Patent Application
20140166287
Polymer formulations in solvents with a high flashpoint, processes for production thereof and use thereof as pour point depressants for crude oils, mineral oils or mineral oil products
The present invention relates to polymer formulations comprising at least two different solvents having a flashpoint ≧60° C., and to polymeric compositions obtainable by free-radical polymerization of at least one alkyl (meth)acrylate in the presence of at least one ethylene-vinyl ester copolymer. It further relates to a multistage process for producing such formulations and the use of such formulations as pour point depressants for crude oils, mineral oils or mineral oil products.
Underground mineral oil formations typically have relatively high temperatures. After the production of the crude oil to the surface, the crude oil produced therefore cools down to a greater or lesser degree according to the production temperature and the storage or transport conditions.
According to their origin, crude oils have different proportions of waxes, which consist essentially of long-chain n-paraffins. According to the type of crude oil, the proportion of such paraffins may typically be 1 to 30% by weight of the crude oil. When the temperature goes below a particular level in the course of cooling, the paraffins can crystallize, typically in the form of platelets. The precipitated paraffins considerably impair the flowability of the oil. The platelet-shaped n-paraffin crystals can form a kind of house-of-cards structure which encloses the crude oil, such that the crude oil ceases to flow, even though the predominant portion is still liquid. The lowest temperature at which a sample of an oil still just flows in the course of cooling is referred to as the pour point (“yield point”). For the measurement of the pour point, standardized test methods are used. Precipitated paraffins can block filters, pumps, pipelines and other installations or be deposited in tanks, thus entailing a high level of cleaning.
The deposit temperature of oil deposits is generally above room temperature, for example 40° C. to 100° C. Crude oil is produced from such deposits while still warm, and it naturally cools more or less quickly to room temperature in the course of or after production, or else to lower temperatures under corresponding climatic conditions. Crude oils may have pour points above room temperature, so such that crude oils of this kind may solidify in the course of or after production.
It is known that the pour point of crude oils can be lowered by suitable additives. This can prevent paraffins from precipitating in the course of cooling of produced crude oil. Suitable additives firstly prevent the formation of said house-of-cards-like structures and thus lower the temperature at which the crude oil solidifies. In addition, additives can promote the formation of fine, well-crystallized, non-agglomerating paraffin crystals, such that undisrupted oil transport is ensured. Such additives are referred to as pour point depressants or flow improvers.
Paraffin inhibitors or wax inhibitors refer to those substances intended to prevent the deposition of paraffins or paraffin waxes on surfaces in contact with crude oils or other wax-containing oils and/or mineral oil products.
The use of ethylene copolymers as flow improvers is known, especially that of copolymers of ethylene and unsaturated esters. Examples thereof are described in DE-A-21 02 469 or EP 84 148 A2.
DE-A-16 45 785 discloses heating oil mixtures with a depressed pour point. The mixtures comprise at least 3% by weight of polymers having unbranched saturated side chains having at least 18 carbon atoms, for example homo- or copolymers of alkyl esters of unsaturated mono- and dicarboxylic acids and homo- or copolymers of various alkyl vinyl ethers.
DE-A-20 47 448 discloses additives for lowering viscosity in paraffin-based crude oils. The additives are mixtures of polyvinyl ethers and ethylene-vinyl acetate copolymers.
EP 486 836 A1 discloses mineral oil middle distillates, for example gas oils, diesel oils or heating oil, which comprise polymeric additives to improve the flow properties under cold conditions. The polymeric additives are a combination of customary ethylene-based flow improvers, for example copolymers of ethylene and vinyl acetate, vinyl propionate or ethylhexyl acrylate and copolymers of C8- to C18-alkyl (meth)acrylates and/or C18- to C28-alkyl vinyl ethers in a weight ratio of 40:60 to 95:5, and the copolymers of the alkyl (meth)acrylates and/or alkyl vinyl ethers and the conventional flow improvers may be in the form of a mixture or the copolymers of the alkyl (meth)acrylates and/or alkyl vinyl ethers may wholly or partly be grafted onto the conventional flow improvers. The solvents proposed for performance of the polymerization are a multitude of very different solvents, for example toluene, xylene, ethyl benzene, cumene, high-boiling aromatic mixtures, aliphatic and cycloaliphatic hydrocarbons such as n-hexane, cyclohexane, methylcyclohexane, n-octane, i-octane, paraffin oils, paraffinic solvent mixtures or tetrahydrofuran and dioxane. In the sole example for preparation of a graft copolymer, n-dodecyl acrylate and n-octadecyl vinyl ether are grafted onto a copolymer of ethylene and vinyl propionate having a mean molar mass Mn of approx. 2500 g/mol. The grafting is performed in isoundecane as a solvent. After the end of the reaction, a high-boiling aromatic solvent mixture and further ungrafted ethylene-vinyl propionate copolymer are added.
U.S. Pat. No. 4,608,411 discloses graft copolymers for prevention of wax deposition from crude oils. The main chain consists of a copolymer of ethylene and a monomer selected from the group of vinyl esters of C2- to C18-monocarboxylic acids, C1- to C12-esters of unsaturated monocarboxylic acids or unsaturated α,β-dicarboxylic acids, or the esters or anhydrides thereof. Onto this are grafted homo- or copolymers of alkyl acrylates, the alkyl group thereof having at least 12 carbon atoms and at least 20% of the alkyl groups having at least 22 carbon atoms. The graft reaction can be effected in aliphatic or aromatic solvents, preferably in toluene, xylene or aromatic solvent fractions. In the examples, xylene is used as the solvent.
