EP0674569A1

EP0674569A1 - A method and apparatus for manufacturing board- and bar-like products, and a product manufactured thereby

Info

Publication number: EP0674569A1
Application number: EP93924625A
Authority: EP
Inventors: Juhani Rautavalta
Original assignee: Individual
Current assignee: Individual
Priority date: 1992-11-09
Filing date: 1993-11-08
Publication date: 1995-10-04
Also published as: FI925063A; FI92566B; FI92566C; WO1994011168A1; FI925063A0; AU5422494A

Abstract

A method and apparatus for manufacturing board- and bar-like products from a thermoplastic or a fibrous material having thermoplastic as the binding agent, and a product manufactured thereby. The raw material used is primarily recycled material which is dry-comminuted to a particle size which is optimal considering the strength and rigidity of the product. The pulp still warm from the comminuting is formed by means of vacuum into a mat of even thickness. It is heated rapidly to the molding temperature by means of hot gas, by using the countercurrent principle, and is thereafter compressed into an endless blank. This blank is molded by extrusion or compression into a product, which is cooled immediately.

Description

A METHOD AND APPARATUS FOR MANUFACTURING BOARD- AND BAR-LIKE PRODUCTS, AND A PRODUCT MANUFACTURED THEREBY

Technical Field

This invention relates to a method and apparatus for manufac¬ turing board-like and bar-like products from a thermoplastic and a fibrous material, the thermoplastic serving as the bind¬ ing agent, and a product manufactured thereby. The raw mate¬ rial used is, in particular, packaging waste which is diffi¬ cult to exploit and which may consist of paperboard, plastic- coated paper, plastic, and plastic-coated aluminum foil, such as drink containers, disposable plates and cups, fastfood packaging, paper, and mixed plastic waste. The proportion of plastic may range from 10 to 100 per cent by weight.

Some examples of the products are building boards, concrete shuttering, and battens. These can often be used for replac¬ ing, for example, chip board, hardboard and plywood.

Background of the Invention

Chip boards and the like are often manufactured by spreading particles cold, for example, onto a conveyor belt to form a mat, which is hot-pressed into a board. The press is often constructed so as to have multiple layers to increase capaci¬ ty. A plurality of boards are compressed and heated simulta¬ neously. The products are separated from each other by sepa¬ rating plates. The heating will require more time the thicker the product, since the material conducts heat poorly. The compressive force must be high, and the press must be of a sturdy construction.

Previously known are also presses in which a mat made by spreading particles cold is continuously both heated and com¬ pressed into a sheet between endless steel bands or between an endless steel band and a drum or between slat conveyors. The first mentioned method is known as the "Mende method", the second method is known as the "Bison-Hydro-Dyn Method" and the third method is known as the "Bison method" .

Patent FI- 48496 describes a method in which board-like pro¬ ducts are manufactured from vegetable fibers and plastics, al¬ so waste plastics. The method refers to artistic handicraft, and it deviates from the present invention as regards the pro¬ duct, the method, and the manufacturing apparatus.

Patent US-2 698 271 describes the forming of a fiber mat by the dry method by using vacuum in the manufacture of laminated multilayer boards, for example paperboard. It deviates somew¬ hat from the present invention as regards a) the type of the particles b) the distributing of the binding agent into the fiber pulp c) the delimiting of the mat thickness d) the warming and heating of the mat e) the molding of the blank into a product f) the cooling of the product

It is known from prior art to use vacuum for the forming of a mat, for example from patent FI-72 926. Therein, however, the delimiting blade will not cut a mat of a predetermined thick¬ ness out of the pulp under suction.

Patent US-3 356 780 describes a method and apparatus for manu¬ facturing a textile cover by using vacuum, the heating being carried out by means of hot gas. The said invention differs from the present invention, especially in the following points a) the cotton-plastic product manufactured is lightweight and flexible b) the fibers are individual, whereas in the present invention they are mostly particles larger than an individual fiber c) the distribution of the binding agent into the pulp is car¬ ried out differently d) the forming and delimiting of the mat take place different¬ ly e) in heating the pulp to the molding temperature the present invention uses the warming up which has taken place during the comminuting and the countercurrent principle, which protects the fiber material f) in the present invention the mat is formed and heated using the same means, a factor which simplifies the structure of the apparatus g) the product is molded by extrusion, the binding agent seep¬ ing between the particles and onto the surface of the product h) the product is cooled differently

The manufacture of particle board by extrusion, for example by the Okal-Kreibaum method is previously known. Therein the pulp is compressed between two parallel plane surfaces by means of a ram making a reciprocal movement. However, it has the disad¬ vantage of the fibers settling mainly in planes which are per¬ pendicular to the board surface. Therefore the bending strength and rigidity of the board are poor in the direction of the axis perpendicular to the direction of the compression.

