GB2337522A - Asphaltene precipitation inhibiting polymer for use in oils - Google Patents

Abstract

An invention relating to a polymer comprising structural units derived from monomers which are at least one of (A) at least one ethylenically unsaturated alcohol, carboxylic acid or ester, (B) an ethylenically unsaturated carboxylic ester with a polar group in the ester, and (C) an ethylenically unsaturated carboxylic amide, wherein at least one of said structural units contains at least one pendant ring group. Alternatively, the pendant ring group may be introduced into the polymer by transesterification. Two examples of the structural unit are p-nonylphenyl methacrylate and p-dodecylphenyl methacrylate.

Description

2337522 POLYMERS AND THEIR USES This invention relates to carboxylic

polymers and their uses in hydrocarbon fluids.

Some of the physical properties of many improve hydrocarbon oils, such as crude oil and, residual oils, are often unsatisfactory. They have a tendency to deposit solids such as asphaltenes especially when subjected to a reduction in pressure. This is due to the fact that asphaltenes are normally maintained in a stable, coalesced/colloidal/dispersed state in hydrocarbon liquids by the resins present therein which are believed to form one or more protective layers around the asphaltene molecules or nuclei and enable them to remain in such a state. However, when the pressure at which such stable behaviour is exhibited is reduced, the resin layers surrounding the asphaltene are removed thereby enabling the asphaltene molecules to agglomerate and precipitate as a solid deposit from the hydrocarbon liquid or oil. The deposition of solids such as asphaltene may also occur when the oil is subjected to a reduction in temperature.

Carboxylic polymers such as polymers of unsaturated esters e.g. alkyl (meth) acrylate esters are described for use as pour point depressants (to stop oil gelling with wax) or wax deposition inhibitors.

Carboxylic polymers have now been discovered which can act to reduce asphaltene deposition.

The present invention provides a polymer (including co, ter and higher polymers) having structural units derived from monomers which are at least one of (A) at least one ethylenically unsaturated alcohol, carboxylic acid or ester, (B) an ethylenically unsaturated carboxylic ester with a polar group in the ester, and (C) an ethylenically unsaturated carboxylic amide, at least one structural unit containing at least one pendant 1 ring group and especially at least one structural unit also containing a pendant non cyclic organic group having at least 1 in particular at least 6 carbon atoms The copolymers may be derived from monomers A and/or B which are ethylenically unsaturated carboxylic acids or esters thereof, or esters of ethylenically unsaturated alcohols. The copolymers, may be acid esters, acid amides, mixed esters, ester amides or acid ester amides, or alcohol esters.

The present invention also provides a method of preparing the polymers of the invention which comprises polymerising the monomer A, B and/or C, especially one or more different A monomers, or at least one A and at least one B or C, in particular, when monomer A is an ester, and especially when each of the monomers is derived from an ethylenically unsaturated carboxylic acid or ester or amide, or each is derived from an ester of ethylenically unsaturated alcohol.

The present invention also provides a method of preparing the polymers of the invention comprising A units which comprises reacting an ester polymer having structural units of A which is an ester of an ethylenically unsaturated carboxylic acid (A), especially consisting essentially of such A' units, with an hydroxy compound containing a ring group and preferably a noncyclic group, or one hydroxy compound with a ring group and preferably one with a noncyclic group added together or stepwise in either order. The hydroxy compound may contain at least one additional polar group.

The ester polymer with A' units may react with an organic primary or secondary amino compound with or without at least one additional polar group but with the ring, and preferably non cyclic groups, present in the same or different amino compounds. The present invention also provides a method of preparing the polymers of the invention with structural units A, and optionally B or C in which structural units A' comprise carboxylic acids and optionally ester units, which comprises breaking an ester link in A' e.g. by hydrolysing a corresponding copolymer of the invention in which structural units A' are carboxylic esters especially ones without a polar side chain and especially of less than 6 carbon atoms in the alcohol part of the ester.

The present invention provides a method of preparing polymers of the invention, which comprises reacting a polymer having structural units of A", which is at least one of an ethylenically unsaturated alcohol, an ester thereof and a mixture of ester units and units from said unsaturated alcohol A" (but especially consisting essentially of such A" 2 units), with a carboxylic acid (or derivative thereof especially an ester) containing at least one ring group and especially the non cyclic group or one carboxylic acid (or derivative) with a ring group and especially another with a non cyclic group.

The invention also provides a soluble concentrate with at least 10% at least 20% by weight of a polymer of the invention, in a solvent especially an organic solvent for oil soluble polymer. For water soluble polymers the solvent may be water. The polymer may also be in a dispersion, with at least 10% e.g. at least 20% by weight of said polymer, the dispersion being in a liquid medium in which the polymer is insoluble or incompletely soluble. For oil soluble polymers the medium is preferably aqueous while for water soluble ones the medium is preferably organic e.g. a hydrocarbon as described above.

The present invention also provides a hydrocarbon fluid comprising asphaltenes e.g. a crude oil or residue oil which comprises at least one polymer of the invention.

The present invention also provides a method of reducing formation of or deposition of solids comprising asphaltenes from a hydrocarbon oil containing asphalteines, which comprises mixing with said oil at least one polymer or complex of the invention or concentrate or dispersion thereof, in particular an oil soluble one and especially one containing a copolymer of an ester A. The addition of the polymer can reduce the flow rate in said oil due to formation of solids therein on cooling said oil.

In at least one structural unit is at least one ring group pendant to the polymer backbone. The ring group may be carboxylic or heterocyclic, saturated or partly or completely unsaturated (including aromatic or hetero aromatic). The carboxylic ring group may contain 5-20 carbons, such as 5-7 ring carbon atoms, such as in a cycloaliphatic ring in a cyclopentyl, cyclohexyl, cycloheptyl group or cyclohexenyl, cyclohexadienyl group or cyclooctadienyl group, or may be an aromatic group, with 1-4 rings, especially 1 or 2 rings, as in benzene, naphthalene, phenanthrene and anthracene rings.

The rings may also be heterocyclic with at least one N, 0, S hetero ring atom which may be in an N, 0, S, SO orS02group. Preferably there is one 0 or S ring atom, or at least one N ring atom, optionally with at least one other hetero ring atom e.g. N, 0 or S. Rings with N, and 0 or another N ring atom are preferred. There may be 1-3 heterorings optionally singly bonded to or fused to each other or one or more carbocyclic 3 is rings (e.g. as defined above). Preferred heteroring rings are as defined for WX'R9 as described further below.

Preferably in at least one structural unit is at least one organic group, with a noncyclic group of at least 1 or 2 especially at least 6 carbon atoms. The group is preferably aliphatic, and especially hydrocarbyl, in particular alkyl or alkenyl and may be linear or branched (e.g. with at least one methyl or ethyl branch). Preferably the noncyclic group contains a chain of at least 6 carbon atoms which may be unbranched or with 1-4 branched groups e.g. methyl groups. Advantageously, the group contains 8-30 carbons, e.g. 8-24 carbons in particular 8-14 carbons, especially nonyl or dodecyl, or '1ranched dodecyP (as in a propylene tetramer group).

The polymers may contain pendant groups, at least 10% or 20% of which contain the ring group, and especially at least 10% or 20% contain the noncyclic group, the total of which may be 100% or 20-85%, the remainder if any being other groups e.g. acyclic of less than 6 carbons, methyl.

