MXPA06008421A - Lime and polymer containing settable mixture - Google Patents

Abstract

The present invention refers to a settable mixture comprising (I) a water absorbing composition and (II) an aqueous emulsion of organic polymer or (III) dispersible organic polymer, wherein the water absorbing composition (I) contains inorganic ingredients which are capable to react with water and the wa -ter absorbing composition (I) contains at least 95 weight lime and wherein the amount of the aqueous emulsion of organic polymer (II) in relation to (I) is such as to provide a ratio of com -bined weight of polymer solids to combined weight of ingredi -ents which are capable to react with water of from 0.5:1 to 10:1, preferably 1:1 to 4:1 and wherein the amount of dispersible organic polymer (III) in re -lation to (I) is such as to give a ratio of combined weight of polymers to combined weight of ingredients which are capable to react with water of from 0.5:1 to 10:1, preferably 1:1 to 4:1.

Description

CAL AND POLYMER CONTAINING A FIXED MIX Field of the Invention The present invention relates to a settable mixture, a coating application method, the coating and the use of coating.

BACKGROUND OF THE INVENTION It has previously been proposed to apply a coating to a rock surface in a mine by spraying an aqueous emulsion of an organic polymer and causing the emulsion to coagulate to produce a flexible coating in the form of a film or skin on the surface . Polymers that have been described for this purpose include polyurethanes and polychloroprene. The latter has been described in South African Patent No. 8203384. More recently, a composition comprising two parts has been described in WO 98/58886. One is an aqueous emulsion of an organic polymer, such as the copolymer of ethylene and vinyl acetate. The other part is a cementitious composition with the capacity to absorb at least its own weight of water. The cementitious composition described is a composition that forms ettringite that contains cement with high alumina, ordinary Portland cement and anhydrous. During use the two parts are sprayed on the surface of the rock of a mine to form a coating. This patent also describes a dry mixture of solids formed from the cementitious composition and a dry polymer emulsion to which the mixing water in the mine is added. The compositions described in the aforementioned WO 98/58886 take an important time to reach adequate early strength, generally not less than 24 hours. Although the coating is developing its resistance, for security reasons, the entrance of the personnel to the treated area is not admitted and, therefore, that part of the mine is not productive. Therefore, it is desired to reduce the time taken for the coating to develop adequate early strength. Recently, a solution to this problem has been described in WO 01/28955 by providing a cementitious composition that forms ettringite richer in calcium aluminate than those described above, and which provides higher early strength. This ettringite cementitious composition contains from 25% to 59% by weight of calcium aluminate, from 0% to 10% by weight of lime and from 0% to 50% by weight of calcium sulfate.

Although the compositions described in WO 01/28955 mentioned above have an improved (shorter) time to achieve adequate early strength, it is desired to further reduce the drying time and further improve the early strength. In addition, the price of said compositions must be reduced.

SUMMARY OF THE INVENTION Therefore, the object of the present invention is to improve an early resistance of a corresponding coating which is applied to a surface. The solution of this object is a compostable mixture, which comprises: (i) a water absorbing composition and (ii) an aqueous emulsion of organic polymer or (iii) organic polymer that can be dispersed, wherein the water absorbing composition (i) contains inorganic ingredients which have the ability to react with water and the water absorbent composition (i) contains at least 95% by weight of lime and wherein the amount of the aqueous emulsion of organic polymer (ii) ) in relation to (i) is such as to provide a combined weight ratio of polymer solids to combined weight of the ingredients, which have the ability to react with water of about 0.5: 1 to 10: 1, preferably of 1: 1 to 4: 1, wherein the amount of organic polymer that can be dispersed (iii) in relation to (i) is such as to provide a combined weight ratio of the polymers to a combined weight of the ingredients. entities which have the capacity to react with water from 0.5: 1 to 10: 1, preferably from 1: 1 to 4: 1. The phrase "ingredients that have the ability to react with water" is intended to include on the one hand ingredients which only react with water (for example, the hydration of CaO), and on the other hand, ingredients that react in a reaction with water and other ingredients (for example, some cementitious ingredients which are reacting in a cementitious reaction with water). According to the present invention, typical "water-reactive ingredients" are cementitious components and fast lime (CaO), while fillers which are frequently used in cementitious compositions are not "ingredients having the ability to react with water "due to the present invention.

Lime can be quick lime (CaO) or can be provided by ordinary Portland cement which releases lime at the time of hydration.

