A method of forming a low emissivity, vapour permeable laminate

Abstract

A method of forming a low emissivity, vapour permeable laminate the method comprising: laminating a low emissivity film to a fibrous support to form a laminate having a film side and a support side; and micro-perforating the film laminated to the support.

Description

[0001] A METHOD OF FORMING A LOW EMISSIVITY, VAPOUR PERMEABLE LAMINATE

[0002] TECHNICAL FIELD

[0003] This invention relates to low emissivity laminates. In particular, though not exclusively, this invention relates to a method of forming a low emissivity, vapour permeable laminate, and to laminates obtainable thereby.

[0004] BACKGROUND

[0005] Low emissivity layers are used in various applications, for example in insulation. In many applications, for example insulation of buildings, such layers are required be vapour permeable and water resistant, as well as offering low emissivity.

[0006] One approach to providing low emissivity materials is described in US7660040 and involves the plasma coating of microfibres. This material is vapour permeable and water resistant and can typically achieve an emissivity of about 0.1.

[0007] Another approach to providing such low emissivity materials is described in GB2466729. This involves applying to a substrate layer an organic coating, suitably a polyurethane, containing infrared reflective matter, such as aluminium platelets. This material is vapour permeable and water resistant and can typically achieve an emissivity of about 0.16.

[0008] However, these approaches are technologically complex and, for some applications, can be uneconomic.

[0009] A technologically simpler solution where vapour permeability is not required, is the use of polymeric films plasma-coated with aluminium or 100% aluminium films. Water resistance and an emissivity of <0.05 can be achieved.

[0010] However, many applications require vapour permeability. For example, UK Building Regulations require that vapour resistance of breathable wall membranes should less than 0.6MNs / g (0.12 Sd) when tested in accordance with BS EN ISO 12572 using the conditions described in set C, 40 to 60 and five test specimens.

[0011] Simple low emissivity microperforated aluminised or aluminium films can be adapted for applications requiring vapour permeability. Micro-perforation can achieve vapour permeability, for example at the level required by UK Building Regulations, whilst maintaining an emissivity of about 0.1.

[0012] However, the process of micro-perforation, whilst making the films breathable, negatively impacts water resistance. This can be problematic since, in many applications, water resistance is required alongside vapour permeability. For example, UK Building Regulations require that breathable wall membranes should be at least Class W2 to BS EN 13859-2 with no water leakage during testing. Water resistance can be tested using BS EN 13111:2010. This method measures whether water penetration is greater than or equal to 100ml and Class W2 to BS EN 13859-2 requires <100ml. However, micro-perforation causes microperforated aluminised or aluminium films to fail this threshold.

[0013] To improve water resistance, it is known to laminate a perforated low emissivity film to a water-resistant breathable film. This film / film laminate may then be further laminated to a support, such as a nonwoven, so as to provide mechanical strength to the whole structure. However, this multi-step process increases complexity and cost.

[0014] There remains a need in the art for methods of making low emissivity materials able to offer a degree of vapour permeability and water resistance.

[0015] SUMMARY OF THE INVENTION

[0016] From a first aspect, the invention provides a method of forming a low emissivity, vapour permeable laminate the method comprising: laminating a low emissivity film to a fibrous support to form a laminate having a film side and a support side; and micro-perforating the film laminated to the support.

[0017] It has been found that micro-perforating low emissivity film that is laminated to a support can achieve both vapour permeability and water resistance. Micro-perforation of the film comprises forming a plurality of holes in the low emissivity film that have a diameter of less than 1 mm. The holes may also extend into the support. Suitably, the plurality of holes may have a diameter in the range of from 5 to 500 microns, optionally in the range of from 10 to 300 microns, such as in the range of from 50 to 200 microns.

[0018] Conveniently, the micro-perforation of the film may extend into or through the fibrous support. Suitably, micro-perforation of the film may comprise micro-perforating the laminate as a whole.

[0019] Advantageously, the film may be micro-perforated by perforating it from the film side of the laminate. It has surprisingly been found that this can greatly enhance water resistance, even when the micro-perforation extends into or even through the fibrous support.

[0020] In some embodiments, the film may be micro-perforated by a perforator comprising a plurality of pins. For example, the perforator may comprise a roller bearing the pins.

[0021] Advantageously, the perforator may be heated, optionally to a temperature in the range of from 100 to 400 °C, for example in the range of from 200 to 400 °C. The temperature of the perforator may be measured, for example, at a core of the perforator bearing the pins, or at the pins themselves.

[0022] Suitably, the perforator may act against a structure. The structure may optionally comprise a roller. The pins of the perforator may extend up to or into the structure. In some embodiments, the structure comprises a brush roller. Suitably, the structure may lift the laminate to present the laminate to the perforator.

