Title of Invention	VOLATILE RELEASING SUBSTRATES AND METHOD FOR PREPARING THEM.
Abstract	Substrates are provided for use in a heating and/or blowing device that dispenses volatile material. The substrates are a porous medium (such as porous ceramic) having their interior pores coated by a polymeric material (such as a polysiloxane). The substrate is impregnated with a volatile such as pyrethrum. The substrate is less susceptible to clogging. Also disclosed are methods of making those substrates in which the polymeric material is wicked into the substrate with a volatile solvent.

Title of Invention

VOLATILE RELEASING SUBSTRATES AND METHOD FOR PREPARING THEM.

Abstract

Substrates are provided for use in a heating and/or blowing device that dispenses volatile material. The substrates are a porous medium (such as porous ceramic) having their interior pores coated by a polymeric material (such as a polysiloxane). The substrate is impregnated with a volatile such as pyrethrum. The substrate is less susceptible to clogging. Also disclosed are methods of making those substrates in which the polymeric material is wicked into the substrate with a volatile solvent.

Full Text	WO 2005/070203 PCT/US2005/000944 1 VOLATILES RELEASING SUBSTRATES AND METHODS FOR PREPARING THEM CROSS-REFERENCE TO RELATED APPLICATIONS [000l] Not applicable STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH/DEVELOPMENT [0002] Not applicable BACKGROUND OF THE INVENTION [0003] The present invention relates to devices, especially heating devices, that dispense volatiles from a substrate such as a wick, that or plug. More particularly, the invention relates to ways to reduce the tendency of such substrates, to clog during dispensing. [0 0 0 4 ] A variety of devices for dispensing volatilizable materials are well known. Such voiatilizable materials may be air scents or deodorizers {e.g. fragrances or masks), pest control materials (e.g., insecticides, insect repellants or insect growth control regulators), allergen control ingredients, disinfectants, or other materials. [0005] In some of these devices a wick (typically an essential!) cylindrical wick) is provided which draws volatile from a reservoir to a dispensing area. An upper/outer end of the wick is heated. See e.g U.S. Pat. No. 4,663,315- The disclosure of this patent and of all other publications referred to herein are incorporated herd a by reference as if fully set forth herein. [0006] In other such devices a porous mat is impregnated with a volatile material. These impregnated mats are placed on heating plates to cause the volatile material to vaporize. Examples of this type of mat are provided in U.S Pat. No. 6,309,986. An example of an electric heater suitable to cause such mats to dispense volatiles is disclosed in U.S. Pat. No. 6,031,967. [0007] In still other types of such device:; a porous mat that has been impregnated with a volatile material is held within a device such that a flow of hot gases from a fuel burner (such as a candle) passes by the mat and thereby causes the volatile material to vaporize. An example of this type of device is disclosed in WO 00/78135 WO 2005/070203 PCT/US2005/000944 2 [0008] In yet another type of such a dispensing device, moving air is directed against or through substrate to thereby volatilize material that the substrate has been impregnated with. An example of this type of device is disclosed in U.S. Patent No. 5.547,616. [0009] Our assignee recently filed a patent application on January 30., 2003' with U.S. Serial No. 10/354,876. That application covered various improvements in wick, mat and plug structures used to dispense volatile materials. That application disclosed providing an array of granular particles (e.g. sand) coated with a binder f e.g. a thermoset polymenematerial) structured to form a network of pores in the wick with the wick being impregnated with a variety of volatiles. While this device was an improvement for many volatiles, it was not optimal for use with certain others of interest (e.g. those containing pyrethrum, a desirable insecticide). [0010] In this regard, many dispensing devices which rely on heat to dispense actives from wick s, mats or plugs can experience clogging problems for certain volatile$. This can be due to the breakdown of the volatile when heated, or due to reactions or binding that occurs involving the volatile when heated. When such clogging occurs, the release rate of the volatile becomes non-uniform, and may in some cases prematurely stop entirely, thus wasting the remaining active trapped in the substrate. Even where some release continues, the release may be at such a low level that the device is not effective for its designed purpose. [0011] For example, pyrethrum insecticide tends to form non-volatile waxes or polymers upon heating which clog wicks, mass and plugs. Similar problems arise with materials containing terpenes. [0012 ] One proposed solution to this problem has been to use antioxidant; in the impregnation liquid. See e.g. U.S. Pat. No. 4,968,487. However this can add cost to the formulation,, and only has some effect when oxidation is central to the clogging issue. Moreover, in spite of the inclusion of antioxidants, some cross-linking of the isoprene units in certain liquid formulations can occur, ultimately leading to the clogging of the wick, mat or plug anyway. This is particularly a problem for wicks intended for presiding long term insecticidal protection. WO 2005/070203 PCT/US2005/000944 3 [0013] Thus, there is a need for an improved dispensing substrate that can be used in such dispensing deuces with reduced clogging tendency BRIEF SUMMARY OF TEE INVENTION [ 0014 ] In one aspect the invention provides a substrate impregnated with a volatile material to be dispensed. The substrate has been formed from a medium having pores and passages, where the medium has a polymeric material coating interior surface of the pores and passages. There is a volatile material disposed in the pores which is selected so that the volatile material is more volatile than the polymeric material. The polymeric material inhibits the volatile material from clogging the substrate if the substrate is heated. [0015] In preferred forms the polymeric material is a polysioxane, especially polyalkylsiloxanes and polyalkylarylsiloxanes where the alkyl group has less than ten carbons. In the mast preferred forms the polysiloxane is selected from the group consisting of poly dimethylsiloxane, polyrnethylphenylsiloxane, and polyrnethyloctylsiloxane, in each case -with the polysiloxane having; a molecular weight of 750 dalton or greater. [0016] Allernatively other polymeric materials can be used such as pheno formaldehyde, polyurethane, and fluorocarbon polymers like polvtetrafluoroethylene and polydifluoroethylene. In any event, preferably the polymeric material is between about 0.2% to about 4% (e.g. about 1%) of the substrate by weight [ 0017 ] In the most preferred forms, the substrate is capable of being heated at 20000 so as to release at least 90 or 95 percent of the volatile material from the substrate, the substrate is selected from the group consisting of wicks, mats and plugs, and the medium is selected from the group consisting of ceramics, sand, sawdust, cellulosic materials and metals. It is desirable that the substrate is designed so that if heated to 2000C for 24 hours the polymeric material thereto will not have decomposed as a result thereof [0018] The volatile material may be selected from a wide variety of formulations. See e.g. U.S. Pat. No, 6,309,986 fox a disclosure of many insect control materials, deodorizers, fragrances and disinfectants known to be suitable for use with WO 2005/070203 PCT/US2005/000944 heating dispensers. Typically there will be at least one hydrocarbon solvent having a high boiling point (as a carrier), one or more actives (e.g. an insecticide), and optionally an antiexidant and a fragrance. The formulation will be tailored for the application, and may have a variety of different ingredients as is conventional for the application. We prefer to use the invention with insecticidal formulations having it combination of pyrethrum and a synthetic insecticide, together with a fragrance (orange oil), isoparaffinic solvents, and an antioxidant (BHT). [0019] Without intending to be limited by theory, the inventors believe that the polymeric; material transforms the interior surface of the substrate from a relatively high contact angle surface to a relatively low contact angle surface for the volatile material that the substrate is employed to transport and dispend. A wick is a series of short intersection capillary segment A lower contact angle provides better wetting and higher capillarity (higher surface energy). [0020] Many volatile materials such as pyrethrum are susceptible to free radical polymerization. In an uncoated wick with a relatively high contact angle, he volatile material will fill the entire pore (see Fig. 12A). When the polymerization is initiated, it occurs across the opening of the core, leading to the clogging of the wick. In a wick that is coated with a polymeric material of the present invention, the volatile material lays flat against the pore surface and thus any polymerization that occurs will proceed along the surface of the pore rather than across the opening of the pore (see Fig. 12B). Accordingly, the polymerization events are less likely to clog the wick. Furthermore, the polymeric coating masks the active polymerization sites in a mineral substrate and thus can reduce the polymerization events from occurring in the first place. [0021] In another aspect the invention provides a method for forming a substrate of the above kind. One provides the porous medium, dissolves the polymeric material in a volatile solvent to form a solution, and allows the solution to wick into (or otherwise impregnate) the pores and passages. One then permits the substrate to expe at least a portion of (preferably essentially