December, 1946
INDUSTRIAL AND ENGINEERING CHEMISTRY
slow, scatter-type construction of the curing pile to eliminate part of the initial heat. Otherwise the hydrolysis of monocalcium phosphate t o form additional free phosphoric acid may nullify the advantage gained by neutralizing the initial free acid, and the oxidation reactions may thus be re-established t o cause excessive heat accumulation. CONCLUSIONS
Reactions in fertilizer mixtures, es ecially base mixtures containing relatively green superphospgte, organic matter, and large amounts of inorganic nitrate have been represented by Equations 1 to 4. Reactions represented by Equations 3 and 4 are highly exothermic and cause an excessive rise of temperature, even to the point of combustion, in curing piles containing sufficient nitric acid to react with the organic matter present. The nitric acid in the mixture is formed by the reaction of inorganic nitrates, such as ammonium nitrate, with free phosphoric acid (Equation 1). The rate of heat development increases with increase in concentration of free phosphoric acid and the consequent increase in formation of nitpic acid. Neutralization of the initial free phosphoric acid in the mixture prevents the excessive accumulation of heat in the curing pile by inhibiting the formation of nitric acid. However, the heat of neutralization should be largely dissipated in order to inhibit the hydrolysis of monocalcium phosphate and the formation of additional free phosphoric acid accordin to Equation 2. Otherwise, the reactions of Equations 1, 3, a n 3 4 are likely t o be re-estab-
1303
lished. The heat of neutralization may be largely dissipated by preneutralization of the superphosphate or by slow construction of the pile when such mixtures are stored for curing. The rare occurrence of combustion in the curing pile of many potentially combustible mixtures indicates that optimum conditions for the development of these reactions seldom exist. However, in certain mixtures-especially base eoods, such as the standard base mixture used in these tests-it is essential that the content of free phosphoric acid be as low as possible if excessive heat development is to be avoided. The results of the tests indicate that, a t the usual temperatures of the fertilizer curing pile, ammonium nitrate is no more haaardous from the standpoint of heat development than are the other inorganic nitrates. Howeverl if for any reason the temperature of the storage pile reaches the ignition point, the resulting fire is more difficult to control in mixtures containing ammonium nitrate than in those containing any of the other inorganic nitrates tested. LITERATURE CITED
(1) Brewer, A. K.,and Dibeler, V. H., J. Raoearch Natl. Bur. Standards, 35, 125-39 (1945). (2) Davis, R. 0.E., and Hardesty, J. O., IND.ENG.CEEM., 37 59-63 (1945). (3) Elmore, K.L.,and Farr, T. D., Ibid., 32,580-6(1940). (4) Hardesty, J. O.,and Ross, W. E., Ibid., 29,1283-90(1937) (5) Hill, W.L.,and Hendricks, S. B., Ibid., 28,440-7 (1936). PRESENTED before the Division of Fertiliaer Chemistry at the 110th Meetine of the AMERICAN C ~ ~ M I CSOCIETY, AL Chicago, Ill. ,
IMIDE-MODIFIED ALKYD RESINS HOWARD J. WRIGHT’ AND ROBERT N. DUPUIS The Miner Laboratories, Chicago 6, Ill, Replacement of part of the ester linkages in an alkyd eesin with amidic linkages was attempted by introducing part or all of the fatty acid radical as an amide of glyceryl monoamine. The amide appeared to undergo a rearrangement resulting in the formation of an N-substituted imide of the dibasic acid used. These imide-modified alkyds, which can be prepared through substitution of a glycerylamine for part of the glycerol, can be made with very low fatty acid content and low acid numbers, and give hard, fast-drying films. Properties of representative imidemodified alkyds are described, and a Wsible mechanism involved in their preparation is given. Evidence is preeented which indicates that a rearrangement takes place when alkyl fatty amides are heated with phthalic anhydride in the presence of hydroxyl groups. A method of calculation was devised for the prediction of the acid number of an alkyd resin from its formula and for reducing the acid number of an alkyd to any desired value by replacing part of the dibasic acid with an N-hydroxyalkyl imide.
A
‘
PREVIOUS report on alkyd resin research (7) showed that
alkyds could be separated into fractions having substantially different properties by a n alcoholic extraction process. The portion insoluble in lower monohydric alcohols is of lesser oil content than the starting material and has superior filmforming properties. The alcohol-soluble fraction is of no utility as a surface coating and acts as a softener of the desirable insoluble part. The unwanted soft material can be reworked into a n ordinary type alkyd, so that, by a cyclic process, a substantial percentage of the insoluble fraction can be continuously produced. Two obvious differences between the two fractions are “oil” oontent and molecular weight; the alcohol-insolubke part has (ess oil and higher molecular weight. It was felt that these differ1 Present address, Department of Chemistry, Northweatern University, Evanston. Ill.
