October 1953
I
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
example, a trifunctional reaction is required t o form such a network. The presence of such unreacted functional groups in molded phenol-formaldehyde polymers was visualized by Houwink (a), and the term “lockerstelle” was used t o designate them. The lockerstelle were considered as possible flaws in the resin structure. Unreacted methylol groups were found t o be present in various melamine resins which had been cured in the form of thin layers (6, 7 ) . The present concern, however, is with the definite stages of condensation of the resin identified with the molding composition and molded state. Both experimental Lm values for molding compositions (Table I) fall on Curve I in Figure 5. The value of 0.69 corresponds with an average degree of polymerization of 3.2 and the value of 0.60 with an average degree of polymerization of 2.5 for straight or branched chain polymers. These compositions could very well be mixtures of polymers of this type, possibly with small amounts of other types present. The latter might include a very small amount of a lattice-type polymer (Curve 11). If any appreciable amount of these latter polymers were present, an offsetting amount of monomer would also of necessity be present t o yield the recorded Lm values. With respect t o the molded compositions a different situation holds. The higher Lm values (Table I) indicate at once a higher state of polymerization. I n assigning values for their degree of polymerization i t is noted that Lm values correspond with a number of possible situations since they can be located on Curves 11, 111, and V. Polymers in the two molded resins, therefore, might be interpreted from the curves as predominantly: (1) A lattice type with DP values of 20 t o 30. (2) A multiring type with a DP value of about 6; (3) The Aranchedchain type with hexahydrotriazine linkages and three- and fivemembered structural units.
.4mixture of all three types is also a justifiable interpretation. The data also permit an interpretation in terms of branched- or straight-chain polymers having a DP of 1000 or higher together with a minor proportion of cross-linked chains, or exclusively long chains with sparsely located cross links. It seems unlikely that large polymers based on the hexahydrotriazine linkage such as
2311
those which might grow indefinitely with a constant Lm value of 1.5 would be present in large amount in view of the Lm values of 1.10 and 1.13 found. Neither predominantly small polymer molecules of this class nor predominantly small multiring-type polymers would seem t o explain logically or harmonize with the known properties of molded resins. Rather infrequently spaced cross links of branched chains producing latticelike or network structures above 20 t o 30 DP would seem a more reasonable type of structure. Highly cross-linked and packed three dimensional molecular structures are ruled out. Neither the ether type nor hexahydrotriazine type linking mechanism as a predominant mechanism is supported by the present evidence. The methylene bridge as the linking device with a large proportion of unreacted methylol groups within the molecular lattice rather than the occasional lockerstelle would seem t o be supported. This in turn would place emphasis on hydrogen bonding, as an important secondary force, in contributing t o the properties of the cured resin. LITERATURE CITED (1) Flory, P. J., J. Am. Chem. SOC.,58, 1877 (1936). (2) Flory, P. J., Ibid., 63, 3083 (1941). (3) Ibid., p. 3091. (4) Ibid., p. 3096. (5) Flory, P. J., Chem. Rem, 39, 137 (1946). (6) Gams, A,, Widmer, G., and Fisch, W.,’ Brit. Plastics, 14, 50s (1943). (7) Gams, A., Widmer, G., and Fisch, W., Helv. Chim. Acta, 24, 302E (1941). ( 8 ) Houwink, R., Trans. Faraday SOC., 32, 122 (1936). (9) Kienle, R. H., Van Der Meulen, F. A,, and Petke, F. E., J. Am. Chem. Soc., 61, 2258 (1939). (10) Kohler, R., Kolloid Z.,103, No 2 , 138 (1943). (11) Marvel, C. S., Elliott, J. R., Roettner, F. E., and Yuska, H., J . Am. Chem. SOC.,68, 1681 (1946). (12) Stockmayer, W. H., J. Chem. Phys., 11, 45 (1943). (13) Thurston, J. T., paper presented a t the Gibson Island Conference, July 1941. (14) Walter, G., and Gewing, M., Kolloid-Beih., 34, 163 (1931). (15) Widmer, G., and Fisch, W., U. S. Patent 2,197,357 (1940). (16) Wohnsiedler, H. P., IND.ENG.CHEM.,44, 2679 (1952). RECEIVED for review January 15, 1953. ACCEFTED May 20, 1953. Presented before the Division of Paint, Varnish, and Plastics Chemistry CHEMICAL SOCIETY, Milwaukee, W e . at the 121st Meeting of the AMERICAN
Copolymerization Reactions of Cinnamic Acid, Its Derivatives, and Some Related Compounds C. S, MARVEL, G. H. MCCAIN, AND MOSES PASSER Yoyes Chemical Laboratory, University of Illinois, Urbana, I l l .
W. K. TAFT AND B. G. LABBE Government Laboratories, University of Akron, Akron, Ohio
T
HE recent studies (24) which have established the fact that
a,fl-unsaturated ketones of the benzalacetophenone type copolymerize readily with butadiene have led to a study of derivatives of cinnamic acid. A number of papers and patents cover copolymerization of cinnamaldehyde (26),cinnamic acid (4, SO), cinnamic esters (1, 5, 8, 8, 17, S l ) , cinnamonitrile and derivatives (9, 29, S I ) , and esters of ~-(or-furyl)-acrylic acid (3, I S , 16) under a variety of conditions, but none of these references give detailed descriptions of the products. Hence a further examination of the copolymerization behavior of these monomers seemed desirable.