The prior known methods and apparatuses for forming board- or bar-like products have some drawbacks in addition to the abo¬ ve-mentioned ones. The apparatuses are large-sized, and they are not constructed so as to be movable. It is difficult to realize an exploitation of waste, to achieve good energy eco¬ nomy, products usable for many purposes, and an emission-free production which involves few variables to be controlled.

Summary of the Invention

The apparatus of the present invention comprises a comminuting unit, a blank-forming unit, and an extrusion unit; a press unit can be used instead of the last-mentioned.

When the raw material is comminuted into a homogenous pulp, the particle size and distribution must be advantageous con¬ sidering the strength and rigidity of the product and its per¬ meability to gas during the heating stage. The pulp is in the main made up of particles larger than an individual fiber. During the comminuting the plastic particles will adhere to the fiber material particles. It was observed that a conside¬ rable proportion of the thermal energy required for molding the product is left in the pulp already during the comminu¬ ting. When the pulp is fed warm into the process, an advantage in terms of heat economy is gained, since 20-60 % of the ther¬ mal energy required for the molding may be derived from the comminution stage. In order to achieve the effect described above, the invention is characterized mainly in what is stated in points A in Claims 2 and 4.

The pulp, warm after the comminuting, is formed in the blank- forming unit into a continuous mat of even thickness, the den¬ sity of which is approx. 0.1 g/cm³ and in which the particles are randomly distributed. To accomplish what has been stated above, the invention is characterized in what is stated in points B in Claims 2 and 4.

When the pulp was heated, it was observed that prolonged heat¬ ing made the fiber material brittle. When the heating tempe¬ rature was raised, the time shortened, but it was difficult to avoid local overheating of the pulp and a detrimental embritt¬ ling of the pulp and disintegration of the plastic. It was ob¬ served that the desired result was obtainable by using for the transfer of thermal energy a gaseous medium, which reaches the particles of a thin mat almost simultaneously. To accomplish the effect described above, the invention is characterized mainly in what is stated in points C in Claims 2 and 4.

A mat heated to the molding temperature is preliminarily com¬ pressed into a blank the strength of which is sufficient to withstand the further treatment in the manufacturing process. In the blank the particles are randomly oriented and mostly parallel to the surfaces of the blank. In order to accomplish the effect described above, the invention is characterized in the main by what is stated in points D in Claims 2 and 4. In the extrusion unit, pieces cut from the blank are combined with each other by extruding them into a product according to Claim 1, in which the fiber orientation is advantageous in terms of rigidity. In order to accomplish the effect described above, the invention is characterized in the main in what is stated in points E in Claims 2 and 4.

During extrusion, the mixture of fiber and plastic is homogen¬ ized as the particles move in relation to each other. It was observed, surprisingly, that a plastic layer seeps onto the surface of the product, making the surface smooth and water- repellent. It also serves as a binding agent when, for examp¬ le, it is desired to hot press a coating onto the surface or to combine a plurality of boards.

A blank of one and the same thickness can be used for manu¬ facturing, by extrusion, products of different thicknesses by replacing the extrusion tool and the ram. The cross-sectional area of the nozzle determines the cross-sectional area of the product. The stroke of the ram is short and the stroke frequ¬ ency is hundreds of strokes per minute, which makes rapid pro¬ duction possible. Depending on the raw material used and the product to be manufactured, the pressure in the extrusion tool is 20-150 bar. The cross-sectional area of the ram is relati¬ vely small and the force it is subjected to is moderate. The extruder is relatively small in size.

Alternatively, the blank may be molded into a product by com¬ pressing instead of extruding. The method described above is characterized mainly by what is stated in Claim 3.