ences were due t o uncontrolled migration of fatty acid groupc during resin formation, resulting in unbalanced distribution Assuming that fatty acid migration is responsible for some of the unwanted portion, i t is conceivable t h a t fixation of the fatty acid linkages in a predetermined position might give an improved resin. I n a 40% oil alkyd, for example, only about one sixth of the ester linkages involve fatty acid radicals. Since there is unbalanced distribution probably resulting initially in some small molecules like di- and triglycerides, there must also be large molecules with such low fatty acid content as t o lead to premature gelation. Such uncontrolled distribution is believed t o be a serious problem in the ordinary alkyd resin. USE OF AMIDE LINKAGE
If the amide linkage were found t o be stable under conditions of resin preparation, some improvement in distribution of fatty acid radicals might be expected if these groups were added as amides of glyceryl a-monoamine (3-amino-1,2-propanediol). The effect of such a n addition was determined. The amides were prepared by dropping one mole of the amine into one mole of fatty acids maintained a t about 220’ C. in an atmosphere of nitrogen. The amides are practically neutral waxy materials with hydroxyl contents corresponding t o the expected structure R-CO-NHCHAHOH-CH2OH Alkyds prepared from fatty acid amides of glycerylamine, phthalic anhydride, and glycerol had greatly improved film characteristics in comparison with those of ordinary alkyds, and showed the additional important advantage of retarded gelation during resin cooking, to the extent that resins of low oil content and low acid number could be produced. However, even though the amides were calculated m requiring two acid groups t o effect reaction with their two hydroxyl groups, the hyhoxyl numbers of the finished resins were much higher than would be predicted on the basis of the formulation. The degree
INDUSTRIAL AND ENGINEERING CHEMISTRY
1304
by which the hydroxyl numbers exceeded calculated values varied directly with the amount of fatty acid amide used in preparing the resin. If the amide were considered to be capable of reacting with three acid groups, then the calculated values corresponded closely with those found experimentally. AMIDE INTERCHAXGE
The following experimental data indicate that amide interchange (I,4,6) takes place when glyceryl fatty acid amides are used in making alkyds in the manner described. In spite of such redistribution of fatty acid linkages, greatly improved alkyds can be prepared from the new basic ingredients. Three equivalents of active hydrogen contained in glyceryl oleylamide (two hydroxyl groups plus the amidic -NHgroup) were heated with three equivalents of phthalic anhydride in the presence of a small amount of xylene to prevent loss of phthalic anhydride by sublimation. It was found possible to bring the acid number of the reaction mixture to 17.5 on the basis of solids content. If the -NHgroup did not react in some manner with acid groups, the acid number could not have been reduced below about 104. Three equivalents, including the -SHgroup, of glyceryl soybean amide and two equivalents of phthalic anhydride, when heated in a manner similar to that described, gave a product of acid number 3.6 and hydroxyl number 106.8. The theoretical hydroxyl number of the product would be 120 if the -SHgroup reacted, and 0 if it did not react, since other experiments showed that the -NHgroup is not acetylated under the conditions used to determine hydroxyl number. Therefore it follows that one equivalent of hydroxyl remained unchanged a t the completion of the reaction. The reaction between three equivalents of glyceryl oleylamide and three equivalents of phthalic anhydride might lead to t x o types of product: ( a ) a three-dimensional molecule of the follorn-ing possible initial structure:
It-co-x-
co co-
I
CO-
CH-0-CO
CHr--O--CO
I
Vol. 38, No. 12
of crude n-butyl phthalimide was prdduced, which was purified and identified by nitrogen analysis, refractive index, and melting point when mixed with a known sample. The physical constants are as follows:
Product of interchange (purified) n-Buty1 phthalimide (3, 5 )
122
2
31.6
6.53 1.5410
124-129
4
31.6
6.77
1,5390
1,5420 1,5407
a T h e melting point of a mixture of the two samples showed no depression: Yanags (6)gives 34' C. as the melting point of pure n-butyl phthalimide. b Theoretical nitrogen content, 6.89%.