Generally, it is possible that lime is provided by a cementitious composition. The aqueous emulsion of the organic polymer which we sometimes refer to in the art as a polymer latex emulsion may contain as one or more polymers a wide range of homopolymers or copolymers. Examples include styrene, styrene divinyl copolymers, styrene butadiene copolymers, methyl methacrylates, styrene and methyl methacrylate copolymers or maleic anhydride, acrylics and acrylic ester resins, vinyl acetate copolymers and copolymers thereof with ethylene and other olefins (for example, ethylene vinyl acetate), plasticized vinyl chloride copolymers. Mixtures of polymers or copolymers can also be used. It is preferred to employ a polymer with a glass transition temperature of about -50 ° C to +50 ° C.

Plasticizers can be added, such as Cerecyor (a chlorinated paraffin), dibutyl phthalate, diethylene glycol to improve flexibility. The contents of suitable solid polymers of the emulsion are from about 5% to 80%, preferably at least 25%, for example, from 30% to 70%, more preferably from 45% to 65% by weight based on the weight of the emulsion. The dispersible organic polymer is conveniently obtained by drying, for example, by spray drying an aqueous polymer emulsion. The dried polymer can be commercially available. The high lime content (at least 95% by weight of the water-absorbing composition (i) causes intense generation of heat of hydration (Ca (OH) 2) as a result, the time for drying it is reduced and early strength is improved Because lime is a relatively cheap raw material, the price of the water absorbing composition (i) is reduced so that the settable mixture according to the present invention is also economical. Because in the preferred embodiment of the present invention the water-absorbent composition (i) comprises approximately 100% by weight of lime. "Approximately 100% by weight" means that it is possible that (i) not only contains lime but also impurities caused by other ingredients, because in another embodiment of the present invention the water-absorbing composition (i) also contains a cementitious composition from which the components preferably form ettringite during the absorption of water. Etringite is a calcium trisulfoaluminate that has 32 water molecules of crystallization and has the formula 3CaO. AL203. 3CaS04. 32H20. Ettringite is produced by the hydration of cementitious materials containing calcium aluminate and calcium sulfate. Unless the context requires otherwise, the term ettringite in the present description is intended to include ettringite analogues. These are defined in "Chemistry of the Cement" (Cement Chemistry) of H. F. W. Taylor, 2A edition 1997 published by Thomas Telford. The cementitious composition generally contains calcium aluminate and calcium sulfate. The term calcium aluminate is intended to include not only the form of calcium aluminate which is often written in the abbreviation of cement as CA, but also other aluminate-containing cements, which are written as CA2, CA3, C12A7, C4AF and CllA7CaF2 and also calcium sulfoalum inato and calcium ferroaluminate and analogs thereof. Calcium aluminate can be provided by a cement with a high alumina content, which we sometimes refer to as Ci ent Fondu which generally contains from about 40% to about 80% by weight of calcium aluminate phases ( or from 40% to 50% by weight of calcium aluminate (CA)). Calcium sulfate can be provided by a material that contains calcium sulfate, such as a beta-anhydrite, plaster or plaster of Paris. References to calcium sulfoaluminate in the description are for pure calcium sulfoaluminate, which is of the formula C4A3S * wherein C is CaO or Ca (OH) 2), A is A1203 and S * is S03. This is sometimes known as a Klein compound and can also be written as 3CaO. 3A1203. CaS0. With respect to the formation of ettringite, the water absorbing composition (i) often contains a stoichiometric excess of lime. The expression "a stoichiometric excess of lime" means that at least a portion of the lime that is used as an eductor can not participate in the cementitious reaction of ettringite - therefore, there is a fast limestone residue which is hydrated. The present invention further relates to a method of applying a coating to a surface whose method comprises forming a settable mixture of a water absorbing composition (i) and an aqueous emulsion (ii) as defined above, and placing the mixture in the surface to form a coating preferably at least 2 mm thick and allow the coating to dry. When an organic polymer emulsion (ii) is used, the water may be the water already present in the emulsion (ii) whereby the water of the aqueous emulsion is used to hydrate the ingredients of the water-absorbing compositions (i). If required or preferred, additional water can be added. The present invention also provides an alternative method of applying a coating to a surface whose method comprises forming a castable mixture of a water absorbing composition (i), and a dispersible organic polymer (iii) as defined above, combining the mixable mixture with the water and placing the mixture on the surface to form a coating with a thickness preferably of at least 2 mm and allowing the coating to dry. In case a dry polymer emulsion (iii) is used with the water absorbing composition (i) it is necessary to add the water required to hydrate the ingredients of the water absorbing composition (i). Whether the dry polymer emulsion is used, the weight of water is generally such that all the ingredients of the water-absorbing composition (i) are converted by reaction with water. Normally the coating is applied to the surface by spraying the mixture on the surface. Other cement accelerators and retarders can be added before spraying the mixture. When it is desired to start or further increase the drying index, this can be effected by the addition of an alkaline.

