FR2498985A1 - CELLULOSIC FIBROUS BEECH BEAM STRUCTURE, PANELS OBTAINED USING SAID STRUCTURES, AND METHOD OF MANUFACTURING THE SAME - Google Patents

Abstract

THE INVENTION CONCERNS A HARD PANEL WITH AN INTERNAL HONEYCOMB STRUCTURE CONSISTING OF A FLAT PLATE WITH AT LEAST ONE FACE OF WHICH A PROJECTION 18 HAS A DENSITY MASS LOWER THAN THAT OF THE FLAT REGIONS 21 SURROUNDING THEM. THE INVENTION ALSO RELATES TO A HARD BOARD LAMINATE STRUCTURE CONTAINING AT LEAST ONE OF SUCH HARD BOARDS WITH INTERNAL HONEYCOMB STRUCTURE AND A PROCESS FOR ITS MANUFACTURING. THE INVENTION APPLIES IN PARTICULAR TO THE REALIZATION OF CONSTRUCTION OR FILLING MATERIALS.

Description

-1 -

  Honeycomb structure of cellulosic fibrous material

  panels obtained by means of said structures and method of

manufacture of this structure.

  It is known to manufacture ligno fiber panels

  felted cellulosic materials (hardboard) designed to be used, for example, as filler and construction materials, starting from a mat of felted fibers which generally have a

certain moisture content.

  To manufacture a panel of this kind, the initial fibrous mat is compressed in a hot press where the removal of moisture is also carried out. Then come a baking process to improve the mechanical strength of the

  panel and a humidification stage.

  The compression stage is usually carried out by introducing the fibrous mat, in the wet state, between

  trays of a hot press. We can do the compres-

  by applying different pressures at different times to obtain panels whose thickness and therefore the density differ correspondingly. when higher pressures are used, to the extent compatible with the properties of the raw materials,

  panels which have physical and mechanical properties

  and a density close to 1000 kg / m3 whereas if lower pressures are adopted, panels of lower density are obtained whose properties

  more than proportionally to the decrease in

pressure.

  The ideally desirable properties of such a hardboard would be a low density (which means that the parts would be noticeably light) but at the same time good physical and mechanical properties such as flexural strength and strength. immersion in water. Since, as previously pointed out,

  the increase of the first property means a decrease

  In contrast, the conventional technology has moved towards a compromise so that hardboard for which satisfactory physical and mechanical properties are required generally have a density of at least 800 kg / cm 2. m3 while the hardboards of

  lower density, given their poor mechanical resistance.

  can only be used for particular purposes and

  restricted as that of filling material.

  The main object of the invention is to provide hardboard which can serve mainly, if not exclusively, structural materials and which therefore have satisfactory physical and mechanical properties but are at the same time noticeably light so as to facilitate their use.

  manufacture, transportation and assembly.

  Another object of the invention is also to obtain hardboards of the species indicated above by a manufacturing method that is easy to perform and inexpensive:

  In this connection, the invention aims to use substantially

  the machines already available according to the technology

  present at most with modifications that do not have a significant impact on the cost price. the above and other objects are achieved according to the invention by a hardboard with an internal structure

  honeycomb is particularly suitable for

  position of multi-layered panels and consists of ureplaque

  plane on at least one side of which is a

  of projections having a density lower than

  that of the flat areas around them.

  A preferred hardboard having an internal honeycomb structure according to the invention has ordered protrusions

  following parallel lines but staggered.

  A structure is made as above, according to

  invention, by a manufacturing process characterized by the following steps: A fibrous mat of lignocellulosic fibrous material is placed between the two plates of a hot press, spaced from one another, inserted between the one or the other trays and the fibrous mat a substantially planar matrix plate of rigid material having, on its face facing the fibrous mat, a cavity arrangement designed according to the arrangement of honeycomb structure that it is desired to give to protrusions to obtain the configuration in nest - 3-

  of bees and hot compress the fibrous mat.

