WO2010109158A1

WO2010109158A1 - Intumescent material

Info

Publication number: WO2010109158A1
Application number: PCT/GB2010/000148
Authority: WO
Inventors: Nigel Julian Walker; Emma Knowles; Michael Edward Caton
Original assignee: Technical Fibre Products Limited
Priority date: 2009-03-21
Filing date: 2010-02-01
Publication date: 2010-09-30
Also published as: GB2480591B; GB201116696D0; GB0904922D0; GB2480591A

Abstract

An electrically conductive intumescent sheet material which may have a thickness of 0.25 to 5 mm, a density of 100 to 500 kg m³, a volume expansion ratio of from 3:1 to 20:1 after 15 minutes at 450°C, a surface resistivity value of from 10⁵ to 2 ohms/square, and/or an insertion loss value of at least 10 dB when measured at a frequency of 10 GHz. The material may comprise an inorganic fibre matrix and further comprise an intumescent substance and an electrically conductive substance. The material may be produced by preparing an aqueous suspension of inorganic vitreous fibres, an intumescent substance, an electrically conductive substance and optionally a binder, wet-laying the slurry on to a water pervious support, withdrawing the water from the slurry to produce a sheet and drying the sheet. The material is useful in remotely activated fire protection systems.

Description

lntumescent Material

The present invention relates to an intumescent material, a method for the manufacture of such a material and also to the use of the material in fire protection applications.

Flexible intumescent materials (e.g. in the form of a sheet or a strip) are used for a variety of passive fire protection applications. Such material may be produced on paper-making equipment and comprise a predominately fibrous matrix (e.g. a bonded fibrous web) loaded with an intumescent substance (e.g. exfoliating graphite). In use, the intumescent material is applied to a surface to be protected by any suitable means, e.g. by use of adhesive. The surface may for example be around the edge of a door. In the event of a fire, the presence of the intumescent substance causes the product to expand in a multiplicity of direction so as to form a seal and provide for protection against fire.

One such material is disclosed in GB-A-2 273 100 and is produced by wet-laying an aqueous suspension incorporating rockwool fibres, an elastomeric binder and exfoliating graphite on a forming fabric such as used for paper- marking, and withdrawing water from the suspension to form a sheet which is then dried.

EP-A-O 949 313 provides a further disclosure of a wet-laid intumescent sheet material. In this case, the wet-laid material incorporates flexible organic fibres and is dried to a moisture content of less than 5% by weight prior to being compressed to provide improved volume expansion properties.

Materials as described in GB-A-2 273 100 and EP-A-O 949 313 are perfectly satisfactory for a wide range of passive, fire protection applications but have limited or no use to meet the needs of certain other fire protection applications. A particular limitation, for example, is that the materials are "passive" and only expand once the temperature has reached a certain value as dictated by the nature and amount of the intumescent substance in the material. For certain applications (e.g. protecting documents from fire) damage may have been done by the time that temperature is reached.

It is therefore an objected of the present invention to obviate or mitigate the above mentioned disadvantages.

According to a first aspect of the invention there is provided an electrically conductive intumescent sheet material.

The intumescent material of the invention provides a number of advantages. Thus, for example, it may be used as part of a fire protection system in which the intumescent material is caused to expand by the passage of an electrical current therethrough (the current serving to effect resistance heating of the material). Thus on detection of the relatively early stages of a fire, such an electrical current may be passed through the intumescent material to cause it to expand and provide much earlier protection than is the case for passive fire protection where temperature must build up to a predetermined (relatively high) level before the intumescent material expands. Thus, purely by way of example, the intumescent material of the invention is well-suited when used in combination with such an automated fire protection system for protecting articles such as documents which need shielding from heat as soon as possible and not just (as in the case of a passive application) when the fire has caused the intumescent material passively to expand. Further applications of the intumescent material in accordance with the invention are in applications where (in addition to fire protection) EMI shielding, static protection and inductive heating are required. In this respect, attention is directed to "Resistivity Control Using Wet-Laid Nonwovens", 45^th SAMPE International Conference, Anaheim, California 1998 which relates to properties required of sheet materials for such applications.

Preferred materials in accordance with the invention have one or more of the following properties (a)-(e) listed below:

(a) a thickness of 0.25 to 5 mm, preferably 0.5-3mm.