Commercially available graft copolymer formulations composed of ethylene-vinyl acetate copolymers and polyacrylates which have long alkyl chains and have been (partly) grafted thereon for use as paraffin inhibitors or pour point depressants are frequently supplied as highly concentrated solutions in toluene. However, a disadvantage of these is that the flashpoint of toluene is only about 6° C. This comparatively low flashpoint complicates the handling of the products, for example in a refinery or on an offshore platform, because appropriate safety measures have to be taken when working with the formulation. There is therefore a demand in the market for pour point depressants formulated in solvents having a flashpoint of at least 60° C.
The use of other solvents, however, is by no means unproblematic, since, for economic reasons, the graft copolymers should not be isolated from the solvents such as toluene used for the synthesis and formulated for use in suitable solvents only in a second step; instead, the formulations obtained in the course of production should be usable directly, without isolating the polymer. Typical use concentrations of pour point depressants of, for example, 500 ppm appear to be small. This number means, however, that 0.5 kg of pour point depressant has to be used per t of crude oil. Global oil production in 2011 was about 4 billion t. Pour point depressants are therefore not small-volume specialty products but products which have to be produced inexpensively in large volumes.
Naturally, the choice of solvent for a polymerization has a quite considerable influence on the polymerization process. If, for example, toluene is replaced by higher-boiling alkylaromatics, for example cumene, this can influence the chain transfer rate and hence the molecular weight of the resulting polymer in the free-radical polymerization.
Moreover, the choice of solvent naturally influences the dissolution characteristics of the polymers. Pour point depressants are generally supplied as concentrated solutions and can be formulated for use in the desired manner by the users on site. The products supplied should be liquid in order to avoid melting on site, and the solutions should also remain stable over a long period and not have a tendency to phase separation, such that they can be stored with great simplicity.
It was therefore an object of the invention to provide a process for producing pour point depressants from ethylene-vinyl acetate copolymers and alkyl acrylates in solvents having a flashpoint of at least 60° C., and the formulations were to have at least the same influence on the pour point as conventional products produced in toluene. It was to be possible to add the formulations in a simple and safe manner to crude oils, and the solutions were to have adequate stability.
Accordingly, a process has been found for producing a polymer formulation at least comprising two different solvents and
The solvents (S1) are preferably saturated aliphatic hydrocarbons having a flashpoint ≧60° C.
The solution of the monomers (A1) is preferably provided in two stages in process step (I), by first esterifying at least one alcohol of the general formula R2-OH with (meth)acrylic acid H2C=CR1-COOH in the presence of solvents (S1) and then mixing the solution formed with at least one ethylene-vinyl ester copolymer (B).
In a second aspect of the invention, polymer formulations have been found, at least comprising
In a third aspect, the use of the polymer formulation as a pour point depressant for crude oil, mineral oil and/or mineral oil products has been found, by adding at least said polymer formulation to the crude oil, mineral oil and/or mineral oil products.
Specific Details of the Invention are as Follows:
Starting Materials Used
Solvents S1
To execute the invention, at least one nonpolar solvent (S1) comprising saturated aliphatic hydrocarbyl groups and having a flashpoint ≧60° C. is used. It is of course also possible to use a mixture of different solvents (S1).
The solvents (S1) should be nonpolymerizable and have no significant regulating action, if any, in the course of free-radical polymerization. Examples of suitable solvents comprise saturated aliphatic hydrocarbons, saturated aliphatic alcohols or esters of saturated aliphatic carboxylic acids and saturated aliphatic alcohols, with the proviso that the solvents each have a flashpoint ≧60° C. Examples of alcohols comprise aliphatic alcohols having at least 8 carbon atoms, such as 1-octanol, 1-decanol or 1-dodecanol. Examples of esters comprise esters of saturated fatty acids having at least 8 carbon atoms with saturated aliphatic alcohols, for example methyl laurate or methyl stearate. Technical mixtures of various aliphatic esters are commercially available. In a further embodiment of the invention, it is possible to use esters of aliphatic or cycloaliphatic dicarboxylic acids, for example dialkyl esters of cyclohexane-1,2-dicarboxylic acid, such as diisononyl cyclohexane-1,2-dicarboxylate.
In a preferred embodiment of the invention, the solvents (S1) are saturated aliphatic solvents or solvent mixtures having a flashpoint ≧60° C. These may be either paraffinic or naphthenic, i.e. saturated cyclic, hydrocarbons. Saturated aliphatic hydrocarbons having a flashpoint 60° C. are high-boiling and typically have a boiling point of at least 175° C. Examples of suitable hydrocarbons comprise n-undecane (flashpoint 60° C., boiling point 196° C.) or n-dodecane (flashpoint 71° C., boiling point 216° C.). It is possible with preference to use technical mixtures of hydrocarbons, for example mixtures of paraffinic hydrocarbons, mixtures of paraffinic and naphthenic hydrocarbons or mixtures of isoparaffins. It will be apparent to those skilled in the art that technical mixtures may still comprise small residues of aromatic or unsaturated hydrocarbons. The content of aromatic and/or unsaturated hydrocarbons should, however, be generally <1% by weight, preferably <0.5% by weight and more preferably <0.1% by weight. Technical mixtures of saturated aliphatic solvents are commercially available, for example technical mixtures of the Shellsol® D series or the Exxsol® D series.
