Ind. Eng. Chem. Prod. Res. Dev. 1980, 19, 107-111
107
New Rubber Peptizers and Coatings Derived from Guayule Resin (Parthenium argentatum Gray) Hector Belmares,' Laura L. Jlmener, and Martha Ortega Centro de Investigacion en Quimica Aplicada, Aldama Ute. 37 1, Saltillo, Coahuila, Mexico
Guayule resin is a byproduct of guayule rubber extraction and its commercial utilization could affect favorably the economics of guayule rubber production. A physical and chemical characterization of the resin has been made and degrading effects upon the rubber determined by viscometry, showing that the resin is a rubber prooxidant. This fact could be important in the field of rubber processing aids (peptizers). Coatings based on guayule resin have been developed which compare favorably in properties (abrasion resistance, gloss, drying time, and water resistance) to a commercial product used as control. A brief summary of the literature survey regarding the resin of guayule is also presented in this paper.
Introduction The Governments of Mexico and the United States are individually and cooperatively planning and instituting programs in two important areas. The first involves the systematic assessment of indigenous plant species for economically useful raw materials and the second involves actions to combat the destruction or desertification of these vast land areas. The role of research and development, economic analysis, and modeling in the management and utilization of renewable natural resources cannot be overemphasized. A relatively small area (50000 square miles) of the Chihuahua dessert has been chosen for our studies. T h e area is rich in naturally growing vegetable resources such as creosote bush (Larrea tridentata), candelilla (Euphorbia antisyphilitica), fiber producing plants (Agaue lechuguilla, Yucca carnerosana), and to some extent guayule (Parthenium argentatum Gray). Present research or the characterization, polymerization, and possible industrialization of creosote bush resin has been published (Belmares et al., 1979a,b,c). The research and development on the quality improvement of candelilla wax and natural fibers has also been published (Belmares et al., 1979c,d,e). Additional work on natural fibers for composite materials is being carried out in cooperation with UNIDO (United Nations Industrial Development Organization). Since 1974 guayule rubber has been studied in our laboratories and its extraction in our pilot plant. It has been shown to have a n all-cis-stereochemistry being equal in this regard to hevea rubber. The naturally growing guayule shrub contains about 10% rubber and 12% resin (dry weight basis)(Campos-Lopez e t al., 1979). Part of the total shrub resin content is obtained as a byproduct in the pilot plant extraction of the rubber (250 kg of resinlton of extracted rubber). Perhaps more than any other factor, the commercial utilization of the byproducts of guayule rubber extraction could affect the economics of guayule rubber production (National Academy of Sciences, 1977). In regard to the chemical composition of guayule resin, its volatile fraction (obtained by steam distillation) has been reported to contain from 3 to 5% terpenes such as a- and 0-pinenes, dipentene, and cadinene, while the nonvolatile fraction has been reported to contain partheniols and their cinnamate esters, fatty acids (as triglycerides) such as linoleic, linolenic, oleic, and palmitic acids, low molecular weight rubber, high molecular weight alcohols, carotenoids, free trans-cinnamic acid, guayulin A, and guayulin B (National Academy of Sciences, 1977; 0196-4321/80/1219-0107$01 .OO/O
Romo et al., 1970; Dorado, 1962; Banigan and Meeks, 1953; Haagen-Smit and Fong, 1948). Pertinent patents related to the composition of guayule resin and the isolation of fatty acids and parthenyl cinnamate are published by Meeks et al. (1951) and Meeks and Banigan (1956). A process for deresinating guayule rubber has also been patented (Clark, 1952). Figure 1 shows the chemical structures for some of the compounds found in guayule resin. In the field of industrial applications for the resin of guayule, the literature does not report any significant studies limiting their scope to report general observations of the possible degrading effects and the lowering of the mechanical properties caused by the resin upon guayule rubber (Morris et