MXPA01009182A - Method of reducing fumes from a vessel of molten asphalt - Google Patents

Abstract

In a method of melting asphalt (24) in a vessel (10), the molten asphalt normally emitting fumes, 0. 2 weight percent to 6 weight percent of a polymer is added to the asphalt to reduce the visual opacity of the fumes by at least 25%over the same asphalt without the polymer. In another embodiment, the total emissions of benzene soluble suspended particulates is reduced by at least 15%over the same asphalt without the polymer. Preferably, the added polymer has a melt flow index of from 15 grams/10 minutes to 95 grams/10 minutes, and the added polymer reduces the visual opacity of the fumes by forming a skim on the upper surface of the molten asphalt.

Description

METHOD TO REDUCE VAPORS OF A CASTED ASPHALT CONTAINER TECHNICAL FIELD AND INDUSTRIAL APPLICABILITY OF THE INVENTION This invention relates generally to asphalt materials for use in roofing, paving and other applications. More particularly, this invention relates to a method for reducing vapors that are emitted from a molten asphalt container. The invention can be useful for providing asphalt for use in places where the vapors of the molten asphalt are considered. BACKGROUND OF THE INVENTION The asphalt of the processing facilities and terminals is transported to end users in one of several ways, including direct pipes of molten asphalt to nearby customers, boarding in cast form by tank car or tanker truck, barge and wagons railways, and boarding in solid form in individual packages. The packages are used primarily by construction contractors as a source of asphalt for roofing applications. The contractor typically places the solid asphalt in a heated pot to melt the asphalt for use. Asphalt shipped in molten form is also usually heated more in a kettle before use.

A problem associated with these heated molten asphalt kettles is that they can emit significant amounts of vapors. Vapors can be unpleasant and irritating to workers and others in the neighborhood. Accordingly, it would be convenient to reduce the amounts of vapors that are normally emitted from a pot or kettle or other container of molten asphalt. It would also be convenient to reduce the release of vapors and odors, without substantial modification of the processed or raw asphalt. In contrast to known polymer modified asphalt compositions, which are highly modified materials where the polymer is employed, for example, to impart elongation properties, an asphalt without this modification is desired for many applications. It would also be convenient to reduce the release of vapors and odors from molten asphalt while allowing a convenient improvement adjustable to the user's size or alteration of the properties of the asphalt. In addition, it would be convenient to produce a low vapor release asphalt in a convenient package. Individual packs of asphalt are typically formed in conventional asphalt processing facilities, by pouring molten asphalt into containers made from a metal bottom and cylindrical paper side walls. The asphalt is typically emptied at temperatures of approximately 177 ° C (350 ° F) and the packs are allowed to cool for up to 24 hours before shipment. One problem with existing asphalt packs is that the removal of the metal and paper container from the solid asphalt is time-consuming. Discarding the metal and paper container material is also a burden. Therefore, it would be convenient to be able to pack asphalt in individual packages and yet eliminate the need to remove the container or discard the container. In particular, it would be convenient to provide an asphalt container that is consumable in such a manner that it melts together with the asphalt. WO 96/40838 discloses a method for reducing vapors from a molten asphalt container by adding a polymer in the form of nodules to the molten asphalt. However, there is no suggestion of adding the nodules to the asphalt by first inserting the nodules into a container and then adding the container to the asphalt. There is no suggestion that the nodes should have a certain minimum diameter to slow down the dissolution rate of the polymer in the asphalt. In addition, there is no suggestion to introduce the polymer in an asphalt package simultaneously with introduction of molten asphalt into the asphalt package, to avoid separation of the polymer from the asphalt during removal of the packaging material. EP 0898018 Al describes placing powder or granular surface material in a polymer bag, and then place the bag and its contents in a heater to melt them together. The surface material contains 30% to 40% aggregate and only 1% to 5% polymer. There is no suggestion of any method that introduces polymer into a molten asphalt container. The surface material D2 does not contain any asphalt and does not mix with the asphalt. COMPENDIUM OF THE INVENTION The above objectives as well as other objectives not specifically listed are achieved by a method of melting asphalt, wherein an amount of unmolded asphalt is placed in a vessel and heated to melt the asphalt, the molten asphalt usually emits vapors of the container, the improvement is characterized in that it comprises: adding about 0.2% by weight to about 6% by weight of a polymer to the asphalt, to reduce the visual opacity of the vapors by at least about 25% on the same asphalt without the polymer. In another embodiment, the total of suspended particulate emissions soluble in benzene is reduced by at least about 15% on the same asphalt without the polymer. Preferably, the aggregate polymer has a melt flow index of about 15 grams / 10 minutes to about 95 grams / 10 minutes, and the added polymer reduces the visual opacity of the vapors by forming a cream on the upper surface of the molten asphalt . In another embodiment of the invention, there is provided a method for containing asphalt wherein an amount of molten asphalt is in a container, the molten asphalt normally emits vapors from the container, the improvement is characterized in that it comprises: adding about 0.2 wt.% To about 6% by weight of a polymer to the asphalt to reduce the visual opacity of the vapors by at least about 25% with respect to the same asphalt without the polymer. The asphalt may be added to the container either in solidified form or in molten form. BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 is a schematic perspective view of an embodiment of an asphalt package, including a consumable container filled with asphalt, useful for reducing the vapors and odors of a molten asphalt container according to the invention .

