Table I.
Effects of Chelate Concentration on Fiber Properties
Tensile Projerties EA,4T,a
Conclusions
c7 /C
0 0.1 0 2 0 25 a Concentration cellulose acetate.
finer than those obtained from the unmodified solutions. As expected, the solutions containing the loiver amounts of dissolved solids produced the finer fibers.
28 25 20
1.6 1.30 1.3 1 24 0 9 1 14 15 0 7 1 22 of ethjil acetoacetate titanium chelate,
30 31 2: 29 based on
230 224 ~~
232 234 w i g h t 01
containing 287, cellulose acetate was prepared and divided into four portions. Increasing amounts of E.4AT dissolved in acetone were added to three of the solutions. Enough acetone was added to each of the modified solutions to make them all have approximately the same viscosity. The amounts of EAAT and solids present in the solutions are shown in Table I . The solutions \\ere spun under identical conditions by using a conventional acetate spinning cabinet. The data in the table indicate that the solution modifier has little or no effect on the physical properties of the fiber. However, the deniers of the fibers from the modified solutions were much
Increasing the viscosity of cellulose acetate solutions by means of certain crosslinking agents offers a promising method for spinning fine denier fibers. Several titanium, aluminum, and zirconium chelates were found to be excellent crosslinking agents for this purpose. The EA4L\ATwas studied in detail. The addition of only 0.27, of this compound. based on the Lveight of the cellulose acetate. to a spinning solution resulted in a threefold increase in viscosity. The modified solution was stable to heat and storage conditions normally encountered in spinning cellulose acetate. Yarns of very fine denier were spun from the modified solutions. Literature Cited
(1) Schmidt, F. (to Farbenfabriken Bayer, A. G . ) , U. S. Patent 2,680,108 (1954). RECEIVED for review March 19, 1965 ACCEPTEDSeptember 22, 1965 Division of Cellulose. LVood. and Fiber Chemistry, 147th Meeting, ACS, Philadelphia, Pa., April 1964.
EPOXIDIZED CELLULOSE M A R T I N E. ROWLEY AND GORDON Cellulose Technoloxy Dicision. Eastman Kodak Go.. Rochester, .V. Y .
D.
ESTERS
H I A T T
Unsaturated cellulose mixed esters were prepared, then treated with peracids to yield epoxidized cellulose esters that retained the solubility characteristics of the original esters. Conversion of the double bond to the oxirane ring ranged from 12 to 8070~the products contained 0.02 to 0.20 equivalent of oxirane oxygen per 100 grams. m-Chloroperbenzoic acid was more efficient than peracetic acid in the epoxidation of cellulose acetate crotonate. Epoxidized cellulose acetate 1 0-undecenoate showed good properties for a wood lacquer. OBJECT of this investigation was to prepare cellulose esters containing potentially reactive groups which could be activated a t the desired time by heat or a suitable catalyst. Specifically, unsaturated cellulose esters were converted to epoxides. Peras (9) has described the oxygenation of an allylcellulose with various reagents to produce derivatives containing up to about 0.1 mole of active oxygen per 100 grams of product ; these oxygenated cellulose ethers were insoluble in organic solvents. The epoxidized cellulose mixed esters described in this article were soluble in organic solvents and readily insolubilized when used as a coating material.
THE
Methods
Table I lists the unsaturated cellulose esters that were epoxidized. Peracetic Acid Epoxidation. Peracetic acid was used to convert the unsaturated esters to the epoxides by two methods. In the first method, the peracid was formed in the presence of the unsaturated cellulose ester, using hydrogen peroxide, acetic acid, and a n acidic ion exchange resin. This method is essentially that described by Greenspan and Gall ( Z ) , but 256
l&EC PRODUCT RESEARCH A N D DEVELOPMENT
\vith some modification since \ve were dealing with solid polymeric esters that required larger amounts of solvent. In the second method, known concentrations of peracetic acid in acetic acid (or mixtures of acetic acid and ethyl acetate) \\ere used. The peracid solutions were prepared in a manner similar to that described in Method I. then added to the unsaturated cellulose ester. Typical examples are cited for the tpco methods
METHOD I. To 5 grams of acetic acid and 20 grams of ethyl acetate was added 15 grams (0.04 mole of unsaturated substituent) of a cellulose butyrate 10-undecenoate containing 43.374 10-undecenoyl. After the ester had completely dissolved, 1.5 grams of Amberlite CG-120 resin (acid form, wet with a n equal weight of acetic acid) \\as added and the flask placed in a 70' C. bath. T o the continuously stirred mixture was slowly added 4 grams (0.07 mole) of 59% hydrogen peroxide (FMC Corp.). Stirring was continued for 4 hours to complete the epoxidation. The solution was diluted with acetone and filtered to remove the resin catalyst. The product \vas isolated by precipitating into distilled water, washed with a 50: 50 mixture of methanol-Lvater, then dried a t room temperature under vacuum. Analysis showed 0.2 equivalent of oxirane oxygen per 100 grams of product (about 807, conversion of the double bond).
