GB2132622A - Articles made of bonded, heated and pressed wood fibres - Google Patents

Abstract

The present invention relates to an article consisting of an intimate aggregation of wood wool brought about by a bonding agent, then compressed and heated. Said wood wool is essentially composed of log trimmings, residues of planing and squaring and similar operations, preferably reduced to thin, elongated laminas formed in a lengthwise direction to the direction of the wood fibres.

Description

SPECIFICATION Articles made otbonded, heated and pressed wood fibres.

The present invention relates to articles made of wood wool bonded with different binders, dried and hot-pressed so as to obtain flat panels or other desired shapes. It is known to produce articles obtained by intimately aggregating chip material by hot-pressing, which material is appropriately comminuted and compacted using large quantities of bonding agents, for exampie urea resin.

However, said articles posses low flexural strength and entail the use of very considerable quantities of bonding agents.

Moreover, they are not produced in thicknesses of less than 2.5 mm, since their mechanical strength does not allow them to be employed usefully in heavy-duty applications.

It is noteworthy that such type of articles have a high percent water absorption which can only in part be eliminated by treatment with water-repellent substances. The chief object of the present invention is to embody articles made of bonded and compressed material such as obviate the aforesaid problems, i.e. such as guarantee excellent mechanical strength and very low water-absorption, without loss of their characteristics even if immersed in and saturated with water and then dried, and which call for only relatively small quantities of bonding agents.

To achieve the said object, the present invention embodies an article characterized in that it consists of an intimate aggregation of wood wool aggregated by means of a bonding agent and then compressed and heated, said wood wool composed essentially of log trimmings, residues of planing and squaring and similar operations.

The structural and functional characteristics and the advantages of an article emboded according to the principles of the present invention will be evidenced in greater detail in the following description thereof, referred to the attached drawings representing a panel, in which: Figure 1 is a plan view of a panel embodied according to the principles of the present invention, and Figure 2 shows a schematic cross-section taken through the line 11-Il of the panel of Figure 1.

With reference to the drawings, a panel indicated overall by ii is composed of the intimate aggregation of so-called wood wool 1 2 by means of binding with bonding agents or resins.

The wood wool is obtained from log trimmings, residues of planing and squaring suitably processed in special machines into fine, elengated laminas of the desired dimensions.

The thin laminas produced in this way posses good individual strength in that they are formed lengthwise to the direction of the wood fibres by processes similar to planing processes.

The resulting wood wool is bonded with suitable synthetic resins, for example phenolic resins, so as to form a so-called mattress.

In the manufacture of the laminas, the different elongated laminas fed bulkwise arrange themselves spontaneously essentially plane-wise, transversely and longitudinally thus forming the aforesaid fibre mattress.

Said mattress is then sent'to a dryer where it loses a large part of the water contained in the wood wool and binding agent.

The mattress treated in this way is pre-compressed and placed into a hot-plate press where it undergoes the combined action of pressure and heat for a pre-set period of time decided on according to the thickness it is wished to obtain.

Of important interest is the fact that the aforesaid drying is performed at temperatures only a few degrees higher than room temperature, as also the fact that as the wood wool surface areas are much smaller than those of article chip-material, the quantities of bonding agent required are very small.

The arrangement and particular elongated shape of the laminas ensure identical mechanical and flexural strength in all the different directions.

The characteristic means that both flat articles and articles having a wide variety of other shapes can be stamped out directly from the mattress as described, and finished and semi-finished articles of remarkable strength and of the desired dimensions are thus obtained. Another highly important characteristic of the articles manufactured according to the invention is their excellent water-resistance, in that when immersed in water they have absorption characteristics practically equal to those of the wood from which they derive, density being equal.

Also noteworthy is the fact that said articles manufactured with relatively low density also possess an excellent coefficient of thermal conductivity.

In order more clearly to illustrate the above-mentioned characteristics and the advantages of articles made of wood wool over articles made of chip-board material, the following two comparative Tables report the results of a series of laboratory tests performed on panels.

Pllysical and mechanical properties of chip-board panels on the market

Thickness mm. 4 6 12 Density Kg/mc. 750 758 770 Flexural strength: - longitudinal N/mm2 18 23 22 - transversal N/mm2 18 22 21 - elastic modulus N/mm2 2500 2650 2700 Water absorption: - n. 2 h % 47 48 47 - n. 24 h % 65 59 58 Swelling % 10 11 14 Wood wool panels

Thickness mm. 12 3 2 1 1 | 0,8 Density Kg./me .450 650 700 800 900 1.100 Flexural strength: longitudinal. N/mm2 28 46 52 70 80 110 -transversal W N/mm2 28 46 52 70 80 110 elastic modulus N/mm2 5300 5800 7400 8200 11800 Water absorption without 9 water-repellency treatment:: 2 h % 40 38 38 35 30 20 24 h % 60 55 52 48 46 40 Swelling % 13 12 11.5 11 11 10,5 Water absorption with water repellency treatment: 2 h 5 5 4. 3 2,5 24h % 32 30 29 22 20 18 Swelling % 12 11 10,5 10,5 9,5 Coeff. of thermal conductivity Kcal at+100C mh C 0,045 0,050 The foregoing Tables show unequivocally that with panels of the two types, having equal density, the strength values are much higher and the percent water absorption very much lower in the panels embodied according to the present invention.

It is further noteworthy that with density of more than 800 kg/sqm there are produced articles, in this specific instance panels, of very low thickness, even less than 1 mm, but in every case possessing outstanding mechanical properties which far exceed those to be found in fibre panels and which are on a par with those of synthetic resins, such as bakelite.

Claims (5)

1. An article consisting of an intimate aggregation of wood wool formed by addition of a bonding agent, followed by compression and heating of the aggregate, said wood wool being composed essentially of log trimmings residues of planing and squaring and similar operations.

2. An article according to claim 1, wherein said wood wool is composed of thin, elongated laminas extending in a direction parallel to the direction of the wood fibres.

3. An article according to claim 1 or 2, wherein the article is in the form of a panel of variabie thickness and density.

4. An article according to claim 1, 2 or 3, wherein it has been stamped out in any desired shape or form.

5. An article according to claim 1 and substantially as hereinbefore described.