Stock material or miscellaneous articles – Fire or heat protection feature
Reexamination Certificate
2000-07-10
2002-04-30
Jones, Deborah (Department: 1775)
Stock material or miscellaneous articles
Fire or heat protection feature
C428S332000, C428S336000, C428S428000, C428S437000, C428S438000, C428S688000, C428S913000, C428S921000
Reexamination Certificate
active
06379825
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This Invention relates to a transparent heat-swellable material and to a fire-resistant glazing panel having multiple layers of glazing material with the said heat-swellable material bonded thereto.
2. Description of the Related Art
The general requirements for a fire-resistant panel are to provide an effective barrier against fumes and fumes and to provide thermal insulation. When all other parameters are constant, the extent of the fire resistance may depend on the type and size of glazing, the type of materials used in its construction and the manner in which it is held in a surrounding frame in an aperture. While glass is non-combustible it may itself soften or break under intense heat from a fire, or its frame may burn or distort, such that the barrier fails and direct fire propagation or escape of fumes can occur.
The use of a transparent heat-swellable material between layers of glazing material to improve the fire-resistant properties of glazing panels is well established to enhance the resistance of the panel both to heating in general and to exposure to fire in particular. The panel is formed as a laminate with a layer or layers of the transparent heat-swellable material each sandwiched between two transparent structural plies, usually thin glass sheets.
GB patent 1590837 teaches the use of an inturnescent material sandwiched between two structural plies in a laminated fire screening panel. It describes the use of hydrated metal salts as the inturnescent material especially hydrated alkali metal silicates such as hydrated sodium silicate. Later proposals have been concerned with modifying the silicate to improve its fire-resisting properties. For example WO94/04355 describes and claims a protective layer comprising a cured polysilicate prepared from an alkali metal silicate and a curing agent. EP-A-0705685 relates to a fire-resistant glazing panel comprising at least two glass sheets and an intermediate layer mainly composed of sodium water glass (sodium silicate) and water, together with hydrated potassium silicate and a small proportion of polyalcohols or sugars.
During the course of a fire, the silicate material slowly swells as the temperature increases, the water of hydration is driven off by the heat of the fire, and the material is converted to a foam which serves as a barrier to both radiated and conducted heat and may also preserve the ability to bond together structural sheets of the panel such as sheets of glass which may become shattered by the fire.
Panels are typically graded according to the length of time of heating under defined conditions until failure occurs in respect of such properties as insulation and integrity In the initial period of a fire, up to about 30 minutes, the panel should provide a high level of thermal insulation in order to facilitate the escape or if necessary the rescue of people in the affected area. This period is normally sufficient to permit the safe exit of everyone other than the fire-fighters who remain to control and extinguish the fire. The panel should also have sufficient integrity to provide a barrier to flame and fumes and a restraint to radiation of heat for at least the first 30 minutes and preferably for at least 60 minutes. With increasing emphasis on safety provisions in the home and at the workplace there is an increasing demand for panels to offer longer periods both of integrity, for example of 90 minutes or more, and of low radiation. Such longer periods are seen as important in seeking to provide sufficient time for fire-fighters to remain in a building and to control and extinguish the fire with minimum loss and damage to the affected property.
The fire-resistance of glazing panels is tested by mounting them in a wall of a furnace whose interior temperature is then increased according to a pre-determined schedule. Such a test is specified in International Standard ISO 834-1975 and is also described in International Standard ISO 9051-1990 which speaks specifically of the fire-resistance requirements for glazed assemblies, Similar European standards are proposed, including draft standard prEN1363 (document CEN/TC127 N 1095) and draft standard prEN1364 (document CEN/TC127 N 1085).
Draft standard prEN1363 includes a “Cotton wool pad” test and a “Gap gauge” test. In the former a cotton wool pad in a frame is placed for a maximum of 30 seconds adjacent to an area of a test glazing specimen under examination for failure of integrity. The time and location at which any ignition of the pad occurs are recorded. In the latter a 6 mm gap gauge and a 25 mm gap gauge are in turn applied without undue force to determine (a) whether the 6 mm gauge can be passed through a gap in the specimen into the furnace and moved 150 mm along the gap and (b) whether the 25 mm gauge can be passed through a gap in the specimen into the furnace.
It is an objective of the present invention to provide a transparent heat-swellable material which offers for fire-resistant glazing panels a period of heat insulation and an extended period of fire-resistance, especially in terms of its “integrity”, i.e. providing a barrier to flame and fumes, and of restrained radiation of heat. These features should moreover be provided without making the panel cumbersome and heavy.
SUMMARY OF THE INVENTION
According to this invention, there is provided a transparent heat-swellable material comprising hydrated alkali metal silicate and at least one additive selected from polyalcohols and mono- or polysaccharides, characterised in that the additive content is in the range 5 to 22% by weight, the water content is in the range 12 to 19.5% by weight, and the hydrated alkali metal silicate has a silicon oxide (SiO
2
):alkali metal oxide molar ratio greater than 3.3 to 1.
The invention further includes within its scope a sheet of transparent vitreous material carrying a layer of the above-defined heat-swellable material, and a fire-resistant panel comprising one or more layers of the said heat-swellable material and a corresponding two or more sheets of transparent vitreous material.
The term “heat-swellable” used herein refers to materials, otherwise known as inturnescent materials, with the properties, when exposed to a flame, of swelling and forming an insulating barrier to propagation of the flame.
The heat-swellable silicate materials of the invention offer considerable improvements in the thermal insulation, integrity (barrier to flame and fumes), and thermal radiation of glazing panels formed from them. The reasons for these improvements are not entirely clear but probably result from the combination of the claimed additive and an unusually low proportion of water. Another important factor appears to be that the silicates with a SiO
2
:alkali oxide molar ratio of greater than 3.3:1 expand less during standard fire tests than known materials obtained by drying alkaline silicate sols with a molar ratio of up to 3.3:1. The reduction in thermal radiation appears to result in part from the good integrity of the panel and the very low rates of flow of the foams arising from heat-swellable material according to the invention upon their exposure to fire.
The improvements are especially surprising in the case of soda-lime glass sheets which are commonly used in laminated glazing since the transformation temperature of the glass remains very largely below the temperatures reached during the fire tests; the transformation temperature of the foams in themselves is again largely less than that of the soda-lime glass.
The preferred alkali metal silicate is sodium silicate with a SiO
2
:Na
2
O molar ratio of about 4:1. A combination of this preferred silicate with a silicate having a lower SiO
2
:Na
2
O molar ratio, such as 3.3:1, also provides a panel with beneficial fire-resistant properties, provided that the total SiO
2
:Na
2
O molar ratio is greater than 3.3:1.
Preferred examples of the additive are glycerol ethylene glycol and saccharose. It is typically to be employed in an amount of 5 to 21% by weight of the tr
Degand Etienne
Goelff Pierre
Glaverbel S.A.
Jones Deborah
Piper Marbury Rudnick & Wolfe LLP
Piziali Andrew T
Schneider Jerold I.
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