Table I.
Unsaturated Cellulose Mixed Esters Equivalent Unsat. Saturated Unsaturated Group3 1 100 G. Groups/ Groups/ Cellulose M i x t d EJter A . G. U. A. G .C:a Ester Acetate crotonateb 1.8 1 1 0.36 Acetate 10-undecenoatec 1.9 0.9 0.23 Butyrate 10-undecenoater 1 4 1.2 0.25 Acetate tetrahvdro-
1.7 0.7 0.14 2.8 0.1 0.04 Butyrate oleate" 1.4 0.3 0.10 a All unsaturated groups determined by bromination. Prepared by reaction of mixture o,f crotonic anhvdride-acetic anhydride znith cotton linters, sulfuric acid catalyst ( 6 ) . Prepared by reaction of unsaturated acid chloride with hydrolyzed cellulose ester, Pyridine catalyst ( 7 ) . Prepared by reaction of tetrahydrophthalic anhydride with hydrolyzed cellulose acetate, sodium acetate catalyst (4). phthalated
METHOD11. T o 350 grams of acetic acid was added 10 grams of Amberlite CG-120 resin (acid form, wet Ivith a n equal weight of acetic acid). T o this stirred slurry (in a 50' C. bath) \vas added, dropwise, 35 grams of 59% hydrogen peroxide. Stirring \vas continued for 6 hours and the mixture alloived to stand a t room temperature overnight. The resin catalyst was removed by filtration and analyses (3) showed 6.170 peracetic acid and 0.3Y0 hydrogen peroxide. T o 7'5 grams of this peracetic acid solution (0.06 mole) was added 15 grams (0.02 mole of unsaturated substituent) of a cellulose acetate tetrahydrophthalate containing 21 yo tetrahydrophthalyl. (As a general safety rule one should add the peracid to the unsaturated material. I n larger quantities, the solid unsaturated ester should first be dissolved in a solvent and the peracid solution added to it.) T h e solution was stirred for 2 hours a t room temperature and diluted with acetone. Precipitation and washing were done in diethyl ether and the product \vas dried at room temperature. Analysis showed 0.07 equivalent of oxirane oxygen per 100 grams of product (about 507, conversion). rn-Chloroperbenzoic Acid Epoxidation. A cellulose acetate crotonate was epoxidized according to a procedure described in a technical data bulletin on rn-chloroperbenzoic acid by the FMC Corp. (7), from which the reagent was obtained. T o 300 grams of ethyl acetate was added 150 grams (0.53 mole of unsaturated substituent) of a cellulose acetate crotonate containing 24.5% crotonyl. T h e mixture was heated on a Steam bath and stirred to dissolve the ester completely. A solution of 150 grams of m-chloroperbenzoic acid (0.87 mole) in 300 grams of ethyl acetate was added to the dissolved cellulose ester over a 45-minute period. After refluxing for 3 hours it was allowed to cool a t room temperature for 1 hour. The solution was diluted with acetone : the product was precipitated into ethyl alcohol, washed with the same alcohol, and dried a t 50' C. Analysis showed 0.2 equivalent of oxirane oxygen per 100 grams of product (about 57y0conversion of the double bond to the oxirane ring).
Table II.
Epoxidation of Cellulose Esters with Peracetic Acid
Reaction Conditions T i m e , Temp., hr. ' C. 5 75 1 80 4 70
Equivalent of Oxirane Oxygen per 100 Conversion, % Grams" 0.04 11 0.18 80 0.20 80
Cellulose Deriuatiues Acetate crotonate Acetate 10-undecenoate Butyrate 10-undecenoate Acetate tetrahydrophthalate 2 25 0.07 50 Butyrate oleate 3 80 0.02 20 a Analytical procedure used for determination of oxirane oxygen (5).