There is no reason t o expect that the reaction which occurred with these easily separable and identifiable reagents would not occur with congeneric materials in the resin kettle. In summary, the reaction may be written as follows:
As the second step in the investigation of the amide interchange reaction, glyceryl phthalimide was prepared and used as an ingredient in the synthesis of new types of alkyds. PREPARATION OF GLYCERYL PHTHALIMIDE
The most satisfactory method found for the preparation of glyceryl phthalimide was the reaction between phthalic anhydride and glycerylamine:
0
+ NH2CH2-CHOH-CH20H
+
COI
0 or ( b ) a linear compound including a cyclic nitrogen-containing unit. Physical characteristics of the products obtained, especially results of molecular weight determinations, pointed to a material of the second type. One of the simplest cyclic nitrogen-containing units which might be present in the new alkyds is the phthalimido radical. Two steps were taken t o test the possibility of its presence: first, proof that a derivative of phthalimide can be formed from phthalic anhydride and a fatty acid amide, and, second, study of the properties of resins prepared from glyceryl phthalimide, phthalic anhydride, fatty acids, and glycerol. When n-butyl stearamide and phthalic anhydride were heated together in molar amounts at a maximum of 235" C., and the reaction mixture was distilled under vacuum, phthalic anhydride was recovered almost quantitatively in the distillate, and the residue appeared from its nitrogen content to be practically unchanged n-butyl stearamide. Hovever, \Then the experiment was repeated with the addition of one mole of ethylene glycol to furnish hydroxy1 groups, about 75% of the theoretical amount
One mole of glycerylamine and one mole of phthalic anhydride are slowly heated in an oil bath with stirring in an atmosphere of nitrogen or carbon dioxide. When the reaction starts, the oil bath is removed until the initial reaction, which is very exothermic, subsides. Heating is then continued a t 150-170" C. The mixture is held in this temperature range until water ceases to be evolved. The crude products obtained were pale yellow crystalline materials which became white solids of well defined crystalline structure when they were recrystallized from appropriate solvents. A similar procedure was used in preparing the phthalimide of glyceryl-m,-pdiamine. The physical constants of these materials are as follows: Phthalimide of: Glyceryl-a-monoamine Glyceryl-a,y-diamine
Crystd from: Water or methanol Methanol
%N Found Theory 6 17 7.89
6.33 8.00
Melting Point, C. Found Literature 115-116 209
Kotreptd. 205 ( 2 1 2\13 ( 6 )
December, 1946
INDUSTRIAL AND ENGINEERING CHEMISTRY
1305
produoed 200 grams of resin, then 10 grams of excess glycerol 7 8 9 10 11 12 4 5 6 Resin No. 1 2 3 were added in the beginning 25 25 25 20 20 20 35 36 35 30 30 30 Oil length, % and the finished batch weighed Reactants, grams 210 grams. The indicated per1 0 3 . 9 93 Phthalic anhydride 1 0 0 . 6 9 5 . 6 9 0 . 6 1 0 8 . 4 9 5 . 4 8 6 . 8 116.2 1 0 3 . 5 9 5 . 3 124 67.4 57.4 67.4 47.8 4 7 . 8 47.8 38.3 38.3 38.3 67 67 67 Soybean fatty acids centages of ingredients, such 30.1 46.3 0 18.8 31.2 0 19.4 32.4 0 7 . 4 14.9 0 Glyceryl monophthalimide 59.3 64.8 50.7 61.1 60.4 43.2 63.3 52.8 4 6 . 0 66.5 4 6 . 6 3 9 . 8 Glycerola as oil and pht,halic anhydride, 62 62 Phthalic anhydride % 5 0 . 3 5 0 . 3 6 0 . 3 6 4 . 2 5 4 . 2 5 4 . 2 6 8 . 1 5 8 . 1 5 8 . 1 62 are based on the resin without Phthalic anhydrid; added as 1 6 . 2 25 0 1 0 . 7 18 0 0 12 20 phthalimide, % 0 5 10 the excess glycerol. The Acid No. 50.2 21.9 10.1 1 7 . 8 1 3 . 8 9 . 2 3 2 . 7 1 4 . 3 5 . 6 3 8 . 5 1 5 . 7 18 alkyds were made with, soy21.2 12.2 3 . 2 35.5 12.0 -3.7 51.2 28.4 13.4 66.6 3 0 . 2 10.6 bean fatty acids. All re9 3 . 0 89.1 84.7 9 6 . 3 8 7 . 9 8 1 . 8 8 7 . 4 9 8 . 0 83.0 7 9 . 8 7 9 . 3 8 3 . 0 4.3 4.5 4.3 5.0 4.8 4.6 5.2 4.8 4.5 4 . 8 5.4 4.5 actants were placed in the 14 13 15 20 15 20 ... 13 18 28 13 15 flask a t the start of the heata All resins contain 5% excess glycerol based on weight of finished product. ing period. The mass was Method of calculation is presented in a later section of this paper. brought to 180" C. in 1 hour and to 235" C. in the next TABLE11. FILMTESTS hour, and held a t the latter Resin No. 1 2 3 4 5 6 7 8 9 1 0 1 1 1 2 temperature until the desired cure time was 35 35 35 30 30 30 25 26 25 20 20 20 Oil length, ,% reached, as determined on a cure plate a t 200 a C. Phthalic anhydride added as (The cure plate was obtained from the Thermohthalimide % ' 0 1 0 . 7 18 0 1 6 . 