WO2008092807A1

WO2008092807A1 - Process for manufacturing panels for constructing articles of furniture such as cupboards, modular kitchens and furniture items in general, and panel obtained by the process.

Info

Publication number: WO2008092807A1
Application number: PCT/EP2008/050872
Authority: WO
Inventors: Roberta Bas
Original assignee: Macber S.R.L.
Priority date: 2007-02-01
Filing date: 2008-01-25
Publication date: 2008-08-07
Also published as: EP2167731A1

Abstract

A process for manufacturing panels, in particular panels for producing articles of furniture, characterised by comprising the following steps: -providing a mass of paper mill sludge in a quantity of 450-900 kg per cubic metre of finished product, -micronizing said paper mill sludge and spreading it over a surface to form a blanket, -pressing said blanket and simultaneously mixing it with a quantity of soluble resin between 600 and 1100 kg per cubic metre of finished product, -drying the blanket impregnated with soluble resin while maintaining said blanket pressed.

Description

PROCESS FOR MANUFACTURING PANELS FOR CONSTRUCTING ARTICLES OF FURNITURE SUCH AS CUPBOARDS, MODULAR KITCHENS AND FURNITURE ITEMS IN GENERAL, AND PANEL OBTAINED BY THE PROCESS The present invention relates to a process for manufacturing panels for constructing articles of furniture such as cupboards, modular kitchens and furniture items in general, and a panel obtained by the process.

In the furniture sector it is known to use substitutes for solid wood such as chipboard panels, plywood and wood fibre panels of low, medium and high density, also known by the respective symbols LDF, HDF and MDF.

These types of panels are produced from wooden chips, which are firstly subjected to grinding processes, after which sawdust, glue and additives such as urea resins or other natural or synthetic polymer products are added. The dried material is fed into moulds to obtain a sort of blanket which is pressed, squared up, cut into sheets and smoothed.

Only about 20% of the wooden chips for producing MDF panels originate from recycling machining scrap. This is due not only to the suitability of the recovered wood for use and to the quantities of such material available, but also to the need to obtain finished panels having good mechanical characteristics while using largely denatured fibres already used for other purposes.

Other known methods comprise mixing lignocellulose material with a polymer material to form a blanket, then pressing the blanket to obtain a sufficiently solid structure to ensure a good result, followed by impregnating with a binding substance. These methods have the drawback of requiring considerable quantities of polymer material to be obtained and treated, with a considerable outlay of financial and energy resources.

The wood industry therefore requires the availability of panels formed from cellulose-based materials as an alternative to those produced from wooden chips, but which possess mechanical characteristics equal to or better than currently known panels. In particular, there is a need for panels manufactured by simple methods which utilize reduced economical resources and low-cost waste materials. An object of the invention is to provide a process for manufacturing a panel for use in the production of articles of furniture which eliminates the defects and drawbacks of the methods and panels of known type.

Another object of the invention is to provide a prefabricated panel starting from recyclable cellulose material. Another object of the invention is to provide a panel possessing better workability than fibrous material panels of known type.

Another object of the invention is to produce panels for use in the construction of furnishing elements by which the consumption of economical and energy resources is reduced compared with currently known panel production methods.

Another object of the invention is to provide a panel usable in the furniture sector presenting mechanical characteristics equal to or better than those of currently known panels, which is made of materials alternative to those currently used for similar products. These and other objects which will be apparent from the ensuing description are attained according to the invention by a panel manufacturing process as described in claim 1 .

A preferred embodiment and a variant of the present invention are described hereinafter.

The process of the invention consists substantially of preparing a mass composed of fibrous material and impregnating this material with a binding agent.

The quantity of the various materials which make up the panels of the invention refer to the production of one cubic metre of finished product.

To produce one cubic metre of finished product the present manufacturing method requires a quantity of between 350 kg and 900 kg of "dry" paper mill sludge, in which the length of the cellulose fibres is too short for its reuse in paper production. To obtain "dry" sludge, the sludge extracted from the paper mill production lines is dried by squeezing it to reduce the aqueous component of the sludge to 30-40% by weight, followed by a drying process which further reduces that percentage to about 5% by weight. At a moisture content equal to or less than 5% by weight, the sludge is defined as "dry". On termination of drying, the dry sludge is in the form of cylindrical blocks which at the moment of use are micronized in machines provided with adjacent rotary discs the position of which can be adjusted to modify the fibre length and diameter.

