GB2563910A

GB2563910A - Device

Info

Publication number: GB2563910A
Application number: GB1710450.6A
Authority: GB
Inventors: Richardson Samuel; Pillow Jon
Original assignee: Sumitomo Chemical Co Ltd
Current assignee: Sumitomo Chemical Co Ltd
Priority date: 2017-06-29
Filing date: 2017-06-29
Publication date: 2019-01-02
Also published as: GB201710450D0

Abstract

A device comprising a heater 101 and a patterned release layer 103 comprising a polymer matrix and at least one volatile compound, the layer comprises a first surface 103A facing a heating surface 101S and a second surface 103B that releases the volatile. The layer may be continuous, comprise a series of voids, or be formed of discrete regions. A coating that may be a metal layer may partially cover the second surface, it may be positioned on surfaces 103B1 parallel to the heater. The polymer may be a polyolefin, polyketone or mixture thereof. The volatile may be an organic compound that is an insecticide, fragrance, air treatment or mixture thereof. The insecticide may be a pyrethroid that may be metofluthrin. The layer may be partially formed around the heater, preformed and applied over the heater, formed unpatterned on the heater and then patterned, or deposited on the heater.

Description

Device

Field of the Invention

The present invention relates to devices for releasing volatile compounds and methods for forming the same.

Background of the Invention

Devices for releasing volatile compounds by heating are known. US7910151B2 describes devices and methods for the controlled release or exposure of reservoir contents, and methods of manufacture thereof. US20150181859A1 describes mats of different sizes formed of single mats having different sizes or a multilayer mat which are provided for area insect repellent devices which contain a heat plate to heat the mat structures carried there above, thereby providing different operating characteristics of the repellent device. US20020131888A1 describes a device for diffusing solutions having a porous element impregnated with a solution having active agents, and a heating element to heat the porous element promoting the evaporation of the active agents contained in the solution absorbed by the porous element. US8897629B1 describes that a filament maybe provided having enhanced solderability and/or heating characteristics configured for heating a substance to release an airborne scent. CA2688238C describes a fragrance distribution device comprising an electrical resistor, a plug or other power source, and a fragrance in a polymer or thermoplastic carrier. IN200101156P2 describes mats for dispensing volatile vapors such as insecticides. EP636314B1 describes a tape including a base layer containing substantially no active agent and a coating film layer containing a heat-vaporizable active agent and being formed on one side of the base layer by application of a coating containing the active agent.

An object of the invention is to provide an energy efficient volatile compound releasing device.

Summary of the Invention

The present inventors have found that efficiency of a volatile compound releasing device may be increased by use of a patterned release layer.

In a first aspect, the invention provides a volatile compound releasing device comprising a heater and a patterned release layer comprising a polymer matrix and at least one volatile compound, wherein the patterned release layer comprises a first surface facing a heating surface of the heater and a patterned second surface for release of the volatile compound.

In a second aspect the invention provides a patterned release layer according to the first aspect.

In a third aspect the invention provides a method of forming the compound releasing device according to the first aspect, the method comprising application of a preformed patterned release layer over the heater surface.

In a fourth aspect the invention provides a method of forming the compound releasing device according to the first aspect, the method comprising forming an unpatterned release layer over the heater and patterning the second surface of the release layer.

In a fifth aspect the invention provides a method of forming the compound releasing device according to the first aspect, the method comprising depositing the polymer over the heater surface and causing the polymer to self-assemble to form the patterned layer.

By a layer “on” a surface as used herein is meant that the layer is in direct contact with the surface.

By a layer “over” a surface as used herein is meant that the layer is in direct contact with the surface or spaced apart therefrom by one or more intervening layers.

The invention is described herein with reference to a device illustrated as having a heating surface below a patterned release layer, however it will be appreciated that the device in use maybe used in any orientation, and the terms “on” and “over” as used herein do not limit said orientation of the device.

