POLYAMINE-ACTIVATED POLYMERIZATION Comparison of Polyalkylene Polyamines G. S. WHITBY, N. WELLMAN, V. W. FLOUTZ, AND H. L. STEPHENS University of Akron, Akron, Ohio 4
Many amines have the ability to decompose organic peroxides, but in peroxide-catalyzed emulsion polymerization only a limited number of amines have an activating effect so powerful that it is possible by adding them to the system to bring about rapid polymerization at a low temperature. Particularly effective are polyethylene and polypropylene polyamines when the peroxide catalyst is of the class represented by cumene hydroperoxide, A comparison of the members of the series of polyethylene polyamines from diethylenetriamine to nonaethylenedecamine indicates that the effectiveness of these polyamines
reaches a maximum in tetraethylenepentamine and pcntaethylenehexamine and then gradually decreases in the higher members. Dipropylenetriamine and tripropylenetetramine are more effective than the corresponding ethylene polyamines. Examples of the effectiveness of the polyamines in bringing about polymerization at low temperatures are as follows: In a soap emulsion at 10” C., with 0.21% cumene hydroperoxide and 0.2Y0 technical tetraethylenepentamine, styrene gave a 73q0 yield of polymer in 1 hour; a 70:30 mixture of butadiene and styrene gave a yield of 700/, in 6 hours.
T
the recipes now used for the low temperature production of GR-S depend essentially on the use of iron compounds as activators. However, the use of such activators would be expected to introduce into the polymer heavy metals which might possibly catalyze subsequent autoxidation and consequent deterioration or have other objectionable effects. Hence a search was made for other agents, free from heavy metals, capable of serving as activators. It was found that many aliphatic and alicyclic amines are capable of decomposing organic peroxides vigorously. Some qualitative observations made in this connection may be noted. Immediate semiexplosive decomposition (“Verpu$ung”) took place when to about 1 gram of benzoyl peroxide was added one drop of the following: piperidine, morpholine, N-methylmorpholine, mono-n-amylamine, phenylhydrazine, n-butylethylenediamine, 1-(2’-aminoethyl)pyrrolidine,dimethvlbenzylamine, diethylenetriamine, triethylenetetramine, tetraethylenepentamine, pentaethylenehexamine, or the dibutylidene derivatives of the four last-mentioned amines. The following amines also were observed to bring about the vigorous decomposition of benzoyl peroxide, although they were apparently somewhat less active than the amines just mentioned as it was necessary to wait a few minutes or t o add more than one drop of the amine before the peroxide verpufft: n-hexylamine, cyclohexylamine, ethylenediamine, propylenediamine, di-n-propylamine, di-n-butylamine, dicyclohexylamine, triethylamine, tri-n-propylamine, tri-n-amylamine, dimethylcetylamine, N,N’-d i e t h y 1c g c 1o h e x y 1a m i n e , ethanolamine, p-diethylaminoethyl alcohol, 2-amino-2-methylp r o p a n o l , l-(2’-aminoethyl)piperidineJ 1,3-bis(2’-aminoethylamino)propane, 1,3-bis(3‘-aminopropylamino)propane. Since the present work was completed, it has been drawn to the authors’ attention that Nozaki and Bartlett (65) and Bartlett and Nozaki (6) had previously observed that amines such as aniline, dimethylaniline, n-butylamine, and triethylamine will bring about the explosive decomposition of benzoyl peroxide. Earlier Gambarjan and associates (10-13) had found secondary and tertiary amines to be readily oxidized in ethereal solution by benzoyl and acetyl peroxides. When amines such as those listed above were added to cumene hydroperoxide or to tert-butylhydroperoxide, they produced decomposition of the peroxide, but the decomposition was not as violent as when they were added to benzoyl peroxide; in most
H E catalyst-activator combinations capable of bringing about rapid polymerization at low temperatures which are described in the present paper were developed on the basis of a study of the influence of various compounds in effecting the decomposition of organic peroxides. When organic peroxides are used as catalysts or, more correctly, initiators of polymerization, it is normally necessary to work at an elevated temperature, because only a t such a temperature do the peroxides decompose to generate free radicals at a sufficient rate to cause polymerization to occur with reasonable rapidity. In order to produce, by means of such catalysts, a practicable rate of polymerization at a low temperature, it is necessary to add to the system a reagent, conveniently termed an activator, adapted to decompose the peroxide at a temperature a t which normally it would remain substantially stable. I t was observed that suitable derivatives of certain heavy metals will decompose cumene hydroperoxide. Thus, for example, the chelated iron compounds, iron phthalocyanine and hemin, actively decompose this peroxide. When 1 mg. of iron phthalocyanine dissolved in 1 ml. of benzene was added to 10 ml. of cumene hydroperoxide (70% pure) in a test tube, evolution of oxygen was soon noticeable; the temperature rose from 25” C. initially to over 40 O C., and decomposition was complete in about 1 hour. (If the cumene hydroperoxide is mixed with styrene, no such decomposition occurs on the addition of iron phthalocyanine.) Cobalt compounds also decompose the hydroperoxide. When to 10 ml. of cumene hydroperoxide in a test tube at room temperature there was added one drop of a cobalt linoleate drier containing 6% cobalt, vigorous decomposition occurred and the temperature rose rapidly and reached 120” C. Cobalt acetylacetone also decomposed cumene hydroperoxide, although less vigorously than the more readily soluble cobalt drier. This cobalt complex was also observed to decompose tertbutylhydroperoxide. The cobalt chelate compound from disalicylalethylenediamine apparently failed to decompose the two hydroperoxides. Manganese and lead in the form of paint driers decomposed cumene hydroperoxide. The manganese drier appeared to be less active than the cobalt and the lead to be less active than either of the other two. Such observations suggest that it should be possible to discover activators of low temperature, peroxide-catalyzed polymeriz& tion among organic derivatives of suitable metals. And in fact 445
