ITMI20110369A1 - GLASS-BASED MATERIAL FOR THE PRODUCTION OF CERAMIC ARTICLES AND METHOD FOR ITS PREPARATION - Google Patents

Description

"GLASS-BASED MATERIAL FOR THE PRODUCTION OF PRODUCTS

CERAMICS AND METHOD FOR ITS PREPARATION "

The present invention relates to a material with a predominantly glass component, for the preparation of ceramic articles, in which said material comprises at least one ground glass, at least one inorganic plasticizer and at least one organic binder. The invention also relates to a method for the preparation of said material, the ceramic articles obtained therefrom and the relative production process.

Traditional ceramic products are the result of the firing, at high temperatures (even over 1250 ° C), of mixtures (or mixtures) of minerals that are mixed / kneaded together with more or less large quantities of water.

Normally, these mixtures are made up of mixtures of different components such as, for example: inert minerals (quartz, blast furnace slag, volcanic ash, pumice and the like), vitrifying substances (feldspar, glass and the like) and clays, often present in large quantities and containing significant quantities of residual water. Î "title of example, the generic formulation of a porcelain stoneware, traditional product for flooring and / or covering widely used in the last 20 years in construction, includes a mixture of: 40-45% clay, 40-50% of sodium and potassium feldspars, 10-15% quartz sand.

However, said mixtures are not without disadvantages; for example, the presence of large quantities of clay makes its preparation and subsequent processing difficult and / or expensive. In fact, the clays tend to incorporate not negligible quantities of air, which must be eliminated during the processing of the mixture through the use of kneading-degassing machines.

Furthermore, clays are very sensitive to temperature variations and also degrade significantly at high temperatures, for example at the temperatures at which it is necessary to produce porcelain stoneware (around 1220 ° C) or porcelain (around 1350 ° C. ). This involves the use of sophisticated ovens built with special materials that have a significant economic impact on the entire production process.

Finally, it should be noted that the need to supply clay (as well as feldspar) to the ceramic industries has important negative consequences at the environmental level, requiring the opening and extensive exploitation of quarries in regions rich in these minerals.

The Italian patent No. IT 1361575 relates to a mixture for the manufacture of ceramic products, particularly porcelain stoneware, which includes a glass matrix preparation in quantities from 5 to 100% by weight, an aqueous mixture of synthetic soluble polymers in a quantity from 10 to 30% by weight, and inert material in an amount from 0 to 95% by weight, the percentages being expressed with respect to the total weight of the glass matrix preparation and of the inert material. The vitreous matrix preparation is common glass, used in the form of finely ground powders, while the inert material can be for example quartz, or glass, basalt, cooked waste of the same ground mixture. No indication is given on the chemical nature or on the physico-chemical properties of the soluble polymer to be used. Small quantities of clayey minerals can also be added to the mixture.

There is therefore a strong need in the sector to have available a mixture suitable for the manufacture of ceramic products with a predominantly glass component, which allows to eliminate the aforementioned drawbacks. A mixture, that is, which can be obtained in a simple and convenient way from an economic and environmental protection point of view and which is made up of components that are easily available on the market and have a limited environmental impact. Furthermore, said mixture must be able to be worked and transformed into the final product through the use of methods and equipment that are relatively simpler than those commonly used today in the ceramic sector.

The Applicants have now quite unexpectedly found that a material comprising at least one ground glass, at least one inorganic plasticizer, water, and at least one water-soluble polymeric binder, of synthetic origin or derived from natural substances, such as, for example, a modified polysaccharide so As defined below, it can provide an adequate answer to the technical problem highlighted above. In particular, the presence of at least one water-soluble polymer, acting as a binder, makes it possible to produce a material with a predominantly glass component, with good plasticity and workability in an aqueous environment, without causing the typical problems of compositions with a prevalently clay base. Furthermore, it is possible to use in this material very high quantities of a recycled glass, obtained for example through separate waste collection, with obvious advantages for its disposal and for the final cost of the ceramic product.

According to a first aspect, the present invention therefore relates to a material for the production of ceramic articles, which comprises: (a) at least one ground glass, in an amount from 60 to 95% by weight; (b) at least one inorganic plasticizer, in an amount of from 5 to 40% by weight; (c) at least one water-soluble polymeric binder, in an amount of 0.1 to 5% by weight; (d) water, in an amount of from 5 to 40% by weight; the percentages by weight being expressed with respect to the total weight of components (a) and (b).