Description of the Drawings

Figure lA illustrates a cross section of a compound releasing device according to an embodiment of the invention in which voids are formed in a surface of a layer containing a volatile compound;

Figure lB is an isometric view of the device of Figure lA;

Figure 2 illustrates a compound releasing device according to an embodiment of the invention as illustrated in Figure lA and further having a low emissivity coating;

Figure 3 illustrates a compound releasing device according to an embodiment of the invention in which a layer containing the volatile compound is formed on and around a heating surface;

Figure 4 illustrates a compound releasing device according to an embodiment of the invention in which the patterned release layer is a discontinuous layer comprising stripes;

Figure 5 illustrates a compound releasing device according to an embodiment of the invention in which the patterned release layer is a discontinuous layer comprising pillars; and

Figure 6 is a graph of power per unit area vs equilibrium temperature for a device according to an embodiment of the invention and a comparative device.

Detailed Description of the Invention

Figure lA illustrates a compound releasing device comprising a heater 101 and a patterned release layer 103 over a heating surface 101S of the heater 101.

The heater 101 comprises a heating element for heating the heating surface 101S. The heating element may convert electrical energy into heat energy when activated. The heating element maybe a thin film resistor. For example, the thin film resistor maybe carbon on Kapton with highly conducting electrodes. Alternatively, the thin film resistor may be a wire wound or etched film element on Kapton or polyethylene. The thin film resistor may be activated by a voltage and/or current. The voltage and/or current may be provided by a battery or any other power supply.

The heating surface 101S transfers the heat energy generated by the heating element to the patterned release layer 103. The heating surface 101S may be substantially flat. The heating surface 101S may have a patterned surface.

The patterned release layer has a first surface 103A facing the heating surface 103S and a second surface 103B. The first surface 103A is closer to the heating surface. The second surface 103B is for release of a volatile compound.

First surface 103A may be in direct contact with the heating surface 101S, as illustrated in Figure lA. In other embodiments, there may be one or more intervening layers between the first surface 103A of the patterned release layer 103 and the heating surface 101S, for example one or more adhesive layers. The intervening layer(s) transfer heat energy from the heating surface 101S to either other intervening layer(s) or the patterned release layer 103. The distance between the first surface 103A of the patterned release layer 103 and the heating surface 101S maybe any distance provided that the heating surface 101S can directly or indirectly transfer heat to the patterned release layer 103. A cross-section through a plane perpendicular to the patterned release layer 103, as illustrated in Figure lA, has a varying thickness. The pattern maybe a regular pattern giving a regular repeating variation in thickness of the patterned release layer 103, as illustrated in Figure lA. In other embodiments, the pattern may be irregular. The second surface comprises second surface regions. The second surface 103B may comprise second surface regions 103B1 that are substantially parallel to a plane extending laterally through the patterned release layer 103 (and substantially perpendicular to the heating surface 103S, if the heating surface 103S is a flat surface) and second surface regions 103B2 that are substantially perpendicular thereto, as illustrated in Figure lA. It will be appreciated that any angle other than 1800 may be formed between different surface regions.

Preferably, the second surface comprises second surface regions facing other second surface regions. Preferably, the second surface regions and facing one another are substantially parallel. Preferably, a surface substantially parallel or perpendicular to another surface or a plane as described herein is preferably with io° or within 50 degrees of the other surface or plane.

The pattern may define voids V in the patterned release layer 103, the voids extending through at least part of the thickness of the patterned release layer 103. Optionally, the voids have an average aspect ratio (depth / width) of between 1 and 10, optionally 1.5 - 4. Each void may have the same aspect ratio, in which case each individiual void has the same aspect ratio as the average aspect ratio, or the aspect ratio of individual voids may vary according to a regular pattern or irregularly.

The patterned release layer 103 may be a continuous layer, for example as illustrated in Figures lA and lB. By “continuous layer” as used herein is meant a layer in which there is an unbroken path through the patterned release layer between any two points of the layer. The second surface regions 103B1 of the continuous layer may form a grid structure as shown in Figure lB.

The thickness of the patterned release layer 103 maybe between 0.1 mm and 10 mm. Preferably, the thickness of the patterned release layer 103 is between 0.5 mm and 2 mm.

Optionally, the void depth is between 0.1 pm and 1 cm, optionally 0.1 pm and 0.5 cm. Optionally, the void depth is at least 10 pm or at least 100 pm.