The ring group and the noncyclic group may be in the same structural unit and may be separate from or bonded to each other, directly or via at least one bridge group. Preferably when the groups are bonded together the non cyclic group is spaced from the polymer backbone at least by the ring group. Examples of such arrangements are in copolymers with at least one aliphatic substituted aromatic or heteroaromatic ring group pendant directly onto ester or amide group joined to the backbone. The ring and especially non cyclic group may be separately bonded to the polymer backbone, via at least one bridge group and in the same or different structural units. The bridge groups between ring and noncyclic groups (if any), or ring and polymer backbone or noncyclic group and polymer backbone may be ester, or amide groups, with a carbonyl or N atom attached to the backbone.

Thus copolymers may be formed from units A and B andlor C, in which at least one of A, B and C contains the ring group and preferably at least one contains a noncyclic group. Advantageously the noncyclic group is in the ester monomer A and the ring group is in monomer A or B. In the copolymers are structural units from at least one monomer A' which is preferably an ethylenically unsaturated acid or ester thereof or mixture of both.

The ethylenic unsaturated carboxylic acid for use, which may be monomer A', 4 may contain the unsaturated group alpha, beta or gamma, or in another location, to the carboxylic group. It may contain 3-17 e.g. 3-6 carbon atoms, and is especially an aliphatic alpha ethylenically unsaturated carboxylic acid of formula R1CH=CR 2CO2R wherein each of R' and R 2 which may be the same or different is hydrogen or an alkyl group e.g. of 1-3 carbons, such as methyl, ethyl or propyl. Methacrylic and especially acrylic acids are preferred. The acid may be a mono, di or tricarboxylic acid, examples of the diacid being fumaric, maleic and crotonic acids.

The esters thereof for use as monomer A' may be from an aliphatic hydrocArbyl alcohol, with a short chain aliphatic group e.g. of 1-5 carbons and/or from a hydroxylic compound with a larger organic hydrocarbyl group such as of 6-40 e.g. 6- 16 or 16-40 carbons.

In the ester each of the aliphatic and/or organic hydrocarbyl groups may be saturated or unsaturated, e.g. all saturated or all unsaturated, but preferably at least one e.g. the short chain one is saturated and the rest saturated or unsaturated.

The larger organic alcohol for use in the ester polymers may be aliphatic and preferably linear, but may be branched (e.g. with a branch methyl group). The alcohol may be saturated i.e. an alkanol in which case preferably at least 40% of the saturated aliphatic groups have 12-35 e.g. 15-35 carbons. The alcohol may be ethylenically unsaturated i.e. an alkenol in which case preferably at least 50% of the aliphatic groups in the copolymer have 12-35 e.g. 15-35 carbons and the molecular weight is at least 20,000 or 40,000. The alcohol may contain at least one unsaturated group e.g. 1-4 such as 1 or 2 or 3 or 4, especially 1 unsaturated group. The unsaturated group may be beta, gamma, or in another location, to the alcohol group preferably non terminal and may be in a cis or trans configuration especially with any unsaturated groups non-conjugated.

The aliphatic alcohol usually contains 14-40 carbons such as 15-25 carbons, especially 16, 18, 20, 22 or 24 carbons. The alcohol may be natural or synthetic e.g. from oxo or ALFOL processes. Examples of suitable alcohoIs are palmityl, hexadecyl, stearyl, octadecyl, eicosyl, docosyl, as well as oleyl alcohol and branched alcohols such as oxo alcohols e.g. 2-methyl eicosyl alcohol. The hydroxylic compound with the larger organic hydrocarbyl group may contain 6-16 carbons, e.g. with an alkyl group such as hexyl, octyl, isooctyl, 2-ethylhexyl, decyl, dodecyl, lauryl, tetradecyl or myristyl group. The larger organic hydrocarbyl group may be a cycloalkyl group e.g. of 5-7 carbon atoms such as cyclo-hexyl or cycloheptyl, cycIopentyl or an aromatic group (which includes alkaryl groups) of 6-30 carbons, such a phenyl, tolyl or xylyl, or aralkyl group e.g. of 713 carbons such as benzyl or 2-phenyl ethyl. Particularly preferred to provide the ring group are aromatic groups, such as ones described above, and especially for combined noncyclic and ring groups are alkyl (or alkenyl) substituted aromatic groups, e.g. with 620 e.g. 8-18 or especially 10-16 carbons in the alkyl or alkenyl group (e.g. as defined for the alkyl group above) attached to a phenyl, especially in a para position to the free valency thereof. Thus preferred for the hydroxylic compounds are alkyl substituted phenols, e.g. nonylphenol, decylphenol, dodecyl phenol and branched chain dodecyl phenol (i.e. from propylene tetramer group). The alcohols especially aliphatic ones saturated or unsaturated may be substantially pure, but are preferably mixtures of alcohols, e.g. as in tallow alcohol or mixtures of alkanols and/or alkenols of even carbon number, with one carbon number predominating with decreasing proportions of alkanols or alkenols of lower and higher carbon number (e.g. of Gaussian distribution) i.e. with carbon numbers distributed on either side of the major one. Such mixtures may contain at least 50% e.g. at least 80 or 90% (by mole) of one alkanol or alkenol. Examples of such mixtures are unsaturated alcohols e.g. of 16 or 18 carbon atoms containing in wt % 50-100% of cis-alkenol, and optionally 1-20% e.g. 5-20% of saturated alkanols, especially C 14, C 16 or C 18 saturated alkanols (such as in commercial oleyl alcohol).

Preferably the monomer A is an ester of an aliphatic hydrocarbyl alcohol with a short chain aliphatic group of 1-5 carbon atoms, and an ethylenically unsaturated acid of 3-6 carbon atoms. Especially preferred are acrylates and methacrylates of methanol, ethanol or tert butanol.

Thus monomer A may be of formula WCH=CR2C02W, wherein each of R', and R2 which may be the same or different represents hydrogen or an aliphatic hydrocarbyl group e.g. an alkyl group of e.g. of 1-4 carbons such as methyl or ethyl and R3 may be as defined for R' or R2 or represents a hydrocarbyl group of at least 6 carbons such as an alkyl or alkenyl group or other group e.g. as described for the larger hydrocarbyl group in the hydroxylic compound above. Preferably R' is hydrogen and R 2 is hydrogen alkenyl or alkyl, especially hydrogen or methyl and R' is hydrogen, alkyl or alkenyl, cycloalkyl, aryl or aralkyl, especially R' as alkyl in one monomer and R 3 as aryl in another or R' as alkaryl in one monomer. In Monomer A R3 can consist essentially of 6 hydrogen or hydrocarbyl or comprises a mixture of monomers A', in which R' as hydrogen and R' as hydrocarbyl may be present, the ratio being 0.5-99. 5:99.5-0.5, such as 0.5-50:99.5-50 or 99.5-50:0.5-50, e.g. 10-40:90-60 or 90-60:10-40.

A mixture of structural units for monomers A' may be present with R 3 hydrocarbyl, in particular ones with short chain alkyl for R 3 and larger hydrocarbyl e.g.

longer chain alkyl and/or aryl and/or alkaryl for R 3 (e.g. so the longer chain aliphatic alcohol or phenol or alkyl phenol described above is of formula R3011). The molar ratio of monomers with such short to larger chain group may be 0.5-99.5:99.5-0. 5, in particular 10-90:90-10 especially 10-40:90-60. Increasing ratios of the larger monomer units tend to increase the hydrocarbon solubility of the copolymers, as well as their molecular weight. The molar ratio of monomers with R 3 as short chain to R 3 as larger may be 0. 1-5:1:0.1-5 in particular 0. 1- 1: 1: 1-5, especially for oil soluble polymers and 1 - 5: 1: 0. 1 -1 for water soluble ones.

