EP3020525A1

EP3020525A1 - Process and plant for producing panels made from waste paper

Info

Publication number: EP3020525A1
Application number: EP15194360.2A
Authority: EP
Inventors: Guido Giovanni Locati
Original assignee: Seccarta Srl
Current assignee: Seccarta Srl
Priority date: 2014-11-13
Filing date: 2015-11-12
Publication date: 2016-05-18
Anticipated expiration: 2035-11-12
Also published as: EP3020525B1

Abstract

The present invention refers to a process and a plant for producing panels made from waste paper, comprising the steps of forming an incoherent mass (M) containing particles of waste paper, depositing the incoherent mass (M) onto a support (13) so as to form a layer (S) of substantially uniform thickness (S1) and applying a pressure to such a layer (S), wherein a first liquid (L1) is sprayed onto or into the incoherent mass (M) during the deposition step before the formation of the layer (S).

Description

The present invention refers to a process for producing panels made from waste paper.
The present invention also refers to a plant for producing panels made from waste paper.
By waste paper it is meant to indicate paper, solid board, corrugated cardboard and the like deriving from industrial or domestic waste.
From EP0990069B1 a process and a plant for producing paper and paperboard sheets starting from waste paper are already known.
According to what is described in EP0990069B1 , the waste paper is ground and chopped until an incoherent mass of particles is obtained, the particles having average dimensions of less than 7mm and, generally, comprised between 2mm and 5mm.
This incoherent mass is distributed onto a support, in practice consisting of a conveyor belt, so as to form a layer of substantially uniform thickness.
A liquid, generally consisting of water and glue, is then sprayed onto the layer thus obtained. The layer thus sprayed is then subjected to a compacting compression at pressure values equal to at least 19.6 MPa (200 kg/cm²) and, preferably, comprised between 29.4 MPa (300 kg/cm²) and 49 MPa (500 kg/cm²).
In a possible alternative embodiment, after the spraying step and before the compression step, a second layer of incoherent mass is deposited onto the first layer.
After pressing, the sheet is air-dried or dried in a possible drier.
EP1232048B1 describes a process and a plant for producing stiff paper or paperboard sheets from waste paper, wherein after the compacting compression step the sheet is subjected to a second pressing at which it is simultaneous formed with a plurality of recesses creating stiffening corrugations.
The paper or paperboard sheets obtained according to what is described in EP0990069B1 have been the object of in-house experiments carried out by the owner and aimed at evaluating, in particular, the heat and sound insulation characteristics thereof to verify the possibility of using it in the building field as components of vertical and horizontal partitions and of insulation coatings.
During the course of such experiments, however, it was found that the paper or paperboard sheets obtained according to what is described in EP0990069B1 do not have sufficient structural and heat and/or sound insulation characteristics suitable for their use in the building field.
The Applicant has, therefore, surprisingly found that by modifying the process parameters, on the other hand, it is possible to obtain panels made from waste paper that have both mechanical characteristics and heat and sound insulation characteristics that make them particularly suitable for making thermic insulations and soundproofings.
Therefore, the object of the present invention is a process and a plant for producing panels made from waste paper that make it possible to obtain panels having mechanical characteristics and both heat and sound insulation characteristics that make them particularly suitable for making thermic insulations and soundproofings.
The process and the plant for producing panels made from waste paper object of the present invention make it possible to obtain panels that have a relatively low thickness and low average density and that have sound and heat insulation characteristics that are comparable, if not better, than those of known insulating panels currently available on the market.
The process and the plant for producing panels made from waste paper object of the present invention make it possible to obtain, with low costs, panels usable, also by themselves, in particular, in building for making vertical and horizontal partitions and coatings of external walls of buildings that are new or undergoing renovation.
The object of the present invention is therefore a process for producing panels made from waste paper of the multi-phase type and that comprises the steps of:

a) forming an incoherent mass containing particles of waste paper;
b) depositing the incoherent mass obtained in step a) onto a support so as to form a layer of substantially uniform thickness;
c) applying a pressure to the layer obtained in step b) ;