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
446
TABLEI. COMPOUKDS L~CJCING IN
ACTIVATISG EFFECT IX I h f U L S I O N POLYXLRIZ.4TIOK O F SI’YRESE COST.4INIXC CCMEKE
HYDROPEROXIDE Methylamine it-Hexylamine n-Dodecylamine Renzylamine @-Phenylethylamine Ethanolamine ?-Anlino-2-methylpropanol 2-.~mino-2-methvlwro~anediol ?-dmino-j-diethyiami’nopentanc Tvramine ” - ~~.~~~ Phenylhydrazine Tetramethylenedianiinc Di-n-propylamine Diisopropylamine Dibenzylamine Aldehyde ammonia Piperidine
Diethanolamine D-8-phenyiethylamine n-A rnylaniline Triethylamine Tri-n-butylamine Di methyibenzylamine i~~-l\iIethylmorpholine 8-Diethvlaminoethvl alcohol
~
-115
benilene Ris(2-hydroxyphen~l)silifide
Vol. 42, No. 3
strong accelerating effect on the rate of emulsion polymerization in the presence of suitable peroxide catalysts. This paper is concerned primarily with this phenomenon, which has been designat,ed “polyamine-activated polymerization.” A convenient, briefer designation, suggest,ed by others, is “peroxamine” polymerization. The so-called polyethylenc polyamines are particularly effective as activators in conjunction with catalysts of the type of cumene hydroperoxide. Unless otherwise indicated, the samples of these polyamines used were technical products from the Carbide and Carbon Chemicals Corporation. The cumene hydroperoxidc (CHP) was the Hercules technical product containing 70% actual CHP, the balance being acetophcnone and dimetliylphcrigl carbinol. I’OLYAMINES 1% RULK I’OLYMERIZATIOh
cases there vas merely a moderate rise in tcmperature tu indicate decomposition of the peroxide. IIov-ever, with the liighcr polyalkylene polyamines, such as tetraethylenepentainr, rraction more violent: the addition of a fen- drops ol this amiiie to 5 ml. of cumene hydroperoxide raised the temperatsure to the point at which the mixture violently boiled off. The polyalkylene polyamines also brought about the violent decomposition of methyl ethyl ketone peroxide (GO% solution in methyl phthalate), methyl isobutyl ketone peroxide (8070 solution in methyl phthalate), di-tvi-butyl diperphthalate and (with a c~onsiderable amount of t,he amine) tertbutyl perbenzoat’e. They also decomposed hydrosyheptyl peroxide, although l e ~violently. They apparently failed to decompose 1-hydroxycvc:lohexyl-lhydroperoxide. Uniperos (a product containing 60% of mixcd hydroperoxides of the type of met’hylcyclohexyl hydroperoxide) behaved similarly to cumene hydroperoxide when treated with amines. When 2,2-bis-tcrt-butyl peroxybutane was treated with tetraethylenepentamine, there was evidence of decomposition as shown by rise in temperature, but decomposition was not violent. A solution of hydrogen peroside ivas wadily decomposed by most or all of the amines mentioned.
\Then polyamines were used in the bulk polymerization of styrene m the piescnce of CHP, they had an activating effect, but the latter was of a rclatively low order, as the results in Tables I1 and I11 indicate
’
I’RELIRIINARY EMULSION POLYRIERIZATION T E S T S WIT11 AMINES
h considerable number of preliminary polymerization esperiments xere carried out in which along with an organic peroxide catalyst a wide variety of amines were introduced. Most of the peroxidedecomposing amines and amino compounds exrimined had no activating effect, but thc polyalkglene polyamines had a powerful activating effect in t,hc emulsion polymerization of styrene, although only a mild effect in the bulk polymerization of the same monomer. The compounds (mostly anlines) listed in Table 1 hat1 no significant ibctivating effect, as judged by the fact that they caused no masked increase in the rate of polymerization of stvi-ene vhen the latter was emulsified in a soap solution and treatcd with cumene hydroperoxide. These screening t’ests were run in corked test tubes of 30 nil. capacity charged with 10 ml. of 2.5% potash soap solut,ion (mostly the myristate or oleate) and 5 grams of styrene, with 1 to 2 parts amine and 2 parts cumene hydroperoxide per 100 parts of styrene. Supernatant air was displaced from the tubes by means of nitrogen. (Xitrogen used throughout this work was high purity, 99.99%,Linde nitrogen.) The tubes were shaken at frequent inteivds for 1 hour at room temperature and their contents m r e then poured into methanol containing a lit& sulfuric acid, to throw out any polymer formed. In control experiments, in vhich no amine TYS introduced, the yield was nil. The screening tests showed that certain aliphatic di- and polyamines containing, in the same molecule, amino groups of different degrees of substitution (primary, secondazy, t,ertimy) had a
TABLE 11. INFLUENCE OF POLYAXINE ON RATEOF BULK POLYOF STYHEKE,UNDER NITROGEN,CATALYZED BY CUMENE HYDROPEROXIDE AT 55 C.
