Industrial asphalt composition
This invention is based upon the discovery that a small amount of lime can be incorporated into industrial asphalt to greatly improve its resistance to oxidative hardening cracking and low temperature thermal cracking. The incorporation of a small amount of lime into industrial asphalt accordingly results in products made therewith offering improved service life. For instance, roofing shingles made with such asphalt that contains a small amount of lime will be more resistant to cracking and failure in both hot and cold weather climates. The subject invention more specifically discloses an asphalt roofing shingle having an upper surface and an underside, said asphalt roofing shingle being comprised of a fiber mat which is coated with an asphalt composition, wherein the upper surface of the asphalt roofing shingle includes a layer of roofing granules, wherein the asphalt composition has a softening point which is within the range of 185° F. (85° C.) to 250° F. (121° C.) and a penetration value of at least 15 dmm, and wherein the asphalt composition contains from 0.1 weight percent to 5 weight percent lime. The subject invention further discloses a method for preparing an industrial asphalt comprising (1) heating a base asphalt to a temperature which is within the range of about 100° F. (38° C.) to 400° F. (204° C.) to produce a hot base asphalt, and (2) mixing from 0.1 weight percent to 5 weight percent lime throughout the hot base asphalt while the mixture of hot base asphalt and lime is maintained at a temperature which is within the range of 100° F. (38° C.) to 400° F. (204° C.) to produce the industrial asphalt.
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The present invention relates to asphaltic materials which are particularly useful in manufacturing industrial asphalt products such as roofing shingles, roll roofing membranes, roofing underlayment, asphalt-based adhesives, asphalt-based sealants and built-up roofing. The present invention also relates to a method for preparing such asphaltic materials.
BACKGROUND OF THE INVENTIONAsphalt offers outstanding binding and waterproofing characteristics. These physical attributes of asphalt have led to its widespread utilization in paving, roofing, and waterproofing applications. However, with exposure to elements of the environment such as solar radiation, high temperatures, rain, snow, etc., the asphalt ages as a result of oxidation. With oxidation, asphalt becomes stiffer, less ductile, and less capable of relieving stress. When the stress in the asphalt builds to a critical limit in excess of what it can withstand, cracking occurs. This type of cracking which is caused mainly by asphalt oxidation or aging is called “oxidative hardening cracking.” This type of cracking is typical and commonly experienced in the Sun Belt where asphalt can be exposed to a grueling sun and high temperatures for an extended period of time.
Exposure to low temperatures can also cause asphalt to crack. Asphalt is a viscoelastic material, meaning it behaves more like a solid at low temperatures and behaves as a liquid at high temperatures. As a result, with drops in temperature, asphalt's viscosity and modulus can increase significantly. In addition, asphalt has a relatively high coefficient of thermal expansion (CTE), and under most conditions, asphalt's CTE is higher than the substrate to which it is applied (such as wood or metal). With considerable temperature drops, asphalt will experience much more contraction than its substrate. However, the substrate keeps the asphalt from contracting freely, and as a result, stress is built inside of the asphalt. When the stress built in asphalt exceeds the critical value that it can withstand, cracking occurs. Cracking caused by low temperature is called “low temperature thermal cracking”. This form of cracking mainly occurs in cold climates, such as in the northern United States and Canada during the winter.
Each year asphalt cracking costs various industries billions of dollars. As a result, it is desirable to have a method to improve the durability and service life of asphaltic materials. To improve asphalt resistance to “oxidative hardening cracking” asphalt has to be modified to be less susceptible to oxidative hardening. To improve asphalt resistance to “low temperature thermal cracking” asphalt has to have better low temperature flexibility.
Hydrated lime, Ca(OH)2, is commonly used in the paving industry as an anti-strip agent to treat aggregate. It is believed that hydrated lime is able to improve asphalt-aggregate interaction (or bonding) to reduce moisture/water damage to asphalt pavement. In this technology, a small amount of dry hydrated lime is blended with the aggregate for a certain time period and then the treated aggregate is mixed with hot asphalt to produce a hot asphalt/aggregate mixture. U.S. Pat. No. 5,512,093 discloses a process to treat aggregate with a quicklime slurry. In this process the properties of hot mix asphalt are improved by treating the aggregate which is combined with bituminous binder and lime. A hot quicklime slurry is produced by slaking quicklime with water at the site of the hot mix asphalt plant using a portable mixing tank. The hot quicklime slurry is then applied to the aggregate. The aggregate is dried and combined with the binder to produce the hot mix asphalt.
