REFERENCES CITED

[0001] 1

BACKGROUND OF THE INVENTION

[0002] The present invention relates to by products of post consumer cardboard, paper and thermoplastics and in particular prefabricated panels formed by the impregnation and lamination of cardboard sheets using resin solutions recovered from post consumer thermoplastics.

[0003] The airspaces created by the corrugated sections of cardboard (corrugated container board) and the micro porosity of the paper present in cardboard are critical structural characteristics that facilitates the impregnation and curing of the panels respectively.

[0004] The internal columnar spaces in the cardboard sheet stock are drenched by the gravity flow of resin solution when said spaces are oriented vertically. Surface adhesive application and lamination of dried internally drenched cardboard sheet stock forms panels with panel cores of appropriate thickness (called aeroboard). The curing of the resin solution is achieved by the forced circulation of hot air through the columnar air spaces present in the cardboard sheet stock. Drying may be done in kilns or directed hot air streams under covered plastic sheets.

[0005] The quest for alternative uses for bulky wastes has led to a range of processes for recycling and reuse of paper plastics and paper products. A large number of outcomes are directed to the fabrication of building insulation materials in shredded molded and compressed forms. The bulk of these wastes continue to be burned or dumped in landfills.

[0006] Various methods of prefabrication of building panels have been developed. U.S. Pat. No. 536,993 to J. T. Allen issued April 1895 describes a method of forming panels from chips of stnre or clay embedded in a plastic material wherein interstices between the chips are partially filled with sand. U.S. Pat. No. 2,839,312 to H. Serliner issued Jun. 24, 1958 claims a structural panel consisting of high strength concrete on both sides of a metal framework. The space between the two high strength layers of concrete is filled with a lightweight low strength concrete. U.S. Pat. No. 5,078,937 to Eela issued Jan. 7, 1992 claimed a method to form a slab like product from fibrous materials mixed in concrete.

[0007] U.S. Pat. No. 1,541,165 to Minache issued Aug. 17, 1923 describes a thin, three layered—load-bearing wallboard composite.

[0008] A number of patents have been directed at the production of insulation material U.S. Pat. Nos. 4,184,311 and 4,300,322 detail molding and shredding and laminating techniques. Methods also employed various combinations of injecting, spraying adhesion and curing processes. The formulation of slurries of shredded waste material is also commonly exploited.

[0009] The pervasive use of high temperatures and pressures in the processing of bulky wastes into remanufactured products is frequently described within the art. These conditions seek to achieve both impregnation, uniformity and heat catalyzed curing. Hunter in U.S. Pat. No. 5,008,359 prescribed temperatures above 150 degree C. and pressures greater than 3000 K Pa in the processing of cellulosic substrates with isocyanate impregnants. Hunter et al in U.S. Pat. No. 5,140,086 prescribed the use of compatible organic solvents for the promotion of uniform dispersion of the impregnant. The prohibitive costs of presses for these high temperature and compression operations however would contribute significantly to increase their production costs.

[0010] Attempts were made by Wallick in U.S. Pat. Nos. 5,292,391 and 5,332,458 described a spray technique using PMDI products to enhance the strength of the corrugated medium of container board prior to the lamination of external facings. Clearly the prior art appreciated the problem of impregnating a multi-ply laminate after assembly. Park et al in U.S. Pat. No. 5,580,922 attempted to overcome the problem of deep cross-section cure by the addition of a catalyst system. J. Maxwell in U.S. Pat. No. 5,729,936 issued in Mar. 24, 1998 employed removable rods that provided conduits for the drying of the compressed slurry.