IIERIZATIOK
Parts/100 Parts Styrene CIII’ Amine Kil Si1 0.7 Si1 0.7 I)iethylenetriamnine, , 5
Yield of Polystyrene in 44 IIours a t 55’ C., R Si1 59.5 84.5
TABLE 111. INFLUENCE OF AKINES ON RATEOF BULKPOLYM E R I Z . ~ ~ T O X OF STYRENE, UNDER NITROGEN, CATALYZED BY CUMEXSE HYDROPEROXIDE AND BENZOYL PEROXIDE AT Rooai TEMPERLTURE Parte Catalyst,’ 100 Parts Styrene 0.7 1.4 0.71 0.71
Parts Amine,’lOO Parts Styrene Catalyzed by Cuinene Hydroperoxide S il Si1 Diethslenet riamine
0.5 1.0
1.41
0.7 0.7 1.4 1.4
0.7 1.4
0.7) 1.4, 1.4 0.7 0.7 0.7
4.3 8.8 18.0 18.7 58.0
1.41
0.7’
Yield of Polystyrene in 6 Days a t Room Temperature, yo
’retraetliylenepentarriine .V-methylmorphoiine Morpholine Triethanolamine Cobalt acstylacetone
1.0
1.0 10.0 1.0
Catalyzed b y Benzoyl Peroxide Nil Nil Diethylenetriamine Tetraethylenepentainine N-methylmorpholine Morpholine Triethanolamine
{I::: 10.0 0.5
0.5
39.4 23.0 4.0 3.7 Trace 39.2 7.9 12.0
Nil Nil Nil 2.5 Nil 12.1 33.7
When benzoyl peroxide is used as the catalyst the polyamines have no activating effect; triethanolamine activates with benzoyl peivxide but not with cumene hydroperoxide. POLYAMINES IN EMULSION POLYMERlZATlON
I n the emulsion polymerization of styrene the polyamines had a much greater activating effect than in its bulk polymerization; the reaction was so vigorous that. in screening tests similar to those described (Table I), the emulsion, originally at room temperature, rose in temperature by 20” or even 30” C. and, unless the temperature was controlled, a conversion of 95 to 100% was obtainable in 10 minutes vith the most ,wtive of the polyamines, in particular triethylenetetvnmine and tetra-
INDUSTRIAL A N D ENGINEERING CHEMISTRY
March 1950
TABLEIV. POLYAMINE-ACTIVATED POLYMERIZATION OF STYRENE IN EMULSION AT 10" C.
three-necked flask equipped with a mercury-sealed, motordriven stirrer and with a tube for removing samples at intervals under nitrogen pressure.
(Charge: water 180 ml.: potaasium laurate, 5 rams. KC1, 0.8 gram; amine, i1.2 gram: styrene, 100 grams; C ~ P0.i1 , gram) Time. Min. Yield, % 1.9 240 Control (no amine)
COMPARISON OF POLYALKYLENE POLYAMINES AS ACTIVATORS
Tetraebhylenepentamine
Pentaethylenehexamine
500 1170 1410 10 20 30 40 60 70 SO 90 20 4 60
80
Triethylenetetramine
Diethylenetriamine distilled: boiling point, 203.5-205° 736 mm.)
b..
100 120 140 15 30 45 60 75 90 105 120 30 60
90
Ethylenediamine
Dipropylenetriamine
Trimethylenediamine
-
447
120 150 180 2113 240 270 300 330 360 60 120 180 240 300 1230 1290 45 65 85 105 125 145 165 185 205 60 120 180 240 1260 1380 1500 1620
3 9.9 15.8 19.1 33.7 56.1 65.2 72.8 77.9 81.3 86.6 24.9 56.9 77.2 90.0 87.0 95.7 91.2
8.8
24.1 39.1 54.4 65.3 75 84.3 90.5
2.6 5.3 10.2 20. I 33.1 42.3 54.5 62.3 64.6 70.3 71.8 79.5 2.5 6.1 13.4 19.0 25.7 88.3 88.0 16.8 29.9 43.4 56.3 64.4 72.3 79.0 82.6
81.8 1.9 1.7 2.2 2.8 11.5 13.8 15.0 16.4
ethylenepentamine. With diethylenetriamine the reaction is also vigorous. A mixture of 10 ml. of 2.5% potassium myristate solution and 5 grams of styrene together with 1.8 parts of cumene hydroperoxide and 2.0 parts of diethylenetriamine per 100 parts styrene, when shaken under nitrogen at room temperature (without control of the temperature rise), gave the following yields: 8 minutes, 69.2%; 12 minutes, 84.4%; and 16 minutes, 95.2%. The simple diamines, ethylenediamine and propylenediamine, however, had only a very mild activating effect; the yields in similar experiments using 1.8 parts of cumene hydroperoxide and 1.5 parts of amine per 100 parts of styrene were only 6.0 and 4.995, respectively, after 30 minutes. Some results of experiments at a controlled, lower temperature are given in Table IV. The strongest activators among the amines tested are tetraethylenepentamine and pentaethylenehexamine (which are roughly equal in activity); triethylenetetramine, dipropylenetriamine, and diethylenetriamine follow in decreasing order of activity, and ethylenediamine is markedly lower in activity. The experiments were conducted under nitrogen in a 500-ml.
