Aromatic acylation with cyclic anhydride for plasticizer production

This application is a divisional application filed under 37 C.F.R. 1.53(b) of parent application Ser. No. U.S. 12/840,715, the entirety of which is hereby incorporated herein by reference, which claims priority to U.S. Provisional Patent Application No. 61/284,789 filed on Dec. 24, 2009, also herein incorporated by reference in its entirety.

This disclosure is related to a potential route to non-phthalate, OXO-(di)ester plasticizers.

Plasticizers are incorporated into a resin (usually a plastic or elastomer) to increase the flexibility, workability, or distensibility of the resin. The largest use of plasticizers is in the production of “plasticized” or flexible polyvinyl chloride (PVC) products. Typical uses of plasticized PVC include films, sheets, tubing, coated fabrics, wire and cable insulation and jacketing, toys, flooring materials such as vinyl sheet flooring or vinyl floor tiles, adhesives, sealants, inks, and medical products such as blood bags and tubing, and the like.

Other polymer systems that use small amounts of plasticizers include polyvinyl butyral, acrylic polymers, nylon, polyolefins, polyurethanes, and certain fluoroplastics. Plasticizers can also be used with rubber (although often these materials fall under the definition of extenders for rubber rather than plasticizers). A listing of the major plasticizers and their compatibilities with different polymer systems is provided in “Plasticizers,” A. D. Godwin, in Applied Polymer Science 21st Century, edited by C. D. Craver and C. E. Carraher, Elsevier (2000); pp. 157-175.

Plasticizers can be characterized on the basis of their chemical structure. The most important chemical class of plasticizers is phthalic acid esters, which accounted for about 85% worldwide of PVC plasticizer usage in 2002. However, in the recent past there has been an effort to decrease the use of phthalate esters as plasticizers in PVC, particularly in end uses where the product contacts food, such as bottle cap liners and sealants, medical and food films, or for medical examination gloves, blood bags, and IV delivery systems, flexible tubing, or for toys, and the like. For these and most other uses of plasticized polymer systems, however, a successful substitute for phthalate esters has heretofore not materialized.

One such suggested substitute for phthalates are esters based on cyclohexanoic acid. In the late 1990's and early 2000's, various compositions based on cyclohexanoate, cyclohexanedioates, and cyclohexanepolyoate esters were said to be useful for a range of goods from semi-rigid to highly flexible materials. See, for instance, WO 99/32427, WO 2004/046078, WO 2003/029339, WO 2004/046078, U.S. Patent Publication No. 2006-0247461, and U.S. Pat. No. 7,297,738.

Other suggested substitutes include esters based on benzoic acid (see, for instance, U.S. Pat. No. 6,740,254, and also co-pending, commonly-assigned, PCT Publication No. WO2009/118261A1, and polyketones, such as described in U.S. Pat. No. 6,777,514; and also co-pending, commonly-assigned, U.S. Patent Application Publication No. 2008-0242895 A1. Epoxidized soybean oil, which has much longer alkyl groups (C 16 to C 18 ) has been tried as a plasticizer, but is generally used as a PVC stabilizer. Stabilizers are used in much lower concentrations than plasticizers. Co-pending and commonly assigned U.S. patent application Ser. No. 12/653,744, filed Dec. 17, 2009, discloses triglycerides with a total carbon number of the triester groups between 20 and 25, produced by esterification of glycerol with a combination of acids derived from the hydroformylation and subsequent oxidation of C 3 to C 9 olefins, having excellent compatibility with a wide variety of resins and that can be made with a high throughput.

U.S. Pat. Nos. 1,909,092 and 2,233,513, both to Brunson and incorporated herein by reference, disclose esters of aryl benzoic acids of the formula R—CO—R′—COOH, wherein R and R′ are aromatic nuclei, including esters derived from saturated monohydric alcohols containing three or more carbon atoms in the molecule, such as iso-propyl, butyl, isoamyl, beta-ethoxyethyl, beta-butoxyethyl, benzyl and cyclohexyl alcohols. The esters are disclosed as useful as plasticizers for nitrocellulose.

