690
INDUSTRIAL AND ENGINEERING CHEMISTRY
can be prepared which dry more rapidly and are more flexible a t low temperatures than ordinary varnishes because of the presence of ethylcellulose. Printing ink bases pigmented with these dispersions possess the same advantages. Pigmented wax and resin preparations are benefited by the hardening and toughening action of ethylcellulose. Ethylcellulose dissolves readily in hot resins, oils, waxes, plasticizers, and mixtures of these in the absence of any volatile solvent. Since such compositions are very thermoplastic, they can be manipulated as molten mixtures a t elevated temperatures. They form the bases for heat-sealing adhesives, coatings, and cheap casting plastics. A selected list of properties of interest from the lacquer standpoint follows: Soecific nravitv 1m % dndr method, 9 ) , gram/hr./sq. cm./cm. Dilution ratio (10% soh. of ethylcellulose in a solvent composed of 80% toluene and 20% ethyl alcohol) With Varnish Makers and Painters’ Naphtha With hydrogenated petroleum naphtha
1.14 0.11 400-700 60-100 10-20 2.72 X 10 - 8 2.4 6.3
The inclusion of 10 per cent paraffin wax in an ethylcellulose film reduces the moisture permeability from 2.72 X to 0.1 X 10-6 gram per hr. per sq. cm. per em. The low specific gravity of ethylcellulose compares with 1.37 for cellulose acetate and 1.65 for cellulose nitrate. This means that 1 pound of ethylcellulose is equivalent to 1.2 pounds of cellulose acetate or 1.44 pounds of cellulose nitrate in covering power. The exceptionally high flexibility and extensibility of ethylcellulose combined with its characteristic toughness and light resistance make it particularly adaptable as a flexible coating for paper, cloth, and leather. These same properties make it adaptable when used as a free film. The electrical properties of ethylcellulose are given in the following table; a few comparative results for cellulose acetate are also included:
Djelectrjc strength (A. S. T. M. method), voltsymil Dielectric constant: 1000 cycles 60 cycles 25’ C. 60 cycles’ 100’ C. Power fact&, %: 1000 cycles 60 cycles 25’ C. Specific mriace resistivity (condition 70 hr a t 78’7 relative humidity and 30° C.), ohms i< 10-100
-1O-Mil Ethylcellulose 1500 3.9 2.6 2.9
FilmCellulose acetate 1400 5.7-7
... ...
0.25 0.3
0.50
2000
15
.o
...
It is evident from a consideration of the electrical properties that ethylcellulose is indicated for use as an electrical insulator in such fields as cable covering, extruded wire insulation, and as an impregnant. This is particularly true when it is recalled that ethylcellulose is very flexible even a t low temperatures, is chemically stable, and is heat stable. It is of interest to note here that ethylcellulose plastic has been extruded as a tube around a wire core with walls as thin as 1 mil.
Acknowledgment The author wishes to acknowledge the assistance of several of his associates a t the Hercules Experiment Station in obtaining the data in this article. He is especially indebted to W. S. Traylor for much of the experimental work and for his interest and many helpful suggestions.
Literature Cited (1) Denham, W., and Woodhouse, H., J. Chew. SOC.,103, 1735
(1913); 105,2357 (1914). (2) Dreyfus, H., British Patent 462,274(March 5,1937).
VOL. 29, NO. 6
“Physical and Chemical Examination of Paints, (3) Gardner, H. 9., Varnishes, Lacqiiers and Colors,” 5th ed., p. 775, Method 111,Washington, Inst. of Paint and Varnish Research, 1930. Haworth, W. N., “Constitution of Sugars,’’ p. 84, London, Edward Arnold and Co., 1929. Leuchs, O., German Patent 322,586 (July 1, 1920). (6) Lilienfeld, L.,British Patent 6035 (1913). (7) Nelson, H. A., Proc. Am. SOC.Testing MGferiaZs, 21, 1111-38 (1921). (8) Suida, W., Monatsh., 26,413 (1905). R ~ C ~ I April V ~ D 17, 1937. Presented a8 part of the Symposium on Organic Plastics before the Division of Paint and Varnish Chemistry a t the 93rd Meeting of the American Chemical Society, Chapel Hill, N. C., April 12 t o 15, 1937.
Durability of Cellulose MixedEster Lacquers W. E. GLOOR Hercules Powder Company, Parlin, N. J.
