Patent Application
20180002234
The present application refers to the fabrication process of micronized sandstone obtained from industrial waste of ceramics manufacturing, such as ceramic white paste natural stones or clinker, treated with TiO2 hydrolyzed or not, and product obtained by the micronized sandstone thereof.
Problems with the environment are increasing everyday due to the unsystematic use of natural resources, as well as the generation and disposal of construction industry solid waste. The large volume of debris produced and discarded by the placement and replacement of ceramic materials are enormous (about 500 million cubic meters/year) and they are improperly managed or thrown into landfields, which block the drains culverts, thus causing floods and subsequent proliferation of diseases.
Therefore, it becomes necessary to recycle and reutilize the ceramics and solid wastes as raw material for construction, in order to control and minimize environmental impacts.
It is known from the state of the art, several patents disclosing different technologies, which attempts to reduce the ceramic industry cost and minimize the environmental impact. One example is the utility patent BRMU8903002-8 which describes a process for production of ceramic plates for floors and coverings, comprising the addition of ash sugarcane bagasse ash as flux material in the formulation, wherein the sugar cane bagasse ash is a residue obtained from the sugar cane processing.
Another example is the patent application BRPI 0600081-9 which discloses the production of red ceramic made of construction machinery wastes such as ferrous slag, sludge, purge and all types of foundry sand, wastes of glass, sodium and natural clay-compositions used in the manufacture of ceramic products that contain in their composition, besides the raw materials commonly employed, also ferrous slag, sludge (or dry mud powder) of exhaustion (thin green sand+bentonite+charcoal) all kinds of foundry sands (green sand, cold box sand, Macharia sand), blasting dust residues (micro glass beads) or other types of vitreous wastes, sodium salts and natural red clay.
Another example is patent application CN101186519 which discloses a porous ceramic material and a preparation process thereof, wherein the invention uses polishing bricks waste and describes an auto mechanism of ceramic foam production.
Patent application AU2014201184 describes materials containing titanium that are able to form high-temperature-resistant and wear resistant titanium compounds, for example, aluminium titanates, magnesium titanates, Ti(C,N) using steel waste (slag).
The applicant also has knowledge of patent EP1834935 which describes an agglomerated stone product obtained by the addition of titanium dioxide particle, preferably as nanosize, in the vibrocompaction phase of the stone material in the presence of resin and cross-linking agents.
Unfortunately, none of the prior art cited above addresses the issue of the use of residual ceramic materials. In contrary, the final product obtained by the processes above described, is not homogeneous and does not meet the required quality standard, nor satisfies the requirements needed for ceramics, because the particle size of the raw materials interferes in various properties such as plasticity, sintering rates, final porosity, density, structural compression, mechanical strength, porosity, resistance to chemical attack, abrasion (hardness), antifreeze property, resistance to stains, etc.
In addition, the use of ceramic waste as raw material in the construction of new floors, terraces, walls, etc., is very important to eliminate any kind of organic matters that can generate mildew, lichens, fungi, bacteria etc. on the new surface. This is of particular interest in the areas where strict hygiene is required (hospitals, schools etc.) and in indoor and outdoor areas exposed to large amounts of moisture, such as vicinity of swimming pools, showers, changing rooms, and similar facilities.
Several technologies have been developed in the area of new materials, which applies TiO2 coatings on the surfaces due to their photoactivity, which is a promising feature of them in the use of environments that require the control of microorganisms.
However, some technologies do not work properly when using heating and/or high temperatures to consolidate the coating and they result in cracks, bubbles, rough surfaces, etc. Other technologies use nanoparticles of TiO2 that are dangerous for human beings and can cause respiratory diseases, cancer, etc. Examples of these technologies can be found in the prior art CN1443605, U.S. Pat. No. 6,210,779, CN102561627 and CN1304336 among others.
In order to resolve the problems described above, the present invention describes a fabrication process of micronized sandstone obtained from industrial waste of ceramics manufacturing, such as ceramic white paste natural stones or clinker, treated with TiO2 hydrolyzed or not, and product obtained by the micronized sandstone thereof.
The present invention refers to a process of manufacturing micronized sandstone obtained from industrial waste of ceramics manufacturing, such as white paste, natural stones, or clinker, treated with TiO2 hydrolyzed and thus produced article.
Ceramics or ceramic wastes are crushed in several steps and the resulting powders are collected by individual filters and then combined in the powder nano-micronizer device for subsequent treatment, in which hydrolyzed TiO2 may be added or not.
