For manufacturing kitchen sinks, especially sit-on and inset kitchen sinks, numerous materials are known. Known are sinks where granules of polymer materials are used for the manufacturing of the mass. The use of granules of polymer materials as a filler does offer a bigger selection of the colours of the final article, but due to the relative "softness"of the granules the surface of such sinks is not resistant to wear and scratches. Thus, using only granules of polymer materials as a filler is not suitable for manufacturing articles whose surfaces are exposed to greater mechanical stress.

An adequate resistance of sinks to mechanical stress was achieved by the use of mineral particles. In the EP 0 361 101 B2 there is described a built-in sink made of a mass that consists of a resin and a filler mainly consisting of particles of a mineral filler with a particle size of about 0.1 mm to 2 mm, which are in the form of unbroken grains and have a colour coating on their surface. The filler constitutes approximately 50 to 85 wt. % of the mass. Further, this patent describes a process for manufacturing this built-in sink.

Hitherto it has not been known to use a composite material on the basis of a mass containing a combination of different kinds of fillers, e. g. a mixture of at least two or more of the following fillers: mineral fillers, aluminium trihydrate, glass spheres and granules of polymer materials or so-called synthetic granules, and from which articles with a good surface resistance to mechanical stress could be manufactured.

The present invention relates to a novel composite material made of a mass essentially consisting of fillers and binders. By selecting a right ratio and composition of fillers and a right binder there is obtained a mass which fills the mould well and, when cured, gives a composite material that has good resistance to wear and scratches as well as to hot water, is of different colours and forms and is suitable for manufacturing kitchen sinks and other articles. By a novel combination of fillers and binders a mass with an improved flowability is obtained, whereby the filling of a mould through a pouring opening and thereby the process of manufacturing the sinks are improved. By an appropriate novel combination of fillers, especially by a mixture of mineral fillers such as silica flour of cristobalite type and granules of silica sand, a more"filled-up"structure is achieved. Thus, less binder has to be used in the mass, whereby the manufacturing costs are reduced; another advantageous consequence are smaller shrinkages at curing.

The composite material according to the invention is prepared from a mass essentially consisting of fillers and binders, with the fillers of mineral or synthetic origin constituting 60 to 80 wt. % of the mass and the binder constituting 18 to 40 wt. % of the mass.

In the mass the fillers are present as a mixture of at least two or more of the following fillers: - mineral fillers constituting 20 to 70 wt. % of the mixture of fillers; - aluminium trihydrate constituting 10 to 35 wt. % of the mixture of fillers; - glass spheres constituting 4 to 35 wt. % of the mixture of fillers; - granules of polymer materials (synthetic granules) constituting 15 to 30 wt. % of the mixture of fillers. As the mineral filler any mineral filler can be used, preferably silica flour of cristobalite type with granular sizes from 0.002 to 0.128 mm. If only silica flour of cristobalite type is present in the mixture of fillers as the mineral filler, it constitutes 20 to 70 wt. % of the mixture of fillers. The surface of cristobalite is specially treated with silanes, which contributes to a better wetting of the grains i. e. the binder wraps well around the grains.

As the mineral filler also a mixture of mineral fillers such as a mixture of silica flour of cristobalite type and of granules of silica sand can be used. In such case the granules of silica sand constitute 45 to 70 wt. % of the mixture of fillers and their granular size is from 0.1 to 1.2 mm. The granules of silica sand give a granite-like appearance to the final article.

In the mixture of fillers aluminium trihydrate can constitute 10 to 35 wt. % and appears in granular sizes from 0.007 to 0.035 mm. Also the surface of aluminium trihydrate grains is specially treated with silanes, whereby the wettability of the grains is increased and the flowability of the mass is improved.

In the mixture of fillers also 4 to 35 wt. % of glass spheres with a granular size from 35 to 70 um can be present. By the use thereof the surface resistance of the final article to scratches is improved.

A further component in the mixture of fillers are granules of polymer materials (so called synthetic granules-"solid surface granules"), which can constitute 15 to 30 wt. % of the mixture of fillers and have a granular size from 0.5 to 1.2 mm.

