batches (up to 10 gallons) with a propeller stirrer (Lightnin Mixer, Model KDV-I, Mixing Equipment Co., Inc., Rochester,
s.Y , ) .
Pumping of carbon black slurries was studied using a diaphragm p u m p (Model No. 2-47, Proportioneers Division. BIF Industries. Inc., Providence, R . I . ) ; a centrifugal pump, high speed open impeller (Model E-1, Eastern Industries, Inc.. New Haven, C o n n . ) ; a peristaltic p u m p (Model 18: Sigmamotor Co., Middleport. N. Y . ) ; and a Moyno pump (Model 2M1, Robbins & Myers, Inc., Springfield, Ohio). T h e latex masterbatches were prepared in a continuous system with a production rate of 10 pounds of masterbatch per hour. T h e latex was pumped with a diaphragm p u m p into a baffled glass tube, in bvhich it was mixed with streams of oil emulsion (pumped by a gear pump) and carbon black slurry (pumped by the Sigmarnotor peristaltic p u m p ) . From the outlet of the mixing tube the mixture dropped into a fanshaped spray of salt-acid solution (8% sodium chloride, 0.4% sulfuric acid. 0.03% phenyl-2-naphthylamine) and then into a 5-gallon coagulating tank in which coagulation was completed with vigorous stirring. T h e slurry of mother liquor and coagulum continually overflowed onto a 16-mesh alumin u m screen, from which it was transferred by hand into a wash tank to be washed continuously for several hours. When \vashing was complete, as judged by p H and ash tests, the c r u m b was dried in a n air convection oven a t 150’ F. for 6 hours. T h e carbon blacks used were manufactured by the Cabot Corp., Boston, Mass., and included a n H A F black (Vulcan 3) and other production blacks as well as several experimental blacks. T h e SBR-1500 latex, of 19y0total solids concentration, was obtained from Copolymer Rubber & Chemical Corp., Baton Rouge, La.
Acknowledgment
‘The authors gratefully acknowledge the experimental assistance of G. Stefanidakis, J. J. Williams, and G. Yeghyazarian. They are indebted to E. M. Dannenberg for his interest and encouragemenL; and to the Cabot Corp. for permission to publish this bvork. Literature Cited ( 1 ) Dannenberg, E. M.. Hagopian, E., Hall, J. P., Jr., Medalia, A. I., Trans. Inst. Rubber I n d . 37, 1 (1961). (2) Dannenberg, E. M., Seltzer, K. P., Ind. Eng. Chem. 43, 1389
(1951). (3f Dodge, D. W., Metzner, A. B., A . I . C h . E . J . 5, 189 (1959). (4) Greek, B. F., Ind. Eng. Chem. 55, 13 (1963). (5) Janssen, H . J. J . , Weinstock, K. V., Rubber Chem. Technol. 34, 1485 (1961). (6) Medalia, A . I., Hagopian, E., Rheof. Acta 3, 100 (1963). (7) Oka, S., “Rheology,” F. R. Eirich, Ed., Vol. 111, pp. 17-82, Academic Press. New York. 1960. (8) Reich, I., Vold, R. D., J . P h y s . Chem. 63, 1497 (1959). (9) Sutherland, J. D., Jr., Division of Industrial and Engineering Chemistry, 144th Meeting, ACS, Los Angeles, Calif., April 4, 1963. (10) Sutherland, J. D., Jr., U. S. Patent 3,055,856 (Sept. 25, 1962). (11) U . S. Dept. Commerce, Current Industrial Reports, Bull. M30A (December 1963). ~~~~
~
RECEIVED for review January 7, 1964 ACCEPTED March 19, 1964 Presented in part at the Southwest-Southeast Regional Meeting, American Chemical Society, New Orleans, La., December 7 to 9, 1961.
STRUCTURE-PROPERTY RELATIONSHIPS I N ONE-STEP UREA-URETHANE ELASTOMERS K.
W .
R A U S C H , R . F. M A A T E L , A N D A . A.
R . S A Y I G H
The Carwin Co., Dzvtsion of The CTpjohn Co., .Vorth Hauen, Conn.
A series of one-step urea-urethane cast elastomers has been prepared employing various diisocyanates with 3,3’-dichloro-4,4’-diaminodiphenylmethane and 3,3’-dichlorobenzidine. The effects of diisocyanate structure are not as pronounced as those previously reported for prepolymer systems. Significant variation in stress-strain properties may be obtained, however, depending on the molecular weight and the backbone structure of the polyglycol. A complex catalyst situation, arising from differences in reactivity of the diisocyanates, may also affect these properties considerably as a result of improper balance of reactions during chain buildup. The use of a newly available diisocyanate, “mixed isomer” MDI, which affords high strength elastomers while eliminating safety hazards and cumbersome handling techniques, i s also described. and properties of urea-urethane elastomers by the one-step casting technique have recently been reported ( 7 . 5, 6 , 7 7 , 72). Although only in the beginning stages, the rapid development of this technology is a result of discoveries in the catalysis of isocyanate reactions. T h e resonance forms (I, 11) which can be drawn for the isocyanate group clearly suggest the possibility of ionic reactions. CaHE PREPARATIOS
I
I1
talysis by Lewis acids and bases could therefore be expected. Generally, it was found that acids are much weaker catalysts than bases. Since the largest commercial applications of isocyanates utilize catalyzed reactions (foams), a great deal of research has been concentrated in this area. However, it was not until
the discovery of the organotin catalysts that one-utep polyether foams and elastomers were possible. M a n y metallic compounds have subsequently been found for the isocyanatehydroxyl reaction. T h e specificity of catalysis of the hydroxylisocyanate reaction and the influence of these catalysts on the isocyanate-amine reaction have been described ( 7 , 4 , 73). T h e one-step method for production of urea-urethane elastomers offers a number of advantages over prepolymrr or solid elastomer processes. T h e latter require the use of specialized casting equipment and more expensive. time-consuming techniques. T h e properties of the one-step elastomers compare favorably with those obtained via the prepolymer route ( 7 ) . Most of the available literature to date has described elastomers obtained using a n 80 to 20 mixture of 2,4- and 2.6toluene diisocyanate (TDI). This paper is concerned primarily with the use of other diisocyanates for the preparation of one-step elastomers. VOL. 3
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JUNE 1 9 6 4
125
Table I. Effect of Curing Conditions on MOCA Elastomers 7 H r . at Room T e m p . 1 H r . at 250' F . a 2 H r . at 250'
+
Pluracol P-2010, equiv. "*/OH ratio T D I , eqniv. MDI, equiv. Excess NCO/lO,OOO grams polymer, e2uiv. T-9. p.p.h ("2 OH) Stress-strain properties Tensile strength, p.s.i. 1007, Modulus 7GElongation at break Graves tear. lb./in. Split tear, lb. /in.
4.0
2 1. o excess
+
4.0
...
0.2 1055 560 460 220 69
Castings uere clear after curing.
b
F.*
2 1 .o 4.0 excess
2 1. o
+
+ excess
...
...
2.0 0.2
2.0
+
a
2 1.o
4.0
+ excess
2.0 0.2
2.0 0.2
715 515 260 200 54
1670 665 615 245 72
1160 600 420 185 51
Castings were opaque after curing.
Table II.
Effect of Various Catalysts on Properties of 4,4'-MDI-Diamine Rubbers",* Split Tear Tensile, P.S.I. 700% Modulus Elongation,c yc .MOCA DCB .MOCA DCB MOCA DCB MOCA DCB
Stannous octoate Stannous oleate Dibutyltin dilaurate Ferric acetylacetonate Lead naphthenate
1480 1300 1430 990 1190
1670 1680 820 1600
650 650 640 560 650
, . .
720 740 660 800 ...
Cured at room temperature for 1 hour followed by 1 hour at 250" F. equivalents shown in Table I . c Per cent elongation at break point. a
Table 111.
TDI 4,4'-MDI "Mixed isomer" MDI DMMDI TODI
7007, Modulus
DCB
.MOCA
530 650 650 820 1070 Based on formulation of Table I with 0 . 2 0 0 p . p . h . (LVH2
1325 1610 1670 1690 1580
890 1475 1480 1430 2290
+ HO-OH H
+ R'(!VH,), O
I 1
OCN-R-1-C-0-
750 750 720 950
830 550 560 460 720
900
O
H
I
,I
I
R-N-C-N-R'
-P
HOH , I l l 0-CNR-NCN-R HOH HO I 'I 1 1 1 NCN-R-YC-0-
OH
111
'(1)
OH
+ -R-NCO
I1
-P
R-NCN-R'
(2)
P\- N H R
0
Biuret apparently occur via biuret formation in preference to allophanate branch points. The relative rates of these reactions have been determined by various researchers (2, 7- 70). Experimental
Materials. All elasromers were based on polypropylene oxyglycols (PPG), Pluracol P-2010 (Wyandotte Chemical Corp.), and Formrez ED-2000 (IVitco Chemical Co.). In addition to 4.4 '-diphenylmethane diisocyanate ( M D I ) 126
l&EC
400 850 750 660 670
+ O H ) stannous octoate.
~
H
...
92 104
161 80 110 106
88
106 66
Catalyst concentration 0.200 p.p.h.
Elongation, yo MOCA DCB
Since preparation of elastomers via the one-step route depends for the most part on rapid chain buildup (Equation l ) and appropriately placed cross-links (Equation 2), catalyst activity and concentration would appear to be quite critical. The cross-linking reactions R(NC0)2
750 590 340 620
...
291 245 260 214 257
325 292 273 344 ...
+ O H )for formulation containing
("2
Effect of MOCA and DCB on Stress-Strain Properties of Various Diisocyanate Elastomersa Tensile, P.S.I. MOCA DCB
a
560 580 620 540 380
Graves Tear MOCA DCB
PRODUCT RESEARCH A N D DEVELOPMENT
Graves Tear MOCA DCB
215 240 290 303 447
242 345 325 418 405
Split Tear Hardness (Shore A ) MOCA DCB M O C A D C F
68 79 92 102 119
102 133 161 131 94
83 82 83 85 89
84 84 77
91 88
(Mobay Chemical Co.), the diisocyanates used were: 3,3'-di-
methy]-4,4'-diphenylmethanediisocyanate ( D M M D I ) (Carwinate 139D), 3,3 '-dimethyL4,4'-diphenyl diisocyanate (TODI) (Carwinate 132T), and "mixed isomer" M D I consisting of a 90 to 10 mixture of 4,4'- and 4,2'-diphenylmethane diisocyanates (Carwinate 125M). The last diisocyanate is easy to handle because it melts a t 31' C. and does not crystallize as readily as the 4,4'-MDI (melting point, 45' to 47' (2.). An 80 to 20 mixture of 2!4- and 2,6-toluene diisocyanate was also used during this study. The diamines used were 3,3 '-dichloro-4,4 '-diaminodiphenylmethane (Curithane M-134, T h e Carwin Co., or MOCA, E. 1. d u Pont de Nemours & Go.) and 3,3'-dichlorobenzidine (DCB) (Curithane C-126). T h e catalyst was stannous octoate (catalyst T-9, Metal and Thermit Corp., or Formrez C-2, Witco Chemical Co.). Procedure. A 500-ml. resin flask, equipped with a thermometer, mechanical stirrer, and an additional funnel, was charged with polyglycol, diamine, and catalyst and heated to 130 to 140 C. a t 3 to 5 mm. of Hg for 1 hour. After cooling to room temperature, the liquid diisocyanate was quickly added (in 5 to 10 seconds). O n e minute after the start of the diisocyanate addition, the vacuum was released and the reaction mass poured into molds. The elastomers were cured for 2 hours at 250' F. and 500 p.s.i., and an additional hour in an air circulating oven a t 250' F. During the development of this procedure, variations in properties and appearance of the elastomers were encountered. This was due primarily to phase separation of ureaisocyanate polymers when the catalyst and temperature were not optimum. This phenomenon occurred a t times even when stannous octoate was used. To avoid this drawback, curing was effected by allowing the castings to remain in a cold press for 20 minutes, followed by a 1-hour cure a t 250' F . Considerable improvement of properties was obtained using
-. .
2soc
h
2250
400 -
2000
350 -
f:
i
$750
a300 -
?
W
a W
a1500
ui
TDI MDI
-'I250
DMMDI
m
I
//
1000 TDI
100
750
= /
// / /
-
/
50 0
A
DMMDI TOO1
J
m
MDI
A
DMMDI TODI I
,l-.--L-
.OO
1.25
1.50 N H2/0 H
2°o'l.oo
1.75
Figure 1. Effect of NH:, to OH ratio on 100% modulus and breaking tensile of Pluracol P-2010-MOCA elastomers
Figure 2. Effect of NH2 to OH ratio on tear properties of Pluracol P201 O-MOCA elastomers
1.50
1.75
Figure 3. Effect of NHP to OH ratio on breakpoint elongation of Pluracol P-2010-MOCA elastomers
- - - - Graves tear
-
- - - - 100% Modulus -- Tensile
this technique ('Table I), and all subsequent elastomers were prepared in this manner. Results
Variation in Catalyst Concentrations and Type. T h e optimum T-9 concentration of 0.025 p.p.h. "(2 OH) for the rDI-based elastomers ( 7 ) was found to be ineffective for M D I systems. T h e latter required 0.200 p.p.h., and this concentration was used for each of the other three diisocyanates. Control experiments, in which the catalyst was added after dehydration of the polyol-diamine mixture, showed very little variation. Thus, the greater catalyst requirement was not due to hydrolytic deactivation. Various catalysts were employed and considered satisfactory for preparation of one-step elastomers (Table II), although the properties varied considerably in each case. Variation of Diisocyanates and Diamines. T h e two weakly basic and sterically hindered diamines, M O C A and DCB, were chosen for this study because of their suitability for preparation of one-step elastomers. T h e properties of these elastomers are shown in Table 111 for five diisocyanates. Variation in NH2 to OH Ratio. Figures 1 to 6 show the effect of NH2 to OH ratio in regard to physical properties for both MOCA and DCB systems.
+
Discussion
Although we were not primarily concerned with determining optimum conditions for preparation of the various elastomers, the expected complexity of the catalyst situation was obvious a t the outset. T h e differences in reactivity of the various diisocyanates. even in the presence of catalysts, may significantly affect the relative rates of the isocyanate-hydroxyl and isocyanate-amine reactions a n d , consequently, chain buildup in a one-step process. This was immediately apparent for the following reasons. A minimum concentration of 0.100 p,p.h. (NHz OH) was necessary for the preparation of M D I based elastomers, as contrasted to a reported optimum of
+
1.25
N H2/0 H
N H2/0 H
Split tear
0.025 p.p.h. for the ' I D 1 case ( 7 ) ; elastomers based on M D I DCB exhibited generally better properties than the M D I M O C A systems, but when dibutyltin dilaurate was employed, this situation was reversed ('I'able 11); and when ferric acetylacetonate was employed. the diffrrence between the M O C A and DCB rubbers was (inconsistently) quite largr. One other point should be mentioned. Figurrs 1 to 6 show the variations of properties with changes in the h'H2 to OI-l of .I'D1 and M D I (where approximately optimum stannous catalyst '1'-9 concentrations were employed), the variation was as expected i.e.. an increase in the strength properties resulting from an introduction of iirea groups in the elastomers. As NH2 to OH ratio increased from 0.75 to 1.75. the tensile strength arid 100% modulus increased, and the percentage elongation a t brrakpoint decreased. This was not true, however, for the TODI and D M M D I cases; in the latter case, strength properties virtually disappeared with S H ? to OF€ ratio between 1.25 and 1 SO. T h e catalyst concentration which was quite efficient for 7'DI and M D I left much to be desired there. T h e eKect of polyisocyanate structure on the strc.ss-strair1 properties of the elastomers (one-step) is sho\vn in Table 111. Variations of tensile. modulus. flexibility, a n d hardness (Shore A ) were much less significant than thoce obtained for prepolymer systems ( 3 ) . T h e strength properties o f the ?I'D1 system, however, were inferior, especially iri regard to tcnsile and tear. T O D I and D M M D I afforded the strongest and most rigid stocks. Softer and more flexibly c1astomri.s werr obtained using the 4,4'- and '.mixed isomer" XIDI. I l a r d ness values did not show any appreciable variation : ho\vrver. these may be increased somewhat with increasrs in the N..I.. Rubher Aqe 82, 96 (1958).
290 453 455
5 60 690 930
83 86 88
(6) Heiss, H. L., Zbid., 88, 89 (1960). 17) Hostettler, F., Cox, E. F.. Znd. Ene. Chem. 52, 609 (1960). . . (8) Kogan, I. C.,.J. Org. Chem. 26, 3504 (1961). (9) Morton, M., Deisz: M. A , , 130th Meeting, ACS, =\tlantic City, N. J., September 1956. (10) Morton, M., Deisz, M. A , . Ohta, M., U. S.Dept. Commerce Rept. PB-131795 (March 1957). (11) Smith, T. L., Magnusson! A . B., Jet Propulsion Lab.. Calif. Inst. Technol., External Publ. No. 598, May 12, 1960. (12) Smith, T. L., Magnusson, A . B., J . Polymer Sci. 42, 391 (1960). (13) Ll.-olfe. H. I\., Jr., E. I. du Pont de Nemours Sr Co., "Catalyst Activity in One-Shot Urethane Foam," March 16, 1960. Feb. 24. 1961. RECEIVED for review December 16, 1963 ACCEPTED March 16. 1964
HIGH-PERFORMANCE T O L U E N E DIISOCYANATE-POLYPROPYLENE
GLYCOL CASTABLE ELASTO PLASTICS S.
E D M U N D BERGER AND WACLAW SZUKIEWICZ
Research CY Deuelopment Department, National Aniline Division, Allied Chemical Cor$., Buffalo, IV. Y .
This paper deals with relatively inexpensive castable polymers based on toluene diisocyanate and polypropylene glycol and having mechanical characteristics of both elastomers and plastics. Formulation changes that increase strength and hardness have an unfavorable effect on elasticity. Generally, the described polymers have better mechanical properties than similar known materials. Polymers produced b y the one-shot method seem to exhibit better heat-aging properties than prepolymer-derived analogs. A range of applications i s suggested. HE USE of cast urethane polymers in mechanical applicaTtions is rapidly gaining momentum, as indicated by their increasing acceptance in areas where conventional rubbers, plastics, and metals were previously used. Generally, cast urethane polymers show outstanding strength, flexibility, toughness, and abrasion resistance combined with high load-bearing and good low-temperature properties, elasticity, and resistance to oil, chemicals, and oxidation. However, as in other polymer systems, a single composition usually does not exhibit. all these desirable characteristics; furthermore, some combinations of properties can be achieved more economically than others. T h e most economical polymers can usually be formulated with toluene diisocyanate (TDI) and a polypropylene glycol. Such systems have found application as sealants, adhesives, potting compounds, etc. In general, however, much of the published literature describing polymers of this type deals with soft materials of relatively low strength (7, 2, 4, 7 7 ) . Work in our laboratories has shown that excellent, low-cost, hard TDI-polypropylene glycol cast urethane polymers of high strength are also feasible.
T h e principles governing urethane polymerization are well known. Processing can be stepwise (prepolymer method) or by the one-shot procedure. In the prepolymer process, a polyol reacts with excess diisocyanate to form an NCOterminated, low molecular weight, liquid prepolymer which, in a second step, is cured with a polyamine or a polyol, usually a t elevated temperature. By the one-shot process, all ingredients, including the curing agent, are mixed just before casting and the mixture is then cured. In either process the amount of diisocyanate used may be equal to or greater than that stoichiometrically required to react with the active hydrogen-containing components (polyols or polyamine). In the first case, an essentially linear polymer will result; in the second, the polymer will be cross-linked. T h e polymers discussed herein are of the one-shot, cross-linked type. Preliminary Work
T h e system based on T D I , polypropylene glycol (mol. wt.
1000) (PPG), 1,4-butanediol (BD), and 4,4'-methylenebis(ochloroaniline) (MOCA) was subjected to a preliminary study. statistically designed to determine the effects of these four components on polymer characteristics. VOL. 3
NO. 2 J U N E 1 9 6 4
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