GB2383005A - Fireproofing coating - Google Patents

Abstract

A fireproofing coating for a substrate comprises an unexpanded intumescent mineral and a binder. The mineral may have a micaceous structure such as unexpanded phyllosilicate for example vermiculite. Alternatively it may be an unexpanded silaceous volcanic glass such as perlite. The binder may be an organic polymer such as vinyl acetate, vinyl versatate, styrene acrylics, urea formaldehyde, phenol formaldehyde, melamine formaldehyde, acrylic, vinylidene chloride, polyurethane, polyamide, styrene butadiene or any grafted combination. A vinyl acetate/vinyl versatate copolymer is preferred. Alternatively the binder may be a silicate. Substrates include metal, minerals, plastic and wood in locations such as roofs, walls and floors, especially wooden roof trusses. In fireproofing an insulating wrap may be provided around the substrate, the substrate and/or the wrap being provided with the fireproofing coating.

Description

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Fire Protection System This invention relates to a composition, system and method for protecting a substrate, particularly although not exclusively a wooden substrate, from fire.

Many fireproofing compositions are known in the art. Such compositions are intumescent, in that they expand on heating to produce a thicker layer of material which insulates the substrate from fire. Such materials also char when exposed to heat. The char insulates the substrate from the heat. Chars of sufficient strength may also act as a physical barrier to the flame.

One well-known composition which is used by many different manufacturers is based on a combination of ammonium polyphosphate, melamine and pentaerythritol.

Typically, such compositions are used in combination with an inorganic filler, such as titanium dioxide, glass flake, mica, barytes, calcium carbonate, dolomite, talc and the like.

Another composition known in the art relies on the production of an intumescent resin from a twin pack system. Part A is a combination of urea-, melamine-and phenolformaldehyde water dispersible resins, which are intrinsically intumescent to a certain extent. Part B is a partial phosphoric acid ester, which facilitates cross-linking of the resins allowing them to intumesce to a much greater extent.

Such known compositions may be used in combination with a multi-layer insulating wrap. Typically, such wraps comprise one or more layers of glass fibres or ceramic fibres interposed between one or more layers of metallic foil, in particular aluminium foil. One particular wrap (FIREFLY 60 available from TBA) comprises four layers: E Glass fabric (a low-alkaline glass strand interwoven with fabric) aluminium foil; ceramic fibre; aluminium foil. Two sheets of this material are typically disposed symmetrically either side of the substrate to form a wrap.

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The function of the multi-layer insulating fabric wrap is twofold. Firstly, it provides a sack for the fireproofing composition to intumesce into and fill, thereby creating a thick, low-density insulating layer. Secondly, it exhibits some insulating effect in its own right, although its insulating effect is insufficient for it to be used alone.

However, a problem exists with the use of such prior art compositions in that it is difficult to produce a hard, volumous char with high enough insulation properties. This results in insufficient protection of the timber. Although addition of certain amounts of inorganic fillers to intumescent formulations may increase the strength of the char, it is difficult to optimise the level of inorganic filler to provide the best fireproofing effect.

When timber coated either with the prior art compositions (either alone or together with a fabric wrap) undergoes fire testing under the time-temperature curve conditions defined in British Standard 476, Part 20,1987, no structurally sound timber survives after 1 hour.

Therefore, it is an object of the present invention to provide a fireproofing coating capable of exhibiting superior strength and insulation properties compared to those of the prior art.

Vermiculite is a layered intumescent mineral, which is capable of incorporating combined water. By"combined water"is meant water molecules retained within the structure of the mineral by means of weak chemical bonds. This makes the mineral less susceptible to fluctuations in the ambient relative humidity. Typically vermiculite contains 8-16 wt. % combined water. On being heated to 100oC, the combined water boils, thereby forcing the layers apart and causing the vermiculite to expand to over 5 times its normal volume. In its expanded form, it is used in cement products to provide thermal and acoustic insulation. However, the use of unexpanded vermiculite in an insulating or fireproofing material has not previously been disclosed.

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With these objectives in mind, there is provided according to a first aspect of the present invention a fireproofing coating for a substrate, comprising an unexpanded intumescent mineral and a binder.

By"fireproofing"is meant protection of the substrate from fire by use of a non- combustible material. This should be contrasted with other insulating materials which, although capable of shielding the substrate from the heat of the fire in use, are consumed by the flames in the process.

