Whilst larninated safety glass is used in building, it is the use thereof in motor vehicles that present. the greatest challenges to recycling. This much is evident from even a cursory comparison of the recycling rate for glass from motor vehicles, which is. relatively low compared to the rate for household waste : 25% or over 440, 000 tonnes in 1997 in the United Kingdom compared to current quantities of less than 0.1 million tonnes of glass waste recovered from motor vehicles in the United Kingdom in the same period.

This low rate of recovery of automotive laminated glass can be attributable, in part, to the fact that the availability of domestic glass waste tends to depress the prices of glass cullet generally. However, the low rate of automotive laminated glass recovery is also a function of the relatively high cost of recycling automotive glass, compared to the relatively low cost of recycling domestic glass waste.

A number of technical problems are inherent in the processing of automotive laminated safety glass The methods used to fix non-movable glazing into a vehicle body aperture are seeing a trend away from"gasket sealing"techniques in favour of the use of"direct bonding" methods, since the latter techniques supplement vehicle body strength and rigidity. The glass is glued into place using adhesives, normally polyurethane adhesives.

These adhesives make the glass difficult to remove in one piece and provide an additional source of cullet contamination.

To further complicate matters, the adhesive zone (that extends around the edge of the fixed glass pane) is normally overprinted with ceramic coatings. that are printed and fired into the glass. The resuttant opaque edgecoatirfg hot ohty coneeais the adhesive zone from external view, but is also necessary to reduce ultra-violet light-induced degradation of the adhesives. However, the ceramic coating introduces additional cullet contaminants, most notably traces of cobalt, which interfere with downstream glass colour-ring processes when recycled cullet containing such ceramic contaminants are jntroduced into the glassmaking. process. The ceramic coating can be cut off if necessary, but it will be appreciated that this introduces an additional process step-and therefore. additional cost.

) n addition ; the PVB interlayer renders laminated safety glass parts much more difficult and hence expensive to remove and recycle. Not only does the glass have to be separated . om the interlayer, : but there is currently almost no market for the residue plastic. The emergence of a market for this high performance plastic, which as a virgin materials very expensive, might go some way to offsetting the cost of laminated safety glass recycling.

It Will be self-evident, therefore, that any process that will reduce costs in the recycling of laminated safety glass and automotive laminated glass in particular, is to tXe welcomed.

A number of processes are known in the processing of scrap automotive windscreens.

Most of these processes involve one or more crushing stages that are used to smash the glass and separate it from the PVB interlayer The fragments of interlayer and other contaminants are then separated from the glass in a screening step.

A typical example of such a process is to be found in a windscreen processing system supplied by Andela Tool & Machine, Inc., Richfield Springs, N. Y. and which is described in United States Patent No. 5,984, 216-Andela. This system uses compression feed rollers to guide scrap windshields through steel flailing arms and flexible impactors that flail the glass off the plastic membrane, while keeping plastic pieces as large as possible for removal during screening. The supplier claims that a single pass through one of these systems separates the glass from the interlayer and pulverizes the glass into a clean, homogenous product of less than 2. 5rnm in size. The interlayer is broken up into pieces of 25mm or larger. These small particle sizes limit the potential uses of the resultant scrap materials, particularly if the resultant cullet is to be used in direct fired furnaces that are unable to operate sustainably with the addition of the large quantities of glass fines

inevitably produced in any pulverising process, such as that proposed by the Andela system.

It is an object of this invention to address the concerns outlined above.

Summary of the invention According to this invention a system is provided for recovering cullet from a laminated glass sheet that includes at least one layer of glass adhered to a plastic interlayer, the. system including means to crush the sheet to break the gtass into smat) gtass pieces and a screen to separate the glass pieces from the interlayer, characterised in that the glass crushing means is constituted by a pressure roller that is adapted. to bear against and roll across nn elasticaily deformable pressure pad which is adapted to support the glass sheet in use, the pressure pad being adapted to deform elastically under pressure applied by the pressure roller, at least partially to adopt the curvature of the pressure rotter.

In use, the sheet of glass located on the pressure pad is forced to deform as the pressure pad deforms to adopt the curvature of the pressure roller. It is this deformation, which can be controlled to some extent by the selection of an appropriate diameter of the pressure roller, which causes the glass to crack and fracture into small pieces. The roller diameter and the degree of deformation of the pressure pad is selected, however, to ensure that the integrity of the intertayer is maintained in the process, thereby yielding a crushed glass sheet consisting of an integral interlayer sheet with the glass still adhered thereto, but broken into small pieces by a network of fractures.

