April, 1945
INDUSTRIAL AND ENGINEERING CHEMISTRY
a light yellow oil, the major portion of which distilled a t 198-205' and 1.0 mm. (Wood's metal bath a t 233-236" C.). This oil darkened slightly on standing to a reddish orange color. 24fraction boiling constantly a t 205' a t 1.0 mm. (Wood's metal bath a t 233-236' C.) was taken for analysis: CALCD. FOR CirHsrO (ANACARDDL) CALOD. FOR Cz1Hs.r0 Mol. wt. 300.5 Mol..wt. 302.6 Cis side chain with 2 double CISside chain with 1 double bonds bond C, 83.94 C. 83.37 H, 10.76 ' H.11.34 tt2g.p 1.5070
399
tions from petroleum ether, the melting point of the pure white crystals remained constant a t 51.0-51.5' C. The yield was 21.5 grams. CALCULATED FOR CziHaaO: C, 82.80; H, 11.95. FOUND: C, 82.74; H, 11.98.
FOUND
Mixtures of these crystals with varying proportions of pure 3-pentadecylphenol (11) obtained as previously described from the raw commercial shell liquid melted a t 51.0-51.5' C. with no C, 83.32 H, 11.23 depression. ...... ...... OXIDATION OF DIHYDRO-CARDANOL (11) A N D ISOLATION OB PALMITIC ACID. To verify further the identity of dihydroDIHYDRO-CARDANOL (11) OR TETRAHYDROANACARDOL. The Cardanol as 3-pentadecylphenol, the length of the side chain of presence of one double bond in the fifteen-carbon side chain dihydro-Cardanol was established by the method used with the (VI) from Cardanol was of the above purified monophenol 3-pentadecylphenol that was obtained from the raw commercial verified by quantitative hydrogenation; 1.688 grams of (VI) in shell liquid. Oxidation of the dihydro-Cardanol with permanga60 cc. of ethanol were reduced with hydrogen a t 30' C. and 763 nate in acetone yielded a white crystalline product which, after mm. pressure, using 0.3 gram of palladium on carbon as a catalyst. three recrystallizations from ethanol, melted a t 61.5-62.0' C. A total volume of 161.4 cc. of hydrogenwas absorbed. The theoJust as in the former case, mixtures of these crystals with varying retical absorption for this amount of the phenol, based on one proportions of pure palmitic acid (melting point 61.5-62 5") double bond in the side chain, is 140.5 cc. Thus a n equivalent melted constantly a t 61.0-62.0' C. of 1.15 double bonds was indicated in the purified phenol (VI). To prepare a larger amount of the dihydro-Cardanol for preLITERATURE CITED parative purposes, 100 grams of (VI) dissolved in 160 cc. of ethanol were reduced under a pressure of 2 atmospheres of hydrogen, (1) Backer and Haaok, Rec. trav. chim., 60, 661-77 (1941). using 2.0 grams of palladium on carbon as catalyst. After the (2) Furukawa, Sci. Papers Inst. Phgs. Chern. Research (Tokyo), 24, 304 (1934). absorption of hydrogen had ceased with an uptake of 1.1 equiva(3) Harvey and Caplan, IND.ENQ.CHEM.,32, 1306 (1940). lents, an additional gram of catalyst was added but no more (4) Organic Syntheses, Coll. Vol. 11, 619 (1943). hydrogen was absorbed. After filtering off the catalyst, the (5) Patel, J . I n d i a n Inst. Sci., 5, 152 (1922). solvent was removed by distillation and the residue was vacuum(6) Perkin and Weismann, J. Chem. SOC.,89, 1649 (1906). (7) Smit, Proc. Acad. 8 c i . Amsterdam, 34, 165 (1931). distilled a t 1.0 mm. in a 250-cc. flask equipped with an electrically (8) Stiideler, Ann., 63, 137-64 (1847). heated Vigreux column. The fraction taken a t 202.5-205.0' (Wood's metal bath a t 232.4' C.) solidified on cooling to yield a THISstudy was made possible by a grant from the Irvington Varnish and light yellow solid melting a t 47-48" C. After four recrystallizaInsulator Company.
...... ......