In the embodiment of Figure lA, voids V in the patterned layer have a depth that is less than 100 % of the thickness of the patterned release layer, and is optionally between 25-95 %, or 25-75 % of the thickness of the patterned release layer.

Optionally, the distance between two opposing second surface regions 103B2 is less than the depth of any void.

Optionally, the distance between two opposing second surface regions 103B2 is 0.1 mm -10 mm.

The continuous patterned release layer 103 may cover all of the heating surface area defined by the perimeter of the patterned release layer 103, as illustrated in Figure lA.

In other embodiments, the continuous patterned release layer may comprise voids which extend through the whole thickness of the patterned layer.

The patterned release layer 103 comprises a polymer matrix and at least one volatile compound.

The polymer matrix comprises at least one matrix polymer. The polymer matrix may be a solid. The polymer matrix maybe a resin or a gel. The at least one matrix polymer may be an organic polymer. The organic polymer may be selected from the group consisting of polyolefins, polyacrylates, polycarbonates, polyketones, or mixtures thereof, for example a polyethylene or polypropylene. The at least one matrix polymer maybe a homopolymer or a copolymer. By “copolymer” as used herein is meant a polymer comprising two or more different repeat units including, without limitation, regioregular, random and block copolymers. A block copolymer may undergo self-assemby to form the patterned release layer, for example as described in Eisenberg and Mai, “Self-assembly of block copolymers”,

Chem. Soc. Rev., Issue 18, 2012, the contents of which are incorporated herein by reference.

The one or more volatile compounds may make up 0.1-40 % w/w of the patterned release layer, optionally 5-30 % w/w.

The at least one volatile compound may be homogenously dispersed within the polymer matrix.

The patterned release layer 103 may consist of the at least one matrix polymer and the one or more volatile compounds or it may comprise one or more further materials.

The at least one volatile compound is not limited to any type or class of volatile compound. The at least one volatile compound may have a vapour pressure of at least of between 1 x io-6 and 100 Pa atmospheres at 25 °C. An insecticide optionally has a vapour pressure in the range of about 1 x io-6 to 1 x io_2Pa at 25 °C. A fragrance optionally has a vapour pressure in the range of about 1-50 Pa at 25 °C.

The at least one volatile compound may be a mixture of two or more volatile compounds. The at least one volatile compound may be selected from the group consisting of insecticides, fragrances and air treatment compounds. The at least one volatile compound may be a pyrethroid insecticide. For example the volatile compound may be metofluthrin.

In use, the patterned release layer 103 is heated by the heater 101 causing release, or an increase in rate of release, of the volatile compound from the patterned release layer 103 through the second surface 103B. It will be appreciated that the patterned second surface 103B of the release layer has a larger surface area than a corresponding unpatterned layer, thus providing the volatile compounds with a larger area for release from the patterned layer compared to an unpatterned layer. Accordingly, the device may allow a higher rate of release of the volatile material at a given temperature or a target release rate may be achieved at a lower temperature than a device having an unpatterned release layer.

The temperature that the patterned release layer is heated to by the heater may be selected according to the volatility of the volatile compound and / or the properties of the polymer matrix. The temperature is optionally in the range of 20-i00°C.

The whole of the second surface 103B may be exposed to the atmosphere, for example as illustrated in Figure lA. In other embodiments, the second surface 103B may be partially covered by one or more coating layers.

In some embodiments the patterned release layer 103 may be coated by one or more coating layers having a lower emissivity than the polymer matrix. Emissivity as used herein is a ratio between the radiative flux from a material and a perfect emitter at a given temperature.

Figure 2 illustrates a device as described with reference to Figure lA except that a low emissivity coating 105 is provided over the second surface of the patterned release layer 103 on regions of the patterned layer that are substantially parallel to the heating surface.

Energy loss by way of thermal radiation through the patterned release layer 103 when the device is in use may be reduced as compared to energy loss through a release layer without a low emissivity coating.

The coating 105 may be impermeable to the volatile compound at an operating temperature of the device, optionally between 2O-ioo°C, in which case the volatile compound may escape from regions of the second surface 103B which are not covered by the coating 105.

