TECHNICAL FIELD

This invention relates to improving abrasion resistance in fibrous building materials. In particular, though not exclusively, this invention relates to multi-layer building materials in which abrasion, for example by bat claws, is mitigated. Aspects of the invention also relate to use of such building materials to provide a breathable membrane in the vicinity of a bat roost, and to methods of providing a breathable membrane and methods of mitigating abrasion.

BACKGROUND

Breathable, i.e. moisture vapour permeable, membranes help reduce heat loss through the fabric of buildings and have largely replaced non-breathable membranes. Low vapour resistance roofing underlays (LR underlays) incorporating such membranes, have largely replaced high vapour resistance bitumen 1 F roofing underlays (HR underlays) in the UK.

The roofing market distinguishes between cold roof and warm roof applications. A cold roof is classified as a roof where insulation is installed in horizontal ceiling joists of a roof structure leaving the roof void above cold. A warm roof has insulation installed at a sloping rafter level enclosing the roof space, creating a warm roof void. In accordance with the standard BS5250 "Code of practice for control of condensation in buildings", there are different requirements for each application regarding ventilation to avoid harmful interstitial condensation. A cold roof will always require ventilation beneath the underlay, whereas it is possible in a warm roof application to provide no ventilation beneath the underlay if a LR underlay is used.

Although LR underlays are used in over 95% of roofs in the UK because they help reduce condensation problems and contribute to efficient thermal insulation, LR underlays are not used where there are bat roosts. The moisture vapour permeable membranes of LR underlays are typically supported by fibrous or filamentous layers. The bats thus break the delicate filaments of the LR underlay, which causes the material to fluff up so that the bat can suffer harm by becoming entangled in the loose broken fibres. In addition, the functional capability of the LR underlay is affected by the bats breaking the filaments of the material.

As a consequence, 1 F felt HR underlays continue to be used in roofs where bats have been observed. 1 F felt is used because the thick, homogenous layer of bitumen used to make the material makes a good tie-point for bat claws and does not break or fluff up. This occurs mostly in old buildings but as a consequence, by using 1 F felt it is often not possible to increase the insulation performance of the roof as required by Building Regulations. More modern types of HR underlay such as bitumen 5U underlays, which could sufficiently increase the performance of roofs, contain polypropylene filaments. The polypropylene filaments pose a risk of entanglement to bats, despite the presence of a bitumen layer, and so these underlays cannot be used in place of 1 F felt HR underlays where there are bat roosts. Accordingly, the Bat Conservation Trust advises against such underlays as well.

It is an object of the present invention to provide a fibrous building material with improved abrasion resistance, with the potential to address one or more of the above-described problems.

SUMMARY OF THE INVENTION

From one aspect, the invention provides a multi-layer building material comprising a fibrous layer and a macroporous shielding layer affixed to the fibrous layer for mitigating abrasion of the fibrous layer.

It has been found that a macroporous shielding layer can mitigate abrasion of the fibrous layer, including bat claw abrasion, with minimal impact on other properties of the building material, e.g. vapour permeability.

The shielding layer is an outermost, exposed layer affixed to the fibrous layer. Conveniently, the shielding layer may comprise macropores defined by a structure standing proud of the fibrous layer. The structure may optionally cover less than 90% of a shielded area of the fibrous layer, with the rest of the shielded area being exposed through the macropores. Suitably, at least 10% or even at least 25% of the shielded area may be exposed through the macropores.

Surprisingly, it has been found that such a light-weight, low-impact, low-cost shielding layer may nevertheless be highly effective in mitigating abrasion.

The fibrous layer preferably comprises continuous fibres, optionally polymeric continuous fibres. Layered building materials containing such continuous fibres have hitherto been unsuitable for use in settings where the fibrous layer may be accessed by bats, since abrasion by bat claws can result in the continuous fibres becoming fluffed up so that bats can become entangled in the loose broken fibres. The macroporous shielding layer resolves this problem by preventing bat claws from accessing the fibrous layer or by restricting such access to only small regions of the fibrous layer within the macropores that are sufficiently small such that any abraded fibres cannot entrap a bat. Moreover, the shielding layer enables the fibrous layer to maintain its breathable properties.

The fibres of the fibrous layer may have a thickness (i.e. an average thickness) of 50 μηι or below. Such fibres provide desirable properties for breathable membranes in building materials, yet suffer the disadvantage when used in prior art materials that they cannot be used in proximity to bats in view of the issues discussed above.

