Cross-Reference to Related Applications

This patent application is related to Italian Patent Application No. 102021000013685 filed on May 26, 2021, the entire disclosure of which is incorporated herein by reference.

Technical Field of the Invention

The present invention relates to tiles whose technical features offer advantages in terms of reducing, if not eliminating, grout lines in building surfaces.

Generally, the laying of ceramic tiles on building surfaces provides for, once the layer of glue has been spread on the surface, arranging the tiles adjacent to one another on the layer of glue. In particular, during laying the tiles are placed side by side with one another to limit as much as possible the presence of empty spaces between one tile and the other. In technical jargon, these empty spaces are commonly called "grout lines".

State of the Art

As is known to those skilled in the art, the presence of grout lines between two tiles causes, in addition to a problem of aesthetics, also a problem of hygiene. In fact, grout lines represent cavities that are difficult to clean and in which dirt and bacteria can accumulate. Moreover, it must be considered how the ingress of water into these grout lines can make them a particularly suitable environment for bacterial growth.

In a commonly used solution, the grout lines are closed by means of a filling component. This component can be a common wall plaster or a polymer material, for example a silicone material. However, this solution suffers from a series of drawbacks in terms of productivity, due both to lengthy execution times and to the high likelihood of having to perform subsequent cleaning operations.

In fact, as can be understood, filling of the grout lines after laying the tiles, besides requiring lengthy execution times, requires a cleaning operation due to the fact that the filling component frequently overflows from the grout lines to soil the exposed surface of the tiles.

Moreover, it is important to consider that the solution described above relies to a significant extent on the operational capacities of the personnel performing the work and, consequently, it is not possible to predict the quality and effectiveness of the result in advance.

Therefore, there was the need to provide a solution capable of overcoming the problems of the prior art set forth above.

The inventors of the present invention have created a tile comprising a peripheral polymer coating, which allows the aforesaid needs to be met through simple and standardized laying operations.

Moreover, the tile of the present invention has the further advantage of guaranteeing protection of the edges of the ceramic portion. In fact, the polymer coating represents a sort of protective element from possible damages of the edges of the ceramic portion, for example during transport and storage.

Subject and Summary of the Invention

The subject matter of the present invention is a tile for a building surface comprising a ceramic portion and a polymer coating arranged on a lateral edge of said ceramic portion; said tile being characterized in that said polymer coating comprises a thermosetting polymer material comprising a polymer and a cross-linking agent having functional groups suitable to create chemical bonds both with said polymer and with said ceramic portion; said functional groups being chemically bonded with blocking groups from which they are freed at a temperature exceeding 100°C once a plurality of said tiles is arranged so as to form said building surface.

For the purposes of the present invention it is extremely relevant that the polymer material is thermosetting. Here and hereinafter, blocking group is meant as a molecule, which when bonded to the functional group of the cross-linking agent, prevents it from reacting with the polymer and with the ceramic portion.

Generally, the release temperatures of the blocking groups are determined by means of gas-mass, if the blocking group is volatile, or by means of differential scanning calorimetry.

Preferably, the weight ratio between polymer and cross- linking agent ranges from 25.0 to 1.0.

Preferably, the polymer is a polyurethane.

Preferably, the polyurethane is a polyether- and/or polyester- and/or polycarbonate-based polyurethane.

Preferably, said functional groups are isocyanate groups.

Preferably, said polymer coating is applied on the edge of said ceramic portion in the form of aqueous dispersion and is subsequently subjected to an evaporation operation.

Another subject matter of the present invention is a tile-covered surface obtained with the tiles according to the invention.

The present invention is based on the presence of a polymer coating that performs the role of glue only after the tiles have been laid. This takes place thanks to the fact that the polymer coating is composed of a thermosetting polymer material, which, once activated, cross-links also causing the formation of chemical bonds both with the ceramic portion of the tile itself and between the polymer materials of two adjacent tiles. In this way, effective filling is obtained and, consequently, any grout lines that are created between the tiles are closed.

It is important that during storage of the tile the polymer coating, not yet cross-linked, remains stable for a time suitable for market requirements.

In order for the present invention to be effective, another need concerns the fact that the thermosetting polymer, once cross-linked, is resistant to the products generally used to clean the surfaces.

Brief Description of the Drawing

Some descriptions of embodiments are set down below, purely for non-limiting illustrative purposes, for a better understanding of the invention with the aid of the accompanying figure, which is a top view of a very schematic representation of a tile according to the present invention. Detailed Description of Preferred Embodiments of the Invention

An aqueous dispersion of a mixture composed of a polyurethane polymer and of a cross-linking agent, which comprises isocyanate groups in blocked form, was created.

