Abstract:
A method for manufacturing a stable gelled fuel composition of diethylene glycol and fumed silica. Polyethylene glycol may also be added to improve burning. Previous related compositions (U.S. Pat. No. 5,264,003) provided methods of making a polymer hydrogel without chemical cross links. The modifications herein create optimal methods for mixing that enhance the range of applications. The gelation process is further modulated by controlling the air entraining of the resultant mixture producing a gellant complex while at the same time reducing the gelling media. The method includes the steps of providing a polymer solution of silicone dioxide (SiO 2 ) wetted into diethylene glycol (DEG) in a first solution. The method further provides physically cross-linked hydrogels produced by controlled gelation of viscoelastic mixture wherein workability is maintained. In a further aspect, the invention provides methodology for mixing other forms of the gelation of polymer hydrogel solutions.

Description:
CROSS REFERENCES TO RELATED APPLICATIONS 
       [0001]    This application claims the benefit under Title 35 United States Code §119(e) of U.S. Provisional Application 61/501,236 filed Jun. 26, 2011 the full disclosure of which is incorporated herein by reference. 
       BACKGROUND OF THE INVENTION 
       [0002]    1. Field of the Invention 
         [0003]    The present invention relates generally to gelled diethylene glycol (DEG) compositions to be used as heat sources or fuels. More particularly, this invention relates to a method for manufacturing a diethylene glycol and a fumed silica product and to the resulting composition product. 
         [0004]    2. Description of the Related Art 
         [0005]    Small portable heat sources have been used for many years in a number of fields including, camping and in military application. To avoid the bulk and impracticality of liquid sources inherent in camp stoves, a number of devices have been invented to provide a source of fuel in a gelled or colloidal form. One such device is a gelled alcohol marketed as Sterno®. Because of its volatile characteristics inherent in alcoholic compositions, this device suffers from several limitations and disadvantages. First, when ignited, the heat degenerates the gel to a liquid form, which may spread a fire rapidly if spilled. Further, due to its volatile nature, it emits fumes and a considerable odor when burned which are harmful to the health of those in close proximity. 
         [0006]    Another gelled heat source is disclosed and defined in U.S. Pat. No. 4,302,208. This invention relates to a fuel for fuel air explosive devices for military uses and its composition consists of a polar fuel, silicon dioxide and a mixture of two alcohols. One of the alcohol compositions contains an ether linkage, with volatile characteristics with such limitations as described above. 
         [0007]    Another fuel source is disclosed and defined in U.S. Pat. No. 4,756,719. This invention relates to a composition consisting of a combustible polymer, an organic solvent and a course powder of fiber material. The disadvantage and limitations inherent in organic based fuels are its tendencies to evaporate quickly and emit fumes and odors which may be poisonous or noxious. 
         [0008]    A preferred composition for a gelled fuel heat source is disclosed in U.S. Pat. No. 5,264,003, the full disclosure of which is incorporated herein by reference. In the referenced patent, a gelled mixture made up of DEG and treated is described for the purpose of providing a portable ration heat source. The present invention provides an improved mixture composition and an improved method of manufacturing the fuel gel. 
         [0009]    It is therefore, an object of the present invention to provide a small efficient gelled fuel heat source primarily for field use in heating food and which is neither poisonous nor noxious and which does not evaporate quickly. It is a further object of the present invention to provide a fuel source which maintains its high degree of viscosity over a long shelf life and during turbulent handling and shipping conditions. 
         [0010]    The present invention represents an improved and novel method for manufacturing a composition. It is characterized by a number of advantages which increases its utility over prior art heat sources. These and other objects and advantages of the present invention will become evident from the following disclosure to those skilled in the art to which this invention pertains. 