Cinnamaldehyde copolymerizes with butadiene in free-radicalinitiated emulsion systems using a variety of initiators. In general the copolymer contained a little less cinnamaldehyde than did the monomer mixture used in the preparation. Copolymers of cinnamaldehyde with acrylonitrile and isoprene m-ere readily obtained in the Mutual recipe ( l l ) ,but no copolymer was obtained with methyl methacrylate or vinyl acetate. I n a bulk system cinnamaldehyde polymerized with methyl vinyl ketone. No homopolymer of the aldehyde could be obtained i n a variety of experiments. Copolymers from mixtures containing 90 parts of butadiene and 10 parts of cinnamaldehyde were prepared for
2312
INDUSTRIAL AND ENGINEERING CHEMISTRY
TABLEI. QUANTITATIVE INFRARED d ~ B 8 0 R P T I O K STUDY" ETHYLHYDROCISSALE ~ T E ~
OB
Concentration. Mg./Ml.
T = 1/10 0.104 0.206 0.248 0.309 0.385 0,497 0.725 a In ester carbonyl region; masiinuui absorption orcurred a t 1729 cin. - - i : cell 1.0 m i x ; slit 0.062 mm. b I n chloroform solution.
TABLE11. QUANTITATIVE ISFRARED ABSORPTIONSTUDY^
OF
BUTADIENE-ETHYL CINSAXIATE COPOLYMERS
Charge Ratio, Butadiene/ Ester
7a
Con-
version
90/10 85/15
Copolymer Concn.. Mg./Ml.
69,7 61.0 66.0 a Under identical conditions namate study of Table I. 80/20
T =
1/10
Ester Concn., Mg./Ml.
7. E b t e l
Incorporation
10.1 0.517 0.77 7.8 1.15 12.0 10.5 0.436 1.06 15.9 7.66 0.454 and with same solvent as in ethyl Iiydrocin-
evaluation rubbers in the azobiaisobut'yronit.rile-initiatedm o d i 6 cat,ion of the Mutual recipe at' 50" C. and in the cumene hydroperoxide recipe a t 0" C. The compounded and cured polymers had stress-strain properties much like GR-S and in addit,ion had improved low-temperature properties. Cinnamic acid did not yield a homopolymer in any solution or emulsion system which was tried. It gave copolymers with styrene and butadiene in acid-side emulsion syst'ems initia,ted by azobisisobutyronitrile. The copolymers produced a t 55 to 60% conversion all contained less of t,he acid than did the monomer mixtures from which they were prepared. The copolymei. prepared from 85 parts of butadiene and 15 parts of cinnamic acid r a s compounded and cured. I t had outst'aiiding tensile (up to 5360 pounds per sq. inch) and low-t.emperature properties (Y1o - 72.5' C.; freezing point -72" C.)>although - 65' C.; in temperature-retraction tests it shon-ed a tendency to crystallize. The introduction of the carhoxyl group did not have the expected effect of improving t,he oil resistance of the copolymer
Vol. 45, No. 10
copolymer of the ethyl ester had stresbstrain properties essentially equal t o GR-S, as well as excellent low-temperature properties ( T I Q 62" C.; Tloo - 68" C.; freezing point -67.5' C.). The hysteresis values were inferior to those of GR-S. The methyl ester copolymer was very similar in properties t o the ethyl ester. The hysteresis was slightly better than for the ethyl ester copolymer but still lower than for GR-S. trans-Cinnamonitrile did not homopolymeriae under any conditions tried. It gave a copolymer Kith methyl vinyl ketone in l d k polymerization and it copolymerized with methyl methac~ y l a t e ,butadiene, and isoprene in the Mutual recipe. A mixlure of the cis and trans isomers produced by decarboxylation of a-cyanoeinnamic acid (15) did not give satisfactory results in polymerization experiments, and it is believed the cis isomer is an inhibitor. The copolymer from butadiene (90 parts) and t i ans-cinnamonitrile (10 parts) did not equal GR-S in tensile .ti ength or hysteresis, It had rather good low-temperature pioperties but showed more tendency to crystallize than did UR-S. It was somewhat surprising to find that this nitrile copolj niei had poorer oil resistance than GR-S. Pome preliminary experiments were carried out on the copolymeiization of butadiene with ethyl a-cyano-b-phenylacrylate (I), nirthyl a-cyano-p-phenylacrylate (11), a-cyano-p-phenylaci1.11~acid (111), oi-cyano-@-(oi-furyl)-acrylic acid (IV) and itcthj 1 e y t e r (V),p-(a-furyl)-acrylic acid (VI), ethyl P-(a-furg.1)cicrylatc (1'1I) and p- (a-furyl)-acr!,loriit rile (TITI)
-
I
II,R-CH., E,RH
-CH'CHCN
mm
W). The homopolymerizations of methyl and ethyl cinnamate have been reported (22). Methyl ciniianiat,e has yielded copolynirrs wit'h styrene, isoprene, and butadiene in the Mutual recipe, but with acrylonitrile under the samc conditions the product appeared, by elemental analysis, t'o be polyacrylonitrile. Copal;-mers of butadiene (90 parts) and ethyl cinnamate (10 parts), and methyl cinnamate (10 parts), were evaluated as rubbers. The
IXCORIWRATIOS IS COPOLYMERS WITH TABLE 111. COMONOMER HGTADIESB
1-onbutadiene llonomer, X Cmnamaldehyde
Charge Ratio. Butadiene/ A'
G-
/c
Absorption Maxima,
Conversion
Cm. - 1
22.8
1729 1729 1729 1715 1715 1715
Cinnamic acid *Cinnamonitrile E t h y l cinnamate
Methyl cinnamate Ethvl a-cvano-Bphenylicrylate a Calculated from nitrogen analyses.
