1. Field of Invention
This invention relates to conductive coatings for wood products. More particularly this invention relates to coatings which conduct electricity sufficiently to allow the use of electrostatic spraying equipment and the application of electrostatic coatings over ordinarily nonconductive wood, glass and plastic articles.
2. Prior Art
The electrostatic spray coating of wooden, glass or plastic, nonconductive articles has been known for many years. An early method of electrostatic spraying of wooden articles is disclosed in U.S. Pat. No. 3,236,679 issued Feb. 22, 1966. This patent discloses the application of monomeric, ionizable, organic materials to a wooden base so as to render the base conductive. The resulting coated wooden base may then be electrostatically spray coated.
Another patent which discloses a means for permitting electrostatic spraying of otherwise nonconductive wooden products is U.S. Pat. No. 4,360,385 issued Nov. 23, 1982.
Other compounds and processes useful in rendering otherwise nonconductive plastic, glass or wooden articles electrostatically coatable include U.S. Pat. No. 3,996,410 (pretreatment of a nonconductive substrate with an alkali metal hydroxide) U.S. Pat. No. 3,578,484, (sulfonating of nonconductive substrate) and U.S. Pat. No. 3,130,067, (pretreatment with ionizing radiation).
However, none of the prior art coating compositions has provided the unique combination of properties which are obtained when the polymeric coatings of this invention are employed. The prior art coatings applied only monomeric substances to the nonconductive surface and these substances contributed to an overall loss of film properties. In addition, they did not work well under low humidity conditions and these monomeric compositions tended to be ineffective when over-coated with more than about 1.0 mils of a thermoplastic coating.
Accordingly, it is an object of this invention to prepare new compositions of matter which will render otherwise nonconductive glass, plastic and wooden materials sufficiently conductive to allow electrostatic spraying.
It is another object of this invention to develop a new electrostatic spraying process which will improve the electrostatic sprayability of otherwise nonconductive wooden and plastic articles.
It is an object of this invention to develop new electrostatic spray coating compositions which are based upon polymeric rather than monomeric materials.
It is yet another object of this invention to prepare polymeric materials which will improve the electrostatic sprayability of wooden, glass and plastic articles.
These and other objectives are obtained by preparing the compositions of the instant invention.