In the polymers may be structural units from at least one monomer B, which is an ester of an ethylenically unsaturated carboxylic acid and an organic mono hydroxy compound with at least one additional polar group (B). The monomers B may be free of the ring and/or noncyclic group or instead of or as well as the structural units of monomer A (if present), there may be at least one ring and/or non cyclic group in monomer B. The acid may be as described with respect to monomer A. The additional polar group may contain an oxygen, nitrogen or sulphur atom, especially one or more 0 andlor N atoms. The or each polar group may be a side chain substituent on a chain of carbon atoms or may interrupt a chain of carbon atoms. Examples of side chain substituents are ether groups e.g. of formula OR5 and thioether groups of formula SW, or corresponding sulphoxides or sulphones, or secondary arnine groups e.g. of formula 6 NR5R ' wherein R' and R6 are as defined below. Preferably the polar atom interrupts a chain of carbon atoms, so that the organic monohydroxy compound is preferably of formula HOR 4 XR', wherein X is 0, S -SO, -S02 -or W, wherein R 4 represents a divalent organic group, in particular a hydrocarbyl group such as one of 1-20 carbons, as in an alkylene group e.g. of 1-6 carbons, a cycloalkylene group e.g. of 5- 7 carbons, an arylene group e.g. of 6-12 carbons, or aralkylene or aryl bis alkylene group e.g. of 7-12 6 or 8-12 carbons respectively, each of R5 and R ' which may be the same or different, represents an organic hydrocarbyl group e.g. of 1-20 carbons such as alkyl e.g. of 1-6 7 carbons, a cycloalkyl group of 5-7 carbons, an aryl group e.g. of 6-12 carbons or an aralkyl group of 7-12 carbons. Examples of R 4 are methylene, 1,2-ethylene (which are preferred) 1,3-propylene and 1,4butylene or 1,4-cyclohexylene, or 1,2 or 1,3 or 1,4phenylene, or 1,4benzyIene or 1,4-phenyl bis methylene (xylylene). Examples of R' and 5 R' are methyl, ethyl, isopropyl or butyl, cyclohexyl, cyclopentyl phenyl,, tolyl, xylyl or benzy], but preferably methyl, ethyl or isopropyl in particular for W and especially for both R' and R 6. Thus preferably the R 4 XR' group in the monohydroxy compound is 2methoxy ethyl and 2methylthio ethyl, 2-ethylthio ethyl, 2,2-dimethyl an-dno-ethyl, and 2p dimethylamino phenyl-ethyl.

The monohydroxy organic compound may also contain a hetero ring, preferably of 5, 6 or 7 ring atoms, and be of formula HO(R)., (Rg)bX'K9wherein X, is 0 S, SO or S02or NR", and each of a and b, which may be the same or different, is 0 or 1, and R7 is as defined above for R 4, R' may be as defined for R4or, with R9 may form a trivalent group, which with the oxygen S, SO orS02or NR10 forms a heterocyclic group, optionally with the ring carbon atoms interrupted with 0 andfor NR10, R9 forms the trivalent group above with R' or with R10 may form a divalent group which with the N atom to which they are bonded may form a heterocyclic group, optionally with the ring carbon atoms interrupted by 0 or NR10 (especially when W0 is as defined for W), and R10 may be as defined for W or as defined above in a ring group with R9 or may with R8 or R9 form an N heterocyclic ring group. Each of R', k9 and R10 when part of a ring can contain 1-5 carbons, subject to the ring containing 5-7 ring atoms.

Thus in the hetero ring containing compounds, when a is 1 and b is 0, the IC group can be bonded directly onto the N atom of the ring formed with NIC W' as in N(2hydroxy methyl or 2 hydroxy ethyl) piperidine N(hydroxy methyl) benzimidazole. When both a and b are 0, the hydroxyl group can be bonded directly to the said ring N atom as in N-hydroxy piperidine. When a is 0 or 1 and b is 1, R8 may form with R9 and NR10 or the oxygen atom a hetero ring as in hydroxy N-methyl piperidine or hydroxy methyl tetra hydrofuran or hydroxy methyl pyridine.

The ring heterocyclic ring formed with WR9 and 0 or NW0, or with R9NW' may be saturated or unsaturated, partly or fully (as in an N hetero aromatic ring) and may contain 1 nitrogen or oxygen atom and optionally 1 additional N and/or 0 atom. There may be 1 or more hetero rings e.g. 2 hetero ring fused or fused to each other, or 1 hetero 8 ring and at least one carbocyclic ring, saturated or unsaturated fused or unfused to the hetero ring. The ring groups can contain 3-12 carbons and 1-3 nitrogens. Examples of the rings are pyridine, piperidine, morpholine, tetrahydrofuran, pyran rings, isoquinoline and quinoline.

Examples of the organic monohydroxy compound with hetero-ring polar group are 2, 3 or 4 (2 hydroxy ethyl) tetrahydropyrrole or morpholine, 2, 3 or 4 hydroxyl N methyl piperidine and 2 hydroxyethyl or hydroxymethyl substituted in a tetrahydropyran or tetrahydrofuran ring, especially with the substituent in a 2 position.

In the polymers may be structural units from at least one monomer C, which is an ethylenically unsaturated carboxylic amide (C). Again monomer C may or may not contain at least one ring and/or non cyclic group. The amide is derived ftom an ethylenically unsaturated carboxylic acid, which may be as described with respect to monomer A', and ammonia or a primary or secondary amine. The amine may be of 2 21 20 formula HNIR OR, where each of R and R", which may be the same or difFerent represents an organic group or hydrogen, preferably one representing hydrogen, or R20 and C together with the N atom to which they are attached may form a heterocyclic ring.

Examples of the organic group are hydrocarbyl groups, such as are defined for or R6above, or hydrocarbyl groups containing at least one polar group, for which the nature and location of polar groups may be as described above in respect of monomer W. Advantageously the amine containing the hydrocarbyl group and a polar group is of formula 112NW2 X2 R', wherein X2 is 0, S_orNR27R22, R' and R7are as defined for R4, R5 and R 6 respectively, or of formula H2N(R 24) (R2)dX2R 26, wherein c is 0 or 1, d is 0 or 1 X2 is 0, S or WO and C, R2' and W' are as respectively defined for R7, R' and W above.

Thus for amines for use in monomer C, which are hydrocarbyl amines R20 is preferably hydrogen while R 21 is preferably a long or short chain alkyl or alkenyl group, e.g. respectively of 14-40, or 1-13 e.g. 1-6 carbons e. g. methyl or ethyl. R2' is preferably a long chain group of 16-24 carbons, in particular dodecyl, stearyl, palmityl, oleyl or octadecyl. Examples of such amines are ethylamine, dodecylamine, stearyl amine and oleyl arnine. Benzylamine may also be used.

For amines in which R 20 and R2' together with the N atom to which they are 9 attached form a heterocyclic ring, the ring usually contains 5, 6 or 7, especially 6 ring atoms, with 1 nitrogen atom. The ring may be saturated or partly ethylenically unsaturated and may be unsubstituted or substituted by one or more alkyl groups e.g. of 1-6 carbons, such as methyl or ethyl. Examples of such amines are piperidine and 5 tetrahydropyrrole and their ring methyl derivatives.