In order to ensure shape stability, the product is cooled im¬ mediately after being molded. In order to accomplish the ef¬ fect stated above, the invention is characterized mainly in what is stated in points F in Claims 2 and 4.

An embodiment of the invention is the manufacture of multilay¬ er boards. In the manufacture of a multilayer board, a plu- rality of hot boards manufactured by extrusion or of blanks compressed into boards are compressed into a thicker board. When this alternative is used, the invention is characterized mainly in what is stated in Claims 5-8.

The strength and rigidity of a multilayer board can be inc¬ reased. In order to accomplish the effect stated above, the invention is characterized mainly in what is stated in Claim 9.

The strength of a board and the properties of its surface can be improved by coating it, for example, with paperboard. In order to accomplish the property stated above, the invention is characterized in what is stated in Claim 10.

Brief Description of the Drawings

The foregoing and other features of the present invention will be more readily apparent from the following detailed descrip¬ tion and drawings of illustrative embodiments of the invention in which:

Figure 1 depicts a cross section of the apparatus of the manu¬ facturing process, when the product is molded by extrusion.

Figure 2 depicts a cross section of the cutting of the blank taking place in the extrusion apparatus of Figure 1.

Figure 3 depicts a cross section of the bending and swaging of a blank piece in the extrusion unit of Figure 1.

Figure 4 depicts continuous-working combining of blanks, co¬ ming from a plurality of blank-making units, by compressing them between plane surfaces into a thicker multilayer board in a sequential-working press.

Figure 5 depicts compressing of blanks, coming from a plura¬ lity of blank-making units, between rolls into a thicker mul¬ tilayer board on a continuous-working basis. Figure 6 depicts a cross section of the press unit.

Figure 7 depicts a cross section of a product manufactured by extrusion and of the orientation of its fibers.

In Figure 1, zone 101 is the comminution unit, zone 102 is the blank-making unit, and zone 103 is the extrusion unit. They constitute a compact entity.

EXAMPLE 1

Weighed raw material components, including 89 per cent by weight drink containers having an Al foil, 10 per cent by weight fast-food PE-HD packaging waste, and 1 per cent by weight boric acid as an additive, are cut into pieces having a surface area of 10 - 150 cm². The mixed components 2, Figure 1, are fed into the silo 1, from where the piston 3 pushes them, compressed, one batch 4 at a time, against moving blades 5, which resemble circular saw blades. They comminute the com¬ ponents into a homogenous, warm pulp in which the particle length is 0.5-4 mm. When the batch has been comminuted, the piston 3 makes a return movement and fetches the next batch. The pulp is directed to the conveyor 6, which spreads it over the width of the feeding shaft 7 and which has not been depic¬ ted in detail, but which may be, for example, a screw convey¬ or. In the blank-making unit (102) replaceable end plates 9 are fastened to the ends of a perforated drum 8 rotating about its axis at a constant speed. The power source rotating the drum is not depicted. In the non-rotating suction box 13 there prevails a vacuum of 0.1 bar, which sucks the pulp against the drum, on which the pulp is turned towards the blade 10, which runs in the direction of the drum axis. The blade mechanism can be moved in the radial direction of the drum so that it will be in alignment with the outer edge of the end plate. The blade detaches from the pulp compacted by the suction a mat 22 of even thickness, its thickness being 30 mm. The pulp de¬ tached by the blade 10 impinges against the surface 11 and curves in the direction indicated by arrow 12 back into the pulp flow. From the suction box 13 the gas sucked in and any particles possibly sucked in through the perforations of the drum are returned to the feeding shaft 7. The mechanical suc¬ tion device is not shown.

The warm mat on the drum is heated to a molding temperature of 200°C in steps according to the countercurrent temperature, by blowing hot gas at 210°C into pressure box 14, by sucking it through the porous mat into suction box 15, from which it is directed to pressure box 16, is further sucked into box 17, etc., until the gas, having yielded part of its thermal ener¬ gy, is ultimately sucked from suction box 21, whereafter it is reheated and blown again into pressure box 14. The mat-heating time is 15 s. The slight overpressure in a pressure box closes the flap 65, hinged at its upper edge, Figure 1, which pre¬ vents the flow of gas from one pressure box to the next. The heater which heats the suction device and the gas is not shown in the figure, but they represent technology known per se. The amount of thermal energy is adjusted by regulating the amount of gas. The suction and pressure boxes are fixed, the drum 8 rotates. The number of boxes need not be the same as in the figure.