It is of course also possible to use mixtures of various solvents (S1). In a preferred embodiment of the invention, the solvents (S1) are exclusively saturated aliphatic solvents or solvent mixtures.
Aromatic Solvents S2
To execute the invention, in addition, aromatic solvents or solvent mixtures having a flashpoint ≧60° C. (S2) are used. Such hydrocarbons are high-boiling and typically have a boiling point of at least 175° C. In principle, it is possible to use any aromatic hydrocarbons having a flashpoint ≧60° C., for example naphthalene. It is possible with preference to use technical mixtures of aromatic hydrocarbons. Technical mixtures of aromatic solvents are commercially available, for example technical mixtures of the Shellsol® A series or the Solvesso® series.
Monomers (A)
The monomers (A) used are monoethylenically unsaturated monomers, with the proviso that at least 70% by weight thereof are alkyl (meth)acrylates (A1) of the general formula H2C=CR1-COOR2. In this formula, where R1 is H or a methyl group, preferably H, and R2 is a linear alkyl radical having 12 to 60 carbon atoms, preferably 16 to 30 carbon atoms, more preferably 18 to 24 carbon atoms and, for example, 18 to 22 carbon atoms. It will be appreciated that it is possible to use mixtures of various alkyl (meth)acrylates (A1). For example, it is possible to use mixtures in which R2 represents C16 and C18 radicals or C18, C20 and C22 radicals.
As well as the monomers (A1), it is possible to use further monomers (A) other than the monomers (A1). With the aid of further monomers (A) as well as the monomers (A1), it is possible to modify the properties of the inventive formulations and match them to the desired properties. The person skilled in the art makes a suitable selection. The selection is limited only by the fact that further monomers (A) have to be miscible with the solvents (S1) and the monomers (A1) at the use concentration selected.
Further monomers (A) may especially be (meth)acrylates which do not correspond to the above definition of the monomers (A1), vinyl esters, vinyl ethers, vinylamides or vinylamines.
In one embodiment of the invention, further monomers (A) are (meth)acrylates (A2) of the general formula H2C=CR1-COOR4 where R1 is H or methyl and R4 is at least one hydrocarbyl radical selected from the group of R4a, R4b, R4c and R4d radicals, where the radicals are each defined as follows:
Examples of linear alkyl radicals R4a comprise ethyl, n-propyl, n-butyl, n-pentyl, n-hexyl, n-heptyl, n-octyl, n-nonyl, n-decyl and n-undecyl radicals, preference being given to n-propyl, n-butyl, n-pentyl, n-hexyl, n-heptyl, n-octyl, n-nonyl and n-decyl radicals.
Examples of branched alkyl radicals R4b comprise i-butyl, t-butyl, 2,2′-dimethylpropyl, 2-ethylhexyl, 2-propylheptyl, i-nonanol, i-decyl, i-tridecyl, i-heptadecyl radicals, preference being given to t-butyl, 2-ethylhexyl and 3-propylheptyl radicals.
An example of a cyclic alkyl radical R4c is a cyclohexyl radical.
Examples of aromatic hydrocarbyl radicals R4d comprise phenyl, 4-methylphenyl, benzyl or 2-phenylethyl radicals.
In a further embodiment of the invention, further monomers (A) are (meth)acrylates (A3) of the general formula H2C=CR1-COOR5 where R1 is H or methyl and R5 is a linear or branched, aliphatic and/or aromatic hydrocarbyl radical which has 1 to 60, preferably 2 to 30, carbon atoms and may be substituted by OH groups and/or in which nonadjacent carbon atoms may be substituted by oxygen atoms. In other words, R3 radicals may thus comprise OH groups and/or ether groups —O—. Examples of (meth)acrylates (A3) comprise hydroxyethyl (meth)acrylate, hydroxypropyl (meth)acrylate, phenoxyethyl acrylate, or polypropylene glycol mono(meth)acrylate.
In a further embodiment of the invention, further monomers (A) are vinyl esters of the general formula H2C=C-O-(O)C-R5(A4) where R6 is a linear or branched alkyl radical having 1 to 60 carbon atoms, preferably 2 to 30 carbon atoms. Examples of R6 radicals comprise methyl, ethyl, n-propyl or n-butyl radicals.
In a preferred embodiment of the invention, further monomers (A) are at least one monomer (A2), preferably those having an R4b radical, especially R4b) radicals having 4 to 17 carbon atoms. Examples of preferred monomers (A2) comprise t-butyl (meth)acrylate, 2-ethylhexyl (meth)acrylate and 2-propylheptyl (meth)acrylate, particular preference being given to t-butyl (meth)acrylate.
According to the invention, the amount of the alkyl (meth)acrylates (A1) based on the total amount of all monomers (A) is at least 70% by weight, preferably at least 85% by weight, more preferably at least 95% by weight, and the monomers (A) used are most preferably exclusively alkyl (meth)acrylates (A1).