all) the volatile solvent from the substrate, preferably facilitated by heating the substrate, or exposing it to WO 2005/070203 PCT/US2005/000944 negative pressure, or passing gas over its surface, or by a combination of these techniques. [0022 ] Preferred solvents for this purpose are selected from the group consisting of chloroform, tetrahydrofuran, dicxans, methylene chloride, acetone, supercritical carbon dioxide and dimethylsulfoxide. Their most desirable feature is the ability to dissolve the polymeric material for wicking purposes, while being able to be readily removed from the substrate thereafter, [0023] Alternatively, to form a substrate of the present invention, resin beads of a suitable polymeric material can be mixed with a material for toming the porous medium. The mixture is subject to the conventional processes for forming a porous medium, which can be readily achieved by a skilled artisan .The substrate so formed will have pores and passages the surfaces of which are coated by the polymeric material. [0024] It w ill be appreciated from the discussions above and below that the present invention provides a way of coating the internal pores of a ceramic wick, mat or plug with a material that helps the substrate avoid clogging. Polysiloxanes are particularly preferred. They are heat-resistant so that they do not cause a separate clogging problem, and they do not emit undesirable odors. [0025] The invention is particularly advantageous in reducing the waste of actives by permitting the substrate to release essentially all active within it. Further, it provides substrates that release actives in a more uniform and predictable manner. [0026] These and still other advantages of the present invention will be apparent from the description which follows and the accompanying drawings. In them reference is made to certain preferred embodiments. However, the claims should be looked to in order to judge the full scope of the invention, and the clams are not to be limited to just the preferred embodiments. BRIEF DESCRIPTION OF THE DRAWINGS [ O027 ] FIG. 1A is a perspective view showing a prior art device for dispensing volatile materials; [0028] FIG. IB is a vertical cross-sectional view of the FIG 1A device; WO 2005/070203 PCT/US2005/000944 6 [0029] FIG. 2 is a vertical cross-sectional view of a portion of the FIG. IB device, but with a wick of the present invention about to be inserted therein; [0030] FIG. 3 is a view similar to FIG. 2, bur with the wick folly inserted; [0031] FIG. 4A is a view similar to FIG. lA, but with an outlet portion slightly modified; [0032 ] FIG. 4B is a view similar to FIG. 1B, but of the FIG. 4A embodiment, [00333 FIG. 5 is a view similar to FIG. 2 but with the device apart from the wick being of the FIG. 4A type, and the wick being a modified wick of the present invention; [0034] FIG. 6 is a view similar to FIG. 3 but with a different embodiment of a wick of the preson invention; [ 0035] FIC:. 7 is a top, perspective view showing a prior art heating device for dispensing volatile materials from a porous mat, with a porous mat of the present invention used therewith; [0036] FIG. 8 is an enlarged top perspective view of the FIG. 7 mat; [0037] FIG. 9 is a top perspective view of a second porous mat of the present invention; [0038] FIG. 10 is a frontal/side perspective view, partially broken away, o f another prior art type of heating device, albeit used with another porous mat of the present invention; [0039] FIG. 11 is a view similar to FIG. 10, but showing a FIG. 10 type of , heating device, albeit used with a porous plug of the present invention; and [0040] FIGS. 12A and I2B depict the effect of polymer coating on volatile material distribution in pores and passages of a substrate of the present invention. DETAILED DESCRIPTION OF THE P REFERRED EMBODIMENT [0041] Referring first to FIGS. 1A and IB, there is shown a prior art dispensing device 20 in which a heat source is used to promote the wicking actor and release of a volatile material from a wick immersed in a volatile liquid contained in a reservoir. The dispensing device 20 includes a to by 21 having a vapor outlet 24 formed in the center of the top of the body 21. A ring heater 25 having an opening WO 2005/070203 7 PCT/US2005/000944 extending vertical!;' there through is provided inside the body 21 below the vapor outlet 24. The ring heater 25 is supported by a stay 26. Provided under the heater 25 is a bottle socket 27 having an opening extending vertically there through. The socket 27 is formed on its inner periphery with a threaded portion 30 adapted for threaded engagement with a threaded portion 29 on the outer periphery of the mouth 28a of a volatile liquid bottle 28. [0042] The bottle 28 is provided with a wick 31 that is insertable into the ring heater 25 concentrically therewith when the bottle 28 is threaded at its mouth 2Sa into the socket 27. The wick 31 is immersed in the liquid 34 in the bottle 28 and upwardly transports the liquid 34 contained in the bottle 28 by capillary action. The wick 31 is typically formed from, a fired porous ceramic or a sintered plastic material. [0043] Electrical plug blades 32 are fixed to the body 21 on its near side. The plug blades 32 are connected 10 the ring heater 25 in a conventional manner. The ring heater 25 is energised by inserting the plug blades 32 into an electrical outlet and activating switch 35, whereby the ring heater 25 produces heat to heat the upper portion of the wick 31, The heat usually promotes upward transport of the liquid 34 in the wick 31. 11: e liquid chemical 34 in the wick 31 is vaporized by the heat from the ring heater 25. A more detailed description of this type of device can be found in U.S. Pat. No. 5,290,546, [0044] It should be appreciated that a wick of the present invention could be shaped in the same shape as wick 31. If this were done, the revised wick could be used in the FIG. 113 device as shown. [0045] Turning now to FIGS. 2 and 3 such a device can be used with a revesed wick/plug 70. The plug shown in FIG. 2 can be made from a standard wick ceramic substrate (e.g., from Rauscheri or CeramTec), which is a ceramic made of alumina. Such a wick can then be coated with a polysiloxane in accordance with the present invention. The resulting substrate can then be used to wick a solution containing natural pyrethrum its a hydrocarbon solvent. [ 0046] The plug 70 has a truncated cone shaped head 72 and a cylindrical body 74 that extends downwardly from the head 72. The body 74 of the plug 70 is WO 2005/070203 8 PCT/US2005/000944 made small enough to be inserted from above into the hole 24 of the dispensing device 20, while the head 72 is made too wide to slip through the hole 24. The body 74 of the plug 70 s also made small enough to be insertable into the ring hearer 2 5 concentrically therewith as shown in FIG. 3 The head 72 at the top of the plug 70 is useful for handling. [0047] The porous plug 70 is inserted into the dispensing device 20 by moving the plug 70 in the direction "A" shown in FIG. 2 (in this orientation downward). The ring heater 25 is then energized by inserting the plug blades 32 into an electrical outlet and activating switch 35, whereby the ring heater 25 produces heat to heat the body 74 of the plug 70. The volatile material 22 in the plug 70 is vaporized by the heat from the ring heater 25 and enters the surrounding atmosphere. [0048] Re erring next to FIGS. 4A and 4B, there is shown another prior art heated volatile dispensing device 20a. This is similar to the FIG. 1A device but for having a different vapor outlet 24a formed in the center of the top of the body 21. The vapor outlet 24a includes inwardly projecting fingers 24b which define a generally rectangular opening 24c. [0049] FIGS. 5 and 6 are similar to FIGS. 2 and 3 but for the different wicks and the slight difference in the upper opening 24a-c. Here a porous plug or peg 80 according to the invention is impregnated with a volatile material. 'The porous pit g 80 includes a disk shaped head 82 and a body 84 that extends downwardly from the head 82. The body 84 of the plug 80 is shown in a side view hi FIG. 5. It can be seen that in a side view, the perimeter of the body 84 of the plug 80 has an essentially rectangular shape. [0050] The body 84 of the plug 80 is shown in a front view in FIG. 6. it c in be seen that in a front view, the body 84 of the plug 80 includes a lower section 8-a having au essentially rectangular perimeter, a middle section 84b having an essentially V-shaped perimeter, and an upper section 83 that extends from the middle section 84b to the head 82. With the plug 84 oriented as shown in FIG. 5, the body S4 of the plug 80 is narrow enough to be inserted from above into the rectangular opening 24c of the dispensing device 20a, while the head 82 is made too wide to slip WO 2005/070203 PCT/US2005/000944 through the rectangular opening 24c. The body 84 of the plug 80 is also made small enough to be insertable into the ring heater 25 concentrically therewith as shown in FIG. 6. [0051] The porous plug 80 is inserted into the dispensing device; 20a by moving the plug 80 in the direction "B" shown in. FIG, 5 (downward in this orientation), The porous plug 80 may then be rotated 90 degrees, into a position as shown in FIG. 6. When the plug 80 is in this position, the inwardly projecting fingers 24b of the vapor outlet 24a are positioned in grooves 83a and 83b between the middle section 84b and the head 82 of the plug 80. The plug 80 is thereby secured in the dispensing device 20a until the plug is rotated 90 and lifted up and out of the dispensing device 20a. Thus, the squared-off shank section of the shape shown fit.; into the existing, rectangular opening 24c in the top of the heater, entering only when turned to the correct position. [0052 ] Onece in place, the plug can be turned, preventing its removal until turned again to its original position. After the plug 80 is inserted, the ring heater 25 is then