U.S. Pat. No. 2,372,947 to Gresham, incorporated herein by reference, discloses polyvinyl halide compositions containing alkyl esters of ortho-benzoyl benzoic acid, wherein the ester group is a C 4 to C 16 alkyl, such as butyl o-benzoyl benzoate, 2-ethylhexyl o-benzoyl benzoate, lauryl o-benzoyl benzoate, and cetyl o-benzoyl benzoate.

U.S. Pat. No. 3,110,724 to Woodbridge et al., incorporated herein by reference, discloses a process of reacting an aromatic anhydride with another aromatic compound over a catalyst and esterifying the resulting intermediate with a polyalkylene glycol to form surfactants.

Co-pending and commonly owned U.S. Provisional Patent Application Ser. No. 61/227,116, filed Jul. 21, 2009, herein incorporated by reference, discloses the esterification of keto acids derived from the acylation of aromatic compounds with cyclic anhydrides.

Thus what is needed is a method of making a general purpose non-phthalate plasticizer having and providing a plasticizer having suitable melting or chemical and thermal stability, pour point, glass transition, increased compatibility, good performance and low temperature properties.

In one aspect, the present application is directed to a process for making non-phthalate plasticizers, comprising acylating an aromatic compound with a succinic anhydride to form a keto-acid, and esterifying the keto-acid with C 4 -C 13 OXO-alcohols to form a plasticizer compound. The aromatic compound may have one or multiple rings.

In a preferred embodiment, the aromatic compound is of the formula:

wherein R 1 is selected from the group consisting of H or C 1 -C 9 linear or branched alkyl, cycloalkyl, or C 1 -C 4 ether and wherein there may be 1 or 2 R 1 groups present on the aromatic or saturated ring which may be the same or different, and the plasticizer compound is of the formula:

wherein R 1 is as set forth above, R 2 is the alkyl residue of the OXO-alcohols, and R 3 is H or C 1 -C 8 linear or branched alkyl group.

In another embodiment, the acylation is catalyzed by a heterogeneous catalyst, a mixed metal oxide or a Lewis acid.

Preferably, the acylation is conducted using a stoichiometric amount of AlCl 3 .

The process can further comprise hydrogenating one or more of the aromatic rings of the aromatic compound.

In a preferred embodiment, the process can further comprise hydrogenating the keto-group(s) of the plasticizer compound to form alcohol groups, and esterifying the alcohol groups with C 4 to C 13 linear or OXO-acids to form plasticizer compounds of the formula:

wherein R 4 is the alkyl residue of said linear or OXO-acids. Another embodiment of the disclosure is directed to a plasticizer compound of the formula:

wherein R 1 is selected from the group consisting of H, C 1- C 9 linear or branched alkyl, cycloalkyl, or C 1 -C 4 ether, and R 2 is the alkyl residue of C 4 to C 13 OXO-alcohols and wherein there may be 1 or 2 R 1 groups present on the aromatic or saturated ring which may be the same or different. R 3 is H or C 1 -C 8 linear or branched alkyl group.

Additionally, the present disclosure is directed to a plasticizer compound of the formula:

wherein R 1 is selected from the group consisting of H, C 1 -C 9 linear or branched alkyl, cycloalkyl, or C 1 -C 4 ether, wherein there may be 1 or 2 R 1 groups present on the aromatic or saturated ring which may be the same or different, R 2 is the alkyl residue of C 4 to C 13 OXO-alcohols, R 3 is H or C 1 -C 8 linear or branched alkyl group, and R 4 is the alkyl residue of C 4 to C 13 linear or OXO-acids.

