6048
Ind. Eng. Chem. Res. 2004, 43, 6048-6054
Effects of the Temperature and Mixing Rate on Foaming in a Polymerization Reaction To Produce Fatty Polyamides in the Presence of Catalyst Heidarian Javad, Mohd Ghasem Nayef, and Mohd Ashri Wan Daud Wan* Department of Chemical Engineering, University of Malaya, 50603 Kuala Lumpur, Malaysia
The effects of the mixing rate and temperature on foaming are investigated, and the time minimization for the polyamidation reaction in the presence of catalyst in a semibatch reactor to prevent foaming was performed using the MATLAB program. The process constraints are the rate of temperature increase and rate of production of water. It is found that with an increase in the mixing rate foaming will start at lower temperatures and with a decrease in the mixing rate foaming will only start at high temperatures. For each mixing rate with an increase the temperature, the duration of foaming is shorter because the increase in the rate of foaming ends. Temperature profiles with time for different mixing rates were generated, and it is found that the reaction time decreases with increasing mixing rate. The generated temperature profiles were verified experimentally, and no foaming was observed. Introduction Fatty polyamides are products of di- and polyfunctional amines and di- and polybasic acids obtained by polymerization of unsaturated vegetable oil acids or their esters. Dimer fatty acids have been traditionally used to synthesize and formulate hot-melt adhesives, flexographic inks, functional coatings, and other engineering materials.1 Equation 1 shows the polymerization reaction between dimer fatty acids and ethylenediamine. To assist
nH2NCH2CH2NH2 + nHOOCC34COOH a H[NHCH2CH2NHCOC34CO]nOH + nH2O (1) the condensation reaction, a catalyst, such as phosphoric acid, may be added to the reaction mixture2 in a catalytic proportion. The catalyst employed in the condensation reaction may be either charged to the reaction mixture at the beginning of the reaction or added slowly just prior to the point at which the reaction rate is slowing. The preferred concentration of the catalyst is within the range of 0.001-3 wt % and more preferably from about 0.01 to 1.0 wt % by weight of the total materials charged.2 Either the condensation polymerization reaction of fatty polyamides may be carried out on a stepwise addition basis or all reactants can be mixed together at once. The former is preferable because if all of the reactants are mixed together at once, there will be a sudden and vigorous expansion of the reaction mixture (foaming), presumably because of the sudden release of a substantial amount of water formed during the reaction.3 Foaming is best considered as the distribution of a gas throughout a continuous liquid phase in a finely divided form. Foam displays an exceptionally large gas/ liquid interface that separates one bubble from its neighbor. Although all liquids tend to exist under * To whom correspondence should be addressed. Tel.: +60379675297. Fax: +60379675319. E-mail:
[email protected].
conditions of the lowest possible energy, foam exists in a high energy state that is only possible when some stabilizing influence such as surfactant fixes the foam within the liquid medium.4 Initially, as the foam is formed, the globular bubbles are discrete, with large amounts of liquid separating each bubble. The walls (lamellae) of the bubble are, therefore, thick within the liquid phase. This type of foam is sometimes called a spherical or wet foam. Over time, the individual bubbles congregate more closely together as the liquid begins to drain from the bubbles so that the walls of the bubbles become thinner. This type of foam in which the bubbles are closely packed together and have little liquid separating them is described as dry foam.4 As the foam walls get thinner, they eventually rupture and the individual bubbles collapse into larger bubbles made up of the gas from the smaller units. These large bubbles then will migrate to the surface. In the work carried out by Joonho et al.,5 the time minimization for the transesterification reaction in a semibatch reactor [poly(ethylene terephthalate)] was performed and one of the constraints for optimization was flooding. In the work carried out by Joonho et al.,5 flooding was controlled using concentration of ethylene glycol (monomer) in the vapor phase, and they mentioned in this reference that the rate of vaporization of methanol (condensation product) is related to flooding and obtained a temperature profile with time with no foaming. In their work, they gradually increased the temperature for preventing foaming. As mentioned in this reference, no theoretical approach has been proposed that can describe the flooding phenomenon. The objective function of the problem in this reference is the reaction time. On the effect of mixing, in a study carried out by James and Chang6 on bubble nucleation in a mixture of volatile liquid and polymer melt under shear flow conditions in an extruder, for a mixture of polystyrene and trichlorofluoromethane that passed through the slit die, they showed that bubble nucleation can be induced by either flow or shear stress. The results also indicate that flow-induced bubble nucleation is the dominant