al., 1942a,b, 1943; Hauser and le Beau, 1942, 1943a,b; Place and Clark, 1945, 1946). Experimental Section Resin Obtainment. For the pilot plant extraction of the rubber we utilized the guayule shrubs that grow naturally in and around the State of Coahuila, Mexico. The resin was obtained from the deresination step of the rubber which is effected with acetone in the pilot plant. Before deresination, the rubber contains about 25% resin and small amounts of foreign solid materials. T o reach this point, the guayule shrub had to be defoliated, ground, treated with diluted sodium hydroxide, floated, washed, and then the rubber-rich mass was passed to deresination. As additional information, after the deresination step, the rubber was dissolved in hexane, filtered, and the recovered rubber (after elimination of the solvent) constituted the ordinary rubber production of the pilot plant (CamposLopez et al., 1979). For purposes of characterization we also extracted guayule resin directly by Soxhlet extraction with acetone (4 h) from the defoliated and ground shrub. For both types of resins, their acetone solution was filtered to remove any foreign solid material and the solvent was evaporated in a rotary evaporator and then under vacuum a t 45 "C for a t least 24 h. Equipment and Test Methods. The proton NMR spectra were taken in a Varian EM-360 spectrometer with 0.5% tetramethylsilane as an internal reference. The differential scanning calorimetry (DSC) studies were performed with a Dupont 990 calorimeter calibrated with indium and tin to ensure the accuracy of caloric data. Due to the relatively high viscosity of the resin a t room temperature, the resin was heated a t 60 "C and then an average sample size of ca. 2.0 mg was transferred to the 1980 American Chemical Society
108
Ind. Eng. Chem. Prod. Res. Dev., Vol. 19, No. 1, 1980 Table I. Iodine Values (Wijs Method) for Guayule Resins and Their Volatile Fraction part heni o 1 s
Ddrtbenyl c i v a r r a t c
cadinene
dipentene
@-pinene
f i - Jinene
Figure 1. Some of the compounds reportedly found in guayule resin.
calorimeter pan. Once in the pan, the sample was then carefully placed in the calorimeter cell, which was previously cooled down to about -40 "C. Then the cell was heated at a rate of 10 OC/min and the corresponding DSC graph was obtained. Three runs were made for each sample of resin in both oxygen and nitrogen. The saponification equivalent (56 100 divided by the saponification value), the acid value, and the iodine value (Wijs method) for the guayule resin were determined by standard laboratory techniques (Gardner and Sward, 1972a). Each value represents the average of eight individual determinations. The guayule resin samples destined for coating applications were prepared under the conditions specified in the following section but in each case chloroform was added after the sample was prepared to bring down the viscosity, although acetone, methyl ethyl ketone or any other appropriate solvent is equally suitable. Usually 50% solutions (by weight) are satisfactory. Three coatings were applied to plywood pieces (15 X 10 cm) that had been sanded smooth with sandpaper no. 000 followed by silicon carbide waterproof paper no. 400. Each coating was about 20 to 30 pm thick and was applied every 24 h, the drying time being recorded for each application (Payne, 1954a) (ASTM Method D1640). About 72 h after the application of the third coating we determined the water resistance of the sample by immersing it in water a t room temperature for 48 h (Payne, 1954a). A good water-resistant sample is obtained when it does not suffer change or if it whitens somewhat but returns gradually to its original appearance after being removed from the water. In a separate identical sample the abrasion resistance was also determined. Two replicas were run for each sample. The abrasion resistance of the coatings was determined with a Gardner abrader (Gardner and Sward, 1972a) Model WG-2000 provided with a hog bristle brush WG-2000-B. In this abrader one complete oscillation (one cycle) is equal to two strokes, performed at a fixed rate of approximately 37 oscillations (74 strokes) per minute. The specimen tested was removed after 6500 oscillations (13 000 strokes) and then visually examined and its damage (if any) determined against a previously established scale. In this scale