Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Mixing of two or more solid polymers; mixing of solid...
Reexamination Certificate
2001-06-05
2003-05-20
Seidleck, James J. (Department: 1711)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Mixing of two or more solid polymers; mixing of solid...
C525S242000, C525S240000, C508S591000
Reexamination Certificate
active
06566454
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to methods of using block copolymers to lower the cold flow temperature (pour point) of crude petroleum.
BACKGROUND OF THE INVENTION
Typical crude petroleum contains paraffinic and isoparaffinic waxy components which are capable of crystallizing. Concentrations of waxy components are much higher in crude petroleum as compared to refined products such as fuels, fuel oil, lubricating oil and the like. Waxy components begin to crystallize in crude petroleum as the petroleum is cooled to temperatures below the petroleum's gel point temperature. Crystallization of waxy components of crude petroleum is undesirable because it increases petroleum viscosity at low temperatures making it difficult for the petroleum to be pumped or poured.
Certain copolymers are known as fuel oil and lubricating oil viscosity modifying additives. See D. Richter et al., Polymer Aggregates with Crystalline Cores: The System Polyethylene-Poly(ethylenepropylene),
Macromolecules
, Vol. 30, pp. 1053-1068 (1997). The copolymers generally interact with waxy components of fuel oil, by multiple nucleation of precipitates, reducing the size of precipitate nuclei with a concomitant reduction in oil viscosity. See W. Leube, et al., Wax Crystal Modification for Fuel Oils by Self Aggregating Crystallizable Hydrocarbon Block Copolymers,
Energy and Fuels
, Vol. 14, pp. 419-430 (2000).
Traditionally, copolymer additives for this purpose are formed by free-radical graft copolymerization of an alkyl ester of acrylic or of methacrylic acid, alone or in combination with a non-paraffin specific monomer such as styrene. In a similar spirit, flow improving copolymers comprisined of ethylene, a paraffin specific segment, and a vinyl acetate, a paraffin non-specific segment, have been synthesized by radical polymerization as well. See U.S. Pat. No. 4,282,132 to Benda et al. which discloses lubricating oil additives, and U.S. Pat. No. 3,627,838 to Ilnyckyj et al. which discloses a process for manufacturing potent pour depressants. Each of the references cited herein are incorporated herein by reference.
More recently, conventional copolymer additives for this purpose are formed by polymerizing one or more conjugated dienes and, optionally, one or more monoalkenylarene compound in solution in the presence of an ionic initiator to form a living polymer. For the purposes of the present invention living polymer is used consistently with Billmeyer, Textbook of Polymer Science, 2d Ed., Wiley-Interscience, John Wiley and Sons, page 318 (1971).
Examples of conventional compounds can be found in U.S. Pat. No. 5,310,814 to Strulinski et al., U.S. Pat. No. 5,543,469 to Strulinski et al., and U.S. Pat. No. 5,703,171 to Strulinski et al. U.S. Pat. No. 5,310,814 discloses hydrogenated polybutadiene comprising monomeric units of 1,4-butadiene and 1,2-butadiene addition products. The copolymer comprises at least 10% by weight of at least one crystallizable segment and at least one low crystallinity segment. U.S. Pat. No. 5,543,469 discloses hydrogenated block copolymers of butadiene and at least one other diene. The copolymer comprises at least 10% by weight of at least one crystallizable segment and at least one low crystallinity segment. U.S. Pat. No. 5,703,171 discloses hydrogenated polybutadiene comprising monomeric units of 1,4-butadiene and 1,2-butadiene addition products. The copolymer comprises at least 10% by weight of at least one crystallizable segment and at least one low crystallinity segment. Each of the references cited herein are incorporated herein by reference.
Traditional lubricating oil or diesel fuel polymer additives have not been synthesized to react specifically with the various components of crude petroleum. The compounds that exist in crude petroleum are significantly different and more diverse than those compounds present in lubricating oils or diesel fuel.
Further, traditional methods of modifying lubricating oil and fuel oil viscosity involve adding copolymers to the lubricating oil or fuel oil as a cold flow additive. The copolymers of polybutadiene disclosed by the prior art are synthesized to form small, uniformly sized wax crystals when added to diesel fuel or lubricating oils. Uniformity of small crystal size is a necessary goal of the traditional copolymer additives because larger crystals would clog fuel filters or hamper the lubrication properties of lubricating oils. As a result, use of conventional lubricating oil or diesel fuel copolymer additives is considered undesirable to lower the gel point of crude petroleum. It is thought that the waxy content of crude petroleum will overload a traditional copolymer additive's capacity to form crystals and synthesize undesirable non-uniform large crystals.
Similarly, traditional methods of modifying lubricating oil and fuel oil viscosity involve the use of copolymer additives that are used in oils that do not solidify at room temperature. Crude petroleums that solidify at low temperatures are believed to overload the ability of conventional lubricating oil or diesel fuel copolymer additives ability to form waxy crystals. Use of conventional lubricating oil or diesel fuel copolymer additives are considered undesirable to lower the gel point of crude petroleum because many crude petroleum compositions solidify at room temperature. Hence, methods which address these needs have long been sought.
SUMMARY OF THE INVENTION
The present invention provides methods of lowering the gel point temperature of crude petroleum. The methods comprise providing a block copolymer and admixing the block copolymer with a crude petroleum. As described herein crude petroleum is unrefined petroleum or partially refined petroleum. Partially refined petroleum is crude petroleum that has been processed to some extent by a form of refining but still retains a significant quantity of paraffinic or isoparaffinic components and can suffer from an undesirably high gel point. Thus, partially refined petroleum as described herein is the liquid, near liquid, or partially solidified product of typical refining techniques that include but are not limited to atmospheric tower fractionation, vacuum tower fractionation, catalytic cracking, light ends fractionation, or processing with a coking unit. Partially refined petroleum may include heavy naptha, light naptha, catalytic naptha, coker naptha, cycle oil, gas oil, and similar refined products or petroleum fractionation distillates or bottoms. James H. Gary, Glenn E. Handwork,
Petroleum Refining
, Marcel Dekker (1975); Ed.Perry, Robert H., Green, Don W.,
Perry's Chemical Engineers Handbook,
7th ed., Ch. 13, p.85-95 (1997); Watkins, R. N.,
Petroleum Refinery Distillation,
2d ed. (1979). Paraffins and isoparaffins as described herein are waxy alkanes that precipitate upon the cooling of a crude petroleum. Paraffins and isoparafins have a relatively low specific gravity when compared to other petroleum components such as olefins, napthenes, or aromatic compounds.
The block copolymers of the present invention are composed of at least 10% by weight of a first block and at least 10% by weight of a second block. The first block of the block copolymer is a polyalkylene having at least about 30% crystallinity. Preferably the first block has a crystallinity between about 35% and about 90%. Preferably the first block is formed from a butadiene, especially a 1,4 butadiene.
The second block is a polyalkylene having less than about 30% crystallinity. The polyalkylene of the second block is preferably branched (with long or short chain branches), substituted, or both. If substituted, the second block is substituted with at least one hydroxyl, halo, or amino group. The second block is preferably formed from an isoprene or butadiene synthesized under conditions which give high 1,2 polybutadiene product.
Crystallinity percentage is determined generally by the following formula:
[
Weight
Crystallized
Polymer
]
[
Total
Weight
of
&
Ashbaugh Henry S.
Prud'homme Robert K.
The Trustees of Princeton University
Woodcock & Washburn LLP
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