Preferably the amine contains an additional polar group as described above. The additional polar group may be a N or 0 atom not bonded in a ring or part of a ring. Preferably the N atom is not part of a ring, so the amine is of formula H2NRNR2W, wherein k22, R3 and R6are defined above. R2is especially alkylene of 1-4 carbons e.g.

methylene or 1,2-ethylene, while R23and R 6 are especially alkyl of 1-6 carbons, such as methyl ethyl or isopropyl. Thus the amine may be 2(dimethylamino)ethylamine or 2(diethylamino)ethylamine. The arnine may also contain an oxygen atom not in a ring such as one of formula H 2NR22 OR 23 wherein R2and R3are as defined above, in particular R 22 being alkylene of 1-4 carbons e.g. methylene or 1,2 ethylene, and R23being especially alkyl of 1-6 carbons such as methyl, ethyl or isopropyl. Examples of such amines are 2-butoxyethylamine and 2-ethoxyethylamine. The amine may also contain an oxygen atom in a ring e.g. be of formulaH2N(R 24) (R 21)d 0k26, wherein R 24 is as defined for k7, and is especially methylene or 1,2-ethylene, and R25 and W' and the 0 atom form a heterocyclic ring in the way R8 and R9 and the oxygen atom above form such a ring.

Examples of such rings are tetrahydrofuran, and tetrahydropyran rings. Examples of such amines are 2-aminomethyl-tetrahydrofuran and tetrahydropyran. N heterocyclic ring substituted alkyl amines may also be used, in particular the an-dno analogues of the alcohols with a hetero cyclic ring described above with the OH group replaced by an NH2group. Examples of these are aminomethyl- and 2 amino ethyPpyridines and piperidines and morpholines.

In the copolymers may be structural units A from at least one ester of an ethylenically unsaturated alcohol, and/or said alcohol itself, including n-tixtures of alcohol and ester units e.g. with 1-50% alcohol with 99-50% ester or 99-50% alcohol and I50% ester. The structural unit A" may consist essentially of said alcohol or said ester or both. The ethylenically unsaturated alcohol may contain the unsaturated group, alpha, beta or gamma to the alcohol group or in another location. It may contain 2-6 carbons, and is preferably allyl alcohol, methallyl alcohol, alpha methyl vinyl alcohol or especially "vinyl alcohoP (CH2=CH01-1), which can form structural units for the ester polymers.

The carboxylic acid for use in the structural units with such unsaturated alcohols, may be an alkanoic acid e.g. of 1-24 carbons, such as 1-5 carbons, especially for alkanoic acids such as formic acetic, propionic and butyric acids, 3-24 carbon alkenoic acid e.g.

oleic acid or 6-24 carbon alkanoic acids, in particular ones which are linear or have at least one methyl or ethyl branch. The carboxylic acid may have a larger organic hydrocarbyl group, such as one of 6-24 carbons, e.g. an alkanoic acid of 6-16 carbons such as hexanoic, octanoic, 2 ethyl hexanoic, isoctanoic, decanoic, lauric, dodecanoic, myristic or palmitic, or a cycloalkanoic e.g. of 6-8 carbons such as cyclohexanoic acid, or aromatic hydrocarbyl carboxylic (including aralkanoic acids) e.g. of 7-30 carbons such as benzoic or toluic, or aralkanoic acid e.g. of gcarbons such as 2-phenyl ethanoic acid. The carboxylic acid may contain the ringgroups e.g. an aromatic group as defined above and/or a combined non cyclic and ring group, as in alkyl (or alkenyl) benzoic acids. The acid may contain 14-40 carbons such as 15-25 carbons, especially 16, 18, 20, 22 or 24 carbons. The acid may be natural or synthetic e.g. derived from oxo or ALFOL process alcohols. Examples of suitable acids are oleic, palmitic, hexadecanoic, stearic, octadecanoic, and eicosanoic. The saturated or unsaturated acids may be substantiaHy pure, but are preferably mixtures of acids, e.g. as in tallow acid or mixtures of acids of even carbon number with one carbon number predominating with decreasing proportions or acids or lower and higher carbon number (e.g. of Gaussian distribution) i.e. with carbon numbers distributed on either side of the major one. Such n-tixtures may contain at least 50% e.g. at least 80 or 90% (by mole) of one alkanoic or alkenoic acid and smaller amount(s) of other alkanoic or alkenoic acid(s). Examples of such mixtures are unsaturated acids e.g. of 16 or 18 carbons containing (in wt%) 50-100% cis-acid, (such as in commercial oleic acid) or saturated acids e.g. behenic acid with a majority of 22 carbon alkanoic acid and smaller amounts of 16, 18, 20 and 24 carbon alkanoic acids.

Preferably the momoner A" is an ester of an unsaturated alcohol with 3-6 carbons and a saturated carboxylic acid of 2-5 or 6-24 carbons. Especially preferred are esters of "vinyl alcohoP and acetic or propionic acids.

1 Thus monomer A" may be of formula R 32CO2CR'O=CHR" 31 wherein each of R30 and R ' which may be the same or different may be as defined for R' or R2, while R32. may be as defined for R, especially where WC02,H represents the carboxylic acid which is an alkanoic acid of 1-6 carbons or one with a larger organic hydrocarbyl group as described above or a mixture thereof in particular ones in which the molar ratio of short to larger acid groups for R' is as described above. Preferably R' and R 2 are hydrogen and R3 is alkyl e.g. 1-5 or 6-24 carbons or aromatic hydrocarbyl of 6-30 carbon such as alkyl phenyl of 12-24 carbons. The monomer A" may also be of formula R"OCR'O=CIEK3', where R3' is hydrogen or R"CO.

A mixture of monomer units from unsaturated alcohols may be present, in particular when R 33 is hydrogen, and when R 33 is R32 CO, especially inmolar ratios of 0.5-99.5 i 99.5-0.5, in particular 5-95:95-5 or 10-50: 90 - 50 or 90-50: 10-50 e.g. 10 40. 90-60 or 90-60: 10-40. Increasing the proportion of R 12C0 groups increases the hydrocarbon solubility and molecular weight of the polymer. Mixtures of units from alcohols with short and larger groups for R3' may have the proportions for W as defined for R3 above. Preferred are polymers from structural units of "vinyP alcohol and vinyl acetate, laurate, palmitate, benzoate and dodecyl benzoate.

The polymers may contain structural units from at least one monomer W' which is an ester of an ethylenically unsaturated alcohol and an organic mono- carboxylic acid with at least one additional polar group. B l l may or may not comprise a ring or noncyclic group. The alcohol may be as described with respect to monomer A". The additional polar group may contain an oxygen, nitrogen or sulphur atom, especially one or more 0 andlor N atoms. The or each polar group may be a side chain substituent on a chain of carbon atoms or may interrupt a-chain of carbon atoms. Examples of side chain substituents are other groups e.g. of formula R05, or secondary arnine groups e.g.

of formula NR5R6, wherein R' and R 6 are as defined above. Preferably the polar atom interrupts a chain of carbon atoms, so that the organic carboxylic acid is preferably of formula HOOCR4)0s, wherein X, R4, R' are as defined and exemplified above.

Preferably the -R 4 XR5 group in the carboxylic acid compound is methoxy phenyl, methoxy methyl, 2-methoxy ethyl and methylthio methyl, 2-methylthio ethyl or 3 methylthio propyl, methylthio phenyl-, 2-phenylthio ethyl-, 2,2-dimethyl amino-ethyl, 2 dimethylan-dno phenyl-ethyl (especially with the dimethylamino group in o or p position, dimethylamino methyl and dimethyl amino phenyl.

The organic carboxylic acid may also contain a hetero ring, preferably of 5, 6 or 7 12 ring atoms, and be of formula HOOC(R 7).,(R8)bX1R9 wherein R 7, R8, R9, X' are as defined and described above.