The glass crushing means is preferably constituted by set of opposed pressure rollers and, interposed therebetween, an elastically deformable pressure pad constituted by a sheet of elastically deformable material which is adapted to support the glass sheet in use, at least the surface of the pressure pad supporting the glass sheet in use being adapted to deform elastically at least partially to adopt the curvature of the pressure roller that bears against that surface, under pressure applied by the pressure rollers in use.

In this embodiment of the invention, the pressure rollers may conveniently be mounted in a relatively stationary roller assembly with the pressure pad constituted by an endless loop of sheet n-material mounted on transport rollers, such as conveyor idler rollers, located on either side of the roller assembly, for movement of the pressure pad between the pressure rollers in the manner of a conveyor belt.

In a developed form of the invention, one or more additional pressure rollers are provided together with control means to operate the pressure rollers such that the downstream pressure rollers, having regard to the notional direction of travel of the glass sheet, are rotated faster than the upstream pressure rollers. The faster rotating rollers tend to draw the glass sheet away from the slower upstream rollers, thereby stretching theiinterlayer and increasing the gaps and interstices between the glass pieces adhered to the interlayer sheet. This will allow better penetration of the alkaline solution between the glass pieces and the interlayer and facilitate the weakening of the adherence between the glass pieces and the interlayer In this embodiment of the invention, each set of pressure rollers may conveniently be mounted in a relatively stationary roller assembly, each with its own pressure pad constituted by an endless loop of sheet material mounted on transport rollers.

The system of the invention may include means to apply an alkali to the sheet to weaken the adherence of the glass pieces to the interlayer before the crushed sheet is screened.

The alkali of preference is soda ash due to its availability in and compatibility with conventtonat glassmaking practices, the system including means to sprinkle the soda ash over a sheet of glass after the glass has been crushed and means to spray the sheet with water.

The invention includes a method of recovering cutlet from a laminated glass sheet that includes at least one layer of glass adhered to a plastic interlayer, the method including the step of crushing the sheet to break the glass into small glass pieces which is characterised by the steps of placing the glass sheet on an elastically deformable pressure pad which is adapted to support the glass sheet in use and rolling a pressure roller over the glass sheet to crush the glass, the pressure pad being adapted to deform elastically under pressure applied by the pressure roller, at least partially to adopt the curvature of the pressure rotter.

The method of the invention may include the steps of treating the glass sheet with an alkali to weaken the adherence of the glass pieces to the interlayer and separating the glass pieces and the interlayer by screening.

In the preferred form of the invention the glass crushing means is constituted by a set of opposed pressure rollers and, interposed therebetween, an elastically deformable pressure pad constituted by a sheet of elastically deformable material which is adapted to support

the glass sheet in use, the method including the steps of locating the glass sheet on the support surface of the pressure pad, transporting the glass sheet through the nip between the pressure pad and the pressure roller that bears against the. pressure pad support surface to crush the glass, at least the surface of the pressure pad supporting the glass sheet in use being adapted to deform elastically at least partially to adopt the curvature of the pressure rotter that bears against that surface, under pressure applied by the pressure rotters in use.

In this specification, the term"roll over"is intended to imply relative movement-of the roller relatively to the sheet. It will be self-evident that the pressure roller can be moved relatively to the sheet or, conversely, the sheet can be moved relatively to the roller in the rolling and crushing process It is more convenient, however, to mount the roller in a stationary pressure roller assembly and to move or convey the glass sheet to be crushed relatively to the roller during the rolling and crushing process.

To this end, the pressure rollers may be mounted in a relatively stationary rotter assembly with the pressure pad being constituted by an endless, of sheet material mounted on transport rollers located on either side of the or both pressure rollers, the method comprising the specific step of moving the pressure pad between the pressure rollers in the fashion of a conveyor belt.

In a developed form of the invention, the glass sheet may be fed through one or more additional sets of pressure rollers which are operated such that the downstream pressure rollers, having regard to the notional direction of travel of the glass sheet, are rotated faster than the upstream pressure rotters.

The intention, with this development, is to stretch the interlayer so as to allow penetration of the alkaline solution between the glass pieces and the interlayer, thereby to facilitate the weakening of the adherence between the glass pieces and the interlayer.

This is achieved through the differential speeds of rotation of the two wets of pressure rollers, with the downstream pressure rollers tending to draw the glass sheet slightly more rapidly through the nip between the roller and pressure pad than the upstream rollers, thereby stretching the interlayer and opening gaps along the fracture lines between the between the fractured glass pieces adhered to the interlayer.

Brief description of the drawings The invention will be further described with reference to the accompanying drawings in which : Figure 1 is a perspective view of a laminated glass sheet ; Figure 2 is a diagram illustrating the step of crushing the sheet, one part of the diagram being enlarged to illustrate the. action. of the pressure rollers on the pressure pad; Figure 3 is a diagram illustrating the step. of treating the sheet with an alkaline solution; Figure 4 is a diagram illustrating the step of separating of the cullet from the . interlayer ; and F igure 5 is a diagram illustrating the glass sheet being fed through an additional set. of pressure rollers.