In particular, an aqueous dispersion with a solid content of 40% of a cross-linking agent, consisting of non ionic prepolymer comprising isocyanate groups blocked with 3,5 dimethylpyrazole, was added to an aqueous dispersion with a solid content of 40% of a polyether-based anionic aliphatic polyurethane.

By way of example, other blocking groups useful in the context of the present invention are e-caprolactam (e-CAP), methylethylketoxime (MEKO) and diethyl malonate (DEM).

The resulting dispersion was mixed manually at room temperature until obtaining a homogeneous dispersion.

The aqueous dispersion of polyurethane is marketed with the name Witcobond® 737 by the company Lanxess.

The aqueous dispersion of the cross-linking agent is marketed with the name Trixene® Aqua BI 220 by the company Lanxess.

The amounts used of the two aqueous dispersions were selected so that the weight ratio between the aliphatic polyurethane and the cross-linking agent was equal to 2.5.

A film of the aqueous dispersion thus created was arranged on a surface and left in the air for 24h in order to obtain evaporation of the water. In this way, a polymer coating material (Material A) according to the invention was created. For comparison purposes, a second polymer coating material (Material B) was considered. This comparison material was produced using only the aqueous dispersion of polyurethane described above for Material A. Also in this case, a film of aqueous dispersion was left in the air for 24h in order to obtain evaporation of the water.

By way of example, other methods for promoting evaporation of the water concern heating in an oven, heating by means of NIR lamp or by means of the action of microwaves.

Material B (comparison) differs from Material A (invention) due to the absence of the cross-linking agent.

Material A and Material B were subjected both to stability tests and to strength tests to the substances generally used in cleaning operations.

- Stability tests -

Material A and Material B were housed in a climate chamber operating with a temperature of 45°C and a humidity of 75%. The films were controlled (evaluation of the consistency and colour of the film and weight of the film) after 6h, after 24h and after 10 days.

Both for Material A and for Material B no visual variation in the quality of the film, no variation in the consistency of the film and only a minimum weight variation were detected.

For correct evaluation of the test described above, it must be pointed out that drastic conditions were used (45°C temperature and 75% humidity), which would be unlikely to occur during normal storage.

- Strength tests -

Material A was maintained in the oven for around 30 minutes at a temperature of 190°C. This heat treatment caused activation of the functional groups of the cross-linking agent and, consequently, cross-linking of the polyurethane polymer.

Following the heat treatment, six samples were taken from Material A, each of which was arranged in a respective test tube. In each of the test tubes, 5 ml of distilled water, ethanol, acetone, bleach, Lysoform (green colour, main component: benzalkonium chloride) and ACE without bleach (blue colour, main component: benzisothiazolinone), respectively, were added. After 1 h of immersion, each of the samples was collected and assessed in terms of consistency, variation of colour and weight.

The same process described above was applied to Material

B.

While Material A showed no significant changes in any of the six test samples, Material B suffered considerable swelling for the test in distilled water and lost its consistency almost completely for the tests in acetone and ethanol.

These tests proved how the material according to the present invention has a significantly higher strength than the material used as comparison. Such result shows that the tiles of the present invention are able to guarantee sealing of the grout lines, even after several cleaning operations to which the tile-covered surface will be subjected.

Another strength test was performed maintaining the samples of Material A and of Material B immersed in a solution of HC1 at 18 % by volume. Both materials were analysed after lh and after 24h of immersion. After lh of immersion, both Material A and Material B showed a slight swelling, but without this having compromised the structure of the material. Instead, after 24h of immersion Material B was almost completely solubilized and without consistency, while Material A, notwithstanding the swelling, maintained its consistency intact.

For further comparison, the same test was repeated on a sample of cementitious mortar "Keracolor FF", which broke down immediately after only a few minutes of immersion.

A further test concerned evaluation of stain resistance. For this reason, substances commonly present in domestic environments, such as coffee and red wine, were used. Two samples of Material A were left immersed for one hour in 5 ml of a coffee based beverage and in 5 ml of red wine, respectively.

The same process with the same substances was repeated with two samples of Material B.

At the end of the period of immersion, all the samples were rinsed with abundant distilled water. While the samples of Material A had no traces of stains, the samples of Material B remained slightly stained.

- Production and joining of the tiles -

In the accompanying figure, the tile of the present invention is indicated as a whole with 1. The tile 1 comprises a ceramic portion 2 and a polymer coating 3 arranged along the lateral edges 4 of the ceramic portion 2.

