PVB Sheet Recycling and Degradation

5 PVB Sheet Recycling and Degradation Michael Tupý1, Dagmar Měřínská1,2 and Věra Kašpárková2,3 1Department of Polymer Engineering, Faculty of Technology, Tomas Bata University in Zlin, Zlin, 2Centre of Polymer Systems, University Institute, Tomas Bata University in Zlin, Zlin, 3Department of Fat, Surfactant and Cosmetics Technology, Faculty of Technology, Tomas Bata University in Zlin, Zlin, Czech Republic 1. Introduction Increasing growth of raw material prices, environmental aspects and still growing landfill fees bring about the increasing interest encountered with the plastics waste recycling. Globally, the problem has been solved for the common plastics such as polyolefins, poly(ethylene terephtalate) and poly(styrene). Though extensively used for the glass lamination, poly(vinyl butyral) (PVB) does not belong to this group. It is generally known that during the glass lamination process, large volume of PVB trim is formed. The PVB polymer is mostly used in the form of plasticized PVB sheet for preparation of laminated safety glass (LSG). At present time, Solutia, DuPont, Seki sui and Kuraray are worldwide PVB manufacturers. The PVB is the material which can stick together float glasses with holding excellent optical and mechanical properties of the glass laminate (Ivanov, 2006; v. Elasticity, mechanical strength, toughness, high light transmission and the adhesion to glass are the most significant PVB properties (Tupý, Měřínská, et al, 2010). Toughness of PVB sheet is based on high molecular weight of PVB chain. Certainly, the PVB has to be plasticized for achieving high material elasticity (Iwasaki, et al, 2006; Keller, Mortelmans, 1999; Svoboda, Balazs., et al, 1988). Admittedly, the plasticizer must not reduce light transmittance through the sheet, PVB adhesion to glass, generate haze and yellowness, and migrate out of the polymer matrix (Wade, D'Errico, et al, 2004). In addition, plasticizer must have perfect compatibility with the polymer and low evaporability during processing conditions. 2. Sources for recycling of PVB sheet Worldwide, 65% of all PVB sheets are used in automotive applications (Dhaliwal, Hay, 2002). According to data from (OCIA, 2007), the worldwide car’s production is estimated around 60 millions cars per a year. Assuming that one windshield contains approx. 1 kg of PVB sheet, total amount gives between 60-70 million kg of PVB sheets per year. In addition, by-products from PVB sheets manufacturing (5%) and trimmings (< 10%) from windshield production must be added (Goroghovski, Escapante-Garcia, et al, 2005). It represents total amount of 80 million kg of automotive PVB sheet waste annually. Total worldwide amount of produced PVB sheets for automotive and architectural industry is estimated around 120 million kg per year. www.intechopen.com Material Recycling – Trends and Perspectives 134 2.1 By-product from sheet manufacturing process This kind of PVB sheet has the best quality for following recycling process. By-product sheets are not contaminated by powder fragments but there may be present some unhomogeneous parts like plasticizer, light and heat stabilizers, adhesion modifiers, pigments and other elements of the system. The reasons why the sheet has to be re-processed are some specified defects in manufacturing technology (thickness, sheet roughness, edges). In every case, sheet edges must be cut approx. 10-20 cm from the edge beginning. The PVB sheet with a width around 2-3 meters has very high material shrinkage in this place. The edges can be replaced back to the extrusion process for re-extruding (Zvoníček, 1999). 2.2 Trim The first step in LSG manufacturing is the lamination of PVB sheet between two glasses. It this part, probable defects on laminate edges must be reduced. It is performed by layering of PVB sheet between glasses with a larger sheet surface than the glass sizes are. Prepared “sandwich” is fixed by nipp-roll pre-lamination process and consequently it is possible to trim off oversized PVB sheet. While the sheet oversize would not be used, the laminate would be produced with visible defects (it does not meet the quality specifications) (Svoboda, Balazs., et al, 1988; Zvoníček, 1999). The quantity of a trim generation depends on the geometry of produced windshield and the geometry of used PVB sheet surface. The width of trim obtained from the pre-laminating process is around 1–20 cm, based on glass geometry. Therefore, the trim quantity is between 5-10% from total amount of processed PVB sheet and the worldwide PVB trim capacity obtained from the windshield laminating process is approx. 