FEBRUARI-, 1940
INDUSTRIAL AND ENGINEERING CHEMISTRY
Fieser and Campbell. J . Am. Chem. Soc., 60, 159 (1938). Fleck and Palkin, Ibid., 59, 1593 (1937). Ibid., 60, 921 (1938). Ibid., 61, 247 (1939). (16) Fonrobert, Chem. rmschau Fetfe, o l e , n‘achse Ilarze, 36, 373 (1929). Fonrobert and Pallauf, Farben-Ztg., 31, 1848-9 (1926). Hasselstrom and Bogert, J . Am. Chem. SOC.,57, 2118 (1935). Haworth, J . Chem. SOC.,1932, 2717-19. Kesler, Lowy, and Faraghen, J . Am. Chern. SOC., 49,2898 (1927). Kraft, Ann., 520, 133 (1935). Ibid., 524, 1 (1936). Levy, Ber., 39, 3043 (1906). Littmann, J . Am. Chem. SOC.,60, 1419 (1938). Xiederl and Niederl, “Micromethods of Quantitative Elementary Analysis”, S e w York, John \Tiley & Sons, 1938. Palkin and Harris, J . Am,. Chem. SOC.,56, 1926 (1934).
(12) (13) (14) (15)
219
(27) Peterson, U. S. Patent 2,067,859 (1937). (28) Ruaicka, Andersmit, and Frank, H e h . Chim. Acta, 15, 1289-94 (1932). (29) Ruaicka, Bacon, Lukes, and Rose, Ibid., 21, 683-91 (1938). (30) Ruzicka, Bacon, Steinbach, and Waldemann, Ibid., 21, 591-7 (1938) (31) Rusicka, de Graaff, and (32) Ruzicka, de Graaff, and Miiller, (1933). (35) Sandermann, Ber., 71, 2005 (1938). (36) Vesterberg, Ibid., 36, 4200 (1903). (37) Vocke, Ann., 497, 247 (1932). (38) Wienhaus and Sandermann, Ber., 69B, 2202-6 (1936). PRESENTED before the Division of Paint and Varnish Chemistry at the 97th Meeting of the American Chemical Society, Baltimore, bld.
Effect of Nonvolatile Material on Solvent Balance JOHN B. DORSCH
PLASTICIZERS1 According to previous work, nitrocellulose and nitrocellulose ester gum solutions show considerable hydrocarbon retention in the later stages of evaporation. The effect of plasticizers (dibutyl phthalate and blown castor oil) was studied in this paper. The data indicate that the addition of these plasticizers increases the hydrocarbon retention approximately 20 per cent in the last stages of evaporation. The influence of the following additional factors was investigated: -4 change in the relative humidity from 15 to 65 per cent apparently had no effect. The aging of the solutions for 6 months apparently had no effect. A change in the temperature of the atmosphere during the evaporation from 8-30’ C. apparently had no effect. A change in the total period of evaporation apparently had no effect; in some cases the total period of evaporation was three to five times as long as in other cases. A change in the aging of the ester gum used apparently had no effect. Indications are that for a rigorous comparison of data, the precaution should be taken that each ingredient be a portion of the same sample.
1
A previoua paper i n this series was published in 1938 ( 1 )
Anderson-Prichard Oil Corporation, Chicago, Ill.
HE composition of the solvent-diluent mixture B (toluene, 20 per cent by volume; butyl acetate of 93
T
per cent ester content, 33; butyl alcohol, 12; Troluoil,
35) as described in a previous paper was used ( 2 ); the purity of the components was approximately the same. The types and concentrations of the plasticizers and nonvolatile materials in mixture 13 (sample 9) are shown in Table I. TABLE I. CONSTITUENTS DISSOLVED IN 100 Cc. Sample No. 20 40 41
42
43
Constituent I/a-sec. nitrocellulose 2-sec. nitrocellulose ster gum (R;) l/a-sec. nitrocellulose Ester gum (R7 Dibutyl phthalate a-sea. nitrocellulose ster gum (R;), Blown castor oil I/a-sec. nitrooellulose Eater gum (R;) Medicinal castor oil
x
OF
Grams of Ingredient 6 6 18
MIXTUREB Total Grams 6 24
6 18
3
6 18 3 6 18 5
27 27 29
Variability of Effect of Nonvolatile Materials The compositions of the solutions were determined at various stages of evaporation, following the procedure previously described (1). From these data composition curves were plotted. A comparison of composition curves for the thinner mixture B, based on different samples, shows the degree of accuracy that can be expected in preparing the thinner mixtures, One set of curves was based on data taken from a previous paper (1). The other curves were based on data from Table IIA (Figure 1A). A similar comparison of composition curves was made for nitrocellulose solutions of thinner mixture B (sample 20).
