CA2380651A1

CA2380651A1 - Method and device for producing moulded parts

Info

Publication number: CA2380651A1
Application number: CA002380651A
Authority: CA
Inventors: Christoph Habighorst; Hans-Gunther Schwarz
Original assignee: Individual
Current assignee: Metso Panelboard GmbH
Priority date: 1999-08-13
Filing date: 2000-07-24
Publication date: 2001-02-22
Also published as: DE50008255D1; EP1202849B1; AU6565800A; WO2001012403A1; DE19938489A1; EP1202849A1; CN1368913A; CN1164407C

Abstract

The invention relates to a method for producing moulded parts, especially plates, made of particles, such as lignocellulose and/or cellulose-like chip s, fibres, cut straw particles, rice husks or the like, which are mixed with at least one binding agent. Said particles are strewn onto a moved base to form a nonwoven fabric that is subsequently pre-compressed and then entirely compressed by heat treatment to form a moulded part, whereby the base is at least partially covered by a support web which is moved together with the base. The particles that form a nonwoven web consisting of one layer or several layers are strewn onto the support web which rests on the base. The invention also relates to a device for carrying out said method.

Description

A method and an apparatus for producing molded parts The present invention relates to a method for producing molded parts, in particular boards, made of particles such as chips, fibers, comminuted straw particles, rice husks or the like containing ligno-cellulose and j or cellulose, which are admixed with at least one binding agent and which are scattered onto a moved base to form a mat which is subsequently initially pre-compacted and then finish pressed under the effect of heat to form a molded part. The invention is furthermore directed to an apparatus for carrying out this method.
It is known that mat particles admixed with a binding agent, for example with an organic isocyanate solution, only tack together relatively loosely even in the pre-compacted state due to a Iack of a sufficient cold bonding effect. As a result of this, structural changes result in the mat configuration on the transport of the mat into a continuously or discontinuously operating finishing press which can have the consequence of operation standstills. This applies in particular in the region of the transfer positions) from one mat carrier belt to the next if the mat carrier belt system forming the base for the mat is made from a plurality of mat carrier belts. But corresponding structural changes in the mat configuration can also occur due to the sticking of mat particles to the base, or to apparatuses which act on the mat during the transport, such as to pre-compacting units.

la A method and an apparatus of the kind initially mentioned is known from DE 44 34 876 A1. In this connection, a lower cover layer is first scattered onto the moved base from a fine chip mixture and subsequently pre-compacted to a fine chip mat. A plurality of layers of oriented elongate chips offset to one another by 90° are scattered in sequence onto the pre-compacted fine chip mat, whereupon subsequently the upper cover layer is scattered from a further fine chip mixture onto an auxiliary scatter belt and is pre-compacted ~to a second fine chip mat. Subsequently, this second fine chip mat is placed onto the uppermost core layer play and thus the pressed material mat is formed which is pressed to form the rnulti-layer hoard after transfer into the main pressing region and cured.
AMENDED SHEET

