INDUSTRIAL AND ENGINEERING CHEMISTRY
452
soluble catalysts such as alkali persulfates and simple monoamines, especially aliphatic tertiary amines, and the magnitude of the acceleration obtained was relatively small and by no means comparable with the great acceleration of polymerization now found when polyamines are used in conjunction with organic hydroperoxides. A typical result in t,he German work was that in the emulsion polymerization of butadiene:styrene (75: 25) at 25’ C. with persulfate as the catalyst the yield after 19 hours was 16.2% in the presence of 0.013 part and 24.1% in the presence of 0.2 part diethylamine ( 7 ) . Amines, including secondary alkaryl amines ( 1 6 ) , di-tertdiallrylarylamines (18), polyethylene polyamines ( 1 7 ) and tri-
Vol. 42, No. 3
ethanolamine ( 2 1 ) have been specified as promoters of the bulk polymerization of mixtures of unsaturated alkyds and styrene in the presence of benzoyl peroxide. The so-called copolymerization of unsaturated alkyds and styrene is a very special case; it probably represents not only graft polymerization as distinct from true copolymerization but a special case of graft polynierization in which a relatively small amount of the vinyl monomer is able to produce a high degree of cross linking. The amineperoxide combinations specified as capable of bringing about rapid reaction in this special caae are ineffective in producing the rapid polymerization of styrene and of butadiene:styrene mixtures obtainable by activator-catalyst combinations described here.
Amine Structure and Activation Preliminary study (pages 445-452) of the relations between the structure of amines and their ability to produce marked activation in emulsion polymerizations catalyzed by cumene hydroperoxide indicates that structural requirements for the possession of activating power are: (1) the presence in the amine molecule of amino groups of different degrees of substitution (primary and secondary or primary and tertiary), and (2) separation of the amino groups by not more than two carbon atoms. Examples illustrating this conclusion are as follows: Whereas ethyl-
enediamine is only a weak activator and its symmetrical disubstitution derivatives, RNH(CH2)2N€IR, have no activating power, its monosubstitution derivatives, ”2(CH&NHR, produce marked activation. Tri(p-ethj 1amino)amine, K(CH~CH~NHZ)~, with two carbon atoms between the nitrogens, is an activator, whereas tri(./aminopropyl)amine, N(CH2CHzCHsNH&, with three carbon atoms between the nitrogens, is not. Triethylenetetramine, H[NH(CH&],R”2, is an activator, whereasl,3-bis (3’-aminopropylamino)propane, Hh”(CH2)&NH2, is not.
€t
In the absence of added alkali the monoethyl derivative of ethylenediamine has noticeably greater activating effect than ethylenediamine itself (Table XIII). It is, however, distinctly less effective than the monobutyl derivative, the difference perhaps being connected with a difference in solubility influencing the distribution of the amines between the oil and the water phase.
ESULTS given in the first section of this paper indicate
that monoamines, whether primary, secondary, or tertiary, have no marked activating effect in low temperature emulsion polymerizations catalyzed by cumene hydroperoxides. The simple diprimary amines-trimethylenediamine, tetramethylenediamine, and hexamethylenediamine-also have no significant activating effect; ethylenediamine and propylenediamihne have slight activating power. The polyethylene and polypropylene polyamines, however, are strong activators, the activating power increasing in the polyethylene series from diethylenetriamine through triethylenetetramine to a maximum in tetraethylenepentamine and pentaethylenehexamine, and, thereafter, as the series is ascended, falling gradually. A11 these polyamines contain two primary amino groups and one or more secondary amino groups. The structural requirements needed in an amine to enable it to activate low temperature emulsion polymerization in the presence of an organic hydroperoxide are discussed in the second section of this report as well as the behavior as activators of a number of di- and polyamines related to the polyethylene polyamines. ALKYL-SUBSTITUTED ETHYLENEDIAMINES
Whereas ethylenediamine, containing two primary amino groups
has only slight activating power (Tables IV, XIII), its Nmonoalkyl derivatives, RNH( CH2)&H2, containing one primary and one secondary amino group, have marked activating power, but the symmetrical dialkyl derivatives, RNH( CHZ)ZNHR, containing two secondary amino groups, are inactive. These statements are illustrated by the results shown in Tables XXIII-
xxv.
Another symmetrical disubstitution derivative found to be inactive was N,N‘-diphenylethylenediamine,which, however contains aryl groups. The tests reported in Table XXLV were carried out with a freshly prepared, colorless sample of the amine. After storage for four months, the amine had become brown in color and had largely lost its activating power, probably because the brown coloring matter acted as a retarder of polymerization.
