CELLULOSE MIXED-ESTER LACQUERS CHARLES R. FORDYCE, MARTTI SALO, AND GEORGE R. CLARKE Eastman Kodak Company, Rochester, N. Y.
Physical properties of cellulose mixed esters have been investigated with the object of finding compositions suitable for use in the lacquer industry. Cellulose acetate propionate and acetate butyrate have been studied in detail. Within limited ranges of composition, products soluble in practical solvent combinations and compatible with resins in sufficient proportions to give surface hardness and adhesion may be obtained.
T
HROUGHOUT the development of lacquers and varnishes containing cellulose derivatives as the basic constituents, cellulose nitrate has met with far greater success as a lacquer material than any other cellulose derivative ( 7 ) . The unique advantages of nitrate have been its lon: cost of manufacture and the fact that it has been possible to incorporate Kith i t a large variety of natural resins, gums, plasticizers, and low-priced solvents such as benzene, toluene, xylene, and solvent naphtha. Thus i t has been possible to produce cheap compositions meeting successfully a variety of requirements. Nitrate lacquer coatings have not, however, been entirely satisfactory. Prolonged exposure t o light results in degradation which eventually causes discoloration, cracking, and peeling of the lacquer coating. Also, when cellulose nitrate is subjected to elevated temperatures for prolonged periods, a break-down of cEL lUL OS€ CEL 1 ULOS€ even the most stable nitrates occurs which results in serious deterioration of the lacquer composition.
BUTHAT-
CELLU 05E PM&ATZ
GRAPHI . SOLUBILITY OF CELLULOSE ACETATE-PROPIOXATE COMPOSITIONS IN ORGASIC SOLVENTS GRAPH2. SOLCBILITY OF CELLULOSE ACET4TE-BUTYRATE
COMPOSITIONS IN
ORGANIC
SOLVENTS GR.4PH 3 SOLCBILITY O F CELLULOSE ACETdTE-PROPIONATE COMPOSITIONS IN L.4CQEER
SOLVENT MIXTURES GRAPH4. SOLCBILITY OF CELLULOSE ACE-
T4TE-BTTl-RATE
COMPOSITIOM3 IN LACQCER
SOLVENT MIXTURES GRAPH 5. COMPATIBILITY OF CELLULOSE .\ICETITE-PROPIONATE
COMPOSITIONS
ESTER G m
WITH
GRAPH 6. COMPATIBILITY O F CELLULOSE ACET4TE-BT'TYRATE COMPOSITIONS KITH
ESTERGUM 1310
INDUSTRIAL AND ENGINEERING CHEMISTRY
NOVEMBER, 1936
With advances in the methods of manufacture of other cellulose derivatives, some of them have been suggested and a few placed on the market as lacquer ingredients. The most commonly suggested cellulose derivative for this purpose has been cellulose acetate, which is now produced in large quantities for other purposes. Cellulose acetate, however, has met with only limited success in the lacquer field. This may be largely attributed t o its limited compatibility with suitable solvents, resins, and gums. It is generally impossible to obtain clear homogeneous solutions with mixtures of cellulose acetate and most natural resins and gums. Although in some cases clear solutions may be obtained with these mixtures, opaque films result upon evaporation of the solvents. Iran Heuckeroth (16) states that only about 5 per cent of the resins now available are a t all compatible with cellulose acetate. This limitation is recogCEUULOSLnized i n a B r i t i s h patent (9) which describes the use of gums and resins derived f r o m
CEL VL02ACkTi77F
CELCW 02ACEI'AE
GRAPH 7. COMPATIBILITY OF CELLULOSE ACETATE-PROPIONATECOMPOSITIONS WITH DAMMAR GRAPH 8. COMPATIBILITY OF CELLVLOSE ACETATE-BUTYRATE COMPOSITIONSVITH DAMWAR GRAPH 9. COMPATIBILITY OF CELLULOSE ACETATE-PROPIONATE COMPOSITIONS TITH ELEMI GRAPH 10. COMPATIBILITY OF CELLULOSE ACETATE-BUTYRATE
COMPOSITIOTS
WITH
ELEMI GRAPH 11. COMPATIBILITY OF CELLVLOSE ACETATE-PROPIONATE
COMPOSITIONS
WITH
ROSIK GRAPH12. COMPATIBILITY OF CELLULOSE ACETATE-BUTYRATE COMPOSITIOSSWITH ROSIK
1311