U.S. Pat. No. 6,027,558 discloses a hot mix asphalt composition in which hydrated lime is added directly to the asphalt binder prior to the addition of the asphalt binder to the mineral aggregate constituent of the composition. The lime-asphalt mixture is then added to the mineral aggregate. The lime component is added to the asphalt binder in an amount which exceeds about 10% by weight, based upon the total weight of asphalt binder in the composition. U.S. Pat. No. 6,027,558 also discloses an improved hot mix asphalt paving composition, comprising: a lime-asphalt mixture and mineral aggregate, the lime-asphalt mixture being first formed by adding a lime component directly to an asphalt binder prior to addition of the asphalt binder to the mineral aggregate material; and wherein the lime component is present in the lime-asphalt mixture in an amount which exceeds about 10% by weight, based upon the total weight of asphalt binder.
When a relatively high level of hydrated lime (for instance, greater than about 10%) is added to asphalt, the hydrated lime will typically act mainly as filler. In such cases, the improvements observed come mainly from physical asphalt-hydrated lime interactions. High levels of lime have been incorporated into paving asphalt compositions for decades as an antistripping agent.
U.S. Pat. No. 6,562,118 discloses a method for the modification of asphaltic compositions such that cellulosic fibers are not degraded by the asphalt at elevated temperatures. This is achieved by the addition of certain inorganic or organic alkaline materials to the composition. The alkaline materials that can be used are selected from the group consisting of hydroxide, carbonates, silicates and basic salts of Group I, II and III metals and suitable organic bases which are thermodynamically stable under the conditions that the asphalt composition will be used.
SUMMARY OF THE INVENTIONThis invention is based upon the discovery that a small amount of lime can be incorporated into industrial asphalt to greatly improve its resistance to oxidative hardening cracking and low temperature thermal cracking. The incorporation of a small amount of lime into industrial asphalt accordingly results in products made therewith offering improved service life. For instance, roofing shingles made with such asphalt that contains a small amount of lime will be more resistant to cracking and failure in both hot and cold weather climates.
In this application, a relatively low amount (0.1 to 5% by weight based upon the weight of asphalt) of lime, preferably hydrated lime, is added to the industrial asphalt to attain improved properties. This improvement is believed to be a result of the chemical interaction between the asphalt and the lime. In any case, industrial asphalt products such as roofing shingles, roll roofing membranes, roofing underlayment, asphalt-based adhesives, asphalt-based sealants and built-up roofing made with such lime treated asphalt offer improved service life under adverse environmental conditions.
The subject invention more specifically discloses an asphalt roofing shingle having an upper surface and an underside, said asphalt roofing shingle being comprised of a fiber mat which is coated with an asphalt composition, wherein the upper surface of the asphalt roofing shingle includes a layer of roofing granules, wherein the asphalt composition has a softening point which is within the range of 185° F. (85° C.) to 250° F. (121° C.) and a penetration value of at least 15 dmm, and wherein the asphalt composition contains from 0.1 weight percent to 5 weight percent lime.
The subject invention also reveals an asphalt roll roofing membrane that is comprised of a reinforcing mat having an upper side and a lower side wherein said reinforcing mat is coated on its upper surface and its lower surface with an asphalt composition that is comprised of asphalt and from 0.1 weight percent to 5 weight percent lime.
The subject invention also reveals a roofing underlayment which is comprised of an asphalt saturated roofing paper or an asphalt saturated glass fiber mat wherein the asphalt contains from 0.1 weight percent to 5 weight percent lime.
The present invention further discloses a built-up roofing which is comprised of multiple layers of roofing paper or felt that are adhered together with asphalt and which is covered on its upper surface with mineral roofing granules or gravel wherein the asphalt contains from 0.1 to 5 weight percent lime.
The present invention further discloses an adhesive composition which is comprised of asphalt and of a block copolymer modifier wherein the asphalt contains from 0.1 to 5 weight percent lime.
The subject invention further discloses a method for preparing an industrial asphalt comprising (1) heating a base asphalt to a temperature which is within the range of about 100° F. (38° C.) to 400° F. (204° C.) to produce a hot base asphalt, and (2) mixing from 0.1 weight percent to 5 weight percent lime throughout the hot base asphalt while the mixture of hot base asphalt and lime is maintained at a temperature which is within the range of 100° F. (38° C.) to 400° F. (204° C.) to produce the industrial asphalt.
The present invention also reveals an industrial asphalt composition comprising asphalt and from 0.1 weight percent to 5 weight percent lime, wherein the asphalt has a softening point which is within the range of 185° F. (85° C.) to 250° F. (121° C.), wherein the asphalt has a penetration value of at least 15 dmm, and wherein the asphalt composition is void of aggregate, such as small stones and crushed rocks.