Thus in the hetero ring containing compounds, when a is 1 and b is 0, the R 7 group can be bonded directly onto the N atom of the ring formed with NR"R'0 as in N(carboxy methyl) piperidine. When a is 0 or 1 and b is 1, W' may form with R and NR'0 or the oxygen atom a hetero ring as in N-methyl piperidine carboxylic acid or tetra hydrofuran carboxylic acid or pyridine carboxylic acid or picolinic acid.

The ring heterocyclic ring formed with WR9 and 0 or WO, or with N9NW' may be saturated or unsaturated, partly or fully (as in an N hetero aromatic ring) and may contain 1 nitrogen or oxygen atom and optionally 1 additional N and/or 0 atom. There may be 1 or more hetero rings e.g. 2 hetero ring fUsed or infused to each other, or 1 hetero ring and carbocyclic ring, saturated or unsaturated fused or unfused to the hetero ring. The ring groups can contain 3-12 carbons and 1-3 nitrogens. Examples of the rings are pyridine, piperidine, morpholine, tetrahydrofuran pyran rings, isoquinoline and quinoline.

Examples of the organic monocarboxy compound with hetero-ring polar group are 2,3 or 4 (carboxymethyl) tetrahydropyrrole or morpholine, N methyl piperidine carboxylic acid and carboxymethyl or carboxy substituted in a tetra hydropyran or tetra hydrofuran ring, especially with the substituent in a 2 position.

The polymers may be homopolymers of A, B or C, or copolymers consisting essentially of structural units of A, B or C (e.g. with 2 or more different structural units) or be copolymers of A with B and/or C.

The copolymer may have structural units from monomers A and B (including A'W or A"B"), in which case the molar percentages may be 30-95%B, e.g. 4080% such as 50-MB (especially when B' is derived from a nitrogenous alcohol) or 60-80% (especially when B' is derived from an ether alcohol), with 70-5%A, e.g. 60-20%A or 50-30%A or 40-20%A; the copolymer especially consists essentially of structural units of such monomers. The copolymers may contain at least 10. 1 % by weight of structural units from B, e. g. 11 -80 such as 3 5 -60wt% in particular in copolymers of A and B, especially when monomers A' comprise both larger (e.g. noncyclic) and short chain aliphatic alcohol groups e.g. from R'OH in particular ones with at least 30% of larger noncyclic groups, based on the total of said aliphatic groups. The copolymers may 13 contain (a) 10-70% e.g. 20-50% of short chain monomer A units (including Al,A') (e.g. alkyl(meth)acrylate or vinyl alkanoate esters with 1-4 carbons in the alkyl or alkanoate group), (b) 10-60% e.g. 20-40% of larger monomer A units (including A',Al') (e.g. alkyl(meth)acrylate or vinyl alkanoate esters with 6-30 e.g. 6-12 carbons in the alkyl or alkanoate group or 6-20 in an aryl or arylcarboxylate or alkaryl carboxylate) and optionally (c) 5-50% e.g. 10-30% of structural units from monomer B (including B' B"), in particular one in which the polar group is 1 or 2 amine or ether groups. The molar 3 proportions of the units (a):(b):(c) are usually 03-4 (e.g. 0.5-3): 03-1. 5 (e.g. 0.8-1.3 especially 1): 03-1.5 (e.g. 0.8-1.3 especially 1). The copolymer may have structural units from monomers A and C including A' C in which case the molar percentages may be 5-MC e.g. 5-50% or 8-25 or 20-45%C and 95-20%A, e.g. 95-50%, or 92-75% or 80-55% A, the copolymer especially consisting essentially of structural units of such monomers. The copolymers may also contain units from monomers A, B and C (including A', A", B', W' C) in which case the molar percentages may be 5- 60%B, e.g.

20-50M 5-MC e.g. 8-25%C, and a preferred total of B and C of 20-95% e.g. 40 80% or 50-70%, and a molar percentage of A of 5-80% e.g. 60-20% or 50-30%, the copolymer especially consisting essentially of structural units of such monomers). The units of monomer A may be from ester, acid or both acid and ester monomers and the above percentages apply to the amounts of ester monomer as sole A unit, or acid monomer as sole A unit or the total of both. Preferred are copolymers with an ester monomer units for A, and basic N containing monomers for B andlor C (i.e. copolymers D) or copolymers with a carboxylic acid units for A, and non basic N containing monomers B and/or C (i.e. copolymers E), or carboxylic acid for A with basic N containing monomers for B and/or C which are zwitterions.

The polymers may be made by direct polymerisation of the monomer units, in particular A, especially when it only contains ester groups and not carboxylic acid ones, and B and/or C, especially when the monomer is free of any NH group. In the direct polymerization, the monomer(s) islare usually all present from the start, though partial or complete polymerization of some monomer(s) e.g. A, followed by addition of monomer 0 e.g. B, and optionally A, as in graft polymerization may be performed. Preferably however, the polymers by direct polymerization are random not graft or block copolymers. Preferably monomers of type A', B' andlor C' react together, or of type 14 A" and B ", though ones of A' and B 1' or A' 1 and B 1 can be reacted.

The polymerisation may be performed in a conventional manner e.g. with or without a diluent e.g. a hydrocarbon solvent, such as hexane, heptane, or a higher boiling hydrocarbon oil, at a temperature of 25-120'C, such as 60-100'C, and optionally in the presence of a free radical catalyst, such as a peroxide (e.g. benzoyl peroxide) or azo catalyst such as azobis isobutyronitrile. The polymerisation is usually performed under inert conditions e.g. under nitrogen or argon. The polymerisation time may be 0.5-40hr, preferably 5-25hrat 60-100'C. At the end of the polymerisation, the reaction product may be purified by evaporation under vacuum to remove unreacted monomer, andlor precipitation of the product with methanol from a liquid aromatic or aliphatic hydrocarbon solution of the product.

Preferably however, the copolymers A or A + B are made by reaction of a polymer of one or more ester monomer units A (i.e. A' or A') which are derived from an unsaturated acid (or unsaturated alcohol), with an organic mono hydroxy compound (or organic carboxylic acid respectively) with at least one ring andlor noncyclic and/or additional polar group, as described above, in particular one of formula HOR 4 XR5 or HOW).(R')bW(or H02CR4XR5 or H02C(R).,(R')bX'1C respectively). Instead of either of the latter carboxylic acids a corresponding lower alkyl (Cl-4) ester (e.g. methyl, ethyl propyl tertbutyl ester may be used.

Preferably copolymers A' + C' derived from an unsaturated acid are made by reaction of a polymer of one or more corresponding ester monomer units A', with ammonia, or a primary or secondary amine, in particular one of formula IDZW'W' or H2NR22X2Rl or H2N(R24),(R21)d X2k21.

