GB1578597A

GB1578597A - Method fo producing building elements

Info

Publication number: GB1578597A
Application number: GB1498/78A
Authority: GB
Original assignee: Produits Chimiques Ugine Kuhlmann; Ugine Kuhlmann SA
Current assignee: Produits Chimiques Ugine Kuhlmann; Ugine Kuhlmann SA
Priority date: 1977-01-14
Filing date: 1978-01-13
Publication date: 1980-11-05
Also published as: IL53798A; DE2801163A1; BE862841A; PT67461A; MX150250A; BR7800206A; PT67461B; SE426811B; FR2377360B1; FR2377360A1; DE2801163B2; LU78853A1; JPS5388824A; OA05850A; NL7800462A; IL53798A0; ZA78197B; SE7800265L; IT1091698B

Description

(54) METHOD OF PRODUCING BUILDING ELEMENTS (71) We, PRODUITS CHIMIQUES UGINE KUHLMANN, a French Body Corporate, 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 present invention relates to a method of producing building elements such as tiles and facing plates intended for floor and wall coverings.

It is known to produce tiles and facing plates from mixtures of granulates or chips of hard materials and Portland cement. But one of the disadvantages of this method of production is the dimensional shrinkage peculiar to all products based on Portland cement. To overcome these disadvantages, we developed a method of producing tiles and other products with a marble appearance based on anhydrite, a binder which avoids dimensional shrinkage. This method, which is described in our co-pending British patent application No. 47487/77 (Serial No.

1578596) presents the disadvantage of still involving the operations of grinding, filling and polishing which increase the price of the resultant products.

The present invention relates to a method of producing by moulding building elements such as tiles and facing plates free from dimensional shrinkage and exhibiting a good surface appearance, characterised by the use as binder of an anhydrite associated with the setting catalysts.

Accordingly, the present invention provides a method of producing building elements such as tiles and facing plates by moulding a composition based on a binder or on a mixture of binder and aggregate wherein the binder is anhydrous calcium sulphate CaSO4 class II or ss, also called insoluble anhydrite, of granulometry comprising, i.e. having a particle size distribution such that, at least 15% by weight of particles which are smaller in diameter than 10 llm and at least 20% by weight of particles which are larger in diameter than 20 Fm with an average diameter of from 5 to 30 llm, associated with one or more anhydrite setting catalysts.

The binder used in the present method is anhydrous calcium sulphate CaSO4 class II or ss, also called insoluble anhydrite. The insoluble anhydrite which can be used may have different origins: it is possible to use natural anhydrite, or anhydrite which is a byproduct of the production of hydrofluoric acid by sulphuric attack on calcium fluoride.

But it is also possible to use anhydrite obtained by roasting natural gypsum or gypsums which are byproducts of the chemical industry. In particular, it is possible to use the anhydrite obtained by roasting a phosphogypsum which is a byproduct of the production of phosphoric acid by wet process. The method of production of such an anhydrite is described in our co-pending British patent application No. 1349/77 (Serial No. 1574623).

In order to obtain a material endowed with optimum properties, the anhydrite used in this application must be characterised by a granulometry comprising at least 15% by weight of particles smaller in diameter than 10 llm and at least 20% by weight of particles larger in diameter than 20 iim with an average diameter of from 5 to 30 llm, and by a BLAINE surface of from 1,000 to 8,000 cm2/g, preferably from 2,000 to 5,000 cm2/g.

In the method according to the invention the building elements are produced by moulding in a mould of any shape, but most commonly of square or rectangular shape, pure pastes of anhydrite or of anhydritebased mortars and of granulates with or without the application of vibration or pressure.

It is possible to make building elements constituted by a single layer presenting a good face obtained by contact with the bottom of the mould and a laying face, and also multiple-layered building elements constituted by a wearing layer exhibiting a good face obtained by contact with the bottom of the mould and supported by a sub-layer or base-layer exhibiting a laying face.

