Claims:
1. A biodegradable, heat stable wick having porosity in range of 45 – 65% for insecticide and perfume absorption and vaporisation applications, wherein the wick comprises a plant-based fibre backbone bound together with a plant-based heat resistant gum.
2. The biodegradable wick as claimed in Claim 1, wherein the plant-based fibre is selected from cotton, raw jute, processed jute, cellulose, lignin and flax based fibres.
3. The biodegradable wick as claimed in Claim 1, wherein the plant-based fibre is mixed with clay.
4. The biodegradable wick as claimed in Claim 1, wherein the plant-based heat resistant gum is selected from the group consisting gum arabica, gum ghatti, joss powder and guar gum.
5. The biodegradable wick as claimed in Claim 4, wherein the plant-based heat resistant gum further consists of 10 – 30% absorbent agent selected from the group consisting of diatomaceous earth, amorphous volcanic glass, kaolin and/or wood charcoal.
6. The biodegradable wick as claimed in Claim 4, wherein the composition of plant-based fibre is in range of 70 – 90% and the composition of the plant-base heat resistant gum is in range of 10 – 30%.
7. The biodegradable wick as claimed in Claim 5, wherein the composition of the wick comprises plant fibre in range of 15 – 20%, volcanic glass powder in range of 25-30%, kaolin clay in range of 8-12%, wood charcoal in range of 25- 30%, Plant gums in range of 8-12% and PVA gum in range of 1-5%
8. The biodegradable wick of Claim 1, wherein the wick can withstand a temperature range between – 10 to +200 degrees centigrade.
9. The biodegradable wick of Claim 1, wherein the wick has mechanical strength of more than 2.5kgs to 6.0kgs.

10. The biodegradable wick as claimed in Claim 1, wherein the biodegradable wick can be used for both heating and non-heating applications
11. A process for manufacturing the biodegradable wick as claimed in Claim 6, wherein the process comprises of:
a. pulverising the spun raw plant fibres to reduce the fibres size to less than 500 microns followed by sieving to obtain desired size fibres, preferably sieved through 20 – 100 mesh sieves;
b. mixing the sieved fibres of step (a) with a combination of one or more plant-based gums in a sigma dry mixture at 25 – 60 rpm for 5 – 10 minutes;
c. increasing the moisture level of the mixture of step (b) till 25-50% by slow addition of hot water having a temperature of 60-80°C and mixing for at least 30 min to form a granular mass;
d. loading the mixed granular dough of step (c) through a pressure screw extruder of desired shapes to obtain wicks of desired shapes;
e. drying the extruded wicks of Step (d) at room temperature for 4 – 6 hours;
f. air drying the wick of step (e) at 40 - 60°C under air blower until they reach moisture content of less than 10 % by weight;
g. heating the wicks of step (f) at 200°C, till the moisture content of wick is below 2%.
12. The process as claimed in Claim 11, wherein the extruded components of step (d) can be in the form of cylindrical rods, or punched sheets.
13. A process for manufacturing the biodegradable wick as claimed in Claim 7, wherein the process comprises:
a. pulverising the spun fibres of raw jute, whereby the fibres size was reduced to less than 500 microns by using hammer pulveriser;
b. mixing the sieved desired size fibres (15 – 20 % w/w) of step (1) with Amorphous volcanic glass material (perlite , Radiolite)(25 to 30%) as pore former and Absorbent materials kaolin clay(8 to 12%) & wood charcoal (25-30%)for uniform heat distribution along with (combination of plant-based gum guar gum (8 to 12%), biodegradable polyvinyl alcohol (1 to 5%),.
c. Dry mixing the mixture of step (2) using sigma mixer at 25 – 60 rpm for 5-10 minutes.
d. Increasing the moisture level of the mixture of step (3) by slow addition of (40 to 50%) hot demineralised water of maintained at 60–80°C, till the moisture content is in range of 25-50% of total concentration;
e. continuing mixing of the mixture of step (4) for at least 10 min in the double sigma blender or mixer;
f. loading the mixed granular dough of step (5) in a pressure screw extruder of desired shapes of extrusion, and
g. drying the extruded wicks of step (6) using combination of natural drying and low temperature oven drying up to 60°C until they reach moisture less than 2% of their weight.
14. The process as claimed in Claim 11, wherein the extruded components of step (d) can be in the form of cylindrical rods, or punched sheets.
15. A vapour dispensing device comprising the biodegradable wick as claimed in Claim 1.

