Nonionie, Anionic, and Cationic Emulsifiers in GR-S Polymerizations
T
H E selection of a surface acA. F. HELIN AND J. 31. GYENGE This paper is principally contive agent for an emulsion cerned with the net effect of the Government Laboratories, polymerization system is a difficult surfactant on the rate of polymerUniversity of Akron, Akron, Ohio process which usually has been ization, the stability of the latex solved by trial and error, aided by produced, and the quality of the D. A. BEADELL experience and intelligent observapolymer obtained. Such a compariCommercial Denelopment Department, tion. By this process, fatty acid son of emulsifiers must be made in General Aniline & Film Corp., 435 Hudson St., and rosin acid soaps have been a standardized formulation of the New York, N . Y . established as suitable emulsifiers other chemicals necessary to obtain for the copolymerization of butaacceptable polymerization. J. H. BOYD diene and styrene to produce 250 Park Awe., New York, N. Y . MATERIALS GR-S. Other types of emulsifiers have A total of 44 emulsifiers, excludR. L. MAYHEW AND R. C. HYATT been proposed and tested-e.g., ing fatty and rosin acid soap conCentral Research Laboratories, p o I y ox y a1k y 1e n e sorbitan monotrols, n-ere examined, 35 of which General Aniline & F i l m Corp., Easton, Pa. stearate ( 2 ) ; I-pimaric acid-maleic were polyoxyethylene glycol derivaanhydride addition products (3, 5 ) ; tives. Of these, 9 were anionic, 6 a n d mixtures of emulsifiers one of were cationic. and 29 were nonionic. Some of these derivatives were classified as both nonionic and which is a colloidal electrolyte (anionic or cationic) and the cationic as governed by the p H of the solution. The ethylene other is nonionizable but forms a true solution ( I d ) . Schulze oxide adducts incorporated one or more of the following funcet al. (7') have reported on the use of alkyl aryl sulfonates tional groups: ethers, esters, alcohols, amines, amides, and as emulsifying agents for GR-S a t 41' F. I n t h e synthetic sulfates. Other types of emulsifiers tested were alkyl aryl rubber industry in Germany, dibutylnaphthalene sodium suland alkyl amide sulfonates, alkyl ester sulfates, and quaterfonates were used extensively as emulsifiers and experiments were conducted with the N-diethylaminoethyl ester of C ~ Z nary ammonium salts. The materials submitted and some of their properties are listed paraffinic acids, a condensation product of oleyl alcohol and in Table I. The various groups are described below: ethylene oxide (4 t o 6 moles), and mixed sodium sulfonates prepared from C14-C17 hydrocarbons with a mixture of CIZ,C I ~ , Nonionics. A11 t h e nonionics were ethylene oxide addition and C14 synthetic paraffinic acids as auxiliaries (10). I n spite of products. Nos. 1 TO 5 . These materials mere polyoxyethylated alkylthe numerous emulsifier types available, few systematic studies Dhenols: of the effect of various emulsifiers in a specific polymerization formula have been reported. However, in one such study fatty acid soaps, rosin acid soaps, and various synthetic emulsifiers, mostly salts of organic sulfates or sulfonates, were tested by Carr where R is a n alkyl group, in this case having 8 t o 10 carbon et al. ( 1 ) . None of the synthetic emulsifiers gave polymerization atoms, and n varies in the range 4 to 30. They are extremely rates comparable to those obtained with fatty acid soaps. stable t o acid or alkaline hydrolysis and are unaffected by all The availability of a series of emulsifiers consisting of ethylene but the very strongest oxidizing and reducing agents. Nos. 12, 14, 15, ~ N 16. D Members of this group are ethylene oxide condensation products in which the number of ethylene oxide adducts of an 18-carbon alcohol having the structure: oxide units can be varied t o change the hydrophobe-hydrophile balance, and in which functional groups of various types can be R - 0 4 , CHZ-CH2-0)n-H incorporated to produce anionic, cationic, and nonionic materials, where n varies from 4 to 28. They are stable to acid and alkaline led to the present investigation. This type of surfactant was hydrolysis and also t o strong oxidizing and reducing agents. discovered by the Germans in the early thirties (6, 9) and proNos. 20 BND 21. These materials are polyoxyethylated heterocyclic alcohols. Emulsifiers of this type exhibit the same genposed as a n emulsifying agent for butadiene-styrene copolyeral stability as the polyoxyethylated alkylphenols (groups 1to 5 ) . merizations as early as 1941 ( 1 1 ) . The emulsifiers examined in Nos. 27, 29, 30, AND 340-R. Materials in this group are polythe present program were prepared by the General Aniline and oxyethylated 18-carbon fatty acids of the following general Film Corp. and tested in emulsion polymerizations a t the Governstructure: ment Laboratories of the University of Akron. 0 I n an emulsion polymerization system, the emulsifier must perI! R-C-4-( CHr-CH2-O),-H form the following three functions (8): 1. Produce a stable and well-dispersed emulsion of the monomer. 2. Form micelles and solubilize the monomer, thus making it more accessible to the free radicals. 3. Stabilize the polymer particles t o prevent precipitation, coalescing, and sedimentation.
Most investigators today agree that the monomer is solubilized in a micellar system and t h a t the polymerization is initiated in t h e micelle (4). The final polymer-monomer particles are stabilized as a dispersion by the adsorption of a monolayer of soap or surfactant.
