GB2064986A

GB2064986A - Building or construction element

Info

Publication number: GB2064986A
Application number: GB8032005A
Authority: GB
Original assignee: Individual
Current assignee: Individual
Priority date: 1979-10-11
Filing date: 1980-10-03
Publication date: 1981-06-24
Also published as: DK150825B; DE3038176A1; FR2467184B1; DK150825C; IT8025244A0; FR2467184A1; DK428679A; JPS56109864A; JPS6317783B2; SE8007081L; IT1133854B; NL8005589A; BE885638A; ES495809A0; GB2064986B; SE447374B; ES8207106A1

Abstract

A building or construction element comprises a core and a decorative coating which contains 2-60 parts by weight of graphite, 98-40 parts by weight of relatively coarse particles of natural stone or artificial material having a grain size of typically 20-5000 mu m and 5-100 parts by weight of organic binder. The building element, which has the appearance of a cut natural stone, has improved durability and weather resistance since the binder is effectively protected by the relatively coarse particles of natural stone or similar material.

Description

SPECIFICATION Building or construction element The present invention relates to a building or construction element which has the appearance of a natural stone having decorative effect.

Natural stone in the form of sawn or cut plates, fragments or building stones is in great demand because of its decorative effect. In particular plates or tiles or slabs of slate or marble are used as floorings, facings or wall coverings. Also granite stone cut into irregular broken flagstone or into the shape of bricks is used in the building industry, e.g.

for the construction of walls, as facings or wall coverings, for fences or as garden slabs.

The use of natural stone in the building industry is prohibited by its high price, and also because these materials are becoming scarse products with the gradual depletion of the deposits. Especially marble and black granite, which are in particular great demand, are only available in limited quantities and are high-priced.

When natural stone is extracted and dressed some waste is produced in the form of small fragments and chips or powder which is of no or iittle value.

Attempts have been made at utilizing this waste by crushing and pressing it, optionally after the addition of a binder, into building stones or plates. It is also known to apply a coating containing particles of natural stone on a core of a cheaper material. The finished products, however, usually do not look like the original natural stone. Owing to crushing and the content of the binder the surface has often got a uniform and unattractive appearance without any structure and character.

Plates of natural stone are generally very brittle and can easily crack or be broken during manufacture, transport or when they are used for the intended building purpose.

The object of the present invention is to provide a building or construction element which, as much as possible, looks like a natural stone, such as a marble plate, a slate plate or a granite stone, and which is considerably cheaper than a corresponding real natural stone. Another object of the invention is to provide such a building or constructional element which has an improved strength, particularly tensile and flexural strength, in relation to a corresponding natural stone.

Accordingly, the invention provides a building or construction element comprising a core and a coating thereon, said coat containing particles of natural stone or an artificial mineral material of decorative effect, said particles being bonded together by an organic binder, said element being characterized in that the coat contains 2-60 parts by weight of graphite, 98-40 parts by weight of relatively coarse particles of natural stone or artificial material and 10-100 parts by weight of organic binder. According to the invention the particularly preferred composition is 10-40 parts by weight of graphite, 90-60 parts by weight of natural stone particles or particles of artificial mineral and 20-60 parts by weight of organic binder.

Thanks to the relatively low content of organic binder and the use of relatively coarse particles of a mineral type the surface obtains approximately the same structure, appearance and character as the corresponding natural stone. The content of graphite is essential because owing to its particular crystal structure it accentuates the structure of the mineral particles, and the combination of graphite and mineral particles imparts an attractive decorative appearance to it because of the contrasting effect.

According to the invention the natural stone particles of the coat are preferably slate, marble or granite. These mineral particles, combined with particles of graphite, provide products which are hardly distinguishable from massive sawn or cut plates or stones of slate, marble or graphite, respectively.

Another embodiment of the invention uses particles of an optionally stained glass frit which may provide special decorative effects. Here too, the content of graphite results in improved contrast and a beautiful structure. The glass frit may consist of glass beads or broken glass.