energized by inserting the plug blades 32 into an electrical outlet and activating switch 35 whereby the ring heater 25 produces heat to heat the body 84 of the plug 80. The volatile material in the plug 80 is then vaporized by the heat from the ring heater 25 and enters the surrounding atmosphere. [0053] Turning now to FIG, 7, there is shown a prior art volatile material dispensing device in which a solid porous mat impregnated with a volatile material is heated to release the volatile material. In FIG. 7, there is shown an electrical heater, indicating general y at 40. The heater is the "FUYI VAPE" heater previously described, except that the mat previously used with that heater has been replaced with a mat 50 of the present invention. The heater 40 is an electrical resistance heater, and has a flat, upwardly exposed heating plate 42 on which is placed a mat 50 of the present invention. [ 0054 ] An electrical plug 46 supplies electricity to the heating plate 42 by means of an electrical cord 47. The heating plate 42 is energized by inserting the plug 46 into an electrical outlet whereby the heating plate 42 produces hear to heat the mat WO 2005/070203 PCT/US2005/000944 10 50. The volatile material is vaporized by the heat from the heating plate 42 The heating plate may be a ceramic or metal plate. [0055] Referring now to FIG. 8, there is shown one embodiment of a mat 50 according to the invention. The mat 50 is made of a substrate (eg, ceramic substrate or vitrified sand), which has had wicked into it a polysiloxane and z solvent, with the solvent then being; expelled. The substrate then had wicked into it a volatile active such as pyrethrtim or pyrethroid. [0056] The mat 50 includes a body 52 and a handle '34 extending out warely from the body 52 The mat 50 is inserted into the heater 40 by moving the mat 50 m the direction "C" shown in FIG. 7 (sideways in the orientation shown), The mat 50 then rests on the heating plate 42. The heater 40 is then energized by inserting the plug 46 into an electrical outlet whereby the beating plate 42 produces heat to heat the body 52 of the mat 50. The volatile material in the mat 50 is then vaporized by the heat from the heating plate 42 and is released from the surface 56 of the mat 50 thereby entering the surrounding atmosphere. [0057] Referring now to FIG. 9, there is shown another embodiment of a mat 60 according to the invention. The mat 60 is made of a substrate of the present invention and includes a body 62 and a handle 64 extending outwardly from the body 62. The mat 60 ciffers from the mat 50 in that the mat 60 has a first region 68 impregnated with a first volatile material and a second region 69 impregnated with a second volatile material. [0058] In FIG. 10, there is shown a prior art volatile material dispensing device in which a solid porous mat according to the invention is used. The mat is impregnated with a volatile material, and is heated to release the volatile material. The dispensing device 110 has a base 112 that supports a removable chirnney 114, the chimney attaching to the base 112 with locking tabs formed on the lower edge of the chimney that made with locking slots 115 formed in die base 112. The chimney 14 can be made of a heat resistant clear or translucent plastic. The base 112 support s a candle cup 116 positioned centrally within the chimney 114. The candle cup 116 WO 2005/070203 PCT/US2005/000944 11 contains a wax candle The base. 112 has a base floor 128 that has z central ventilation opening 129. [0059] A ceiling 138 is positioned within the chimney 114 at its upper end The ceiling 138 has ceiling vents 1-10 and an insert slot 142 that communicate between the interior of the chimney 114 and the outside an above the chimney, Hot gases flowing upwardly from the burning candle 1 i 8 can escape the chimney 1 1 4 through the ceiling vents 140. The insert slot 142 is sized to receive a mat 144 according to the invention. The mat 144 includes a volatile bearing section 146 with laterally extending, ears 148. The volatile bearing section 146 of the mat 144 is made small enough to be inserted from above into the insert slot 142, while the ears 148 are made too wide to slip through the insert slot 142. [0060] By this arrangement, the volatile bearing section 146 can be suspended within the chimney 114. with the mat 144 hanging by the ears 148. A baffle strip 150. made of a heat resistant material such as metal, is fastened to the underside of the ceiling 138. The baffle strip 150 protects the downwardly facing edge of the volatile bearing section 146 from the direct impact of the hottest gases rising from the candle. In the dispensing device 110 of FIG. 10, hearing is accomplished by the direct exposure of the vela tile bearing section 146 to gases from the candle. As the volatile bearing section 146 is heated by the gases, volatile material is released and is carried out of the dispensing device 110 with the escaping hot gases. [0061] In .FIG. 11, there is shown a prior art volatile material dispensing device 110a in which, another solid porous structure according to the invention is used. The solid, porous structure is impregnated with a volatile material, and is heated to release the volatile material. The volatile material dispensing device 110a of FIG. 11 has the same features as the dispensing device 110 of FIG. 10 except the mat 144 of the dispensing device 110 of FIG. 10 has been replaced by a porous plug 144a in the dispensing device 110a of FIG. 11. The porous plug 144a is installed in a circular hole 188 in the ceiling 138a of the dispensing device 110a. [00 62] The porous plug 144a includes a disc shaped head 144b and a cylindrical body 144c that extends downwardly from the head 144b. The body l44c WO 2005/070203 PCT/US2005/000944 12 of the plug 144a is made small enough to be inserted from above into the hole 188, while the head 144b is made too wide to slip through the hole 188. By thus arrangement, the porous plug 144a can be suspended within the chimney i 14, with the body 144c hanging by the bead 144b. In the dispensing device 110a of FIG. 11, heating is accomplished by the direct exposure of the -porous plug 144a to gases from , the candle. As the porous plug 144a is heated by the gases, volatile material is released and is caned out of the dispensing device 110a with the escaping hot gases. The volatile material can be applied to the lower part of the plug 144a so that a user, by handling only he head 144b (the top-most part of the plug 144a) can avoid touching any volatile material. [0063] Heating devices of the above kind typically produce temperatures along the substrate surface of between 10Q°C and 180°C, albeit some higher temperatures may be experienced immediately above candle flames, or on some inexpensive heating devices where hot spots arise. Thus, it is preferable to select the polymeric material so as to be stable even in the face of temperatures of 200°C for 24 hours or more. [0064] The polymeric coating material can be either a homo- or a co-poly mer. Examples of polymeric materials that can be used in the present invention include, but are not limited to, polysiloxanes, phenolics (e.g., phenol formaldehyde), polyuretaane, and fluorocarbon polymers (e.g., polytetrafluorciethylene and polydifluoroethylerie). Examples of polysiloxanes that can be used include but are not limited to polyalkylsiloxanes (e.g. polydialkylsiloxancs such as polydlmethylsiloxane and porymethyloctyluloxane) and polyalkylarylsiloxanes (e.g., polymethylphenylsiloxane). Preferably, the amount of polymeric materials used to coat the porous medium is between about 0.2% to about 4%, and most preferably about 1%, of the porous medium by weight. [ 0065 ] Porous media is presented in the form of a wick, a mat, a plug or other dispensing form, with the media being ceramic, vitrified sand, cellelosic, sawdust, or metal, Ceramics are most preferred, particularly porous ceramics with a pore size of about 35 to about 130 µm. WO 2005/070203 PCT/US2005/000944 13 [ 0066] Examples of the volatile materials that can be dispensed by a substrate of the present invention include but are not limited to pyretlurum, pyrethroid insecticides, carba mate insecticides and organic phosphate insecticides, fragrances such as natural and artificial perfumes (e.g., hydrocarbons, terpenes such as d-limonece and ciironellal, alcohols, phenols, aldehydes, ketones, lactoses, oxides and esters), deodorants, germicides and repellants.. See generally U.S. Pat. Nos. 5,038,394, 4,968,487 and 4,663,315. [0067 ] To form a substrate of the present invention, one can form or obtain a conventional poro is ceramic medium. A suitable polymeric material for coating the ulterior surface of the conventional substrate can then be dissolved in a solvent. For example, a solution of 14 percent OV-17 (Ohio Valley Speciality Chemical, Marienta, OH - polymethylphenylsiloxane) can be dissolved into 86 percent chloroform. Alternatively, the polysiloxane could be between 1 and 15 percent of the mixture. The wick or other substrate can then be placed in the solvent/polymere material bath and allowed to wick the mixture into the pores and passages of the substxate over a period of severed minutes to several hours. For example, we have observed that approximately I g of solvent/polymeric material displaced air in a 4 g ceramic wick in about 4 minutes, in other experiments we have used polydimethylsiloxane (OV- 2 31, Ohio Valley Specialty Chemical, Marietta, OH). [0068] The wick can then be dried in a vented oven at 50°C for 1 hour. Alternatively, the Wick can be left to dry at room temperature overnight. This expels the chloroform, while leaving the polymeric material coated on the incerior surfaces of the pores and passages of the substrate. [0069] The wick can be in the shape shown in FIG. IB, and be used with the FIG. IB heater. The volatile material can be, for example, 2.5% Kenya pyrethrum (50% extract), about 93% hydrocarbon solvent (e.g. a mixture of