Figure 2 is a cross-sectional view of the consumable container taken on line 2-2 of Figure 1. Figure 3 is a cross-sectional view of a pair of consumable asphalt containers, with one of the containers stacked on the other. Figure 4 is a schematic perspective view of another embodiment of a container for an asphalt package of the invention. Figure 5 is a schematic view of one embodiment of an asphalt package of the invention. DETAILED DESCRIPTION AND PREFERRED EMBODIMENTS OF THE INVENTION Advantageously, it has been found that in addition to a minor amount of a polymer to asphalt, it helps in reducing vapors emitted from a molten asphalt container. The term "container" means any cauldron, kettle, container or other receptacle suitable for containing molten asphalt such as a pot of roofers or roof specialists, an asphalt package, a bulk storage tank, a tank car or tank truck, a rail car or a barge. While the asphalt remains in the container, it can be retained for heating, storage, transport or assortment. The asphalt contained in the container can be placed in molten form, or alternatively it can be placed in the container in solid form and then melted. The polymer material can be added to the container when the asphalt is added to the container, or it can be added later. The polymer material can be added to the container before the asphalt is melted, or it can be added to the asphalt that is already melted. The polymer material can be added in either solid or liquid form. When the aggregate polymer is melted, some of the polymer rises to the upper surface of the molten asphalt in the container, to form a cream that reduces the release of vapors. The term "cream" means a layer, film or coating that floats, forms or is collected on the upper surface of the molten asphalt. Preferably, the polymer forms a cream through at least 80-90% of the upper surface of the molten asphalt and more preferably through substantially all of the upper surface of the molten asphalt. It is understood that when additional asphalt is placed in the container, the cream may break, but usually returns to form quickly on the surface. While not intended to be limited by any theory, it is considered that the cream reduces vapor release from the container by acting as a barrier or cooling cap to the exposure of the molten asphalt to the air. The thickness of the cream is a function of the polymer addition rate minus the dissolution rate of the polymer. The rate of dissolution is a function of fundamental polymer properties, as well as the temperature of the vessel and the level of agitation. The thickness of the cream is usually from about 3 mm to about 13 mm and typically about 6 mm. However, it is considered that a cream thickness of at least about 0.025 mm, more preferably at least about 0.25 mm, is adequate to reduce the release of vapors from the container. The inclusion of polymers to form these creams can be advantageously employed with any asphalt product which is generally heated in an open kettle or cauldron in preparation for use. As used herein, the term "asphalt" is intended to include asphalt bottoms from petroleum refineries as well as naturally occurring vituminous materials such as asphalts, gilsonite, tars and pitches, or these same materials that have been blown into the air or processed or chemically treated in another way. For example, the asphalt can be blown into the air with catalysts such as ferric chloride and the like. The asphalt may be a flux asphalt or bituminous material usually liquid used to soften other bituminous materials for conventional roofing or a paved grade asphalt as well as other types of asphalts, including specialty asphalts such as waterproof asphalts, battery composites and sealants. Mixtures of different types of asphalts can also be used. The polymer added to the asphalt may be any polymer capable of melting and forming a cream with sufficient viscosity on the upper surface of the molten asphalt to reduce vapors release from the kettle. The polymer should have a lower relative density than that of the asphalt in such a way that it rises to the top surface of a pot of molten asphalt, and should be miscible and compatible with the asphalt. Exemplary polymers that may be employed include polyolefin polymers such as polypropylene, ethylene-propylene copolymers and butylene copolymers; ethylene vinyl acetate copolymers; copolymers of acrylates and methacrylates, such as butyl, propyl, ethyl or methyl acrylate or methacrylate copolymerized with ethylene, propylene or butylene; epoxy functionalized copolymers such as a terpolymer of ethylene, butyl acrylate and glycidyl methacrylate, available from E.l. duPont de Nemours & Co. (Wilmington, Delaware) as Elvaloy * 1 AM; and synthetic rubber such as styrene-butadiene-styrene (SBS), styrene-butadiene rubber (SBR), styrene-ethylene-butylene-styrene (SEBS), or terpolymer made from ethylene-propylene diene monomer (EPDM) and its mixtures Preferably, the polymer is selected from polypropylenes, ethylene-propylene copolymers, ethylene-vinyl acetate (EVA) copolymers, ethylene-methyl acrylate (EMA) copolymers, synthetic rubbers and mixtures thereof. Particularly preferred are ethylene-methylacrylate copolymers and ethylene vinyl acetate copolymers. Useful ethylene vinyl acetate copolymers preferably have a vinyl acetate content of from about 5% to about 40% by weight, more preferably from about 9% to about 28% by weight, such that they are conveniently soluble in the asphalt. Preferred ethylene vinyl acetate copolymers include the Elvax ™ series from duPont, such as Elvax 360 to 750, preferably Elvax 450 or 470. Ethylene vinyl acetate copolymers are also available from USI Chemicals under the trademarks Ultrathene ™ and Vynathene ™. The cream preferably is sufficiently viscous such that it remains attached as a continuous layer to reduce vapor evolution of the container. If the viscosity of the cream is very low, vapors from the molten asphalt may break through the holes in the cream and escape from the container. In contrast, if the viscosity is very high, the polymer will not easily form a continuous cream over the entire exposed surface of the asphalt, nor will it redisperse or dissolve easily in the bulk asphalt over time. To provide a preferred viscosity, the aggregate polymer preferably has a melt flow index of from about 15 to about 95 grams / 10 minutes, more preferably from about 25 to about 85 grams / 10 minutes, and even more preferably from about 35 to approximately 75 grams / lOminutes. A lower melt flow index generally indicates a more viscous polymer. The melt flow index is measured at 190 ° C (374 ° F) under a load of 2.16 kg, according to method B ASTM D1238. Although a wide range of polymeric materials are useful in the invention, the polymer selected for use with a particular asphalt should not undesirably modify the properties of the asphalt in the aggregate amount. For example, when asphalt is intended to be used as an asphalt for roofing, it is preferred that both the asphalt without (before addition of) the polymer, and with the polymer, meet the requirements for at least one type of asphalt roofing. in accordance with ASTM D312, more particularly ASTM D312-89. Accordingly, it is preferred that the addition of the polymer to the asphalt reduces vapor evolution, but does not significantly change the properties of the asphalt. More preferably, the asphalt with the aggregate polymer meets the following specifications ASTM D312 for a type III roofing asphalt: softening point (by ASTM D36) of 85 to 96 ° C (185 to 205 ° F); flash point of 246 ° C (475 ° F) minimum; penetration (by ASTM D5) at 0 ° C (32 ° F) of 6 dmm minimum, at 25 ° C (77 ° F) of 15-35 dmm, and at 46 ° C (115 ° F) of 90 dmm maximum; ductility (per ASTM D-113) at 25 ° C (77 ° F) of 2.5 cm minimum; and solubility (by ASTM D2042) in trichlorethylene of at least 99%. Preferably, the addition of the polymer to the asphalt does