Tiles 1 comprising a peripheral polymer coating 3 obtained with Material A (Tiles A) and tiles 1 comprising a peripheral polymer coating 3 obtained with Material B (Tiles B) were produced.

Preparation method of Tile A: the aqueous dispersion of Material A was collected with a pipette and deposited on the edge of a ceramic portion 9 x 4.5 cm in size. After being deposited, the aqueous dispersion A was levelled taking care not to leave any bubbles and to leave a homogeneous thickness.

Subsequently, the water was evaporated. This operation was carried out using, by way of example, three different methods:

(i) evaporation in air: the article was left exposed to the air for 24 h;

(ii) the article was left in the oven at a temperature of around 60°C for 30 minutes;

(iii) the article was subjected to the irradiation of an NIR lamp, at a distance of around 50 mm, for total time of 30 s. The power of the lamp was set at 50%. The Tiles A were produced in this way.

The process described above was repeated using Material B in place of Material A. The Tiles B were produced in this way.

Joining of two of the tiles produced as above was performed by way of example following three different methods. In particular, the first two methods concerned laboratory methods, while the third method concerned a laying method for producing a tile-covered surface on an industrial scale.

(i) Laboratory method - The tiles were placed side by side and held in position by means of portable clamps. The tiles held in position by means of the clamps were left in the oven at a temperature of around 190°C for around 30 minutes.

(ii) Laboratory method - The tiles were placed side by side and held in position with a bench clamp. The tiles held in position by means of the bench clamp were heated to a temperature of around 190°C for a time of 15 minutes by means of the action of an industrial heat blower.

(iii) Method of producing a tile-covered surface - The tiles were placed side by side and maintained under pressure by means of a threaded bar fastening system. Subsequently, the tiles were heated in the joining area to a temperature of

190°C for a time of 15 minutes by means of the action of an industrial heat blower.

- Mechanical strength tests of the join between two tiles - This test was deemed significant as the mechanical strength of the join between two tiles is considered to be correlated to its compactness and, consequently, to the effectiveness of the sealing action of the grout lines by the polymer coating.

A pair of Tiles A that were joined using the laboratory method (i) were placed resting on a prism and a load was applied in the area of the join with a tip. A 5000 N load cell was used and the test was conducted with a movement velocity of the cross member of around 10 mm/min.

The same measurement process was repeated on a pair of Tiles B that were joined with the laboratory method (i).

Both for the pair of Tiles A and for the pair of Tiles B a maximum load exceeding 300 N was registered. This value was without doubt higher than the values detected using the cementitious materials generally used to fill the grout lines.

In this regard, the mechanical test described above was repeated using two materials generally used as materials for filling grout lines, such as silicone and cementitious mortar. In particular, silicone marketed with the trade name MAPESIL LM and cementitious mortar marketed with the name KERACOLOR FF were used.

The test provided for arranging two tiles, consisting only of the ceramic portion, side by side on a surface at a distance of around 2 mm. This distance was selected as it generally represents the dimensions of the grout lines in tile-covered surfaces. Subsequently, the space of 2 mm between the two tiles was filled with silicone or cementitious mortar, as occurs in the filling operations of grout lines after the tiles have been laid.

The pairs of tiles were subjected to the mechanical test seven days after the filling operation with silicone or cementitious mortar.

The tiles between which the cementitious mortar "Keracolor FF" had been applied separated as soon as they were lifted and, therefore, it was not possible to subject them to the mechanical test.

Instead, the tiles joined with the silicone Mapesil LM were subjected to the mechanical test in the same conditions indicated for the tiles of the invention, and registered a maximum load value of around 70 N.

This comparison test shows how the mechanical strength of the join of the tiles of the present invention is much greater than that of prior art materials.

From the above it is evident how the tiles of the present invention are able to guarantee the production of a tile- covered surface practically without grout lines, without incurring the problems of the prior art relating both to lengthy execution times and to the need to perform subsequent cleaning operations. In fact, after laying of the tiles, the only operations that must be performed by the operators consist in heating the polymer coating between the tiles, to promote activation of the functional groups of the polymer material and, consequently, cross-linking.

In other words, the tiles of the present invention will be available on the market with a peripheral polymer coating that, besides protecting the edges of the ceramic portion from possible damage, guarantees the formation of an effective filling of the spaces between the tiles once laid. The effective filling is created thanks to cross-linking of the polymer material by means of the functional groups once activated. As mentioned above, besides involving the polymer material of a single tile, cross-linking causes the formation of covalent bonds between the polymer materials of two adjacent tiles and between the polymer material and the ceramic portion on which it has been deposited.