A number of polyalkylene polyamines were compared to determine their effectiveness in activating the low temperature emulsion polymerization of 70:30 mixtures of butadiene and styrene in the presence of cumene hydroperoxide. The experiments were conducted in 4ounce, screw-capped bottles, each charged with 20 grams of monomers and rotated end-over-end at 35 r.p.m. in a thermostatically controlled water bath. The amine was added to the water phase and the peroxide to the styrene. The results show certain irregularities (mostly minor) which seem inevitably, with present knowledge, to affect such emulsion polymerization experiments, but the trend of the results is usually su5ciently clear to indicate the broad conclusions to be drawn. Unless otherwise stated, the polymerization recipe used in the experiments (called the general recipe) was as follows: Parta by Weight Butadiene Styrene Wttsr Water
PotGiium Potaasium Iaurate laurate Potassium ohloride Potasrium hydroxide CHP Amine
70 30 180 6
0.8 0 : 112
Vaned Varied
The purpose of the potassium chloride in the recipe was to maintain fluidity in the emulsions. As polymerization under the influence of the cumene hydroperoxide-polyamine combinations proceeded, the emulsion rapidly lost its original milky appearance and became almost translucent; further, the system became very viscous and in some cases actually gelled at high conversions, unless there was included a salt such as potassium chloride, which served to maintain fluidity. In explanation of the inclusion of potassium hydroxide in the recipe, the polyamines are capable of forming soaps with fatty acids, but amine which is thus tied up does not function effectively as an activator; only the free amine is a powerful activator in polymerization. This is illustrated by the results in Table V which show that when the amine is present as a soap there is little polymerization but when potassium hydroxide is added to liberate the free amine and form a potash soap, rapid polymerization occurs.
TABLE V. INFLUENCEOF KOH ON CHP-CATALYZED POLYMERIZATION OF STYRENE EMULSIFIED BY SOAPFROM TRIETHYLENETETRAMINE AND LAURIC ACID [Charge: 2.5% solution of soap from triethylenetetramine (1 mole) and lauric acid (2 moles), 10 ml styrene 5 gram. CHP 0.09 gram. KOH varied. Emulsion initially 'At room hnperatdre; tehperature Got con: trolled 1
.
KOH added
Run 2
These results suggest that in polymerizations in which polyamines are used as activators in alkali-soap solutions, i t would be advantageous to add a proportion of caustic alkali. When the polyamines are added to solutions of alkali metal soaps, it is expected that an equilibrium will establish itself between alkali metal soap and amine soap, with the result that a certain amount of the amine will become tied up with the fatty acids and rendered more or less useless as a polymerization activator. Accordingly, the addition of caustic alkali, by displacing the equi-
Vol. 42, No. 3
INDUSTRIAL AND ENGINEERING CHEMISTRY
448 ~
TABLEVI. TETRAETHYLENEPENTAUINE AS ACTIVATORIN EMULSION POLYhIERIZATION O F BUTADIENE: STYRENE AT 10' c. (General recipe) Parts/100 Parts Monomers Yield, % of Polymer CHP Pentamine 6 hours 7 hours 8 hours 2.1a Si1 1.8U 0.21 3.0b Nil 1.8a 0.35 67.6 72.8 0.1 63.4 0.14 81.0 80.5 0.2 73.0 0.14 80.9 73.6 0.2 70.2 0.21 84.4 81.8 0.3 76.0 0.21 84.0 86.0 79.0 0.4 0.21 78.3 90.2 73.8 0.3 0.28 0.4 83.8 82.6 77.1 0.28
.. .. ..
4
6
White powder, apparently polystyrene. Apparently polystyrene largely.
(General recipe) Parts/100 Parts Monomers DipropyleneCHP triamine 6 hours 0.21 29.1 0.2 42.2 0.21 0.3 48.7 0.21 0.4 44.6 0.28 0.3 47.5 0.28 0.4 48.8 0.35 0.4 0.36 62.4 0.5
O
Yield, % 7 hours 55.3 58.9 62.4 62.6 68.3 67.3 70.0
8 hours 58.1 62.5 67.9 70.0 71.3 71.9 68.9
(0.21 C H P and 0.2 amine used) Yield, Recipe 5 hours 6 hours Run 1. Diethylenetriamine General recipe 3.9 6.0 Without KOH 20.7 34.2 With 0.112 extra KOH 4.0 4.4
General recipe Without KOH With 0.112 extra KOH
Dipropylenetriamine 26.3 39.1 22.8
Run 2.