not change the softening point of the asphalt by more than about 9 ° C (48 ° F), more preferably not more than about 3 ° C (37 ° F), and does not change the penetration of asphalt in more than about 10 dmm at 25 ° C (77 ° F). further, in some cases, the selected polymer for use with a particular asphalt and the aggregate amount, may be selected to improve the physical properties of the resulting composition. For example, the selected polymer for use with cold flow paving asphalts can be advantageously selected to improve the properties of these asphalts, such as their high temperature performance as measured for example by the specification of the Strategic Highway Research Program (SHRP = Strategic Highway Research Program) of the Federal Highway Association. Exemplary polymers for improving the paving properties of asphalt include ethylene-vinyl acetate copolymers, styrene-butadiene-styrene rubber, polypropylene and ethylene-methyl acrylate copolymers. The polymer is typically added to the asphalt in an amount sufficient to reduce the visual opacity of the vapors in the container by at least about 25% with respect to the same asphalt without the polymer. The visual opacity of vapors is a measure of the blocking of natural light by vapors. The more vapors are emitted from the container, the greater the visual opacity. Conversely, a reduction in visual opacity indicates a reduction in the amount of vapors emitted from the vessel. Preferably, the polymer is added in an amount sufficient to reduce the visual opacity of the vapors by at least about 35%, more preferably at least about 50 to 60%, and even more preferably at least about 70 to 80%. The reduction in visual opacity of the vapors increases at higher temperatures, when steam evolution is worse with conventional asphalt products. Asphalt roof kettles are typically heated to temperatures from approximately 232 ° C (449 ° F) to approximately 288 ° C (550 ° F). Preferably, the aggregate polymer reduces the visual opacity of the vapors by at least about 35% at 260 ° C (500 ° F), and more preferably at least about 50% at 260 ° C (500 ° F). In addition, the total emissions of benzene-soluble suspended particles from the vessel are typically reduced by at least about 15% on the same asphalt without the polymer. Preferably, the total is reduced by at least about 25%, still more preferably at least about 40 to 50%, and even more preferably at least about 60 to 70%. The total emissions of benzene-soluble suspended particles are made up of small particles of benzene-soluble solids present in the vapors, so that a reduction in these particulate emissions indicates a reduction in the amount of vapors emitted. Preferably, the total of suspended particulate emissions is reduced by at least about 25% to 260 ° C (500 ° F) and more preferably at least about 50% at 260 ° C (500 ° F). To provide a polymer cream that achieves these reductions in vapor release, the concentration of the polymer is preferably sufficient to form a cream over the entire exposed surface of the asphalt in the container. Preferably, the amount of added polymer is within the range of from about 0.2% to about 6% by weight, based on the total weight of the asphalt and polymer. More preferably, from about 0.2% to about 2% and even more preferably from about 0.3% to about 0.5% polymer, are added based on the total weight of the asphalt and the polymer. At these levels, the amount of vapors normally emitted from a molten asphalt container is significantly reduced without any noticeable modification of the properties of the asphalt. The polymer in general can be added to the asphalt in almost any way to reduce vapor release. The polymer can be added to the asphalt before it is transported to the end user or the polymer can be added to the asphalt by the end user. The end user can add the polymer directly to the molten asphalt container. The polymer can be added to the asphalt in liquid form or in solid form, for example in the form of nodules, granules, flakes, particles, powders or other structured forms (hereinafter referred to collectively as "nodules"). The addition can also arrive in any of the above encapsulated or otherwise contained forms in a polymer bag, which can be easily added to any asphalt container. When the polymer bag is added to the molten asphalt, the bag melts releasing the contained polymer and polymeric material from the bag. The polymer can be added to the net asphalt, but preferably the polymer is added to the asphalt in the form of a mixture of polymer and asphalt, more preferably a solidified mixture such as polymer / asphalt composite nodes. These polymer / asphalt blends typically provide better reductions in hydrocarbon emissions than the creams resulting from the pure polymer melt, and the presence of the asphalt with the polymer aids in melting the polymer and increases its dispersibility. Preferred polymer / asphalt mixtures, for example polymer / asphalt composite nodes, may contain from about 30% to about 90% by weight polymer and from about 10% to about 70% asphalt. Preferably, these mixtures contain from about 40% to about 80% polymer. More preferably, these mixtures comprise from about 20% to about 60% asphalt and from about 40% to about 80% polypropylene. Convenient polymer / asphalt composite nodes can be formed by co-extruding the asphalt and polymer through a heated extruder, where the materials are heated over their softening points and mixed together, as in conventional extruders and then formed the mouldable mixture in nodules. Accordingly, the polymers used to provide the cream and the asphalts, preferably have melting points and viscosities which are suitable for co-extrusion. Preferred asphalts generally have a ring and ball softening point greater than about 90 ° C (194 ° F) measured in accordance with ASTM D36. It is not necessary that the asphalt component of the nodules be the same as the molten asphalt in the container. Suitable asphalts include asphalt with an air-blown paving grade and air-blown roofing flux in the range of AC-2 to AC-50, more preferably AC-10 or AC-20. Optionally, non-polymeric chemical additives and modifiers such as synthetic wax can be added to the nodule composition. This feature advantageously allows the use of one or a few standard asphalts to fill the container, with the desired chemical additives to optimize the asphalt for the intended application added to the asphalt by the nodules. Additionally, one or more filler materials such as broken stone, glass fibers, talcum, calcium carbonate or silica can be added to the pellet formulation if desired. However, these filling or loading materials would be undesirable in some final uses of asphalt and are generally not preferred. Accordingly, it will be understood that filling or loading materials will be ignored when calculating the percentages of other specified materials in the asphalt.; in this manner, the percentages by weight of ingredients herein given are based on total weights of the materials or compositions excluding any fillers or fillers or the like present in the material or composition. Polymer nodules or asphalt / polymer composite nodes can be of any geometrical configuration and size conveniently formed, which exhibit adequate dissolution and / or melting rates. In general, the rate of dissolution and melting increases as the ratio of surface area to mass increases. Consequently, to obtain the maximum benefit of the polymer, it may be preferred to maximize the mass of the nodule and minimize the surface area to slow the rate of dissolution of the polymer in the molten asphalt. In addition, nodules having a size and shape exhibiting good fluidity can be advantageous in automated processing equipment. For these reasons, spherical nodules having a diameter of about 1.59 mm to about 6.35 mm, and cylindrical nodules having a comparable diameter and length of about 1.59 mm to about 12.70 mm, are generally preferred.

