GB1578596A - Floor or wall covering - Google Patents

Description

(54) FLOOR OR WALL COVERING (71) We, PRODUITS CHIMIQUES UGINE KUHLMANN, a French Body Corporate, of 25 boulevard de l'Amiral Bruix, 75116 Paris, France, do hereby declare the invention for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement: The invention relates to articles such as tiles, flagstones, panels and other elements intended for covering floors and walls, more particularly such articles having the appearance of marble or other conventional products, particularly marble mosaic tiles, and to a process for producing such articles.

Articles of this type are very widely manufactured and generally comprise two layers. An upper layer, referred to as a wearing layer, constituted essentially of hard stone or marble granules or chips coated with white or grey cement to which, if desired, pigments, powdered marble and powdered hard stone may be added, and an underlayer or backing layer obtained from a mixture of sand and cement. The wearing layer is polished on its visible or outer surface.

Unfortunately, the use of cement in the preparation of these articles as defined in French Standard NF P 61-302 has two major drawbacks. These are the slowness of setting and the dimensional shrinkage of the products.

Hardening prior to polishing is relatively slow. Thus, French Standard NFP61-302 (relating to marble mosaic tiles) provides for a minimum hardening time of five days at a temperature of at least 12"C for tiles of granulation 0/2 to 10/20 mm and a minimum hardening time of 12 days at a temperature of at least 120C for those made from chips and slabs.

Shrinkage, which is a feature of all cement-based mortars, is the principle drawback of the manufacturing process. Indeed, the products can be marketed only when their dimensions are stable. Although French Standard NF P 61-302 stipulates that at the moment of their delivery tiles must have been made for at least four weeks, it is generally agreed that this period is insufficient for shrinkage to be completed. In practice, manufacturers are obliged to stock-pile products, once they have been sanded and polished, for two months prior to delivery, because it is only after this considerable time that shrinkage of the cement is complete.

An object of the present invention is to alleviate these drawbacks by replacing, in conventional formulations, cement by a binder which sets more rapidly and which avoids shrinkage by imparting to the products dimensional stability. Thus, the present invention provides a floor or wall covering such as a tile, flagstone or panel, consisting of an upper wearing layer having a polished outer surface, which wearing layer is obtained by setting a mixture comprising granules or chips of marble or other hard materials, a binder, and at least one setting catalyst, and, optionally, coloured pigments, marble powder and/or hard stone powder and an underlayer obtained by setting a mixture of sand, binder, and at least one setting catalyst, the binder in each layer being calcium sulphate, CaSO4, grade II or (also referred to as insoluble anhydrite) which has a BLAINE specific surface area of from 1,000 to 8,000 sq.cm/g.

According to another aspect of the present invention, there is provided a process for manufacturing the floor or wall covering of the invention, which process includes forming an underlayer of a mixture comprising sand, binder and at least one setting catalyst, and on top of the underlayer forming an upper layer of a mixture comprising granules or chips of marble or other hard materials, binder, and at least one setting catalyst, and, optionally, coloured pigments, marble powder and/or hard stone powder; setting the under layer and upper layer to form a floor or wall-covering having an upper wearing layer over an underlayer; and polishing the outer surface of the wearing layer; the binder in each layer being calcium sulphate, CaSO4, grade II or ss (also referred to as insoluble anhydrite) which has a BLAINE specific surface area of from 1,000 to 8,000 sq.cm/g.

The binder used in the present invention is anhydrite, often referred to as insoluble anhydrite. The binder is usually associated with setting catalysts and possibly other adjuvants, particularly water-repellent adjuvants. The insoluble anhydrite or even anhydrous calcium sulphate, grade II or ss, used in the method of the present invention may have various origins. It may be natural anhydrite or the anhydrite which is obtained by calcination of gypsum CaSO4.2H2O, natural gypsum or a by-product of the chemical industry such as phosphogypsum, or even the anhydrite which is a by-product of the manufacture of hydrofluoric acid by the action of sulphuric acid on calcium fluoride.

The granulometry of the anhydrite used must be such as to produce a well-defined specific surface area. Suitable granulations are those corresponding to a BLAINE specific surface area of from 1,000 to 8,000 sq.cm/g and preferably from 2,800 to 6,000 sq.cm/g.

The valuc of the specific surface area directly influences the rates of setting and hardening. Setting and hardening will be all the more rapid the greater is the BLAINE specific surface area.

