EP0799943A1

EP0799943A1 - Fireproof plate material

Info

Publication number: EP0799943A1
Application number: EP97200997A
Authority: EP
Inventors: Nicolaas Dirk Brouwer
Original assignee: Individual
Current assignee: Individual
Priority date: 1996-04-05
Filing date: 1997-04-07
Publication date: 1997-10-08
Also published as: NL1002806C2

Abstract

A fireproof plate material comprises at least two panels (1,2,3) separated by a cavity (5). A fireproof, or at least fire-inhibiting substance (7) is provided in the cavity (5). The fireproof substance (7) comprises a solid substance which undergoes at least one phase transition in the temperature range from normal ambient temperature to the temperature prevailing in a fire, while the fireproof substance comprises a mixture of solid sodium silicate particles and liquid sodium silicate.

Description

The invention relates to a fireproof plate material comprising at least two at least substantially parallel panels which enclose a cavity between them, in which cavity a fireproof, or at least fire-inhibiting material is accommodated comprising a solid substance which undergoes at least one phase transition in the temperature range from normal ambient temperature to a temperature prevailing in a fire.
Such a plate material is used in particular for the manufacture or shielding of cabinets and other spaces in which flammable substances or valuable goods or data are stored. Examples of these are fireworks, valuable papers, and computer files stored on suitable carriers. The primary function of the plate material here is to retard for as long as is possible any temperature rise within the relevant space resulting from a fire raging outside it.
British Patent GB-B-138758 discloses such a plate material provided with two panels where the cavity is provided with a framework into which a powder is sprinkled. Upon heating (for example in the case of fire), the panels will detach themselves from the framework and the powder will expand by foaming, so that the cavity is filled up.
The present invention has for its object to provide a plate material of the kind mentioned in the opening paragraph which has an improved fire-inhibiting effect compared with a known plate material of the same thickness.
According to the invention, a plate material of the kind mentioned in the opening paragraph is for this purpose characterized in that the fireproof substance comprises a mixture of solid sodium silicate particles and dissolved sodium silicate.
It was found that mixing of solid sodium silicate particles with liquid sodium silicate leads to a much higher concentration of sodium silicate than had been possible until now. Owing to this higher concentration, the sodium silicate will not only form a gel upon heating, for example in a fire, but also expand by foaming, which is not possible at lower concentrations. Highly satisfactory results were obtained with this material in practice. In contrast to the fireproof substance known from the cited British Patent, which comprises a powder only, the fireproof substance according to the invention comprises a mixture of a solid and a liquid material. The use of a mixture of solid sodium silicate particles and liquid sodium silicate now renders it possible to obtain a fireproof substance which forms a foam in the case of fire and similar circumstances without the addition of other (solid) substances.
It is noted here that American Patent US-A-4,746,555 discloses a fireproof material provided with two panels and a core, the latter being manufactured in liquid form and subsequently compressed. The core comprises a mixture of alkali metal silicate and a phenolic resin.
The fireproof substance according to the present invention differs from this in that the fireproof substance contains no solid substance other than sodium silicate and in that the fireproof substance is not compressed.
A preferred embodiment of the plate material according to the invention is characterized in that the sodium silicate is mixed with a compressible filler material. The addition of the compressible filler material renders it possible for the space between the two panels to be completely or substantially completely filled up. Any expansion of the fireproof substance foaming out at an elevated temperature can thus be accommodated by the compressible filler material, so that it is avoided that the plate material becomes seriously deformed during this. A special embodiment of such a filler material is formed by foamed globules which can be added at a comparatively low cost.
It is alternatively possible to use a filler material of, for example, perlite or vermiculite.
To prevent the fireproof contents of the cavity from sagging down, which would seriously detract from the fire-inhibiting properties of a (major) portion of the surface area of the panel, it is known to subdivide the cavity into a number of separate chambers by means of partition walls which may or may not be interconnected and which extend transversely to the two panels. The partition walls in that case keep the contents of the cavity in place before, during, and after said phase transition, so that the fire-inhibiting properties of the plate material are continuously ensured over the entire surface area thereof.
A preferred embodiment of the fireproof plate material is characterized in that at least one partition wall of each chamber is provided with an opening. The provision of openings in the partition walls of the chambers achieves that any excess air can escape during the foaming process of the sodium silicate.
A preferred embodiment of the fireproof plate material is characterized in that chipboard is used as a basic material for the fireproof plate material. It is achieved thereby that the fireproof plate material is immediately ready for processing, fastening, etc. after its manufacture.
The invention also relates to a method of manufacturing a fireproof substance, which method consists in that sodium silicate is dissolved, the dissolved sodium silicate is mixed, and the sodium silicate mixture is dried.
A method according to the invention is characterized in that the liquid sodium silicate is mixed with dry sodium silicate during mixing. Sodium silicate is obtained in much higher concentrations in this way than had been possible until now, with the result that the sodium silicate foams out after forming a gel upon heating, for example owing to a fire.
The invention will now be explained in more detail with reference to an embodiment and an accompanying drawing, in which:

Fig. 1 is a cross-sectional view of an embodiment of the fireproof plate material according to the invention; and
Fig. 2 is a cut-away plan view of the fireproof plate material of Fig. 1.

parallel panels

individual panels

partition walls

wide cavities

panels

strips

The partition walls 5 form part of a coherent framework 25 having a honeycomb structure, cf. Fig. 2, which simplifies its mounting. The framework 25 is made from a cardboard of sufficient strength and is commercially available in the thickness of 20 mm as used here. The cavities 5 of the plate material are thus subdivided into a number of separate chambers 51, 52, 53, etc.
In a preferred embodiment, at least one partition wall of each chamber is provided with an opening.
According to the invention, a fireproof substance 7 undergoing a phase transition in the temperature range from ambient temperature to a fire temperature is provided in the cavity 5. A mixture of solid sodium silicate particles and liquid sodium silicate mixed with a compressible substance in the form of foamed globules of, for example, perlite or vermiculite has for this purpose been introduced into the chambers 51, 52, 53 in the present case before the second or third panel, as the case may be, is provided thereon. The globules may be made from any suitable material, for example also from polyurethane.
The mixture may comprise an adhesive substance (the sodium silicate itself can also provide adhesion) and is adequately wetted so as- to provide a good adhesion to the panels 1, 2, 3, so that it will remain distributed over the entire surface area thereof and will ensure a good fire protection over this entire surface area. Further filler materials may also be added to the mixture, such as in particular vermiculite particles, which promote a weight reduction of the filled panel.
In the present example, in practice, a fill is used of approximately 60% mixture of solid sodium silicate particles and liquid sodium silicate (the preparation of which will be discussed below) as the fireproof substance, in accordance with the material of the panels 1, 2, 3, 20% compressible polyurethane globules, and 20% weight-reducing vermiculite globules, all percentages relating to the respective occupied volumes.
In case of fire, the fireproof mixture 7 will first become liquid at a certain moment under the influence of the rising temperature and subsequently foam out. This phase transition consumes energy, which leads to an instantaneous drop in temperature and a resulting improved fire resistance within the plate material. The foam which has been formed provides an adequate heat insulation after that. The panel shown here was thus found to be capable in practice of reducing a temperature rise to an acceptable level for a period of two hours at a side of the plate material opposed to a side where a standardized, controlled fire was made to burn. A known plate material filled with rock wool would require a thickness of approximately 200 mm to achieve this, which would lead to a considerable increase in cost. Depending on the degree of fireproofness required in any given case, the plate material may be expanded to include more panels, or no more than two panels may be used. The invention offers a plate material having an enhanced fire resistance in all these cases compared with known panels of the same thickness.
The provision of openings in the partition walls of the chambers 51, 52, 53 ... achieves that any excess air can escape during foaming of the sodium silicate. The sodium silicate mixture according to the invention is obtained in that sodium silicate in liquid form is mixed with sodium silicate in dry form. The sodium silicate is finally dried. Sodium silicate is obtained in much higher concentrations thereby than had hitherto been possible. Owing to this higher concentration, the sodium silicate will not only form a gel when heated, for example in a fire, but also foam out subsequently, which is not possible at lower concentrations.
Although the invention was explained in detail with reference to only this one embodiment, it will be obvious that the invention in by no means limited to the example given. On the contrary, many more variations and modifications are possible to those skilled in the art within the scope of the invention.

Claims

A fireproof plate material comprising at least two at least substantially parallel panels which enclose a cavity between them, in which cavity a fireproof, or at least fire-inhibiting material is accommodated comprising a solid substance which undergoes at least one phase transition in the temperature range from normal ambient temperature to a temperature prevailing in a fire, characterized in that the fireproof substance comprises a mixture of solid sodium silicate particles and liquid sodium silicate.
A fireproof plate material as claimed in Claim 1, characterized in that the sodium silicate is mixed with a compressible filler material.
A fireproof plate material, characterized in that the compressible filler material comprises foamed globules.
A fireproof plate material as claimed in any one of the preceding Claims, in which the cavity has been subdivided into a number of separate chambers by means of partition walls which may or may not be interconnected and which extend transversely to the two panels, characterized in that at least one partition wall of each chamber is provided with an opening.
A fireproof plate material as claimed in any one of the preceding Claims, characterized in that chipboard is used as a basic material for the fireproof plate material.
A method of manufacturing a fireproof substance comprising the dissolving of sodium silicate, mixing of the molten sodium silicate, and drying of the sodium silicate mixture, characterized in that the liquid sodium silicate is mixed with the dry sodium silicate during the mixing process.