Hiroharu Ohsugi

A new resin system for super high solids coating

Abstract This paper concerns a super high solids coating composed of two polymers; a silicone polymer containing SiH groups, and an acrylic or polyether polymer containing CC groups. The silicone polymer was prepared by the equilibrium reaction of SiH containing polysiloxane and other organosiloxanes in the presence of sulfuric acid. Acrylic polymers were obtained by free radical polymerization of a monomer having an alkenyl group and other vinyl monomers. Homogeneous clear paints were available by adjusting compatibility of polymers, and VOCs of the paints were very low due to the low viscosity of a silicone polymer and the absence of polar functional groups in the coating system. The crosslinking reaction of this coating occurred through the hydrosilylation reaction between SiH and CC groups. The performances of cured films, such as etch resistance and durability, were excellent.

Surface properties of polymer films including multiblock copolymer

B(AB)n multiblock copolymers of which the A block and the B block are hydrophobic and hydrophilic, respectively, were blended into crosslinkable coating compositions for preparing a hydrophilic surface, and compared with the graft copolymers including A and B as the pendant groups. The main constituent of A was polydimethyl-siloxane and that of B was poly(ethylene oxide). While the block copolymer slightly increased the hydrophobicity of the surface, it quickly became hydrophilic on contact with water. On the contrary, the graft copolymer increased the hydrophobicity even after its contact with water. Elementary analysis with ESCA demonstrated that both the silicon atoms and ether groups were concentrated on the very top of the surface in the films including the block copolymers but only silicon atoms were concentrated on the film surface which included the graft copolymers. In spite of their propensity to remain in the bulk due to their high surface energy, hydrophilic poly(ethylene oxide) moieties in the block copolymers migrated onto the near surface accompanying the movement of the hydrophobic polydimethyl-siloxane. because their mobility would be restricted by the bonding of both sides. Inclusion of the block copolymers significantly improved soil resistance. The advantage of the block copolymers as a surface modifier was further developed as an adhesion promoter. The introduction of a larger amount of the hydroxyl group into the hydrophilic block was effective for this purpose. This was discussed with respect to the change in the γp parameter.