2 25 0 5 10 0 12 20 Firms baked l'hr. at 155' C." Electric Company.) Sward hardnessb at ap rox. relative humidity of! Table I indicates that the acid number of a nw73 50 55 67 65 67 52 6 0 6 0 57 64 76 resin may be reduced to practically any value, 51 62 6 9 37 61 34 64 52 6 0 50 56 40 46 53 29 48 34 38 40 3 0 33 33 depending on the amount of phthalic anhydride + + introduced as glyceryl monophthalimide. The fJms described in Table I1 were prepared basis) '15 10 6 12 Dust-free time0 min. 20 10 18 5 15 15 7 14 from the resins of Table I. They were cast in 23 15 20 13 Tack-free timed: min. 30 20 27 15 25 20 20 35 Sward hardnessb at approx. duplicate with a Bird film applicator on glass relative humidity of: plates, except that those used in the brittleness 28 26 24 28 15 30 25 18 28 22 15 29 28 24 13 26 58% 13 15 14 16 25 19 12 28 tests were cast on 30-gage tin plate. After bak24 18 12 14 9 13 11 10 18 13 7 15 100% ing or air-drying the films were stored a t the inAvera e film thickness, about 1.1 mil dicated relative humidity for 24 hours before b Recorjed af*r 24-hour storage at indicated humidity. C Dust-free time was determined by drawing a thread from a piece of cheesecloth slowly the reported Sward hardness readings were taken. across the surface of the film. If the string moved jerkily, the film was not considered Film hardness a t high humidity was found to be dust-tree. d Tack-free time was determined by rubbing a strip of paper in contact with the film surroughly proportional to water resistance. The face and then pulling off the paper. If there was any audible evidence of adhesion when thickness of the films was determined by cutting the two surfaces were separated, the film was not considered tack-free. , a 0.5-cm. square out of the film in the center of the plate and measuring the thickness all around this square with an Ames Upright gage . _ _ No. 13 and No. 100indicator. It was found that the hardness of films thickerhhan Glyceryl phthalimides were used in a number of alkyd-type the standard 1.1 mil, a t least up to 2 mils thickness, corresponds formulas, as will be described. Alkyds made from glyceryl closely to that calculated by multiplying the hardness of the thin phthalimide in comparison with those from fatty acid amide refilm by the ratio of the thickness of the thin to the thick film. tain all of the desirable characteristics of the latter and, in addiTable I1 indicates that film hardness of resins of a given oil tion, cook faster and give resins of lighter color. The evidence is length tends to be of the same order of magnitude irrespective of therefore reasonably strong that a rearrangement such as that of imide content, but, with the lower oil contents, the high acid amide to imide may take place when fatty acid amides are used as numbers of nonimide alkyds make them unusable. the source of nitrogen. Table I11 gives thejesults of several film tests on various alkyd compositions which had been baked for 20 minutes a t 83" C. PREPARATION AND TESTING OF RESINS (181 F.) with 0.01 % cobalt drier. Changes in film hardness and brittleness are given over a period of 42 days of storage a t fixed An extensive series of imide-modified alkyds and related resinous materials was prepared and tested. Information was relative humidity (r.h.). Table IV shows the hardness of films obtained on the effect of varying (a) the percentage replacement obtained by baking white, black, and unpigmented films from a of dibasic acid by imide, (b) fatty acid content, (c) aminohydroxy 30% soybean oil imide alkyd of acid number less than 10 and a compound used, ( d ) dibasic acid used, and (e) type of fatty acids widely known commercial 42% linseed oil alkyd of acid number 8. aa the source of fatty modifier. Rosin derivatives .of hydroxyThe greater hardness and water vapor resistance of the imide amines were prepared and characterized. films are apparent. The average hardness a t the three humidities Twelve standard and imide-modified alkyds of 20 to 35% oil of the black imide films is about the same as that of the commer.length (50.3 to 62% phthalic anhydride) give a comparison becial white standard alkyd. Table V gives the hardness of films tween the new imide-modified alkyds and standard alkyds. baked for 20 minutes a t 83 C., using the black and white enamels Table I lists pertinent data on these resins. Since the m&nner of of Table IV. Table VI presents the hardness readings of the same formulating alkyds seems to vary, and since terminology may be white enamels on air-drying. An air-dry test of short duration on easily confused, the actual amounts of reactants which were used the white imide enamel gave a hardness of 10 in 20 minutes and of 14 in 40 *minutes, with laboratory air of 28% relative humidity. in preparing the resins are given in the table. In formulating the resins in the table, the amounts of ingredients were calculated The same enamel without drier gave a hardness of 8 in 20 minutes and of 10 in 40 minutes; this indicates that the resin is quite hard 80 as to produce a desired amount of resin, usually 200 grams; 6% more glycerol, based on the weight of resin, was then added to and has fast solvent release. the ingredients. For example, if the reaction of the stoichioThese films show promise for automotive finishes and other uses where short-time, low-temper&ture baking schedules are demetric amounts of glycerol, phthalic anhydride, and fatty acids VES TABLEI. ALKYDDBRIVATI
OF
, PHTHALIMIDE GLYCERYL
+
+ + i?+
O
1306
Vol. 38, No. 12
I N D U S T R I A L AND E N G I N E E R I N G CHEMISTRY
TABLE111. FILMTESTS~, Low TEMPERATURE BAKES 35% S O , 10% G P 9.2
Acid No. Sward hardness Hotf Goldg Stored 2-3 days 0% r.h. 50% r.h. 100% r.h. Stored 7 days 0% r.h. 50% r.h. Stored 30 days 0% r.h. 50% r.h. Stored 42 days, 50y0 r.h Hrittleness index ColdQ Stored 2 days Stored 7 days Stored 42 days
9
30% SO 12% G P 14.3
30% SO, 20% G P 5 6
-
Ble;d
B
5.8
20% 8 0 , 15% 25%Adipio GP!