By the term "relatively coarse particles" is understood particles of such a size as will provide a distinct surface structure which is visible to the naked eye. The practical lower limit to the grain size is about 20 Fm because an unaided eye cannot or not very well distinguish individual grains of a diameter below this value. The mixture may, however, contain a small amount of fine powder of a grain size below 20 calm without this having any adverse effects. The upper limit of the particle size in the coat is 5000 um (5 mm). The preferred range is 50-10001lm and a particularly preferred grain size is 50-250 um. This range of grain size provides the most advantageous decorative effect.

The preferred ratio of mineral particles to organic binder also provides a certain relief effect as the amount of binder is too small to bring about a completely smooth and plane surface. This relief effect may be considerably accentuated by the application of the coating, particularly if this is done by spreading. Even though the content of mineral binder is relatively small in relation to the mineral particles, said particles are nevertheless strongly anchored in the coating. The mineral particles are very closely spaced and protect the organic binder against climatic effects so as to provide great durability for a long time.

The graphite particles, too, expediently have a particle size of 20-1000 ym, preferably 50-250 Rm.

Graphite grains of this size have visible crystal faces which contribute to the desired surface structure.

Another advantage offered by the addition of graphite is that even though the content of solids is large, an expedient consistency may be imparted to the coating material, which is used for forming the coating, because of the lubricating properties of the graphite. This is important no matter whether the coating is formed by spraying or spreading.

If the material particles consist of glass frit, which is crushed to the desired particle size, the glass frits normally employed in the pottery industry may be used. Thus, the glass particles may be used which are stained as desired, e.g. in red, green, yellow, blue or other colours. White opal glass or black glass may be used as well.

The invention is not restricted to the use of the mineral particles specifically mentioned in the foregoing; any mineral particulate material may be used which provides a desired decorative effect. Nor is it necessary to use the materials separately. Thus, it is possible to mix particles of several different natural stones andlor artificial mineral materials. This may result in attractive surfaces which do not look like specific natural stone but has nevertheless a structure and character like a natural stone.

A special artifical mineral material which may be used in connection with the present building or construction element, is glass which is made partly or wholly crystalline by a heat treatment and is then crushed to the desired particle size. An example of a material of this type is a product which is commercially available under the trade mark "Synopal".

The core used for the building or construction element may consist of any sufficiently cheap material. According to the invention an expedient core material is a shaped article of burned clay, such as a brick. This provides an extremely cheap product, particularly if the present coating is only applied on one or two faces of the brick.

In another embodiment of the invention the core may comprise a plate of wood, asbestos cement, plaster, concrete or a foamed inorganic or organic material.

The use of wood, such as a plate of waste wood or a chipboard, for the core material brings about a light material of good mechanical strength so that the product does not easily crack or break. Also asbestos cement, plaster or concrete results in inexpensive products of good strength, especially if provided with reinforcements of wires, glass fibres or a network or fabric of natural or artificial fibres, such as polyamide or polyester fibres.

Particularly light products are achieved when the core comprises a foamed material, and examples of this polyurethane foam or polystyrene foam. Also naturally occurring porous or foam materials may be used as core material. A case in point is the mineral Vermiculite in expanded form.

The invention is illustrated by the examples below.

Example 1 100 g of marble powder (Gris Italia) of a grain size of about 200 mesh are mixed with 20 g of graphite powder, 200 mesh, and the mixed is stirred into 50 g of a liquid epoxy resin. Following addition of an amine hardener the mixture is spread on a rough wooden plate, and the coating is hardened on standing for 24 hours at room temperature. The mass is extremely easy to spread and provides a grey coating which when polished does not noticeably differ from the normal appearance of marble.

Example 2 100 g of slate powder (blue-black) of a particle size of about 200 mesh are mixed with 50 g of graphite powder, 200 mesh. The mixture is stirred into 90 g of polyurethane, the mixture being kneaded well. The finished mixture is spread on a wooden plate and left to stand for 8-10 hours at 20-30"C.

After hardening the surface is ground with an abrasive material of grain size 280, the surface is then brushed with a steel brush and is polished with wax.

The surface obtained is undistinguishable from an ordinary slate plate.

