07/10/2012

www.gupta-verlag.de/polyurethanes

Structural elements for the construction industry

The innovative process reduces by 66 % the thickness of the tile, still maintaining all the good characteristics - impact resistance, flatness, extended variety of surface decorations - in a product which weighs two thirds less than a competing, even if not yet existing in this size, ceramic tile. The robustness of these shatter-proof decorative elements is provided by a mat of glass fiber, glued onto their back using a very thin layer of two-component polyurethane adhesive. A dedicated metering, mixing and spraying solution has been designed by Cannon for this sophisticated application. An intense, joined effort has characterised the development phase of this innovative technology, with System and Cannon R&D specialists playing as a team to achieve the desired result. The customer
System S.p.A. is located in Fiorano, near Modena, the hearth of the Italian ceramic district, and operates in three major areas of activity: Ceramics, Logistics and Electronics. System is today recognized as a leading supplier of automated factories that provide the highest quality standards in the field of ceramics. The range of available solutions includes equipment and know-how for raw materials blending, pressing, decoration, firing, composite tiles production, cutting, quality control and sorting, packaging and handling. They quickly extended the initial ceramics technology to logistics and controls, two fundamental components of success in a very competitive, cost-driven field. Internal development of electronic controls and LGV's (Laser Guided Vehicles) provides their technological offer with a further integration of dedicated equipment. The System Group includes 28 local branches in 18 countries, devoted to the distribution and service of their equipment, with three local manufacturing sites in Spain, China and Brasil. The Group employs today a staff of 1,300, with a total turnover of EUR 280 million. [image_0] The Lamina process
Lamina is a highly automated productive process composed by seven main macro functions: deposition of raw material, pressing in press which vary from 15,000 to 26,000 tons, wet or dry decoration, gas/electric hybrid kiln cooking, composite tiles line, dry laser cut of final product and the packaging. The entire process rotates around a special compacting system which turns raw materials, such as clays and feldspars, into slabs. Lamina also revolutionises logistic systems for traditional ceramics because it deletes the final product storing as cutting and packaging of the slabs happens upon shipment on the basis of the specific order. Lamina indicates the assembly of deliverable products which lead to the use of 3.5 mm thick slabs, 1,000 x 3,000 mm or 1,200 x 3,600 mm and specific gravity of only 7 kg/m2. A 0.5 mm glass fiber layer, duly coupled with this Laminate, confers notable resistance and flexibility features. It is therefore possible to obtain different combinations from this fiber Laminate (doubled or tripled Laminates with fiber intervals) for applications where the physical features are essential. Lamina can be applied in the building field for coverings, floors and restructuring, for interior decoration (partition walls, false ceilings, doors and tables) and coverings, for design and for infrastructure (motorway galleries) including the photovoltaic field. The whole production cycle occurs here with a fully-automated concept, completely designed and built by various System Group's companies: raw material's milling and mixing, distribution of powder batches, pressing, trimming of the obtained slabs, decoration with up to six colours or three-dimensional patterns, cooking at high temperature, composite production, intermediate storage of the large tiles, laser (or traditional) cutting into the ordered sizes, optical control of final quality, packing and labelling. The request
The fragile nature of tiles is a fact well known for centuries. Even a porcelain gres tile features relatively poor impact resistance, and shatters in very sharp, dangerous fragments when hit by a violent impact. One can decide to make a thicker tile to improve impact resistance, but the weight, the raw materials, the energy required to cook it, the efforts made to transport and install it, the waste in case of defects and - final and fundamental - the cost increase with a linear growth. System was looking for a different solution. [image_1_right] Initial developments
When System decided to concentrate on the manufacture of the largest, lightest and thinnest ceramic slab ever, they realized that the solution to these problems would have been a radical innovation for the conservative world of ceramics: a continuous production process utilizing a non-conventional reinforcement. Several options were examined and - at the end of a wide selection of materials and processes - a true composite part was conceived, combining the aesthetic and wear resistant properties of a surface layer of porcelain gres with the mechanical strength and assembling capability of a flat layer of glass fiber. This approach - due to the peculiar characteristics of the chosen reinforcement, which is commonly supplied in large rolls of glass tissue, called mat - required a number of dedicated solutions. System started evaluating polyurethane as the adhesive for the glass mat reinforcing the grès layer. The Cannon solution