HOMOLOGS OF POLYETHYLEKE POLYAMINES
Activating powers of the following homologous polyallrylene polyamines were compared: ( A ) triethylenetetramine, ( B ) 1,3bis(2’-aminoethylamino)propane, and (C) 1,3-bis(3’-arninopropy1amino)propane.
It n-as found that B possessed activating power but was markedly less effective than A , and that C was almost entirely lacking in activating power. The only differences in structure between these compounds are related to length of the carbon chains between nitrogen atoms. In B the central ethylene group of A is replaced by a trimethylene group, and this reduces notably but does not eliminate activating power in peroxide-catalyzed polymerization. In C all three ethylene groups of A are replaced by trimethylene groups, and this leads to almost complete loss of activating effect. As mentioned later, such differences may quite possibly be explained by electronic effects which influence the strength of the C--S bonds and the oxidizabilityof the amines, and are themselves influenced by the length of the carbon chain between the nitrogen atoms. Other similar results were as follows: Triethylenebis( trimethylene)hexamin,e, NH2( C H Z ) Z ~CH&H( NH( CH,)zNH(CH2)3NH(CHz)2NH2,in which trimethylene groups take the place of two of the ethylene groups of pentaethylenehexamine, is markedly less active in polymerization than is the latter. The reaction product of ethylene dibromide and hexamethylenediamine, which may be presumed to consist of a product of
INDUSTRIAL AND ENGINEERING CHEMISTRY
March 1950
TABLEXXIII. EFFECT OF ALKYL-SUBSTITUTED ETHYLENEDIAMINES IN EMULSION POLYMERIZATION OF STYRENE
TABLEXXVI. HOMOLOGS OF POLYETHYLENE POLYAMINES AS ACTIVATORS IN EMULSION POLYMERIZATION OF STYRENE
(Recipe: 2.5% solution of potassium myristate, 10 ml: styrene, 5 grams; KC1, 0.02 gram: CHP, varied; amine, varied. Emulsibn, initially a t room temperature, shaken under nitrogen) Yield of Parts/100 Polystyrene Parts Styrene Titne, Amine C H P min. % 1.1 20 30.8 N-mono-n-butylethylenediamine 0.8 1.6 1.8 30 43.4 1.1 60 1.6 N , N'-di-n-butyletbylenediamine 0.8 1.6 1.8 30 0.6 N,N'-diethylethylenediamine 0.8 1.1 60 Nil
(Recipe: 2.5% solution of 80:20 mixture of potassium laurate and Rubber Reserve potassium soap, 10 ml.; KCl, 0. 2 gram; amine, varied: styrene, 5 grams: CHP, 0.055 gram. Emulsion, under nitrogen, initially a t room temperature) Parts/ Yield, %, 100 of Parts Time, PolyAmine Styrene Min. styrene Triethylenetetramine 1.4 15 100.0 1.4 15 34.6 1,3-Bis(2'-aminoethylamino)propane 1.4 30 60.0 2.8 15 69.6 1,3-Bis (3'-aminopropylamino) propane 1.4 60 1.6 Triethylenebis(trimethy1ene)hexamine 1.5 15 21.0 3.0 15 26.6 Polyamine prepared by reaction of ethylene 1.4 60 0.2 dibromide and hexamethylenediamine
~
w
453
TABLE XXIV. EFFECT O F N-MONO-n-BUTYLETHYLENEDIAMINE ON POLYMERIZATION OF BUTADIENE :STYRENE AT 10O C. (General reoipe) Partdl00 Parts Monomers CHP Amine 0.21 0.2 0.3 0.21 0.28 0.3 0.28 0.4 0.35 0.4 0.26
0.5
6 hours 28.8 28.2 32.5 32.2 31.7 35.1
Yield, % 7 hours 33.3 29.3 36.7 36.9 40.2 40.5
8 hours 36.4 33.6 39.0 42.3 42.6 43.6
TABLEXXV. N-ETHYLETHYLENEDIAMINE AS ACTIVATOR IN POLYMERIZATION OF BUTADIENE: STYRENE AT 10 C. O
(General recipe with and without KOH) Parts/100 Parts Monomers Yield, % C H P Amine KOH 5 hours 6 hours 7 hours 13.1 13.5 0.000 12.3 0.21 0.2 2.3" 2.35a 2.4'' 0.21 0.2 0.112
"
8 hours 19.9 2.45"
White powder, apparently polystyrene.