In a preferred embodiment of the invention, the polymer is added to the asphalt and the mixture is formed in a consumable container for the asphalt. The container comprises by weight from about 40% to about 90% asphalt and from about 10% to about 60% polymer. The container is consumable, so that it can be melted together with the asphalt in the container without requiring undue mixing. For a roofing asphalt package, the container preferably does not significantly change the properties of the asphalt (as described above for the addition of the polymer to the asphalt). In this way, the consumable container overcomes problems associated with conventional metal and paper containers. In addition, the added polymer reinforces the container as well as reduces vapors release from the kettle. Consumable asphalt containers can be added to a pot of roofers during the day as required to supply more asphalt for roofing, for example at intervals of 30 minutes to one hour. Now with reference to a preferred embodiment of a consumable asphalt container shown in the drawings, a consumable container 10 is illustrated in Figures 1 and 2. In the embodiment illustrated, the container is generally cylindrical in shape having an open end and a closed end. However, the container can be any other convenient shape, such as a solid rectangular shape. Although rectangular solid shapes can provide efficiencies in shipping and storage, these advantages can be overcome by the advantage of providing separable containers at a convenient distance during the emptying process in order to facilitate rapid cooling. The illustrated embodiment of a consumable container 10 includes a receptacle 11 for containing the asphalt. The receptacle has a cylindrical side wall 12 and a circular base 13 defining a closed end. A pair of concentric annular projections 14 extend downwards from the base a short distance. The projections can increase the dimensional stability of the container. The side wall includes a lower end 15 adjacent to the base and an upper end 16 at a distance from the base. As illustrated in Figure 1, preferably the diameter of the upper end of the side wall is larger than the diameter of the lower end. This structure provides the ability to easily stack a container over another container, as will be described below. In a preferred embodiment, the diameter of the side wall is 35.6 cm at the upper end and 31.8 cm at the lower end. Preferably, the container is molded with a tapered side wall having a lower side wall thicker than the upper side wall to increase the strength of the container. In the illustrated embodiment, the side wall has a thickness of 0.20 cm at the lower end and 0.17 cm at the upper end. The receptacle is approximately 38.1 cm high. An annular flange 17 extends outwardly from the upper end of the side wall, a short distance, preferably approximately 0.64 cm. The container 10 further includes a lid 18 which is generally circular in shape. The lid includes a circular cover 19 and a generally cylindrical skirt 20 extending upwardly from the perimeter of the cover. The skirt includes a lower portion 21 that forms an outward angle from the cover, and an upper portion 22 that angles very slightly outwardly from the lower portion. The outer diameter of the upper portion of the skirt is substantially the same as the inner diameter of the upper end of the receptacle, such that the cover can be received and tightly secured within the upper end of the receptacle. The cap also includes an annular flange 23 extending outward from the skirt portion, a short distance. The receptacle is filled with asphalt 24. Then, the lid is placed in the receptacle to close the container, with the flange of the lid that engages the flange of the receptacle. With reference to Figure 3, it can be seen that the preferred container has a structure that allows a first container 10 to be stacked on a second container 10 ', to reduce shipping and storage costs. The base 13 of the first container is placed inside the lid 18 'of the second container. The side wall 12 of the first container fits within the skirt 20 'of the lid of the second container. Preferably, concentric annular projections 14 of the first container rest on the circular cover 19 'of the second container, which is shown filled with asphalt 24' to form an asphalt package. The container has a weight composition of from about 40% to about 90% asphalt and about 10% to about 60% polymer, more preferably from about 55% to about 75% asphalt and from about 25% to about 45% of asphalt. polymer. It is preferred to use a high proportion of asphalt in the composition of the roofing asphalt container due to the lower cost of the asphalt compared to the cost of the polymer. Also, a higher percentage of asphalt results in greater compatibility with the asphalt in the container.

