Ind. Eng. Chem. Res. 1998, 37, 4835-4843
4835
Relationships between Structure and Lubricating Properties of Neopentylpolyol Esters Vale´ rie Eychenne and Ze´ phirin Mouloungui* Laboratoire de Chimie Agro-Industrielle UA INRA 31A1010, Ecole Nationale Supe´ rieure de Chimie de Toulouse, INP Toulouse, 31077 Toulouse Cedex 4, France, and Laboratoire de Chimie Agro-Industrielle, Ecole Nationale de Chimie de Toulouse, 118 route de Narbonne, 31077 Toulouse Cedex 4, France
Neopentylpolyol esters are high performance lubricants because of their high thermo-oxidative stability, their high flash point, and their low volatility. In this paper, we studied the influence of parameters such as functionality of the alcohol, length of the fatty acid hydrocarbon chain, degree of unsaturation of the acyl group, fatty acid mixture, and amount of diacid on the main properties for a lubricant such as viscosities at 40 and 100 °C, viscosity index, flash point, and pour point. Therefore, qualitative and quantitative relationships are presented for esters from alcohols including trimethylolpropane, pentaerythritol, and neopentylglycol hydroxypivalate and from acids from C5:0 to C22:1. Introduction Neopentylpolyol esters have applications as highperformance lubricants because of their high stability to thermo-oxidation, high flash point, and low volatility (Eychenne et al., 1996). The excellent thermal stability of neopentylpolyol esters stems from their β-substituted alcohol structure based on trimethylolpropane, pentaerythritol, or neopentylglycol. The esters of these polyhydroxyl alcohols have low volatility, and their bulky structure confers excellent resistance to hydrolysis. In view of these properties, lubricants based on these esters are economical in use and have seen considerable development as synthetic lubricants in automotive applications, marine diesel engines, transmission systems, and the aerospace industry (Mortier and Orszulik, 1993). Four main properties (Karleskind, 1992; Reid, 1989) are crucial for lubricants: viscosity, viscosity index, flash point (high-temperature behavior), and pour point (lowtemperature behavior). Numerous authors (Barnes and Fainman, 1957; Kohashi, 1990; Nutiu et al., 1990; Randles, 1993) have evaluated these properties as a function of the length of the acyl chain and the functional groups on the neopentylpolyols. However, scant attention has been paid to the structure-property relationship (Nutiu et al., 1990), and most studies have been devoted to shortchain (4-10 carbons) fatty acid esters of the neopentylpolyols. More recently, Randles (1990) and Kohashi (1990) have reported the characteristics of neopentylpolyol esters based on oleic acid, although they did not describe how the various parameters were related to the structure of the molecule. Barnes and Fainman (1957) had shown earlier that linear esters have a high viscosity index, high flash point, and high pour point. On the other hand, the branched chain esters have a low viscosity index, a low flash point, and also a low pour point. Niedzielski (1976) reported that the presence of branched chains * To whom correspondence should be addressed. Phone: (33) (0)5 61 17 57 24. Fax: (33) (0)5 61 17 57 30. E-mail: lcacatar@ cict.fr.
reduced thermal stability and resistance to oxidation and gave rise to a poor viscosity index. Use of linear long chains would thus be expected to improve lubricating properties and the viscosity index, although at the expense of low-temperature fluidity. Although certain properties may be improved by use of additives, thermal stability is an inherent property of the structure of the molecule (Tayler et al., 1994). It is thus preferable to use linear long-chain fatty acids, which have the added advantage of being biodegradable (natural products). After investigation of the total esters of trimethylolpropane, pentaerythritol, and neopentylglycol, Nutui et al. (1990) came to the following conclusions: (1) To improve viscosity, there must be an increase in the molecular weight (chain length or neopentyl moiety), the number of functional groups in the polyol, or the size or degree of branching. (2) To increase the viscosity index, there must be an increase in either the lengths of the acyl or neopentyl chains or the linearity of the molecule. (3) To reduce the pour point, the degree of the branching needs to be increased, the length of the acyl chain needs to be reduced, or the molecule must be less symmetrical. A single molecule does not usually possess the required viscosity, viscosity index, and pour point; properties which may be mutually exclusive. These considerations prompted us to prepare compounds with a variety of structures (Eychenne, 1997) including the following: (a) Total esters: a single monocarboxylic fatty acid associated with a neopentylpolyol. (b) Mixed esters: neopentylpolyol esterified with various monocarboxylic fatty acids. These are, in fact, total esters but bear chains of different lengths. (c) Complex esters: prepared by partial esterification of neopentylpolyol with a diacid in nonstoichiometric amounts, followed by esterification with a monocarboxylic fatty acid. Depending on the molecule or the mixture of molecules, we studied the influence of the following parameters: functionality of the alcohol, length of the fatty acid hydrocarbon chain, degree of unsaturation of the acyl group, fatty acid mixture, and amount of diacid.