WO 01!12403 PCTIEP00107077 The present invention has the underlying object of providing a method and an apparatus of the kind initially mentioned which allow a continuoLtsly damage-free transport of the mat up to the finally pressed molded part.
Starting from a method of the kind initially mentioned, the object relating to the method is satisfied in that the base is covered at least regionally by a support web, in that the support web is moved along with the base and in that the particles forming the single layer or multi-layer mat are scattered onto the support web resting on the base. The part of the object relating to the apparatus is satisfied, starting from an apparatus initially mentioned, in that a supply unit for a support web is provided at the input side of the forming station and in that the support web can be supplied from the supply unit to the upper run of the mat carrier belt system and can be placed on this.
Since the support web, which covers the lower broad side of the mat, now acts as a stable support for the mat in the previously very critical region of the transfer position(s), the layer thickness and the structure of the pre-compacted mat are maintained such that a problem-free long-term operation is ensured. Moreover, a uniform surface structure and bulk density distribution of the mat finally pressed to form a molded part is achieved as the support web covering the lower side of the mat also prevents the risk of the adhering of mat particles, in particular to metal surfaces of the means of transport arranged in front of and in the final press.
In accordance with an advantageous embodiment of the invention, the upper side of the single layer or multi-layer mat scattered onto the base is - WO 01!12403 PCTIEP0010T077 covered by a cover web. In this way, the scattered and pre-compacted mat is given an even higher stability so that the risk of a structural change during the transport is even further reduced. In addition, a uniform surface structure and bulk density distribution is also achieved at the upper side of the mat finish pressed to form a molded part, since the cover web covering the upper side of the mat also prevents the risk of the adhering of mat particles, in particular to metal surfaces of the means of transport and/or pre-compacting units arranged in front of and in the finishing press.
The support web and/or the cover web can preferably be made as a web of paper, of fabric, of plastic or the like or as ~a combination thereof. They are advantageously made substantially impermeable to liquid in order to prevent a penetration of the binding agent through the support web and/or cover web and thus an adhering of the respective web to elements arranged in the transport path.
In accordance with a further preferred embodiment of the invention, the mat is scattered in one layer or in a plurality of layers, at least one .
scattered mat layer is pre-compacted after one or more scattering procedures and the pre-compacted mat is again pre-pressed as a unit before the finish pressing. Due to the respective pre-pressing, the residual air amount still present in the pre-compacted mat escapes almost completely and without vorticities at the mat. As a result of this, such a mat can be finish pressed at a higher run-through speed than before, in particular to form a board strand which has both high quality surfaces and a uniform bulk density distribution in the transverse and longitudinal WO 01!12403 PCTIEPOOf07077 directions. This applies in particular when the second pre-pressing takes place directly before the finish pressing.
It is expedient to admix the particles forming the single layer or multi-layer with an organic isocyanate solution such as poly-isocyanate, in particular a polymeric 4,4'-methylene diisocyanate (PMDI), and/ or starches and/or lignosulfonate and/or proteins and/or polyols and/or insecticides and/or fungicides and/or flame retardants and/or dyestuffs and/or fillers and/or reaction accelerants for the binding agent. With the exception of the reaction accelerants for the binding agent, in this connection the additives and auxiliary substances are particularly important which result in a better tack of the mat particles against their elastic resilience.
In accordance with another aspect of the invention, the finished molded parts are ground and the particles of paper, fabric, plastic or the like, including dust, which are incurred during the grinding of the finished board web or boards, are returned to the production process and reused together with the particles to form the rnat layer(s). Even any defective mat sections, which can arise due to causes unrelated to the problem underlying the invention, for example due to scattering errors, are mixed in comminuted form with the particles which form the mat layer(s).
Further advantageous features of the invention are set forth in the dependent claims and will also be explained in the embodiment description.