In another embodiment, the present disclosure is directed to a composition comprising a polymer and a plasticizer of the formula:

wherein R 1 is selected from the group consisting of H, C 1 -C 9 linear or branched alkyl, cycloalkyl, or C 1 -C 4 ether, wherein there may be 1 or 2 R 1 groups present on the aromatic or saturated ring which may be the same or different, R 2 is the alkyl residue of C 4 to C 13 OXO-alcohols, and R 3 is H or C 1 -C 8 linear or branched alkyl group.

Conveniently, the composition contains a polymer selected from the group consisting of vinyl chloride resins, polyesters, polyurethanes, ethylene-vinyl acetate copolymer, rubbers, poly(meth)acrylics and combinations thereof, preferably polyvinylchloride.

In another embodiment, the disclosure is directed to a composition comprising a polymer and a plasticizer of the formula:

wherein R 1 is selected from the group consisting of H, C 1 -C 9 linear or branched alkyl, cycloalkyl, or C 1 -C 4 ether wherein there may be 1 or 2 R 1 groups present on the aromatic or saturated ring which may be the same or different, R 2 is the alkyl residue of C 4 -C 13 OXO-alcohols, R 3 is H or C 1 -C 8 linear or branched alkyl group, and R 4 is the alkyl residue of C 4 -C 13 linear or OXO-acids.

Preferably the polymer is selected from the group consisting of vinyl chloride resins, polyesters, polyurethanes, ethylene-vinyl acetate copolymer, rubbers, poly(meth)acrylics and combinations thereof, and more preferably is polyvinylchloride.

FIG. 1 is a graph showing a comparison of the long term stability against hydrolysis of various plasticizers (DINP=diisononyl phthalate; C 9 BPA=OXO—C 9 benzoyl propionate (Ex. 18); C 9 BBA=OXO—C 9 benzoyl benzoate (Ex. 3).

All numerical values within the detailed description and the claims herein are modified by “about” or “approximately” the indicated value, and take into account experimental error and variations that would be expected by a person having ordinary skill in the art.

There is an increased interest in developing new plasticizers that are non-phthalates and which possess good plasticizer performance characteristics but are still competitive economically. The present disclosure is directed towards non-phthalate, OXO-(di)ester plasticizers that can be made from low cost feeds and employ fewer manufacturing steps in order to meet economic targets. The process for making the non-phthalate plasticizers disclosed herein is to produce a single or multi ring aromatic acid, made from single or multi ring aromatic molecule acylation with a cyclic anhydride, followed by esterification of the acid with OXO C 4 -C 13 alcohols. Two additional steps may also be optionally utilized for fine tuning plasticizer compatibility, volatility, or stability, which are: i) converting the carbonyl group to an alcohol group using hydrogenation technology and esterifying the alcohol with OXO C 4 -C 13 acids; and ii) hydrogenating one or more of the unsaturated aromatic rings.

Branched aldehydes can be produced by hydroformylation of C 3 -C 12 olefins; in turn, some of these olefins have been produced by propylene and/or butene oligomerization over solid phosphoric acid or zeolite catalysts. The resulting C 4 -C 13 aldehydes can then be recovered from the crude hydroformylation product stream by fractionation to remove unreacted olefins. These C 4 -C 13 aldehydes can then hydrogenated to alcohols (OXO-alcohols) or oxidized to acids (OXO-acids). Single carbon number acids or alcohols can be used in the esterification of the aromatic acids described above, or differing carbon numbers can be used to optimize product cost and performance requirements. The “OXO” technology will provide cost advantaged alcohols and acids. Other options are considered, such as hydroformylation of C 4 -olefins to C 5 -aldehydes, followed by hydrogenation to C 5 -alcohols, or aldehyde dimerization followed by hydrogenation or oxidation to C 10 -alcohols or acids.

