Stripping composition and method for stripping a road or highway surface

#This invention relates to a striping composition for use on a road or highway surface, a method for striping or marking a road or highway surface, and the resulting striped or marked road or highway. The striping composition is a two-part polyurethane forming system having fast cure properties; good adhesion characteristics to a road or highway surface; good weathering and abrasion resistance; and ambering resistance over time.

#Various striping or marking compositions have been used on roads and highways for many years. The first class of striping compositions used on roads and highways with some success were alkyd-based paint compositions such as those disclosed in U.S. Pat. Nos. 2,897,732; 2,897,733; and 3,326,098. Alkyd-based paint compositions are generally slow to dry and contain ester linkages which are susceptible to hydrolysis from the alkaline condition of roads. This hydrolysis, in part, causes the applied paint to have poor wear resistance. Accordingly, it is desireable to provide a striping composition having a much faster cure time and improved wear resistance.

#Most alkyd-based paint compositions require the addition of a solvent or drying oil to decrease the viscosity so that the paint composition can be sprayed onto road surfaces. For example, see U.S. Pat. No. 3,326,098. The presence of a solvent during highway marking creates a pollution problem since the solvent evaporates into the atmosphere. Accordingly, it is desireable to provide a striping composition which is 100% solids, and does not contain solvents or drying oils.

#The striping composition of the invention can be 100% solids. The term "solids" in this context is borrowed from paint chemistry, wherein "solids" includes any components (be they liquid or solid) which becomes a part of the ultimately obtained solid coating. That is, the term "solids" excludes essentially volatile solvents or carriers. The phrase "essentially volatile" is meant to include a liquid which has a boiling point or initial boiling point below 150.degree. C. at normal atmospheric pressure.

#The striping composition can have fast cure properties. The phrase "fast cure" has been used in the prior art to describe a striping composition having a "no track time" of about 5-10 minutes at room temperature. See U.S. Pat. No. 4,255,468. As used herein, the phrase "fast cure" is intended to describe a striping composition which achieves a "no track time" in at least about four minutes at room temperature. The "no tracking time" is defined as the amount of time necessary for the striping composition, once applied to a road or highway surface, to cure to an extent sufficient to resist tracking by standard automobile and truck traffic. Preferably, the no track time is an amount of time sufficient to eliminate the need for coning to prevent tracking without significantly disrupting regular traffic patterns. More preferably, the no track time is less than 2 minutes, even more preferably 10 seconds to about 50 seconds, and most preferably, about 20 seconds to about 40 seconds at 75.degree. F.

#It is desireable for the striping composition to be relatively "no track." "Instant no track" may be possible from an application and curing standpoint but it is usually desirable to have an "open time" to both wet the surface of the road or highway and to receive the glass beads. If the curing polymerization is too rapid, the resulting striping composition has too much cohesion and not enough adhesion to the road or highway surface. Although it is desireable to decrease no track time, it should not be so short as to seriously sacrifice adhesion to a road or highway surface. For most applications, a no track time of 20 or 30 seconds is sufficient to provide adequate adhesion at room temperature (75.degree. F.). On cold surfaces, it may be desirable to provide a longer no track time in order to provide sufficient adhesion to the road or highway surface. While providing fast cure properties, the striping composition of the present invention adheres sufficiently well to a road or highway surface so that it has a long life expectancy and can resist peeling or abrasion caused by traffic including snow plows.