I
N W-IDENIKG the field of usefulness of cellulose ester lacquers, investigators have been particularly active in trying to develop a cellulose ester with the heat and light resistance of cellulose acetate but with better resin compatibility, improved solubility, and increased water resistance. The use of cellulose mixed esters, particularly a triester acetobutyrate called “Hercose C” (6),has made some headway in this field during the past few years, chiefly because of the improved miscibility and extraordinary durability obtained with clear lacquers made from this ester. Recently Fordyce, Salo, and Clarke (2) described a whole series of cellulose mixed esters made from acetic and propionic or butyric acids, some of which had properties of solubility and miscibility with resins which made them particularly well adapted as film-forming materials for lacquer use. The purpose of the present discussion is to present results obtained withmixed esters, such as those described by Fordyce, Salo, and Clarke, studied in relation to their physical properties, their suitability for use with newer resins in the lacquer field, and their actual durability on test fences. From these data an idea of the probable fields of utility of these esters can be obtained and also a picture of the factors that enter into the selection of these materials for certain uses. Charts giving the composition of the esters tested are shown in Figure 1 for the acetopropionates and in Figure 2 for the acetobutyrates. The materials were selected in order to make two comparisons: (a) to determine the differences to be expected between high and low content of high fatty acid, and ( b ) to determine the effect of hydrolysis on the properties of esters of approximately equal substitution of acetyl and higher acyl groups. T o convert the compositions (shown on Figures 1 and 2 as the number of hydroxyls acylated or unesterified) into the per cent acetyl, propionyl, and butyryl determined by analysis, or vice versa, the following reduced equations are useful :
JUNE, 1937
INDUSTRIAL AND ENGINEERING CHEMISTRY
Acetobutyrates are slightly more durable, more miscible with resins, slightly softer, and, in the case of the higher substitutions, less stable than the corresponding acetopropionates. Acetopropionates and acetobutyrates give durable, hard lacquers which are resistant to discoloration when properly formulated in clear finishes. Maroon and green lacquer enamels, with less tendency to fade than when a nitrocellulose base is used, can be prepared with these finishes. Durability of such lacquers is enhanced if a nondrying-
691
oil-modified alkyd resin is used in place of dammar gum. A finishing system composed of a color coat of mixed-ester enamel and a finish coat of mixed-ester clear lacquer promises to provide a finish that will hold gloss without chalking for years. This new mixed ester gives promise in the airplane and cloth-finishing fields. For all-round work, an acetopropionate of 29.5 per cent propionyl and 15.7 per cent acetyl content is indicated from cost, solubility, miscibility, and durability data.
I Acetopropionates : - A =
162
4300n 42n
+
+ 56m;
162 4300
A
Acetobutyrates: 4300
A = 162
+ 42n + 70m;
=
-43400 _
- 42.2 P - 42
43n P ; m=-
57A
A
162 4 2 . 4 -B - 4 2 _A_
43nB ;m=71 A
where A = per cent acetyl P = per cent propionyl B = per cent butyryl Z = unesterified hydroxyl = 3 - (m n) n = No. of hydroxyls acetylated per C Sunit m = No. of hydroxyls acylated with higher fatty acid per Ce unit
+
These equations are accurate to 0.02 hydroxyl, since molecular weights were rounded off to the nearest whole number.
raises tolerance to diluents to a great extent, as with nitrocellulose. The dilution ratios in butyl acetate are considerably lower than that found with RS l/*-second nitrocellulose. The very low values obtained with butyrate esters 4 and 5 are thought to be out of line because of the somewhat higher viscosity of the samples used.
Physical Properties The physical properties of these esters are summarized in Table 11. They were made to have a viscosity somewhat close to that of RS '/2-second nitrocellulose, and their physical properties approach those of the nitrocellulose; the tensile strengths are generally 20 to 40 per cent lower. For comparative purposes a few materials of higher viscosity are also included. The esters have better ability to transmit ultraviolet
Solubility
TABLE I. SOLUBILITY OF MIXEDESTERS" Solubility of these materials in comSolvent b Acetopropionate-Acetobutyrate1 2 3 4 6 6 1 2 3 4 5 mon lacquer solvents has been indicated Acetone S s S S s S S S S b y F o r a y c e , S a l o , and Clarke ( 2 ) . Ethyl acetate S S S S S S S S s Ethylene dichloride S S Table I presents the usual lacquer soluS Sw S S S S SW 1 w w Denatured alcohol 1 W S w w w bility data in order to demonstrate soluw \v Butyl alcohol 1 W w w nButyl acetate S \V sw S Sw sw S S bility differences in the specific material w w Hexyl acetate S\v \1' Gel w s w tested. The only point worth noting 1 1 Troluoilc 1 I 1 1 1 Toluene s w s w s w 9m SW SW SW S w is that triesters are soluble in chlorinated Methyl Cellosolve S PS IV S S sw s S Cellosolve acetate s s S S S W PS s S materials but not in Cellosolve type solvents; the reverse is true of highly S = soluble, PS = ptrtly soluble, S W = swollen by solvent, W = wet by solvent, 1 = not afh y d r o l y z e d materials. As shown by 'ec~&,!