[0011] The problem of flame retardancy has been confronted in many patents related to building panels. Some include U.S. Pat. Nos. 5,729,936; 5,715,637; 6,368,529 and 5,880,243. The last mentioned by Park et al in U.S. Pat. 5,880,243 issued Mar. 9, 1999 detailed trials were described in the quest of flame retardancy in lignocellulose composites. Herein the virtues of mono-ammonium phosphate, diammonium phosphate, halogenated phosphates, borates aluminum trihydrate and antimony oxide were explored. Commercially prepared (brand name) flame retardants were also documented. The volume of plastics in the solid waste is approximately 25%. This represents 90% of the total volume of plastics actually produced and can be regarded as a considerable drain on the non-renewable resource base, mankind, governments and the environment. The recycling of thermoplastics has been integral to the industry from its inception. Early recycling involved the fragmentation and reuse of factory generated scraps. Later techniques involved heating, compaction, shredding and granulation. These methods extended the range of products developed from recycled post-consumer thermoplastics. New products included fabrics, carpets, household durables and packaging. Lately research has been aimed at efficient methods of identifying, sorting and separation of post consumer thermoplastics. Sommer et al in U.S. Pat. No. 6,313,423 issued Nov. 6 2001, applied Raman Emission Spectroscopy to identify and sort Post consumer thermoplastics. Allen III et al in U.S. Pat. No. 6,335,376 issued Jan. T 2002, describes a method of separation of post consumer thermoplastics by a process of density differential alteration. What is not disclosed in the prior art is the non-destructive remanufacture of panels from cardboard as well as the application of resin solutions recovered from post consumer thermoplastics as the impregnant for the fabrication and decoration of said panels. The methods disclosed in this invention therefore regards the cardboard sheetstock as an intermediate per form whose characteristics are exploited in the impregnation drying and lamination stages of panel fabrication

SUMMARY OF INVENTION

[0012] The invention herein described is directed to new and useful light weight lignocellulosic fibre-polymer sheeted products. The sheeted products may be fabricated to form partitions walls roof, ceiling, insulation, floors and furniture of domestic (permanent and relocatable) recreational, agricultural, marine and commercial buildings Cardboard sheet stock (post consumer or ex-factory) are inspected for openness of those spaces formed by their corrugated interior. Where edges are damaged these are cut with a sharp instrument to expose the entrance to the interior columnar spaces. Constrictions in the columns may also be removed by cutting away sections along which folding was done to form boxes. Dents and fractured sections may also be similarly trimmed to expose the interior columnar spaces. Sections breached by staples may also be removed, since they will obstruct the drenching/impregnation process. Cardboard sheet stock so prepared are neatly stacked, clamped and oriented such that the columnar spaces are oriented in the vertical plane. Resin solution recovered from post consumer thermoplastic is then poured into the vertically oriented columnar spaces until the excess flows out at the lower openings of said columnar spaces. The stack is then laid horizontally and allowed to dry. Drying may be achieved by wheeling into a kiln, or wrapping in a plastic or leatherette sheet under which hot air is circulated. Microwave and RF radiation are also feasible methods. The addition of a compatible exothermic catalyst system to the resin solution immediately prior to drenching is also a feasible drying technique. Other additives may be added to the drenching resin solution complex including insecticides, flame retardants, water proofing agents and wood preservatives. Where cardboard sheet stock demonstrates large bore columnar spaces, lamination and lay-up may be done prior to drench/impregnation. The viscosity of the resin solution is adjusted to the diameter of the columnar spaces in the cardboard stock prepared for impregnation. An adequate drench does not result in saturation of the surface layers of the cardboard sheet stock and they continue to be separable by gentle delamination efforts after drying. Repeated drenching may be done to achieve a threshold impregnation. These successive drenches, however, must not clog the columnar spaces.