65.6 65.6 56.9 61.5 58.7 60.0 54.0 53.0 59.7 61 .O 66.0 50.2 50.0 56,5 41,2
..
li29 1729 1729 1736 1736 1736
..
7%
Incorporation of
X
7.1 9.6 13.4 9.2 9.6 10,5 8.26n 8.45" 9.41" 7.6 12.0 15.9
7,Fl 9.1 12.1 24.3a
i l l oi thcA>e except (IV) and (V) copolymerized, but [lone of the polymcw Heemed t o show interesting properties as elastomers. Ik~polymerbalso were obtained from (I) with styrene and from (11) nith methyl vinyl ketone. In all of the copolymerizations studied the entrance of the u,8-unSaturafed component into the polymer was established by iiifraied data on the copolymer. When t hE aopolymerization was carried out using compounds that cont,ained an element other than carbon, hydrogen, or oxygen. the analysis of the copolymers produced was simple, since ordinaiy elemental analysis could be used, For example, in copolymers of cinnamonitrile it is only necessary to have R nitrogen analysis to determine the nitrile incorporation in the product. However, because elemental analysis is not sensitive enough for use with other monomers, the development of an alternative method became necessary. Investigation showed that quantitative ultraviolet absorption analysis was not feasible because the saturated analogs (hydrocinnamaldehyde, hydrocinnamic acid, cthyl hydrocinnamate, and methyl hydrocinnamate) which were used as standards fluoresce, when irradiated with light, in the region where phenyl absorption occurs. -4 method involving the use of infrared absorption was therefore developed.
All infrared determinations were made on a Perkin-Elmer Model 12-C infrared spectrophotometei, using 1.0-mm. potassium bromide cells a t a slit width of 0.062. except. that of ethyl a-
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
October 1953
TABLE IV. Charging Ratio 95/5 95/5 95/5 90/10 90/10 85/15 80/20 75/25 70/30
G.
The absorption of the standard, ethyl hydrocinnamate, followed Beer’s law, the graph of log T against concentration being essentially linear. This graph was then used to convert the experimentally observed T values for the copolymer to concentration of the ester moiety, -CH-CH(fourth and fifth columns
COPOLYMERIZATION OF BUTADIENE A N D CINNAMALDEHYDE CqnBenzene Temp., Time sersion, Solubility, C. Hour; % % 1. Mutual Recipe with Potassium Pelgulfate Initiation
Initiator,
Modifier, G.
0.060 0.060 0.060 0.060 0.060 0.060 0.060
0.060 0.050 0.050 0.050 0.050 0.050 0.050 0.050
30 30 50 30 50 50 50 50 50
94 51 24 53 21 16 17 17 16
60 47 85 24 60 50 48 47 53
Inherent Viscosity
73 100
4.6 2.6
100 100 87 80 71
1.4 3.6 2 :9 2.3 2.7
...
Insol.
2313
1
1
CBHB COOC2HS 0.060 0.050 80 3.0 of Table 11). The correction factor B. Mutual Recipe with Azobisisobutyronitrile Initiation 176/178, t o compensate for the differ90/10 0.02 0.050 50 18 91 Insol. ... ence in molecular formula between the 90/10 0.01. 0.050 50 16 60 91 3.2 90/10 0.01 0.075 50 18 53 95 1.8’ cinnarnate and hydrocinnamate, was less 90/10 0.01 0.100 50 18 59 91 1 .7 50 17 85/15 0.01 0.075 38 92 1.8 than the infrared precision (13%), and 85/15 0.02 0.125 50 15 54 90 0.9 85/15 0.03 0.125 50 15 60 87 1.6 so was neglected. m /20 0 .01 0.075 50 17 39 93 2 5 Comparison of the charge ratio with 80/20 0.03 0.125 50 . 15 65 84 2 .. 0 C. Cumene Hydroperoxide Recipe the per cent of comonomer incorporation 3.0 affords information as t o relative rate at 90/10 0.04 0.050 0 15 50 88 90/10 0.04 0.100 0 19 52 93 3.2 which each monomer enters the chain. 90/10 0.04 0.150 0 24 60 93 2.2 90/10 0.04 0.200 0 24 44 97 0.7 The incorporation of cinnamaldehyde, 85/15 0.04 0.150 0 30 46 96 2.5 3 4 cinnamic acid, cinnamonitrile, ethyl 80/20 0.04 0.125 0 24 67 91 cinnamate, and methyl cinnamate was in each case less than the concentration TABLEv. COPOLYMERIZATION O F BUTADIENE A N D CINNAMIC ACID of that particular monomer in the (Acid-side recipe with azobisisobutyronitrile initiation at BO0 C.) original charge ratio, from which it is concluded that in these Benzene co?soluInherent cases butadiene enters the copolymer chain at a faster rate than Charging Initiator, Modifier, Time, version, bility. Visthe other monomer. The situation is reversed, however, in the G. G. Ratio % 9, cosity Hours case of butadiene-ethyl a-cyano-0-phenylacrylate. 0.01 0.050 16 90/10 47 99 1.4 The results of these analyses are listed in Table 111. 0.02 0.025 15 61 48 2.4 90/10 90/10 0.02 0.050 15 54 100 1.5 These data d o not permit accurate calculations of reactivity 0.03 0.050 15 75 100 1.6 85/15 m/20 0.02 0.050 15 57 100 1.8 ratios (d6), but do indicate little tendency for alternation of SO/20 0.03 0.050 15 65 100 1.1 monomer units such as occur with maleic anhydride (SS), except possibly in the case of ethyl a-cyano-b-phenylacrylate. o.oB0