the type of NH2( CH&NH( CHZ)ZNH( CH&NH*, in which a majority of the ethylene groups of the corresponding polyethylene polyamine are replaced by hexamethylene groups, has no activating power. Results in illustration of these statements are given in Tables XXVI and XXVII. Although, as these results show, the separation of the nitrogen atoms of polyalkylene polyamines by three or more carbon atoms in the form of a straight chain, as in trimethylene groups, is unfavorable to polymerization activity, their separation by three carbon atoms in the form of a propylene group-that is, a substituted two-carbon chain [-CH( CH3).CH2-]-is favorable, as was shown by the comparisons of corresponding polyethylene and polypropylene polyamines. Results given in the first section of this report show also that the influence on activating power of the length of the carbon chain between the nitrogen atoms is evident in the behavior of simple aliphatic diamines. Ethylenediamine and propylenediamine have some, albeit only weak, activating power, whereas trimethylenediamine, tetramethylenediamine, and hexamethylenediamine, in which the amino groups are separated by more than two carbon atoms, have none. TRI(AMIN0ALKYL)AMINES
Activating power is not confined to amines which like those discussed hitherto comprise within their molecules both primary and secondary amino groups. Examples of activators have been encountered among compounds in which primary and tertiary amino groups occur. I n such compounds, as in the primary-secondary amines discussed previously, it appears again that a condition for the possession of activating power is
TABLE XXVII. HOMOLOGS OF POLYETHYLENE POLYAMINES AS ACTIVATORS IN POLYMERIZATION OF BUTADIENE :STYRENEAT 10" c. (General recipe with only 0.4 KC1) Parts/100 Parts Monomers Yield, % CHP Amine 6 hours 7 hours 8 hours 0.14 0.21
Triethylenetetramine 0.1 44.7 0.2 58.8
50.8 64.4
60.0 70.7
0.14 0.21
1,3-Bia(2'-aminoethylamino)propane Equiv. to 0 . 1 tetramine 16.6 22.1 Equiv. to 0.2 tetramine 22.0 23.7
24.7 24.9
0.14 0.21
1,3-Bis (3'-aminopropylamino)propanea 1.5 1.7 Equiv. to 0 . 1 tetramine 1.7 1.5 Equiv. to 0 . 2 tetramine
1.5 3.0
Triethylenebis(trimethy1ene)hexamine Equiv. to 0.1 penta35.1 ethylenehexamine 25.0 31.8 0.21 Equiv. to 0 . 2 penta25.3 30.2 ethvlenehexamine 35.6 a The products were white powders, apparently polystyrene. result8 were similar to those in control experiments in which no amine was'included (Table VI). 0.14
that not more than two carbon atoms shall separate the nitrogen atoms. Tri( p-aminoethyl)amine, N( C H ~ C H Z N H Z containing )~, three primary and one tertiary amino groups, the nitrogens being separated by chains of two carbon atoms, is an activator, whereas tri( yaminopropyl)amine, N( C H ~ C H ~ C H ~ N, H also Z)~ containing three primary and one tertiary amino groups, but with three carbon atoms separating the nitrogens, has no activating power. Tri( p-aminoethy1)amine is not as powerful as triethylenetetramine, in which two of the amino groups are primary and two tertiary. However, tri( 6-aminoethy1)amine was, in the polymerization of butadiene: styrene in the general recipe, more of which it active than diethylenetriamine, NH( CHZCHZNHZ)~, can be regarded as a 6-aminoethyl derivative. An experiment with tri( p-aminoethy1)amine was run as follows:
A test tube was charged with 10 ml. of a 2.5y0 solution of an 80: 20 mixture of potassium laurate and Rubber Reserve potassium soap, 0.02 gram of KCl, 0.126 gram (0.0005 mole) of N(CHr CH,NH3)3.3HCl, 0.101 gram of KOH (20% excess on the amine hydrochloride), 5 grams of styrene, and 0.09 gram of CHP. Air was displaced by nitrogen and the tube corked. The tube was shaken continuously for 30 seconds and then a t intervals, The foam collapsed after 1.75 minutes. After 15 minutes, the temperature, initially 31 ', was 42' C., and the yield of polymer was 55.4%. In a parallel experiment with tri( .c-aminopro yl)amine, the yield of polymer was nil. In an experiment on tRe use of tri(paminoethy1)amine as an activator in the polymerization of butadiene:styrene a t 10" C. in the general recipe, yields were as follows: with 0.21 part CHP and 0.2 part amine, 28.3% in 6 hours and 35.4% in 8 hours; with 0.35 part CHP and 0.5 part amine, 31.3% in 6 hours and 42.0%in 8 hours.
