Asphalt, also known as bitumen, is sticky, black and highly viscous liquid or semi-solid present in most crude petroleums and in some natural deposits. Asphalt is composed primarily of a mixture of highly condensed polycyclic aromatic hydrocarbons, and is classed as a “pitch” or a viscoelastic, solid polymer.
Asphalt is a thermoplastic material that softens as it warms, and stiffens as it cools. Asphalt has both adhesive and waterproofing characteristics, making it useful in a variety of applications including paving, waterproofing, roofing and others. Asphalt is available in a wide range of stiffnesses for various uses, and is also commonly modified or compounded with various additives to enhance properties for certain uses. Asphalt that must be heated to lower the viscosity for installation is referred to as hot applied asphalt. Asphalt is also commonly processed with solvents or emulsified to make it into a liquid composition that can be applied with little or no heat, and then cures after application. These are normally referred to as “cold applied” asphalts. “Hot applied” type asphalts are normally supplied to the user in two manners depending on the type of use. For large use volumes such as for pavement construction, asphalt is usually supplied hot and fluid in a large capacity bulk truckload type tank which can range up to 6000 gallons, for example. For many others uses such as roofing, waterproofing, and crack or joint sealing, smaller volumes are used and the asphalt is usually supplied as a solid at ambient temperature in packages, generally weighing from approximately 20 up to 100 pounds (lbs), and a required amount for the particular application is heated to a desired use temperature at the jobsite.
Because asphalt does not go through a solid-liquid phase change when heated, it does not have a true melting point. Rather, as the temperature is raised, asphalt gradually softens or becomes less viscous. Asphalt is produced in several standard types with different stiffness for certain applications. For example, ASTM D312 is the “Standard Specification for Asphalt Used in Roofing,” incorporated herein by reference in its entirety. ASTM D312 was originally published in 1929, and covers four different stiffness grades. ASTM D449 is the “Standard Specification for Asphalt used in Dampproofing and Waterproofing,” incorporated herein by reference in its entirety. ASTM D449 was published in 1937, and covers three different stiffness grades.
Over the last 60 or so years, there have been several types of specifications used for paving asphalts. ASTM D946 was originally published in 1947, and is the “Standard Specification for Penetration-Graded Asphalt Cement for Use in Pavement Construction,” incorporated herein by reference in its entirety, and includes five grades based on penetration testing at 77° F. ASTM D3381 is the “Standard Specification for Viscosity Graded Asphalt Cement for Use in Pavement Construction,” incorporated herein by reference in its entirety. ASTM D3381 was originally published in 1975, and covers 11 different viscosity grades for use in different temperature areas.
The most recent specification for paving asphalt is ASTM D6373, entitled “Standard Specification for Performance Graded Asphalt Binder,” incorporated herein by reference in its entirety. ASTM D6363 was published in 1999, and covers 37 different grades based on specific properties suited for varying climates temperature ranges.
There are also many different specifications for modified asphalt compositions for various uses including ASTM D6154 for Chemically Modified Asphalt, ASTM D6626 for Trinidad Lake Asphalt, ASTM D6114 for Asphalt Rubber Binder, ASTM D6297 for Asphaltic Plug Joints for Bridges, ASTM D3141 for Asphalt for Undersealing Portland Cement Concrete Pavements, ASTM D5078 for Crack Filler, Hot Applied, for Asphalt Concrete and Portland Cement Concrete Pavements, ASTM D6690 for Joint and Crack Sealants for Concrete and Asphalt Pavements, ASTM D5710 for Trinidad Lake Modified Asphalt, all of which are incorporated by reference in their entireties, and many others.
The stiffness characteristics of the many different types of asphalts and modified asphalts vary widely depending on climate and use. Two types of properties that can be used to classify stiffness of asphalts are penetration and softening point. Penetration can be measured by the ASTM D5 penetration test, entitled “Standard Test Method for Penetration of Bituminous Materials” and incorporated herein by reference in its entirety. This test measures the depth that a specific needle under controlled conditions penetrates into a prepared specimen of asphalt. Low penetration results, such as less than approximately 25, indicate stiffer, more flow resistant materials, and higher results over 25 indicate softer materials that can experience cold flow at ambient temperatures.
Softening point can be measured by the ASTM D36 ring and ball softening point test, entitled “Standard Test Method for Softening Point of Bitumen (Ring-and-Ball Apparatus)” and incorporated herein by reference in its entirety. This test indicates the temperature that a specific ball falls through a prepared sample of the asphalt while heating under controlled conditions. High softening point results, such as approximately 210° F. or more, indicate stiffer materials that may resist flow at ambient temperatures, while lower results, under 210° F., indicate materials that will experience cold flow.
