GB2271362A

GB2271362A - Intumescent sheet material

Info

Publication number: GB2271362A
Application number: GB9309104A
Authority: GB
Inventors: Adrian Michael Steer; Barry Turner
Original assignee: T&N Technology Ltd
Current assignee: Federal Mogul Technology Ltd
Priority date: 1992-10-06
Filing date: 1993-05-04
Publication date: 1994-04-13
Anticipated expiration: 2013-05-04
Also published as: GB9309104D0; GB9220949D0; GB2271362B

Abstract

A modification of the procedure of GB 2,233,678 for making intumescent sheet material containing heat-expandable graphite as intumescent agent and having a matrix whose predominant ingredient is an unfired kaolinitic clay comprising ball clay reinforced by in organic vitreous fibre (for example, mineral wool) comprises dewatering an aqueous suspension of the various ingredients in the form of a layer which includes cellulose fibre as web-forming agent to form paper, not board, and the paper is then converted to corrugated form, prior to plying with sheets of the same or similar paper to form a block or slab in which at least most of the corrugations are parallel to one another so as to extend from one face of the block to the opposite face. Each corrugated layer may have one or two flat sheets which may be of the same intumescent paper as the corrugated sheet of non-intumescent paper or heat-reflective material such as aluminium foil. The product may be used in a ventilator panel in a door.

Description

Intumescent material This invention relates to intumescent material.

In the specification of our British Patent 2,233,678 there is described intumescent sheet material such as is suitable for attachment to doors or the like to provide that, if fire breaks out, the sheet will swell to seal the gap between door and frame or other adjacent element of structure, and so prevent the passage of flame and hot gases. The intumescent sheet material of that patent has a matrix whose predominant ingredient is an unfired kaolinitic clay comprising ball clay reinforced by inorganic vitreous fibres, and includes an organic binder, preferably a starch or an elastomer (eg styrene-butadiene).The material is made by dewatering an aqueous suspension of the various ingredients in the form of a layer which includes cellulose fibre as web-forming agent, said suspension containing an amount (for example, 10 per cent by weight of the solids of the suspension) of head-expandable graphite sufficient to swell the sheet in a fire.

Specifically, dewatering of the aqueous suspension is carried out either in a filter press, to obtain a monolithic product, or, preferably, using standard board-making machinery followed by winding onto the drum of the machine so that a laminar product, typically 2.5mm thick and of flexural strength 7 MPa or more, is obtained.

It has occurred to us that a more-widely utilisable form of intumescent sheet material could be obtained by modifying the procedure of British Patent 2,233,678 in this way : that is, by dewatering the aqueous suspension so as to obtain (as by use of a standard Fourdrinier flat wire machine) an intumescent product in the form of paper instead of board, and converting that paper into corrugated form. The flat (ie non-corrugated) face of the corrugated product may itself be formed of the intumescent paper, or may itself be formed of the intumescent paper, or may for example be of heat-reflective material such as aluminium foil.

"Corrugated" in this present context means that the paper is formed into a generally sinusoidal configuration and thereafter stuck or otherwise adhered to at least one flat sheet which serves to preserve the sinusoidal configuration. It will be appreciated that either one sheet or two flat sheets adhered to opposed crests of the sinusoidal waveform may be used for this purpose.

By the term "paper" we mean flexible sheet material, of dry thickness no more than about 1.25mm and preferably not greater than lmm.

Corrugation may be carried out with the use of conventional machinery, and with the employment of standard heat- or pressuresensitive adhesives.

The corrugated intumescent paper product can be used as a lowdensity wrapper for pipes or in cable trays, or - rolled up to cylinder for by hand in situ - as a temporary stuffing for walls or other separating structures in which holes have to be filled up. Additionally, relatively strong low-density panels of any desired thickness (eg 20mm) can be made by cross-plying the corrugated paper product with further applications of adhesive so that the corrugations in successive layers are at right angles to one another. Such panels find use as filler material in hollow doors to improve their performance as fire barriers.

According to the invention there is provided a method of making intumescent sheet material containing an amount of heatexpandable graphite sufficient to swell the sheet in a fire and having a matrix whose predominant ingredient is an unfired kaolinitic clay comprising ball clay reinforced by inorganic vitreous fibre, said material including an organic binder, said method comprising dewatering an aqueous suspension of the aforesaid ingredients in the form of a layer which includes cellulose fibre as web-forming agent; the dewatering being carried out so as to obtain an intumescent product in the form of paper as distinct from board; the paper being then converted to corrugated form, sheets of which are thereafter plyed with other sheets of the same or similar corrugated paper to form a block or slab in which at least most of the corrugations are parallel to one another.

Preferably all of the corrugations in a slab or block thus produced extend parallel to one another so as to define a plurality of channels which extend through the slab or block from one face thereof to an oppositely directed face.

