Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Processes of preparing a desired or intentional composition...
Reexamination Certificate
2002-08-27
2004-08-31
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...
C525S007100
Reexamination Certificate
active
06784229
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to cement-based mortars and grouts for installing tile, stone and other masonry products over surfaces including concrete, masonry, brick and plywood, and, in particular, to thin-set mortars, medium bed mortars, and underlayments (leveling mortars) and grouts (pointing mortars) having enhanced overall performance properties including sag resistance, high tensile bond and shear bond strength, long open time, flexibility, water immersion strength, heat aging and freeze and thaw resistance.
2. Description of Related Art
Tiles, particularly ceramic tiles and stone, are predominantly installed using thin-bed (or thin-set) mortars because significantly thinner and lighter applications of mortar, typically and approximately ⅛″ (3 mm) to ½″ (12 mm) can be made to set the tile.
Traditionally, tile has been installed over a substrate with a Portland cement mortar bed approximately 2″ (50 mm) thick to ensure sufficient moisture is present to properly hydrate the cement content and develop strength. Also referred to as the ‘conventional method’ or the ‘mud method’, this installation technique generally requires a separate, thin ‘bond coat’ or ‘slurry bond coat’ be applied between the tile and the surface of the thick bed mortar to provide proper adhesion. In addition, if not bonded to the underlying surface, the thick bed mortar also needs galvanized, welded steel reinforcing wire placed at its midpoint to provide tensile and flexural resistance to structural deflection. These factors make the thick bed method heavier, more material intensive, more laborious, slower and needing higher skill levels. For these reasons, thick bed installations have increasingly been replaced by thin-set and medium bed mortars that incorporate various Portland cement modifiers to improve physical performance and to allow bonding of tile to substrates with far less material.
For convenience, the following description will be directed to thin-set mortars but it will be understood to those skilled in the art that the invention also applies to mortars in general and in particular cementitious medium bed mortars, which are applied in a similar manner but at greater depth to accommodate more uneven substrates and/or tile thickness variations, and underlayments (or leveling mortars) as well as cement grouts and pointing mortars, which are used to fill the spaces between the set tiles. The term “tile” will be used herein to refer to other masonry products such as stone, bricks, pavers, and the like and the term “mortar” will be used herein to refer to thin-set mortars, medium bed mortars, underlayment or leveling mortars and grouts and pointing mortars.
Currently, most cement-based thin-set mortars, medium bed mortars, underlayments and grouts and pointing mortars contain cement, such as Portland or calcium aluminate cement, a water retention aid and sand. In addition, so called ‘multi-purpose’ or ‘polymer modified’ mortars and grouts contain spray dried polymers that enhance physical properties, such as compressive strength, or, in the case of mortars, the ability to bond to non-masonry substrates such as exterior grade plywood.
The thin-set mortars, medium bed mortars, underlayments and grouts and pointing mortars are typically delivered to the job site in dry powder form and water or a liquid polymer such as latex is then added while mixing to produce a plastic, wet consistency. Thin-set and medium bed mortars are typically then trowelled over the substrate using a notched trowel, or similar tool, having dentations ranging in size from {fraction (3/16)}″ (5 mm) to ¾″ (19 mm) depending on mortar and tile type. The tiles are then placed into the wet mortar, aligned with tiles already set or other reference marks and beaten in until level. Once the tiles are firmly set, the joints or spaces between them are filled with a grout mortar, typically cement-based, using a rubber float or similar device.
The above mortars and grouts for installing tile require a combination of performance properties to be commercially acceptable including high bond and shear bond strength, flexibility, water immersion strength, sag resistance, open time, heat aging and freeze and thaw resistance depending on type and application. Many mortars and grouts satisfy one or more of the above properties but it is highly desirable to provide mortar and grout products which has enhanced overall performance properties.
Sag resistance is particularly important, for mortars and grouts used for installing tile over vertical and inclined substrates. Preventing tiles from dropping down out of alignment after being placed, and reducing the slumping of grout in joints, have material effects on installation productivity, quality, profitability and, ultimately, on market acceptance. Moreover, high sag resistance in mortars is beneficial in horizontal applications involving heavy tiles, where it provides additional support against flooring units ‘sinking’ and causing the common installation defect known as ‘lippage’. Finally, high sag resistance grouts also benefit horizontal installations in the instance where void spaces caused by inadequate bedding of tiles frequently produce ‘sinkholes’ in the finished grout application.
This invention is also useful in underlayments (or leveling mortars) whose primary, but not sole, functions are to prepare uneven substrates to receive tile installed by the thin or medium bed methods, to accommodate differences in tile thickness or stone ‘gauge’ and to improve the deflection resistance of certain substrates to a degree that permits proper support for the hard, more brittle tiles placed over them, thereby reducing the common problems of tile crazing, cracking and de-lamination. Moreover, the synergistic effects of combining the novel components of this invention produce an underlayment with superior flexural resistance, improved ‘cohesive’ (internal shear) strength, better workability and ‘heal’ time, reduced water demand and the ability to be ‘placed’ without subsequent slumping or shrinkage. In general, a cement based underlayment powder is mixed with water to a very fluid consistency (usually 1.5-1.75 gallon of water per 50 pound bag powder). The fluid mixture is poured or pumped on the floor and a rake used to distribute the underlayment evenly and a long handle flat trowel or squeegee used to make the surface even.
It is known to incorporate finely divided inorganic fibers, for example, mineral wool, glass wool, and asbestos in hydraulic cement-based thin-set mortars for improved sag resistance as discussed in U.S. Pat. No. 4,218,258 assigned to the assignee of the present invention. Latex is also disclosed as being useful for improving shear bonding and increasing the resistance to the effects of freeze-thaw cycles. U.S. Pat. No. 4,065,319 discloses the use of inorganic and organic fibers such as asbestos, mineral wool, glass fibers, fibrous low substitution or cross linked carboxymethyl cellulose and the like to increase the sag resistance. In U.S. Pat. No. 4,402,752, it is disclosed to incorporate long-chain organic polymers such as anionic and nonionic long-chain polyacrylamide materials to improve sag resistance of the mortar. It is also noted therein that the use of clay has also been developed for use in mortars both alone and in combination with the long-chain organic polymers.
Mortars such as thin-set mortars, medium bed mortars, underlayments and grouts and pointing mortars, however, require more than sag resistance as noted above and it is a continuing goal of industry to provide such mortars having enhanced overall performance properties so that a single mortar product can be used in a variety of applications such as setting both vertical and horizontal tiles in interior as well as exterior applications.
Conventional cement-based mortars contain a cement, preferably Portland or calcium aluminate cement or other hydraulic cements, fillers such as sand, clay and calcium carb
DeLio & Peterson LLC
LATICRETE International, Inc.
Szekely Peter
Tomaszewski John J.
LandOfFree
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