&~&e,"f";~t~ $ ~ 10 ~cc of ~ ~ e ~ F o r d y c e and eo-workers, the aceto0 A petroleum diluent butyrates are generally more soluble than the acetopropionates. light than does nitrocellulose. Of interest are the trends inDilution ratio, run in a comparative manner on 15 per cent dicated by these data as to the effect of substitution on tensile solutions of these materials in solvents with toluene diluent, strength; the esters with greater content of higher fatty acid follows: were lower in tensile strength and higher in distensibility, as might be expected from the data of Hagedorn and Moeller Aceto- Toluene DiluAceto- Toluene Dilupropi- tion buty- tion ( 3 ) . These esters are of good stability, except the high butySolvent late Ratio Solvent onate Ratio rate samples (90s. 1 , 4 , 5 ) which after 12-month storage de3 8 Acetone Acetone l 2 8 1 2 2 5 Acetone 2 3 2 Acetone velop odor and are no longer completely soluble in ester sol3 0 Ethyl acetate Ethyl acetate 3 4 3 6 vents. This property can probably be improved by manuEthyl acetate Ethyl acetate 4 3 1 5 2 9 6 1 0 Ethyl acetate 5 1 6 Ethyl acetate facturing refinements. In moisture absorption they approach Butyl acetate Butyl acetate 4 0 8 5 1.5 5 0 5 Butyl acetate RS '/Z-second nitrocellulose, but all have a definitely greater permeability constant, indicating that water penetrates them Again, better solubility of higher acylation esters is found, faster. The data show that the lower the degree of esterificasince hydrolyzed samples are generally less tolerant to hydrotion, the greater are the moisture absorption and water percarbon than triesters. Addition of alcohol to these solvents meability, 1.
0
INDUSTRIAL AND ENGINEERING CHEMISTRY
692
VOL. 29, NO. 6
other resins as t,he compatibility tests (Table 111) would justify. Limit of Results of this series of tests are given Stability Water Ultraviolet Tensile Elonga- BergmannMoisture Perme- Melting TfaFin Table N. Figure 3 shows typical reViscosity@ Strength tion Junk Test Absorptionb ability Pointc misslon a s c o m p a r ed with the same CentiKQ./ G./sq. cm./ poises sq. om. 7% % cm./hr. C. A. f o r mul a s using lacquer-grade cellulose RS I/a-Second Nitrocellulose acetate. Judging from t h e s o l v e n t 20 650-750 7-12 .. 3.0 2.0 lo-' 185 formula, general lacquer properties, and Aoetopropionates weathering resistance, an acetopropio1 9.5 271d 14d 0.03 3.3 4.1 195 2800e 2 19.5 327d 3d 0.14 2.7 3.7 264 26506 nate corresponding to No. 5 in FigPhigh 241 631 3.5 0.01 2.6 4. ..1. 246 2650' ure 1, or an acetobutyrate corresponding 3 27.6 502 4 Trace 4.3 ... ... 3high 650 471 11 Trace 4.1 ,.. . . . to No. 4 in Figure 2, would be most use4 35 T o o brittle ... 2.2 ... 226 ... ful in this field. 5 42 570 7 ,.. 3.2 ... 207 ... 6 90 594 9 ... 4.4 ... 205 ... In Table IV only formulas 1, 2, and Acetobutyrates 5 , u s i n g nondrying-oil-modifled alkyd 1 8.0 191d 21d 1.43 2.7 3.7 189 2800' 2 15.0 250d 7d 0.19 2.6-2.8 3.3 233 26508 resin give hardness in the generally de0.19 2.7 2high 346 539 4 3... .7 230 2650e sirable range, and of these, formula 2 550 3 ... 2.2 229 ... 3 51 4 53 585 8.3 . . . 2.8 ... 215 . . . gives the longest life. With vinyl resin 5 84 582 6 ... 3.6 ... 190 ,.. the test panels all showed some rusting, a 10% solution in acetqne at 25' C. although they were excellent in color b At 85% relative humidity. c Capillary tube method. and of fair hardness. Dammar gum d Determined on films plasticized 10 parts ester to 1.5 parts dibutyl phthalate and 1.5 parts trigave formulas prone to crack, as has phenyl phosphate; other tests on unplasticized film. Determined by E . A. Georgi, Hercules Experiment Station. been observed previously; ester gum behaved similarly. The effect of ester substitution on fence life was not marked The flexibility of films before and after Uviarc irradiation is for propionates, but with the acetobutyrates, increasing hya good measure of the inherent resistance of a cellulosic matedrolysis seemed to hasten rusting and failure by cracking. rial to ultravialet degradation; the following table gives some Variation in proportion of acetate to propionate in the ester comparative results: TABLE 11. PROPERTIES OF CELLULOSE MIXEDESTERS
0
--EmbrittlementSchopper After S fold as hr. in aged Uviarc
Material
RS I/%-seo.nitro-
cellulose Acetopropionate 1 2 3 4 5 6 Aoetobutyrate 1
2
3 4 5
20-25 14 5 9 10 36 38 15 3 15 33 34
0
0-1 0
0
2-l 5 3 0 1 5 5
CELLULOSE
Loas,
%
100 97 100 100 97 89 87 80 100 94 85 85
The films were all cast 0.004 inch thick from 1-1 acetoneethylene dichloride solution, plasticized 10 parts ester to 1.5 parts dibutyl phthalate and 1.5 parts triphenyl phosphate, and aged 1 week a t room temperature and 24 hours a t 65" C. before testing. Discoloration of the mixed-ester films resulting from Uviarc exposure was scarcely noticeable. The esters which had a greater content of higher fatty acid or were more fully hydrolyzed remained most flexible upon irradiation.