Red Lead-Alkyd Resin Reactions J
A. J. EICKHOFF, L. M. KEBRICH, AND J. GEORGE WILLS National Lead Company Research Laboratories, 105 York Street, Brooklyn, N . Y
ED lead-alkyd resin paints have been used for the protection of structural iron and steel for approximately fifteen years. Many specifications (7, I S , 14, 16) have been written to cover paints of this type. Red lead is a pigment of basic character. It is known that all basic pigments react to some degree with oleoresinous vehicles. The presence of limited amounts of reaction compounds formed from red lead and oleoresinous vehicles has been found to impart beneficial properties to the paint film. This investigation concerps the factors influencing the reaction between red lead and alkyd (phthalic) resin vehicles. In order to study these factors, the following points were considered: variations in degree of reactivity of red leads of varying true red lead (PbaOd) content; effect of time and temperature on the formation of these reaction compounds; degree of reaction between red lead and the alkyd resin vehicles; solubility of the reaction compounds in the vehicle. Analytical methods for determining phthalates in such paint systems presented a problem; therefore special attention wm given to the methods involved. The important steps in determining phthalic reaction products are the centrifugal separation of the pigment from the vehicle and the determination of the phthalic anhydride content of the pigment and vehicle portions. The extent to which reaction products formed wm determined
by analysis of pigments and vehicles extracted from paints of known composition and history. Several methods have been described for the quantitative determination of phthalic anhydride in alkyd resin varnishes. The two in general use are the Kappelmeier (3) and the U. S. Navy method (8), which were discussed by Sanderson (9). The Kappelmeier method has been modified (6, 6), but the original method (3) was used in this investigation for the analysis of extracted vehicles. It was necessary to determine the volatile portion since the phthalic anhydride in the vehicle should be reported on the solids basis. Here, again, various methods were used. They include the A.S.T.M. standard method (f), a vacuum method (IO),and a method using castor oil (4). The determination of the phthalate in the pigment portion presented a still different problem. The Kappelmeier (3) and Navy (8) methods were modified by the authors; the Kappelmeier modified method wm found to be more satisfactory. A qualitative method for phthalic anhydride in extracted pigments has been reported (18). Reference has been made to the reaction between red lead and alkyd resin vehicles (11). No quantitative method for determining phthalate was given. For simplicity, paints were made according to the formulation given under "Experimental Work". Six samples of each
'
400
Vol. 37, No, 4
INDUSTRIAL AND ENGINEERING CHEMISTRY Red lead-alkyd resin paints have come to be widely used for protecting steel from corrosion. Red lead is known to be reactive with drying oils and the older types of oleoresinous vehicles, but the reaction between red lead and the alkyd resin vehicle in these paints has not been thoroughly studied. In this investigation the degree of reaction, the effects of varying true red lead (Pb304) content of the pigment, time, temperature, and moisture, a s well as the solubility of the reaction products in the vehicle were considered. Various grades of red lead were made into paints with a linseed-oil-modified glycerol phthalate vehicle. A portion of each paint was centrifuged at varying time intervals, and the separated pigment and vehicle were analyzed. Physical tests were made on some of the paints as well as a study of the reactions of red lead and phthalic acid in an aqueous medium. This investigation indicates that: (a) The true red lead (Pb304) portion of the pigment does not react with the alkyd resin, while ( b ) the free PbO portion reacts with the free fatty acids present in the vehicle, and (c) on aging paints made with 977” Pb304 grade red lead, they do not change in film flexibility. A quantitative method for phthalates is given.
