US3231345A - Shaped-form stable rigid compositions and their preparation - Google Patents

Description

United States Patent 3,231,345 SHAPED-FORM STABLE RiGiD CUMPOSITIQNEZ AND THEIR PREPARATION Charles R. Wilder, Bartlesville, Okla, assignor to Phillips Petroleum Company, a corporation of Delaware No Drawing. Filed Mar. 15, 1962, Ser. No. 180,003 6 Claims. (Ci. 447) This invention relates broadly to shaped form stable, rigid hydrocarbon-containing compositions. In accordance with one aspect, this invention relates to shaped hydrocarbon-polymer compositions which are not deformed during the process of burning and the ordinary forces of gravity. In accordance with another aspect, this invention relates to a method for preparing shaped form-stable, rigid articles from a minor proportion of a normally solid polymer and a major proportion of a normally liquid hydrocarbon. In accordance with a further aspect, this invention relates to a novel fuel package comprising a shaped form-stable hydrocarbon-polymer article confined and sealed within a combustible covering material that is substantially impervious to hydrocarbon liquid and vapor flow therethrough.

Heretofore, there has been developed a considerable art relative to the manufacture of gelled fuels, the principal purpose of such product being as incendiary compositions for use in military operations. In some instances, highly viscous solutions of natural or synthetic rubber in gasoline or similar hydrocarbon fuels have been used for such applications. However, these solutions are viscous liquids which flow to take the form of the containing vessel and are adhesive to surfaces with which they are contacted. By increasing the concentration of the rubber, viscosity is increased but even at high concentrations of rubber, such compositions are not form-stable.

Recently, it has been discovered that new and useful compositions comprising liquid fuels or hydrocarbon frac tions and normally solid polymers can be prepared which exhibit a physical state and appearance, which are, quite unexpectedly, those of the polymer alone in the sense that the composition obtained is a relatively hard or rigid material. Although compositions of varying degrees of hardness are obtained, the composition is at all times a solid, as distinguished from the semi-solid viscous character of a gel or the oily and syrupy character of an oil. The resulting products are form-stable solids at ambient conditions and are readily ignitible and burn freely.

While it is one of the advantages of these fuel compositions that they are form-stable under conditions of storage and shipment, it has been found that when ignited, they melt from the heat of combustion and unless contained, tend to flow to a greater or lesser extent. The loss of form stability of these fuel compositions during burning limits the applicability of these fuels for some purposes and can prevent complete burning when in contact with metal or other heat conducting materials, and further can lead to fire hazards when not confined. Furthermore, these fuels burn at a fixed rate, frequently providing more heat than necessary for the use to which they are applied, with a corresponding reduction in burn time. In other words, these compositions cannot be turned down.

The present invention relates to novel form-stable shaped'compositions formed from normally-solid polymers and normally-liquid hydrocarbons, which are not deformed by heat during the process of burning and the ordinary forces of gravity, but which retain their form stability or geometric form throughout burning, and to a method of preparing these compositions.

Accordingly, an object of this invention is to provide a form-stable rigid composition derived from a normally 3,231,345 Patented Jan. 25, 1966 solid polymer, the normally solid polymer constituting but a minor proportion of the product.

Another object of this invention is to provide a method for the preparation of a shaped hydrocarbon-polymer fuel product or body that is form-stable when subjected to heat and burning.

A further object of this invention is to provide a rigid geometrically-shaped fuel body adapted to be stored for long periods of time without loss of hydrocarbon fuel.

It is a further object of this invention to provide a form-stable igniting composition which can be conveniently and safely packaged and yet which is readily available for use when needed. I

Other aspects, objects and the several advantages of this invention are apparent from a study of this disclosure and the appended claims.

According to the invention, a form-stable hydrocarbon composition, which is not deformed by heat or the ordinary forces of gravity, is provided which comprises a solid or rigid combustible composition comprising a major proportion of a normally-liquid hydorcarbon and a minor proportion of a normally-solid polymer selected from high molecular weight polymers of l-olefins of 2 to 8 carbon atoms, a trans-diene polymer of a 4-5 carbon atom conjugated diene, and mixtures thereof, and, per 100 weight parts of said combustible composition, from about 5 to about 20 weight parts of at least one finelydivided substantially anhydrous pyrogenic oxide selected from the group consisting of the oxides of Al, Zr, Ti and Si.