I n acid or alkaline systems, hydrolysis of the ester linkage might he ex-oected but not necessarilv under mild conditions. ?z varies in- the range 5 to 40. No. 34. This compound is a polyoxyethylated diester of a dimerized fatty acid of the general structure:
0 E€( O-CHZ-CH2)n4-
0
;t:-R-R-C-O-(I/
CH2-CH2-0)n-H
Nos. 35, 36, 37, AND 38. These agents are ethylene oxide adducts of castor oil and hence are ester ethers. n varies in t h e range 10 to 40. No. 40. This material is a n ethoxylated tall oil ester. 1330
I N D U S T R I A L A N D E N G I N E E R I N G CHEMISTRY
June 1953
Nos. 45 TO 52. This group is composed of alkyl aryl amides with ethyleneoxy chains substituted on the nitrogen atom. Nos. 53 TO 55. These materials are alkyl polyoxyethylene ammes. They are primarily nonionic but will exhibit varying degrees of cationic activity depending on the p H of the system. The general formula and the reaction with acid are (CH2-CHz-O)nH R-N
R
+
/
\
HA[ \hr/ I(\
H
(CHz-CHz-O)nH
(CH2-CHz-O)wH
(CHz-CH2-O)nH
I+ +
460-BR. This material differs from the previous group only in that the hydrophobic group is carbocyclic rather than aliphatic, Anionics. No. 62. This product is .an alkyl amide sulfonate, commercially known as Igepon T, having the structure (R =
ANTARON R275. This material is.a commercial alkyl aryl sulfonate containing the same active mgredent as No. 64, but supplied as a dry solid containing more inorganic salts. No. 67. This product is an alkyl ester sulfonate of the same type as the commercial material Igepon A, which is produced by reaction of a high molecular weight fatty acid chloride and the sodium salt of isethionic acid (hydroxyethane sulfonic acid). Such materials are readily hydrolyzed but can be used in mildly acid or basic systems. A5-370. This product is a sulfated fatty ester. ANTARON K-430 AND K-460. K-430 is the sodium salt and K-460 the ammonium salt of an alkyl phenoxy polyoxyethylene sulfate. Cationic& 3410-DA AND 3430-DA. Both of these agents are new quaternary ammonium compounds. PROCEDURE
nlevl) :
R-
..
i
The emulsifiers to be studied were tested first by polymerization a t 41' or 122" F. in 8-ounce glass bottles according to the following formulas:
-N-CH2--CH2-SOaNa
AH3 Surfactants of this type are highly resistant to hydrolysis, especially in alkaline solutions. No. 64. This material is an alkyl aryl sulfonate, known commercially as Nekal BX, and was the emulsifying agent used in Germany in Buna S polymerization. ORONITE S. This IS a commercial alkyl aryl sulfonate, manufactured by the Oronite Chemical Go., believed to consist of a 12-carbon alkyl group attached to a sulfonated benzene ring. ULTRAWET K. This material, a commercial alkyl aryl sulfonate manufactured by the Atlantic Refining Co., is believed to contain a benzene ring with a branched 12-carbon chain.
Parts by Weight At 41' F. At 122' F.. 71.5Q 71. 5a 28. 5a 28.5" 0.18-0.26 b ...... 0.58-0.866' Varied Varied 0.06-0.125a ...... 0.23 0.12 ...... 0.17 ...... 1.0 ...... 180 180
Ingredients
Butadiene Styrene Sulfole B-8 D D M (commercial n-dodeosl mercztptan) Emulsiher Cumene hydroperoxide (CHP) Potassium persulfate Ferrous sulfate heptahydrate Potassium pyrophosphate Dextrose Water " Charged on basis of purity. Varied t o obtain copolymers with a Mooney viscosity of about 50 ML-4.
.....*
......
TABLEI. CHEMICAL STRUCTURE AND PROPERTIES OF SURFACTANTS
50 51 52 53 54 55 460-BR 62 64 Oronite S Ultrawet K Antaron R-275 67 8-370 K-430 K-460 3410-DA
Surfactant Type Nonionic Nonionic Nonionic Nonionic Nonionic Nonionip Nonionic Nonionic Nonionic Nonionic Nonionic Nonionic Nonionic Nonionic Nonionic Nonionic Nonionic Nonionic Nonionic Nonionic Nonionic Nonionic Nonionic Nonionic Nonionic Nonionic Nonionic Nonionic Nonionic Nonionic Nonionic Nonionic Nonionic Anionic Anionic Anionic Anionic Anionic Anionic Anionic Anionic Anionic Cationic
3430-DA
Cationic
Code No. I
2 3 4 5 12 14 15 16 20 21 27 29 30 340-R 34 35 36 37 38 40 45 46 47 48 49
1331
Chemical Structure .\lkyl phenoxy polyoxyethylene ethanol Alkyl ylienosy polyoxyethyltne ethanol Alkyl phenoxy polyoxyethylene ethanol Alkyl phenoxy polyoxyethylene ethanol Alkyl phenoxy polyoxyethylene ethanol Alkvl Dolvoxvethvlene ethanol Alkyl bolyoxyethGlene ethanol Alkyl polyoxyethylene ethanol Alkyl polyoxyethylene ethanol Rosin alcohol polyoxyethylene ethanol Rosin alcohol polyoxyethylene ethanol Alkyl polyoxyethylene ester Alkyl polyoxyethylene ester Alkyl polyoxyethylene ester Alkyl polyoxyethylene ester Alkyl polyoxyethylene diester Alkyl polyoxyethylene ester-ether .\lkyl polyoxycthylene ester-ether .\lkyl polyoxyethylene ester-ether Alkyl polyoxyethylene ester-ether Tall oil polyoxyethylene ester Alkvl arvl Dolvoxvethvlene amide Alkyl aryl polyoxleth>lene amide Alkyl aryl polyoxyethylene amide Alkyl aryl polyoxyethylene amide Alkyl aryl uolyoxyethylene amide Alkyl aryl polyoxyethylene amide Alkyl aryl polyoxyethylene amide Alkyl aryl polyoxyethylene amide Alkyl polyosyethylene amine Alkyl polyoxyethylene amine Alkyl polyoxyethylene amine Aryl polyoxyethylene amine -41kyl amide sulfonate Alkyl aryl sulfonate Alkyl aryl sulfonate Alkyl aryl sulfonate Alkyl aryl sulfonate Alkyl ester sulfate Alkyl ester sulfate Alkyl phenoxy polyoxyethylene sulfate Alkyl phenoxy polyoxyethylene sulfate
Water Solubility" Insoluble Soluble Soluble Soluble Soluble Insoluble Soluble Soluble Soluble Soluble Soluble Insoluble Soluble Soluble
Solubility Indexb 44 100 167 212 334 50 175 250 350 200 250 50 100 133
Insoluble Insoluble Insoluble Soluble Soluble Soluble Soluble Soluble So1ub 1e Soluble Soluble Soluble Soluble Soluble Insoluble Soluble Soluble Soluble Soluble Soluble Soluble Soluble Soluble Soluble Soluble Soluble Soluble
71 50 90 133 200 129 120 160 200 240 120 160 200 240 63 188 625
....
