Coating processes – With post-treatment of coating or coating material – Heating or drying
Reexamination Certificate
1997-10-07
2001-02-13
Reddick, Judy M. (Department: 1713)
Coating processes
With post-treatment of coating or coating material
Heating or drying
C427S154000, C427S136000
Reexamination Certificate
active
06187386
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a liquid sealant composition for application to materials such as concrete which rely upon hydration reactions for curing in order to prevent loss of water during the curing process. This allows the material to develop maximum strength and wear resistance during curing. The present invention also relates to a method of applying a liquid coating composition to a material such as concrete which relies upon hydration for curing in order to reduce or prevent water loss therefrom.
2. Description of the Prior Art
Wax emulsions made with fatty acids are known for use as sealants for the purpose of sealing against liquid water. However, such wax emulsions do not prevent passage of water vapor and therefore do not adequately seal in the moisture of hydration of concrete. An example of such a compound is Mastercure® W which has been taken off the market since it is relatively ineffective in preventing loss of water vapor from concrete during curing.
Several products exist which meet the ASTM specification C 309-95 for liquid membrane-forming compounds for curing concrete. Typical products used for this purpose are primary epoxy compounds and urethanes. However, these compositions suffer from the problem that they contain hazardous components such as volatile organic compounds.
Although polyvinyl alcohol is known as both a film-forming agent and an emulsifier, it does not meet ASTM standard C 309-95 when tested as a liquid membrane-forming compound for curing concrete. The reason for this is that although polyvinyl alcohol typically exhibits a low permeability to gases, it does not exhibit a low permeability to either ammonia or water vapor. As a result, polyvinyl alcohol is insufficient to prevent significant loss of water from concrete during curing.
Paraffinic compounds are known to be water repellant and thus paraffin is typically used as a component of wood preservative agents. For example, U.S. Pat. No. 4,389,446 discloses a composition useful as a wood preservative agent which includes an organic solvent, solid paraffin as a water repellant agent and a biocide.
U.S. Pat. No. 4,539,047 relates to clear coatings for preventing wood from discoloring as a result of exposure to ultraviolet rays. A coating composition which includes an unsaturated oil-containing resin dissolved in a solvent medium containing at least 50% of mineral spirits which has dispersed therein from about 13 to about 63 parts of granulated paraffin wax and from 0.5-20 parts of transparent ultraviolet-absorbing pigment per 100 parts of the resin, is disclosed for this purpose.
However, paraffin based coatings are not typically employed as liquid membrane-forming compounds for curing concrete since they suffer from a number of disadvantages. In particular, paraffin wax would be difficult to remove once the concrete is completely cured. Further, paraffin wax would be difficult to apply since it must be heated to melting prior to application. Further, paraffin wax does not form a strong film and it can be very messy particularly if it is employed in warm climates.
Accordingly, there remains a need in the art for a coating composition which can be used as a coating compound for the curing of concrete and other materials which rely on a hydration reaction for hardening.
There is also a need in the art for coating compounds for the curing of concrete and other similar materials which does not contain hazardous materials and/or volatile organic compounds.
These and other objects of the present invention will be apparent from the summary and detailed descriptions which follow.
SUMMARY OF THE INVENTION
In a first aspect, the present invention relates to an aqueous composition for use as a coating for application to materials which undergo a hydration reaction during hardening in order to reduce the loss of water vapor during the hardening period. The aqueous composition includes 1.0-10.0% by weight of polyvinyl alcohol, 5.0-45.0% by weight of a hydrocarbon wax, 0-1.0% by weight of a biocide, and the balance of water. All weight percentages are based on the total weight of the composition.
The aqueous composition of the present invention provides the unexpected advantage that it meets the ASTM specification C 309-95 for liquid membrane-forming compounds for curing concrete and it does not contain any hazardous materials and/or volatile organic compounds.
In an alternative embodiment, the aqueous composition of the present invention may optionally contain a light-reflective material such that the coating composition exhibits sufficient daylight reflectance to meet the ASTM C 309-95 specification for type 2 liquid membrane forming compounds. Such compositions are employed to reduce solar heating due to ultraviolet rays.
In a second aspect, the present invention relates to a method of coating a material which undergoes a hydration reaction during hardening in order to reduce the loss of water vapor from the material during hardening. The method comprises the step of applying, to an uncured concrete-like material, a coating of an aqueous composition which comprises 1.0-10.0% by weight of polyvinyl alcohol, 5.0-45.0% by weight of hydrocarbon wax, and the balance of water.
In preferred methods, the coating composition further includes a light reflective pigment, a filler and/or up to 1.0% by weight of a biocide.
In a third aspect, the present invention also relates to an article of manufacture which comprises a material which undergoes an hydration reaction during hardening and having applied thereto a sufficient amount of a coating to reduce the loss of water vapor from the material. The coating comprises 1.0-10.0% by weight of polyvinyl alcohol, 5.0-45.0% by weight of a hydrocarbon wax and the balance water.
The composition, article of manufacture and method of the present invention surprisingly provide a concrete sealant material which meets ASTM specification C 309-95 and does not contain any hazardous materials and/or volatile organic compounds.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
The compositions of the invention generally comprise at least one hydrocarbon wax dispersed in an aqueous emulsion which can form a film on a concrete-like substrate. The emulsions used in the composition of the present invention are preferably made using polyvinyl alcohol as the emulsifying agent. Thus, in its broadest form, the present invention relates to an aqueous composition comprising a hydrocarbon wax, a polyvinyl alcohol emulsifying agent, and the balance of water.
The aqueous composition of the present invention is designed for use as a coating for application to materials which undergo a hydration reaction during hardening. The purpose of the coating of the present invention is to reduce the loss of water vapor from the material during the hardening period. In this manner, it is ensured that the maximum amount of water remains available for the hydration reaction whereby the material hardens to the desired hardness and durability.
Typical materials to which the aqueous coating composition of the present invention may be applied include materials such as concrete, gypsum-based products, plaster of paris and other materials which undergo a hydration reaction during hardening.
The aqueous coating composition of the present invention may be applied to a number of different concrete-like structures. For example, highway pavement, airport runways, parking garage surfaces, curbs and gutters, commercial floors and formed concrete and bridge constructions can all be coated with the aqueous coating composition of the present invention during the curing period in order to ensure the development of maximum strength and wear resistance in the concrete-like material during curing.
Representative non-limiting examples of the hydrocarbon waxes of the present invention include paraffin wax, slack wax, microcrystalline wax, olefin waxes and other conventional, known hydrocarbon waxes. More preferred hydrocarbon waxes are those made up of relatively high mo
Hundley Joseph W.
Larson & Taylor PLC
Reddick Judy M.
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