The invention will be described in more detail in the following with reference to an embodiment and to the drawing, in which are shown:
Fig. 1 a schematic side view of an apparatus made in accordance 5 with the invention; and Fig. 2 a section of a board made with this apparatus in cross-section.
Figure 1 shows by way of example a forming station 50 comprising three scattering apparatuses 55, 56, 57 for the continuous manufacture of boards made of straw particles admixed with at least one polymeric 4,4'-methylene diisocyanate (PMDI).
A mat carrier band system 52 is provided as the mat carrier and consists of endless belts 1, 2 and 3 which are impermeable to air, are arranged behind one another, are guided via deflection and drive rolls and move continuously in the direction of the arrows 4, 5 and 5.
A metering hopper 7, in which a plurality of back-scraping rakes 8 are arranged, is first arranged above the mat carrier belt 1 on the input side.
Cover layer straw particles admixed with at least one polymeric 4,4'-methylene diisocyanate (PMDI) are poured into the metering hopper 7 as is indicated by the arrow 9.
The discharge 10 of the metering hopper 7 is followed by belt scales 11, beneath which an endless scraper belt 12 guided over two deflection rolls is installed which, in accordance with German patent 197 16 130, interacts with a vibrating screen 13 which is movable to and fro. It is thus possible to scatter a lower cover layer of a mat 51 (Figure 2) made of straw particles admixed with at least one polymeric 4,4'-methylene diisocyanate (PMDI) onto the upper run 53 of the mat carrier belt 1.
It is essential to the invention that beforehand a support web 14, for example in the form of a web of paper, of fabric, of plastic or the like or of a combination thereof, is drawn off a supply unit 14 which has at least one roll 15 in the embodiment and is guided to the upper run 53 of the mat carrier belt 1. The web 16 forms a stable lower support for the mat 51 in the region of the transfer positions 54 and 33 from the mat carrier belt 1 to the mat carrier belt 2, from the mat carrier belt 2 to the mat carrier belt 3 and from the mat carrier belt 3 into a heatable, continuously operating double belt finishing press 17. At the same time, the web 16 prevents a sticking of mat particles to the means of transport arranged in front of and in the finishing press 17.
A pre-compacting unit 18 for the venting of the lower cover layer of the mat 51 is positioned downstream of the first scattering apparatus 55 which includes the metering hopper 7, the belt scales 11, the scraper belt 12 and the vibrating screen 13, which is movable to and fro. This unit 18 can consist of one or more pre-compacting rolls with or without endless belts, with a law pre-compacting of between approximately 0.5 and 1 bar being sufficient.
The second scattering apparatus 56 is positioned downstream of the pre-compacting unit 18. It includes a metering hopper 19, which includes a plurality of back-scraping rakes 20, belt scales 21 and a roller scattering head 22. Middle layer straw particles admixed with at least one PMDI are poured into the metering hopper 19 in the direction of the arrow 23, leveled, weighed and finally scattered onto the pre-compacted lower cover layer of the mat 51.
A pre-compacting unit 24, which has the same structure as the pre-compacting unit 18, follows the second scattering apparatus 56. The pre-compacting pressure should, however, amount to between approximately 1 and 1.5 bar in order to vent the middle layer of the mat 51 more strongly. An additional venting of the lower layer and of the middle layer of the mat by means of a vibration table 25 in the region of the roller scattering head 22 at the lower side of the upper run 53 of the mat carrier belt 1 is also advantageous.
A third scattering apparatus 57 on the output side is positioned downstream of the pre-compacting unit 24 and comprises a metering hopper 7', a plurality of back-scraping rakes 8', belt scales 11', a scraper belt 12' and a vibrating screen 13' which is movable to and fro. Since the third scattering apparatus 57 on the output side is formed in accordance with the first scattering apparatus 55 on the input side, the reference numerals were merely provided with a mark.
An upper cover layer made of straw particles admixed with PMDI is scattered by the third scattering apparatus 57 on the output side. As soon as the upper cover layer has been scattered on the middle layer of the mat 51 pre-compacted together with the lower cover layer, this multi-layer mat 51 enters into a pre-compacting unit 26. Its design corresponds to that of WO 01!12403 PCTlEP00107077 the pre-compacting units 18 and 24. The same applies to the pre-compacting pressures there.
After the pre-compacting unit 26, the multi-layer mat 51 - together with the support web 16 - is properly transferred from the upper run 53 of the mat carrier belt 1 onto the upper run 59 of the mat carrier belt 2 in the direction of the arrows 27 which indicate the production direction in the apparatus in accordance with the invention. The spacing between these belts 1, 2 can be increased in the double arrow direction 28 and/or 29 to take up any defective mat sectioris into a collection funnel 30 provided beneath the belts l, 2 and to return them into the production process by means of return screws 31, 32, whereby they are mixed in comminuted form with the particles to form the mat layers.
A supply unit 34 is provided above the mat carrier belt 2 and in the vicinity of the transfer position 33 from the mat carrier belt 2 to the mat carrier belt 3 and in the example has at least one roll 35 from which a drawn off cover web 36, for example in the form of a web of paper, of fabric, of plastic or the like or of a combination thereof, is placed onto the surface of the multi-layer and pre-compacted mat 51.
Downstream of the supply unit 34 is a pre-press 38 comprising an upper and a lower endless belt 37, 37' and the finishing press 17 which includes an upper and a lower endless belt 39, 39' between which a press nip 43 is formed with a run-in mouth 58 to receive the mat 51.
The cover web 36 forms an effective protection against a sticking of mat particles to the lower run of the upper endless belt 37 of the pre-press 38 and to the lower run of the upper endless belt 39 of the heatable, continuously operating double belt finishing press 17.
Alternatively to the supply unit 36, a supply unit 40 comprising at lest one roll 41 and transport web 42 can also advantageously be arranged above the pre-press 38, as is indicated in Figure 1 by broken lines, such that the transport web 42 is only combined with the surface of the mat 51 at the start of the press nip 43 of the heatable, continuously operating double belt finishing press 17.
A section of a mat 51 scattered by the apparatus of the invention in accordance with Figure 1 or a correspondingly manufactured board 44 can be seen in cross-section in Figure 2. It includes a lower cover layer 45 covered by a web 16 of paper, fabric, plastic or the like or a combination thereof, a middle layer 46 and an upper cover layer 47 which is covered by a web 36 or 42 of paper, fabric, plastic or the like or a combination thereof. These respective covers can, however, also be ground off again in a corresponding grinding process.