Soluble Soluble
Determined for 1% ' solution. (number of ethylene oxide units) solubility index = (number of C atoms i n base) a constant solubility of base hydrocarbon.
...
... ... ... ... ... ... ... ...
.... .. ... ...
Active Ingredient,
%
"
100
100 100 100 100 100 100
100 100 100 100 100 100 100
...
100 100 100 100 100 95 100 100 100 100 100 100 100 100 100 100 100 100 28 28.3
... ...
88'
50 30 60
100 100
Q
+
loo'
Constant adjusts for inherent water
The effects of variation in emulsifier and pH levels were i n v e s t i g a t e d . The p H was varied by adjusting the emulsifier solution to the desired value by the addition of sodium or potassium hydroxide, trisodium phosphate, acetic acid, hydrochloric acid, or sodium acetate. Control polymerizations with Dresinate 214 or 731 or sodium fatty acid (NaFA) soap as emulsifier were also made. Dresinate 214 or 731 was used in the polymerizations carried out a t 41" F. and sodium fatty acid soap in the polymerizations conducted a t 122" F., as indicated in Table 11. (Dresinate 214 is the potassium and 731 the sodium soap of disproportionated rosin acids, manufactured by the Hercules Powder Co.) Emulsifiers that appeared promising in bottle studies were then tested with the same formulas in polymerizations a t 41' or 122" F. in 5-gallon r e a c t o r s , e q u i p e d witlh marine-type impefiers 3 inches in diameter rotated a t 1125 r.p.m. The control charges for the 5-gallon reactors were emulsified with Armour potassium fatty acid (KFA) soap. The extent of polymerization was calculated from the total solids content of samples of latex remoyed from the reactor by syrmge. Charges polymerized a t 41' F. were stopped a t 60 3y0 conversion with 0.10 part of sodium nitrite, 0.20 part of hydroquinone, and 0.30 part of d i - t e r t - b u t y l h y d r o quinone (per 100 parts of' monomers), and those polym e r i z e d a t 122' F. w e r e
INDUSTRIAL AND ENGINEERING CHEMISTRY
1332
TABLE 11.
SUMbL4RIZED
BOTTLEP O L Y > I E R I Z A T I O S DATA
Emulsifier Chemical tvne
Code No.
Parts
Anionic Alkyl amide sulfonate Alkyl aryl sulfonate
62 64
5.0 5.0
Alkyl ester sulfate
67
6.0
Alkyl aryl polyoxyethylene sulfate
K-430
5.0
K-460
5.0
Alkyl ester sulfate
S-370
5.0
3410-DA
5.0
3430-DA
5.0
Cationic Alkyl polyoxyetliylene benzyl ammonium chloride
Nonionic Alkyl phenoxy polyosyethylene ethanoi
Alkyl polyoxyethylene ethanol
1 2
5.0 5.0
3
5.0
4
5.0
5
5.0
12 14
5.0 5.0
15
5.0
16
6.0
5.0 5.0 5.0 5.0 5.0 5.0 5.0 5.0 5.0
Rosin alcohol polyoxyethylene ethanol Alkyl polyoxyethylene ester Alkyl polyoxyethylene diester Alkyl polyoxyethylene ester-ether
5.0
5.0 5.0
Tall oil polyoxyethylene ester Alkyl aryl polyoxyethylene amide 46
5.0
47
5.0
48
5.0
49 50
51 52 Alkyl poiyoxyethylene ainine
53 54
5.0
5.0 5.0
5.0
5.0
Poly. Temp.,
F.
41 41 122 41 122 41 122 41 122 41 122 41 122 41 122 41 41 122 41 122 41 122 41 122 41 41 122 41 122 41 122 122 122 41 41 41 41 41 41 41 41 4s 41 122 41 122 41 122 41 122 41 41 41 41
122 41 41 122
Aryl polyoxyethylene amine
55 460-BR
5.0
41 41 122
Anionic-Nonionic Combinations Alkyl aryl sulfonate-alkyl phenoxy polyoxyethylene ethano
64/2
1/3
2/2
64/4
!%A
K-460/2 64/47
3/1
Alkyl aryl sulfonate-alkyl polyoxyethylene amine
64/54
1/3
Alkyl aryl sulfonate-aryl polyoxyethylene amine
64/460-BR
1/3
Alkyl phenoxy polyoxyethylene sulfate-alkyl phenoxy polyoxyethylene ethanol Alkyl aryl sulfonate-alkyl aryl polyoxyethylene amide
Vol. 45. No. 6
Ultrawet K/460-BR
1/3
0.5/4
Soap Solution, pHa I
E
6.8
7. Od 5.Odse 4.9;>8 6.0 8.91 6.0 10.0f 6.0 5.9 4.2 7.9f 3.6
8 . Of c
6.ldie 4. 8 d t e c
0
9.7, C
c C C
c c c c e C
c C E
c c c c c c 0
c c c c C
10. f f C
e c c c c c
5.8e 10.6 5.0dse 10.7d
Conversion Rate %/Hoiirb 4.1 7.5 1.7 2.5 2.4 5.1(8) 5.0
7.4(5) 4.5 6.8
l.l(S5)
0.7 4.7(16) 0.4 3.6(15) Nil 1.5(15) 0.5(35) 2.9 1.8(15) 2.6(15) 2 , 4 (15) 2.9 1.8 Xi1 2.4 1.7 2.6 2.2 2.7 2.0 0.8 2.4 0.2 1.7 1.7 1.6 0.3 1.7 1.7 1.5 1.5 2 8 2.0 2.7 2.8 2.9 5.0(15) 2.9 2.7 0.2 2.2 2.1 2.5 2.7 Si1 1.7 1.9 8,O
2.5
c
1.8 3 2 Nil I?. ? d 3.4 o . ~ d < ~6 . 7 7,p,e
5,od,*
4s 41 41 41
8.:
41 41 122 41 122 41 122 122
6.1 9.
