PRODUCT AND PROCESS DEVELOPMENT
Amines as Activators for Polymerization of Butadiene and Acrylonitrile in Emulsion J. W. L. FORDHAM'
AND
H.
LEVERNE WILLIAMS
Research and Development Division, Polymer Corp., Itd., Sarnia, Onfario, Canada
T
HE first paper in this series (10)described activators for
the cumene hydroperoxide-initiated, low-temperature polymerization recipe for butadiene and styrene. The combination stressed was dextrose and the ferrous iron complex with ethylenedinitrilotetraacetic acid. Whitby and others ( $ 7 ) found that polyethylenepolyamines with traces of iron were effective activators in the absence of dextrose. Spolslry confirmed this (26) and showed that ferrous iron and dextrose could be used to modify the effectiveness of the polyethylenepolyamine activators. Kolthoff and Meehan have published similar types of recipes, the veroxazine (9) and the sodium sulfide (lO)-activated. Embree and others (3) studied the polyethylenepolyamhe-activated recipes further, showing that these could be used when butadiene and acrylonitrile were copolymerized. Recipes activated b y amine compounds, iron salts, and a coreducer have found widespread use in the copolymerization of butadiene and styrene with an oil-soluble initiator such as cumene hydroperoxide. It was of interest to study some of the variables of the system as influenced by the presence of water-soluble monomer such as acrylonitrile and a water-soluble initiator such as potassium persulfate.
ponent of the catalyst activator system over wide ranges of concentrations. Cumene Hydroperoxide-Dextrose Tetraethylenepentamine Recipe. The above recipe is simplified by using tetraethylenepentamine as combined reducer and complexing agent and omitting the dextrose and ferrous iron, although the addition of either or both may alter the rate of conversion. A survey of the variables is given in Figure 2. The rates of conversion increase with increasing concentration of dextrose, but there is no conclusive evidence of optimal concentrations. The recipe is insensitive to changes in concentration of any one component over wide ranges of concentration. Representative time-conversion curves a t 5' C. in Table I show that the addition of tetraethylenepentamine results in a sustained regular rate, whereas the presence of ferrous sulfate causes irregular data suggestive of exhaustion of the catalyst.
-
Table 1.
Studies of various recipes show influence of variables on conversion
Polymerization reactions were conducted in 8-ounce bottles as described in earlier apers (10,SS-16). The polymerization recipe was composed o f butadiene and acrylonitrile in the ratio of 65 to 35 parts. There were 250 parts of water er 100 of monomers; the recipe contained 0.45 part of triso&m phosphate, the emulsifier, and caustic to adjust the p H to a constant value, usually 10.5 to 11.0. Unless otherwise noted, the emulsifiers were 3.0 parts of Daxad 11and 0.6 part of Nacconol NRSF (Table VII). Potassium persulfate was added as an aqueous solution and cumene hydro eroxide as a solution in benzene. The activators were addecf in aqueous solution, except the cyanoethylated amines, which were added in acrylonitrile. The dextrose in all cases was digested by boiling for 10 minutes in 0.1% potassium hydroxide solution in the ratio of 0.4 part of potassium hydroxide to 1.0 part of dextrose. The reaction times and temperatures are indicated below. The reactions were stopped by adding an inhibitor such as hydroquinone or sodium dimethyldithiocarbamate and the conversion of monomer to polymer was determined by drying a sample of latex to constant weight. Cumene Hydroperoxide-Dextrose-Iron-Ethylene Dinitrilotetraacetate Complex Recipe. The effects of variations of the concentration of the components of the catalyst activator system are recorded in Figure 1. There are optimal concentrations for each chemical, the effect being most marked for ferrous sulfate and dextrose. All three compounds in the activator are required for good rates of conversion of monomers to polymer. The exact quantities can be chosen t o result in the desired rate. The recipe is insensitive to the oxidation-reduction state of the iron, to the presence of stabilizers of acrylonitrile such as p-dimethylaminopropionitrile, and to changes in concentration of a com1 Present address, Technical Center, Diamond Alkali Co., Painesville, Ohio.
1714
a
.
Effect of Variation of Activator Components on Time-Conversion Curve
(Cumene hydroperoxide 0.10 part, dextrose 1.0 part) Conversion. 70 Polyamine, Part 3 hr. 6 hr. 9 hr. 0.0 18 21 23 0.19 19 43 65 26 41 41 0.19" Ferrous sulfate heptahydrate 0.028 part.