Blend Cd 6 4
Acid
5.6
Extn. Residue6 5.4
40 % LO 8
15
32
13
12 18
11 21
d 19
14 25
Tacky 8
20 15 13
25 22 15
47 35 18
22 16 12
27 24 19
36
31
16 12
42 37 26
24 22 10
32
36
56
38
37
+ri
46
26
51
51
40
44 ’ 13
10.1
’
14
10
32 27 17
Blend Ab 9.0
..
..
46
, .
53
-
+++
63
-
I+
30
‘LO
63
..
..
54
60 60
52
++
-
++
-
t
I
+t
34 36
+
-
All experimental alkyds contain 5y0 excess glycerol on basis of finished resin. All films baked 20 minutes a t 83’ C , wing 0.01% Co. basis solids. “4Y‘ glyceryl phthalimide” means 47* of the phthalic anhydride was replaced with an equivalent amount of glyceryl phthaliniida Average film thickness, ahout 1.1 mil. SO = soybean oil G P = glyceryl phthalimide, LO = linseed oil. b 5 parts 20% SO, 25% 6P, 5 parts commercial 40%.LO alkyd. 9 parts 3 0 7 SO, 20% GP, 1 part commercial,40% LO alkyd. d 7 parts 2 5 d SO, 10.7% G P , 3 parts commercial 40% LO alkyd Residue from alcoholic extraction of a 40% SO length alkyd I Hardness taken immediately after removal from the oven 0 Hardness taken when films had rooled to room temperature a
eired. Melamine-alkyd blends, vhich have been used where exceptionally hard films are required, were found to be tacky when removed from the oven after the 83 C. baking schedule. With the increasing emphasis on faster drying and lower baking temperatures, the imide-modified alkyds may open up new fields for alkyds and maintain others under the more stringent specifications being set up by users. The imide-modified alkyds of low oil content are almost equal in film hardness to the extraction residues mentioned previously and are easier to produce. The imide-modified resins contain alcohol-soluble material, hut this problem has not yet been thoroughly investigated. The brittleness test used in evaluating the films comprised bending the tin plat’e and film over a */8-inchmandrel within a period of 2 seconds. Any sign of a pattern a t the bend, as seen through a 6 X magnifying glass, was taken as an indication of brittleness, and is reported as a brittleness index in the t,able. Since this is a rather drastic test, it is probable that some of the resins which have been termed “brittle” would not show tha.t characteristic in other types of tests. For practical purposes the flexibility appears to be satisfactory except in the very short oil Lengths. The tendency to brittleness is reduced without serious loss in hardness by replacing part of the phthalic anhydride with adipic acid or by blending brittle with nonbrittle resins (Table 111). The latter method is not of universal application, since some of the shorter oil imide-modified resins are incompatible with medium oil alkyds which are suitable plasticizers. Sebacic acid has about the same effect as adipic acid in reducing brittleness. Although most of the resins in this study were made with fatty acids rather than triglycerides because of convenience, it was found that both sources of fatty acid modifier can give satisfactory imide-modified alkyds. The oil can be alcoholized with glycerylamine, after which the other ingredients can be added in the usual manner, but these resins tend to be dark. Also, after alcoholysis with glycerol, the phthalic anhydride, glycerylamine, and glycerol can be added, although the amine must be added t o the hot mixture, with care. Another procedure is to alcoholize with glycerol according t o standard practice, and then add the alcoholized mixture t o the glyceryl phthalimide, phthalic anhydride, and glycerol. Imide-modified alkyds modified with linseed fatty acids were prepared from linseed oil as well as from linseed acids. These O
+
I
resinb were riot very different from those modified with soybeail fatty acids. The use of aliphatic dibasic acids, such as adipic and sebacic, iu place of part of the phthalic anhydride has already been men. tioned, and the plasticizing effect of such substitution was noted The use of maleic and fumaric acids was studied briefly. T h e nat,ure of the products indicates that side reactions take place, tind this 13-orkwill require more extensive investigation. The color of the imide resins is of the same order of niagnitude a5 that of regular alkyds. As might be expected, the solubilitj decreases with decreasing oil content, so that 25 and 30% oil resins require aromatic solvents, and 20% oil resins require esters Glyceryl succinimide, which can be prepared from equimolar quantities of succinic acid and glycerylamine, was found to be substantially equivalent’ to glyceryl phthalimide in imide-modified alkyds. Table VI1 gives data on a typical glyceryl succinimide resin. The characteristics of the imide-modified alkyds are such that it, may be possible t,o adapt them to uses for which ordinary alkyds
TABLEIV.