280
IXDIJSTRIAL AND ENGINEERING CHEMI STRY
FIGURE 1. COMPOSITION CURVES
VOL. 32, N O . 2
As in the case above, one set of curves was based on data taken from a previous paper (1). The other set of curves was based on data taken from Table IIB. This comparison is shown in Figure 1B. There is good agreement up to approximately the point where 50 per cent of the thinner mixture remains. Beyond this point a divergence is noted. Comparison of the curves a t the point which represents 25 per cent of the samples unevaporated brings out the following relation: Only one fifth of the quantity of hydrocarbons due to the nitrocellulose is retained by the present sample 20 as compared to the former sample 20. Likewise, a comparison a t the point where only 20 per cent of the thinner mixture remains indicates that about two fifths the quantity of hydrocarbons due to the nitrocellulose is retained as in the former case. This would indicate that the retentions of the hydrocarbons by the new sample 20 are less than by the former sample 20. A similar comparison of composition curves was made for a solution of nitrocellulose and ester gum in mixture B (sample 40). This comparison is shown in Figure lC, and data for the new curves were taken from Table IIC. There is good agreement up to the point where 50 per cent of the thinner mixture remains. A comparison of the curves a t the point which represents 25 per cent of the thinner mixture remaining brings out the following relation: Between 55 to 60 per cent of the quantity of hydrocarbons due to the nitrocellulose and ester gum in the new sample 40 is retained as compared to the quantity of hydrocarbons retained by the previous sample. At the point where only 20 per cent of the thinner remains, 55 per cent of the quantity of hvdrocarbons due to the nitrocellulose and ester gum is retained as compared to the former sample. I
FEBRUARY, 1940
INDUSTRIAL AND ENGINEERING CHEMISTRY
281
Under these conditions good agreement of the data is indiANALYSISOF VOLATILE CONSTITUENTS cated by their proximity to the composition curves. Unless TABLE 11. PERCENTAGE OBTAINED FROM SAMPLES AFTER EVAPORATION these factors cancel one another, variations in the evaporaRemaining -Hydrocarbons--. -ButylEvapotion conditions probably have a negligible effect on solvent after Evapn. Total Aromatic Acetate Alcohol rated balance. A , Sample 9 (Mixture B) 0 24.0 25.0 52.5 52.5 55.0 63.1 68.0 72.5 74.0 76.0 84.5 88.0 89.8 95.0
100 76.0 75.0 47.5 47.5 45.0 36.9 32.0 27.5 26.0 24.0 15.5 12.0 10.5 5.0
0 32.0 34.4 37.1 50.5 59.P 62.5" 74.5 74.6 75,3a 83.0 85.5
100
0 34.8 38.2 48.2 61.4 61.8 67.65 75.9a 76.60 77.3 78.20 78.5a
85.0
100 65.2 61.8 51.8 38.6 38.2 32.4 24.1 23.4 22.7 21.8 21.5 19.9 15.0
0 39.8 50.3 53.3 58.9 65.0 65.5 70.8 72.4 80.5 87.2
100 60.2 49.7 46.7 41.1 35.0 34.5 29.2 27.6 19.5 12.8
0 30.0 37.2 52.7 62.0 65.2 67.75 73.5 73.6 85.5
100 70.0 62.8 47.3 38.0 34.8 32.3 26.5 26.4 14.5
55;O 46.3 46.5 29.2 28.5 27.0 17.5
.
22.2 19.9 20.2 14.6 14.0 13.5
.. ..
8.8
4:s
i:3
0.1 0.0 0.0
.. ..
0.0 0.0 0.0 0.0
30.6 35.8 35.8 46.6 46.4 47.6 50.6 53.2 56.0 56.5 57.5
14.4 17.9 17.7 24.2 24.1 25.4 31.9
..
3617
6014 55.5
39:6 44.5
30.5 39.2 39.8 41.9 46.6 51.8 52.7 56.7 57.0
14.5 19.7 21.0 21.5 24.6 28.0 28.9 36.1 36.2
5612 63.6
35:6 36.1
30.5 39.5 40.0 44.0 50.3 49.2 53.4 57.1 55.4 56.3 57.0 57.6 58.1 58.2
14.5 21.1 21.8 24.1 28.9 28.7 29.7 30.7 30.2 31.7 32.0 30.8 31.5 31.8
30.5 41.9 45.5 46.1 49.0 50.6 52.1 52.4 53.6 54.7 55.8
14.5 20.7 24.7 25.6 27.4 29.2 28.8 30.5 29.9 32.5 33.8
30.5 37.9 40.6 46.9 49.0 51.2 54.0 52.4 53.5 54.5
14.5 19.6 20.9 25.6 28.8 29.2 30.0 29.5 31.6 33.4
30.5 53.8 52.5 53.9
14.5 29.2 29.0 30.9
..* . ..
