Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Processes of preparing a desired or intentional composition...
Reexamination Certificate
2000-02-14
2001-07-31
Cain, Edward J. (Department: 1714)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Processes of preparing a desired or intentional composition...
C524S008000
Reexamination Certificate
active
06268410
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a method for producing colored concrete bodies, particularly colored concrete roof tiles, whereby pigment is added to the unprocessed concrete mix.
2. Background Information
Colored concrete bodies are used, for example, as roof tiles, pavers, slabs, etc. Normally, such concrete bodies are colored with inorganic, preferably mineral, pigments. Iron oxides, but also chromium oxides or spinel compounds such as cobalt aluminium oxide, are used. These types of pigments 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 color intensity of these pigments is relatively low.
OBJECT OF THE INVENTION
The object of the present invention is to provide a method to produce permanently colored concrete bodies with reasonably priced pigments which are stable in outdoor exposure and resistant to light, particularly UV (ultra-violet light), alkalis and heat.
SUMMARY OF THE INVENTION
The present invention accomplishes this object 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 any of the usual known ways.
Organic pigments were hitherto considered unsuitable for coloring concrete bodies, as is stated by A. M. Veit in his article “Suggestions for 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 eluted, 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 of the present 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 present invention is that a dispersion is produced which contains at least dispersed organic polymer and coloring. If the coloring is dispersed as pigment in an aqueous polymer dispersion, polymer particles can be 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 present invention is achieved, i.e. the production of permanently colored concrete bodies.
Some organic pigments have a coloring power up to about 20 times that of the same color inorganic pigments. In other words, a much smaller amount of organic pigment is needed to produce the same intensity of color.
In addition, a much greater color intensity of the concrete body can be achieved at a 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 styrene 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 grams/Mol.
It is advantageous for the polymer dispersion to contain about 5-30% by weight of the organic pigment.
In order to increase the color 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 about 0.002 and 0.05.
A light-fast substance such as phthalocyanine or quinacridone pigment is particularly suitable as organic pigment. Phthalocyanine pigment in particular can be produced in various colors, 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 present invention, it is also possible to permanently bind pigment such as carbon black into concrete.
The organic coloring molecules can contain substituents which, for example, make possible a copolymerization with the dispersion polymer, so that the organic pigment is bound chemically in the polymer chain.
The above discussed embodiments of the present invention will be described further hereinbelow with reference to the accompanying figures. When the word “invention” is used in this specification, the word “invention” includes “inventions”, that is, the plural of “invention”. By stating “invention”, the Applicants do not in any way admit that the present application does not include more than one patentably and non-obviously distinct invention, and maintains that this application may include more than one patentably and non-obviously distinct invention. The Applicants hereby assert that the disclosure of this application may include more than one invention, and, in the event that there is more than one invention, that these inventions may be patentable and non-obvious one with respect to the other.
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“Vorschläge zur Verbesserung farbiger Betonwaren” “Suggestions for Improving Coloured Concrete Products”, Adolf M. Veit, Walluf, Concrete Precasting Plant and Technology, Issue Nov. 1994, pp. 92-100.
Drechsler Andreas
Neupert Daniel
Werner Silke
Cain Edward J.
Laferge Braas GmbH
Nils H. Ljungman & Associates
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