       SUMMARY OF THE INVENTION 
       [0011]    The preferred embodiment of the present invention relates to a gelled fuel heat source consisting of diethylene glycol and a fumed silicon product. Use of diethylene glycol as a fuel source has many advantages over the prior art such as alcohol and organic based fuel sources. Diethylene glycol burns clearly without fumes or odor. When mixed with a fumed silica product as a gelling agent, a gel forms with a high degree of viscosity capable of being packaged in an envelope, can, or tube. Addition of the fumed silica product produces good wicking characteristics with a high flash point. Further, the diethylene glycol contributes a high caloric value to the gel which requires only a small portion for each use. The composition may be used directly a field use includes fuel for heating food or as a starter for igniting firewood. 
         [0012]    The above is a mechanical means for gelling, however, several chemical means have also been found to produce desirable results. One chemical means for gelling or solidifying the diethylene glycol is to react the diethylene glycol with stearic acid. When 5%-40% by weight of stearic acid is heated with the diethylene glycol until dissolved, upon cooling, a wax-like candle is formed. Because the material is semi-solid, a conventional wick can be used to ignite the material. If 1%-5% of fumed silica is added to the total mixture, sufficient wicking is provided by the silica alone. One added feature of this mixture, if reacted long enough, is that the material can be used as a soap in addition to being a fuel source. 
         [0013]    A second means of chemically gelling or solidifying diethylene glycol is to react it with 10%-40% by weight of polyethylene glycol. This mixture must also be heated to dissolve the polyethylene glycol. If 1%-5% by weight of fumed silica is added for wicking, an easily ignitable mixture can be prepared which burns with a pale blue flame that is very difficult to extinguish. 
         [0014]    Another means of chemically gelling diethylene glycol is to react it with 10%-40% by weight of polyvinyl alcohol. When heated to 200° F.-300° F. and cooled to room temperature, the mixture forms a rubbery semi-solid material. While burning it melts like a wax candle. 
         [0015]    A preferred means of gelling diethylene glycol is a combination mechanical and chemical process using a batch mixer capable of modifying rotational mixing rates as well as settling times and dispensing modes. the present invention includes many of these advantageous method steps. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0016]      FIG. 1  is a partial cross-sectional view of a batch mixer structured appropriately for implementing the method of manufacturing of the present invention. 
           [0017]      FIG. 2  is a detailed perspective view of the interior of the batch mixer shown in  FIG. 1 . 
           [0018]      FIG. 3  is a detailed perspective view of the edge of the Cowles Blade of the batch mixer of  FIG. 1 . 
           [0019]      FIG. 4  is a schematic block diagram flow chart showing the process of the method of the present invention. 
           [0020]      FIG. 5  is a flow chart showing a sample process of the method of the present invention involving the use of a batch mixer. 
       
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
       [0021]    The composition of this invention is made up by mixing diethylene glycol and a fumed silica product. This very fine silica product increases the viscosity of the diethylene glycol from a liquid to a gelled form. Such silica products are commercially available under the trade names CAB-O-SIL and AEROSIL. Even though the vapor pressure is very low for diethylene glycol, the fumed silica acts like a wick for the mixture and can be easily ignited with a match. The product when heated does not melt or soften but remains in its semi-solid condition. It burns clean with no smoke or odor and leaves only the silica residue. 
         [0022]    It has been discovered that while this composition has desirable viscous characteristics upon formulation, it has a tendency to become less viscous with severe agitation. A trace quantity of a caustic compound when added to the aforementioned composition will stabilize the viscous characteristics of the gelled mixture. Examples of caustic compounds suitable for use include sodium hydroxide, potassium hydroxide, and calcium oxide. Tests have disclosed that traces of a caustic compound in the range of about 0.05%-0.5% by weight is sufficient to retain the gel&#39;s viscous characteristics. The preferred weight percentages for the composition consists of 5%-25% of fumed silica, 75%-95% diethylene glycol and 0.05%-0.5% of a caustic compound. 
         [0023]    In an alternative composition, fly ash may be used to replace some of the more expensive fumed silica in a range of 10%-40% by weight. This substitution may result in more than a 50% formulation cost savings using a mix by weight of fly ash of 40% and a 2% mix by weight of fumed silica. Additionally, the fly ash provides the caustic characteristics which retains the viscous quality of the gelled composition. The composition may be packaged with military field rations where a simple envelop would be used to heat water for soup and coffee. The tubes will also find ready application among the military, scouts, and campers. The canned material can be used. 