The reaction may be performed in the absence of but preferably in the presence of a liquid aromatic or aliphatic hydrocarbon solvent, by reaction of an ester hydroxyl, acid, acid ester or hydroxy ester polymer from monomer A, especially an ester with 1-4 carbons in the alcohol (or acid) group with the organic monohydroxy compound (or carboxylic acid) having the polar group, or ammonia or said amine in the case of unsaturated acid polymers. The reaction may be performed with an amount of the said compound or ammonia or amine substantially corresponding to the amount needed for the degree of conversion required, or an amount in excess of this e.g. substantially corresponding to an equimolar amount (based on the units of monomer ester A in the starting polymer) may be used and the reaction stopped when the desired degree of reaction has occurred e.g. as found from the amount of distilled by product lower alcohol or carboxylic acid or ester thereof e. g. methyl acetate. The reaction may be performed at 50-180'C e.g. 60- 120'C or 120-180'C for 1-30 e.g. 5-20 hours, in the absence or presence of a catalyst e.g. an organic soluble strong acid such as an aromatic sulphonic acid e.g. p-toluene sulphonic acid or a basic catalyst, such as an alkali metal alkoxide e.g. sodium methoxide or ethoxide (added as such or prepared in situ from alkali metal and by product lower alkanol) or a polyvalent metal alkoxide such as tetra methyl, tetra ethyl or tetraisopropyl titanate. Amounts of the catalyst e.g. basic ones such as alkali metal alkoxide may be 0.05-5% e.g. 0. 1 - 1 % by weight of the feed polymer. Basic catalysts are preferred for the reaction of the polymer esters derived from the unsaturated acids, while acid catalysts are prefrred for the reaction of the polymeric esters derived from unsaturated alcohols. During the reaction the by product lower alcohol or lower alkyl carboxylate is preferably evaporated. At the end, any solvent is advantageously evaporated, while optionally unreacted polar mono hydroxy compound or acid or arnine may be evaporated e.g. under reduced pressure. The reaction which is transesterification may be performed substantially to completion e.g. 90-100% especially 95M00%, with substantially no unreacted starting polymer e.g. 0-10% especially 0-5%, but advantageously the amount of reaction is 30-90% e.g. 55-75% or 70-90%, but especially 20-70% or 15-35%. At the end of the transesterifi cation any unreacted hydroxy compound e.g. polar hydroxyl or amine compound may not be separated from the polymer, but can remains in amount of 10-40% with respect to the total weight of polymer.

In the transesterification the ester polymer which can be reacted with the hydroxy compound e.g. with the ring, non cyclic and/or polar group, may comprise only short chain alkyl(meth) acrylate monomer units or larger alkyl(meth) acrylate polymer units or both larger and short chain units. The last copolymers may themselves have been made by copolymerization or transesterification from the short chain alkyl polymers and larger alcohols e.g. long chain alcohols or phenols or alkyl phenols according to the general procedure described above. In a similar way the ester polymer to be reacted with the organic carboxylic acid (or ester) may comprise short chain alkanoate side chains, or larger organic carboxylate side chains or both. The latter may be made from the 16 corresponding short chain alkanoate polymers and reaction with the larger acids.

The reaction of ester polymers with the amines may be performed in a similar manner to that of the polar alcohols, but in this case the reaction may be performed to the extent as described for the transesterification above but in particular 30-90% e.g. SO 80%; however preferably the reaction may be performed to 5-90% reaction, such as 5 50% such as 10-40% e.g. 10-20% or 30-50%.

Copolymers of A and B and/or C, in which the structural units from monomer A contains free carboxylic groups as sole monomer A units or mixed with ester units or free hydroxyl groups may be made by cleavage of the ester link in A, e.g. by hydrolysis or hydrogenolysis (e.g. for benzy] esters) of the corresponding copolymer in which A is an ester monomer. The hydrolysis, which is usually performed in solution in an organic solvent, may be acid or base catalysed e.g. with an alkane or aromatic sulphonic acid, e.g. methane sulphonic or toluene sulphonic acid or a base such as sodium or potassium hydroxide, especially with distillation of by product alcohol from the ester. Weight amounts of the catalyst may be 0. 1-5% by weight or preferably 1 - 10 equivalents per carboxylic ester group in monomer A in the copolymer. When carboxylic acid groups are required copolymers with ester monomers A based on lower alkyl or lower alkanoate esters are preferred as starting materials. The product free acids or acid esters may be isolated if desired by extraction into aqueous base, e.g. sodium hydroxide solution which can be separated from unreacted ester copolymers A+B and then the free acids or acid esters recovered by filtration or extraction after acidification of the aqueous solution.

The product from alcohols e.g. polyvinyl alcohol derivatives may be isolated by extraction.

The nitrogen containing polar group in the copolymers may be present in the form of a primary, secondary or tertiary amine or a quaternary salt. Quaternisation may be performed by reacting a copolymer of the invention having basic nitrogen atoms with a quaternising agent e.g. an organic halide e.g. chloride or organic sulphate, in either of which the organic group is an alkyl group e.g. of 1-20 carbons such as methyl, ethyl, dodecyl, stearyl, alkenyl group of 3-20 carbons e.g. 3-6 such as allyl, cycloalkyl e.g. of 57 carbons such as cyclobexyl, aralkyl e.g. a hydrocarbyl group of 7-30 carbons such as benzyl, 2-phenyl ethyl or dodecyl benzyi. Thus a copolymer (derived from an unsaturated acid or alcohol) having ester groups from a polar amino alcohol (or an-dno 17 acid) e.g. structural units ftom 2 dimethyl amino ethyl acrylate (or (pyridine methyl)acrylate) and e.g. methyl acrylate (and optionally larger organic acrylates) or units from vinyl 2-dimethyl (amino propionates) and e.g. vinyl acetate (and optionally a vinyl larger alkanoate., may be reacted with dimethyl or diethyl sulphate or benzylchloride, preferably with the desired proportion of quaternisation agent to basic nitrogen and in a hydrocarbon solvent. The amount of quaternisation may be such as to provide 1-20% molar of structural units with a quaternary group, e.g. 510%; there may also be present 0-20% molar of structural units with a basic nitrogen atom i.e.

unquaternised, preferably when the total of basic nitrogen and quaternised nitrogen is 5 20%. Thus the degree of quatemisation may be partial or substantially complete. At the end of the quaternisation, any excess of quatemisation agent may be separated e.g. by evaporation, and the polymer product, if desired, isolated.

The polymers of the invention may be crystalline but are preferably noncrystalline e.g. amorphous. The ester polymer of the invention is usually oil soluble e.g. dissolves to an extent of at least 5Oppm e.g. at least 20Oppm in kerosene at 25'C. The acid or alcohol copolymers of the invention is usually water soluble e.g. to an extent at 25'C of at least 50ppm e.g. at least 20Oppm at at least one pH in the range 1-14, especially 2-7 or 8-13, in particular to at least 1%.

The monomer All may also be derived from an ester of an ethylenically unsaturated alcohol with a carboxylic acid, and in this case the monomer B' l is usually derived from the ester of an ethylenically unsaturated alcohol and carboxylic acid with at least one extra polar group. Such copolymers of A" and W' are obtained by or are obtainable by reaction e.g. transesterification of the ester of the unsaturated alcohol with the polar carboxyl i.e. acid or an ester (or acid halide) thereof The reaction may be performed to at least 30% e.g. 30-90% completion.

The present invention also provides blends of one or more of the polymers of the invention, e.g. solely of different polymers of the same type e.g. esters A, esters B or amides C or ester A+B or ester A+C polymers or acid A+B or acid A+C polymers, the differences lying in different molecular weights, different chain lengths for the ester or nature of the polar group in B or nature of the amide in C. Blends may contain 90 10: 10-90 e.g. 30-70:70-30 proportions of the 2 copolymers.

The present invention also provides a soluble concentrate of at least 10% by 18 weight of a polymer of the invention, e.g. 10-40% such as 20-30% by weight in a solvent e.g. water (for water soluble copolymers) or an organic solvent, such as an aromatic hydrocarbon e.g. toluene or xylene or a mixture of methyl benzenes for oil soluble copolymers. If desired the solvent may be a mixture e.g. of the aromatic hydrocarbon and a polar oxygenated solvent such as methanol ethanol or isopropanol. The polymer may be made as such in the above solvent, which may be concentrated if required, but preferably they are made in a solvent, the solvent evaporated and/or the copolymer isolated if desired and the above concentrate made with the specifically desired solvent (or especially solvent mixture). A concentrate is often easier to handle for the proposed uses than pure product or a dilute solution.

