GB832098A - Improvements in or relating to water repelling agents for materials containing calcareous substances and methods of manufacturing and incorporating same - Google Patents

Abstract

A water-repelling agent which is a stabilized water or solvent dispersable amphoteric metal abietate composition is prepared by reacting an alkali with a metal or a suitable compound of a metal, the oxide of which is amphoteric, to produce an alkali metal salt of the amphoteric base in the presence of an excess of alkali; reacting a further quantity of alkali with a suitable source of abietic acid in the presence of sufficient heat to produce a physically stable alkali metal or ammonium abietate and mixing the alkali metal salt of the amphoteric base with the alkali metal or ammonium abietate in relative quantities sufficient and the alkali metal salt of the amphoteric base having an excess of alkali such as to ensure that an excess of alkali is present to stabilize the abietate for a reasonable length of time (i.e. up to 2-3 years) during storage, the resultant agent being such that when applied to or combined with materials containing calcareous substances it will cause to be developed therein a material degree of repellance or resistance to absorption and/or movement of water or moisture. The agent is preferably prepared by dissolving 20 g. zinc oxide in 100 g. sodium hydroxide and 600 c.cs. water, adding this solution to a hot solution prepared from 18 lbs. colophony (containing 90% abietic acid), 2 lbs. sodium hydroxide and 1 1/2 gallons water, and then completing the preparation by adding 1/2 gallon boiling water, 6 pints industrial alcohol when the mixture has cooled to 65 DEG C. and 25 c.cs. paraldehyde when the mixture has cooled to room temperature. The volume is then brought up to 4 gallons with a 25% aqueous solution of industrial alcohol. The sodium hydroxide may be replaced by potassium or ammonium hydroxides and the zinc by aluminium or tin. The agent may be applied to calcareous substances such as masonry, dense or lightweight concrete, mortors, cements, plasters containing added lime &c. by painting, spraying or dipping or incorporated in such substances by mixing the agent with the gauge water or aggregate used in the preparation of the calcareous materials.ALSO:A method of producing a building or structural material containing a calcareous substance e.g. materials such as masonry, dense and light weight concretes, mortars, cements and plasters containing added lime, and having water-repellent properties comprises the step of applying to or combining with the material a water repelling agent prepared by reacting an alkali with a metal or a suitable compound of a metal, the oxide of which is amphoteric, to produce an alkali metal salt of the amphoteric base in the presence of an excess of alkali; reacting a further quantity of alkali with a suitable source of abietic acid in the presence of sufficient heat to produce a physically stable alkali metal or ammonium abietate and mixing the products in such relative quantities and with sufficient excess alkali as to ensure that the abietate is stabilized for a reasonable length of time (i.e. up to 2-3 years) during storage. The repellant is generally prepared in liquid form e.g. as a solution in aqueous industrial alcohol to which a small quantity of paraldehyde is added, although it may be prepared in paste or powder form. It is preferably prepared using sodium hydroxide, zinc oxide and colophony containing at least 85% abietic acid. Plastered and concrete surfaces which have not been painted may be brushed or sprayed with or dipped into the repellant e.g. as a 1% aqueous or alcoholic solution and cast concrete objects may be dipped into the repellant. The repellant may be incorporated in calcareous substances by, for example, adding it to gauge water or aggregate which is used in the manufacture of the calcareous material. The drying characteristics of the concrete are said to change when the repellant is mixed with the gauge water and less gauge water is needed during mixing. Materials said to respond satisfactorily to treatment with the repellant include practically all forms of dense concrete prepared with grey or white Portland cement with sand or other coarse aggregate light weight concrete having as aggregate perlite, pumice, vermiculite, crushed brick, expanded slate, diatomite and cellulosic materials, Portland cement plasters, cements and slurries, mortars and renderings, high alumina cements, concretes and plasters, pozzolanic cements, concretes, mortars and lime plasters and gypsum plasters with added lime and/or cement.