Classifications

• • C—CHEMISTRY; METALLURGY
  • C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
  • C10L—FUELS NOT OTHERWISE PROVIDED FOR; NATURAL GAS; SYNTHETIC NATURAL GAS OBTAINED BY PROCESSES NOT COVERED BY SUBCLASSES C10G, C10K; LIQUEFIED PETROLEUM GAS; ADDING MATERIALS TO FUELS OR FIRES TO REDUCE SMOKE OR UNDESIRABLE DEPOSITS OR TO FACILITATE SOOT REMOVAL; FIRELIGHTERS
  • C10L1/00—Liquid carbonaceous fuels
  • C10L1/10—Liquid carbonaceous fuels containing additives
  • C10L1/14—Organic compounds
  • C10L1/18—Organic compounds containing oxygen
  • C10L1/192—Macromolecular compounds
  • C10L1/195—Macromolecular compounds obtained by reactions involving only carbon-to-carbon unsaturated bonds
• • C—CHEMISTRY; METALLURGY
  • C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
  • C10L—FUELS NOT OTHERWISE PROVIDED FOR; NATURAL GAS; SYNTHETIC NATURAL GAS OBTAINED BY PROCESSES NOT COVERED BY SUBCLASSES C10G, C10K; LIQUEFIED PETROLEUM GAS; ADDING MATERIALS TO FUELS OR FIRES TO REDUCE SMOKE OR UNDESIRABLE DEPOSITS OR TO FACILITATE SOOT REMOVAL; FIRELIGHTERS
  • C10L1/00—Liquid carbonaceous fuels
  • C10L1/10—Liquid carbonaceous fuels containing additives
  • C10L1/14—Organic compounds
  • C10L1/146—Macromolecular compounds according to different macromolecular groups, mixtures thereof
• • C—CHEMISTRY; METALLURGY
  • C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
  • C10L—FUELS NOT OTHERWISE PROVIDED FOR; NATURAL GAS; SYNTHETIC NATURAL GAS OBTAINED BY PROCESSES NOT COVERED BY SUBCLASSES C10G, C10K; LIQUEFIED PETROLEUM GAS; ADDING MATERIALS TO FUELS OR FIRES TO REDUCE SMOKE OR UNDESIRABLE DEPOSITS OR TO FACILITATE SOOT REMOVAL; FIRELIGHTERS
  • C10L1/00—Liquid carbonaceous fuels
  • C10L1/10—Liquid carbonaceous fuels containing additives
  • C10L1/14—Organic compounds
  • C10L1/18—Organic compounds containing oxygen
  • C10L1/192—Macromolecular compounds
  • C10L1/195—Macromolecular compounds obtained by reactions involving only carbon-to-carbon unsaturated bonds
  • C10L1/196—Macromolecular compounds obtained by reactions involving only carbon-to-carbon unsaturated bonds derived from monomers containing a carbon-to-carbon unsaturated bond and a carboxyl group or salts, anhydrides or esters thereof homo- or copolymers of compounds having one or more unsaturated aliphatic radicals each having one carbon bond to carbon double bond, and at least one being terminated by a carboxyl radical or of salts, anhydrides or esters thereof
  • C10L1/1963—Macromolecular compounds obtained by reactions involving only carbon-to-carbon unsaturated bonds derived from monomers containing a carbon-to-carbon unsaturated bond and a carboxyl group or salts, anhydrides or esters thereof homo- or copolymers of compounds having one or more unsaturated aliphatic radicals each having one carbon bond to carbon double bond, and at least one being terminated by a carboxyl radical or of salts, anhydrides or esters thereof mono-carboxylic
• • C—CHEMISTRY; METALLURGY
  • C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
  • C10L—FUELS NOT OTHERWISE PROVIDED FOR; NATURAL GAS; SYNTHETIC NATURAL GAS OBTAINED BY PROCESSES NOT COVERED BY SUBCLASSES C10G, C10K; LIQUEFIED PETROLEUM GAS; ADDING MATERIALS TO FUELS OR FIRES TO REDUCE SMOKE OR UNDESIRABLE DEPOSITS OR TO FACILITATE SOOT REMOVAL; FIRELIGHTERS
  • C10L1/00—Liquid carbonaceous fuels
  • C10L1/10—Liquid carbonaceous fuels containing additives
  • C10L1/14—Organic compounds
  • C10L1/22—Organic compounds containing nitrogen
  • C10L1/234—Macromolecular compounds
  • C10L1/236—Macromolecular compounds obtained by reactions involving only carbon-to-carbon unsaturated bonds derivatives thereof
  • C10L1/2364—Macromolecular compounds obtained by reactions involving only carbon-to-carbon unsaturated bonds derivatives thereof homo- or copolymers derived from unsaturated compounds containing amide and/or imide groups
• • C—CHEMISTRY; METALLURGY
  • C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