The resulting C 4 -C 13 OXO-alcohols (and acids) may be used individually, or together in mixtures to make mixed carbon number materials to make esters for use as plasticizers. The mixing of carbon numbers and levels of branching may be required to achieve the desired compatibility with PVC for the respective aromatic acid used for the polar end of the plasticizer, and to meet other plasticizer performance properties. The feed can be propylene, butenes, pentenes, hexenes, heptenes, octenes or nonenes as the starting olefins. The selected from C 4 -C 13 OXO-acids or alcohols have an average branching of from about 0.2 to about 4.0 branches per molecule. Average branching is determined by NMR. The average branching of the alkyl groups incorporated into the plasticizers as the residues of the OXO-acid or alcohol reagents may range from 0.2 to 4.0, or 0.5 to 3.5, or 1.0 to 3.0, or 1.5 to 2.5 branches per residue.

An “OXO-ester” is a compound having at least one functional ester moiety within its structure derived from esterification of either an acid or alcohol compound with an OXO-alcohol or OXO-acid, respectively.

An “OXO-alcohol” is an organic alcohol, or mixture of organic alcohols, which is prepared by hydroformylating an olefin, followed by hydrogenation to form the alcohols. Typically, the olefin is formed by light olefin oligomerization over heterogeneous acid catalysts, which olefins are readily available from refinery processing operations. The reaction results in mixtures of longer-chain, branched olefins, which subsequently form longer chain, branched alcohols, as described in U.S. Pat. No. 6,274,756, incorporated herein by reference in its entirety.

An “OXO-acid” is an organic acid, or mixture of organic acids, which is prepared by hydroformylating an olefin, followed by oxidation to form the acids. Typically, the olefin is formed by light olefin oligomerization over heterogeneous acid catalysts, which olefins are readily available from refinery processing operations. The reaction results in mixtures of longer-chain, branched olefins, which subsequently form longer-chain, branched acids.

Alternatively, the OXO-acids or OXO-alcohols can be prepared by aldol condensation of shorter-chain aldehydes to form longer chain aldehydes, as described in U.S. Pat. No. 6,274,756, followed by oxidation or hydrogenation to form the OXO-acids or OXO-alcohols, respectively.

Tables 1A and 1B below provide branching characteristics for typical OXO-alcohols and OXO-acids, measured by 13 C NMR.

“Hydroformylating” or “hydroformylation” is the process of reacting a compound having at least one carbon-carbon double bond (an olefin) in an atmosphere of carbon monoxide and hydrogen over a cobalt or rhodium catalyst, which results in addition of at least one aldehyde moiety to the underlying compound. U.S. Pat. No. 6,482,972, which is incorporated herein by reference in its entirety, describes the hydroformylation (OXO) process.

“Hydrogenating” or “hydrogenation” is addition of hydrogen (H 2 ) to a double-bonded functional site of a molecule, such as in the present case, addition of hydrogen to the ketone functionality of the plasticizer to give an alcohol functionality, or to the aldehyde moieties of an OXO-aldehyde, to form the corresponding alcohol. Hydrogenation may also be the addition of hydrogen (H 2 ) to one or more aromatic rings of the plasticizer or a precursor thereof, to form a saturated cyclic structure. Conditions for hydrogenation are well known in the art and include, but are not limited to temperatures of 0-300° C., pressures of 1-500 atmospheres, and the presence of homogeneous or heterogeneous hydrogenation catalysts such as Pt/C, Pt/Al 2 O 3 or Pd/Al 2 O 3 .

“Esterifying” or “esterification” is reaction of a carboxylic acid moiety with an organic alcohol moiety to form an ester linkage. Esterification conditions are well-known in the art and include, but are not limited to, temperatures of 0-300° C., and the presence or absence of homogeneous or heterogeneous esterification catalysts such as Lewis or Brønsted acid catalysts.