acetate 10-undecenoates about 1 hour a t 80" C. Longer reaction times in either case caused gelling of the reaction solutions, and an insoluble product resulted. \Vith the less reactive epoxidized cellulose acetate crotonate, the reaction time was as long as 24 hours a t 65" C. with no apparent change in solution viscosity. The amount of oxirane oxygen or per cent conversion does not necessarily regulate the reactivity of the product, since the cellulose acetate tetrahydrophthalate required much milder reaction conditions (and special isolation techniques) than the 10-undecenoate esters with only onethird the oxirane content. During the washing with water of the epoxidized cellulose acetate tetrahydrophthalates Ive observed insolubilization (as periodically tested in acetone). This we attributed to the carboxyl group present. By precipitating and washing in diethyl ether we \%ere able to isolate an organic solventsoluble epoxide in the free acid form. T o obtain a watersoluble product, the epoxide was precipitated into water, converted to the sodium salt using sodium bicarbonate, reprecipitated, and washed in 2-propanol. The dried product \vas Lvater-soluble until heated a t elevated temperatures. I n a review of epoxidations, Swern ( 7 7 ) pointed out that alpha, beta-unsaturated carbonyl compounds do not yield as high conversions to the epoxides as d o other unsaturated compounds. This has been attributed to the fact that the electron-attracting carbonyl group lowers the electron density of the double bond and therefore hinders the epoxidation. T h e low yield of oxirane oxygen in the epoxidized cellulose acetate crotonate ester, therefore, was expected. T h e use of either a nonacidic medium (ethyl acetate) or a dehydrated ion exchange resin as described by Pearce ( 8 ) did not appreciably increase the yield (see Table 111). Employing rn-chloroperbenzoic acid in ethyl acetate gave a much increased conversion (70).
Experimental and Results
Epoxidations. The use of peracetic acid as described in Method I was found more convenient, since one step was eliminated completely. The resin catalyst was readily removed from the reaction mixture by filtering the solution through a sintered-glass funnel after dilution. Using the solid resin catalyst required somewhat more solvent to facilitate good stirring. The per cent conversions (Table 11) are the maximum values obtained. These values cannot be compared directly; reaction conditions (time and temperature) were different because of the relative reactivities of the products. For example, the reaction time for the cellulose acetate tetrahydrophthalates \\as about 2 hours a t room temperature and for the cellulose
Table 111.
a
Epoxidations of Cellulose Acetate Crotonate Converbion to Oxirane, yo Method of Epoxidation
Peracetic acid with wet resin catalyst In acetic acid In ethyl acetate Peracetic acid with dehydrated resin catalyst in ethyl acetate' m-Chloroperbenzoic acid in ethyl acetate As described by Pearce ( 8 ) .
VOL.
5-8 11 11
57
4 NO. 4 D E C E M B E R 1 9 6 5 257
In the same review by Swern, a terminal double bond was found to be less susceptible to epoxidation than a nonterminal Iiond. We found that the oleate ester gave a very poor conversion, while the 10-undecenoate esters gave high conversion. ... I his poor conversion of the oleate may be due to the fact that the unsaturated group is attached to a polymer, which makes the internal bond less accessible. Reactivity of Epoxy Esters. STABILITYTO STORAGE. Table I V shows the relative stability of the epoxidized cellulose ehters in the flake form a t 150" C. Products from the more readily epoxidized cellulose esters (the first three listed in Table I\' and those requiring limited reaction times to prevent gelling of the reaction mixtures) were the least stable to the dry heat test. To test whether the better stability of some of (he epoxides was due to inactivity or decomposition of the mirane ring, the epoxidized cellulose acetate crotonate was reanalyzed after heating l l / z hours a t 150" C. The sample was still acetone-soluble and analysis showed the oxirane oxygen content to be unchanged. One epoxidized cellulose ester from each of the groups in Tdble 1V (each containing about 0.2 equivalent of oxirane oxygen per 100 grams of product) was tested for room temperature stability. The acetate IO-undecenoate showed slight crosslinking after 1 month, while the more stable acetate crotonate was unchanged after 1 year. Therefore, the elevated heat test was concluded to be a valid indication of the storage life of the esters. The more reactive epoxidized ester, the acetate 1O-undecenuate, can be stored as a solution. A 10% solution (in a lacquer-type solvent) showed no increase in viscosity or gelling Sor 6 months. The relative stabilities of these KATEO F INSOLUBILIZATIOS. epoxidized esters a t room or a t elevated temperatures correlate with the ease of insolubilization as coatings. I n the case of the epoxidized cellulose acetate 10-undecenoate (0.1 8 equivalent of oxirane oxygen per 100 grams), a solution containing 5% dibutyl hydrogen phosphate (based on the ester) gave a film ;chich converted to insolubility in about 5 hours a t room temperature. An epoxidized cellulose acetate crotonate (0.20 equivalent of oxirane oxygen per 100 grams) was only partially converted after 3 days a t 120' F. with the same catalyst. There was no evidence of insolubilization when films were coated from the unepoxidized cellulose acetate crotonate under the same conditions. Properties of Epoxy Esters. The epoxidized cellulose Acetate 10-undecenoate previously described was tested as a lacquer finish on various surfaces. .4 10% solution was prepared by dissolving the epoxidized cellulose ester in a standard lacquer-type solvent (butyl acetate, 33 ; toluene, 25 ; xylene, 1 7 ; ethanol, 15; butanol, 10). To this solution was added .?yodibutyl hydrogen phosphate (based on the weight of the cster) prior to application. Since this catalyzed solution had a
Stability of Epoxidized Esters Time Required to Insolu bilize Dry Flake at 750" C. EpoAidized Cellulose Mixed Ester Acetate 1O-undecenoatea Less than 15 minutes Butyrate 10-undecenoate Table IV.