  • C10L—FUELS NOT OTHERWISE PROVIDED FOR; NATURAL GAS; SYNTHETIC NATURAL GAS OBTAINED BY PROCESSES NOT COVERED BY SUBCLASSES C10G, C10K; LIQUEFIED PETROLEUM GAS; ADDING MATERIALS TO FUELS OR FIRES TO REDUCE SMOKE OR UNDESIRABLE DEPOSITS OR TO FACILITATE SOOT REMOVAL; FIRELIGHTERS
  • C10L1/00—Liquid carbonaceous fuels
  • C10L1/10—Liquid carbonaceous fuels containing additives
  • C10L1/14—Organic compounds
  • C10L1/18—Organic compounds containing oxygen
  • C10L1/192—Macromolecular compounds
  • C10L1/195—Macromolecular compounds obtained by reactions involving only carbon-to-carbon unsaturated bonds
  • C10L1/196—Macromolecular compounds obtained by reactions involving only carbon-to-carbon unsaturated bonds derived from monomers containing a carbon-to-carbon unsaturated bond and a carboxyl group or salts, anhydrides or esters thereof homo- or copolymers of compounds having one or more unsaturated aliphatic radicals each having one carbon bond to carbon double bond, and at least one being terminated by a carboxyl radical or of salts, anhydrides or esters thereof
  • C10L1/1966—Macromolecular compounds obtained by reactions involving only carbon-to-carbon unsaturated bonds derived from monomers containing a carbon-to-carbon unsaturated bond and a carboxyl group or salts, anhydrides or esters thereof homo- or copolymers of compounds having one or more unsaturated aliphatic radicals each having one carbon bond to carbon double bond, and at least one being terminated by a carboxyl radical or of salts, anhydrides or esters thereof poly-carboxylic
• • C—CHEMISTRY; METALLURGY
  • C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
  • C10L—FUELS NOT OTHERWISE PROVIDED FOR; NATURAL GAS; SYNTHETIC NATURAL GAS OBTAINED BY PROCESSES NOT COVERED BY SUBCLASSES C10G, C10K; LIQUEFIED PETROLEUM GAS; ADDING MATERIALS TO FUELS OR FIRES TO REDUCE SMOKE OR UNDESIRABLE DEPOSITS OR TO FACILITATE SOOT REMOVAL; FIRELIGHTERS
  • C10L1/00—Liquid carbonaceous fuels
  • C10L1/10—Liquid carbonaceous fuels containing additives
  • C10L1/14—Organic compounds
  • C10L1/18—Organic compounds containing oxygen
  • C10L1/192—Macromolecular compounds
  • C10L1/195—Macromolecular compounds obtained by reactions involving only carbon-to-carbon unsaturated bonds
  • C10L1/197—Macromolecular compounds obtained by reactions involving only carbon-to-carbon unsaturated bonds derived from monomers containing a carbon-to-carbon unsaturated bond and an acyloxy group of a saturated carboxylic or carbonic acid
  • C10L1/1973—Macromolecular compounds obtained by reactions involving only carbon-to-carbon unsaturated bonds derived from monomers containing a carbon-to-carbon unsaturated bond and an acyloxy group of a saturated carboxylic or carbonic acid mono-carboxylic
• • C—CHEMISTRY; METALLURGY
  • C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
  • C10L—FUELS NOT OTHERWISE PROVIDED FOR; NATURAL GAS; SYNTHETIC NATURAL GAS OBTAINED BY PROCESSES NOT COVERED BY SUBCLASSES C10G, C10K; LIQUEFIED PETROLEUM GAS; ADDING MATERIALS TO FUELS OR FIRES TO REDUCE SMOKE OR UNDESIRABLE DEPOSITS OR TO FACILITATE SOOT REMOVAL; FIRELIGHTERS
  • C10L1/00—Liquid carbonaceous fuels
  • C10L1/10—Liquid carbonaceous fuels containing additives
  • C10L1/14—Organic compounds
  • C10L1/22—Organic compounds containing nitrogen
  • C10L1/234—Macromolecular compounds
  • C10L1/236—Macromolecular compounds obtained by reactions involving only carbon-to-carbon unsaturated bonds derivatives thereof
  • C10L1/2368—Macromolecular compounds obtained by reactions involving only carbon-to-carbon unsaturated bonds derivatives thereof homo- or copolymers derived from unsaturated compounds containing heterocyclic compounds containing nitrogen in the ring

Definitions

• the invention relates to low-temperature petroleum middle distillates containing polymers of vinylaromatic units and olefinically unsaturated monocarboxylic acids which are reacted with secondary fatty amines and have improved cold flowability and better dispersion of the separated wax crystals.