The present invention also relates to a coating, which can be manufactured according to a method which was defined above. In addition, the present invention provides the use of said coating as a rock support medium. It has been found that a coating of approximately 4 mm (eg, 3 to 7 mm) in thickness can be used as a replacement for a wire mesh used to prevent landslides and loose rock fragments from falling into the mine. The coatings can be used in mines, which are known as "hard rock mines" such as nickel or gold mines and also in coal mines.

The coatings can be used, for example, in coal mines due to the space method and pillars to reduce the size of the pillars which are left to provide a support and therefore recover more carbon. This is achieved by spraying the coating under the pillar thereby increasing its load bearing capacity. The coating can also be used to stabilize the edges. The coatings can also be applied to reduce or prevent wear, which is the erosion of rock surfaces recently exposed by the air of the mine or for the suppression of a radon gas in a uranium mine or for the stabilization of banks , for example, in a quarry, to stabilize the roofs of tunnels or similar. The present invention also relates to the use of a coating as defined above, as a water impermeable medium. Therefore, the coating is applied to at least a partially hanging surface. The water resistance of mines and tunnels is often greatly appreciated, because if water finds its way into the mine or tunnel, work activities can be disrupted. The present invention has an application in the Construction Industry for the treatment of buildings that includes external and internal walls, floors and ceilings. As described above, it is not only intended to improve the early strength (the early strength should be defined as the coating strength applied after the one hour drying time) of the corresponding coating, but also to reduce the price of the coating. It is generally intended that the elongation at break and the ultimate strength should also be sufficient. Especially if the coating is used as waterproof media, a high elongation at break is desired - in this case, the elongation at break should be at least 70% and preferably 110%. In the case where a corresponding coating is used as rock support means, the final resistance parameter is very important - in this case the final resistance (final resistance according to the present invention must be defined as what is the resistance to the tension after the drying time of 28 days) must be at least 3 MPa, preferably 3.5 Mpa, depending on the specific application).

Generally, it is preferred that the tensile strength after a one-hour drying time (early strength) is at least 0.4, preferably at least 0.5, and more preferably at least 0.75 MPa. The tensile strength and the elongation at the breaks were measured according to a standard measurement method of DIN 53504: S2, where S2 is the test sample. The optimization of the characteristics of "early high strength and price" also leads to the following result: The water-absorbent composition (i) must contain at least 95% by weight and more preferably approximately 100% by weight of lime and optionally a cementitious composition. The content of the cementitious composition is variable (but not more than 5% by weight). Approximately 100% by weight of lime should mean that it is possible that the absorbent composition in water (i) also contains impurities caused by other ingredients. The settable mixture containing a water-absorbent composition which only consists of lime is generally cheaper than a settable mixture which also contains a cementitious composition. further, lime is often easy to obtain (but cementitious compositions are often difficult to obtain).

BRIEF DESCRIPTION OF THE DRAWINGS The present invention is further described below by means of the figures. The figures show: FIG. 1 a diagram in which the early resistance of the coating according to the present invention against the lime content in the water-absorbing composition (i) is plotted, Detailed Description of the Invention The coatings whose characteristics are shown in present drawings are based on a consistent settable blend of 40% by weight of the water absorbent composition (i) and 60% by weight of dispersible organic polymer (iii ). The base of the water-absorbent composition (i) is three parts by weight of a CSA Linker (a cement containing about 75% by weight of 4Ca0. 3A1203. S04 (Yeeli it) and 10% by weight of Na2S04 (Tenardite)) and two parts by weight of a CSA Expanding Agent (a cement containing approximately 63% by weight of CaS04 (anhydrous), approximately 28% by weight of CaO (Stabilite / Cal) and 8% by weight of 4CaO 3A1203, S04 (Yeelimit)). The lime content varies by the addition of CaO and Ca04 (anhydrite), respectively, to said mixture of the CSA Linker and the CSA Expansive Agent. The dispersible organic polymer (iii) consists of VINAPAS RE 5044 N, which is a powder that essentially comprises copolymers of vinyl acetate and ethylene. In the diagram of figure 1, X (in the ordinate) places the "early resistance [MPa]" and n (in the abscissa) for the "% by weight of CaO in the water-absorbing composition (i)". An early strength of 0.4 MPa is achieved, if the water-absorbent composition (i) contains approximately at least 13% by weight of lime. It is considered that an early strength of at least 0.4 MPa is necessary to provide a satisfactory "coating technology". But it is preferred that the early coating resistance be at least 0.5 MPa. It is important to note that it was not possible to measure the early strength of the coatings which are based on water-absorbing compositions (i), which contain less than 6% by weight of lime.The present invention is further described with reference to the following non-limiting examples: Example 1 The settable mixture contains 60.00% by weight of VINNAPAS® RE 5044 N (vinyl acetate-ethylene copolymer) and 40.00% CaO This means that the water absorbing composition (i) consists of lime (rapid) Results: Early strength> 0.5 MPa Elongation at break (with respect to drying time of 28 days)> 100% Final strength (28d)> 1 MPa Example 2 The mix contains 30.00% weight of Arconal0 430P (a powder containing polyacrylate) and the 70. 00% by weight of CaO. Therefore, the water absorbing composition (i) consists of lime (fast). Results: Early resistance > 0.5 MPa Elongation at break (with respect to drying time of 28 days) - not measured Final resistance (28d) > 2 MPa The results of the previous examples show that the good values of the characteristics of early resistance and elongation at break, as well as more or less acceptable values of the final resistance characteristic, can also be achieved, if the parameters are varied as the type of polymer and the proportion of the polymer and the water absorbing composition (i).