Advantageously, the incoherent mass consists solely of particles of waste paper.
According to a further aspect of the present invention, before step b), there is provided a step a1) consisting of wetting the support with a second liquid.
According to another aspect of the present invention, before step b), there is provided a step a0) consisting of depositing a first continuous sheet of paper onto the support. In this case, it is possible to provide, after step a0) and before step b), a step a1') consisting of wetting the first sheet deposited on the support with a second liquid before the incoherent mass is deposited onto the first sheet, thus wetted, to form said layer.
According to yet another aspect of the present invention, after step b) and before step c), there is provided a step b1) consisting of wetting the surface of the layer - which was formed in said step b) - opposite that resting on said support with a third liquid.
According to a further aspect of the present invention, after step b) and before step c), there is provided a step b2) consisting of depositing a second continuous sheet of paper onto the surface of the layer - which was formed in step b) - opposite that resting on said support. In this case, step b1), if present, is carried out before step b2); i.e. the surface of the layer formed in step b) which is opposite that resting on the support is wetted with the third liquid before the second continuous sheet of paper is deposited on it.
According to yet another aspect of the present invention, the pressure applied during step c) is comprised between 20 kg/cm² (1.96 MPa) and 70 kg/cm² (6.86 MPa) and, preferably, it is comprised between 30 kg/cm² (2.94 MPa) and 50 kg/cm² (4.9 MPa).
Step a) takes place by grinding or in any case crumbling or shredding of pieces of waste paper into particles of average dimensions of the order of a few millimetre units.
In a preferred embodiment of the process object of the present invention, the particles have average dimensions comprised between 4 mm and 10 mm and preferably comprised between 5 mm and 7 mm.
It should be noted that for the purposes of the present invention, the term "particles" is meant to indicate fragments or small pieces of waste paper that, as already indicated above, have average dimensions of the order of a millimetre or a few units of millimetres and less than ten millimetres. Such "particles" should not therefore be confused with or considered as cellulose fibres that make up paper or paperboard.
It should also be specified that the term "incoherent mass" is meant to indicate a group of particles, comprising the particles of waste paper, not mutually cohesive or in any case joined. Preferably, the incoherent mass consists of only particles of waste paper.
The term "waste paper" is meant to indicate paper, solid board, corrugated cardboard or similar deriving from industrial or domestic waste.
Step b) takes place by letting the incoherent mass fall from a greater height than that of the support onto the support itself.
Step b), therefore, takes place by distributing by "sprinkling" the incoherent mass onto the support so as to form a layer of substantially uniform thickness.
Such a layer has, in a preferred embodiment, a thickness S1 comprised between 30 mm and 100 mm and, even more preferably, comprised between 50 mm and 80 mm.
As indicated above, during step b), a first liquid is sprayed onto the incoherent mass, into the incoherent mass or in any case so as to cover the entire incoherent mass penetrating and distributing into the incoherent mass before the latter forms the layer of thickness S1 (hereinafter also indicated as "layer S" or "layer S1").
Such a first liquid is sprayed onto the incoherent mass, into the incoherent mass or in any case so as to cover the entire incoherent mass while said mass is deposited onto the support and before said mass forms the layer of thickness S1.
Such a first liquid is sprayed onto the incoherent mass, into the incoherent mass or in any case so as to cover the entire incoherent mass while the latter is falling onto the support and so that said first liquid is distributed into the incoherent mass both along a direction that passes through such an incoherent mass along the dimension thereof that forms the thickness S1 of the layer S and along a direction that forms the width of such a same layer.
In particular, such a first liquid is sprayed so as to form one or more jets directed along at least one direction having a component parallel to the laying plane of the support itself. Even more specifically, such a first liquid is sprayed so as to form one or more jets each of which propagates along a direction that passes through the incoherent mass along the dimension thereof that forms the thickness S1 of the layer and/or along a direction that forms the width of such a same layer.
Each jet can be of different shapes: "sprinkling", "sheets" or other and can hit the incoherent mass falling onto the support from the outside (i.e. laterally) or from inside it. Thus, the number of such jets can vary as a function of their shape and size.
What is important is that the first liquid is sprayed so as to cover the entire incoherent mass and be distributed into it in a substantially uniform manner.