9.5
'I
SO. 6
10.5 10.6 10.6
5.O*
3.4 4 2U3.5) R 9(15) 4 5 5 6
3 8 2 3 3 1 a d
2 5 3 0 4 7
Alkyl phenoxy polyoxyethylene sulfate-aryl polyoxyK-460/460-BR 122 9.1 4.4 ethylene ainine 1/4 122 S-370/4GO-BR 0.5/4 3.3 5.0e Alkyl ester sulfate-aryl polyoxyethylene amine Nonionic-Cationic Combinations 122 341O-DAl460-BR 7.5 5.3e uaternary ammonium salt-aryl polyoxyethylene 2/4 122 3430-DA&/460-BR 6.7 5.3e amine 2/4 Nonionic-Nonionic Combinations Aryl polyoxyethylene amine-alkyl phenovy polyoxy460-BR/2 122 5 .Oe ethylene ethanol 5.7 411 Aryl polyoxyethylene amine-alkyl polyoxyethylene 4/0.5 460-RR/340-R 122 5 .0 e 5.9 ester Anionic Controls 11.1g Dresinate 214 41 5.0 4.6 Potassium rosin acid soap C SaPA 122 4.3 5.4 Sodium f a t t y acid soap a pH of emulsifier solution not adjusted. b R a t e calculated by dipiding 7% coni.rrsion by hours of polymerization; where time was other t h a n 10 hours, actual hours are c p H of emulsifier solution not determined. . d 0.50 part sodium acetate added as a buffer. e pH of emulsifier solution adjusted with acetic acid. f pH of emulsifier solution adiusted with sodium hydroxide. 0 pH of emulsifier solution adjusted with potassium hydroxide and trisodium phosphate.
Latex Stability a n d Viscosity Heavy prefloc Si. prefloc Phase separation Satisfactory
......
Prefloc Satisfactory Satisfactory Satisfactory Satisfactory
....
........
Heavy prefloc
........
Heavy prefloc
Phase separation Satisfactorv Phase sepaiation Very viscous Fluid, foamy 91. prefloc Satisfactory, foam> Viscous. foamy SI. prefloc foamy Fluid, oil bn top S1. viscous. foamv Fluid, foamy . Heavy prefloc Fluid, foamy Viscous, foamy Fluid, foamy Fluid, foamy S1. prefloc, foamy Phase separation Satisfactorv Very viacoks, foamy Satisfactory Satisfactory Very viscous, foamy Heavy prefloc, riscour Viscous, foams Heavy prefloo S1. prefloc Satisfactorv
Satisfactory Satisfactory el. prefloc Satisfactory Sat isf ac t orv Satisfactor4 Satisfactory El. prefloc Phase separation
........
IIeavy prefloc Satiifactory, foamy Heavy prefloc Prefloc Prefloc
........ ........
S1. prefloc Satisfactory Satisfactory S1. prefloc Satisfactory
SI.prefloc and foamy
61. prefloo and foamy SI. prefloc a n d foamy Prefloc SI. prefloc a n d foamy SI. oreAoc 91. prrfloc S1. prefloc Prefloc Prefloc
Prefloc Prefloc Satisfactory Satisfactory shown in parenthesis.
INDUSTRIAL AND ENGINEERING CHEMISTRY
lune 1953
stopped a t 72 f 3% conversion with 0.20 part of hydroquinone. The standard procedures for removing residual monomers from the latex and coagulating and drying the polymers have been described (3). The olymers in the final latices were stabilized with 1.5% of pheny?-2-naphthyIamie added on the basis of the total solids in the latex. Because the standard procedures (addition of salt and acid) did not coagulate latices emulsified with the various experimental products, it was necessary to conduct a preliminary study on a portion of the latex from each batch to discover a satisfactory procedure for coagulation. Most of thecharges that were polymerized a t a pH of 9.0 or above could be coagulated a t 120' to 130" F. by addition of about 4 parts of aluminum sulfate per 100 parts of polymer and a quantity of Polyamine H equivalent to 20% by weight of the emulsifier. Some latices which were prepared at a p H value below 7 were coagulated with sodium hydroxide. Several charges were coagulated by the aid of a water-insoluble alkyl phenoxy polyoxyethylene ethanol. The polymers prepared a t 122" F. were dried a t 155" F. and those prepared a t 41" F. were dried at 140' F. The polymers were evaluated by the following tests: combined styrene, gel content and dilute solution viscosity, Mooney viscosity, mill processing, stress-strain, hysteresis-temperature rise, flex-life, and rebound. The procedures and the significance of these tests have been described ( 3 ) . The polymers were compounded on 6 X 12 inch mills according to the following test recipes:
Another point to be considered is that these emulsifiers are less soluble in hot than in cold water because the association occurring between the ether linkages and the water is partially destroyed by heating. This phenomenon may account for some of the variations in emulsifier efficiency a t 41' and 122" F. None of the polyoxyethylene ethanols yielded conversion rates comparable to those obtained with the potassium rosin or sodium fatty acid soaps. The best rate a t 41' F. was about 58% of that exhibited by the control. The polymerizations were not affected greatly by variations in the pH and the stabilities of the latices were variable.
8 ?ARTS EYULSlFlER PH NOT ADJUSTED REAGTiON TIME. 10-13 WURS
SOCUBlLlTY INOEX
Figure 1. Parts by Weight Ingredients
A
Polymer 100 EPC black 40 Zinc oxide 5 Sulfur 2 Benaothiazyl disulfide (Altax) 1.75 Stearic acid
.,..
B 100 40
5 2 8.0
1.5
C
D
100 40
100 40 5 2
5 2 1.75 1.5
1.0 1.5
E 100 40 5 2
0.5 1.5
RESULTS AND DISCUSSION
A summary of the data for charges polymerized in 8-ounce bottles is shown in Table 11. The anionic emulsifiers gave generally good conversion rates a t 41" F.; but, a t 122' F., the rates were good with some of them and poor with others. The latex stability was mostly satisfactory, but it is noteworthy that poorer stability occurred with the sodium salt (K-430) than with the ammonium salt (K-460) of an alkyl phenoxy polyoxyethylene sulfate. The cationic emulsifiers provided low rates a t 41" F. and higher rates a t 122" F. with very poor latex stability. As a group, the nonionic emulsifiers were unsatisfactory because of low conversion rates and the variable stabilities of the resulting latices. The data fail to show a correlation between the solubility index and the conversion rate in the sense that the performance of the emulsifier can be predicted from solubility data alone. It was obvious that at values below a minimum value of the solubility index, which, although not very sharply defined, is probably in the rang? of 70 to 120, little or no polymerization occurred. Possibly this was because of poor emulsification of the monomer or because the emulsifier was too insoluble to reach the critical micelle concentration in the water phase. Above this minimum range of values, conversion rates did not depend on the solubility index. However, within certain classes of compounds, correlation was established between solubility index and conversion rate, as is shown in Figure 1. Maxima in conversion rate occur for solubility indices of 200 and 250, respectively, in the cases of alkyl aryl polyoxyethylene amides and alkyl phenoxy polyoxyethylene ethanol. This information may be of value in selecting a starting point for future investigations with other types of emulsifiers. The latex stability was apparently unrelated t o the solubility index. In the discussion of nonionic emulsifiers which follows, materials that gave poor conversion rates because of insolubility are excluded.
