Classifications

• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
  • C08L95/00—Compositions of bituminous materials, e.g. asphalt, tar, pitch
  • C08L95/005—Aqueous compositions, e.g. emulsions
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08L—COMPOSITIONS OF MACROMOLECULAR COMPOUNDS
  • C08L53/00—Compositions of block copolymers containing at least one sequence of a polymer obtained by reactions only involving carbon-to-carbon unsaturated bonds; Compositions of derivatives of such polymers
  • C08L53/02—Compositions of block copolymers containing at least one sequence of a polymer obtained by reactions only involving carbon-to-carbon unsaturated bonds; Compositions of derivatives of such polymers of vinyl-aromatic monomers and conjugated dienes

Definitions

• the present invention relates to asphalt emulsions for treatment of road surfaces. More specifically, the present invention relates to improvements in methods for treatment of aged, cracked or otherwise deteriorated road surfaces paved with asphalt. The improvements provide stronger, more stable and less costly emulsions than those previously available.
• Asphalt road surfaces typically consist of asphalt and aggregate. Oxidation of asphalt binder during its service time, climate conditions and use of road surfaces, particularly by heavy loads, result in deterioration of the road surfaces over time. For example, repeated contraction of the road surface during the cold winter nights due to temperature changes results in formation of perpendicular cracks in pavement, known as cold fractures. The asphalt binder becomes too soft during the hot summer days, resulting in a permanent deformation of the road surface under repeated heavy loads, termed "rutting". In addition, as a result of continuous mechanical stress, road surfaces become fatigued, resulting in formation of alligator skin- like cracks, known as fatigue fracture.
• PASS is also used as a tack coat, chip seal, scrub seal and fog seal as well as for crack filling.
• An advantage of PASS is that it can be applied in a single step, over existing pavement. Moreover, PASS rejuvenates and prevents further oxidation of the underlying pavement. Moreover, PASS can be applied over a wide temperature range.
• a composition for rejuvenating asphalt pavement according to the present invention comprises an asphalt binder, water, a cationic surfactant, a recycling agent, and a cationic coagglomerated styrene butadiene rubber latex, which includes sulfur and a vulcanizing agent.
• the composition is also useful as a scrub seal, fog seal, sand seal as well as for crack filling and prevention of reflective cracking.
• the inventive composition may be used in emulsions with different setup times.
• the invention also includes a method for treatment of aged and cracked asphalt pavement by application of the disclosed composition.
• the present invention relates to an improved asphalt emulsion for restoring and rejuvenating aged, cracked and deteriorated asphalt pavement.
• the invention reflects an improvement over United States patent 5,180,428. More specifically, the disclosed invention improves on the performance of the modifier of the '428 patent by providing a stronger, more flexible surface, useful over a wider range of climatic conditions, yet at a lower cost.
• the following sections describe the preparation of the various components of the invention.
• the invention is a mixture of components that interact with one another.
• the concentration of one component may be increased if the concentration of another is decreased, without altering the properties of the resulting emulsion.
• Asphalts ranging from AC-5 to AC-30 may be used.
• a key aspect of the invention is providing a sufficient quantity of maltenes, which are the non-asphaltene fraction of asphalt, and often referred to as the deasphalted or deasphaltened oil.
• the maltene fraction of asphalt consists of polar resins, and aromatic and saturate solvents.
• PASS as well as the present invention, works best with a recycling agent that is rich in aromatics and resins, with small amounts of saturates.
• the maltene oils may be provided by the asphalt or the recycling agent. If the asphalt is low in maltenes, the deficiency may be made up by increasing the amount of recycling agent used. It has been discovered that a sufficient amount of recycling agent is present when the viscosity of the mixture of recycling agent and asphalt lies between 1,000 and 3,000 centipoise at 60°C.
• a range of different asphalts will be used depending on the desired time for setup and climate, especially maximum and minimum road surface temperature, in summer and winter, respectively.
• an AC-5 asphalt is preferred for a quick break emulsion, and cold climate.
• An AC- 10 to 20 asphalt will be used for an intermediate setup, such as a sand seal, and an AC-20-30 for a slow setup and/or hotter regions.