Isopav M and V) (Exxon Mobil, Industrial Chemicals), about 1% of a natural fragrance (e.g. orange oil), optionally about 1% of one or more synthetic insecticides (e.g. pralleThrin). and optionally about 1 % of an antioxidant such as 2,6-ditertiarybutylphenol. Of couse. numerous other formulations for the volatile can be used if desired. WO 2005/070203 PCT/US2005/000944 14 [0070] A preferred weight of the ceramic medium for such A wick is around 4 grains. With the chloroform filling the voids in the ceramic medium the typical weight was 5 grains [0071] An alternative method for forming a substrate of the present invention is to mix a polymeric material with a material for forming a porous medium and then subject the mixture to a process for forming the porous medium. Fox example, alumina, a material that is sometimes used for making ceramic wicks, can be mixed with polysiloxanee beads of a particular diameter for generating a desired pore size. A slurry of alumina and the polysiloxane can then be extruded through a die head to form a "green" wick. The wick can next be "fired," which chemically bonds the alumina and drives off most of the polysiloxane sxcept for a layer of the polysiloxane left behind to coa me pores and passages of the wick. [0072] Polymer-coated wicks formed by impregnating the wicks with a polymer-containing solution were evaluated in comparison to ceramic wicks of similar structure which were not polymer coated. Wick performense was evaluated using a solution of high-boiling isoparaffinic solvent (isopar-V) containing 1% of a 50% pyrethrum concentrate (pyrethrum - Board of Kenya). As a control, blank Isopar-V was elce used with each type of wick. [ 0073 ] Performance of the wicks were evaluated by simulating a typical consumer use of such products to control insects. The wick and refill bottles were connected to wal -mounted electric vaporizer units (Baygon, EV-7; Raid Mazda-,I, All-out). The vaporizer units were powered by a special circuit that kept the line voltage at 230 volte AC 4/- 0.2 volts. The room where the test units were installed was maintained at 80°F with a draft-free condition. Each test unit was cycled 8 hours on and 4 hours off to simulate, albeit accelerate; a daily 8-hour cycle of insect-control. The weight of delivered liquid was assessed by determining the mass of each refill bottle using a precision analytical balance (Mettler) after each 8-hour cycle. [0074 ] With Isopar-V for only controls, the ceramic untreated wicks delivered steady-state rates of 45 +/- 3 mg/h and 49 4+/- 4 mg/h, respectively. An uncoated wick with a 0,5% pyre thrum solution declined from a peak of 47 mg/h to nearly zero over WO 2005/070203 PCT/US2005/000944 15 time. A wick coated with OV-101 maintained a delivery rate of47 +-/ 11 mg/h with a 0.5% pyrethrum solution at 350 hours even after the uncoated wick had gone to zero within 100 to 180 hours. [0075] Similar tests were conducted with wicks that were made of vitrified sand. Pyrethrum solutions clogged these wicks easily and caused a substantial decline of the delivery rate of the solutions. Coating the wicks with OV-17 or OV-101 prevented the clogging and the decline of the delivery rate for a period extending after the controls had greatly reduced performance. [0076] Hence, the present invention provides ways of efficiently treating substrates to essentially overcome clogging issues due to a variety of volatiles that are heated. The substrates can be inexpensively and easily manufactured. Further, they provide a reliable and predictable source of volatile delivery. [0077] While the above describes a number of preferred embodiments, it should be appreciated that other embodiments are also within the scope of the invention. For example, tie substrates can have other shapes. [0078] Further, the impregnation of the substrate with the polymeric material and/or the volatile can be by dosing, dipping, or other techniques (as distinguished from just wicking). Also, while a number of types of dispensing devices: have been disclosed, the exact nature of the heater or blower is not critical. [0079] Thus, the claims which follow should be looked to in order to judge the full scope of the invention. Industrial Applicability [0080] The present invention provides improved wicks, mats, plugs and the like for dispensing volatiles, particularly for use in dispensing pyrethrum insecticles from electrical hunting devices. WO 2005/070203 PCT/US2005/000944 16 CLAIMS We clam: 1. A substrate impregnated with a volatile material to be dispensed from the substrate, the substrate comprising: a substrate formed from a medium having pores and passages, and having a polymeric material coating interior surfaces of the pores and passages; and volatile material disposed in the pores; wherein the volatile material is more volatile than the polymeric material and the polymeric material inhibits the volatile material from clogging tine substrate if the substrate is heated 2. The substrate of claim 1, wherein lie polymeric material is a polysiloxane. 3. The substrate of claim 2, wherein the polysiloxane is selected from the group consisting of poly alky lsiloxanes and polyalkylarylsiloxanes. 4. The substrate of claim 3, wherein an alkyl group in the polysiloxans is a C1 to C10 alkyl group. 5. The substrate of claim 4, wherein the polysiloxaae is selected from the group consisting cf polydimethylsiloxane, polyinethylphenylsiloxane, and polymethyloctylsi oxane. 6. The substrate of claim 1, wherein the polysiloxane has a moleculan weight of 750 dalton or greater. 7. The substrate of claim 1, wherein the substrate is capable of being heated at 200°C so as to release at least 90 percent of the volatile material from the substrate. 8. The substrate of claim 7, wherein the substrate is capable of being heated at 200°C to release at least 95 percent of the volatile material from the substrate. 9. The substrate of claim 1, wherein the substrate is selected from the group consisting of wicks, mats and plugs. WO 2005/070203 PCT/US2005/000944 1 7 10. The substrate of claim 1, wherein the medium is selected from the group consisting of ceramics, sand. sawdust, cellulosic materials and modals. 11. The substrate of claim 10, wherein the medium is a ceramic. 12. The substrate of claim 1. wherein if the substrate is heated to 200°C for 24 hours the polymeric material therein will not have decomposed as a result, thereof 13. The substrate of claim 1, wherein the polymeric material is a phenolic material. 14. The substrate of claim 13, wherein the phenolic material is a phenol formaldehyde. 15. The substrate of claim 1, wherein the polymeric material is a polyurethane. 16. The substrate of claim 1. wherein the polymeric material is a fluorocarbon polymer. 17. The substrate of claim 16, wherein the fluorocarbon polymer is selected from the group consisting of polytetrafluoroethylene and polydifluoroethylene. 18. The substrate of claim 1, wherein the polymeric material is less than 4% of the substrate by weight. 19. The substrate of claim 1, wherein the volatile material is selected from the group consisting of insecticides. insect repellants and insect growth regulators. 20 The substrance of claim 19, wherein. the volatile material is pyrethrum and the medium is a ceramic. 21. The substrate of claim 19, wherein the volatile material is a terpene. WO 2005/070203 PCT/US2005/000944 18 22. A method for forming a substrate impregnated with a volatile material, the substrate comprising: a substrate formed from a medium having pores and passages, and having a polymeric material coating interior surfaces of the pores and passages; and a volatile material disposed in the pores; wherein the volatile material is more volatile than the polymeric material and the polymeric material inhibits the volatile material from clogging the substrate if the substrate is heated; the method comprising: providing the porous medium; dissolving the polymeric material in a volatile solvent to form a solution; allowing the solution to wick into the pores and passages; and permitting the substrate to expel at least a portion of the volatile solvent from the substrate. 23. The method of claim 22, wherein the solvent is selected from the group consisting of tetrahydrofuran, dioxane, methylene chloride, chloroform, acetone, supercritical carbon dioxide and dimethylsulfoxide. 24. The method of claim 22, wherein the expelling of the solvent is aided by heat, negative pressure, and/or passing a gas over a surface of the substrate. 25. The method of claim 22, wherein the medium is a ceramic medium and the polymeric material is a polysiloxane material. WO 2005/070203 PCT/US2005/000944 19 26. A method for forming a substrate impregnated with a volatile material, the substrate comprising: a substrate formed from a medium having pores and passages, and having a polymeric material coating interior surfaces of the pores and passages; and a volatile material disposed in the pores: wherein the volatile material is more volatile than the polymeric material and the polymeric material inhibits the volatile material from clogging the substrate if the substrate is heated; the method comprising. mixing a polymeric material with a second material that can form a porous medium having pores and passages; and subjecting the mixture to a process that can be used with the second material alone to form a porous medium having pores and passages. 27. The method of claim 26, wherein the polymeric material is in the form of beads. Substrates are provided for use in a heating and/or blowing device that dispenses volatile material. The substrates are a porous medium (such as porous ceramic) having their interior pores coated by a polymeric material (such as a polysiloxane). The substrate is impregnated with a volatile such as pyrethrum. The substrate is less susceptible to clogging. Also disclosed are methods of making those substrates in which the polymeric material is wicked into the substrate with a volatile solvent.