SWARDHARDNESS VALUESOF ENAMELS BAKEDAT HIGHTEMPERATURE^
-
White enamels (vehicle: Ti02 1: 1) 30% spyhean imide alkyd, acid No. 10 42% linseed corn. alkyd, acid No. 8 Unpigmented alkyds, Above 3 0 7 oil imide alkyd Above 4 2 g oil alkyd Black enamels ( 3 7 carbon black) Abo*e 30% oil h i d e alkyd Above 42% oil alkyd Q
R.H.
47 35
22
40 15
54 19
47 11
38 4
26 12
25 10
20
50% 46
7
1 hour a t 150’ C., no drier.
TABLE
V. SWARD HARDNESSO F ENAMELS BAKED
White enamels 30% soybean imide alkyd 42% linseed com. alkyd Black enamels 30% soybean imide alkyd 42% linseed com. alkyd a
1 $ 0 2
0% R.H.
TEMPERATTRE~ Hot
Cold
16 Tacky
22
4
Taoky
20 minutes a t 83’ C . , no drier.
IJOV
After 24-Hr. Storage a t 0% 50% 100% r.h. r.h. 1 h
16
33 1 18
Tacky
4
6
AT
2
14
16 6 11
4
2
27
8
INDUSTRIAL AND ENGINEERING CHEMISTRY
December, 1946
SWARDHARDNESS VALUESOF AIR-DRIEDWHITE
TABLEVI.
ENAMELS
(0.65% Pb, 0.05% Mn, 0.02% Co drier, based on resin solids) 50% R.H. 100% R.H. Air0% R.H. 30% oil 42% oil 3’0% oil 42% oil Drying 30% oil 42% oil Time
imide eom. alkyd
24 33
8 16
imide
oom. alkyd
imide oom. alkyd
16 23
TABLE VII. DATAON A GLYCERYL SUCCINIMIDE RESIN OF 30% OIL LENGTH
Succinimide Phthalimide a
13.2 13.2
16 11.1
70.2 76.2
56 54
64 47
38 38
Baked 1 hour a t 150’ C.
are entirely unsuited. For example, imide resins of very low acid and hydroxyl numbers and as little as zero oil content can be made and are of potential usefulness in the plastics industry, since they are initially rather high melting and give off only negligible amounts of water on further heating and polymerization. Imidemodified alkyds might also be useful in heat sealing compositions because of their satisfactory melting point range, toughness, good adherence, and flexibility in proper oil length. These are also possible subjects for further research. The reaction of glycerylamine with rosin gives an ester amide which melts a t a substantially higher temperature than does ester gum, and which might therefore be expected to find use in varnishes and other surface coating materials. DISCUSSION
In an effort to explain the findings reported and to predict results of using other irregular ingredients of alkyd resins, a theory and method of calculation were devised. It is assumed that alkyd polymerization in the kettle is predominantly linear, and that the effective functionality of all polymerizing constituents may be considered as two in the finished resin. For example, glycerol, which is trifunctional, uses only two of its reactive groups in polymer formation during the resin cooking procedure. Taking the standard glycerol-phthalic anhydride-fatty acid alkyd as an example, it is seen that glycerol is the only ingredient having a functionality greater than two. There are three methods by which the functionality of the glycerol is reduced t o two so that the resin is substantially a linear polymer: 1. Fatty acids in combination with glycerol reduce its functionality to two or even to one by the formation of mono- or diglycerides. 2. I n a simihr way, phthalic anhydride which reacts only partially with glycerol reduces the functionality of glycerol. This t pe of action leaves unreacted carboxyl groups, which are identiled with the acid number of the resin.
1307
3. Excess hydroxyl groups in an alkyd constitute the third method of reducing the functionality of glycerol. If there is for exam le, one mole equivalent of “free glycerol” in a resin there are tgree equivalents of free hydroxyl groups. This “excess glycerol” is not present as such but is probably made up of one free hydroxyl group from eacbof three glycerol residues. A glycerol residue containing one free and two combined hydroxyl groups can form only linear molecules. Therefore one mole equivalent of “free glycerol” in a resin will render three moles of glycerol direactive. This method of reducing the functionality of glycerol, which means controlling the gelation of alkyds in the kettle, is one of the most important and can be easily expressed in terms of the hydroxyl number of the resin. Examples of the control of the functionality of glycerol by varying the amount of excess glycerol in a resin are given in Table VIII.