12 hr. 24 76 50
~
Potassium Persulfate-Dextrose-Iron-Ethylene Dinitrilotetraacetate Complex Recipe. The reverse type of redox system, one in which the oxidant such as potassium persulfate was watersoluble and the reductant such as disalicylethylenediamine or benzoin was oil-soluble, was tried a t 13" C. Compared with the results obtained with water-soluble iron complexes (Figure 3), the data were far from encouraging and further attempts to obtain a workable recipe were abandoned. More reactive reducers with favorable distributions between the oil and water phases might be effective as the iron complex. The use of a completely water-soluble redox system, including digested dextrose as a reducer, was studied at 13" C. The results (Figure 4) are in surprisingly good qualitative agreement with those observed when cumene hydroperoxide was used (Figure 1). There is the same tendency for optimal concentrations t o be required, the same marked effect of the first small additions of catalyst and activator components, and the same insensitivity to variations in concentration over the broad optimal ranges. Unlike the former recipe, i t was sensitive to the concentration of p-dimethylaminopropionitrile. Ammonium persulfate was less effectiveand hydrogen peroxide was ineffective as oxidant. I n Table I1 are representative time-conversion data for the two redox systems and mixtures of them at 13' C. Those based on cumene hydroperoxide start a t a high rate and slow down, whereas those containing potaesium persulfate start slowly and accelerate. A mixture of the two oxidants results in more linear time-conversion curves.
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
Vol. 47, No. 9
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PRODUCT AND PROCESS DEVELOPMENT
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Potassium Persulfate-Cyanoethylated Amine-Iron Recipe. T h e next step was t o replace the dextrose and the ethylene dinitrilotetraacetate by representative amines which had been cyanoethylated with acrylonitrile. The crude propionitriles were prepared by the methods indicated in the literature ( g ) with a 1 t o 1 mole ratio of acrylonitrile t o amine during cyanoethylation and dilution of the reaction mixture with the monomer just before addition t o the reaction bottle, unless it was reported that the propionitrile was formed very rapidly a t room temperature. Under these conditions the amine was added to the total acrylonitrile (monomer and activator). If no information was available in the literature on the cyanoethylation of a particular amine, the former procedure was used, with a reaction time of
60 -
50-
2
40-
v)
K
w
i 01
0
I
I
1.0
2.0
DEXTROSE,PTS.
:E0
630tol
0,(05 ,
0.15
, [ 1
0.05 ,
,
/
I
,
,
o
0.10 0.30 EDTA. PTS.
0.15
FeS0,.7HE0 PTS.
(7) 1.0 ,
o
2.0
3.0
l
a4 0.s 1.0 DEXTROSE.PTS.
Figure 1. Effect of concentration of cumene hydroperoxide (CHP), ferrous sulfate heptahydrate, ethylene dinitrilotetraacetate (EDTA), and dextrose on conversion 1. 1 9 hours 2-8. 17 hours 1, 3, 5, 7. At 5' C. 2, 4, 6, 8. At 13' C. 1. Ferrous sulfote 0.18 EDTA 0.18, dextrose 1.0 port 2. Ferrous sulfate 0.028, EDTA 0.38, dextrose 0.2 port 3. CHP 0.1, EDTA 0.1 5 dextrose 1 .O part 4. CHP 0.1 5, EDTA 0.38, dextrose 0.2 port 5. CHP 0.1, ferrous sulfate 0.1 8, dextrose 1 .O part 6. CHP 0.1 5, ferrous sulfate 0.028, dextrose 0.02 part 7. CHP 0.1, ferrous sulfate 0.18, EDTA 0.17 port 8. CHP 0.1 5, ferrous sulfate 0.028, EDTA 0.38 port
Table
II.
Cumene Hydroperoxide, Part
Time-Conversion Data for Recipes with Catalyst Activator Systems Indicated K2S208,
Part
0.076
0.0
0.0
0.135
0.076 0.076 0.060
0.054
0 108
0.135 0.135
September 1955
I
I
0.05
0.10
r 0.15
TEPA,PTS.
Figure 2. Effect of concentration of cumene hydroperoxide, dextrose, and tetraethylenepentamine (TEPA) on conversion
CHP,PTS.
IO
/
3.0 0
Dextrose, Part
4 hr.
0.2 0.4 0.2
17 27 Q
0.8
31
0.4
24
0.4 0.8
20
0.2
0.2
28 14 10
Conversion, % 8 hr. 12 hr. 16 hr. 20 hr. 35 61 76 Qf3 48 75 77 92 18 32 52 71 43 65 78 89 63 83 91 96 37 54 71 81 59 80 80 92 37 62 80 89 23 39 53 64
1 6 hours at 5 ' C. 1 . 0.05 CHP, TEPA 0.1 2. 0.1 CHP, TEPA 0.1 3. 0.2 CHP, TEPA 0.1 4. 0.02 CHP, dextrose 1 .O 5. 0.05 CHP, dextrose 1 .O 6. 0.2 CHP, dextrose 1.0 7. 0.5 part CHP, dextrose 0.0
approximately 20 hours a t room temperature. The propionitriles were tested, by adding 1 millimole to the 100-gram monomer charge in the absence and presence of 0.0278 part (0.1 millimole) of ferrous sulfate heptahydrate. The result8 in Table I11 show t h a t the polyethylenepolyamines, the short-chain primary amines, and the ethanolamines are effective as activators when cyanoethylated and in the absence of dextrose or ferrous iron. When ferrous iron is added, there is slightly more conversion in 17 hours a t the reaction temperature of 13' C. The amines must be cyanoethylated prior to their addition. There was very little conversion in 17 hours (