The BLAINE surface area likewise affects the final mechanical properties, e.g. strength, of the product. The larger the BLAINE surface area, the better these properties will be.

The quantities of anhydrite to be used for most practical purposes correspond to those which are currcntly recommcnded for use in those cases where the hydraulic binder is cement. One of the advantages of the present process is that it is possible easily to increase the rate of use of anhydrite to the detriment of the powdered marble and so improve the mechanical properties of the material. This is not feasible in the case of cement because shrinkage would be greatly increased.

For the anhydrite to set in the normal way, it is necessary to use one or more anhydrite setting catalysts. There are numerous catalysts to assist the setting of anhydrite and they are well-known to a man skilled in the art. They are for example alkaline, neutral or acid sulphates, alums, and alkaline hydroxides, carbonates or nitrates. They are used alone or in mixture. Preferably, potassium sulphate or potassium alum will be used. A catalytic system which is particularly advantageous to achieve rapid hardening of the wearing layer consists of a mixture of sodium sulphate and potassium nitrate. Preferable amounts of catalyst are 0.25 to 3% by weight, preferably 0.5 to 1.5% by weight, based on the anhydrite.

The setting catalyst or catalysts makes or make it possible to obtain good mechanical properties but these are further enhanced if in addition one or a plurality of co-catalysts are employed for setting purposes, which may be metallic hydroxides such as the hydroxides of calcium, magnesium or zinc or metallic sulphates such as ferrous sulphate heptahydrate or zinc sulphate heptahydrate. Suitable amounts of co-catalyst are 0.25 to 5% by weight, and preferably 0.5 to 2% by weight, based on the anhydrite. The ferrous sulphate does however produce a certain ycllowish colouring in the product due to the transformation of the ferrous ions into ferric ions.If this colouring is troublesome, the ferrous sulphate can be reserved in the mixture intended for the backing and another co-catalyst, for example calcium hydroxide or zinc sulphate heptahydrate can be used in the composition which in the product will be the wearing layer.

Setting catalysts and co-catalysts may be contained in the anhydrite or may be added at the time of mixing. However, more rapid hardening and setting and also better mechanical properties will be obtained if first all the ingredients except the setting catalyst and co-catalyst are mixed together, the setting catalyst and co-catalyst being added in aqueous solution or dispersion after the first mixing.

To ensure that the wearing layer has only a very low water absorption, it is advisable to introduce a water-repcllent into the mixture which will form the wearing layer in the final product. Among the many water repellents which may be used, those preferred are sodium or potassium siliconates or acrylic copolymers particularly copolymers of the methyl methacrylate - butyl methacrylate-butyl acrylate type. These products may be used in amounts of 0.1 to 0.5% by weight, based on the anhydrite. Of course, a water-repellent may also be incorporated into the backing layer, but this is of no great interest.

Since the colouring of anhydrites is generally minimal, the anhydrites themselves usually have no effcct on the colourings and shades achieved by the addition of various pigments to the mixture used for the wearing layer. However, anhydrite emanating from calcination of phosphogypsum has a slightly pink colouring due to the presence of ferric oxides. If this colouring is troublesome. it might well be obviated by incorporating into the mixture 0.5 to 1% by weight copper sulphate, based on the anhydrite.

The manufacturing process according to the present invention can be a process which relies on moulding by successive vibrations and compressions or equally well a process in which compression is not employed.

When compression is not used in the present process, the resultant products may be removed from their moulds after 24 hours. On the other hand, in installations for moulding tiles by successive vibrations and compressions, the resultant products may be removed from their moulds as soon as possible after compression as in the case of cement-based products.

In either case, with or without compression, hardening is carried out for a period of approx. 3 to 5'days in any environment where the relative humidity is in the vicinity of 66%, at a temperature of from 10 to 40"C but preferably close to 25"C.

After hardening, the operations of sanding, filling and polishing are the same as those carried out on cement-based products. Filling involves the use of an anhydrite-based paste containing the ingredients mentioned above - catalysts, co-catalysts and water-repellent agents.

As soon as polishing is completed, the products may be delivered to customers without prior storage because of their lack of shrinkage, which is the great advantage of the present invention.

The following Examples illustrate the present invention.