TABLEVIII. PESTAETHPLEKEHEXAVINE AS ACTIVATOR IN EMULSIOK POLYMERIZATION OF BUTADIENE :STYRENE AT 10' C. (General recipe) Parts/100 Parts RIonomers CHP Hexamine 6 hours
0.14 0.14 0.21 0.21 0.21 0.28 0.28
0.1 0.2 0.2 0.3 0.4 0.3 0.4
0.14 0.21
0.1 0.2
Run 1 55.8 67.3 67.2 74.9 81.0 76.2 76.6
Yield, % 7 hours
8 hours 48.9 57.8 59.3 58.0 59.9 57.2 62.0
General recipe Without KOH
36.6 47.9 25.8
7 hours 2.6 42.95 3.8 34.4 55.1 3 .5
Diethylenetriamine
... ...
7.4 35.6
4.1 42.5
8 hours
64.0 72.6 71.7 79.0 79.5 80.0 83.1
68.9 75.3 82.8 84.5 86.6 85.4 85.5
63.2 81.5
68.2 81.1
Run 2 57.3 74.9
Yield, % 7 hours 38.4 49.8 51.0 47.7 53.4 55.3 52.9
TABLEX. DIETHYLENETRIBBIISE COUPARED WITH DIPROPYLESETRIAMINE AS ACTIYATORI N EXLSIOX POLYMERIZ-4TIOK O P BUTADIENE :STYRENE AT 10 C.-EFFECT O F ADDED L~LK.4LL!
TABLEVII. TRIETHYLEKETETRAMINE AS ACTIVATOR IN EMULSION POLYMERIZATION OF BUTADIENE :STYREKE AT 10 C. (General recipe) Parts/100 Parts RIonomers 6 hours CHP Tetramine 0.14 0.1 51.9 0.14 0.2 53.1 0.21 0.2 58.1 0.3 57.9 0.21 0.21 0.4 61.9 0.28 0.3 60.6 0.4 67.6 0.28
TABLE IX. DIPROPYLEKETRIAMINE AS ACTIVATOR IN EMULSION POLYYERIZATIOX OF BUTADIENE : STYRESEAT 10 O C.
librium in the direction of the alkali metal soap, will have a favorable effect on the rate of polymerization. Data given in a subsequent section show that several of the polyamines have a greater activating effect when potassium hydroxide is included in the recipe. However, with other members of the polyamine series, greater activation is shown when alkali is omitted from the recipe. It would seem that the p H of the polymerization system may influence the result, not only by its effect on the equilibrium between alkali soap and amine soap and the consequent availability of the free amine, but also by a direct influence on the reaction between peroxide and amine. Tetraethylenepentamine. Table VI s h o w that increase in the amounts of peroxide and polyamine beyond a certain low level has only a relatively small effect in increasing the rate of polymerization. Triethylenetetramine. Typical data for polymerizations in which triethylenetetramine is used in place of tetraethglenepentamine are given in Table VII, which shows that, although the tetramine is a vigorous activator, it is appreciably less efficient on a weight-for-weight basis than is the pentamine. Further, as with the pentamine, increase in the proportions of peroxide and amine used has only a moderate effect in increasing the rate of polymerization. Pentaethylenehexamine. From the results in Table VI11 it appears that pentaethylenehexamine as an activator in the co-
polymerization of butadiene and styrene is of about the same order of potency as tetraethylenepentamine. The hexamine used was a laboratory sample (supplied by the Carbide and Carbon Chemicals Corporation) whereas the pentamine was a technical sample. The former distilled more sharply (60% came over a t 189" to 193" C., 2 mm., when 50 ml. was distilled from a Claisen flask) than the latter, which distilled over a wide range. Dipropylenetriamine. Dipropylenetriamine appears to come next (lower) to triethylenetetramine in its activating effect on a weight-for-weight basis, as shown by the results in Table I X (see also Table VII). The triamine sample was obtained from the Bersworth Laboratories in 1943. Diethylenetriamine. This polyamine proved to be less effective than dipropylenetriamine in bottle polymerizations a t 10" C. Furthermore, it showed significant activating effect only when used without the inclusion of caustic alkali in the recipe. The quantity of alkali in the general recipe was sufficient to render the diethylene compound almost inactive. This quantity also reduced appreciably the activity of the dipropylene compound but had not the drastic effect with the latter that i t had with the former. Results illustrating these statements are given in Table X. Although diethylenetriamine was not very effective in the experiments at 10" C. (Table X), this amine led to high rates oT polymerization in experiments a t a somewhat higher temperature, especially when fairly high proportions of peroxide and amine were used (Table XI). Tripropylenetetramine. When examined in parallel with triethylenetetramine in a polymerization test, this propylene compound proved (as in the previous comparison of ethylene and propylene triaminesj to be appreciably more effective, even on an equal weight basis, than the corresponding ethylene compound. Results are given in Table XII. Tripropylenetetramine appears to be little if at all less effective than tetraethglenepentamine. Ethylenediamine. This diamine, unlike the higher members of the series of alkylene amines, proved tQ be only a weak activator, as shown in Table XIII.