DETAILED DESCRIPTION OF THE INVENTIONThe process of this invention is useful in treating asphalt to produce industrial asphalt with improved durability. Such industrial asphalt can be used in making articles of manufacture having improved resistance to cracking at both low and high temperatures. Articles made with the improved industrial asphalt of this invention are typically more resistant to deterioration and provide a longer useful service life. The improved industrial asphalt made by the technique of this invention is particularly useful in manufacturing asphalt roofing products, such as asphalt roofing shingles. Roofing shingles made with the industrial asphalt of this invention offer a higher level of resistance to cracking and deterioration than do roofing shingles made with conventional asphalt. This advantage is of particular importance in cases where roofing shingles will be used on buildings that are located in geographic regions that experience extremely hot and/or cold weather conditions. In any case, roofing shingles made with the improved industrial asphalt of this invention normally provide a longer useful service life.
The technique of this invention can be used to improve the crack resistance of virtually any industrial asphalt. The base asphalt treated by the process of this invention is normally the petroleum residue from a vacuum distillation column used in refining crude oil. The asphaltic material used as the starting material can also be air blown asphalt, solvent extracted asphalt, naturally occurring asphalt, or synthetic asphalt. Blends of such asphaltic materials can also be treated by the process of this invention. The asphalt flux can also include polymers, recycled tire rubber, recycled engine oil residue, recycled plastics, softeners, antifungal agents, biocides (algae inhibiting agents), and other additives. Tar and pitch can also be used as the starting material for treatment by the technique of this invention.
The industrial asphalt that is used in manufacturing roofing shingles will normally have a softening point which is within the range of 185° F. (85° C.) to 250° F. (121° C.) and a penetration value of at least 15 dmm. Preferably, industrial asphalt that is used in making roofing shingles will have a softening point which is within the range of 185° F. (85° C.) to 235° F. (113° C.), and a penetration value which is within the range of 15 dmm to 35 dmm. Finally, industrial asphalt employed in manufacturing roofing shingles will more preferably have a softening point which is within the range of 190° F. (88° C.) to 220° F. (104° C.) and a penetration value which is within the range of 15 dmm to 25 dmm.
For purposes of this invention, asphalt softening points are measured following ASTM D 36-95 “Standard Test Method for Softening Point of Bitumen (Ring-and Ball Apparatus)” and asphalt penetrations are measured following ASTM D 5-97 “Standard Test Method for Penetration of Bituminous Materials”.
In other embodiments of this invention the asphalt can be (1) a Type I asphalt which has a softening point of from 135° F. (57° C.) to 151° F. (66° C.) and a penetration of from 18 dmm to 60 dmm at 77° F. (25° C.), (2) a Type II asphalt which has a softening point of from 158° F. (70° C.) to 176° F. (80° C.) and a penetration of from 18 dmm to 40 dmm at 77° F. (25° C.), (3) a Type III asphalt which has a softening point of from 185° F. (85° C.) to 205° F. (96° C.) and a penetration of from 15 dmm to 35 dmm at 77° F. (25° C.), or (4) a Type IV asphalt which has a softening point of from 210° F. (99° C.) to 225° F. (107° C.) and a penetration of from 12 dmm to 25 dmm at 77° F. (25° C.).
The asphalt treated by the technique of this invention can be air blown to attain the desired softening point. In such an air blowing procedure the asphalt is heated to a temperature which is within the range of 400° F. (204° C.) to 550° F. (288° C.) and an oxygen containing gas is blown (sparged) through it. This air blowing step will preferably be conducted at a temperature which is within the range of 425° F. (218° C.) to 525° F. (274° C.) and will most preferably be conducted at a temperature which is within the range of 450° F. (232° C.) to 500° F. (260° C.). This air blowing step will typically take about 2 hours to about 8 hours and will more typically take about 3 hours to about 6 hours. However, the air blowing step will be conducted for a period of time that is sufficient to attain the ultimate desired softening point and penetration value. In making industrial asphalt for roofing shingles the asphalt will typically be air blown until a softening point which is within the range of 185° F. (85° C.) to 250° F. (121° C.) and a penetration value of at least 15 dmm is attained.
The oxygen containing gas (oxidizing gas) used in such an air blowing step is typically air. The air can contain moisture and can optionally be enriched to contain a higher level of oxygen. Chlorine enriched air or pure oxygen can also be utilized in the air blowing step. Air blow can be performed either with or without a conventional air blowing catalyst. Some representative examples of air blowing catalysts include ferric chloride (FeCl3), phosphorous pentoxide (P2O5), aluminum chloride (AlCl3), boric acid (H3BO3), copper sulfate (CuSO4), zinc chloride (ZnCl2), phosphorous sesquesulfide (P4S3), phosphorous pentasulfide (P2S5), phytic acid (C6H6[OPO—(OH)2]6), and organic sulfonic acids.