• Middle distillates such as gas oils, diesel oils or heating oils, which are obtained from petroleum by distillation, have different paraffin contents depending on the origin of the crude oil.
• solid paraffins are excreted (cloud point or cloud point, CP).
• cloud point or cloud point, CP cloud point
• the platelet-shaped n-paraffin crystals form a "house of cards" structure and the middle distillate stops, although the majority of the middle distillate is still liquid.
• the fluidity of the petroleum distillate fuels is significantly impaired by the unusual n-paraffins in the temperature region between the cloud point and pour point or pour point.
• the paraffins clog filters and cause uneven or completely interrupted fuel supply to the combustion units. Similar problems occur with heating oils.
• suitable additives can be used to modify the crystal growth of the paraffins in the petroleum middle distillate fuels.
• Well-effective additives on the one hand prevent middle distillates from forming such house of cards structures and, at temperatures a few degrees Celsius below the temperature at which the first wax crystals crystallize, already become solid and, on the other hand, they form fine, well-crystallized, separate wax crystals, which filters in motor vehicles and heating systems pass or at least form a filter cake permeable to the liquid part of the middle distillates, so that trouble-free operation is ensured.
• a disadvantage of the additives mentioned is that the failed paraffin crystals tend to settle more and more on the bottom of the container during storage due to their higher density than the liquid part. This creates a homogeneous low-paraffin phase in the upper part of the container and a two-phase paraffin-rich layer on the bottom. Since both in vehicle tanks and in storage or delivery tanks of mineral oil dealers, the middle distillate is mostly a little above the Bottom of the container takes place, there is a risk that the high concentration of solid paraffins leads to blockages of filters and metering devices. This danger increases the further the storage temperature falls below the paraffin separation temperature, since the amount of paraffin excreted is a function of the temperature and increases with decreasing temperature.
• the paraffin crystal modifiers are polymers which change the crystal growth of the n-paraffins through co-crystallization (interaction) and improve the flow properties of the middle distillate at low temperatures.
• the effectiveness of the flow improver is expressed indirectly according to DIN 51428 by measuring the "Cold Filter Plugging Point” (CFPP).
• ethylene copolymers especially copolymers of ethylene and unsaturated esters, are used.
• the polymers added to the petroleum middle distillates are advantageously obtained by reacting copolymers of vinyl aromatics and olefinically unsaturated monocarboxylic acids of the general formula II and optionally other copolymerizable olefinically unsaturated compounds with secondary amines of the general formula III prepared, wherein R1, R2 and R3 have the meaning given above.
• Suitable vinyl aromatics (component a) on which the polymers are based include, for example, styrene, substituted styrenes such as mono-, di- or trialkyl-substituted styrenes, the alkyl groups of which generally have 1 to 5 C atoms, e.g. Vinyl toluene, isopropyl styrene, tert-butyl styrene, dimethyl styrene, 2,4-diethyl styrene, and ⁇ -methyl styrene. Styrene and ⁇ -methylstyrene are preferably used.
