METHOD FOR PRODUCING COLOURED CONCRETE BODIES

Abstract: The invention relates to a method for producing coloured concrete bodies, particularly coloured concrete roof tiles, whereby pigment is added to the unprocessed concrete mix. In order to provide a method which makes possible the production of permanently coloured concrete bodies with reasonably priced pigments which are stable in outdoor exposure and are resistant to light, particularly UV, alkalis and heat, it is proposed that a cement compatible aqueous polymer dispersion in which organic pigment is dispersed be added to the unprocessed concrete mix. Suitable cement compatible polymer dispersions are aqueous polymer dispersions based on styrol and/or pure acrylate. Phthalocyanine or China acridon pigments are particularly suitable as organic pigments.

Description: Description Method for producing coloured concrete bodies The invention relates to a method for producing coloured concrete bodies, particularly coloured concrete roof tiles, whereby pigment is added to the unprocessed concrete mix. Coloured concrete bodies are used, for example, as roof tiles, pavers, slabs, etc. Normally, such concrete bodies are coloured with inorganic, preferably mineral, pigments. Iron oxides, but also chromium oxides or spinel compounds such as cobalt aluminium oxide, are used. These types of pigment have been well established for many years and have proved to be durable. However, relatively expensive inorganic pigments are needed, in particular for the production of blue shades. Moreover, the colour intensity of these pigments is relatively low. The purpose of this invention is to provide a method which makes it possible to produce permanently coloured concrete bodies with reasonably priced pigments which are stable in outdoor exposure and resistant to light, particularly UV, alkalis and heat. The invention serves this purpose in that a cement compatible aqueous polymer dispersion, in which organic pigment is dispersed, is added to the unprocessed concrete mix. The unprocessed concrete mix can then be shaped into bodies and cured in the usual way. Organic pigments were hitherto considered unsuitable for colouring concrete bodies, as is stated by A.M. Veit in his article "Proposed ways of improving coloured concrete products" in the periodical "Betonwerk + Fertigteil-Technik", volume 11/1994, pp 92 - 100. Organic pigments cannot be properly bound into the hydraulically hardening matrix. Consequently, these pigments are gradually elutriated, and the concrete body fades with time, inevitably giving rise to complaints. However, because of their binding into a cement compatible polymer dispersion, the method as per the invention makes it possible to incorporate organic pigments permanently in the matrix of the concrete body, so that elutriation does not occur. What is crucial for the success of the method as per the invention is that a dispersion is produced which contains at least dispersed organic polymer and colouring. If the colouring is dispersed as pigment in an aqueous polymer dispersion, polymer particles are deposited on the surface of the pigment particles and ultimately surround the latter. Hence the pigment particles are surrounded and protected by polymer particles. When the dispersion desiccates, the pigment particles are bound into the plastic matrix. This also applies to chemically bound pigment. In the case of aqueous dispersions, the dispersion is non redispersible and of high molecular weight. In other words, following desiccation of the original dispersion, a plastic results which cannot be converted back into a dispersion with the addition of more water. Hence the purpose of the invention is achieved, i.e. the production of permanently coloured concrete bodies. Some organic pigments have a colouring power up to 20 times that of the same colour inorganic pigments. In other words, a much smaller amount of organic pigment is needed to produce the same intensity of colour. In addition, a much greater colour intensity of the concrete body can be achieved at far lower cost than with mineral pigments. Furthermore, shades can be achieved which are not possible with mineral pigments. As a suitable cement compatible polymer dispersion, preference is given to an aqueous polymer dispersion whose polymer contains styrol and/or pure acrylate. However, any polymer dispersion which is of high molecular weight, stable in cement and non redispersible is suitable. The molar mass of the typical high molecular weight polymer is about 10 6 g/Mol. It is advantageous for the polymer dispersion to contain 5 - 30% by weight of the organic pigment. In order to increase the colour intensity, a wetting and/or dispersing agent can be added to the preparation; also possible are admixtures to prevent the pigment from precipitating. It is advantageous for the polymer dispersion to be added to the unprocessed concrete mix in such a quantity that the pigment/cement ratio is between 0.002 and 0.05. A light-fast substance such as phthalocyanine or China acridon pigment is particularly suitable as organic pigment. Phthalocyanine pigment in particular can be produced in various colours, from blue copper phthalocyanine to green hexadecachlorophthalocyanine. The pigment preparation can of course also contain a blend of various organic pigments, and mineral pigment can be added if required. In the method as per the invention, it is also possible to permanently bind pigment such as carbon black into concrete. The organic colouring molecules can contain substituents which, for example, make possible a copolymerisation with the dispersion polymer, so that the organic pigment is bound chemically in the polymer chain. The method as per the invention is explained below using four embodiments. Embodiment 1 50 g of copper phthalocyanine was dispersed in a dissolver for 15 minutes with 950 g of a styrol acrylate dispersion (LDM 6880, 50% proportion, Hoechst). 16.8 g of this preparation was added to an unprocessed concrete mix of 1350 g of sand with a grain size of 0 to 3 mm, 420 g of cement CEM I 42.5 R and 135 g of water. The coloured concrete mix was shaped into a body. Following curing of the shaped body, a light blue concrete body was obtained. Embodiment 2 300 g of copper phthalocyanine was dispersed in a dissolver for 15 minutes with 700 g of a pure acrylate dispersion (B60A, 50% proportion, Rohm & Haas) . 70 g of this preparation was added to an unprocessed concrete mix of 1350 g of sand with a grain size of 0 to 3 mm, 420 g of cement CEM I 42.5 R and 120 g of water. Concrete bodies made from this mix had an intense blue colour. Embodiment 3 100 g of China acridon pigment was dispersed in a dissolver for 15 minutes with 600 g of a styrol acrylate dispersion (LDM 6880, 50% proportion, Hoechst) . 43 g of this preparation was added to an unprocessed concrete mix of 1350 g of sand with a grain size of 0 to 3 mm, 420 g of cement CEM I 42.5 R and 109 g of water. After shaping and curing, a light violet concrete body was obtained. Embodiment 4 150 g of China acridon pigment was dispersed in a dissolver for 15 minutes with 300 g of a styrol acrylate dispersion (LDM 6880, 50% proportion, Hoechst). 63.3 g of this preparation was added to an unprocessed concrete mix of 1350 g of sand with a grain size of 0 to 3 mm, 420 g of cement CEM I 42.5 R and 109 g of water. After shaping and curing, an intense violet concrete body was obtained.