It is possible to use a moulding method with delayed mould removal consisting in removal of the product from the mould when the product exhibits sufficient mechanical strength to be handled. This method is applied to building elements of large area or to building elements made from a particularly fluid mixture.

It is also possible to use a method of moulding which includes the steps of vibration compression and immediate mould removal, such methods being currently used in modern high turn-over installations. This method is applied to articles of relatively restricted dimensions and generally requires the use of relatively dry mixtures when the moulded article has a single layer or, when articles with two layers are to be made, at least one of the layers being made from a relatively dry mixture.

According to a particular embodiment of the invention, a gloss finish (brilliant) or matt surface film or plate, which is uniform or exhibits a decorative motif, intended to form a replica on the good face of the building material, may be placed in the bottom of the mould. It may be advantageous to maintain said film or plate integral with the building material even after removal of the mould, until the time when hardening is sufficient for the detachment of the film or plate from the building material to leave a perfect replica. This method is used advantageously for elements with two layers made by compression and immediate mould stripping, where the wearing layer is made from a perfectly fluid mixture and where the base layer is made from a relatively dry mixture.

The mixture used to make the single layer in single layer elements, or the wearing layer in two-layer elements, is obtained by mixing 100 parts by weight of anhydrite, 0.5 to 5 parts by weight of one or more anhydrite setting catalysts, water and optionally other ingredients such as granulate, pigments, fluidisers, plaster to accelerate setting, and waterproofing and waterretaining agents.

The mixture used to make the base-layer in the case of two-layer elements is obtained by mixing 100 parts by weight of granulates, at least 7, and preferably 10 to 100, parts by weight of anhydrite, 0.5 to 5 parts by weight, based on the weight of anhydrite, of one or more anhydrite setting catalysts, water and optionally other ingredients, more particularly fluidisers, plaster to accelerate setting, and waterproofing and waterretaining agents.

The anhydrite setting catalysts may be chosen from among the catalysts known to the expert, such as for example the sulphates, alums nitrates, carbonates, oxides or hydroxides of alkali metals or alkaline earth metals.

The granulates which may optionally occur in the composition of the wearing layer may vary widely. For example, it is possible to use alone or as mixtures, siliceous sands, silico-calcareous sands and hard stone dusts. The granulates used in the base layer may also vary widely. For example, it is possible to use, alone or as mixtures, siliceous sands, silico-calcareous sands, fly ash, slag sands, ground products based on schist, pumice stone, pozzuolana or clinker.

The fluidisers used in the compositions from which the various layers are made make it possible to reduce the water content of the compositions whilst retaining the same workability and consequently to increase the mechanical properties of the material. Above all, the fluidisers make it possible to obtain for the wearing layer particularly fluid mixtures with a relatively low water content and particularly mixtures which are self-levelling and which are therefore favourable to the achievement of good surfaces which are accurate replicas of the mould bottom. The fluidisers may be of various types. However, the most efficacious are resins of low molecular weight substituted with sulphonic groups such as the polystyrene sulphonates of low molecular weights or sulphonic group containing low molecular weight condensates of formaldehyde with naphthalene, phenol, urea or melamine. The quantity of fluidiser to be used is 0.1 to 2 and preferably 0.5 to 1 part by weight per 100 parts by weight of anhydrite.

The pigments suitable for use may be metallic oxides and mineral pigments.

The plaster used is calcium sulphate hemihydrate CaSO4. 1/2 H2O. Different types of commercially available plaster may be used such as: building plaster, prefabricating plaster and moulding plaster. The advantageous plaster contents are from 1 to 20, and preferably from 1 to 10, parts by weight per 100 parts by weight of anhydrite.