• the preferred recycling agents are available from Sunoco under their Hydrolene® brand ashpalt oils.
• Asphalt oils meeting the ASTM standard D4552, and classified as RA-1 are preferred for harder asphalt, such as AC-20 and AC-30.
• RA-5 oils may also be used with lower viscosity asphalt, such as AC-5.
• SBR styrene-butadiene rubber
• SBR styrene-butadiene rubber
• the styrene-butadiene rubber (“SBR”) latex dispersion of the invention is preferably prepared using a low temperature method as discussed, e.g., in R.W. Brown et al., "Sodium Formaldehyde in GR-S Polymerization", Industrial and Engineering Chemistry, vol. 46, pp. 1073 (1-954) and B.C. Pryor et al., "Reaction Time for Polymerization of Cold GR-S” Industrial and Engineering Chemistry, vol. 45, pp. 1311 (1953), both of which are incorporated by reference herein in their entirety.
• the SBR latex is prepared by polymerizing styrene and butadiene monomers at a temperature less than or equal to about 25°C, and more preferably between 5°C and 25°C, in an aqueous emulsion polymerization reaction.
• the styrene-butadiene rubber latex dispersion used in the invention is preferred to be non-functionalized, i.e., is preferably prepared by polymerizing monomers consisting essentially of styrene, and butadiene.
• the styrene-butadiene rubber latex dispersion used in the invention is preferably substantially free (e.g.
• the styrene-butadiene rubber latex dispersion of the invention is prepared by polymerizing a mix of monomers that includes styrene, butadiene and that is free of functional monomers.
• the styrene-butadiene rubber latex dispersion can be prepared by polymerizing monomers consisting only of styrene, butadiene or it could be only with butadiene for special cases.
• the SBR polymer latex used in the present invention can be produced using either a continuous or batch process.
• the SBR polymer latex is produced using a continuous method by continuously feeding a monomer stream, a soap stream and an
• EL937667137 US f activator stream to a series of reactors.
• the monomers in the emulsion stream are preferably fed at a butadiene to styrene weight ratio from about 70:30 to about 78:22.
• the soap stream includes a soap, a free radical generator (e.g. organic peroxide) that is used in the redox initiator system, and water.
• the soap in the emulsion stream is preferably a natural soap such as sodium or potassium oleate or the sodium or potassium salt of rosin acid.
• the soap is typically present in the emulsion feed in an amount from about 0.5 to about 5 weight percent, based on total monomer weight.
• the free radical generators used in the soap stream generally include organic peroxygen compounds such as benzoyl peroxide, hydrogen peroxide, di-t-butyl peroxide, dicumyl peroxide, 2,4-dichlorobenzoyl peroxide, decanoyl peroxide, lauroyl peroxide, diisopropylbenzene hydroperoxide, cumene hydroperoxide, p-menthane hydroperoxide, -pinene hydroperoxide, t- butyl hydroperoxide, acetyl acetone peroxide, methyl ethyl ketone peroxide, succinic acid peroxide, dicetyl peroxydicarbonate, t-butyl peroxyacetate, t-butyl peroxymaleic acid, t-butyl peroxybenzoate, and the like, as well as alkyl perketals, such as 2,2-bis-(t-butylperoxy)butane, ethy
• the activator stream includes the other components of the redox initiator system.
• the redox initiator system in addition to the free radical generator fed with the soap stream, includes a reducing agent and a water-soluble metal salt of iron, copper, cobalt, nickel, tin, titanium, vanadium, manganese, chromium or silver.
• Suitable reducing agents for use in the initiator stream include sulfur dioxide; alkali metal disulfites; alkali metal and ammonium hydrogen sulfites; thiosulfate, dithionite and formaldehyde sulfoxylates; hydroxylamine hydrochloride; hydrazine sulfate; glucose and ascorbic acid.
• the reducing agent is sodium formaldehyde sulfoxylate dihydrate (SFS).
• FSS sodium formaldehyde sulfoxylate dihydrate
• the reducing agent is typically present in an amount between about 0.01 and 1% by weight based on total monomer weight.