4-6 million kg (Svoboda, Balazs., et al, 1988; Zvoníček, 1999). The trim is created also at manufacturing of architectural LSG. Nevertheless, the ratio of a collected architectural trim is lower than amount of automotive trim. It is influenced by a higher glass powder contamination of this trim (different trimming technology) (Zvoníček, 1999). 2.3 PVB sheet from windshield Some specialized companies deal with the re-application possibility of PVB sheet obtained from recycled windshield. All present recycling processes produce a good quality of glass scrap which is fully re-used in the glass batch. However, the separated PVB waste is not recyclable due to high amount of glass, water content in the sheet, parts of color PVB sheets, mixed of various PVBs (after blending a haze is created) and foreign plastic matters (Zvoníček, 1999; Plaček, 2006; Recycling .., 2007; Tupý, Měřínská, 2011). Nevertheless, if somebody would develop the recycling technology ensures high-grade of glass separation, obtained PVB sheet may be re-processable to new PVB sheet without optical defects (Tupý, Měřínská, 2011). Moreover, it is necessary to remain that the laminated (interglassed) PVB is not essentially exposed to UV radiation (up to 320 nm), mechanical stress, elevated temperature, oxygen and any various substances. Thus, the interglassed PVB sheets should keep very similar www.intechopen.com PVB Sheet Recycling and Degradation 135 physical properties as extruded material before the lamination process and it can be reextruded and re-laminated to new PVB sheet again. 3. PVB sheet composition 3.1 Poly(vinyl butyral) The way assigned for PVB production is not easy. Firstly, it is necessary to produce poly(vinyl acetate) (PVAc) by the radical vinyl acetate polymerization. Consecutive hydrolysis at acidic or basic ambient creates poly(vinyl alcohol) (PVAl) which provides poly(vinyl butyral) by acetalization with butyraldehyde at acidic environment. The final structure of high-molecular PVB is used for LSG manufacturing and it is compounded from atactic copolymers 80% of vinyl butyral, 18-23% of vinyl alcohol and up to 1% of vinyl acetate [Wade, D'Errico, et al, 2004; Dhaliwal, Hay, 2002; D'Errico, Jemmott, et al, 1996; Nghuen, Berg, 2004; Svoboda, et al., 1970). This chemical structure, viewed in Fig.1, is the same for every manufacturer today. Nevertheless, exact consequence and properties of every PVB sheet depends on every PVB type, manufacturer and PVB sheet composition. The sheet is mostly stabilized by antioxidants and thermal stabilizers in many times (Saflex, 1993). Fig. 1. PVB chain structure with composition of functional groups: vinyl butyral 81%, vinyl alcohol 18-23%; vinyl acetate <1%. Final PVB properties are assigned by polymerization degree of input PVAc, distribution curve of molecular weight, PVAl hydrolysis degree, catalyst acid strength, reaction temperature and PVAl conversion degree to PVB. The last one is crucial for final polarity of produced PVB. The PVB polymer is white powder, dissolvable in ethanol, THF, ketones and other semi-polar dissolvent (Mrkvičková, Daňhelka, 1984). The PVB solubility depends on – OH group content in the polymer chain and PVB molecular weight (Physical prop.SekiSui, 2001). 