(19) |
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(11) |
EP 0 244 964 A1 |
(12) |
EUROPEAN PATENT APPLICATION |
(43) |
Date of publication: |
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11.11.1987 Bulletin 1987/46 |
(22) |
Date of filing: 13.04.1987 |
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(84) |
Designated Contracting States: |
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AT BE DE ES FR IT NL SE |
(30) |
Priority: |
09.05.1986 GB 8611317
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(71) |
Applicant: T&N Materials Research Limited |
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Manchester M3 2NL (GB) |
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(72) |
Inventors: |
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- Stevenson, Alasdair Ian
Warrington
Cheshire, WA4 2RY (GB)
- Crabtree, John Dinsdale
Worsthorne,
Burnley (GB)
- Hargreaves, Brian
Flixton,
Manchester (GB)
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(74) |
Representative: Newman, Dennis Daniel Ernest (GB) et al |
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3 Lower Goodwin Close
Harwood GB-Bolton, Lancashire BL2 4HQ GB-Bolton, Lancashire BL2 4HQ (GB) |
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(54) |
Manufacture of flexible intumescent sheet |
(57) Flexible intumescent sheet according to British patent 1 513 808, comprising heat-expandable
micaceous mineral, inorganic fibrous material and organic binder, is made on standard
board-making machinery incorporating a winding drum, so that a laminar product is
obtained, not a monolithic one. The mineral particles in the sheet are thus more uniformly
distributed across its thickness, and the product shows less tendency to premature
failure in use.
[0001] This invention relates to the manufacture of flexible intumescent sheet.
[0002] In the specification of British patent 1 513 808 published June 1978 there is described
flexible intumescent sheet comprising heat-expandable micaceous mineral, such as vermiculite;
inorganic fibrous material, for example refractory aluminosilicate fibres, rockwool
or glass fibres; and organic binder, such as natural rubber, styrene-butadiene rubber,
butadiene-acrylonitrile rubber, or other elastomeric material. The sheet is suitable
for use as a mounting for ceramic catalyst-supports in metal containers, particularly
in automobile exhaust systems. The sheet is of dry bulk density at least 0.5gm/ml
and is typically of thickness 2.5mm. In the manufacture of it a standard paper-making
technique is employed, in which an aqueous suspension of the ingredients is de-watered
as a layer on a Fourdrinier screen, and the resulting green sheet is compressed to
a bulk dry density of 0.5gm/ml or more, and dried at about 90
0C to give the final paper. Now, although precautions may be taken to attain substantially
uniform distribution of the solid particles of the aqueous suspension across the thickness
of the paper, yet it is a matter of great difficulty to ensure this when forming paper
of thickness above 2.5mm. What happens is that the particles, especially those of
the micaceous mineral, tend to concentrate at that surface of the layer undergoing
dewatering which is adjacent to the Fourdrinier screen. A consequence of this lack
of uniformity in distribution of the heat-expandable micaceous mineral is that, when
the product is used as a mounting for ceramic catalyst supports in automobile exhaust
systems, non-uniform expansion of it occurs and there is a tendency (through the strains
which are then set up) for premature failure of the mounting to occur.
[0003] We have now found that this tendency to non-uniform distribution of the mineral is
much reduced if the dewatered sheet is wound onto a drum so as to obtain a laminar
product (as in standard board making techniques) instead of forming it (as in paper
making techniques) to its desired thickness as a monolithic product.
[0004] The invention is further illustrated by the following Example:
EXAMPLE
[0005] An aqueous suspension of vermiculite ore (70 parts by weight), aluminosilicate fibres
sold under the name FIBERFRAX (20 parts by weight) and styrene-butadiene latex sold
under the name HYCAR (equivalent to 10 parts by weight solids) is prepared as in Example
1 of British patent specification 1 513 808, and to it is added alum solution to reduce
the pH to 4.5. The suspension is then pumped to the head box (flow box) of a standard
board making machine ("intermittent machine"), generally as described on page 291,
Chapter 12, 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 distributed from the head box over the width of the water-permeable
conveyor felt of the machine and is progressively de-watered as it travels on the
felt. From the felt, the de-watered layer is passed to the drum (or 'making roll')
of the machine, on which it is wound until a thickness of 5mm has been built up. The
hollow laminar cylinder formed is then slit axially, and the sheet thus released is
laid flat and dried to moisture content of about 2% by weight.
[0006] If desired, operation of the drum can be continued until a thickness of 10mm or more
has been built up.
1. A process for the manufacture of flexible intumescent sheet by dewatering a layer
of aqueous suspension comprising heat-expandable micaceous mineral, inorganic fibrous
material, and organic binder, and drying the dewatered layer to a sheet of bulk dry
density at least 0.5 gm/ml, characterised in that the dewatered layer is before drying
wound onto a drum so as to obtain a laminar product.
2. A process according to claim 1, in which the laminar layer formed on the drum is
of thickness greater than 2.5mm.
3. A process accoring to claim 1 or 2, in which the inorganic fibrous material is
refractory aluminosilicate fibre.