Synthesis Of Hyperbranched Polyester And Its Application In UV-Curable Waterborne Coating

Hyperbranched polymers have spherical structures and a large number of peripheral functional groups,which have the advantages of good solubility,low viscosity,high fluidity and high reactivity.At present,it has great application potential in the field of coatings.Previous works were commonly based on the modification of the commercial hydroxyl-terminated hyperbranched polyester which is under the trade name of Boltorn produced by Perstorp.However,its AB₂ monomer only uses 2,2-dimethylolpropionic acid,making the internal hyperbranched structure monotonous.It is vital to develop new methods for preparing novel hyperbranched polymers.In addition,Boltorn is a non-renewable material.In this regard,the introduction of bio-based monomers to achieve green chemistry and sustainable development of hyperbranched polyester is also significant.In order to solve the above problems,A₂+B₃ monomer copolymerization method was used to prepare carboxyl-ended hyperbranched polyester and hydroxyl-carboxyl-ended hyperbranched polyester,named as CHP and HCHP,respectively,and applied to UV-curable waterborne coating.named as WCHPA and WHCHPA respectively.The detailed research content is as follows:1.CHP resin were synthesized with trimellitic anhydride（TMA）and neopentyl glycol（NPG）as the main monomers.The structure was confirmed by Fourier Infrared Spectroscopy（FT-IR）and Proton Nuclear Magnetic Resonance Spectroscopy（¹H NMR）.The best reaction temperature is 150℃;with the increase of the amount of TMA,the acid value of the resin increases and the molecular weight decreases.The acid value of the resin is between 256～285mg KOH/g;the test of Differential Scanning Calorimeter（DSC）and Thermal Gravimetric Analyzer（TGA）shows that the glass transition temperature（T_g）is 52.8℃,and the initial degradation temperature is 183℃～192℃.2.HCHP resin were synthesized with citric acid（CA）and 1,4-Cyclohexanedimethanol（CHDM）as main monomers.The structure was confirmed by FT-IR.The reaction temperature is 130℃;the acid value of the resin is between 255～274 mg KOH/g;the test of DSC and TGA shows that T_g is 28.1～30.1℃,which is lower than that of CHP,and the initial degradation temperature is 204.6℃,which is higher than CHP.3.Part of the terminal carboxyl groups of CHP were used to react with glycidyl methacrylate（GMA）to introduce acrylate groups.And the remaining carboxyl groups were neutralized with TEA to obtain water solubility.The obtained product is UV-curable waterborne coating WCHPA.The test of Laser Particle Size Analyzer and Rotary Rheometer indicated the effect of particle size on viscosity,and the results showed that the higher-COO^-content,the better water solubility.The water dilution can reach up to 20.wt%;FT-IR and TGA proved that The more acrylate content,the lower double bond conversion and the better thermal stability.The initial degradation temperature is 190～211℃,which is slightly higher than that of CHP resin.The Dynamic Thermomechanical Analysis（DMA）test showed that with acrylate groups increases,the T_g increases.The T_g of the cured film is 67.25～82.15℃;the test of the mechanical properties showed that as the acrylate groups increases,the hardness is higher,the flexible decreases and the adhesion decreases.4.Part of the terminal hydroxyl groups and carboxyl group of HCHP were used to react with GMA to introduce acrylate groups.And the remaining carboxyl groups were neutralized with TEA to obtain water solubility.The obtained product is UV-curable waterborne coating WHCHPA.The mechanical performance test results showed that the cured film of WHCHPA had a significantly improvement in comprehensive performance compared with WCHPA,in which the pencil hardness is 2H,the flexibility is 2 mm,and the adhesion is 2B.