October 2013 Archives

Paint is needed to form a coating film. Though the details of paints will be introduced later, paints in general are in flowable liquids, and surfaces to be painted (hereafter called painted surface) are coated using this fluid nature. There are many coating procedures,
In order to form coating films that have performance to fulfill the expectations, as the same as other surface treatments, foreign substances such as oil, dusts, and rust must not exist in between the paint film and the panted surface, thus preconditioning processes are required. Additionally, if order for the paint film to firmly bond to the base material surface, the paint element polymers must be oriented depending on the nature of the base material surface. To achieve this, it is advantageous for the paint to be in liquid forms where molecular motion is free. Therefore, most paints in use today are in liquids.

Painting process outline is as follows.

(1) Pretreatment Process

Surface to be painted is cleaned by removing foreign substances such as oil, dusts, and rust. Degreasing and Acid Washing correspond to this process. In addition as requested, mechanical polishing such as buff polishing and sand blasting, and chemical conversion treatments to improve the film adhesion and corrosion resistance such as phosphating and etc. are applied.

(2) Preparation of paints

Fluidity of the paints are adjusted to suit the painting method. Also, color adjustments are applied to obtain intended finished colors. For multi-liquid type paints, main component, hardener, and accelerator are prepared according to the best ratio for the purpose.

(3) Applying paint on painted surface

Brush, spraying, airless spraying, hot spraying, electrostatic painting, electrodeposition painting procedures are used.

(4) Drying of paint coating film

　Paint is cured into coating film. The change of fluid paint film into viscoelastic solids is called Drying. It is a transformation of Sol to Gel. The mechanisms of paint drying differ depending on the types and compositions of the paint. There are cooling solidification, evaporative drying, oxidation drying, polymerization drying, and combinations of these.

(5) Post-processing

If required, as the dried paint coating film post-processing, Surfacer (undercoating) surface is polished.

(6) Recoating

Depending on the purpose, recoatings are applied several times on this. Primer, intermediate, and overcoat.

Painting

Painting is probably the oldest of the surface treatment procedures we have so far introduced. Painting which uses paint to give beautiful aesthetics on objects and to protect them is said to be in practice since the prehistoric times.
Lacquer is used on Egyptian mummies and arrowheads found in ancient tombs. Of course these coatings used were naturally derived resins, drying oils, raw lacquer, and animal proteins. Paints were formulated by mixing colored rock powders to these coating materials.
The solvent diluted paints that are close to the concept of the paints used today came into use in the 18th century. In Japan, the western paints (Oil Paints) were first imported in the 1st year of Meiji, and the production of such paints had begun replacing raw lacquer and astringent juices.
Today, wood, steel, non-steel metal and plastic products are being painted in all aspects of our daily necessities such as construction materials, home appliances in large construction, transportation equipment, electrical, communication, marine and farming industries.

The purpose of painting

Painting is intended to achieve the following goals by creating organic paint layers on the surface of objects.

(1) Chemical protective effects

With paint layers strongly bonded to the object surfaces, paints prevent rusts and corrosion by isolating the objects from surrounding corrosive elements such as water, oxygen, sulfur, electrolytes.

(2) Mechanical effects

Prevention of damages by externally applied forces, wear prevention, and improving sliding characteristics by reduced coefficient of friction. In addition on the other hand, increased friction resistance, making sliding more difficult.

(3) Appearance value enhancements

By painting and giving visual effects different from the original appearances, artistic and product values are enhanced.

(4) Added functionality

In recent times, other than mentioned above, there are paints to keep off living organisms and aquatic plants (ship bottom paints, pesticidal paints) due to bio-repellant nature. There are a number of paints that give functionality to products are in extensive development, such as electrically conductive paint, electrically isolating paint, temperature sensitive paint, flame retardant paint, and sound-proof paint.