Example 1 The two following compositions corresponding to the wearing layer and the backing are mixed separately for approx. 3 minutes. The anhydrite used is a phosphoanhydrite obtained by calcination of a phosphogypsum followed by crushing using the process described in our French Patent No. 76.00678. The BLAINE surface area of the anhydrite is 3,000 sq. cm/g.

Wearing layer Anhydrite (BLAINE specific surface area: 3,000 sq. cm/g) 25 kg Finely powdered marble 10 kg Powdered marble 5 kg Marble granulate 0/2 mm 8 kg Marble granulate 2/5 mm 15 kg Marble granulate 8/13 mm 35 kg Mixing water 10 kg Potassium sulphate 0.250 kg 45% by weight potassium siliconate solution 0.100 kg Weight of the mixture 108.350 kg Backing Anhydrite (BLAINE specific surface area: 3,000 sq.cm/g) 25 kg Quarry sand 0/3 mm 110 kg Mixing water 5 kg Potassium sulphate 0.250 kg Weight of the mixture 140.250 kg In order to determine the mechanical properties; three samples are prepared using moulds measuring 4 x 4 x 16 cm. 230 g of the mixture corresponding to the wearing layer are placed in the bottom of each mould and, after vibration, filling of the mould is finished by the addition of 299 g of mixture corresponding to the backing layer.After vibration and compression at 80 bars, the samples are removed from the moulds and stored at 25"C at a relative humidity of 66%; they have a thickness of 3.6 cm in the direction of compression.

The balance of the mixture is used for making 22 tiles measuring 40 x 40 cm. Into each vibrated mould are placed approx. 4.900 kg of the mixture corresponding to the wearing layer, then approx. 6.350 kg of the mixture corresponding to the backing. After compression at 80 bars, the tiles, which have a thickness of about 31 mm, are removed from the moulds and placed on a slab in a room at 25"C and 66% relative humidity. After five days, the tiles are sufficiently hard to be sanded. After sanding, the tiles are covered with a paste containing, by weight, 50 parts finely powdered marble, 50 parts powdered marble, 100 parts anhydrite (the same as that used for the wearing layer and the backing layer), 1 part potassium sulphate, 1 part slaked lime, 0.5 parts of a 45% by weight solution of potassium siliconate and 32 parts water.After polishing, tiles of a very nice appearance and a brilliant shine are obtained. Upon removal from the mould and after being stored for two months, the lateral dimensions are identical. The thicknesses immediately after polishing and after two months' storage are likewise identical.

The samples measuring 3.6 x 4 x 16 cm prepared as stated hereinabove are tested according to standard NF P 15 - 451. In the traction-flexion test, the sample is disposed in such a way that the wearing layer is turned upwards and works under compression conditions. In the compression test, the sample is positioned in such a way that the pressure is exerted at right-angles to the wearing layer. The results after 7 days are 25 bars in traction-flexion and 177 bars in compression.

It should be noted that the traction-flexion figure obtained with samples measuring 3.6 x 4 x 16 em and in accordance with standard NF P 15 - 451 is not comparable with the traction-flexion figure ascertained with the same material when complying with standard NF P 61-302 which relates to marble mosaic tiles. The value obtained in this latter case is indeed greater by far since in the present example it is 60 bars at 7 days.

Example 2 Example 1 is repeated, except that initially, the two compositions indicated are mixed for 3 minutes without potassium sulphate and with only 80% of the mixing water, the two mixtures then being left to stand for an hour whereupon the potassium sulphate is added, diluted in the remaining 20% of the mixing water, followed by a second 3- minute mixing step. In this case, sanding can likewise take place after 5 days but the mechanical properties at 7 days according to standard NF P 15-451 are 30 bars under traction-flexion and 230 bars under compression.

Example 3 Example 1 is repeated except that in addition to the two compositions indicated, a quantity of zinc sulphate heptahydrate equal to the quantity of potassium sulphate is added.

In this case, sanding is likewise possible at 5 days but the mechanical properties at 7 days according to standard NF P 15-451 are 29 bars under traction-flexion and 237 bars under compression.

Example 4 Example 1 is repeated except that each of the two compositions also contains a quantity of potassium nitrate equal to the amount of potassium sulphate. In this case, hardening is sufficiently rapid that sanding can take place after 4 days. The mechanical properties at 7 days according to standard NF P 15-451 are 39 bars under traction-flexion and 291 bars under compression.