N.D. corresponds to no damage; S.D. to slight damage; D to damaged; H.D. to heavily damaged. Regarding their initial appearance, the samples were classified as glossy (G) or nonglossy (N.G.). The control was the commercial product Glid-Tone, a fast drying, clear coating for wood, made by Glidden Coatings of Mexico, subsidiary of Glidden Coatings and Resins, Cleveland, Ohio. (Mention of a product by us does not imply approval or recommendation of it.) The viscosity determinations were made by the use of the Gardner-Holdt bubble viscometer Cat. VG-7375 (ASTM Method D1545). Viscosities were determined a t 25 "C for the rubber solutions (2.692 g of pilot plant rubber/ 100 mL chloroform). For the rubber-resin com-
sample
iodine value
density, g/mL
shrub resin pilot plant resin volatile fraction of shrub resin volatile fraction of pilot plant resin pilot plant resin without volatile fraction
110-116 140-1 50 230-235
0.928 a t 2 3 " C
240-245
0.870 at 27 " C
125-135
Table 11. Comparison of Some Chemical Properties of Guayule Resins
I, value sample
sapon equiv
shrub resin pilot plant resin
550 970
sapon matter, acid 7% value 25.1 10
22 5
of unsapon matter 118 127
positions the solutions contain 2.692 g of pilot plant rubber and 2.692 g of pilot plant resin, both in 100 mL of chloroform. The experiments were carried out in the absence of light. The pilot plant rubber production usually contains from 2 to 4% resin. No efforts were made to reduce the guayule resin initial color since its color did not interfere with the coatings appearance to this point. If a lightening of the color is desired, available standard techniques are recommended (Payne, 1954b). The linseed oil used for the coating formulations was a nonboiled commercial product and was used without further preparation. Results and Discussion Characterization of Guayule Resin. Table I shows the iodine values for the resin extracted directly from the guayule shrub (shrub resin) and for the resin obtained in the pilot plant in the rubber deresination step (pilot plant resin). Both resins contain 2 to 4% volatile fraction (obtained by steam distillation) with iodine values also shown in Table I. The iodine value for the pilot plant resin compares favorably with the iodine values for the common drying and semidrying oils such as dehydrated castor, 135; fish, 158; linseed, 180; rapeseed, 127; safflower, 145; soybean, 135; sunflower, 135; tung, 170; cottonseed, 105; (Gardner and Sward, 1972b). In our laboratories, recent gas-liquid chromatography studies (of fatty acid methyl esters) have shown that the guayule resin extracted directly from the ground shrub (15% resin, dry weight basis) contains a 22.8% fatty acids (present as triglycerides) and 2.3% trans-cinnamic acid (present mostly as parthenyl cinnamate). Thus, the total of saponifiable matter is 25.1% of the shrub resin and its fatty acid composition is: linoleic, 64.3%; linolenic, 14.6%; oleic, 10%; palmitic, 9.7%; stearic, 1.3%; miristic, traces; and araquidic, traces (Maldonado-Garcia, 1977). However, for the resin obtained from the pilot plant, the saponifiable matter content was lowered to l o % , apparently due to the sodium hydroxide treatment that is given to the ground shrub in the early parts of the process. Similar trends occur for the acid values and the saponification values of both resins. The results are summarized in Table 11. Tables 111 and IV show the results obtained by differential scanning calorimetry (DSC) for the shrub resin and the pilot plant resin. The pilot plant resin appears to be the most stable to oxidation since its first oxidation exotherm has a maximum a t 288 "C while the shrub resin has it a t 183.5 "C. Under nitrogen, both resins present a
Ind. Eng. Chem. Prod. Res. Dev., Vol. 19, No. 1, 1980
10
9
8
7
PPm
Table 111. Guayule Resins. Differential Scanning Calorimetry Analysis in Oxygen
1st exotherm,' sample
"C
2nd exotherm,= "C
shrub resin pilot plant res:n
184 288
296 none
Exotherm maximum. The exotherms start a t 1 2 6 and 1 3 8 " C for the shrub resin and the pilot plant resin, respectively, DSC Analysis of Guayule Resins in Nitrogen 1:it entlotheriqU
sample shrub resin pilot plant resin
c
r,
I&,
2 2
" Endotherm minimum.
5
4
3
2
1
0
PPm
Figure 2. Proton NMR spectrum of guayule resin extracted directly from ground guayule shrub. Solvent: CDC13/Me2S0 (Me4Si as standard).
Table IV.