The asphalt treatment process of this invention is conducted by first heating the asphalt being treated to a temperature which is within the range of about 100° F. (38° C.) to 400° F. (204° C.) to produce a hot base asphalt. Then from about 0.1 weight percent to about 5 weight percent lime, preferably hydrated lime, is mixed throughout the hot base asphalt while it is maintained at a temperature which is within the range of 100° F. (38° C.) to 400° F. (204° C.) to produce the industrial asphalt. In most cases this mixing step will be conducted over a time period which is within the range of about 10 minutes to about 4 hours. The lime will typically be mixed into the asphalt over a period of about 20 minutes to 2 hours. Typically about 0.5 weight percent to about 4 weight percent of the lime will be added to the hot base asphalt. It is generally preferred to mix 1 weight percent to 3 weight percent of the lime into the base asphalt.
For purposed of this invention “lime” refers to compounds that include at least one of following functional components: (1) quicklime (CaO); (2) calcium hydroxide (Ca(OH)2); (3) dolomitic quicklime (CaO.MgO); (4) dolomitic normal hydrate (Ca(OH)2.MgO); (5) dolomitic pressure hydrate (Ca(OH)2.Mg(OH)2); and (6) mixtures of any or all of these functional components. It is preferred for the lime to be hydrated lime.
In the practice of this invention it may be advantageous to add the lime to the base asphalt at the end of the air blow procedure while the blown asphalt is still hot. By adding the lime to the hot asphalt at the end of the air blowing step it is not necessary to heat the asphalt from ambient temperature to the required mixing temperature. This can save energy because the lime is added to the base asphalt after it is being cooled from the temperature used in the air blowing procedure. The lime can optionally be mixed into the base asphalt in the vessel used for the air blowing in which case agitation can be provided by continuing to blow air or some other gas into the asphalt being treated to homogeneously disperse the lime through it. After the lime is dispersed throughout the asphalt it is, of course, cooled to ambient temperature to produce the improved industrial asphalt of this invention.
The improved industrial asphalt of this invention can be used in making roofing products and other industrial products using standard procedures. For instance, the industrial asphalt can be blended with fillers (such as, limestone, stonedust, sand, mica, slate flour, diatorriaceous earth and the like), stabilizers, polymers, recycled tire rubber, recycled engine oil residue, recycled plastics, softeners, antifungal agents, biocides (algae inhibiting agents), and other additives. The filler can optionally be a glass filler, such as chopped glass fibers.
Asphalt roofing shingles can be made by coating a fiber mat with the improved industrial asphalt composition of this invention and subsequently applying a layer of roofing granules to the upper surface thereof to produce the roofing shingle. This is normally accomplished by (1) unwinding a roll of fiber roofing mat, (2) coating the fiber roofing mat with the industrial asphalt of this invention which has been heated to an elevated temperature while the fiber roofing mat is being unwound, (3) applying mineral roofing granules to the asphalt-covered surface of the mat and embedding the granules in the hot asphalt to form a single-layer sheet of shingle material, (4) cooling the sheet of shingle material to ambient temperature, and (5) cutting the sheet of shingle material into roofing shingles of the desired size and shape.
The fiber roofing mat will typically be comprised of an inorganic fiber, such as a glass fiber. For instance, the fiber roofing mat can be comprised of a polysiloxane compound having —[SiO]— repeating units. However, the fiber roofing mat can optionally be comprised of one or more organic polymeric fibers, such as polyethylene, polypropylene, polyester, nylon, or acrylic fibers. On the other hand, the fiber roofing mat can be void of organic fibers, such as cellulosic fibers (wood or pulp particles).
In cases where the fiber roofing mat is comprised of a polysiloxane it can be modified with various substituents which include linear, branched, or aromatic end-groups. Such end groups can optionally contain oxygen, sulfur and/or nitrogen. Generally, the polysiloxanes are classified as polyalkyl-silanes, polyaryl-silanes, polyalkylaryl-silanes, and polyether-siloxanes. The polysiloxanes that are typically the most useful have a weight average molecular weight (MW) of at least 600. A preferred class of polysiloxanes is polydialkylsiloxanes, with polydimethylsiloxane being highly preferred.