10.1021/ie9801204 CCC: $15.00 © 1998 American Chemical Society Published on Web 10/28/1998
4836 Ind. Eng. Chem. Res., Vol. 37, No. 12, 1998 Table 1. Composition of Mixtures of Fatty Acids Used for the Preparation of Mixed Esters
polyol PE (4 OH)
TMP (3 OH)
HPNPG (2 OH)
proportion of several acids (%) C22:1 C18:1 C9:0 25 50 75 25 50 75 50 33 50 67 33 50 67 33 67 25 50 75 25 50 75
75 50 25
25 67 50 33
33 17 75 50 25
75 50 25 25
67 50 33 33 17
75 50 25
name of the mixture of mixed esters PE 1C22:1 3C18:1 PE 2C22:1 2C18 PE 3C22:1 1C18:1 PE 1C22:1 3C9:0 PE 2C22:1 2C9:0 PE 3C22:1 1C9:0 PE 2C22:1 1C18:1 1C9:0 TMP 1C22:1 2C18:1 TMP 1.5C22:1 1.5C18:1 TMP 2C22:1 1C18:1 TMP 1C22:1 2C9:0 TMP 1.5C22:1 1.5C9:0 TMP 2C22:1 1C9:0 TMP 1C22:1 1C18:1 1C9:0 TMP 2C22:1 0.5C18:1 0.5C9:0 HP 0.5C22:1 1.5C18:1 HP 1C22:1 1C18:1 HP 1.5C22:1 0.5C18:1 HP 0.5C22:1 1.5C9:0 HP 1C22:1 1C9:0 HP 1.5C22:1 0.5C9:0
We present here our findings on the relationships (both qualitative and quantitative) between the main structural parameters and the properties of total, mixed, and complex bulky esters designed for application as lubricants. We initially investigated esters based on erucic acid from rapeseed and crambe oils, which have been found to produce esters of neopentylpolyols with interesting properties (Van Dyne et al.). We extended this to other applications and further structure-function relationships. We studied esters from alcohols including trimethylolpropane, pentaerythritol esters and the hydroxypivalate neopentylglycol esters, which has been little studied and has shown considerable promise. Experimental Part Materials. Pentaerythritol (PE, 98%), trimethylolpropane (TMP, 98%), neopentylglycol hydroxypivalate (HPNPG, 98%), and pelargonic acid were supplied by Acros (Noisy Le Grand, France). Erucic acid (C22:1, >95%) and the catalyst, p-toluenesulfonic acid (p-TSA, >99%), were purchased from Fluka (L’Isle d’Abeau Chesnes, France). Lauric acid (C12:0, >99%) and the diacids brassylic (diC13, 94%) and azelaic acid (diC9, 95%) were obtained from Sigma (St. Quentin Fallavier, France). Oleic acid (C18:1, 72%, Prolabo, France) also contained 11% linoleic acid (C18:2). Preparation of Total Esters. One mole of alcohol and a stoichiometric amount of fatty acid (2 mol of fatty acid for HPNPG, 3 mol for TMP, and 4 mol for PE) were placed in a 2 L reactor with 100 mL of xylene and 2% p-TSA (per weight of alcohol). The reactor was equipped with a mechanical stirrer, thermometer, Dean-Stark trap, and cooling system. The reaction was conducted under a stream of nitrogen for 8 h between 170 and 200 °C. Preparation of Mixed Esters. The methods described above were employed except that the fatty acids were mixtures of monocarboxylic acids in the proportions listed in Table 1. For example, an ester denoted PE 1C22:1 3C18:1 was prepared from pentaerythitol and a molar mixture of fatty acids (25% erucic acid, 75%
Table 2. Reaction Mixture for the Synthesis of Complex Esters polyols TMP (3 OH)
diacida
0.1 diC13 0.2 diC13 0.3 diC13 0.2 diC13 0.2 diC13 0.2 diC9 PE (4 OH) 0.13 diC13 0.27 diC13 0.4 diC13 0.27 diC13 0.27 diC13 0.27 diC9 HPNPG (2 OH) 0.07 diC13 0.13 diC13 0.2 diC13 0.13 diC13 0.13 diC13 0.13 diC9 a