In a second aspect, the present invention relates to a process for the preparation of a material according to the above, which comprises: dry mixing said at least one ground glass with said at least one inorganic plasticizer; adding said at least one water-soluble polymeric binder and, optionally, at least one pigment to the mixture thus obtained; incorporate water in a predetermined quantity into the mixture.

According to another aspect, the present invention relates to a ceramic product obtained from a material as described above.

According to a further aspect, the present invention relates to a process for the production of a ceramic article, which comprises subjecting a material as described above to a cold forming step and a subsequent hot consolidation step.

Further features and advantages of the present invention will become clearer from the following description.

In a preferred embodiment, the material according to the present invention comprises: from 60 to 95% by weight, preferably from 70 to 95% by weight, more preferably from 80 to 95% by weight, of at least one ground glass; from 5 to 40% by weight, preferably from 5 to 30% by weight, more preferably from 5 to 20% by weight, of at least one inorganic plasticizer, said percentages being expressed with respect to the total weight of components (a) and (b) .

In a preferred embodiment, the material according to the present invention comprises: said at least one water-soluble polymeric binder is present in an amount from 0.1 to 5% by weight, preferably from 0.2 to 4% by weight, more preferably from 0.5 to 3% by weight, with respect to the total weight of components (a) and (b). Preferably, said at least one ground glass has an average particle size lower than 600 µm, more preferably lower than 500 µm, even more preferably lower than 400 µm.

The glass can be of any type and origin, however, in a particularly preferred embodiment of the invention, the aforementioned ground glass comprises at least 60% by weight, more preferably at least 80% by weight, with respect to the total weight of the glass, of at least one waste glass.

Recycled glass can come from various sources (in particular, falling within the waste code according to the European Waste Catalog-CER updated to the law 272/20 August 2004), for example:

201002 - bell glass coming from MSW separation;

191205 - glass from mechanical waste treatment (post reclamation of TVs and monitors, fluorescent lamps, other WEEE);

101112 - waste from ceramic frits;

150107 - glass packaging;

160120 - glass from the dismantling of end-of-life vehicles;

post production glass residues from vials; glass residues / waste from other compartments not included in the previous classifications (the numbers shown above are the European CER codes that classify waste).

In the material according to the present invention, said at least one inorganic plasticizer is preferably a clayey mineral; preferably said clay mineral is a clay, a kaolin, or their mixtures. More preferably, said clay mineral is a kaolin. Preferably, said at least one inorganic plasticizer has an average particle size lower than 50 µm, more preferably lower than 40 µm, even more preferably lower than 20 µm.

In the material according to the present invention, said at least one polymeric binder is a water-soluble polymer of synthetic origin or a modified polysaccharide, which is capable of exerting a binding and plasticizing action on the inorganic glass / inorganic plasticizer mixture even when added in very limited quantities (generally less than 5% by weight, with respect to the total weight of components (a) and (b)).

The water-soluble polymer of synthetic origin can be in particular a vinyl polymer containing hydrophilic groups (for example hydroxide, carboxyl, carboxylate, ester, amide groups). Preferably, this can be chosen from: polyacrylates or polymethacrylates (for example polyhydroxyalkyl (meta) acrylate, polyalkyl (meta) acrylate, poly (meta) acrylamide), polyvinyl alcohol (PVA), polyvinyl acetate, alcohol / vinyl acetate / vinyl alcohol / terpolymers ethylene / vinyl acetate; and their mixtures.

The modified polysaccharide is generally a water-soluble modified polysaccharide, in particular an etherified polysaccharide. The basic polysaccharide can be, for example, cellulose, arabinoxylan, guar gum. More preferably, said modified polysaccharide is selected from: hydroxymethylcellulose, hydroxyethylcellulose, hydroxypropylcellulose, hydroxypropyl guar, and their mixtures.

The material according to the present invention further comprises a variable quantity of water according to the type of ceramic manufactured article to be made and also according to the type of processing to which the aforesaid material is to be subjected. Therefore, depending on the amount of water used, a more or less fluid mixture will be obtained which will be subjected to different types of processing.

As a rule, the amount of water present in the material of the invention is from 5 to 40% by weight, preferably from 10 to 35% by weight, more preferably from 20 to 30% by weight, with respect to the total weight of the components (a ) and (b).

The material according to the present invention can be made in multiple combinations of colors and shades or even be enamelled according to the applications (for example: internal and / or external coatings, furnishing accessories, office decorations and high quality artistic products, such as ceramic stoves). Therefore the aforesaid material may further comprise at least one pigment; preferably, at least one inorganic pigment, which is generally added in an amount of from 0.5 to 5% by weight, preferably from 1 to 4% by weight, with respect to the total weight of components (a) and (b).