3.2 PVB sheet Certainly, achievement of high PVB toughness must be proved by polymer plasticizing. However, the plasticizer must not considerably reduce light transmittance through the sheet, increase haze and yellowness, reduce PVB adhesion to glass and migrate out of the polymer matrix (Svoboda, Balazs, et al, 1988; Zvoníček, 1999). The plasticizer also must have perfect compatibility with polymer matrix and its evaporability during the processing is prohibited (Zvoníček, 1999). Different plasticizers, used in beyond, were for example triethylenglycol-di-2-ethylbutyrate, dibuthylsebacate, tetraethylenglycol-di-heptanoate and www.intechopen.com Material Recycling – Trends and Perspectives 136 dihexyladipate (Dhaliwal, Hay, 2001; Zvoníček, 1999). Mentioned plasticizers have different molecular polarity. There through, due to this it was indispensable to produce PVBs with different amount of hydroxyl groups in PVB chain (Dhaliwal, Hay, 2001; D'Errico, Jemmott, et al, 1996; Phillips, 2005). The final polymer system has a different absorbability of the plasticizer and water (Mrkvičková, Daňhelka, 1984). At present time, produced PVB sheets assigned for the glass lamination are plasticized with 28% of applied plasticizer; mostly triethylenglycole-bis(2-ethylhexanoete), (labeled 3GO) (Wade, D’Erricco, 2004; Phillips, 2005; Mister, Bianchi, et al, 2007; Smith, Rymer, et al, 2008). Due to mentioned sheet physical properties, the most important characteristics of windshield are high mechanical strength and absorbability of kinetic energy during carcrash (Keller, Mortelmans, 1999; Svoboda, Balazs, 1988). However, PVB interlayer must keep glass particles on its surface [2, 3]. All these described properties provide an exactly adjusted adhesion grade of PVB to glass. Because the PVB has exceedingly high adhesion degree it cannot be used for automotive glass lamination. Thus, high adhesion degree it is necessary to reduce to ½ of the original adhesion value (Keller, Mortelmans, 1999; Wade, D’Erricco, 2004; Dhaliwal, Hay, 2004; Smith, Rymer, et al, 2008). The virgin adhesion is reduced by an addition of organic salts of alkali metals or alkaline-earth metals during an extrusion process of plasticized PVB sheet. This is described in several patents (Smith, Rymer, et al, 2008; Aoshima, Shohi, 2000; D'Errico, 1995; D'Erroco., 1997; Fowkes, 1987 Herman, Fabian, et al, 1984; Shichiri, Miyai, et al, 2002). The mostly used substances modifying the adhesion are organic salts of Na+, K+ and Mg2+. Ion ratio and its total amount are strictly specified (Smith, Rymer, et al, 2008; Aoshima, Shohi, 2000; D'Errico, 1995; D'Errico., 1997; Fowkes, 1987 Herman, Fabian, et al, 1984; Shichiri, Miyai, et al, 2002). Moreover, the water content in PVB sheet must be in range 0.3-0.5% which is necessary for a maintaining the required adhesion grade (Keller, Mortelmans, 1999; Wade, D’Errico, 2004; D’Errico, Jemmot, 1995; Shichiri, Miyai, 2002). 4. Extrusion of PVB sheet The formation of the PVB trim is the consequence of the production technology, in which laminated glass without defects having irregular shape are manufactured. The PVB assigned for re-processing is usually recycled together with the waste sheets originating from the PVB manufacturing (Tupý, Zvoníček, et al, 2008). However, to find the ideal PVB re-processing conditions is not easy. Due to its composition, PVB is very sensitive to the degradation and the migration of plasticizer. It was found, that at the atmospheric pressure, plasticizer migrates at the temperature of 260 °C (Dhaliwal, Hay, 2002). During repeated processing of plasticized PVB, both water and plasticizer were reported to be extracted from polymer by vacuum. However, the loss of plasticizer at the common processing temperatures (up to 200 °C) is minimal (Svoboda, Balazs, 1998). Based on several authors (Keler, Mortelmans, 1999, Svoboda, Balazs, 1998; Nagai, 2001; Neher, 1936; Svoboda, 1987), all PVB sheet manufacturing technologies are based on similar principle. Melt plasticized PVB is extruded by sheet extrusion die at temperature 160-220°C into water. The screw placement is evacuated in order to adjust the water content in the www.intechopen.com PVB Sheet Recycling and Degradation 137 sheet. The PVB melt retains its shape, thickness and specific sheet surface which are necessary for de-aeration at pre-lamination process (Svoboda, Balazs, 1998; Zvoníček, 1999). Plasticizer and additives addition runs at mixing equipments before the extruder in many times. The PVB sheet is mostly manufactured at the thickness 0.38 mm (LSG for architectonical industry) and 0.76 mm (LSG for automotive and architectonical use). Special applications require thicknesses 1.14 and 1.52 mm. The width of PVB sheet can be up to 3.5 meters. Manufactured PVB sheet