Some representative examples of suitable polysiloxanes that can be employed in the fiber roofing mats employed in making the asphalt roofing shingles of this invention include, but are not limited to, polyalkylene oxide-modified polydimethylsiloxane-dimethylsiloxane copolymer (MW=13,000); polyalkylene oxide-modified polydimethylsiloxane-dimethylsiloxane copolymer (MW=3000); polyalkylene oxide-modified polydimethylsiloxane-dimethylsiloxane copolymer (MW=4000); (carboxylatepropyl)methylsiloxane-dimethylsiloxane copolymer (MW>1000); dimethylsiloxane-(60% PO-40% EO) block copolymer (MW=20,000); (hydroxyalkyl functional) methylsiloxane-dimethylsiloxane copolymer (MW=5000); aminopropylmethylsiloxane-dimethylsiloxane copolymer MW=4500); aminoethylaminopropylmethoxysiloxane-dimethylsiloxane copolymer (MW>1000); glycidoxy propyl dimethoxy silyl end-blocked dimethyl siloxane polymer (MW=5000); methacryloxy propyl dimethyoxy silyl dimethyl siloxane polymer (MW=40,000); vinyl dimethoxy silyl end-blocked dimethyl siloxane polymer (MW=6500); aminoethylaminopropyl dimethoxy silyl end-blocked dimethyl siloxane polymer (MW=3800); amine-alkyl modified methylalkylaryl silicone polymer (MW=7800); epoxy functional dimethylpolysiloxane copolymer (MW=8300); dimethylpolysiloxane (MW=26,439); dodecylmethylsiloxane-hydroxypolyalkyleneoxypropyl methylsiloxane copolymer (MW=1900); (dodecylmethylsiloxane)-(2-phenylpropylmethylsiloxane) copolymer (MW>1000) and polyalkylene oxide-modified polydimethylsiloxane-dimethylsiloxane copolymer (MW=600).
U.S. Pat. No. 6,737,369 discloses coated fiber roofing mats that can be utilized in the practice of this invention. These cured, non-woven roofing mats are comprised of a mixture of fibers having different fiber lengths which are fixedly distributed in a binder, wherein the fibers contain a polysiloxane compound. The mixture of fibers used in these fiber mats contain from about 0 weight percent to about 100 weight percent fibers having an average length of from about 0.5 mm to about 60 mm and from about 0 weight percent to about 100 weight percent fibers having an average length of from about 10 mm to about 150 mm. More preferably, from about 20 weight percent to about 80 weight percent of the fibers will have an average length of from about 10 mm to about 45 mm and from about 20 weight percent to about 80 weight percent of fibers having an average length of from about 30 mm to about 80 mm. The fibers having differing fiber lengths typically have an average diameter of from about 1 μm to about 100 μm, with an average diameter of from about 5 μm to about 25 μm being more highly preferred. Such fibers can be obtained from commercial sources or made by techniques well known to those skilled in the art. The binders that can be used in making such fiber roofing mats are described in detail in U.S. Pat. No. 6,737,369 and the teachings of U.S. Pat. No. 6,737,369 are incorporated herein by reference in their entirety.
Virtually any type of conventional roofing granules can be used in making the asphalt shingles of this invention. For instance, the roofing granules can be comprised of greenstone, nephylene syenite, common gravel slate, gannister, quartzite, greystone, and the like. The roofing granules used will typically be of a size that is within the range of about 420 micrometers to 1680 micrometers (40 mesh to 12 mesh). However, the use of larger or smaller granules is within the scope of this invention. For aesthetic purposes the roofing granules will typically be colored. In many cases two or more different colors of roofing granules will be mixed to attain the desired color for the roofing shingle. Colored roofing granules can be prepared by first preheating mineral rock granules having a size of about 420 micrometers to about 1680 micrometers (40 to 12 US mesh) to a temperature which is within the range of 100° F. (38° C.) to 1000° F. (538° C.). Then, a paint slurry containing a pigment is applied to the heated granules in a mixer. The color coated granules are subsequently heated in a kiln to a temperature of about 350° F. (175° C.) to 1200° F. (650° C.). Then, the colored granules are cooled and passed to a post-treatment stage where the colored granules are treated with an oil formulation in a rotary mixer. The oil formulation is applied to reduce dust and promote adhesion of the granules to the asphalt substrate. After the oil treatment, the granules are removed from the post-treatment stage, transported, and subsequently applied to the asphalt substrate. U.S. Pat. No. 5,286,544 discloses a specific process for preparing colored roofing granules that involves treating the granules with a composition that contains an oil and an elastomeric rubber that is compatible with the oil. The teaching of U.S. Pat. No. 5,286,544 are incorporated herein by reference with respect to types of roofing granules that can be utilized in the practice of this invention and with respect to techniques for making such roofing granules.
U.S. Pat. No. 4,717,614 and U.S. Pat. No. 5,860,263 describe asphalt roofing shingles that can be made utilizing the improved industrial asphalt compositions of this invention as well as techniques for manufacturing such roofing shingles. The teachings of both U.S. Pat. No. 4,717,614 and U.S. Pat. No. 5,860,263 are incorporated herein by reference in their entirety.