Vol. 42, No. 3
INDUSTRIAL AND ENGINEERING CHEMISTRY
454
The fact that N ( C H ~ C H Z N H is Z )a~ polymerization activator p-Hydroxyethyl ethylenediamine appears to be of about the same order of activity as diethylenetriamine (Table X), a conwhereas K( CH2CH2CH2NHz)a is not provides another example in agreement with the conclusion indicated previously: When the clusion in accord with results reported by others (8). nitrogen atoms in a polyamine are separated by a chain of more Mention may be made here of some tests on polyethyleneimine as an activator. The sample of this polyamine, supplied by than two carbon atoms the amine possesses little or no capacity Monomer-Polymer, Inc., was a clear, colorless, viscous liquid. to activate peroxide-catalyzed polymerization. This conclusion I t was stated to have an average degree of polymerization of 23, is in accord with some electrometric considerations put forward and it presumably consisted largely of material of the average by Mann and Watson (24). These authors argue the thesis that formula H [XH(CH2)2]230H, containing only one primary amino in certain di- and polyamines there is an inductive electronic group per molecule. It gave the results shown in Table XXX in effect, as a result of which one nitrogen atom may influence the experiments on the copolymerization of butadiene and styrene. activity of another nitrogen atom, provided always that the length of the carbon chain separating the atoms is only short. And among the cases they quote in support of this thesis are the two amines mentioned here; the latter, N( CHZCHZCHZNHZ)~, TABLEXXX. POLYETHYLENEIMINE AS ACTIVATOR IN with chains of three carbon atoms separating the nitrogens, forms POLYMERIZATION OF BUTADIENE :STYRENE AT 10 C. a stable tetrahydrochloride, whereas the former, N(CHzCHzNH&, (General recipe with and without XOH) forms a stable trihydrochloride only, because, it is contended, Parts/100 Parts Monomers Yield, % the inductive effect of the primary amino groups, transmitted, C H P Polyimine KOH 5 hours 6 houra 7 hours as it is, through only two carbon atoms, is sufficient to inactivate 0.21 0.2 0.000 42.45 55.45 68.5 0.4 0.000 63.0 67.65 75.5 0.28 the tertiary nitrogen a t o m O
0.21 0.28
0.2 0.4
0.112 0.112
22.25 42.15
35.85 51.10
42.75 57.65
OTHER PRIMARY-TERTIARY AMINES
Uther compounds containing primary and tertiary amino groups which showed some, although only a mild, activating effect were the first three amines listed in Table XXT'III. In small scale experiments similar to those described in the preceding section results were as given in Table XXVIII.
TABLE XXVIII IXFLUENCE OF N-A~~IINOALKYL DERIVATIVES 01'ALICYCLICBASESON ENULSION POLYMERIZATION OF STYRENE AT ROOM TEMPERATT.RE Amine 1-(2'-axiiinoethyl)pyrrolidine 1-(2'-aminoethyl) piperidine 1-(2'-aminoethyl) morpholine 1-(3'-aminopropyl) morpholine
P a r t d l 0 0 Parts Styrena .4mine CHP 1.1 1.1 1.1 1.1 1.4 1.1 1.4 1.1
yield, %, in 1 hour 12.2 2.8 8.6 0.8
The pyrrolidine and piperidine derivatives were tested ab activators in the emulsion polymerization of butadiene: styrene a t 10" C., using 0.21 part CHP and 0.2 part amine; but neither was powerful enough to show appreciable activating effect. Comparing the two morpholine derivatives (samples of which were supplied by the Carbide and Carbon Chemicals Corporation), again the compound in which the primary and tertiary amino groups are separated by two carbon atoms shoivs some activating power, whereas the compound in which they are separated by three carbon atoms is almost inactive.
The polyimine is apparently somewhat less active than nonaethylenedecamine (Table XIV) and apparently more active than polyethylene tetracosamine, although data are available currently for the latter only in the KOH-containing recipe (Table XIV). OTHER ACTIVE DERIVATIVES OF POLYETHYLENE POLYAMINES
Derivatives of the polyethylene polyamines formed by condensing the latter (1 mole) with aldehydes (2 moles) were found to be polymerization activators but in no case to give such a high rate of polymerization as an equivalent quantity of the amine itself. The acetaldehyde condensation products appeared to be more active than either the propionaldehyde or n-butyraldehyde products and were in fact not much less active than the corresponding free polyamines. Table XXXI gives the results derived from bmall scale experiments. The products formed by the addition of polyethylene polyamines to maleic anhydride, which are presumably maleamic acids, COOH.CH:CH CO.SIIXNH2 ( NH2XYH2 represents the polyamine), were also found to function as activators. Polymerization tests (Table X X X I I ) with the maleamic acid made from maleic anhydride and tetraethylenepentamine run in parallel with tests with the free pentamine showed the maleamic acid to be only a s e a k activator a t a low catalyst level but to be reasonably effective at a higher catalyst level, although still not as effective as the free pentamine.
HYDROXYETIIYL AMINES
Tlie symmetrically substituted di-p-hydrosyethyl ethylenediamine, OH(CH2)&H(CH&NH( CH&OEI, in w-liich both nitrogens are secondary, was found to possess no activating power in experiments on the emulsion polymerization of styrene The corresponding monosubstituted compound, NHL( C€L),KH(CH*)sOH, in which one nitrogen is primary and the other secondary, is, hom-ever, an activator, as shown in Table XXIX.