To be able to be classified as flow resistant at ambient temperatures, asphalt materials need to be both high softening point and low penetration. The stiffest most flow-resistant standard asphalt type is ASTM D312 Type IV Roofing Asphalt, characterized with a Ring and Ball Softening Point range of 210 to 225 F, and a Penetration range of 12 to 25. This stiffness range of asphalt is generally characterized as being very flow resistant at normal roof exposure temperatures, and so stiff, that at normal storage temperatures in packages it is also very cold flow resistant. Packages for this very stiff, cold flow resistant asphalt needs to be strong enough to be able to contain the asphalt after it is poured into them while it cools, but since the asphalt is so stiff and cold flow resistant after cooling, support strength from the package is generally not needed, except that the packaging mainly assures that the blocks do not adhere together during storage and transport, and is easily useable at the job site.
There are many asphalt and modified asphalt types that are high softening point, but also high penetration, that experience cold flow. Most other asphalt types that have lower softening points and higher penetrations than the Type IV Roofing Asphalt, can experience cold flow at ambient storage temperatures, and if supplied in a packaged form, must be contained in a durable package for storage, shipping and handling at the jobsite. Some of the softest asphalt types are for paving and include ASTM D946 85-100, 120-150, and 200-300 grades, with penetration ranging from 85 to 300 at 77° F., and ASTM D 3381 AC-2.5, AC-5 and AC-10 with penetration ranging from 70 minimum to 200 minimum.
Asphalt meeting ASTM D6373 PG (penetration grade) 46, 52 and 58 Grades is also very soft, but standard properties are not measured using penetration. Typical penetration results for these PG grades are from 80 to over 200. The Ring and Ball Softening Point of these soft grades is generally less than 130° F. These asphalts are normally supplied in hot bulk truckloads, and if packaged will experience cold flow. Modified asphalt sealants meeting requirements of ASTM D5078 and D6690 generally have penetration ranges from 70 or 90 maximum to 150 maximum, and softening points from 150 F to approximately 200 F, and experience cold flow at ambient temperatures.
For the sake of simplicity and clarity, these asphalts, i.e. asphalts having a low or high softening point coupled with high penetration, such as above 25, and that can experience cold flow, will be referred to throughout the specification as “cold flowable asphalts.”
It is common practice to place molten asphalt or molten asphalt compositions in packaging such as containers at a manufacturing facility and ship a desired quantity to a job site on an as needed and when needed basis. When the asphalt is needed at a job site, the containers are torn open and the asphalt, which has since cooled and thus, solidified, is placed in a heating vessel such a tank to reheat the asphalt. When the desired temperature of the molten asphalt is reached, normally in a range of about 300° F.-400° F., it is applied in accordance with procedures suitable for the particular job.
Molten asphalt can be a difficult material to handle due to inherent characteristics of the material itself which makes containerization and transport of the molten asphalt a slow, messy and relatively costly operation if the container does not have adequate durability, strength, or integrity to contain the asphalt within. Specifically, asphalt is initially molten or at least flowable during containerization of the material, and is subsequently cooled to solidify the asphalt for storage and transport. However, asphalt does not necessarily remain solid until use, and can become flowable (i.e. cold flow) during storage and transport, before finally being melted to a molten state for use at the job site, creating various challenges in storage and transport.
Known packaging system have attempted to address the many issues tied to each stage of containerization, storage, and transport of asphalts, and particularly cold flowable asphalts. However, these known packaging systems either fail to adequately address all issues, or create new issues during the process of solving other issues.
First, softer grades of molten asphalt can be pumped at temperatures as low as about 200° F.; however, it is very viscous at such low temperatures which makes the pumping thereof a slow process. At higher temperatures, the molten asphalt will inherently become less viscous and thus is easier on the pumps and otherwise makes the filling of the containers a faster, easier, and less costly operation. However, at the elevated temperatures at which the molten asphalt will more easily flow, such elevated temperatures can destroy certain containers that do not have sufficient integrity at such temperatures. It will be seen from the above that a limiting factor in the prior art asphalt containerization process is the container itself which requires that the asphalt be cooled to temperatures low enough, depending on the packaging type, so that it will not destroy or degrade the containers, or, alternatively, require special container design that withstands these elevated temperatures, i.e. maintains container durability and integrity at such temperatures for extended periods of time.