1333
Conversion Rate us. Solubility Index for Nonionic Emulsifiers
The ester derivatives provided conversion rates which were comparable to each other but considerably lower than those obtained with the control charges; the best rate was 34% of that exhibited by the potassium rosin acid (KRA) soap emulsified control, and the degree of stability was very inconsistent. Of the nonionics, the alkyl aryl polyoxyethylene amides yielded the best conversion rates. At 41' F., the rates averaged 46% of that for the KRA soap control, and a t 122' F. the rates for the charges polymerized without adjustment of the p H averaged 58% of that for the NaFA soap control. A representat've (Code No. 47) of this category, for which the pH was adjusted to approximately 10.4, afforded a rate 93% as great as that of the control charge. Stability was satisfactory for the majority of the charges and only a slight amount of prefloc developed in some of the charges that were emulsified with the amides, Conversion rates obtained with amine derivatives a t 41' F. were poor at a low p H (where they presumably act as cationic emulsifiers) and varied from poor to moderately good a t a high pH; the best rate was 64% as much as that of the KRA soap control. At 122' F., the rates of polymerization varied from excellent ( 148y0 of that of the NaFA soap control) a t a low pH, through good (approximately equal to the control) a t a pH near the neutral point, to fair (56% of that of control) a t the high p H levels. However, a t 122" F., the latex stability was very poor. Combined emulsifiers occasionally produced good results. An alkyl phenoxy polyoxyethylene ethanol (No. 2 ) in combination with an alkyl aryl sulfonate (No. 64) or an alkyl phenoxy polyoxyethylene sulfate (K-460) yielded comparatively good conversion rates with satisfactory stability a t 41 'F. In combination with an amide (No. 47) or with amines (Nos. 54 and 46O-BR), alkyl aryl sulfonates yielded only fair rates with varying stability of the final latex. An alkyl phenoxy polyoxyethylene sulfate (K-460) combined with an amine gave good conversion rates and mostly satisfactory latex stability at 122" F., but other amine combinations were too unstable to be considered useful in spite of rates that were good to excellent. The data for polymerizations in 5-gallon reactors are sumrnarized in Table 111. With the exception of emulsifier 64, an alkyl aryl sulfonate, the polymerization rates in 5-gallon reactors were
1334
INDUSTRIAL AND ENGINEERING CHEMISTRY
Vol. 45, No. 6
combination (alkvl arvl sulf o n a t e-ar y 1 polyoxyethylene amine) a t a pH level of 5.0 to Soap Reaction Final Sulfole VisCharge Emulsifier Soh, Time, Conv., B-8, cosity 5.2 had a low conversion rate NO. Typea Code No. Parts pH Hours 7" Part ML-4 a t a 1 to 4 ratio but a good Polymerized a t 41' F. by Low-Suaar CHP-Dextrose Formula rate at 2 to 4 ratio. 64 49LA3 Alk. ar. sulfonate 3 8.9 19.5 60.3 0.22 48 b A4 64 Alk. ar. sulfonate 3 9.2 26.0 59.5 0.22 42 6 The latices stabilized with 64 Alk. ar, sulfonate 3 A5 9.1 0.21 36.0 57.0 59 b alkyl aryl sulfonates or alkyl A6 64 Alk. ar. sulfonate 3 8.9 59.70 0.22 32.0 54d A1 Alk. ar. sulfonate-alk. ester sulfates could be coagu64/2 ph. POE ethanol 9.2 22.8 61.5e,f 0.20 90a 3/1 A2 Alk. ar. sulfonate-alk. lated by addition of brine, 1yo 64/2 ph. POE ethanol 9 . 1 1 3 . 3 6 0 . 5 8 0.20 92h 3/2 A1 1 Alk. ar. sulfonate-alk. s ilfuric acid, and a polyamine, 64/2 2.5/1.5 9.1 32.8i 55.5e 0.23 76, sich as tetraeth! lenepentamine A10 64/2 9.1 24.0 57.5 0.23 51 i 2/1 (TEPA) or Polyamine IT (a A16 64/2 m i x t u r e of p o l y a m i n e s ) . 8.7 18.0 60.0 72 i 0.23 2g1 A9 Alk. ester sulfate 5-370 10.5 24.5 23.2 0.23 30d Latices stabilized with a mixAI5 5-370 Alk. ester sulfate 3 6.8 10.2 58,2 0.23 47 d A17 K-460 Alk. ph. POE sulfate 12.3 61.2 7.2 0 26 36k ture of an alkyl aryl sulfonate 4 K-460 A18 Alk. ph. POE sulfate 5.6 0.23 9.6 60. O e 41k and an alkyl phenoxy polgoxyK-460 A19 Alk. ph. POE sulfate 5 5.6 13.0 0.20 58.0e 45h Alk. ph. POE sulfate K-460 A20 5 5.4 9.4 64.6 0.18 89 k ethylene ethanol (KO.64-No. Oronite S Alk. ar. sulfonate A13 3 9.4 57.5 11.8 0.23 86d 414 Antaron R-275 Alk. ar. sulfonate 3 10.3 37.3e 0.23 43.5 464 2) proved to be extremely A7 Potassium fatty acid stable. Brine, a c i d , a l u m , KFA soap 3 10.1 10.31 60.0 0.22 990 A8 Potassium f a t t y acid tetraethylenepentamine, a n d KFA soap n.. 2~. 3 7no 3 10.4 1 2 . 0 m 60 n e . " A12 Potassium fatty acid glue were ineffective in floccusoap KFA 3 11.0 1 2 . 3 % 60.6 0.25 228 lating these latices and it was Polymerized a t 122' F. by Persulfate Formula Alk. ar. sulfonate/ar. Ultrawet Kl/4 5 . 0 2 4 . 5 7 1 . 4 0 . 7 0 % 1000 possible to freeze and then thaw 49LB1 POE amine 460-BR the latex from charge 49LA2 Alk. ar. sulfonate/ar. Ultrawet K2/4 5.2 14.0 73 2e 0.80n 63p B2 without inducing coagulation. POE amine 460-BR .41k. ph. P O E sulfate K-460 B3 5 9 . 8 1 4 . 0 7 2 . 0 0 . 8 3 % 33k However, coagulations of the B4 Alk. ph. POE sulfate K-460 5 9.8 13.8 72.3 0.70. 