Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Compositions to be polymerized by wave energy wherein said...
Reexamination Certificate
2000-10-27
2003-10-14
Berman, Susan W. (Department: 1711)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Compositions to be polymerized by wave energy wherein said...
C522S080000, C522S088000, C522S120000, C522S121000, C522S141000, C522S142000, C523S300000, C524S356000, C524S361000, C524S379000
Reexamination Certificate
active
06632852
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to coating compositions for wood and other surfaces. The compositions are characterized by their component thermoplastic and thermosetting resin solids formulated in a solvent mixture selected to allow the composition to dry to a low profile, dry-to-touch surface coating. The dried coating is thereafter subjected to conditions selected to initiate polymerization of the component thermosetting resin solids to provide a low profile chemically resistant surface coating.
BACKGROUND AND SUMMARY OF THE INVENTION
In the manufacture of finished articles such as wood furniture, the most aesthetically pleasing finishes are obtained using nitrocellulose lacquers in a predefined finishing protocol using rubbing and buffing operations. The resulting finishes, while having high clarity and beauty, are not without some disadvantage, not only in the manufacturing process itself, but as well in several undesirable properties in the resultant coated surfaces. Firstly, the rubbing and buffing operations required to obtain high quality nitrocellulose finishes are very labor intensive. Further, the coatings themselves exhibit poor resistance to abrasion, marring, and solvent/chemical attack.
There has been significant research and development effort to design new coating formulations to provide nitrocellulose lacquer-like finishes that do not suffer the disadvantages of poor resistance to abrasion and chemical attack nor the labor intensive manufacturing operations. Thus, for example, coating formulations have been proposed that include high solids UV curable coatings, to provide good chemical resistance. However, the coating formulations developed to contain high solids levels of thermosetting components are expensive and do not have the dry-to-touch property of a conventional nitrocellulose lacquer. On the other hand, new nitrocellulose lacquers have been developed to have good flowability and low drying rates to provide smooth dried coatings without need for subsequent rubbing and buffing steps. The use of slow-drying formulations complicates the manufacturing process because of the required lower line speeds. Other technologies, including modified UV-curable coatings, for example those described in U.S. Pat. Nos. 4,654,223 and 4,407,885 have been used as protective topcoats with the dry-to-touch property, but at higher cost and the requirement of some rubbing/buffing to produce the desired quality lustrous finishes. Other researchers have sought to address these issues by combining UV curable resins with low amounts of nitrocellulose polymers to improve coating holdout (see U.S. Pat. No. 4,066,582). Still other researchers have sought to provide coatings capable of providing low labor-intensive quality finishes with good chemical resistance by formulating photocurable coating compositions comprising polyfunctional ethylenically unsaturated cellulosic polymers. In other words, the classical thermoplastic polymer components of the coating compositions are functionalized with UV curable moieties that allow the polymers to be photochemically crosslinked on the substrate surfaces (see U.S. Pat. No. 4,861,629). Such coatings, while exhibiting good aesthetic properties and chemical resistance, are also expensive.
The present invention provides novel coating formulation technology based on selection of both thermoplastic resin and thermosetting resin components in a predefined weight ratio in a solvent composition including a solvent capable of dissolving the thermoplastic resin solids and a solvent miscible co-solvent capable of dissolving the thermosetting resin solids. Preferably at least one of the solvent or co-solvent or at least one of the thermosetting resin components is hydroxyfunctional. The presence of hydroxyfunctionality in the present formulation has been found to improve flow characteristics during application and during pre-set drying to provide low profile, high luster surfaces without need for rubbing or buffing operations. The resulting dry-to-touch coating composition can then be exposed to predetermined conditions calculated to effect crosslinking/setting of the thermosetting resin solids component of the pre-dried coating. The resultant coatings in accordance with this invention not only exhibit a high quality, lustrous finish, but they also exhibit excellent resistance to marring, abrasion and solvent/chemical attack. The coating formulations can be adjusted to control gloss, they can be formulated to be low-Haps or Haps-free, and they are extremely cost competitive when used as a substitute for nitrocellulose lacquers and other finishing compositions in, for example, furniture finishing protocols. Further, the compositions can be readily used on other surface substrates including metal, leather and plastics.
The self-leveling finishing compositions of the present invention, in addition to the major components mentioned above, can be formulated to include other art-recognized coating excipients/modifiers including, for example, wetting agents, flow and leveling aids, slip and mar resistant aids, thermoset solids dependent photoinitiators, gloss control agents, pigments and the like. The use of such additives to fine tune the properties of coating compositions is well known in the art and such knowledge can be applied to adjust the properties of the present coating compositions to meet the functional requirements of each targeted application of the present formulations.
DETAILED DESCRIPTION OF THE INVENTION
The present invention is based in part on the discovery that the appearance and other surface properties provided by solvent-based coating compositions including both thermosetting and thermoplastic resin solids components can be controlled significantly by selection of solvents used to formulate such coating compositions. The production of dried low profile coatings on substrate surfaces requires that the compositions be formulated so that the high molecular weight oligomers and polymer components in such composition are able to disaggregate and settle under the influence of gravity even in the late stages of the drying process. The intramolecular affinities of polymer components, even in the presence of the organic solvent medium used to formulate coating compositions, are such that the polymer components tend to aggregate in the composition and such polymer aggregates can often be more pronounced in the later stages of drying of applied films of the coating composition (i.e., when the solvent concentrations are reduced) resulting in irregularity in the surface of the dried coating films. It has been found in accordance with the present invention that coating compositions can be formulated with both thermoplastic resin solids and thermosetting resin solids, to take advantage of the functional properties available from each of such resin components, by dissolving such resin solids in a solvent composition comprising a solvent capable of dissolving the thermoplastic resin solids and a solvent miscible co-solvent capable of dissolving the thermosetting resin solids. Preferably at least one of the solvents or co-solvents is hydroxyfunctional or ketone-functional. The polar nature of such solvents facilitate the disaggregation of the higher molecular weight resin components and tend to promote disaggregation of polymer components and flow of the applied coating to help provide low profile, dry-to-touch coatings that can be subsequently subjected to conditions capable of initiating polymerization of the thermosetting resin solids components of the composition. The resulting thermoset coatings are characterized by their low profile and high luster and, consequent to the thermoset processing of the thermosetting resin components, excellent mar/chemical resistance.
Additional solvents or coupling agents can be added to enhance the miscibility of the solvent and co-solvent and/or the compatibility of the thermosetting and thermoplastic resin components, particularly in the late stages of drying to help prevent the partial/selective preci
Chen Frank Bor-Her
Forrest Harvey Richard
Matton George
Muselman Gregory David
Safta Eugen
Barnes & Thornburg
Berman Susan W.
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