In one embodiment of the invention, the monomers (A) used are a mixture of alkyl (meth)acrylates (A1) and alkyl (meth)acrylates (A2), for example a mixture of 70 to 99% by weight of monomers (A1) and 1 to 30% by weight of monomers (A2), preferably a mixture of 70 to 95% by weight of monomers (A1) and 5 to 30% by weight of monomers (A2).
Ethylene-vinyl Ester Copolymers (B)
The ethylene-vinyl ester copolymers (B) used comprise ethylene and vinyl esters of the general formula H2C=CH-O-(O)C-R3. In this formula, R3 is H or a C1- to C4-hydrocarbyl radical, for example a methyl, ethyl, n-propyl or n-butyl radical. R3 is preferably H, methyl or ethyl and more preferably methyl.
As well as ethylene and the vinyl esters, further monomers may optionally also be present. The amount of such further monomers should, however, not exceed 20% by weight, preferably 10% by weight, based on the amount of all monomers, and particular preference is given to the presence of no further monomers aside from ethylene and the vinyl esters.
The amount of ethylene in the ethylene-vinyl ester copolymers (B) is 55 to 85% by weight and the amount of vinyl esters is 15 to 45% by weight based on the amount of all monomers.
Preferably, the amount of ethylene is 55 to 75% by weight and the amount of vinyl esters 25 to 45% by weight, more preferably 30 to 40% by weight, and, most preferably, the amount of ethylene is 60 to 70% by weight and the amount of vinyl esters 30 to 40% by weight.
The weight-average molecular weight Mw of the ethylene-vinyl ester copolymers (B) used is preferably at least 30 000 g/mol, for example 30 000 g/mol to 200 000 g/mol, preferably 50 000 g/mol to 150 000 g/mol.
Process step (I)—Provision of a Solution of the Starting Materials for the Polymerization
In process step (I), a solution at least comprising the monomers (A) and an ethylene-vinyl ester copolymer (B) in at least one solvent (S1) is provided. According to the invention, the monomers (A) comprise at least 70% by weight of at least one alkyl (meth)acrylate (A1) and optionally further different monomers (A).
This can be effected by dissolving the monomers (A), including at least 70% by weight of alkyl (meth)acrylates (A1), and at least one ethylene-vinyl ester copolymer (B) in at least one solvent (S1). This can be effected by mixing solid ethylene-vinyl ester copolymer (B), the monomers (A), including the alkyl (meth)acrylates (A1), vigorously with the solvents (S1), for example by stirring. The dissolution can be accelerated by increasing the temperature, for example to about 50 to 80° C. Alternatively, the monomers (A) and the ethylene-vinyl ester copolymer (B) can each be dissolved separately in solvents (S1) and the solutions obtained can be mixed with one another. It will be appreciated that further variants for the mixing are also possible.
The mixing ratio of monomers (A) and ethylene-vinyl ester copolymers (B) is selected according to the desired properties of the polymeric composition to be synthesized, and the amount of the monomers (A) should be at least 50% by weight based on the sum of monomers A and ethylene-vinyl ester copolymers B. In general, the amount of the monomers (A) is 70 to 90% by weight and that of the ethylene-vinyl ester copolymers (B) 10 to 30% by weight. Preferably, the amount of the monomers (A) is 75 to 85% by weight and that of the ethylene-vinyl ester copolymers (B) 15 to 25% by weight.
The resulting solution of alkyl (meth)acrylates (Al1, optionally further monomers (A), for example further monomers (A2), (A3) and/or (A4), and ethylene-vinyl ester copolymers (B) in solvents (S1) is used for process step (II).
Two-Stage Process for Providing the Solution of the Monomers (A)
In a preferred embodiment of process step (I), the solution is provided in a two-stage process comprising process steps (Ia) and (Ib).
Process Step (Ia)
In process step (Ia), a solution of alkyl (meth)acrylates (Al) of the general formula H2C=CR1- COOR2 in solvents (S1) is prepared by esterifying at least one alcohol of the general formula R2-OH with (meth)acrylic acid H2C=CR1-COOH in the presence of solvents (S1), where the R1 and R2 radicals are each as defined above. Preference is given to acrylic acid.
The alcohols R2-OH used for esterification may be defined linear alcohols. Examples comprise hexadecan-1-ol (cetyl alcohol), octadecan-1-ol (stearyl alcohol), nonadecan-1-ol, eicosan-1-ol (arachyl alcohol), heneicosan-1-ol, docosan-1-ol (behenyl alcohol), tetracosan-1-ol, hexacosan-1-ol, octacosan-1-ol or tricontan-1-ol. It is advantageously also possible to use technical mixtures of various linear alcohols, which may be fatty alcohols or synthetic alcohols. Examples of preferred mixtures comprise mixtures of C16/C18 alcohols (tallow fat alcohols) or mixtures of C18/C20/C22 alcohols, and such mixtures may of course also comprise further alcohols as secondary components in small amounts.
According to the invention, the esterification is performed in saturated aliphatic hydrocarbons as solvents (S1). Details of saturated aliphatic hydrocarbons and hydrocarbon mixtures and preferred saturated aliphatic hydrocarbons and hydrocarbon mixtures have already been given above. The amount of the hydrocarbons is preferably selected here such that the concentration of the alkyl (meth)acrylates A1 formed in the saturated aliphatic hydrocarbons after the end of the esterification is 40 to 90% by weight, more preferably 50 to 85% by weight, based on the sum of all components of the solution.
