SUBSTITUTED CARBOXYLATED DERIVATIVES

Abstract: This invention is a process for making a substituted carboxylated derivative by reacting a polyolefin in which at least 35 % of the unsaturated linkages are vinyl and/or vinylidene groups with a molar excess of an unsaturated carboxylic compound at an elevated temperature. The process comprises of (a) reacting in an initial mild stage the polyolefin with the carboxylic compound in the absence of any other acidic or catalytic additive at a temperature in the range from 140-202 DEG C until at least 30 % of the vinyl and/or vinylidene groups in the polyolefin have reacted with the carboxylic compound, and (b) continuing the reaction in a subsequent severe stage in which the temperature is allowed to rise at least 10 DEG C above the maximum temperature of stage (a) so that the temperature does not rise above 250 DEG C in this severe stage. A highly desirable hydrocarbyl substituted succinic anhydride is produced which has a lower apparent succinylation ratio and viscosity. Furthermore the level of insoluble tar formed in the product is significantly reduced.

Description: SUBSTITUTED CARBOXYLATED DERIVATIVES The present invention relates to a method of making hydrocarbyl substituted carboxylated derivatives, and to the use of such derivatives as such or after further functionalisation. It is well known in the art to prepare hydrocarbyl substituted carboxylated derivatives, such as eg hydrocarbyl substituted succinylating agents (hereafter "HSSA"), and specifically poly(iso)butenyl succinic anhydrides (hereafter "PIBSAs") by the reaction of a poly(iso)butene with maleic anhydride and to further functionalise the PIBSAs to the corresponding succinimides. These succinimides are used as fuel and lubricating oil additives in view of their ability to clean and/or maintain in a clean condition carburettors, manifolds, inlet valve ports and the like in an internal combustion engine They are also useful additives to fuels and lubricants, especially for inhibiting rusting, wear, carburettor deposits and/or icing, corrosion and smoke, and as dispersants and viscosity index improvers. They are an important means of maintaining engine performance either by cleaning and/or lubricating moving parts of the engine. However, methods of making such carboxylated derivates, eg the PIBSAs, by conventional routes, eg by thermal malenisation of conventional poly(iso)butenes (PIB) or highly reactive poly(iso)butene (HRPIB), can give rise to tars, resins and coloured products and such products may also have relatively high viscosity. If the maleinisation is kept to low conversions in order to alleviate the above problems, this results in considerable wastage of the reactant PIB and maleic anhydride. Several expedients have been suggested to overcome such problems. For instance, US-A-3819660 suggests the addition of acetic anhydride/alkylbenzene sulphonic acid during the thermal maleinisation of alkene polymers having a molecular weight in the range from 168-900 Similarly, US-A-3855251 describes the use of sulphonic acid/anhydride mixtures as catalysts to control the product composition of the polyalkenyl succinic anhydrides formed during the thermal maleinisation of a polyalkene Again, US-A-4086251 describes the use of a series of agents to suppress resm formation during the thermal maleinisation of polyalkenes Yet another expedient described in US-A- 4235786 is the use of oil soluble organic acids of pK_ less than 4 0 as catalyst for reducing the sediment formed during thermal maleinisation Furthermore, US-A-4883996 describes a method of reducing tar and resin formation during thermal maleinisation by adding a resin suppressing agent in two stages and carrying out the reaction at constant temperature Also, US-A-5420207 uses dicarboxyhc acids to suppress resin formation and bi-succination during the thermal maleinisation of highly reactive PIB reaction but results in reduced conversion of the reactant PIB EP-A-0 542 380 also shows the use of minor quantities of aryl sulphonic acids as an agent to suppress poly-addition during the maleinisation of HRPIB thereby reducing sediment formation and consequently reduces succinylation ratio thereof However, as will be shown later, carrying out the high temperature thermal maleinisation of PIB in a single stage with an initial acid addition, the level of insoluble tar formation is unacceptably high In the examples in US-A-5420207 and EP-A-0 542 380, reaction times are of the order of 24 hours signifying slow or reduced conversion In fact, in US-A-3819660, it is claimed that by carrying out the thermal maleinisation in the presence of acids, the colour of the product is increased, whereas, according to the teaching of US-A-4235786 the product viscosity increases when the maleinisation is