cyanohydrocinnamate, ,which was made in a 0.30f~-miii.sodium EXPERIMENTAL WORK chloride cell. The measurements were carried out on the abbutadiene sorption maxima caused b the presence of carbonyl groups, and MATERIALS. Phillips Petroleum Co. Research @;rade was used throughout this work. Acrylonitrile, cinnamaldehyde, the saturated analom of txe monomers were used for the standards. cinnamic acid, -ethyl cinnamate, methyl cinnamate, isoprene, The procedure employed was as follows. A stock solution of methyl methacrylate, styrene, vinyl acetate, and azobisisofrom 60 to 80 mg. of the proper standard in 10 ml. of reagentbutyronitrile were obtained on the market and carefully purified grade chloroform was prepared. One-milliliter portions of this before use. tians-Cinnamonitrile was prepared by the method solution were then diluted with varying amounts of chloroform, of Plaut and Ritter ($7) and the portions used boiled at 94-97 “.C. to make a series of solutions of varying concentrations. The (0.4 mm.); 1.6031. 0-Cyano-0-phenylacrylic acid melting transmittance of these solutions was then determined in the cara t 180” C. was prepared by the method described in “Organic bonyl region, and the logarithms of those values were plotted Syntheses” (19). a-Cyano-0-(0-fury1)-acrylicacid melting a t against the concentrations in milligrams per milliter. 218” C. was prepared in 84.101,yield by a strictly analogous The sample for analysis was prepared by covering 0.4000 to 0.60oO gram of the thrice-reprecipitated copolymer with 50 ml. of chloroform (from the same T I R L E l r I . COPOJ,,YMERIZATION O F B U T A D I E K E AND hnS-CINNAMONITRILE bottle t h a t was used t o make up the CqnBenzene standard solutions) in a small glassCharginq Initiator, Modifier, Temp., Time, version, Solubiliby, Inherent stoppered flask. This was allowed t o Ratio G. G. C. Hours % % Viscosity stand until solution was complete, about A . filutual Recipe with Potassium Persulfate Initiation 24 hours. and the transmittance of the 1.2 12 100 47 solution in the carbonyl region was de95/5 0.050 30 0.060 1.6 72 30 95/5 0.050 0.060 40 , , , 100 termined, using the same cell that had ... Insol.‘ ’ 80 22 50 90/10 0.050 0.060 been used for the ‘stand&rds. The 2.1 h0 67 24 94 .. 0.050 85/15 0.060 2.5 81 24 61 monomer incorporation was then deter50 0.080 0.050 80/20 1.8 72 59 68 30 0.060 0.050 75/25 mined by referring to the calibration 2.0 70 90 67 30 70’80 0.050 0.060 curve and dividing the value found by B. Mutual Recipe with Azobisisobutyronitrile Initiation the amount of copolymer placed in - solution. 90/10 0 02 50 13 61 95 1 6 0 050 I
nv
n
f
As a typical example, the details of the quantitative infrared analysis for the incornration of ethvl cinnamate in a series of butadiene-ethyl cinnamate copolymers are given in Tables I and 11. In Table I are found the data for the model compound used as the standard, and, Table I1 the corresponding data for the copolymer.
90/10 85/15 85/15 80/20 80/20
0 04 0 04 o4
90/10 90/10 90/10 85/15 85/15 80/20
0 04 0 04 0 04 0 04 0 04
0 04 0 04
0.050 0.025 0 050 0 050 0 025
50 50 50 50 50
13 12 12 12 12
63 50 60 61 54
C. Cumene Hydroperoxide Recipe
004
0 025 0 075 0 150 0 025 0 075 0 025
0 0 0 0 0 0
12 12 8 8 8 8
60 66 56 59 63 63
.
96 87 97 89 89
2.6 2.6 2.2 1.7 3 9
97 96 90 90 86 96
3 3 1 2 1 1
4 5 8 1 6 8
Vol. 45, No. 10
INDUSTRIAL AND ENGINEERING CHEMISTRY
2314 TaBLE
Charging Ratio
Initiator,
G.
A. 95/5
0.060
90/10
0.060
85/15 SO/ZO 75/25 70/30
0.060 0.060 0.060 0.060
90/10 90/10 90/10 85/15
0.01 0.02 0.04 0.02 0.02
90/10 90/10 90/10 90/10 85/13 80/20 80/20
0.04
B.
so/zo
cumene hydroperoxide recipe ($3) were used as described before. An aaobisisobutyronitrile-initiated acid-side recipe of t,he following type, developed by Richard M. Potts in this laboratory, was employed in the copolymerization of cinnamic acid and the other unsaturated organic acids employed in this work with butadiene.