paint were stored in suitable airtight containers. Freshly opened samples were therefore used a t TTarious time intervals, so that the effect of time and storage on the reaction could be studied. I n the first stages of the investigation, each sample was extracted with four portions of hot benzene and centrifuged. The clear vehicle portions from the extractions were combined, t’he volatile matter.driven off, and the residue analyzed. This method was abandoned as being inaccurate; instead, the paint itself was centrifuged. The pigment was extracted to remove residual vehicle and air-dried. The pigment portion was analyzed for phthalic anhydride and examined petrographically for lead phthalate. Two analytical methods for phthalic anhydride were tried on the pigment portion. The Navy method (8) was employed first, and the results obtained on samples extracted from the paints and on known mixtures of red lead and potassium acid phthalates, are shown in Table I. I n all tables portions A and B are duplicate parts of the same sample. The modification of the n’avy method was discarded, and the following revised Kappelmeier method was used: A weighed amount of the extracted pigment, varying from 1 t o 8 grams, was treated in a 250-ml. glass-stoppered soil digestion flask with 150 ml. of 0.5 N anhydrous alcoholic potassium hydroxide. An aircooled condenser was attached, and the mixture was refluxed for 3-4 hours on a steam bath with intermittent agitat’ion. After refluxing, t’he samples were allowed to cool, and the condenser was washed with absolute ether. The red lead containing precipitated potassium phthalate was filtered on a fritted-glass Gooch crucible, washed with a 50-50 mixture of absolute ether and absolute alcohol, and dried a t 60” C. for 10 minutes. The crucibles were allowed t o stand overnight in an evacuated sulfuric acid desiccator and weighed the next morning. The red lead and potassium phthalate on the crucibles were washed thoroughly with distilled water, dried a t 105” C., and then reweighed. The difference in weight represented potassium phthalate containing one molecule of alcohol of crystallization and was calculated t o per cent phthalic anhydride. A determination for lead was made on the filtrate from the water washings to aicert,ain whether any water-soluble lead products were washed
out. KO trace of lead was found. The accuracy of the method was checked by analyzing mixtures containing known amounts of lead phthalate and red lead. The results obtained with such mixtures containing 0.3 to 34% phthalic anhydride are shown in Table 11. The extracted pigments were analyzed for true red lead content as follows: A one-gram sample of the dry pigment was wet with a small amount of ethanol and distilled water, and the “red lead solution” of sodium acetate, potassium iodide, and acetic acid was added. The free iodine was then titrated with standard sodium thiosulfate, using starch solution as indicator. The presence of phthalate was found to interfere slightly with the end point of the red lead titration. Therefore, true red lead was subsequently determined on the residue from which the phthalate had been removed by washing in the phthalic anhydride determination. Total lead content of the extracted vehicles was also determined. MATERIALS USED. The pigments were three red leads varying in true red lead content as follows: 85% grade, 92% grade, and 97% grade. I n addition, two experimental pigments were prepared from the 97% grade. The free litharge had been removed from one pigment by treatment with acetic acid, and the second was treated with phthalic acid to convert the free litharge to lead phthalate. This was done to determine the effect of any free PbO. The alkyd resin solution contained 50.1% mineral spirits and 49.9% resin. The nonvolatile vehicle was a linseed-oil-modified glyceryl phthalate resin, analyzing 34.5% phthalic anhydride and having an acid number of 6.5. The volatile thinner for the paints was high-solvency petroleum spirits. This was used also wherever a thinner was needed in the subsequent centrifuging. The drier in the red lead paints was a cobalt naphthenate solution (6% cobalt). The extraction mixture (4) was composed of 10 volumes ethyl ether, 6 volumes benzene, 4 volumes methanol, and 1 volume acetone. EXPERIMER-TAL WORK
The red lead paints were made according t o the following formulation: Pigment 68% Red lead
Vehicle 32% Alkyd resin solution 79.2% Volatile thinner 19 8 Cobalt naphthenate (6% Co)O 1 . 0
I n the paints containing the two treated pigments the drier ooneiated
of 0.4% cobalt naphthenate (6% Co) and 1.43% lead naphthenate (24% Pb).
The paints were mixed in a laboratory mixer and given one pass over a three-roll laboratory mill (0.002-inch clearance). They
ANHYDRIDEEXTRACTED FROM TABLE I. PER CENTPHTHALIC PIGMEXTS BY NAVY METHOD Sample No. Portion A Portion B Known Mixt. No. Calod. Found
1 1.84 3.76
2 3.04 2.76 2 3.60 2.94
1 3.60 2.54
3 2.05 1.86 3 0.80 0 93
4 3.52 2 07
TABLE 11.
P E R CEXT PHTHALIC ANHYDRIDE EXTRACTED FROM PIGUENTS BT hfODIFIED XAPPELMEIER I I E T H O D
Sample No. Portion A Portion B Known Mixt No. Portion .4 Portion B Calcd.