TR'dcErA TE FIGURE 1.
TR//FWOP/ONAi%
SUBSTITUTION OF ACETOPROPIONATES TESTED, HYDROXYLS PER Cg UNIT
IN
Use in Clear Lacquers Since a good deal of experience with Hercose C finishes had shown that a nondrying-oil-modified alkyd resin was the best resin available for durable, clear finishes, a representative series of formulations was prepared based on this resin, as well as with the more conventional dammar and ester gums:
Cellulose ester Dibutyl phthalate or Santicizer M-17 Resin
1 12 2
2
Formula, No. . 2 3 4 12 12 12 2.7 3 6 5.3 9 6
5 12 5 3
Experience with Hercose C had shown that films containing only plasticizer would not adhere well, and that films containing resin only had a tendency to bloom; hence only the above formulas, which cover the range of usual lacquer proportions, were tested. All samples were tested with nondrying-oil-modified alkyd resin, dammar, and ester gums, and with such
T R I 8 U ?-YF?ATE
TR/ACET;~;~E
FIGURE2.
s~~~~~~~~~~~ OF ACETOBUTYRATE~ TESTED,IN HYDROXYLS PER Ca UNIT
JUNE, 1937
INDUSTRIAL AND ENGINEERIKG CHEMISTRY
did not have a great effect o n hardness of finish obtained but seemed to affect the acetobutyrates; the high-butyryl ester was lower in hardness, especially with soft formulas. With durable formula 2, using the alkyd resin, satisfactory coatings for brass, copper, Allegheny metal, stainless steel, Duralumin, and aluminum sheet were made; little difference has been observed between the various esters.
Pigmented Lacquers
693
OF MIXED ESTERS WITH RE SINS^ TABLE111. COMPATIBILITY
For- -Acetopropionatemulab 1 2 3 4 5 H 1 H 1 1 A H H H l 1 B H l H l H A B C C H H H
Resin Ester gum Dammar gum Satd. alkyd, oil-modified: M. p., 52-67' C.
1 1 H H H H H H C H C H B C C C C A C H C C B C H C C -4 1 1 H C B H l C C A H H C C B C H C C All show sweating
A B
A
M. p., 60-66' C. Balsam type alkyd Vinyl acetate polymer Phenol-formaldehyde, hard class I
H H C C C C C C C C out
6 H H H H H H C C H C H H C C
-Acetobutyrate-1 2 3 4 H 1 1 1 C H 1 H C l H H C C C C H H C C H C
1 H H C H C
C H H
H 1 l
H 1
H H H C C C H H C C
H H C C C C C C C C
5 1 H H H
RS I/$Sec. Nitrocellulose C C C C
H H C C C C H C C C
C C C C:
5 C
C C C C C C
One comparison made on mixed esters Sebacic ester of approximately triester substitution, . . l . . 1 H H . . l H H H Modified alkyd plastic, soft A with low and high ratios of higher fatty B . . l . . H H H . . l H H H . . l . . H H H . . l H H H C Modified alkyd (phenol), hard A acid to acetic in the cellulose ester, was B . . l . . H H H . . l H H H C carried out using green, black, white, C H H H H C A C H C C C C Polyacrylic B C H C C C C C H H C C C and gray lacquers. Formulation and A C H H H H H C H H H H C Terpene-maleic glycol test results are given in Table V. The B C H C H C C C H H C C C . . 1 1 1 2 3 3 1 1 2 3 3 3 Solvent usedo esters do not give as good gloss as the nitrocellulose enamels, and the higha C = compatible; H = hazy translucent film; 1 = white incompatible film. b A = 10 ester, 5 resin; B = 10 ester, 2 resin. propionyl or high-butyryl esters give c Solvent 1: ethyl acetate 45, acetone 55. 2: ethyl acetate 30 methyl Cellosolve acetate 10 acetone 20,toluene 20, butanol 10; 3: ethyl aletate 20,butyl acetate io, denatured alcohol 10, butyi most gloss of any of the mixed esters alcohol 10, toluene 40. tested.. I n the blacks the high-acetyl materials are poorer in w e a t h e r i n g r e s i s t a n c e than the others, although give promise of improving fading of greens, but show no their hardness is somewhat higher. The mixed esters generparticular advantages in the other colors from the viewpoint ally showed less fading than nitrocellulose after 1 year in green of general durability. enamels. Here the high-acetyl acetopropionate again gave To follow up the indication of better resistance to fading, poorest life. The failures in the white and gray panels were a series of maroon, green, and blue lacquers was exposed, using complicated by a reaction with zinc oxide which gave brittle standard nitrocellulose formulas. A few whites, pigmented films after 90-day exposure, and a crack resulted. Gelation with the less reactive titanium dioxide, were also included. of these solutions also occurred, probably because of the ethyl The formulation is shown in detail in Table VI. Results of lactate used in the solvent. In this work the mixed esters
8
(ON TABLE Iv. DURABILITY
Laoq u er Formula
Resin Used Satd. oil-modified alkyd, m. p. 6066' C.