The plaster permits the setting time to be shortened and, consequently, earlier mould removal in the delayed mould removal technique. The use of plaster is also advantageous in a particular embodiment of the invention which consists in producing twolayer elements, using a fluid mixture of self-levelling character for the wearing layer. Indeed, by using a relatively dry mixture for the base layer and placing in the bottom of the mould a film or loose plate it is possible, after placing the mixture corresponding to the base layer, optional vibration and compression, to remove the moulds immediately retaining the film or free plate integral with the good face.However, pressure can only be applied if the mixture corresponding to the wearing layer exhibits a certain minimum consistency, otherwise, one finds a certain displacement of the mixture of the wearing layer towards the edges of the mould. The use of a chosen quantity of plaster, which may be of the order of 5 to 10 parts by weight per 100 parts by weight of anhydrite, in the mixture of the wearing layer makes it possible to reduce a few minutes the time which must pass before the minimum requisite consistency is obtained.

Among the many waterproofing agents suitable for use, the best are the siliconates of potassium or sodium or vinylic and acrylic polymers and copolymers, more particularly copolymers of the methyl methacrylate butyl methacrylate - butyl acrylate type.

These products are suitable for use at the rate of 0.1 to 1 part by weight per 100 parts by weight of mixture.

The water-retaining agents are useful particularly in the case of single-layer elements prepared by compression. Indeed, compression has a tendency to make part of the mixing water exude. Now it is advantageous to retain in the compressed mixture at least 8 parts by weight of water per 100 parts by weight of anhydride. The waterretaining agents make it possible to limit or to prevent the exudation of the water under compression. Among the products known for their water-retaining properties, the following are preferred: kieselguhr, kaolin, colloidal clays such as bentonite or montmorillonite, colloidal products such as alginates, stearates, and derivatives of cellulose such as methylcellulose, methylethylcellulose, hydroxypropylmethylcellulose and car boxymethylcellulose.

For production on an industrial scale it may be advantageous, if it is desired to avoid the disadvantages of premature setting of the anhydrite-based mixtures, especially if said mixtures contain plaster which accelerates setting, to mix a master mixture comprising all the ingredients except the plaster and optionally the catalytic system or a part of the catalytic system and to add these last ingredients separately, just before filling the moulds, to a part of the master mixture.

It may also be advantageous to apply mould release agents to the walls of the mould. The products currently employed in the moulding of cement may be used. The walls of the mould may also be provided with an anti-adherent coating based on a plastics material and more particularly on a fluorinated polymer such as polytetrafluoroethylene which may be applied in the form of an adherent film, of a varnish or of a powder of low molecular weight used as an aerosol.

It is particularly surprising to discover the excellent gloss finish (brilliant aspect) exhibited by the good face when the latter is formed in contact with a smooth, glossy (brilliant) mould bottom and where the mixture used to make the wearing layer in contact with the mould bottom is constituted by a pure anhydrite paste exhibiting sufficient fluidity to have a self-levelling character.

The products produced according to the invention are particularly appropriate as floor covering tiles or as facing plates for interior or exterior walls.

The invention will now be illustrated by the following examples.

Example 1 A mixture is prepared composed of 100 parts by weight of anhydrite of BLAINE surface 5,000 cm2/g obtained by roasting a phosphogypsum, 1 part by weight of potassium sulphate, 1 part by weight of calcium hydroxide, 0.75 part by weight of a fluidiser based on sodium polystyrene sulphonate and 24 parts by weight of water. The paste obtained is fluid and exhibits self-levelling properties which may be characterised by the diameter of spread of 23 cm obtained 3 minutes after the commencement of mixing as measured by SMIDTH'S test which consists in spreading on a horizontal brass plate the contents of a ring of 60.8 mm inside diameter, 65.0 mm outside diameter and 47.0 mm height. This paste is used to fill a rectangular mould of poly(vinyl chloride) with brilliant internal faces and of internal dimensions 20 cm x 40 cm by 4 cm high.

The mould is removed the following day to yield a plate of dimensions 4 cm x 20 cm x 40 cm exhibiting a good face and also perfectly brilliant lateral faces. The mechanical properties of the product measured on the 28th day according to standard NF P 15 451, are 122 bars in traction-flexion and 670 bars in compression.