Synthetic granules can be e. g. on acryl or polyester basis and can be of an optional colour, which makes possible a large selection of colours and gives a granite-like appearance to the final article.

The binder constitutes 18 to 40 wt. % of the mass depending on the type of the resin and the recipe used. It can be a synthetic resin such as an unsaturated polyester resin of NPG (neopentyl glycol) type, an acrylic resin or an epoxide resin.

To the mass prepared from fillers and binders, there are added reagents which set on the reaction of polymerization i. e. curing. The selection of the reagent-curing component-depends on the binder used. An organic peroxide of the type of methylethylketone peroxide, benzoyl peroxide or polyamine can be used.

The mass can be prepared in a vacuum mixer or by an automated mixing-pouring machine with built-in vacuuming. The prepared mass is poured into a specially prepared closed mould having a rough surface coated with a release agent. By the rough surface of the mould such roughness of the final articles is achieved which gives a better resistance to scratches but does not hinder the cleaning of the article.

The curing of the mass can proceed according to a process of hot or cold curing. The process of hot curing is well known. By the use of cold curing by means of a special curing system, which represents a novel solution in the manufacturing of kitchen sinks, especially where acrylic resin is used as the binder, the production of kitchen sinks has been made less costly and simplified. Compared to the process of hot curing, simpler and thus cheaper casting tools may be used for the cold curing. Since it is not necessary to warm the moulds these can be made of a cheaper material, e. g. of various laminates on the basis of plastic materials.

After the curing reaction has been completed, the article can be demoulded and subsequently cured at an elevated temperature from 70°C to 120°C.

The invention is exemplified but in no way limited by the following examples.

Examples Example 1 Into the reaction vessel there were weighed: - 28 to 32 wt. % of a polyester resin, - 47 to 52 wt. % of silica flour of cristobalite type (Silbond) with a granular size from 0.002 to 0.128 mm, and - 18 to 23 wt. % of synthetic granules with a granular size from 0.5 to 1.2 mm.

All components were intimately mixed together and vacuumed for 15 to 20 minutes at 0.2 bar. Than a curing component in an amount of 1 to 2 wt. % with regard to the resin was added. It was stirred under vacuum for further 5 minutes and then poured into a mould. Approximately 60 minutes after gelling the article was demoulded and subsequently cured at approximately 70°C.

Example 2 Into the reaction vessel there were weighed: - 18 to 21 wt. % of an acrylic resin, - 13. 5 to 15. 5 wt. % of silica flour of cristobalite type (Silbond) with a granular size from 0. 002 to 0. 128 mm, - 13. 5 to 15.5 wt. % of glass spheres with a granular size from 35 to 70 pm, and - 38 to 45 wt. % of granules of silica sand with a granular size from 0.1 to 1.2 mm.

All components were intimately mixed together and vacuumed for 15 to 20 minutes at 0.2 bar. Than a curing component in an amount from 1 to 2 wt. % with regard to the resin was added. It was stirred under vacuum for further 5 minutes and then poured into a mould. Approximately 60 minutes after gelling the article was demoulded and subsequently cured at approximately 70°C.

Example 3 Into the reaction vessel there were weighed: - 20 to 25 wt. % of a polyester resin, - 12. 5 to 15 wt. % of silica flour of clistobalite type (Silbond) with a granular size from 0.007 to 0.035 mm, - 12. 5 to 15 wt. % of aluminium trihydrate with a granular size from 0.007 to 0.035 mm, and - 45 to 50 wt. % of granules of silica sand with a granular size from 0.1 to 1.2 mm.

All components were intimately mixed together and vacuumed for 15 to 20 minutes at 0.2 bar. Than a curing component in an amount from 1 to 2 wt. % with regard to the resin was added. It was stirred under vacuum for further 5 minutes and then poured into a mould. Approximately 60 minutes after gelling the article was demoulded and subsequently cured at approximately 70°C.