monoacid
name of the mixture of complex esters
C22:1 C22:1 C22:1 C18:1 C9:0 C22:1 C22:1 C22:1 C22:1 C18:1 C9:0 C22:1 C22:1 C22:1 C22:1 C18:1 C9:0 C22:1
TMP 0.1diC13-C22:1 TMP 0.2diC13-C22:1 TMP 0.3diC13-C22:1 TMP 0.2diC13-C18:1 TMP 0.2diC13-C9:0 TMP 0.2diC9-C22:1 PE 0.1diC13-C22:1 PE 0.2diC13-C22:1 PE 0.3diC13-C22:1 PE 0.2diC13-C18:1 PE 0.2diC13-C9:0 PE 0.2diC9-C22:1 HPNPG 0.1diC13-C22:1 HPNPG 0.2diC13-C22:1 HPNPG 0.3diC13-C22:1 HPNPG 0.2diC13-C18:1 HPNPG 0.2diC13-C9:0 HPNPG 0.2diC9-C22:1
Number of moles of diacid per mole of alcohols.
oleic acid; i.e., 1 mol of erucic acid and 3 mol of oleic acid for four hydroxyl groups of PE). Preparation of Complex Esters. The methods described above for the total esters were employed but were carried out in two stages. In the first stage, 0.1, 0.2, and 0.3 mol of diacid were reacted with 3 mol of OH (Kleiman and Ponsker, 1973), and we applied the following conditions: (a) 0.1, 0.2, or 0.3 mol of diacid for 1 mol of TMP, (b) 0.13, 0.27, or 0.4 mol of diacid for 1 mol of PE, and (c) 0.07, 0.13, or 0.2 mol of diacid for 1 mol of HPNPG. The alcohol was in large excess and the reaction was pursued for 4-5 h to ensure reaction of all of the diacid. In the second stage, the polyol was fully esterified by addition of a monocarboxylic acid. The various mixtures prepared are listed in Table 2. Thus, an ester denoted as TMP 0.1diC13-C22:1 was prepared with 0.1 mol of brassylic acid for 1 mol of trimethylolpropane, and esterification was completed by reaction with a stoichiometric amount of erucic acid. Purification. At the end of the reaction, the xylene was evaporated, and after cooling, the residual oil was deacidified with anionic resin to remove catalyst and excess acid (Eychenne and Mouloungui, 1998). After deacidification, the determination of acid values (NF T60-204 norm) gave values below 1 and even, in most cases, below 0.1 whatever the nature of the esters. Analyses. Chromatographic analyses (TLC-FID, Iatroscan apparatus) (Eychenne et al., 1998a) showed a low content of partial esters (esters with remaining OH groups). The purity of total and mixed esters was between 95 and 98%. In the case of complex esters, it was more difficult to have a complete reaction because of the viscosity and the steric hindrance. GPC (gel permeation chromatography) analyses of complex esters (Eychenne, 1997) were made on an ICS apparatus with a RI detector 8110. Two columns were in series: column of 500A + PL gel mixed E (Polymer Laboratories). The eluant was THF with a flow of 0.8 mL/min. For the esters of trimethylolpropane, weights are between the monomer weight (the corresponding total ester) and M ) 2984 and even 3600 (which are molecules with three or four molecules of diacid). For the esters of pentaerythritol, weights are between the monomer weight and M ) 5352 (molecules with four molecules of diacid). For the esters of neopentylglycol
Ind. Eng. Chem. Res., Vol. 37, No. 12, 1998 4837
Figure 1. Plot of viscosity at 40 °C (mm2/s) against length of the acyl chain.