Steps a1) and a1') comprise applying the second liquid, respectively, directly onto the support or onto the first sheet, through spraying or nebulization in one or more jets so as to distribute it substantially uniformly over the entire portion of the surface, respectively, of the support or of the first sheet on which the layer S1 is subsequently deposited.
In a preferred embodiment, such jets are directed transversally, advantageously orthogonally, to the plane defined by the support or by the first sheet resting on it.
Also in this case, such jets can be of various shapes: "sprinkling", "sheets" or other. Thus, the number of such jets can vary as a function of their shape and sizes.
Similarly, step b1) comprises applying the third liquid directly onto the face of the layer S1 opposite that resting on the support, through spraying or nebulization in one or more jets so as to distribute it substantially uniformly over the entire portion of the surface of the layer S1.
In a preferred embodiment, such jets are directed transversally, advantageously orthogonally, to the plane defined by the layer S1 (i.e. by the support).
Also in this case, such jets can be of various shapes: "sprinkling", "sheets" or other. Thus, the number of such jets can vary as a function of their shape and sizes.
The first sheet and the second sheet of paper, if present, each have a "weight" (grammage) comprised between 35 gr/m² and 100 gr/m², preferably equal to 50 gr/m².
The first liquid, the second liquid and the third liquid are the same or different from each other.
In a preferred embodiment, the first liquid, the second liquid and the third liquid are equal to each other.
In a further preferred embodiment, the first liquid, the second liquid and the third liquid each comprise water and a glue in proportions comprised, respectively, between 20% and 40% (water) and between 80% and 60% (glue), advantageously equal to 30% water and 70% glue, as a function of or excluding the percentage of water or humidity possibly present in the glue in the form in which it is commercialised.
The glue is, for example, a silicate-based glue, of the silicate type and, in particular, of the sodium-silicate type.
The first liquid, the second liquid and the third liquid each consist solely of water and a glue in the proportions indicated above, in which the glue is preferably silicate-based and even more preferably of the sodium-silicate type. The first liquid, the second liquid and the third liquid are sprayed as such, respectively, into or through the incoherent mass, onto the support or onto the first sheet of paper and onto the upper surface of the layer of particles deposited.
The quantities, per unit surface of the layer S1 or in any case of the final panel, respectively of the first liquid, of the second liquid and of the third liquid are the same or different from each other.
In a preferred embodiment, the quantities, per unit surface of the layer S1 or in any case of the final panel, respectively of the first liquid, of the second liquid and of the third liquid are equal to each other.
In a further preferred embodiment, the first liquid, the second liquid and the third liquid are equal to each other and comprise water and a glue and the quantities, per unit surface of the layer S1 or in any case of the final panel, respectively of the first liquid, of the second liquid and of the third liquid are equal to each other.
In this case, the total quantity of liquid applied overall per unit surface of final panel is divided into three equal fractions: one third is sprayed onto the support or onto the first sheet in step a1) or a1'), one third is sprayed into the incoherent mass in step b) and one third is sprayed onto the surface of the layer S1.
It will be clear to the person skilled in the art that the degree of distribution of humidity and the "wetting" of the particles therefore varies along the thickness of the panel. Generally and on average, therefore, the particles at and close to the opposite faces of the panel or of corresponding surface layers thereof are wetter than those at the centre thereof.
The overall quantity of the first liquid, of the second liquid and of the third liquid is comprised between 0.5 kg/m² and 1 kg/m² of final panel and preferably equal to 0.7 kg/m².
The layer S1, possibly with the first sheet and the second sheet applied on one or both of its opposite faces, respectively, is subjected to a compression action at a pressure comprised between 20 kg/cm² (1.96 MPa) and 70 kg/cm² (6.86 MPa) and, preferably, comprised between 30 kg/cm² (2.94 MPa) and 50 kg/cm² (4.9 MPa).
Due to the application of such a pressure, the layer S1 undergoes a reduction in thickness; the thickness S2 of such a layer after step c) is equal to about 1/10 of S1.
Such pressures, the values of which are relatively low in particular if compared to those applied according to the teachings of EP0990069B1 , have the effect of promoting a "light" compacting of the layer S1 and the cohesion thereof with the possible first and second sheet; such pressures, however, do not promote the evacuation of the liquid, the overall quantity of which is small.
The layer S2 obtained with step c) is cut into single panels and left to air-dry.