Effect of Plasticizers All previous work was done without considering the effect of plasticizers. The plasticizers used in this work might be classed in two types, based on the solubility of the petroleum diluent : the solvent type plasticizers-e. g., dibutyl phthalate (sample 41) and medicinal castor oil (sample 43)-and the relatively nonsolvent type plasticizer-e. g., blown castor oil (sample 42). The solubility of Troluoil, the petroleum diluent in these plasticizers, is as follows:
B . Sample 20
80.1"
0
68.0 65.6 62.9 49.5 40.2 37.5 25.5 25.4 24.7 17.0 14.5
0 100 31.1 68.ga 69.4" 30.6 74 na 26.0 See Table 111.
55.0 22.2 41.1 19.5 39.2 18.7 36.6 18.2 28.8 14.8 21.2 11.7 18.4 10.8 7.2 4.3 6.8 3.8 6.6 3.6 2.2 1.2 0.0 0.3 C. Sample 40 55 0 22.2 39 4 20.0 38.2 18.9 31.9 16.7 20.8 10.9 22.1 11.7 17.1 9.4 12.2 6.9 14.4 7.8 12.0 5.9 11.0 5.9 11.6 6.4 10.4 5.4 10.0 5.0 D. Sample41 55.0 22.2 37.4 18.3 29.8 15.7 28.3 15.1 23.6 13.0 20.2 11.0 19.1 10.3 17.1 8.1 16.5 8.8 12.8 6.5 10.4 4.8 E. Sample 42 55.0 22.2 42.5 20.0 38.5 18.8 27.5 14.5 22.2 11.6 19.6 10.5 16.0 9.1 18.1 8.9 14.9 7.3 12.1 6.0 F. Sample 43 55.0 22.2 17.0 9.7 18.5 10.4 15.2 8.2
Both the samples of nitrocellulose and ester gum used in this work were from different batches from those used in the previous paper. The ester gum in the previous work had been stored for some time before being put into solution. (According to unpublished data of G. C. Hook, of this laboratory, the solubility of ester gum may be decreased on standing.) From the foregoing it would appear that the variations in the solvent balance noted so far might originate in the group of nonvolatile material.
Effect of Evaporation Conditions Data which are marked in Table I1 were obtained under evaporation conditions that were different from the unmarked data. The variation of these conditions is found in Table 111.
50 Cc. of Plasticizer Dibutyl phthalate Medicinal castor oil Blown oaator oil
-Volume At Z O O C. 1000 135 37
of Troluoil, Cc.Cloud At point 25' C. No 750 Yea 1000 Yea 37
Cloud Point No No Yea
The composition curves from the data of Table IID, obtained in the analysis of sample 41 where dibutyl phthalate is the plasticizer, are given in Figure 1D. For comparison, the curves of sample 40 without a plasticizer are also shown. The two sets of curves are identical up to the point where 40 per cent of the thinner mixture remains. Comparing samples 40 and 41 (without and with plasticizer, respectively) at the point where 25 per cent of the thinner mixture remains brings out the following relation: The retention of the hydrocarbons in the presence of plasticizer is approximately 20 per cent greater than in the absence of plasticizer as indicated in Figure 1D. At the point where only 20 per cent of the thinner mixture remains, this retention increases to approximately 30 per cent. Beyond the 40 per cent point the divergence is such that a greater retention of hydrocarbons is noted for the curves of sample 41, apparently a t the expense of the butyl acetate. The differences in the butyl alcohol are the least. TABLE 111. VARIABILITY OF EVAPORATION CONDITIONS Relative humidity, % Aging of solution Temperature, C.. Relative evaporation rate
Data Marked5 Unmarked Data 15-30 55-65 6 mo. Relatively fresh 8-30 24-26 3-5 times the length of time of corresponding unmarked data
The composition curves plotted from the data of Table IIE, obtained in the analysis of sample 42, where blown castor oil is the plasticizer are found in Figure 1E. For comparison, the curves of sample 40 without a plasticizer are also given. Likewise Figure 1F shows a comparison of the composition curves plotted from the data of Table IIF, obtained in the analysis of sample 43 where medicinal castor oil is the plasticizer, to the composition curves of sample 40. Figure 1G compares the composition curves of samples 41, 42, and 43 where dibutyl phthalate, blown castor oil, and medicinal castor oil are the plasticizers, respectively. The curves for all three of these samples show little or no difference.