, Description:Technical Field:
The present invention relates to the porous materials for transporting liquids from a reservoir in a vapour dispensing device. More particularly, the present invention relates to a highly porous, biodegradable wick with high mechanical strength and high temperature stability, for emitting volatile liquids from a reservoir in a vapour dispensing device and process for preparation of such wicks.

Background of the invention:
Various methods and vaporizing devices have been reported in the prior art to regulate the diffusion of volatile materials, especially, with regard to the vapour delivery of fragrances and/or deodorizers.

The primary function of these types of devices has generally been for neutralising malodours by delivering pleasant fragrance vapours or insecticide vapours for repelling insects into the environment. Liquid air fresheners, insect repellents and other vapour-dispensing products currently available in the market typically have a fluid reservoir and a transport system from which the fluid is evaporated and/or dispensed into the surrounding air/environment.

The prior art has reported different approaches for dispensing fluids or fragrances into the environment. In one approach, fragrances or liquid fluids drips from the reservoir onto a porous substrate of relatively large surface area from where the fragrance evaporates.

In another approach, evaporation of the fluid/fragrances from partially immersed wick which consist of porous material in a liquid fragrance-reservoir wherein, the liquid is transported through the wick by capillary action. In this method, the fragrance is evaporated from the exterior surface of the wick into the surrounding air or environment.

In one more approach, the wick is heated by an electrical heating element which results in delivery of the vapourisable material to the environment. This type of delivery device is often referred to as an electric liquid air freshener. In such devices, the heating element delivers kinetic energy to molecules of the fragrance solution on the exterior surface of the wick thereby increasing the rate of evaporation to obtain higher fragrance intensity and uniform delivery density over time. This approach can also be used to dispense vapourisable insect repellent.

The products currently available in the market utilize the wicks constructed of various compressed materials such as polymeric fibres, graphite, porous ceramic or clay.

For instance, US2010/0176210 discloses hydrophilic porous fibre wick comprising a sintered synthetic bicomponent fibres, optionally combined with synthetic monocomponent fibres or natural monocomponent fibres. The wick is optionally treated with plasma or finishing agents for improved hydrophilicity. The wick is capable of wicking aqueous and/or non-aqueous fragrances or other vaporizable materials and evaporate them into the air without the use of heat, convection air, or atomization. Although this patent application discusses about the capability of the wick to wick aqueous and/or non-aqueous fragrances, US ‘210 fails to address the issues of high heat stability and high mechanical strength of the wick. It further appears that the wick as disclosed in US ‘210 is not biodegradable.

US20110108630 describes a hydrophilic porous wick comprising thermally bonded synthetic bicomponent fibres having pores between the thermally bonded synthetic bicomponent fibres. This application also fails to address high heat stability and high mechanical strength of the wick.

Ideally, the wick shall possess the following characteristics;
a) ability to efficiently transport liquid in a controlled manner by means of capillary action;
b) maintain its structural integrity and resistance to breakage or deformation during manufacture and use;
c) wick must support high and low burst of vapour emission rates according to the changes in the heater temperature;
d) the wick must possess a high thermal stability, such that the wick is capable of uniformly pulling up the liquid, even at high temperatures, and
e) wick structure with high capillary action that enables quick saturation and retention of in the liquid in the wick.

However, the wicks currently available in market, or described in available prior art, do not exhibit most of these characteristics.

For example, wicks can be made of fibrous, non-woven materials, such as those disclosed in US20110108630, tend to be mechanically weak and can be easily distorted or even disintegrate. Graphite or ceramic wicks generally tend to be brittle and can fracture under stress. Clay wicks do not support high release due to low capillary action. Further, all the above wicks and other polymeric wicks come with issues of non-biodegradability and low temperature stability.
Therefore, it is desirable to provide an effective wicking material that offers advantages, such as, high heat stability, high porosity, high mechanical strength, biodegradability and higher absorption over existing materials at affordable costs.

Hence, it is an object of the current invention to provide a wick which overcomes the problems faced by the wicks of the prior art.

Objects of the Invention:
Therefore, in view of above, it is an object of the present invention to provide a wick:
a) which is highly porous and biodegradable;
b) which possess high temperature stability of above 200°C which enables the use of the wick in all types of heaters without any limitations;
c) which demonstrates good mechanical strength ensuring damage free handling on manufacturing lines and in use;
d) which emits volatile liquid, more particularly fits in a refill that provides quick onset of action when plugged in to the electrical heater to provide;
e) which can effectively handle an initial high burst of release of volatile liquids into the surrounding environment and further continues to release low doses;
f) which supports all kinds of non-polar solvents and perfumes which are used in insecticide and perfume formulations, and
g) which has a high absorption and capillarity which can support wide range of release per hour (0.1 gram to 1.0 gram per hour) where the current clay wicks will not support high release due to low capillary action.

