COLOURED STEARATES

Abstract: A process for preparing a coloured stearate or stearic acid based preparation comprising the steps of: i) high speed dry mixing a stearate or stearic acid based powder and colour agent, until the colour of the mixture is homogeneous, ii) friction blending the mixture prepared by step i) at a temperaturre sufficient to allow the particles of colour agent to combine with the particles of the stearate or stearic acid powder so as to form a compounded preparation, and until said preparation has attained the desired colour intensity.

Description: COLOURED STEARATES FIELD OF THE INVENTION This invention relates to a process for preparing a coloured stearate or stearic acid based preparation, the coloured preparations produced thereby as well as to methods which employ said preparations. BACKGROUND ART Stearates and stearic acid are widely used in industry owing to their many advantageous properties and wide availability. These factors have stimulated much activity in both finding greater uses for stearates and stearic acid and improving their role in the areas where they are presently being used. In the concrete industry, stearates are conventionally employed as aquaphobic releasing agents to facilitate the removal of patterned moulds from concrete. Stearate powder is applied to the surface of the concrete after the bleed water has evaporated off the concrete but while the concrete is still in its plastic state. The stearate acts to reduce any suction effects between the concrete and the mould when the mould is lifted. In one application of this technique, the patterned moulds form a "slate-like" topography on the concrete slab. The suction has the undesirable effect of distorting the three dimensional imprint of the mould left on the concrete. Application of the stearate at the interphase between concrete and mould results in a patterned and textured finish to the concrete complementary to the three dimensional aspect of the mould. Therefore the desired pattern may faithfully be pre-cast in the form of the mould pattern, so that the final pattern and texture of the concrete will be.produced in situ. A problem arises however in producing the desired colour finish to the patterned concrete. The concrete is normally coloured by the addition of colour agent to the concrete mix. In order to produce a "slate-like" topography, darkly coloured concrete is-preferred. However the stearate powder which is applied to the surface of the concrete is white (the natural colour of isolated stearate powder) . This will have the effect that during the imprinting of the coloured concrete by the mould, the white coloured stearate at the interphase will leave colour imperfections appearing as light patches on the coloured finish. These patches are attributable to the incorporation of the white stearate powder in the surface regions of the coloured concrete under the conditions of the imprinting. So while the method of producing the desired concrete topography has improved through the use of stearates, the imprinted concrete displays colour imperfections attributable to the white colour of the stearate powder. Much of the white patchiness may be removed after the concrete has dried by washing with water at high pressure or bleaching and scrubbing with detergent. At best, these steps will remove up to 80& of the white colour. Yet where a darkly coloured finish is required to enhance the "slate-like" topography of the surface, remnant white patches appear unsightly. There is no known prior art method which has been used to colour stearate powders. Hitherto, it has only been theorized that stearate powders may be coloured by an alcohol borne dye technique which would involve treatment of the stearate powder with an alcohol borne dye whereby the stearate dissolves in the alcohol to produce a liquid of a colour determined by the accompanying dye. The alcohol would then be evaporated off to leave a coloured stearate powder. However, in theory the stearate particles and dye particles would be present as a mixture in the coloured powder and so would still be separable. If such a coloured stearate preparation were to be applied as the aquaphobic agent between concrete and mould it is conceivable that colour imperfections would still appear as light patches on the concrete surface due to separation of the white stearate particles from the dye particles with subsequent incorporation of the stearate into the concrete surface under the conditions of imprinting. Therefore, the answer to the problem of colour imperfections on imprinted concrete rests in producing a stearate based preparation which is coloured by virtue of being compounded with the colour agent rather than by being mixed with the colour agent. It is obvious that such a process would equally apply to stearic acid based preparations. DISCLOSURE OF THE INVENTION It is therefore one object of this invention to provide a process of preparing a coloured stearate or stearic acid based preparation which is in a form where the particles of stearate or stearic acid and the particles of colour agent have been compounded together. It is another object to overcome or substantially ameliorate the disadvantages inherent in the prior art. According to one aspect of the present invention there is provided a process for preparing a coloured stearate or stearic acid based preparation comprising the steps of: i) high speed dry mixing a stearate or stearic acid based powder with colour agent, 'until the colour of the mixture is homogeneous, ii) friction blending the mixture prepared by step i) at a temperature sufficient to allow the particles of colour agent to combine with the particles of the stearate or stearic acid powder so as to form a compounded preparation, and until said preparation has attained the desired colour intensity. Preferably the stearate is any one of calcium, aluminium and zinc stearate and the stearic acid is in the form of Ca C0 3 surrounded by a stearic acid coating. The colour agent is preferably one or more iron based oxide. In order to retain the aquaphobic properties of the compounded stearate or stearic acid based preparation for its preferred application as a release agent, the relative proportion by weight of stearate or stearic acid with colour agent must be selected appropriately. For instance, using a calcium stearate based powder and an iron based oxide, the high speed dry mixing is preferably carried out with the weight percent of colour agent in the mixture preferably being between 1% and 3395. The friction blending is carried out at a temperature of preferably between 95° and 110°C to enable the colour agent to be compounded to the stearate powder. At higher temperature, the stearate begins to flux or liquify. Complete liquification of the mixture at a temperature of 140°C will produce a solid when cooled. The solid,which consists of stearate and colour agent compounded together, will need to be pulverised in order to prepare the powder. According to another aspect of the invention there is provided a coloured stearate or coloured stearic acid based preparation in a form where the particles of colour agent are combined with the particles of the stearate or stearic acid so as to form a compounded preparation thereof. According to a further aspect of the invention there is provided a method of imprinting a patterned mould on concrete, comprising the steps of: i) applying a coloured stearate or coloured stearic acid based preparation of a form where the particles of colour agent are compounded with the particles of the stearate or stearic acid, to the surface of the concrete to be imprinted, ii) applying a patterned mould to the surface of the concrete treated as in step i), and iii) removing the patterned mould from the said concrete surface to leave the imprint thereon. Preferably the colour of the coloured stearate or coloured stearic acid based preparation will be selected to provide desirable colour contrasts with the three dimensional aspect of the Imprint. The coloured stearate or stearic acid based preparations of the invention may also be used in the polymer industry as, for example, a filler, lubricant, flattening base in enamels, or colour dispersion agent. Further uses as a coloured fire retardant and a coloured sheathing of electrical conduit are also contemplated. In fact the coloured stearate or stearic acid based preparations of the invention may be used in any field where stearate or stearic acid is employed. DESCRIPTION OF THE DRAWINGS Fig 1 is a side view of the preferred blade arrangement used during the dry mixing and friction blending stages. DESCRIPTION OF THE PREFERRED EMBODIMENT In order that the invention may be more readily understood and put into practical effect, reference will now be made to the following example. Example 1 In to a four litre capacity Werring Blender (having baffles on the inside and the blade arrangement shown in Fig 1) is added 50 grammes of calcium stearate and 15.5 grammes of brown coloured iron oxide. The blender is switched on with the setting at 4000 RPM for 10-15 seconds till the stearate and oxide is mixed and the mixture takes on a fluffy consistency. UT SHEET The setting is then gradually increased to 5000 RPM whereupon the mixture is agitated with a whirlpool-like action. The shearing action of the blades and the heat built up within the blender, commonly referred to in the art as • friction blending, causes gas to build up between the particles until, at between about 95°C to 110°C, the gas is released by bubbling through the powder to the surface. The powder then settles under its own weight whilst still being agitated. At this stage the powder has a t± reddish brown colour. The resultant powder comprises calcium stearate compounded with the iron oxide. The powder does not comprise merely a mixture of calcium stearate particles and iron oxide particles. Reflux extraction of the powder prepared by the above method with pyrldine (a known solvent for calcium stearate) gave 9.6% weight per weight of pyr-dine solu bles. Infra red spect ral anylsis of these pyrldine solu bles is consistant with calcium stearate. The remaining 90.4% weight per weight pyrL.dine insolubles produced an infra red spectrum consistant with the presence of calcium stearate and iron oxide. Given that the original weight per weight percentage of calcium stearate in the powder was 76%, the presence of only 9.6% free calcium stearate after pyrldine extraction indicates that the calcium stearate that constitutes the difference has been transformed into a pyrldine insoluble form by virtue of the method of the invention. This showing of a diminution of solubility of calcium stearate is consistant with the calcium stearate being compounded with the iron oxide. As will be readily recognised, various modifications can be made in the detail of the steps of preparing the coloured stearate or stearic acid based preparation without departing from the scope and ambit of the invention.