Asphalt roll roofing membranes can be made by coating a reinforcing mat on both its upper surface and its lower surface with the improved industrial asphalt composition of this invention. The reinforcing mat will typically be a non-woven mat that is comprised of a polymeric material, such as polyester, which has the ability to stretch under tension. This is important so that the asphalt roll roofing will be flexible enough to withstand normal roof movement as well as expansion and contraction over the temperature range experienced in the geographic region where the asphalt roll roofing is installed. Typically, the improved industrial asphalt composition of this invention will also contain a polymeric modifier to provide the asphalt with an ability to stretch when used in such applications. The polymer modifier will typically be a rubbery polymer and can optionally be a block copolymer such as a styrene-butadiene-styrene block copolymer. The asphalt roll roofing will also preferably be coated on its upper surface with roofing granules such as those that can be used in making roofing shingles.
Roofing underlayment can be made with the improved industrial asphalt of this invention by using such asphalt to saturate roofing paper or fiber mat.
Built-up roofing can be made with the improved industrial asphalt of this invention by using such asphalt to adhere multiple layers of roofing paper or felt together in manufacturing the built-up roofing material. The built-up roofing will typically be covered on its upper surface with roofing granules or gravel.
The improved industrial asphalt of this invention can also be used in manufacturing asphalt based adhesive compositions and asphalt based sealant compositions. This can be done by simply substituting the improved industrial asphalt of this invention for the conventional asphalts that are conventionally used in making asphalt based adhesives and asphalt based sealant compositions. Such compositions will typically also include one or more elastomeric materials, such as ground rubber from used tires. Such sealant and adhesive compositions can also contain one or more synthetic rubbers, natural rubber, or an elastomeric block copolymer, such as a styrene-butadiene-styrene block copolymer.
This invention is illustrated by the following examples that are merely for the purpose of illustration and are not to be regarded as limiting the scope of the invention or the manner in which it can be practiced. Unless specifically indicated otherwise, parts and percentages are given by weight.
1. Durability Improvement
In this invention, asphalt durability (weathering resistance) is defined as the cycle-to-failure in a weather-o-meter according to ASTM D 4798-00 “Standard Test Method for Accelerated Weathering Test Method Conditions and Procedures for Bituminous Materials (Xeon-Arc Method)” Cycle A. Asphalt failure is determined according to ASTM D 1670.
COMPARATIVE EXAMPLE 1 AND WORKING EXAMPLE 2The base asphalt 1 utilized in Comparative Example 1 was tested and determined to have a durability of 34 cycles. This asphalt was not treated in accordance with the technique of this invention.
In Working Example 2 the same asphalt that was tested in Comparative Example 1 (asphalt 1) was treated with mixing hydrated lime into it at a temperature of 300° F. (149° C.) with the mixing being conducted over a period of about 0.5 hours. The asphalt made by this procedure was subsequently tested for durability and was determined to have a durability of 60 cycles. This experiment accordingly shows that the durability of base asphalt can be improved by treating it with hydrated lime at an elevated temperature.
The results attained in this series of experiments at a Ca(OH)2 level of 0 weight percent and 2 weight percent are summarized in Table 1.
In this series of experiments a second base asphalt sample (asphalt 2) was treated in accordance with the method of this invention and compared to a control. The base asphalt 2 tested in Comparative Example 3 was determined to have a durability of 46 cycles. In Working Example 4 hydrated lime was mixed into the base asphalt at a temperature of 300° F. (149° C.) over a period of 0.5 hours. The hydrated lime modified asphalt 2 prepared in Working Example 4 was determined to have a durability of 74 cycles. This experiment again shows that the durability of base asphalt can be improved by treating it with hydrated lime.
The results attained in this series of experiments at a Ca(OH)2 level of 0 weight percent and 2 weight percent are summarized in Table 2.
In this series of experiments a second base asphalt sample (asphalt 3) was treated in accordance with the method of this invention and compared to a control. The base asphalt 3 tested in Comparative Example 5 was determined to have a durability of 46 cycles. In Working Example 6 hydrated lime was mixed into the base asphalt at a temperature of 300° F. (149° C.) over a period of 0.5 hours. The hydrated lime modified asphalt 3 prepared in Working Example 6 was determined to have a durability of 74 cycles. This experiment again shows that the durability of base asphalt can be improved by treating it with hydrated lime.
The results attained in this series of experiments at a Ca(OH)2 level of 0 weight percent and 2 weight percent are summarized in Table 3.