6
109
2nd endotherm,a 'C
18 11
3rd endotherm,= "C
exotherm,b "C
49 none
8 7
Exotherm maximum.
complex thermal profile due to the large number of compounds present. The proton NMR spectra for both resins are shown in Figures 2 and 3. Prooxidant Activity of t h e Guayule Resin. The pilot plant resin was tested for prooxidant activity toward the guayule rubber. Table V shows the degrading effect that the resin has upon the rubber and also shows that the pilot plant rubber production with 2-4% resin is stable under these conditions. On the other hand, the presence of a strong antioxidant such as Larrea resin (Belmares et al., 1979a) inhibits the prooxidant activity of guayule resin (from Table V). Of special industrial interest for the production of rubber goods are the compounds called prooxidants or peptizers (Mayo et al., 1968) which ordinarily are synthetic products and generally toxic. In view of the results presented in Table V, guayule resin (or possibly a selected fraction of it) is a potentially useful prooxidant for polyisoprene with the added advantage that it is also a natural product. Development of Coatings from t h e Guayule Resin. Four variables have been chosen to screen and evaluate
Figure 3. Proton NMR spectrum of guayule resin obtained from the deresination step of the pilot plant. Solvent: CDC13 (Me4Sias standard).
the coatings. The variables are abrasion resistance, drying time, water resistance, and appearance (gloss and color). They show some dependence on each other but are relatively independent of the different resin lots from the pilot plant even when there were some slight changes in the overall rubber extraction process. Table VI shows that cobalt naphthenate (drying agent, 0.5% Co based on metal) gives an acceptable drying time, abrasion resistance, and appearance comparable to the commercial sample used as a control. The incorporation of methyl ethyl ketone peroxide and cobalt naphthenate (a combination used for the polymerization of unsaturated polyester resins) in the coating formulation increased the drying time and decreased the abrasion resistance of the coatings. Table VI also shows that thermal pretreatment of the guayule resin (a normal procedure for linseed oil in coating applications) increases the drying time of the coatings, which is the opposite of what ordinarily happens to linseed oil based compositions subjected to the same thermal pretreatment. None of the samples (except the control) has good water resistance because they become irreversibly white after the water testing treatment. Additionally when the amount of the sole drying agent cobalt naphthenate was doubled (1% Co based on metal), the drying time or the water resistance of the coatings did not change significantly. For another formulation, the proportion of triglycerides in the guayule resin was increased by adding 20% (by weight) of unboiled (no thermal pretreatment) linseed oil. In Table VI1 are given the results obtained after applying different thermal pretreatments to the mentioned formulation. The coating drying time goes through a minimum when the mix is thermally pretreated at 89 "C. Note that only the samples 150 and 151 showed good water resistance. In order to find alternate formulations with acceptable physical properties, we experimented with drying agents based on combinations of cobalt and lead salts that reputedly yield coatings of good water resistance (Klebsattel, 1948; Witharn, 1948; Anderson, 1947). Table VI11 shows the physical properties of a formulation of guayule resin/
Table V. Viscometry Determination of t h e Effect of Guayule Resin upon Guayule Rubber
-
air blanket; time, h -
sample" pilot plant rubber pilot plant rubber with guayule resin pilot plant ruliber. guayule resin, and a strong antioxidant (Larrea resinb
0 130 100
24 125
112
nitrogen hlanket; time, h
-iu
48 125 70
72 130 40
96 130 32
120 130 6
0 130 100
24 130 7.5
48 130 75
72 150 40
96 165
13
120 182 1
100
100
75
75
58
112
112
112
100
75
40
a Viscosity is given i n centistokes f o r the chloroform solutions a t 2 5 ' C. g i l 0 0 mL.
The antioxidant is a t a concentration of 0.307
110
Ind. Eng. Chem. Prod. Res. Dev., Vol. 19, No. 1, 1980
Table VI. Physical Properties of Formulations with Guayule Resin, Cobalt Naphthenate, and MEK Peroxide a t Different Thermal Pretreatments concn, % MEK sample no.
Table VIII. Physical Properties of the Formulation Comprising Guayule Resin/Linseed Oil 8 0 :20 with Cobalt and Lead Salts (0.04% Co and 0.6% Pb based on Metal) at Different Thermal Pretreatmentsa
drying time, min
drying time, min
per1st 2nd 3rd abr appearCo oxide applnb appln appln resa ancea
control
sample n0.b
1st appln
2nd appln
3rd appln
abrasion resistance
appearance
N.D.
G
control
N.D.
G
76, 77 90,93
Pretreatment: 8 9 ° C for 1 0 min 0.5 0.0 66 65 8 5 N.D. 0.5 1.0 105 117 135 D
G G
Pretreatment: 1 6 6 C for 10 rnin 148, 1 4 9 116 235 222 N.D.