• olefinically unsaturated monocarboxylic acids (component b) on which the polymers are based are acrylic acid and methacrylic acid.
• olefinically unsaturated compounds which are copolymerizable with components a) and b) include into consideration maleic anhydride, itaconic anhydride, citraconic anhydride, esters or amides of acrylic acid, methacrylic acid, maleic acid, itaconic acid, fumaric acid with alcohols with generally 1 to 30 C atoms or with NH3, primary and secondary amines with generally C1- to C30- Alkyl groups, preferably C1 to C9 alkyl groups, N-vinylpyrrolidone, N-vinylimidazole, N-vinylformamide, N-vinyl acetamide, N-vinyl propionic acid amide.
• dialkylamines of formula III are generally used dialkylamines in which R2 and R3 are straight-chain alkyl radicals having 10 to 30, preferably 14 to 24, carbon atoms.
• Dioleylamine, dipalmitylamine, dicoconut fatty amine and dibehenylamine and preferably ditallow fatty amine may be mentioned in particular.
• the polymers added to the petroleum middle distillates are expediently obtained by reacting the copolymers of vinyl aromatics, olefinically unsaturated monocarboxylic acids and, if appropriate, further monomers with the secondary amines III at temperatures of generally 80 to 300 ° C., preferably 100 to 300 ° C., in particular 120 to 280 ° C. , in the course of 5 to 80, preferably 10 to 60 hours.
• the secondary amine is in amounts of about one mole per mole of polymerized olefinically unsaturated monocarboxylic acid, ie Ca. 0.9 to 1.1 mol / mol used. The use of larger or smaller amounts is possible, but has no advantage.
• the copolymers are prepared by known discontinuous or continuous polymerization processes such as bulk, suspension, precipitation or solution polymerization and initiation with customary radical donors such as acetylcyclohexanesulfonyl peroxide, diacetyl peroxidicarbonate, dicyclohexyl peroxidicarbonate, di-2-ethylhexyl peroxidicarbonate, 2,2'-butodecanoate, tert.-butodecylate, tert-t-butyl Azobis (4-methoxy-2,4-dimethylvaleronitrile), tert-butyl perpivalate, tert-butyl per-2-ethyl-hexanoate, tert-butyl permaleinate, 2,2'-azobis (isobutyronitrile), bis (tert.- butylperoxy) cyclohexane, tert.-butylperoxyisopropyl carbonate, tert
• the polymerization is generally carried out at from 40 to 400 ° C., preferably from 80 to 300 ° C., and when solvents are used, boiling temperatures below the polymerization temperature are advantageously carried out under pressure.
• the polymerization is conveniently carried out in the absence of air, i.e. if it is not possible to work under boiling conditions, e.g. carried out under nitrogen, since oxygen delays the polymerization.
• the reaction can be accelerated by using redox coinitiators such as benzoin, dimethylaniline, ascorbic acid and organically soluble complexes of heavy metals such as copper, cobalt, manganese, iron, nickel and chromium.
• the amounts usually used are 0.1 to 2000 ppm by weight, preferably 0.1 to 1000 ppm by weight.
• regulators are, for example, allyl alcohols, such as buten-1-ol-3, organic mercapto compounds such as 2-mercaptoethanol, 2-mercaptopropanol, mercaptoacetic acid, mercaptopropionic acid, tert-butyl mercaptan, n-butyl mercaptan, n-octyl mercaptan, n-dodecyl mercaptan and tert-dodecyl mercaptan, which are generally used in amounts of 0.1% by weight to 10% by weight.
• allyl alcohols such as buten-1-ol-3
• organic mercapto compounds such as 2-mercaptoethanol, 2-mercaptopropanol, mercaptoacetic acid, mercaptopropionic acid, tert-butyl mercaptan, n-butyl mercaptan, n-octyl mercaptan, n-dodecy
• Equipment suitable for the polymerization is e.g. Conventional stirred kettles with, for example, armature, blade, impeller or multi-stage impulse countercurrent stirrers and for the continuous production of stirred kettle cascades, tubular reactors and static mixers.
• the simplest method of polymerization is bulk polymerization.