Full Text

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1
VOLATILES RELEASING SUBSTRATES AND METHODS FOR PREPARING THEM
CROSS-REFERENCE TO RELATED APPLICATIONS [000l] Not applicable
STATEMENT REGARDING FEDERALLY SPONSORED
RESEARCH/DEVELOPMENT [0002] Not applicable
BACKGROUND OF THE INVENTION
[0003] The present invention relates to devices, especially heating devices, that dispense volatiles from a substrate such as a wick, that or plug. More particularly, the invention relates to ways to reduce the tendency of such substrates, to clog during dispensing.
[0 0 0 4 ] A variety of devices for dispensing volatilizable materials are well
known. Such voiatilizable materials may be air scents or deodorizers {e.g. fragrances
or masks), pest control materials (e.g., insecticides, insect repellants or insect growth
control regulators), allergen control ingredients, disinfectants, or other materials.
[0005] In some of these devices a wick (typically an essential!) cylindrical
wick) is provided which draws volatile from a reservoir to a dispensing area. An upper/outer end of the wick is heated. See e.g U.S. Pat. No. 4,663,315- The disclosure of this patent and of all other publications referred to herein are incorporated herd a by reference as if fully set forth herein. [0006] In other such devices a porous mat is impregnated with a volatile material. These impregnated mats are placed on heating plates to cause the volatile material to vaporize. Examples of this type of mat are provided in U.S Pat. No. 6,309,986. An example of an electric heater suitable to cause such mats to dispense volatiles is disclosed in U.S. Pat. No. 6,031,967.
[0007] In still other types of such device:; a porous mat that has been impregnated with a volatile material is held within a device such that a flow of hot gases from a fuel burner (such as a candle) passes by the mat and thereby causes the volatile material to vaporize. An example of this type of device is disclosed in WO 00/78135

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[0008] In yet another type of such a dispensing device, moving air is directed
against or through substrate to thereby volatilize material that the substrate has been impregnated with. An example of this type of device is disclosed in U.S. Patent No. 5.547,616.
[0009] Our assignee recently filed a patent application on January 30., 2003'
with U.S. Serial No. 10/354,876. That application covered various improvements in
wick, mat and plug structures used to dispense volatile materials. That application
disclosed providing an array of granular particles (e.g. sand) coated with a binder f e.g.
a thermoset polymenematerial) structured to form a network of pores in the wick
with the wick being impregnated with a variety of volatiles. While this device was an
improvement for many volatiles, it was not optimal for use with certain others of
interest (e.g. those containing pyrethrum, a desirable insecticide).
[0010] In this regard, many dispensing devices which rely on heat to dispense
actives from wick s, mats or plugs can experience clogging problems for certain volatile$. This can be due to the breakdown of the volatile when heated, or due to reactions or binding that occurs involving the volatile when heated. When such clogging occurs, the release rate of the volatile becomes non-uniform, and may in some cases prematurely stop entirely, thus wasting the remaining active trapped in the substrate. Even where some release continues, the release may be at such a low level that the device is not effective for its designed purpose.
[0011] For example, pyrethrum insecticide tends to form non-volatile waxes
or polymers upon heating which clog wicks, mass and plugs. Similar problems arise with materials containing terpenes.
[0012 ] One proposed solution to this problem has been to use antioxidant; in
the impregnation liquid. See e.g. U.S. Pat. No. 4,968,487. However this can add cost to the formulation,, and only has some effect when oxidation is central to the clogging issue. Moreover, in spite of the inclusion of antioxidants, some cross-linking of the isoprene units in certain liquid formulations can occur, ultimately leading to the clogging of the wick, mat or plug anyway. This is particularly a problem for wicks intended for presiding long term insecticidal protection.

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[0013] Thus, there is a need for an improved dispensing substrate that can be
used in such dispensing deuces with reduced clogging tendency BRIEF SUMMARY OF TEE INVENTION
[ 0014 ] In one aspect the invention provides a substrate impregnated with a
volatile material to be dispensed. The substrate has been formed from a medium having pores and passages, where the medium has a polymeric material coating interior surface of the pores and passages. There is a volatile material disposed in the pores which is selected so that the volatile material is more volatile than the polymeric material. The polymeric material inhibits the volatile material from clogging the substrate if the substrate is heated.
[0015] In preferred forms the polymeric material is a polysioxane, especially
polyalkylsiloxanes and polyalkylarylsiloxanes where the alkyl group has less than ten carbons. In the mast preferred forms the polysiloxane is selected from the group consisting of poly dimethylsiloxane, polyrnethylphenylsiloxane, and polyrnethyloctylsiloxane, in each case -with the polysiloxane having; a molecular weight of 750 dalton or greater.
[0016] Allernatively other polymeric materials can be used such as pheno
formaldehyde, polyurethane, and fluorocarbon polymers like polvtetrafluoroethylene
and polydifluoroethylene. In any event, preferably the polymeric material is between
about 0.2% to about 4% (e.g. about 1%) of the substrate by weight
[ 0017 ] In the most preferred forms, the substrate is capable of being heated at
20000 so as to release at least 90 or 95 percent of the volatile material from the substrate, the substrate is selected from the group consisting of wicks, mats and plugs, and the medium is selected from the group consisting of ceramics, sand, sawdust, cellulosic materials and metals. It is desirable that the substrate is designed so that if heated to 2000C for 24 hours the polymeric material thereto will not have decomposed as a result thereof
[0018] The volatile material may be selected from a wide variety of
formulations. See e.g. U.S. Pat. No, 6,309,986 fox a disclosure of many insect control materials, deodorizers, fragrances and disinfectants known to be suitable for use with

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heating dispensers. Typically there will be at least one hydrocarbon solvent having a
high boiling point (as a carrier), one or more actives (e.g. an insecticide), and
optionally an antiexidant and a fragrance. The formulation will be tailored for the
application, and may have a variety of different ingredients as is conventional for the
application. We prefer to use the invention with insecticidal formulations having it
combination of pyrethrum and a synthetic insecticide, together with a fragrance
(orange oil), isoparaffinic solvents, and an antioxidant (BHT).
[0019] Without intending to be limited by theory, the inventors believe that
the polymeric; material transforms the interior surface of the substrate from a relatively high contact angle surface to a relatively low contact angle surface for the volatile material that the substrate is employed to transport and dispend. A wick is a series of short intersection capillary segment A lower contact angle provides better wetting and higher capillarity (higher surface energy).
[0020] Many volatile materials such as pyrethrum are susceptible to free
radical polymerization. In an uncoated wick with a relatively high contact angle, he volatile material will fill the entire pore (see Fig. 12A). When the polymerization is initiated, it occurs across the opening of the core, leading to the clogging of the wick. In a wick that is coated with a polymeric material of the present invention, the volatile material lays flat against the pore surface and thus any polymerization that occurs will proceed along the surface of the pore rather than across the opening of the pore (see Fig. 12B). Accordingly, the polymerization events are less likely to clog the wick. Furthermore, the polymeric coating masks the active polymerization sites in a mineral substrate and thus can reduce the polymerization events from occurring in the first place.
[0021] In another aspect the invention provides a method for forming a substrate of the above kind. One provides the porous medium, dissolves the polymeric material in a volatile solvent to form a solution, and allows the solution to wick into (or otherwise impregnate) the pores and passages. One then permits the substrate to expe at least a portion of (preferably essentially all) the volatile solvent from the substrate, preferably facilitated by heating the substrate, or exposing it to

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negative pressure, or passing gas over its surface, or by a combination of these techniques.
[0022 ] Preferred solvents for this purpose are selected from the group consisting of chloroform, tetrahydrofuran, dicxans, methylene chloride, acetone, supercritical carbon dioxide and dimethylsulfoxide. Their most desirable feature is the ability to dissolve the polymeric material for wicking purposes, while being able to be readily removed from the substrate thereafter,
[0023] Alternatively, to form a substrate of the present invention, resin beads of a suitable polymeric material can be mixed with a material for toming the porous medium. The mixture is subject to the conventional processes for forming a porous medium, which can be readily achieved by a skilled artisan .The substrate so formed will have pores and passages the surfaces of which are coated by the polymeric material.
[0024] It w ill be appreciated from the discussions above and below that the present invention provides a way of coating the internal pores of a ceramic wick, mat or plug with a material that helps the substrate avoid clogging. Polysiloxanes are particularly preferred. They are heat-resistant so that they do not cause a separate clogging problem, and they do not emit undesirable odors. [0025] The invention is particularly advantageous in reducing the waste of actives by permitting the substrate to release essentially all active within it. Further, it provides substrates that release actives in a more uniform and predictable manner. [0026] These and still other advantages of the present invention will be apparent from the description which follows and the accompanying drawings. In them reference is made to certain preferred embodiments. However, the claims should be looked to in order to judge the full scope of the invention, and the clams are not to be limited to just the preferred embodiments.
BRIEF DESCRIPTION OF THE DRAWINGS
[ O027 ] FIG. 1A is a perspective view showing a prior art device for dispensing
volatile materials;
[0028] FIG. IB is a vertical cross-sectional view of the FIG 1A device;