TABLEXXIX.
~ H Y D R O X Y E T HETHYLENEDIAMINE YL AS
ACTIVATOR IX POLYMERIZATION O F BUTADIEKE: STYRENEA T
(General rccipe with and nithout KOH) Parts/100 Parts Monome3 Yield, % ___.. 6 hours 7 hours 5 hours CHP Amine KOH 30.1 39.1 22.1 0.21 0.2 0.000 2.0" 2.1" 1.96= 0.2 0.112 0.21 a White powder, apparently polystyrene
10 e c.
~
8 hours
37.0 2.3"
PREPARATIONS
The following is a record of the preparation oi compounds, some of them new, made specially for use in the present work. I t includes the preparation of the octamine and decamine which were reported on in the preceding section of the paper.
Mono- and Di-n-butylethylenediamines,. In order to realise as high a yield as possible of the monosubstltution product, ethylenediamine was used in excess. To the diamine (65 grams, 1.1 mole) dissolved in 75 ml. of isopropyl alcohol and contained in a 500-ml. Erlenmeyer flask there were added slowly with shaking 75 grams (0.55 mole) of n-butyl bromide in 85 ml. of isopropyl alcohol. Considerable heat was developed during the addition. The reaction mixture was then heated under reflux (slowly at hrst) for 1 hour. After cooling somewhat, pelleted potassium hydroxide (50 grams) was added with vigorous shaking for 5 minutes; then thereaction mixture was heatedtogentlorefluxingfor 15 minutes. When cooled to room temperature, the mixture was filtered, and the'filtrate was distilled up to a temperature of 130O C in order to remove isopropyl alcohol and unused diamine.
March 1950
INDUSTRIAL A N D ENGINEERING CHEMISTRY
455
grams) and trimethylenediamine (50 grams) ; cooling was applied
during the mixing of the reactants to keep the temperature a t CONDENSATION PRODUCTS O F TABLE XXXI. ALDEHYDE 50" to 60" C. The product (12 grams) consisted of an almost POLYAMINES AS ACTIVATORS IN EMULSION POLYMERIZATION OF
colorless liquid, soluble in water t o give a strongly alkaline solution, and boiling a t 153" to 145' C., 4 mm. I n addition there was a still residue (11.5 grams) which presumably represents higher polyamines. It was a yellow liquid which with water formed a gummy mass somewhat soluble in excess water to give Yield, a strongly alkaline solution. % Reaction of Igexamethylenediamine and Ethylene Dibromide. 97.6a This reaction wm carried out in a manner similar to that in which 51.2 the preceding reactions were conducted. However, during 76.2 mixing of the reactants (redistilled diamine, 68 grams, and ethyl; 28.0 ene dibromide, 32 grams) the reaction vessel was heated to 55 to 60" C. The reaction mixture was then heated under reflux for 2 hours, and, after the addition of solid potassium hydroxide, refluxing for 0.5 hour, and filtering, it was heated in a Claisen OF MALEAMIC ACIDFROM MALEIC flask up to 200" C. to remove alcohol and unused diamine. The TABLE XXXII. COMPARISON top layer was transferred to a smaller Claisen flask and heated ANHYDRIDE AND TETRAETHYLENEPENTAMINE WITH TETRAETHYLto an oil-bath temperature of 200" C. under 4 mm. pressure. ENEPENTAMINE , AS ACTIVATORS IN POLYMERIZATION OF BUTAThis gave only very little distillate, and accordingly the undisDIENE:STYRENE AT 10" C. tilled residue was considered to be the desired reaction product (General recipe) (30 grams). It was a clear, light-yellow, viscous liquid, which Parts/100 Parts Monomers Yield, % immediately formed a white crystalline hydrate with water. CHP Activator 6 hours 7 hours 8 hours The h drate was slowly soluble in water to give a strongly alkaline soLtion Maleamic acid Tri(p-am6oethyl)amine Trihydrochloride. p-BromoethyI0.14 0.1 8.9 12.6 16.8 phthalimide, prepared by Gabriel's method (91, was converted, 0.21 0.2 44.8 46.8 51.4 by treatment with ammonia, to triphthalimidotriethylamine Tetraethylenepentamine (M),and this was hydrolyzed by hydrochloric acid to yield t h e 0.14 0.1 63.1 68.5 70.8 desired product. (3.21 0.2 66.6 72.3 76.8 Tri(-paminopropyl)amine Tetrahydrochloride. This (meltting point 228' C. uncorrected) was prepared as described by Mann and Pope ( 2 2 ) from phthal-ybromopropylimide through triphthalimidotripropylamine hydrobromide. In pre aring the first of these two intermediates (from potassium phthayimide and The product separated into two layers, the lower of which partrimethylene dibromide), if, following Mann and Pope, the reactially solidified on cooling. The top layer was removed and distion was strictly carried out like that between potassium phthalitilled to yield two fractions: up to 105" c., 30 mm., and above mide and ethylene dibromide-namely, a t the boiling point of 105" C., 30 mm. Fraction 1 was distilled a t room pressure and the dibromide until all solid dissolved and a sirup resulted-the gave monobutylethylenediamine (10 grams) boiling a t 173' to reaction product was diphthalimidopropane. However, by 176' C., 735 mm., soluble in water, having an ammoniacal odor, heating the reactants for 5 hours a t a lower temperature (under and fuming somewhat in air, Fraction 2 on redistillation gave reflux in an oil bath a t 140' to 150" C.) the desired phthal-7di-n-butylethylenediamine (7 grams) boiling at 104" to 109" C., bromopropylimide was obtained satisfactorily. 