G
28, 6 5 64,66
Pretreatment: 8 9 C for 50 min 0 . 5 0.0 71 76 1 1 5 N.D. 0.5 1.0 125 135 107 D
G G
Pretreatment: 1 6 6 O C for 50 rnin 144, 1 4 5 126 245 259 N.D.
G
70, 7 9 78,91
Pretreatment: 1 3 0 ° C for 30 rnin 0.5 0.0 85 85 100 N.D. 0 . 5 1.0 175 170 130 D
G G
Pretreatment: 200 ' C for 30 min 1 4 6 , 147 148 225 222 N.D.
G
Pretreatment: 225 " C for 10 rnin 188, 1 8 9 145 215 355 N.D.
G
Pretreatment: 2 2 5 ° C for 50 rnin 142, 143 145 215 215 N.D.
G
35
54
55
Pretreatment: 1 6 6 ' C for 1 0 rnin 1 2 4 , 1 2 7 0 . 5 0.0 128 1 0 8 1 0 0 N.D.
G
Pretreatment: 1 6 6 C for 50 rnin 0.5 0.0 130 1 6 0 1 7 5 N.D. 0.5 1.0 105 210 145 D
G G
95,96 90, 100
35
54
55
a The combined linseed oil, lead, and cobalt salts are
abr res = abrasion resistance; N.D., n o damaged; D, damaged; G, glossy. appln = application.
subjected t o the thermal pretreatment indicated in this table and then the guayule resin is added t o the pretreated mix a t room temperature. All the samples listed in this table showed a good water resistance.
Table VII. Physical Properties of the Formulation Comprising Guayule Resin/Linseed Oil 80:20 with Gobalt Naphthenate (0.5% Co Based o n Metal) at Different Thermal Pretreatments
Table IX. Physical Properties of the Formulation Guayule ResiniLinseed Oil 8 0 : 2 0 with Cobalt and Lead Salts a t Different Content Ratiosa,
a
drying time, min sample no. control
1st 2nd appln appln 35
54
3rd appln 55
abrasion resis- appear, tance ance
N.D.
G
N.D.
G
Pretreatment: None
150, 151a
135
165
195
Pretreatment: 8 9 C for 1 0 min 110,111
80
60
90
N.D.
G
Pretreatment: 8 9 " C for 50 min 104, 1 1 9
75
65
80
N.D.
G
Pretreatment: 1 3 0 " C for 50 rnin
G
117, 118 108 137 140 N.D. Pretreatment: 1 6 6 ° C for 1 0 rnin 122,123 120 133 120 N.D.
G
Pretreatment: 1 6 6 C for 50 rnin 120, 1 2 1 120 125 90 N.D.
G
a These t w o samples showed good water resistance.
linseed oil 80/20 (by weight) with 0.04% Co and 0.6% lead. All the samples showed good water resistance, although the drying time required for coatings is larger than for cobalt-based formulations. Note that guayule resin is incorporated a t room temperature to avoid any possible additional lengthening of coating drying time (see Table VI). From additional experiments with different Pb/Co ratios, the water and the abrasion resistance of the coatings were good when the Co concentration was kept below 0.08%. For higher Co concentrations the water resistance was poor. The results are shown in Table IX. Finally, the samples with good water resistance (from Tables VI1 to IX) also showed good abrasion resistance (N.D.) when tested a t 100% relative humidity a t room temperature.
sample no. control 1 6 1 , 162' 163, 1 6 4 165, 1 6 6 167, 1 6 8
metal content, %
Co
Pb
0.05 0.08 0.3 0.6
0.6 0.3 0.08 0.05
drying time, min 1st 2nd 3rd abr appearappln appln appln resd ance 35 285 210 145 120
54 245 225 185 135
55 270 240 160 70
N.D. N.D. N.D. N.D. N.D.
G G G G G
a The mix of linseed oil and the lead salt is thermally pretreated a t 1 6 6 " C for 50 min and then cooled down a t room temperature. At this point the guayule resin and the cobalt salt are added t o the mix. The table shows the relative concentrations of lead and cobalt (based on The solvent metal) obtained from the respective salts. used for application o f the coatings was a mix of chloroform and methanol (1:l by volume). These t w o samples showed good water resistance. Abrasion resistance.