Claims (20)

1. NOVELTY OF THE INVENTION Having described the present invention, it is considered as a novelty and, therefore, the content of the following is claimed as property: CLAIMS 1. A settable mixture, characterized in that it comprises: (i) a water absorbing composition and (ii) an aqueous emulsion of organic polymer or (iii) a dispersible organic polymer, wherein the water absorbing composition (i) ) contains inorganic ingredients which have the ability to react with water and the water absorbent composition (i) contains at least 95% by weight of lime and wherein the amount of the aqueous emulsion of organic polymer (ii) in relation to (i) is such as to provide a ratio of the combined weight of the polymer solids to the combined weight of the ingredients having the ability to react with water from 0.5: 1 to 10: 1, and wherein the amount of the Dispersible organic polymer (iii) in relation to (i) is such as to provide a ratio of combined weight of polymers to combined weight of ingredients having the ability to react with water of 0.5: 1 to 10: 1.
2. 2. A settable mixture according to claim 1, characterized in that the water absorbing composition (i) comprises approximately 100% by weight of lime.
3. 3. A method for applying a coating to a surface whose method comprises forming a settable mixture according to claim 1, which contains a water absorbing composition (i) and an aqueous emulsion of organic polymer (ii) and placing the blending mixture on a surface to form a coating.
4. 4. A method for applying a coating to a surface whose method comprises forming a settable mixture according to claim 1, which contains a water absorbing composition (i) and a dispersible organic polymer (iii), combining the mix with water and placing the mixture on the surface to form a coating.
5. 5. The coating made according to the method defined in claim 3.
6. 6. A method for using the coating according to claim 5, as a rock support means.
7. 7. The method for using the coating according to claim 5, as waterproof media.
8. The settable mixture according to claim 1, characterized in that the amount of aqueous emulsion of organic polymer (ii) in relation to (i) is such as to provide a ratio of combined weight of polymer solids to combined weight of the ingredients that have the ability to react with water from 1: 1 to 4: 1.
9. 9. The settable mixture according to claim 8, characterized in that the water absorbing composition (i) comprises approximately 100% by weight of lime.
10. The waterable mixture f according to claim 1, characterized in that the amount of dispersible organic polymer (iii) in relation to (i) is such as to provide a ratio of combined weight of polymers to combined weight of the ingredients that have the ability to react with water from 1: 1 to 4: 1.
11. The settable mixture according to claim 10, characterized in that the water absorbing composition (i) comprises approximately 100% by weight of lime.
12. 12. A method for applying a coating to a surface whose method comprises forming a settable mixture according to claim 2, which contains a water absorbing composition (i) and an aqueous emulsion of organic polymer (ii) and placing the mixture settable on the surface to form a coating.
13. The method according to claim 12, characterized in that the coating has a thickness of at least 2 mm.
14. The method according to claim 3, characterized in that the coating has a thickness of at least 2 mm.
15. 15. A method for applying a coating to a surface whose method comprises forming a settable mixture according to claim 2., which contains a water absorbing composition (i) and a dispersible organic polymer (iii), combining the water-setting mixture and placing the mixture on the surface to form a coating.
16. 16. The method according to claim 15, characterized in that the coating has a thickness of at least 2 mm.
17. 17. The method according to claim 4, characterized in that the coating has a thickness of at least 2 mm.
18. 18. A coating made in accordance with the method defined in claim 4.
19. 19. A method for using the coating according to claim 18, as rock support means.
20. 20. A method for using the coating according to claim 18, as a waterproof medium.