It is also the objective of the invention to provide a combination of a fibrous material and clay or similar materials in order to achieve the thermal stability.

Summary of Invention:
The following is a simplified summary of the invention in order to provide a basic understanding of some aspects of the invention. This summary is not an extensive overview of the present invention. It is not intended to identify the key/critical elements of the invention or to delineate the scope of the invention. Its sole purpose is to present some concept of the invention in a simplified form as a prelude to a more detailed description of the invention presented later.

In line with the above objective, the present invention provides a highly porous, biodegradable wick with high mechanical strength and high temperature stability.

Accordingly, the present invention provides a wick made of raw plant fibres with low density and high porous nature and plant-based heat resistant gums, which is characterised by having porosity greater than 50%; temperature stability of more than 200°C; high mechanical strength of at least 2.5Kg and above and having a capillary pull of 70-100 sec per centimetre.

In another aspect, the invention provides process for preparation of highly porous biodegradable wick with high mechanical strength & high temperature stability, wherein the process comprises:
a) pulverising the spun fibres of raw plant with low density and high porous nature to reduce the size of fibres to less than 500 microns followed by sieving to obtain desired size of fibres;
b) mixing the desired size fibres with combination of one or more plant-based gums in a sigma dry mixer;
c) loading the mixed granular dough to pressure screw extruder of desired shapes of extrusion to obtain wicks of desired shapes, and
d) drying the extruded wicks until they reach moisture level of less than 2% of their weight.

In another aspect, the wick obtained by the manufacturing process (as per example 1) is characterised for its product performance as shown in table 1.

In another aspect, the invention provides, wick to attain higher mechanical strength with higher porosity. The plant fibres mixed with inorganic porosity building agents like amorphous volcanic glass powder along with charcoal and kaolin for uniform heat distribution and strength.

The wick in accordance with the above aspect is manufactured by a process comprising steps of:
a) pulverising the spun fibres of raw plant with low density and high porous nature to reduce the size of fibres to less than 500 microns followed by sieving to obtain desired size of fibres;
b) mixing the desired size fibres with combination of amorphous volcanic glass along with charcoal, kaolin and plant-based gums in a sigma dry mixer;
c) loading the mixed granular dough to pressure screw extruder of desired shapes of extrusion to obtain wicks of desired shapes, and
d) drying the extruded wicks until they reach moisture level of less than 2% of their weight.

Detailed Description of Invention:
The present invention describes a highly porous, biodegradable wick with high mechanical strength & high temperature stability prepared from plant-based fibres, for emitting volatile liquids from a reservoir in a vapour dispensing device.

Accordingly, in an embodiment, the present invention provides a biodegradable wick that is made from raw plant fibres with low density and high porosity and plant-based heat resistant gums. The wick has a porosity of more than 50% of its volume.

Further, the wick, as per this embodiment, demonstrates a temperature stability of more than 200°C; higher mechanical strength of at least 2.5Kg and above and has a capillary pull of 70-100 sec per centimetre.

In accordance with the above embodiment, the wick of the present invention is made of plant-based fibres backbone, whereby the plant-fibre is selected from such plant-fibres which have high content of lignin fibres and demonstrate high capillarity in comparison with existing wicks of same applications. Further, the plant-based fibres should demonstrate non-polar solvent stability, lower elasticity, higher strength and high thermal conductivity.

Accordingly, the raw plant fibre material is selected from cotton, raw jute, processed jute, cellulose, lignin and flax based fibres and other plant-based fibres known in the art having a high capillarity. Alternatively, the raw plant fibre material may be mixed with clay to enhance thermal stability of the wick.

In accordance with the above embodiment, the raw plant-based fibres or the combination of the plant-based fibres and clay is present in range of 60% to 95% and heat resistant gum is present in range of 10 – 30%.