Preferably, the coating 105 has an emissivity of below 0.1. Preferably, the coating 105 comprises or consists of a metal. The metal may be selected from the group consisting of aluminium, copper, silver, gold, or alloys thereof. Optionally, the thickness of the coating 105 is at least 0.01 pm thick. Optionally, the coating 105 is up to 100 pm thick, optionally up to 10 pm thick.

Figure 3 illustrates a volatile compound release device according to a further embodiment. The device of Figure 3 is as described with reference to Figure lA except that the patterned release layer is formed over and around the heating surface 103A.

The patterned release layer may be a discontinuous layer comprising a plurality of discrete regions, i.e. regions comprising the polymer matrix and volatile compound which are not connected. Figures 4 and 5 illustrate devices with a plurality of discrete regions.

In Figure 4, each discrete region comprises a strip extending across a width or length of the heating surface, the patterned layer being formed by a plurality of the stripes over the heating surface.

In Figure 5, each discrete region comprises a pillar, the patterned layer being formed by a plurality of pillars over the heating surface.

It will be appreciated that each discrete region of a discontinuous layer may have any shape and / or thickness, and the patterned release layer may comprise discrete regions having only one shape and / or thickness, or the patterned layer may comprise discrete regions differing in shape and / or differing in thickness.

Optionally, the shortest distance between each one of the plurality of discrete regions is between 0.1-10 mm. Preferably, a void area between discrete regions has an aspect ratio as described hereinbefore.

Alternatively, the pattern of the patterned release layer may be a three dimensional structure such as a cubic gyroid or primitive structure, for example as formed by self-assembly of a block copolymer.

The pattern of the patterned release layer may reduce the overall energy loss of the compound releasing device due to heat loss through thermal radiation, conduction and convection losses. A reduction in any one of these components of heat loss therefore leads to an increase in device efficiency.

The convective component of heat loss may be affected by increasing or decreasing the surface area of the compound releasing device.

The radiative component (thermal radiation) of the heat loss of the compound releasing device is related to the total surface area of the patterned release layer and the pattern of the patterned release layer. Thermal radiation that is emitted from one surface region of the release layer may be absorbed by another, facing region of the release layer which may reduce heat loss through thermal radiation as compared to a flat film.

The patterned release layer maybe preformed and applied to the heater. For example, the pattern maybe formed by embossing, etching and / or photolithography. Suitable embossing processes are disclosed in Peng et al, “Micro hot embossing of thermoplastic polymers: A review”,Journal of Micromechanics and

Microengineering 24(1):013001 · January 2014, the contents of which are incorporated herein by reference. An unpatterned film of the polymer matrix may be patterned in a roll-to-roll process.

The release layer maybe adhered to the heating surface before or after patterning either by self-adhesion between the release layer and the heating surface or by an adhesive layer.

The heater may be embedded within the release layer in which case there may or may not be adhesion between the release layer and the heating surface.

An unpatterned release layer maybe formed over and / or around the heating surface followed by patterning by any method know to the skilled person, for example by embossing as described hereinbefore.

The patterned release layer may be formed on the heater by deposition of a composition comprising the at least one matrix polymer and the at least one volatile compound onto and / or around the heating surface. The composition may be deposited by a printing process suitable for forming the patterned release layer, for example 3D printing, or the composition may be deposited to form an unpatterned layer followed by treatment to form the pattern.

Patterns such as cubic gyroid and primitive 3D structures may be formed by block copolymer self-assembly and etching methods.

If a coating is present over the second surface of the patterned release layer then it may be formed by any method known by the skilled person, for example by vapour deposition, optionally vapour deposition through a shadow mask.

Embodiments of the present invention will be further exemplified in the following examples.

Examples

Power requirements and device lifetimes for devices with a 3.7 V 4000 mAh lithium ion battery were modelled for device operation at 6o°C in still air at 20°C as described in http://thermopedia.com/ content/660/.