         [0024]    The compositions of the present invention when prepared according to the ranges of weight percentages set forth above, may be packaged in a variety of manners. For single use applications, the gel may be packaged in envelopes of aluminum foil, plastics, or plastic lined paper. For multiple use applications, the gel may be packaged in plastic or foil tubes (like toothpaste), and the desired amount can be squeezed out and ignited. Additionally, the gel may also be packaged in metal cans of various shapes. 
         [0025]    As indicated above, the disclosure of the present application is related to the issued patent entitled Gelled Fuel Heat Source; U.S. Pat. No. 5,264,003, the full disclosure of which is incorporated herein by reference. The basic components of the gelled fuel are described therein as comprising a mixture made up of DEG and treated for the purpose of providing a portable ration heat source. 
         [0026]    The present invention relates to the mixing of components, one of which is that of a fuel (DEG) and a media for gelling ( ) all of which allows for a consistent heat source, safe and having little effect on the environment. In an international context characterized by the fast growth in particular heat sources in the outdoor community, there is a need for new greener energy sources that can be integrated in fire starting and field preparation of rations, especially with military application. 
         [0027]    In this respect, integration of new products of safe and green energy sources are in strong demand. Furthermore, the processes known to date that use petrochemical based fuels produce significant emissions, known for their negative effects on the environment. The earlier patent “Gelled Fuel Heat Source” represents an improvement since it provides a composition and a method for heating using only small amounts of a clean efficient fuel for specific purposes. While manufacturing the previous product, it was learned that optimal mixes were possible, greatly more efficient and considerably more economical. 
         [0028]    The previous manufacturing methods however involved several drawbacks. The first drawback lies in the difficulty in achieving a consistent mixture. It was not until research was conducted on the various mixing methods that a more improved product evolved, less costly and much more efficient. The second drawback of prior methods lies in the production of air in the product, and when changed over to a system requiring a vacuum feed, this shortfall was illuminated. Greater heat production was achieved with the increase of the fuel base (diethylene glycol). The final improvement was that of time to mix, it was cut by 50% and at the same time improved mixing safety. With a closed vacuum system of feed there was no opportunity for silicosis in mixing. 
         [0029]    The present invention relates to the method of mixing and the modification of the apparatus used in this process. Prior, all mixing was conducted in a 55 gal barrel using a Cowles blade, which made it very difficult to insure consistent, homogeneous mix. After some research, it was determined that a better mixing system was required and a large mixer was selected that was programmable in both RPM and strata mix time (depth of mix). In order to disperse a silica material ( ) into a glycol (DEG) as a thickening and gelling agent, a system was perfected and developed to insure that a timed mixing, at various strata would be achieved. Also critical to the mix was the mixing container, specially designed to insure complete material turnover and total exposure to the modified Cowles blade, while mixing in a complete vacuum. 
         [0030]    Owing to its low tapped density, fumed silica&#39;s can be a source of nuisance dust if handled incorrectly. Not only is this annoying, it is also something that must be strictly avoided in order to ensure compliance with industrial health and safety regulations. This new system eliminated this problem. The method according to the invention allows better mixing stability through the proper timing of the mix within each stratum without over shearing the mix. 
         [0031]    Similarly, the activity of the modifications to the Cowles blade produces a “pumping” effect, creating additional energies perpendicular to the vortices created by the blade. It is believed that this rapid pulsing, aids in creating the chains of silica needed to form a stabilized gel and to lock this suspension. This new mixing process allows for low dispersing demand due to separation of the high-speed dispersing and low-speed circulation of the batch. With the variable height of the dispersing disk (Cowles blade) a homogeneous cavity free dispersing is achieved. A nearly residue-free discharge is created by wall and bottom scrapers. 