hydroxypivalate, the range of weight is from the monomer weight to M ) 2024 (molecules with three molecules of diacid). Determination of Physical Properties. The tests were conducted according to ASTM standard methods. Viscosity: ASTM D445, kinematic viscosity of opaque and transparent liquids. Viscosity index: ASTM D2270, calculation of viscosity index from viscosity at 40 and 100 °C. Flash point: ASTM D93, flash point in a closed bowl. Pour point: ASTM D97, pour point of petroleum oils. Data analysis. The data were analyzed graphically and regression equations determined using Cricket Graph software running on an Apple Macintosh computer. Results and Discussion Viscosities of Total Esters. In general, viscosity increased with the length of the acyl chain and the functionality of the polyol. It also fell with a rise in temperature. It can be seen from Figure 1 that the plot of viscosity at 40 °C against chain length is linear. Three regression equations were determined from these plots:
y1 ) -4.56 + 4.23x1 y1 ) -7.84 + 3.38x1 y1 ) -7.16 + 2.44x1
r2 ) 0.999 for PE
(1)
r2 ) 0.985 for TMP (2) r2 ) 0.979 for HPNPG (3)
where x1 is the number of carbon atoms in the acyl chain and y1 the viscosity at 40 °C. The correlation coefficients (r2) in all cases were close to 1, and so the equation y ) ax + b is well adapted to establish the relationship between the viscosity at 40 °C of linear fatty acid esters of the neopentylpolyols and the number of carbons atoms in the acyl chain. These equations can be used to predict the viscosity of the esters of neopentylpolyols with linear fatty acids of chains from C5:0 to C22:1. However, these equations do not take account of the presence of double bonds, and it is difficult to compare the fatty acids with saturated and unsaturated chains. Above 12 carbons, the saturated esters are solid. How the number of hydroxyl
Figure 2. Plot of viscosity at 40 °C (mm2/s) against molecular weight. y2 ) -20.537 + 7.78 × 10-2x2 (eq 4).
Figure 3. Plot of viscosity at 100 °C (mm2/s) against length of the acyl chain.
groups (functionality of the polyol) affected the plots can also be noted in Figure 1: PE > TMP > HPNPG. From these observations, it would be more logical to relate the viscosity to the molecular weight of the molecule. For the neopentylpolyol esters tested, we obtained a plot as shown in the Figure 2 with the following regression equation:
y2 ) -20.537 + 7.78 × 10-2x2
r2 ) 0.991 (4)
with x2 ) molecular weight of the ester and y2 ) viscosity at 40 °C Niedzielski (1976) has described a similar correlation (y ) -21.72 + 0.798x) for molecular weights ranging from 350 to 750, which correspond to the esters of neopentylglycol (NPG), TMP, and PE with fatty acids from C6:0 to C12:0. Our equation has the advantage of being valid for esters of PE, TMP, and HPNPG and fatty acids with linear chains over a range of molecular weights from 400 to 1500. In addition, this equation also fits the esters of NPG (Eychenne, 1997). Similar plots were obtained for the total esters at 100 °C. Figures 3 and 4 show the plots of viscosity at 100 °C against the length of the acyl chain and molecular weight, respectively. The following regression equations were obtained:
y3 ) -0.37 + 0.75x3
r2 ) 0.998 for PE
(5)
4838 Ind. Eng. Chem. Res., Vol. 37, No. 12, 1998
Figure 4. Plot of viscosity at 100 °C (mm2/s) against molecular weight. y4 ) -2.91 + 1.38 × 10-4x4 (eq 8).