In preferred embodiments the fibrous layer comprises a spunbond (also referred to as spunlaid, or spunbonded) nonwoven layer, for example a spunbond polymer such as a spunbond polypropylene.

The building material is preferably liquid water impermeable and water vapour permeable. It preferably comprises a liquid water impermeable, water vapour permeable membrane supported or protected by the fibrous layer.

The shielding layer preferably comprises macropores defined by an exposed structure standing proud of the fibrous layer.

Preferably, the structure covers less than 90% of a shielded area of the fibrous layer, with the rest of the shielded area being exposed through the macropores.

The shielding layer preferably comprises a mesh (or net). The mesh preferably comprises a plurality of strands arranged to form a grid defining an array of macropores. Each strand preferably has a thickness (or width, or diameter) of 100 μηι or above, 200 μηι or above, 300 μηι or above, 400 μηι or above, 500 μηι or above and/or 3000 μηι or below, 2000 μηι or below, 1000 μηι or below, 900 μηι or below, 800 μηι or below, 700 μηι or below.

The shielding layer is preferably fixed to the fibrous layer by an adhesive layer. There are preferably no further intervening layers between the shielding layer and the fibrous layer. The adhesive layer preferably comprises an adhesive mesh layer bonded to both the fibrous layer and the shielding layer.

Advantageously, the macropores of the macroporous shielding layer may have a maximum dimension (diameter, width etc) of about 20 mm or less, optionally about 15 mm or less, about 6 mm or less, about 4 mm or less, or about 2 mm or less. This has been found to be of benefit in mitigating abrasion by bat claws. Conveniently, the structure may be continuous. For example, the structure may comprise interlaced threads or strands. While a more discontinuous structure is also possible and contemplated, an interlaced structure can facilitate manufacture.

Conveniently, the structure may comprise a net defining a regular array of macropores. Suitably, the net may define macropores having a maximum dimension of at most about 20 mm, optionally in the range of from about 0.1 mm to about 15 mm, e.g. in the range of from about 0.5 mm to about 6 mm.

The shielding layer may advantageously have a thickness standing proud of the fibrous layer of in the range of from about 0.1 to about 3 mm (100 to 3000 μηι), optionally in the range of from about 0.5 to about 2 mm (500 to 2000 μι ι).

In various embodiments, the shielding layer may comprise a polymeric material, for example a polyolefin. Optionally, the shielding layer may comprise one or more polymers selected from the group of: polypropylene, polyethelene, polyethylene terephthalate, polyester, polyvinylidene chloride, or a combination thereof.

For ease of handling, the shielding layer may advantageously be flexible. For example, the shielding layer may be capable of forming a roll.

The fibrous layer may be of any type, but may in particular be prone to linting or fluffing on abrasion. As aforesaid, fluffing can have serious repercussions in bat roost environments.

The fibrous layer may comprise a polymeric material, for example a polyolefin. Optionally, the fibrous layer may comprise one or more polymers selected from the group of: polypropylene, polyethelene, polyethylene terephthalate, polyester, polyvinylidene chloride, or a combination thereof. Advantageously, the fibrous layer may comprise polypropylene or polyethelene.

Advantageously, the fibrous layer may comprise a non-woven material. In various embodiments, the fibrous layer comprises a spunbond material, optionally a polypropylene spunbond material.

Advantageously, the building material may be liquid water impermeable and water vapour permeable. Suitably, the building material may comprise a liquid water impermeable, water vapour permeable membrane supported or protected by the fibrous layer.

In various embodiments, the building material has a hydrostatic head of at least 200 cm and/or a moisture vapour transmission rate (MVTR) of at least 500 g/m ² .24hr or preferably greater than 1000 g/m ² .24hr, or greater than 1500 g/m ² .24hr.

MVTR may be determined using a Lyssy Model L80-5000 Water Vapor Permeability Tester at 100%/15% RH, i.e. 85% RH difference and 23 °C.

Advantageously, the building material as a whole may be flexible. For example, the building material may be capable of forming a roll.

Suitably, the building material may have a thickness in the range of from 0.05 to 10 mm, optionally 0.1 to 2 mm.

The building material may advantageously constitute a roofing underlay, in particular a LR roofing underlay.

The macroporous shielding layer may conveniently be affixed to the fibrous layer by any suitable form of bonding, for example, flame bonding, thermobonding, ultra-sonic bonding or adhesive bonding. Advantageously, the macroporous shielding layer may be affixed to the fibrous layer by intermittent bonding. This can aid flexibility and save weight and cost.