The container should have a sufficiently high softening point to withstand the high temperatures associated with the molten asphalt, and with shipping and storage, without softening. Preferably, the composition of the container has a ring and ball softening point greater than about 107 ° C (225 ° F), more preferably greater than about 125 ° C (257 ° F). and even more preferably greater than about 149 ° C (300 ° F). The ring and ball softening point can be measured by ASTM D36. The container can be formed by any convenient process. For example, the side wall of the receptacle may be attached to the base. However, preferably the container is formed as an integral or unitary structure by a molding process such as injection molding, blow molding or rotary molding. An injection molding process is particularly preferred. As known to persons of skill in the art, an injection molding process usually involves the use of a heated barrel structure and spindle to heat soften the composition to be molded. The heat-softened composition is then injected into a closed mold, usually by the action of the advancing spindle. The composition cools and solidifies taking the shape of the mold cavity. Molding processes offer advantages in cost, design flexibility and features that can be incorporated into the container. The molding process allows a variety of features to be easily incorporated into the container as desired. For example, the molding process can be used to mold an enhancement in the receptacle or lid for purposes such as labeling, instructions or marketing logos. Preferably, the lid of the container is labeled with the type of asphalt retained by the container. The container can also be adapted with handles, which can be molded in the container for easy handling. In addition, ribs can be molded into the container to increase its strength during the emptying phase in the container. In a preferred embodiment, one or more circumferential ribs are provided on the outer surface of the wall of the receptacle, which remains cooler than the wall during pouring and thus provides dimensional stability to the container. Also, the container may have one or more recesses that accelerate the melting process again by allowing the hot asphalt in the kettle to penetrate interior portions of the asphalt package. The recesses also accelerate the cooling process after the molten asphalt is emptied into the container. An alternate embodiment of a container and asphalt package is illustrated in Figures 4 and 5. With reference to Figure 4, container 100 is conveniently formed, for example by a molding process such as injection molding, blow molding. or rotation. The container can also be formed by joining the side wall 120 to a base or bottom 140. The container 100 can be provided with handles 160 that can be molded into the container for easy handling. To increase the strength of the container to withstand the stress of filling it with molten asphalt during filling, the container can be made with a tapered side wall 120 having a lower side wall portion 180, which is thicker than an upper side wall portion 200. The asphalt pack 110 shown in Figure 5 comprises the container 220 and an asphalt body 240 within the container. The asphalt container may be of any convenient shape such as a rectangular solid shown in Figure 5. The asphalt container may be molded with ribs 260 to provide strength to the container during the phase of emptying and filling the package. As an alternative or in addition to the internal reinforcement ribs, external reinforcement ribs can be provided to help prevent bulging during emptying or filling. As well, the container may have one or more recesses 280, which accelerate the melting process again by allowing hot asphalt in a kettle to penetrate the interior portions of the asphalt package. The recesses also accelerate cooling after the molten asphalt is emptied into containers. The recesses may be of any size or shape suitable for increasing heat transfer to or from the asphalt package. It has been found that adding the polymer to traditional paper and metal asphalt packaging is less than straightforward. In particular, it has been found that introducing polymer to the package prior to filling the package with molten asphalt, often results in the polymer migrating to the top and side (s) of the package instead of being embedded in the asphalt. As a result, when the packing materials are removed from the solidified asphalt at the construction site, a significant amount of the polymer is separated from the asphalt and thrown away with the packaging materials. The present invention provides a method and apparatus for introducing the desired polymer into the asphalt contained in a standard paper and metal package in such a way that the polymer integrally binds to the solidified asphalt contained in the package (hereinafter referred to as "packaged asphalt"). ") such that it does not separate during the removal of packaging materials, however it is separated from the asphalt by melting in a kettle and floating to the surface to form a vapor-reducing cream. In the method of the invention, the polymer pellets or the polymer / asphalt composite pellets are combined with the molten asphalt, such that the pellets are covered with molten asphalt as they enter the package. This can be achieved by injecting the nodules in a stream of molten asphalt as it fills the package, or by introducing the asphalt and the nodes in the package separately but simultaneously, so that the nodes are completely coated with asphalt as they enter the package. As a result, although the nodules are typically less dense than the molten asphalt and tend to rise to the top of the pack, the nodules are wrapped in the asphalt and have a very reduced tendency to separate from the asphalt upon removal of the pack. Consequently, packaging materials can be detached from the packaged asphalt and thrown away without significantly reducing the amount of polymer that is added to the melting kettle with the packaged asphalt.

