MOULD RELEASE COMPOSITIONS TECHNICAL FIELD The present invention relates to compositions for use as mould release agents, particularly in the manufacture of moulded silicaceous products. For the purposes of the present invention, moulded silicaceous products are defined as cementitious products produced from fluid composites being allowed to set solid within a mould, and clay bricks and other clay based products formed by extrusion of pliable composites.

The invention also relates to processes for the preparation of such compositions and to methods of improving the surface quality of moulded products by the use of such compositions.

BACKGROUND ART Wet cement tends to stick tenaciously to steel or timber moulds used to contain concrete until it sets. Mould release agents comprising a large variety of compositions have been produced over the past century to assist in reducing or eliminating this sticking. Their primary action is to provide a waterproof barrier between the concrete and the mould, but a secondary action is lubrication of the mould so that setting concrete may slide rather than adhere to the mould as it passes through expansion and contraction phases.

Oleic acid, gum rosin, mineral and vegetable oils and other natural and synthetic oleiferous products have been used for many years in diverse preparations designed for release of moulded silicaceous products. The common form of these oleiferous products has been either neat or as solutions in petroleum derived solvents, such as distillate, turpentine, and other fractions.

Concerns in recent years about environmental and health effects of petroleum based products have led to increasing demand to replace petroleum derived solvents with water-based systems, and many such systems have been

described. In critical applications, water-based systems have failed to provide performance equal to that of comparably priced petroleum based products.

Petroleum in one form or another has been used for 80 years as a mould release agent with both film-forming and lubricating functions. Standard "off the shelf"products used for many decades to prevent the sticking of wet cement to steel or timber moulds have been solutions of either gum rosin or oleic acid with concentrations between 2% and 30% in a cheap, petroleum derived solvent, such as distillate or mineral turpentine. As mentioned earlier, recent concerns about the environmental and health effects of these solvents are reflected in tighter regulator attention from health, safety and environmental authorities. Several water-based systems designed to replace petroleum derived solvents have been described in the prior art, but these are uneconomical and cannot replace petroleum derived solvents in all applications. The present invention seeks to address these shortcomings.

Another approach which has been taken by the prior art over a long time has been to prepare dry mould release films from water or other solvent solutions. However, for manufacture of pipes, concrete slabs and the vast majority of concrete moulding, films preformed on moulds are far too weak to withstand the aggressive conditions of concrete pouring, vibration, centrifugation, heating and other treatments normally used in these applications, and so permanent or semi-permanent preformed films have very limited applicability. The overwhelming industrial demand is for a liquid mould release composition which can be applied to a mould by brushing or spraying, then overlaid with wet concrete immediately or not much later. The present invention directly addresses this demand.

Water is the component of wet concrete which tends to bond cement to uncoated moulds. Conventional wisdom is that gum rosin and oleic acid in

petroleum derived solvents perform as mould release agents by reacting quickly with calcium ions dissolved in the water of freshly mixed concrete to form calcium soaps which are insoluble in water. These soaps precipitate and congregate in the interface between the wet concrete and the mould, where they form a film, thus excluding water from the interface and so preventing bonding or sticking of wet cement to the mould. Petroleum derived solvents are themselves repelled by water and so tend to congregate in the same region, helping to lubricate the interface and to keep the active mould release agents at the interface. However, the same results have not occurred when those same agents have been applied in a water-based system. Instead, mould release agents in water based systems tend to be greatly diluted and dispersed by the overwhelming amount of water in wet concrete. This dilution tends to make mould release agents in water based systems very inefficient unless some counter-measure is taken.

Conventionally, the liquid mould release compositions of the prior art seem to provide a high enough concentration of solubilized water-repellent components, i. e. hydrocarbons, fatty materials in many forms, silicones, waxes, rosin, and other materials, to perform their required mould release function either from solution or emulsion or by being precipitated at the interface by the massive influx of water when wet concrete is poured into the mould.

In contrast, it is a preferred object of the present invention to create a water repellent interface by another mechanism, namely, by the rapid formation of calcium soaps by reaction of calcium ions dissolved in the water of freshly mixed concrete with amine soaps of organic acids. Those calcium soaps immediately precipitate and so become independent of their water carrier and, being highly water repellent, remain at or close to the interface at a concentration sufficient to form an effective film. Thus, this mechanism of

calcium soap and film formation is unaffected by dilution with water added via the wet concrete mix to the region of the applied mould release, and provides in that region a water repellent film of the same kind as that formed by gum rosin and oleic acid in petroleum derived solvents.

Sodium, potassium and ammonium soaps are too stable to react with dissolved calcium in this type of system, and so they are unable to form a water repellent film. Prior art mould release compositions containing those stable soaps seem to rely for their mould release function upon, either, the soap being present in sufficient concentration to act as a lubricant within the diluted water phase, or the soap being present primarily to solubilize esters, hydrocarbons or other oily agents which become destabilised and precipitated when diluted with water added into the concrete mix.