Sward hardness, % ' Failure
72 Rust
2a 66 Rust
Felice life, days
104
262
Sward hardness, % Failure
57 Rust
60 OK
Fence life, days
356
445+
Sward hardness, % Failure
45 Slight rust 445f
58
la
Fence life, days Sward hardness, % ' Failure Fence life, days Sward hardness, % Failure Fence life, days Vinyl resin
Sward hardness, %
Failure
Fence life, days Ester gum
13ammar gum
a b
STEEL) O F CELLULOSE
siight rust 356+
OK
445+ OK'
445-k
Acetopropionate 30 4b
...
...
...
...
445f
62 OK
O 59K
O 41K
OK 59
365+
Slight 54 rust 356
OK 61
365+
445+
365+
365-1- 365f
38 OK
O 53K
Slight 32 rust 356f
O 42K
356+
365+
Slight 45 rust 365f
OK 41
365f
Slight 36. rust 356
O 43K
365+
... OK
26 OK
41 Slight
35 Slight
365+
rust 365f
rust 365+
279
5b 72 Slight rust 285
O 58K
365f
Slight ...
365+
rust 365+
rust 356+
di;'
51 Slight
47 Slight
52 OK
S&ht
... Rust
35 Slight
49 Slight
:Tight
365+
269 rust
365+ rust
365f
356rust
356
rust 365+
rust 365+
rust 365+
47 Rust
55 Rust
2Layer soln.
... ...
43 Rust
56 Rust
51 Rust
47
100
...
...
75
100
100
43 Crack, rust 06
57 Crack
Crack
53 Rust
55 Crack
66
185
150
105
35 Crack rust 45
50 Crack 180
46 Crack 150
51 Crack 105
...
...
...
...
Sward hardness, % Failure Fence life, days
40 Crack 38
58 Crack Crack: Rust 45 218
Sward hardness, % Failure
53 Crack
47 Crack
Crack Rust
41 Crack
Fence life, days
38
38
232
122
Paneis exposed July 1935 read Oct 1936 Panels exposed Marbh, 1996,read &oh, '1937.
70 Rust
35 Slight
...
...
183
%ght rust 230
rust 365+
...
...
A4cetobutyrate 36 46 71 74 OK Slight rust 262 365f 365 25 72 Rust
iyight
rust 445f
445+
*..
LACQUERS
22 OK
siight
$Lei, rust 262
O K
5b 73 Rust
CLEAR
. -1"
6b 69 Slight rust 230
Slight 51. kist, crack rust 365+ 78 OK
MIXED ESTERS IK
56 Crack (Fil~;.~
...
FiL;ry]
122 57 Crack 90
57 Crack 90
... ...
40 Crack, rust 66
445f
VOL. 29, NO. 6
INDUSTRIAL AND ENGINEERING CHEMISTRY
694
C O M P ~ R ~OP S OCELLULOSE X MIXED ESTERS.WITH HIOHAND Low RATIOSOF ACETICTO HIGHERALIPHATIC ACIDS.
TABLEV.
IN
Black 78 cellulose ester base
Eater:
5 dibutyl phthalate
PIGMENTED LACQUERS
Green ;E cellulose ester base 14 50% soh. alkyd resin, x i i . p. 60-66O C.
Gray
White
62 ccllulose ester base 24 r h i t c paste
62 oellalosa ester bass 6 dammar soh.
5 dibutyl phthnlate 15 gray paste 05 solvent
?i pigment base 60 solvent 30 diluent
37 dileent 11.2% black pigment 50% ester glim
Pigment:
88.2%
soin.
