WO1996024478A1

WO1996024478A1 - An apparatus for processing and forming plastics scrap materials

Info

Publication number: WO1996024478A1
Application number: PCT/IT1996/000021
Authority: WO
Inventors: Renato Rimoldi; Franco Rimoldi
Original assignee: Rimoldi S.R.L.
Priority date: 1995-02-10
Filing date: 1996-02-07
Publication date: 1996-08-15
Also published as: ITMI950241A1; ITMI950241A0; IT1275184B

Abstract

An apparatus for processing plastics scraps, in particular an apparatus constituting an automatic supply, extrusion, and molding line for a thermoplastic composite which is mainly or entirely comprised of scrap or even waste materials, comprising means of forming a thermoplastic composite and feeding conformant portions thereof into a press for the production of semi-finished and/or finished pieces.

Description

AN APPARATUS FOR PROCESSING AND FORMING PLASTICS SCRAP MATERIALS

DESCRIPTION 5 Technical Field

This invention relates to an apparatus for processing plastics scrap materials, and in particular to an apparatus constituting an automatic supply, extrusion, and molding line for a composite which is mainly or entirely comprised of scrap or even waste materials l<) Background Art

Known apparatus for manufacturing generic plastics parts include, inter alia, extruding machines and injection molding machines which are fed raw materials in granulated or powdered form for processing into semi-finished and/or finished products, using draw plates, molds, dies, etc..

15 With many of the known apparatus, forming is carried out as a separate step on dedicated equipment; also separate being the steps of preparing and batching the material for use on such equipment. With few exceptions, these steps cannot be automated into a continuous processing line Furthermore, to ensure uniformity for the end product, high-purity raw materials with constant characteristics must be used, even

20 when such processing steps can be interlinked and automated.

Especially where the aim is sectional stock extruded from a composite thermoplastic material (plastics and wood, for example), a known technique for providing the composite is to mix the plastics and wood together with optional additives, and force the mixture through a single extruder inlet. However, this requires that the

25 particle size of the plastics and wood particulates be homogeneous and that the plastics/wood mixing ratio be strictly maintained, to produce at most sheet stock up to 3mm thick.

A recent technique utilizes a two-inlet extruder, but still involves the use of highly homogeneous fine materials This technique does not meet the primary

^"»<⁾ requirement of supplying the extruder with materials which have different apparent volumes and physical shapes and may have a significant moisture content (such as wood, plastics granulates, etc.), as well as with large amounts of inert materials that, even though not intended for melting, still demand heat to have their moisture removed by evaporation. Disclosure of the Invention

It is a primary object of this invention to provide an apparatus for manufacturing semi-finished and/or finished products from a thermoplastic composite, which apparatus can be operated on a continuous cycle basis using starting materials with varying characteristics, wherein the material characteristics would not affect its

4⁽i constant output of end product because the apparatus is self-adjusting in the respect of several of its functions to accommodate the varying characteristics of the input material. while being capable of so adjusting itself to the material as to keep the output of stock product constant

Another object of the invention is to provide an apparatus for

45 manufacturing semi-finished and/or finished pans from a composite thermoplastic material, wherein all the working stations, consisting of machines, each designed to perform a specific function, are interlinked and interact with one another to provide a continuous-cycle production line, from the "raw" material feed-in end to product storage, all this being controlled by one or more programs from one or more interacting computerized control units, such as a control unit and a control sub-unit served by a network of sensors for monitoring several values tied to the material processing and the equipment operation

A further object of the invention is to provide an apparatus for manufacturing semi-finished and/or finished products from a composite thermoplastic material, which apparatus operates on a continuous cycle basis and can accept, mainly but not solely, scrap and/or waste input materials, as both the inert filler and the thermoplastic constituent, and in particular can be operated using, as the inert filler scrap materials of any description, such as sawdust, shavings and chips from woodworking, chunky cuttings from shake boards, even faced ones, paint smudge and dust, and the like untreated materials, and as the thermoplastic constituent, regenerated polyolefine-based plastics materials, such as polypropylene, polyethylene, etc. to various degrees of purity and/or mixtures of plastics and inert materials being residual from different processes or from sorted city waste.