The material according to the present invention can be produced according to a process which comprises: dry mixing said at least one ground glass with said at least one inorganic plasticizer; adding said at least one water-soluble polymeric binder, and optionally at least one pigment, to the mixture thus obtained; then incorporate water into the mixture in a predetermined quantity.

The method of adding water is not binding. It is in fact possible to add the mixture of solid powders to the water or it is also possible to add water to the aforementioned mixture.

As regards said at least one water-soluble polymeric binder, this can be added, according to its chemical-physical characteristics, in the form of a powder or in the form of an aqueous solution. By way of example only, hydroxyethylcellulose is generally available on the market in powder form so it can be mixed with other powders and water is then incorporated into the resulting mixture. On the contrary, PVA is generally available in the form of an aqueous solution, which can be directly added to the mixture when it is in the form of a powder, or when water has already been added to it.

Advantageously, thanks to the very high quantity of glass used and the low percentage of added water (generally substantially lower than that present in conventional ceramic slips) it is not necessary to use mixing equipment, such as turbodissolvers, commonly used in the ceramic field. Instead, it is sufficient to resort, for example, to the use of simple mechanical mixers, commonly used, for example, in the food sector.

Given the versatility of the characteristics of the material in accordance with the present invention, it is possible to produce a wide range of ceramic products. By way of an absolutely non-limiting example of the wide applicative potential of the invention, among said ceramic articles the following can be mentioned: tiles, glazed tiles, ceramic slabs for flooring and / or coverings; ceramic bodies for kitchen worktops or ceramic stoves, bathroom fixtures, art objects, interior and / or exterior finishes, and so on.

The present invention is further directed to a process for the production of a ceramic product, which comprises subjecting a material according to the present invention to a cold forming step and a subsequent hot consolidation step.

Said cold forming phase can be carried out using equipment and methodologies commonly used in the ceramic sector, but methods known in other sectors can also be advantageously used, but which are not generally applicable for the industrial production of ceramics, such as for example the stamping and lamination. Among the traditional methods, for example, pressing and casting can be mentioned.

The cold forming phase is then followed by a hot consolidation (or firing) phase, preferably carried out in normal industrial kilns / dryers or muffles, as well as in industrial roller kilns.

The temperature at which this cooking step is carried out is on average between 700 and 1100 ° C, preferably between 800 and 1000 ° C. These are therefore considerably lower temperatures than those usually used for the production of vitrified ceramic materials or flooring materials (up to 1250 ° C).

The time required to carry out this heat consolidation treatment is also relatively short: a period of time generally less than 90 minutes is in fact sufficient; preferably less than 75 min. Preferably, the heat consolidation treatment is carried out for a time of at least 60 minutes.

All this is advantageously reflected on the quality of the final product and on the economy of scale of the preparation process of the ceramic articles in accordance with the present invention. Furthermore, thanks to the use of a high quantity of recycled glass and the elimination of other components whose extraction and transport cause a considerable environmental impact (fluxes and aggregates), the process of the present invention is particularly advantageous also from the point of view with a view to safety and environmental compatibility.

However, it is understood that, in the light of everything described in the present description and in the attached claims, the skilled person in the field will be able to make and carry out further modifications and developments without however departing from or departing from the protective framework of the invention itself.

By way of non-limiting example only, the invention is further described in greater detail in the following experimental section.

EXAMPLE 1 - Forming by lamination

1) Basic paste

Through dry mixing, the following composition was created:

Glass 77% by weight

Kaolin 20% by weight

Boric glass 3% by weight

Glass had an average particle size of less than 500 Î1⁄4ιΠ·, boric glass less than 45 pm, kaolin less than 20 pm.

This mixture of powders was mixed with water in a ratio of 1: 4 (liquid / solid). A polyvinyl alcohol (PVA) in the form of an aqueous solution was added to this mixture as an organic binder, in an amount equal to 1% by weight (of dry polymer) with respect to the total weight of the powders.

2) Homogeneously colored bulk paste

An inorganic pigment was added to the base paste, prepared as described above (in a quantity ranging from 0.5 to 5% by weight, with respect to the total weight of components (a) and (b)). To improve the homogeneity of the coloring, the pigment was premixed in water. A homogeneously colored mass-colored paste was obtained, which can be used as it is or to prepare the striped pasta described below.