37.5 chrome green 12.5 trieroayl phosphate 25.0 blown oil 25.0 xylene
Aoeropropionate 1 Original gloss Original Sward hard-
Eggshell gloss, OK after 1 year Medi"n,
Fist gloss, slightly isded after 1 year Medium
50.0 zinc oxide 20.0 alkyd b:ilsrm resin 20.0 dibutyl phthalate 10.0 naphtha
Craoked niter HZ days. failed after 150 days
32
Medium 32
Flat ~108s. ali&ly iaded. peeled aiter 280 day8
Craohed after 92 days, failed aiter 150 days
31.75 1 .GO 53.30 13.35
vim oxide drop black toluene butyl alcohol
Cracked after 51 dags, peeled after 90 day8 Medium 53
ness. % Acetopropionate 2 Original gloss
Eggshell gloss, after 280 days
peeled
LOW
LOW
LOW
35
38
50
Eggshell gloss, OK after 1 year
Flat gloss. slightly fnded niter 1 YBBT
Slightly cracked after 92 days, failed hiter 150
;Medium
Medium 41
dab8 Medium 50
Blistered after 90 d w a , cracked. failed after 150 days Medium
Flat gloss, slightly faded after 1 year
Cracked after 65 days, failed after 91 dnss
Blistered after 90 dnga, craoked. failed after 150 days
LOW
Original Sward hard0898,
%
Original gloss Origiinal Sward hardness, % Aoetobutpate 2
..
Eggshell
~IOSS.
peeled
after 280 days, rusted in 564 days Original gloss Original Sward hard-
ness. %
RS
Blistered after 90 daye, oraeked, failed after 150 days
~,fS-sec.nitrocellulose
Original gloss Nitrocellulose Solvent, and Diluent Mixture: 24 Butyl noetate Ethyl aeetnte 5 Butyl alcohol 5 Denatured alcohol 5 miiene 31
FIQCKE
LOW
47
..
LOW
LOW
.Low
4i
36
54
Eggshell gloss, O K utter 1 year
Flat gloss, fnded after 1 year
Best
B&
Solrent. Mired Esters: Ethyl lact,ilte Biityi alcohol
30
Hl?XO"e
5 20
Ethyl aeetiire
45
Diluent: TOlUeDe Ethyl acetate
50
50
Faded after 1 appcn*nnee Fair Sitrocelldose Baee Solution: RS i / ~ e c nitro. OdlulOSli
Toluene Bury1 acetate
is
beat
Base Solution: Celiulosa ester
Acetune Ethyl aceiate
18 41 41
41 41
OF ACETOPROPIOYATE NO. 5 ( E l , E3) AND CELLULOSE ACIBTTE( A t , AS) LACQUERS SPR.4TED O X STEEL, AFTER &hIOhTH EXPOSTRE AT 45" F l C I X G POOTA. 1 9 n'ILWIICGToK
3. COMPARATIVE DUR.4BILITY
SCILT,
CLE~R
INDUSTRIAL AND ENGINEERING CHEMISTRY
JUNE, 1937
TABLEVI.
COMPARISON OF
M1
Formula Acetopropionate 4
....
+ 7 mo. +
FENCE LIFE
M2 7 mo.
+, OK
Acetopropionate 5 7 mo.
7 nio. f , O K
Acetopropionate 6
7 mo.
....
Acetobutyrate 3 Aoetobutyrate 4
+, +,
7 mo. OK 7 mo. OK
Acetobutyrate 5
+, O K
7 mo. f, OK 7 mo. f, OK
+, OK 7 mo. +, OK 7 mo.
Hercose C
....
RS l/s-seo. nitro-
....
7mo.+,OK (slightly faded)
60 6 4.2 11.3
60 6 3 18.7
cellulose Ester base Dammar 80111. Dibutyl phthalate Maroon paste Ti02 paste Blue paste Green paste Solvent
.... .... ....
61.5
Acctopropionate 5 Cellulose ester Ethyl acetate Ethylene dichloride Butyl acetate Denatured alcohol Butyl alcohol Toluene Acetone
20 8
..
16 16 8 32
..
T2 .... 3.5 mo. chalked, cracked, peeled 7 mo., cracked 6 mo., cracked and and peeled peeled .... 3mo., crackedand scaled 3.5 mo., chalked .... and cracked .... 7 mo. f, OK (chalked) 3.5 mo., chalked .... and cracked .... 3.5 mo., chalked, cracked, peeled .... 7 mo. OK (chalked only)
+,
60 6
4.2
....
....
12
....
....
.... ....
62.3
67.8
.
test exposures thus far indicate the following trends : Less fading occurs in maroon and green than with nitrocellulose; the materials are definitely inferior to nitrocellulose as a vehicle for titanium dioxide and Prussian blue; the butyrates have slightly better fence life than the propionates; the hydrolyzed esters acetopropionate 5 and acetobutyrate 4 are distinctly better than the corresponding triester or more fully hydrolyzed ester in fence life in titanium dioxide formula. The gloss of these panels was not exceptional, even after polishing with Parko polish and rubbing. All pigmented finishes were applied in three coats and dried on polished body steel panels given a coat of oil primer and baked 1 hour a t 105' C.