2. Low Temperature Flexibility Improvement
In this experiment the asphalt samples of Comparative Example 5 and Working Example 6 were evaluated to determine their low temperature flexibility. Modulus data was obtained from a dynamic mechanic analyzer (DMA) at different temperatures. At a fixed temperature, as the modulus of the asphalt increases its stiffness also increases and its flexibility decreases. In other words, lower modulus is indicative of better flexibility. In Working Example 6 where the asphalt 3 was modified with 2% hydrated lime (based on the asphalt weight), there is significant drop in modulus, meaning the modified asphalt had better flexibility at low temperature than did the control asphalt. For example, at −20° C., asphalt 3 had a modulus of 852.8 MPa, and the modified asphalt 3 has a modulus of 634.2 MPa, which shows a reduction of 218.6 MPa in modulus. In other words, the lime modified asphalt 3 exhibited a better resistance to “low temperature thermal cracking” than the control asphalt.
The modulus of the control and the lime modified asphalt over a range of different temperatures is reported in Table 4.
3. Oxidative Hardening Resistance Improvement
In this experiment a lime modified asphalt composition was made and compared to a control that was not modified with lime. In this procedure, 2 weight percent hydrated lime was mixed into asphalt 4 in the working example. The control asphalt (asphalt 4) and the 2% hydrated lime modified asphalt 4 were subjected to weathering in a weather-o-meter for 10 days according to ASTM D 4798-00 “Standard Test Method for Accelerated Weathering Test Method Conditions and Procedures for Bituminous Materials (Xeon-Arc Method)” Cycle A. The results of this experiment are reported in Table 5.
Aging index was defined as the ratio of modulus of weather-o-meter aged asphalt to modulus of unaged asphalt:
Aging index=modulus of weather-o-meter aged asphalt/modulus of unaged asphalt
Modulus was measured on a dynamic shear rheometer (DSR) at 76° C. at different angular frequencies.
Data indicates that there is a significant drop in aging index with hydrated lime modification especially at low angular frequency, meaning the addition of hydrated lime into asphalt can significantly reduce the rate of asphalt aging or oxidation. In other words, an addition of a small amount of hydrated lime, into asphalt can dramatically increase asphalt's resistance to “oxidative hardening cracking”.
While certain representative embodiments and details have been shown for the purpose of illustrating the subject invention, it will be apparent to those skilled in this art that various changes and modifications can be made therein without departing from the scope of the subject invention.
Claims
1. A method for preparing an industrial asphalt comprising (1) heating a base asphalt to a temperature which is within the range of about 100° F. to 400° F. to produce a hot base asphalt, and (2) mixing from 0.1 weight percent to 5 weight percent lime throughout the hot base asphalt while the mixture of hot base asphalt and lime is maintained at a temperature which is within the range of 100° F. to 400° F. to produce the industrial asphalt.
2. A method as specified in claim 1 wherein the lime is in the form of solid particles or a solid powder.
3. A method as specified in claim 1 wherein the lime is added to the asphalt as an aqueous slurry.
4. A method as specified in claim 1 wherein the mixing in step (2) is fulfilled by mechanical agitation.
5. A method as specified in claim 1 wherein the mixing in step (2) is fulfilled by bubbling an inert gas through the hot lime modified base asphalt.
6. A method as specified in claim 1 wherein the lime is mixed into the asphalt in step (2) for a period of time which is within the range of about 10 minutes to about 4 hours.
7. A method as specified in claim 1 wherein the amount of lime added to the hot base asphalt in step (2) is within the range of 0.5 weight percent to 2 weight percent.
8. A method for preparing an industrial asphalt comprising (1) heating a base asphalt to a temperature which is within the range of about 100° F. to 400° F. to produce a hot base asphalt, (2) adding from about 0.1 weight percent to about 5 weight percent of a lime compound to the hot base asphalt, (3) mixing the lime compound throughout the hot base asphalt to prepare a lime compound containing base asphalt, (4) heating the lime compound containing base asphalt to a temperature which is within the range of about 400° F. to about 550° F. to produce a hot lime compound containing base asphalt, (5) sparging an oxygen containing gas through the hot lime compound containing base asphalt for a period of time which is sufficient to produce the industrial asphalt.
9. An industrial asphalt composition comprising asphalt and from 0.1 weight percent to 5 weight percent lime.
10. An industrial asphalt composition as specified in claim 9 wherein the lime is present in the asphalt composition at a level which is within the range of 0.5 weight percent to about 2 weight percent.
11. An industrial asphalt composition as specified in claim 9 wherein the asphalt has a softening point which is within the range of 185° F. to 250° F., and wherein the asphalt has a penetration value of at least 15 dmm.
