PRODUCTS CONSISTING OF AGGLOMERATED STONES MANUFACTURED BY VIBRO-COMPRESSURE, WHICH CONTAIN TECHNOPOLYMERS DESIGNED TO IMPROVE THEIR TECHNICAL AND AESTHETIC CHARACTERISTICS

Abstract: Disclosed are products called agglomerated stones, manufactured by the technology known as vibro-compressure under vacuum in the form of blocks or slabs, which are destined for use in the construction industry as floor and wall coverings, and have improved technical and aesthetic characteristics.

Description: PRODUCTS CONSISTING OF AGGLOMERATED STONES MANUFACTURED BY VIBRO-COMPRESSURE. WHICH CONTAIN TECHNOPOLYMERS DESIGNED TO IMPROVE THEIR TECHNICAL AND AESTHETIC CHARACTERISTICS The present invention relates to products called "agglomerated stones" manufactured by the known technology of vibro-compressure under vacuum in the form of blocks or slabs, which are destined for use in the construction industry as floor and wall coverings, and have improved technical and aesthetic characteristics. For centuries, stone materials like marble, granite and stone in general have been used in the form of tiles or slabs, sometimes of very large size, for flooring and wall coverings in public and private buildings; this use has always been promoted by the decorative attributes of the material, together with its technical characteristics, especially its durability. The manufacturing cycle for stone materials has changed little over the years, basically involving the following processes. The stone materials are quarried in the form of blocks, which subsequently undergo numerous onerous and expensive operations to give them the required size and appearance; these operations normally include at least the stages of cutting the blocks into slabs, polishing the surface of the slabs, and cutting them to size. Despite the continual research undertaken to optimise it, this manufacturing technology still presents a number of drawbacks which reduce its value and cost-effectiveness. The first is that during quarrying of the blocks, part of the material becomes unusable, and this amount is even greater after the subsequent processing. This waste can amount to over 60%, thus prejudicing the cost- effectiveness of using natural stone and aggravating the environmental impact problem deriving from the management of this waste. The second drawback is the unevenness of the natural material; two blocks quarried at a short distance apart often present such differences in colour as to prejudice their use on large surfaces, together with technical differences, mainly the presence of veins or cracks, which increase the wastage still further. The third drawback is that although natural material is very attractive, which makes it valuable, depending on the quantities available, it also presents colour and technical limitations associated with the increasingly ambitious demand by architects and designers for innovative solutions. The technology employed to manufacture agglomerated stones industrially, using quarry waste as raw material and exploiting the binding properties of synthetic resins that harden to the consistency of stone, indissolubly bonding the granules of marble, granite or stone together, thus represents an innovation in the industry. In the past 30 years, alternative materials have been developed which are often preferred to natural ones precisely because of their technical, and sometimes aesthetic aspects. In relation to this latter aspect, attempts have always been made to embellish the natural slabs used in mosaic compositions by inserting coloured, mirror or polished fragments which constitute a chromatic break between the tiles or slabs of natural stone. Decorative fragments of various nature have also been inserted in the original clay or lime agglomerates in order to attain innovative chromatic results. These fragments, generally constituted by glass, mirror glass, natural stone or pearly, are unable to meet present-day aesthetic requirements, and can also weaken the structure of the floor or wall, because they lack certain properties which would make them particularly suitable for use. In the industrial manufacture of stone agglomerates, the use of these decorative fragments can also involve limitations on appearance and compatibility with other materials, thus influencing their use. For example, the use of glass or mirror fragments in the manufacture of slabs or blocks of agglomerated marble granulates bonded with polyester resin requires the use of expensive additives to guarantee the bond between the resin and the glass material; if these additives are omitted, the product will have dubious mechanical properties, which in some cases may prejudice its use for certain applications. The purpose of this invention is to provide a new type of decorative fragment designed to be inserted into a mixture suitable for the manufacture of stone agglomerates, with no limitation on type (ie. with any type of raw material or binder), which does not require any adhesion-promoting additive, does not present any colour limitations, and gives the end product particular technical properties. This objective is achieved by inserting into the mixture fragments of special technopolymers with given technical and aesthetic qualities, such as polymethyl methacrylate (PMMA) and polycarbonate (PC) (listed by way of example but not of limitation), reduced to the required size. The fragments are obtained from slabs or bars made by casting or extrusion in accordance with the latest plastic processing technologies, and are subsequently ground to the required size with a suitable grinder. The said technopolymers, which are colourless and exceptionally clear, can be coloured in numerous shades, and are therefore suitable, without any limitation, to provide all the light and colour transmission and diffusion effects required to produce a wide variety of aesthetic effects in the agglomerate. The special aesthetic characteristics of these materials, which make them suitable for use with the said technology, are consequently their very high transparency, colourability, and long-term resistance to atmospheric agents. Moreover, their chemical nature makes them particularly suitable to bond indissolubly during the cross-linking process with the unsaturated polyester resin used as binder in the manufacture of agglomerated stones, without the aid of any adhesion promoter, as would be necessary if decorative fragments of glass or mirror were used. Moreover, the advantages deriving from the use of technopolymers in mixtures suitable for forming blocks or slabs of agglomerates with the vacuum vibro-compressure technology are not limited to appearance. An industrially designed composite material is characterised by the fact that its technical properties can be predicted on the basis of the initial raw materials, and more in general on the basis of their constituents; this is crucial to ensure that the material produced has the characteristics best suited to the required application and can be used in a wide variety of contexts. The characteristic feature of these materials is that the properties best suited to solving the technological problem can be obtained, such as mechanical properties, and in this case in particular, elasticity properties. The ability to produce a material with excellent mechanical characteristics, such as flexural strength under load, but with suitable elastic properties (in this case deriving from the modulus of elasticity of the component materials), definitely represents a success factor. In the case of agglomerated materials in general, unless there are any particular interactions between the components, the solution necessitates mediating the properties of the individual granules or phases in some way, using as weights a distribution function that takes account of the distribution of the orientations in the case of textured materials, together with the volumetric fractions of the constituents in the case of composites. As shown by the annexed figure, the logarithm model provides a far more effective method of predicting the modulus of elasticity of agglomerated materials than other formulas of similar simplicity, such as the parallel model or the Hirsh model, and satisfactorily interprets the experimental points (represented by the values identified by the triangle). As demonstrated by the graph, the required reduction in the modulus of elasticity of the compound (which is required to make the product more suitable for all applications for which it will be used in the construction industry, and more durable) is obtained almost exclusively by varying the percentage of the binder phase in the formula (the one with the lowest modulus of elasticity). As this variation is impossible when agglomerated stones are manufactured with vibro-compressure under vacuum technology, for reasons of compatibility with the manufacturing process, an alternative method of reducing the modulus of elasticity of the compound is proposed, namely introducing granular materials with a lower modulus of elasticity into the formula. The use of technopolymers with a much lower modulus of elasticity than that of natural stone achieves this object; in fact, no granular materials with such a low modulus of elasticity as thermoplastics like polymethyl methacrylate and polycarbonate exist in nature. Finally, these materials have the advantage that they can be used (added, mixed, distributed in the mixture and subsequently bonded in the mass) in the same way as any granular material; there is no need for any change in the conventional agglomerated stones manufacturing process, but they produce a more attractive appearance because of their nature as a decorative fragment. During the agglomerated manufacturing process, fragments of polymethyl methacrylate or polycarbonate can conveniently be added to the mixture during the primary or secondary mixing stage, or can be added to the mixture later; for example, the distribution can be limited to part of the mixture if required. Polymethyl methacrylates with a density of between 1.1 and 1.2 g/cm , light transmission of not less than 80%, and a modulus of elasticity of between 2500 and 3000 MPa, are particularly preferred. They are typically added to the mixture of stone material and resin in percentages ranging between approximately 1% and 20% in volume; preferably between approximately 2% and 5%. The shape and size of the technopolymer fragments can vary within a wide range, depending on the aesthetic effect sought. For example, the technopolymer fragments can take the form of flakes, needles, granules, rods, discoids, etc., and their size will range from a few tenths of a millimetre to a few centimetres. The other constituents of the mixture, such as resin, sand, powders, dyes and the like, can be the conventional type. The marble and/or quartz granulates usable in accordance with the invention typically have particle sizes of between 0.4 and 4.0 mm. The following examples illustrate the invention in greater detail. Example 1 % by volume Resin 17.5 Micronised powder 25.8 Sand with particle size of 0.1-0.3 mm 17.7 Quartz granulate with particle size of 0.4-0.7 mm 16.1 Quartz granulate with particle size of 0.7-1.2 mm 19.6 Dye 0.9 PMMA type 1 2.4 Example 2 % by volume Resin 16.9 Micronised powder 18.3 Crystalline powder with particle size of 0.1-0.3 mm 9.3 Marble granulate with particle size of 0.4-0.7 mm 10.7 Marble granulate with particle size of 0.7-1.2 mm 12.3 Marble granulate with particle size of 1.2-2.0 mm 29.9 Dye 0.2 PMMA type l 1.2 PMMA tyρe 2 1.2