10.1021/ie030779w CCC: $27.50 © 2004 American Chemical Society Published on Web 07/28/2004
Ind. Eng. Chem. Res., Vol. 43, No. 19, 2004 6049
mechanism at the positions near the center of the die opening, and shear-induced bubble nucleation is the dominant mechanism at positions near the die wall. The study also indicates that bubble nucleation in a shear flow field can occur in an unsaturated condition. From the above-mentioned works and other literature,7-9 it can be concluded that the reaction temperature has a significant effect on foaming, and in order to prevent it, the reaction should be started at lowest possible temperatures. It should then be gradually increased so that the rate of production of water will be low enough, thus preventing the onset of foaming. By a gradual increase in the temperature, the evaporation of ethylenediamine will also be prevented.10 As mentioned in the literature,7-10 the rate of production of water, which is directly related to the rate of reaction, is an important criteria for the control of foaming. It can be inferred that, to prevent foaming, besides a gradual increase in the temperature, the mixing rate should be low, as practiced in industry. This low mixing rate condition should be maintained until the rate of reaction becomes acceptably low, which subsequently lowers the rate of water production. After foaming is over, the mixing rate can be increased to increase heat transfer and the temperature can be raised to increase the rate of reaction. Although foaming is a general problem in the manufacturing of fatty polyamides,7-9 there is no substantial work found on the effects of the mixing rate and temperature on foaming in the presence of catalyst, and this includes the generation of a temperature profile to prevent the formation of foam. In the previous work,11 the effects of the mixing rate and temperature on foaming for fatty polyamides without catalyst were carried out. In this work, the effects of the mixing rate and temperature on foaming in the presence of catalyst are investigated. To avoid foaming for a batch polymerization reaction, the temperature is gradually increased from 405 to 475 K, using MATLAB software, the temperature profile with time that prevents foaming at each mixing rate is obtained, and the criterion used for controlling foaming is the rate of production of water or rate of reaction. At each temperature and mixing rate, the minimum rate of reaction at which foaming is over is used as the criterion for controlling foaming. Usually, in the literature and industry, the temperature range employed is from 405 to 475 K, and a gradual increase in the temperature is carried out to prevent foaming. The purpose of increasing the reaction temperature is to increase the rate of reaction, thus minimizing the reaction time, and to obtain the temperature profile at which it prevents foaming, and this is the aim of this work. Mathematical Model of the Polyamidation Stage. The reactor model for the kinetics is based on the work of Joha et al. (refer to ref 12). In this model, mass balances for components are applied, and for the flow leaving the reactor and concentrations of ethylenediamine and water, empirical equations are introduced. The forward and reverse rate constants and empirical parameters were obtained. Tables12 1-3 show the kinetic rate constants, Arrhenius parameters, and empirical parameters at a mixing rate of 75 rpm, respectively. For a variable-temperature profile during optimization, the Arrhenius parameters (forward rate constant) are used. Because the monomers are added at low temperature and the temperature is increased
Table 1. Kinetic Rate Constants at 75 rpm Mixing Rate12
T (K)
second-order rate constant k1 (kg mol-1 min-1)
k2 (kg mol-1 min-1) (before 90% conversion)
405 420 435 450 475
0.004 349 918 3 0.027 150 420 0 0.044 401 941 0 0.062 853 302 0 0.238 872 970 0
0.001 788 528 4 0.004 637 723 3 0.007 688 209 6 0.003 538 052 5 0.033 338 116 0
Table 2. Arrhenius Parameters of the Kinetic Rate Constants at 75 rpm Mixing Rate12 rate constant
AE (kg mol-1 min-1)
EaE (kJ mol-1)
k1
362 306 102.7
83.2
Table 3. Empirical Parameters of the Kinetic Model12 at 75 rpm Mixing Rate T (K)
A
B
C
D
E
405 420 435 450 475
0.039 179 0.029 006 0.051 534 0.054 995 0.115 608
0.008 236 0.005 461 0.051 461 0.137 821 0.349 627
0.451 932 0.658 584 0.624 457 0.621 654 0.954 555
0.018 111 0.947 065 0.623 231 0.149 542 0.186 976
0.547 793 0.341 415 0.375 543 0.378 342 0.045 445
gradually, the evaporation of diamine is considered to be marginal; therefore, the same concentrations of diamine and diacid are used for optimization. Because during optimization a catalyst is used, the second-order reaction rate is applied (eq 2)5 and the change in the
r ) k1CCOOHCNH ) k1CCOOH2
(2)
concentration of acid or amine with time will become that in eq 3.