natural sources with cellulose acetate, even though opaque films are obtained upon evaporation of the solutions. The claim is made that this opacity is not objectionable in lacquer compositions containing pigments. A French patent (11) describes the use of natural resins such as colophane, mastic, dammar, and sandarac in compositions with cellulose acetate of 53 to 62 per cent combined acetic acid. The best compatibility is obtained with fully esterified or only mildly hydrolyzed acetate. Other patents on the use of cellulose acetate with natural resins (4) state that acaroid and guaiacum resins are compatible with cellulose acetate; a German patent (12)describes the use of wood tars such as pine tar in lacquers containing cellulose esters such as the acetate. Because of the incompatibility of natural resins with cellulose acetate, methods have been devised to make them compatible by chemical treatment. Congo-copal resin is made compatible by treatment with organic acids such as acetic ( 3 ) . Treatment with nitric acid has also been proposed for this purpose ( I O ) . Rosin is made compatible by chlorination ( 6 ) . The fact that a lacquer coating must adhere tenaciously to all types of surfaces and that it has been dificult to find resins sufficiently compatible with cellulose acetate to produce this degree of adhesion has led to methods where cellulose acetate is sprayed onto a substratum of a cellulose nitrate lacquer composition ( 1 ) . Following this has come the discovery that certain organic compounds with the ability to absorb most of the light rays that are destructive to the nitrate may be incorporated in the cellulose acetate top coating ( 5 ) . A vast field of synthetic chemistry has been opened in the preparation of synthetic resins whose molecular size and polarity can often be controlled so as to make them compatible with various cellulose derivatives including the acetate (14). Even though it may be possible to impart the necessary adhesion with these synthetic resins, there still remains the obstacle of limited solubility of the acetate in le solvents. This is an important factor, since the commercial value of a lacquer depends largely upon the availability of suitable solvents. It has been suggested that the limitations of both cellulose acetate and nitrate for lacquer purposes can be overcome by the use of cellulose esters of higher aliphatic acids. Cellulose butyrate was early sug-
INDUSTRIAL .4XD ENGINEERIUG CHEMISTRY
1312
gested for this purpose (18). Cellulose acetate propionate and acetate butyrate are described in the patent literature as compatible with exceptionally large amounts of plasticizers (9). A number of other patents also point out the wider range of solubility and compatibility of these esters (15). During the course of experimental work on a variety of cellulose esters, i t has been found that products of definite advantage for lacquer purposes may be obtained; but all of the requirements of a lacquer material may be met only within definite limits of composition. Cellulose mixed esters, such as the acetate propionate and acetate butyrate, appeared especially suitable for this purpose. Owing to the limited amount of information of these cellulose derivatives in the literature, it was thought desirable to determine the limits of composition of these mixed esters suitable for lacquer purposes and to study their physical properties and compatibility with materials most widely used in the lacquer industry with cellulose nitrate.
Properties of Higher Cellulose Esters The higher fatty-acid esters of cellulose have not yet found wide commercial application. Experimental work, however, indicates that they possess certain distinct differences from cellulose acetate in their physical and chemical characteristics. For example, the higher triesters are soluble in a number of compounds in which cellulose triacetate is distinctly insoluble. Table I gives solubilities of cellulose higher esters in a number of typical solvents.
OF CELLULOSE TRIESTERS" TABLEI. SOLUBILITY
Cellulose Triester
Tetra- Ethylene chloroDiEthyl ethane chloride Acetone Acetate
Acetate Propionate Butyrate Valerate Caproate Heptoate Caprylate Pelargonate Caprate Laurate Myristate Palmitate Stearate z . soluble:
+
++ ++ +++ ++ ++ ++
-
++ + +++ + ++ +-
- insoluble.
