GB2126611A - Weatherproof coatings for roof decks - Google Patents

Abstract

A fabric for use as a reinforcing membrane in a cold applied weather-proof coating for roof decks is a non-woven fabric formed by welding together a layer of composite fibres each having a thermoplastic component forming a surface part. Following known practice, a weather-proof coating is produced by applying a bituminous liquid or paste to a roof deck, laying the reinforcing fabric membrane into the wet liquid or paste, impregnating and coating the membrane with the bituminous liquid or paste and allowing the liquid or paste to dry and set. Preferred composite fibres comprise a core of polyester or nylon 66 polyamide within a sheath of nylon 6 polyamide.

Description

SPECIFICATION Weatherproof coatings for roof decks Roof decks, for example those formed from timber or concrete, are usually provided with a weatherproof or water-resistant coating.

Weatherproof coatings are known which comprise one or more layers of bitumenised felt, nailed or adhered to the surface of the roof deck. Such coatings are relatively easy to apply, the felt usually being supplied in rolls of 1 metre width which are simply unrolled across the roof deck and secured with nails and/or bitumen adhesive applied by brushing. However, unless great care is taken to ensure that the felt, as it is unrolled, is firmly bonded to the roof deck or to a previous layer of felt thereon, especially at the seams, points of potential weakness may be built into the structure. The weatherproof coating may then fail at a disappointingly early age, by blistering or parting at the seams.

Weatherproof coatings are also known in which a bituminous liquid or paste is applied to the roof deck or to an underlay placed over the roof deck and a reinforcing fabric membrane is laid into the wet liquid or paste coating and impregnated and coated with further liquid or paste. The liquid or paste may be an aqueous bitumen emulsion or a solution of bitumen in an organic solvent and may include other components in solution or suspension. A further layer or layers of liquid or paste may be applied for additional protection, followed, if desired, with a decorative finishing coat. Such waterproof coatings are more durable than felt coatings since the whole coating is integral when the liquid or paste has dried and it is adhered to the whole surface of the roof deck. Weatherproof coatings of this kind can be used to repair or cover damaged areas of felt coatings.This invention is concerned with weatherproof coatings of this kind, which are commonly called, and will for convenience be referred to as, "cold applied" weatherproof coatings.

Hitherto, the reinforcing fabric membranes used in cold applied weatherproof coatings have been woven fabrics of hessian treated with a rot-resistant preparation or of glass fibre yarns or other rot-resistant yarns.

Hessian, even when treated with rot-resistant preparations, tends to rot after a few years, resulting in considerable loss of strength of the coatings. Glass fibre membranes tend to crack along lines of concentrated stress or movement, for example, if a crack forms in an underlying concrete roof deck or where there is a sharp change in contour, such as at the corner of a parapet wall and roof deck. Non-woven fabrics, such as polyester fleece, have been tried but hitherto have not been satisfactory due to their stiffness and lack of drape and because such fabrics with adequate strength to resist the stresses caused by thermal expansion and contraction have not been sufficiently porous for speedy impregnation with the bituminous liquid or paste.

According to this invention, in a cold applied weatherproof coating for roof decks, the reinforcing fabric membrane is a non-woven fabric formed by thermally welding together a layer of composite fibres each comprising at least two components, one of which, forming at least a part of the surface of the fibre, is of thermoplastic material.

The invention includes a method of producing a cold applied weatherproof coating on a roof deck in which the reinforcing fabric membrane is a non-woven fabric formed as aforesaid.

Further, the invention includes a roof having a cold applied weatherproof coating produced by the said method.

In the reinforcing fabric membrane, the composite fibres may comprise the whole or a part of the non-woven fabric. They may be of various materials. The component of thermoplastic material preferably encloses the other component or components (which may also be of thermoplastic material, but with a higher melting point) as a sheath. A preferred non-woven fabric comprises composite fibres of polyester each having a sheath of nylon 6 polyamide.

Various methods are known for producing non-woven fabrics suitable for use in performing the invention.

Several methods are described, for example, in British Patent Specification No. 1,073,181 and 1,073,182. In a preferred method, bi-component synthetic filaments are spun from two components having different melting points so that one component, having a higher melting point, forms a core enclosed in a sheath formed from the other component. The filaments are cut into staple fibres which are laid in a sheet and heated, whereupon the sheath component is softened and the fibres become welded together at their contact points to form a fabric. As mentioned, one suitable fabric comprises fibres having a core of polyester within a sheath of nylon 6 polyamide. Another example comprises fibres having a core of nylon 66 polyamide within a sheath of nylon 6 polyamide. Other components which provide appropriate properties in the fabric may alternatively be used.