(b) a density of 100 to 500 kg m^'3, preferably 200 to 400 kg; m^"3; (c) a volume expansion ratio of from 3:1 to 20: 1 ;

(d) a surface resistivity value of from 10⁵ to 2 ohms/square; and/or

(e) an insertion loss value of at least 10 dB when measured at a frequency of 10 GHz.

Preferred intumescent materials in accordance with the invention, and which provide a second aspect thereof, are non-woven (preferably wet-laid) sheet materials comprising an inorganic fibre matrix and further comprising an intumescent substance and an electrically conductive substance. A preferred embodiment of such a sheet material is a bonded fibrous web and therefore further comprises a binding agent for effecting such bonding.

Sheet materials in accordance with the second aspect of the invention may be prepared by wet-laying an aqueous slurry of inorganic fibres, and intumescent substance and an electrically conductive substance (and preferably further comprising a polymeric binding agent) on to a water-previous support, and withdrawing water from the slurry to form a sheet.

Inorganic fibres for use in the invention may comprise glass fibres, asbestos fibres, ceramic fibres, zirconia fibres, alumina fibres, mineral wool, rockwool, slag wool and/or any other appropriate inorganic vitreous fibres.

Sheet materials in accordance with the invention preferably comprise both mineral, (rockwool) and glass fibres. Ideally if the mineral (rockwool) fibres have a length in the range 0.5-2. Omm whereas the glass fibres have a length in the range 3-25mm.

The conductive material may take a number of physical forms and may, for example, be fibrous, spherical, granular or flake-like. If fibrous, the conductive material preferably has a fibre length of 3mm-25mm.

The conductive material may consist solely of an electrical conductor or may comprise an electrical conductor in association with a non-conducting substrate on or in which the electrical conductor is provided. Examples of electrically conducting materials include carbon, metal and metal coated carbon (all of which act as electrical conductors per se), metal coated materials (e.g. textiles) and carbon loaded textile fibres. Specifically carbon fibres with the length of 3mm-25mm and Cu/Ni coated carbon fibres with a length of 3mm- 25mm have been found to be useful.

The intumescent material may for example be intercalated graphite, vermiculite, perlite, sodium silicate, an ammonium phosphate or an intumescent material comprising a blowing agent (e.g. melamine) with a charring agent (e.g. dipentaerythritol).

Sheet materials in accordance with the invention may be prepared by a wet-laying process using standard paper making techniques. Therefore as applied to production of a material of the second aspect of the invention the method comprises wet-laying an aqueous slurry of inorganic fibres, and intumescent substance and an electrically conductive substance on to a water- pervious support withdrawing water from the slurry, and drying the sheet. In preferred embodiments of the invention, the slurry incorporates a binding agent whereby a bonded fibrous material is produced.

The sheet material as manufactured by the wet-laying process may be further modified by compression by passing between two rollers.

The properties of the sheet material may be controlled by varying the proportions of conductive, non-conductive and intumescent materials.

For example a sheet material with high insertion loss value and low resistivity values would be achieved by maximising the conductive component whereas a sheet with a high degree of expansion would require the intumescent component to be maximised. The wet-laying process presents no barriers to the relative proportions ( unlike e.g. a weaving process) thus allowing the properties to be "tailored" to suit specific end uses.

Intumescent sheet materials in accordance with the invention are as indicated above suitable for use in a fire protection system which can be activated remotely by applying an electric current to the material thereby generating sufficient temperature to expand ("activate") the intumescent material in advance of the arrival of a fire.

The invention will be illustrated by the following non-limiting Examples.

Example 1

An aqueous slurry with a solids content of 14 grams per litre was prepared from the following formulation and formed into a sheet using standard papermaking techniques.

Component Weight percent

Mineral ( rockwool ) fibre - 0.7mm 35

Carbon fibre - 12mm 10

Intercalated Graphite 35

Glass fibre - 12mm 15

Poly vinyl alcohol binder 5

In this Example the sheet was fully dried ( zero % moisture) and was not compressed .

The sheets formed had the following characteristics:

Basis Weight 400 gm^"2

Thickness 2mm

Surface Resistivity 4 DD

Through Plane Resistivity 10³ Ω

Expansion Ratio 8:1 ( after 15 minutes at 45O⁰C )

Insertion Loss @ 10Ghz -25 dB

Example 2 An aqueous slurry with a solids content of 14 grams per litre was prepared from the following formulation and formed into a sheet using standard papermaking techniques.

