FIELD OF THE INVENTION

The present invention relates generally to water repellent agents to achieve desired hydrophobic qualities of building products, such as gypsum, concrete and other building products, and particularly to the use of foamed water repellents.

BACKGROUND OF THE INVENTION

Water repellent additives are used in different industries to achieve desired hydrophobic qualities of the finished products. In the production of building products, such as but not limited to gypsum, concrete and others, the use of dispersions of water repellent additives is well known. Well-known water repellent additives include, but are not limited to, waxes (e.g., paraffin, natural waxes, synthetic waxes, plant waxes or others), silicone, siloxane, asphalt, bitumen, water based polyurethane and the like. Such water repellent additives are usually used in the form of emulsions, dispersions or suspensions.

Foaming agents are also commonly used in many of the above products. Products, such as gypsum board, or similar products having low bulk densities, particularly so- called foam or aerated gypsum, can be manufactured in two main processes. In one process, gas formers (propellants) are added to mixing water used in the production process. The gas formers are activated by the water to create foaming gas which creates gas bubbles in the gypsum slurry.

In another process, separately prepared foam is added to the mixture in the mixer and immediately causes pores to form in the slurry. Foam is mainly produced by a foam generator that atomizes water and air enriched with surface-active substances (various types of foam generators may be used).

Though both foaming agents and water repellent additives are extensively used to make products, such as but not limited to, gypsum products, it is difficult to obtain the desired water-repellent or hydrophobic product, which is sufficiently hydrophobic and, at the same time, facilitate the desired foam effect. The foaming agents and water repellent agents tend to counteract each other.

SUMMARY OF THE INVENTION

The present invention seeks to provide a novel foamed water repellent (hydrophobic) dispersion for use in making products, such as but not limited to, gypsum, and other building products, as is described more in detail further below. It has been surprisingly found that the foamed hydrophobic dispersions (such as, but not limited to, foamed wax, silicone, polyurethane and other foamed dispersions) improve the water repellency of the finished product. It was also surprisingly found that they not only improve the water repelling qualities, but in addition the foamed hydrophobic dispersions affect other qualities and are significantly synergetic with the foaming agents, if such agents are used in the manufacturing process. The invention provides synergistic effects: it may enable using less water repellent agents and improve foaming qualities or the foaming action of the foaming agents so that less foaming agents can be used and/or better product qualities can be achieved. A non-limiting example of such better qualities is weight reduction or an increase in strength (e.g., bending strength, nail pull strength or others) of the final product. Another non-limiting example of such better qualities is improved distribution of the water repellent additives and any other chemicals for which the water repellent additive is a carrier. Foaming agents used for the foamed hydrophobic substance can be water based, oil based or any combination thereof.

DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS

The term dispersion is used in the specification and claims to encompass suspension, emulsion and dispersion, among other types of mixtures.

"Emulsion" herein is defined as a stable dispersion of immiscible materials. It is noted that some wax/water emulsions may require emulsifiers to maintain stability. The emulsifiers prevent the water particles from adhering to or merging with themselves. It is noted that an emulsion may be formed at an elevated temperature in which wax is in liquid form and then used as a solid at room temperature.

"Suspension" herein is defined as a buoyant dispersion of immiscible materials. It is noted that some wax/water suspensions may require constant agitation, such as but not limited to, merging, immersion, or floatage. It is noted that a suspension may be formed at an elevated temperature in which wax is in liquid form and then used as a solid at room temperature.

It is noted that although the term dispersion encompasses suspensions and emulsions, the use of a foamed hydrophobic suspension is one embodiment of the invention and the use of a foamed hydrophobic emulsion is another embodiment of the invention that is not obvious in light of foamed hydrophobic suspensions. Emulsions and suspensions have different properties and do not have the same behavior; success of one does not follow automatically from the other.

A dispersion of a hydrophobic substance, such as but not limited to wax, , (e.g., such containing paraffin wax, montan wax, candelilla wax, carnauba wax, beeswax, polyethylene wax, maleated hydrocarbons, synthetic wax, Fischer- Tropsch wax, Alfa olefin wax and others), asphalt, bitumen, silicone compounds, siliconates, siloxanes, polyurethane and many others, or any combination thereof, is foamed to form a foamed hydrophobic dispersion. The term "foam" or "foamed", as used herein, refers to a substance that has trapped gaseous bubbles. Foaming may be carried out by the use of any type of foaming agents, such as but not limited to, ammonium ether sulfate (e.g., ALPHAFOAMER® or CEDEPAL®), ammonium alkyl ether sulfate (e.g., PETROSTEP®), or sodium or ammonium laureth sulfate (e.g., STEOL®), all commercially available from STEP AN Co., or a surfactant, which helps foam formation by affecting foam stability by inhibiting or enhancing the coalescence of bubbles or other means. Alternatively or additionally, foaming can be carried out by various types of foam generators.

The dispersions used in the present invention include, but are not limited to, suspensions, emulsions, solid solutions, liquid solutions, dispersions of melted substances and others. The dispersions of the hydrophobic substance may be in water, oil or any other suitable fluid.

The hydrophobic substances used in the present invention include, but are not limited to, a wax or wax-blend, silicone, siloxane, asphalt, bitumen, polyurethane or any mixture (blend) thereof. The wax may include, but is not limited to, organic wax (soft paraffin wax, macro-crystalline paraffin wax, micro-crystalline paraffin wax, montan wax etc.), plant wax (candelilla wax, carnauba wax, soy wax, etc.), animal wax (beeswax etc.), any type of synthetic wax (polyethylene wax, polypropylene wax, etc.) maleated hydrocarbons and others, or any mixture (blend) thereof.

The dispersion may be added to a slurry on-line during the preparation of the slurry. The dispersion may be added to a slurry on-line at a production line where a gypsum product is produced. The dispersion may be manufactured at a site where the gypsum product is produced. The term "slurry" as used herein relates to any blend or mixture of the raw materials made as part of the preparation of the finished product.