However, in some cases the polymer may not dissolve in the desired organic solvent to the desired extent for a concentrate, so in these cases a dispersion in an organic solvent e.g. an aromatic hydrocarbon (as above) may be made. When the polymer does not dissolve in water, a dispersion in water of the copolymer may be made e.g. with at least 5% such as 5-40 or 10-30% by weight of the copolymer. The dispersion may contain water as continuous medium and the copolymer as such or in a solution in organic solvent (e.g. an aromatic hydrocarbon as above) as the disperse phase. A polar organic solvent e.g. as described above may also be present. The dispersion preferably also contains a surfactant to stabilise it (e.g. in amount 0. 1-5% by weight) especially one compatible with the overall nature of the copolymer, e.g. basic polymers preferably have nonionic or cationic surfactants, while acid polymers preferably have nonionic or anionic surfactants.

The polymers of the present invention may have a molecular weight of 20, 000 to 500,000 and especially at least 30,000 or at least 40,000, such as 40,000 to 200,000, 50000-150000 preferably 80,000 to 160,000 (Mw, weight average molecular weight) and the molecular weight distribution (Mw/Mn) may be 1.2-20 e.g. L2-10, preferably, L4-2 or 2-20 e.g. 5-15. As used herein, unless otherwise specified, the term "Molecular Weighf' of an ester or amide polymer produced by reaction of the corresponding precursor ester polymer and alcohol, ammonia or amine means the weight average molecular weight of the ester polymer obtained by calculation from the percentage conversion (based on spectroscopic analysis) and the molecular weight of the precursor ester or amide polymer, or the weight average molecular weight of the ester or amide 19 polymer itself, the molecular weight being determined by gel permeation chromatography (GPC) against polystyrene standards as described in the Aldrich Chemical Company's Standard Test Method for GPC. The term Molecular weight of an acid polymer made from ester polymer e.g. by hydrolysis is likewise defined. The term 'Nolecular Weighf' of an ester or amide polymer produced by direct polymerisation of the corresponding ester or amide means the weight average molecular weight of the ester or amide polymer determined by gel permeation chromatography (GPC) against polystyrene standards as described in the Aldrich Chemical Company's Standard Test Method for GPC. The term molecular weight of an acid polymer made by direct copolymerization is likewise defined.

The polymers, whether in solution, concentrated dispersion form or otherwise, may be used to reduce formation of or deposition of asphaltene solids, which cause pipe blocking or increase pipe pressures, especially in crude oil lines. The problem overcome concerns deposition of solids, especially on cooling e.g. in a pipeline or around the Bubble Point temperature, when the solids are asphaltenes.

The oil usually comprises a liquid hydrocarbon, especially a mixture of hydrocarbons of final boiling point higher than that of lubricating oils.

The hydrocarbon is usually primarily aliphatic in nature, but may contain up to 50% w/w liquid aromatic compounds. The hydrocarbon may be a crude or black oil or non volatile fraction from a distillation of crude oil, such as a vacuum, atmospheric or thermal residue. Preferably the hydrocarbon is an oil field product, e.g. either a whole well product, the multiphase mixture in or from the well bore, or one at the well head after at least partial separation of gas and/or water (and may be a condensate) e.g. an oil export fraction substantially free of separate phase gas and/or water. The liquid hydrocarbon may be flowing up a well bore, or on a production platform or between platforms or from a platform to a collection or storage facility e.g. from offshore to onshore. The oil, e.g. crude oil can contain at least 0.05% e.g. 0.1-10% especially I 10% of asphaltenes. The hydrocarbon may contain up to 50% by weight of wax usually 0.5-30% or 1-15%. The hydrocarbons may contain dissolved gas (e.g. with amounts of up to 10% gas) or water or water droplets e.g. with 5-40% water (e.g. as in water in oil emulsions, so called "chocolate mousse"). There may also be, in addition to the oil, gas and/or water as a physically separate phase. The hydrocarbons may in the absence of the compounds of the invention, have a wax appearance temperature (WAT) value which approximates the cloud point value of at least O'C e.g. 0-60'C or 10-501C, 20-45'C or 20-40'C; pour point of such hydrocarbons may be 10- 50'C e.g. 20-50T lower than the WAT value and may be - 3 O'C to 20'C e.g. -20'C to + 1 O'C.

The polymers concentrates or dispersions may be mixed in a portion with the hydrocarbon to be protected or may be mixed batchMse, continually or continuously with a body of the hydrocarbon e.g. oil usually moving liquid body, preferably added to a line containing flowing hydrocarbon to be protected, upstream of a cooler location where asphaltene deposition may occur in the absence of said compound or other location where asphaltene deposition is otherwise likely e.g. on reduction of pressure of a crude oil containing dissolved gas. The cooler location may be less than 20' e.g. +20 to -50, especially, + 10 to O'C. If desired the polymers concentrates or dispersions may be added to a tank of the oil e. g. to inhibit deposition of asphaltenes. The amount of polymer, whether as such or in concentrate or dispersion, added may be 10-10,000 ppm e.g. 1005000 ppm based on the weight of oil e.g. hydrocarbon. The polymer preferably dissolves in said oil to an extent of at least 1Oppm e.g. at least 10Oppm such as 100-500Oppm.

The polymers of the invention may be used in a blend with at least one surfactant which may be a cationic, anionic, ampholytic or nonionic one. Examples of cationic ones are quaternary ammonium salts having at least long chain group, such as dodecyl benzyl trimethyl ammonium chloride. Examples of nonionic ones are alkylene oxide condensates of fatty a-lcohols or fatty acids, fatty amindes or long chain alkyl phenols, e.g. nonylphenol polyethylencOxYlates. Examples of anionic ones are carboxylic and sulphonic acids (and salts thereof e.g. Na salts) with at least one long chain aliphatic group e.g. of 8-40 carbons, such as an alkyl or alkenyl group of 10-24 carbons such as stearic acid, or lauric acid or oleic acid, or an alkaryl e.g. an alkyl phenol group with 820 carbons in the alkyl group, such as linear or branched dodecyl.. dodecylbenzene sulphonic acid (or sodium salt), linear or branched (as in propylene tetramer) benzene sulphonic acid is preferred. The amount of surfactant may be 0.05-5% e.g. 0.5-2% by weight of the total weight of dispersion.

The invention is illustrated in the following Examples. General Procedur A solution of polymethyl acrylate (Mw 40000, 8.6g) in a mixture of methyl 21 benzenes sold as Solvesso 150 (100m1) and p-alkyl phenol were heated to 17WC for 1hr. Sodium methoxide in methanol (25% solution) 0.6mI was added and the solution heated at 170'C in the dry nitrogen sparging. At periodic intervals further aliquots of sodium methoxide were added every 8hr. The reaction product was concentrated to dryness to 5 afford the transesterified polymer. Examples 1-3 The general procedure was used with 7.7g, 12. lg and 16.5g of p-nonyl phenol, totals of 2.4, 4.2 and 4.2mI sodium methoxide solution and reaction times of 48, 72 and 72hr respectively. The molar product analyses were 17, 19, 20% esterified nonyl phenol 52, 26 and 13% unreacted methyl ester group and 31, 55, 67% unreacted nonyl phenol giving degrees of transesterification based on polymer of 25, 42 and 6 1 % respectively and calculated molecular weights of 61900, 76700, and 93300 respectively.