COPOLYMERIZITIOY O F BUTADIENEAND ETHYL CIXNAMATE
VII.
Temp., C.
Modifier,
G.
Time, Hours
Cqnversion,
%
Benzene Solubility,
Mutual Recipe with Potassium Persulfate 0,050 30 94 0.050 30 50 48 0,050 30 49 0,050 30 0.050 30 49 64 0.050 30
Initiation 80
Mutual Recipe with Azobisisobutyronitrile 50 15 0.050 50 12 0,025 50 10 0,025 50 12 0.025 0.025 50 10 C. Cumene Hydroperoxide Recipe
Initiation 69 62
0.025 0.050 0.125 0.200 0.175 0.075 0.125
0 0 0 0 0
8 8
76
60 72 76 90
62 62 66
57 58 47 59
%
Inherent Viscosity
67 98 86 90 76 80
2.0 2.6 1.4 2.2 1.8 2.0
94
97 100 99
100
2.7 3.5 3.1 3.2 2.6
91 97 88 99 97 85 95
4.0 3.3 3.0 1.7 1.9 2.6 1.7
Monomers (total) grams 20.0 Azobisisobutyroni'trile, gram 0 , 0 2 to 0 . 0 5 Water (boiled to remove oxygen), ml. 38 MP-63543 (a sodium Cia alkane2.0 sulfonate mixture), ml. Technical lauryl mercaptan, gram 0 . 0 2 5 toO.100
BUTADIEXECoPoLYhfERs. The copolymerizations with butadiene of the 65 various a#-unsaturated compounds were 0 4.5 54 carried out in the standard manner and 0.04 0 5 73 the polymerizations and products are list'ed in Tables IT' to IX. In each of TABLE VIII. COPOLYMERIZATION O F BUTADIENE AND METHYL C1NXA4MATE ConBenzene these tables t'he charging ratio is the Charging Initiator, Modifier, Temp., Time, version, SolubilInherent weight ratio of reactants, but,adiene to Ratio G. G. ' C. Houra % ity, % Viscosity comonomer; the initiator is specified in A. Mutual Recipe with Potassium Persulfate Initiation the recipe and the modifier is technical Y5/6 0.060 0,050 30 72 76 90 2.1 lauryl mercaptan; temperature and time 0.060 0,050 90/10 30 50 80 100 2.4 85/15 0.060 0,050 30 48 53 82 1.4 refer t o the polymerization process; con0.060 0.030 30 57 81 76 1.8 70130 version is the yield of copolymer; 8,116 B Mutual Recipe with daobisisobutyronitrile Initiation solubility and viscosity are t,hose of the 90/10 0.02 0,025 .50 10 56 97 2.3 copolymer. 85/16 0.02 0 023 60 11 65 90 3.7 10 85/16 0.02 0,050 50 63 92 1.6 The copolymers of butadiene arid 80/20 0.02 0.02; 50 10 68 92 3.3 cinnamaldehpde listed in Table Is' were C . Curnene Hydroperoxide Recipe examined in the infrared and all showed 90/10 0.04 0,030 0 4 47 94 3.2 the carbonyl band characteristic of the 90/10 0.04 0.100 0 4 48 93 2.4 85/15 0.04 0.100 0 8 63 94 3.5 aldehyde group at 1729 em.-' 85/15 0.04 0,200 0 5 67 95 2.0 80/20 0.04 0.125 0 8 63 97 3.2 Infrared showed absorption at 1700 em.-' characteristic of the carboxy! group, which confirmed the presence of TABLEIX. COPOLYMERIZATION O F BUTADIENE AND ETHYL WCYASO-~ PHENYLACRYLATE the cinnamic acid in the copolymer Co,nBenzene (Table V). Charging Initiacor Xodifier, Temp., Time, version, Solubility, Inherent Ratio G. G. C. Hours % 76 Viscosity The copoIymers prepared wit,h f r a w A . Mutual Recipe with Potassium Persulfate Initiation cinnamonit,rile . showed absorption a t 95/5 0.060 0,050 30 54 52 100 1.9 22-18 em.-', confirming the presence of 0.060 0 050 30 50 90/10 37 100 1.3 the nitrile group (Table VI). 0.060 0,050 30 72 85/16 47 93 1.0 0.050 80/20 0.060 30 72 52 82 1.3 The ethyl c i n n a m a t e c o p o l y m e r s 75/25 0.060 0.050 30 72 44 89 1.2 showed absorption bands at 1736 C I U . - ~ 75/25 0,060 0.050 50 15 58 88 3.0 charact'eristic of the ester carbonyl group B. Mutual Recipe with .%zobisisobutyronitrile Initiation (Table VII). 90/10 0.01 0.025 50 21 76 100 1.6 90/10 0.01 0.050 50 17 48 93 1.9 The methyl cinnamate copolymers showed absorption at 1733 cm.-l, which is characteristic of the ester group in the saturated model compound (Table VIII). method. Ethyl @-cyano-@-( a-furyl)-acrylate, melting Point These copolymers gave charact,eristic carbonpl absorption a t 92." c., was prepared by the method Of (')' 173s and nitrile absorption 22-10 cm.-f (Table I X ) , p-(a-fury])-acrylate melting point 2-1." C., was prepared by the rnet,hod of Posner ($8). Ethyl CY-cyano-P-phenylacrylatemeltEVALUATION OF BUTADIENE COPOLYMERS AS RUBBERS ing point 49.9" C., mas prepared by the directions in "drganic Syntheses" (18). Ethyl and methyl hydrocinnamates were h r g e samples (250 grams or more) of copolymers of butadiene prepared by the procedure of Erlenmeyer ( 1 0 ) . Methyl acyano-p-phenylacrylate? melting point 87-89 ' C., was prepared with cinnamaldehyde, cinnamic acid, cinnamonitrile, ethyl cinby the method of Carrick ( 7 ) . Ethyl a-cyanohydrocinnamate namate, and methyl cinnamate have been evaluated as rubbers. was prepared by the reduction with hydrogen, in the usual manThey were Cured in the tread-st,ock recipe and earcass-stock ner, of 20.1 grams of et,hyl a-cyano-p-pheny]acry]ate in 100 ml. recipe listed below, and the stress-strain, low-temperature, oiiof 95% ethanol over 0.20 gram of platinum oxide catalyst a t room temperature a t a pressure not exceeding 50 pounds per sq. resistance, and hysteresis properties were determined b y standard inch. The product boiled a t 132" C. (1.2 mm.); nz&'1.5108; testingprocedures ( 1 2 , 1 4 , ~ $ ) . yield 16.8 grame. 0.04
0.04 0.04 0.04 0.04
A s r ~ ~ s r s Calculated . for CnHi302XI FOUND.