Example 5 Example 4 is repeated except that the anhydrite which is used is prepared by the same process, but has a BLAINE surface area of 5,000 sq-cm/g instead of 3,000 sq.cm/g. In this case, the hardening rate is sufficiently rapid that sanding can take place after 3 days. The mechanical properties at 7 days according to standard NF P 15.451 are 45 bars under traction-flexion and 371 bars under compression.

Example 6 (comparative) Example 1 is repeated except that the anhydrite is replaced by white Portland cement CPA 400 in the composition used for the wearing layer and grey Portland cement CPA 325 in the composition used for the backing layer, the potassium sulphate and potassium siliconate being omitted from the composition used for each of the two layers. In this case, sanding can be carried out after 4 days and the mechanical properties at 7 days according to standard NF P 15-451 are 41 bars under traction-flexion and 311 bars under compression.

WHAT WE CLAIM 1S: 1. A floor or wall covering such as a tile, flagstone or panel, consisting of an upper wearing layer having a polished outer surface, which wearing layer is obtained by setting a mixture comprising granules or chips of marble or other hard materials, a binder, and at least one setting catalyst, and. optionally coloured pigments, marble powder and/or hard stone powder and an underlayer obtained by setting a mixture of sand, binder, and at least one setting catalyst, the binder in each layer being calcium sulphate, CaSO4, grade 1I or ss (also referred to as insoluble anhydrite) which has a BLAINE specific surface area of from 1000 to 8,()()() sq-cm/g.

2. A floor or wall covering according to Claim 1, in which the insoluble anhydrite has a BLAINE specific surface area of from 2,800 to 6.000 sq.cm/g.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims (21)

**WARNING** start of CLMS field may overlap end of DESC **. part potassium sulphate, 1 part slaked lime, 0.5 parts of a 45% by weight solution of potassium siliconate and 32 parts water. After polishing, tiles of a very nice appearance and a brilliant shine are obtained. Upon removal from the mould and after being stored for two months, the lateral dimensions are identical. The thicknesses immediately after polishing and after two months' storage are likewise identical. The samples measuring 3.6 x 4 x 16 cm prepared as stated hereinabove are tested according to standard NF P 15 - 451. In the traction-flexion test, the sample is disposed in such a way that the wearing layer is turned upwards and works under compression conditions. In the compression test, the sample is positioned in such a way that the pressure is exerted at right-angles to the wearing layer. The results after 7 days are 25 bars in traction-flexion and 177 bars in compression. It should be noted that the traction-flexion figure obtained with samples measuring 3.6 x 4 x 16 em and in accordance with standard NF P 15 - 451 is not comparable with the traction-flexion figure ascertained with the same material when complying with standard NF P 61-302 which relates to marble mosaic tiles. The value obtained in this latter case is indeed greater by far since in the present example it is 60 bars at 7 days. Example 2 Example 1 is repeated, except that initially, the two compositions indicated are mixed for 3 minutes without potassium sulphate and with only 80% of the mixing water, the two mixtures then being left to stand for an hour whereupon the potassium sulphate is added, diluted in the remaining 20% of the mixing water, followed by a second 3- minute mixing step. In this case, sanding can likewise take place after 5 days but the mechanical properties at 7 days according to standard NF P 15-451 are 30 bars under traction-flexion and 230 bars under compression. Example 3 Example 1 is repeated except that in addition to the two compositions indicated, a quantity of zinc sulphate heptahydrate equal to the quantity of potassium sulphate is added. In this case, sanding is likewise possible at 5 days but the mechanical properties at 7 days according to standard NF P 15-451 are 29 bars under traction-flexion and 237 bars under compression. Example 4 Example 1 is repeated except that each of the two compositions also contains a quantity of potassium nitrate equal to the amount of potassium sulphate. In this case, hardening is sufficiently rapid that sanding can take place after 4 days. The mechanical properties at 7 days according to standard NF P 15-451 are 39 bars under traction-flexion and 291 bars under compression. Example 5 Example 4 is repeated except that the anhydrite which is used is prepared by the same process, but has a BLAINE surface area of 5,000 sq-cm/g instead of 3,000 sq.cm/g. In this case, the hardening rate is sufficiently rapid that sanding can take place after 3 days. The mechanical properties at 7 days according to standard NF P 15.451 are 45 bars under traction-flexion and 371 bars under compression. Example 6 (comparative) Example 1 is repeated except that the anhydrite is replaced by white Portland cement CPA 400 in the composition used for the wearing layer and grey Portland cement CPA 325 in the composition used for the backing layer, the potassium sulphate and potassium siliconate being omitted from the composition used for each of the two layers. In this case, sanding can be carried out after 4 days and the mechanical properties at 7 days according to standard NF P 15-451 are 41 bars under traction-flexion and 311 bars under compression. WHAT WE CLAIM 1S:

1. A floor or wall covering such as a tile, flagstone or panel, consisting of an upper wearing layer having a polished outer surface, which wearing layer is obtained by setting a mixture comprising granules or chips of marble or other hard materials, a binder, and at least one setting catalyst, and. optionally coloured pigments, marble powder and/or hard stone powder and an underlayer obtained by setting a mixture of sand, binder, and at least one setting catalyst, the binder in each layer being calcium sulphate, CaSO4, grade 1I or ss (also referred to as insoluble anhydrite) which has a BLAINE specific surface area of from 1000 to 8,()()() sq-cm/g.

2. A floor or wall covering according to Claim 1, in which the insoluble anhydrite has a BLAINE specific surface area of from 2,800 to 6.000 sq.cm/g.

3. A floor or wall covering according to Claim 1 or 2, in which the setting catalyst is

chosen from alkaline, neutral or acid sulphates, alums, and alkaline hydroxides, carbonates, and nitrates.

4. A floor or wall covering according to any one of Claims 1 to 3, in which the catalyst includes a co-catalyst chosen from hydroxides of calcium, magnesium or zinc, and metallic sulphates.

5. A floor or, wall covering according to Claim 4, in which the metallic sulphate is ferrous sulphate heptahydrate or zinc sulphate heptahydrate.

6. A floor or wall covering according to any one of Claims 1 to 5, in which a water-repellent agent is associated with the anhydrite.

7. A floor or wall covering according to Claim 6 in which the water-repellent agent is potassium siliconate or sodium siliconate.

8. A floor or wall covering according to Claim 6 in which the water-repellent agent is an acrylic copolymer.

9. A floor or wall covering according to Claim 8, in which the water-repellent agent is a methyl methacrylate - butyl methacrylate - butyl acrylate terpolymer.

10. A floor or wall covering substantially as described in any one of the foregoing Examples 1 to 5.

11. A process for manufacturing a floor or wall covering according to Claim 1, which process includes forming an underlayer of a mixture comprising sand, binder and at least one setting catalyst, and on top of the underlayer forming an upper layer of a mixture comprising granules or chips of marble or other hard materials, binder, and at least one setting catalyst, and, optionally, coloured pigments, marble powder and/or hard stone powder; setting the underlayer and upper layer to form a floor or wall covering having an upper wearing layer over an underlayer; and polishing the outer surface of the wearing layer; the binder in each layer being calcium sulphate, CaSO4, grade II or ss (also referred to as insoluble anhydrite) which has a BLAINE specific surface area of from 1,000 to 8,000 sq.cm/g.

12. A process according to Claim 11, in which the insoluble anhydrite has a BLAINE specific area of from 2,800 to 6,000 sq.cm/g.

13. A process according to Claim 11 or Claim 12, in which the setting catalyst is chosen from alkaline, neutral or acid sulphates, alums, and alkaline hydroxides, carbonates, and nitrates.

14. A process according to any one of Claims 11 to 13, in which the catalyst includes a co-catalyst chosen from hydroxides of calcium, magnesium or zinc, and metallic sulphates.

15. A process according to Claim 14, in which the metallic sulphate is ferrous sulphate heptahydrate or zinc sulphate heptahydrate.

16. A process according to any one of Claims 11 to 15, in which a water-repellent agent is associated with the anhydrite.

17. A process according to Claim 16, in which the water-repellent agent is potassium siliconate or sodium siliconate.

18. A process according to Claim 16, in which the water-repellent agent is an acrylic copolymer.

19. A process according to Claim 18, in which the water-repellent agent is a methyl methacrylate-butyl methacrylate - butyl acrylate terpolymer.

20. A process according to Claim 11 substantially as described in any one of the foregoing Examples 1 to 5.

21. A marble like floor or wall covering according to any one of Claims 1 to 10 when manufactured by a process as claimed in any one of Claims 11 to 20.