CCOOH )
CCOOH0 1 + k1CCOOH0∆t
(3)
In the eqs 2 and 3, r is the rate of reaction, k1 is the second-order rate constant, CCOOH and CNH are the acid and amine concentrations in the reaction mass, respectively, CCOOH0 is the initial concentration of acid at each time interval, and ∆t is the reaction time interval. Process Constraints and Formulation of the Optimization Problem and Solution Method. As mentioned above, the process constraints should be considered in order to obtain a feasible operating condition. The aim is to minimize the time required to increase the temperature from 405 to 475 K in order to get an optimum temperature profile. To obtain this, the temperature should be increased as high as possible; however, the increase should be kept such that the reaction rate remains less than the minimum rate for foaming. Besides, the rate of temperature increase is constrained by the heat flux from the reactor jacket: for example, the heater duty has a finite capacity, and the heat transfer may be limited by the overall heat-transfer coefficient; for the laboratory-scale semibatch reactor used, the maximum rate of temperature increase is 2.5 K min-1. The constraints can be formulated as follows (eqs 4 and 5).
r ermin
(4)
dT dT e dt dt U
(5)
|
6050 Ind. Eng. Chem. Res., Vol. 43, No. 19, 2004
Figure 1. Schematic diagram for melt polymerization of fatty polyamides.
In the above equations, rmin is the minimum rate of reaction above which foaming will start to take place. To obtain a temperature profile, MATLAB software is used. First, time discrete is applied to some steps, and at each step, the temperature is increased stepwisely. At each step, the rate is checked to see if it remains less than the minimum rate for foaming (rmin) and the temperature remains as high as possible but less than the maximum rate of the temperature increase (2.5 K min - 1). This optimum temperature at each time interval will be saved, and after that, the program will compute the next time step. In this programming, only the temperature is allowed to increase or remain constant. Then the program will retrieve the saved temperature profile over time that satisfies the process constraints. Experimental Section Materials. Dimer fatty acid (PRIPOL 1013 from Uniqema, Gouda, The Netherlands) with 97% purity (monomer 0.1%, dimer 97%, and trimer 3%) and an acid value of 195 was used. Ethylenediamine was of laboratory reagent grade having a purity above 98% as determined by titration with standard acid. o-Phosphoric acid was also laboratory reagent grade with 85% purity. All other materials used were of reagent grade. Methodology. The experimental setup as shown in Figure 1 consists of a 1.5 L stainless steel reactor (11 cm diameter), equipped with a variable stirrer (with an anchor-type four-blade stirrer with 5 cm diameter), nitrogen inlet tube, and foam sensor based on electrical
conductivity, and the reactor is connected to two condensers. A cooling coil was placed inside the reactor, and the reactor temperature is controlled using an automatic temperature controller. The equipment is connected to a computer for monitoring the temperature and motor speed. In a typical operation, 240 g of dimeric fatty acids and 1.57 cm3 of o-phosphoric acid were charged into the reactor, and the mixture was heated to 10 K below the desired operating temperature. An extra molar amount of ethylenediamine (based on moles of dimer fatty acid) was preheated to 391 K and added to the reactor. Extra amine was used to compensate for the amount evaporated during the preheating process. The stirring speed was set at 75, 300, and 500 rpm. Besides, enough free space was provided in anticipation of foaming. The reaction was carried out at five different temperatures in the range of 405-465 