According to the invention, it has been discovered that the versatility of solid fuels formed from normally liquid hydrocarbons and normally solid polymers, as described herein, is substantially extended by incorporating therein a small amount of a finely-divided pyrogenic oxide as defined herein. By such incorporation, the hydrocarbonpolymer compositions remain form-stable throughout the burning period. Thus, flow from the burning site or sticking to the environment does not occur and burning of the fuel is complete. A further advantage of the improved hydrocarbon-polymer compositions of the invention lies in the reduction of burning rate that is realized. It has been found that by incorporation of about 10 parts by weight of one of a finely-divided pyrogenic oxide, e.g., SiO per 100 parts of total hydrocarbon-polymer mixture, burning time is at least double that observed in its absence. For example, a pellet which, in the absence of the finely-divided pyrogenic oxide additive, will be completely consumed in about five minutes will continue to burn for ten minutes, or longer, if it contains at least 5 parts per 100 of the oxide.

The polymer portion of the solid or rigid fuel compositions of the invention comprises one of the high molecular weight l-olefin polymers obtained from polymerizing l-olefins having from 2 to 8 carbon atoms per molecule, a trans-polymer of a conjugated diene having 4 to 5 carbon atoms, and mixtures thereof.

The term polymers of l-olefins includes homopolymers of the above described l olefins' as well as copolymers of these l-olefins with each other. Representative examples of suitable l-olefins include ethylene, propylene, butene-l, pentene-l, hexene-l, heptene-l, 4-methylpentene-l, S-methylhexene-l, 4,4-dimethylhexene-1, 4- ethylhexene-l, octene-l and the like. Suitable olefin polymers include polyethylene, polypropylene, poly-1- butene, poly-l-pentene, and the like, as well as copolyrners of ethylene with minor amounts, generally 5% or less, of propylene, l-butene, l-hexene, b'utadiene, isoprene and the like. The preferred ethylene polymers have a density ranging from 0.93 to 1.0, preferably 0.94 to 0.98. The preferred polypropylenes and poly-l-butenes have an isotactic content of at least The more preferred polymers are polyethylene and particularly polyethylene having an average molecular weight greater than 100,000 (as determined from inherent viscosity).

The preferred olefin polymers or polyolefins as described herein can be prepared according to the method described and claimed in US. Patent 2,825,721 to Hogan and Banks. However, the polymers applicable according to the invention can be prepared by any known method so long as the polymers have the above-described properties. The olefin polymers can be prepared by any of the known solution processes as Well as the particle form process (polymerization of l-olefin is carried out in suspension and below temperature at which anysubstantial portion of the polymer formed is in solution in the suspending medium).

The trans-diene polymers used in the fuel compositions of the invention include high trans-polybutad-iene, high trans-polyisoprene, high trans-polypiperylene, and naturally occurring polymers of high trans-content such as balata and gutta percha. These trans-diene polymers ordinarily have at least 70% of their molecular structure in the trans-1,4-configuration, preferably at least 85% of the polymer formed by trans-1,4 addition of the conjugated diene.

The synthetic trans-diene polymers are prepared from 1,3-butad-iene, isoprene or piperylene using any suitable polymerization procedure by which such structures can be obtained. One convenient process for the production of such polymers involves solution polymerization of a conjugated diene having 4-5 carbon atoms in the presence of an initiator system comprising lithium aluminum hy dride and titanium tetra-iodide. Polymers prepared in this manner will contain 90% or more of materials of trans- 1,4-configuration.

It is also within the scope of the invention to employ polymer mixtures of the l-olefin polymers and trans-diene polymers in all proportions. The mixture of trans-diene polymer and olefin polymer can be made by conventional dry blending of the polymers after which the polymer blend is incorporated along with the pyrogenic Oxide in the liquid hydrocarbon, or the two polymers and pyrogenic oxide can be sequentially or simultaneously added separately to the liquid hydrocarbon.