is rolled and either separated by thin patterned polyethylene sheet or rolled under-cooled (Tg = 15°C) because the PVB sheet must not be stuck for following use (Svoboda, Balazs, 1998; Zvoníček, 1999; Saflex, 1973). Shear and thermo oxidative degradation of polymer represents more serious problem observed during reprocessing. Both degradation types induce the cleavage of polymer chains, albeit the degradation mechanism is not the same. Generally, the shortening of polymer chains negatively influences mechanical properties of PVB, resulting in an undesirable lowering of safety characteristics of the produced sheet. The deterioration of mechanical properties of PVB consequently decreases its ability to absorb the mechanical energy (when it is used for the safety car glass) in the case of an accident (Tupý, Zvoníček, 2008; Tupý, Měřínská, 2010). On the other hand, a decreasing of molecular weight and a decreasing of viscosity caused by the degradation can favorably influence rheological properties of PVB melt during the extrusion on the flat die (Měřínská, Tupý, 2010; Grachev, Klimenko, et al, 1974). In order to decrease power consumption during re-processing, PVB hygroscopicity can be utilized. Because water contained in PVB matrix can act as an additional plasticizer and lower the rigidity of the material, processing of “wet” PVB can be advantageous (Mrkvičková, Daňhelka, 1984). However, during the re-processing of material containing high moisture content (8 %), water can react with butyric groups, which induces the change of the polymer structure. As the consequence, hydrolysis occurs significantly changing the final properties of the re-processed PVB (Dhaliwal, Hay, 2002; Měřínská, Tupý, 2010). The aim of the following test was to determine the degradation of PVB sheet at different kneading conditions and to estimate an influence of temperature, air oxygen content and mechanical stress on the course of degradation process. The work is also focused on the possibility to find optimal re-processing conditions of PVB whereat the mechanical and thermal degradation as well as yellowness of the re-processed polymer are minimal. 5. PVB sheet degradation by thermogravimetric analysis First of all, the relative thermal stability of commercial PVB sample was measured by thermogravimetric analysis, from mass loss against temperature plots. As the Fig.2 shows, weight loss occurred in two distinct regions between 175–325 and 325–500 °C and corresponding to about 27-28 and 65-70% mass loss. No marked differences were observed between the various commercial grades. The first part of temperature range is the plasticizer evaporation. The final weight loss was the same for all the samples and a brown residue, approximately 5% of the original mass (Tupý, Měřínská, 2011). The evolved volatiles were analyzed by mass spectrometer as a function of time and temperature at fixed m/z ratios. www.intechopen.com Material Recycling – Trends and Perspectives 138 These corresponded to the top m/e ratio for acetic acid, butenal, butyraldehyde, benzene and toluene the expected products from the thermal decomposition of PVB (Wade, D’Errico, 2004). Fig. 2. TGA evaluation of plasticized Butacite PVB sheet. Little or no degradation products were observed below 250 °C although the PVB samples had lost about 10–12% of mass under these experimental conditions were initially. The major products of the decomposition were observed above 260 °C. Acetic acid was a minor component of the volatile degradation products. Aromatic species, such as benzene and toluene, were also observed. These have been attributed to the break down of the polyene products produced by the elimination reactions. From the relative % mass loss and the absence of volatiles detected by the mass spectrometer it was deduced that the PVB was primarily losing plasticizer in the temperature volatilization process between 200 and 260 °C. The loss of additives from a polymer is a complex process involving diffusion, transport and evaporation from the surface of the polymer. 