Example 3 The procedure of example 2 is repeated, but instead of spreading mixture, acetone is added to the mixture to provide painting or spraying viscosity, optionally admixed with a float (bentonite). The finished mixture is sprayed on to a wooden plate, and on standing for 8-10 hours at 20-30 C the treatment from example 2 is repeated with grinding and brushing with the same final result.

Example 4 There is produced a mixture of 100 g of granite powder and 50 g of graphite powder, both having a particle size of 200 mesh, and 85 g of styrene containing liquid polyester containing 2% of benzoyl petroxide and a little accelerator. The mixture is carefully kneaded and spread on a wooden plate; after drying in a kiln or a heating tunnel at about 80"C for 15 minutes the surface is brushed with a steel brush, and if the structure of the object resembles granite the surface obtained can be mistaken for granite.

Example 5 70 g of marble powder or granite powder or slate powder, all having a particle size of 200 mesh, are admixed with polyurethane so as to just obtain a consistency which might be called a "dry" filler then acetone is added to provide the desired spreading, painting, dabbing or spraying consistency.

After application on a wooden plate and drying, the surface is grounded and/or brushed, and the result achieved is hard to distinguish from ordinary marble, granite or slate.

Example 6 A mixture of 100 g of crushed black granite of a particle size of 50-250 um and 50 g of graphite of a particle size of 50-100 um is stirred into 90 g of polyurethane and is diluted with acetone to provide spraying viscosity.

Under continuous stirring the product is sprayed onto a plaster plate, an asbestos cement plate and a concrete plate, respectively. In all cases the plates produced closely resemble cut plates of granite.

Example 7 The procedure of example 6 is repeated except that the said coating material is sprayed on to a plate of rigid polyurethane foam having a specific weight of about 200 kg per m3. The product looks like a cut granite plate, but is much lighter and yet has a very great strength.

Example 8 A mixture of 100 g of crushed white opal glass of a particle size of 20-2501lm and 3 g of graphite powder of a particle size of 50-100 Fm is admixed with 30 g of polyurethane and acetone so as to just impart spreading consistency to the mixture.

This coating material is applied to a side face of an ordinary brick by means of a roll. Hardening of the coating for 8-10 hours at 20-30 "C results in a brick whose coated surface is whitish or white grey, but has a beautiful rough structure which is rich in contrast.

Claims

1. A building or construction element comprising a core and a coating thereon, said coating containing particles of natural stone or an artificial mineral material of decorative effect, said particles being bonded together by an organic binder, characterized in that the coat contains 2-60 parts by weight of graphite, 98-40 parts by weight of relatively coarse particles of natural stone or artificial mineral material and 5-100 parts by weight of organic binder.

2. A building or construction element according to claim 1, characterized in that the coating comprises 10-40 parts by weight of graphite, 90-60 parts by weight of particles of natural stone or artificial mineral material and 20-60 parts by weight of organic binder.

3. A building or construction element according to claim 1 or 2, characterized in that the particles of natural stone in the coating consist of slate, marble or granite.

4. A building or construction element according to claim 1 or 2, characterized in that the artificial mineral material particles in the coating consist of an optionally stained glass frit.

5. A building or construction element according to any one of the preceding claims, characterized in that the core consists of a shaped article of burned clay, such as a brick.

6. A building or construction element according to any one of claims 1-4, characterized in that the core consists of a plate of wood, asbestos cement, plaster, concrete or a foamed inorganic or organic material.

7. A building or construction element according to claims 1-6, characterized in that the particles of natural stone or artificial mineral material have a grain size of 20-5000 um, preferably 50-1000 um.

8. A building or construction element according to claim 7, characterized in that said particles have a grain size of 50-250 Fm.

9. A building or construction element according to claims 1-8, characterized in that the graphite has a particle size of 20-1000 um, preferably 50-2501lm.

10. A building or construction element according to claims 1-9, characterized in that the organic binder is a hardening resin, preferably a polyester, an epoxy resin or a polyurethane.

11. A building or construction element substantially as hereinbefore described.

12. A building or construction element substantially as hereinbefore described in any one of the specific Examples.