The solid or rigid fuel compositions of the invention can be prepared from normally-liquid hydrocarbons which boil as low as hexane and as high as heavy cycle oils, i.e., about 100 F. to about 900 F. Ordinarily, hydrocarbons boiling from about 200 to about 700 F. are preferred. Hydrocarbons that can be employed include saturated and unsaturated acyclic, saturated and unsaturated cyclic and aromatic hydrocarbons, or combinations or mixtures thereof. Paraflinic materials, including hexanes, octanes, decanes, dodecane, pentadecane, and the like, as well as mixtures of these materials are preferred when smokelessness is particularly desirable. Petroleum refinery hydrocarbon fractions such as gasolines, kerosenes, stove oils, furnace oils, gas oils, cycle oils, diesel oils, crude oil, topped crude, and the like are especially useful in the invention. Hydrocarbon fractions having flash points ranging from about 100 F. to about 250 F. are usuallypreferred, Hydrocarbons or mixtures most preferred are those boiling between about 300 and about 500 F.

The proportions of hydrocarbon and polymer employed for preparation of the solid or rigid fuel compositions of the invention depend upon the nature of the hydrocarbon and more particularly upon the nature of the polymer. In general, the fuel composition will contain from about 4 to about 40 weight percent of polymer or polymer blend, ordinarily from about 5 to about weight percent of polymer or polymer blend, and the remainder a hydrocarbon as defined above. The hydrocarbon-polymer compositions prepared according to the invention ordi narily have a gross heat of combustion ranging from about. 20,000 to about 21,000 B.t.u.s per pound.

According to the invention, the form stability of shaped articles formed from the hydrocarbon-polymer or polymer blends of the invention is materially improved by incorporating therein, based on weight parts of hydrocarbonpolymer mixture, from about 5 to about 20 weight parts of a finely divided pyrogenic oxide. By finely-divided pyrogenic oxides is meant nonhydrated and substantially anhydrous (i.e., not over about 5% volatile matter) oxides having an average discrete particle size of not over 100 millimicrons, preferably less than 50 millimicrons, and! produced by vapor phase hydrolysis or oxidation of com-'- pounds of the corresponding metals and/or metalloidsz. Such vapor phase reactions are generally carried out at; temperatures of about 1000 F. or higher. For example,. halides or other vaporiza-ble compounds of one or more of the stated elements (Al, Zr, Ti and Si), may be mixed! with high temperature steam or carried into a combustionzone in which excess oxygen is present or in which high' temperature water vapor is being produced by combustion of a hydrogen-containing fuel. The resultant reaction produces a fine aerosol of solid oxides or mixed oxides in gaseous by-products from which the oxides may be recovered in aerogel form made up of very small discrete particles. Since the gaseous by-products are separated from the solid oxide at temperatures above that at which any of said by-product condenses, the resultant oxides are not hydrated and, instead, are very pure and substantially anhydrous. For example, silica produced in this way is about 99% pure, while alumina of this type usually con"! tains about 5% or less volatile matter. 7

As indicated above, combination of more than one type of polymer can be used, if desired, according to the invention. Furthermore, small amounts of other solid hydrocarbon materials such as paraffin wax can also be added if desired. The compositions are also receptive to conventional oil-soluble dyes and pigments for decorative effects or identification purposes.

In the exercise of this invention, the hydrocarbon, polymer or polymer blend, and finely-divided pyrogenic oxide are brought together in a vessel or other suitable apparatus and blended at a temperature and for a sufiicient length of time to yield a homogeneous mixture.- The temperature employed should be kept below that at which any appreciable degradation occurs. Temperatures of 10 to 60 C. above the melting point of the polymer or polymer blend have been most found satisfactory for' the blending operation. The temperature employed during blending will vary depending upon the polymer employed, i.e., olefin polymer or trans-diene polymer or a mixture of the two, in the polymer portion of the composition. However, in general, the temperature utilized will range from about 40 to about C. and if this temperature is above the boiling point of the hydrocarbon, the operation is carried out in a pressurized vessel to maintain the component substantially in the liquid state. The blending operation is carried out until the contents of the vessel are completely homogeneous as indicated by its physical appearance, and agitation and milling or other forms of mixing during the plending period is generally desirable. As little as 2 minutes at the higher temperature may be sufficient or as long as 24 hours may be required at a lower temperature. Also, blending time will be dictated by the particular blending apparatus em-- ployed. Blending of the polymer and hydrocarbon and pyrogenic oxide according to the invention can be carried. out under batch, semi-continuous or continuous conditions; using suitable equipment therefor.