[0013] The clamping technique must be such that the individual cardboard sheets are tightly packed prevention resin flows about their external surfaces. The dried impregnated cardboard sheet stock is then laid up to the desired form and thickness. This is done by roller application of adhesive followed bv superposing. Where impregnated sheets vary in size they may be staggered to prevent joint alignment. Plies should be of uniformed thickness, cutouts may be done at this stage for doors, windows, roof rafters, fastening metal inserts, plumbing, electrical, heating and margins for mated joints. The completed lay-up is clamped then dried by directing hot air through the open columnar spaces as described above. Clamping must achieve contact pressure alone. This can be still considerably higher than that applied during post impregnation drying due to the increased compressive loading capability of the impregnated corrugated units within. At threshold production volumes, vacuum evaporation can be used to achieve solvent condensation and recovery. Scale economies may be feasible during the drying process using such solvent condensation techniques. Panels destined for use as high load bearing units are encased in wire mesh of appropriate density. The wire mesh is secured using twisted wire connected to either side through drilled holes. Such panels are transported positioned and finished using portland cement mortar. Delamination guards are installed by deploying nuts and bolts with washers of appropriate diameters over the exposed superficial face of the cured panel but before lay up of the external crust. Nuts and bolts are introduced to secure metal inserts and partially function as delamination guards simultaneously.

[0014] Panels destined for low and moderate load bearing applications may be surface finished by a range of optional treatments. These options are arranged below in ascending order of sophistication.

[0015] 1. The outer surfaces are strengthened using several laminations of paper. These panels may then be painted using, decorative coating formulated from resin solutions recovered from post consumer thermoplastics.

[0016] 2. The outer surfaces are laminated with a fabric gauze of appropriate texture and porosity using an adhesive formulated using resin solutions recovered from post consumer thermoplastics.

[0017] 3. Coarse fabric gauze is laid up on the outer surfaces using an adhesive formulated from resins recovered from post consumer thermoplastics. A 4 mm layer of Portland cement mortar is applied to smoothness. In this method delamination guards may be located after the coarse fabric gauze has been laid up to also assist in the securing of the gauze itself

[0018] 4. The cured panel may also be finished using a polymeric mortar consisting of resin solution recovered from post consumer thermoplastics chopped fibre, micronized mineral particles and small particle building aggregates. When partly cured these lay-ups may be planed using a fresh mix of easy flowing polymeric cement mortar. Planing may be done using hand float, draw board, guided edges or rotary devices. Where indicated flame retardants may be included in this polymeric cement mortar.

[0019] 5. The cured panel may also be finished after securing a fibre mat to the outer surfaces using polymeric adhesives as described above. Delaminating guards may then be deployed strategically. Upon drying 8 mm of Portland cement mortar is applied to smoothness.

[0020] Dried panels destined for use as roof panels require further variations. These are laid up to half of their final thickness. A layer of wire mesh of an appropriate density is then laid up along with a slick of polymeric cement sufficient to slightly cover the wire mesh. The other plies are laid up and cured. Alternatively the other half of the panel may be superposed upon the wire mesh/polymeric cement secondary core. Upon curing ribs are attached corresponding to rafters and purlins of conventional roofing. The interval used between these ribs must match recesses left on the relevant upright wall panels. These ribs are formed by cutting off suitably sized (5-8 mm)×(16-21 m)×L from cured panels. The rafter sections are then secured to the roof panel by polymeric adhesive cements and fabric gauze. Dedicated purlin elements may be fabricated with an internal reinforcement of wire mesh of appropriate density. As described above a slick of polymeric cement must also accompany the reinforcing wire mesh.

[0021] The exposed surface of the roof panel is thickened with two to three laminations of paper and polymeric adhesive. Alternatively a fabric gauze of suitable density and weatherability may be applied and secured with a polymeric adhesive. Voids created at the surface where sheets are joined may be solidified using a polymeric cement mortar or putty. Upon drying a fabric gauze is also secured to said exposed surface using a polymeric adhesive. A pigmented decorative coating is applied. Said decorative coating is formulated from resin solution formulated from post consumer thermoplastics.

[0022] The dry cardboard panel may also be used in the fabrication of furniture. In this application it can replace some classes of compressed composite boards in countertops, troughs, table tops, bed heads, ceilings, sidings and awnings. Where high stress joints are contemplated the aeroboard may be strengthened locally by injection of quick setting polymer cements into the columnar air spaces and cutouts around inserts. Dimensional stability may also be enhanced by attachment to lengths of timber. Such furniture can be surfaced finished using veneers coatings and laminations.