It is assumed that the only reaction occurring in the+resin kettle, except possible amide interchange, is esterification. This is believed to be substantially true except with highly unsaturated fatty acids. The results obtained by the use of hydroxyimides can probably be explained on the basis that these compounds, being mono- or dihydroxy materials containing no other acid-reactive grouping, control or prevent gelation because, in replacing part of the glycerol, they prevent or reduce cross linking; yet they do not reduce the hardness of the resins as do slmple mono- and dihydric alcohols. It was found that any glyceryl phthalate resin of a given oil content, no matter whether it is a regular alkyd or an imide alkyd, tends to have a fixed hardness corresponding to that oil length. APPLICATION OF THEORY
A method of calculating the formulation of regular or imidemodified alkyds was devised which allows the prediction of the acid number of the finished products. Given the fatty acid and excess hydroxyl content of the alkyd, the calculation directs the preparation of an imide-modified resin by showing the percentage of phthalic anhydride which must be replaced by a phthalimide to effect the desired acid number. All resins were cooked to a cure time of about 20 seconds on a hot plate a t 200” C. Since methods of calculating the formulas of regular alkyds are not standarieed, the calculation procedure will be carried through from the beginning. Repeated checks of the method on laboratory batches of resin resulted in remarkably close agreement of theory and practice. The procedure assumes no loss of phthalic anhydride or other ingredients from the kettle during cooking. In the following paragraphs the identity of CALCULATIONS. numbers otherwise unidentified is as follows: 92 280 56,108 221
df glycerol av. mol. wt. of soybean oil fatty acids mg. per mole KOH = mol. wt. of glyceryl phthalimide = mol. wt.
= =
% oil (oil length)
= 100
% alcohol phthalate
- % alcohol phthalate
=
(
wt. phthalate % phthalic anhydride x mol. mol. wt. phthalic anhydride
For glycerol: TABLEVIII. DATAON 30% OIL LENGTHRESINS Excess Glycerol, %
Acid NO.
0% r.h.
62
Sward Hardness‘ 60% r.h. 100% r.h.
48
Baked 1 hour a t 160” C., no drier. Imide resin, 34.6% phthalic anhydride substituted by glyceryl phthslimide. a b
yo alcohol phthalate
=
yo phthalic anhydride
X 1.29
To make A grams of resin containing B% excess alcohol, based on the weight of the finished product, the calculation is made as follows:
Grams phthalic anhydride = % phthalic anhydride 100
x
Grams fatty acid = % oil X A X % fatty acid in oil 10,000
A
I N D U S T R I A L A N D E N G I N E E R I N G CHEMISTRY
1308
% ' fatty acid in oil
=
95.7 for glycerol
[If oil is used to make resin, then (% oil X A)/100 is used.] Grams alcohol =
mg. KOH equivrtlent to acid groups hydroxyl number of alcohol
+ ( A x .B)
To predict the acid number of a resin from its formula, the assumptions regarding the substantially linear structure of alkyds and the methods by which glycerol is rendered difunctional are carried out as follows (specific examples will be given in order to clarify the explanation): An alkyd of 40% oil length containing the equivalent of 570 excess glycerol based on the entire resin was made from the following ingredients: 7 6 . 5 grams soybean fatty acids, 93.0 grams D h t h a lie anhydride, and 57.2 grams glycerol; the weight of finished resin was 210 grams. T h e f a t t y acids would render (76.5 X 92)/280 = 25 grams
Vol. 38, No. 12
formula actually to deduct 4/3 X 8.8 = 11.7 grams glycerCJl in order to maintain approximately the same hydroxyl number. The formula for the new batch of predicted acid number 10 would then be: 57.4 grams soybean fatty acids, 94.2 grams phthalic anhydride, 49.4 grams glycerol, and 21.2 grams glyceryl phthalimide. (Using the factors given previously, it is found that 21.2 grams glyceryl phthalimide are formed from 21.2 X 0.412 = 5.7 grams glycerylamine and 21.2 X 0.670 = 14.2 grams phthalic anhydride.) In an experimental batch using this formula, the acid number obtained was 11.6. Additional examples of the correlation betmen predicted a i d observed acid numbers using the method of calculation described are given in Table I as acid number, calculated. Finished batchcof resin in all cases weighed 210 grams. The calculations v m e made according to the follo.iringformulas:
(a) For resins not modified with glyceryl phthalimidc: Wt.
Bcid S o .