In general, for every polymer to be plasticized, a plasticizer is required with the correct balance of solvating properties, volatility and viscosity to have acceptable plasticizer compatibility with the resin. In particular, if the 20° C. kinematic viscosity is higher than 150 mm 2 /sec as measured by the appropriate ASTM test, or alternately if the 20° C. cone-and-plate viscosity is higher than 150 cP, this will affect the plasticizer processability during formulation, and may require heating the plasticizer to ensure good transfer during storage and mixing of the polymer and the plasticizer. Volatility is also a very critical factor which affects the long-term plasticizer formulation stability. Higher volatility plasticizers can migrate from the plastic resin matrix and cause damage to the article. The plasticizer volatility in a resin matrix can be roughly predicted by neat plasticizer weight loss at 220° C. using Thermogravimetric Analysis.

The present disclosure discloses unexpected structure-property relationships arising from the addition of specific substituents to the aromatic ring of the aromatic acid fragment of the plasticizer molecule. These manipulations allow for the preparation of novel ketoester plasticizers having improved volatility-viscosity balances.

One potential route to non-phthalate plasticizers is by acylating an alkyl aromatic acid with a succinic anhydride of the general structure

wherein R 3 can be H or C 1 -C 8 alkyl, (ex: methylsuccinic anhydride, isopropylsuccinic anhydride, n-butylsuccinic anhydride, n-octylsuccinic anhydride) followed by esterification of the free acid group with an OXO-alcohol. When there are two R 3 groups present on the anhydride, they may also form a fused C 6 aromatic ring, as in phthalic anhydride. Non-limiting exemplary aromatic compounds for acylation are as follows:

wherein R 1 is selected from the group consisting of H, C 1 -C 9 linear or branched alkyl, cycloalkyl, or C 1 -C 4 ether and wherein there may be 1 or 2 R 1 groups present on the aromatic or saturated ring which may be the same or different.

The general reaction mechanism is illustrated as follows:

In the above structure, R 1 is selected from the group consisting of H, C 1 -C 9 linear or branched alkyl, cycloalkyl, or C 1 -C 4 ether, wherein there may be 1 or 2 R 1 groups present on the aromatic or saturated ring which may be the same or different, R 2 is the alkyl residue of C 4 -C 13 OXO-alcohols, and R 3 is H or a C 1 -C 8 linear or branched alkyl group.

Following the esterification step with the OXO-alcohol (or, alternately, following the acylation step with the cyclic anhydride), one or more of the aromatic rings of the aromatic compounds depicted above may also be hydrogenated using typical hydrogenation catalysts known in the art, and in particular the platinum group metals, such as palladium, ruthenium, or combinations thereof on a silica, carbon, or alumina support at a metals loading level on the support of 0.1-10, or 0.5-7, or 1-5 wt. %. The hydrogenation conditions may be at a temperature of 80-300, or 100-280, or 150-250° C. at a pressure of 100-3000, or 500-2500, or 1000-2000 psig. Hence, the plasticizer compound depicted above may be unsaturated, partially saturated, or fully saturated depending upon hydrogenation of the one or more aromatic rings of the compound. The general mechanism is illustrated as follows:

An extra two steps may then be optionally used to convert the carbonyl group of the above products to an alcohol group using hydrogenation technology, and then the alcohol may be esterified per the schematic below:

The general reaction mechanism above as broadened to include both single and multi-ring aromatic substrates is illustrated as follows, wherein the OXO-diester can be formed by hydrogenating the remaining carbonyl group to form an hydroxyl moiety, followed by esterification with an OXO-acid.

In the above structure, R 1 is selected from the group consisting of H, C 1 -C 9 linear or branched alkyl, cycloalkyl, or C 1 -C 4 ether wherein there may be 1 or 2 R 1 groups present on the aromatic or saturated ring which may be the same or different, R 2 is the alkyl residue of C 4 -C 13 OXO-alcohols, R 3 is H or C 1 -C 8 linear or branched alkyl group, and R 4 is the alkyl residue of C 4 -C 13 linear or OXO-acids.