• the weight ratio of reducing agent to free radical generator is preferably between about 0.2:1 and 1 :1.
• the water-soluble metal salt of iron, copper, cobalt, nickel, tin, titanium, vanadium, manganese, chromium or silver can be chosen from a wide variety of water- soluble metal salts.
• Suitable water-soluble metal salts include copper (II) amine nitrate, copper (II) metaborate, copper (II) bromate, copper (II) bromide, copper perchlorate, copper (II) dichromate, copper (II) nitrate hexahydrate, iron (II) acetate, iron (III) bromide, iron (III) bromide hexahydrate, iron (II) perchlorate, iron (III) dichromate, iron (III) formate, iron (III) lactate, iron (III) malate, iron (III) nitrate, iron (III) oxalate, iron (II) sulfate pentahydrate, cobalt (II) acetate, cobalt (II)
• the metal can also be complexed with a compound such as ethylene diamine tetracetic acid (EDTA) to increase its solubility in water.
• EDTA ethylene diamine tetracetic acid
• iron/EDTA complexes or cobalt/EDTA complexes can be used.
• the water soluble metal salt is used as an iron (II) sulfate EDTA complex.
• the water-soluble metal salt is typically present in an amount less than 0.01% by weight based on total monomer weight.
• the polymerization reaction can be conducted in the presence of C8 to C12 mercaptans, such as octyl, nonyl, decyl or dodecyl mercaptans, which are used as molecular weight regulators
• EL937667137 US g or chain transfer agents to reduce the molecular weight of the SBR polymer.
• n- dodecyl or t-dodecyl mercaptan is used and t-dodecyl mercaptan is the most commonly used.
• the amount of t-dodecyl mercaptan used will depend upon the molecular weight that is desired for the SBR. Larger quantities of t-dodecyl mercaptan cause greater reductions in the molecular weight of the SBR.
• the amount of t-dodecyl mercaptan is preferably between about 0.05 and 0.5%.
• the monomer feed, soap feed and activator feed are separately fed to a reactor where polymerization of the styrene and t-butadiene monomers occurs.
• the total amount of water in the reactors is typically 60-75% by weight based on total monomer weight.
• the emulsion polymerization reaction normally produces between about 60% and about 80% conversion of the styrene and butadiene monomer into poly(styrene-butadiene) or SBR particles.
• a shortstop to the last of the reactors in series, which reacts rapidly with free radicals and oxidizing agents, thus destroying any remaining initiator and polymer free radicals as well as preventing the formation of new free radicals.
• exemplary shortstops include organic compounds possessing a quinoid structure (e.g., quinone) and organic compounds that may be oxidized to quinoid structures (e.g.
• hydroquionone optionally combined with water soluble sulfides such as hydrogen sulfide, ammonium sulfide or sulfides or hydrosulfides of alkali or alkaline earth metals; N-substituted dithiocarbamates; reaction products of alkylene polyamines, with sulfur containing presumably sulfides, disulfides, polysulfides and/or mixtures of these and other compounds; dialkylhydroxylamines; N,N'-dialkyl-N,N'-methylenebishydroxyl-amines; dinitrochlorobenzene; dihydroxydiphenyl sulfide, dinitrophenylbenzothazyl sulfide and mixtures thereof.
• the shortstop is hydroquinone or potassium diethyl dithiocarbamate. The short stop is typically added in an amount between about 0.01 and 0.1% by weight based on total monomer weight * .
• the SBR polymer can also be produced using a batch process, i the batch process, the monomers, the soap, the free radical generator and water are all added to the reactor arid agitated. After reaching the desired polymerization temperature, an activator solution, including the reducing agent and one of the previously water soluble metal salts are added to initiate polymerization. A short stop is added to terminate the polymerization once the desired conversion level is reached.
• the unreacted monomers are then typically removed from the latex dispersion.
• the butadiene monomers can be removed by flash distillation at atmospheric pressure and then at reduced pressure.
• the resulting styrene monomers can be removed by steam stripping in a column.
• the resulting SBR latex at this point typically has a solids content of less than 50%.
• the SBR latex is then preferably agglomerated, e.g., chemical, freeze or pressure agglomeration, and water is removed to increase the total solids content up to about 72%.