3) Colored striped base paste

Various colored pastes were prepared as described above, which were superimposed at varying thicknesses forming layers. The product thus obtained was rolled, cut and laminated, thus obtaining an artifact that presented on the surface veins of different colors that can simulate wood, natural stones.

4) Colored base paste with marble effect

The base paste was prepared as previously described in (1). To obtain the marble effect, once the compound was prepared, the pigment was mixed with glass powder in order to avoid agglomeration, and then added to the mixture previously prepared during mixing.

Once the mixture was obtained, it was dried in normal industrial ceramic dryers and subjected to firing with thermal cycles in the 950-1000 ° C range for 60 minutes.

EXAMPLE 2 - Forming by pressing

Through dry mixing, the following composition was created:

Glass 77% by weight

Kaolin 20% by weight

Boric glass 3% by weight

Glass had an average particle size below 500 µm, boric glass below 45 µm, kaolin below 20 µm.

An etherified polysaccharide (i.e. hydroxymethylcellulose in powder - Gelogum® commercial product of the Barzaghi S.r.l. company) was then added as an organic binder in a quantity equal to 1% by weight with respect to the total weight of the powders. .

Subsequently, water was added in a percentage equal to 6-7% by weight, with respect to the total weight of the powder components, and the resulting mixture was kept in an airtight container for 24 hours to improve its homogenization.

The agglomerated powder thus obtained was sieved (through a sieve with a 1 mm mesh) in order to obtain a granular powder ready for pressing. The forming was carried out using an isostatic press with variable pressures depending on the application of the product (30-50 MPa). Also in this case it is possible to obtain products made up of base paste (1), colored paste in bulk (2) and enamels (5).

Once the mixture was obtained, it was dried in normal industrial ceramic dryers and subjected to firing with thermal cycles in the 950-1000 ° C range for 60 minutes.

EXAMPLE 3 - Forming by putty trowel

Through dry mixing, the following composition was created:

Glass 80% by weight

Kaolin 20% by weight

Glass had an average particle size below 500 µm and kaolin below 20 µm.

30-35% by weight of water was added to the above powder mixture, with respect to the total weight of the powder components.

A polyvinyl alcohol (PVA) in the form of an aqueous solution was then added to the mixture as an organic binder, in an amount equal to 0.5% by weight (of dry polymer) with respect to the total weight of the powders.

The mixture produced appeared as a workable plastic paste by putty knife, and was used to fix and / or decorate the artifacts obtained in Examples 1 and 2, using the same cooking conditions.

k k k k k k

The recovery of waste and the market for recyclable materials play and will play an increasingly important role in the waste management system. As already highlighted above, one of the particularly innovative aspects of the present invention is therefore based on the engineering of new formulations of glass paste with a high content in recycled glass, to safeguard virgin raw materials, such as clays and feldspar often present in large quantities in traditional ceramic products. The characteristic of these new mixtures is to obviate and reduce various drawbacks that are usually encountered in traditional ceramic processes (low workability, high consolidation temperatures and so on) and to achieve the manufacture of products in a practical and easy way to start. from a secondary raw material (recycled glass) easily available on the market, low cost and particularly limited environmental impact. The workability of this paste is so versatile that it allows to obtain products with variable thickness (up to 5 mm) with a reduction in the final cost of the same.

Other advantages over current or alternative technologies are as follows.

1) Ability to create an auxiliary material with a predominantly glass component (on average from 60 to 90%) "mixed" with other inorganic / organic materials, innovative compared to existing formulations for which% of glass on average in the order of: 15% (ceramic bodies); 25% (cement); 75% of a mixture of glass with other organic materials (kitchen worktops). Some application examples can be the creation of high quality artistic floors or walls.

2) High degree of versatility (color: compact or shaded; workability: laminable or pressable, consolidable at relatively low temperatures) of the glass paste produced so as to be able to cover various market sectors. The presence of the organic polymer in the mixture gives rise to a mixture that can be easily worked by hand or by machine, so as to be able to create surfaces or artistic products as well as coatings with thin thicknesses. Consolidation can take place at lower temperatures than traditional thermal cycles (around 200-300 ° C less), nevertheless acquiring mechanical properties comparable to commercial materials.

3) Obtaining an environmentally sustainable semi-finished product that can contribute to the creation of finished products with possible access to ECOLABEL certifications (the European ecological quality label that rewards the best products and services from an environmental point of view, which can thus diversify from the competitors present on the market, while maintaining high performance standards), LEED (the US system for classifying energy efficiency and the ecological footprint of buildings) and can be included in the policy of Green Public Procurement ("green purchases": representing the purchase of goods and services by public administrations, which takes into account not only the price and other conditions of sale, but also the environmental impact of the goods and services over the entire life cycle).