'10 Reference numeral list 1 mat carrier belt 2 mat carrier belt 3 rnat carrier belt 4 arrow direction 5 arrow direction 6 arrow direction 7,7' metering hopper 8,8' back-scraping rake 9,9' arrow direction 10 discharge of the metering hopper 11,11' belt scales 12,12' endless scraper belt 13,13' vibration screen 14 supply unit 15 roll 16 carrier belt 17 double belt finishing press 18 pre-compacting unit 19 metering hopper 20 back-scraping rake 21 belt scales 22 roller scattering head 23 arrow direction 24 pre-compacting unit ' 25 vibration table 26 pre-compacting unit ' CA 02380651 2002-O1-30 27 arrow direction 28,29 double arrow direction 30 collection funnel 31,32 return screw 33 transfer position 34 supply unit 35 roll 36 cover web 37 upper endless belt 37' lower endless belt 38 pre-press 39 upper endless belt 39' lower endless belt 40 supply unit 41 roll 42 cover web 43 press nip 44 board 45 lower cover layer 46 middle layer 47 upper cover layer 50 forming station 51 mat 52 mat carrier belt system 53 upper run 54 transfer position 55 scattering apparatus 56 scattering apparatus WO 01!12403 PCTfEP00l07077 57 scattering apparatus 58 run-in mouth 59 upper run

Claims

1. A method for producing molded parts, in particular boards, made of particles such as chips, fibers, comminuted straw particles, rice husks or the like containing ligno-cellulose and/or cellulose, which are admixed with at least one binding agent and which are scattered onto a moved base (52) to form a mat (51) which is subsequently initially pre-compacted and then finish pressed under the effect of heat to form a molded part, characterized in that the base (52) is covered at least regionally by a support web (16); in that the support web (16) is moved along with the base (52); and in that the particles forming a single layer or multi-layer mat (51) are scattered onto the support web (16) lying on the base (52).

2. A method in accordance with claim 1, characterized in that the upper side of the single layer or multi-layer mat (51) scattered onto the base (52) is covered by a cover web (36).

3. A method in accordance with claim 1 or claim 2, characterized in that a web of paper, of fabric of plastic or of a combination thereof is used as the support web (16) and/or as the cover web (36).

4. A method in accordance with claim 1, claim 2 or claim 3, characterized in that a support web (16) substantially impermeable to liquid and/or a cover web (36) is used.

5. A method in accordance with any one of the preceding claims, characterized in that the mat (51) is scattered in one layer or in a plurality of layers (45, 46, 47); in that at least one scattered mat layer is pre-compacted after one or more scattering processes and in that the pre-compacted mat (51) is main pre-pressed as a unit before the finish pressing.

6. A method in accordance with claim 5; characterized in that the repeat pre-pressing of the pre-compacted mat (51) takes place directly before the finish pressing.

7. A method in accordance with claim 5 or claim 6, characterized in that the cover webs is placed on the surface of the pre-compacted mat (51) before or after its pre-pressing.

8. A method in accordance with any one of the preceding claims, characterized in that the particles forming the one layer or multi-layer mat (51) are admixed with an organic isocyanate solution.

9. A method in accordance with claim 8, characterized in that the particles forming the single-layer or multi-layer mat (51) are admixed with poly-isocyanate, in particular a polymeric 4,4'-methylene diisocyanate (PMDI) and/or starches and/or lignosulfonate and/or proteins and/or polyols and/or insecticides and/or fungicides and/or flame retardants and/or dyestuffs and/or fillers and/or reaction accelerants for the binding agent.

10. A method in accordance with any one of the preceding claims, characterized in that the mat (51) is finish pressed to form boards.