Claims: Claims 1. Method for producing coloured concrete bodies, particularly coloured roof tiles, whereby pigment is added to the unprocessed concrete mix, characterised in that a cement compatible aqueous polymer dispersion is added in which an organic pigment is dispersed. 2. Method as in claim 1, characterised in that the polymer of the polymer dispersion contains styrol and/or pure acrylate. 3. Method as in claim 1 or 2, characterised in that the polymer dispersion contains 5 - 30% by weight of the organic pigment. 4. Method as in one of claims 1 to 3, characterised in that the polymer dispersion contains a wetting and/or dispersing agent. 5. Method as in one of claims 1 to 4, characterised in that the ratio of the pigment to cement in the unprocessed concrete mix is between 0.002 and 0.05. 6. Method as in one of claims 1 to 5, characterised in that the organic pigment is a phthalocyanine pigment. 7. Method as in one of claims 1 to 6, characterised in that the organic pigment is a China acridon pigment. 8. Method as in one of claims 1 to 7, characterised in that the organic pigment is chemically bound in the polymer chain.

Inventors: DRECHSLER ANDREAS, NEUPERT DANIEL, WERNER SILKE, DRECHSLER, ANDREAS, NEUPERT, DANIEL, WERNER, SILKE
Applicants: BRAAS GMBH, DRECHSLER ANDREAS, NEUPERT DANIEL, WERNER SILKE, DRECHSLER, ANDREAS, NEUPERT, DANIEL, WERNER, SILKE
Application year: 1996
Main classification: C04B20
IPC codes: C04B20, C04B28, C04B40, C04B103, C04B111