Other methods according to the invention can also be used to prevent the polymer from sticking to the bottom of the paper and metal container of a traditional asphalt packaging. For example, a release agent may be applied to the bottom of the container, optionally, the release agent may be mixed or formulated into the polymer. A different coating can be used on the bottom of the container. The polymer can be encapsulated in a polymer bag; the bag melts releasing the polymer in the asphalt and floats in the package, not adhering to the bottom of the container. The bag can be suspended in the middle of the package and on it empty hot asphalt; this prevents the polymer from coming into contact with the bottom of the container. A molded geometric piece can be used to hold the polymer inside the package (again, this will prevent the polymer from reaching the bottom of the container); the piece will have sufficiently thin walls to melt and allow the polymer inside to free and float on the asphalt. A polyolefin film liner (e.g. polypropylene) can be placed inside the package prior to introduction of the polymer and asphalt, to prevent the polymer from sticking to the container as the asphalt solidifies. The liner will also provide additional polymer. Any of the above forms can be added directly to any molten asphalt container as described above. In addition to reducing vapor release in the melting kettle, the incorporation of polymer pellets or polymer / asphalt composite pellets into the formed asphalt packs can also reduce the vapors emanating from the packs during cooling. As the nodules contact the hot melt asphalt introduced into the packages, the nodules begin to melt and due to their lower density, they float to the top of the package where they form a cream that reduces vapors as the package cools. This beneficial attribute can be improved by including a small percentage of a polymer that has a high melt flow index or that is highly soluble in asphalt. For example, formulations that include 60% asphalt and a combination of 38% polypropylene and 2% EVA; or 37% polypropylene having a melt flow index of about 5% to about 50 grams / 10 minutes and 3% polypropylene, which has melt flow index from about 50 to about 400 grams / 10 minutes (measured at 230 ° C (446 ° F) under a load of 21.60 g) can ensure that a sufficient amount of polymer melts during filling of the package to form the desired cream.