As'indicated above, any kind of oil-soluble pigment: used in adding color to paints can be used to color the compositions of the invention. It is within the scope of the invention to add coloring material during blending toassist in determining the degree of mixing since unblended' particles of polymer appear white, and, therefore, can

be easily detected. This provides a convenient means for determining when a homogeneous mixture is obtained.

After the homogenization is complete, the mixture of polymer, hydrocarbon and pyrogenic oxide is allowed to cool and solidify, preferably without agitation. It is generally desirable to transfer the hot and still fluid product to a more convenient location before solidification begins where the desired geometrical shape of the finished product can be obtained. The solidified hydrocarbon according to the invention can be cast or molded into pellets, disks, briquets, spheres, cubes, logs, twigs or bars or any shape possible with a hot viscous liquid and in any size depending upon the apparatus available and its capacity for heating, cooling and handling. When desired, the fuel composition of the invention can be extruded as rods or cylinders and cut into disks or other shapes of suitable sizes for difierent applications. When desired, the extrudate can be coated, either before or after cutting, with either a combustible or non-combustible material depending upon the ultimate use of the product. When a mold is used, it is frequently desirable to preheat the mold in order to prevent premature harden ing before the desired shape is attained.

When the product has solidified sufiiciently, the product can be packaged and sealed within a suitable wrapping material or a coating or sealer can be applied prior to packaging or further use of the product. When desired to avoid all or substantially all loss of hydrocarbon by evaporation, such as in storage, the product can be stored in a container or wrapper that is substantially impervious to hydrocarbon liquid or vapor flow therethrough, e.g. aluminum foil, metal cans, glass jars and bottles, cellulose acetate, cellophane, Mylar (saturated polyester film), Saran (polymer of vinylidene chloride), polyvinyl alcohol, polyvinyl chloride bags, and the like, capable of withstanding. temperatures and pressures which may be reached under the conditions of storage. Further, application of a thin coating of a substantially non-porous resinous or plastic solid material to the solidified hydrocarbon product which effectively seals the same and prevents substantially all loss of volatiles therefrom can be employed. The coating can be conveniently applied by dipping, but can also be applied by spraying, brushing or other means. Coatings which are satisfactory for the purposes are commercial cellulose acetate-butyrate resins dissolved in a xyleneketone solvent for purposes of application of the coating. Other coating materials that can be employed include cellulose nitrate-type lacquers, phenolic coatings, alkyd resins, carboxymethylcellulose, thermosetting resins such as phenol formaldehyde, melamine resins, and the like.

The utility of the form-stable shaped compositions of the invention is readily apparent. These novel compositions are non-tacky, can be cut to any desired shape or size, and will retain their original form indefinitely. The compositions of the invention are useful as a quick source of heat for numerous applications. Since they are for rnstable during burning as well as under storage conditions, they are particularly useful as a replaceable element for candle lighters, cigarette lighters, fire starters and the like. They can be used as fuels for quick cooking and a source of heat for on-the-job repairs, starter fuel for outdoor grills and fireplaces and numerous other applications in which a quick, clean and readily portable source of heat is desired. They can be cast into large cylinders for use as outdoor warning lights for temporary street repairs or construction in which application they are preferably employed in spring-fed cylinders by which means end burning is realized. However, if desired, such cylinders can be covered with a non combustible material such as asbestos, asphalts, pitches, etc. to restrict the area of burning to end burning and, thereby, extend burning life of the product.