The hot mat is compressed between the drum 8 and the roll 23 into a blank 24 having a density of approx. 0.7 g/cm³, and the blank is detached from the drum, whereafter it curves on the roll into the heated tunnel 25. The blank, manufactured at a constant speed, is momentarily stored in the storage container 26 and is fed therefrom, one 35-mm-long piece at a time, into the extrusion unit (103) , which is made up of an extrusion tool 27, a punch 28, a ram 29, and a cooler 30. At the start¬ up stage the extrusion tool 27 is heated to the molding tempe¬ rature. The mechanism which feeds the blank 24 from the con¬ tainer 26 is not shown. It operates in synchronization with the movement of the piston 28 and represents technology known per se. The mechanism which moves the ram reciprocally is not depicted, but it may be, for example, an eccentric or toggle- joint mechanism. Figure 2 shows how the punch 28 cuts a piece from the blank 24 and transfers it to position 32. In Figure 3 the punch stops and the ram 29 continues its movement, trans¬ ferring the piece into position 33.

In the blank 24 the fibers are randomly oriented, but are in the main parallel to its surfaces. When a piece of the blank is bent into position 33, swaged, and extruded in pulses into a product 35, a 10-mm-thick board, the particles of the pulp move in relation to each other. The ram stroke frequency is 180 strokes per minute. The fiber orientation 31, Figure 7, is in the vicinity of the product surface parallel to the surface and in the center of the product the fibers are mainly in a plane which is perpendicular to the surface and to the ext- • rusion direction. Finally the product travels via the cooler 30, in which it is cooled to a temperature of 60°C. The appa¬ ratus turns out product at a rate of approx. 1500 mm/min, and the width of the product is determined by the width of the apparatus.

EXAMPLE 2

In this alternative treatment of the hot blank, Figures 4 and 5, hot blanks 36, 37 and 38 coming from a plurality of paral¬ lel blank-making units have, after preliminary compression, been compressed at high pressure into a board, for example, between two rolls, the rolls not being shown, and thereafter they are directed, while hot, one on top of another, and are compressed to form a multilayer board 44. The compression is carried out sequentially between two plane surfaces 43, Figure 4, or continuously between rolls 45, Figure 5. The blanks may be different in their composition, a net-like reinforcement 39, 40 may be placed between them, and one or both surfaces of the board may be provided with coatings 41, 42. The surface of the plane surfaces 43 may have an embossed pattern, in which case a negative of the pattern will be copied on the board surface. The plane surfaces in this case also serve as coolers of the board. In continuous-working compression the product is cooled in a separate cooler 46. The thermal energy which has transferred from the product to the cooler is removed from the system by using a liquid which flows through the cooler. The number of layers in a multilayer board need not be in ac¬ cordance with Figures 4 and 5.

Figure 4 shows the principle of sequential and Figure 5 that of continuous compression. To produce the compression effect it is possible to use systems known per se, such as single- or multiple-layer pressing, rolling, compression between two band-like conveyors, between two slat conveyors, or between a drum and a band-like conveyor.

While the present invention has been particularly shown and described with reference to preferred embodiment thereof, it will be understood by those skilled in the art that various changes in form and details may be made therein without depar¹ ting from the spirit and scope of the invention.

For reasons of strength and outer appearance the product may be coated on one or both sides with, for example, paperboard, paper, plastic or textile.

The method presupposes few variables to be controlled. The most important of these are the composition and quantity of the raw material, its particle size, and the mass flow and temperature of the gas used for the heating. The capacity of the comminuting unit is higher than that of the rest of the apparatus. When necessary, the feeding in of raw material is interrupted, while the rest of the apparatus operates conti¬ nuously.

The mat-forming method used and the short heating time make a small-sized heating unit possible.

The bending strength of the extruded product is almost the same in the direction of the extrusion and in the direction of the axis perpendicular to the extrusion direction.

The advantages of the invention include the useful exploita¬ tion of waste difficult to recycle, good energy economy, small-sized movable apparatus, products usable for many pur¬ poses, and an emission-free manufacturing method which invol¬ ves few variables to be controlled.

