Abstract:
A method for recycling of glass laminates ( 10 ) is disclosed. The glass laminates ( 10 ) comprise at least one glass layer ( 30, 40 ) and at least one polymer layer ( 20 ). The method comprises mechanical removal of at least part of the glass ( 30, 40 ), placing residual waste ( 350 ) with glass particles in a vat ( 360 ) comprising a separation fluid ( 375 ) to produce a mixture of glass particles and polymer pieces from the residual waste, from which the polymer pieces can be screened off, washed and dried for reuse. The separation fluid ( 375 ) comprises water and at least one alcohol.

Description:
FIELD OF THE INVENTION 
       [0001]    The invention comprises a method and apparatus for recycling laminated glass comprising a laminate of at least one glass layer and at least one polymer layer. 
       BACKGROUND OF THE INVENTION 
       [0002]    Laminated glass is a type of safety glass that holds together when the glass is shattered. In the event of breakage, the glass is typically held in place by a further polymer layer, which may be made of a polymer layer comprising polyvinyl butyral (PVB). 
         [0003]    Typically, the polymer layer is one or more interlayers sandwiched between two or more glass layers. The interlayer(s) keeps the glass layers bonded to the interlayer, even when one or both of the two glass layers are broken. The high strength of the interlayer prevents the glass layer(s) from breaking up into large sharp pieces. 
         [0004]    Laminated glass is typically used in car windscreens, but finds other applications such as in skylights in buildings or in hurricane regions, in which the glass needs to be prevented from shattering when exposed to high winds. The polymer layer also gives the glass a higher sound insulation rating, which means that the laminated glass can also be used near freeways or railway lines to improve the sound insulation of interior rooms. 
         [0005]    Bullet-resistant glass is also known which is made of an interlayer of polycarbonate thermoplastic sandwiched between two glass layers. Similarly aircraft windshields use three layers of glass with thick PVB layers sandwiched between the glass layers. 
         [0006]    The laminated glasses have many applications, as discussed above. However, disposal of the laminated glass is problematic. The laminated glass used in car windscreens may no longer be disposed in landfill sites in the European Union. One method of recycling is to place the laminated glass into a rolling mill to fragment the laminated glass. The application of heat then melts the laminating plastic in the interlayer, thus allowing both the glass and the laminating plastic layer to be recycled. This requires the application of energy, which is inefficient. 
       Prior Art 
       [0007]    The use of microemulsions for the separation of laminates is known, for example, from the Applicant&#39;s co-pending patent application No. WO 2012/101189, which teaches the separation of layers in laminates from each other. The teachings of that disclosure are directed towards the separation of laminates used in photovoltaic modules and there is no mention of their application to laminated glass. 
         [0008]    A number of patent applications are known that deal with the recycling of laminated glass. For example, German patent application No. DE 198 111 99 teaches the dissolution of the entire polymer layer. 
         [0009]    German patent No DE 42 13 450 also describes the separation of the polymer layer from glass using a chemical method. The chemicals used include acetic acid and sodium hydroxide solution. 
         [0010]    U.S. Pat. No 8,530,531 also teaches the use of acetic acid for separating the glass layers. 
         [0011]    International patent application No. WO 99/02460 uses two filtration steps to separate the materials in a recycling plant. One issue known from the teachings of the international patent application is that the material being recycled tends to clog up the piping in the recycling plant. 
         [0012]    European patent application No. EP 2 380 736 teaches a method and apparatus for separating a laminate comprising at least two glass sheets bonded together by at least one polymeric interlayer film made of PVB. The method comprises adhering the laminate using one of the glass sheets to one or more suction cups, and attaching at least one other glass sheet to a fixation means. The laminate is heated above the softening point of the polymeric interlayer film and the suction cups are moved relative to the fixation means, thereby sheering off the interlayer film and separating the glass sheets. 
         [0013]    A subsequent step is used to remove any remaining traces of the interlayer polymer film from the glass sheets. This is done at an elevated temperature (50° C. to 150° C.) and pressure (up to 15 bar), optionally using an organic solvent, such as ethanol or isopropanol. The elevated temperature and pressure require a large amount of energy and furthermore the use of these flammable alcohols means that there is a risk of an explosion. 
       SUMMARY OF THE INVENTION 
       [0014]    A method for the separation of at least one polymer layer from at least one glass layer in a laminate is disclosed. The method comprises placing the laminate in a vat comprising a separation fluid. The separation fluid comprises a mixture of water and at least one alcohol. 