Butyl Acetate
Benzene
Toluene
-
-
4-
++ +++ ++ ++ ++
++ ++ +
+++ ++
OF CELLULOSE TRIESTERS TABLE11. PROPERTIES
Tensile Total Per Cent Moisture Melting Regain (13) Point ( 1 3 ) , Strength ( 8 ) , Elongation ( 8 ) , Cellulose ' C. % 50% R H 100% R H Triester Kg./Sq. Mm. 2.3 10 0 245(D) 9-12 15-2 5 Acetate Propionate 6-7 10-15 1.3 4 4 239 %lo(?) 0.7 3 5 183 Butyrate 5-6 18-25 0.5 1.7 160 Valerate 4-5 Caproate 2.5 60 0.3 0.9 87 ... ... 0.2 0.8 97 Hentoate 0.1 0 9 85 Caprylate 20-30 0.1 1.0 3.514 66 Pelargonate 0.3 1.5 64 Caprate 1.4 80 0.3 i00Li30 0 . S-i. o Laurate ... 1.5 87 ... ... Myristate 140 . . . , . . . .. 0 . 5 Stearate
Other physical properties of the cellulose higher esters, such as tensile strength, elasticity, moisture absorption, and melting point, vary decidedly with increasing molecular weight of the acid (Table 11). Certain properties of these aliphatic cellulose esters, such as solubility and moisture resistance, Fould make them superior to cellulose acetate as lacquer materials: but in other respects, notably tensile strength and softness, there would be a loss of quality. Wiggam and Gloor (17) pointed out that cel!ulose butyrate is too soft to compare favorably with the nitrate
VOL. 28. NO. 11
Cellulose Mixed Esters I n the experimental work an attempt was made to outline the compositions of cellulose mixed esters which are especially suitable for lacquer purposes from the standpoint of solubility and compatibility with gums and resins. A limited number of solvents and natural resins have been chosen as typical of the most widely used lacquer ingredients with the hope that these data will point out the trend in change of physical properties of the cellulose esters with varying composition. Cellulose mixed esters involving two acids may be conveniently represented graphically on triangular charts ; the three variables are the proportions of hydroxyl groups of the cellulose esterified by each of the acid radicals or left unesterified. By identifying a variety of compositions on such charts and studying the properties of these materials, we may outline areas including mixed-ester compositions suitable for different purposeq. Introduction of an appreciable amount of combined propionic or butyric acid in the manufacture of cellulose acetate propionate or butyrate yields products which are readily soluble in the types of solvents most commonly used in lacquer compositions. Graphs 1 and 2 show areas of solubility of these esters in a few solvents and solvent mixtures. Without approaching too closely the cellulose esters composed entirely of the higher fatty acids, a fairly wide range of solubility is obtained. As examples of solvent mixtures suitable for commercial application of lacquers, solubility areas of cellulose acetate propionate and acetate butyrate in four different lacquer formulas are shown in Graphs 3 and 4. The compositions of these solvent mixtures are as follows: Ethyl acetate Butyl acetate Ethyl alcohol Butyl alcohol Cellosolve Toluene Naphtha (65-105)
A
B
C
D
10% 20 20 10
15%
15% 20 15 10
15%
..
40
..
15 10 15 45
20
20
..
15 10 15 25 20
The limited number of resinous materials which are compatible with cellulose acetate show a t least equally as good compatibility with esters containing acyl groups of higher acids. In addition, a number of resins which are entirely incompatible with cellulose acetate may be incorporated in appreciable amounts with mixed esters of cellulose and upon evaporation of their solutions clear, homogeneous films are obtained. Graphs 5 t o 12 show the amounts of gum elemi, dammar, ester gum, and rosin which are compatible with varying compositions of cellulose mixed esters. It will be noticed that cellulose acetate butyrate exhibits considerably wider areas of compatibility with resins than acetate propionate. I n determining these areas of compatibility, solutions of the various cellulose esters were prepared in t h e following solvent mixture, which was varied by addition of larger quantities of methyl acetate for testing samples within areas of limited solubility: methyl acetate, 10 per cent; 1 4 dioxane, 20; ethyl alcohol, 20; butyl alcohol, 10; and toluene, 40. To measured aiiiounts of the cellulose ester solutions, resins t o be tested were added in quantities of 25, 50, and 75 per cent of the weight of the cellulose ester. Films were coated from the resulting solutions and, after complete evaporation of the solvent, were classified as compatible or incompatible according to appearance. Only films entirely free from haze or bloom were designated compatible. The resins used were of commercial lacquer quality. Ester gum, elemi, and WW rosin were used as purchased. Dammar was dewaxed by adding methyl alcohol t o a solution of the resin in quantities sufficient to precipitate the wax, leaving the purified resin in solution.
NO\ EMBER, 1936
INDUSTRIAL AND EKGINEERING CHEMISTRY
In using the compositions described above for lacquer purposes, incorporation of a certain amount of plasticizer is usually desirable, Although no extensive study of plasticizers was made in this investigation, it was found that some plasticizers tend t o decrease the compatibility of resins with the cellulose mixed esters, while others increase or have little effect on the maximum amounts which may be used. Below are described lacquer compositions which have been found satisfactory in experimental work from the standpoints of compatibility, adhesion, surface hardness, and uniformity in spraying (in weight per cent) : Cellulose Acetate Propionate (Acetyl 12.5%, Propionyl 32.5%) Cellulose ester Resin Plasticizer Solvent
100 25 50 1000
Cellulose Acetate Butyrate (Acetyl lo%, Butyryl 38%) 100 75 50 1000
The solvent used was composed of 10 per cent ethyl acetate, 20 butyl acetate, 20 ethyl alcohol, 10 butyl alcohol, and 40 toluene. Compositions containing esters, gum, elemi, dammar, and rosin were each employed with the following plasticizers: methyl phthalate, butyl phthalate] tricresyl phosphate] and butyl tartrate.