A further object of the invention is to provide an apparatus for manufacturing, on a continuous cycle basis, semi-finished and/or finished products from a composite plastics material, which incorporates all the equipment needed for pre- treating and transporting the material to the various processing stations, as well as for batching, mixing, additivating and delivering the material to such stations, as well as any equipment required for monitoring all the operations, so as to gather useful information for the apparatus self-adjusted mode of operation and optimize the process Brief Description of the Drawings These and other objects are achieved by the apparatus of this invention as schematically illustrated by the accompanying drawings, in which Figure 1 is a general block diagram for the apparatus. Figure 2 is a flowchart for the apparatus; Figure 3 illustrates in schematic form the arrangement for post-cut weighing the composite material issuing from the extrusion head through the pre-forming rotary press. Description of the Preferred Embodiment

As shown in the accompanying drawings, the automatic apparatus of this invention for manufacturing semi-finished and finished products from a composite thermoplastic material, using scrap materials from different processes as the start material, comprises a means (A) of picking up and automatically supplying to a transport (B) a primary inert filler consisting, for example, of shake and uncrushed waste from woodworking processes, a means (C) of conveying waste, not previously crushed, to a crusher (D), and an associated means (not shown) of separating ferrous scraps, a storage means (E) for the crushed material, a storage means (K 1 ,K 2,K 3) for regenerated and/or waste and/or fresh polyolefine-based thermoplastic materials, a means (K) of ensiling compounded granulate from an inertizing line which may be provided on the site and consists of a storage means (F), a byweight batching means (G), a mixing means (H), a melting/consolidating means (I), and a granulating means (J), or supplied from external sources, and a means of conveying said regenerated and/or waste and/or fresh thermoplastic materials, and optionally said compounded granulate and crushed process rejects itself, to the respective means (L) of weighing, mixing (M), and ensiling into daylong storage silos (N) serving an extruder (O), and is characterized in that it comprises

I a means (P) of conveying to a batching device, preferably but not exclusively of the volumetric type (Q), the mixed thermoplastic granulates from the silo(s) (N) and said batching device (Q) to a first inlet (O 1) of the extruder (O), said extruder being, preferably but not exclusively, of the type having two counter-rotating screws, for the melting step,

II. a means (R) of conveying the primary inert filler from the silo(s) (E) to a drier (S) and thence to a byvolume or byweight batching device (T), and subsequently through a driver (U) to a second inlet (0.2) of said extruder

(O),

III a means consisting of an extrusion head (O.3) for pre-forming the blended composite within the extruder (O), and a means (V) of degassing the formed composite prior to it exiting the extruder; IV a means (not shown) of detecting pressures of the composite thermoplastic material within the extruder (O) or extrusion head (0.3),

V a means of post-extrusion pre-forming the composite material issuing from the extruder, consisting of a rotary press (Z) serving the extrusion head (0.3) of the extruder (O); VI. a cutting means (Z. l ) for severing the extruded material exiting the rotary press (Z),

VII a means of transporting and weighing (X) the severed extruded material,

VIII a means (not shown) of monitoring and controlling the cutting cycle and the severed extruded material transport means, the weighing and transport to the molds and for rejecting non-conformant portioned material, and all the other functions of the apparatus;

IX a molding means consisting of an oil-operated press (Y) having a plurality of even different molds;

X. a means (not shown) for picking up and placing into the press (Y) molds the severed extruded material conformant with specifications, and a means of automatically rejecting the non-conformant portions of the severed material,

XI a means (not shown) of shaking out, discharging and taking away the pieces molded in the press molds In a preferred but not exclusive embodiment of the apparatus according to the invention, the pick-up/feed means (A) may be any type, although it preferably comprises bins (not shown) for gradually unloading the primary inert filler yet to be processed and as composed, for instance, of scraps from woodworking processes, onto a belt conveyor (B) and another belt conveyor (C), in turn feeding a crusher (D) and, by means of a further conveyor, a hammer mill (D 1 ), at the last-mentioned conveyor there being provided a means of magnetically sorting the material, and the conveyor (B) feeding the crusher (B) over the conveyor (C) is equipped with detection systems operative to control the movements for emptying the bins of the wood scraps The hammer mill (D 1 ) is, in turn, connected by suitable ducts to one or more closed storage receivers (silos) (E) for storing the refined inert therein The means of bvweight batching, mixing, melting, extruding, consolidating, granulating and ultimately ensiling any further s different inert fillers from the pnmary filler by quality, physical shape, and amount, including interacting fillers, such as calcium carbonate, paint smudge and dust, and the like, and plastics scraps stored in dedicated bins (F), comprise at least one crusher, a specific scale (G), a turbine mixer (H), a mixer (H 1 ), daylong silos (F 1 ), an extruder (I), a crusher (J), and a ducted means of conveying the resultant thermoplastic granulate to o respective storage silos (K)