According to a further, particularly preferred aspect of the invention, said slab or block is thereafter sectioned to form a panel with a plurality of channels extending therethrough, said panel being particularly suitable for us in a ventilation application requiring minimal impedance to airflow, but which on exposure to fire will seal said channels substantially completely so as to at least temporarily prevent the passage of flame and/or fumes therethrough.

Suitable methods by which heat-expandable graphite can be obtained are well-known : see for example GB 2,128,629 and US 4,350,576. The heat-expandable graphite preferably forms at least 5 per cent by weight of the paper (and therefore 5 per cent by weight of the solids of the suspension that is dewatered); and a graphite content of at least 10 per cent by weight of the paper is particularly preferred.

To control the rate of drainage of water from the layer of aqueous suspension undergoing dewatering during manufacture, the suspension may contain bentonite clay (a montmorillonite clay), suitably in an amount up to about 5 per cent by weight of suspended solids.

The organic binder, which desirably forms no more than about 10 per cent by weight of the sheet material, may be a starch, such as farina starch, or a synthetic polymeric material, the latter being conveniently added in latex form, eg an acrylic latex. To improve binding at high temperatures, an inorganic binder such as colloidal silica may be incorporated in the paper-making suspension, which may include a small proportion of rayon fibres in order to increase the green strength of the layer formed from it during paper-making.

The total content of organic material (in particular organic binder + web-forming cellulose fibres + rayon fibres) is desirably no greater than 20 per cent by weight.

The invention is further illustrated by the following Examples.

Example 1 An aqueous suspension was prepared from the following ingredients.

Drv weight % Mineral wool (fibre length, 2.8mm 25 Lapponia wood pulp 7 Ball clay (HYMOD AT) 49 Rayon fibres (6mm long) (.fl9 3 Polyacrylamide flocculating agent (PERCOLLE24) 0.05 Acrylic latex (45% solids) 3 Farina starch 3 Heat-expandable graphite 10 100.05 The heat-expandable graphite employed was a commercially available product prepared electrolytically from natural crystalline flake graphite of 95 per cent carbon content, 5 per cent ash. Its bulk density was 560kg/m3.

The suspension, diluted with water to 3 per cent solids content, is pumped to a standard Fourdrinier flat wire paper-making machine such as is described in Chapters 10 and 11 of "Paper and Board Manufacture" by Julius Grant, James H Young and Barry G Watson (Publishers : Technical Division, the British Paper and Board Industry Federation, London, 1978). The slurry is progressively dewatered as it travels on the water-permeable conveyor of the machine, and the dewatered material is consolidated by pressing between rollers. The flexible sheet material thus formed is dried on heated rollers and would into reels.

The properties of a typical intumescent paper product were: Thickness 0.3mm Density 0.657gm/cm3 Tensile strength Machine direction 5.1 MPa Cross direction 3.4 MPa Compression at 1000 psi (+ 7 MPa) 15.4% Recovery 21.58 Maximum pressure generated on expansion 5 bar, at 4500C Conversion of this paper to a corrugated paper product was carried out by means of a LANGSTEN THRISSEL Corrugator (Type GPC), with the use of sodium silicate solution as adhesive, which was applied by a coating roll to the corrugated layer issuing from between the two independent corrugating rolls of the machine. Still in contact with the lower corrugating roll, the adhesive-treated corrugated layer was joined with an uncorrugated layer of the same paper in passage over a plain steel roll.

The corrugating operation can be carried out in a number of ways to product materials of differing construction, but in its simplest form features feeding two rolls of material into the machine. The first roll is corrugated between fluted rollers, and the second roll of material is then glued flat across the corrugations so that the corrugated shape is retained on exiting the machine. It is also possible to produce a product with flat surface sheets on both sides of the corrugated sheet, for example by starting with three rolls of material, only one of which is actually corrugated between fluted rollers. The two rolls of material used to form the corrugated product need not be of the same material.Thus, whilst the corrugated layer is preferably composed of the intumescent paper, the flat face could be of a non-intumescent paper or a metal foil, the selection of which would depend on the particular end use.

The properties of a typical corrugated intumescent paper product were: Thickness 5.5mm Density 0.09gm\cm3 Example 2 Following generally the procedure of Example 1, an intumescent paper was prepared from an aqueous suspension of the following ingredients.

Drv weight % Mineral wool 31.2 Lapponia wood pulp 4.7 Ball clay 28.1 Calcined china clay 5.4 Polyacrylamide flocculant 0.05 Bentonite 2.0 Colloidal silica (30% SiO2) 5.0 Heat-expandable graphite 14.0 Acrylic latex 7.8 Pigment 2.0 100.25 The properties of a typical intumescent paper product were: Thickness 0.5mm Density 0.757gm\cmj Tensile strength Machine direction 3.2 MPa Cross direction 3.6 MPa Compression at 1000 psi (= 7 MPa) 11% Recovery 35.3% Maximum pressure generated on expansion 6 bar, at 450" C This can be formed into a corrugated paper product as described earlier.