The building material may of course comprise a plurality of fibrous layers and associated shielding layers, e.g. as described hereinabove. In various embodiments, the building material comprises first and second fibrous layers and first and second shielding layers on opposed sides of the material. The shielding layer may cover all exposed faces of the building material.

The building material may comprise first and second fibrous layers sandwiching a microporous membrane. A shielding layer may be affixed to each fibrous layer to provide shielding on opposed sides (exposed faces) of the material.

From another aspect, the invention provides a method of making a building material according to the first aspect of the invention, the method comprising bonding the shielding layer to the fibrous layer, e.g. using the techniques described above. The building material may be of particular use in the presence of bats. Surprisingly, it has been found that, despite being macroporous, the shielding layer can be highly effective in mitigating abrasion by bat claws. Indeed, it has been found that ecological risks to bats can be effectively minimised with the building material, opening the door to the use of fibrous, optionally vapour permeable materials in the vicinity of bat roosts.

From yet another aspect, the invention provides use of a building material according to the first aspect to provide a breathable membrane in the vicinity of a bat roost. For example, a breathable roofing membrane in which the outermost shielding layer is exposed to a building void, such as a roof space, which may contain a bat roost.

From still another aspect, the invention provides a method of providing a breathable membrane in a roof or wall, the method comprising installing a building material according to the first aspect in a roof or wall. The roof or wall may comprise a bat roost, or a building void, such as a roof space, that may contain a bat roost. The building material may, for example, be installed in a warm roof application or a cold roof application.

From yet still another aspect, the invention provides a method of mitigating abrasion in a fibrous layer of a building material, the method comprising: affixing a macroporous shielding layer to the fibrous layer.

The method may further comprise providing an adhesive mesh layer between the macroporous shielding layer and the fibrous layer, and applying heat and/or pressure to the adhesive mesh layer to affix the macroporous shielding layer to the fibrous layer.

The invention provides for the use of a macroporous shielding layer for mitigating abrasion in a fibrous layer of a building material.

The abrasion may be specifically bat claw abrasion. The building material, fibrous layer and/or shielding layer may be as described in respect of other aspects of the invention.

Throughout the description and claims of this specification, the words "comprise" and "contain" and variations of the words, for example "comprising" and "comprises", mean "including but not limited to", and do not exclude other components, integers or steps. Moreover the singular encompasses the plural unless the context otherwise requires: in particular, where the indefinite article is used, the specification is to be understood as contemplating plurality as well as singularity, unless the context requires otherwise. Preferred features of each aspect of the invention may be as described in connection with any of the other aspects. Within the scope of this application it is expressly intended that the various aspects, embodiments, examples and alternatives set out in the preceding paragraphs, in the claims and/or in the following description and drawings, and in particular the individual features thereof, may be taken independently or in any combination. That is, all embodiments and/or features of any embodiment can be combined in any way and/or combination, unless such features are incompatible.

BRIEF DESCRIPTION OF THE DRAWINGS

One or more embodiments of the invention will now be described, by way of example only, with reference to the accompanying drawings, in which:

Figure 1 is a schematic section of a roofing underlay comprising macroporous shielding layers; and

Figure 2 is a bottom view of a lower side of the roofing underlay of Figure 1.

DETAILED DESCRIPTION

With reference to Figures 1 and 2, a shielded roofing underlay 2 comprises a liquid water impermeable, moisture vapour permeable membrane 4 sandwiched between first and second fibrous polypropylene spunbond layers 6, and first and second opposed shielding layers 8.

The moisture vapour permeable membrane is a microporous film of known time and is intermittently bonded to each of the spunbond layers 6 for support.

The shielding layers 8 are affixed to the outer faces of the spunbond layers 6, to shield against abrasion.

Roofing underlays according to various embodiments of the invention having this general structure are further illustrated by the following non-limiting examples.

Example 1 - Initial Bat Trial

Initial testing was carried out on samples of roofing underlays that were placed within a Bat aviary at the Isle of Wight Bat hospital. Testing was carried out on 4 development samples, comprising non-woven TLX ® UV 25 roofing underlay with HDPE net/mesh shielding layers (supplied by Conwed Plastics) of varying mesh size applied to surface of the underlays, as shown in Table 1 below.

TLX ® UV 25 is a roofing underlay comprising polypropylene spunbond layers sandwiching a microprorous film, available commercially from TLX ® Insulation. It has a thickness of about 0.25 mm.

Samples A-D were prepared from 630 mm x 1500 mm sheets of TLX ® UV 25. The shielding layers were adhered to one of the spunbond layers by either blobs of hot melt adhesive for larger (open) gauge meshes (samples A and B) or by intermittent lines of adhesive for smaller gauge meshes (samples C and D).