In an alternative embodiment, after step c) there is provided at least one further step of processing the layer S2, like, for example, a surface finishing step, a step of application onto its opposite faces of further layers of heat and/or sound insulating materials such as, for example, bands of felt or nonwoven fabric (NWF) made of recycled polypropylene (PP) or other material and/or of stamping of indentations or corrugations.
Such further processings can also be carried out on the single panels cut from the layer S2.
In a preferred embodiment the layer S2 or the panels obtained from it are subjected to an indentation machining aimed at stamping a plurality of discreet indentations in them. The indented panels thus obtained are particularly suitable for making floor insulation or in any case horizontal partitions; the indentations, indeed, make discrete contact points with the slab that minimise the transfer of vibrations and, therefore, contribute to better soundproofing.
Figures 2 to 4 show schematic section views of different possible panels obtained with a process according to the present invention.
With reference to such figures, a panel obtainable with the process object of the present invention is indicated with P1, P2 and P3.
The panel P1 (figure 2) consists of only the layer of incoherent mass and, generally, has a thickness S2 comprised between 5 mm and 10 mm and weight comprised between 2 kg/m² and 3.5 kg/m².
It should be noted that the innermost portion of the panel P has a substantially "sponge-like" configuration of lower average density than that of the outermost surface portions thereof. The term "outermost surface portions" is meant to indicate the portions of the panel that define the opposite faces thereof and that each have a thickness S4, whereas the term "innermost portion" of the panel is meant to indicate the portion of the panel comprised between the two "outermost surface portions" thereof and having thickness S3>S4, in which, defining the thickness of the panel after step c) as S2, S3+2S4=S2 with S2<S1.
In a preferred embodiment, S2 is less than S1 and S3 is equal to about 60% of S2 and S4 is equal to about 20% of S2.
As schematically represented in the attached figures 2 to 4 and illustrated, in particular, in the schematic diagrams according to figures 3A and 4A the density of the innermost portion S3 and of the outermost surface portions S4 is not uniform (i.e. constant in their entire thickness); the density of the panel P1, indeed, varies along its thickness and, in particular, it should be noted that its density increases starting from the centre towards the outside thereof along a direction orthogonal to the opposite faces thereof.
In particular it has been found that in the innermost portion S3 of the panel P1 a greater number of air bubbles is concentrated, said bubbles being thought to contribute in giving the panel P1 heat insulation characteristics.
This particular "sponge-like" configuration and this particular distribution of mass and air in the more central portion S3 of the panel P1 is obtained thanks to the application of the first liquid so that it covers the incoherent mass and is distributed in the incoherent mass while the latter is deposited onto the support and before forming the layer S1.
The surface application of the second and third liquid, on the other hand, contributes to creating the two outermost surface portions S4 with greater average density and compacting.
The application of a pressure comprised between 20 kg/cm² (1.96 MPa) and 70 kg/cm² (6.86 MPa) and, preferably, comprised between 30 kg/cm² (2.94 MPa) and 50 kg/cm² (4.9 MPa), cooperates synergically with the application of the first liquid and of the possible second and third liquid in obtaining a panel P1 with a stratified and diversified structure, in particular with variable density along the thickness, as described above.
It should be noted that, thanks to such a stratified and diversified structure, the elastic yield of the panel P1 considered along a direction orthogonal to its faces is greater at its central portion S3 and lesser at the outermost surface portions S4 thereof. Overall, therefore, the panel P1 behaves like a "spring"; it is thought that such a structure contributes to giving the panel P1 soundproofing characteristics.
Inside the panel P1 vitreous particles deriving from the dried glue are dispersed, which it is thought also contribute to giving the panel P1 soundproofing characteristics by reflecting the sound waves in various directions.
The panel P2 differs from the panel P1 solely in that its two opposite faces are respectively covered with a first sheet F1 and a second sheet F2 of paper.
The panel P3 is like the panel P2 at the opposite faces of which respective layers T1 and T2 of felt or nonwoven fabric (NWF) made of recycled polypropylene (PP) or other insulating material have been applied, for example by gluing.
In this case, there is a multiplication of the "spring" effect.
With reference to the attached figure 1 a plant 10 for producing a panel according to the present invention will now be illustrated as a non-limiting example.
The plant 10 is suitable for continuously producing panels according to the present invention.
The plant 10 comprises:

a formation group 11 for forming an incoherent mass M containing particles of waste paper,
a distribution group 12 for depositing the incoherent mass M onto a support 13 so as to form a layer S of substantially uniform thickness S1;
a pressing group 14 for applying a pressure to the layer S; and
a first spraying group 15 for spraying a first liquid L1 onto or into said incoherent mass M dispensed by the distribution group 12 and before the formation of the layer S.

The plant 10 also comprises:

a second spraying group 16 that is arranged upstream with respect to the distribution group 12 to spray a second liquid L2 onto the support 13 before the formation of the layer S, and
a third spraying group 17 that is arranged downstream of the distribution group 12 to spray a third liquid L3 onto the surface of the layer S opposite that resting on the support 13.

The support 13 advantageously consists of a plane that is mobile along an advancement direction and sense and, for example, consists of the upper branch of a continuous conveyor belt that is drawn in motion by a pair of pulleys 18 as indicated by the arrows shown in figure 1.
The "upstream" and "downstream" arrangement refers to the advancement sense of the upper branch of such a conveyor belt.
Advantageously, in a preferred embodiment, the plant 10 comprises, upstream of the distribution group 12, a first deposition group 19 for depositing a first continuous sheet F1 of paper onto the support 13 before the incoherent mass M is deposited onto it and the layer S forms.
Advantageously, the first sheet F1 is laid onto the support 13 before the second liquid L2 is applied onto it, which, therefore, is applied onto the first sheet F1.
Advantageously, moreover, downstream of the distribution group 12, there is a second deposition group 20 for depositing a second continuous sheet F2 of paper onto the surface of the layer S opposite that resting on the support 13, i.e. on the upper surface of the layer S.
Preferably, the second group 20 is arranged downstream of the third spraying group 17, in which case, therefore, the third liquid L3 is applied on the upper surface of the layer S before the second sheet F2 is deposited onto it.
Downstream of the pressing group 14 a cutting group 21 is arranged for obtaining a plurality of panels that are then collected in piles in a collection station 22.
The formation group 11 comprises means for grinding waste paper collected in accumulators 23. Such grinding means can consist of rotary toothed drums or other chipping and cutting systems. Such a formation group 11 reduces the paper and/or paperboard into particles of average dimensions comprised between 4 mm and 10 mm and preferably comprised between 5 mm and 7 mm.
The particles thus formed are conveyed, for example by means of conveyors 24, to the distribution group 12.
The latter comprises a hopper 25 in which means 26 for mixing or in any case agitating the incoherent mass M are housed.
The bottom of the hopper 25 is arranged above the support 13 and at a greater height with respect to it.
At the bottom of the hopper 25 dosing means 27 are arranged - for example of the type of a rotary drum equipped on its outer side surface with toothings, grooves or brushes - which dose the incoherent mass M distributing it onto the support 13.
The incoherent mass M falls from above onto the support 13 on which it collects to form the layer S.
The first spraying group 15 is arranged and configured to generate at least one jet of the first liquid L1 that is directed along at least one direction having a component parallel to the laying plane of the support 13 and that engages the incoherent mass M while it is falling onto the support 13 and before it forms the layer S thus being distributed inside it.
The first spraying group 15 can be arranged outside of the incoherent mass M coming out from the distribution group 12 and, in particular, laterally and upstream of it, or inside it.
The first spraying group 15 can consist of one or more nozzles generating jets in "sprinkled", "sheet" or other shapes.
Such nozzles are in any case configured, arranged and sized so as to generate jets that engage the incoherent mass M along the dimensions thereof that form the thickness of the layer S and the width of the layer S so as to cover it entirely.
With reference to the embodiment represented in figure 1, the first spraying group 15 can comprise one or more nozzles distributed in a row along the width of the support 13 and oriented so as to generate jets that pass transversally through the incoherent mass M dispensed by the distribution group 12.
The second spraying group 16 and the third spraying group 17 each comprise one or more nozzles distributed in a row along the width of the support 13 and each adapted for generating a jet that hits the support 13 in a direction orthogonal to it.
Also in this case, such jets can be of the "a sprinkle", "sheet" or other type.
The first liquid L1, the second liquid L2 and the third liquid L3 can be the same or different from each other; in a preferred embodiment they are equal to each other and they consist of a liquid obtained by mixing water and a glue, for example of the silicate type and preferably of the sodium-silicate type.
In this case, there is a common reservoir 28 into which the water and the glue material are fed, taken in the desired percentages from respective containers 29 and 30.
Three distribution lines 31, 32 and 33, along which adjustment and control means, not shown, are provided, distribute desired doses of the liquid respectively to the first, second and third spraying group 15, 16 and 17.
Preferably, the doses of liquid fed to the three spraying groups 15, 16 and 17 are equal to each other.
The first deposition group 19 and the second deposition group 20 each comprise a respective reel from which the first sheet F1 and the second sheet F2, respectively, is unwound at controlled speed and synchronous with that of the support 13.
The pressing group 14 can consist of a plurality of pairs of opposite and counter-rotating rollers 34 between which the layer S (on the opposite faces of which the first sheet F1 and the second sheet F2 are possibly applied) supported by the support 13 passes.
Advantageously, a band 35 is wound around the rollers 34 that face the upper surface of the layer S.
The pressing group 14 is shaped and sized so as to apply a pressure comprised between 20 kg/cm² (1.96 MPa) and 70 kg/cm² (6.86 MPa) and, preferably, comprised between 30 kg/cm² (2.94 MPa) and 50 kg/cm² (4.9 MPa).