Components Weight percent

Mineral ( rockwool ) Fibre - 0.7mm 35

Cu/Ni Coated Carbon Fibre - 12mm 20

Intercalated Graphite 35

Glass Fibre - 12mm 5

Poly Vinyl Alcohol Binder 5

The sheets formed had the following characteristics:

Basis Weight 400 gm

Thickness 2mm

Surface Resistivity 2 DD

Through Plane Resistivity 10² Ω

Expansion Ratio 8:1 ( after 15 minutes at 450⁰C )

Insertion Loss ®. 10Ghz -48 dB

Example 3

The material produced in Example 1 was impregnated with 400 gm-² of epoxy resin mixed with dicyandiamide hardener. The resulting mat was pressed and cured in a hydraulic sheet press at a temperature of 200° C for 5 minutes. The material thus produced had the following characteristics. Basis weight - 800 gm^~2

Thickness - 0.5mm

Expansion Ratio - 32:1 ( after 15 minutes at 450⁰C )

Insertion Loss @ 10Ghz - -40 dB

The presence of the resin makes the material surface an electrical insulator - yet conductivity is maintained within the body of the sheet as demonstrated by the "Insertion Loss" value.

Example 4

A sample of the material produced in Example 1 was connected to a variable voltage power supply using conductive tapes.

After connection, the voltage was increased to the maximum (36V) with the current being limited to 3A.

Approximately 20 seconds after connection to the full available power the intumescent material underwent a rapid expansion - reaching a 10 :1 expansion ratio within 30 seconds of the full power application.

This Example demonstrates the effectiveness of the material of the invention for use in a remotely activated fire protection system.

Claims

1. An electrically conductive intumescent sheet material .

2. A material as claimed in claim 1 having a thickness of 0.25 to 5 mm.

3. A material as claimed in claim 2 having a thickness of 0.5 to 3.0 mm.

4. A material as claimed in any one of claims 1 to 3 having a density of 100 to 500 kg m^'3.

5. A material as claimed in claim 4 having a density of 200 to 400 kg m-³.

6. A material as claimed in any one of claims 1 to 5 having a volume expansion ratio of from 3:1 to 20:1 after 15 minutes at 45O⁰C.

7. A material as claimed in any one of claims 1 to 6 having a surface resistivity value of from 10⁵ to 2 ohms/square.

8. A material as claimed in any one of claims 1 to 7 having an insertion loss value of at least 10 dB when measured at a frequency of 10 GHz.

9. A material as claimed in any one of claims 1 to 8 comprising an inorganic fibre matrix and further comprising an intumescent substance and an electrically conductive substance.

10. A material as claimed in claim 9 comprising 10-50% by weight of the inorganic fibres, 10-50% by weight of electrically conducted material and 10- 50% by weight of electrically conductive substance.

11. A material as claimed in claim 9 or 10 wherein the inorganic fibres are vitreous fibres.

12. A material as claimed in claim 11 wherein the inorganic vitreous fibres comprise glass fibres, asbestos fibres, ceramic fibres, zirconia fibres, alumina fibres, mineral wool, rockwool or slag wool.

13. A material as claimed in any one of claims 9 to 12 wherein the electrically conductive component is in the form a fibre, sphere, granule or flake.

14. A material as in any one of claims 9 to 13 wherein the electrically conductive material comprises carbon, a metal or a metal coated material.

15. A material as claimed in any one of claims 9 to 14 wherein the intumescent material is selected from intercalated graphite, vermiculite, perlite, sodium silicate, ammonium phosphates or intumescent materials comprising blowing and charring agents.

16. A material as claimed in any one of claims 9 to 15 which is a bonded web.

17. A method of producing a material as claimed in any one of claims 9 to 16 comprising preparing an aqueous suspension of the inorganic vitreous fibres, the intumescent substance, the electrically conductive substance and optionally a binder, wet-laying the slurry on to a water pervious support, withdrawing the water from the slurry to produce a sheet and drying the sheet.

18. A remotely activated fire protection system comprising a conductive intumescent sheet material as defined in any one of claims 1 to 16, said material being associated with a source of electrical current which is caused to pass through the material at a predetermined temperature condition as detected by the system so as to cause expansion of the intumescent material.