The invention will now be further illustrated by reference to the following examples. EXAMPLE 1 Tests were performed to measure the capacity of a smaller amount of asphalt / polymer composite pellets, incorporated in a conventionally packaged asphalt product to reduce vapors release from a pot of molten asphalt during melting again. In this test, the vapor release of an asphalt type III BURA standard (melting asphalt from roofers of Amoco blown into the air at a softening point of about 85 ° C (185 ° F) to about 96.1 ° C (205 ° F) ), packed in a conventional metal and paper container, was tested with both the aggregated composite nodules ("low vapor release product") and without the nodules containing added polymer ("standard product"). The nodules added to the low vapor release product were prepared by pelletizing a mixture of air-blown asphalt at a softening point of approximately 143 ° C (290 ° F), polypropylene (Montel 6301 or Solvay Fortilene 12, homopolymer with index of melt flow), and ethylene-vinyl acetate copolymer (Elvax 450) in a single screw extruder at a rate of 60:30:10 by weight.

The equipment used for the test includes a 625-liter pot of roofers heated by a propane burner. In the test, the low vapor release product and the standard product were added separately to the kettle and melted to fill the kettle. Each of the products was tested at a temperature of 260 ° and 288 ° C (500 ° and 550 ° F), and the low vapor release products were tested at polymer concentrations in the range of 0.16 to 0.96 percent by weight. weight of the total asphalt and polymer in the composition. To simulate current usage conditions, 75.7 liters of melted product were drained from the kettle every 20 minutes and replaced by additional product added to the kettle. The test was conducted outdoors, with the area around the pot enclosed to block the wind. The vapors emitted from the kettle were measured by visual opacity, and total suspended benzene-soluble particles, as described below. The test for visual opacity was performed in accordance with the Code of Federal Regulations (CFR) 40, Part 60, Appendix A, Method 9 of the EPA, with the title "Visual Determination of the Opacity of Emission from Stationary Sources." (Visual Determination of Opacity of Emission of Stationary Sources). A certified opacity reader records the visual opacity every 15 seconds for 2 hours. The reader observed the vapors of the kettle and determined a percentage of opacity or blockage of natural light. Low opacity indicates very few vapors, while high opacity indicates a large amount of vapors coming out of the kettle. The results of the visual opacity readings are illustrated below in Table I, where the opacity in percent is the average over the two-hour test: TABLE I. VISUAL OPACITY The results of the visual opacity readings show that the low vapor release product had visibly less vapors release from the kettle than the standard product at polymer concentrations of 0.32 weight percent and above. In addition, it was observed that at polymer loads of 0.32 percent and higher, the low vapors product polymer formed a cream substantially throughout the upper surface of the molten asphalt. The test for total benzene-soluble suspended particles was performed according to "Standard Operating Procedure: Benzene Solubles Method for Asphalt Institute Round Robin Study" (Standard Operating Procedure: Benzene Solubles Method for the Study with return to the starting point of the Asphalt Institute) which is a modified version of the 5023 method of the National Institute of Occupational Safety and Health (NIOSH = National Institute of Occupational Safety and Health) 3rd edition.

Two high-volume samplers were lifted in position (Hi-Vol) TSP (suspended particles in total) to place the sample inlets slightly over the edge of the kettle near the opening of the kettle. Each of the samplers removed a stream of vapors from the kettle through a previously weighed 929 cm2 (1 square foot) filter. Each sampler operated for two hours. Subsequently, the filter elements were removed, covered with benzene (HPLC grade with evaporation residue not greater than .00005%) and left for at least one hour. The benzene extract is then passed through a Millipore Miliflex SR disposable filter under nitrogen pressure (approximately .492 to .7031 kg / cm2 (7 to 10 psi) The benzene was then concentrated in a heating block at 85 ° C. (185 ° F), transferred to pre-weighed cups and placed in a vacuum oven at room temperature and 20-25 mm Hg vacuum at night. The cups were then weighed to determine the amount of benzene-soluble particles. The results of the measurements of the total suspended particles soluble in benzene are illustrated below in Table II. The measurements are given in micrograms of particles per standard cubic meter (sem) of vapor in standard conditions of a pressure atmosphere and 20 ° C (68 ° F). TABLE II. SOLUBLE SUSPENDED PARTICLES IN TOTAL BENZENE These results, like the results of visual opacity, show that the product of low vapors release, reduces the amount of vapors in the kettle compared to the standard product. The benzene-soluble particles were consistently lower for the product of low vapor release against the standard product at polymer levels greater than 0.32%. EXAMPLE 2 The emitted benzene soluble particles were measured by 16 additional samples of standard product and low vapor release product having 0.32% by weight of polymer. The results are illustrated below in Table III.

TABLE III. TOTAL SUSPENDED PARTICLES SOLUBLE IN BENZENE These results show that the benzene-soluble particles are also less than 0.32% of the polymer than for the standard product. EXAMPLE 3 A supply of molten asphalt is transported in a tank car or truck to an end user, who places a quantity in a pot of roofers to heat at a temperature suitable for application as asphalt for roofing. The end user is supplied with meltable polymer bags, each of which is encapsulated in a plurality of polymer / asphalt composite nodes. The end user periodically throws a bag into the kettle, where the nodules are melted and released. The polymer of the nodules and the bag forms a cream on the surface of the molten asphalt that reduces the vapors' release from the kettle. EXAMPLE 4 A consumable asphalt container is formed in accordance with the following method of low vapor release. Asphalt Amoco AC-20 air-blown to a softening point of 121 ° C (250 ° F), polypropylene (Profax 6301), and ethylene-vinyl acetate copolymer (Elvax 450) were pelleted in a twin-screw extruder in a proportion of 60:30:10 in weight. The spindle temperature is set to 177 ° C (351 ° F). The nodules were used to injection mold a consumable container as illustrated in Figure 1. The container has a melt flow index of approximately 46.6 grams / 10 minutes. The vessel was hard and impact-resistant and has an Izod impact strength without scoring 4.5 joules, a tensile strength of 95.5 kg / cm2 at 22 ° C (72 ° F), a tensile strength of 25.3 kg / cm2 at 93 ° C (199 ° F), and a tension module of 336 kg / cm2 at 93 ° C (199 ° F). After molding, the container is filled with a BURA Type III roofing asphalt at a temperature of 166 ° C (331 ° F). The container does not bulge or deform significantly and the thermocouples on the outside of the container do not exceed 113 ° C (235 ° F). The asphalt package (the container and the asphalt contained in the container) weighed 27.24 kg when full (0.91 kg of container and 26.33 kg of asphalt). The asphalt package meets the requirements for Type III roofing asphalt in accordance with ASTM D312. The container can be melted together with the asphalt contained in the container without significantly changing the properties of the asphalt. The softening point of the asphalt was only 89 ° C (192 ° F), and the softening point of the combined asphalt and container was 95 ° C (203 ° F). The asphalt only had a penetration of 19 dmm at 25 ° C (77 ° F), and the combined asphalt and vessel had a penetration of 17 dmm at 25 ° C (77 ° F). EXAMPLE 5 Polypropylene Montel 6301 and coating asphalt having a softening point of 110 ° C (230 ° F), were pelleted in a twin screw extruder at a ratio of 30:70 by weight. The spindle temperature is set to 177 ° C (350 ° F). The nodules were used for injection molding containers in the shape of a tray with dimensions of 25.4 x 33.0 x 8.9 cm) (10 x 13 x 3.5") and a thickness of 2.54 mm (100 mils).