4) For the industrialization of the present invention it is possible to combine, for the phase of preparation of the dough and for the shaping, already existing machinery on the market used in the food industry (spiral mixer and mechanized dough sheeter) and as regards the drying and firing phases are used in the already existing plants of the ceramic industry (dryers and roller kilns).

5) Given its versatility, the mixture can be processed at temperatures much lower than those used in traditional ceramic processes, with a consequent reduction in energy costs associated with consolidation.

6) The recycled glass that is used, coded as "special non-hazardous waste", will be in effect a "secondary raw material" when it enters the production cycle of making the pasta described above, as it does not present problems of transport management, not requiring the compilation of specific forms, thus reducing administrative time and costs.

Claims (16)

CLAIMS 1. A material for the production of ceramic products, which includes: (a) at least one ground glass, in an amount of 60 to 95% by weight; (b) at least one inorganic plasticizer, in an amount of from 5 to 40% by weight; (c) at least one water-soluble polymeric binder, in an amount of 0.1 to 5% by weight; (d) water, in an amount of from 5 to 40% by weight; the percentages by weight being expressed with respect to the total weight of components (a) and (b). The material according to claim 1, wherein: said at least one ground glass is present in an amount from 70 to 95% by weight, more preferably from 80 to 95% by weight; said at least one inorganic plasticizer is present in an amount from 5 to 30% by weight, more preferably from 5 to 20% by weight; And said at least one water-soluble polymeric binder is present in an amount from 0.2 to 4% by weight, more preferably from 0.5 to 3% by weight; the percentages by weight being expressed with respect to the total weight of components (a) and (b). The material according to claim 1, wherein water is present in an amount of 10 to 35% by weight, more preferably 20 to 30% by weight, with respect to the total weight of components (a) and (b ). The material according to any one of the preceding claims, wherein said at least one ground glass has an average particle size of less than 600 Î1⁄4Ï € ι, preferably less than 500 µm, more preferably less than 400 µm. The material according to any one of the preceding claims, wherein said at least one ground glass comprises at least 60% by weight, more preferably at least 80% by weight, with respect to the total weight of the glass, of at least one waste glass. The material according to any one of the preceding claims, wherein said at least one inorganic plasticizer is a clay mineral, preferably selected from: clays, kaolins, and their mixtures. 7. The material according to any one of the preceding claims, wherein said at least one water-soluble polymeric binder is a vinyl polymer containing hydrophilic groups, preferably selected from: polyacrylates or polymethacrylates (for example polyhydroxyalkyl (meth) acrylate, polyalkyl (meta) acrylate, poly (meta) acrylamide), polyvinyl alcohol (PVA), polyvinyl acetate, vinyl alcohol / vinyl acetate copolymers, ethylene / vinyl alcohol / vinyl acetate terpolymers; and their mixtures. The material according to any one of claims 1 to 6, wherein said at least one water-soluble polymeric binder is a modified polysaccharide, in particular an etherified polysaccharide selected for example from: hydroxymethyl cellulose, hydroxyethyl cellulose, hydroxypropyl cellulose, hydroxypropyl guar, and their mixtures . The material according to any one of the preceding claims, further comprising at least one pigment. 10. The material according to claim 9, wherein said at least one pigment is an inorganic pigment present in an amount from 0.5 to 5% by weight, preferably from 1 to 4% by weight, with respect to the total weight of the components ( a) and (b). 11. A process for the preparation of a material according to any one of the preceding claims, which comprises: dry mixing said at least one ground glass with said at least one inorganic plasticizer; adding said at least one water-soluble polymeric binder, and optionally at least one pigment, to the mixture thus obtained; incorporate water in a predetermined quantity into the mixture. The process according to claim 11, wherein said at least one water-soluble polymeric binder is added to the mixture in the form of a powder or in the form of an aqueous solution. 13. A ceramic product obtained from a material according to any one of claims 1 to 10. 14. A process for the production of a ceramic article, which comprises subjecting a material according to any one of claims 1 to 10 to a cold forming step and a subsequent hot consolidation step. 15. The process according to claim 14, wherein said cold forming step is chosen from: molding, rolling, pressing and casting. 16. The process according to claim 15, wherein said hot consolidation step is carried out at a temperature from 700 to 1100 ° C, preferably from 800 to 1000 ° C; and for a period of time less than 90 min; preferably less than 75 min.