Overcoating Lacquers One of the most attractive fields of protective coatings research, as well as one of the most discouraging from the standpoint of results, is that related to applying a durable gloss coat on an enamel-lacquered article. Early work with nitrocellulose clear finishes on nitrocellulose enamels soon showed that the clear finishes were not durable; later work using more durable acetate or Hercose C finishes over nitrocellulose colors, even though the latter contain light-filtering agents, resulted in failure because of the chalking or bubbling of the nitrocellulose film a t the interface. Similar tests made over baked synthetics have thus far failed because of adhesion or wrinkling difficulties; but recent experimental work with a system comprising oil primer, color coats made from these esters, and a top coat of clear mixed-ester lacquer on the color, after 15-month exposure over white and green made using nondrying-oil alkyd resin, gives promise of providing such a durable system. As yet neither failure nor much loss in gloss
B1
....
+, +,
7 mo. OK 7 mo. OK
....
7 mo. OK 7 mo. OK
+, +,
.... ....
B2 6 mo., blistered 6 mo., blistered
6 mo., blistered
7 mo.
+, OK
7 mo. f,slightly bronzed 7 mo. slightly bronzed 6 mo., bronzed, cracked, rusted 7 mo. f,bronzed only
60 6 4.2
60 6 3
21
....
..
....
.... ....
15
....
....
61.2
G1
64.8
G2 7mo. + , O K
.... 7 mo. OK 7 mo. OK
+, OK +, 7 mo. +, OK
....
....
+,
60 6 1.8
Base Solutions Acetopropionate 6. Acetobutyrate 3. acetobutyrate 4-5 acetopropionate4 20 20 8 .. 40 .. 16 16 .. 8 .. 32 .. 10 40 I
MIXEDESTERSOF VARYING HYDROLYSIS
O F PIGMENTED LACQUERS USING
TI
695
f,
7mo.
7 mo. f, OK (dull gloss) 7 mo. + . O K 7 mo. f,OK
+, OK 7 mo. +, OK 7 mo.
....
(color faded)
60 6
4.5
60 6 3
..
....
25
....
..
.. 56
7.5 72
15 66
..
Solvent Acetopropionate 5-6, Acetopropionate 4, acetobutyrate 4-5 acetobutyrate 3 30 Ethyl acetate 10 .. Butyl acetate 20 .. Denatured alcohol 20 10 Butyl alcohol 10 40 To1uen e 30 10 Methyl Cellosolve ." acetate Acetone .. 20
has occurred. Checks on these results are being run a t present in Florida. It is believed that this field may broaden the use of lacquer colors which hitherto have shown fading (maroons, blues, greens) in automobile finish lines which are now equipped to handle lacquer but which do not have the cumbersome baking ovens for synthetics. The durability of these mixed-ester finishes seems to be sufficient for such use.
Miscellaneous Uses For airplane lacquers, better water resistance and durability than is obtained with acetate can be expected from these materials. While coatings made with the triesters seem to develop most tautness, these coatings are slow to tighten when applied to the fabric and have a tendency to lose tautness on weathering. The hydrolyzed esters such as acetopropionates 1, 3, 5, and 6, or acetobutyrates 1,4,and 5 , tighten the fabric more quickly and do not slacken on weathering so much as the triesters. The useful formulas in this field are given by Kline (7); in the case of the most soluble esters examined, such as acetopropionate 5 or acetobutyrate 4, the following clear dope formula was useful: High-viscosity cellulose mixed ester Triphenyl phosphate Ethyl acetate
10.00
1.05 17.80
Butyl acetate Denatured alcohol Butyl alcohol Toluene
17.80 8.90 8.90 35.55
This may be pigmented according to the usual practice for nitrate dopes, substituting tricresyl phosphate or dibutyl phthalate for the castor oil which is customarily added when nitrate dopes are pigmented. For textile fabrics, supple, glossy, wash-resistant finishes can readily be made with these materials through the use of
INDUSTRIAL AND ENGINEERING CHEMISTRY
696
chemical plasticizers. A coating of the following formula, applied to a canvas or broadcloth surface, can be used either as a washable stiffening size of improved oil and flame resistance, or in heavier coatings to bring up gloss: High-viscosity highpropionate ester Alkyd balsam resin Tributyl phosphate
12 6 0
Ethyl acetate Butyl acetate Denatured alcohol Toluene
25
10 10 31
A great many variations of this formula, within the limitations of the compatibility and solubility characteristics of the mixed esters, will suggest themselves to those interested in special textile coatings.