10 mm., having a fishy odor and being insoluble or sparingly sol1-(2'-Aminoethy1)pyrrolidine. This was prepared from tetrauble in water. Graf (14) gives the boiling point of the mono demethylene dibromide (75 grams) and ethylenediamine (110 rivative as 62" to 64" C., 10 mm., and that of the di derivative grams) according to the procedure of van Alphen (4). The as 98"to 102"C., 10 mm. product (16.5 grams) was a water-white liquid, soluble in water, N-Ethylethylenediamine. To ethylenediamine (60 grams) having a strong fishy odor, and boiling a t 168" to 171" C., 737 dissolved in 75 ml. of absolute alcohol there was added slowly mm. a solution of ethyl bromide (72 g r a m ) in 75 ml. of absolute 1 4 2 '-Aminoethyl)piperidine, This w m prepared similarly alcohol. Noticeable heat was evolved. The mixture was heated (,?) from pentsmethylene dibromide (50 grams) and ethyleneunder reflux for 1.5 hours; solid potassium hydroxide (50 grams) diamine (60 grams). The product (13 grams) was a clear, colorwas then added, and the mixture, after being heated to reflux for less liquid, soluble in water to give a highly alkaline solution, 15 minutes, was allowed to cool and was filtered. The liquid was and boiling a t 93 C., 50 mm. distilled up to 114" C. through an 8-inch Vigreaux column, in Diethylidene Triethylenetetramine. This was prepared from order to remove alcohol and, as far as possible, unreacted ethylredistilled triethylenetetramine (16 grams, boiling point 152 to enediamine. The residue in the flask consisted of two layers; 154" C., 18 mm.) and acetaldehyde (10 grams) in accord with the upper layer was fractionally distilled through the column the general procedure given by Campbell, Armiger, and Campbell just mentioned. The product coming over between 120" and ( 6 ) for the pre aration of aldimines. The reaction product, 150' C. did not show any fraction of reasonably narrow boiling after being d r i e i over potassium hydroxide, was decanted from range, but after repeated fractionation there was obtained a the latter before being distilled, as otherwise foaming made disfraction at 129' to 133" C. which was considered to be the detillation impossible. The product (5 grams) boiled a t 130" to sired com ound (8.5 grams, colorless). A small quantity of higher boiring liquid (1 gram) was collected at 145' to 149" C. 132" C., 5 mm., and was a pale-yellow liquid, which solidified when cooled in an ice bath and which had a pyridinelilre odor. It was probably N,N'-diethylethylenediamine, the boiling point of which is give: in the literature as 149 O to 150 ' C. Dipropylidene Diethylenetriamine. This wm prepared siniilarly from diethylenetriamine (0.15 mole) and propionaldehyd: (A) 1,3-Bis(2 -aminoethylamino)propane and (B) Triethylene(0.30 mole). The main fraction of the product distilled a t 131 bis(trimethy1ene)hexamine. These were prepared as described to 135" C., 30 mm. It was a clear, colorless liquid, soluble in by van Alphen (2) by reacting trimethylene dibromide with water, and having a faint, pleasant odor. an excess of ethylenediamine. The dibromide (75 grams), disDiethylidene Tetraethylenepentamine. Tetraethylenepentasolved in absolute alcohol (125 ml.), was added slowly in small mine (94.7 grams, 0.5 mole) and acetaldehyde (44 grams, 1.0 portions over the course of 7.5 hours to the amine (redistilled, mole) were reacted in accord with the procedure of Campbell, 125 grams). Considerable heat was generated. The mixture Armiger, and Campbell (6) for the preparation of aldimines. was heated under reflux for 1 hour, and, after it had cooled Prior to the treatment with potassium hydroxide, ether was somewhat, potassium hydroxide (100 grams) was added graduadded to the reaction product to thin it and t h m facilitate the ally with vigorous agitation. The mixture was then heated for removal of water. The roduot (120 grams) was a Oear, amber, 