'
6
6 6
C, 70.94; H, 6.45 C , 71.54: H, 6.29
POLYJIERIZATIOS RECIPES. The hrlutual recipe (11), the azobisisobutyronitrile-initiated PIlutual recipe (Sq), and the 0" C.
Tread Stock Recipe Polymer grams E P C b h c k grams Zinc oxide 'grams Sulfur, grime Altax, grams
60 24
3 1.2 1.0;
Carcass Stock Recipe Polymer, grams 100 Statex 93, grams 30 Red lead grams 2.5 Circosol x H, grartia 20 Sulfur, grams ? Altax, gram
i
INDUSTRIAL AND ENGINEERING CHEMISTRY
October 1953
2315
TABLE X. MISCELLANEOUS COPOLYMERIZATIONS A/B,
G.
hfonomer B Monomer A Butadiene P-(a-Furyl)-acrylic acid Butadiene Ethyl P-(ol-furyl) -acrylate Butadiene P- (a-Fury1)-acrylonitrile Acrylonitrile Cinnamaldehyde Isoprene Cinnamaldehyde Methyl methacrylate Cinnamaldehyde Vinyl acetate Cinnamaldehyde Methyl vinyl ketoned Cinnamaldehyde Styrene Cinnamic acid Isoprene trans-Cinnamonitrile Methyl methacrylate trans-Cinnamonitrile Methyl vinyl ketoned trans-Cinnamonitrile Acrylonitrile trans-Cinnamonitrile Vinyl acetate trans-Cinnamonitrile Isoprene , Methyl cinnamate Styrene Methyl cinnamate Acrylonitrile Methyl cinnamate Butadiene a-Cyano-p-phenylacrylic acid Butadiene Methyl a-cyano-P-phenylacrylate Methyl vinyl ketoned Methyl a-cyano-P-phenylacrylate Methyl methacrylate Ethyl a-cyano-P-phenylacrylate Styrene Ethyl qpyano-P-phenylacrylate Recipe 1. Acid-side rccipe with arobisisobutyronitrile initiation. Recipe 2. Mutual recipe with azobisisobutyronitrile initiation. Recipe 3. Marvel-Meinhardt ($9)acid-side recipe. Recipe 4. Mutual recipe with persulfate initiation. Recipe 5. Bulk system with benzoyl peroxide initiation.
Temp., C. 50 50 30 50
Recipe
18/2 18/2 19/1 18/2
50
18/2
18/2 18/2 24/3 18/2 18/2 18/2 25/2 18/2 18/2 18/2 18/2 18/2
50 50 50 50 50 50 50 50 50 50 50 50 50 30 50 50 50
4
5 1
4 4 5 4
18/2 l8/2
25/2 18/2 18/2
Time, Hours 17 24 116 24 16 16 24 7 24 16
Infrared Band (Cm.-1) for Characterization carbonyl carbonyl nitrile phenyl aldehyde aldehyde aldehyde carbonyl carbonyl nitrile nitrile nitrile
Conversion,
%
2 24
carbonyl carbonyl carbonyl carbonyl nitrile carbonyl nitrile nitrile carbonyl
24 16 7 24 17 54
7
13 19
This couolvmer was 9195 soluble in benzene and had an inherent viscositv of 2.6.
TABLE XI. EVALU$TION SAMPLES Sample No. Comonomer with butadicne
X-603 Styrene
X-672 Styrene
XP-99 Styrene
1z Bld.20 None
Ratio, butadiene t o comonomer Gel % DilAte solution viscosity Conversion, Yo Mooney viscosity ML-4 Temperature of pblymeriration, - 0 C. Recipe used
71 5 / 2 8 5
75/26
72/29
100/0
2
,..
2 4 I
69.9 29
3:i 54 122.5
50 Mutual
50 Mutual
,.. .
63 155
.
53
5
47 Mutual
TABLE XII.
p-To1yldiaaothioP-naphthy1 ether
STRESS-STRAIN D a T A
AT
i)
Tensile strength, ib./sq. in.
Elongation, % TT
Min. Cured at 292O F.
X-603
1z Bld. 20
25 50 75 100 150
650 1500 1940 2210 2390
25 50 75 100 150
258
273
274
360 530 770 790 1000
1140 ..
1466 1800 2050 2000 1910
1820 2110 2460 2400 2640
2090 3919 3770 2670 3010 650 560
460 1020 1430 1420 1640 400 480
1050 1380
2550 2350 2390 2370 2120 430 360
5360 5370 4910 5010 3690 370 360
100 75
460 350 340
440 410
270
340 320 320
300 310 240
25 50 75 100 150
13 13
6 7 6 6 5
7
8 5 4 4 4
2 3 1 31
25
50
150
8% %
Sample No.
3
4 4
..
.. .. l3iO
..
290 270
..
5
5
..
273 Cinnainaldehyde 90/lO 2 2.7 60 137 0
Cumene hydroperoxide
274 Cinnamic acid 85/15 28 1.25 59 123
277 Cinnamonitrile 90/10 5 3.76 59 119
252 Ethyl cinnamate 90/1o
50 Acid-side aaobisisobutyronitrile
50 Mutual
30 RIutual
5
i 2 53 45
253 Methyl cinnamate 90/10
8 2.7 49 79
77' F.
(Tread-type recipe)
300% lb./sq.inoduliis, inch
258
Cinnamaldehyde 90/10
The cinnamaldehyde-butadiene copolymer prepared in the Mutual recipe (azobisisobutyronitrile initiated) showed a somewhat low tensile strength in the tread-type recipe. Its low-temperature properties were very good but its oil resistance was no better than that of GR-S. The sample prepared in the cumene hydroperoxide recipe had a high Mooney viscosity. It showed good low-temperature properties and not too much tendency to crystallize, but its oil resistance was poor. The hysteresis values
wcre not improved over those of hiyhviscosity GR-S. The cinnamic acid-butadiene co277 252 253 polymer had outstandingly good tensile 990 600 710 strength and low-temperature prop1450 1130 1170 1570 1310 1220 erties. However, the t e m p e r a t u r e 1580 1340 1350 .. 1420 1390 retraction tests showed a tendency to1310 3760 3560 ward crystallization. Its oil resistance 2160 3090 3620 was rather poor and the hysteresis 2030 3070 2360 2090 2470 3280 values were slightly lower than those 1350 2930 3410 of standard GR-S. 350 830 740 550 590 The cinnamonitrile-butadiene copoly380 430 510 490 510 mer (Mutual recipe, azobisisobutyroni360 350 350 460 510 trile initiated) had a relatively. high 7 18 14 Mooney viscosity. I t s low-tempera9 10 10 7 6 6 ture properties were good, but it showed 6 5 6 a tendency toward crystallization. I t s 4 6 7 oil resistance was poor and its hysteresis values were slightly lower than those of standard GR-S. The ethyl cinnamate-butadiene copolymer had stress-strain values about equal to those of GR-S. I t s low-temperature properties were excellent, its oil resistance was poor, and its hysteresis properties were slightly better than those of standard GR-S. The methyl cinnamate-butadiene copolvmer was similar to the copolymer prepared with ethyl cinnamate. Its hysteresis values, however, were better than those of the latter, but still inferior to those of high-viscosity GR-S.
2316
INDUSTRIAL AND ENGINEERING CHEMISTRY 2
00000
03003
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o w mmo. w m mo mr n~m (m r~n mo--no n -m- e m md
d-CQC
Vol. 45, No. 10
e=-
Mh7. irN-
mmm
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XN01
i i -
-3-
h
mmm
OM-
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
October 1953
ACKNOWLEDGMENT
The work discussed was performed as a part of the research project sponsored by the Reconstruction Finance Corp., Office of Synthetic Rubber, in connection with the Government Synthetic Rubber Program. The authors are indebted t o Elizabeth Peterson Leighly and Helen Miklas for the infrared data on the cinnamaldehyde copolvmers. The other infrared data were furnished by the Anderson Physical Laboratories, Champaign, Ill., and the authors are especially indebted to R. L. Bohon for his aid in their interpretation. The Micro-Tech Laboratories, Skokie, Ill., performed the microanalyses reported. The authors are indebted to Stanley Detrick, E. I. du Pont de Semours & Co., for the MP-635-S used as an emulsifier in the acid-side recipes. This emulsifier had the following percentage composition : Sodium alkanesulfonates, approximately Cle
Vnreacted hydrocarbons
Sodium chloride Sodium sulfate Balance water, and about 3% isopropyl alcoho
49 5
10.3 0.86 0.4
2317
acid derivatives, and the copolymerization of a-cyano-@-phenylacrylic acid derivatives. LITERATURE CITED
Bartlett, J. H., U. S. Patent 2,612,475(Sept. 30,1952). Bechert, C.,J . prakt. Chem., 50 (2),1 (1894). Blicke, F. H., Ber., 47, 1352 (1914). BobaIek,E.G.,U.S.Patents2,470,752,2,470,757 (May24,1949). Britton, E. C.,Marshall, H. B., and LeFevre, W. J., Ibid., 2,341,175(Feb.8,1944).
Carpmael, A., and I. G. Farbenindustrie A,-G., Brit. Patent 387,381(Feb. 6,1933). Carrick, J. T., J . prakt. Chem., 45 (2),501 (1892). Du Pont de Nemours & Co., Inc., E. I., Brit. Patent 494,752 (Oct. 25, 1938). Emerson, W. S., U. S. Patent 2,498,616(Feb. 21,1950). Erlenmeyer, E., Ann., 137,334 (1866). Frank, R. L., Adams, C. E., Blegen, J. R., Deanin, R., and Smith, P. V., IND. ENG.CHEM.,39,887 (1947). Garvey, B. S., Jr., Am, SOC.Testing Materials, D 471431‘. Gavatin, J., Swedish Patent 121,341 (April 6, 1948). Gehman, S. D.,Woodford, D. E., and Wilkinson, ‘3. S., Jr., IND. ENG.CHEM.,39, 1108 (1947). Gohsez, J., Bull. sac. chim. belg., 41,477 (1932). Habgood, B. J., Hill, R., Isaacs, E., and Morgan, L. B., U. S. Patent 2,231,623(Feb. 11, 1941). I. G. Farbenindustrie A.-G., Brit. Patent 368,567 (March 10, 1932).
SUMMARY
h study of the cwolymerization of butadiene with cinnamaldehyde, cinnamic acid, methyl cinnamate, ethyl cinnamate, and trans-cinnamonitrile showed that all these monomers yield rubbery copolymers with butadiene and certain of these have been evaluated and compared to current synthetic rubbers of the GR-S type. In general, these monomers to the extent of 10 to 90 parts of butadiene yield copolymers roughly equivalent to the standard GR-S which contains approximately 25 parts of styrene. The cinnamic acid-butadiene copolymer has excellent tensile strength. The trans-cinnamonitrile copolymer shows no improvement in oil resistance over GR-S. These cinnamic acid derivatives all enter the growing butadiene copolymer chain somewhat more slowly than does butadiene, so that the copolymers contain a lower percentage of the comonomer than does the charging stock used. Some experiments were conducted on the copolymerization of these cinnamic acid derivatives with other monomers than butadime, the copolymerization of the furan analogs of the cinnamic
Inglis, J. K.H., “Organic Syntheses,” Coll. Vol. I, 2nd ed., p. 254, New York, John Wiley & Sons, 1941. Lapworth, A., and Baker, W., Ibid., p. 181. Marvel, C. S., Fukuto, T. R., Berry, J. W., Taft, W. K., and Labbe, B. G., J. Polymer Sci., 8,599 (1952). Marvel, C. S., and McCain, G. H., J . Am. Chem. Soc., 75,3272 (1963).
Marvel, C . S., and Meinhardt, A., J . Polymer Sci., 6,733 (1951). Marvel, C. S., Menikheim, V. C., Inskip, H. K., Taft, W. K., and Labbe, B. G.,Ibid., 10,39 (1953). Marvel, C. S., Peterson, W. R., Inskip, H. K., Taft, W. K., and Labbe, B. G., IND. ENQ.CKEM., 45, 1532 (1953). Marvel, C. S., and Wright, J. C., J . Polymer Sci., 8 , 495 (1952). Mayo, F. R., and Walling, C., Chem. Revs., 46, 191 (1950). Plaut, H., and Ritter, J., J. Am. Chem. SOC.,73,4076 (1951). Posner, T.,J . prakt. Chem., 82 (21,425(1910). Seymour, R. B., U.S. Patent 2,465,318(March 22,1949). Stoesser, S. M., and Lowery, R. D., Ibid., 2,232,930(Feb.25, 19411. (31) Swart, G.H., Ibid., 2,594,824(April 29,1952). (32) Vanderbilt Co., R. T., New York, N. Y., “Vanderbilt Rubber Handbook,” 9th ed., p. 65,1948. (33) Wagner-Jauregg, T.,Ber., 63, 3213 (1930). RECEIVBD for review May 8, 1953.
ACCEPTED July 18, 1953
Temperature-Indicating Paints J. E. COWLING, PETER KING, AND ALLEN L. ALEXANDER Naval Research Laboratory, Washington, D. C . D
I
MMEDIATELY prior to World War 11, a few materials of foreign origin evoked considerable interest in this country as a result of their ability t o change color on reaching specific temperatures. When applied t o equipment that becomes heated during operation, they provide a convenient means for estimating the peak temperature reached during the period of use. For example, the application of small spots or stripes of several colored materials to an operating mechanism, such as a commutator on an aircraft, each of which assumes well-defined but strikingly different color characteristics a t progressive temperatures, provides a useful means of recording the top temperatures reached during flight. Furthermore, by coating an aircraft cylinder completely with a film of selected temperature-sensitive paints, a record may be produced of the maximum temperatures involved during a given operation or evaluation. Obviously such color changes should be permanent, and the
paints should not return t o their oTiginal shades before a reading can be made. The value of such data in the design of remote or difficulty accessible components is obvious. Most materials of this nature, including pigmented crayons, being of foreign origin became unavailable at the beginning of World War 11, and for this reason this work was undertaken t o establish a source of supply based on domestically available materials. During the past 2 years considerably more information has been released on the products manufactured abroad, and it has been revealed t h a t some of the compounds described herein have been studied elsewhere; however, a great many others are quite novel. Mayer (8) has described a number of compounds t h a t change color when heated. A number of patents have been issued which describe in general terms the reaction of a variety of materials sensitive t o heat. Two of these (4,6) discuss color changes occurring in selected compounds with the liberation of ammonia and