5 1 39 1.38 5 1.66 1.69 1.4
6
7
0 30 0 32
0 27 0 30 6
34.03
34.17 33,87
8 1 43 1 49 7 19.61 19.63 19.0
9 0 33 0 33 8 30.12 30.95 30.18
10 0 61 0 57
INDUSTRIAL AND ENGINEERING CHEMISTRY
April, 1945
401
the third portion was intimately mixed with 1% of its weight of water and allowed to stand for 3 weeks a t room temperature. The three portions were then analyzed with the results shown in Table VIII. It was decided that an investigation of the reactions of red lead and phthalic acid in an aqueous medium as well as in paint would give a more complete picture. A 97% grade red lead was treated, in water, with varying amounts of powdered phthalic anhydride. The solid residues were washed thoroughly, dried a t 80' C., and analyzed for total lead monoxide (PbO), lead dioxide (PbOt), and phthalic anhydride. From the analytical data the compositions of the residues were computed in terms of unchanged red lead, n-lead phthalate, and free lead dioxide. The results are shown in Table IX. The product from experiment 1 had about the same color as EXTRACTED the original red lead. The products obtained in the other three experiments were dark brown, due to the presence of free lead % Phth,alic dioxide. The products of experiments 2 to 4 also had a lustrous Anhydridea sheen imparted by free n-lead phthalate. It follows from these C D data that true red lead, in contrast to its behavior in alkyd resin 29.63 28.96 36.17 36.55 vehicles, reacts in water containing appreciable amounts of free 32.07 32.01 phthalic acid. The results of these experiments lead to the belief that the following reactions take place:
were put in 4-ounce glass containers, filled to the top, tightly sealed, and stored a t room temperature until analyzed. At the time of analysis, the samples were thoroughly mixed and two 50-gram portions were centrifuged. The clear vehicles from the two portions were combined for analysis. The pigment was extracted with five 50-ml. portions of the extraction mixture and air-dried overnight. I n determining the phthalic anhydride in the vehicles, the per cent volatile was determined by two different methods (Table 111). The phthalic anhydride in the vehicle was run by the Kappelmeier method (Table IV). The anhydride and the true red lead in the pigment were determined as previously described.
TABLE111. PHTHALIC ANHYDRIDE CONTENTOF VEHICLES ON SOLIDS BASIS
(8a%%% Method) Portion Sample 1 Sample 2 Sample 3
o/ Volatilea
(&hg$l
% Phthalic Anhydride A B
A B 70.12 70.01 34.21 34.04 72.91 72.63 37.49 37.32 77.79 78.01 3 4 . 5 0 34.61
C
D
7 1 . 7 1 71.77 67.60 67.83 61.64 61.66
(A.S.T.M. Method)
(A.S.T.M. Method) Sample 4 7 1 . 4 8 7 1 . 0 8 3 4 . 0 8 Sample 5 6 6 . 7 1 .. 3 6 . 2 8 Sample 6 $ 0 . 0 9 .. 3 3 . 1 6 Portions C and D are duplicates
..
34.13 70.90 71.98 36.03 67.51 61.41 32.76 79.86 8 0 . 5 9 of the same sample.
PbsO4
H20 + 2CsHa(COOH)2-+ PbO2 + 2PbCJIHl(COO)z + 2H20
(1)
TABLEIV. PER CBNT PHTHALIC ANHYDRIDEIN EXTRACTED VEHICLE8 BY KAPPELMEIER METHOD
First tests PortionA PortionB Repeat teats PortionA PortionB
Calod. Amount
Sample 7
Sample
Sample
30.64 30.48
8 24.77 24.31
34.5 34.5
28.44 28.30
34.5 34.5
31.06 31.49
.30.37 29.98
9
,
Sample 10 21.67 22.96
Sample 11 23.08 23.99
31.47 33.32
The first series of paints included the phthalic-acid-treated red lead, the acetic-acid-treated red lead, and commercial 97% grade red lead, aged a t various intervals (Table V). Film flexibility tests were also conducted. Films of uniform thickness were spread with a doctor blade on l/sz-inch rolled steel, immediately baked a t 160" F. for 6 hours, chilled in a mixture of ice and water, and bent over a conical mandrel (2). The results are shown in Table VI. A second set of paints was prepared with commercial grades of red lead. They were made, stored, and examined in the same way as those of the first series except for the