K. Within this temperature range, the materials remained in a molten state. The water generated during the reaction and evaporated diamine were purged out of the reactor using a nitrogen feed rate of 20 mL min-1. These materials were later condensed and collected in a prepared container for analysis. The temperature of the condenser cooling water was kept at 279 K. The amount of distillate collected with time was measured, and the sample refractometery index was analyzed using a refractometer (model NAR-1T). The foam sensor was placed 1.8 cm above the reaction mass surface. If the volume of the reactants increased by 75% because of foaming, it will touch the foam sensor and trigger the alarm. Also, when the foaming period
Ind. Eng. Chem. Res., Vol. 43, No. 19, 2004 6051 Table 4. Times at Which Foaming Ends and Occurrence of Foaming at Each Mixing Rate and Temperature time at which foaming ends (min) T (K)
75 rpm
300 rpm
500 rpm
405 420 435 450 475
no foaming 19 17.8 4.9 4.8
no foaming 40.6 34 8.4 3.6
4.17 60 48.3 8.4 9.2
was over, the alarm will go off. To obtain the rate of reaction at which the foaming is over, first, the time at which foaming ends at each mixing rate and temperature was recorded. At this time, from the kinetic model12 the concentrations of acid, amine, and water were determined. This also included the kinetic rate constants. These procedures were carried out at all temperatures and mixing rates. For a particular mixing rate, the minimum rate at which foaming ends is known as the minimum rate of foaming. To verify the temperature profile generated, variabletemperature experiments were carried out. First, 240 g of dimeric fatty acids and 1.57 cm3 of o-phosphoric acid were charged into the reactor, and the mixture was heated to 395 K. An equivalent molar amount of ethylenediamine (based on moles of dimer fatty acid) was preheated to 391 K and added to the reactor. The temperature is increased to 405 K adiabatically in less than 30 s; because of heat evolved from the exothermic reaction, the temperature profile for that mixing rate will be adjusted through the automatic controller. The foam sensor will check whether there is foaming or not. The acid and amine values were obtained using ASTM D-1980-67, and then experimental rates were obtained using eq 2. Results and Discussion Influence of the Mixing Rate and Temperature on Foaming. The times at which the foaming ended and the occurrence of foaming at each mixing rate and temperature are shown in Table 4. It is worthwhile to mention that in some cases foaming starts to occur from the beginning of reaction; however, in most of the cases, foaming only starts to occur after the reaction has taken place for some time. As can be seen from Table 4, at mixing rates of 75 and 300 rpm, foaming does not occur at a temperature of 405 K, while at a mixing rate of 500 rpm, foaming occurs at all temperatures. The occurrence of foaming at high temperatures is attributed to the high rate of water production, and because higher mixing rates will cause nucleation of bubbling even when the concentration of gas in the polymer is less than the saturated concentration as explained by James and Chang6 and explained in the Introduction, too high mixing rates will cause more nucleation of bubbling; at high mixing rates even at a low rate of production of water, foaming still exists. At high mixing rates, foaming lasts longer, although the rate of reaction is sufficiently low as shown in Table 4. Table 4 shows that, with respect to temperature, at a specific mixing rate, as the reaction temperature decreases, the duration of foaming becomes longer. This could be attributed to the relatively high concentration of reactants remaining in the reactor as a result of low rate of reaction.