ExaMles 4-6 The process of Examples 1-3 was repeated with 9.17g, 14.4 1 g and 19.65g of p dodecyl phenol, totals of 3.6, 3.0 and 4.2mis sodium methoxide solution and reaction times of 48, 64 and 96hr. The molar product analyses were 20, 29, 41% esterified dodecyl phenol, 67, 52, and 30% unreacted methyl ester groups and 13, 19, 30% unreacted nonyl phenol, giving degrees of transesterifi cation based on polymer of 23, 36 and 58% respectively and calculated molecular weights of 64600, 78500, and 102000 respectively.

Example 7

The copolymers of Ex. 1-6 were tested for their effect on removing asphaltenes adsorbed on to quartz and for preventing deposition of asphaltenes onto the quartz. The asphaltenes were in precipitates from Alaskan crude oil containing 7.4% asphaltenes (according to IP 143).

Procedure to test removal of asphaltenes from quartz 1. A 10% solution of B4 asphaltene extract is made up in toluene.

2. 7mI of this solution is made up to 50OmI in toluene to produce a stock solution of asphaltene extract with an absorbance between 0.7 to 0.9 at a wavelength of 600 run in 1 cm' cell in the LTV spectrophotometer.

3. Quartz powder (0.4g, 200 mesh) is weighted into a test tube, asphaltene extract in toluene (10 cml) was added and the test tube stoppered.

22 5.

4. The test tubes were placed into an shaker, agitating for 30 minutes at 250rpm., then removed and centrifuged for 15 minutes (300Orpm).

The supernatant was carefully removed, the absorbance was measured at 600 run.

6. The remaining quartz was then contacted with chemical inhibitor solution in toluene (10 CM3, 1 OOOPPM).

7. The test tubes were placed back into the shaker, agitating for 30 minutes at 250rpm., then removed and centrifuged for 15 minutes (300Orpm). The supernatant was carefully removed, the absorbance was measured at 600 nm.

Care was taken to ensure that no quartz was removed with the supernatant.

Calculations Asphaltenes adsorbed onto quartz (A)= (Absorbance of Asphaltene Extract) - (Absorbance of first Supernatant) Asphaltenes removed from quartz (R)= (Absorbance of second Supernatant) Therefore:

% Asphaltenes removed= (RIA) 100 Procedure to test prevention of asphaltene adsorption onto quart 1. A 10% solution of B4 asphaltene extract is made up in toluene. 7n-d of this solution is made up to 50OmI in toluene to produce a stock

solution of asphaltene extract with an absorbance between 0.7 to 0.9 at a wavelength of 600 nrn in 1 cm' c-ell in the UV spectrophotometer.

Quartz powder (0.4g, 200 mesh) is weighted into a test tube, chemical solution (10 CM1), normally 100Oppm, was added and the test tube stoppered.

The test tubes were placed into an shaker, agitating for 30 minutes at 250rpm., then removed, centrifuged for 15 minutes (3 00Orpm). The supernatant was carefully removed.

The remaining quartz was then contacted with asphaltene extract in toluene (10 cm3).

6. The test tubes were placed back into the shaker, agitating for 30 minutes at 25Orpm., then removed and centrifuged for 15 minutes (300Orpm). The supernatant was carefully removed, the absorbance was measured at 600 nm.

Calculations Absorbance of Asphaltene Extract = E Asphaltenes not-adsorbed (B) = absorbance of the supernatant 2.

4.

23 Therefore:

% Asphaltenes not-adsorbed = (B/E) 100 The tests were performed with 1 00Opprn and 20Opprn levels of the copolymers in the solution contacting the quartz.

is The results were as follows:- Example 1 4

Level of addition 1 OOOPPM Removed 68.9 59.1 Nonabsorbed 71.8 69 Level of addition 20Oppm Removed 60.0 o Nonabsorbed 49.0 24 Case 9000(2)

Claims (23)

1. Claims: 1. A polymer comprising structural units derived from monomers

   which are at least one of (A) at least one ethylenically unsaturated alcohol, carboxylic acid or ester, (B) an ethylenically unsaturated carboxylic ester with a polar group in the ester, and (C) an ethylenicalIy unsaturated carboxylic amide, wherein at least one of said structural units 5 contains at least one pendant ring group.
2. A polymer as claimed in claim 1, which comprises at least one structural containing a pendant non cyclic organic group.
3. 3. A polymer as claimed in any preceding claim wherein the ring group is carboxylic, heterocyclic, saturated or partly or completely unsaturated.
4. 4. A polymer as claimed in claim 3, wherein the ring group is a carboxylic ring group containing 5-20 carbons.
5. 5. A polymer as claimed in claim 3, wherein the ring group is a heterocyclic ring group with at least one N, 0, S hetero ring atom which may be in an N, 0, S> SO orS02 group.
6. 6. A polymer as claimed in any of claims 2 to 5, wherein the pendant non cyclic organic group is an alkyl or alkenyl group.
7. 7. A polymer as claimed in any of claims 2 to 6, which contains a number of pendant groups, at least 10% or 20% of which contain the ring group, and especially at least 10% of which contain the noncyclic group.
8. 8. A polymer as claimed in any of claims 2 to 7, wherein the ring group and the noncyclic group are in the same structural unit and are bonded to each other, either directly or via at least one bridge group.
9. 9. A polymer as claimed in any preceding claim wherein monomer A is an ester of an aliphatic hydrocarbyl alcohol with a short chain aliphatic group of 1-5 carbon atoms, and an ethylenically unsaturated acid of 3-6 carbon atoms.
10. 10. A polymer as claimed in any preceding claim, wherein monomer B is an ester of an ethylenically unsaturated carboxylic acid and an organic mono hydroxy compound with at least one additional polar group (B).
11. 11. A polymer as claimed in claim 10, wherein B is free of the ring and/or noncyclic group.
12. 12. A polymer as claimed in any preceding claim, wherein C is an ethylenically unsaturated carboxylic amide (C) derived from an ethyIenicalIy unsaturated carboxylic acid.
13. 13. A polymer as claimed in claim 12, wherein C is free of the ring or noncyclic is is.

    group.
14. 14. A polymer as claimed in any preceding claim which is crystalline or amorphous.
15. A polymer as claimed in any preceding claim, which is in the form of a soluble concentrate comprising at least 10% by weight of said polymer in a solvent.
16. 16. A polymer as claimed in any one of claims 1 to 14, which is in the form of a dispersion comprising at least 10% by weight of said polymer, said dispersion being in a liquid medium in which the polymer is individual or incompletely soluble.
17. 17. A hydrocarbon fluid comprising asphaltenes and at least one polymer as claimed in any preceding claim.
18. 18. A hydrocarbon fluid as claimed in claim 17 comprising crude oil.
19. 19. A method of reducing formation of or deposition of solids comprising asphaltenes from a hydrocarbon oil containing asphaltenes, said method comprising: 25 mixing with said oil at least one polymer as claimed in any one of claims 1 to 16.
20. 20. Use of a polymer as claimed in any one of claims 1 to 16 for reducing the formation or deposition of asphaltenes from a hydrocarbon oil.
21. 21. A polymer as described herein, and with reference to the foregoing Examples.
22. 22. A hydrocarbon fluid as described herein, and with reference to the foregoing 30 Examples.
23. 23. Use of a polymer as described herein, and with reference to the foregoing examples.

    26