1313
Absorption of Carbon Dioxide by Amines Di- and Triethanolamine and Tetramine L. L. HIRST AND I. I. PINKEL U. S. Bureau of Mines, Experiment Station, Pittsburgh,Pa.
Literature Cited British Celanese, British Patent 298,608 (1930). I b i d . , 307,292 (1929). DeStubner, I b i d . , 297,679 (1930). Dreyfus, Ihid., 222,168 (1934); 345,531 (1930). Eastman Kodak Co., U. S. Patents 1,958,707, 1,958,714, 1,958,715, 1,969,473, 1,973,488, 1,976,359 (1934).
Eberlin and Blanchard, I b i d . , 1,899,186 (1933). Gardner, Natl. Paint Varnish Lacquer Assoc., Circ 338, 657 (1928).
Hagedorn and Moeller, Cellulosechem., 12, 29 (1931) I. G. Farbenindustrie, British Patent 367,932 (1930) ; French Patent 716,397 (1931) ; German Patent 564,771 (1932). Kocher, U. S. Patent 1,973,489 (1934). Kodak Path& French Patent 736,211 (1931). Schnuerle, German Patent 399,911 (1922). Sheppard and Newsome, J. Phz/s. Chem., 39, 143 (1935). U. S. Patents 1,185,514; 1,558,442; 1,812,335; 1,828,449; 1,849,108; 1,881,219; 1,897,015; 1,902,255; 1,902,256; 1,902,257; 1,902,337; 1,907,554; 1,909,195; 1,940,727; 1,941,262; 1,941,708; British Patents 285,049: 296,675; 298,616; 299,066; 299,067; 307,289; 311,657; 315,807; 315,808; 316,322; 317,454; 322,540; 322,541; 322,543; 335,582; 338,002; 338,024; 340,102; 340,104; 341,413; French Patents 669,278; 344,626; 366,586; 367,759; 453,395; 47,104; German Patents 404,024; Canadian 293,641; 295,242; 297,081 ; 297,082; 297,083; 297,084; 317,117; 319,150; 319,151; 319,152; 319,729; 319,730; 319,731; 324,633; 325,615; 329,371; 329,708; 329,709; 329,710. U. S. Patents 1,896,581; 1,896,915; 1,917,407; 1,983,006; British Patents 367.817: 399.191: 402.733: French Patents 517,451; 527.706; 679,607; 704,862;' 732,663; Canadian Patents 293,807; 345.673. Van Heuckeroth, Natl. Paint Varnish Lacquer Assoc., C ~ T C 458 . 97-100 (1934). Wiggam and Gloor, IKD. ENQ.CHEM.,26, 551 (1934). Worden, "Technology of Cellulose Esters," Vol. VIII, p, 2639, New York, D. Van Nostrand Co., 1921.
RECEIVED September 12, 1936. Presented before the Division of Paint a n d Varnish Chemistry a t t h e 92nd Meeting of t h e American Chemical Society, Pittsburgh, Pa., September 7 t o 11. 1936.
To select a solution for scrubbing carbon dioxide from hydrogen-carbon dioxide mixtures, laboratory experiments were made using a glass column packed with glass rings. Fifty per cent solutions of di- and triethanolamine and 5, 10, and 25 per cent solutions of Tetramine were used to reduce the carbon dioxide content of the scrubbed gas to less than 0.1 per cent. Fifty per cent triethanolamine solution is much less efficient than either 50 per cent diethanolamine or 5 per cent Tetramine solutions. Equal volumes of 50 per cent diethanolamine or 10 per cent Tetramine solutions are necessary to reduce the carbon dioxide content of the scrubbed gas to 0.1 per cent or less.
QH
YDROGEN for use in the Bureau of
Mines coal hydrogenation program will be produced in a three-step process. Water gas will be generated by the reaction between steam and natural gas, most of the carbon monoxide will be oxidized by additional steam a t a lower temperature, and carbon dioxide will be removed from the resulting gas by scrubbing. The gas to be scrubbed will consist of approximately 80 per cent hydrogen and 20 per cent carbon dioxide, along with small percentages of nitrogen, carbon monoxide, and methane; it is desired to reduce t h e carbon dioxide content to 0.1 per cent or less. The laboratory experiments reported in this paper were intended to select the most suitable scrubbing solution and to furnish data needed for t h e design of t h e larger equipment. The apparatus is shown diagrammatically in Figure 1: The column, g, is 3.6 em. in diameter andispackedfor alength of 150 cm. with glass rings 0.87 cm. in diameter and 1 cm. long. Scrubbing solution from the 8-liter reservoir, a,flows through the 0.5-liter preheater, 6 , the constant-head vessel, c, the flowmeter,