• the vinyl aromatics and the acid group-containing monomer are polymerized in the presence of an initiator and in the absence of solvents.
• all monomers are mixed in the desired composition and a small part, e.g. about 5 to 10%, in the reactor before, heated to the desired polymerization temperature with stirring and metered in the remaining monomer mixture and the initiator and optionally coinitiator and regulator evenly within 1 to 10 hours, preferably 2 to 5 hours. It is expedient to meter in the initiator and the coinitiator separately in the form of solutions in a small amount of a suitable solvent.
• the copolymer can then be converted to the paraffin dispersant according to the invention to be added to the petroleum middle distillate directly in the melt or after dilution with a suitable solvent.
• a continuous high-pressure process which allows space-time yields of 1 to 50 kg of polymer per liter of reactor and hour is also particularly suitable and preferred for producing the desired copolymers.
• the monomers are preferably polymerized from vinylaromatics and monoolefinically unsaturated compounds containing acid groups in at least 2 polymerization zones connected in series.
• One reaction zone can consist of a pressure-tight vessel, the other of a heatable static mixer. You get sales of more than 99%.
• a copolymer of styrene and acrylic acid can be prepared, for example, by continuously feeding the monomers and a suitable initiator to a reactor or two reaction zones connected in series, for example a reactor cascade, and the reaction product after a residence time of 2 to 60, preferably 5 to 30 Minutes, continuously discharged from the reaction zone at temperatures between 200 and 400 ° C.
• the polymerization is expedient at pressures of more than 1 bar, preferably between 1 and 200 bar.
• the copolymers obtained with solids contents of over 99% can then be further converted to the corresponding amides.
• the continuous polymerization can be carried out in the presence or in the absence of free radical binders, as described in EP 0 100 443.
• solvents are used in which the monomers are soluble and the copolymer formed is insoluble and fails.
• solvents are ethers such as diethyl ether, dipropyl ether, dibutyl ether, methyl tert-butyl ether, diethylene glycol dimethyl ether, toluene, xylene, ethylbenzene, cumene, high-boiling aromatic mixtures such as Solvesso 100®, 150 and 200, aliphatic and cycloaliphatic hydrocarbons and mixtures with one another.
• a protective colloid When carrying out the precipitation polymerization, it is expedient to use a protective colloid to prevent the formation of aggregates, in particular when working at concentrations of more than 40% by weight.
• Suitable protective colloids are polymeric substances which are readily soluble in the solvents and which do not react with the monomers.
• copolymers of maleic anhydride with vinyl alkyl ethers and / or olefins with 8 to 20 C atoms and their monoesters with C10 to C20 alcohols or mono- and diamides with C10 to C20 alkyl amines and polyalkyl vinyl ethers whose alkyl group is 1 to 20 C are suitable -Atoms contains, such as polymethyl, polyethyl, polyisobutyl and polyoctadecyl vinyl ether.
• the amounts of protective colloid added are usually 0.05 to 4% by weight (based on the monomers used), preferably 0.1 to 2% by weight, it often being advantageous to combine several protective colloids.
• the solvent, the protective colloid and part of the monomer mixture in the reactor it is expedient to put the solvent, the protective colloid and part of the monomer mixture in the reactor and to meter in the rest of the monomer mixture and the initiator and, if appropriate, the coinitiator and regulator at the selected polymerization temperature with vigorous stirring.
• the feed times for monomer and initiator are generally between 1 and 10 hours, preferably 2 and 5 hours. It is also possible to polymerize all of the starting materials together in one reactor, but problems with heat dissipation can occur, so that such a procedure is less appropriate.
• the concentrations of the monomers to be polymerized are between 20 and 80% by weight, preferably 30 to 70% by weight.
• the polymers can be isolated directly from the polymer suspensions in evaporators, for example belt dryers, paddle dryers, spray dryers and fluidized bed dryers.
• Another embodiment for the preparation of the copolymers is solution polymerization. It is carried out in solvents in which the monomers and the copolymers formed are soluble. All solvents that meet this requirement and that do not react with the monomers are suitable for this. For example, these are acetone, methyl ethyl ketone, diethyl ketone, methyl isobutyl ketone, ethyl acetate, butyl acetate, ethylene glycol dimethyl ether, diethylene glycol dimethyl ether, ethylene glycol diethyl ether, diethylene glycol diethyl ether, tetrahydrofuran and dioxane.