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[0029] FIG. 2 is a vertical cross-sectional view of a portion of the FIG. IB device, but with a wick of the present invention about to be inserted therein; [0030] FIG. 3 is a view similar to FIG. 2, bur with the wick folly inserted; [0031] FIG. 4A is a view similar to FIG. lA, but with an outlet portion slightly modified;
[0032 ] FIG. 4B is a view similar to FIG. 1B, but of the FIG. 4A embodiment, [00333 FIG. 5 is a view similar to FIG. 2 but with the device apart from the wick being of the FIG. 4A type, and the wick being a modified wick of the present invention;
[0034] FIG. 6 is a view similar to FIG. 3 but with a different embodiment of a
wick of the preson invention;
[ 0035] FIC:. 7 is a top, perspective view showing a prior art heating device for dispensing volatile materials from a porous mat, with a porous mat of the present invention used therewith;
[0036] FIG. 8 is an enlarged top perspective view of the FIG. 7 mat;
[0037] FIG. 9 is a top perspective view of a second porous mat of the present
invention;
[0038] FIG. 10 is a frontal/side perspective view, partially broken away, o f
another prior art type of heating device, albeit used with another porous mat of the present invention;
[0039] FIG. 11 is a view similar to FIG. 10, but showing a FIG. 10 type of , heating device, albeit used with a porous plug of the present invention; and [0040] FIGS. 12A and I2B depict the effect of polymer coating on volatile material distribution in pores and passages of a substrate of the present invention.
DETAILED DESCRIPTION OF THE P REFERRED EMBODIMENT [0041] Referring first to FIGS. 1A and IB, there is shown a prior art dispensing device 20 in which a heat source is used to promote the wicking actor and release of a volatile material from a wick immersed in a volatile liquid contained in a reservoir. The dispensing device 20 includes a to by 21 having a vapor outlet 24 formed in the center of the top of the body 21. A ring heater 25 having an opening

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extending vertical!;' there through is provided inside the body 21 below the vapor outlet 24. The ring heater 25 is supported by a stay 26. Provided under the heater 25 is a bottle socket 27 having an opening extending vertically there through. The socket 27 is formed on its inner periphery with a threaded portion 30 adapted for threaded engagement with a threaded portion 29 on the outer periphery of the mouth 28a of a volatile liquid bottle 28.
[0042] The bottle 28 is provided with a wick 31 that is insertable into the ring
heater 25 concentrically therewith when the bottle 28 is threaded at its mouth 2Sa into
the socket 27. The wick 31 is immersed in the liquid 34 in the bottle 28 and upwardly
transports the liquid 34 contained in the bottle 28 by capillary action. The wick 31 is
typically formed from, a fired porous ceramic or a sintered plastic material.
[0043] Electrical plug blades 32 are fixed to the body 21 on its near side. The
plug blades 32 are connected 10 the ring heater 25 in a conventional manner. The ring heater 25 is energised by inserting the plug blades 32 into an electrical outlet and activating switch 35, whereby the ring heater 25 produces heat to heat the upper portion of the wick 31, The heat usually promotes upward transport of the liquid 34 in the wick 31. 11: e liquid chemical 34 in the wick 31 is vaporized by the heat from the ring heater 25. A more detailed description of this type of device can be found in U.S. Pat. No. 5,290,546,
[0044] It should be appreciated that a wick of the present invention could be
shaped in the same shape as wick 31. If this were done, the revised wick could be used in the FIG. 113 device as shown.
[0045] Turning now to FIGS. 2 and 3 such a device can be used with a revesed
wick/plug 70. The plug shown in FIG. 2 can be made from a standard wick ceramic substrate (e.g., from Rauscheri or CeramTec), which is a ceramic made of alumina. Such a wick can then be coated with a polysiloxane in accordance with the present invention. The resulting substrate can then be used to wick a solution containing natural pyrethrum its a hydrocarbon solvent.
[ 0046] The plug 70 has a truncated cone shaped head 72 and a cylindrical
body 74 that extends downwardly from the head 72. The body 74 of the plug 70 is

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made small enough to be inserted from above into the hole 24 of the dispensing device 20, while the head 72 is made too wide to slip through the hole 24. The body 74 of the plug 70 s also made small enough to be insertable into the ring hearer 2 5 concentrically therewith as shown in FIG. 3 The head 72 at the top of the plug 70 is useful for handling.
[0047] The porous plug 70 is inserted into the dispensing device 20 by moving
the plug 70 in the direction "A" shown in FIG. 2 (in this orientation downward). The
ring heater 25 is then energized by inserting the plug blades 32 into an electrical outlet
and activating switch 35, whereby the ring heater 25 produces heat to heat the body
74 of the plug 70. The volatile material 22 in the plug 70 is vaporized by the heat
from the ring heater 25 and enters the surrounding atmosphere.
[0048] Re erring next to FIGS. 4A and 4B, there is shown another prior art
heated volatile dispensing device 20a. This is similar to the FIG. 1A device but for having a different vapor outlet 24a formed in the center of the top of the body 21. The vapor outlet 24a includes inwardly projecting fingers 24b which define a generally rectangular opening 24c.
[0049] FIGS. 5 and 6 are similar to FIGS. 2 and 3 but for the different wicks
and the slight difference in the upper opening 24a-c. Here a porous plug or peg 80 according to the invention is impregnated with a volatile material. 'The porous pit g 80 includes a disk shaped head 82 and a body 84 that extends downwardly from the head 82. The body 84 of the plug 80 is shown in a side view hi FIG. 5. It can be seen that in a side view, the perimeter of the body 84 of the plug 80 has an essentially rectangular shape.
[0050] The body 84 of the plug 80 is shown in a front view in FIG. 6. it c in be seen that in a front view, the body 84 of the plug 80 includes a lower section 8-a having au essentially rectangular perimeter, a middle section 84b having an essentially V-shaped perimeter, and an upper section 83 that extends from the middle section 84b to the head 82. With the plug 84 oriented as shown in FIG. 5, the body S4 of the plug 80 is narrow enough to be inserted from above into the rectangular opening 24c of the dispensing device 20a, while the head 82 is made too wide to slip

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through the rectangular opening 24c. The body 84 of the plug 80 is also made small enough to be insertable into the ring heater 25 concentrically therewith as shown in FIG. 6.
[0051] The porous plug 80 is inserted into the dispensing device; 20a by moving the plug 80 in the direction "B" shown in. FIG, 5 (downward in this orientation), The porous plug 80 may then be rotated 90 degrees, into a position as shown in FIG. 6. When the plug 80 is in this position, the inwardly projecting fingers 24b of the vapor outlet 24a are positioned in grooves 83a and 83b between the middle section 84b and the head 82 of the plug 80. The plug 80 is thereby secured in the dispensing device 20a until the plug is rotated 90 and lifted up and out of the dispensing device 20a. Thus, the squared-off shank section of the shape shown fit.; into the existing, rectangular opening 24c in the top of the heater, entering only when turned to the correct position.
[0052 ] Onece in place, the plug can be turned, preventing its removal until
turned again to its original position. After the plug 80 is inserted, the ring heater 25 is then energized by inserting the plug blades 32 into an electrical outlet and activating switch 35 whereby the ring heater 25 produces heat to heat the body 84 of the plug 80. The volatile material in the plug 80 is then vaporized by the heat from the ring heater 25 and enters the surrounding atmosphere.
[0053] Turning now to FIG, 7, there is shown a prior art volatile material
dispensing device in which a solid porous mat impregnated with a volatile material is heated to release the volatile material. In FIG. 7, there is shown an electrical heater, indicating general y at 40. The heater is the "FUYI VAPE" heater previously described, except that the mat previously used with that heater has been replaced with a mat 50 of the present invention. The heater 40 is an electrical resistance heater, and has a flat, upwardly exposed heating plate 42 on which is placed a mat 50 of the present invention.
[ 0054 ] An electrical plug 46 supplies electricity to the heating plate 42 by means of an electrical cord 47. The heating plate 42 is energized by inserting the plug 46 into an electrical outlet whereby the heating plate 42 produces hear to heat the mat