Another characteristic of the asphalt which must be considered in all containerization processes is that asphalt will adhere to virtually anything and upon cooling will form a very tenacious bond with the contacted item. This inherent characteristic of asphalt has dictated the basic design parameters of the containers used since the beginning of this type of containerization.
A traditional container for asphalt products, and specifically sealants, includes a metal pail lined with a polymeric liner bag or pail. These metal pails can range from five gallon pails to 55 gallon metal drums. However, due to the increased cost of steel to make the pails or drums, the container tends to be expensive. Furthermore, once the asphalt has been removed from the container, the pail or drum then creates waste product that needs to be removed from the job site. Finally, the drums or pails are relatively heavy, which can result in increased cost of transportation and storage, because, for example, a limited number of drums or pails can be transported or stored in a single load due to weight restrictions.
A modification of the steel drum container is a cardboard keg, such as a two foot by thirteen inch diameter keg, and typically includes a release coating on the inside of the keg so that the asphalt can be readily removed. Although this container is significantly lighter and less expensive than the steel drum or pail container, it similarly suffers from the drawback of generating waste product at the job site. Additionally, if the cardboard is not completely removed, it can cause contamination of the asphalt, and/or melting difficulties, such as clogging of plugging of the melting equipment. Furthermore, this container is typically limited to the containerization of stiffer or flow resistant asphalts, such as roofing asphalt, as it may not have sufficient durability for containing, storing, and transporting some types of cold flowable asphalts.
One conventional container system for asphalt that attempts to address the containerization and storage and transport issues includes a corrugated cardboard carton or box into which a bag is inserted as a liner. The liner bag is formed of a synthetic plastic material having a wall thickness such as, for example, of about 0.001 to about 0.006 inches (1 to 6 mils). The plastic material can comprise polypropylene which is capable of withstanding temperatures of up to a maximum of about 275° F., and will melt at or somewhat higher than that temperature, such as at about 325° F. During containerization, a liner bag is typically placed in the carton or box, and then heated or molten asphalt is pumped, poured, or otherwise placed into the bag, the heated asphalt being at a temperature lower than melting point of the plastic of the liner bag. The outer cartons or boxes are necessary to provide stacking stability and durability of the packaging for transport of the asphalt or asphalt composition, particularly when used for cold flowable asphalts.
However, this packaging, well suitable for containerization and stackability purposes creates other issues or problems, especially during transport and storage. Even after the asphalt has cooled and solidified, increased pressure and temperature from the stacking of materials as well as fluctuations in temperature during storage and/or transport can cause the asphalt composition to flow. The outer protective cartons or boxes provide the necessary stacking stability to accommodate for this flow. However, the structural integrity of the boxes can be compromised in a number of ways during storage and transport. For example, if the cardboard boxes are exposed to water, the structural integrity of the cardboard boxes is compromised, thereby comprising the internal liner or bag filled with asphalt. Similarly, if the box is punctured or ripped during storage or transport, the structural integrity of the cardboard box is compromised, as well as the internal liner or bag filled with asphalt. The flow of the asphalt coupled with damage to the packaging during storage or transport can result in breached packaging. A breached box with leaking product not only makes a mess in the storage facility or transport vehicle, but results in unusable product because the asphalt adheres to other boxes, making it impossible to remove the cardboard from the asphalt. The asphalt is then unusable because it cannot be placed in a heating vessel or melter, because contamination of the cardboard can clog the heating vessel. Furthermore, if the box is weakened by getting wet or otherwise damaged, the box can become unstable causing an entire pallet of material to slump, and even leak. Any of these scenarios costs both time and money to replace unusable product and in restacking and clean-up.
When the molten asphalt is pumped into the plastic liner bags during containerization it will adhere thereto which makes subsequent removal difficult if not impossible to accomplish. Therefore, when readying the containerized asphalt for use at a job site, it is a common practice to tear open the carton, remove the plastic liner bag having the solidified asphalt therein and place it, liner bag and all, in the vessel which is to be used to heat the asphalt. Due to the nature of the plastic material, and because the mass of the plastic is small in comparison to the mass of the asphalt, the plastic does not appreciably affect the integrity of the asphalt. This common practice places further design parameters on the nature and characteristics of the plastic liner in addition to its being capable of withstanding the hereinbefore described containerization temperatures. These further considerations are that the liner bag ideally should be as thin as possible, and should melt readily at asphalt reheat temperatures in a range of about 300° F.-400° F. which is an ideal temperature at which the molten asphalt will, for example, properly flow into cracks and expansion joints in paved surfaces.