In the case of both examples, sheets cut from the corrugated paper were plyed one on top of another with adhesive to form a block in which all the corrugations were parallel to one another to constitute parallel channels extending from one face of the block to another, opposed face.

A section was cut from the block thus produced to make a small panel. This was then installed between a pair of decorative grills on a panelled door so as to constitute a ventilator permitting free passage of air through the door.

On subjecting the door to fire conditions, the intumescent component in the panel swelled, thereby closing completely the ventilator and at least temporarily preventing passage of flame and/or fumes from one side of the door to the other.

Claims

1. A method of making intumescent sheet material containing an amount of heat-expandable graphite sufficient to swell the sheet in a fire and having a matrix whose predominant ingredient is an unfired kaolinitic clay comprising ball clay reinforced by inorganic vitreous fibre, said material including an organic binder, said method comprising dewatering an aqueous suspension of the aforesaid ingredients in the form of a layer which includes cellulose fibre as web-formed agent; the dewatering being carried out so as to obtain an intumescent product in the form of paper as distinct from board; the paper being then converted to corrugated form, sheets of which are thereafter plyed other sheets of the same or similar corrugated paper to form a block or slab in which at least most of the corrugations are parallel to one another.

2. A method according to claim 1, in which the flat face of the corrugated product is itself of intumescent paper.

3. A method according to claim 1, in which the flat face of the corrugated product is of heat-reflective material.

4. A method according to claim 3, in which the heat-reflective material is aluminium foil.

Amendments to the claims have been filed as follows CLAIMS 1. A method of making a ventilator panel from an intumescent sheet material containing an amount of heat-expandable graphite sufficient to swell the sheet in a fire and having a matrix whose predominant ingredient is an unfired kaolinitic clay comprising ball clay reinforced by inorganic vitreous fibre, said material including an organic binder, said method comprising forming a paper therefrom, said paper being then converted to corrugated form, sheets of which are thereafter plyed with other sheets of the same or similar corrugated paper to form a block or slab in which at least most of the corrugations are parallel to one another, followed by a step of sectioning said block or slab to form a panel with a plurality of channels extending therethrough, to form a ventilator panel having minimum impedance to airflow, but which an exposure to heat, will swell to substantially completely seal said channels so as to at least temporarily prevent the passage of flame and/or fumes therethrough.

2. A method of making a ventilator panel from an intumescent sheet material containing an amount of heat-expandable graphite sufficient to swell the sheet in a fire and having a matrix whose predominant ingredient is an unfired kaolinitic clay comprising ball clay reinforced by inorganic vitreous fibre, said material including an organic binder, said method comprising dewatering an

5. A method according to any preceding claim wherein all of the corrugations in the block or slab extend parallel to one another from one face thereof to an oppositely directed face.

6. A method according to any preceding claim including a step of sectioning said block or slab to form a panel with a plurality of channels extending therethrough, to form a ventilator panel having minimum impedance to airflow, but which an exposure to heat, will swell to substantially completely seal said channels so as to at least temporarily prevent the passage of flame and/or fumes therethrough.

7. A method according to claim 1, substantially as described herein with reference to the Examples.

8. A ventilator panel made by the method of claim 7 and substantially as herein described.

8. A ventilator panel made by the method of claim 6 and substantially as herein described.

aqueous suspension of the aforesaid ingredients in the form of a layer which includes cellulose fibre as web-formed agent; the dewatering being carried out so as to obtain an intumescent product in the form of paper as distinct from board; the paper being then converted to corrugated form, sheets of which are thereafter plyed with other sheets of the same or similar corrugated paper to form a block or slab in which at least most of the corrugations are parallel to one another, followed by a step of sectioning said block or slab to form a panel with a plurality of channels extending therethrough, to form a ventilator panel having minimum impedance to airflow, but which an exposure to heat, will swell to substantially completely seal said channels so as to at least temporarily prevent the passage of flame and/or fumes therethrough.

3. A method according to claim 1, or claim 2 in which the flat face of the corrugated product is itself of intumescent paper.

4. A method according to claim 1, or claim 2 in which the flat face of the corrugated product comprises a heat-reflective material.

5. A method according to claim 4, in which the heat-reflective material is aluminium foil.

6. A method according to any preceding claim wherein all of the corrugations in the block or slab extend parallel to one another from one face thereof to an oppositely directed face.

7. A method according to claim 1, or claim 2 substantially as described herein with reference to the Examples.