What is the Lacquer?
Lacquers are compounds formed by a combination of nitrocellulose, resin, plasticizer, and solvent. Nitrocellulose is the main ingredient in lacquers. They are used for industrial and domestic purposes.
Lacquer is a type of varnish. The difference is that varnish is used for wood products while lacquer is used for metal products. Resins and rosins are predominant in varnishes, while nitrocellulose is predominant in lacquers.
Nitrocellulose makes lacquers hard and strong. Resins produce stickiness, plasticizers bring softness and elongation properties, and solvents help to dry the lacquers.
Cellulose Products
As mentioned earlier, nitrocellulose is considered the main ingredient of lacquers. Esters should also be standard for high-class lacquers. Nitrocellulose is obtained from waste films used in filmmaking.
Types of Nitrocellulose
In the lacquer industry, various grades are used, such as R-S Grade, S-S Grade, and A-S Grade.
R-S Grade
Most of the lacquers used for general purposes are of this grade. Nitrocellulose has a nitrogen weight ratio of 11.9 to 12.3%. It is usually supplied in 5-second and 40-second standards in viscosities of ½, ¼, 1/10 inch. For coating the outer parts of metals, nitrocellulose with a viscosity of ½ inch is used. High-viscosity nitrocellulose (40 seconds) is added to lacquers used for coating fabrics in the aircraft and textile industries.
S-S Grade
Spirit-soluble nitrocelluloses are of the SS grade. Lacquers made from this grade are used for coating cellophane paper and other high-quality products. This grade contains 10.9 to 11.1 percent nitrogen by weight, with a viscosity of ¼ inch and 5 seconds.
A-S Grade
These also dissolve in alcohol solutions. They have a nitrogen weight ratio of at least 11.3%, with a maximum of 11.6%. The same resins are used in this grade, which easily dissolve in alcohol solutions.
Solvents
Solvents that dissolve nitrocellulose include ketones, acetone, glycols, ethers, spirits, and alcohols. Spirits and alcohol are used for A-S and S-S graded nitrocellulose.
Diluents
These include xylene and toluene.
Solvent and Diluents
Lacquers made from nitrocellulose contain 30 to 40 percent of high-impact solvents. Low-impact solvents include alcohol and spirits. Similarly, the ratio of diluents is kept at 45 to 55 percent.
Nitrocellulose Lacquer Manufacturing
Transparent types of lacquers are prepared similarly to varnishes, but with less need. Compared to varnish, the consistency of lacquers is thicker and more viscous. This hybrid form is easiest to control by starting with a small amount of nitrocellulose and a small amount of solvent, mixed well. Then the rest of the nitrocellulose and solvent are added. In this way, the synthesis of lacquers becomes easier.
The resin and diluent are mixed together, and the nitrocellulose dissolves in the solvent. The remaining part is ground together. Resin solution, nitrocellulose solution, and pigment paste are prepared separately and then mixed together in the mixer.
Manufacturing Processes
- Mix Resin and Solvent: First, the resin is thoroughly mixed with the solvent. Once they are combined, they are kept separate.
- Mix Solvent and Nitrocellulose: In the second step, the solvent is added to the nitrocellulose solution and mixed well. Once combined, it is also kept separate.
- Prepare Pigment Paste: Pigments are made into a paste with thinner and kept separately.
- Combine Solutions: In the fourth step, these three solutions are put into the mixer and mixed together. This process should be done gradually.
Use of Lacquers
Lacquers are mostly used for interior decoration, including wooden furniture and other household items. They are also widely used for automobile coatings. Lacquers are used for coating leather, paper, cotton fabrics, and transformer coils. They are applied as coatings on aluminum, copper, and bronze products. Additionally, lacquers are used to coat concrete, blocks, ceramic tiles, and bricks for decoration and protection. Lacquers are also used as a coating on the bodies of airplanes and cellophane.