Description of embodiments of the invention Laminated glass, more commonly referred to as safety glass, normally comprises one or more layers of glass laminated with a vinyl interlayer.

In typical configuration as a motor vehicle windscreen 1, such as that Htustrated in Figure 1, a pair of glass plies 2 are formed to matching shape at temperature and then cooled to room temperature before an interlayer layer 3 is sandwiched between them. The interlayer material most commonly used is polyvinyl butyrate (PVB) and it is initially opaque. It becomes transparent upon completion of lamination. This involves a niechanical or vacuum squeezing process to remove any air trapped in the glass-PVB san<wich, which is then heated to bond the two glass plies 2 to the PVB interlayer 3.

To recycle the windscreen 1, it is necessary to separate the glass 2 and the interlayer 3.

The method in accordance with the invention begins with the removal nf plastic and

metallic parts (not shown) from the windscreen 1. In cases where the windscreen is overprinted with opaque glasslceramic coatings it might be necessary to remove the edge zones of the windscreen concemed, depending on whether or not the cullet to be obtained from recycling is to be used in a coloureritical glassmaking process.

The windscreen 1 is now ready for crushing. in the examples illustrated, the glass crushing assembly forming part of the system of this invention is constituted by a pair of opposed pressure rotters 5 that bear against and roll across an elastically deformable pressure pad 4 which supports thewindscreen 1 in use.

The pressure rovers 5 are mounted in a stationary rotter assembly 16.) n this configuration, the pressure rollers 5 constitute a pair of pinch rollers.

The pressure pad 4 is constituted by a sheet of elastically defoririable rnaterial such as a : rubber mat or/more conveniently, a rubber conveyoj-bettwhich is adapted to support the windscreen 1 in use. To this end, the pressure pad 4 (in the illustrated examples) is constituted by an endless loop pressure pad belt4 mounted on idlerrollers 12, 14 located on either side of the roller assembly 16; for movement of the pressure pad belt 4 between the pressure rollers 5 in the fashion of a conveyor belt.

The pressure pad belt 4 is driven by the pressure rollers 5. Whilst this is not absolutely necessary, the pressure rollers 5 could be made to be reversible to allow backwards and forwards movement of the pressure pad belt 4.

In use, the windscreen 1 is placed on the pressure pad belt 4 with the convex side up and run forwards through the pressure rollers 5. Normally only one pass is required.

In the process the glass layers 2 of the windscreen 1 are fractured'into small glass pieces.

This is t) est illustrated with reference to Figure 5 which shows the pressure pad belt 4 being deformed elastically under pressure applied by the pressure rollers 5 so that, in the pressure area, the pressure pad belt 4 is compressed and adopts the curvature of the pressure rollers 5 on either side thereof.

In use, however, the windscreen 1 located on the pressure pad belt 4 is forced to deform complementally as the pressure pad belt 4 deforms. The glass plies 2 are incapable of maintaining their integrity in the process of curving to adopt the curvature of the upper pressure roller 5 and the deformation causes the glass to crack and fracture into small

pieces.

The glass plies 2 fracture along cracks 18 that radiate outwardly from the upper surface of the windscreen 1 (which is adjacent the upper pressure roller 5) to the undersurface of the windscreen 1 (which is adjacent to the : pressure pad bett 4) The radiating cracks 18 tend to stretch the interlayer 3 thereby ensuring that the cracks 18 remain open after deformation of the windscreen 1 once the windscreen 1 is again flattened.

The result is a crushed windscreen 1 consisting of an integral interlayer sheet 3 with the glass still adhered thereto, but broken into small pieces by a network of fractures It is preferable that the pieces are relatively uniform in size between 5 and 30mm across.

This is achieved by the selection of the diameter : of the pressure rollers (particularly the upper. roller) and the degree of deformation of the pressure pad belt 4 (by selecting the hardness thereof) which make it possible to ensure that the integrity : of the interlayerq3 is maintained in the glass crushing processthe glass plies 2 are fractured into appropriately sized pieces. The interlayer 3 is stretched just sufficiently to keep the glass cracks 18 open ; but not to. rupture the interlayer 3.

The applicant has found that this crushing process is most effective using a 16mm thick pressure pad belt 4 with a Shore hardness of between 55 and 60 running through pressure rollers 5 with a diameter of at least 160mm.

The rollers 5 must be set such that they are just capable of pulling the pressure pad belt 4 through the rollers 5 when no glass is present and must be parallel to ensure uniform size in the glass pieces across the sheet.