0.5 hour, was cooled and filtered. The filtrate was distilled up highly viscous liquid. was not distilled in view of the lack to 130" C. to remove alcohol and unreacted amine. It was then of homogeneity of the technical pentamine used for its preparacooled and the top layer was fractionated and gave 22 grams of tion. A, boiling point 157" to 158" C., 12 mm.; 7.5 grams of B, boiling Reaction Product from Maleic Anhydride and Tetraethylenepoint 204" to 205' C., 1 mm.; and 6.5 grams of a stillresidue conpentamine. The pentamine (28.4 grams) dissolved in 125 nil. sisting of a clear amber colored liquid. A and B were clear, of benzene was added slowly, with stirring, to the anhydride colorless liquids, highly hygroscopic, and formed crystalline hydrates in a moist atmosphere. (16.2 grams) dissolved in 125 ml. of benzene. The resulting 1,3-Bis(3 -aminopropylamino)propane. This (new) compound gummy solid was collected on a suction filter, and, after rapid waa prepared similarly to A from trimethylene dibromide (53 removal of benzene, was immediately washed on the filter with STYRENE
(Emulsion, under nitrogen, initially at room temperature) Parts/100 Parts Styrene ActiTime, Activator vator CHP pin. 1.0 1.1 15 Diethylidene triethylenetetramine 0.4 0.5 10 Triethylenetetramine 0.4 0.35 10 Dipropylidene diethylenetriamine 1.8 1,O 23 a Final temperature: 50° C.
,
O
O
&
456
INDUSTRIAL AND ENGINEERING CHEMISTRY
anhydrous ether. After removal of the ether, the product was placed without delay in a vacuum desiccator over solid potassium hydroxide. Benzene and ether which separated overnight were later drawn off. The product was highly hygroscopic, but by handling i t rapidly while i t was in the air it was obtained as a dry, pulverable solid. The yield (41 grams) agreed satisfactorily with that expected for the maleamic acid. Heptaethyleneoctamine. This was prepared as described by Jones, Langsjoen, Neumann, and Zomlefer (19), who followed the general procedure of van Alphen (1). I n the first place a sample of technical triethylenetetramine was fractionally distilled to obtain a purer sample of the amine. The fractions collected were: 129" to 154' C., 18 mm., 15.2%; and 154" to 158.5" C., 18 mm., 71.8%, ng 1.4963. Fraction 2 was used in preparing the octamine. To triethylenetetramine (59.8 grams, 0.5 mole plus 16.8 grams excess) in 25 ml. of absolute alcohol in a three-necked, 500-ml. flask fitted with a stirrer, condenser, and dropping funnel, ethylene dibromide (47 grams, 0.25 mole) in 25 ml. of absolute alcohol was added over a period of 1 hour, the temperature being prevented from rising above 55" C. The mixture was then refluxed for 1 hour. Potassium hydroxide (36 grams in 200 ml. of absolute alcohol) was added and the mixture refluxed for a further period of 1 hour. Potassium bromide was removed by filtration and alcohol by distillation, after which the product was fractionally distilled in an allglass apparatus comprising a 6-inch T'igreaux-type column: fraction 1, 101.5" to 117" C., 3 mm., was 51.9 grams, of a faint yellow liquid, representing recovered, unreacted tetramine, ng 1.4965; fraction 2, 117" to 129" C., 3 mm., 2.5 grams; and fraction 3, 230" C., 3 mm., to 228" C., 2 mm., 14.1 grams of This fraction represents an amber-colored liquid, ~ 2 %1.5132. ~ the octamine. Still residue was 13.5 grams. The figure for the refractive index of the octamine-% 1.4986-which is given by Jones et al. (IQ),not only disagrees with the figure found in the present work, but also seems to be out of line with their other figures for the refractive indexes of members of the polyethylene polyamine series. Nonaethylenedecamine. This was prepared similarly from tetraethylenepentamine (141.2 grams, 0.6 mole plus 27.7 grams excess) and ethylene dibromide (56 grams, 0.3 mole). The pentamine used consisted of a blend of the main fractions obtained by distilling two samples of technical pentamine. These fractions were: boiling point 174" to 178" C., 5 mm., n y 1.5058; and boiling point 178' to 185" C., 6 mm., ng 1.5060. Fractional distillation of the product of reaction with ethylene dibromide gave: (1) a first fraction, up to 162' C., 2 mm., con-
Vol. 42, No. 3
sisting of recovered, unreacted pentamine (79 grams, 72%5 1.5045); (2) a small intermediate fraction; (3) the decamine, at 282" to 284" C., 9 mm. (36.7 grams, nZ,51.5161); and (4) a still residue (24.1 grams). LITERATURE CITED
(1) Alphen, J. van, Rec. true. chim., 55, 412 (1936). (2) Ibid.. a. 835: 56. 343 (1937).