Claims

1. A method for the manufacture of a board-like or bar-like product of a raw material which consists primarily of recycled material, characterized in that a) the raw material, which consists of thermoplastic 10-100 per cent by weight, preferably 15-35 %, the balance being fibrous material and possibly an additive, is dry-commi¬ nuted, the components having been mixed, into a pulp the particles of which are mainly larger than an individual fiber and preferably have torn edges, b) from the pulp there is formed a mat of even thickness, in which the particles are randomly oriented, c) the mat is rapidly heated to the molding temperature of the plastic, d) the mat is preliminarily compressed into a blank in which the fibers are randomly oriented and in the main parallel to the blank surfaces, e) the obtained blank is processed further into a board-like or bar-like product.

2. A method according to Claim 1, characterized in that the further processing includes as steps:

- the blank is extrusion molded in strokes, one piece at a time, into a product the cross-section of which is de¬ termined by the shape of the nozzle so that, at the ini¬ tial stage of a stroke, a piece is cut from the blank and is bent on a wedge-like ram and, at the final stage of the stroke, it is left between the ram and the pulp re¬ maining in the extrusion tool after the previous stroke, and as the ram presses with a pressure of 20-130 bar, the pulp particles between the extrusion tool and the ram mo¬ ve relative to each other in planes which are in the main parallel to the wedge surfaces of the ram,

- the product is cooled under compression immediately af¬ ter the molding, whereupon the fiber orientation (31) close to the surface of the product is in the main paral¬ lel to the product surface and changes continuously to¬ wards the center of the product, so that in the center the fibers are mainly in a plane which is perpendicular to the plane of the surface.

3. A method according to Claim 1, characterized in that the further processing includes as steps:

- the blank is molded by compressing, under a pressure of 30-150 bar, into a board in which the randomly oriented fibers on the surface of the product and inside the product are mainly parallel to the surfaces,

- the board is cooled under compression immediately after the molding.

4. A method for the manufacture of a board-like or bar-like multilayer product of a raw material which consists primarily of recycled material, characterized in that a) the raw material, which consists of thermoplastic 10-100 per cent by weight, preferably 15-35 %, the balance being fibrous material and possibly an additive, is dry-commi¬ nuted, the components having been mixed, into a pulp the particles of which are mainly larger than an individual fiber and preferably have torn edges, b) from the pulp there are formed two mats of even thick¬ ness, in which the particles are randomly oriented, c) the mats are rapidly heated to the molding temperature of the plastic, d) the mats are preliminarily compressed into blanks in which the fibers are randomly oriented and in the main parallel to the blank surfaces, e) the blanks obtained are processed further each separate¬ ly, and are thereafter combined with each other.

5. A method according to Claim 4, characterized in that the further processing and combining include as steps:

- each blank is extrusion molded in strokes, one piece at a time, into a product the cross-section of which is de¬ termined by the shape of the nozzle so that at the ini¬ tial stage of the stroke a piece is cut from the blank and is bent on a wedge-like ram, and at the final stage of the stroke it is left between the ram and the pulp remaining in the extrusion tool after the previous stro¬ ke, and as the ram presses with a pressure of 20-130 bar, the pulp particles between the extrusion tool and the ram move relative to each other in planes which are in the main parallel to the wedge surfaces, of the ram,

- the products obtained are combined with each other by pressing them against each other while hot, the layer of thermoplastic which has seeped onto the surface during the extrusion serving as a binding agent between the boards,

- the multilayer product obtained is cooled under comp¬ ression.

6. A method according to Claim 4, characterized in that the further processing and combining include as steps:

- each blank is molded by compressing, under a pressure of 30-150 bar, into a board in which the randomly orien¬ ted fibers on the surface of the product and inside the product are mainly parallel to the surfaces,

- the boards are combined with each other by pressing them against each other while hot, the layer of ther¬ moplastic which has seeped onto the surface serving as a binding agent between the boards,

- the multilayer product obtained is cooled under comp¬ ression.

7. A method according to Claim 5 or 6, characterized in that some of the blanks are molded by compressing into boards and some of the blanks are extrusion molded into boards, the layer of thermoplastic which has seeped onto the surface serving as a binding agent between the boards when the board are com¬ bined.

8. A method according to Claim 4, characterized in that the raw material used for the forming of at least one mat deviates from the raw material of the other mats.