The nature of the intumescent mineral is not particularly limited, provided that it is noncombustible, is unexpanded in the composition as applied, and is capable of intumescing on exposure to heat. The unexpanded intumescent mineral may be, for example, selected from unexpanded minerals having a micaceous structure with a multiple layer construction. In one embodiment, the unexpanded intumescent mineral may comprise an unexpanded phyllosilicate. It is especially preferred that the unexpanded intumescent mineral is unexpanded vermiculite.

Alternatively, the intumescent mineral may be an unexpanded silaceous volcanic glass.

Such glasses do not typically have the layered structure of vermiculite and similar materials. However, the vermiculite volcanic glasses are capable of incorporating combined water and expand to many times their normal volume when heated to temperatures in the region of 870 C. (However the silaceous volcanic glasses expand when heated in a manner akin to foaming, i. e. in more than one dimension, as opposed to the one-dimensional expansion of vermiculite by forcing the layers apart). Preferably the silaceous volcanic glass is perlite, which typically contains 2-6 wt. % combined water.

The nature of the binder is not particularly limited provided that it is capable of binding the unexpanded intumescent mineral sufficiently so that it adheres to the substrate. The binder typically comprises a resin, the nature of which is well known to those skilled in the art. The resin is preferably selected from organic polymers and silicates. Typical types of resin are vinyl acetate, vinyl versatate, styrene acrylics, urea formaldehyde, phenol formaldehyde, melamine formaldehyde, acrylic, vinylidene chloride,

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polyurethane, polyamide, silicates, styrene butadiene or any grafted combination. A vinyl acetate/vinyl versatate copolymer is especially preferred.

The weight ratio of intumescent mineral to binder may vary depending on the degree of fire protection required. Typically, the intumescent mineral and binder are present in a ratio of 0. 5: 1 to 5: 1 by weight, preferably 1: 1 to 2: 1 and more preferably 1.3 : 1 to 1.7 : 1.

The fireproofing composition of the present invention may also comprise additives, the nature of which is well-known to those skilled in the art. Examples of possible additives include in-can preservatives such as organoethoxy nitrogen compounds, chlorinated isothiazolones and the like, coalescing solvents, pH modifiers such as ammonia, amines (eg triethylamine or 2-amino-2-methyl-1-propanol) and the like, defoamers such as mineral oils, polysiloxanes, alcohols and the like, and rheology modifiers such as cellulose, xanthan gum, clay, polyurethane, acrylic and the like.

The fireproofing composition may applied to the substrate by any convenient means known in the art, eg by painting (by brush or spray).

The insulating coating of the present invention is generally used in conjunction with a fabric wrap. As described above, the function of this fabric wrap is twofold. Firstly, it provides a sack for the intumescent mineral to intumesce into and fill, thereby creating a thick, low-density insulating layer. Secondly, it exhibits some insulating effect in its own right which enhances the insulating effect of the composition of the present invention.

Therefore, there is provided according to a second aspect of the invention a fireproofing system for a substrate comprising a fireproofing coating according to the invention and an insulating wrap.

There is also provided according to a third aspect of the invention a method for fireproofing a substrate comprising providing a fireproofing coating according to the invention; providing an insulating wrap; coating the substrate and/or the insulating wrap with the fireproofing coating; and wrapping the substrate with the insulating wrap.

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The wrap may be any suitable insulating wrap known in the art, and generally comprises a multi-layer insulating wrap such as those described above. Preferably the wrap is that available from TBA under the trade mark FIREFLY, examples of which are described above. Preferably the wrap completely surrounds the coated substrate.

Alternatively, the coated substrate may form part of a sandwich composite, such as a duct wrap. Both flexible and rigid composites may be envisaged. Such fire protection systems also form part of the present invention.

In the fireproofing system according to the invention, the fireproofing coating is preferably applied directly to the substrate before the coated substrate is wrapped with the insulating wrap. However, the fireproofing coating may be applied to one or more layers of the wrap in addition to, or instead of, to the substrate. In this case, the coating may be applied to any layer of the wrap, provided that at least one layer of wrap is present between the coating and the external face of the fireproofing system (ie the coating must not be applied solely to the external face of the system).

It is preferred that the fireproofing coating is allowed to dry before wrapping.

The coated substrate may preferably adhere to the wrap. However, the wrap may also simply surround the coated substrate without adhesion thereto.

In further preferred embodiments, all joints and overlaps in the wrap are sealed after wrapping.

The amount of the coating used and the characteristics of the wrap used may be varied according to the desired temperature the fireproofing system is to withstand and the desired protection time.