Claims: CLAIMS 1. Agglomerated stones, obtainable by vibro-compressure under vacuum of resin and stone granulate mixtures in which fragments of technopolymers are dispersed. 2. Agglomerated stones as claimed in claim 1, in which the technopolymers are polycarbonate and polymethyl methacrylates. 3. Agglomerated stones as claimed in claim 2, in which the technopolymers are polymethyl methacrylates. 4. Agglomerated stones as claimed in claim 3, in which the polymethyl methacrylates have a density of between 1.1 and 1.2 g/cm , light transmission of not less than 80%, and a modulus of elasticity of between 2500 and 3000 Mpa. 5. Agglomerated stones as claimed in any one of claims 1 to 4, in which the granulate is marble or quartz. 6. Agglomerated stones claimed in any one of the preceding claims, also containing sand and dyes. 7. Agglomerated stones as claimed in any of the preceding claims, in which the stone granulate has a particle size of between 0.4 and 4.0 mm.

Inventors: GODI ALESSANDRO, TASSONE PIERPAOLO, GODI, ALESSANDRO, TASSONE, PIERPAOLO
Applicants: GODI ALESSANDRO, QUARELLA S P A, TASSONE PIERPAOLO, GODI, ALESSANDRO, QUARELLA S.P.A., TASSONE, PIERPAOLO
Application year: 2001
Main classification: C04B26
IPC codes: C04B26