Following (or, alternately, preceding) the esterification step with the OXO-acid, one or more of the aromatic rings of the aromatic compounds depicted above may also be hydrogenated using typical hydrogenation catalysts known in the art, and in particular the platinum group metals, such as palladium, ruthenium, or combinations thereof on a silica, carbon, or alumina support at a metals loading level on the support of 0.1-10, or 0.5-7, or 1-5 wt. %. The hydrogenation conditions may be at a temperature of 80-300, or 100-280, or 150-250° C. at a pressure of 100-3000, or 500-2500, or 1000-2000 psig. Hence, the plasticizer compound depicted above may be unsaturated, partially saturated, or fully saturated depending upon hydrogenation of the one or more aromatic rings of the compound. The general mechanism is illustrated as follows:

The same acylation, hydrogenation, and esterification chemistry that is applied hereinabove could be also used for already partially hydrogenated multi-ring molecules, and with separate or simultaneous hydrogenation steps (for example, the overall reaction scheme shown below):

As discussed above, the resulting C 4 -C 13 acids or alcohols can be used individually or together in acid mixtures or alcohol mixtures having different chain lengths, to make mixed carbon number esters to be used as plasticizers. This mixing of carbon numbers and levels of branching can be advantageous to achieve the desired compatibility with PVC for the respective polyol or polyacid used for the polar moiety end of the plasticizer, and to meet other plasticizer performance properties. The selected from C 4 -C 13 acids or alcohols have an average branching of from about 0.2 to about 4.0 branches per molecule. Average branching is determined by NMR. The average branching of the alkyl groups incorporated into the plasticizers as the residues of the acid or alcohol reagents ranges from 0.2-4.0, or 0.5-3.5, or 1.0-3.0, or 1.5-2.5 branches per residue. The starting olefin feed can be C 3 ═, butenes, C 5 ═, C 6 ═, C 7 ═, C 8 ═ or C 9 ═.

We have found that when C 4 -C 13 OXO-alcohols, OXO-acids or linear acids are used as reactants for the esterification reactions described above, the resulting OXO-esters are in the form of relatively high-boiling liquids (having low volatility), which are readily incorporated into polymer formulations as plasticizers.

General Procedure for Esterification

Into a 4-necked 500 mL round bottom flask equipped with an air stirrer, thermometer, N 2 inductor, Dean-Stark trap and chilled water cooled condenser were added the amounts of carboxylic acid (commercially purchased benzoyl and alkylbenzoyl benzoic acids) and alcohol specified in the following Examples. The Dean-Stark trap was filled with additional alcohol. Toluene and/or xylenes were optionally also added to control the temperature and to provide adequate reflux for water removal. The contents of the flask were stirred at the specified temperature for the specified time and water was collected in the Dean-Stark trap. The crude reaction mixture was optionally washed with a 3 wt % NaOH solution to remove residual acid prior to vacuum distillation to remove excess alcohol, and/or treated with 2 wt % decolorizing charcoal by stirring at room temperature for 2 hours, followed by double filtration to remove the charcoal. In some examples the product (rather than only residual alcohol) was distilled overhead. The specific reaction conditions and product workup are indicated in the following tables and examples. The general esterification reaction is shown in Equation 1, below. The product purity was evaluated by gas chromatography (GC) analysis, conducted using a Hewlett-Packard 5890 GC equipped with a HP6890 autosampler, a HP flame-ionization detector, and a J&W Scientific DB-1 30 meter column (0.32 micrometer inner diameter, 1 micron film thickness, 100% dimethylpolysiloxane coating). The initial oven temperature was 60° C.; injector temperature 290° C.; detector temperature 300° C.; the temperature ramp rate from 60-300° C. was 10° C./minute with a hold at 300° C. for 14 minutes. The calculated %'s reported for products were obtained from peak area, with an FID detector uncorrected for response factors.

Examples 1-8 demonstrate esterification of benzoylbenzoic and toluoylbenzoic acids with different alcohols, the results of which are set forth in Table 2, below (where R is equivalent to R 1 as described previously).

