Yasuharu Nakayama

Polymer blend systems for water-borne paints

The resin blend technique is a simple and useful method for improving paint properties. It is more important for water-borne paints in which design of resins needs more sophisticated techniques. Combinations of special emulsions, microgels and water-soluble resins have yielded excellent aqueous binders for various coatings. The concept of resin blend in our research is based on (1) blending of resins to reinforce their advantages to each other and (2) blending of minor resin components to compensate for the major resins weakness. This paper describes several specific examples of the resin blend for water-borne paints.

Curing of paint films with film-penetrative crosslinker at ambient temperature

The study deals with a method for curing paint films at ambient temperatures with a film-penetrative crosslinker without heating. The method is based on the phenomenon that when a wet paint film turns into the thermoplastic state, it is dipped in a solution of a crosslinker, the crosslinker penetrates and it can be cured with time. Here diacetone acrylamide copolymers were employed as a matrix resin and carbohydrazide as a film-penetrative crosslinker. As a result, it was found that (1) the penetrating rate had a close relationship to film curing speed, (2) the rate was accelerated with increase in the content of organic solvent in the crosslinker solution, with increase in the compatibility between the solvent and the resin, and with rising dipping temperature, and (3) the curing speed rose with acids in the reaction system. If the method is set up technically and properly engineered, industrial paints can be cured practically without bulky heating devices for hardening paint film.

High performance coating films cured by novel penetrating method: Anionic resin paints

This study deals with a method of curing paint film at ambient temperature with a film-penetrative crosslinker. The method is based on the phenomenon that, after a wet coating film becomes thermoplastic, it is dipped in an aqueous solution of crosslinker. The crosslinker then penetrates into the film, and the film can be cured with the passage of dipping time.Herein an anionic copolymer containing diacetone acrylamide was employed as the main resin and carbohydrazide as the film-penetrative crosslinker. Cured films can be prepared with a short dipping time using this method. Excellent films were obtained when they were dipped in a suitable crosslinker solution containing the proper organic solvents (accelerator of penetration rate) and an appropriate acid (promoter of the reaction). In particular, the adhesion after the water resistance test was excellent compared with that of the coating film obtained by the two-component coating method.

Decomposable crosslinking paint

This study describes a novel paint technology that meets the recycling needs of industrial products. The decomposable crosslinking paint exhibits good properties throughout its use in the natural environment, and after use, it can be easily eliminated in a special process to recover the substrates.The paint was cured by a reaction between a carbonyl group of resins and a hydrazide group of crosslinking agents. The reverse reaction could be promoted by three essential components: water (reactive material), an acid (catalyst), and a solvent (diluent between active groups). The paint film was eliminated by dipping the paint in the solution containing these three components. The rates of dissolution were determined by water content, acid strength, swelling intensity of solvent, and dipping temperature.

High performance coatings based on novel penetrative curing: Cationic electrodeposition coatings cured at ambient temperature

Cationic electrodeposition coatings were cured with a penetrative crosslinker at ambient temperature. This method is based on a novel technology in which coating films are dipped in aqueous crosslinker solution which moves into the film, accompanied by crosslinking. Pencil hardness, impact strength, solvent resistance and water resistance were improved with dipping time, that is, with the penetration of crosslinking. On the contrary, corrosion resistance was controlled by two opposing factors arising from the crosslinking—strengthening of the coating barrier property and weakening of the adhesion force. Excellent protective coatings were obtained by selection of resins and control of crosslinking.This system is well suited for the coatings on huge, complex structures in finished condition incorporated with glass, plastic, etc.

Decomposable crosslinking paint : Waste minimization

A paint film crosslinked by a reaction between a carbonyl group and a hydrazide group could be easily decomposed by dipping it in a solution containing water, solvents, and acids. The method was studied to minimize the waste produced by the elimination of the decomposable paint film. This was performed in two steps: a dipping in aqueous solution containing solvents and acids, and a successive wash with solvents. Decomposition of the crosslinking bonds and the elution of the decomposed free crosslinker took place in the first dipping process, and the elimination of the decomposed resins in the second washing process. The aqueous solution could be used for a long time without contamination by the decomposed resins, and the decomposed resin could easily be recovered from the resin solution containing no other contaminants.