The esterification can be performed by methods known in principle to those skilled in the art, for example by the processes described by EP 486 836 A1. The esterification can be performed using customary acidic esterification catalysts such as sulfuric acid, p-toluenesulfonic acid, methanesulfonic acid or acidic ion exchangers. It is additionally advisable to use polymerization inhibitors, for example hydroquinone derivatives or 4-methoxyphenol. The esterification can be undertaken in a manner known in principle by heating the mixture, preferably to a temperature >100° C., for example 100° C. to 160° C., with distillative removal of water of reaction formed. Saturated aliphatic hydrocarbons distilled off as well as the water can be separated from water in a customary manner in water separators. The hydrocarbons can be recycled into the reaction mixture.
Process Step (Ib)
The solution of alkyl (meth)acrylates (A1) in solvents (S1) provided in process step (Ia) is mixed in process step (Ib) with at least one ethylene-vinyl ester copolymer (B). It is of course also possible to use a mixture of several different ethylene-vinyl ester copolymers (B). It is optionally also possible for further monomers (A) to be present in the mixture in process step (II). Process step (Ib) is preferably performed in the same apparatus in which process step (II) is also performed.
Process Step (II)—Free-Radical Polymerization
In process step (II), the monomers (A) dissolved in the solvents (S1), comprising at least 75% by weight of monomers (A1), are free-radically polymerized in the presence of the ethylene-vinyl ester copolymers (B).
The free-radical polymerization is performed by adding at least one thermal initiator for free- radical polymerization to the solution obtained in process step (I). Naturally, the initiators used are selected such that they are soluble in the polymerization medium. Preferred polymerization initiators comprise oil-soluble azo compounds, especially those having a 10 h half-life of 50° C. to 70° C. Examples of suitable initiators comprise dimethyl 2,2′-azobis(2-methylpropionate) (10 h half-life approx. 66° C.), 2,2′-azobis(2-methylbutyronitrile) (10 h half-life approx. 67° C.) or 2,2′- azobis(2,4-dimethylvaleronitrile) (10 h half-life approx. 51° C.). Such initiators are commercially available (from Wako). The weight ratio of monomers (A) to the initiators is generally about 100:1 to 150:1, preferably 125:1 to 140:1. It is possible for the entire amount of the initiators to be present at the start of the polymerization, but preference is given to adding the initiator gradually. The addition may be in portions or continuous, preferably continuous.
For use in the polymerization, the polymerization initiators are preferably dissolved in solvents (S1) and/or solvents (S2) and the solution can be added to the reaction mixture.
In addition, molecular weight regulators can be added in a manner known in principle. Examples of regulators comprise alcohols such as isopropanol, allyl alcohol or buten-2-ol, thiols such as ethanethiol, or aldehydes such as crotonaldehyde. The amount of the molecular weight regulators is generally 1 to 4% by weight based on the monomers (A), preferably 2 to 3% by weight based on the monomers (A).
The free-radical polymerization is triggered in a manner known in principle by heating the reaction mixture. The polymerization temperature should be above the 10 h half-life of the initiator and is generally at least 50° C. A useful polymerization temperature has been found to be from 50 to 90° C. In general, the polymerization is undertaken in a manner known in principle under a protective gas such as nitrogen or argon.
The polymerization can be undertaken by initially charging the solution obtained in process step (I) in a suitable, typically stirred reaction vessel, process step (II) advantageously being performed actually in the same apparatus as process step (I) or (Ib). If desired, one or more molecular weight regulators are added to the solution. After the desired polymerization temperature has been attained, a solution of the polymerization initiator is added gradually to the mixture to be polymerized. The duration of addition may be 0.5 h to 10 h, without any intention to restrict the invention to this range. The completion of addition of the initiator should generally be followed by a further polymerization time. This may, for example, be 0.5 to 5 h. It will be appreciated that the initiator can also be added prior to the heating.
According to the invention, the reaction medium is diluted with solvents (S2) during and/or after the polymerization.
The expression “after the polymerization” means that the addition is effected once the polymerization is complete or has at least substantially ended, but the reaction mixture has not yet cooled completely from the polymerization temperature to room temperature. It is generally effected in the apparatus used for polymerization. Preferably, an addition “after the polymerization” immediately follows the polymerization, at a time when the temperature of the reaction medium has not yet fallen, or has not yet fallen more than 20° C., preferably not more than 10° C., below the reaction temperature at the end of the polymerization.
In a preferred embodiment of the invention, a portion of the solvents (S2) is added during the polymerization and a portion of the solvents (S2) thereafter. In one embodiment of the invention, 1 to 40% by weight, preferably 5 to 30% by weight, of the total amount of solvents S2 used is added during the polymerization, and the rest after the polymerization.
The addition of the aromatic solvents (S2) during the polymerization can be effected, for example, by dissolving the polymerization initiators in solvents (S2) and adding the solution gradually.
Instead of or in addition to this embodiment, a portion of the solvent (S2) can be added after addition of a portion of the initiator. Such an addition can be effected, for example, after addition of 40 to 70% of the initiator, and this addition may be 1 to 40% by weight, preferably 5 to 30% by weight, of the total amount of solvents (S2).