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50. The volatile material is vaporized by the heat from the heating plate 42 The heating plate may be a ceramic or metal plate.
[0055] Referring now to FIG. 8, there is shown one embodiment of a mat 50 according to the invention. The mat 50 is made of a substrate (eg, ceramic substrate or vitrified sand), which has had wicked into it a polysiloxane and z solvent, with the solvent then being; expelled. The substrate then had wicked into it a volatile active such as pyrethrtim or pyrethroid.
[0056] The mat 50 includes a body 52 and a handle '34 extending out warely from the body 52 The mat 50 is inserted into the heater 40 by moving the mat 50 m the direction "C" shown in FIG. 7 (sideways in the orientation shown), The mat 50 then rests on the heating plate 42. The heater 40 is then energized by inserting the plug 46 into an electrical outlet whereby the beating plate 42 produces heat to heat the body 52 of the mat 50. The volatile material in the mat 50 is then vaporized by the heat from the heating plate 42 and is released from the surface 56 of the mat 50 thereby entering the surrounding atmosphere.
[0057] Referring now to FIG. 9, there is shown another embodiment of a mat
60 according to the invention. The mat 60 is made of a substrate of the present invention and includes a body 62 and a handle 64 extending outwardly from the body 62. The mat 60 ciffers from the mat 50 in that the mat 60 has a first region 68 impregnated with a first volatile material and a second region 69 impregnated with a second volatile material.
[0058] In FIG. 10, there is shown a prior art volatile material dispensing
device in which a solid porous mat according to the invention is used. The mat is impregnated with a volatile material, and is heated to release the volatile material. The dispensing device 110 has a base 112 that supports a removable chirnney 114, the chimney attaching to the base 112 with locking tabs formed on the lower edge of the chimney that made with locking slots 115 formed in die base 112. The chimney 14 can be made of a heat resistant clear or translucent plastic. The base 112 support s a candle cup 116 positioned centrally within the chimney 114. The candle cup 116

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contains a wax candle The base. 112 has a base floor 128 that has z central ventilation opening 129.
[0059] A ceiling 138 is positioned within the chimney 114 at its upper end
The ceiling 138 has ceiling vents 1-10 and an insert slot 142 that communicate between the interior of the chimney 114 and the outside an above the chimney, Hot gases flowing upwardly from the burning candle 1 i 8 can escape the chimney 1 1 4 through the ceiling vents 140. The insert slot 142 is sized to receive a mat 144 according to the invention. The mat 144 includes a volatile bearing section 146 with laterally extending, ears 148. The volatile bearing section 146 of the mat 144 is made small enough to be inserted from above into the insert slot 142, while the ears 148 are made too wide to slip through the insert slot 142.
[0060] By this arrangement, the volatile bearing section 146 can be suspended
within the chimney 114. with the mat 144 hanging by the ears 148. A baffle strip 150.
made of a heat resistant material such as metal, is fastened to the underside of the
ceiling 138. The baffle strip 150 protects the downwardly facing edge of the volatile
bearing section 146 from the direct impact of the hottest gases rising from the candle.
In the dispensing device 110 of FIG. 10, hearing is accomplished by the direct
exposure of the vela tile bearing section 146 to gases from the candle. As the volatile
bearing section 146 is heated by the gases, volatile material is released and is carried
out of the dispensing device 110 with the escaping hot gases.
[0061] In .FIG. 11, there is shown a prior art volatile material dispensing
device 110a in which, another solid porous structure according to the invention is
used. The solid, porous structure is impregnated with a volatile material, and is heated
to release the volatile material. The volatile material dispensing device 110a of FIG.
11 has the same features as the dispensing device 110 of FIG. 10 except the mat 144
of the dispensing device 110 of FIG. 10 has been replaced by a porous plug 144a in
the dispensing device 110a of FIG. 11. The porous plug 144a is installed in a circular
hole 188 in the ceiling 138a of the dispensing device 110a.
[00 62] The porous plug 144a includes a disc shaped head 144b and a
cylindrical body 144c that extends downwardly from the head 144b. The body l44c

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of the plug 144a is made small enough to be inserted from above into the hole 188, while the head 144b is made too wide to slip through the hole 188. By thus arrangement, the porous plug 144a can be suspended within the chimney i 14, with the body 144c hanging by the bead 144b. In the dispensing device 110a of FIG. 11, heating is accomplished by the direct exposure of the -porous plug 144a to gases from , the candle. As the porous plug 144a is heated by the gases, volatile material is released and is caned out of the dispensing device 110a with the escaping hot gases. The volatile material can be applied to the lower part of the plug 144a so that a user, by handling only he head 144b (the top-most part of the plug 144a) can avoid touching any volatile material.
[0063] Heating devices of the above kind typically produce temperatures
along the substrate surface of between 10Q°C and 180°C, albeit some higher temperatures may be experienced immediately above candle flames, or on some inexpensive heating devices where hot spots arise. Thus, it is preferable to select the polymeric material so as to be stable even in the face of temperatures of 200°C for 24 hours or more.
[0064] The polymeric coating material can be either a homo- or a co-poly mer.
Examples of polymeric materials that can be used in the present invention include, but are not limited to, polysiloxanes, phenolics (e.g., phenol formaldehyde), polyuretaane, and fluorocarbon polymers (e.g., polytetrafluorciethylene and polydifluoroethylerie). Examples of polysiloxanes that can be used include but are not limited to polyalkylsiloxanes (e.g. polydialkylsiloxancs such as polydlmethylsiloxane and porymethyloctyluloxane) and polyalkylarylsiloxanes (e.g.,
polymethylphenylsiloxane). Preferably, the amount of polymeric materials used to coat the porous medium is between about 0.2% to about 4%, and most preferably about 1%, of the porous medium by weight.
[ 0065 ] Porous media is presented in the form of a wick, a mat, a plug or other
dispensing form, with the media being ceramic, vitrified sand, cellelosic, sawdust, or metal, Ceramics are most preferred, particularly porous ceramics with a pore size of about 35 to about 130 µm.

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[ 0066] Examples of the volatile materials that can be dispensed by a substrate
of the present invention include but are not limited to pyretlurum, pyrethroid insecticides, carba mate insecticides and organic phosphate insecticides, fragrances such as natural and artificial perfumes (e.g., hydrocarbons, terpenes such as d-limonece and ciironellal, alcohols, phenols, aldehydes, ketones, lactoses, oxides and esters), deodorants, germicides and repellants.. See generally U.S. Pat. Nos. 5,038,394, 4,968,487 and 4,663,315.
[0067 ] To form a substrate of the present invention, one can form or obtain a
conventional poro is ceramic medium. A suitable polymeric material for coating the ulterior surface of the conventional substrate can then be dissolved in a solvent. For example, a solution of 14 percent OV-17 (Ohio Valley Speciality Chemical, Marienta, OH - polymethylphenylsiloxane) can be dissolved into 86 percent chloroform. Alternatively, the polysiloxane could be between 1 and 15 percent of the mixture. The wick or other substrate can then be placed in the solvent/polymere material bath and allowed to wick the mixture into the pores and passages of the substxate over a period of severed minutes to several hours. For example, we have observed that approximately I g of solvent/polymeric material displaced air in a 4 g ceramic wick in about 4 minutes, in other experiments we have used polydimethylsiloxane (OV- 2 31, Ohio Valley Specialty Chemical, Marietta, OH).
[0068] The wick can then be dried in a vented oven at 50°C for 1 hour.
Alternatively, the Wick can be left to dry at room temperature overnight. This expels the chloroform, while leaving the polymeric material coated on the incerior surfaces of the pores and passages of the substrate.
[0069] The wick can be in the shape shown in FIG. IB, and be used with the
FIG. IB heater. The volatile material can be, for example, 2.5% Kenya pyrethrum (50% extract), about 93% hydrocarbon solvent (e.g. a mixture of Isopav M and V) (Exxon Mobil, Industrial Chemicals), about 1% of a natural fragrance (e.g. orange oil), optionally about 1% of one or more synthetic insecticides (e.g. pralleThrin). and optionally about 1 % of an antioxidant such as 2,6-ditertiarybutylphenol. Of couse. numerous other formulations for the volatile can be used if desired.