Another problem with this packaging system is that once the liner with asphalt has been removed, discarded boxes are generated, causing handling and disposal issue out on the job site. For example, the emptied boxes create increased construction waste product. Furthermore, if there are not adequate facilities closely available to dispose of or store the emptied boxes, the boxes must then be transported to such facility to dispose of or store the boxes, which consumes valuable time and costs money.
Another example of a packaging system similar to the corrugated cardboard carton is a multilayered flexible bag and liner assembly. An inner liner bag is formed of a synthetic plastic material, such as low density polyethylene, having a wall thickness such as, for example, of about 0.002 to about 0.010 inches (about 2-10 mils). A number of layers are then layered on the liner bag including a first inner layer of kraft paper of about 4 mils thick, an intermediate layer of a nonwoven film such as a spun bonded, heat sealed fabric of about 9 mils thick which is similar to a very light piece of fabric of about 3 ounces per square yard in weight, and another, outer layer of kraft paper of about 4 mils thick. The inner layer of kraft paper can also include a release coating on an inner surface to ensure that the liner bag does not stick thereto in the event of a liner bag breach.
In use, the multilayered package is filled with molten or heated asphalt heated to a temperature below the melting temperature of the liner bag. The multilayered package is then stitched closed. Multiple outer layers over the liner bag are necessary to provide stacking stability and durability of the packaging for transport of the asphalt or asphalt composition, particularly when used for cold flowable asphalts.
When readying the bagged asphalt for use at a job site, it is a common practice to tear open the outer layers to remove the plastic liner bag having the solidified asphalt therein and place it, liner bag and all, in the vessel which is to be used to heat the asphalt. Due to the nature of the plastic material, and because the mass of the plastic is small in comparison to the mass of the asphalt, the plastic does not appreciably affect the integrity of the asphalt.
Although this multilayered bag system provides a tough, durable, and strong puncture resistant packaging solution, it is expensive due to the many layers needed to provide adequate strength and durability. Furthermore, because the outer layers need to be removed before use, it creates increased waste product at the job site, similar to the cardboard box system. Finally, if the outer layers are not entirely removed, it can contaminate the asphalt, thereby rendering the asphalt unusable, or cause clogging or plugging of the heating vessel.
A container and method has recently been developed to address the issues described above with respect to the box and liner system. In particular, a way to reduce waste generation at jobs sites stems from the development of containers for asphalt that include an entirely consumable container. One such container is disclosed in U.S. Pat. No. 8,017,681 to Guymon et al. The container is a non-asphalt, thermoplastic, waterproof container made of an expanded polymer, such as Styrofoam®. The container can be in the shape of stacking blocks. At the job site, the entire container having the solidified asphalt therein is placed in the vessel which is to be used to heat the asphalt.
Another example of an entirely consumable container system can be found in U.S. Pat. No. 5,733,616 to Janicki et al. The container is molded from a composition comprising 40 to 90 weight percent of an asphalt and 10 to 60 weight percent of a polymer material, such as a blend of polypropylene (PP) to impart heat resistance, and ethylene vinyl acetate (EVA) to impart toughness and impact resistance. The container is entirely consumable and can be melted along with roofing asphalt held in the container.
However, these packaging options can cause logistics and handling issues during manufacturing. For example, because of the material used for the container, the asphalt is poured into the containers at a lower temperature than the melting temperature of the bag and box packaging described above so as not to melt the container. These types of containers can be significantly more expensive than the conventional box and liner packaging described above as careful design of materials is needed to obtain a container having adequate integrity to hold shape when molten asphalt is poured directly into it.
Another problem with the expanded polymer container is that the packing density is significantly reduced because the expanded polymer containers are not able to be nested causing storage and handling issues. For example, approximately 20,000 to 25,000 boxes of the boxes and liner configuration can fit on a single semitrailer, whereas only approximately 4,000 of the expanded polymer containers can fit on the semitrailer. Similarly, the expanded polymer containers require significantly more storage space than the boxes for the same amount of asphalt.
Furthermore, these consumable packaging systems may be prone to leakage when stacked, particularly when used in combination with cold flowable asphalts. For example, the packaging system of Janicki et al. does not include a lid and is heavy enough that when the containers are stacked, the load due to the weight of the stacked containers can cause the asphalt composition in the bottom or lower layer containers to flow, which can in turn, collapse under the weight, and/or the asphalt is forced out of the container. Therefore, the applications for these containers may be limited to higher softening point asphalts, such as roofing asphalts having a penetration grade of about 25 or less, and softening points of approximately 210° F. or more.