9. A method according to any of Claims 5-8, characterized in that a net-like reinforcement is placed between the layers before the layers are combined, the thermoplastic which has seeped onto the surfaces of the boards serving as the binding agent bonding the boards and the net to each other when the boards are combined.

10. A method according to any of Claims 5-8, characterized in that, when the boards are combined, a coating is placed on the outer surface of the outermost boards, the coating being bon¬ ded to the board by the thermoplastic which has seeped onto the board surface.

11. An apparatus for manufacturing a board-like or bar-like product of a raw material which consists primarily of recycled material and thermoplastic, characterized in that the appara¬ tus comprises: a) a piston (3) which forces a batch of raw material (4) towards blades (5) which move perpendicularly to the pis¬ ton movement, the forcing speed of the piston being capa¬ ble of being varied to produce the desired particle size and distribution, b) a continuously rotating cylindrical, perforated, hollow drum (8) ; vacuum prevailing in a non-rotating suction box (13) inside the drum sucks the raw-material pulp from the feeding shaft (7) against the outer periphery of the drum, the pulp being delimited in the longitudinal direc¬ tion of the drum by end plates parallel to the end surfa¬ ces (9) of the drum, c) a blade (10) which is parallel to the drum axis and at a distance from the outer surface of the drum and which de¬ taches a mat (22) of even thickness from the pulp compac¬ ted by the suction and possibly still warm after the com¬ minution, there being above the blade in the wall of the feeding shaft an outwardly curved surface (11) which di¬ rects that pulp not constituting the mat separated by the blade back into the pulp flow being sucked towards the drum, the gas sucked out of the suction box (13) also being directed into the pulp flow, d) a plurality of successive sector-like blocks, each being made up of a pressure box (14, 16, 18, 20) outside the drum periphery and a suction box (15, 17, 19, 21) in the corresponding area inside the drum, e) means for feeding hot gas, the temperature of which ex¬ ceeds the molding temperature of the plastic, succes¬ sively from the last block (14, 15) relative to the ro¬ tational direction of the drum to the first block (20, 21) relative to the rotational direction, the travel di¬ rection of the gas within each block being from the pres¬ sure box to the suction box, and for feeding the gas further from the first block to the last block, and for heating this gas to the original temperature, in which case in principle the same gas circulates continuously, f) a roller (23) parallel to the drum axis and at a distance from the drum (8) surface for pre-compressing the mat (22) , heated to the molding temperature, into a blank (24) between the drum (8) and the roller, g) means for further processing of the blank into a final product.

12. An apparatus according to Claim 11, characterized in that the means for further processing include:

- a container (26) located at a point after the roller (23) ; the container momentarily stores the blank arriving as a con¬ tinuous flow and feeds the blank forward sequentially,

- an extrusion unit (103) which includes a stationary tool (27) having a nozzle aperture which determines the cross-sec¬ tion of the product, one end of the nozzle aperture conjoining a hollow which widens to the inside of the tool, and an aper¬ ture for feeding the blank (24) to the inside of the tool

(27) , the distance between the said aperture and the inner surface of the tool opposite it determining the height of the piece aperture, as well as a punch (28) and a ram (29) which move in parallel reciprocally, the punch (28) cutting off that part of the blank (24) which is inside the tool, and the ram (29) conveying the blank piece which has been cut off towards the nozzle aperture, characterized in that

- the height of the piece aperture (53) is substantially higher than the height of the nozzle aperture,

- the tip part of the ram (29) , facing the nozzle aperture, is wedge-like, so that when the ram is in its nozzle-side extreme position there are formed between the tool and the ram tip part two symmetrical spaces widening towards the nozzle, so that when the ram conveys the blank piece forward, its edges are bent backwards and the central part of the blank piece is forced between the backwardly bent edges of the previous blank piece.

13. A board-like and bar-like product manufactured by the method according to Claim 1 of thermoplastic or of a fibrous material with thermoplastic as the binding agent, the raw ma¬ terial being primarily recycled material, characterized in that the fiber orientation (31) close to the surface of the product is in the main parallel to the product surface and changes continuously towards the center, so that in the center the fibers are mainly in a plane which is perpendicular to the surface plane and to the manufacturing direction of the product.