Example 2 Example 1 is repeated, introducing additionally into the mixture 100 parts by weight of siliceous sand 0.050/0.250 mm and using 1.5 part by weight of potassium sulphate instead of 1 part by weight, and 38 parts by weight of water instead of 24 parts by weight. The mortar obtained is fluid and exhibits self-levelling properties characte rised by a spread diameter of 23 cm in SMIDTH's test performed under the same conditions as in example 1. The mould is removed the following day to yield a plate exhibiting a good face and brilliant lateral faces. The mechanical properties, measured on the 28th day by standard NF P 15 - 451, are 71 bars in traction-flexion and 380 bars in compression.

Example 3 A mixture is prepared consisting of 100 parts of anhydrite of the same quality as in example 1, 1 part by weight of calcium hydroxide, 1 part by weight of colloidal kaolin and 15 parts by weight of water.

6,250 g of the pulverulent paste obtained is introduced into a rectangular stainless steel mould 20 cm x 40 cm by 5 cm high. After vibration and compression under 100 bars, a plate 3.6 cm x 20 cm x 40 cm exhibiting matt faces is stripped from the mould. In order to determine the mechanical properties, 3 stainless steel moulds 4 cm x 16 cm by 5 cm high are filled each with 500 g of the same mixture. Aftcr vibration and compression at 100 bars, the moulds are stripped to obtain specimens 3.6 cm x 4 cm x 16 cm which are placed in a room at 250C at 66% relative humidity before testing them according to standard NF P 15 - 451. In the traction-flexion tests the specimens are arranged in such a way that the good face is turned upward and works in compression.

In the compression tests the specimens are arranged in such a way that the pressure is exerted perpcndicularly to the good face.

The results taken on the 28th day are 100 bars in traction-flexion and 535 bars in compression.

Example 4 Example 3 was repeated, but preparing a mixture consisting of 1()0 parts by weight of anhydrite of the same quality as in example 1, 100 parts by weight of an 0/0.5 mm sand, 1 part by weight of potassium sulphate, 1 part by weight of zinc sulphate heptahydrate and 19 parts by weight of water. The mortar obtained was relatively dry and pulverulent.

After vibration and compression at 100 bars, a plate with matt faces was removed from the mould. The mechanical properties determined on the specimens on the 28th day, kept and tested according to the method of example 3, were 82 bars in traction-flexion and 423 bars in compression.

Example 5 In order to produce a two-layer element, first of all a mixture intended to form the wearing layer is prepared comprising 100 parts by weight of anhydrite of the same quality as in example 1, 1 part by weight of potassium sulphate, 1 part by weight of calcium hydroxide, 0.75 part by weight of a sodium polystyrene sulphonate-based fluidiser, 5 parts by weight of building plaster PFC 2 (No. 2 fine building plaster) 0.5 part by weight of a 45% by weight solution of potassium siliconate and 24 parts by weight of water.The paste obtained is fluid and exhibits self-levelling properties characterised by a spread diameter of 23 cm in the SMIDTH test performed under the same conditions as in example 1. 2,500 g of this paste is poured into a poly(vinyl chloride) mould with brilliant internal faces and with the internal dimensions 20 cm x 40 cm by 4 cm high and 200 g into each of 3 stainless steel moulds 4 cm x 4 cm x 16 cm.

A mixture intended to form the base layer is then prepared, comprising 100 parts by weight of anhydrite of the same quality as in example 1, 300 parts by weight of 0/2 mm sand, 1 part by weight of potassium sulphate, 1 part by weight of zinc sulphate heptahydrate and 15 parts by weight of water. Ten minutes after the preparation of the mixture corresponding to the wearing layer is commenced, the relatively dry mixture corresponding to the base layer is placed upon the first layer at the rate of 3,750 g in the case of the large mould and of 300 g in the case of each of the three small moulds. The second layer is smoothed by troweling. The plate and specimens are removed from the moulds on the following day. The thickness of the elements is 4 cm.