6. Degradation by kneading 6.1 Samples preparation By the reason of finding degradation mechanism of plasticized PVB, this material was reprocessed by kneading, rolling and pressing. Both dry (0.5 % water) and wet (8% water) sheets were tested. Increasing moisture content was reached by the soaking of “dry” PVB sheet in water for 14 days (Grachev, Klimenko, 1974). Samples stressed by kneading were prepared in the Brabender kneader with two blunders W50 at the friction of 2:3. Volume of the heated chamber was of 55 cm3. Constant amount of www.intechopen.com PVB Sheet Recycling and Degradation 139 40 g PVB was placed in the chamber and processed for 10 minutes at different temperatures (100, 130, 160, 190, 220 °C) and rotation speeds (40, 60, 80 rpm). The chamber of kneader was filled only to the ¾ of the volume in order to have the sufficient amount of oxygen in order to study thermo-oxidative degradation. During kneading, both thermo-oxidative and shear degradation are assumed to take place. In order to simulate solely shear degradation with absence of thermal stress, PVB sheets were re-processed by rolling at the temperature of 78°C in the presence of air. Laboratory double-roller was used. Rollers were preheated to 60-70°C in order to allow the PVB calendaring corresponding to processing of the rubber. After the initial preheating, the roller temperature was kept only by the energy dissipation. After 10 minutes the temperature reached 78°C and this value remained almost unchanged. Pure thermal degradation with low shear stress was simulated by pressing. PVB was placed between two PET sheets preventing the contact with air and thus oxidative degradation. Then, the material was pressed at 1 MPa at temperature of 160, 190 a 220°C for 10 minutes. Dry PVB was tested at all the above presented conditions; wet one was tested at all temperatures but only with 60 rpm. 6.2 Analysis and methods Mechanical properties of the stressed samples were determined using a T 2000 Tensile tester (Alpha Technologies) with the displacement rate of 500 mm/min at room temperature. For testing, material was pressed onto the plates with the thickness of 1.0 mm at the temperature of 130°C and the standard testing specimens were prepared. Tensile strengths and strain were determined. Rheological properties of re-processed samples were tested in terms of MFI measurements using the extruding plastometer M201 (Haake) according to EN ISO 1133. Samples were conditioned at 25% relative humidity and then extruded at 150 °C through the 2 mm capillary using the load of 100 N. The MFI correlates to the polymer mass passing through a standard capillary in an interval of 10 minutes, at a given load. Quantification of water content was carried out by the Karl Fischer method (Metrohm AG). The method is based on the conductometric determination of water evaporated from the sheet into the iodine solution and sulphur dioxide in methanol. Yellowness was evaluated using the CIE Lab. colour scale. Handy Color (BYK Gardner) instrument was applied and calibrated with the white and black standards. Measurement was carried out against the white background at the angle of 10°. Illumination type of D65 corresponding to daylight was applied. Yellowness YID, was calculated from the measurements of spectroscopic values L, a and b. The obtained value was converted to the value corresponding to the PVB sheet with the standard thickness of 0.76 mm, which is typical for applications in automotive industry and in architecture. Thermo-gravimetric analysis (TGA) was determined by thermogravimetric analyzer TGA Q500 (TA Instruments, New Castle, USA) in open platinum crucibles and weighed-in. Amount of PVB sample for thermal analysis was approx. 8 mg and measurements were www.intechopen.com Material Recycling – Trends and Perspectives 140 taken in temperature interval 20-500 °C, dT/dt = 10 °C min-1 in protective nitrogen atmosphere (150 mL min-1). GPC analyses were conducted using a PLGPC-50 (Polymer Laboratories) equipped with a PL differential refractometer (DRI) and on-line viscometer detectors (VIS). Analyses were performed with a PL gel Mixed-C column (7.8 x 300 mm; Polymer Laboratories) at 30 °C with the mobile phase flow rate of 1 mL/min. Tetrahydrofurane was used as the mobile phase. The column was calibrated using narrow molecular weight polystyrene standards (Polymer Laboratories Ltd, Church Stretton, UK) with molecular weights ranging from 580 to 451 000 g.mol-1 (given by supplier). A 100 μL injection loop was used for all measurements. For the determination of molecular weight, universal calibration was applied. Data processing was performed with Cirrus GPC, Multi Detector Software. The concentration was of about 0.2 g /100 ml and samples were dissolved at room temperature for 20 hours under stirring. The combination of both types of detectors enabled to exactly determine molecular weight as well as detect the PVB aggregation. 