Acknowledgment We thank the Consejo Nacional de Ciencia y Tecnologia (CONACYT), the Comision Nacional de Zonas Aridas (CONAZA), and the Centro de Investigacion en Quimica Aplicada (CIQA) for the grants that supported this work. Literature Cited Anderson, L. E. Paint Varn. Prcd. Manager, 1947, 27(7), 178. Banigan, T F.; Meeks, J. W. J . Am. Chem. SOC.1953, 75, 3829. Beimares, H.: Barrera, A,; Castillo, E.; Ramos, L. F.; Hernandez, F.; Hernandez, V. Ind. Eng. Chem. Prod'. Res. Dev. 1070a, 18, 220. Belmares, H.; Barrera, A. J . Appl. Polym. Sci. 1070b, 24, 1531. Beimares. H.:Barrera, A,; Hernandez, F.; Castliio, E.; Gonzaiez, V.; Jimenez, L. L.; Motomochi, B. "Las Zonas Aridas como una Fuente de Materias Primas Organicas" in "Recursos Vegetales de Importancia para el Desarrollo de las Zonas Aridas", CONACYT (National Councli for Science and Technology): Mexico, D.F.. 1979c; in press. Belmares, H.; Castillo, E.; Barrera, A. Textile Res. J. 1079d, 49, 619. Belmares. H.:Barrera. A,: Castillo. E.: Moniaras, M.: Tristan, J. M. E. Inferciencia, 19798, 4 ( 6 ) , 320. Campos-Lopez, E.; NeavezCamacho, E.: Ponce-Velez, M. A,; AngubSanchez, J. L. CHEMTECH, 1979, 9 , 50. Clark. F. E. (to United States of America as represented by the Secretary of Agriculture), U.S. Patent 2618 670 (Nov 18, 1952). Dorado, E. B. Chim. Ind. 1962, 87(5),617. Gardner, H.; Sward, G. "Paint Testing Manual. Physical and Chemical Examination of Paints, Varnishes, Lacquers and Colors", ASTM Special Technical
Ind. Eng. Chem. Prod.
Res.
Publication 500, 13th ed; The American Society for Testing and Materials: Philadelphia, Pa., 1972a; Chapters 2.3 and 5.2. Haagen-Smit, A. J.; Fong, C. T. 0. J . A m . Chem. SOC. 1948, 70, 2075. Gardner, H.; Sward, G. "Paint Testing Manual. Physical and Chemical Examination of Paints, Varnishes, Lacquers and Colors", ASTM Special Technical Publication 500, 13th ed; The American Society for Testing and Materials: Philadelphia, Pa., 1972b; Chapter 2.1. Hauser, E. A.; le Beau, D. S. India Rubber World, 1942, 106(5),447. Hauser, E. A.; le Beau, D. S. India Rubber World, 1943a, 107, 568. Hauser. E. A.: le Beau. D. S. India Rubber WorM. 1943b. 108. 37. Klebsanel, C:A. Paint'Varn. Prod. Manager, 1948, 28(11), 332. Mayo, F. R.; Egger, K.; Irwin, K. C. Rubber Chem. Techno/. 1988, 4 7, 271. MaMonad*Garcia, R., Report to the Program CONAZA (National Commission of Arid Lands, MexicohCONACYT (National Council for Science and Technology, Mexico), 1977; Chapter 4. Meeks, J. W.; Banigan, T. F. (to United States of America as represented by the Secretary of Agriculture), U S . Patent 2 744 125 (May 1, 1956). Meeks, J. W.; Banigan, T. F.; Planck, R. W. (to United States of America as represented by the Secretary of Agicutture), US. Patent 2 572046 (Oct 23, 1951). Morris, R. E.; James, R.R.; Werkenthin, T. A. India Rubber World, 1942a, 705(6). 565. Morris, R. E.; James, R. R.; Werkenthin, T. A. India Rubber World, 1942b, 707(5). 31.