Further, according to the invention, a safe readily ignitible solid fuel composition which has just the right balance of properties for an ideal all-purpose lighter is provided. The ideal igniting compound should be readily ignitible by a match and should burn with a hot flame for a sufficient length of time to ignite the solid fuel near which it is located. Yet it should have a relatively low and controlled volatility so that it can be readily and safely handled, stored and transported. All of these qualities are found in the novel compositions of the invention.

A better understanding of the invention can be obtained by referring to the following illustrative examples which are not intended, however, to be unduly limitative of the invention.

Example I A solution of 20 grams of trans-polybutadiene (91% trans, 25 ML-4 230 F.) in 200 ml. of white mineral oil was prepared by heating at about C. on an oil bath. A portion of this solution was poured into ball molds and allowed to cool (Sample A). Another portion ofthe solution was poured over 10 grams of finely divided silicon dioxide (Cab-O-Sil) and stirred to form a slurry. This slurry wastransferredto the ball moldand allowed to cool (Sample B). Burning tests were made by placing one ball from each sample on ametal sheet and igniting. Data on'these tests are shown below:

A solution was prepared by heating the following materials at 100 C. on an oil bath:

Trans-polybutadiene (same as above) -gr 15 Soltrol 170 .(isopara'ffinic HC) ml Normal heptane ml 150 White mineral oil ml 75 Soltrol 170 is a commercial isoparaflinic solvent having a boiling range of about 420475F. and a specific gravity of 0.77. When the polymer was completely dissolved, 30 grams of silicon dioxide (Cab-O-Sil) was added with stirring. The system formed a gel which was transferred to a mold and formed into balls about 1 inch in diameter by cooling. One ball was formed from a similar solution which contained no silica. Burning tests on these materials provided the following data:

Silica Burn Time, Burning Behavior minutes None 5-6 Mellteizd and flowed over area. Stuck to p a e. Present. 15-18 No melting. Did not stick to plate.

Example III A solid fuel composition was prepared by heating 20 grams of high density polyethylene (0.96 density) with 200 ml. of Soltrol 170 (isoparatfinic hydrocarbon) at C. on an oil bath. The solution Was divided into two equal portions, to one of which was added 10 grams of finely divided silicon dioxide (Cab-O-Sil). Balls about 1 inch in diameter were molded from each portion. Burning tests were made as described above. Results of these tests are shown below.

Example IV A series of tests was made to determine the comparative effect of other materials than the silicon dioxide employed in the previous runs. For these tests the polymer 7 used was trans-polybutadiene (same as used in Example 1). Thirty grams of this polymer was added to 300 ml. of Soltrol 170 and heated at 100 C. until dissolved. From this solution, 50 ml. portions were molded into cylinders, 5 grams of additive being incorporated in each 50 m1. portion for each test. Data on these runs are shown below.

@ Hydrous aluminum silicate (particle size 2 microns).

Precipitated calcium carbonate (0033-0040 micron).

* Hydrated calcium silicate (av. particle size 0.03 micron).

' Hydrated silica pigment (particle size 0,022 micron, 87% SiOz).

0 Silicon dioxide (particle size 0.015-0020 micron, 99.0-99.7% SiO These data show that when using silicon dioxide, long burning, fully form stable compositions are obtained while with other siliceous materials, the advantages are not realized.

Although the preceding examples have employed pyrogenic silica (SiO as the sole pyrogenic oxide, it should be realized that other finely-divided pyrogenic oxides such as A1 0 TiO and ZrO can be used as the sole oxide or mixtures of two or more pyrogenic oxides can be employed according to the invention to provide a form-stable solid fuel composition. Mixed pyrogenic oxides in which silica is the predominating ingredient, i.e., at least 50% by weight being silica (99% SiO are usually superior and are preferred when mixtures are utilized. Mixed oxides can be either mechanical mixtures of two or more separate pyrogenic oxides or a single uniform product containing two or more oxides conformed in a single pyrogenic process.

As will be evident to those skilled in the art, many variations and modifications of this invention can be practiced in view of the foregoing disclosure. Such variations and modifications are clearly believed to come within the spirit and scope of the invention.

