Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – At least one aryl ring which is part of a fused or bridged...
Reexamination Certificate
2000-02-02
2002-09-03
Wu, David W. (Department: 1713)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
At least one aryl ring which is part of a fused or bridged...
C524S457000, C524S475000, C524S575000, C524S578000, C524S801000
Reexamination Certificate
active
06444738
ABSTRACT:
TECHNICAL FIELD
The present invention relates to emulsions containing alcohol and/or water in a dispersed phase and a hydrocarbon liquid in the continuous phase. More particularly the present invention relates to such emulsions which are resistant to breaking or stratification of the emulsion under the influence of heat.
BACKGROUND ART
It is known from the applicant's Australian patent specification 544,728 that emulsions containing alcohol and/or water in one phase and a hydrocarbon liquid in the other may be formed using an emulsifier that is a block copolymer of ethylene oxide and styrene type monomers. These emulsions are of particular utility as liquid transport fuel in which hydrated methanol or hydrated ethanol are dispersed in diesel oil or gasoline. Hydrated alcohol in diesel oil (termed AW/D) emulsions represent a new and potentially cost effective option for significantly reducing particulate and NOx emissions from diesel engines. Emulsions of hydrated alcohol in gasoline exhibit reduced vapour pressure, increased water tolerance and reduced NOx emission on combustion as compared with anhydrous alcohol solutions in gasoline. When the alcohol is ethanol produced from biomass there can be a reduction in the net emission of carbon dioxide (“greenhouse gas”) as compared with the use of unblended petroleum fuel.
The arrangement described in the above mentioned specification utilised not only a block copolymer as the emulsifier but also a block copolymer as a coupling agent. The coupling agent typically comprised a block copolymer of butadiene and styrene type monomers. The coupling agents described in that specification contain butadiene and styrene in weight ratios of at least 2:1, more preferably at least 3:1. The emulsifier and the coupling agent are described in that specification as being present in the emulsion in a ratio of from 1:3 to 3:1. In these ratios solutions of the two copolymers are compatible.
It has been found that while the emulsions described in the aforementioned Australian patent specification produce generally stable emulsions they do suffer from a problem in that the emulsions are not as heat stable as may be desired. This problem is particularly relevant in situations where the emulsions are to be used as fuels. When an engine, particularly a diesel engine, is switched off fuel is left stationary in parts of the engine and fuel supply system that are relatively hot. It has been found that the emulsions disclosed in the aforementioned patent specification are inclined to break or stratify under these “hot scale” conditions. This leaves undispersed alcohol or water in the engine. This can make subsequent starting of the engine difficult, if not impossible, and/or may cause corrosion of the engine.
DISCLOSURE OF INVENTION
The present invention relates to an emulsion containing in a continuous phase a hydrocarbon liquid and in a dispersed phase an alcohol and/or water in the presence of:
(a) an emulsifier being a copolymer containing at least one relatively hydrophobic polymeric block of at least one monomer selected from the group comprising styrene and ring substituted styrenes, and at least one relatively hydrophilic polymeric block of at least one monomer selected from the group having the formula H(O—R)
n
OH where R is an aliphatic radical containing from 1 to 4 carbon atoms and n is a number between 20 and 300, and
(b) a coupling agent being a copolymer containing at least one polymeric block of at least one monomer selected from the group comprising styrene and ring substituted styrenes, and at least one block being a saturated or unsaturated aliphatic hydrocarbon moiety, in which the coupling agent contains the styrene monomer and the hydrocarbon moiety in a weight ratio of at least 1:1, preferably from 1:0.42 to 1:0.66 depending upon the aromatic content of the hydrocarbon liquid.
The coupling agent is preferably a copolymer containing at least one polymeric block of at least one monomer selected from the group comprising styrene and ring substituted styrenes and at least one polymeric block of at least one compound selected from the group comprising butadiene or isoprene. Alternatively the hydrocarbon may comprise a single long chain hydrocarbon moiety rather than a polymer made up of a plurality of recurring monomeric entities. The coupling agent is preferably a pure diblock copolymer or a tapered block copolymer. Such copolymers are preferably produced by anionic solution polymerisation as this technique produces copolymers with a defined structure and a narrow molecular weight distribution. It is preferred that the coupling agent contains styrene and the aliphatic hydrocarbon in the weight ratio of from 1:0.3 to 1:1, most preferably from 1:0.42 to 1:0.66. As the aromatic content of the continuous phase increases so the preferred ratio of the styrene to the aliphatic hydrocarbon will rise. These ratios are outside the range of at least 1:2 and most preferably 1:3 stated to be desirable in Australian patent specification 544,728 and lead in an opposite direction from the teaching of that specification.
The coupling agent preferably has a molecular weight of from 13,000 to 400,000, more preferably the 100,000 to 170,000, most preferably 120,000 to 150,000. It is preferred that styrene comprises from 50 to 77% by weight of the coupling agent, most preferably 50 to 70% depending on the aromatic content of the continuous phase of the emulsion. It has been found that when the aromatic content of the continuous phase is less than 22% it is preferable for the styrene content of the coupling agent to be in the range of from 50 to 60% by weight. By contrast when the aromatic content of the continuous phase is more than 23% it is preferable for the styrene content of the coupling agent to be in the range of from 60 to 70% by weight.
The emulsifier is preferably a copolymer containing at least one polymeric block of at least one monomer selected from the group comprising styrene and ring substituted styrenes and at least one polymeric block of at least one monomer selected from the group having the formula H(O—R)
n
OH, where R is an aliphatic bivalent hydrocarbon radical containing from 1 to 4 carbon atoms and n is a number between 22 and 130. The emulsifier is preferably a pure di-block copolymer or a reaction mixture containing principally di-block copolymer and tri-block copolymer having two blocks of the styrene monomer, together with some unreacted homopolymer of the H(O—R)
n
OH monomer.
In a particularly preferred embodiment of the present invention the emulsifier is a polyethylene oxide-polystyrene copolymer. The polyethylene oxide block is preferably formed first with a molecular weight of between 1,000 and 10,000. The polyethylene oxide and the polystyrene are preferably present in a weight ratio of 1 part of polyethylene oxide to from 0.8 to 1.5 parts of polystyrene, more preferably from 1.0 to 1.25 parts of polystyrene. In preferred embodiments of the invention the emulsifier is produced by the reaction of styrene monomer with polyethylene oxide homopolymer in the presence of a free radical initiator. The reaction product formed without chain transfer agents, comprising polyethylene oxide-polystyrene di-block copolymer, polystyrene-polyethylene oxide-polystyrene tri-block copolymer, unreacted polyethylene oxide homopolymer, and a minor proportion of various other higher molecular weight dimeric and trimeric species and polystyrene homopolymer, is particularly suitable for use in the present invention.
The absolute amounts of the emulsifier and the coupling agent can be determined for any given emulsifier and coupling agent by quantitative testing. It is apparent to the present inventor that the amount of the coupling agent in the emulsion is important and typically approaches the solubility limit of the coupling agent in the continuous phase. If the amount of the coupling agent is lower than the critical amount it will not couple effectively with the micelles of the emulsifier and therefor stratification of the dispersed phase of
Apace Research Limited
Christie Parker & Hale LLP
Egwim Kelechi C.
Wu David W.
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