Table 5. Concentrations of Acid, Amine, and Water and the Rate of Reaction When Foaming Ends mixing acid amine water rate T concn concn concn rate -1 -1 (rpm) (K) (mol kg ) (mol kg ) (mol kg-1) (mol kg-1 min-1) 75
300
500
420 435 450 475 420 435 450 475 420 435 450 475
0.978 0.730 1.260 0.692 0.690 0.550 0.911 0.731 0.640 0.502 0.911 0.619
1.863 1.498 2.019 0.649 2.189 1.175 1.452 0.895 1.469 1.068 1.452 0.365
1.993 1.433 1.581 1.076 1.543 1.217 1.724 1.379 2.154 1.105 1.724 0.491
0.0302 0.0232 0.1500 0.0278 0.0049 0.0055 0.0704 0.0565 0.0013 0.0023 0.0704 0.0165
Temperature Profiles with No Foaming at Different Mixing Rates. To obtain a temperature profile with no foaming, first the rate of reaction at the end of foaming should be obtained. Table 5 shows the concentrations of acid, amine, and water and the rate of reaction at the time at which foaming ends. The rates are calculated from eq 6. k1 and k2 are the forward and
r ) k1CCOOHCNH - k2CH2OCCONH
(6)
reverse rate constants, respectively. Table 5 also shows the change in the rate of reaction with respect to the reaction temperature at different mixing rates. For optimization purposes, at each mixing rate, the minimum value of the reaction rate is chosen. To ascertain that, foaming will not take place and 95% of that minimum value of the reaction rate is used for optimization. For example, at 300 rpm, the minimum rate that is used for optimization is 0.0049 mol min-1; this rate is known as the minimum rate of foaming. As can be seen from Table 5, with an increase in the mixing rate, the minimum rate for foaming decreases; this is attributed to the increase in shear rates at higher mixing rate.12 At each mixing rate, it is found that when the temperature is decreased, the rate at which foaming ends also decreases, and this is attributed to the different conditions that exist such as the temperature, viscosity, and vapor pressure of water. The minimum rate for foaming at 300 rpm is at 420 K. Although the rate of reaction at the beginning of the reaction at 405 K is higher than this rate, as can be seen from Table 4, at 405 K there is no foaming, and this is due to different conditions exist at these two temperatures such as the viscosity and vapor pressure of water. Figure 2 shows the temperature profile for 75 rpm with no foaming that is derived from optimization; the results show that for the first 35 min the temperature should be kept constant because the rate is higher than the minimum rate of foaming. After that, the temperature should be increased, and as can be seen from Figure 2, the slope is less than 2.5 K min-1, so it is not constrained by the heater duty. Although at the first 35 min the rate of reaction is higher than the minimum rate of foaming, no foaming exists because at this time interval the temperature is between 405 and 435 K (the temperature at which the minimum rate of foaming is obtained); the reason behind this is explained above. Again, as shown in Figure 2, after 35 min the maximum allowable temperature is constrained by foaming and the plot can be divided into two regions. The first region has a slope of 0.66 K min-1 up to 438 K, and the second
6052 Ind. Eng. Chem. Res., Vol. 43, No. 19, 2004
Figure 2. Optimum temperature profile for 75 rpm for no foaming: (9) experimental data.
Figure 4. Optimum temperature profile for 500 rpm for no foaming: (b) experimental data.
Figure 3. Optimum temperature profile for 300 rpm for no foaming: (2) experimental data.
Figure 5. Rate of reaction over time for different mixing rates for the optimum temperature profiles for 75 [(9) experimental data] and 300 rpm [(2) experimental data].