The good face and the lateral faces of the wearing layer of the 20 cm x 40 cm plate exhibit a very brilliant apperance. The mechanical properties on the 28th day, determined on the 4 cm x 4 cm x 16 cm specimens kept and tested as in example 3, are 76 bars in traction-flexion and 420 bars in compression.

Example 6 Example 5 is repeated, with the difference that the moulds are of stainless steel and are 5 cm high. that a smooth plate of methyl polymethacrylate of the dimensions of the bottom of the mould, 4 mm thick and of very brilliant surface is placed on the bottom of each of the moulds, and that as soon as the layer corresponding to the base plate has been introduced and levelled, a pressure of 100 bars is applied. The moulds are removed immediately, leaving the plate of methyl polymethacrylate adhering to the element. The plates of methyl polymethacrylate are removed the next day and reveal a highly brilliant good face. The thickness of the element is 3.6 cm. The mechanical properties. determined on the 3.6 cm x 4 cm x 16 cm specimens kept and tested as in example 3, are 88 bars in traction-flexion and 470 bars in compression.

Example 7 Example 6 is repeated, with the difference that the mixture of the wearing layer comprises additionally 100 parts of 0.050/ 0.250 mm siliceous sand and 0.50 part of a 40% by weight emulsion of a methyl methacrylate - butyl methacrylate - butyl acrylate copolymer and that the quantity of water is 38 parts by weight instead of 24 parts by weight. The good face is brilliant and the thickness of the elements is 3.6 cm.

The mechanical properties on the 28th day, determined on the 3.6 cm x 4 cm x 16 cm specimens kept and tested as in example 3, are 55 bars in traction-flexion and 282 bars in compression.

Example 8 Example 6 is repeated, with the difference that the methyl polymethacrylate plates are omitted and that the mixture corresponding to the wearing layer comprises 100 parts of anhydrite of the same quality as in example 1, 100 parts of 0/0.Smm siliceous sand, 1 part of potassium sulphate, 1 part of zinc sulphate heptahydrate and 50 parts of water. The good face has a sandstone appearance comparable to that of natural sandstone. The thickness of the elements is 3.6 cm. The mechanical properties on the 28th day determined on the 3.6 cm x 4 cm x 16 cm specimens kept and tested as in example 3 are 49 bars in traction-flexion and 320 bars in compression.

WHAT WE CLAIM IS: 1. Method of producing building elements such as tiles and facing plates by moulding a composition based on a binder or on a mixture of binder and aggregate wherein the binder is anhydrous calcium sulphate CaSO4 class II or ss, also called insoluble anhydrite, of granulometry comprising at least 15% by weight of particles smaller in diameter than 10 Fm and at least 20% by weight of particles larger in diameter than 20 llm with an average diameter of from 5 to 30 Fm, associated with one or more anhydrite setting catalysts.

2. Method according to Claim 1, wherein the building elements consist of a single layer, and are formed by introducing into a mould a mixture from which the single layer is to be formed.

3. Method according to Claim 1, wherein the building elements consist of a wearing layer arranged on a bottom layer or base layer and are formed by successive introduction into a mould of a mixture from which the wearing layer is to be formed followed by the introduction of a mixture from which the base layer is to be formed.

4. Method according to any one of Claims 1 to 3, wherein the elements are removed from the moulds only after a time delay which enables the elements formed to exhibit sufficient mechanical strength to be handled.

5. Method according to any one of Claims 1 to 3, wherein the moulding includes a compression step, which is optionally preceded by a vibration step, followed by immediate removal of the elements from the moulds.

6. Method according to any one of Claims 1 to 5, wherein a brilliant finish or matt surface film or plate, which is uniform or comprises a decorative motif, is placed on the bottom of the mould before the mixture or mixtures from which the building element is to be formed is or are introduced.