The means of extruding the composite thermoplastic matenal compπses an extruder (O), preferably but not exclusively of the type with two counter-rotating screws, which has two separate inlets (0, 1, O 2) for the materials to be supplied to the extrusion head (0 3), specifically an upstream inlet (O 1 ) overlaid by a volumetric batcher (Q) for the thermoplastic material mixture which is preferably, but not exclusively, pre-heated from the sιlo(s) (N), and a second inlet (O 2) downstream from the former which is also overlaid by a batcher preferably, but not exclusively, of the volumetnc type (T) including a driver (U) for introducing the inert filler issuing from a drier (S) located on the inert filler conveyance duct downstream from the respective 0 storage receιver(s) (E)

Advantageously, the extruder (O) is provided with a device (V) for closed-loop degassing the blend of thermoplastic composite formed within the extruder Said degassing device, and a similar one provided on the other extruder (I), includes a dedusting means which also removes vapors by condensation of the wet fraction and 5 conveys the liquid into a dedicated collector, dry gas (air) being exhausted to the atmosphere

Also advantageously, the thermoplastic composite blend formed within the extruder is extruded into preferably, but not exclusively, rectangular sectional stock and is severed by a knife (Z 1) operated to perform a vertical or oblique cut and to o traverse frontally Located adjacent to the cutting point is a first conveyor belt which receives the extruded material issuing from the rotary press (Z) at the slowest speed (I speed = extrusion rate of the material) after cutting and subsequently at the knife (Z 1 ) traversing speed Provided next to said first belt, is a second conveyor belt having a loading/unloading rate that matches the second speed of the first belt, being equipped s with a weighing means (X) operated with the belt held stationary and followed by a third conveyor belt operated at the same speed as the weighing belt, said third belt serving a molding means consisting of the press (Y) equipped with respective molds (not shown), preferably a four-station oil-operated press

The weighing means located at the second conveyor belt comprises a o scale (X) for measuring the weight of the severed piece of material resting on said belt and sending the information to the computerized control unit, where the information is compared with stored data which includes data about the pressure of the material being melted and pre-formed in the extruder (O) and the extrusion head (O 3 ), respectively The cutter that operates the knife (Z 1 ) is also controlled by the control unit according ^ to the information received, such that, if the weight does not match, the control unit will change the cutting rate by decreasing or increasing the time interval between cuts in order to control the amount of material to be supplied to the press (Y) such that the weight of each portion will conform with the preset particle size within a predetermined tolerance range.

Every out-of-weight piece is discharged and subsequently re-introduced upstream into the production cycle after undergoing crushing together with the plastics binder.

The press (Y) provided downstream from the extruder (O) molding the composite thermoplastic material is a press having multiple, preferably but not exclusively four, separate mold-holding stations, and capable of molding different pieces, since it can accept different molds by dimensions and shape. In particular, the heads can be operated in the single mode or be paired, in either cases using no stringent cycle, but rather independently programmed cycles by the control unit according to the characteristics of the extrusion cycle, and are double-acting so as to allow for a first step of mold clamping and a subsequent step of pressure application for press molding

The aggregate of the machinery downstream from the extruder (O), being also controlled by the computerized control unit through respective programs, allows finished and/or semi-finished moldings of widely apart weights to be produced according to necessity and in particular the trade demands, while keeping the extruder operation constantly at its best output condition.

A system incorporating the apparatus of this invention can accommodate, and restore to tolerance, fluctuations in the extruder flow rate, whether caused by distinctive characteristics thereof or variations in batching or variations in the behavior of the materials used, during their processing.