y3 ) -0.70 + 0.60x3 y3 ) -0.39 + 0.45x3
r2 ) 0.982 for TMP (6) r2 ) 0.955 for HPNPG (7)
Figure 5. Viscosity at 40 °C (mm2/s) of mixed esters of the C18: 1-C22:1 type.
with y3 ) viscosity at 100 °C and x3 ) number of carbons in the acyl chain. The regression line from Figure 3 is
y4 ) -2.91 + 1.38 × 10-2x4
r2 ) 0.980
(8)
with y4 ) viscosity at 100 °C and x4 ) molecular weight of the ester. Viscosities of Mixed Esters. The viscosity of the esters of erucic acid was modified by making the mixture of either erucic and oleic (C18:1) acids or erucic and pelargonic (C9:0) acids. In these mixed structures, the long-chain (C22:1) fatty acid was associated with medium-chain (C18:1) and short-chain (C9:0) fatty acids. The values obtained for the viscosity at 40 °C as a function of the proportion of erucic acid are shown in Figures 5 and 6. The regression equations relate x5 as the molar proportion of erucic acid and y5 as the viscosity at 40 °C (or 100 °C). We observed a linear increase in viscosity with an increase in the proportion of erucic acid, along with the above-mentioned influence of the functionality of the polyol: PE > TMP > HPNPG. The slopes of the curves were similar for the same type of mixed ester, and the influence of the fatty acid mixture was not affected by the nature of the polyol. We also observed that the slopes of the regression lines for C9:0-C22:1 esters were higher than those for esters of the C18:1-C22:1 type. An increase in the amount of erucic chains had a more marked effect on viscosity at 40 °C for esters of the C9:0-C22:1 type as the viscosity of the total esters of pelargonic acid was below that of the total esters of oleic acid. In summary, the viscosities of total and mixed esters were found to be a direct function of the molecular weight of the oil. After calculation of the mean molecular weights of the mixed esters (Eychenne, 1997), eq 4 gives the corresponding viscosities of mixtures of mixed esters. The calculated values were then compared to those obtained experimentally (Table 3). It can be seen from the results in Table 3 that there was good agreement between the two, and eq 4 was thus considered to be adapted for
Figure 6. Viscosity at 40 °C (mm2/s) of mixed esters of the C9: 0-C22:1 type.
calculation of viscosities at 40 °C of mixed esters of the C9:0-C22:1 and C18:1-C22:1 types. Figures 7 and 8 show plots of the experimental viscosities at 100 °C as a function of the proportion of erucic acid. In a way similar to that for the viscosities at 40 °C, comparison of the values calculated from the molecular weights of the mixtures of mixed esters from eq 8 to the values obtained experimentally at 100 °C validated the equations employed (Table 3). This indicated that the viscosity was a direct function of the molecular weight of the ester. Thus, the introduction of short- and medium-chain fatty acids into the synthesis of esters of neopentylpolyols and long-chain fatty acids reduced the viscosity at both 40 and 100 °C. The linear relationship for total esters between viscosity and molecular weight was generalized to all types of mixed esters with linear acyl chains. Viscosities of Complex Esters. The introduction of a diacid in the two-stage synthesis of the complex
Ind. Eng. Chem. Res., Vol. 37, No. 12, 1998 4839 Table 3. Calculated and Experimental Values of Viscosity at 40 and 100 °C for Mixed Esters viscosity at viscosity at 40 °C (mm2/s) 100 °C (mm2/s) mixed esters
mol wt
calc
exp
calc
exp
TMP 1C22:1 2C18:1 TMP 1.5C22:1 1.5C18:1 TMP 2C22:1 1C18:1 PE 1C22:1 3C18:1 PE 2C22:1 2C18:1 PE 3C22:1 1C18:1 HP 0.5C22 1.5C18:1 HP 1C22:1 1C18:1 HP 1.5C22:1 0.5C18:1 TMP 1C22:1 2C9:0 TMP 1.5C22:1 1.5C9:0 TMP 2C22:1 1C9:0 PE 1C22:1 3C9:0 PE 2C22:1 2C9:0 PE 3C22:1 1C9:0 HP 0.5C22:1 1.5C9:0 HP 1C22:1 1C9:0 HP 1.5C22:1 0.5C9:0
981.5 1010 1039 1249 1304 1361 761 789 817 733 824 916 877 1056 1236 575 664 755
55.8 58.04 60.30 76.64 80.91 85.35 38.67 40.85 43.03 36.49 43.57 50.73 47.7 61.6 75.6 24.2 31.1 38.2
55.4 62.15 66.7 72.1 83.1 92.2 37.8 42.8 47.8 40 49.5 58.5 50.8 66.6 85.9 23.7 30.3 42.3
10.63 11.03 11.43 14.33 15.09 15.87 7.59 8 8.36 7.21 8.46 9.73 9.19 11.66 14.15 5.03 6.25 7.51
11 12 12.7 13.6 16.1 16.45 8.6 8.9 9.7 8 9.7 11.2 9.5 12.3 15.1 5.4 6.7 8.75 Figure 8. Viscosity at 100 °C (mm2/s) for mixed esters of the C9: 0-C22:1 type.