[0023] The pins may optionally have a length in the range of from 1 to 100 mm, suitably in the range of from 5 to 50 mm. Advantageously, the pins of the perforator may be profiled with a wider base and narrower tip. The pins may be tapered.

[0024] A maximum diameter of the pins, e.g. at their base, may suitably be in the range of from 0.1 to 1 mm, optionally in the range of from 0.2 to 0.7 mm.

[0025] Suitably, the pins may have a tip diameter in the range of from 0.05 mm to 0.4 mm, such as in the range of from 0.1 to 0.3 mm.

[0026] In some embodiments, the perforator may comprise 50 to 500 pins per square inch, optionally 100 to 250 pins per square inch, or 120 to 200 pins per square inch.

[0027] The pins may conveniently be arranged in a regular array.

[0028] Optionally, micro-perforation may be performed at a speed in the range of 5 to 40 metres per minute, for example in the range of from 10 to 30 metres per minute.

[0029] The low emissivity film may advantageously constitute an outermost layer of the laminate so that the film side of the laminate is exposed.

[0030] The low emissivity film to be micro-perforated may suitably comprise a monolithic, pinhole- free layer having an emissivity consistent with a desired emissivity on the film side of the laminate.

[0031] "Low emissivity" is understood in the art. "Emissivity" is a known expression of the amount of energy radiated by a material, matter or surface. An ideal material or surface emitting the highest theoretical level of radiant energy would have an emissivity, e, of 1 and an ideal material or surface emitting no radiant energy would have an emissivity of 0. In practice all objects have an emissivity between 0 and 1. All emissivity values (e) herein are given at a temperature of 25 C.

[0032] Optionally, the low emissivity film to be micro-perforated may have an emissivity, e, of less than 0.2, optionally less than 0.1, or even less than 0.05. Advantageously, the micro-perforated low emissivity film may have an emissivity, e, of less than 0.3, optionally less than 0.2, or even less than 0.1 on the film side of the laminate.

[0033] The laminate is "vapour permeable", (i.e. breathable) in the sense that it permits the passage of water vapour to an extent consistent with a desired moisture vapour transmission rate in the insulation material.

[0034] Suitably, the micro-perforated low emissivity film or laminate as a whole may have a vapour resistance of less than 0.6MNs / g (0.12 Sd) when tested in accordance with BS EN ISO 12572 using the set of conditions C and using five test specimens.

[0035] The micro-perforated low emissivity film or laminate as a whole may suitably have a moisture vapour transmission rate (MVTR) of at least 360 g / m2 / day, advantageously at least 820 g / m2 / day, or even least 1000 g / m2 / day. The moisture vapour transmission rate (MVTR) may be tested with a Lyssy Model L80-5000 Water Vapor Permeability Tester at 100% / 15% RH, i.e. 85% RH difference and 23 C.

[0036] Advantageously, the laminate may be water resistant in the sense of Class W2 to BS EN 13859-2, measured using BS EN 13111 :2010, with water penetration <100ml.

[0037] Suitably, the low emissivity film may comprise a polymeric film that is metallised. Optionally, the polymeric film may be aluminised by plasma deposition. Metallisation and aluminisation processes for forming low emissivity films are known in the art.

[0038] Optionally, the low emissivity film may comprise a polyolefin. Suitably, the low emissivity film may comprise polypropylene, optionally bi-axially oriented polypropylene or cast polypropylene.

[0039] Advantageously, the film may be coated with an anti-oxidation layer, for example comprising nitro-cellulose, acylic, PVDC, or another suitable layer.

[0040] Biaxially oriented polypropylene film is film stretched in longitudinal (machine) and transverse directions, producing molecular chain orientation in two directions. Bi-axially oriented polypropylene film can suitably be produced, as is known in the art, by a tubular process, in which a tubular bubble is inflated, or a tenter frame process, in which a thick extruded sheet is heated to its softening point (not to the melting point) and is mechanically stretched by 300-400%.

[0041] Cast polymeric films can be produced by casting through a die, as is known in the art.

[0042] An alternative film structure is a metal foil, for example aluminium foil. In some embodiments, the low emissivity film may have a thickness in the range of from 10 to 100 microns, optionally in the range of from 20 to 70 microns, or even 30 to 50 microns.

[0043] The fibrous support may in principle be any layer that provides structural support. Suitably, the fibrous support may comprise fibres with an average diameter in the range of from 1 to 20 microns, optionally in the range of from 2 to 10 microns.

[0044] Suitably, the fibrous support may comprise polymeric fibres. Optionally, the fibrous support may comprise a polyolefin. Suitably, the fibrous support may comprise polypropylene fibres.

[0045] Advantageously, the fibrous support may comprise a nonwoven material. Suitably the fibrous support may comprise a spunbond.

