the formulation onto porous-substrate, such as paper, the viscosity of the formulation was increased by the addition of thickeners. Several polysaccharides were tested and suitable rheology control was achieved with xanthan gum [5]: the thickened dispersions were successfully coated on paper. The barrier to liquid water was increased up to 50% with respect to the uncoated paper, the exact effect depending on the coating composition and morphology.I documenti in SFERA sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