Several of the molded asphalt containers were added to a Type III BURA bitumen asphalt body. The weight of the containers was 4 percent of the total weight of the asphalt and container. The properties of the asphalt before and after the addition of the containers were measured, with the results given in the Table below, together with the specifications Type III ASTM D312 for comparison. TABLE IV. EFFECTS OF ADDITION OF MOLDED CONTAINERS, TO CASTED ASPHALT It can be seen that the addition of the container to the asphalt had only a slight effect on the property of the asphalt with the more pronounced change being the increased viscosity. EXAMPLE 6 Polypropylene Montel 6301, a blasted altp asphalt, and Type III BURA asphalt were pelleted in a twin screw extruder in a ratio of 40:20:40 by weight. The high-blown asphalt was a Trumbull material from a mixture of washed asphalts with propane that had been blown to a softening point of 149 ° C (300 ° F). The screw temperature was 177 ° C (350 ° F). The nodules were used to mold by injection a vessel having a diameter of 20.3 cm (8") and a height of 19.1 cm (7.5") with a thickness of 2,286 mm (90 mils). After molding, the vessel was filled with asphalt at 149 ° C (350 ° F). The container did not bulge or deform. Thermocouple temperature readings placed on the outside never exceeded 71 ° C (160 ° F). The asphalt package of the container and the asphalt weighed 4.5 kg (10 lbs) full. The vessel was lowered into a wire basket in a rooftop asphalt pot containing molten asphalt at 246 ° C (475 ° F). Without shaking, the package was completely dissolved by natural convection without visible traces some in 15 minutes. The properties of the asphalt before and after the emission of the containers were measured with the results given in the following Table in comparison with the specifications ASTM D312 Type III. TABLE V. EFFECTS OF THE ADDITION OF MOLDED CONTAINERS FILLED WITH ASPHALT, TO CASTED ASPHALT The results are similar to those of Example 5. The asphalt softening point of the molten vessel was slightly above the Type III specification. Although the invention has been described in detail with reference to preferred features and modalities, appropriate modifications will be apparent to the person skilled in the art. In this way, the invention is not intended to be limited by the foregoing description but rather defined by the appended claims and their equivalents.

Claims (10)

1. CLAIMS 1. In a method for containing asphalt wherein a quantity of molten asphalt is in a container, the molten asphalt normally emits vapors from the container, the method includes the step of adding from about 0.2 weight percent to about 6 percent by weight. weight of a polymer in the form of nodules, to the asphalt to reduce the visual opacity of the vapors at at least about 25% compared to the same asphalt without the added polymer, the improvement herein is characterized in that it comprises adding the nodes to the asphalt at insert the nodules first in a container and then add the asphalt to the container.
2. 2. The method according to claim 1, characterized in that the container is a polymer bag.
3. 3. The method according to claim 1, characterized in that the container is an asphalt gasket.
4. 4. The method of compliance with the claim 1, characterized in that the container is a polymer bag inside an asphalt packing.
5. 5. In a method for containing asphalt, wherein a quantity of molten asphalt is contained in a container, the molten asphalt normally emits vapors from the container, the method includes the step of adding from about 0.2 weight percent to about 6 percent by weight of a polymer in the form of nodules to the asphalt, to reduce the visual opacity of the vapors by at least about 25%, compared to the same asphalt without the added polymer, the improvement is characterized in that it comprises adding the polymer in the shape of nodules that have a minimum diameter of about 1.59 mm.
6. 6. The method according to claim 5, characterized in that the nodes are spherical in shape and have a diameter of about 1.59 to 6.35 mm.
7. The method according to claim 5, characterized in that the nodules are cylindrical in shape and have a diameter of about 1.59 to 6.35 mm and a length of about 1.59 to 12.70 mm.
8. 8. In a method for melting asphalt, wherein the amount of unmelted asphalt is placed in a vessel and heated to melt the asphalt, the molten asphalt usually emits vapors from the vessel, the method includes the step of adding about 0.2 percent by weight to about 6 weight percent of a polymer, to the asphalt to reduce the visual opacity of the vapors by at least about 25% compared to the same asphalt without the polymer added, the polymer is added in the form of a pack of asphalt containing asphalt and polymer, the improvement is characterized in that it comprises introducing the polymer into the asphalt package simultaneously by introducing molten asphalt into the asphalt package, so that the polymer is coated with the molten asphalt and introduced into the asphalt. asphalt package.
9. 9. The method according to claim 8, characterized in that the polymer is inverted in a stream of molten asphalt as the molten asphalt is introduced into the asphalt package.
10. 10. The method according to claim 8, characterized in that the polymer is introduced into the asphalt package in the form of nodules.