Claims: CLAIMS 1. A process or preparing a coloured stearate or stearic acid based preparation comprising the steps of: i) high speed dry mixing a stearate or stearic acid based powder with a colour agent, until the colour of the mixture is homogeneous, ii) friction blending the mixture prepared by step i) at a temperature sufficient to allow the particles of colour agent to combine with the particles of the stearate or stearic acid powder so as to form a compounded preparation, and until said preparation has attained the desired colour intensity. 2. A process according to claim 1 wherein the stearate is selected from any one of calcium, aluminium and zinc stearate. 3. A process according to claim 1 wherein the stearic acid is in the form of calcium carbonate surrounded by a stearic acid coating. 4. A process according to any one of claims 1 to 3 wherein the colour agent is iron oxide. 5. A process according to claim 1 wherein the stearate based powder is calcium stearate and the colour agent is iron oxide and the high speed dry mixing is carried out the weight percentage of colour agent in the mixture being between 1% and 33%. 6. A process according to claim 1 wherein the friction blending is carried out at a temperature of between 95°C and 110°C. 7. A coloured stearate or coloured stearic acid based preparation whenever prepared by a process according to anyone of claims 1 to 6. 8. * A method of imprinting a patterned mould on concrete, comprising the steps of: i) applying a coloured stearate or coloured stearic acid based preparation of a form where the particles of colour agent are compounded with the particles of the stearate or stearic acid, to the surface of the concrete to be imprinted, ii) applying a patterned mould to the surface of the concrete treated as in step i), and iii) removing the patterned mould from the said concrete surface to leave the imprint thereon. 9. A method according to claim 8 wherein the coloured stearate or coloured stearic acid based preparation is prepared in accordance with any one of the claims 1 to 6.

Inventors: ROBERTS STEVEN, TAYLOR GARY, ROBERTS, STEVEN, TAYLOR, GARY
Applicants: ROBERTS STEVEN, TAYLOR GARY, ROBERTS, STEVEN, TAYLOR, GARY
Application year: 1989
Main classification: B28B7
IPC codes: B01F7, B01F15, B28B7, C04B20, C04B41, C09C1