region has a slope of 1.85 K min-1 from 438 to 475 K. After 105 min, the temperature will reach 475 K, and the reaction can proceed at this temperature without any foaming occurring. It can be concluded that for 75 rpm, in order to prevent foaming, first the temperature should be set at 405 K for 35 min, then it must be at 438 K for 50 min (0.66 K min-1), and then increased to 475 K for 20 min (1.85 K min-1). After that, the reaction can be continued at 475 K until the desired conversion is achieved. Figure 3 shows the temperature profile for 300 rpm with no foaming, and the results show that the temperature must be kept constant in the first 133 min constrained by foaming. It takes 280 min to increase the temperature from 405 to 475 K with a heating rate of less than 2.5 K min-1. Again, the region can be divided into two smaller subregions. The first one is with a slope of 0.308 K min-1 from 405 to 438 K (107 min), and the second one is with a slope of 0.925 K min-1 from 438 to 475 K (40 min). By comparison with the time taken for 75 rpm, the total time required to reach 475 K at 300 rpm is longer than that at 75 rpm; this is due to the higher minimum rate of foaming at this mixing rate. Figure 4 shows the temperature profile for 500 rpm with no foaming; as shown in the figure, the temperature must be kept constant in the first 300 min because it is constrained by foaming. It takes 278 min to increase the temperature from 405 to 475 K with a heating rate of less than 2.5 K min-1. Again, the region can be divided into two different subregions. The first one is with a slope of 0.172 K min-1 from 405 to 442 K
(215 min), and the second one is with a slope of 0.524 K min-1 from 442 to 475 K (63 min). Compared with the time taken for 75 and 300 rpm, the total time required to reach 475 K at 500 rpm is longer because of the lower minimum rate of foaming at this mixing rate. Although at low mixing rate the time to increase the temperature is shorter, one must consider that a higher mixing rate is better than a lower mixing rate in terms of heat transfer. Influence of the Rate on Foaming. Figure 5 shows the rate of reaction versus time at 75 and 300 rpm of the optimum temperature profiles. Figure 6 shows that for 500 rpm. The results indicate that, for all mixing rates, the rate at the beginning is higher than the minimum rate of foaming, as shown in Table 4, and the phenomenon has been explained. For the rate profile, the fluctuation in the rate of reaction is due to the increase in the temperature and the decrease in the concentration over time as depicted in Figure 5. For all mixing rates, at first, the rate is higher than the minimum rate of foaming, while the temperature during this interval is constant (Figures 2 and 3); after that, the rate is almost constant nearly to 95% of the minimum rate of foaming. The temperature profile generated can be used to prevent foaming and at the same time satisfy the minimum time required to reach 475 K. Figure 7 shows the concentrations of acid or amine at 75 and 300 rpm mixing rates at the optimum temperature profile. Figure 8 shows those for 500 rpm. It shows that the concentrations decrease with time. The concentration for 500 rpm is higher than those at the other mixing rates, and this is due to the low
Ind. Eng. Chem. Res., Vol. 43, No. 19, 2004 6053
Figure 6. Rate of reaction over time for different mixing rates for the optimum temperature profile for 500 rpm: (b) experimental data.
tion profiles, the experimental data are in good agreement with the calculated optimum as shown in Figures 6-8. In comparison to noncatalytic profiles obtained in previous work,11 the duration of foaming using catalyst under the same conditions is longer and the minimum rate of foaming is lower. Besides, foaming will occur even at low mixing rate and low temperatures, this is attributed to the increase in the rate of reaction due to the presence of catalyst. In addition, the temperature profile using catalyst at the same conditions is longer due to the lower minimum rate of foaming. Generally, it can be concluded that the addition of catalyst to the reaction will cause foaming to last longer. At a fixed temperature, the viscosity increases with increasing time because the molecular weight increases with increasing time (predictable from the kinetic model11); the increase is not considerable especially at the beginning when foaming takes place. For other fatty polyamides such as reactive fatty polyamides, the reaction rate constants are different, so the results for verifying foaming should be different, and a new comprehensive experiment is needed but a similar procedure can be used. Conclusions
Figure 7. Concentration of acid or amine over time at different mixing rates for the optimum temperature profiles for 75 [(9) experimental data] and 300 rpm [(2) experimental data].