time intervals. Results are shown in Table VII. On aging, the pigments in the paints settled with the clear vehicle above them. I n between these two portions a layer of white flocculent precipitate settled out. Although the precipitate seems very voluminous, i t is only a small percentage of the total paint by weight. To obtain more information on this precipitate, the clear supernatant vehicle was carefully removed, The white precipitate was then removed, mixed with benzene, and centrifuged. The precipitate which was insoluble in benzene waa dried and analyzed. Analysis showed 0.8% lead and 18% phthalic anhydride. The remainder was complex glycerides. A microscopic examination of this precipitate showed it to have B waxlike character. It was definitely not lead phthalate. A 31-month-old commercial sample of red lead-alkyd resin paint of similar composition was obtained. This sample was divided into three parts. The first part was analyzed, as received, to determine the extent of any reaction which might occur on long storage. The second portion was maintained a t 90' C. for 5 hours to ascertain the effect of temperature on any reaction which might occur. To evaluate the effect of water,
Reaction 1 may occur t o some extent a t room temperature. Reaction 2 takes place appreciably only at elevated temperatures. Gas evolved during reaction 2 was identified as oxygen. A small percentage of carbon dioxide, which was present in the original red lead as basic lead carbonate, was also evolved. DISCUSSION OF DATA
The phthalic anhydride in the extracted pigments of the 92 and 97% grades of red lead was low (0.45 to 0.55%) on the day made (Table VII) and showed no appreciable increase during 19-week storage. However, the 85% grade started with 1.47% phthalic anhydride and showed an increase t o 2.02% during the same period. The phthalate in the 85% grade pigment on the day made and in the 92 and 97% grade pigments after storage waa not lead phthalate but unextractable resinous material. This material is present in two forms: (a) vehicle retained by the pigment and
TABLE V. CHANGES IN COMPOSITION OF FIRST SERIES OF RED LEAD-ALKYD RESINPAINTS ON STORAGE original Age of Paint Samples Material 1 wk. 2 wk. 3 wk. 8 wk. Phthalic-acid-treated, '97% grade red lead % PbaOi in extd. pigment 97.3 96.7 96.7 95.7 9' pigment 68.0 68.6 67.b 68.2 67.9 P.A.O in nonvolatile vehiole 34.5 30.6 34.9 31.3 32.4 % P.A. in red lead ... 1.3 1.4 1.4 Acetic-acid-treated, 97% grade red lead Pbxoi in extd. pigment 99.4 99.3 98.7 98.0 pigment 68.0 67.4 66.'9 6 8 . 0 6 7 . 6 P.A.innonvolatilevehic1e 34.5 24.5 33.6 2 8 . 0 30.1 P.A. in red lead None ... 0 . 1 8 0 . 2 2 Untreated commercial 97% grade red lead PbaOd in extd. pigment 98.2 98.3 97.9 97.5 igment 68.3 68.1 68.'3 7 0 . 0 66.9 % g , A . in nonvolatile vehicle 34.5 28.4 33.6 32.4 27.6 % P.A. in red lead "one , , . 0.28 0.31 0 P.A. phthalic anhydride.
9
...
...
I
-
.
..
INDUSTRIAL AND ENGINEERING CHEMISTRY
402 T.4BLE
VI.
PER
CENT ELONGATION 4T CRACKING POINT P 4 I X T FILM
Red Lead ’ Pigment Phthalic-acid-treated Acetic-acid-treated Commercial 9770 grade
2 days 6 0 6 5 6 5
Age of Paint 3 dais 7 6.8 6 8 6 5
Sample dais 7 0 6 5 6.8
OF
23 5 uk.
7.0
6.2 7.0
TARLE 171. CHANGES I N COMPOSITION OF SECOND SERIESOF REDLEAD-ALKYD RESIS PAINTS ON STORAGE Original Material
Age of Paint Samples Same 2 wk. 8 ak. 19 M k . day
8570 grade red lead 85.5 e5.0
% PbaOa in extd. pigment 70 PbaOa in treated pigment. yo P.A.Q in red lead pig-
...
..
Sone 1.47 as P b in non..... 1.2 3,olatile vehicle 927, grade red lead [iPbsOain extd. Digmelit 92.1 92.1 % PbsOa in treatled pigment ..... .... 5% P . S , i n r e d l e a d p i g m e n t None 0.55 5 total lead as P h .i .n. n..nIn..volatil e vehicle 2.0 979’0 grade red lead % PbaOa in extd. pigment 98.9 98.2 % ’ PbsOd in treated pigment
7 ‘ total lead
~
.....