• the solvent and part of the monomer mixture for example about 5 to 20%
• the concentrations of the monomers to be polymerized are between 20 and 80% by weight, preferably 30 and 70% by weight.
• the solid copolymer can be isolated easily by evaporating the solvent. But here, too, it is expedient to choose a solvent in which the further reaction with amines can take place.
• the additives according to the invention are added to the petroleum middle distillates in amounts of 50 to 1000 ppm by weight, preferably 100 to 500 ppm by weight.
• middle distillates already contain flow improvers such as ethylene-vinyl ester copolymers.
• Preferred copolymers b) are those which essentially contain ethylene and 25 to 45% by weight of vinyl acetate, vinyl propionate or ethylhexyl acrylate. Also to be mentioned are copolymers which contain, for example, fumaric acid esters.
• the molecular weight of the flow improvers is generally 500 to 5000, preferably 1000 to 3000.
• Examples 1 to 6 describe the preparation of the polymers, which are then reacted according to Examples 7 to 12 with secondary amines to give the paraffin dispersants according to the invention.
• the copolymers have K values from 6 to 50, preferably 8 to 40.
• styrene and 40 g of acrylic acid were continuously metered into a 1000 ml pressure vessel with a downstream pressure tube with double volume and pressure regulator.
• the system was heated to 310 ° C.
• the pressure was kept in the range between 5 and 50 bar and varied once in one minute by periodic pressure regulation in this range.
• the residence time was 11 minutes, and the copolymer melt was drawn out in quantity to the extent that fresh monomer mixture was fed in.
• the copolymer had a K value of 17.0, measured in cyclohexanone.
• a reaction mixture of 51.7 g of ditallow fatty amine and 24.3 g of copolymer from Example 3 was stirred at 180 ° C. until an acid number of approx. 25 was reached (approx. 30 hours). 69 g of product were obtained in the form of a brown, waxy solid.
• middle distillate I Diesel fuels in commercial West German refinery quality were used as middle distillates for the following tests. They are referred to as middle distillate I, II, III. Middle distillate I. II III Cloud point (° C) - 7th - 7th - 8th CFPP (° C) -10 -12 -12 Density at 20 ° C (g / ml) 0.820 0.821 0.826 Initial boiling point (° C) 160 168 174 20% boiling point (° C) 214 215 223 90% boiling point (° C) 309 323 314 End of boiling point (° C) 354 364 352
• the middle distillates were tested with different amounts of flow improvers alone and / or together with paraffin dispersants at temperatures below the cloud point.
• the cooling was carried out using a temperature program.
• the middle distillates I, II, III were cooled from room temperature to -12 ° C at a cooling rate of 1 ° C / hour and stored at -12 ° C for 24 hours.
• the experiments were carried out with 100 ml and 1000 ml middle distillate volumes.
• Tables I to III list: volume of the sedimented paraffin phase (%), cloud point (CP) and cold filter plugging point (CFPP) of the lower area (lower 40% by volume), CP and CFPP of the upper area (upper 60 vol .-%) and the CP and CFPP of the middle distillate containing the additives before the storage test.

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• Chemical & Material Sciences (AREA)
• Oil, Petroleum & Natural Gas (AREA)
• Engineering & Computer Science (AREA)
• Chemical Kinetics & Catalysis (AREA)
• General Chemical & Material Sciences (AREA)
• Organic Chemistry (AREA)
• Health & Medical Sciences (AREA)
• Emergency Medicine (AREA)
• Addition Polymer Or Copolymer, Post-Treatments, Or Chemical Modifications (AREA)

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Citations (6)

• 1990
  • 1990-08-11 DE DE4025586A patent/DE4025586A1/de not_active Withdrawn
• 1991
  • 1991-07-30 EP EP91112771A patent/EP0475052A1/fr not_active Withdrawn
  • 1991-08-09 NO NO91913106A patent/NO913106L/no unknown

Patent Citations (6)

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