I claim:

1. A form-stable shaped fuel composition which is not deformed by heat or the ordinary forces of gravity comprising 96-60 weight percent of a normally liquid hydrocarbon boiling at a temperature from about 100 F. to

about 900 F., 4-40 weight percent of a normally-solid polymer selected from the group consisting of polymers formed by polymerizing at least one l-olefin having 2-8 carbon atoms per molecule, trans-diene polymers having ;at least about percent trans-configuration formed by polymerizing at least one conjugated diene having 4-5 carbon atoms per molecule, and mixtures thereof and per weight parts of polymer and liquid hydrocarbon, from about 5 to about 20 weight parts of at least one sub stantially anhydrous pyrogenic oxide having an average particle size less than 100 millimicrons selected from the group consisting of oxides of Al, Zr, Ti, and Si.

2. A composition according to claim 1 wherein said composition is encapsulated within a material substantially impervious to hydrocarbon flow therethrough.

3. A composition according to claim 1 wherein said normally-solid polymer is a mixture of a polymer formed by polymerizing at least one l-olefin having 2-8 carbon atoms per molecule and a trans-diene polymer having at least 70 percent trans-configuration formed by polymerizing at least one conjugated diene having 4-5 carbon atoms per molecule, said hydrocarbon boils at a temperature in the approximate range of 300 F. to 500 F., and said finely divided pyrogenic oxide is predominantly composed of SiO 4. The composition of claim 3 wherein said polymer is a mixture of polyethylene and polybutadiene.

5. A method of preparing a form-stable shaped fuel composition which comprises blending together 4-40 weight percent of a normally-solid polymer selected from the group consisting of polymers obtained by polymerizing at least one l-olefin having 2-8 carbon atoms per molecule, trans-diene polymers obtained by polymerizing at least one conjugated diene having 4-5 carbon atoms per molecule, and mixtures thereof, 60-96 weight percent of a normally-liquid hydrocarbon fuel boiling at a temperature of from about 100 F. to about 900 F., and based on 100 parts of polymer and hydrocarbon, 5-20 Weight parts of at least one pyrogenic oxide having an average particle size less than 100 millimicrons selected from the group consisting of oxides of Al, Zr, Ti, and Si at a temperature above the melting point of the polymer and for a period of time such that a homogeneous liquid mixture is obtained, cooling and shaping said mixture to form a rigid composition of a desired geometrical configuration, and recovering said shaped composition.

6. The method of claim 5 further comprising sealing said shaped composition within a substantially hydrocarbon impervious material to prevent loss of hydrocarbon from said composition.

References Cited by the Examiner UNITED STATES PATENTS Kelly et al. 44-7 DANIEL E. WYMAN, Primary Examiner.

Claims (1)

1. A FORM-STABLE SHAPED FUEL COMPOSITION WHICH IS NOT DEFORMED BY HEAT OR THE ORDINARY FORCES OF GRAVITY COMPRISING 96-60 WEIGHT PERCENT OF A NORMALLY LIQUID HYDROCARBON BOILING AT A TEMPERATURE FROM ABOUT 100*F. TO ABOUT 900*F., 4-40 WEIGHT PERCENT OF A NORMALY-SOLID POLYMER SELECTED FROM THE GROUP CONSISTING OF POLYMERS FORMED BY POLYMERIZING AT LEAST ONE 1-OLEFIN HAVING 2-8 CARBON ATOMS PER MOLECULE, TRANS-DIENE POLYMERS HAVING AT LEAST ABOUT 70 PERCENT TRANS-CONFIGURATION FORMED BY POLYMERIZING AT LEAST ONE CONJUGATED DIENE HAVING 4-5 CARBON ATOMS PER MOLECULE, AND MIXTURES THEREOF AND PER 100 WEIGHT PARTS OF POLYMER AND LIQUID HYDROCARBON, FROM ABOUT 5 TO ABOUT 20 WEIGHT PARTS OF AT LEAST ONE SUBSTANTIALLY ANYHYDROUS PYROGENIC OXIDE HAVING AN AVERAGE PARTICLE SIZE LESS THAN 100 MILLIMICRONS SELECTED FROM THE GROUP CONSISTING OF OXIDES OF AL, ZR, TI, AND SI.