The micronized sandstone bio-treated with TiO2 is used in the production of plasters, mortars, grouts, and/or as additives for paints and/or epoxy micronized additive with TiO2.
The micronized sandstone bio-treated with TiO2 may be submitted to two additional embodiments of the process: treatment with or without the use of pigments.
In order to obtain the final article that can be used in the production of blocks, floors and other products of different sizes and dimensions, it is added to the micronized sandstone treated with TiO2 a binder, also comprising a TiO2 additive, which is mixed in aqueous solution or dry, with the addition of colored oxides, if desired.
The process is carried out at room temperature and use particulate material obtained from ceramics or industrial waste of ceramic manufacturing.
Unless define otherwise, all technical and scientific terms herein used have the same meaning as generally understood by one skilled in the art to which this invention belongs.
An illustrative example of a typical composition of materials is showed below:
Modalities of this invention will be now described as an illustrative example, referring to the block diagram of
The ceramics or ceramic wastes are crushed in mills/grinders (1,2,3) that break down the raw material in several stages and in specific granulometry, resulting in a micronized sandstone raw material (4), whose particle size ranges from 0 mm to 30 mm. The number of mills and/or crushers is variable, depending on the desired size. The last grinder (3) is a micronized mill. Although in
Grinding powders resulting from this process are collected by the individual filters 7A, 7B and 7C which separate the vitreous materials. Those filters are water-based. As can be seen through
Hydrolyzed TiO2 is added to the nanomicronized powder obtained in (9).This final product (11) is used for the production of plaster, mortars, grouts and/or as additives for paint and/or epoxy additive with TiO2. Block 7D represents the separation of waste, which is forwarded to recycling (7E).
The nanomicronized material (4) contains small particles having particle size from 0 mm to 30 mm and that can be used in two additional embodiments of the process: First Embodiment—treatment with the use of pigment and Second Embodiment—treatment without the use of pigment.
In this embodiment, the micronized sandstone raw material (4) is colored with addition of pigments (5) followed by treatment with hydrolytic solution or hydrolyzed TiO2 (5B) and further drying (S1), thus obtaining a product of colorful micronized ceramic sandstone product treated with TiO2 (P1).
In this embodiment, the micronized sandstone raw material (4) does not receive pigments, but proceeds to be treated with a hydrolytic solution or hydrolyzed TiO2 in (6) and further drying (S2), thus obtaining a product of micronized sandstone treated with TiO2 (P2).
In this final step, both P1—the micronized colored sandstone with TiO2 as P2—the micronized sandstone, already comprising TiO2 additive are mixed with a binder also comprising with TiO2 additive, mixed in an aqueous solution (M) or dry (M2), with addition of colored oxides, if desired.
The formation process of the layers can be accomplished through various deposition processes known from the prior art, such as chemical vapor deposition (CVD), physical vapor deposition (PVD), sol-gel and dip-coating processes, this last one, aiming an uniform coating with hydrophilic properties photo induced. The final product (B) is used in the production of blocks, floors, new ceramics and products with variable dimensions.
Unexpected results were achieved by this process using micronized sandstone obtained from ceramics or ceramic manufacturing waste as white paste, natural stones, or clinker, treating these materials with TiO2 hydrolytic, because the crystalline structure of the ceramics or their residues are formed by a three dimensional network of extended crystals, similar to pores.
Therefore, when the micronized sandstone is immersed in the hydrolytic TiO2 solution, the interstices and the crystalline lattice of the material are impregnated, forming not only an outer covering, but a dense and compact internal structure.
Several experiments were carried out testing porosity of residual materials used by this invention. We used the standard ABNT/NBR 15097:2004 and their values determined by equation 1:
It was verified that the apparent porosity of the material decreases with the increasing of the temperature, and this can be explained because of the efficient formation of a liquid phase, in which a lower surface tension and capillary action helps to keep the particles together, retracting the material, thus reducing the porosity.
As a result, the present invention does not use heating or UV or infrared radiations, as described in the prior art, but the process described by the present invention can be performed at room temperature or with heating (100° C./200° C.), which provides a better and more efficient impregnation of the TiO2 in the sandstone.
The final treatment of P1—micronized sandstone colored with TiO2 or P2 micronized sandstone treated with TiO2, with binder aggregated with TiO2 mixed in an aqueous solution (M) or dry (M2), with addition of colored oxides, if desired, serves to “seal” this impregnated product, thus producing a resistant layer also containing TiO2.