carried out in the presence of acids It is also unusual in commercial practice to have thermal maleinisation processes operating for as long as 24 hours Such reactions, especially when operated as a batch reaction, ai e usually carried out over a much shorter reaction time eg under six to eight hours during which period optimum/economic conversion can be achieved Typically, such reactions are carried out foi four to six houis at reaction temperatures ranging from 220 to 235°C and using a significant molar excess (2- to 3-fold excess) of the reactant maleic anhydride with respect to the polybutene In such processes excess maleic anhydride is removed bv evaporation and the by-product tar formed is filtered out of the product PIBSA PIBSAs formed from HRPIB are of a greater colour intensity than PIBSAs formed from conventional PIB when the maleinisation reactions are run under substantially identical conditions Since pure PIBSAs are essentially colourless, it is reasonable to assume that the colour of the product from the above reactions is due to some impurity in the product such as tar which is known to be highly coloured and is partially soluble in the product Thus it would be desirable to reduce the colour of such products and also to produce a PIBSA which has a low viscosity, especially if such PIBSAs are to be eventually functionalised to derivatives which are to be used as additives in fuels and in lubricants Thus, to summarise it would appear that if a single step high temperature maleinisation is carried out in the absence of an acid, then unacceptably high apparent succinylation ratios and viscosities are obtained On the other hand, if a single step high temperature maleinisation is carried out in the presence ot an acid, many advantages accrue such as eg high conversion, low product viscosity etc but the level of insoluble tar formed is unacceptably high It has now been found that the above problems can be mitigated and highly desirable hydrocarbyl substituted succinic anhydrides produced by carrying out the thermal maleinisation in two stages under appropriate conditions Accordingly, the present invention is a process for making a hydrocarbvl substituted carboxylated derivative by reacting a polyolefin which is a homopoiymer or a copolymer of a C2-C 18 monoolefm and has at least 35% of its unsaturated linkages in the form of vinyl and/or vinylidene groups with a molar excess ot a carboxylic compound which has an unsaturated carbon-carbon linkage in its structure at an elevated temperature, said process comprising (a) l eacting in an initial mild stage the polyolefin with the carboxylic compound in the substantial absence of any other acidic or catalytic additive at a temperature in the range from 140- 202°C for a duration until at least 30% of the vinyl and/or vinylidene groups in the polyolefin have reacted with the carboxylic compound, and (b) continuing the reaction in a subsequent relatively severe stage in which the temperature is allowed to rise at least 10°C above the maximum temperature of the reaction in the mild stage (a), subject to the temperature not rising above 250°C in this severe stage, until the the desired conversion of the polyolefin to the corresponding substituted carboxylated derivative is achieved. The polyolefin is a homopolymer of a C2-C18 monoolefin, which may in itself be straight or branched chain, or a copolymer of two or more such monoolefins or a copolymer of one or more such monoolefins with a minor amount of a non-conjugated diolefin having 5 to 18 carbon atoms. The polyolefin suitably has a number average molecular weight (Mfϊ) in the range from 250 - 5000, preferably from 500-3500 Highly reactive polyolefins such as atactic polypropylene and poly(iso)butylene having the desired degree of terminal vinyl and/or vinylidene unsaturation are most preferred. Specific examples of a highly reactive poly(iso)butene (HRPIB) are ULTRA VIS® or GLISSOPAL® range of polybutenes By the expression "carboxylic compound" as used herein and throughout the specification is meant that said compound has an unsaturated carbon-carbon linkage in its structure, which unsaturated linkage may be olefinic or acetylenic, and said compound has at least three carbon atoms and at least one carboxyi group which may be in the form of a free acid, an ester or an anhydride group The carboxylic compound suitably has at least four carbon atoms and an olefinic unsaturation and is preferably one or more of maleic acid, ethyl maleic acid, citraconic acid, itaconic acid and dialkyl esters of any of these acids, maleic anhydride, ethyl maleic anhydride, citraconic anhydride, itaconic anhydride, glutaconic anhydride and homoesaconic anhydride. Of these maleic anhydride is most preferred. The molar ratio of carboxylic compound to the polyolefin used for