The weight ratio of the saturated aliphatic solvents to the aromatic solvents S1/S2 is generally 1:5 to 2:1.
The concentration of the monomers A in the solvents (S1) at the start of process step (II) is selected by the person skilled in the art according to the desired properties of the formulation to be produced. In a preferred embodiment of the invention, the concentration is 50 to 85% by weight. Such a concentrate has the advantage that the transport costs from the site of production to the site of use, for example an oil production installation, can be kept low.
The amount of the solvents (S1) and (S2) together is likewise selected according to the desired properties. In a preferred embodiment, it is such that the concentration of all polymers prepared together at the end of process step (II) is 40 to 50% by weight based on the sum of all components of the solution.
By means of the process described, a polymeric composition in a mixture of solvents (S1) and (S2) is obtainable. The polymerization of the monomers (A) in the presence of the ethylene-vinyl ester copolymers (B) prevents the polymer components from separating from one another. The result of the polymerization reaction is different when the monomers (A)—under otherwise identical conditions—are polymerized separately from the ethylene-vinyl ester copolymers (B) and the solution of the polymer formed from the monomers (A) and the ethylene-vinyl ester copolymers (B) are combined after the polymerization. Such solutions can separate again.
Although we do not wish to be bound to a particular theory, this effect can be explained by at least partial grafting of the monomers (A) onto the ethylene-vinyl ester copolymer (B) in the course of polymerization. A further portion of the monomers may polymerize without being grafted on. This gives rise to ethylene-vinyl ester graft copolymers with side groups comprising monomers (A), and homo- or copolymers comprising monomers (A). In a manner known in principle, the partial grafting prevents separation of the two polymer components. It is also possible that no significant grafting occurs, but that an “interjacent complex” forms from the ethylene-vinyl ester copolymers (B) and the homo- or copolymers of monomers (A). In such a complex, the polymers are predominantly physically bound and nevertheless stable, as described, for example, in U.S. Pat. No. 7,001,903 B2.
The inventive polymer formulation comprises at least
Preferred embodiments, for example with regard to the type of monomers (A), copolymers (B), and the amounts and mixing ratios thereof, have already been detailed above.
In a preferred embodiment of the invention, the weight ratio of the aliphatic solvents to the aromatic solvents S1/S2 is 1:5 to 2:1.
In a further preferred embodiment of the invention, the concentration of all polymers together is 40 to 50% by weight based on the sum of all constituents of the solution.
In a further preferred embodiment of the invention, the polymer formulation is obtainable by means of the process detailed above.
Use of the Formulations as a Pour Point Depressant
The above-detailed polymer formulations in hydrocarbons (S1) and (S2), especially the polymer formulations obtainable by means of the process according to the invention, can be used in accordance with the invention as pour point depressants for crude oil, mineral oil and/or mineral oil products, by adding at least one of the polymer formulations detailed to the crude oil, mineral oil and/or mineral oil products. In addition, it is of course also possible to use further formulations which act as pour point depressants.
Pour point depressants reduce the pour point of crude oils, mineral oils and/or mineral oil products. The pour point (“yield point”) refers to the lowest temperature at which a sample of an oil, in the course of cooling, still just flows. For the measurement of the pour point, standardized test methods are used.
For the inventive use, the abovementioned concentrate, for example a concentrate with a total polymer content of 50% by weight to 80% by weight, can be used as such. However, it is also possible to dilute with further solvent, preferably with solvents (S1) and/or (S2), and/or to formulate it with further components. For example, additional wax dispersants can be added to the formulation. Wax dispersants stabilize paraffin crystals which have formed and prevent them from sedimenting. The wax dispersants used may, for example, be alkylphenols, alkylphenol-formaldehyde resins or dodecylbenzenesulfonic acid. The concentration of a usable formulation may, for example, be 20 to 50% by weight, preferably 25 to 40% by weight, of polymers prepared in accordance with the invention and optionally further components except for the solvents, this figure being based on the total amount of all components including the solvents. While the inventive formulations are naturally typically produced in a chemical plant, the ready-to-use formulation can advantageously be produced on site, i.e., for example, directly at a production site for oil.
The inventive use is effected by adding the inventive formulations optionally comprising further components and/or dilute formulations to the crude oil, mineral oil and/or mineral oil products, preferably to the crude oil.
The formulations are typically used in such an amount that the amount of the polymeric composition added is 50 to 1500 ppm based on the oil. The amount is preferably 100 to 1000 ppm, more preferably 250 to 600 ppm and, for example, 300 to 600 ppm. The amounts are based on the polymeric composition not including the solvents (S1) and (S2) and optional further components of the formulation.
In a preferred embodiment of the invention, the oil is crude oil and the formulation is injected into a crude oil pipeline. The injection can preferably be effected at the oilfield, i.e. at the start of the crude oil pipeline, but the injection can of course also be effected at another site. More particularly, the pipeline may be one leading onshore from an offshore platform. Explosion protection is particularly important on offshore platforms and in refineries, and the inventive formulations based on solvents having a flashpoint ≧60° C. accordingly simplify working quite considerably. Moreover, the cooling of crude oil in underwater pipelines leading onshore from an offshore platform is naturally particularly rapid, especially when the pipelines are in cold water, for example having a water temperature of less than 10° C.