         [0015]    The at least one alcohol is selected from the group of water-soluble alcohols such as butyl diglycol or butyl glycol and the polymer layer is made of polyvinyl butyral (PVB). The use of butyl diglycol and/or butyl glycol reduces the risk of an explosion compared to the use of flammable alcohols, such as ethanol and isopropanol alcohol, as known in the prior art. 
         [0016]    A method for recycling laminated glass is also disclosed. The laminated glass comprises at least one polymer layer and at least one glass layer. The method comprises shredding the laminated glass to produce glass and residual waste (comprising polymer pieces with embedded glass particles), placing the residual waste in a vat comprising the separation fluid to produce a mixture of glass particles from the glass layers and polymer pieces from the polymer layer and the separation fluid. The method of this disclosure is performed at normal atmospheric pressure and only mildly elevated temperatures (30-50° C.), which reduces the amount of energy required for performing the recycling as well as substantially simplifying the apparatus used. 
         [0017]    The method further comprises extraction of, washing and drying the polymer pieces from the mixture. The separating fluid and any remaining washing water can be re-cycled, which reduces disposal costs and environmental damage. 
         [0018]    An apparatus for the recycling of the laminates is also disclosed. The apparatus comprises a vat having the separation fluid, a device for adding portions of the laminates into the vat and a sieving device for sieving polymer pieces from the separation fluid comprising the separated glass particles. 
         [0019]    The apparatus may also comprise a shredding device for shredding the laminated glass and removal of a substantial proportion of the glass particles, prior to transportation of the objects comprising the polymer pieces with remaining ones of the glass particles to the vat. 
     
    
     
       DESCRIPTION OF THE FIGURES 
         [0020]      FIG. 1  shows one illustrative example of a laminated glass, which is recycled using the method of this disclosure. 
           [0021]      FIG. 2  shows a flow diagram of the method using the teachings of this disclosure. 
           [0022]      FIG. 3  shows an overview of the apparatus for recycling using the teachings of this disclosure. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0023]    The invention will now be described on the basis of the drawings. It will be understood that the embodiments and aspects of the invention described herein are only examples and do not limit the protective scope of the claims in any way. The invention is defined by the claims and their equivalents. It will be understood that features of one aspect or embodiment of the invention can be combined with the feature of a different aspect or aspects and/or embodiments of the invention. 
         [0024]      FIG. 1  shows a non-limiting example of a laminate  10  used in a car window glass. The laminate  10  comprises a polymer layer  20 , which is laminated as an interlayer between a first glass layer  30  and a second glass layer  40 . 
         [0025]    The laminate  10  is used, in one aspect of the invention, in a car windscreen (also called windshield). It was noted in the introduction that the laminates also find application in a number of other fields and the teachings of this disclosure are not limited to laminated glass for car windscreens. In a further aspect of the invention, the laminate  10  comprises to three glass layers between which two polymer layers are interlaid. 
         [0026]    In one non-limiting example of the invention, the polymer layer  20  is made of polyvinyl butyral (PVB), which is typically used in car windscreens. Other thermoplastics can be used as the polymer layer. 
         [0027]      FIG. 3  shows an example of a recycling plant for the recycling of the laminates  10 . It will be appreciated that the plant shown in  FIG. 3  is merely exemplary and is not limiting of the invention. The plant includes a shredder  310  and a vat  360 . The shredder  310  crushes and shreds the glass laminate  10  mechanically. The vat  360  has a fluid dispenser  370  for dispensing separating fluid  375  into the vat  360  and a mixing device  365 . The vat  360  has an outlet  390  for removing materials  380  from the vat  360 . It will be noted that the shredder  310  and the vat  360  do not need to be co-located. In one aspect of the invention, at least some of the elements of the plant will have anti-adhesive PTFE coatings, which reduces the risk of clogging of the pipework in the plant. The outlet  390  leads to a sieving device  393  to sieve out the polymer pieces, a washing device  395  and a drying device  396 . Device  399  represents schematically a device to package and reuse the polymer pieces, which could be an extruder or a melting device. 
         [0028]    Washing water from the washing device  395  can be treated in a treatment device  397  to enable reuse of the washing water. A filtering device  394  is connected to the sieving device  393  to clean used separating fluid  375  from glass particles and return the filtered separating fluid  375  back to the fluid dispenser  370  for re-use. 