In trials performed by the applicant, the applicant has found that it is able to process glass through the rollers at a rate of approximately one windscreen every 10 seconds.

Once broken, the fractured glass plies 2 will delaminate naturally as atmosphere penetrates and destroys the vacuum created between the glass plies 2 and lhe interlayer 3 during manufacture of the windscreen 1. This natural process is greatly accelerated, however, when the crushed windscreen 1 is subjected to the surface action of soda ash 6 and water 7.

Soda asn 6 is a material used in the manufacture of glass and is typically in abundant

supply in glass manufacturing plants. Whilst the relatively high cost of soda ash might be seen as a deterrent, it should be borne in mind that this cost is recovered, since most of the soda ash goes back into the mix and can then be worked back into the batch when the . cullet is used in the glassmaking process. In addition, the soda ash and water mixture can be collected for recycling and re-use by way of one or more drains.

In, the process as carried out-by the applicant, the soda ash 6 is dispensed onto the windscreen. 1 from a hopper 8, and the windscreen sprayed. liberally with water.

Similarly treated windscreens 1 are then placed in stacks of up to 2.1 m high and covered to retain moisture where they are allowed to lie for a period of two weeks or more If necessary, the windscreens are again sprayed to keep them moist . Once the fractured glass pieces of the glass plies 2 start to delaminate easily, the cutlet 10 is separated from the interlayer 3 in a trommel screen 9 with a. screen aperture size of a. bout, 25, mm. The separated cu) tet 10 is discharged into a cullet bin 11 in pieces varying in size between 5mm and 30mm across. The relatively intact interlayer 3 remains behind.

Once separated, the cullet 10 and interlayer 3 are processed separately for recycling purposes.

In the example of the invention illustrated in Figure 6, the windscreen 1 is fed through an additional set of pressure rollers 20.

The intention, with this development, is to stretch the interlayer 3 even more to allow better penetration of the alkaline solution between the glass pieces and the interlayer 3.

Each set of pressure rollers 5, 20 is mounted in an independent stationary roller assembly, each with its own pressure pad 4. 1,4. 2 constituted by an endless loop of sheet material mounted on transport rollers 12,14, the first roller assembly 5 having a pressure pad 4. 1 mounted on a set of rollers 12. 1, 14. 1 and the second set of rollers 20 having a pressure pad 4.2 mounted on a set of rollers 12.2, 14.2. The pressure rollers 5,20 can be operated independently at different speeds of rotation of the two sets of pressure rollers 5, 20.

In the drawing, the first set of pressure rollers 5 serves as upstream rollers and the second set 20 as downstream rollers.

In this arrangement and using the direction of motion illustrated in Figure 6 (by means of

arrows 22), the downstream pressure rollers 20 are operated at a speed of rotation that is between 5% and 10% faster than the speed of rotation of the upstream rollers 5.

In such an arrangement, the windscreen 1 is first drawn into and through the nip between the pressure pad belt 4.1 and the first set of rollers (the upstream rollers 5) When the windscreeni ts drawn into and through the nip between'the pressure pad hett 4. 2 and the second set of rollers (the downstream rollers 20), the windscreen 1 is placed under tension as a result of the faster rotation of the downstream rollers 20, which tends to draw the glass sheet 1 more rapidly, thereby stretching the windscreen 1.

It will be appreciated that the glass plies 2 do not stretch as such. It is the interlayer 3, which is of a resiliently deformable plastic that stretches.

During the crushing process described above, the deformation of the. glass plies 2 by the pressure rollers 5 does tend to open gaps along the fracture lines formed in the glass during crushing. However, by strething the interlayer 3 in the manner just described, the gaps so formed are opened out to a much greater and more permanent. extent. This allows better penetration of the soda ash and water mixture to be applied to the windscreen 1 in the next stage of the process and greatly accelerates the process of detamination.

The system and process of this invention, unlike most other delaminating methods, uses relatively slow moving components As a result the wear rate is low and maintenance costs are therefore much lower.

In addition, the process and system have the additional advantage that the PVB interlayer, which is removed essentially in one piece, is more readily available for recycling. This feature provides an additional advantage in that a number of newer model automotive windscreens have scan winding of tungsten wire laminated between the glass plies, for use as a windscreen heater. This is a potentially major contaminant, but the wire typically adheres to the PVB interlayer and comes off with the interlayer in situations where the glass is separated without breaking the interlayer. Using the system and process of the invention, this object can be achieved.

It will be appreciated that the invention is described above with reference to the recovery of cutlet from redundant laminated automotive safety glass, the invention will find much wider application than this and can be used in the recovery of all types of laminated safety glass.