=
=
glyc. -
acids X mol. wt,. [wt. fatty mol. wt.fatty acids
glyc.
mol. mt. glycerol 2.91 [wt. glycerol
+- 3 x rn t. exccss glyc.
x wt. finished resin
1
mg. KOH pri molt
- (0.329 X wt. fatty acids) + 301
( b ) For resins modified with glyceryl phthalimide:
__
10 X 3 = 30 grams = calcd. acid ?To. of unmodified resin - (1.21 x wt. glyceryl phthalimide used) glycerol d i r e a c t ive. This leaves 57.2 (25 30) = 2.2 grams trireactive glycerol, which must be made The method of calculation and the theory outlined can rcadiljdireactive by forming a half-ester of phthalic anhydride; this will be adapted to types of alkyds other than those specifically menleave an equivalent amount of free acid groups, which will be tioned, as well as to alkyds made from ingredients and by prowresponsible for the acid number of the resin. In this case, the dures different from those specified in the examples. predicted acid number is (2.2 X 56,105)/(92 X 210) = 6.4. In an In theory at least there is no reason why a great many resins of' experimental batch using this formula, the acid number obtained improved properties cannot be made by the use of modifying was 10.5. materials quite different from those described, as long as they conThe following example shows how to calculate the amount of form to the general principle of reduction in functionality ~ r i t h glycerylphthalimidenecessary to reduce the acid number of a 30y0 little or no loss in hardness. For example, it is conceivable t'hat oil glyceryl phthalate alkyd to the desired value. Although it was certain high melt,ing monobasic acids, polyhydroxy ethers, monofound convenient to calculate the addition of glycerylamine as or dihydric alcohols, or hydroxyamino or -amido derivatives of glyceryl phthalimide, it may in some cases be desirable to add the polybasic acids could give results as good as those described for amine directly. In converting the following data to the latter polyhydroxyamino compounds. Use of the principle described i i i basis, the factor for glyceryl phthalimide to glycerylamine is this paper might also make possible the preparat,ion of alkyds dc0.412, and to phthalic anhydride, 0.670. rived from fatty materials ordinarily difficult to handle, such a i A 30$& oil alkyd containing 57, excess glycerol on the basis of bodied or blown oils and tung oil. the finished resin mas made from the following ingredients:
+
-
57.4 grams soybean fatty acids, 105.4 grams phthalic anhydride, and 61.1 grams glycerol; the weight of finished resin was 210 grams. The fatty acids would render (57.4 X 92)/250 = 15.9 grams glycerol direactive, The 10 grams excess glycerol would render 10 x 3 = 30 grams glycerol direactive. This leaves 61.1 - (15.9 30) = 12.2 grams trireactive glycerol, which must be made direactive by forming a half-ester of phthalic anhydride. The predicted acid number of this resin is (12.2 X 56,105)/(92 X 210) = 35.5. In an experimental batch using this formula, the acid number obtained was 32.7. If it is desired to reduce the acid number of this formula to 10 by replacing part of the phthalic anhydride with glyceryl phthalimide, the formula is revised in accordance with the following calculation: An acid number of 10 would allow the presence of (92 X 10 X 210)/56,105 = 3.4 grams trireactive glycerol. Therefore, in the above formula 12.2 3.4 = 8.5grams glycerol must be replaced with (221 X 5.5)/92 = 21.2 grams glyceryl phthalimide, which in turn would replace (21.2 x 148)/221 = 14.2 grams phthalic anhydride. Since the 8.8 grams of trireactive glycerol are being replaced with tetrareactive glycerylamine, it is necessary in calculating the new
+
-
ACKh-OWLEDGIIENT
The authors wish to acknowledge the assistance of Pauline. Stein, Vella King, and Thomas Kucera in various phases of thc experimental work, and of C. S. Miner, Jr., in the preparation of the manuscript. This research is part of a program sponsored by the Glycerine Producers' Association. LITERATURE CITED
(1) C l a r k , R. H., a n d W a g n e r , E. C., J . Org. Chem., 9, 55 (1944). ( 2 ) Goedeckemeyer, Ber., 21, 2689 (1S88). (3) Sachs, Ibid., 31, 1228 (1898). (4) S p r u n g , M. AI., J. Am. Chem. SOC.,61, 3381 (1939). ( 5 ) Vanaas, G., Acta Univ. Latuienais, Kim. Fakultat., Ser. 4 , N o . 6 . 405-22 (1939). ( 6 ) Vanags, G., a n d Veinbergs, A,, Ber., 75B,1558 (1942). (7) Wright, H. J., a n d D u Puis, R. N., IND. ENC.CHEM.,36, 1004 (1944).
PRESENTED before t h e Division of Paint, Varnish, and Plastics Chemistry a t t h e 109th Meeting of the A V E R I C .CHEMICAL ~ SOCIETY,Atlantic CitS, N. J.