Several are the advantages of this finished product:
Titanium dioxide (TiO2) is an amphoteric metallic oxide semiconductor, which can crystallize in three polymorphic forms: anatase (tetragonal), rutile (tetragonal) and brookite (orthorhombic), being rutile, the more thermodynamically stable phase. When deposited in a thin film form, the crystalline form of TiO2 depends on the nature of the raw materials, their composition, method of deposition and heat treatment temperature.
The manufacturing process of micronized sandstone obtained from ceramics or waste of the ceramics industries, such as as white paste, natural stone or clinker, treated with TiO2 hydrolytic, and article so produced, developed by the present invention utilizes the photocatalytic ability of the titanium dioxide, which is induced by the absorption of photons of ultraviolet radiation from sunlight or appropriate lights (band gap of anatase is 3.2 eV and it is equivalent to a wavelength of 388 nm).
As the photons have energy greater than the energy of the band gap of the material, i.e., sufficient energy to excite electrons in the valence band, then this causes its passage to the conduction band. The absorption of energy withdraws an electron from the valence layer and transfers it to the conduction band. As in the conduction band lays a vacant site, called hole or vacancy, then the electron-hole pair moves across the network of nanocrystals.
Then the titanium dioxide acts as a catalyst, when it comes in contact with the light, wining enough power so that the electron passes by valence to the conduction band, thus enabling its displacement by interstices of material. Upon reaching the surface, this electron participates in reactions with oxygen and water forming hydroxyl radical, nascent oxygen or hydrogen peroxide.
The strong oxidizing power of hydroxyl radical (OH−) ions and peroxides (O2−) contribute in removing debris, molds, lichens, etc. when start their dissociation, thus contributing to its disintegration. The oxidant effect of TiO2, when subjected to ultraviolet radiation, reduces the angle of internal friction of water causing the surface of the material to be hydrophilic, which contributes to an increase of the self-cleaning effect.
The vacant space left by the electron in the valence band is actually an entity carrier with a positive electrical charge that, in the same way as the electron can move through the crystal. To reach the surface, it reacts with the oxygen in the TiO2, where the two hydroxyl radicals are absorbed, and the free energy of the surface increases considerably. This high free energy allows the TiO2 to completely spread forming a continuous film, which is coated and sealed by aggregating materials (cements, binders, etc.)
This mechanism can be represented by the equation below and starts when a photon with sufficient energy impacts the TiO2 net forming an electron-hole pair:
TiO2+2hv→2e−+2h+
where hv represents the photon energy, h being the Plank constant, v the light speed, e− the electron and h+ the hole created. If the crystal is large, the electron-hole pair recombines the defects of the system and does not reach the surface of the crystal. If the crystal is too small, there will be no formation of sufficient pairs. If the crystal is of an adequate size, the pair moves on the net and reaches the surface.
In general, nano-sized particles present big surface area and attest to a tendency of high reactivity and, when these are added in cement based materials or binders, a great impact occurs on their properties, both in the fresh as well as hardened states.
Thus, the micronized sandstone manufacturing process using ceramic or wastes produced from the ceramic industries such as white paste, natural stone, or clinker, treated with TiO2, comprises two embodiments, and can be defined by the following steps:
The second embodiment can also include an optional step j with the addition of pigments or colored oxides to the agglomerate product obtained (M2).
Products (P1) or (P2) obtained by the two modalities can be mixed with the binder already comprising TiO2 additive in dry or in aqueous solution.
The number of mills/grinders in both embodiments is variable, but the last mill/crushed is always a micronizer. The number of filters may or may not be equal to the number of mills/grinders in the two modalities.
In both embodiments, the interstices of crystalline micronized sandstone (12) are filled with TiO2, which forms a bond with the ceramic material and where the binder treated with TiO2 makes a sealing with layer interstices crystalline micronized sandstone (12) filled with TiO2. Both the micronized sandstone treated with TiO2 colored or not can have a photocatalytic property.
Also in both modalities, one or more layers of binders additive(s) also treated with TiO2 can be used on the layer of micronized sandstone treated with TiO2.
Therefore, based on the process herein described, new generations of products and ceramic tiles can be considered as part of a set of architectural elements for external and internal uses, because as it was disclosed, they provide a wide range of surfaces properties and functions without prejudice to the aesthetic qualities, not changing the characteristics of the ceramic materials.
The invention thus described will be apparent that it will vary in several ways. Such variations cannot be regarded as a deviation from the spirit and scope of the application of the invention and all modifications as it would be obvious to a person skilled in the art are intended to be included within the scope of the following claims.
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/BR2014/000219 | 7/3/2016 | WO | 00 |