Figure 7. Viscosity at 100 °C (mm2/s) for mixed esters of the C18: 1-C22:1 type.
esters produced esters with higher molecular weights than those of the total esters. The increase in molecular weight led to an increase in viscosity. The influence of various parameters could be evaluated using different categories of complex esters. An increase in viscosity was obtained by increasing (i) the proportion of diacid (Figures 9 and 10), (ii) the functionality of the polyol, and (iii) the length of the monocarboxylic acid chain (Figures 11 and 12). A linear relationship was observed in all cases and was associated with an increase in the average molecular weight. For the relationship with the proportion of diacid, the equations related x6 to the amount of diacid (moles of diacid per moles of alcohol) and y6 to the viscosity at 40 °C (or 100 °C). For the relationship with the length of the monocarboxylic acid chain, x7 was the length of the chain and y7 the viscosity at 40 °C (or 100 °C). The influence of the length of the diacid chain was investigated using two types of diacid (Table 4). Unexpectedly, we obtained the highest viscosities with azelaic acid (diC9). If viscosity depends ultimately on the molecular weight, the polyesterification of diC9 was
Figure 9. Plot of viscosity at 40 °C (mm2/s) against amount of diacid for complex esters.
assumed to be more complete than that of diC13, and so the molecular weights of the esters of diC9 would be higher than those of the larger diacid. Viscosity Indices of Total Esters. It can be seen from the values listed in Table 5 that viscosity increased with the length of the acyl chain. For the total esters of C22:1 and C18:1, the viscosity index, at least for the long-chain compounds, did not appear to be influenced by the nature of the polyol or the number of functional groups. On the other hand, for the total esters of C9:0, the viscosity index fell with an increase in the number of hydroxyl groups on the polyol. Since temperature has less influence on viscosity the higher the viscosity index oils with a high viscosity index may retain viscosity at high temperature and the remaining fluid at ambient temperature. The erucates of neopentylpolyol fulfill this criterion as the best index (around 200) was obtained with the heavy total esters. Viscosity Indices of Mixed Esters. The viscosity indices of the different mixed esters and those of the
4840 Ind. Eng. Chem. Res., Vol. 37, No. 12, 1998
Figure 10. Plot of viscosity at 100 °C diacid for complex esters.
(mm2/s)
against amount of
Figure 12. Plot of viscosity at 100 °C (mm2/s) against monoacid chain length for complex esters. Table 4. Experimental Viscosity at 40 °C of Complex Esters of Different Diacid Acyl Chain Lengths complex esters
viscosity at 40 °C (mm2/s)
TMP 0.2diC13-C22:1 TMP 0.2diC9-C22:1 PE 0.2diC13-C22:1 PE 0.2diC9-C22:1 HP 0.2diC13-C22:1 HP 0.2diC9-C22:1
100.77 109.6 145.67 156.2 63.7 64.18
Table 5. Viscosity Indices of Total Esters PE TMP HPNPG
C22:1
C18:1
C9:0
201 200 201
182 176 182
136 140 150
Table 6. Viscosity Indices of Mixed Esters and Their Corresponding Total Esters mixed esters of type C18:1-C22:1
Figure 11. Plot of viscosity at 40 °C (mm2/s) against monoacid chain length for complex esters.