BRIEF DESCRIPTION OF THE FIGURES

Figure 1 is a diagram of a plant for producing panels made from waste paper according to the present invention;
figures 2, 3 and 4 show schematic section views of different possible panels made from waste paper obtained with a process according to the present invention;
figures 3A and 4A schematically show the graph of the state of the average density along the thickness of the panels according to figures 3 and 4, respectively.

EXAMPLE

Waste paper was chopped into particles of average dimensions of about 5 mm to form an incoherent mass.
On a conveyor belt moving at a speed of 5 m/min a first continuous sheet of paper of grammage equal to about 50 gr/m² was deposited, onto which an incoherent mass of such particles in a quantity equal to about 2. 3 kg for every m² of panel obtained was continuously distributed.
Such an incoherent mass was distributed onto the conveyor belt so as to obtain a layer of substantially uniform thickness S1 equal to about 70 mm.
Onto the upper surface of the layer S1 a second continuous sheet of paper of grammage equal to about 50 gr/m² was deposited.
A liquid consisting of 30% water and 70% glue (i.e. commercial silicate, specifically "Nacoren F" - sodium salt of silicic acid with molar ratio >3.2 and content <40% of Ingessil S.r.l.) was applied in a quantity equal to 0.7 kg for every m² of panel produced.
In particular, such a quantity was sprayed for one third onto the first sheet before the layer S1 was formed on it, for one third in the incoherent mass falling onto the conveyor belt and before the formation of the layer S and for one third onto the upper surface of the layer S before the second sheet was deposited on it.
The layer S was then subjected to a pressure of about 30 kg/cm² with a reduction of the thickness from S1 to S2, where S2 is equal to about 7 mm.
Such a layer was cut to obtain panels of dimensions 100 mm x 100 mm on the opposite surfaces of which a respective layer of nonwoven fabric in PP of thickness of 3 mm and weight equal to about 400 gr/m² was applied.
The panels thus obtained were subjected to sound and thermic insulation tests according to current standards and it was found that for floor sound insulation they have a sound-insulating power ΔL_w equal to about 24, for wall insulation they have a sound-insulating power Rw comprised between 48 and 52 and for thermic insulation they have a heat conductivity coefficient λ comprised between 0.034 and 0.040.
It was also found that such panels according to the example given and, in general, obtained according to the process object of the present invention have mechanical characteristics of flexural strength that are better than those of the sheets obtained with the process object of EP0990069B1 . Such characteristics, as it is easy for the person skilled in the art to understand, facilitate the manipulation, the application and, in particular, the use of vertical partitions of the "plasterboard" type of the panels obtained with the process object of the present invention.
The panels obtained with the process and with the plant object of the present invention have the advantage of having good mechanical characteristics and good thermic and sound insulation characteristics; therefore, they can be used, even by themselves, to make insulation elements and in particular to make vertical and horizontal partitions or insulation coatings in the field of building both in new buildings and in buildings under renovation.
The panels obtained with the process and with the plant object of the present invention have the advantage of also having an overall thickness that is low and relatively low average densities, which makes them usable, even by themselves, to make insulation elements not only for vertical partitions - thus leaving more useful walking surface - but also of external walls (coatings).
The panels obtained with the process and with the plant object of the present invention have the advantage of being obtained with essentially waste materials and with a low use of water and energy. This on the one hand reduces the production costs of such panels and on the other hand favours environmental protection.
The present invention has been described for illustrating, but not limiting purposes according to preferred embodiments thereof, but it should be understood that variations and/or modifications can be made by the person skilled in the art without for this reason departing from the relative scope of protection, as defined by the attached claims.