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[0070] A preferred weight of the ceramic medium for such A wick is around 4
grains. With the chloroform filling the voids in the ceramic medium the typical weight was 5 grains
[0071] An alternative method for forming a substrate of the present invention
is to mix a polymeric material with a material for forming a porous medium and then subject the mixture to a process for forming the porous medium. Fox example, alumina, a material that is sometimes used for making ceramic wicks, can be mixed with polysiloxanee beads of a particular diameter for generating a desired pore size. A slurry of alumina and the polysiloxane can then be extruded through a die head to form a "green" wick. The wick can next be "fired," which chemically bonds the alumina and drives off most of the polysiloxane sxcept for a layer of the polysiloxane left behind to coa me pores and passages of the wick.
[0072] Polymer-coated wicks formed by impregnating the wicks with a
polymer-containing solution were evaluated in comparison to ceramic wicks of similar structure which were not polymer coated. Wick performense was evaluated using a solution of high-boiling isoparaffinic solvent (isopar-V) containing 1% of a 50% pyrethrum concentrate (pyrethrum - Board of Kenya). As a control, blank Isopar-V was elce used with each type of wick.
[ 0073 ] Performance of the wicks were evaluated by simulating a typical
consumer use of such products to control insects. The wick and refill bottles were
connected to wal -mounted electric vaporizer units (Baygon, EV-7; Raid Mazda-,I,
All-out). The vaporizer units were powered by a special circuit that kept the line
voltage at 230 volte AC 4/- 0.2 volts. The room where the test units were installed
was maintained at 80°F with a draft-free condition. Each test unit was cycled 8 hours
on and 4 hours off to simulate, albeit accelerate; a daily 8-hour cycle of insect-control.
The weight of delivered liquid was assessed by determining the mass of each refill
bottle using a precision analytical balance (Mettler) after each 8-hour cycle.
[0074 ] With Isopar-V for only controls, the ceramic untreated wicks delivered
steady-state rates of 45 +/- 3 mg/h and 49 4+/- 4 mg/h, respectively. An uncoated wick with a 0,5% pyre thrum solution declined from a peak of 47 mg/h to nearly zero over

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time. A wick coated with OV-101 maintained a delivery rate of47 +-/ 11 mg/h with a
0.5% pyrethrum solution at 350 hours even after the uncoated wick had gone to zero
within 100 to 180 hours.
[0075] Similar tests were conducted with wicks that were made of vitrified
sand. Pyrethrum solutions clogged these wicks easily and caused a substantial decline
of the delivery rate of the solutions. Coating the wicks with OV-17 or OV-101
prevented the clogging and the decline of the delivery rate for a period extending after
the controls had greatly reduced performance.
[0076] Hence, the present invention provides ways of efficiently treating
substrates to essentially overcome clogging issues due to a variety of volatiles that are
heated. The substrates can be inexpensively and easily manufactured. Further, they
provide a reliable and predictable source of volatile delivery.
[0077] While the above describes a number of preferred embodiments, it
should be appreciated that other embodiments are also within the scope of the
invention. For example, tie substrates can have other shapes.
[0078] Further, the impregnation of the substrate with the polymeric material
and/or the volatile can be by dosing, dipping, or other techniques (as distinguished
from just wicking). Also, while a number of types of dispensing devices: have been
disclosed, the exact nature of the heater or blower is not critical.
[0079] Thus, the claims which follow should be looked to in order to judge the
full scope of the invention.
Industrial Applicability
[0080] The present invention provides improved wicks, mats, plugs and the
like for dispensing volatiles, particularly for use in dispensing pyrethrum insecticles from electrical hunting devices.

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CLAIMS
We clam:
1. A substrate impregnated with a volatile material to be dispensed from the substrate, the substrate comprising:
a substrate formed from a medium having pores and passages, and having a polymeric material coating interior surfaces of the pores and passages; and
volatile material disposed in the pores;
wherein the volatile material is more volatile than the polymeric material and the polymeric material inhibits the volatile material from clogging tine substrate if the substrate is heated
2. The substrate of claim 1, wherein lie polymeric material is a
polysiloxane.
3. The substrate of claim 2, wherein the polysiloxane is selected from the
group consisting of poly alky lsiloxanes and polyalkylarylsiloxanes.
4. The substrate of claim 3, wherein an alkyl group in the polysiloxans is
a C1 to C10 alkyl group.
5. The substrate of claim 4, wherein the polysiloxaae is selected from the
group consisting cf polydimethylsiloxane, polyinethylphenylsiloxane, and
polymethyloctylsi oxane.
6. The substrate of claim 1, wherein the polysiloxane has a moleculan
weight of 750 dalton or greater.
7. The substrate of claim 1, wherein the substrate is capable of being
heated at 200°C so as to release at least 90 percent of the volatile material from the
substrate.
8. The substrate of claim 7, wherein the substrate is capable of being
heated at 200°C to release at least 95 percent of the volatile material from the
substrate.
9. The substrate of claim 1, wherein the substrate is selected from the
group consisting of wicks, mats and plugs.

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10. The substrate of claim 1, wherein the medium is selected from the
group consisting of ceramics, sand. sawdust, cellulosic materials and modals.
11. The substrate of claim 10, wherein the medium is a ceramic.
12. The substrate of claim 1. wherein if the substrate is heated to 200°C for
24 hours the polymeric material therein will not have decomposed as a result, thereof
13. The substrate of claim 1, wherein the polymeric material is a phenolic
material.
14. The substrate of claim 13, wherein the phenolic material is a phenol
formaldehyde.
15. The substrate of claim 1, wherein the polymeric material is a
polyurethane.
16. The substrate of claim 1. wherein the polymeric material is a
fluorocarbon polymer.
17. The substrate of claim 16, wherein the fluorocarbon polymer is
selected from the group consisting of polytetrafluoroethylene and
polydifluoroethylene.
18. The substrate of claim 1, wherein the polymeric material is less than
4% of the substrate by weight.
19. The substrate of claim 1, wherein the volatile material is selected from
the group consisting of insecticides. insect repellants and insect growth regulators.
20 The substrance of claim 19, wherein. the volatile material is pyrethrum and the medium is a ceramic.
21. The substrate of claim 19, wherein the volatile material is a terpene.

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22. A method for forming a substrate impregnated with a volatile material, the substrate comprising:
a substrate formed from a medium having pores and passages, and having a polymeric material coating interior surfaces of the pores and passages; and a volatile material disposed in the pores;
wherein the volatile material is more volatile than the polymeric material and the polymeric material inhibits the volatile material from clogging the substrate if the substrate is heated; the method comprising: providing the porous medium;
dissolving the polymeric material in a volatile solvent to form a solution; allowing the solution to wick into the pores and passages; and permitting the substrate to expel at least a portion of the volatile solvent from the substrate.
23. The method of claim 22, wherein the solvent is selected from the group
consisting of tetrahydrofuran, dioxane, methylene chloride, chloroform, acetone,
supercritical carbon dioxide and dimethylsulfoxide.
24. The method of claim 22, wherein the expelling of the solvent is aided
by heat, negative pressure, and/or passing a gas over a surface of the substrate.
25. The method of claim 22, wherein the medium is a ceramic medium and
the polymeric material is a polysiloxane material.

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26. A method for forming a substrate impregnated with a volatile material, the substrate comprising:
a substrate formed from a medium having pores and passages, and having a polymeric material coating interior surfaces of the pores and passages; and a volatile material disposed in the pores:
wherein the volatile material is more volatile than the polymeric material and the polymeric material inhibits the volatile material from clogging the substrate if the substrate is heated; the method comprising.
mixing a polymeric material with a second material that can form a porous medium having pores and passages; and
subjecting the mixture to a process that can be used with the second material alone to form a porous medium having pores and passages.
27. The method of claim 26, wherein the polymeric material is in the form of beads.

Substrates are provided for use in a heating and/or blowing device that dispenses volatile material. The substrates are a porous medium (such as porous ceramic) having their interior pores coated by a polymeric material (such as a polysiloxane). The substrate is impregnated with a volatile such as pyrethrum. The substrate is less susceptible to clogging. Also disclosed are methods of making those substrates in which the polymeric material is wicked into the substrate with a volatile solvent.

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Patent Number

258246

Indian Patent Application Number

2104/KOLNP/2006

PG Journal Number

52/2013

Publication Date

27-Dec-2013

Grant Date

20-Dec-2013

Date of Filing

26-Jul-2006

Name of Patentee

S.C. JOHNSON & SON, INC

Applicant Address

1525 HOWE STREET, RACINE, WISCONSIN 53403-2236

Inventors:

#	Inventor's Name	Inventor's Address
1	KENNETH WELCH	141 OREGON STREET RACINE, WISCONSIN 53405
2	MICHAEL J. AULOZZI	5725 BROOKHAVEN DRIVE RACINE WISCONSIN 53406
3	ROBERT R. EMMRICH	6340 DOUGLAS AVENUE RACINE WISCONSIN 53402

PCT International Classification Number

A01M 1/20

PCT International Application Number

PCT/US2005/000944

PCT International Filing date

2005-01-12

PCT Conventions:

#	PCT Application Number	Date of Convention	Priority Country
1	10/758,650	2004-01-15	U.S.A.