INDUSTRIAL AND ENGINEEBING CHEMISTRY
March 1950
TABLE XI. POLYMERIZATION OF BUTADIENE: STYRENE AT 22' C. WITH
CUMENE HYDROPEROXIDE AND DIETHYLENETRIAMINE
TABLE XIV. HIGHER POLYETHYLENE POLYAMINES AS ACTIVATORS IN POLYMERIZATION OF BUTADIENE:~TYRENE AT 10" C.
[Recipe (parts by weight): ButadiFne, 70; styrene,, 30. water, 180; potassium oleate, 5; CHP, varied; diethylenetriamine, varied] Parts/100 Parts Monomers Yield, % ' C H P Triamine 2 hours 3 hours 4 hours 5 hours 6 hours 8 hours 0.7 2.0 62.0 81.0 90.0 .. 1.0 .. .. 75.0 .. 87:O 96:O 0.5 .. 68.5 . 83.0 83.0 0.25 .. . 34.0 .. 75.5 62.5 , , .. 10.5 .. 68.0 82.5 0.125
..
.
(General recipe with and without KOH) Yield, '?& 6 hours 7 hours 8 hours
Parts/100 Parts Monomers C H P Amine KOH 5 hours Ootamine
.
TABLE XII. COMPARISON OF TRIPROPYLENETETRAMINE AND TRIETHYLENETETRAMINE AS ACTIVATORS IN POLYMERIZATION OF BUTADIENE :STYRENE AT 10O C. (General recipe) Parts/100 Parts Monomers Yield, % CHP Amine 6 hours 7 hours
449
0.14 0.21 0.28 0.21
0.1 0.2 0.4 0.2
0,112 0.112 0,112 Nil
0.21 0.21 0.28
0.2 0.2 0.4
Nil 0.112 Nil
0.14 0.21
0.1 0.2
0.112 0,112
.. ..
..
..
48.4 50.8 60.5 74.3
45.2 63.1 71.9 80.0
57.1 73.4
39.5 42.9 60.9
54.5 43.7
..
56.8 51.6 64.7
63.2 66.9
68.6 72.3
70.8 76.4
83:4
Tetracoaamine
.. 52:s Pentamine
8 hours
0.14 0.21
Tripropylenetetramine 48.2 0.1 63.6 0.2 69.2 76.2
65.7 78.8
0.14 0.21
Triethylenetetramine 0.1 53.5 51.5 0.2 61.5 63.8
57.3 71.9
..
TABLEXV. INFLUENCE OF ADDEDALKALI IN POLYAMINEACTIVATED POLYMERIZATION OF BUTADIENE :STYRENE AT 10 ' C. (General recipe with variations in KOH and KC1 content) Parts/100 Parts Monomers C H P Amine
TABLE XIII. ETHYLENEDIAMINE AS ACTIVATOR IN THE POLYMERIZATION OF BUTADIENE :STYRENE AT 10 O C. (General recipe with and without KOH) Parts/100 Parts Monomers Yield, % CHP Amine KOH 6 hours 7 hours 0.28 0.3 0.112 7.0 7.6 0.28 0.3 Nil 6.7 7.9
..
KOH KC1
3
5
hours
hours
Yield, 6
'?&
hours
7
8
hours
hours
Tetraethylenepentamine (technical) 0.21
0.2
8 hours 9.4 9.2
..
0.000 0.056 0.112, Nil 0.168 0.224< 0.000 0.056. 0 . 4 0.112 0.000' 0.056 0 . 8 0.112,
.... ..
..
4i:5 74.7 66.0 59.0 73.5 70.0
63:5 85.5 75.5 68.4 78.5 72.3
..
..
Tetraethylenepentamine (purified)
Higher Polyethylene Polyamines. The results of polymerization tests in which polyethylene polyamines, higher in the series than the hexamine, were used as activators in the cumene hydroperoxide-catalyzed polymerization of butadiene: styrene are given in the Table XIV. These amines were heptaethyleneoctamine, nonaethylenedecamine, and polyethyleneamine 1000. The first two were synthesized by the methods described under Preparations in the succeeding section of this paper. The third, a commercial product with a molecular weight of 1000, corresponds to a mean formula of approximately H [NH(CH&]zsNHzthat is, to a tetracosamine. Results for a sample of technical pentamine which was run in parallel with the higher polyamines are included in Table XIV. I n the general recipe the activity of the higher polyamines is less than that of the pentamine and the activity falls as the molecular weight rises-that is, as the proportion of secondary to primary amino groups increases. Effect of Added Alkali. As shown in the tables, diethylenetriamine, dipropylenetriamine, and polyethylene octamine, decamine, and tetracosamine gave higher rates of polymerization when caustic alkali was omitted than they did in the general recipe. However, with triethylenetetramine, tetraethylenepentamine, and pentaethylenehexamine, the inclusion of caustic alkali has a favorable effect on the rate of polymerization. This is shown by the results in Table XV, although, owing to some irregularities, the results do not serve to establish with certainty the optimum level of alkali. I n view of the fact that with some of the polyamines the addition of caustic alkali had a favorable effect on the rate of polymerisation, whereas with others the effect was unfavorable, measurements were made of the p H of aqueous sdutioss containing soap,
0.105
0.1
0.000 0.112
O"
23.5 51.0 42.2 57.4
58.6 70.3 67.4 74.4
..
72.8 80.2
.. ..
..