making the hydrocarbyl substituted carboxylated derivative is suitably in the range from 1 1 to 4 1 , preferably from 1 5 1 to 3 5 1 The carboxylic compound reactant can be added to the reaction mixture at the start of the reaction or in two or more aliquots and the addition can be split between the two stages (a) and (b) The reaction temperature in the relatively mild stage (a) is suitably in the range from 140- 195°C, preferably in the range from 175-190°C. This reaction stage (a) is continued within this temperature range until at least 30% of the vinyl and/or vinylidene linkages in the polyolefin have reacted with the carboxyi compound. This degree of conversion can be achieved either by varying the reaction temperature within the specified range or by increasing the relative mole ratios of the carboxylic compound to the polyolefin in the reaction mixture. The degree of conversion achieved can be monitored either in situ or by removing sample aliquots of the reaction mixture and analysing the samples eg by IR or NMR spectroscopy. When this degree of conversion has been achieved then the reaction mixture can be allowed to proceed to the next, relatively more severe stage (b). The relatively more severe conditions in stage (b) can be achieved in various ways. For instance it may be achieved by: (i) ramping up the reaction temperature suitably in the range from 203- 250°C, preferably in the range from 220-250°C and more preferably from 230-250°C, or (ii) introducing into the reaction mixture an amount of a strong acid sufficient to inhibit the formation of PIBSA soluble tar, or (iii) introducing into the reaction mixture a further amount of the reactant carboxylic compound, or (iv) using any combination of the methods (i) - (iii) above Where the relatively severe stage (b) involves ramping up the temperature as in (i) above, it is preferable that the change of temperature is at least in part in the form of a temperature profile from the mild stage (a) to the relatively severe stage (b), and the average temperatures in each of these stages are preferably within the ranges specified above for said stage. It has been found particularly beneficial to carry out the stage (b) using a combination of all three, especially ' where a strong acid has been added to the reaction mixture and the reaction temperature is raised to between 220 and 250°C and then maintained under these conditions until the desired conversion (eg at least 70%) of the polyolefin has been achieved to the corresponding hydrocarbyl substituted carboxylated derivative. In this context, the strong acid when introduced to stage (b) can be added from an external source or may be generated in situ during the second stage Where it is added from an external source it is suitably an acid which is preferably soluble in the reaction mixture and is suitably a non-volatile organic acid such as eg an alkyl, aryl or aralkyl substituted sulphonic acid in which the alkyl or aryl group has up to 24 carbon atoms, and is preferably /;αrø-toluene sulphonic acid or benzene sulphonic acid. Other suitable acids include niter alia trichloroacetic acid, phosphoric acid, aluminium trichloride and acid functionalised solids such as eg alumina impregnated with hydrochloric acid or phosphoric acid The amount of the strong acid added is suitably in the range from I to 500 ppm with respect to the initial amount of polyolefin to be reacted The strong acid may be added as such or as a solution thereof in a solvent inert under the reaction conditions such as eg acetic anhydride If the hydrocarbyl substituted carboxylated derivative so produced is of the desired purity, it can be further functionalised by reaction with a an amine to form the corresponding imide, b an alcohol to form the corresponding ester, or, c with a metal compound such as eg the hydroxide or oxide to form the corresponding salt These reactions are particularly applicable when the hydrocarbyl substituted carboxylated derivative is a poly(iso)butenyl succinic anhydride (PIBSA) In this particular case, the process of the present invention is able to give rise to a PIBSA in which the apparent succinylation ratio, ie the ratio of succinyl groups per PIB group in the PIBSA is below 1 3 Such relatively low succinylation ratios indicate that the PIBSA has a relatively low amount of dissolved resins and hence the viscosity of the PIBSA is relatively low As more generally described above, such PIBSAs can be used to make the corresponding succinimides, esters and/or salts which are then usable as additives for fuels or lubricants When a substituted succinic anhydride such as eg PIBSA is reacted especially with a polyamine to produce the corresponding poly(iso)butenyl succinimide, this may be a mono- or bis-succinimide and will hereafter be referred to as "PIBSI" Such PIBSls are also useful as detergent additives in fuel and lubricating oil formulations PIBSAs made according to the invention can also be used as intermediates in paint manufacturing or for treatment of paper This reaction between the PIBSA and the polyamine can be carried out optionally in the presence of a solvent The reactant polyamine used for this step is suitably an amine which has at least two basic nitrogen atoms of which at least one is a primary amino group A polyamine substituted with -OH groups, alkoxy groups or polyoxyalkylene groups can also be used in this step Specific examples of the polyamines that may be used include ethylene diamine, dimethylamino propylamine, triethylene tetramine, tetraethylene pentamine, N-hydroxyethyl ethylenediamine, polyether amines and the like The reaction between the substituted succinic anhydride such as eg PIBSA and the polyamine is suitably carried out at a temperature in the range from 100 to 200°C, preferably from 50 to 190°C and a pressure from 0 to 500 Kpa (0 to 5 bar gauge) The relative molar ratios of the substituted succinic anhydride to the polyamine in the reaction mixture is suitably in the range from 3 1 to 1 0 7 Irrespective of the relative ratios of the two components in this reaction, it must be ensured that the l esultant product is substantially free of any unreacted polyamine before being incorporated in a fuel formulation The present invention is further illustrated with reference to the following Examples & Comparative Tests In the Examples and Comparative Tests the reactions were carried out in an autoclave unless otherwise specified The reactants and reaction conditions used and the results achieved are tabulated beiow In the table, the following abbreviations have been used * - signifies the addition of acid before commencement of the second heating stage, and after the first relatively mild stage ASR - means apparent succinylation ratio /;-TSA - means /wra-toluene sulphonic acid MA - means maleic anhydride PIB - means poly(ιso)butylene PIBSA - means poly(ιso)butenyl succinic anhydride CT - means Comparative Test not according to the invention Uitravis and Glissopal - wherevei used represent Registered Trade Marks of that name In the Examples and Comparative Tests, the following general procedures were used a Autoclave Experiments Weighed quantities of polyisobutylene and maleic anhydride were placed in a 600 ml Parr autoclave and the autoclave was purged with nitrogen and sealed The autoclave was then heated quickly to the control temperature and the contents thereof stirred at 500 rpm for the duration of the initial, relatively mild stage of the two-stage reaction The autoclave was then cooled rapidly to 100°C and depressuπsed, opened under nitrogen and an acid solution introduced from a syringe Additional maleic anhydride was added, where appropriate, at this point The autoclave was then re-sealed and heated rapidly to the new reaction conditions of the second, relatively severe stage of the reaction Where no acid or additional maleic anhydride was added, the second stage of the reaction was commenced without opening the reactor after the initial stage After the desired duration of the second stage was complete, the autoclave pressure was released and the autoclave and the contents thereof were cooled rapidly to 100°C and then discharged into a Buchi rotavapour flask b Glassware Experiments Weighed quantities of polyisobutylene and maleic anhydride were placed in a S00 ml three-necked round-bottomed flask equipped with a stirrer, a thermocouple and an an condenser (topped with a bubbler containing silicone oil) and containing an atmosphere of dry nitrogen The contents of the flask were stirred and quickly heated to the control temperature of the initial, relatively mild stage of the reaction and held at that temperature for the duration of this stage The heating was switched off and the contents of the flask were transferred to a dry nitrogen purged autoclave under an atmosphere of dry nitrogen Additional maleic anhydride was added, where appropriate, and the autoclave was then re-sealed and the second, relatively severe stage of the reaction was carried out When this second stage was complete, the autoclave pressure was then released, the contents thereof cooled rapidly to 100°C and then discharged into a Buchi rotavapour flask c Pilot Plant Experiments A weighed quantity of polyisobutylene was added to a 600 litre reactor equipped with a temperature and pressui e conti ol system, a stirrer and connected via a pressure control valve and pump to a reservoir of molten maleic anhydride The desired quantity of maleic anhydride was introduced into the reactor via the pump at the beginning of the first, relatively mild stage of the reaction and, where appropriate, at the