[0046] Conveniently, the fibrous support may have a basis weight greater than or equal to 10 g / m2, optionally greater than or equal to 25 g / m2. Suitably, the fibrous support may have a basis weight of less than or equal to 100 g / m2, for example less than or equal to 75 g / m2. In some embodiments, the fibrous support may have a basis weight in the range of from 10 g / m2to 100 g / m2, optionally in the range of from 25 g / m2to 75 g / m2.

[0047] The low emissivity film, the fibrous support, or both may optionally comprise a flame retardant (FR) material. Suitable flame retardants include phosphorus-based, nitrogenbased, mineral, carbon-based, bio-based, and hybrid flame retardants.

[0048] Flame retardant materials are known in the art. For example, suitable flame retardants for polypropylene materials are discussed in Seidi, F.; Movahedifar, E.; Naderi, G.; Akbari, V.; Ducos, F.; Shamsi, R.; Vahabi, H.; Saeb, M.R. Flame Retardant Polypropylenes: A Review. Polymers 2020, 12, 1701. https: / / doi.org / 10.3390 / polyml2081701.

[0049] Laminating the low emissivity film to the fibrous support may suitably comprise adhesive lamination. For example a layer of adhesive, which may be continuous or intermittent, may be applied between the film and support. Suitably, lamination may comprise pressing the low emissivity film and the fibrous support together.

[0050] The method may comprise laminating or otherwise affixing one or more further layers to the laminate on the support side. Conveniently, this may also be achieved by adhesive lamination. Examples of further layers include further insulation layers, such as wadding layers or phase change material layers, or additional support layers or low emissivity layers.

[0051] The invention also provides, from a second aspect, a low emissivity, vapour permeable laminate obtainable by a method according to the first aspect of the invention. From a third aspect, the invention provides a low emissivity, vapour permeable laminate comprising: a micro perforated low emissivity film laminated to a fibrous support, wherein the low emissivity film is optionally micro perforated from the film side.

[0052] A fourth aspect of the invention provides the use of a laminate according to the second or third aspect of the invention as insulation. Optionally, the use may be building insulation or cargo insulation.

[0053] Optional features described in respect of the first aspect of the invention are also applicable to the second, third and fourth aspect of the invention.

[0054] 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.

[0055] 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.

[0056] BRIEF DESCRIPTION OF THE DRAWINGS

[0057] One or more embodiments of the invention will now be described, by way of example only, with reference to the accompanying drawings, in which:

[0058] Figure 1 is a schematic sectional view of showing a low emissivity laminate;

[0059] Figure 2 is a schematic sectional view of showing micro-perforation of the laminate of Figure 1 in accordance with a first embodiment of the invention;

[0060] Figure 3 is a schematic sectional view of showing micro-perforation of the laminate of Figure 1 in accordance with a second embodiment of the invention;

[0061] Figure 4 is a film-side scanning electron microscope (SEM) image showing a hole formed by microperforation in accordance with Figure 2; and

[0062] Figure 5 is a film-side scanning electron microscope (SEM) image showing a hole formed by microperforation in accordance with Figure 3. DETAILED DESCRIPTION

[0063] With reference to Figure 1 a low emissivity laminate 2 was formed by laminating a low emissivity film 4 taking the form of an aluminised bi-axia I ly oriented polypropylene film with an emissivity of 0.09 to a fibrous support 6 in the form of a spunbond with a basis weight of 50 g / m2and fibres with an average diameter of about seven microns.

[0064] Lamination was performed adhesively using a solvent-based PU adhesive, following which the emissivity rose to 0.10.

[0065] Micro-perforation of the film 4 laminated to the support 6 was then performed to provide vapour permeability.

[0066] In a first embodiment, shown in Figure 2, micro-perforation was performed with a perforator 8 pushed into the laminate from the film side 10 of the laminate 2. In a second embodiment, shown in Figure 3, micro-perforation was performed with the same perforator 8 pushed into the laminate from the support side 12 of the laminate 2.

[0067] In each of the embodiments of Figures 2 and 3, the perforator 8 was a rotating roller comprising an array of tapered pins 14. The pins 14, shown only schematically in the drawings, had a length of 5 mm, and a base diameter of 0.6 mm tapering to a tip diameter of 0.2 mm. The pins 14 were arranged in a regular array of 160 pins per square inch and the perforator 8 was heated to 340 °C core temperature. The perforator 8 was positioned to act against a brush roller 16, with the pins 14 extending a small distance into the brush roller 16. Thus, in both embodiments, the perforator went all the way through the laminate, i.e. through both film, and support. The laminates 2 were perforated at a speed of twenty metres per minute.

[0068] The resulting micro-perforated laminates 18 were each found to have an emissivity of 0.11, as well as a good degree of vapour permeability and water penetration resistance.