11. A method according to any one of the preceding claims, characterized in that the finished molded parts are ground and the dust incurred during the grinding, which can include particles of the support web and/or of the cover web, is returned into the production process and is reused together with the particles to form the mat layer(s)(45, 46, 47).

12. A method according to any one of the preceding claims, characterized in that the mat (51) is scattered onto a continuously moved base (52) for the continuous manufacture of the molded parts.

13. An apparatus for the manufacture of molded parts, in particular of boards, made of particles such as chips, fibers, cut straw particles, rice husks or the like containing ligno-cellulose and/or cellulose admixed with at least one binding agent, comprising a forming station to form a single layer or multi-layer mat (51) consisting of the particles on a mat carrier belt system (52) arranged beneath the forming station (50) and serving as a moved base for the particles admixed with a binding agent and scattered on by the forming station, an apparatus (18, 24, 26) for the pre-compacting of the scattered mat (51) and a finishing press (17) adjacent to the forming station (50), in particular for the carrying out of the method in accordance with any one of the preceding claims, characterized in that a supply unit (14) for a support web (16) is provided on the input side of the forming station (50) and in that the support web (16) can be supplied from the supply unit (14) to the upper run (53) of the mat carrier belt system (52) and can be placed onto this.

14. An apparatus in accordance with claim 13, characterized in that the supply unit (14) includes at least one roll (15), from which the support web (16) can be wound off.

15. An apparatus in accordance with claim 13 or claim 14, characterized in that a supply unit (34, 40) for a cover web (36, 42) is provided above the mat carrier belt system (52) and in that the cover web (36, 42) can be placed from the supply unit (34, 40) onto the surface of the mat (51) arranged on the mat carrier belt system (52).

16. An apparatus in accordance with claim 15, characterized in that the supply unit (34, 40) includes at least one roll (35, 41) from which the cover web (36) can be wound off.

17. An apparatus in accordance with any one of claims 13 to 16, characterized in that a pre-press (38) for the pre-pressing of the pre-compacted mat (51) is arranged between the apparatus (18, 24, 26) for pre-compacting the scattered mat (51) and the finishing press (17),

18. An apparatus in accordance with claim 17, characterized in that the supply unit (34, 40) for the cover web (36, 42) of the pre-press (38) is disposed upstream of, downstream of or above the pre-press (38).

19. An apparatus in accordance with any one of claims 13 to 18, characterized in that the mat carrier belt system (52) includes at least two mat carrier belts (1, 2, 3) which are respectively adjacent to one another at a transfer position (33, 54) for transferring the mat from the one mat carrier belt (1, 2) to the mat carrier belt (2, 3) adjacent to it.

20. An apparatus in accordance with claim 19, characterized in that the spacing between the mat carrier belts (1, 2) is adjustable.

21. An apparatus in accordance with claim 19 or claim 20, characterized in that the supply unit (34, 40) for the cover web (36, 42) is arranged downstream of the transfer position (54, 33).

22. An apparatus in accordance with any one of claims 13 to 21, characterized in that the forming station (50) includes one or more scattering apparatuses (55, 56, 57), in particular having a roller scattering head (22) or the like, and in that a pre-compacting unit (18, 24, 26) is disposed downstream of each or at least one part of the scattering apparatuses (55, 56, 57) and consists in particular of one or more pre-compacting rolls with or without endless belts.

23. An apparatus in accordance with claim 22, characterized in that one vibration table (25) is respectively provided at the lower side of the upper run (53) of the mat carrier belt system (52) in the region of at least of one part of the scattering apparatuses (55, 56, 57), in particular of the roller scattering head (22).

24. An apparatus in accordance with any one of claims 13 to 23, characterized in that the finishing press (17) includes a press gap (43) and a run-in mouth (58) disposed upstream of the press gap (43) and in that a part of the pre-press (38) projects into the run-in mouth (58) close up to the start of the press gap (43) of the finishing press (17).

25. An apparatus in accordance with any one of claims 13 to 24, characterized in that the finishing press (17) is formed as a double belt finishing press.

26. An apparatus in accordance with any one of claims 13 to 25, characterized in that the support web (16) and/or the cover web (36, 42) is formed as a web of paper, of fabric or of plastic or as a combination thereof.