D e v . 1980, 19, 111-116
111
Morris, R. E.; James, R. R.; Werkenthin, T. A. India Rubber World, 1943, 107(5). 463. National Academy of Sciences, "Guayule: An Alternative Source of Natural Rubber", Contract No. K51 C14200978 for the Bureau of Indian Affairs (Department of the Interior): Washington, D.C., 1977; Chapter 9. Payne, H. F. "Organic Coating Technology", Vol. 1; Wiley: New York, 1954a; pp 640, 653. Payne, H. F. "Organic Coating Technology". Vol. 1; Wiley: New York, 1954b; p 65. Place, W. F. L.; Clark, F. E. India Rubber World, 1945, 67. Place, W. F. L.; Clark, F. E. India Rubber WorM. 1946, 370. Romo, J.; Romo de Vivar, A.; Ortega, A.; Diaz, E . Rev. Latinoam. Quim. 1970, 1 , 132. Witharn, F. Paint Varn. Prod. Manager, 1948, 28(7), 195.
Received for review September 4, 1979 Accepted October 30, 1979 A preliminary part of this work entitled, "Resin of Guayule. Characterization and Possible Industrial Use", was presented at the International Symposium on Guayule held in Saltillo, Coahuila, Mexico, Aug 1977.
Novel Alkanecarboxylic Acids via the Koch Reaction. A Route To Replace Isostearic Acid Johann G. D. Schulz, Anatoli Onopchenko," and Robert J. Hartle Gulf Research d Development Company, Chemicals and Minerals Division, Pittsburgh, Pennsylvania
15230
Optimum conditions were developed for the synthesis of Cj9 to C25alkanecarboxylic acids via the Koch reaction. For many applications these new products can replace isostearic acid, which has been in uncertain and fluctuating supply.
Introduction Isostearic acid, a byproduct from the dimerization of tall oil t o produce unsaturated dimer acids, is used commercially in the preparation of lubricants, pharmaceuticals, cosmetics, and functional fluids. Its excellent properties, particularly its liquidity a t ambient temperature, demand a premium in cost over the less useful solid n-stearic acid. Availability of isostearic acid and consequently its cost are linked to the production of dimer acids. For this reason, we became interested in developing a synthetic product, independent of the dimer acid market, which could replace isostearic acid. The process chosen involves the Koch reaction (Koch, 1955) which provides an inexpensive and convenient route from olefins to acids having one more carbon atom than the feed. These acids have branched chains which should lend desired liquidity to the product. T h e Koch reaction essentially involves carbonylation of an olefinic double bond, catalyzed by a large excess of a strong acid which must act both as a protonating agent and solvent. Hydrolysis of the resulting intermediate affords the final product. (See eq 1-3.) While this reaction has been practiced with olefins up to C12,no work was reported with olefins in the range of CIBand higher. E x p e r i m e n t a l Section A p p a r a t u s a n d Analytical. Carbonylations were carried out in a 1-L 316 stainless steel magnetically stirred autoclave (Autoclave Engineers, Inc., Erie, Pa.). The autoclave was equipped with a cooling coil and was connected to a cylinder of CO as well as temperature and pressure 0196-4321/80/ 1219-01 11$01.OO/O
CqHg -CH=CH2
+ H+
CqHg -CH-CH3
+
-
-C=O+
C4Hg -&H-CH3
(11
C4Hg -CH-CH3
--cCqHg
I
+
(2)
f+ 0 + H20
--C
CqHg-CH-CH3 i
+ H+
(31
COOH
(+ ISOMERS)
controllers and recording instruments. Olefins were introduced into the autoclave through the top using Milroy pumps. With solid olefins, Cm (mp 28.5 "C) and C, Jmp 42-44 "C), the addition lines were traced with steam lines. The NMR spectra were obtained on a Varian T-60 spectrometer (CC14,Me4%). Chemical shifts are in 6 units, in parts per million. IR spectra were recorded on a PerkinElmer Model 237 spectrometer. Product acids were analyzed by GLC as the trimethylsilyl derivatives on a 2.5 ft X 1/8-in.,3% OV-1 column, programmed from 100 to 250 "C a t 4 "C/min. 2,2-Dimethylpentanoic and 3-methyl-3ethylbutanoic acids as well as 2,2-dimethylheptanoic and 3-methyl-3-ethylhexanoic acids were separated on a capillary carbowax column. Olefins used were commercial samples. The carbon number distribution of internal C18 olefin was: C12,0.3%; C13,1.1%; C14, 1.2%; C15,2.3%; C16,
0 1980 American Chemical Society