In another embodiment, the invention provides a process for manufacturing the biodegradable wick containing only plant fibres of the present invention, whereby the process comprises of:
1. pulverising the spun raw plant fibres to reduce the fibres size to less than 500 microns followed by sieving to obtain desired size fibres, preferably sieved through 20 – 100 mesh sieves;
2. mixing the sieved fibres of step (1) with a combination of one or more plant-based gums in a sigma dry mixture at 25 – 60 rpm for 5 – 10 minutes;
3. increasing the moisture level of the mixture of step (2) till 25-50% by slow addition of hot water having a temperature of 60-80°C and mixing for at least 10 min to form a granulated solid mass;
4. loading the mixed granular dough of step (3) through a pressure screw extruder of desired shapes to obtain wicks of desired shapes;
5. drying the extruded wicks of Step (4) at room temperature for 4 – 6 hours;
6. air drying the wick of step (5) at 40 - 60°C under air blower until they reach moisture content of less than 10 % by weight;
7. heating the wicks of step (6) at 200°C, till the moisture content of wick is less than 2%.

the raw plant fibres, as described hereinbefore, are bound together by a plant-based heat resistant gum, selected from gum arabica, gum ghatti, joss powder and guar gum, or a biodegradable polymer binder such as poly vinyl alcohol and an absorbent agent selected from diatomaceous earth, amorphous volcanic glass, kaolin and/or wood charcoal. The plant-based heat resistant gum is present in concentration range of 5 – 30%.

In accordance with an alternative embodiment, the wick of the invention may comprise plant fibres in range of 15-20%; volcanic glass powders in range of 25-30%; Kaolin clay in range of 8-12%; wood charcoal in range of 25- 30%; Plant gums in range of 8-12% and PVA gum in range of 1-5%.

The wick in accordance with the above embodiment, is manufactured by a process comprising following steps:
1. Pulverising the spun fibres of raw jute, whereby the fibres size was reduced to less than 500 microns by using hammer pulveriser;
2. mixing the sieved desired size fibres (15 – 20 % w/w) of step (1) with Amorphous volcanic glass material (perlite , Radiolite)(25 to 30%) as pore former and Absorbent materials kaolin clay(8 to 12%) & wood charcoal (25-30%)for uniform heat distribution along with (combination of plant-based gum guar gum (8 to 12%), biodegradable polyvinyl alcohol (1 to 5%),.
3. Dry mixing the mixture of step (2) using sigma mixer at 25 – 60 rpm for 5-10 minutes.
4. Increasing the moisture level of the mixture of step (3) by slow addition of (40 to 50%) hot demineralised water of maintained at 60–80°C, till the moisture content is in range of 25-50% of total concentration;
5. continuing mixing of the mixture of step (4) for at least 10 min in the double sigma blender or mixer;
6. loading the mixed granular dough of step (5) in a pressure screw extruder of desired shapes of extrusion, and
7. drying the extruded wicks of step (6) using combination of natural drying and low temperature oven drying up to 60°C until they reach moisture less than 2% of their weight.

The overall composition of the wick, as per the above embodiment, provides the wick with high break strength and the required high porosity.

Furthermore, the fibrous structure of the wick together with high capillary action enables quick saturation, which enable immediate use of refills. Additionally, the wick of the invention efficiently supports high and low burst of vapour emission rates according to the changes in the heater temperature.

The high release of active ingredient or Perfume liquid for quick onset is achieved by:
1. Lowering the gaps between the fibres to increase the capillary action between the fibres;
2. High porous structure due to low density and high porous nature of fibres, and
3. Heat resistant gums to give proper compaction and structure to wick without internal cracks.

In an advantageous embodiment, the wick of the invention is a biodegradable, as the raw material used for manufacturing the wick is a plant-based material which can be easily degraded by microbial flora of the typical environment. Further, as the raw material is a plant based raw material, the incineration of the same does not load the atmosphere with toxic gases.

In another advantageous environment, the use of heat resistant plant resin gives a wick a very high thermal stability, over a temperature range of -10°C - +200°C.

The wick of the invention inherently exhibits a high capillary pull of 70 – 100 cm/sec.

The fibres produced by process of this embodiment, contain at least 60% cellulose together with lignin and hemicellulose. The composition of the fibres makes the fibres resistant to most of the organic solvents, including benzene and ether, which may be used as dissolution media for insecticide and/or perfume.

Further, the use of plant-fibre as backbone of the wick, eliminates the need of polymers/plastics, which require very high temperature for extrusion, thereby reducing the overall cost of manufacturing to 1/3 the manufacturing cost. Also, the process of the invention is eco-friendly as the current process requires much lesser water-consumption as compared to the processes known in the art.

