Nitrocellulose varnish
Nitrocellulose lacquers ( nitro , NC or CN lacquers ), alternative spelling nitrocellulose lacquers are a family of coatings (or in a broader sense, paints ), which after the binder used cellulose nitrate - is named - often incorrectly referred to as "nitrocellulose".
history
Nitro lacquers, based on synthetic resins synthesized from cotton , were developed in the United States in the early 1920s as quick-drying paint for automobile production. Until then, the only paint that would dry in a reasonable time (approx. 48 hours) was the so-called Japan Black . This led Henry Ford to say that you could get his cars in any color as long as it was black - other colors were reserved for luxury vehicles at the time. This only changed in 1923 with the introduction of DuPont's Duco True Blue nitrocellulose paint , which was first used on General Motors' 1925 Oakland models . Nitro lacquers were used in the automotive industry until the 1950s.
The German chemist Alfred Kraus (1899–1979) carried out fundamental research and extensive development of nitrocellulose lacquers .
dilution
The so-called nitro thinner or solution is used for thinning, dissolving or cleaning brushes . It usually consists of esters and other hydrocarbons . Alternatively, universal thinner can also be used.
Use, benefits
Nitro lacquers have good mechanical resilience and are therefore primarily used to refine wood indoors, in particular furniture or musical instruments, and for metals indoors.
They are easy to process and dry quickly due to the high solvent content. For the same reason, however, they are difficult to paint over with nitrocellulose varnish, because the solvent in the fresh layer dissolves the old layer underneath. That is why they are often only injected. In aircraft construction and model aircraft construction, however, this property is very desirable, since repair areas connect seamlessly with the remaining areas (see tensioning varnish ).
Contraindications and the balance between benefits and harm
In addition to being difficult to recoat with nitro lacquers, these are considered to be comparatively sensitive to weathering (i.e. more suitable for indoor use), not very lightfast and not very resistant to chemicals, water and heat.
These lacquers are preferred in the furniture industry. They are inexpensive and easy to work with. Usually, nitro lacquers are applied with a spray gun.
Because of the overall negative benefit-harm analysis, alternatives such as B. Consider acrylic paint .
ingredients
In addition to cellulose nitrate, nitro lacquers usually contain other synthetic resins, pigments or dyes (except for clear lacquers), thinners and solvents as well as plasticizers , matting agents , grinding agents and light stabilizers . Others: xylene and toluene .
Disposal, environmental and health aspects
Due to their high solvent content of up to 70% and their very low solids content of only 30%, there are health risks for the processor. Disposal is also problematic: leftovers or waste must be disposed of as hazardous waste and must never end up in the wastewater - or even the groundwater.