The insulating coating according to the invention may be used to protect from fire a wide range of materials in a wide variety of locations. Examples of protectable materials include metal, minerals, plastic and wood. Examples of locations protectable

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include roofs, floors and walls. The coating is particularly suitable for protecting wood, especially wooden roof trusses.

The invention will now be described in relation to the following, non-limiting Example.

Formulation Example The formulation by weight consists of the following:

Crude Vermiculite-PALABORA (trade mark) (available from Dupre) 58.8 Water 1.6 Emulsion Resin (50% weight solids) (vinyl acetate/vinyl versatate)Resad 3250 (trade mark) (available from Resad Polymers) 7.0 Cosolvent (Monopropylene Glycol) (available from Ellis and Everard Chemicals) 1.8 In can preservative (isothiazolone)-Parmetol A26 (trade mark) (available from Aquacryl) 0.1 pH Modifier (2-amino-2-methyl-l-propanol)-AMP95 (trade mark) 0.1 (available from Samuel Banner & Co.) Thickener (cellulose ether)-Natrosol 250HXR (trade mark) (available from Hercules) 0.4 Defoamer: (mixed mineral oils)-BEVALOID 6685 (trade mark) (available from Rhone-Poulenc) 0.2 The emulsion resin and vermiculite were introduced into a mixing vessel. After mixing had commenced, the defoamer, in-can preservative and cosolvent were added. The water and thickener were pre-mixed in a separate vessel before being added to the mixture. The pH modifier was then added until the pH of the mixture reached between 8 and 9.

The formulation was applied by spraying to timber trusses suitable for fixing to a domestic roof. After being allowed to dry, the coated trusses were wrapped in a fabric wrap (available from TBA under the trade mark FIREFLY) and all joints and overlaps

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were sealed with an inorganic silicate-type high temperature adhesive (FIREFLY (trade mark) High Temperature Adhesive, available from TBA).

Test Example The coated, wrapped trusses were exposed to a fire meeting the time-temperature conditions disclosed in British Standard 476, Part 20, 1987. After 1 hour's exposure, the trusses had survived sufficiently to allow the construction built therefrom to be structurally sound.

Claims (21)

CLAIMS:

1. A fireproofing coating for a substrate, comprising an unexpanded intumescent mineral and a binder.

2. A fireproofing coating according to claim 1, wherein the unexpanded intumescent mineral is an unexpanded mineral having a micaceous structure with a multiple layer construction.

3. A fireproofing coating according to claim 2, wherein the unexpanded intumescent mineral is an unexpanded phyllosilicate.

4. A fireproofing coating according to claim 3, wherein the unexpanded intumescent mineral is unexpanded vermiculite.

5. A fireproofing coating according to claim 1, wherein the unexpanded intumescent mineral is an unexpanded silaceous volcanic glass.

6. A fireproofing coating according to claim 5, wherein the unexpanded intumescent mineral is unexpanded perlite.

7. A fireproofing coating according to any one of claims 1 to 6, wherein the binder comprises a resin selected from an organic polymer and a silicate.

8. A fireproofing coating according to any one of claims 1 to 7, wherein the intumescent mineral and binder are present in a ratio of 0.5 : 1 to 5: 1 by weight.

9. A fireproofing coating according to claim 8, wherein the intumescent mineral and binder are present in a ratio of 1 : 1 to 2: 1 by weight.

10. A fireproofing coating according to claim 9, wherein the intumescent mineral and binder are present in a ratio of 1.3 : 1 to 1.7 : 1 by weight.

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11. A fireproofing system for a substrate comprising a fireproofing coating according to any one of claims 1 to 10 and an insulating wrap.

12. A fireproofing system according to claim 11, wherein the wrap completely surrounds the coated substrate.

13. A fireproofing system according to claim 11 or claim 12, wherein the fireproofing coating is applied directly to the substrate.

14. A fireproofing system according to claim 13, wherein the fireproofing coating adheres to the substrate in use.

15. A fireproofing system according to any one of claims 11 to 14, wherein the fireproofing coating is applied to the wrap.

16. A method of fireproofing a substrate, comprising: providing a fireproofing coating according to any one of claims 1 to 10; providing an insulating wrap; coating the substrate and/or the insulating wrap with the fireproofing coating; and wrapping the substrate with the insulating wrap.

17. A method according to claim 16, wherein the fireproofing coating is allowed to dry before wrapping.

18. A method according to claim 16 or claim 17, wherein all joints and overlaps in the wrap are sealed after wrapping.

19. A fireproofing coating substantially as described herein.

20. A fireproofing system for a substrate substantially as described herein.

21. A method of fireproofing a substrate substantially as described herein.