38k B5 Alk. ph. P O E sulfate K-460 5 10.1 15.0 72.0e 0.58% 691. latices were accomplished with B6 Blk. ph. POE sulfate K-460 5 9.8 13.7 72.0e 0.64% 5lk salt, acid, and tetraethyleneRefer t o Table I for unabbreviated names of emulsifiers. b Coagulated with salt, acid, Polyamine H, and Antifoam A. pentamine, by adding a methanol solution of emulsifier dC Slight Coagulated prefloc. with salt, acid, and TEPA. e Extrapolated value. 1 (Table I ) , a water-insoluble f Heavy prefloc. alkyl phenoxy polyoxyethylene Q Coagulated with salt and acid. h Coagulated with salt, acid, and emulsifier I . ethanol. This emulsifier, bei Booster consisting of 0.025 part of C H P added a t 5070 conversion (26.1 hours) increased reaction rate $emporarily. cause of its solubility characi Coagulated with salt, acid, TEPA, and emulsifier 1. teristics, is a type which tends b Coagulated with Polyamine H and alum. 2 Reduced level of initiating ingredients used: 0.08 part C H P , 0.096 part FeSOa.7Hz0, 0.136 part KaPz07,0.8 to form a nater-in-oi] part dextrose. n Lower level of initiating ingredients used: 0.06 part CHP, 0.072 part F e S 0 4 . 7 H ~ 0 0.102 , part KapZo7,0.6 sion, and its addition to a latex part dextrose. induces instability resulting in n DDhI part. o Coagulated with sodium hydroxide. coagulation. P Coagulated with salt and sodium hydroxide. $ny of the latices produced in this program could be coagulated with methanol, ethanol, essentially similar t o those in bottles. At 41" F., charges emulsi2-propanol, or butanol. A polyamineand aluminum sulfate comfied with KO.64 reacted more s l o ~ d yin 5-gallon reactors than in bination was effective in coagulating latices stabilized with alkyI bottles. With mixtures of Nos. 64 and 2, an alkyl phenoxy phenoxy polyoxyethylene sulfates. The latices stabilized with a polyoxyethylene ethanol, a high conversion rate was obtained a t combination of aryl polyoxyethylene amine and alkyl aryl sul3 to 2 rat'io and lower rates were obtained a t other ratios. At a fonate Tvere coagulated by sodium hydroxide with or without ad3 to 1 ratio, pronounced instability was encountered, with about dition of brine. 50% of the polymer forming prefloc. The modifier requirements Chemical analysis showed that the ash contente of the polyappeared t o be higher with combinations Of YOs. 64 and.2 than mers emulsified with the synthetic emulsifiers Tvere comparable to with 64 alone. those of the control polymers emulsified with rosin acid or fatty S-3'70, an ester at 410 F. gave a low conversion acid soaps. Polymer 49LA6, an alkyl aryl sulrate a t a high pH, but, at a pH slightbr belorn the point, fonate, had a high styrene content(26.2%), and one the rate was high. 49L811, emulsified with an alkyl aryl sulfonate-alkyl phenoxy With K-460, an alkyl phenoxy polyoxyethylene sulfate, a t p o l ~ o x 2 ~ e t h ~ lethanol ene combination, had a low styrene content 410F.and pH levels of 5.4 to 7.2, conversion rates were high and (17.9%), but these values were not representative of polymers were the highest obtained with any of the synthetic emulsifiers prepared with these types of emulsifiers. In general, the styrene tested. Rates to 70% conversion in 13 'to 15 hours were also content of the experimental polymers was comparable to that of obtained with K-460 a t 122" F. and pH levels of 9.8 t o 10.1. Gel determinations showed that the controls (22.5 f 1.1%). A charge po]5merized at 410 F. with Antaron R-275 as the the 41' F. polymers emulsified with synthetic emulsifiers were emulsifier reacted very &n.]y, WThereas qTith Oronite s the po]ygel-free; t'he 122" F. polymers emulsified n-ith combinations of high, Control charges, containing 3 parts merization rate a n aryl polyoxyethylene amine and an alkyl aryl sulfonate had of KFA soap emulsifier, polymerized at 41' F., showed rates aphigh percentages of gel, up t o 6270, whereas those emulsified with proximately equal t o those obtained with the best synthetic emulsifiers, but, because the activation level of the control an alkyl phenoxy polyoxyethylene sulfate were gel-free. charges was intentionally lowered to obtain conversion of about The processing properties and extrudibility of the polymers prepared with the synthetic emulsifiers were generally satisfactory 60% in 10 to 12 hours, the rates are not strictly comparable. A t 122" F., charges emulsified with an Ultrawet K-460-BR and did not differ greatly from those of the cont'rol polymers.
TABLE 111. SUMMARIZED POLYMERIZATION DATAFOR ~ - G . ~ L L oCHARGES K
.
Q
>
"
"
INDUSTRIAL AND ENGINEERING CHEMISTRY
June 1953 ~~
1335
~
STRESS-STRAIN DATAAT 77' F. TABLE IV. SUMMARIZED Polymer No. 49LA Bld 1 Polymerization temp., OF. 41 Emulsifier, type 64 Emulsifier parts 3 Compounding recipe B Min. Cured a t 292' F. 300% modulus, 25 690 lb./sq. inch 50 1290 100 1590 Tensile 25 3180 50 3370 strength 100 3330 lb./sq. i h h Elongation, '70 25 760 50 640 100 470 Set, %
25
Polymer No. Polymerization temp., Emulsifier, type c
x
B
500 1100 1480 2910 3540 3260 860 610 500
1420 2070 2160 3010 2490 2390 500 350 320
1010 1640 1990 3040 3680 2650 660 420 360
23 14 9
8 4 5
15
21
50 100
12 10
F.