12. An industrial asphalt composition as specified in claim 9 wherein the industrial asphalt has a softening point which is within the range of 185° F. to 235° F. and wherein the industrial asphalt has a penetration value which is within the range of 15 dmm to 35 dmm.
13. An industrial asphalt composition as specified in claim 9 wherein the industrial asphalt has a softening point which is within the range of 190° F. to 220° F. and wherein the industrial asphalt has a penetration value which is within the range of 15 dmm to 25 dmm.
14. An industrial asphalt as specified in claim 9 wherein the industrial asphalt is a Type I asphalt which has a softening point of from 135° F. to 151° F. and a penetration of from 18 dmm to 60 dmm at 77° F.
15. An industrial asphalt as specified in claim 9 wherein the industrial asphalt is a Type II asphalt which has a softening point of from 158° F. to 176° F. and a penetration of from 18 dmm to 40 dmm at 77° F.
16. An industrial asphalt as specified in claim 9 wherein the industrial asphalt is a Type III asphalt which has a softening point of from 185° F. to 205° F. and a penetration of from 15 dmm to 35 dmm at 77° F.
17. An industrial asphalt as specified in claim 9 wherein the industrial asphalt is a Type IV asphalt which has a softening point of from 210° F. to 225° F. and a penetration of from 12 dmm to 25 dmm at 77° F.
18. An industrial asphalt composition as specified in claim 9 wherein the lime is hydrated lime.
19. An industrial asphalt as specified in claim 9 wherein the lime compound is dolomitic normal hydrate.
20. An industrial asphalt as specified in claim 9 wherein the lime is a dolomitic pressure hydrate.
21. An industrial asphalt as specified in claim 9 wherein the lime is quicklime.
22. An industrial asphalt as specified in claim 9 wherein the lime compound is a dolomitic quicklime.
23. An asphalt roofing shingle having an upper surface and an underside, said asphalt roofing shingle being comprised of a fiber mat which is coated with an asphalt composition, wherein the upper surface of the asphalt roofing shingle includes a layer of roofing granules, wherein the asphalt composition has a softening point which is within the range of 185° F. to 250° F. and a penetration value of at least 15 dmm, and wherein the asphalt composition contains from 0.1 weight percent to 5 weight percent lime.
24. An asphalt roofing shingle as specified in claim 23 wherein the industrial asphalt has a softening point which is within the range of 185° F. to 235° F., and wherein the industrial asphalt has a penetration value which is within the range of 15 dmm to 35 dmm.
25. An asphalt roofing shingle as specified in claim 23 wherein the industrial asphalt has a softening point which is within the range of 190° F. to 220° F., and wherein the industrial asphalt has a penetration value which is within the range of 15 dmm to 25 dmm.
26. An asphalt roofing shingle as specified in claim 23 wherein the lime is present in the asphalt composition at a level which is within the range of 0.5 weight percent to about 2 weight percent.
27. An asphalt roofing shingle as specified in claim 23 wherein the lime is hydrated lime.
28. An asphalt roofing shingle as specified in claim 23 wherein the fiber mat is comprised of glass fibers.
29. An asphalt roofing shingle as specified in claim 23 wherein the fiber mat is comprised of at least one polymeric fiber selected from the group consisting of polyethylene fibers, polypropylene fibers, polyester fibers, nylon fibers, and acrylic fibers.
30. An asphalt roofing shingle as specified in claim 23 wherein the lime is dolomitic normal hydrate.
31. An asphalt roofing shingle as specified in claim 23 wherein the lime is dolomitic pressure hydrate.
32. An asphalt roofing shingle as specified in claim 23 wherein the lime is quicklime.
33. An asphalt roofing shingle as specified in claim 23 wherein the lime is dolomitic quicklime.
34. An asphalt roll roofing membrane that is comprised of a reinforcing mat having an upper side and a lower side wherein said reinforcing mat is coated on its upper surface and its lower surface with an asphalt composition that is comprised of asphalt and from 0.1 weight percent to 5 weight percent lime.
35. A roofing underlayment which is comprised of an asphalt saturated felt wherein the asphalt contains from 0.1 weight percent to 5 weight percent lime.
36. A built-up roofing which is comprised of multiple layers of roofing paper or felt that are adhered together with asphalt and which is covered on its upper surface with mineral roofing granules or gravel wherein the asphalt contains from 0.1 to 5 weight percent lime.
37. An adhesive composition which is comprised of asphalt and of a polymer modifier wherein the asphalt contains from 0.1 to 5 weight percent lime.
Type: Application
Filed: Mar 28, 2006
Publication Date: Oct 4, 2007
Applicant:
Inventor: Yonghong Ruan (Wayne, NJ)
Application Number: 11/390,643
International Classification: E01F 9/04 (20060101);