On termination of micronization a downy mass is obtained, which is spread uniformly over a surface to form a blanket of homogeneous consistency. The blanket obtained in this manner is pressed in a press and simultaneously impregnated with a binding agent consisting of a soluble resin preferably chosen from sodium silicate and acrylic, phenolic, urea and vinyl resins. The dry residue of this resin is between 30% and 50%, the resin quantity being between 600 kg and 1 100 kg per cubic metre of finished product. Specifically, the sodium silicate (known also as waterglass) suitable for the present invention has a dry residue of about 35-36%.

To facilitate impregnation of the mass of micronized paper mill sludge and attain an optimal degree of permeation, the binding agent is forced between the interstices of the blanket by subjecting this latter to a pressure gradient between its lower and upper surface.

In particular, impregnation with waterglass gives the product fireproof and self-extinguishing properties.

The blanket impregnated with binding agent is dried to eliminate the solvent component of the binding agent by maintaining it pressed i.e. without interrupting the pressing applied during its impregnation. The drying temperature is preferably between 200 and 220⁰C, while the drying time is generally equal to one minute for each millimetre of thickness of the finished panel. It is essential to maintain blanket pressing during drying to avoid the strong shrinkage to which the panel is subjected during formation by the evaporation of the binder solvent portion from causing crumbling and/or permanent deformation of the panel.

On termination of the drying procedure, a cubic metre of finished product comprises a soluble resin quantity of 180-550 kg. If waterglass is used as the binding agent, said quantity is between 200 kg and 400 kg. When using waterglass, if the drying time is to be reduced to facilitate binder hardening, this drying can take place in a saturated carbon dioxide atmosphere. This gas enables the drying temperature to be raised without running the risk of burning the fibres of the processed product as oxygen is not present in a form suitable for participation in a combustion reaction. In addition, hardening of the waterglass is favoured by the presence of carbon dioxide, with a further reduction in drying time. The chemical reaction taking place between the sodium silicate and the carbon dioxide is the following: Na₂CnSiO₂ + H₂O -» NaHCO₃ + nSiO₂ Advantageously, the carbon dioxide used in the sodium silicate solidification can be withdrawn from the atmospheric air, so contributing to reducing the presence of this component and favouring air quality improvement.

This chemical reaction can also take place at ambient temperature (conventionally fixed at 20⁰C), so that, if following drying of the product being processed there is still a quantity of sodium silicate present which has not participated in the reaction, this quantity can participate in it even after the finished panel has been formed. The processing waste which is produced when the panel is trimmed to size and/or machined can also be used as a material usable to reduce the presence of carbon dioxide in the atmospheric air.

The products of the aforesaid chemical reaction, i.e. sodium bicarbonate and silicon oxide, are to be considered as ecological products: these are in fact widely used in the food industry. Hence this production of a panel for constructing articles of furniture does not produce environmentally polluting substances. The following is a list of the quantities of components usable in the method of the invention for manufacturing a panel for use in the construction of articles of furniture. The specific quantities used for manufacturing a preferred embodiment of a panel are also given. The main mechanical characteristics found in the panels produced by the method of the present invention are also indicated hereinafter. The indicated component masses refer to one cubic metre of finished product.

To produce a panel in a preferred form for practical use, 800 kg of sodium silicate are used per cubic metre of finished product to be obtained. In a finished product manufactured in this manner the sodium silicate density is 280 kg/m³.

The quantities of the aforesaid components can be combined on the basis of the use for which the panel is intended, i.e. of the particular mechanical characteristics to be obtained.

Dry sludge quantities between 450 kg and 670 kg per cubic metre increase the panel fragility as the lower limit of the range is approached. If a sludge quantity less than 450 kg is used, the panel is no longer usable for manufacturing articles of furniture.

Sludge quantities greater than 900 kg disadvantageously increase the total panel weight, resulting in transport and handling difficulties during working.

The mechanical characteristics found for a panel of 20 millimetre thickness manufactured in accordance with the invention are as follows:

* Screw extraction resistance (EN 320/93):

- On the panel face: > 1000N; - On the panel edge: > 400N

^* Tensile strength perpendicular to the panel faces (En 319/93): > 0.35 MPa;

* Bending test (EN 310): > 13 MPa:

* Swelling after 24 hours of immersion in water (EN 317) < 12% From the aforegoing it is apparent that the process of the invention has the advantage of enabling a further saving of resources to be achieved and the advantage of recycling materials, such as paper mill sludge which is normally intended for destruction.