Discussion Perhaps the outstanding point about the results described here is the superior resistance of the clear formulas to weathering. The reason for this is obviously the superior light resistance of these materials as compared with nitrocellulose, and their superior water resistance as compared with cellulose acetate. This water resistance is reflected in both permeability and absorption values in Table 11; as a matter of interest, the permeability values given there are set down against the dielectric constants of the various materials used : a t 20’
C. (8)
5.0 3.0-3.1 4.1-4.3
from normal behavior on the part of the nitrocellulose which is responsible for the uncommonly good permeability shown by this material. One possible explanation is that the nitrate groups are present in the nitrocellulose in the ester form or “pseudo nitric” acid of Hantsch (1,4) which, being much less polar than the ionized or normal form, would give the low dielectric constant shown, and might account for the very low permeability because of environmental factors. The mixed esters bear a normal relation to cellulose acetate in this respect. As has been pointed out by Fordyce et al. @),it is not practical to go above cellulose butyrate in search of moisture resistance because of softness of the resulting esters; also since cellulose in itself has a rather polar unit cell, reasoring by Hildebrand’s rule leads to the conclusion that any cellulose ester must have a definitely greater permeability for moisture than a hydrocarbon such as paraffin.
Acknowledgment Samples of the acetate-propionate and higher butyryl acetate-butyrate esters tested in this program were kindly furnished by Malm and Farrow of the Eastman Kodak Company, as well as a description of the properties as they found them.
Literature Cited
Dielectric Constant Material Cellulose nitrate (12% Na) Cellulose acetate-propionate or -butyrate Cellulose acetate (54-56% acetic acid)
VOL. 29, KO. 6
Kperm.
2.0 x 10-0 3.3-4.1 X 10-8 6 . 6 X 10-6
It would seem that the permeabilities shown here do not follow the suggestion of Hildebrand (6) who states that the dielectric constant of a solid is a rough measure of its permeability by polar gases. Although there are several fine examples of the truth of this rule (i. e., the moisture-proofing of Cellophane), it seems that there must be a certain deviation
(1) Farmer, J. SOC.Chem. I d . ,50, 75-9T (1931). (2) Fordyce, Salo, and Clarke, IND.ENG.CHEM.,28, 1310 (1936). (3) Hagedorn and Moeller, Cellulosechem., 12,29 (1931). (4) Hantsoh, Be?., 58,612,941 (1925); 60,1933 (1927). 28, 157 (1936). (5) Hercules Powder Co., IND.ENG.CHEM., (6) Hildebrand, “Solubility,” 1st ed., pp. 138-9,New York, Chemical
Catalog Co., 1922. (7) Kline, IND.ENG.CHEM.,27, 556 (1935). (8) Nowak, P.,A ~ Q ~Chem., w . 37, 584-7 (1933).
R E C E W ~April D 17, 1937. Presented before the Division of Paint and Varnish Chemistry at the 93rd Meeting of the American Chemical Society, Chapel Hill, N. C., April 12 to 16, 1937.
COKE-CARBON DIOXIDE RELATIONS KENNETH 0. SKINNER Northwest Experiment Station, U. S. Bureau of Mines, University Campus, Seattle, Wash.
EVERAL manufacturers prepare precipitated calcium
S
carbonate by passing carbon dioxide, produced by burning coke under a boiler, through a suspension of milk of lime. The solids contained in the gases are removed by some type of scrubber, and steam from the boiler is used for general heating purposes. I n this process, important factors are as follows: 1. What weight of coke must be burned with varying amounts of excess air (weight basis) t o produce V cubic feet of gas, and what weight of carbon dioxide is contained in the gases? 2. What is the total volume of gases, containing M per cent carbon dioxide by weight, required t o supply X pounds of carbon dioxide? 3. How many pounds of coke are required t o supply V cubic feet of gas containing N per cent carbon dioxide by volume?
Equations were derived to show the relations between the weights of coke and carbon dioxide and the total volume of gases produced. Complete combustion was assumed; that is, all the carbon was burned to carbon dioxide. Therefore, corrections would have to be made for coke lost in the ash or for other losses. The final equations were simplified by assuming the absence of sulfur. Coke used in the manufacture of precipitated calcium carbonate should contain less
than 1 per cent sulfur, unless the sulfur dioxide in the gas is removed. Figure 1 is drawn from the equation:
+ +
2350 (14.7 G)V (100 - A ) (100 Y ) (460 where W = coke required] Ib. V = gas, cu. f t . G = gage pressure, lb./sq. in. Y = excess air, yo A = ash in coke, weight ter cent t = temperature of gas, F. E
+ 6)
Equation 1 shows the pounds of coke required to deliver V cubic feet of gas a t t O F., G pounds gage pressure, using Y per cent excess air. The vertical line between the third and fo6rth quadrants indicates the weight of carbon dioxide contained in the gases. The weight of carbon dioxide was calculated from the expression, 0.0367 W (100 - A ) . The following equation,
where M
= carbon dioxide, per cent by weight X = carbon dioxide required, lb.