         [0032]    Optimized mixing cycles are operable in conjunction with the described batch mixer of the present invention. These optimized mixing cycles include variations in the order, repetition, frequency, and duration of the various mixing actions. The two basic actions afforded by the batch mixer of the present invention include the angular rotation of the Cowles Blade and the axial displacement of the mixing blade through the upper to lower and back again levels of the batch mixer.  FIG. 5  represents an example of the programmed process for operating the batch mixer that controllably varies the parameters associated with these mixing actions.  FIG. 5  discloses the basic stages of the mixing process and the manner in which the critical Stage II activation of the mixture provides for an end product optimally manufactured for efficient heat production and long shelf life. 
         [0033]      FIG. 1  is a partial cross-sectional view of a batch mixer structured appropriately for implementing the method of manufacturing of the present invention.  FIG. 2  is a detailed perspective view of the interior of the batch mixer shown in  FIG. 1 .  FIG. 3  is a detailed perspective view of the edge of the Cowles Blade of the batch mixer of  FIG. 1 . Batch mixer  10  includes mix containment  12 , scraper blades  14 , containment access port  15 , Cowles blade  16 , Cowles blade shaft  18 , scraper blade drive mechanism  20 , drive motor  22 , containment lid  24 , vertical shaft seal  26 , Cowles blade drive shaft pulley  28 , drive motor  30 , drive belt  32 , and vertical lifter  34 . 
         [0034]      FIG. 2  shows in greater details the internal components of the batch mixer, including scraper blades  36   a  &amp;  36   b,  as well as blades  38   a  &amp;  38   b.  Strata blades  40  extend from these scraper blades as shown. Structural blade drive supports  42  as well as  44   a - 44   c  are also shown.  FIG. 3  shows in greater detail the structure of the modified Cowles blade  16  to include apertures  48   a - 48   n  and  50   a - 50   n  which contribute to the pumping action that the rotating Cowles blade provides. 
         [0035]      FIG. 4  is a schematic block diagram flow chart showing the process  100  of the method of the present invention. These steps generally include the start of the process Step  102  and the initial provision of bulk ingredients at Step  104 . Within closed system  120 , Step  106  involves Ingredient A: Diethylene Glycol (DEG) 93.0%-97.5% by weight. Step  108  involves Ingredient B: Silica Dioxide ( ) 2.5%-7.0% by weight. Step  110  involves optionally Ingredient C: NaCl (salt) or (boric acid). Steps  114 - 118  involve operation of the bulk mixer  112  as described in  FIG. 5  in more detail below. Finally Steps  122 - 126  provide for the dispensing and packaging of the product. 
         [0036]      FIG. 5  represents those steps shown generally in  FIG. 4  comprising operation of bulk mixture  112  programming the rotational RPM at Step  114 , programming the strata mix time at Step  116 , and the operation of the bulk mixer according to the program through Step  118 . Stage I comprising Step  140  in this sub process involves creating a homogenous mixture after the various ingredients identified in  FIG. 4  have been added to the batch mixer. The process of creating a homogenous mixture represents the initial stage of evenly distributing the ingredients throughout the batch by utilizing the Cowles Blade rotation set at a range of RPMs. In addition, the scraper blades associated with the edges of the mixing container are rotated (or counter-rotated) at a variable rpm. Finally, in Stage I, Step  140  of the process, a Cowles Blade is moved axially through the various strata in the mixture from an elevation at a top reference 0 to a bottom reference 10 progressing in timed increments according to the optimal means for obtaining a homogenous mixture. 
         [0037]    Stage II of the process shown in  FIG. 5 , involving Step  142 , represents the activation of the mixture now made homogenous by Step  140  above, wherein the specific functions associated with the pumping and pulsing action of the Cowles Blade in creating energies perpendicular to the vortices created by the blade aid in creating the chains of silica required to form stabilized gel and to lock the suspension of the product. This activation stage at Step  142  involves the variations in the same parameters as described above, namely, Cowles Blade rotation in rpm, scraper blade rotation or counter-rotation in rpm, and the Cowles Blade elevation from top to bottom through the various strata in the mixture. Optimal values for cycling these mixing parameters depend upon the characteristics of the specific product desired and its potential application in the field. 