Conclusions 1. The variation in characteristics of the nonvolatile materials due to age or other conditions may affect the solvent balance. 2. The variability of physical conditions during evaporation appear to have little effect on the solvent balance. 3. The effect of the plasticizers observed appears to cause a greater retention of hydrocarbons. 4. The types of plasticizers used apparently had little effect on solvent balance.
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INDUSTRIAL AND ENGINEERING CHEMISTRY
Acknowledgment Grateful acknowledgment is due some of the leading lacquer chemists for to suggestions’ The author is the assistance Of Dunlap and the variOUB members of the staff of this laboratory who rendered and assistance in the work* The author wishes also to thank J. K. Stewart, director of this labora-
VOL. 32, NO. 2
tory for his encouragement, advice, and permission to release the results. Literature Cited (1) Dorsch, J.B., a n d s t e w a r t , J. K., IND. ENQ.CHEM.,30,325 (1938). (2) Stewart, J. K., Dorsch, J. B., and Hopper, C. B., Ibid., 29, 899 (1937). PRESENTED before the Division of Paint and Varnish Chemistry a t the 97th lleeting of the American Chemical Sooiety, Baltimore, &Id.
Colloidal Structure of Rubber in Solution Colloidal Aspects of Vulcanization S. D. GEHMAN AND J. E. FIELD The Goodyear Tire & Rubber Company, Akron, Ohio Colloidal changes in solutions of purified rubber due to a vulcanizing system consisting of piperidinium pentamethylene dithiocarbamate, sulfur, and zinc propionate have been followed by means of measurements of the depolarization and intensity of the transversely scattered light and by viscosity measurements. A study wab made of the time required for vulcanization of benzene solutions of rubber with the above vulcanizing agents. The temperature coefficient of vulcanization was approximately the same as that for cures of solid sfocks. The light scattering results are interpreted as showing that, upon the addition of the vulcanizing
HE work here reported is a continuation of studies T(8,9 on) the colloidal structure of rubber in solution, by means of viscosity measurements and measurements of the intensity and depolarization of the transversely scattered light. The previous papers dealt with reversible colloidal changes. The work has now been extended to cover the irreversible changes which occur when a solution of rubber is gelled or vulcanized by a system of curing agentsnamely, piperidinium pentamethylene dithiocarbamate (P. P. D.), zinc propionate, and sulfur. The advantage of studying the colloidal aspects of vulcanization in solution rather than in solid cures lies in the fact that the colloidal changes are more accessible for direct observation in solution. In a gelled solution, the colloidal structure of the solid rubber may be thought of as existing in an expanded condition, so that in a sense the structure under examination is magnified. Chemical explanations of vulcanization restricted to the rate of sulfur addition and the type of sulfur bonding (3, 11, 19) cannot be expected by themselves to account for the physical properties of the vulcanizates because these properties depend upon the colloidal structure formed during vulcanization. Van Rossem (14) discussed the status of theories of vulcanization and emphasized that a chemical theory should regard vulcanization as a type of polymerization in which a three-dimensional network of primary valence link-
agents to the solutions, the colloidal units become larger. The decrease in viscosity is explained as being due to a diminished “interlocking” of the units. In the vulcanization of the solutions, an equilibrium of colloidal processes occurs which results in a constant viscosity for the larger part of the time required for vulcanization, although the light scattering measurements show a continuous change. The magnitude of the light scattering changes indicates that the molecular clusters in the gelled solution are probably not very different from those in the original solution. The viscosity measurements show that the forces between the clusters have been radically strengthened.
ages is built up between large molecules. Such a structure is essentially colloidal in nature, but van Rossem restricted the use of the word to theories of vulcanization in which soft vulcanized rubber is regarded as a colloidal dispersion of hard rubber. In a broader sense than this greatly restricted historical usage, the vulcanization of rubber should be regarded as a colloidal process initiated by chemical reactions. Furthermore, it appears that the amount of chemical action, by which is meant change in primary valence linkages, required to produce the colloidal changes and affect the physical properties is small (4, 17). Presumably a single cross linkage can tie together more or less effectively entire colloidal units or clusters of molecules instead of just single large molecules, as van Rossem considered the structure to be. The importance of paying more attention to the colloidal aspects of the situation thus becomes apparent. The colloidal nature of the process of vulcanization has not been entirely ignored in fundamental work on vulcanization. Williams (18) made a detailed study of colloidal phenomena in gels of lightly vulcanized rubber. Many instances of vulcanization in solution are reported in the literature. Vulcanization with solutions of sulfur chloride was studied by Garvey (7) and earlier workers. Garvey’s suggestion that a change occurs in the cis-trans relations of the units in the long-chain molecules upon vulcanization with sulfur chloride