The operation of the inventive apparatus will be discussed, by way of example, with reference to the manufacture of finished or semi-finished products by a manufacturer of wooden furniture and/or room furnishings, using for a "raw" material solid waste or scraps from its own processing as supplemented with fresh, regenerated, or waste thermoplastic polymers.

The following useful waste is available:

- wood flour, chips and chunks of wood and/or shake, whether bare or painted and/or faced;

- pigments from polyurethane, urea, acrylic paints, etc., in dry powder and/or smudge form,

- plastics containers contaminated with paints;

- spent filters from spraying booths; - packaging plastics films;

- packaging paper, cartons and derivatives,

- generic fabrics and coverings

The process is carried out as follows

The dried paint pigments are loaded onto the feed conveyor belt to a crusher, and then deferrized and fed into a turbine mixer whereinto the following is introduced automatically: wood flour, additives (where required), a plastics binder (reclaimed plastics) as picked up from their respective silos and weighed on a scale All these are mixed together, stored into daylong silos, and subsequently extracted and, following a further deferrization step, supplied into an extruder that will melt them, and ultimately granulated The resultant granulate (compounded granulate) is delivered into the storage silos for optional utilization at a later stage of the composite production for --

- 6 -

molding. The aforementioned additional materials to be processed (primary inert filler), consisting of pieces of wood and shake, are loaded, by tipping over their collectors, into a hopper whence they are transferred onto a feed belt to a crusher From there, they will be transferred, by means of a belt conveyor provided with a magnetic means for a first removal of ferrous metal slag and metal pieces, into a refiner for reducing the particle size of the crushed material to no more than 6-7mm

The resultant grindings, having the consistency of sawdust, are then ensiled as sorted lots into storage silos, using rope and auger transports or their equivalents During this conveyance, further deferrization is applied and, if necessary, an appropriate external lubricant added

The apparatus of this invention automatically picks up from the storage silos, under control by the program control unit, the plastics binder, preferably a waste plastics binder but on occasion fresh binder as well, and the inert fillers and additives and pre-granulated paints (compounded granulate) and ground process rejects, to take them through augers to a scale and a mixer, and then, over a suitable transport arrangement whatever, to the daylong silos serving the main extruder for the production of the plastics composite to be extruded, and the subsequent molding. The apparatus of this invention can supply, through byvolume or byweight batchers, the two extruder inlets, respectively with the mixture of granulates and optional additives and the wood (primary inert filler) The latter, once picked up automatically from the storage silos, is progressively dried along the line, by going through the drier provided for the purpose, and then further deferrized prior to being fed into the extruder through its dedicated batcher and driver. Following the melting and degassing steps (the latter being carried out on a special structure for removing the water fraction from the gases and releasing a dry gas (air) to the atmosphere), a composite thermoplastic materials issues from the extruder whose plasticity is held constant by the apparatus to ensure its workability during the subsequent compression molding step by means of a press positioned downstream from the extruder and being served by an aggregate of belt conveyors which are interlinked and cooperate with pre-forming and cutting means located at the extruder outlet end and with transfer means for transferring the conformant portioned extruded composite material into the press molds and the reject to a respective unloading conveyor belt or its equivalent.

It is considered that the invention commands no further explanations in order to bring out that the apparatus as a whole provides an automatic system for processing waste from manufacturing processes, which can be operated without deadtime and is capable of reusing most of the waste from one or more industrial manufacture cycles which would otherwise have to be disposed of to dumping sites or by incineration (where feasible)

The dimensions may be selected to suit, and details may be replaced with equivalents thereof, while different combinations of equipment may be contemplated to produce plants of different size, without by so doing departing from the protection scope of the present patent as described, illustrated in the accompanying drawings, and claimed hereinafter