In a further preferred embodiment of the invention, the oil is crude oil and the formulation is injected into a production well. Here too, the production well may especially be a production well leading to an offshore platform. The injection is preferably effected approximately at the site where oil from the formation flows into the production well. In this way, the solidification of the crude oil in the production well or an excessive increase in its viscosity can be prevented.
Further Uses of the Formulations
The inventive formulation can of course also be used for other purposes.
In a further embodiment of the invention, the above-detailed polymer formulations in hydrocarbons (S1) and (S2), especially the polymer formulations obtainable by means of the process according to the invention, are used to prevent wax deposits on surfaces in contact with crude oil, mineral oil and/or mineral oil products. The use is effected by adding at least one of the polymer formulations detailed to the crude oil, mineral oil and/or mineral oil products. Preferred formulations have already been mentioned, and the manner of use is also analogous to the use as a pour point depressant. In addition, it is of course also possible to use further formulations which act as wax inhibitors.
The following examples are intended to illustrate the invention in detail:
A Production of the Polymer Formulations Used
In the examples, the polymer formulations are produced in a two-stage process. In the first stage, acrylic acid is esterified with the desired alcohol in a solvent. In the second stage, the resulting solution of the alkyl acrylates is used without further purification and is reacted with an ethylene-vinyl acetate copolymer to give a graft copolymer in which the polyacrylates are at least partly grafted onto the ethylene-vinyl acetate copolymer. The product obtained may, as well as the graft copolymer, also comprise as yet ungrafted polyacrylates. For use, the products remain dissolved in the solvents in which they were dissolved in the synthesis.
Starting Materials Used:
Polymer 1
Stage 1
A reactor with stirrer, water separator, jacketed coil condenser and gas inlet tube is initially charged with 1888.2 g of C16/18 tallow fat alcohol (Hydrenol® D), 5.6 g of p-toluenesulfonic acid, 3.6 g of 4-methoxyphenol and 541.1 g of a commercially available high-boiling aliphatic solvent mixture (Shellsol® D70). The water separator is charged with 35 g of Shellsol® D70. The reaction mixture is purged with lean air (6% O2) and heated to 80° C. while stirring (50 rpm) in order to dissolve the C16/18 tallow fat alcohol. After increasing the stirrer speed to 250 rpm, 519.1 g of acrylic acid are metered in and the temperature is increased to a maximum of 165° C., such that water of reaction formed can be distilled off. After 8 to 10 h, the reaction is ended. A solution of 1-hexadecyl acrylate and 1-octadecyl acrylate in Shellsol® D70 is obtained (concentration 80% by weight of acrylates).
Stage 2
In a four-neck flask with Teflon stirrer, jacketed coil condenser and Dosimat, 424.5 g of the monomer solution (80% by weight of acrylates) are heated to 75° C. while stirring (300 rpm) under an N2 blanket, and 84.0 g of the abovementioned ethylene-vinyl acetate copolymer are added and dissolved. Then 9.2 g of Shellsol® D70 are added. After adding 6.9 g of allyl alcohol, 1.8 g of the initiator dimethyl 2,2′-azoisobutyrate (Wako V-601) dissolved in 29.5 g of a high- boiling aliphatic solvent (Shellsol® D70) are metered in at an internal temperature of 72° C. over 3 hours. In order to counteract the rise in viscosity and the rise in temperature, after half of the initiator has been added, the mixture is diluted with 50.0 g of Solvesso® 150 ND. After further polymerization at 72° C. for 2.5 hours, the mixture is diluted with 270.1 g of Solvesso® 150 ND and stirred for 30 min, before being filtered through a 400 μm fast sieve.
A solution is obtained which comprises 50% by weight of graft copolymers (approx. 20% by weight of ethylene-vinyl acetate copolymer and approx. 80% by weight of polyacrylate, based in each case on the graft copolymer), 10% by weight of high-boiling aliphatic solvent having a flashpoint of 74° C. (Shellsol® D70) and 40% by weight of high-boiling aromatic solvent (Solvesso® 150 ND) having a flashpoint of 65° C.
Polymer 2
Stage 1
A reactor with stirrer, water separator, jacketed coil condenser and gas inlet tube is initially charged with 575.8 g of a C18/C20/C22 mixture of aliphatic linear alcohols (Nafol® 1822), 2.2 g of p-toluenesulfonic acid, 1.5 g of 4-methoxyphenol and 177.2 g of a high-boiling aliphatic hydrocarbon mixture (Shellsol® D70). The water separator is charged with 31 g of Shellsol® D70. The reaction mixture is purged with lean air (6% O2) and heated to 80° C. while stirring (50 rpm) in order to dissolve the aliphatic alcohol. After increasing the stirrer speed to 200 rpm, 135.5 g of acrylic acid are metered in and the temperature is increased to a maximum of 160° C., such that water of reaction formed can be distilled off. After 6 h, a further 363.4 g of Shellsol® D70 are added and the reaction is ended. A solution of alkyl acrylates having C18/C20/C22 alkyl radicals in Shellsol® D70 is obtained (concentration 55% by weight of acrylates).