total esters are listed in Table 6. It can be seen that the viscosity indices of the mixed esters of the C18:1C22:1 type were in general higher than those of the C9: 0-C22:1 type. In both series, an influence of the acyl chain length was observed. The viscosity index of the mixed esters of the C18:1-C22:1 type was considerably increased by combination with C22:1. The viscosity indices exceeded those of the total oleate esters used as reference. This was even more noticeable with the mixed esters of the C9:0-C22:1 type where at least 40 units of viscosity index were gained by combination with a small amount of C22:1. For example, the tripelargonate of trimethylolpropane (TMPC9) had a viscosity index of 140, while the mixed ester TMP 2C9:0 1C22:1 had a viscosity index of 180. All of the compositions of mixed esters prepared from a mixture of the two acids in low or high proportions with long-chain acyl esters were found to be subjected to this effect. The long-chain mixed esters based on erucic acid thus appear to have viscosity superior to that of the mixed esters. The
mixed esters of type C9:0-C22:1
molecule
viscosity index
molecule
viscosity index
TMP C18:1 TMP 2C18:1 1C22:1 TMP 1.5C18:1 1.5C22:1 TMP 1C18:1 2C22:1 TMP C22:1 PE C18:1 PE 3C18:1 1C22:1 PE 2C18:1 2C22:1 PE 1C18:1 3C22:1 PE C22:1 HP C18:1 HP 1.5C18:1 0.5C22:1 HP 1C18:1 1C22:1 HP 0.5C18:1 1.5C22:1 HP C22:1
176 195 194 194 200 182 195 209 183 201 182 200 196 193 200
TMP C9:0 TMP 2C9:0 1C22:1 TMP 1.5C9:0 1.5C22:1 TMP 1C9:0 2C22:1 TMP C22:1 PE C9:0 PE 3C9:0 1C22:1 PE 2C9:0 2C22:1 PE 1C9:0 3C22:1 PE C22:1 HP C9:0 HP 1.5C9:0 0.5C22:1 HP 1C9:0 1C22:1 HP 0.5C9:0 1.5C22:1 HP C22:1
140 180 185 189 200 136 174 185 187 201 150 177 187 193 201
erucates of neopentylpolyols in particular appeared to have a positive influence on the viscosity index. Viscosity Indices of Complex Esters. The viscosity indices of the different complex esters are listed in Table 7. It can be seen that the viscosity indices of the complex esters depending on the nature of the monocarboxylic acid chain were lower or slightly higher than those of the corresponding total esters. The values for the oleic and pelargonic esters were improved. The viscosity indices ranged from 136 to 150 for the total pelargonates and from 155 to 160 for the complex esters
Ind. Eng. Chem. Res., Vol. 37, No. 12, 1998 4841 Table 7. Viscosity Indices of Complex Esters complex ester
viscosity index
complex ester
viscosity index
PE 0.1diC13-C22:1 PE 0.2diC13-C22:1 PE 0.3diC13-C22:1 TMP 0.1diC13-C22:1 TMP 0.2diC13-C22:1 TMP 0.3diC13-C22:1 HP 0.1diC13-C22:1 HP 0.2diC13-C22:1 HP 0.3diC13-C22:1
193 245 197 192 192 192 191 190 186
PE 0.2diC13-C18:1 TMP 0.2diC13-C18:1 HP 0.2diC13-C18:1 PE 0.2diC13-C9:0 TMP 0.2diC13-C9:0 HP 0.2diC13-C9:0 PE 0.2diC9-C22:1 TMP 0.2diC9-C22:1 HP 0.2diC9-C22:1
189 194 190 155 160 156 194 191 190
Table 8. Low-Temperature Behavior of Total Esters molecule
pour point (°C)
cloud point (°C)
PE C22 TMP C22 HP C22 HP C22 HP C18 HP C9
9.5 -5.6 -17 -17 -31