..
..
74:8 82.6
..
Pentaethylenehexamine 0.21
0.21
0.2
0.2
i
0.000 0.056 0.112 0 . 4 0.224 0.280
..
..
42.5 50.0 60.5 71.0 67.0
54.0 86.7 84.0 78.0 59.3
60.2 66.3 87.0 69.6 70.0
47.4 57.1 59.4
48.7 62.7 64.3
47.6 65.7 69.9
Triethylenetetramine
0.000 0.280
..
a This colorless sample of pentamine was prepared from the technical material by recrystallization of the hydrochloride from aqueous methanol treatment with decolorizing carbon, and distillation of the liberated amine: b.p. 157-159O C., 1.5 mm., ng 1.5022.
TABLEXVI. p H
OF SOLUTIONS OF SOAP AND WITH AND WITHOUT ADDEDKOH
Water Potassium laurate Potassium chloride Polyamine Potassium hydroxide Amine Diethylenetriamine Dipropylenetriamine Triethylenetetramine Tetraethyleneuentamine Pentaethylenehexamine Heptaethyleneoctamine Nonaethylenedecamine
POLYAMINES
Parts by Weight Solution A Solution B 180 180 5 5 0.8 0.8 0.2 0.2 0.112
..
pHofA 10.84 10.90 10.78 10.87 10.68 10.93 10.87
pHofB 11.62 11.60 11.57 11.68 11.58 11.80 11.80
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
450
Vol. 42, No. 3
OTHER VARIABLES
TABLE XVII. INFLUENCE OF I M ~ MODIFIER ~ ~IN ~ PENTAMINE-ACTIVATED POLYMERIZATION OF BUTADIENE : STYREKE AT 10" C. (General recipe with 0.21 CHP, 0.2 amine, and various proportions of KOH) Parts/100 Parts Monomers Mercaptan KOH
Yield, 'X 7 hours
6 hours
8 hours
teit-Dodec31 Aieicaptan (Sulfole 8B) Nil
0.075
61.6 68.0 65.7 69.3 71.1 72.9 71.8 71.8 70.7 70.2
0.000 0.056 0.112 0.168 0,280 0.000 0.056
0.112 0.168 0.280
84.4 72.9 73.5 71.6 75.0 84.7 76.9 73.6 76.5 76.3
Mixed Tertiary Mercaptans (MTAI, Philips Petroleum) Nil
:; 0.2 Nil 0.2
0.000 0.000 0.112 0.112 0.280 0,280
71.1 76.6 62.4 67.6 69.5 70.4
81.6 80.6 68.2 67.8 73.7 76.2
80.7 82.6 73.2 76.95 77.4 80.5
TABLEXVIII.
EFFECT O F PARTIAL REPLACEhIENT O F WATER BY METH.4KOL I K PENTAMINE-ACTIVATED POLYhIERIZ.4TION OF
BUTlDIENE :STYRENE
Parts/100 parts Monomers PentaCHP mine 0.14
0.21
0.1
0.2
AT
(General recipe) Water Rep1aced by Methanol, % by 1'01. 6 hours 0
10 15 20 0 l15 o 20
62.9
57.7 39.6 23.3 71.3 70.7 64.4
69.7
10
c.
Yield, $% 7 hours
68.4 65.6 61.0 36.8 77:l 67.5 63.2
8 houis 64.6 73.6 50.2 49.5 77.2 81.6 77.2 71.9
potassium chloride, and the polyninines in concentrations corresponding to the general recipe. The effect on pH of adding potassium hydroxide in the proportion used in the general recipe was also measured. Results are given in Table XVI. The difl'erences in pH produced by the different polyamines are only slight. And presuniably explanation of the fact that the addition of caustic alkali reduces the act,ivity of some of the polyaniines whereas it raises the activity of others does not lie merely in pH differences. It may be connected in some way with differences in the ease of hydrolysis of the initial products formed by the action of the peroxide on the different amines. Discussion. Comparing the members ;f the ethylene amine series as activators of polymerization, the experiments to date show that ethylenedianiine is a very weak activator, and that activating pover rises in the triainine, rises further in the tetramine, reaches what is for practical purposes a maximum in the pentamine (commercially available) and the hexamine, and then tends to fall gradually as the series is ascended further. I t is, hov-ever, impossible a t the present stage of investigation to make a definitive comparison between the pentamine and the next higher members because the pH of the system seems to affect the reaction differently n-ith different polyamines, and because of differences in purity beheen the amines. Thus, whereas in the general recipe-in the presence of added alkali-the octamine, which was prepared from redistilled tetramine, is less active than the technical pentamine, in the absence,of added alkali, the octamine is more active than the technical pentamine. However, the technical pentamine i s by no means a pure chemical. It distills over a wide range, and the middle fractions are more active than the head and tail fractions. The middle fractions are as active in the general recipe as is the octamine under its optimum condit,ions of no added alkali. Furthermore, a purified, colorless sample of the pentamine w-as markedly more ac,tive than the octamine (Table XVI).