Acetate tetrahydrophthalate (Na salt), Butyrate oleate More than 1 hour .Acetate crotonateb b Stable for a Stable for approximately 7 month at room temperature. more than 7 year at room temperature.
1
258
I&EC PRODUCT RESEARCH A N D DEVELOPMENT
Table V.
Epoxidized Cellulose Butyrate 10-Undecenoate as Coating Tests Results
Sward hardness Conversion to insolubility Adhesion to Glass Steel Aluminum Print paper Wood On wood coating, resistance to LVater overnight Hot dish imprintR Alcohol-water (1 :1) Cold checkb a Over cloth. 120' F., 7 hr. to
22 70 5 hours at R T
Poor Poor at R T and after ' / Z hr. at 300' F. Poor at R T and after 1 1 2 hr. at 300' F. Good Good (very good after 1 month) Good Good Good Good - 70"F., I hr. (20 cycles).
shelf life of only 24 hours, it was applied soon after the catalyst addition. The solution was slightly hazy in appearance and had a No. 4 Ford cup viscosity of 28 seconds. A coating made on glass was clear on drying and was insoluble after curing a t room temperature. Tests and observations made on the coatings are noted in Table V. T h e Sward hardness value was not as high as for the best wood finishes. Adhesion of the epoxidized ester to aluminum or glass when applied by spraying was poor, even after curing a t elevated temperature. However, a low-melting epoxidized cellulose butyrate 10-undecenoate showed good adhesive properties when tested between aluminum or glass (applied under heat and pressure, no solvent). Adhesion of the epoxidized cellulose acetate 10-undecenoate coating to wood and paper was good. This coating was further tested for physical properties on wood (see Table V). Except for the low Sward hardness, we rated the epoxidized cellulose ester as a good lacquer material for wood surfaces. I n Table V I are listed the results of employing the epoxidized cellulose acetate 10-undecenoate as a crosslinking agent for a commercial cellulose acetate butyrate. Employing curing temperatures up to 110' C. required the use of a weak acid catalyst to give insolubilization. The 1 to 1 ratio of commercial ester to epoxy ester did not greatly increase the amount of insolubilization over that obtained with the 4 to 1 ratio. Also, room temperature curing was about as effective as the elevated temperature except when the lower percentage of
Table VI.
Epoxidized Cellulose Ester as lnsolubilizing Agent
Epoxidized ester, cellulose acetate 10-undecenoate Commercial ester, Cellulose acetate butyrate (2% OH) Dibutyl Phosphate Catalyst, m -z yo Weight OC.'... JLCl . 70 ."J, Curing T e m p . of Ext. with Epoxidized Ejoxidized Acetone Films from Ace tone,. C. Ester Ester 1:l 5 Room temp. 43.8 110 ( l / z hour) 40.2 4:l 5 Room temp. 53.2 110 ( l / * hour) 51.8 4:1 2.5 Room temp. 70.6 110 (l/z hour) 58.7 4:l 0 110 ( I hour) 98 .O
catalyst \\as used. In all cases. the epoxidized ester showed only moderate qualities as a crosslinking agent when used \+ith a cellulose ester. Conclusion
Soluble epoxidized cellulose esters 11ere prepared b) treating the unsaturated esters ~ i t an h organic peracid. The epoxidized cellulose acetate 10-undecenoate had good properties as a lacquer-type ester, but the unsaturated ester was costly to prepare by the acid chloride-pyridine method. T h e epoxidized cellulose acetate crotonate \\as somew hat slower to insolubilize as a film and required some heating. Although the cellulose acetate crotonate is a commercially feasible ester, its epoxidation was best accomplished by the somewhat expensive rn-chloroperbenzoic acid.
literature Cited
(1) FMC Corp., New York, N. Y,, "Technical Data on rn-Clllorci. perbenzoic Acid," 1963. (2) Greenspan, F. P.! Gall, R. J . (to Food Machinery and C ! h r t ~ l i cal Corp.), U. S. Patent 2,919,283(Dec. 29, 1959). ( 3 ) Greenspan, F. P.. MacKellan, D. G., Anal. Chern. 20, 1061 (1948). (4) Hiatt, G. D., Mench. J. \V.> Emerson. 3. (to Eastnian K o d a h Co.), U. S.Patent 2,759,925 (hug. 21, 1956). (5) Kline, G. M., ed., "Analytical Chemistry of Polymers:" Part I, p. 124. Interscience, Xew York. 1959. (6) Malm, C. J.. Hiatt. G. D., in "Cellulose and Cellulose Deri\