6.3 The influence of kneading conditions on the change of plasticized PVB sheet properties From the theory and practice it is confirmed that the PVB re-processing brings about the shortening of macromolecular chains, which induces the change of its mechanical properties. The results show that increasing of the re-processing temperature brought the lowering of melt rigidity (measured as MFI), lowering of tensile strength and strain. These changes are visualized in Figs. 3-4. The MFI values are shown in Fig.3. To sum up, the MFI increases with the increasing of reprocessing temperature and the increasing of rotation speed systematically up to 60 rpm. Fig. 3. The change of MFI at the different conditions of the kneading of PVB sheet with water content 0.5%. www.intechopen.com PVB Sheet Recycling and Degradation 141 It is consequence of thermo-oxidative degradation, which causes reduction of polymer molecular weight. However, at the rotation speed of 80 rpm, the MFI values behave differently. Degradation of PVB macromolecular chains (expressed as increasing of MFI) is reduced at the temperatures above 190 °C, which is indicated by no rising or even slight drop of MFI (see Fig.3). The lowering of the degradation at the higher rotation speed (above 80 rpm) is possible to explain by the sliding of polymer chains in the stressed melt resulting in the lower effect of kneading. The results obtained from the measurement of tensile strength of the “dry” PVB samples (0.5 % moisture content) in dependence on speed of the kneading shaft are shown in Figure 4. At lower temperatures, degradation of “dry” PVB is proportional to increase of the rotation speed. For example, during processing at 100 °C degradation increased, which can be concluded from the lowering of stress at break values (shape of the curve in concave). On the other hand, increasing of temperature caused straightening of this dependence and for the samples processed above 160 °C the curves exhibit the convex curving. Minima on the curves observed at rotation speed of 60 rpm and temperatures 190 and 220 °C indicate, hence, the highest degradation of PVB. Samples re-processed by pressing were used as a background for the kneaded samples at the same temperatures. Slight increase of tensile strength, strain at break, MFI and yellowness were observed for the samples pressed for 10 minutes at the all tested temperatures. Fig. 4. Tensile strength of the re-processed PVB sheet at the different conditions of the kneading of PVB sheet with water content 0.5%. 6.4 The transformation of the process energy into heat During the PVB re-processing on the Brabender kneader the temperature of the kneading chamber was measured. The chamber was tempered on the required temperature, but with on-going process of kneading, the temperature slightly increased. The course of temperature www.intechopen.com Material Recycling – Trends and Perspectives 148 parameters and degradation was examined. The obtained results show that, based on the evaluation of MFI and mechanical properties, the optimal conditions for PVB re-processing by kneading occur at the temperature of about 150°C and rotation speed of kneader lower than 60 rpm. These conclusions are in the good agreement with the measurement of PVB yellowness. Below 150 °C yellowness remained almost unchanged and increased significantly above this temperature. GPC measurements corroborate the above conclusions showing minimal changes of PVB molecular weigh for this temperature. Increased amount of water in PVB sheet can act as and additional plasticizer improving workability of polymer melt and decreasing this energy consumption. However the “wet” samples are more susceptible to hydrolytic degradation and compromise decision has to be taken to find the balance between these two effects. 