commencement of the second, relatively severe stage of the reaction At the end of the two stages of the reaction excess maleic anhydride was removed from the reactor under vacuum via the pressure control valve and transferred to the reservoir The hot products from this first stage were then discharged from the reactor and filtered through a Celite filter cake and the filtrate analysed d Product Work-up Procedure (Autoclave & Glassware Experiments ' ) The reaction product was stripped of unreacted maleic anhydride on a Buchi rotavapour at between 100° and I 80°C under vacuum (<266 7 Pa (< 2mm Hg)) The stripped product was dissolved in two volumes of heptane and filtered through a prepared Celite filter cake The filter cake was rinsed through with heptane and the combined filtrates were stripped of heptane on a rotary evaporator Analyses for viscosity, acid number and conversion were performed on this material Freshly prepared 5% w/w solutions of this material in heptane were used to measure colour by the ASTM D 1500 method The tar in the autoclave was rinsed with heptane, dried and weighed The tar on the filter cake was dissolved in acetone and the tar solution evaporated under vacuum to remove the solvent, the tar was then weighed TABLE I o ■ # - 062 molar /;-TSA IHjO in acetic anh dride TABLE 2 # - the first mild stage earned out in glass apparatus (atm press) ij - different mole ratiqs of PIB MA used for the stages (a) and (b) The results in Tables I and 2 above show that only by controlling the reaction conditions of both the mild stage (a) and the severe stage (b) as herein described does the thermal maleinisation reaction give rise to high conversions of the polyolefin and a hydrocarbyl substituted carboxylated derivative of low colour and low viscosity For instance, the results in Table 1 show that the addition of a strong acid together with increased temperature during the relatively severe stage (b) results in products which show conversions which are as good as or better than those achieved in a single stage process but have a much lower viscosity and are much lighter in colour intensity than those obtained in a single stage process Similarly, the results in Table 2 show that reduction in colour and viscosity can be achieved without the use of any strong acids provided that the mole ratio of the reactants m the mild stage (a) is controlled and the reaction temperatuie and/or mole ratio of reactants is increased in the relatively moie severe stage (b) as described herein It can also be seen from the results in Table 3 below that under conditions of the first, relatively mild stage of Examples 2 and 5, over 30% of the vinylidene end groups in the polyolefin are converted u - TABLE 3 TABLE 4 *dιfferent mole ratios used for the two stages The results in Table 4 show that the present invention is equally applicable to polyoletins of moleculai weight above 1000 and is operable on a commercial scale

Claims: Claims 1 A process for making a hydrocarbyl substituted carboxylated derivative by reacting a polyolefin which is a homopolymer or a copolymer of a C2-C18 monoolefin and has at least 35% of its unsaturated linkages selected from vinyl and vinylidene gioups with a molar excess of a carboxylic compound which has an unsaturated carbon-carbon linkage in its structure at an elevated temperature, said process comprising (a) reacting in an initial mild stage the polyolefin with the carboxylic compound in the substantial absence of any other acidic or catalytic additive at a temperature in the range from 140- 202°C for a duration until at least 30% of the vinyl and/or vinylidene groups in the polyolefin have reacted with the carboxylic compound, and (b) continuing the reaction in a subsequent relatively severe stage in which the temperature is allowed to rise at least 10°C above the maximum temperature of the reaction in the mild stage (a), subject to the temperature not rising above 250°C in this severe stage, until the desired conversion of the polyolefin to the coi responding substituted carboxylated derivative is achieved 2 A process according to Claim 1 wherein the polyolefin is a copolymer of two or more C2-C 18 monoolefins containing a minor amount of a non- conjugated diolefin having 5 to 18 carbon atoms 3 A process according to anyone of the preceding claims wherein the polyolefin has an average molecular weight (Mn) in the range from 250 - 5000 4 A process according to anyone of the preceding Claims wherein the polyolefin is a polypropylene oi a polybutene A process according to anyone of the preceding Claims wherein the carboxylic compound has an unsaturated carbon-carbon linkage in its structure, and at least three carbon atoms and one carboxyi group which is in the form of a free acid, an ester or an anhydride group. 