Each of samples A-D were exposed in an aviary with 40 pipistrelle bats for 3 months.

The level of protection provided to each roofing underlay surface from fibre pull through/fluffing by bats was assessed. Sample Underlay Shielding layer Mesh size

A TLX UV 25 (X03812) HDPE mesh approx.290gsm 23 mm x 23 mm

B TLX UV 25 (XN0521) HDPE mesh approx.450gsm 15 mm x 15 mm

C TLX UV 25 (XN1233) HDPE mesh 6 mm x 6 mm

D TLX UV 25 (XN0520) HDPE mesh 4 mm x 4 mm

Table 1 - Initial samples A-D tested

Testing with the bats showed that the larger gauge meshes provided some protection to the surface of the underlays in samples A and B, but there was still evidence of the fibres fluffing on the underlays in these samples.

It was found that the smallest gauge mesh provided the best protection to the surface of the TLX ® UV 25 underlay in samples C and D.

The results of the initial testing showed that a shielding layer having a mesh size < 6 mm provided the best results, since it either prevented access to the TLX ® UV 25 underlay by the bat or, even if the bat did break some fibres, the length of the fibres was limited to the size of the mesh and therefore could not fluff.

It was found that bat claws started to come into contact with the TLX ® UV 25 underlay for nets having a mesh size of 15 mm or greater.

The waterproof and breathable properties of TLX ® UV 25 were maintained throughout.

However, an issue with all of samples A-D was the inherent rigidity of the shielding layer, which made the samples impractical for use as a breather membrane even at the smallest mesh sizes (samples C and D).

Example 2 - Further Bat Testing

A second trial was conducted at the Isle of Wight Bat hospital following identification of alternative mesh materials for assessment. Two types of smaller gauge mesh shielding layers were trialled under the same conditions as used in Example 1 above. Samples E and F shown in Table 2 below were prepared from 400 x 1000 mm sheets of TLX UV ® 25 underlay with the shielding layer adhered to the underlay by intermittent blobs of hot melt adhesive. Samples E and F were exposed to the bats for 4 months.

Table 2 - Further samples E and F tested

The shielding layer used in Sample E had a wider strand profile and, being coated mesh, had a softer feel, which was seen as an advantage both from a finished product perspective and in that it was thought to provide a surface more similar to a bitumen based felt (e.g. 1 F roofing underlay) for bats to grip.

The shielding layers in both samples E and F provided good protection to the surface of the TLX UV 25 underlay with no fluffing noted over the length of the test, and so were both considered by the Isle of Wight Bat hospital to be good options.

Example 3 - Material screening

Due to the length of time required to arrange and carry out tests at the Isle of Wight Bat hospital, a mechanical screening method was developed to assess the suitability of various shielding layers when exposed with bats. The test adopted was carried out using a SDL Atlas ^(RTM) Crockmeter/Rubbing colourfastness tester. The rubbing finger of the Crockmeter was covered with a Velcro hook strip, which was fixed to the housing of the Crockmeter.

Samples G to L were prepared from 220 mm x 80 mm sheets of TLX ® UV 10 roofing underlay with the shielding layer adhesively adhered to the underlay. TLX ® UV 10 is a roofing underlay built up like TLX ® UV 25 but with a thickness of about 0.1 mm.

A control test was also carried out on a sample of TLX ® UV10 roofing underlay alone, without any shielding layer to provide a baseline against which to compare the results of the testing. The results of the screen are shown in Table 3 below.

A Hard Mesh 190gsm impact impact impact

Table 3 - Abrasion testing of samples

All of samples G-L assessed showed a significant improvement in abrasion resistance when compared to unprotected TLX ® UV 10 roofing underlay by itself (i.e. the control sample). A very soft lightweight shielding layer like the X03600 (Sample I) was destroyed quickly, but still provided a level of surface protection. Heavier, stiffer shielding layers were found to provide the best surface protection to the material, but due to the more rigid nature of these shielding layers, they may not be suitable for use in flexible roofing underlays.

Further Improvements

It has been found that an effective bond between the fibrous layer (underlay) and the shielding layer can be most effectively achieved by way of an adhesive mesh layer. The adhesive mesh layer is positioned between the fibrous layer and the shielding layer, and heat and/or pressure applied to cause the adhesive to create a durable and even bond between the fibrous and shielding layers. It has been found that this method provides a better adhesion between the layers, with minimum weight penalty, than other methods such as those using adhesive powders or spray adhesives.