  The internal honeycomb structure thus obtained is particularly suitable, according to the invention, for the composition of multi-layer hardboard for various uses such as structural materials.

  One embodiment of the invention will be described below.

  FIGS. 1 and 2 show the various stages of forming an internal honeycomb structure according to the invention. FIG. 3 is a drawing of FIG. of the structure thus formed; Figure 4 is a section along the line IV-IV of the

  FIG. 3, showing the structure adapted to a second structure

  FIG. 5 is a section along line V-V of FIG. 3, showing the multi-layered panel of FIG.

figure 4.

  With reference to FIG. 1, a compact and moist fibrous mat 11 of a lignocellulosic material is inserted between the upper plate 12 and the plate 13 of a hot press, which are spaced apart from one another ; the press is

  of the very classical type controlled hydraulically, serv-

  to manufacture conventional hardboard

  upper being mobile and the lower plate fixed.

  On the lower plate, there is a wire frame 14 which serves to promote the evaporation of the water of the

  fibrous mat 11 while the latter is pressed while hot.

  Between the upper plate 12 and the fibrous mat 11 is placed a die plate 15 formed of a piece of plate, for example stainless steel. This matrix plate is flat and smooth on its surface in contact with the upper plate 12

  while on its surface turned towards the fibrous mat, that is to say

  the inner face, it has a honeycomb configuration defined by an arrangement of cavities 16 arranged in parallel lines and staggered so that flat areas 17 are interposed between the cavities: the cavities of the example of Figure 1 have a

frustoconical shape.

  Starting from the position represented by FIG. 1, the hot compression is carried out as shown in FIG. 2: once the trays have been heated properly, they actuate

  the press by lowering the upper plate 12 under a pres-

  chosen in advance: this coincides with the pressure

  it would take to obtain a massive hardboard of

  conventional cation having a thickness "h". The effect of the matrix plate inserted between the upper plate and the fibrous mat is to distribute the pressure applied by the upper plate to the fibrous mat in a differential manner.

  at the location of cavities 16 and planar areas 17. The result

  The state, as shown above in FIG. 2, is to form, starting from the fibrous mat in question, a honeycomb structure comprising a flat plate on the upper surface of which there is a projection arrangement of which the density is significantly lower than that of the surrounding flat areas 21. The hardboard structure in

  honeycomb as it is removed from the press is

  3 o the entire structure is indicated in 20 and the planar zones, compressed more strongly

  and therefore of greater density, are indicated in 21.

  The projections 18 are frustoconical protuberances whose

summit is small bay 19.

  Figures 4 and 5 show a multi-section panel

  22 as obtained by assembling, for example by

  bonding, honeycomb units 20, the assembly is

  by the small base of projections 18.

  A multilayer panel according to the invention is

  characterized by zones 21 of high alternating density

  with areas 18 of lower density between which are disposed in an orderly manner cavities 23:

  the overall density of such a multi-layered panel

  tiples is roughly half the size of a hardboard

  solid of the same overall thickness as it is manufactured

  However, despite this, mechanical properties are almost the same order of magnitude as a panel

  solid hard having a density of at least 0.8.

  For example, when starting from a fibrous mat

  initial gnocellulose having a mass per unit area of about 2.5 kg / m2 and compressed with a matrix plate

  metal in order to obtain a honeycomb structure

  having a thickness of 2.5 mm in the more compressed flat areas and a thickness of 5 mm at the location of

  projections, it is possible, by assembling two of these structures

  honeycombs, to manufacture a layered panel

  multiples of the kind shown in Figures 4 and 5, the thick

  the overall thickness of the panel being 10 mm, the density of approximately 500 kg / m3 and the flexural strength of approximately

19.6 to 22.6 MPa.

  Such a hardboard, subjected to tests of resistance to immersion in water, gives the following results: 7%

  after 2 hours and 25% after 24 hours.

  These data show that the physical and mechanical properties of a multi-layer hardboard including

  a honeycomb structure according to the invention are entirely

  satisfactory, the thickness being equal to that of conventional solid hardboard while the density of the composite panel is much lower than that of the panels

  classics. This achieves the main purpose of the invention.

