In order to prepare high-solid coatings, first acrylic resins (HSAs) which contain 80% solid were synthesized, and then the prepared resins were cured with isocyanate at room temperature. In the synthesis of HSAs, viscosity, number average molecular weight (Mn) and conversion were 1372~2700 cps, 1520~1650 and 83~87%, respectively. Among the four kinds of initiators used, tert-amylperoxy-2-ethyl hexanoate was the most proper one in the synthesis of HSAs. With increasing Tg values, viscosity increased rapidly and molecular weight increased slowly. As a result of the examination of coated films, it was found that 60˚ specular gloss, impact resistance, heat resistance and cross-hatch adhesion were good, and pencil hardness, drying time and pot life were poor.
The high-solid coatings were prepared by blending the synthesized acrylic resin in the previous paper, and hexamethylene diisocyanate-trimer and curing it at room temperature. The characterization of the films of the prepared coatings was performed. The 60˚ specular gloss, impact resistance, cross-hatch adhesion, and heat resistance of the films proved to be good, and the pencil hardness, drying time, and pot-life proved to be slightly poor. From a viscoelastic measurement using a rigid-body pendulum, curing was accelerated with the Tg value.
Acrylic resins (HSCs : EA/EMA/2-HEMA/CLA) which contain 80% solid content were synthesized by the copolymerization of monomers (ethyl acrylate, ethyl methacrylate, 2-hydroxyethyl methacrylate) and functional monomer (caprolactone acrylate : CLA) which improves the crosslinking density and physical properties of films. The physical properties of the prepared acrylic resins (HSCs) containing CLA, are as follows: viscosity 1440~2630 cps ; Mn 1590~1660 ; and conversions, 81~86%, respectively. From the correlation of Tg values, viscosities, and Mn of the HSCs, it was found thst viscosity and Mn increased with Tg value.
Copolymers (HSA-98-20, HSA-98-0, HSA-98+20) which are acrylic resin containing 80% solid content were synthesized by the reaction of monomers, including methyl methacrylate, n-butyl acrylate, and 2-hydroxyethyl acrylate with a functional monomer, such as acetoacetoxyethyl methacrylate (AAEM), which may improve in cross-linking density and physical properties of films. The physical properties of prepared acrylic resins, containing AAEM, are as follows : viscosity, 1420~5760cps ; number average molecular weight, 2080~2300 ; polydispersity index, 2.07~2.19 ; conversions, 88~93%, respectively. To prepare acryl resins, four kinds of initiators including α,α'-azobisisobutyronitirile (AIBN), di-tert-butyl peroxide (DTBP), t-amylperoxy-2-ethyl hexanoate (APEH), benzoyl peroxide (BPO) were used. The viscosity of the acrylic resins prepared with these initiators was increased in the order of DTBP〉APEH〉AIBN〉BPO. APEH was proved as a suitable initiator in this study. Shear rates of acrylic resins were constant in respect to viscosity. From these results, it would appear that the resins have Newtonian flow characteristics and good workability.