Claims

1. An apparatus for processing plastics scraps, in particular an apparatus constituting an automatic supply, extrusion, and molding line for a thermoplastic composite which is mainly or entirely comprised of scrap or even waste materials, comprising a means (A) of picking up and automatically supplying to a transport (B) a primary inert filler consisting, for example, of shake and uncrushed waste from woodworking processes; a means (C) of conveying waste, not previously crushed, to a crusher (D) and then to a hammer mill (D 1 ), and an associated means (not shown) of separating ferrous scraps; a storage means (E) for the crushed material, a storage means (K.1,K.2,K 3) for regenerated and/or waste and/or fresh polyolefine-based thermoplastic materials; a means (K) of ensiling compounded granulate from an inertizing line which may be provided on the site and consists of a storage means (F), a byweight batching means (G), a mixing means (H,H.1 ), a melting/consolidating means (I), and a granulating means (J), or supplied from external sources, and a means of conveying said regenerated and/or waste and/or fresh thermoplastic materials, and optionally said compounded granulate, to the respective means (L) of weighing, mixing (M), and ensiling into daylong storage silos (N) serving an extruder (O), and characterized in that it comprises

I a means (P) of conveying to a dedicated batching device (Q), the mixed thermoplastic materials from the silo(s) (N) and said batching device (Q) to a first inlet (0 1) of the extruder (O), said extruder being, preferably but not exclusively, of the type having two counter-rotating screws, for the melting step;

II a means (R) of conveying the primary inert filler from the silo(s) (E) to an on¬ line drier (S) and thence to a dedicated batching device (T), and subsequently through a driver (U) to a second inlet (0.2) of said extruder (O),

III a means consisting of an extrusion head (O.3) for pre-forming the blended composite within the extruder (O), and a means (V) of degassing the formed composite prior to it exiting the extruder,

IV a means (not shown) of detecting pressures of the composite material within the extruder (O) or extrusion head (0.3),

V a means of post -extrusion pre-forming the composite material issuing from the extruder, consisting of a rotary press (Z) which serves the extrusion head (0.3) of the extruder (O),

VI a cutting means (Z.1 ) for severing the extruded material exiting the rotary press (Z),

VII a means of transporting and weighing (X) the severed extruded material,

VIII a means (not shown) of monitoring and controlling the cutting cycle of the extruded material, the transport means for the severed extruded material, the weighing and transport to the molds and for rejecting non-conformant portioned material, and all the other functions of the apparatus,

IX a molding means consisting of an oil-operated press (Y) having a plurality of even different molds. - 8 -

X a means (not shown) for picking up and placing into the press (Y) molds the severed extruded material conformant with specifications, and a means of automatically rejecting the non-conformant portions of the severed material,

XI a means (not shown) of shaking out, discharging and removing from the press the pieces molded in the molds

2 An apparatus for processing plastics scraps according to Claim 1 , characterized in that the main extruder (the extruder on the molding line) comprises an extruder (O), preferably but not exclusively of the type with two counter-rotating screws, being provided with two separate inlets (0.1,0.2) for the materials to the supplied to the extrusion head (0.3), specifically an upstream inlet (0.1 ) overlaid by a dedicated batcher (Q) for the, optionally pre-heated, thermoplastic material mixture from the silo(s) (N) and a second inlet (0.2) downstream from the former and also overlaid by a dedicated batcher (T) supplemented by a driver (U) for introducing the primary inert filler issuing from an on-line drier (S) disposed along the inert filler conveyance duct downstream from of the storage receiver(s) or silos (E) therefor

3. An apparatus for processing plastics scraps according to Claims 1 and 2, characterized in that a device (V) for closed-loop degassing the thermoplastic composite mixture formed within the extruder (O) is provided on the extruder (O) ahead of the extrusion head (0.3), said device (V) being also provided on the other extruder (I) and including a means of first removing the dust and then the vapors, by condensation of the wet fraction, and of conveying the liquid into a dedicated collector, thereby exhausting dry gas (air) to the atmosphere.

4. An apparatus for processing plastics scraps according to the preceding claims, characterized in that the extrusion head (0.3) of the extruder (O) includes a replaceable pattern nozzle or pattern drawplate, preferably but not exclusively having a rectangular cross-sectional shape.