Device Example l A first patterned release layer as illustrated in Figure 4 and with no coating over the patterned release layer was modelled in which each discrete strip of the patterned release layer had a length of 4cm, a height of 0.5 cm and a width of 0.1 cm. Each strip was spaced apart from each adjacent strip by 0.2 cm, giving an aspect ratio of 0.5 / 0.2 = 2.5.

Device Example 2 A patterned release layer as described for Device Example 1 and with a low emissivity coating was modelled.

Comparative Device 1 A comparative release layer of a flat (unpatterned) film was modelled.

Comparative Device 1, having an unpatterned release film and no coating layer, requires a higher power consumption to maintain a temperature of 6o°C than Device Example 1 or 2, resulting in shorter battery life.

With reference to Figure 6, the power required to achieve any given equilibrium temperature above 20°C is higher for Comparative Device 1 than for Device Example 1 or 2.

Although the present invention has been described in terms of specific exemplary embodiments, it will be appreciated that various modifications, alterations and/or combinations of features disclosed herein will be apparent to those skilled in the art without departing from the scope of the invention as set forth in the following claims.

Claims

1. A volatile compound releasing device comprising a heater and a patterned release layer comprising a polymer matrix and at least one volatile compound, wherein the patterned release layer comprises a first surface facing a heating surface of the heater and a patterned second surface for release of the volatile compound.

2. The compound releasing device of claim 1, wherein the patterned release layer is a continuous layer.

3. The compound releasing device of claim 2, wherein the patterned release layer comprises voids in the second surface extending through the whole thickness of the patterned release layer.

4. The compound releasing device of claim 2, wherein the patterned release layer comprises voids in the second surface extending through part of the thickness of the patterned release layer.

5. The compound releasing device of claim 4, wherein the void depth is greater than 5% of the thickness of the patterned release layer.

6. The compound releasing device of claim 4, wherein the void depth is greater than 10% of the thickness of the patterned release layer.

7. The compound releasing device of claim 4, wherein the void depth is greater than 50% of the thickness of the patterned release layer.

8. The compound releasing device of any one of the preceding claims, wherein the patterned release layer has a thickness of between 0.1 mm and 1 cm.

9. The compound releasing device of claim 1, wherein the patterned release layer is a discontinuous layer comprising a plurality of discrete regions spaced apart from one another by void regions.

10. The compound releasing device of any one of the preceding claims, wherein an average aspect ratio of void depth / void width is at least 1.5.

11. The compound releasing device of any one of the preceding claims, wherein an average aspect ratio of void depth / void width is at least 4.0.

12. The compound releasing device of any one of the preceding claims, wherein a coating partially covers the second surface.

13. The compound releasing device of claim 12, wherein the coating is selectively positioned on regions of the second surface parallel to the heater surface.

14. The compound releasing device of claim 12 or 13, wherein the coating comprises a metal layer.

15. The compound releasing device of any one of claims 12-14, wherein the coating has a thickness of between 0.01 pm and 10 pm.

16. The compound releasing device according to any one of the preceding claims, wherein the at least one polymer is selected from the group consisting of polyolefins and polyketones, or mixtures thereof.

17. The compound releasing device of any one of the preceding claims, wherein the at least one volatile compound is selected from the group consisting of volatile organic compounds.

18. The compound releasing device of claim 17, wherein the volatile organic compound is selected from the group consisting of insecticides, fragrances , air treatment compounds, and mixtures thereof.

19. The compound releasing device of claim 18, wherein the insecticide is a pyrethroid insecticide.

20. The compound releasing device of claim 19, wherein the pyrethroid insecticide is a metofluthrin.

21. The compound releasing device of any one of the preceding claims, wherein the patterned release layer is formed at least partially around the heating surface.

22. A patterned release layer as defined in any one of the preceding claims.

23. A method of forming the compound releasing device of any one of claims 1-21, comprising application of a preformed patterned release layer over the heater surface.

24. A method of forming the compound releasing device of any one of claims 1-21, the method comprising forming an unpatterned release layer over the heater and patterning the second surface of the release layer.

25. A method of forming the compound releasing device of any one of claims 1-21, the method comprising depositing the polymer over the heater surface and causing the polymer to self-assemble to form the patterned layer.