Further, combination of natural drying and low temperature oven drying (up to 70°C) reduces the fuel consumption of the manufacturing process, thereby reducing the overall input cost of the process. Therefore, the current process is economical.

The extruded components can be in the form of cylindrical rods, or punched sheets and can be used due to higher porosity on emanation of insect repellent, perfume and other volatile liquids.

The biodegradable wick of the invention has the following advantages:
1. The non-polymeric natural fibre-based wick according to the invention can be used for both insecticide and perfume vaporization & which is 100% biodegradable.
2. Highly porous (>50% porosity) wick system of the invention provides higher emission rate which is unique and not demonstrated by regular clay wicks.
3. The plant based fibrous material wick demonstrates a high heat stability of up to 200 degrees centigrade and provides uniform release.
4. The novel material and process according to the invention facilitates making of high mechanical strength wicks that can be handled at the manufacturing lines without damages.
5. The wick of the present invention supports high and low burst of vapour emission rates according to the changes in the heater temperature.
6. The fibrous structure of the wick of the invention exhibits high capillary action enables quick saturation, which enable immediate use of refills.
7. Unlike plastic wicks the wick manufacturing process according to the invention does not require high temperatures (for fibre extraction & melting of polymers) and high-water consumption.
8. The natural plant-based fibres are bonded with plant resins or gums which reduces the manufacturing process complexity so that the wick can be produced at 1/3 cost of the existing plastic wicks used in same type of applications.

The biodegradable wick of the present invention can be used for both heating and non-heating applications with higher stability in presence of organic solvents.

The present invention further covers a vapour dispensing device containing the biodegradable wick of the invention.

Examples:
Example 1
Manufacturing process:
Spun fibres of raw jute taken for pulverisation process. In pulverisation the fibres size was reduced to less than 500 microns by using hammer pulveriser. Sieved desired size fibres (60 – 75 % w/w) were mixed with combination of plant-based gums like joss powder (15 to 30%), guar gum (1 to 10%), used at a concentration of 5-30 % w/w of the spun fibres. Dry mixing was done using sigma mixer at 25 – 60 rpm for 5-10 minutes. The moisture level of the mix was increased by slow addition of 60–80°C hot water. The addition of water stopped when the mixture achieves a moisture range in between 25-50% of total concentration. The mixture was continued to mix for at least 30 min in the double sigma blender or mixer. Mixed granular dough was loaded to pressure screw extruder of desired shapes of extrusion. The extruded wicks thus obtained were dried using combination of natural drying and low temperature oven drying up to 70°C until they reach moisture less than 2% of their weight.

Finally, the wicks achieved less than 2% moisture were kept under temperature test at which the wick should not change or deform the structure up to 200 degrees centigrade.

Example 2:
Manufacturing process:
Spun fibres of raw jute taken for pulverisation process. In pulverisation the fibres size was reduced to less than 500 microns by using hammer pulveriser. Sieved desired size fibres (15 – 20 % w/w) were mixed with Amorphous volcanic glass material (perlite , Radiolite)(25 to 30%) as pore former and Absorbent materials kaolin clay(8 to 12%) & wood charcoal (25-30%)for uniform heat distribution along with (combination of plant-based gum guar gum (8 to 12%), biodegradable polyvinyl alcohol (1 to 5%),. Dry mixing was done using sigma mixer at 25 – 60 rpm for 5-10 minutes. The moisture level of the mix was increased by slow addition of (40 to 50%) of 60–80°C hot de mineralised water. The addition of water stopped when the mixture achieves a moisture range in between 25-50% of total concentration. The mixture was continued to mix for at least 10 min in the double sigma blender or mixer. Mixed granular dough was loaded to pressure screw extruder of desired shapes of extrusion. The extruded wicks thus obtained were dried using combination of natural drying and low temperature oven drying up to 60°C until they reach moisture less than 2% of their weight.

Finally, the wicks achieved less than 2% moisture were kept under temperature test at which the wick should not change or deform the structure up to 200 degrees centigrade.

Example 3
The wick is characterised for its temperature stability, breaking strength, absorption, capillary pull and porosity. The results are depicted in table 1.
Table 1:
Wick Bending / Breaking Strength Heat stability @ 200 degrees centigrade Absorption 1.5g Min (carbitol) Capillarity pull
Example 1 Above 2.5kg Stable Min. 1.6g 70- 100 sec per centimetre
Example 2 Above 3.0 kg Stable Min. 1.1g 40- 70 min per centimetre