Table 3 (where R is equivalent to R 1 as described previously and R′ is equivalent to R 2 as described previously) below provides neat properties of the benzoyl benzoic and toluoyl benzoic acid esters prepared in Examples 1-8. Thermogravimetric Analysis (TGA) was conducted using a TA Instruments AutoTGA 2950HR instrument (25-600° C., 10° C./min, under 60 cc N 2 /min flow through furnace and 40 cc N 2 /min flow through balance; sample size 10-20 mg). Differential Scanning calorimetry (DSC) was also performed, using a TA Instruments 2920 calorimeter fitted with a liquid N 2 cooling accessory. Samples were loaded at room temperature and cooled to −130° C. at 10° C./min and analyzed on heating to 75° C. at a rate of 10° C./min. T g s given are midpoints of the second heats (unless only one heat cycle was performed, in which case the first heat T g , which is typically in very close agreement, is given). Kinematic Viscosity (KV) was measured at 20° C. according to ASTM D-445-20, the disclosure of which is incorporated herein by reference, or as footnoted in the Tables.

The data in Table 3 show that, in order to decrease volatility, heavy alcohols had to be used which at the same time adversely affect viscosity. The addition of a methyl group to the benzene ring resulted in higher viscosity than without a methyl group. A different group (—CH 2 CH 2 —) separating the keto and ester functionalities was used in order to modify the volatility/viscosity balance. The synthesis of benzoyl and alkylbenzoyl propionic acids via acylation is shown in Equation 2 (where R is equivalent to R 1 as described previously). Those of skill in the art will recognize that any suitable acylation catalyst, such as a heterogeneous catalyst, a mixed metal oxide or a Lewis acid such as a homogeneous Lewis acid, such as AlCl 3 , can be used to catalyze the reaction.

Representative Procedure for the Synthesis of Aromatic Keto Acids:

99.5 g (0.94 mole) o-xylene, 31.3 g (0.31 mole), succinic anhydride, and 190 mL nitrobenzene were placed into a 1 liter round bottom flask fitted with an addition funnel, thermometer, mechanical stirrer and nitrogen purge. The flask was cooled to 0° C., then 83.4 g (0.63 mole) of aluminum trichloride, dissolved in 350 mL nitrobenzene, was added dropwise maintaining the temperature at 0° C. After addition, the solution was stirred overnight and the temperature was allowed to reach room temperature. The solution was poured into a 2 liter beaker containing 120 mL concentrated aqueous HCl, 500 mL water, and 1000 g ice. The mixture was extracted twice with 1000 mL ethyl ether. The ether layers were combined and washed with 500 mL water, then extracted twice with 500 mL 5% aqueous potassium hydroxide. The aqueous layers were combined and washed with 500 mL ether. The aqueous layer was acidified with 100 mL concentrated aqueous HCl to precipitate the product. The product was collected by filtration and washed with 500 mL water. The product was dissolved in chloroform and the solution was dried over magnesium sulfate, filtered, and stripped of chloroform under vacuum to give 61.4 g (95.4% yield) of crude product. The product was crystallized from benzene giving a weight of 59.9 g.

A number of aromatic keto acids of the general structure shown in Equation 2 were prepared by acylation of alkylaromatics with succinic anhydride, using an aluminum trichloride reagent (rather than a heterogeneous catalyst). The following procedure is representative. The syntheses of aromatic keto acids prepared by this method are summarized in Table 4 (Examples 9-16), where R is equivalent to R 1 as described previously.

The following examples illustrate the synthesis and properties of ketoesters prepared by esterification of aroylpropionic acids, including the acids prepared in Table 4 and others from commercial sources. The general esterification procedure already described was used. Tables 5 and 6 (where R is equivalent to R 1 as described previously and in these instances is H, and R′ is equivalent to R 2 as described previously) summarize the synthesis and performance of esters made from benzoylpropionic acid (which may be derived from benzene acylation with succinic anhydride) with and various alcohols as shown in Equation 3, below, where R′ is equivalent to R 2 as described previously.

