Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Processes of preparing a desired or intentional composition...
Reexamination Certificate
1999-04-05
2001-05-08
Szekely, Peter (Department: 1714)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Processes of preparing a desired or intentional composition...
C427S136000, C427S137000, C428S489000, C428S500000, C524S501000, C524S522000, C524S523000, C524S555000, C524S556000, C524S521000
Reexamination Certificate
active
06228901
ABSTRACT:
FIELD OF THE INVENTION
This invention generally relates to a method of producing traffic markings on road surfaces and more particularly to producing wear resistant traffic markings on road surfaces.
BACKGROUND OF THE INVENTION
White and yellow traffic markings used for demarcating traffic lanes is a common sight on almost all roads. These markings ensure safe driving conditions under varying weather conditions. The term “roads” generally means routes, highways, airport runways, exit and entry ramps, passes, pavements, side walks or parking lots for vehicles, such as, autos, bikes, trucks, and the roads are usually paved with asphalt, wood, metal or from concrete, generally made from Portland cement. The majority of these traffic markings, such as, solid, transverse or interrupted stripes, are paint-based and traditionally include solvent-borne binders, which are predominantly alkyds and chlorinated rubber-modified alkyds. However, since the 1980s environmentally safer waterborne traffic paints have also been used. These waterborne traffic paints are primarily based on acrylic emulsions and produce dramatically lower VOC emissions than traditional solvent-based traffic paints.
However, these conventional waterborne traffic markings tend to be less wear resistant than traditional alkyd based traffic paints when exposed to traffic conditions, such as, wear and tear resulting from exposure to vehicular traffic. The term wear resistance means the degree of resistance of the traffic markings to detaching from the road surface when the marking is exposed to the traffic conditions and to UV degradation. The wear resistance is expressed as the percentage area of a film of traffic marking still remaining on the road surface after its extended exposure to such traffic conditions. It has been found that substantial portions of conventional waterborne traffic markings tend to wear away in less than a few months after exposure to such accelerated traffic conditions.
Attempts have been made to solve the problem of the excessive traffic marking wear. For example, Clinnin et al. in the U.S. Pat. No. 5,340,870 describe a fast dry wear resistant traffic marking paint containing a hydrophobic polymer emulsion polymerized in the presence of a water-soluble support polymer that is polymerized from a monomer mixture consisting of acid, styrene and substituted styrene monomers, preferably in equal proportions. One of the problems associated with such a styrene based traffic paint is that it tends to degrade over time when exposed UV radiation from sun that is typically experienced by traffic markings. Thus, a need still exists for a waterborne traffic paint having improved wear resistance under typical traffic conditions.
STATEMENT OF THE INVENTION
The present invention is directed to a method of producing a wear resistant traffic marking on a road surface, the method comprising:
applying on the road surface a layer of an aqueous traffic paint, which comprises a polymer polymerized from a monomer mixture that includes in the range of from 80 percent to 99.9 percent, all in weight percentages based on polymer solids, of one or more hydrophobic monomers; and
drying the layer to form the wear resistant traffic marking on said road surface.
One of the advantage of the method of the present invention is that it produces traffic markings, that are wear-resistant even under exposure to UV radiation from sun, which is typically experienced by traffic markings.
DESCRIPTION OF THE PREFERRED EMBODIMENT
As used herein:
“Polymer” means a dispersed, solubilized or a sequential polymer, defined below.
“Dispersed polymer” means particles of polymer colloidally dispersed and stabilized in an aqueous medium.
“Solubilized polymer” includes “Water soluble polymer”, “Water reducible polymer” or a mixture thereof. Water soluble polymer means a polymer dissolved in an aqueous medium. Water reducible polymer means a polymer dissolved in water and a water miscible organic solvent, such as, methanol, ethanol and glycol ethers. Solubilized polymer results in a polymer solution characterized by having the self-crowding constant (K) of the Mooney equation [1/ln
72 rel
=1/BC−K/2.5] equal to zero. By contrast, dispersed polymer has (K) equal to 1.9. The details of Mooney equation are disclosed in an article entitled “Physical Characterization of Water Dispersed and Soluble Acrylic Polymers” by Brendley et al., in “Nonpolluting Coatings and Coating Processes” published by Plenum Press, 1973 and edited by Gordon and Prane. “Sequential polymer” means particles of a polymer colloidally dispersed and stabilized in an aqueous medium having a core/shell morphology.
“Tg of a polymer” is a measure of the hardness and melt flow of the polymer. The higher the Tg, the lesser will be the melt flow and the harder will be the coating. Tg is described in
Principles of Polymer Chemistry
(1953), Cornell University Press. The Tg can be actually measured or it can be calculated as described by Fox in
Bull. Amer. Physics Soc.,
1, 3, page 123 (1956). Tg, as used herein, refers to actually measured values.
For the measurement of the Tg of a polymer, differential scanning calorimetry (DSC) can be used. To measure the Tg by the DSC method, the polymer samples were dried, preheated to 120° C., rapidly cooled to −100° C., and then heated to 150° C. at a rate of 20° C./minute while data was being collected. The Tg was measured at the midpoint of the inflection using the half-height method.
“GPC number average molecular weight” means the number average molecular weight determined by gel permeation chromatography (GPC) which is described on page 4, Chapter I of The Characterization of Polymers published by Rohm and Haas Company, Philadelphia, Pa. in 1976, utilizing polymethyl methacrylate as the standard. The GPC number average molecular weight can be estimated by calculating a theory number average molecular weight. In systems containing chain transfer agents, the theory number average molecular weight is simply the total weight of polymerizable monomer in grams divided by the total molar amount of chain transfer agent used during the polymerization. Estimating the molecular weight of an emulsion polymer system that does not contain a chain transfer agent is more complex. A cruder estimate can be obtained by taking the total weight of polymerizable monomer in grams and dividing that quantity by the product of the molar amount of an initiator multiplied by an efficiency factor (in our persulfate initiated systems, we have used a factor of approximately 0.5). Further information on theoretical molecular weight calculations can be found in
Principles of Polymerization
2nd edition, by George Odian published by John Wiley and Sons, N.Y., N.Y. in 1981 and in
Emulsion Polymerization
edited by Irja Pirma published by Academic Press, N.Y., N.Y. in 1982.
“Polymer particle size” means the diameter of the polymer particles measured by using a Brookhaven Model BI-90 Particle Sizer supplied by Brookhaven Instruments Corporation, Holtsville, N.Y., which employs a quasi-elastic light scattering technique to measure the size of the polymer particles. The intensity of the scattering is a function of particle size. The diameter based on an intensity weighted average is used. This technique is described in Chapter 3, pages 48-61, entitled Uses and Abuses of Photon Correlation Spectroscopy in Particle Sizing by Weiner et al. in 1987 edition of American Chemical Society Symposium series. To measure the particle diameter, 0.1 to 0.2 grams of a sample of acrylic polymer was diluted to a total of 40 milliliters (mLs) with distilled water. A two mLs portion was delivered into an acrylic cell, which was then capped. The particle size in nanometers was measured for 1000 cycles. The measurement was repeated three times and an average was reported.
“Polymer solids” means the polymer in its dry state.
“(meth)acrylate” includes acrylate and methacrylate.
“Hydrophobic monomer” means a monomer having a Hansch &pgr; value of 2.2 or more.
“Hydrophilic mono
Brown Ward Thomas
Hermes Ann Robertson
Rohm and Haas Company
Szekely Peter
LandOfFree
Method of producing wear-resistant traffic marking and... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Method of producing wear-resistant traffic marking and..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Method of producing wear-resistant traffic marking and... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2464756