Fuel and related compositions – Liquid fuels – Containing organic -c
Reexamination Certificate
2000-05-24
2001-05-22
McAvoy, Ellen M. (Department: 1764)
Fuel and related compositions
Liquid fuels
Containing organic -c
Reexamination Certificate
active
06235069
ABSTRACT:
The invention relates to ethylene-vinyl formate copolymers, to a process for their preparation, to the use of the copolymers as flow improvers, especially in petroleum middle distillates, such as diesel fuels and light heating oils, and to fuel compositions and propellant compositions comprising them.
U.S. Pat. No. 3,159,608 relates to the production of pour point depressants, in particular for use with middle distillates. A process is described for the copolymerization of ethylene and up to about 50% by weight of vinyl acetate, vinyl propionate, methyl methacrylate, allyl ethyl ether, divinyl ether, acrylonitrile or vinylacetonitrile. Preference is given to ethylene-vinyl acetate copolymers.
U.S. Pat. No. 3,389,979 relates to improving the flow properties of oils, especially middle distillates. It describes how good handling or flow properties of a fuel and propellant oil are obtained at low temperatures using a copolymer of ethylene and vinyl acetate.
U.S. Pat. No. 3,567,639 relates to a pour point depressant for crude oil, shale oil or fuel and propellant oil. This pour point depressant is a copolymer of ethylene and vinyl propionate, vinyl hexanoate, vinyl octanoate, vinyl dodecanoate, vinyl behenoate, isopropenyl acetate or octadecyl myristoate. A particularly preferred ester in this context is vinyl acetate.
The known ethylene-vinyl acetate copolymers have the disadvantage that their flow improver action is not equally good universally, in all petroleum distillates. Their action depends, inter alia, on the origin of the crude oil on which the petroleum distillate is based, on the processing technique employed for the crude oil, and on the nature and quantity of n-paraffins in the petroleum distillate.
Processes for the polymerization and copolymerization of ethylene are known and are described, for example, in Ulmanns Enzyklopädie der Technischen Chemie, 4th edition, Volume 19, pp. 169-223, especially pp. 169-175.
It is an object of the present invention to provide a flow improver which avoids the disadvantages described for ethylene-vinyl acetate copolymers.
It is a further object of the present invention to provide a flow improver for petroleum distillates which is effective for a large number of petroleum distillates.
It is another object of the present invention to provide a process for preparing this flow improver.
It is a further object of the present invention to provide fuel and propellant compositions having improved flow properties.
We have found that these objects are achieved by the novel copolymers comprising ethylene units and vinyl formate units, the preparation processes, wherein the monomers ethylene, vinyl formate and, if used, further monomers are subjected to free-radical polymerization in a stirred autoclave, a tubular reactor or a stirred autoclave with downstream tubular reactor at a pressure of from 500 to 3500 bar at from 150 to 330° C. in the presence of at least one free-radical initiator comprising preferably organic peroxides which decompose to form free radicals, or air or oxygen, and in the presence, if used, of a molecular weight regulator, for a reaction time of from 60 to 240 s, the use of the copolymers and the fuel and propellant compositions, as described in the following. We have also found that other objects are achieved by means of the preferred embodiments.
In accordance with the invention it has been found that copolymers comprising ethylene units and vinyl formate units (ethylene-vinyl formate copolymers) can be used as flow improvers for petroleum distillates and that they give the petroleum distillates better properties than is the case when ethylene-vinyl acetate copolymers are used.
ETHYLENE-VINYL FORMATE COPOLYMERS
The novel copolymers include ethylene units and vinyl formate units. According to one embodiment of the invention, the vinyl formate units make up 1-50%, preferably 10-40%, in particular 20-35%, by weight of the copolymer. According to one embodiment the ethylene units form the remainder of the copolymer; in other words, the copolymer consists of ethylene units and vinyl formate units (apart from residues of a free-radical initiator or molecular weight regulator).
The copolymer can also include other kinds of monomers, for example vinyl acetate, vinyl propionate, acrylates and methacrylates, such as methyl acrylate and ethyl, propyl, butyl, amyl, ethylhexyl, decyl, dodecyl and stearyl acrylates and methacrylates.
The amounts of these other monomers are preferably in a range from 0.1 to 20% by weight, preferably from 1 to 10% by weight, based on the copolymer.
The number-average molecular weight of the novel copolymer is, according to one embodiment of the invention, 500-200,000, preferably 500-10,000, in particular 500-5000 g/mol. This molecular weight can be determined by means of vapor phase osmometry.
It is common to determine, rather than the number-average molecular weight, the melt viscosity of the resulting copolymer, which permits conclusions to be drawn about the molecular weight.
This melt viscosity is determined using a rotary viscometer in accordance with DIN 53019 at 120° C. According to one embodiment of the invention, the copolymers have melt viscosities at 120° C. of from 10 to 10,000 cst, preferably from 50 to 1000 cst, in particular from 100 to 500 cst.
In addition to the abovementioned units the novel copolymers include small amounts of free-radical initiators and, if used, molecular weight regulators, which are added to the monomer mixture in order, respectively, to initiate and to regulate the polymerization. In the course of polymerization, these substances are bonded at least in part in the polymer main chain.
The novel copolymers can be employed in combination with one or more customarily used additives, examples being antioxidants, corrosion inhibitors, conductivity improvers, lubricity additives, paraffin dispersants, detergent additives, cetane number improvers, antifoam additives, stability improvers or other flow improvers.
PREPARATION OF THE ETHYLENE-VINYL FORMATE COPOLYMERS
The vinyl formate used to prepare the novel copolymers can be prepared by the method described in WO 95/09877.
Processes for the polymerization of ethylene and, if desired, of comonomers are known and are described, for example, in Ullmanns Enzyklopädie der Technischen Chemie, 4th edition, Volume 19, pp. 169-175.
In accordance with one embodiment of the invention, this polymerization is carried out in a stirred autoclave, which can for example be a compact autoclave or an elongate reactor. It is advantageous if the contents of the autoclave can be mixed thoroughly using a stirrer.
In the polymerization of ethylene and vinyl formate, the conversion is generally within a range from 1 to 35%.
For polymerization, a compressed gas mixture of the monomers is supplied to the reactor simultaneously with a free-radical initiator used to start the free-radical polymerization. According to one embodiment of the invention, use is made of preferably organic peroxides which decompose into free radicals and which are introduced, if appropriate, in the form of a solution in a solvent. The use of air and/or oxygen is likewise possible.
Reaction temperature and product data (such as comonomer composition or melt index) are established by adapting the reaction conditions (initiator, pressure, gas input temperatures, molecular weight regulator if present) to preset target figures. In the case of an elongate reactor type, the reaction can be controlled with precision by means of a plurality of initiator feed pumps arranged along the reactor.
In accordance with one embodiment of the invention reaction is carried out at 150-330° C. under a pressure of 500-3500 bar.
The reaction time or residence time in the reactor is, according to one embodiment of the invention, 60 to 240 s, so that the free vinyl formate content in the copolymer is low: not more than 5000 ppm.
According to another embodiment of the invention, a tubular reactor is used for the polymerization of the ethylene and vinyl formate.
In this case the reactor length, accordi
Deckers Andreas
Klimesch Roger
Muller Hans-Joachim
Ruhl Thomas
Wenderoth Bernd
BASF - Aktiengesellschaft
Keil & Weinkauf
McAvoy Ellen M.
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