System contacted Cannon Afros to evaluate the availability of a dedicated machine for this application. Cannon Afros was at the same time System's supplier of dosing units for silicone resin processing (used by System to produce their own cast silicone printing rolls for the decoration of ceramics) and System's customer, having installed four of their automatic warehousing towers for their factory in Caronno Pertusella, near Milano, Italy. The response was prompt and positive. The specifications were well within those familiar to Afros for their range of machines, and the application was appealing. A preliminary set of trials in Cannon R&D labs would have verified the feasibility of the request, to be further refined with the most appropriate technical adjustments. Due to the characteristics of the formulation, a spray application was defined as the optimal method to evenly distribute the adhesive on the back of the large tiles. All the factors considered, Cannon set up in their lab a suitable Cannon B2 low pressure dosing unit connected to a dedicated spray mixing head mounted on a standard robot and organised a first set of trials with System's ceramic slabs and chemicals. The first trials provided soon very promising results. The layer of adhesive was evenly distributed, although a solution had to be designed to avoid a minimum build-up of material at the two extremes of the pouring pattern. The idea of applying a method widely used in the painting shops - a controlled air-assisted atomization of the liquid formulation, immediately after the mixing chamber -was evaluated. This method required the interruption of the flow of material at the end of each stroke. A very fast control and actuation was demanded, to follow the demanding performance of the head's manipulator. The existing model of low-pressure, low-output mixing head was fitted with an atomizer specially designed and promptly made for the viscosity and output of the chemical formulation selected by System for their needs. An extensive testing program submitted the new head to more than 60,000 spraying cycles both with and without chemicals, to prove the industrial usability of the new tool. The design proved to be adapt to the task. Since the response of the PLC controlling the spraying process was not fast enough to guarantee repetitive results under extreme speed conditions, a dedicate electronic circuit was designed and made in-house, able to provide as quickly as requested the commands to the injectors mounted on the mixing head. This final solution optimised the spraying process, guaranteeing an even application of few grams of a bi-component rigid, compact Polyurethane adhesive on each square meter of ceramic slab. [image_2][image_3] Composite production
The spray head ensures a perfect mix and deposition of the liquid blend, while the closed loop control system of the Cannon B2 dosing machine keeps all the variables (temperature, viscosity, mixing ratio, recirculation), within the desired working range. After the application of the adhesive the slabs go to the glass fiber application area, where a precisely cut-to-size piece of bi-directionally oriented glass fiber mat, is simply laid over the rigid support. A tooled antropomorphous robot then carries out the squeegeeing operation, to fully wet the glass mat with the still creamy polyurethane adhesive, to ensure top bonding and to prevent any air spots from being left. Then, the curing step to harden the bonding agent is made in a vertical stacker/drier. The product stops here for several minutes, then the protective film is removed and the finished slab is loaded automatically on the unloading tray. Two types of products can be obtained with this process: Lamina 3+, a 3 mm ceramic slab with a glass fiber structural reinforcement, for a total thickness of 3.5 mm.Lamina 7, a sandwich of 2 Lamina 3+ with an interposed glass fiber mat applied with polyurethane adhesive. Its physical features allow to pass the car crashing tests recommended for ventilated façades. A triple Laminate is also produced for special heavy-duty applications. A single line can manufacture 70 standard slabs per hour, while the more complex one can produce up to 35 double and triple slabs per hour. The stacks of finished slabs are brought to the central storage, where they stay parked until they are requested by the order processing software for a customized delivery. When tiles are ordered in sizes smaller than the large 3,000 x 1,000 mm, the slabs are sent to the automatic laser-cutting area. Product performances
Being 3 m2 and just 3.5 mm thick, Lamina can be used in the building sector to cover indoor and outdoor surfaces, new and existent walls and surfaces, ventilated and curtain walls, insulated walls, partition walls, tunnels and undergrounds; it can also be used in the ship building sector and in the healthcare, hospital and medical sector. Thanks to its lightness and good aesthetic quality, Lamina is an ideal solution to enrich interior design projects and give life to new applications in bathrooms, kitchens, on cupboards, tables, desks and furnishings in general. Lamina is the first surface that combines reduced thickness with large format, high resistance to mechanical stress, chemical attacks, scratching, deep abrasion and bending. The advanced technology adopted to produce the slabs makes them easy to clean and sanitise and resistant to frost, fire, mould and UV rays without altering colour, specifications and properties. Lamina is the first graffiti proof ceramic surface; it is easy to clean and even the strongest paints can be easily removed. The project jointly developed by Cannon and System Lamina has generated a composite laminate characterised by outstanding mechanical and aesthetic properties.

www.gupta-verlag.de/polyurethanes