The data in Table 6 show that the ester made from 2-ethylhexanol (2EH) is a very volatile product. Replacing the 2EH chain with an OXO—C 9 chain dramatically lowers the volatility of the ester and affects the viscosity. Using a heavier alcohol (C 13 ) resulted in a much lower volatility and still gives a viscosity lower than that for DINP. Linear alcohols (e.g., n-nonanol) show better volatility and viscosity than OXO-branched alcohols with the same carbon number.

Another approach for decreasing volatility is to use alkylated aromatic groups to increase molecular weight, which affects volatility. Therefore, different esters were made using aromatic keto acids bearing a methyl group (this acid may be made from toluene acylation with succinic anhydride) as shown in Equation 4, below (where R′ is equivalent to R 2 as described previously).

Examples 21-24 in Table 7 (where R is equivalent to R 1 as described previously) demonstrate esterification of methylbenzoylpropionic acid with different alcohols. The volatility, viscosity, and glass transition properties of the neat plasticizers prepared in Examples 21-24 are set forth in Table 8 (where R is equivalent to R 1 , and R′ is equivalent to R 2 , as described previously), below.

The data in Table 8 show that when a C 13 alcohol and 3-(4-methylbenzyl)propionic acid were used to synthesize the ketoester plasticizer, the viscosity and the volatility were close to those for the commercial general purpose plasticizer DINP. However, this will practically limit the use of this plasticizer platform to the C 13 alcohol derivative. Therefore, in order to design a better plasticizer structure in which other OXO-alcohols can be used. The di-methyl-substituted (Me 2 ) alkyl aromatic acids shown in Equation 5 (where R is equivalent to R 1 as described previously) were used to prepare related keto esters, as disclosed in Table 9 (where R is equivalent to R 1 as described previously), below. The volatility, viscosity, and glass transition properties of the neat plasticizers prepared in Examples 25-30 are set forth in Table 10 (where R is equivalent to R 1 , and R′ is equivalent to R 2 , as described previously), below.

The data in Table 10 show that indeed, addition of another methyl group to the aromatic ring resulted in a decrease in the volatility using C 9 alcohols compared to the toluoylpropionic acid ester plasticizers; at the same time, viscosity remains below DINP viscosity. For comparison (two methyl groups vs one ethyl group), the C 9 ester of the ketoacid analogous to the product of ethylbenzene acylation with succinic anhydride was prepared and evaluated. The data shows that the volatility is similar to the analogous ester which would be derived from acylation of o-xylene, but the viscosity is much lower. The viscosity of the ethyl-substituted ester is similar to the viscosity of the ester which has two methyl groups at the meta and para positions to the acyl functionality. These data indicate that a mixed acylation feed of C 8 alkylaromatics could be used to prepare a plasticizer, which would be much cheaper than using pure C 8 alkyaromatic isomers.

Further improvement on the plasticizers made using this approach was performed by using other alkyl substituents with more than 3 carbons and a methoxy substituent (equation 6, where R is equivalent to R 1 , and R′ is equivalent to R 2 , as described previously). Data are summarized in Tables 11 and 12 (having similar equivalencies for R and R′).

The data in Table 12 show that, indeed, addition of higher carbon number (≧C 4 ) alkyl group substituents to the aromatic ring, with the use of C 9 alcohols, resulted in a decrease in volatility compared to analogous plasticizers with smaller substituents (all of the compounds in Table 12 show 220° C. weight losses of less than 9%, which is close to the weight loss of DINP). The viscosity remains within the target range except for the sample derived from a cyclohexylbenzene substrate.

The use of naphthalenes, alkyl naphthalanes, and partly hydrogenated (alkyl)naphthalenes (tetralins), as more stable aromatics towards acid catalysis, can also be used as a technique to improve plasticizer performance, particularly to decrease volatility without increasing the complexity of the manufacturing process through aromatic alkylation (equation 7, below).