Claims

Process for producing panels made from waste paper, comprising the steps of:
a) forming an incoherent mass (M) containing particles of waste paper;

b) depositing said incoherent mass (M) onto a support (13) so as to form a layer (S) having a substantially uniform thickness (S1);

c) applying a pressure to said layer (S);
wherein a first liquid (L1) is sprayed onto or into said incoherent mass (M) during said step b) before the formation of said layer (S).
Process according to claim 1, comprising, before said step b), a step a1) of wetting said support (13) with a second liquid (L2).
Process according to claim 1, comprising, before said step b), a step a0) of depositing a first continuous sheet (F1) of paper onto said support (13).
Process according to claim 3, comprising, after said step a0) and before said step b), a step a1') of wetting said first continuous sheet (F1) of paper with a second liquid (L2).
Process according to one or more of the previous claims, characterised in that it comprises, after said step b) and before said step c), a step b1) of wetting the surface of said layer (S) opposite the one resting on said support (13) with a third liquid (L3).
Process according to one or more of the previous claims, comprising, after said step b) and before said step c), a step b2) of depositing a second continuous sheet (F2) of paper onto the surface of said layer (S) opposite that resting on said support (13).
Process according to claims 5 and 6, wherein said step b1) precedes said step b2).
Process according to one or more of the previous claims, wherein said pressure is comprised between 20 kg/cm² (1.96 MPa) and 70 kg/cm² (6.86 MPa), preferably between 30 kg/cm² (2.94 MPa) and 50 kg/cm² (4.9 MPa).
Process according to one or more of the previous claims, wherein said step b) occurs by making said incoherent mass (M) fall, from a greater height than that of said support (13), onto said support (13) itself, wherein said first liquid (L1) is sprayed onto or into said incoherent mass (M) falling onto said support (13), wherein said first liquid (L1) is sprayed along at least one direction having a component parallel to the laying plane of said support (13).
Process according to one or more of the previous claims, wherein at least one of said first liquid (L1), said second liquid (L2) and said third liquid (L3) comprises water and glue in quantities respectively comprised between 20% and 40% (water) and between 80% and 60% (glue).
Process according to one or more of the previous claims, wherein the quantities, per unit surface of said layer (S), respectively of said first liquid (L1), of said second liquid (L2) and of said third liquid (L3) are equal to or different from one another, wherein the overall quantity of said first liquid (L1), of said second liquid (L2) and of said third liquid (L3) is comprised between 0.5 kg/m² and 1 kg/m².
Plant (10) for producing panels made from waste paper, characterised in that it comprises:
- a formation group (11) for forming an incoherent mass (M) containing particles of waste paper;

- a distribution group (12) for depositing said incoherent mass (M) onto a support (13) so as to form a layer (S) having a substantially uniform thickness (S1);

- a pressing group (14) for applying a pressure onto said layer (S);

- a first spraying group (15) for spraying a first liquid (L1) onto or into said incoherent mass (M) dispensed by said distribution group (12) and before the formation of said layer (S).
Plant (10) according to claim 12, characterised in that it comprises a second spraying group (16) arranged upstream with respect to said distribution group (12) for spraying a second liquid (L2) onto said support (13) before the formation of said layer (S).
Plant (10) according to claim 12, characterised in that it comprises, upstream of said distribution group (12), a first deposition group (19) for depositing a first continuous sheet (F1) of paper onto said support (13) before the formation of said layer.
Plant (10) according to claim 14, characterised in that it comprises, upstream of said distribution group (12) and downstream of said first deposition group (19), a second spraying group (16) for spraying a second liquid onto said first continuous sheet (F1) of paper before the formation of said layer (S).
Plant (10) according to one or more claims 12 to 15, characterised in that it comprises, downstream of said distribution group (12), a third spraying group (17) for spraying a third liquid (L3) onto the surface of said layer (S) opposite that resting on said support (13).
Plant (10) according to one or more claims 12 to 16, characterised in that it comprises, downstream of said distribution group (12), a second deposition group (20) for depositing a second continuous sheet (F2) of paper onto the surface of said layer (S) opposite that resting on said support (13).
Plant (10) according to claims 16 and 17, characterised in that said second deposition group (20) is arranged downstream of said third spraying group (17).
Plant (10) according to one or more claims 12 to 18, characterised in that said pressure is comprised between 20 kg/cm² (1.96 MPa) and 70 kg/cm² (6.86 MPa) preferably between 30 kg/cm² (2.94 MPa) and 50 kg/cm² (4.9 MPa).