Reaction products of carboxylic acids with water soluble amines to form soaps and amides have been described for many applications, including release of concrete moulded products, but their usefulness in the presence of high water content as found in wet concrete has depended upon compounding with hydrocarbons, organosilicon compounds or other petroleum based compounds whose presence is generally regarded as undesirable for reasons of cost, health, safety or environmental concern.

SUMMARY OF INVENTION Therefore, it is an object of this invention to provide practical and inexpensive mould release compositions with performance equal to or exceeding that of commonly used petroleum based products, together with environmental and health impacts substantially lower than that of those petroleum based products.

It is another object of this invention to provide mould release compositions comprised of stable, aqueous mixtures of amine soaps of organic

acids which retain a high level of efficacy in conditions of high water content normally experienced when performing as a mould release agent, while reducing or eliminating components generally regarded to be undesirable.

It is still another preferred object of the present invention to form mould release compositions of a highly active kind that utilize aqueous solutions of gum rosin and fatty soaps prepared with water-soluble amines. The formation of such compositions is readily facilitated in the present invention because the aqueous mixtures of amine soaps present in the mould release compositions of the invention behave quite differently from those made with conventional inorganic alkalis.

It is yet another preferred object to use the calcium ions in wet concrete to precipitate active mould release agents from an aqueous carrier.

It is a still further preferred object of the invention to provide a mould release composition that is free of silicones, hydrocarbons, alcohols, esters and metal soaps, which have been the basis for the aqueous concrete mould release agents of the prior art.

According to the invention, there is provided a mould release composition for moulded silicaceous products, comprising an aqueous mixture of amine soaps of organic acids.

Preferably, the composition includes silicaceous solids, together with other compounds which provide surfactancy, dispersion, suspension and storage stability.

Preferably, the silicaceous solids comprise talc and/or attapulgite.

Preferably, the composition includes insoluble nucleation agents for calcium soaps.

It is preferred that both the silicaceous solids and insoluble nucleation agents assist in forming a film at the interface by acting as nucleation agents

for calcium soaps as they are created, forming physical composites with those soaps whose relatively high density tends to concentrate them at the interface.

Preferably, the acidic portion of the organic acid soaps is comprised of a compound or mixture of compounds each with the general formula :- R-COOH(I) where R is any moiety containing from 8 to 50 C atoms and which may also contain any combination of non-metallic elements, provided that the overall activity of the molecule remains acidic with respect to an aqueous base.

Preferably, the basic portion of the organic acid soaps is comprised of an amine or mixture of amines chosen from :- (i) primary and/or secondary and/or tertiary amines chosen from:- (a) those amines containing the moiety ll :- >N-CR1R2-CR3R4-O- (II) where Ri and/or R2 and/or R3 and/or R4 is H or any alkyl or aryl group, and/or (b) those amines containing the moiety III :- >N-CR1R2-CR3R4-N < (III) where R1 and/or R2 and/or R3 and/or R4 is H or any alkyl or aryl group, and/or (c) those amines with the general formula IV :- HO-NRRi(IV) where R or Ri is H or any alkyl or aryl group, and/or (d) any amine salt which might produce any of the above amines by simple neutralization, and/or

(ii) the cationic portion of any quaternary amine or amines.

Preferably, the composition of the invention includes silicaceous solids which improve the usefulness of the composition in certain applications.

Preferably, such silicaceous solids are chosen from the group consisting of talc, palygorskite (attapulgite), and smectite clays, and may be both crude and refined. Preferably, the composition of the invention includes one or more members of the group consisting of magnesium silicates, aluminium silicates and magnesium aluminium silicates.

Preferably, the composition of the invention includes auxiliary ingredients which assist the desired function of the aforementioned components and/or which stabilize the composition by controlling homogeneity, rheology, viscosity, foaming, wetting, anticorrosivity and biological degradation.

Such auxiliary ingredients are chosen from:- (a) carboxylic acid esters of polyols with optional polyoxyethylene sidechains, such polyols being chosen from ethylene glycol and its dimers and higher condensates, propylene glycol and its dimers and higher condensates, sorbitans, glycerol, pentaerythritol, and/or trimethylol alkanes and arylalkanes ; (b) polyoxyethylene-polyoxypropylene (EO-PO) block polymers of the general formula V:- where the sum of x + z is from 5 to 160 and y is from 15 to 60; (c) ester and/or phosphatide emulsifying agents chosen from wool grease, egg yolk, soybeans and their extracted components including lanolin, lanolin alcohols and their esters, and lecithin, all being present in smaller amounts than the amine soaps;

(d) polysaccharide-based rheological modifying agents chosen from hydroxyethylcellulose, methylhydroxyethylcellulose, sodium carboxymethylcellulose, xanthan gum, guar gum, tragacanth, pectin, acacia gum, carrageenin and/or salts of alginic acid; (e) antifoam agents being chosen from commercial siloxane-based products designed for such functions; and (f) preservative agents with anticorrosive, antioxidant and antimicrobial functions chosen from commercial products designed for such functions.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS In order that the invention may be readily understood and put into practical effect, reference will now be made to the following Examples.