Moreover, the panel produced by the method of the invention presents mechanical characteristics suitable for its use in furniture production and improved workability.

In a modified embodiment, the method of the invention requires a total quantity between 450 kg and 700 kg of paper mill sludge to which a quantity between 70 kg and 250 kg of natural or synthetic polymer-type material is added, comprising a mixture of different thermoplastic and/or thermosetting types such as ABS (acrylonitrile-butadiene-styrene), polystyrene, or phenolic, epoxy or polyurethane resins, previously micronized.

The mixture obtained in this manner is uniformly spread over a surface to form a blanket of homogeneous consistency and pressed under hot conditions in a press.

The pressing temperature is greater than or equal to that required to melt the polymer material, the temperature being in particular at least 180⁰C.

Hot-pressing the mixture blanket or layer of paper mill sludge and polymer material results in a semifinished product having the form of a thick sheet consisting of fibre aggregate.

As in the previous case the semifinished product is transported into an impregnation station in which it is permeated by a binding agent. The component quantities to be used to manufacture a panel usable for constructing articles of furniture are shown below.

Claims

C L A I M S

1 . A process for manufacturing panels, in particular panels for producing articles of furniture, characterised by comprising the following steps:

- providing a mass of paper mill sludge in a quantity of 450-900 kg per cubic metre of finished product,

- micronizing said paper mill sludge and spreading it over a surface to form a blanket,

- pressing said blanket and simultaneously mixing it with a quantity of soluble resin between 600 and 1 100 kg per cubic metre of finished product, - drying the blanket impregnated with soluble resin while maintaining said blanket pressed.

2. A process as claimed in claim 1 , characterised in that the quantity of said sludge mass is between 670 and 690 kg per cubic metre of finished product.

3. A process as claimed in claim 1 , characterised in that the soluble resin is a sodium silicate.

4. A process as claimed in claim 1 , characterised in that the soluble resin is an acrylic resin.

5. A process as claimed in claim 1 , characterised in that the resin is a phenolic resin.

6. A process as claimed in claim 1 , characterised in that the resin is a urea resin.

7. A process as claimed in claim 1 , characterised in that the resin is a vinyl resin.

8. A process as claimed in claim 3, characterised in that the sodium silicate is used in a quantity of 800 kg per cubic metre of finished product.

9. A process as claimed in claim 1 , characterised in that the drying step is carried out in a carbon dioxide-rich atmosphere.

10. A process as claimed in claim 1 , characterised in that the drying step is carried out at a temperature of 200-220⁰C.

1 1 . A process as claimed in claim 1 , characterised by comprising the following steps:

- providing a first mass of paper mill sludge in a quantity of 450-900 kg per cubic metre of finished product,

- providing a second mass of polymer material in a quantity of 70-250 kg per cubic metre of finished product,

- mixing said first and second mass together to obtain a mixture and spreading said mixture over a surface to form a homogeneous blanket,

- pressing said blanket at a temperature at least equal to the melting point of said second mass of polymer material to obtain a semifinished product, - impregnating the semifinished product with a quantity of soluble resin between 600 and 1 100 kg per cubic metre of finished product,

- drying the impregnated semifinished product.

12. A process as claimed in claim 10, characterised in that said soluble resin has a dry residue between 30% and 50%.

13. A panel for producing articles of furniture, characterised by comprising

- paper mill sludge of density 450-900 kg/m³,

- a dry soluble resin residue of density 180-550 kg/m³.

14. A panel as claimed in claim 13, characterised in that the density of the paper mill sludge is between 450 and 700 kg/m³, and by also comprising a polymer material of density between 70 and 250 kg/m³.

15. A panel as claimed in claim 13, characterised in that the soluble resin is a sodium silicate.

16. A panel as claimed in claim 13, characterised in that the soluble resin is an acrylic resin.

17. A panel as claimed in claim 13, characterised in that the resin is a phenolic resin.

18. A panel as claimed in claim 13, characterised in that the resin is a urea resin.

19. A panel as claimed in claim 13, characterised in that the resin is a vinyl resin.

20. A panel as claimed in claim 14, characterised in that the polymer material is composed of a mixture of thermoplastic and thermosetting polymer materials.