         [0038]    At Step  144  shown in  FIG. 5 , Stage III of the batch mixing process involves the settling of the mixer in a manner that maintains the suspension achieved through Stage II activation of the mixture. The settling of the mixer while maintaining the suspension involves both the removal of the Cowles Blade from the mixture and the efficient progress into Stage IV, Step  146  of the process, dispensing the batch from the mixer. Efforts are made during the settling and dispensing steps to maintain the suspension by not over-pumping or over-shearing the mixer in the process of removing it from the batch mixer and introducing it into the preferred packaging containers. 
         [0039]    With a closed system; no emission situation is present, and vacuum feeding is optional. 
         [0040]    The composition of this invention is made up of mixing diethylene glycol (DEG) and fumed silica products ( ). This fine silica product increases the viscosity of the DEG from a semi-viscous liquid to that of a gelled form and allowing wicking of the DEG for burning. When ignited the mix does not melt a remains in a semisolid condition. It burns with no smoke or odor and leaves a silica residue, all environmentally “green”. 
         [0041]    Initially, it was discovered that while this composition remained in a gelled form until vibrated, as agitated, it became less viscous and additional caustic materials needed to be added for stability. With research, new mixing procedures achieved desired results of stability and lessened the silica requirements. 
         [0042]    The new preferred weight percentages for the composition consist of 2.5%-7.0% by weight of fumed silica, 97.5%-93.0% of DEG by weight. With this increase of DEG a better burn is achieved releasing greater BTU output and “greener” emissions are achieved. With a more stable composition, it has become easier to achieve better packaging and open new applications for use. 
         [0043]    In the above mentioned U.S. Pat. No. 5,264,003, a fumed silica mix of diethylene glycol is used as a fuel source with the BTU output and heat characteristics similar to liquid propane (LP) and natural gas (NG) flames. The lower limits of the fumed silica&#39;s required for gelling was found to be in the range of 7%-9% by weight, resulting in costly materials and undue residual ash. 
         [0044]    Further research efforts on more specific fumed silica with special treatments has allowed the amount of silica to be reduced to the lower range of 3%-2.5% by weight greatly increasing BTU output, and reducing costs. With the reduction of the silica ( ), additional fuel (DEG) could be brought into the gel formulation increasing the heat output and length of burn improving emissions. 
         [0045]    In addition, further research has found that the type of mixing at various strata levels, as well as the methodology of how the batches are mixed at a higher shear rate was achieved, producing a more homogenized mix resulting in a cleaner burn, thusly becoming more “green”. 
         [0046]    Additional research has resulted in mixing blade modification which creates a pumping effect, reduces time of mix decreasing cost and further increases combustion efficiency. This modification has reduced the amount of material being used, thusly reducing the amount of released into the environment. Add to this new methodology, new flame colors have been achieved with the addition of minor amounts of various salts. For example NaCl (table salt) will give off a reddish flame, more visible in daylight for safety. Boric acid in small amounts imparts a green flame. The final change comes from the modification of the use of a system using a vacuum, which removes all opportunities for air entraining and produces a clear gel, and allows for continuous mixing on demand. 
         [0047]    Although the present invention has been described with a number of preferred embodiments associated with the systems and methods described, those skilled in the art will recognize modifications to these system and method embodiments that still fall within the scope of the invention. Variations in the size, structure, and operation of the bulk mixer described as appropriate for the implementation of the present invention that may be required according to the specific quantity and characteristic needs of the product are anticipated. Also anticipated are variations in the type and quantity of additives to the basic ingredients described that perform secondary functions (such as flame color) in the use of the end products achieved by the method of manufacturing described. Various levels of automation in the operation of the system are also anticipated. A given mixing process may be readily implemented through the operation of a computer controlled programmable mixing batch mixer or through the manual operation of a mixer capable of implementing the same mixing actions described above. Such variations as to quantity, size, and duration of the steps within the mixing process are anticipated to fall within the spirit and scope of the claimed invention.