Another problem with the packaging system of Guymon et al, for example, is that it requires a separate lid. The lids are prone to unwanted removal, such as by wind, transport, and the like, causing unwanted waste product. Additional components and/or manufacturing steps may be needed to secure the lid to the container, thereby increasing the cost of the packaging system. The lid can also compromise the otherwise water-tight design. The lack of a water-tight seal may cause potentially significant hazards during use as any water in the container can cause eruptions when melted, and ultimately unwanted boil over at the job site.
Finally, the consumable container of these packaging systems is a significant portion of the total weight of the packaging system, e.g. about 1.5 weight percent or more, such that the container material can be detrimental to the integrity of asphalt composition. For example, the increased plastic content may negatively affect the melt and/or setting properties of the asphalt, and/or the container may not completely melt causing contamination of the asphalt, potentially rendering it unusable. Furthermore, some of the so-called meltable containers do not completely melt, causing build-up of residue and even plugging of the melting unit or heating vessel.
Another packaging system that attempts to resolve many of the problems described above includes a film-only wrap or envelope. For example, U.S. Pat. No. 3,837,778 to Parker discloses a thermoplastic resin film for use as roofing asphalt packaging. Specifically, Parker discloses that a polyester resin film is preferred, and that polyethylene and saran resins have been found to be unsatisfactory (see, for example, Col. 6, lines 44-50). Furthermore, the films disclosed in Parker are limited to asphalts that have little tendency to cold flow. Specifically, Parker discloses that the film disclosed “does not produce satisfactory results with respect to low soft point asphalts as they are so fluid and cold flow so readily as to require totally impractical thickness of film.” (Col. 6, lines 57-61)
Other examples of film packaging are found in U.S. Pat. No. 5,452,800 to Muir and U.S. Pat. No. 4,137,692 to Levy. Muir discloses a polypropylene film having a thickness from 1.0 to 1.8 mils with a melting point between 275° F. and 335° F. as the sole containment for blocks of roofing asphalt. However, this packaging system, due to the inherent characteristics of polypropylene at ambient temperatures and conditions, is limited to asphalts that have little tendency to cold flow, i.e. higher melting point roofing asphalts, and is not applicable to cold flowable asphalt materials. If used with cold flowable asphalts, the packaging would be compromised during handling and storage. Particularly, as the blocks are stacked, stored, and transported, the asphalt can soften and flow, and the polypropylene packaging alone lacks sufficient strength to prevent the asphalt from breaching the package when stacked. Alternatively, to achieve adequate strength, the film thickness required would be so great that it would be more difficult to melt and could potentially influence properties of the asphalt.
Similarly, U.S. Pat. No. 4,137,692 to Levy discloses a polyethylene biaxially-oriented stretched and heat-shrinkable film. However, this film, without more, would suffer the same drawbacks as the film of Levy if used with cold flowable asphalts.
U.S. Pat. No. 3,366,233 to Roediger discloses an entirely consumable package for paving asphalt comprising a multilayered or laminated container or encasement of sheeting or film, composed of polyethylene, polypropylene or a copolymer of ethylene and polypropylene. The thickness of the film ranges from about 2 to about 6 mils. As shown in some of the Examples, single walled films had moderate to severe oil transfer and tackiness, as well as unsatisfactory to marginal package suitability. Furthermore, the Examples set forth that the bags were stored for a period of 70 days at a temperature of 150° F., and under loading conditions equivalent to the bottom bag of a four bag high stack (about 10 pounds per square foot or about 0.07 pounds per square inch). These conditions are significantly less than typical pallet storage and transport conditions. In commercial use, pallets are typically stacked six to eight packages high, and are of a weight such that the bottom bag is subjected to loads of about 1.2 pounds per square inch (172 pounds per square foot). It is highly unlikely, although unknown, that the packages of Roediger would have similar durability and integrity results when at these higher load conditions when used to package cold flowable asphalts.
Therefore, a need exists for a new and improved container or packaging solution for asphalt and asphalt compositions, and particularly cold flowable asphalts, which not only overcomes the problems associated with the packaging and transporting of asphalt and other hot melt materials, but also overcomes the shortcomings of the prior art, the shortcomings including one or more of lack of adequate consumability and meltability of the container, lack of adequate packaging integrity during stacking, storing, and transporting, the need for additional non-consumable materials to provide adequate packaging integrity thereby creating job site waste product, uneconomical or economically unrealistic, and manufacturing infeasibility or difficulty.