  It should be noted that these properties can be obtained by using the hot presses which are used in the conventional methods of manufacturing conventional solid panels, the only

  the necessary expedient of inserting the matrix plate

  this embossed between the fibrous mat and the upper plate of the press. This fact makes it possible, while applying to the press working pressures of the same order of magnitude as those conventionally applied to uniformly compress the mat.

  fibrous material used as a raw material, to apply a

  difference in the various regions of the fibrous mat of

  so that the result is a final structure in nest of abbe-

  presenting them with regions of different density.

  An additional and very surprising advantage of the invention is that which is obtained in the manner explained

in the following example.

  A hardboard consisting of two honeycomb structures

  like those represented here, having the

  previously indicated, has a coefficient of isolation

  thermal energy, which is only 0.065 W / m. OC at 10 0.

  A classic solid hardboard has a reaching coefficient

  0.11 to 0.12 W / om.OC approximately so that the calorific value

  classic solid panel fuge is about half

  of that of a composite panel according to the invention.

  Thanks to such a property, the multilayered panel

  tiples is particularly interesting for uses in which large heat-insulating powers are needed. If we consider the noticeable lightness of the product, we can see that it is particularly suitable as a building material

for prefabricated buildings.

  the composite honeycomb structure proposed by

  the invention as well as the individual honeycomb panels

  they may be variously modified in relation to what is described above; for example, by using at the compression stage two embossed matrix plates, it becomes possible to obtain a honeycomb structure whose deformations are distributed over the two surfaces of the fibrous mat used as raw material. The resulting honeycomb composite product can be joined to other honeycomb structures according to the invention to make multi-layer panels. It has been found, by practical tests, that a honeycomb structural unit according to the invention has in the thinnest regions a flexural strength of about 43.2 MPa. According to the invention, it is also possible to manufacture the honeycomb structure with

  a perforated die plate instead of embossed.

  The exposed surface of the multilayer hardboard

  it can be smooth or you can directly

  quer with decorative designs by inserting a properly embossed matrix plate between the press platens

  and the surface of the panel that must be outside.

  In the case where it is desired to further improve the physical and mechanical properties of the products, each unit of honeycomb panel may be impregnated with substances such as drying oils, synthetic resins and other materials such as those which are conventionally used in the manufacture of hardboard to obtain massive products. Honeycomb structure

  according to the invention can advantageously, alone and without accou-

  other uses, such as dubbing and filler materials, and can also be coupled to solid olassic panels or panels of other

  composite panels suitable for various applications.

- -8-

REVNDICATIONS

  1) - Honeycomb structure of lignocellulosic fibrous material, characterized in that it comprises a plate (11) substantially flat to at least one surface of which is arranged a projection arrangement (18) having a

  lower density than the surrounding areas (21).

  2) - Structure according to claim 1, characterized in that the projections (18) are arranged according to

parallel lines.

  3) - Structure according to claim 2, characterized in that the lines are both parallel and staggered. 4) - Structure according to claim 1, characterized

  in that the projections (18) are frustoconical.

  5) - Multi-layer hardboard characterized by having at least one honeycomb structure

  (11) according to one of claims 1 to 4.

  6) - Panel according to claim 5, characterized by

  the fact that it comprises at least two structures in abel of

  the (20) assemblies at the location of the projections (18).

  7) - A method of manufacturing a structure according to claim 1, characterized by the following steps s place a fibrous mat of lignocellulosic material (11) between the trays (12, 13) heated 4'a press while they are

  spaces between each other, insert between one or the other

  water (12, 13) and the mat (11) at least one matrix plate (15) of rigid material, substantially planar configuration, whose surface turned to the fibrous mat has a

  provision of cavities (16) or tzous according to the configuration

  honeycomb ration that is desired to communicate with the projections (18), so as to form the structure, and compress

hot fibrous mat (11).