Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – At least one aryl ring which is part of a fused or bridged...
Reexamination Certificate
1997-07-30
2001-03-27
Reddick, Judy M. (Department: 1713)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
At least one aryl ring which is part of a fused or bridged...
C523S172000, C523S212000, C523S214000, C524S492000, C524S493000, C524S556000, C524S560000, C427S137000, C427S421100, C427S426000, C427S447000
Reexamination Certificate
active
06207742
ABSTRACT:
The invention relates to an aqueous marking composition for horizontal markings on roads or other traffic areas, which comprises a drying-accelerated binder on the basis of an anionically stabilized emulsion polymer, and color pigments and also fillers. Furthermore, the invention relates to processes for preparing such an aqueous marking composition.
By the expression “drying-accelerated binders” used here there are understood polymer preparations which through an integrated physico-chemical mechanism ensure that marking compositions prepared with such binders dry substantially more rapidly after they have been laid than do marking compositions comprising a conventional binder. Only through this accelerated drying can these marking compositions be employed in a suitable manner in traffic engineering, since long, traffic-hindering road closures caused by long drying times can be done away with.
[Known drying-accelerated binders of this kind, which are intended above all for horizontal marking on roads, are described for example in particular in EP-B-0 322 188 and EP-A-0 409 459 and] Drying-accelerated binders of this kind are well known in the art. Landy et al. (EP 0 409 459 A) disclose fast-drying binder systems that are aqueous coating compositions containing anionically stabilized emulsion polymer having a Tg greater than about 0° C., an effective amount of polyfunctional amine and a volatile base in an amount effective to raise the pH of the composition to a point high enough for the polyfunctional amine to be essentially in a non-ionized state (deprotonation) thereby eliminating polyamine interaction with the anionically stabilized emulsion and anionic ingredients in the coating. The anionic stabilization of the emulsion polymer is accomplished either through addition of anionic stabilizers (e.g., surfactants) to the dispersion or through incorporation of anionic moieties on the polymeric backbone of the emulsion polymer. Such anionic moieties include, for example, carboxylic acid groups. When these fast drying aqueous coating compositions are applied to a surface as a thin layer, the volatile amine evaporates rapidly. The rapid loss of amine allows protonation of the polyfunctional amine. The protonated polyfunctional amine then rapidly interacts with the anionic stabilizer, forming ion pairs that destabilize the aqueous dispersion to cause rapid film formation.
Chou et al. (EP 0 322 188 B) disclose a drying-accelerated binder system for scavenging anionic species during film formation. The anionic species present in the aqueous dispersion prior to film formation are scavenged and sequestered into the discontinuous phase of the film, thus rendering the film less susceptible to attack by moisture. The aqueous coating composition of Chou includes latex particles of polymers containing weak base-functional groups, such as tertiary amines. Also included in the aqueous coating composition is a volatile base (for example ammonia or amines) adapted to maintain the pH of the aqueous coating composition above the pKa of the weak base-functional groups prior to and during the application of the composition. Once a thin layer of the aqueous coating composition has been applied to a surface, the volatile amine evaporates, allowing protonation of the weak base moieties. The protonated weak base moieties then form ion pairs with the anionic species, effectively sequestering them.
The invention of Chou et al. includes mixed aqueous compositions containing both weak base-functional polymer particles and binder-forming polymer latex particles. Often the binder-forming latex polymer particles contain carboxyl functional groups. Under suitable conditions, the carboxyl groups are ionized and the resultant charges on the latex particle surface electrostatically stabilize the latex against premature agglomeration. Often a volatile base is used to adjust the pH of the composition. When the composition is applied to a substrate, the volatile base is lost and the pH of the composition drops, destabilizing the latex particles of the binder and thus encouraging agglomeration to form a continuous binder film. When weak base-functional latex particles (i.e., polyfunctional amines) are included in such compositions, the weak base becomes protonated as the pH drops when the volatile base is lost. Subsequently, anionic species such as anionic surfactant are believed to diffuse to and to form ion pairs with the protonated weak base.
Drying-accelerated binders of the kind above described are for example currently obtainable commercially as customary commercial products of the company ROHM and HAAS, Philadelphia, Pa., USA, under the trade marks FASTRACK® 2706 aqueous binder and PRIMAL® 3031 aqueous binder.
To achieve the accelerated drying these known polymer preparations consist of water-insoluble, anionically stabilized plastics polymer particles and a polyfunctional water-insoluble or water-soluble amine. These two constituents are preferably incompatible with one another and are unable, given a sufficiently high pH value, to react. If, however, the pH value of the preparation falls below a particular value, then a physico-chemical reaction of the binder components ensues, leading to drying. The initially stabilizing high pH value is obtained by addition of a volatile base, preferably amonia. If the pH value of a paint formulation on the basis of such a binder falls below a particular value through evaporation of the volatile base, then the marking composition solidifies or dries very rapidly, and in fact relatively independently of the external climatic conditions and also of the layer thickness.
However, marking compositions which comprise known, drying-accelerated binders as described in the documents mentioned and such as, in particular, for example the abovementioned PRIMAL 2706 binder, and also a conventional appropriate combination of solid inorganic particles such as color pigments, customary additives and fillers, have to date been prepared and tested only in the form of a sprayable marking paint with a proportion of volatile substances of at least 20%, and these sprayable marking paints have to date exclusively been able to be used for the preparation of markings whose layer thickness was less than 1 mm. Thus, for example, the trials described in EP-A-0 409 459 with the drying-accelerated binder relate to wet film thicknesses of about 0.3 mm and to dry film thicknesses of 0.09 mm. The reason for this lies in the fact that the paint formulations known to date, which to obtain a rapid drying speed as required for traffic engineering are based on a drying-accelerated binder, exhibit severe cracking even at layer thicknesses of less than one millimeter and have surface defects which considerably impair their quality.
For horizontal markings with layer thicknesses of at least on millimeter, as are frequently required, the rapidly drying marking compositions known to date are therefore unsuitable.
The thick-layer markings which have layer thicknesses of approximately 1 to 3 mm are laid predominantly, owing to their high viscosity, by the so-called drawing shoe method. In the case of works such as the preparation of direction arrows it is also possible to work with the filling knife. In accordance with other application techniques small piles of up to 3 mm in height are thrown onto the marking line by a kind of sling, for example, and in this way a profiled road marking with enhanced night visibility in the wet is obtained. Furthermore, various other application techniques are known for preparing profiled markings having very different profile forms. For thick-layer markings use is made very frequently of two-component systems in which polymeric methacrylates serve as binders. The material is cured by mixing the composition with peroxides, whereby polymerization of the material is brought about. The drying times of these two-component marking compositions are in general between 20 and 35 minutes. Processing is laborious and, once combined with peroxide, compositions must be used up within
Reddick Judy M.
Rohm and Haas Company
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