5 An apparatus for processing plastics scraps according to the preceding claims, characterized in that the pattern nozzle or drawplate of the extrusione head (0 3) is connected operatively to a post-extrusion forming means comprising a rotary press (Z) feeding an underlying belt conveyor operable at two speeds (VI ,V2)

6 An apparatus for processing plastics scraps according to the preceding claims, characterized in that a cutter having a knife (Z. l ) or an equivalent means of severing the extruded material being carried on the underlying belt conveyor is provided after the rotary press (Z) close to the extrusion head (O 3), said severing means being also driven of traversing motion

7 An apparatus for processing plastics scraps according to the preceding claims, characterized in that a second belt conveyor including a weighing means and operable at one speed (V2) is arranged adjacent to the belt conveyor that extends beneath the rotary press (Z) outlet, in alignment therewith 8 An apparatus for processing plastics scraps according to the preceding claims, characterized in that a third belt conveyor operable at one speed (V2) is provided adjacent to the belt conveyor that includes a weighing means (X), in alignment therewith

9 An improved apparatus for processing plastics scraps according to the preceding claims, characterized in that the second and third belt conveyors located downstream from the extrusion head (O 3) of the extruder (O) can alternate intervals of standstill (F) with intervals of operation at a higher speed (V2) than the primary speed (VI) of the first belt conveyor (movements with deceleration and acceleration ramps and stepped movement)

10 An improved apparatus for processing plastics scraps according to the ^■ preceding claims, characterized in that the first belt conveyor receives the extruded material issuing from the extrusion head (0 3) through the rotary press (Z) while running at the lowest speed (extrusion speed of the material) and subsequently, after the severing, at the knife (Z 1 ) traversing speed, the load/unload speed of the second belt conveyor that includes a weighing means (X) being the same as the second speed of the first belt 0 conveyor (traversing speed of the knife) which is equivalent to the speed of the third belt conveyor serving the molding means comprised of the press (Y) and respective even different molds

11 An improved apparatus for processing plastics scraps according to the preceding claims, characterized in that the weighing means located at the second belt 5 conveyor comprises a scale (X) operatively connected in a discontinuous manner (with the belt conveyor stopped) to said belt conveyor for measuring the weight of the severed extruded material piece lying thereon, and a means of transmitting the weight measurement information to the computerized control unit for comparison with data stored therein, including data about the pressure of the material being melted and pre- 0 formed within the extruder (O) and the extrusion head (O 3), respectively

12 An apparatus for processing plastics scraps according to the preceding claims, characterized in that the molding means is located downstream from the extruder (O) and comprises a double-acting oil-operated press (Y), as derived with appropriate modifications from a draw-forming press, and wherein the second action has 5 been moved to the upper portion instead of the lower portion

13 An apparatus for processing plastics scraps according to the preceding claims, characterized in that the press (Y) has several, preferably but not exclusively four, separate mold-holding stations, i e stations capable of molding even different pieces because adapted to mount different molds with heads which can operate o in the single mode or be paired into a non-stringent but independently programmed cycle by the control unit according to the characteristics of the extrusion cycle

14 An apparatus for processing plastics scraps according to the preceding claims, characterized in that the press (Y) equipped with independent double-acting heads uses molds having a means of confining the extruded mass received 5 therein, said confining means being a containment ridge provided on the upper moving portion of the mold and operated in two stages clamping by bringing the two shells together (I-effect) and subsequent compression through the pressing portion of the mold (if-effect)

15 An apparatus for processing plastics scraps according to the o preceding claims, characterized in that the press (Y) is automatically served by at least two lift carriers equipped with a gπpper means, such as suction cups or the like arranged to fit the shape of the material portion to be formed, for transferring, from the feed belt conveyor (third belt conveyor) to the molds, the portions of conformant portioned extruded material and removing from said molds the molded pieces and taking them to a storage room delivery belt conveyor or, at any rate, away from the press (Y)

16 An apparatus for processing plastics scraps according to the preceding claims, characterized in that the monitoring and control means comprise one or more computerized control units adapted to control, according to respective programs and the information supplied from sensors disposed throughout the processing line defined by the inventive apparatus, the operation of the cutter, the belt conveyors, the weighing system, the means of feeding the portions of severed material which conform with specifications to the press (Y) molds, the operation cycle of the press (Y) including discharging the molded pieces and reiecting and re-cycling the non-conformant severed portions, all this in an interacting automatic manner

17 An apparatus for processing plastics scraps, in particular an apparatus constituting an automatic supply, extrusion, and molding line for a thermoplastic composite which is mainly or entirely comprised of scrap or even waste materials, as herein descnbed, illustrated, and claimed for the specified objects