(6) Campbell, K. K'., Armiger, H. S.,and Campbell, B. K., Ibid., 66. 82 (1944). (7)
Falk; report t o I. G. Farbenindustrie (Nov. 27, 1941) [Compare Ital. Patent 370,482 (Feb. 2, 1939); French Patent 850,-
210 (Dec. 11, 1939)l. (8) Firestone Research Laboratories, private communication t o Office of Rubber Reserve (May 15, 1949). (9) Gabriel, S., Berichte, 22, 1137 (1899).
(10) Gambarjan, S.,Ibid., 58B, 1775 (1925). (11) Gambarjan, S., and Cialtician, O., Ibid., 60B, 390 (1927) (12) Gambarjan, S., Cialtician, O., and Babajan, A . , BzdZ. ~ n s t . sei. R.S.S. Armhie, No. 1, 265 (1931). (13) Gambarjan, S., and Kaaarian, L., J . Gen. Chem. (U.S.S.R.), 3, 222 (1933). (14) Graf, R., U. 8. Patent 2,317,757 (April 27, 1943). to be (15) Hobson, R. W., and D'Ianni, J. D., 1x-n. ENG.CHERI., (16)
aublished. Hurdis, E. C., U. S. Patent 2,449,299 (Sept. 14, 1948).
(17) Ibid., 2,450,552 (Oct. 5, 1948). (18) Ibid., 2,467,033 (April 12, 1949). (19) Jones, G. D., Langsjoen, A., Neumann, M. M. C., and Zomlefer. J.,J . Org. Chem., 9,125 (1944). (20) Kern, W., Die Xakromol. Chem.,B1, 209 (1948). (21) Levine, M. M., U. S. Patent 2,452,669 (Nov. 2, 1948). (22) Mann, F. G., and Pope, W.J., J. Chem. Soc., 1926,p. 489. (23) Mann, F. G., and Pope, W. J.,Proc. Rov. Soe. (London), 109A, 448 (1925). (24) Mann, F. G., and Watson, J., J . Org. Chem., 13, 502 (1948). (25) Nozaki, K., and Bartlett, P.D., J . Am. Chem. Soc., 68, 1686 (1946). RBCEIVED October 14, 1949. Presented before the Division of Rubber Chemistry, AMERICANCHEMICAL SOCIETY, AtIantic City, September 22, 1949. This work was sponsored by the Office of Rubber Reserve, and the authors w e indebted to t h a t office for permission t o publish it.
INFRARE RADIANT HEATING HAROLD J . GARBER University of Tennessee, Knoxville, Tenn.
AND
In a previous paper the theory of radiant heating of thin metallic panels was established. As a result of recent theoretical and experimental investigations, the scope has been widened and generalized to include the radiant heating of thick objects possessing low thermal conductivities, in which the temperature distribution is nonuniform during the transient and steady-state periods. In this article the use of radiation in the heating of materials of low thermal conductivity, with charts for calculating the variation of temperature with time, is discussed. In a third paper the detailed mathematical analysis of radiant heating of thick solids with low thermal conductivities will be presented. The equations derived in the third paper are summarized in the form of Fourier series in the present paper. Simplified graphical solutions are presented for the temperature us. time at the top, center, and bottom of the slab subjected to radiation. With high radiant intensities, it is possible to heat the surface of a thick material having a low thermal conductivity to a high temperature in a short period of time without greatly elevating the subsurface temperatures. The production
F. & TILLER !I. Vanderbilt Unicersity, h7ash2;ille,Tenn.
of this "skin effect" opens up the possibility of baking high temperature finishes on the surface of wood and related materials without undue dissipation of heat or warping and buckling. In addition to the discussion of wood heating, a review of metal heating is presented.
I
SFRARED radiant heating is nom extensively employed in many industries. It has found use in metal heating for baking enamels ( I ) , in vaporization processes including the drying of textiles and explosives (9), as an auxiliary to hot air heating in overloaded installations (e),in mirroring (5), and in localized directional heating (6). Primary emphasis has been placed on paint baking on metals, and the use of radiation for heating mood and similar materials having low thermal conductivities has not attained corresponding prominence. This has been due largely to the existence of certain inherent difficulties which frequently were not overcome in early installations. Nonuniformity of radiant beams directed upon materials possessing low thermal conductivities prevented the use of infrared radiation in many cases. Attempts t o use radiation for drying finishes on soft woods met with failure be-
