Preparation And Modification Of The Polyester Resin Used In Two-Component Water-borne Polyurethane

This thesis conducts the preparation and modification of polyester resin used inthe two-component waterborne polyurethane coatings and is divided into two parts.The first part is about the synthesis and preparation of polyester resin dispersion,andthe second part is about the modification of polyester resin dispersion modified withacrylic resin.In the first part, a optimized process for synthesizing a waterborne polyesterresin was achieved. Experiments are as follows,xylene used as the reflux solvent, theK value of safety factor designed1.18, the beginning and ending of reactiontemperature from165℃to235℃, and the reaction time4h, then ratio of10%trimellitic anhydride was added to blocking system after cooling to120℃. Afterreacting at170℃for1.5hours, the acid value was controlled in order to achievewaterborne polyester resin. Then the above obtained polyester resin was neutralizedby amines with the neutralized degree of85%at the temperature of65℃, and thenwas dispersed in a high-speed dispersion machine at the speed control of2500r/min,and dispersed another for35min after dropping the deionized water. Taking thepolyester dispersion as a hydroxy compound, Bayer2487as the curing agent, awaterborne polyurethane coatings can be produced,and the dispersion and coatingfilm were characterized by the methods of infrared spectroscopy, particle size testing,and coated performance testing.The results showed that the film has good glossiness,hardness, flexibility, adhesion and the resistance of impact but less stability.In the second part, this thesis adopts the acrylic synthetic resin to modify thepolyester resin synthesized in the first part, and two modification methods, physicalmixing and chemical grafting were designed to synthesize water-basedpolyester-acrylic resin. The dispersion and coating film were characterized by themethods of infrared spectroscopy, particle size testing, and the key factors such as thecontent of acid in the system, the control of acid in the system, the neutralizer ofdispersoid, the molecular weight of polyester-acrylic resin, and particle sizedispersion impact on the performance of the dispersion and coating film were studied.The results showed that dispersions with reliable performance and averaged particlescan be achieved by taking the chemical grafting method to modify polyester resin.After cured with Bayer2487, the coating exhibits good adhesion，hydrolysis and acid-alkali resistance,and its the pencil hardness was2H, the glossiness up to110,impact resistance50kg.cm, the flexibility1mm respectively.With modified by acrylicresin with the content of10%, the performance of aqueous dispersion,particularly thestability can be greatly improved.