• the solids content is below 50%, and also latex particle size is below lOOnm, typically 50-70nm.
• latex viscosity becomes above lOOOcP (lPas) at above 50% solids content.
• This latex is then agglomerated to produce larger particles, with a distribution of particle size ranging from lOOnm to between 2 and 3 microns. The result is to substantially decrease the viscosity of the latex, to about 50mPas or less at about 50%.
• Agglomeration can be carried out by two basic chemical or physical methods. Agglomeration processes are described in detail in Polymer Latices, Science and Technology, Volume 2: Types of Latices by D.C. Blackley, 2 nd Edition, Chapman & Hall. The presently preferred methods are physical methods. The physical methods include (a) agglomeration by subjecting the latex to freezing and thawing, and (b) agglomeration by subjecting the latex to mechanical agitation. Freeze agglomeration simply involves freezing the latex dispersion, followed by thawing.
• Agglomeration by mechanical agitation may be effected by pumping the latex through a confined space, which subjects the latex dispersion to high pressure, and thus causes agglomeration of the latex particles.
• Coagglomeration may be defined as a process in which the particles of two or more dissimilar latices are agglomerated to form heterogeneous composite particles in which the particles of one type of latex have become embedded in the particles of another, but otherwise retain their identity.
• Coagglomeration has been applied particularly to mixtures of synthetic latices of rubbery polymer and glassy polymers. The objective is to produce latices which contain composite particles comprising both rigid domains and rubbery domains. Films dried down from such latices comprise an intimate mixture of the two types of particles, and in consequence exhibit some degree of particulate reinforcement.
• elemental sulfur is added at 2% as a dispersion is preferred.
• Bostex 410 (68% elemental sulfur as a dispersion), available from Akron Dispersions is most preferred.
• the preferred vulcanizing agent is diphenylguanidine, available as Paracure DPG-38 from Parachem Specialties, which is added at 0.2%.
• Coagglomeration may be carried out by either of the methods already discussed. Freeze coagglomeration involves a single cycle of freezing and thawing, followed by removal of water. For pressure coagglomeration the mixture is subjected to high shear.
• An important advantage of co-agglomeration of the asphalt emulsion of the present invention is that the sulfur and accelerator are not diluted, but remain at a relatively high concentration.
• Asphalt emulsions used in road construction and maintenance are either anionic or cationic, based on the electrical charge of the asphalt particles, which is determined by the type of the emulsifying agent used.
• the asphalt contents of these emulsions are, in most cases, from 55 to 75% and prepared using a high shear mechanical device such as a colloid mill.
• the colloid mill has a high-speed rotor that revolves at l,000-6,000rpm with mill-clearance settings in the range of 0.2 to 0.5mm.
• a typical asphalt emulsion has a mean particle size of 2-5 micrometer in diameter with distribution from 0.3 to 20 micrometer.
• United States patent 5,180,428 refers to a non-ionic surfactant for ease of emulsion preparation with non-ionic chloroprene latex.
• This invention employs a cationic emulsifier-cationic latex, or non-ionic emulsifier-cationic latex combination for better asphalt adhesion to aggregate, which results in enhanced asphalt antistripping capability.
• Cationic emulsifying agents useful in the preparation of asphalt emulsions in accordance with the present invention are available from Akzo Nobel under the brand Redicote, including Redicote E-4819; E-64R, E4819-3, E-9, E-9A, and E-5.
• Arosurf brand cationic emulsifiers made by Goldshmidt for CRS, CMS and CSS are also useful.
• the emulsifier level in the asphalt emulsion can be ranging from 0.2 to 0.5 percent to the asphalt by weight for the rapid setting emulsion, to as much as 2.0 to 3.0 percent for the slow setting emulsions.
• Asphalt emulsions in accordance with the invention may be prepared by mixing the emulsifying agent and co-agglomerated latex into water and adjusting this emulsifier solution to pH below 3 with an inorganic acid.
• the emulsifier solution could be adjusted from slightly above the room temperature to up to 40°C.