Whilst a satisfactory weatherproof coating can be produced using one reinforcing fabric membrane, it is preferable to use at least two such membranes, which may be of similar or different fabrics. The membranes are applied separately, in succession, the bituminous liquid or paste coating into which the or each preceding membrane has been laid being allowed to dry before applying a further bituminous liquid or paste coating and laying the succeeding membrane into it. In this way, the whole weatherproof coating is compacted into a unitary mass and adhered to the whole underlying surface of the roof deck.

Thus, according to a further feature of the invention, a cold applied weatherproof coating for roof decks includes two superimposed reinforcing fabric membranes, each formed by thermally welding together a layer of composite fibres each comprising at least two components, one of which, forming at least a part of the surface of the fibre, is of thermoplastic material.

The two superimposed reinforcing fabric membranes, which may be of similar or different fabrics, preferably extend in different directions, for example perpendicular to each other. By this means any directional characteristic of strength can be balanced so as to obtain substantial uniformity in the strength of the coating in all directions along the surface of the roof deck. Coincidence or paralleiism of seams between lengths of membrane fabrics are also avoided. Seams can be lines of weakness in cold applied weatherproof coatings, but by avoiding coincidence of seams in the superimposed membranes a seam in one membrane is reinforced by the adjacent membrane.

There may be additional reinforcing fabric membranes superimposed on the said two superimposed membranes, again preferably in different directions.

The superimposed reinforcing fabric membranes may be impregnated and coated with different bituminous liquids or pastes to provide different properties. For example, an outer membrane may be impregnated with a liquid or paste incorporating an elastomer such as neoprene with the bitumen, providing enhanced flexibility and weather-resistance. For an inner membrane, on the other hand, it is preferred that the impregnating liquid or paste is formulated so as to provide good wetting of the membrane and good adhesion to the roof deck and/or to the adjacent membrane or membranes.

As known in the art, the bituminous liquids or pastes may be emulsions or solutions. In both cases, after the weatherproof coating is laid, the volatile component or components evaporate, laving a solid weatherproof coating comprising the reinforcing fabric membrane or membranes embedded in the bitumen and other solids, if any, contained in the liquids or pastes.

Following normal practice, the weatherproof coating may, if desired, be finished with a decorative and/or protective layer of a bituminous liquid or paste including a colouring pigment and/or reflective metallic particles to provide protection from solar radiation.

In an example, a non-woven reinforcing fabric membrane formed from fibres each comprising a polyester core with a nylon 6 polyamide sheath, of weight 50 gm. per metre and thickness 0.45 mm., was used in coating a roof. The fabric membrane had a breaking load of 160 N/5 cm. with 40% elongation at break. The roof was first coated with a paste having the following composition in percentage parts by weight: Bitumen 40 to 60 Inorganic mineral fibres 1 to 10 Sodium aluminium hydroxy silicate 0.1 to 5 Water remainder The fabric membrane was laid on and pressed into the paste coating, ensuring that it was wholly impregnated with the paste and adhered to the whole surface of the roof deck.When the paste was dry a further coating of paste was applied and a second membrane, of the same fabric, was laid on and pressed into this, at right angles to the first fabric membrane. A final layer of paste was then applied to impregnate and coat the second membrane and compact it against the first membrane.

For test purposes, a similar weatherproof coating was prepared on a surface treated with a release agent so that when the paste had dried and set the coating could be peeled off. Test pieces of width 50 mm. were cut from the coating for fatigue testing by the method described by J.M. Dinwoddie and C. Holland in a paper presented to the Society of Chemical Industry's Second International Symposium on Roofs and Roofing, Brighton, September 1981. The test involves clamping a test piece between clamps spaced 11 mm. apart and moving the clamps repeatedly towards each other by 1 mm. and apart so as to flex the test piece at 10 cycles per minute. Flexing is continued until failure of the test piece occurs, as detected by the penetration of water in a separate test, and the number of cycles is then noted.

Tests were made on the weatherproof coating produced as described in the above example (Specimen "A") and on a second weatherproof coating similarly produced but with the outer reinforcing fabric membrane impregnated and coated with a bituminous liquid incorporating neoprene elastomer with the bitumen (Specimen "B"). In each case, five tests were made and the average number of cycles to failure was calculated. The materials were tested as produced and also after ageing for 28 days at 80to. In the following table, the results are compared with the results of similar tests on various bitumenised roofing felts, and on a cold-applied weatherproof coating of construction similar to Specimen A but in which the reinforcing fabric membranes were of conventional hessian fabric.