Emulsifier, .parts Compounding recipe 300% modulus, 25 Ib./sq. inch 50 100 Tensile 25 strength 50 100 lb./sq. i6oh Elongation, % 25 50 100 25 Set, % 50 100 a 200% modulus.
49LA14 41 Antaron R-275 3
B
500 1030 1330 2960 3800 3500 860 670 570 24 15 13
4QLAll 41 64/2 2.5/1,5 B C D
49LA6 41 64 3
49L-410 41 64/2
'/'B
1140 1580
670 1490 1920 3350 3410 3040 780 500 410 18 9 6
..
3130 3120
..
630 490
..
17 10
6 5
..
49LA13 49LA7 49LA8 41 41 41 Oronite S KFA Soap KFA Soap
X-558 41 Dres. 214
3 B 1400 2000 2390 4600 3290 3140 590 400 350 12 6 5
4.6 B 360 910 1470 2100 4510 4160 890 740 570 27 14
3 B 660 1300 1640 3750 3860 3710 740 570 490 17 13 10
~
3 A B 490 880 l l Q 0 1170 2350 2940 3900 4190 3380 , . 2630 830 690 630 460 . 320 23 12 14 7 3
..
.
..
The stress-strain data for compounded stocks cured a t 292' F. and tested a t 77" F. are shown in Table IV. Polymers prepared with the commercial alkyl aryl sulfonates, Antaron R-275 and Oronite S (49LA13 and 49LA14), and those prepared with the alkyl phenoxy polyoxyethylene sulfate, K-460, exhibited maximum tensile strength values superior to those of the other experimental polymers and about the same as those of the polymers emulsified with KFA soap. The cure rates varied with the different emulsifiers. This was compensated for, to some extent, by variations in the compounding recipes. The data for special physical tests are summarized in Table V. The physical properties of the polymers tested did not appear to be significantly better or worse than those of the control. A possible exception was polymer 49LA9 prepared with an alkyl ester sulfate (S-370) which had a hysteresis-temperature rise t h a t may be good, considering the relative set value, and a favorable quality index. I n evaluating the tensile strength and physical properties of the experimental polymers, it should be recognized that the scope of the project did not permit a detailed study of compounding recipes which were, therefore, not necessarily adjusted to produce the optimum possible results. The polymers also varied considerably in Mooney viscosity, which should be considered in making comparisons. CONCLUSIONS
The anionic emulsifiers (sulfates and sulfonates) generally Drovided good conversion rates with adequate latex stability. Rates of conversion were unaffectedby variations in the p H level. The cationic e m u l s i f i e r s (quaternary ammonium salts and amine salts) yielded poor Conversion rates at 41" F. and
Q
49LA16 41 84/52 2/1 C B
760 1250 1470 4120 4080 3870 740 590 530 20 14 10
@LA9 41 8-370 3 B
49LA15 41 5-370 3 B
4QLA17 41 K-460 5 B
4QLAlQ 41 K-460 5 B
400 1010 1430 2110 3420 3230 950 650 510 37 18 12
570 1220 1570 3070 3610 2810 800 580 430 24 14 7
440 850 1110 2700 3430 3370 920 710 610 28 25 19
580 840 990 3270 3130 3230 770 640 610 29 23 18
1090 1610 1710 3650 2980 3080 590 430 430 14 7 6
49LB1 122 Ultrawet K/460-BR
49LB6 122 K-460
GR-S-1002 122 Dres. 731
2/4
5 B 540 890 1070 2570 3160 3100 770 650 590 26 21 15
4.3
E
1/4
B
49LB2 122 Ultrawet K/460-BR
184O5
.. ..
1940 2290
2050 2170 2120 220 210 180 4 3 1
2160 2410 2230 330 320 280 9 6 3
B 1710 1910 2050 2520 2470 2490 390 370 350 14 8 6
..
1170 1380 1550 2730 2560 2810 510 450 440 22 13 10
B
340 820 1350 1520 3150 3290 800 870 530
19 14 9
high rates a t 122' F., but generally failed t o stabilize the latex adequately. Of the series of nonionic polyoxyethylene glycol derivatives tested, only the amides, a t favorable p H levels, were approximately equal to the sodium fatty acid soap control in conversion rate and stability. The ethanols, esters, and amines gave only fair conversion rates with large variations in latex stability. Mixing emulsifiers sometimes improved the conversion rates or stability of the latex or both, but the results were unpredictable. Among the nonionic emulsifiers, no regular variation of emulsifier efficiency with solubility index was observed above a poorly defined minimum value, below which rates were low or negligible. The final latices obtained from charges in which no prefloc developed, after removal of residual monomers, were extremely stable and required special procedures for flocculation. At least one of the latices could be frozen and subsequently thawed without inducing coagulation. The chemical, gel, and mill-processing properties of the polymers prepared in 5-gallon reactors with the various synthetic emulsifiers were similar to those of the GR-S controls. All experimental polymer stocks were to some degree inferior t o the control polymers in maximum tensile strength. The other physical properties of the polymers were not sufficiently superior to those of the
TABLE V. SUMMARIZED SPECIAL PHYSICAL TESTDATA Emulsifier Polymer
No.
Type
Parts
Min. Cured at 292' F. 65 40
HysteresisTemp. Rise a t 30 Min..
Set, 15.2 4.6 9.2 10.2 10.2 17.9 13.4 15.2
22.6 13.2
F.
49LA6 All
64 84/2
A16 A9 A15 A17 A19 X-624
64/2 8-370 8-370 K-460 K-460 Dres. 214
241 3
6
6 4.6
85 85 55
66 61 54 42 52 76 72 68
49LB6 GR-S-1002
K-460
Dres.731
5 4.3
85 70
79 51
3 2.5/1.5
g;55
%
DeMattia Flexures X 10-8 25 1 10 12 7 14 9 12
3 4
Quality Index 6.'6 0.3 4.2 7.6 3.1 2.7 2.1 4.4 0.4 1.9
Goodyear Re bound, % ' at 77O F. 212'F.
.... .. 55
.. 48 .. .. .. ..
.. ..
..
66
..
62
.. .. *.
..