5. A process according to anyone of the preceding Claims wherein the carboxylic compound has at least four carbon atoms and an olefinic unsaturation and is selected from one or more of maleic acid, ethyl maleic acid, citraconic acid, itaconic acid and dialkyl esters of any of these acids, maleic anhydride, ethyl maleic anhydride, citraconic anhydride, itaconic anhydride, glutaconic anhydride and homoesaconic anhydride. 6 A process according to anyone of the preceding Claims wherein the molar ratio of carboxylic compound to the polyolefin is in the range from 1 : 1 to 4 1 7 A process according to anyone of the preceding Claims wherein the carboxylic compound reactant is added to the reaction mixture at the start of the reaction 8 A process according to anyone of the preceding Claims 1 to 9 wherein the carboxylic compound reactant is added to the reaction mixture in two or more aliquots and the addition is split between the two stages (a) and (b). 9 A process according to anyone of the preceding Claims wherein the relatively more severe conditions in stage (b) are achieved by either (i) ramping up the reaction temperature to a range from 203-250°C, or (ii) introducing into the reaction mixture an amount of a strong acid sufficient to inhibit the formation tar that is soluble in the hydrocarbyl substituted carboxylated derivative, or (iii) introducing into the reaction mixture a further amount of the reactant carboxylic compound, or (iv) using any combination of the methods (i) - (iii) above. 1 1. A process according to Claim 10 wherein the reaction temperature is ramped up to a range of 220-250°C 12. A process according to Claim 10 wherein the strong acid when introduced to stage (b) is added from an external source. 13 A process according to Claim 10 wherein the strong acid when introduced to stage (b) is generated in .situ during the second stage 14. A process according to Claim 12 wherein the strong acid is selected from an alkyl, aryl or aralkyl substituted sulphonic acid in which the alkyl or aryl group has up to 24 carbon atoms, /;αrø-toluene sulphonic acid, benzene sulphonic acid, trichloroacetic acid, phosphoric acid, aluminium trichloride, acid and functionalised alumina impregnated with hydrochloric acid or phosphoric acid. 15. A process according to Claim 12 or 14 wherein the amount of the strong acid added is suitably in the range from 1 to 500 ppm with respect to the initial amount of polyolefin to be reacted. 16. A process for functionalising the hydrocarbyl substituted carboxylated derivative derived by a process according to Claim 1 , by the reaction of said derivative with an amine to form the corresponding imide. 17. A process according to Claim 16 wherein the hydrocarbyl substituted carboxylated derivative is a substituted succinic anhydride. 18. A process according to Claim 16 or 17 wherein the amine has at least two basic nitrogen atoms of which at least one is a primary amino group. 19 A process according to anyone of the preceding Claims 16 or 17 wherein the amine is a polyamine. 20. A process according to Claim 19 wherein the polyamine is substituted with -OH groups, alkoxy groups or polyoxyalkylene groups. 21 A process according to Claim 19 wherein the polyamine is selected from ethylenediamine, dimethylamino propylamine, triethylene tetramine, tetraethylene pentamine, N-hydroxyethyl ethylenediamine, and polyether amines 22. A process according to anyone of the preceding Claims 19-21 wherein the hydrocarbyl substituted carboxylated derivative is a substituted succinic anhydride and the relative molar ratios of the substituted succinic anhydride to the polyamine in the reaction mixture is in the range from 3 : 1 to 1 :0.7 23. A process for functionalising the hydrocarbyl substituted carboxylated derivative derived by a process according to Claim 1 by the reaction of said derivative with an alcohol to form the corresponding ester. 24. A process according to Claim 23 wherein the hydrocarbyl substituted carboxylated derivative is a substituted succinic anhydride. 25. A process for functionalising the hydrocarbyl substituted carboxylated derivative derived by a process according to Claim 1 by the reaction of said derivative with a metal compound selected from a hydroxide and an oxide of the metal to form the corresponding salt. 26. A process according to Claim 25 wherein the hydrocarbyl substituted carboxylated derivative is a substituted succinic anhydride. 27. A process according to anyone of the preceding Claims 16-26 wherein the functionalisation is carried out at a temperature in the range from 100 to 200°C and a pressure from 0 to 500 Kpa ( 0 to 5 bar gauge).

Inventors: BLACKBOROW JOHN RICHARD, BLACKBOROW, JOHN, RICHARD
Applicants: BP CHEM INT LTD, BP CHEMICALS LIMITED
Application year: 1997
Main classification: C08F8
IPC codes: C08F8, C08F10