Specimen Cycles to failure As produced Aged "A" 73,700 15,750 "B" 93,820 35,800 Asbestos-based felt to B.S.S. 747 153 33 Glass-basedfeltto 8.5.5.747 150 75 Polyester-based felt 6,250 3,200 Polyester polymer-modified felt 140,000 20,000 Cold applied weatherproof coating with hessian fabric membranes 80,450 28,333 These results show that the fatigue-resistance of cold applied weatherproof coatings embodying the invention is comparable with that of a conventional cold applied coating with hessian fabric membranes, and is distinctly superior when one of the membranes of welded non-woven fabric is impregnated with a bituminous liquid or paste incorporating rubber or other elastomer.With improved rot-resistance due to the use of synthetic fibre fabrics for the reinforcing membrane or membranes, weatherproof coatings embodying the invention are expected to have a substantially longer useful life than conventional cold applied weatherproof coatings. The welded non-woven fabrics can be produced with greater strength than the woven fabrics used hitherto, yet can be much lighter than those woven fabrics and thus be easier to handle during the production of the weatherproof coatings. We have found that they are wetted more easily with the bituminous liquids and pastes used in the production of cold applied weatherproof coatings than previous fabrics. A continuous layer throughout the coating, without voids, is thus more easily accomplished, resulting in stronger and more durable coatings. The welded non-woven fabrics have substantially improved drape compared with other non-woven fabrics which have been tried, and thus can readily be made to conform to the shape of the roof deck and associated parts of a building such as the junctions between the roof deck and surrounding walls or parapets and chimneys, ventilators or other protections through the roof deck. It is at these junctions that failures in weatherproof coatings frequently occur, both in felt coatings and cold applied coatings, due to difficulty in shaping the felt or the membrane without weakening it, and it is believed that this difficulty will be reduced substantially by the present invention.

Claims (11)

1. A cold applied weatherproof coating for roof decks wherein the reinforcing fabric membrane is a non-woven fabric formed by thermally welding together a layer of composite fibres each comprising at least two components, one of which, forming at least a part of the surface of the fibre, is of thermoplastic material.

2. A cold appied weatherproof coating for roof decks including two superimposed reinforcing fabric membranes, each of a non-woven fabric formed by thermally welding together a layer of composite fibres each comprising at least two components, one of which, forming at least a part of the surface of the fibre, is of thermoplastic material.

3. A cold applied weatherproof coating for roof decks as claimed in Claim 2 wherein the two superimposed reinforcing fabric membranes extend in different directions.

4. A cold applied weatherproof coating for roof decks as claimed in Claim 2 or Claim 3 including at least one additional reinforcing fabric membrane, superimposed on the said two superimposed reinforcing fabric membranes.

5. A cold applied weatherproof coating for roof decks as claimed in any of Claims 2 to 4 wherein superimposed reinforcing fabric membranes are respectively impregnated and coated with different bituminous liquids or pastes.

6. A cold applied weatherproof coating for roof decks as claimed in any of Claims 2 to 5 wherein at least one of the impregnating and coating bituminous liquids or pastes incorporates an elastomer.

7. A cold applied weatherproof coating for roof decks as claimed in any of Claims 2 to 6 wherein superimposed reinforcing membranes are of different fabrics.

8. A cold applied weatherproof coating for roof decks as claimed in any preceding claim wherein the thermoplastic component of the composite fibres of the or a reinforcing fabric membrane encloses the other component as a sheath.

9. Method of forming a cold applied weatherproof coating on a roof deck comprising the steps of coating the roof deck or an underlay placed thereon with a bituminous liquid or paste, laying into the wet liquid or paste a reinforcing fabric membrane and coating and impreganting the laid reinforcing fabric membrane with a bituminous liquid or paste, characterised in that the reinforcing fabric membrane is a non-woven fabric formed by thermally welding together a layer of composite fibres each comprising at least two components, one of which, forming at least a part of the surface of the fibre, is of thermoplastic material.

10. A roof deck having cold applied weatherproof coating produced by the method claimed in Claim 9.

11. A roof deck having a cold applied weatherproof coating as claimed in any of Claims 1 to 8.