[0069] Surprisingly and contrary to expectations, it was found that micro-perforation from the film side 10 consistently led to better water penetration resistance.

[0070] Water resistance measured using BS EN 13111:2010 established that micro-perforation from the film side (Figure 2) led to Class W2 water resistance under BS EN 13859-2, whereas micro-perforation from the spunbond side (Figure 3) led to Class W3 water resistance under BS EN 13859-2. In more detail, the average volume of water penetration (ml) based on three samples was 65 ml for the micro-perforation from the film side (Figure 2) and 302 ml micro-perforation from the spunbond side (Figure 3).

[0071] To further understand this effect, electron microscope images were obtained of the microperforations of each sample. Hole sizes in the film were roughly the same with each approach. However, it was noticeable that micro-perforations from the film side in the first embodiment (Figure 5) appeared to lead to holes that were more hindered by fibres of the supporting spunbond compared to micro-perforations in the second embodiment (Figure 6). Without wishing to be bound by theory, this may have been facilitated by the perforator being withdrawn from the holes from the film side, drawing fibres of the support towards the holes.

[0072] The laminates of Figure 2 and Figure 3 were found to offer a vapour resistance of less than 0.6MNs / g (0.12 Sd) when tested in accordance with BS EN ISO 12572 using the set of conditions C and using five test specimens. Vapour resistance did not appear to be materially affected by the direction of perforation.

[0073] It was also noted that emissivity of the film side of the laminate did not differ between the embodiments of Figure 2 and Figure 3, presumably because the hole sizes on the film side were substantially the same (in the region of 200 microns).

Claims

CLAIMS1. A method of forming a low emissivity, vapour permeable laminate the method comprising: laminating a low emissivity film to a fibrous support to form a laminate having a film side and a support side; and micro-perforating the film laminated to the support.

2. The method of claim 1, wherein the film is micro-perforated by perforating it from the film side of the laminate.

3. The method of any preceding claim, wherein the film is micro-perforated by a perforator comprising a plurality of pins.

4. The method of claim 3, wherein the perforator comprises a roller bearing the pins.

5. The method of claim 4, wherein the perforator is heated, optionally to a temperature in the range of from 100 to 400 °C.

6. The method of any one of claims 3 to 5, wherein the perforator acts against a structure, optionally comprising a roller.

7. The method of claim 6, wherein the pins of the perforator extend up to or into the structure.

8. The method of claim 6 or claim 7, wherein the structure comprises a brush roller.

9. The method of any one of claims 3 to 8, wherein the pins are profiled with a wider base and narrower tip.

10. The method of any one of claims 3 to 9, wherein the pins have a length in the range of from 1 to 100 mm and / or a diameter in the range of from 0.1 to 1 mm, optionally in the range of from 0.2 to 0.7 mm.

11. The method of any one of claims 3 to 10, wherein the perforator comprises 50 to 500 pins per square inch, optionally 100 to 250 pins per square inch, or 120 to 200 pins per square inch.

12. The method of any preceding claim, wherein the micro-perforated low emissivity film has an emissivity of less than 0.2 on the film side of the laminate.

13. The method of any preceding claim, wherein the laminate has a vapour resistance of less than 0.6MNs / g (0.12 Sd) when tested in accordance with BS EN ISO 12572 using the set of conditions C and five test specimens and / or is water resistant in the sense of Class W2 to BS EN 13859-2, measured using BS EN 13111 :2010, with water penetration clOOml.

14. The method of any preceding claim, wherein the low emissivity film comprises a polymeric film that is metallised, optionally aluminised by plasma deposition.

15. The method of claim 14, wherein the low emissivity film comprises a polyolefin.

16. The method of claim 15, wherein the low emissivity film comprises polypropylene, optionally bi-axially oriented or cast polypropylene.

17. The method of any preceding claim, wherein the film has a thickness in the range of from 10 to 50 microns.

18. The method of any preceding claim, wherein the fibrous support comprises fibres with an average diameter in the range of from 1 to 20 microns.

19. The method of any preceding claim, wherein the fibrous support is polymeric and optionally comprises a non-woven material, optionally a spunbond.

20. The method of any preceding claim, wherein the fibrous support has a basis weight greater than 20 g / m2, optionally greater than 30 g / m2.

21. The method of any preceding claim, comprising laminating or otherwise affixing one or more further layers to the laminate on the support side.

22. The method of any preceding claim, wherein micro-perforation of the film comprises forming a plurality of holes having a diameter in the range of from 5 to 500 microns.

23. A low emissivity, vapour permeable laminate, optionally a laminate obtainable by the method of any preceding claim, comprising: a micro perforated low emissivity film laminated to a fibrous support.

24. Use of a laminate according to claims 23 as insulation.

25. Use according to claim 24, wherein the use is building insulation, optionally wall insulation, or cargo insulation.

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