~ Effect ~ of . Mercaptan. ~ ~ In connection with the practical use of polyamine-activated recipes for the low temperature copolymerization of butadiene and styrene, it is important to know whether the rate of reaction is affected by the inclusion of a modifier, as is required (albeit in smaller amount than required for standard polymerizations at 50" C.) to ensure that the polymer formed is plastic and soluble. The experiments recorded in Table XVII indicate that the presence of mercaptan modifiers is without any import,ant effect on the rate of polymerization. Other experiments showed that when diisopropyl xanthogen disulfide was used as the modifiei, the rate of polyamine-activated polymerization \\'as lower t,hari when a mercaptan was used as the modifier. Presence of Methanol. Another question of importance in connection with the practical use of polyamine-activated polymerization is whether the addition of methanol to the medium, for the purpose of working a t temperatures below the freezing point of an aqueous medium, will affect the rate of polymerization. Results given in Table XVIII indicate that reasonably large proportions of methanol can be included in the recipe without seriously affecting the rate of polymerization provided that the concentration of catalyst reagents is not too low. Peroxides. Of a number of peroxides other than cuniene hydroperoxides which w r e tested as catalysts in conjunction with polyamines in emulsion polymerization, only diisopropylbenzene monohydroperoxide was fouiid to be more efficient, than cumene hydroperoxide. Some preliminary results on polyamine-activated polymerization with this peroxide in comparison with cumene hydroperoxide are given in Table XIX.
TABLE XIX. COMPARISON O F DIISOPROPYLBENZENE HYDROPEROXIDE AND CUNENE HYDROPEROXIDE IN POLYAMINEACTIVATED POLYXERIZATIOS OF BUTADIENE :STYRENE AT 10' C. [Recipe (parts by wetght) : butadiene 70; styrene 30. water 180. potassium laurate, 5 ; KCI, 0.4; KOH, vaiied;. tetraethyleheDenta;nine,'varied: peroxide, varied] Parts/100 Parts Monomers Diisopropylbenzene Yield, % hydroPentaCHI' peroxide mine KOH 7 hours 8 hours 0.2 0.000 43.3 63.4 0.21 0.2 41.2 .. 0.056 53.a 56.2 0.112 64.1 0.2 38.6 0.000 .. 46.0 0.1 0.105 38.2 0.112 41.3 0.1 0.21 80.3 78.0 0.2 0.000 79.1 96.5 0.21 0.2 0.056 73.2 86.2 0.112 0.21 0.2 57.5 0.105 0.1 0.000 65.0 88.5 0.106 0.112 91.0 0.1
In experiments carried out in test tubes on the polymerization of styrene emulsified by potassium oleate, the peroxides listed in Table XX were activated to a greater or lesser extent by a polyamine but in no ease gave such vigorous polymerization as the cumene hydroperoxide-pentaniine combination.
TABLExx. EMULSION POLY.VERIZATION O F STYRENE WITH OTHER PEROXIDES IN COMBINATION WITH 1.36 PARTS TETRAETHYLENEPENTAMINE PER 100 PARTS STYREXE (Emulsion initially a t room temperature) Time Peroxide Methyl ethyl ketone peroxide Methyl isobutyl ketone peroxid? Bis-tert-butyl peroxy butane Same without pentamine Di-tert-butyl peroxide Hydroxyheptyl peroxide
Parts/ 100 Parts Styrene 0.96
{i:::
1.20 1.20 1.12 1.38
before
\Varm
to Hand,
Min. 8 8 5
5
..
Yield,
Time, min. 23 23
yo 31.1 23.7
20
27.8 22.6
30
Nil 4.2 2.0
20 30 30
March 1950
I(
I N D U S T R I A L AND E N G I N E E R I N G C H E M I S T R Y
The following combinations produced no active polymerizatertbuty1hydroperoxide:diethylenetriamine; tert-butyl tion: perbenzoate :diethylene triamine; 1-hydroxycyclohexyl hydroperoxide :diethylenetriamine; benzoyl peroxide :tetraethylenepentamine ; benzoyl peroxide :triethanolamine. Monomers. Only a cursory survey has so far been made of the response to polyamine activation of monomers other than styrene and butadiene. Acrylate monomers appear to respond with great vigor even in bulk polymerization. In the polyamineactivated polymerization of methyl methacrylate in an aqueous system, the presence of an emulsifier is necessary for rapid polymerization, despite the fact that the monomer has a measure of water solubility. A mixture of 25 ml. of water, 10 ml. of methyl methacrylate, 0.09 gram of cumene hydroperoxide and 0.18 gram of pentamine, shaken at room temperature, gave no polymerization after 30 minutes, whereas if the water contained 2.5% potassium oleate a yield of 92% polymer was obtained in 12 minutes. The pentamine-activated copolymerization of butadiene and methyl methacrylate was approximately twice as rapid as that of butadiene and styrene, as shown in Table X X I (see also Table VI).
451
an oxygen atmosphere there was a partial vacuum after polymerization had proceeded a considerable way. This was shown by difficulty in removing the cork. Clearly, oxygen had been consumed during an induction period.
INFLUENCE OF OXYGENON POLYAMINEACTIVATEDPOLYMERIZATION OF STYRENE
TABLE XXII.
Time to Collapse of Foam, Min.
Supernatant Gaa
Perceptibly Warm to Hand, Min.
Yield of Polystyrene Time from start, min.