I N D U S T R I A L AND E N G I N E E R I N G CHEMISTRY
1336
controls to indicate an advantage in the use of the synthetic emulsifiers investigated in this study in preparing GR-S polymers. The results of investigations carried out in the rubber industry concurrently with those described in this paper suggest the following applications of the more satisfactory emulsifiers for producing and compounding latices.
Vol. 45, No. 6
LITERATURE CITED (1) Carr, C.
W.,Kolthoff, I. M., Meehan, E. J., and Williams,
(2)
D. E., J . Polymer Sci., 5 , 201-6 (1950). Danforth, J. D. (to Universal Oil Products Co.’, U. S. Patent
(3)
Feldon, A I . , AlcKennon, F. L., and Lawrence, R.Y,, IKD. EXG.
2,466,212 (April 5, 1949).
CHCX.,
44, 1662-4 (1962).
Harkins, W.D., J. Polymer Sci., 5, 217-51 (1950). ( 5 ) XcKennon, F. L., and Lawrence, R. V. (to United States of rimerica represented by Secretary of Agriculture), U. S. Patent 2,465,901 (March 39, 1949). (6) Schoeller, C., and Wittwer, 51. (to I. G. Farbenindustrie X.,G.), (4)
The excellent chemical, physical, and light stability afforded by the nonionic emulsifiers recommends their use in coating latices. A number of these emulsifiers are now being sold commercially for such purposes. Of particular interest in the paper coating and paint application is the indication that nonionic emulsifiers produce a butadiene-styrene latex of relatively large particle size. Such particle size control might contribute greatly to obtaining better fluidity in a high-solids latex. These agents can also be used to advantage for the inhibition of excessive foaming, freeze-thaw coagulation, instability to mechanical agitation, and instability to addition of compounding chemicals. Such application can also be made to latex in compounded form such as emulsion paints. The method developed for the selection of “tailor-made” emulsifiers for use in butadiene-styrene copolymerizations can be extended and adapted to other emulsion polymerization and bead polymerization systems, including copolymers based on acrylonitrile or vinyl chloride. The broad range of properties available in the individual nonionic, anionic, and cationic emulsifiers and in mixtures of these materials should assist the polymerization research chemist greatly in developing new emulsion copolymerization products and improving those already in use.
IEid., 1,970,578 (Aug. 21, 1934).
(7)
Schulse, W ,A., Tucker, C. >I., and Crouch, W. W.,Ixn. ENG.
(8) (9)
Staudinger, J. J. P., Chemistra and Industry, 1948, 563-8. Steindorff, A . , Balle, G., Horst, K., and Michel, R. (to Gcneral Aniline and Film Corp.), E. 6. Patent 2,213,477 (Sept. 3,
(10) (1 1 )
Weidlein, E. R., Jr., Ckem. Bng. Yews, 24, 771-4 (1946). Wolthan, H., and Becker, W. (to Jasco, Inc.), U. S. Patent
(12)
Znicker, B. PI.G. (to B. F. Goodrich Co.), Ibid., (Oct. 16, 1946).
CHEM.,41, 1699-1603 (1949).
1940). 2,222,967 (Kov. 26, 1941). 2,386,764
RECEIVED for review Kovember 4 , 1959. ACCEPTED March 16, 1953. Presented before the Diviaion of Rubber Chemistry, AMERICAE; CmmIcAL SOCIETY, a t Buffalo, N. Y . , October 29,1952. The laboratory and pilot plant work reported herein was carried out under the sponsorship of the Office of Synthetic Rubber, Reconstruction Finance Corp., in connection with the government synthetic rubber program.
Mechanism. of Combustion Chamber
Deposit Formation with Leaded Fuels W. E. NEWBY AND L. F. DUMOIVT Jackson Laboratory and Petroleum Laboratory, Organic Chemicals Department, E . I . d u Pont de Nemours & Co., Inc., Wilmington, Del.
T
HE formation of deposits on the combustion chamber walls
during normal operation of Otto-cycle engines increases the tendency of fuels to knock. Some of the factors responsible for this effect have been described ( 3 , 4,6), but very little information is available about the reaction mechanisms which result in the accumulation of these deposits from fuels containing tetraethyllead. Because such information would give a better understanding of ways to prevent or reduce deposit formation, a study of these reactions x a s undertaken a t the D u Pont laboratories.
experiments conducted in a single-cylinder engine used as a “reaction vessel” to confirm laboratory predictions. The lead salts in deposit8 have been found by x-ray diffraction techniques to consist of simple and complex compounds of lead chloride, lead bromide, lead sulfate, and lead oxide. Those identified a6 deposit constituents are listed in Table I. The relatively volatile lead halides are present because organic halogen compounds are used with tetraethyllead to promote elimination of lead compounds from hot engine surfaces. Lead sulfate is found, as all commercial gasolines contain some organic sulfur compounds.
SOURCES OF DEPOSITS
Practically all the gasolines used today contain tetraethyllead t o improve their octane number or their resistance to knock. Although almost all of the tetraethyllead decomposition products are removed from the combustion chamber with the exhaust gases, a small amount remains on the combustion chamber walls in the form of inorganic lead salts. In addition to lead salts, deposits contain carbonaceous materials resulting from incomplete combustion of the fuel and lubricating oil and minor amounts of metallic and nonmetallic compounds introduced into the combustion chamber with the air, fuel, and oil, and as a result of engine wear. Any investigation aimed a t defining the mechanisms leading to the formation of such a complex structure must involve a systematic isolation and study of each of the influencing factors. In this particular work the studies were limited to investigating the reactions involved in the formation of the lead salt portion of deposits. These studies consisted of theoretical thermodynamic calculations, laboratory bench test experiments, and
CHEMICAL REACTIONS OF DEPOSIT FORMATION
The !Tide variety of lead salts in deposits is formed as a result of chemical reactions which occur in the combustion chamber after the fuel-air charge is burned. The stages in vhich reactions may influence deposit composition are: 1 . Combustion of the fuel and additives. 2 . Vapor state reactions of the gases present from combustion. 3. Condensation of the gaseous lead compounds on the chamber m-all. 4. Gas-solid reactions between solid lead salts and the gases present in the chamber. 5 . Solid state reactions between lead salts in the deposit. 6. Vaporization of the volatile lead salts.
Each of these stages was studied and the reaction sequence shown in simplified form in Figure 1 was developed after their relative importance had been established. The reactions which occur in each stage can be summarized as follows:
