exhaust tests to determine the extent of such conversion with the ruthenium-containing catalysts. In no case was there observed an increase in hydrocarbon content over that a t the reactor inlet (i.e., normally 500 ppm as (26). The high concentration of water vapor may have supressed CH4 formation as indicated by Shelef and Gandhi (1972b).
LUnt, R. S., Bernstein, L. S., Hansel, J. G., Holt, E. L., SAE Paper No. 720209 ( 1972). Meguerian. G. H., Lang, C. R . . SA€ Paper No. 710291 (1971). Meguerian, G. H., Rakowsky, R. W., Hirschberg, E. H., Lang, C. R . , Schock. D. N.. SAE Paper No. 720480 (1972). Shelef, M . , Gandhi, H. S.,Ind. Eng. Chern.. Prod. Res. Develop., 11, 2 (1972a). Shelef, M . , Gandhi. H. S., Ind. Eng. Chern., Prod. Res. Develop., 11, 393 (1972b) Taylor. K. C.. Klimisch, R. L., J. Catal., 30, 478 (1973)
Literature Cited Bernstetn. L. S . , Kearby, K. K., Raman, A. K. S., Vardi. J , Wigg, E. E., SAE Paper No 710014 (1971). Hunter, J. E., Jr.. Gen. Mot. Res. Pub/. GMR-7067, March 23 (1971). Jones, J. H., Kummer, J. T . , Klaus, 0..Shelef, M . , Weaver, E. E., Environ. Sci. Techno/.. 5 , 790 (1971). Klimisch, R. L.. Barnes. G. J., f n v i r o n . Sc;. Techno/., 6, 543 (1972) Klimisch, R . L., Taylor, K. C., Envvon. Sci. Techno/., 7, 127 (1973).
Receired for recieu. F e b r u a r y 8, 1974 Accepted M a y 6, 1974 T h i s w o r k was s u p p o r t e d by t h e C a l i f o r n i a A i r Resources B o a r d P r o j e c t No. 2-009-10.. Presented a t t h e D i v i s i o n o f W a t e r , Air a n d Waste Chemistry, 165th N a t i o n a l M e e t i n g of the American Chemi c a l Society, Dallas, Tex., April 1973.
Polyester and Polyurethanes from y,y-Dimethyl-8-valerolactone Katsumi Hayashi The Lubrizol Corporation, Cleveland, Ohio 441 17
y,y-Dimethyl-6-valerolactone(DMVL) was synthesized from acrolein and isogutyraldehyde. D M V L poly-
merized anionically and cationically to form polyester(P-DMVL). T h e crystalline melting point of PD M V L is 110-120°. P-DMVL depolymerized completely above 130" in t h e presence of a trace amount of an alkoxide. However, alkoxide-free P-DMVL did not depolymerize beloH 200". When P-DMVL was treated with 1-5% by weight of tolylene diisocyanate at 160-180°, t h e molecxlar weight of t h e polymer increased. T h e resulting polymers were plastic materials with good mechanical properties. P-DMVL formed an insoluble tough resin w h e n treated with triisocyanate. Macroglycols were prepared by treating D M V L with varying amounts of 1,4-butanediol with an alkoxide initiator. T h e polyurethanes derived from t h e macroglycols were not elastomeric b u t plastic materials. They are hyd olytically stable.
Introduction
Results and Discussion
The homo- and copolymerizations of P-propiolactone, m,n-dimethyl-d-propiolactone,6-valerolactone, and e-caprolactone have been investigated in detail (Frisch and Reegen. 1969: Hall and Schneider, 1958; Mark and Whitby, 1940). The polyester from a,m-dimethyl-P-propiolactone has a high polymer melt temperature, 237", in contrast to other aliphatic polyesters which have polymer melt temperatures below 100". The high melt temperature for poly-n,a-dimethyl-~3-propiolactone is related to the presence of the qem-dimethbl groups N to the ester carbonyl, as will be discussed This paper deals with the preparation and polymerization of y,y-dimethyl-6-valerolactone(DMVL)which contains gem-dimethyl groups at the y position. Starting raw materials for DMVL are acrolein and isobutyraldehyde. Macroglycols were prepared from DMVL and 1.4-butanediol and were evaluated as intermediates for polyurethanes.
Preparation of DMVL. An equimolar mixture of acrolein and isobutyraldehyde was added dropwise to a dilute aqueous solution of sodium hydroxide a t 10-20". The product was sodium y,y-iimethyl-6-hydroxyvalerate which formed DMVL upon acidification. The intermediate is probably cup-dimethyl g utaraldehyde which undergoes an intramolecular Canniz iaro reaction to form sodium y ,y -dimethyl4-hydroxyvalerate. CH,=CHCHO
+
CH(CHs&CFO
-
OH
[OHCCH,CH2C(CH3)2CHOl 'OzCCH2CH2C(CH3)~CH20H
The intramolecular Cannizzaro reaction of a,a-dimethyl glutaraldehyde may form another isomer, sodium ( Y , N dimethyl-6-valerolactone. The nmr analysis shows that the product is in fact, DMVL. The Cannizzaro reaction involves attack of hydroxyl ion on the carbonyl carbon. In Ind. Eng. Chem., Prod. Res. Develop., Vol. 13, No. 3, 1974
193
cup-dimethylglutaraldehyde, the hydroxyl ion attacks the unhindered carbonyl group. The next step is the migration of hydride ion from the 5 position to the carbonyl carbon at the 1 position through a six-membered ring transition (I).
820
-
LLo o
-
0
L40 k
/Cbo
H/\o
H
I
-
0
E60
-
80
t 100
200
300
400°C
Figure 1. Thermogravimetric curves (20"/min);A, P-DMVL ( q l l l h = 0.28) containing 0.1% by weight of lithium methoxide; B, basefree P-DMVL ( q l l , h = 0.29).
,A\
c
Meerwein (1918, 1920) has synthesized a series of 6-valerolactones having three or more aliphatic and/or aromatic substituents by the reaction of a$-unsaturated aldehydes with an aldehyde or a ketone in the presence of a base. Hagemeyer, et al. (19561, and Hausermann (1951) have prepared tetrasubstituted-6-valerolactonesfrom isobutyraldehyde and substituted acroleins. It was found that under the reported reaction conditions (Hagemeyer, et al., 1956; Hausermann, 1951; Meerwein, 1918, 1920), the yield of DMVL from acrolein and isobutyraldehyde was near zero due to the formation of a resinous mass. The use of an aqueous alkaline solution and control of the reaction temperature below 25" are important to minimize the resin formation. The best yield obtained was 63%. Under the same conditions, the reaction of methacrolein and isobutyraldehyde gave a , y , ? -trimethyl-6-valerolactone in a yield higher than 90%. On the other hand, the reaction of propionaldehyde and acrolein gave a mixture of a - and pmethyl-6-valerolactones in less than 10% yield. The results indicate that less substituted lactones are more difficult to form. The roles of the substituents in increasing the yield of lactones are: (1) the substituents stabilize the postulated ring transition structure and thus promote the intramolecular Cannizzaro reaction and (2) a-substituents in the intermediate dialdehydes reduce competitive reactions such as aldol type condensations. a,a-gem substituents eliminate the possibility of base-catalyzed aldehyde condensation. It has been reported that the Cannizzaro reaction of dialdehydes may proceed either intramolecularly or intermolecularly. 1,4-, 1,5-, and 1,6-dialdehydes favor intramolecular reactions, particularly when they are highly substituted. The following dialdehydes form exclusively the intramolecular products: phthaldehyde (Thiele and Gunther, 1906) 2,2,4,4-tetramethyl-3-thiaglutaraldehyde (Hayashi and Zalar, 1974), 2,2,5,5-tetramethyl-3,4-dithiaadipaldehyde (Hayashi, 1970), and 2,2,5,5-tetramethyladipaldehyde (Hayashi and Zalar, 1974). DMVL has been synthesized by various routes from starting materials other than acrolein and isobutyraldehyde (Bowman, 1954; Falbe, et al , 1965; Freidrichsen, 1957, Hall, 1954; Julia and Ronault, 1959). Polyester from DMVL. The polymerization of DMVL has been initiated by diethylzinc (Schulz and Vollkommer, 1970) and organic aluminum-zinc complexes (Charpentier, et a1 , 1969) to form poly-y,y-dimethyl-6-valerolactone(P-DMVL). In the present work, both anionic and cationic initiators were used. They included butyllithiums, alkyl aluminums, alkali metal alkoxides, boron trifluoride, and trifluoroacetic acid. The highest inherent 194
Ind. Eng. Chem., Prod. Res. Develop., Vol. 13, No. 3, 1974
Table I. Polymer Melt Temperature of Polylactones
Polylactone
Polymer melt temp, "C
Poly-8-propiolactone Poly-a, a-dimethyl-& propiolactone Poly-6-valerolactone
86 237
Poly- 7, r-dimethyl-6valerolactone
120
55
Lit. citation Gresham, et al. (1948) Reynolds and Vickers (1947) Carothers and VanNatta (1933) This paper
viscosity of P-DMVL was 0.5 (chloroform) which was obtained from rigorously purified DMVL with n-butyllithium catalyst. P-DMVL is a crystalline polymer having a melt temperature of 110-120". This is approximately 70" higher than that of poly-6-valerolactone. The effect of the gem-dimethyl groups on increasing the melting temperature of these polymers is clear, but the extent is smaller than that observed with the gem-dimethyl groups of polycu,a-dimethyl-/3-propiolactone(Table I ) . P-DMVL is soluble in aromatic hydrocarbons and chlorinated hydrocarbons. It gives an opaque film by solution casting or by melt processing. P-DMVL depolymerizes thermally, as does poly-6-valerolactone. When P-DMVL is heated at a temperature above 130" under vacuum, it depolymerizes rapidly and completely to form pure monomer, DMVL. The combination of polymerization and depolymerization is an efficient process to purify DMVL. It was found that the depolymerization was catalyzed by a trace amount of a base such as lithium alkoxide. P-DMVL which is freed from base does not decompose a t temperatures below 200". This was shown by thermogravimetric analysis (Figure 1). Saotome and Kodaira (1965) have reported that when the terminal hydroxyl groups were blocked by acetyl groups, poly-6-valerolactone did not depolymerize under the conditions which caused depolymerization of the nonacetylated poly-6-valerolactone. Carothers and VanNatta (1933) proposed that the mechanism of the depolymerization of poly-6-valerolactone was through ester interchange. The base-catalyzed depolymerization of P-DMVL supports the ester interchange route rather than the unzipping mechanism from the hydroxyl end groups. As it will be shown in the next section, the diisocyanate treated P-DMVL in which the terminal groups are blocked by the carbamoyl groups is stable thermally. It did not show any appreciable weight loss below 250" but depolymerized below that temperature in the presence of a small amount of potassium tert-butoxide (Figure 2 ) . This is consistent with the ester interchange mechanism. Reaction of P-DMVL with Isocyanates. P-DMVL was treated with 1-670 by weight of tolylene diisocyanate
I
100
I
I
I
I
l
J 400°C
300
200
Figure 2. Thermogravimetric curves of P-DMVL treated with 2% by weight of TDI (q,,,h = 0.63): A, 5% by weight of lithium methoxide: B, 1%by weight of potassium tert-butoxide; C, base free. Table 11. Macroglycols from DMVL and 1,4-Butanediol
Mol of DMVL/mol of 1,4Run butanediol 1
5
2 3 4
10 14
20
OH no."
Acid no.
96.5 72.8 54.9 40.3
5.4 5.3 6.2
3.1
Mol wt Foundb Calcd 1100 1430 1830 2580
730 1370 1880 2650
Determined by the acetic acid-pyridine method (Ogg, et al., 1945). Based on the hydroxy and acid numbers. (TDI) or 4,4'-methylenedi(pheny1 isocyanate)(MDI) a t 160-180". P-DMVL had a low molecular weight unless prepared from rigorously purified monomer. P-DMVL having an inherent viscosity of 0.2 formed a brittle film. After the diisocyanate treatment, the inherent viscosity increased from 0.2 to 0.6. A film from the TDI treated polymer had a tensile strength of 5500 psi; its elongation a t rupture was 100% and yield strength was 5400 psi. The increase in molecular weight is due to chain extension through the reaction between the end groups of P-DMVL and diisocyanate. The end groups are hydroxyl groups and carboxyl groups. The P-DMVL-diisocyanate reaction shows the characteristics of a polycondensation reaction between two difunctional compounds. When the inherent viscosities of the products were plotted against the ratio of the two reactants, there was a peak a t which chemical stoichiometry was reached (Figure 3). The diisocyanate treated polymers are stable thermally as shown in Figure 2. When a triisocyanatra, tris(4-isocyanatopheny1)methane is used in this reaction, a cross-linking reaction takes place to give a flexible, tough, insoluble material. The treatment of P-DMVL with monoisocyanate causes no appreciable increase in inherent viscosity. Macroglycols and Polyurethanes. The reaction of DMVL with 1,4-butanediol in the presence of an alkoxide formed macroglycols which are low molecular weight hydroxyl terminated polyesters. The molecular weight of the macroglycols was varied by changing the ratio of DMVL to 1,4-butanediol (Table 11). These macroglycols were treated with an excess MDI to form isocyanate terminated prepolymers. The prepolymers were extended with water, hydrazine, or ethylene glycol. Mechanical, thermal, and electrical properties of the resulting polyurethanes were measured in comparison with those of polyurethanes derived from a commercial polyadipate macroglycol (Tables I11 and IV). The polyurethanes derived from P-DMVL have low elongation and high modulus. They are not highly elastomeric materials as are the polyurethanes from polyadipate macroglycol.
0
I
2
3 T D l ( g ) / I O O g P-DMVL
Figure 3. Reaction of P-DMVL ( q , , , h = 0.1'7) and I.
The macroglycol from DMVL with 1,4-butanediol (14:l mol ratio) forms a polyurethane which is cold-drawable and forms oriented fibers and films. The polyurethane films from the DMVL-l,4-butanediol (10:l mole ratio) were soaked in water a t 70°C and the mechanical properties were determined a t time intervals over a period of 14 days (Table V ) . These polyurethane films are hydrolytically stable. However, they harden gradually during this treatment. The hardening possibly is caused by crystallization of the polyester segments from DMVL. The same test was conducted with the polyurethane derived from a commercial polyadipate macroglycol. This material did not crystallize but was hydrolyzed extensively. The gemdimethyl groups of DMVL most likely increase the tendency of crystallization of the resulting polymers. Experimental Section
y,y-Dimethyl-&valerolactone(DMVL). To a stirred solution of 1200 g (30 mol) of sodium hydroxide in 4800 ml of water was added dropwise a mixture of 840 g (15 mol) of acrolein and 1080 g (15 mol) of isobutyraldehyde. The temperature of the reaction mixture was maintained a t 15" by external ice-water cooling. After the addition was completed, stirring was continued for 1 hr a t 15". The mixture was acidified with hydrochloric acid. The organic layer was separated and the aqueous layer was extracted twice with ether. The organic layers were combined and dried over anhydrous sodium sulfate. After removal of the solvent, the remaining liquid was flash-distilled at 0.5 mm and 250". The distillate and the tarry residue weighed 1340 and 425 g, respectively. The distillate was fractionally distilled. The fraction boiling at 54-58"/0.1-0.2 mm weighed 1216 g (63%). It was a colorless liquid and 96% pure by gas chromatography; nZ5D = 1.4511; (reported values: nZ5D = 1.4512 (Julia and Ronault, 1959); nZ5D = 1.4520 (Bowman, 1954)). Anal. Calcd for CsH1402: C, 67.57; H, 9.93; 0. 22.49; mol wt, 142. Found: C. 67.47; H, 10.06; 0, 22.77; mol wt (vapor pressure osmometer. in chloroform) 144. Poly-y,y-dimethyl-6-valerolactone(P-DMVL). To 230 g of DMVL (nZ5D= 1.4517), was added with vigorous agitation 2.5 ml of a 1.6 A4 solution of n-butyllithium in nhexane at room temperature. An exothermic reaction started; the mixture became viscous and soon solidified. The solid was allowed to stand a t room temperature overnight. The powdered product was washed four times with water and three times with methanol by means of a Waring Blendor. The dried polymer was dissolved in chloroform and reprecipitated in methanol. The precipitates were washed repeatedly with methanol and dried. The product was a colorless, fibrous material and weighed 167 g (76%). The inherent viscosity was 0.49 (concentration = 0.5 g/100 ml of chloroform a t 30°C). Polymer melt temperature by differential thermal analysis: 110-120" (lit. Ind. Eng. Chem., Prod. Res. Develop., Vol. 13, No. 3, 1974
195
Table 111. Polyurethanes"
Run no.
Macroglycol
1-A 2-A 3-A 4-A 5-A 6-A
DMVL-1,4-butanediol DMVL-l,4-butanediol DMVL-l,4-butanediol DMVL-l,4-butanediol DMVL-l,4-butanediol Multrathane R14h
Chain extender
Inherent viscosity,~ g d1-I
Water Water Water Hydrazine Hydrazine Water
0.72 0.90 0.93 0.86 0.98
(14: 1 mol) (10: 1 mol) (5: 1 mol) (10: 1 mol) (5: 1 mol)
0.86
lC M D I was used. The ratio of M D I t o macroglycol was 2 t o 1. Polyadipate macroglycol (molecular weight about 2000) from Mobay Chemical Co. c Concentration = 0.5 g/lOO ml of N,N-dimethylacetamide a t 30".
T a b l e IV. Thermal, Mechanical, and Electrical Properties of' Polyurethane
Run1L 1-B 2-B 3-B 4-B 5-B 6-B
degradation, "C
temp, "C
tensile, psi
150-170 130-150 160-180
- 13 -5 8 -1 5 - 40
8200 4900 5400 6600 7600
150-180
160-180 150-180
elongation, %
modulus, psi
290 270 270 270 190 780
5800
humidity
90 % humidity
x
10'5
6 . 1 x 1014 0 . 7 x 1014
x 3.7 x
10'5
50 %
1740
5.5
560 1080
0.9 x 1015 0.6 X 1Ol5
1530 2700
1.0
1015
1 . 6 X 10"
180
1 . 2 x 10'4 0 . 3 X 10l4
1.1 x 1014 1 . 6 X 10"
The samples 1-B, 2-B, 3-B, 4-B, 5-B, and 6-B correspond t o the samples 1-A, 2-A, 3-A, 4-A, 5-A, and 6-A, of Table 111, respectively. Differential scanning calorimetry. c Thermomechanical analysis. Table V. Hydrolytic Stability of Polyurethanes Tensile strength (psi)/Elongation
(%)/loo%
Modulus (psi)
Samplea
Initial
24 hr
7 days
14 days
1
4210 /380/340 3110/500/240
3810/320/1200 2410/670/180
4370/220,3120 1940/690/180
4680/210/3240 840:780/130
2
Sample 1 = macroglycol: DMVL-l,4-butanediol (10: 1 mole ratio)-TDI-ethylene glycol (1:7.2: 1 mole ratio). Sample 2 = Multrathane R14 (Mobay)-TDI-ethylene glycol (1:2.4: 1 mole ratio). (1
(Schulz and Volkommer, 1970) 120-122"). Decomposition temperature by thermogravimetric analysis: 225". Depolymerization of P-DMVL. A mixture of 380 g of P-DMVL and 0.9 g of lithium methoxide was heated at 160" and a t 0.1 mm in a distillation apparatus. The distillate(DMVL) was a colorless liquid and weighed 368 g (97%). Upon fractionation, a cut boiling a t 58-59" (0.03 mm) was collected; it weighed 320 g (84%); n 2 5 = ~ 1.4517. Reaction of Poly-y,y-dimethyl-6-valerolactone and TDI. A mixture of 100 g of poly-y,y-dimethyl-6-valerolactone ( v l n h = 0.23) and 2.0 g of TDI was heated at 160" and 0.05 mm for 6 hr. The polymer was dissolved in chloroform and reprecipitated in methanol. Inherent viscosity of the product was 0.63 a t a concentration of 0.5 g/100 ml of chloroform at 30". The molecular weight by vapor pressure osmometry was 11,700. It gave a tough translucent film by solution casting or by melt pressing. Macroglycol from DMVL and 1,4-Butanediol at 10: 1 mole ratio. A mixture of 27 g (0.30 mol) of 1,4-butanediol and 0.35 g (0.015 atom) of sodium metal was heated a t 100" under nitrogen. When the sodium had reacted, the mixture was cooled to room temperature. To this was added 384 g (3.0 mol) of DMVL a t one time with vigorous agitation. An exothermic reaction took place, the viscosity of the mixture increased rapidly, and the entire mixture s m n solidified. It was allowed to stand overnight at room temperature. The solid was dissolved in 800 ml of ethanolfree chloroform. The solution was washed with water, dilute hydrochloric acid, and water successively and dried over anhydrous sodium sulfate. After removal of the solvent, the residue was dried a t 55" and at 0.1 mm for 4 days. The product consisted of colorless flakes and weighed 408 g (99%). Inherent viscosity: 0.059 at a con196
Ind. Eng. Chem., Prod. Res. Develop., Vol. 13, No. 3, 1974
centration of 0.5 g/100 ml of chloroform at 30"; hydroxy number, 74.8; acid number, 5.3. Polyurethanes from Macroglycols and Diisocyanates. Both TDI and MDI were used at varying ratios of macroglycol to diisocyanate. The chain extenders used were water, hydrazine, and ethylene glycol. A typical example is shown below. A mixture of 143 g (0.1 mol) of the macroglycol prepared above and 50 g (0.2 mol) of MDI was heated at 80" for 1 hr. This prepolymer was dissolved in 450 ml of dry N,N-dimethylacetamide. To the stirred solution was added dropwise a solution of 0.32 g (0.1 mol) of hydrazine in 10 ml of N,N-dimethylacetamide at room temperature. The viscosity of the solution increased upon addition. The resulting viscous solution was used for casting films without further work-up. A portion of the solution was poured into water. The precipitated polymer was washed repeatedly with water and dried a t 60" in a vacuum oven. Inherent viscosity of the polymer was 0.90 a t a concentration of 0.5 g/100 ml of N,N-dimethylacetamide at 30". Acknowledgment The author wishes to thank Dr. L. E. Miller for useful discussions, Mr. K. B. Grover for a portion of the preparative work, Dr. A. T. Riga for the thermal analyses, and Mr. J. J . Rysek for the determination of the mechanical properties. Literature Cited Bowman, R . E.. J. Chem. SOC..4303 (1954). Carothers. W. H . . VanNatta. F. J . , J. Amer. Chem. Soc.. 5 5 , 4714 (1933). Charpentier. R.. Miieo, J. C.. Silion, German Patent, 1,815,061 (1969). Falbe. J.. Schulze-Steinen, ti. J., Korte, F., Arenz. E I . , Laqua, R., Zirnrnerrnann. D . . Chem. Ber.. 98, 886 (1965). ~~
pers of w . H. Carofhers," Wiley-lnterscience, New York, N. y . . 1940. Meerwein, H., J. Prakt. Chem., 97, 225 (1918). Meerwein, H.,Chem. Ber., 53, 1829 (1920). Ogg, C. L., Porter, W. L., Willits, c. O.,lnd. € n g . Chem., Anal. Ed.. 17, 394 (1945) Reynolds, R. J. W., Vickers. E. J.. British Patent 766,347 (1947). Saotome, K., Kodaira, Y.. Makromol. Chem., 82, 41 (1965). Schulz, R., Vollkommer, N.. German Patent, 1,812,133 (1970). Thiele. J.. Gunther, 0..Ann., 347, 108 (1906).
Freidrichsen, W., German Patent, 962,429 (1957). Frisch, K. C., Reegen, S. L.. Ed., Kinetic and Mechanisms of Polymerization, Vol. I I , Ring Opening Polymerization." Lactones, Lundburg, R . D.. Cox. E. F.. Marcel Decker, New York, N. Y.. 1969. Gresham, T. L.,Jansen. J. E., Shaver, F. W., J. Amer. Chem. SOC., 70, 998 (1948). Hagemeyer. H. J., Hudson. G. V . , Johnson, S. H.. Edwards, M . B., Wright, H. N., A Symposium on Chemicals from Petroleum, Preprints, p 63, Division of Petroleum Chemistry, 130th National Meeting of the American Chemical Society, Dallas, Tex., 1956. Hall. H. K., Jr.. Schneider, A. K., J. Amer. Chem. SOC.,80, 6409 (1958). Hall. R. H., J. Chem. SOC.,4303 (1954) HBusermann, M . , Helv. Chim. Acta. 34, 1482 (1951). Hayashi, K., Zalar. F . V., unpublished paper from Lubrizol Corp., 1974. Hayashi, K., Macromolecules, 3, 5 (1970) Julia, M., Ronault. A., Bull. Chem. SOC.F r . , 1833 (1959). Mark. H.. Whitby, G . S.,Ed., "High Polymers, Vol. I , The Collected Pa-
Aminimide Modified Acrylics-Thermoset
Received for reuieu: F e b r u a r y 15, 1974 Accepted April 23, 1974 Presented a t t h e S y m p o s i u m o n N e w P o l y m e r C a n d i d a t e s f o r Coatings, D i v i s i o n o f O r g a n i c Coatings a n d P l a s t i c s C h e m i s t r y , 1 6 7 t h N a t i o n a l M e e t i n g o f t h e A m e r i c a n C h e m i c a l Society, Los Angeles, Calif., April 1974.
Coatings
W . J. McKillip, B. M . Culbertson,* G. M. Gynn, and P. J. Menardi Research Cenler, Ashland Oil, Inc., Columbus, Ohio 43216
Specialty monomers containing t h e aminimide functional group were used to prepare modified thermosetting acrylic solution, emulsion, a n d powder coatings. Since t h e aminimide residue is a heat-activated isocyanate precursor, acrylic polymers with urethane cross-links are possible. Coatings of excellent film performance and outdoor durability were obtained from a n u m b e r of formulations and are described. Attenuated total reflectance infrared spectroscopy was used to determine rate of cure. T h e reaction kinetics or cross-linking rates were shown to b e a function of baking time/temperature relationship.
Presently available acrylic resins provide quality surface coatings. As binders, they are used because of their color, color retention, flexibility, non-yellowing properties, resistance to outdoor weathering, and film durability. Such wide-ranging applications as lacquers, thermoplastic airdry emulsion paints, thermosetting emulsion or solution industrial bake finishes, and water-dispersible or watersoluble resins for industrial metal bake primers show the wide utility of these resin systems. Additional versatility is being demonstrated by the fact that thermosetting acrylic resins are also designed for powder coatings. In this paper, we will discuss the thermosetting type which requires baking. We will describe recently available specialty monomers based on the aminimide functional group (-COS~-N-RS) and their utility in solution, emulsion, and powder coatings of the acrylic type. This investigation was aimed a t producing one-package coatings for general industrial purposes, utilizing the isocyanate-hydroxyl reaction to give acrylic copolymers cross-linked uia the urethane moiety. Experimental Section Polymer Preparation for Self-Reactive AcrylicsType A . Self-reactive acrylic polymers based on 1,l-dimethyl-l-(2-hydroxypropyl)amine methacrylimide (DHA3 ) (Slagel, 1968) were prepared for initial investigation. It has been amply demonstrated that aminimide monomers such as DH.4-3 ( A ) are effective for preparing self-reactive polymers, with pendent acyl aminimide residues (Culbertson and Freis, 1970; Culbertson and Randen, 1971; Culbertson and Slagel, 1968; Culbertson, e t al.. 1968a. b ) . Further. since the aminimide group is a heat-activated isocyanate precursor (McKillip, e t al., 1967; Slagel and
c H3
-+
CH2=k-CONN(CH3)~CH&HCH~
I
OH
(A)
DHA-3
Bloomquist, 1961; Wawzonek and Gueldner, 1965), formulation with active hydrogen containing polymerizable comonomers results in a potential thermoset coating (eq 1).
(cH,-c
A)-(B)-(x)-
I
3'
7;
I
1
A
---+
F H 3
CONN-CH,
\CH2CHCH3
I
OH y = active hydrogen residue OH, "2, NHR
N=C=O
I
I
t'
(c-cH~)-(x)-(B)-
I S
I
(A)
y' = 0, NH, NR
+ N(CH3)2CH,CHOHCH, I n d . Eng. Chem., Prod. Res. Develop., Vol. 13, No. 3, 1 9 7 4
197