         [0029]      FIG. 2  shows an outline of the method for recycling of the glass laminates  10  of this disclosure. The glass laminates  10  are collected together as portions  300  of the glass laminates  10 . On arrival in step  200  at the recycling plant, the glass laminates  10  are placed into the shredder  310  and crushed or shredded in step  210  to produce glass from the glass layer  30  and  40 , as well as pieces of the polymer layer  20  with residual particles of glass ( 350 ), partially impregnated therein as splinters. 
         [0030]    The pieces of the polymer layer  20  are separated in step  220  from the glass of the glass layers  30 ,  40 . The glass is recycled, as is known in the art. In step  240 , the remaining laminate portions comprising the polymer pieces with the residual glass particles  350  are added to the vat  360  with a separation fluid  375  from the fluid dispenser  370 . The mixture of the separation fluid  375  and the polymer pieces is then mixed in step  260  in the vat  360 . The effect of the separation fluid  375  is thought to be to swell the surface of the polymer pieces and thus “expel” the glass particles from the surface of the polymer pieces. This is achieved at a given temperature, for example between 0° C. and 50° C., at atmospheric pressure during a treatment time of between 10 and 180 minutes. 
         [0031]    The material  380  comprising the separating fluid  375  and the polymer pieces, as well as any residual glass pieces, can be removed in step  270  from the vat  360 . The polymer pieces can be removed in step  280  by sieving in device  393 . It will be noted that the separating fluid  375  and any residual glass pieces pass through the device  393 . The separating fluid  375  is then filtered with device  394  for recycling in step  281  and placed back into the fluid dispenser  370 . The filtering step  281  removes substantially all of the residual glass pieces and any other impurities from the separating fluid  375 . 
         [0032]    The polymer pieces are washed in washing water in step  283  in a washer  395  and dried in step  286  in the dryer  396 . The polymer pieces can be extruded or packaged for reuse in step  290 , e.g. for use in the manufacture of new windshields. The washing water needs to be treated in step  293  before the water is also reused. The treatment of the washing water is done by filtering out any glass and other impurity particles from the washing water and by removing any remaining separating fluid from the washing water in the treatment device  397 . The filtering and the removal of the separating fluid is done, for example, by regular and/or cross flow filtration techniques and reverse osmosis, which allows reclaiming chemicals of the separation fluid from the washing water. 
         [0033]    The separation fluid  375  used in the vat  360  and coming from the fluid dispenser  370  is a solution of a water-soluble alcohol in water. Non-limiting examples of such water-soluble alcohols include lower alcohols such as methanol, ethanol, n-propanol, isopropanol, n-butanol, sec.-butanol, tert.-butanol and 2-methylpropanol, pentanols, benzyl alcohol, glycol ethers such as methyl glycol, ethyl glycol, propyl glycol, isopropyl glycol, butyl glycol, butyl diglycol, butyl triglycol, methyl diglycol, methyl triglycol, ethyl diglycol, to phenyl glycol, phenoxy propanol, methoxy propanol, methoxy butanol, ethoxy propanol, propylene glycol butyl ether, di(propylene glycol) butyl ether, tri(propylene glycol) methyl ether, tri(propylene glycol) butyl ether and others, such as diacetone alcohol or ethyl lactate. 
         [0034]    The separation fluid  375  is kept between 0 and 50° C., and at pH values of around 7. The speed of the reaction depends to a large extent on the diffusion rate into the surface of the polymer layer, which itself is governed by the choice of the alcohol, the concentration of the alcohol, and the temperature. 
       Examples of the Separating Fluid and Process Conditions 
       [0035]    The examples listed below are merely illustrative examples of a suitable separating fluid and the process conditions and are not limiting of the invention. 
         [0036]    A 25% solution of butyl diglycol in water was used as the separating medium  375 . The treatment time was 2 hours at 40° C. at normal atmospheric pressure. 
         [0037]    A 25% solution of butyl diglycol in water was used as the separating medium  375 . The treatment time was 3 hours at 30° C. at normal atmospheric pressure. 
         [0038]    A 25% solution of butyl diglycol in water was used as the separating medium  375 . The treatment time was 2 hours at 35° C. at normal atmospheric pressure. 
         [0039]    A 20% solution of butyl diglycol in water was used as the separating medium  375 . The treatment time was 2 hours at 40° C. at normal atmospheric pressure. 
         [0040]    A 10% solution of butyl glycol in water was used as the separating medium  375 . The treatment time was 1.5 hours at 40° C. at normal atmospheric pressure.