Example 1 Part A-Gum rosin was crushed to pass through a 2.5mm screen. To 74g of demineralized water were added 60g of sorbitan monooleate (Ecoteric S80), 10g of polyoxyethylene (15) oleylamine (Teric 16M15), 10g of polyoxyethylene (5) stearylamine (Teric 18M5), then 26g of morpholine. This mixture was heated and stirred until its temperature reached 80°C, then 1 OOg of crushed gum rosin was added in small aliquots, allowing time for each aliquot to be dissolved before adding the next aliquot. When all the rosin was added and the mixture had become homogeneous, this mixture was set aside to cool.

Part B-2.4g of xanthan gum (Kelzan D) was dispersed with high speed shearing in 117. 6g of demineralized water. This mixture was set aside overnight, then blended again shortly before use.

Part C-70g of talc (Commercial Minerals T38B, 98% < 38pm) was dispersed in 130g of demineralized water together with 40g of an EO-PO block

polymer dispersant (Teric PE68), the talc and dispersant being added to the water in small lots, alternating between the two additives.

To 400g of demineralized water was added all of Part C, then all of Part B, then the mixture was stirred for 20 minutes at moderate speed. A further 958g of demineralized water was added together with 2g of 37% aqueous or aqueous/methanolic formaldehyde (37% formalin). This mixture was stirred for 3 to 5 minutes, then all of Part A was added. Stirring was resumed and continued for 30 minutes.

This product remained homogeneous for at least two months at all temperatures between 0°C and 40°C. This product was useful for release of concrete pipes produced by conventional spinning and heat-cure processes.

Pipes thus produced had a rate of occurrence of defects and general surface appearances similar to that of pipes produced using a conventional petroleum- based mould release agent.

Example 2 Part A-Gum rosin was crushed to pass through a 2.5mm screen. To 14.8g of demineralized water were added 12g of sorbitan monooleate (Ecoteric S80), 2g of polyoxyethylene (15) oleylamine (Teric 16M15), 2g of polyoxyethylene (2) stearylamine (Teric 18M2), then 5.2g of morpholine. This mixture was heated and stirred until its temperature reached 80°C, then 20g of crushed gum rosin was added in small aliquots, allowing time for each aliquot to be dissolved before adding the next aliquot. When all the rosin was added and the mixture had become homogeneous, this mixture was set aside to cool.

Part B-1.2g of xanthan gum (Kelzan D) together with 1.2g guar gum (Guar Gum NP3500FG, Germantown International) was dispersed with high speed shearing in 296.4g of demineralized water. 1.2g of 37% formalin was

added, then blended slowly into the mixture which was set aside overnight, then blended again shortly before use.

40g of EO-PO block polymer dispersant (Teric PE68) was dissolved in 73.2g of demineralized water. To this mixture was added 30g of talc (WMC Westmin 8,98% < 8 ; j. m) with stirring at medium speed for 30 minutes to form a thin paste, then 0.8g of formalin and all of Part B were added to the mixture with stirring for 3 to 5 minutes. 1500g of demineralized water was added, the mixture was stirred for 3 to 5 minutes, then all of Part A was added. Stirring was resumed and continued for 30 minutes.

This product remained homogeneous for at least two months at all temperatures between 0°C and 40°C. This product was useful for release of concrete roofing tiles cast on aluminium templates and concrete blocks cast in vibrated or static moulds without heating. The surface of concrete produced using this product was less sandy than controls produced with a conventional petroleum-based mould release agent. Residues remaining on uncleaned, recycled templates after six cycles were similar to control samples produced by conventional processes.

Example 3 Part A-56g produced by the process described in Example 2.

Part B-40g of attapulgite (Attagel 50) was dispersed with high speed shearing in 460g of demineralized water. This was ready for immediate use.

40g of EO-PO block polymer dispersant (Teric PE68) was dissolved in 210g of demineralized water. To this mixture was added 30g of talc (Westmin 8) with stirring at medium speed for 30 minutes to form a thin paste, then 2g of formalin and all of Part B were added to the mixture with stirring for 3 to 5 minutes. 1160g of demineralized water and 2g Antifoam S (Castrol) were

added, the mixture was stirred for 3 to 5 minutes, then all of Part A was added.

Stirring was resumed and continued for 30 minutes.

This product remained homogeneous for at least one month at all temperatures between 0°C and 60°C. This product was useful for release of concrete roofing tiles cast on aluminium templates and concrete blocks cast in static moulds with or without heating. This product better withstood prolonged hot storage conditions than Examples 1 and 2.

It is an advantage of the mould release compositions of the present invention that they: (a) avoid the dangers to health, safety and the environment associated with petroleum based products; and (b) enable easy separation of moulds from their moulding with low incidence of surface defects, including chalky or tacky residues, adhesion of moulding material to the mould, pitting, and colour variations.

Various modifications may be made in details of components and processes for the preparation of the composition of the present invention without departing from the scope and ambit of the invention.