7. Method according to any one of Claims 3 to 6, wherein the mixture from which the wearing layer is to be formed exhibits a sufficient fluidity to be selflevelling and the mixture from which the base layer is to be formed is poured onto the wearing layer mixture before the wearing layer mixture finally sets.

8. Method according to any one of Claims 2 to 7, wherein the single layer in single layer elements or the wearing layer in multi-layer elements is formed from a mixture of 100 parts by weight of anhydrite, 0.5 to 5 parts by weight of one or more anhydrite setting catalysts, water and optionally other ingredients such as granulates, pigments, fluidisers, plaster and waterproofing or water-retaining agents.

9. Method according to any one of Claims 3 to 7, wherein the base layer is formed from a mixture of 100 parts by weight of granulates, 7 to 100 parts by weight of anhydrite, 0.5 to 5 parts by weight of one or more anhydrite setting catalysts per 100 parts by weight of anhydrite, water and optionally other ingredients such as pigments, fluidisers, plaster, and waterproofing or water-retaining agents.

10. Method according to Claim 8 or 9, wherein the mixtures contain from 0.1 to 2 parts by weight of one or more fluidisers per 100 parts by weight of anhydrite.

11. Method according to any one of Claims 8 to 10, wherein the mixtures contain from 1 to 20 parts by weight of plaster per 100 parts by weight of anhydrite.

12. Method according to any one of Claims 8 to 11, wherein the waterproofing agent is potassium or sodium siliconate or an acrylic copolymer used at the rate of 0.1 to 1 part by weight per 100 parts by weight of mixture.

13. Method according to any one of Claims 8 to 12, wherein a master mixture is prepared comprising all the ingredients except the plaster and optionally the setting catalyst or catalysts or a part of the setting catalyst or catalysts and the withheld ingre

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

Claims

**WARNING** start of CLMS field may overlap end of DESC **. Example 7 Example 6 is repeated, with the difference that the mixture of the wearing layer comprises additionally 100 parts of 0.050/ 0.250 mm siliceous sand and 0.50 part of a 40% by weight emulsion of a methyl methacrylate - butyl methacrylate - butyl acrylate copolymer and that the quantity of water is 38 parts by weight instead of 24 parts by weight. The good face is brilliant and the thickness of the elements is 3.6 cm. The mechanical properties on the 28th day, determined on the 3.6 cm x 4 cm x 16 cm specimens kept and tested as in example 3, are 55 bars in traction-flexion and 282 bars in compression. Example 8 Example 6 is repeated, with the difference that the methyl polymethacrylate plates are omitted and that the mixture corresponding to the wearing layer comprises 100 parts of anhydrite of the same quality as in example 1, 100 parts of 0/0.Smm siliceous sand, 1 part of potassium sulphate, 1 part of zinc sulphate heptahydrate and 50 parts of water. The good face has a sandstone appearance comparable to that of natural sandstone. The thickness of the elements is 3.6 cm. The mechanical properties on the 28th day determined on the 3.6 cm x 4 cm x 16 cm specimens kept and tested as in example 3 are 49 bars in traction-flexion and 320 bars in compression. WHAT WE CLAIM IS:

1. Method of producing building elements such as tiles and facing plates by moulding a composition based on a binder or on a mixture of binder and aggregate wherein the binder is anhydrous calcium sulphate CaSO4 class II or ss, also called insoluble anhydrite, of granulometry comprising at least 15% by weight of particles smaller in diameter than 10 Fm and at least 20% by weight of particles larger in diameter than 20 llm with an average diameter of from 5 to 30 Fm, associated with one or more anhydrite setting catalysts.

dients are added separately to a portion of the master mixture just before moulding.

14. A method according to claim 1 of producing building elements such as tiles and facing plates substantially as described in any one of the foregoing Examples 1 to 8.

15. Building elements when prepared by a method as claimed in any one of the preceding claims.