Stage 2
In a four-neck flask with Teflon stirrer, jacketed coil condenser and Dosimat, 1224.0 g of the monomer solution (55% by weight of acrylates) are heated to 75° C. while stirring (300 rpm) under an N2 blanket, and 166.1 g of the abovementioned ethylene-vinyl acetate copolymer are added and dissolved. Then 8 g of Shellsol® D70 are added. After adding 20.37 g of allyl alcohol, 2.9 g of the initiator dimethyl 2,2′-azoisobutyrate (Wako V-601) dissolved in 78.4 g of a high-boiling aliphatic solvent (Shellsol® D70) are metered in at an internal temperature of 77-82° C. over 4 hours. After further polymerization at 78-87° C. for 2.5 hours, the mixture is diluted with 265.7 g of Solvesso® 150 ND and cooled to 40° C., before 1.1 g of triethanolamine are added and the mixture is stirred for a further 30 min. Finally, the mixture is filtered through a 400 μm fast sieve.
A solution is obtained which comprises 49% by weight of graft copolymers (approx. 20% by weight of ethylene-vinyl acetate copolymer and approx. 80% by weight of polyacrylate, based in each case on the graft copolymer), 32% by weight of high-boiling aliphatic solvent having a flashpoint of 74° C. (Shellsol® D70) and 19% by weight of high-boiling aromatic solvent (Solvesso® 150 ND) having a flashpoint of 65° C.
Further polymer formulations were obtained by varying the above experimental conditions:
B Test of the Properties of the Copolymer Formulations Obtained
The solutions of the copolymers obtained were used to conduct each of the following tests:
Determination of the K Values of the Copolymers
The K values of the copolymers obtained (measured according to H. Fikentscher, Cellulosechemie, volume 13, pages 58 to 64 and 71 to 74 (1932)) were determined in 2% (wt./vol.) toluenic solution. The values are compiled in tables 1 to 3.
Molecular Weight Determination
The number-average molecular weight Mn and the weight-average molecular weight Mw of each of the copolymers obtained were determined by means of gel permeation chromatography in tetrahydrofuran as the solvent. The values are compiled in tables 1 to 3.
Determination of Viscosity:
The kinematic viscosity of each of the solutions of the graft copolymers obtained in the experiments described above was measured with an Ubbelohde viscometer at 50° C. The values are compiled in tables 1 to 3.
Assessment of Stability
The stability of each polymer solution was examined, specifically with respect to whether a solution which has prolonged stability and does not have a tendency to phase separation is maintained. For this purpose, the formulations produced, after synthesis, were stored at room temperature. If noticeable phase separation occurs within 24 h after commencement of storage, the assessment is negative (−), otherwise (+). The values are compiled in tables 1 to 3.
Determination of the Pour Point
The determination of the pour point was conducted to ASTM D 5853 “Standard Test Method for Pour Point of Crude Oils”. The pour point is the minimum temperature at which a sample of a tested oil is still just free-flowing. According to ASTM D 5853, for this purpose, a sample of the oil is cooled in steps of 3° C. each and the flowability is tested after each step. For the tests, a crude oil from the “Landau” oilfield in south-west Germany (Wintershall Holding GmbH) having an API gravity of 37 and a pour point of 27° C. was used. To determine the lowering of the pour point, the graft copolymers to be tested were used to the oil in a concentration of 100 ppm, 300 ppm or 1500 ppm, in each case of polymer based on the crude oil. The values are compiled in tables 1 to 3. Double or triple determinations were conducted on some samples. In these cases, all values are reported in the table.
The examples and comparative examples show the advantages of the process according to the invention. C1 (with C16/C18 acrylates) and C2 (with C18/C20/C22 acrylates) are products according to the prior art which have been prepared in toluene (flashpoint 6° C.). The product with C16/18 acrylates is liquid, and both products are stable. The pour point of the test oil (27° C.) is reduced to 6 to 9° C. by formulation C1 according to the amount, and to 6 to 9° C. by formulation C2.
The formulations 1 (with C16/C18 acrylates) and 2 (with C18/C20/C22 acrylates) which have been obtained by means of the process according to the invention and have been prepared using solvents S1 and S2 are likewise stable and actually lead to somewhat lower pour points in the test (0° C. to 9° C. in each case). What is surprising is the concentration dependence of the reduction in the pour point, the experiments showing a minimum of only 0° C. to 3° C. at 300 ppm both for C1 and for C2, while 3° C. to 6° C. are measured at 100 ppm and 6° C. to 9° C. at 1500 ppm for C1, and 6 to 9° C. both at 100 ppm and at 1500 ppm for C2.
If toluene as the solvent (boiling point 111° C., flashpoint 6° C.) is replaced exclusively by aromatic solvents having a flashpoint >60° C. (C3, C4, C5, C6), this choice of solvent distinctly influences the course of the polymerization. Both the number-average molecular weight Mn and the weight-average molecular weight Mw of the polymers increase compared to the corresponding experiments in toluene, and the polydispersity increases. The resulting formulations no longer have adequate stability and are either biphasic or waxy solids. Moreover, the lowering of the pour point is no longer as good in all concentration ranges as the products in toluene.
If toluene as the solvent is replaced exclusively by aliphatic solvents having a flashpoint >60° C. (C7, C8), solid or waxy solid products are obtained, which have to be melted for use. The lowering of the pour point is smaller than in the case of the inventive experiments with a mixture of solvents (S1) and (S2).
| Number | Date | Country | |
|---|---|---|---|
| 61738417 | Dec 2012 | US |