An optimization study on the polymerization of fatty polyamides and the effects of the mixing rate and temperature on foaming using a catalyst was performed. The optimal temperature trajectory was obtained using MATLAB software. The process constraints (heating rate and foaming) were considered and treated in the numerical study. It is found that with an increase in the mixing rate, foaming will start at lower temperatures and, with a decrease in the mixing rate, foaming will only occur at high temperatures. The minimum rate of foaming obtained for different temperatures at a fixed mixing rate decreases with an increase in the mixing rate; this minimum rate was used to obtain the optimum temperature profile for a variable-temperature reaction. The induction of catalyst has increased the duration of foaming and reduced the minimum rate of foaming. In addition, the catalytic reaction temperature profile takes longer as compared to the noncatalytic reaction. The obtained temperature profiles were verified experimentally, and the results show that no foaming takes place. Acknowledgment We thank Malaysian Technical Corporation Program for financial help.
Figure 8. Concentration of acid or amine over time at different mixing rates for the optimum temperature profile for 500 rpm: (b) experimental data.
minimum rate of foaming. For the same reason as that at 300 rpm, the concentration is higher than that at 75 rpm. The optimum temperature profiles were verified experimentally; no foaming occurred within the temperature profiles except for the first 2 min at 300 and 500 rpm as expected because at 405 K, as can be seen from Table 4, at 300 and 500 rpm foamings do take place. The start of the temperature profile from 405 K is due to industrial practice. For the rate and concentra-
Nomenclature AE ) frequency factor (kg mol-1 min-1) A, B, C, D, E ) empirical parameters12 Ci ) concentration (mol kg-1) EaE ) activation energy (kJ mol-1) k ) rate constant (kg mol-1 min-1) r ) generation rate of a functional group (mol kg-1 min-1) rmin ) minimum rate at which foaming ends (mol kg-1 min-1) t ) time (min) T ) temperature (K) U ) upper conditions of the rate of temperature increase in eq 5
6054 Ind. Eng. Chem. Res., Vol. 43, No. 19, 2004 Abbreviations COOH ) carboxylic acid NH ) amine H2O ) water CONH ) amide of amine and carboxylic acid
Literature Cited (1) Xiao, D. F.; Yulin, D.; John, W.; Peter, P. Synthesis and characterization of polyamide resins from soy-based dimer acids and different amines. J. Appl. Polym. Sci. 1998, 68, 305. (2) Parker, D. W. U.S. Patent 5,455,326, 1995. (3) David, W. P. Ink-jet printing compositions. U.S. Patent 5,455,326, 1995. (4) Clive, H. H. Foaming and defoaming. JPCL 2001, 18 (6), 63. (5) Joonho, S.; Yunghyo, L.; Sunwon, P. Optimization of prepolymerization step of polyethylene terephthalate (PET) production in a semi-batch reactor. Chem. Eng. J. 1999, 75, 47. (6) James, H. H.; Chang, D. H. A study of bubble nucleation in a mixture of molten polymer and volatid in a shear flow field. Polym. Eng. Sci. 1988, 28, 1616. (7) Don, E. F.; Robbinsdale, D. W. G.; St. Minn, P. Polyamides of improved solubility from polyalkylene polyamines, hydroxy
monocarboxylic acid, and hydrocarbon polymeric fat acids. U.S. Patent 3,224,893, 1965. (8) John, C. C.; Lee, B. F.; Howard, M. T.; Peoria, P.; Urbana, S. S. Polyamides from polymeric fat acids. U.S. Patent 2,450,940, 1948. (9) Paul, D. W.; Anne, E. S. Polymeric fat acid polyamide resins for use in flexographic ink vehicles having reduced solvent emissions. U.S. Patent 4,508,868, 1985. (10) Malcom, M. R.; Haold, W.; Niles, K. Paper containing polyamide resins and process of producing same. U.S. Patent 2,767,089, 1956. (11) Javad, H.; Nayef, M. G.; Wan, M. A. W. D. Effect of temperature and mixing rate on foaming in polymerization reaction to produce fatty polyamides. Chem. Eng. Sci. 2003, submitted for publication. (12) Javad, H.; Nayef, M. G.; Wan, M. A. W. D. Study on Kinetic of Polymerization of Dimer Fatty Acids with Ethylenediamine. J. Appl. Polym. Sci. 2003, in press.
Received for review October 20, 2003 Revised manuscript received May 29, 2004 Accepted May 29, 2004 IE030779W