• the asphalt is heated to 130 to 160°C, depending upon the viscosity of the asphalt used.
• a low viscosity asphalt such as AC-5 could be only heated to 130°C, in contrast, it could be as high as 160°C for AC-20 and AC-30 asphalts.
• the emulsifier solution and heated asphalt are injected into the colloid mill to produce the asphalt emulsion.
• the ratio of the asphalt and emulsifier solution is adjusted to produce the asphalt emulsion containing a desired amount asphalt contents, which can be from 55 to 75%.
• the co-agglomerated latex is added into the aqueous emulsifier solution.
• the asphalt emulsion can be produced with direct injection, where the emulsifier solution without the latex and asphalt are injected into the colloid mill through a series of pipes, while the latex is directly injected into the asphalt line just ahead of the colloid mill.
• the latex modified asphalt can also be produced by post-addition, where the desired amount of the co-agglomerated cationic latex is added into a pre-manufactured asphalt emulsion prepared without the latex.
• Asphalt emulsions are classified with their charge and on the basis of how quickly the asphalt will coalesce, which is commonly referred to as breaking, or setting.
• the terms RS, MS and SS have been adopted to simplify and standardize this classification. They are relative terms only and mean rapid-setting, medium-setting and slow setting.
• a rapid setting, RS, emulsion has little or no ability to mix with an aggregate.
• a medium setting, MS, emulsion is expected to mix with coarse but not fine aggregate, and a slow setting, SS, emulsion is designed to mix with fine aggregate.
• the cationic emulsions are denoted with the letter "C" in front of the emulsion type, and the absence of the "C” denotes anionic.
• CRS is a cationic rapid setting emulsion typically used for chip seal application.
• This new invention disclosed herein utilizes the cationic latex instead of non-ionic, thus opens new possibilities of preparing the asphalt emulsions having different setting characteristics such as CRS, CMS, and CSS to take advantages of well-practiced industrial methods for producing the asphalt emulsions for specific applications, such as chip seal, slurry seal, microsurfacing, sand seal, fog seal, etc., by choosing desired types and amount of cationic emulsifiers to prepare the emulsion.
• PASS emulsion without latex polymer was obtained from Western Emulsion.
• This emulsion was produced according to their original patent with Oxnad AC-20 asphalt, RA-1 and non-ionic surfactant (Indulin XD-70 from WestVaco).
• Neoprene and cationic co-agglomerated SBR latex modified PASS emulsions were prepared by adding desired amount of the latex dispersion into this unmodified emulsion.
• the asphalt emulsion residue was recovered at room temperature by drying the emulsion for 1 day under forced airflow described in (K. Takamura, Comparison of emulsion residues recovered by the forced airflow and RTFO drying, AEMA/ISSA Proceedings, 2000, 1-17).
• Table 1 lists measured complex modulus of the emulsion binder at 50°C as a function of the polymer content in the PASS emulsion.
• the complex modulus represents the strength of the emulsion residue under controlled stress and strain representing the traffic condition.
• One day drying under forced airflow represents initial strength development of the asphalt emulsion binder after application.
• Table 1 demonstrates that the cationic coagglomerated SBR latex develops the strength at lower polymer level than the Neoprene latex.
• the strength development of the PASS emulsion binder for few weeks to months after application was tested using the same Dynamic Shear Rheometry.
• the PASS emulsions containing 2% and 3% polymer by weight against asphalt + RA-1 were dried as example 1.
• the emulsion residue was stored in an oven at 60°C for 10 days and the complex modulus of the residue was measured at 1 day, 3 days, 7 days and 10 days curing in the oven at 60°C. This temperature represents the maximum road surface temperature in use.
• Table 2 and 3 list measured complex modulus as a function of curing time.

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• 2002
  • 2002-05-14 CA CA002483621A patent/CA2483621A1/en not_active Abandoned
  • 2002-05-14 JP JP2004506413A patent/JP4204544B2/ja not_active Expired - Fee Related
  • 2002-05-14 AU AU2002367972A patent/AU2002367972A1/en not_active Abandoned
  • 2002-05-14 WO PCT/US2002/015718 patent/WO2003097746A1/en active Application Filing
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