[0023] The recovery of resin solutions from post consumer thermoplastics has been the source of binders for the fabrication of panels in this invention. In so doing an attempt is made to utilize two classes of bulky wastes simultaneously into new and useful remanufactured products. Of the polymer species recovered polystyrene foam is the most abundant; and the most soluble. For commercial recovery of polystyrene solution from polystyrene foam (expanded polystyrene) the peculiarities of its structure had to be observed and exploited. Upon exposure to potent organic solvents polystyrene foam dissolves rapidly. If the foam specimens are added to the solvent in a container rapid dissolution begins. The low specific gravity of the polystyrene foam causes flotation at the surface of the solvent. The dissolution slows down progressively as the solution at the base of the floating foam mass thickens. The specific gravity of the floating gel is reduced by the entrapment of pockets of liberated blowing agent from the collapsing closed cells of polystyrene foam. The increasingly viscous gel becomes a mechanical barrier between relatively pure and unsaturated solvent below it and the intact mass of expanded foam above it (the viscous gel). These events militate against efficient application of immersion as an effective and viable method for commercial recovery of resin solution from post consumer polystyrene foam.

[0024] In this invention the foam digester is applied to overcome the difficulties outlined above. The key element in the superior productivity of the foam digester is the dispersing of the solvent from locations above the charge of polystyrene foam specimens. The dispersion of the solvent from above the foam specimens allows the escape of the blowing agent from the collapsing closed cells. These pockets of blowing agent escape directly through the surface of films of highly unsaturated resin solution flowing over the unstable surface of dissolving foam specimens. The moving film of solution does not allow strong surface tension to be achieved due to the effervescence of migrating pockets of blowing agent. Pockets of blowing agents are also liberated by abandonment due to the downward movement of the solution. The effervescence of the blowing agent also lubricates the downward flow of the resin solution. Further, continuous dilution of the resin solution so formed allows continued solvent attack on the closed cells at the surface of intact polystyrene foam specimens. Said dilution results from the continuing release of solvent from solvent dispenser located above the polystyrene charge.

[0025] Polystyrene foam specimens at the lower regions of the charge also benefit from good wetting out and surface cling achieved by the increasingly viscous solution in its downward flow. Penetration is also achieved by the upward displacement of the blowing agent and the entrapment of solvent in the freshly opened empty cells.

[0026] The control valve supplying the dispersion system must therefore be adjusted to allow a final solution that can flow readily into collection drums. Accumulated solution is drained off periodically. Solvent flow adjustments are influenced by the foam density, the solvent potency and the height of the polystyrene foam charge in the digestion chamber.

[0027] Solvent action in the foam digester is therefore rapid and productive. Any solvent pump in use is adjusted with the help of a valve-controlled return line. Solvent delivery rate is a function of frictional losses based on column height, initial pump pressure, tank-to-pump frictional losses and the pressure deflation created by setting variations at the two control valves. Solvent delivery at the dispenser is the residual pressure occasioned by these adjustments.

[0028] The dissolution of other plastics is not as rapid as obtains in polystyrene foam. The method for recovering other species therefore involves immersion in solution vats containing solvents of assessed potency. The table below matches various polymer species to their respective solvents. 2

[0029] The resin solutions recovered from these consumer thermoplastic wastes are used in the preparation of adhesives, polymeric cements, sealants and pigmented coatings for the prefabricated panels. Resin solutions recovered from PVC wastes and the cases of computer monitors IR and FR (ABS, ASA, PC/ABS) confer flame retardancy to preparations of which they are a component and are particularly valued for this purpose. These flame retardant components are used in conjunction with other flame retardants such as boron, ammonium, phosphates and halogenated compounds mentioned earlier.

[0030] Water soluble flame retardants can be applied to the cardboard sheet stock before impregnation as a drench. Stacking, drenching and drying may be done similar to the methods described for resin solution impregnatioli. Water insoluble flame retardants are dispersed into impregnating solution, adhesives and polymeric cements used in the fabrication of the cardboard panels.