10. Acknowledgement This article was written with support of Operational Program Research and Development for Innovations co-funded by the European Regional Development Fund (ERDF) and national budget of Czech Republic, within the framework of project Centre of Polymer Systems (reg. number: CZ.1.05/2.1.00/03.0111). 11. References Aoshima Y., Shohi H., (Jun 6, 2000), Intermediate film for laminated glass and laminated glass, European Patent EN1227070A1, D'erric J.J., Jemmott B.A., et al, (Dec 29, 1995), Plasticized polyvinyl butyral and sheet, United States Patent 6,559,212 D'errico J.J., Jemmott B.A., et al, (Dec 24, 1996), Plasticized polyvinyl butyral and sheet, European Patent EP 0,877,665 D'errico J.J., (Nov 12, 1997), Control of adhesion of polyvinyl butyral sheet to glass, European Patent EP 0,938,519B1 Dhaliwal A.K., Hay J.N., (2002), The characterization of poly(vinyl butyral) by thermal analysis. Journal Thermochemica acta, Vol. 391, pp. 245-255 E.E. 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Glass union concern: Research and developing institute of industrial glass in Teplice, Issue C(1) Tupý M., Zvoníček J., et al, (2008), Problems of recycling PVB sheet used for production laminated safety glass, Tomas Bata University, Faculty of Technology: Plastics and Rubbers, Vol.45, pp. 208-211 www.intechopen.com Material Recycling – Trends and Perspectives 150 Tupý M., Měřínská D., et al, ( 2010), Influence of water and magnesium ion on the optical properties in various plasticized PVB sheets, Accepted for publication in Journal of Applied Polymer Science, Vol. 118, pp. 2100-2108 Tupý M., Měřínská D., (2010), Water and acid-base reactants impact to adhesives properties of various plasticized PVB sheets, The Paper submitted to Journal of Applied Polymer Science Tupý M., Měřínská D., et al, (2001), Windshield recycling focused on effective separation of PVB sheet, The Paper submitted to Resources, Conservation and Recycling Wade B.E., D'errico J., et al, (Mar 16, 2004), Polymer sheets and methods of controlling adhesion of polymer sheets to glass, United States Patent Application US 20050208315 Zvoníček J., (1999), Collection of findings close to PVB extrusion process, Non-publish message, Retrim-CZ, Zlín www.intechopen.com Material Recycling - Trends and Perspectives Edited by Dr. Dimitris Achilias ISBN 978-953-51-0327-1 Hard cover, 406 pages Publisher InTech Published online 16, March, 2012 Published in print edition March, 2012 InTech Europe University Campus STeP Ri Slavka Krautzeka 83/A 51000 Rijeka, Croatia Phone: +385 (51) 770 447 Fax: +385 (51) 686 166 www.intechopen.com InTech China Unit 405, Office Block, Hotel Equatorial Shanghai No.65, Yan An Road (West), Shanghai, 200040, China Phone: +86-21-62489820 Fax: +86-21-62489821 The presently common practice of wastes' land-filling is undesirable due to legislation pressures, rising costs and the poor biodegradability of commonly used materials. Therefore, recycling seems to be the best solution. The purpose of this book is to present the state-of-the-art for the recycling methods of several materials, as well as to propose potential uses of the recycled products. It targets professionals, recycling companies, researchers, academics and graduate students in the fields of waste management and polymer recycling in addition to chemical engineering, mechanical engineering, chemistry and physics. This book comprises 16 chapters covering areas such as, polymer recycling using chemical, thermo-chemical (pyrolysis) or mechanical methods, recycling of waste tires, pharmaceutical packaging and hardwood kraft pulp and potential uses of recycled wastes. How to reference In order to correctly reference this scholarly work, feel free to copy and paste the following: Michael Tupý, Dagmar Měřínská and Věra Kašpárková (2012). PVB Sheet Recycling and Degradation, Material Recycling - Trends and Perspectives, Dr. Dimitris Achilias (Ed.), ISBN: 978-953-51-0327-1, InTech, Available from: http://www.intechopen.com/books/material-recycling-trends-and-perspectives/pvb-sheetrecycling-and-degradation-