E5.9
...
87.6 93.3
1.30
1.46
5.2
...
89.5 95.4 2.02 17.5
92.8
93.3
.,.
0.39
96.4 0.37
Y7.0 0.51
3.3
...
8.2
97.5
98 0
98 3
..
95.0
until the major portion of the free PbO is formed into lead soaps. The appreciable increase in the percentage of phthalic anhydride in the extracted 85% Pb& pigment during 19-week storage, and the findings upon microscopic examination of the same pigment, provide the only evidence of the possible occurrence of the second reaction. However, even with high free-Pb0 (85To Pb304) red leads there is no conclusive evidence of the formation of lead phthalate, and the occurrence of the reaction under the test conditions is highly improbable. Table V substantiates the discussion of the data of Table VII. Table V refers to a duplicate 97% grade red lead paint; yet at 8 weeks the results are the same as those indicated in Table VII. The treated red leads, from which the free PbO has been removed, behave in the same manner as the commercial 97% grade red leads and shox no increase in phthalic anhydride contcnt. According to the data, the “per cent pigment” value is not sufficiently accurate to form the basis for any conclusions regarding the extent of reaction. The data which show a worthwhile picture arc the “per cent elongation” values (Tablc VI). K i t h 97% grade red lead paint there is no loss of flexibility, evcn after 23.5 weeks of storage. This indicates that changes in paint on storage do not adversely affect the flexibility of the paint film
TABLE VIII. EFFECTOF OS
Q
olatile vehicle P A . = phthalic anhydride.
.....
Vol. 37, No. 4
COl1POSITIOX
OF A
TIbfE, TEMPERATURE, AND MOISTURE COMMERCI.4L RED LEAD-ALKYD RESIN PAINT
034
not extractable for this reason and ( b ) the small amount, of white flocculent precipitate thrown down with the pigment,. The retention of resinous vehicle (a) seems to be a function of the litharge content of the pigments, as shown by the relatively high phthalic anhydride figure for the 85% red lead sample the same day the paint was made. The small amount of flocculent precipitate ( b ) forms as the paints age. This material is not lead phthalate. The analyses show that it contains only 0.8% lead and about 18% phthalic anhydride. The remainder consists of complex glycerides. During the separation of the pigment and vehicle by centrifuging, this flocculent precipitate is thrown down with the pigment portion. The amount of this precipitate formed is also a function of the litharge or free PbO content of the red lead. A theory advanced for the formation of this insoluble material is that, as the soluble lead soaps form in the vehicle, this product precipitates, as explained above. That the per cent phthalate in Table VI1 is unextractable material and not lead phthalate has been shown by microscopical examination of the pigments a t 1000 magnifications. Only on the Ig-week sample of 85% grade red lead was it possible to isolate any crystals which remotely resembled lead phthalate. The number of crystals found was fern and could not be positively identified as belonging to the family of known lead phthalates. On the other pigments none of these crystals could be detected a t 1000 magnifications. However, on all pigments identification was made of particles of red lead coated with dried resinous materials. Considering the entire system, the only possible reactions beh e e n pigment and vehicles are the formation of soluble lead soaps by free PbO with the fatty acids and other components of the vehicle, and the reaction of free PbO with the alkyd resin vehicle to form lead phthalate. The first of these two possible reactions is substantiated by a chemical examination of the paints. The second reaction does not take place in paints of low free-PbO content. The data from this investigation make its occurrence appear improbable even in red leads of high PbO content, in the absence of water. The total lead content of the extracted vehicle is sufficient eridence of the occurrence of the first reaction, which proceeds
Paint 1. -4fter 31 mo. in container 2. Same as 1, refluxed 5 hr. a t 90’ L.
3.
Same as 1, with
17@ Hg0 added
TABLEIx.
Expt. No. 1 2 3 4
P 4. /n R@xt,d: in Pigment
% Pb304 Extd. Pigment
% PbsOa in
7a Total P b in
0 37
97.5
98.8
...
0 56
97.3
98.6
0 54
97 2
99.0
DATA ON
Reactants, Phthalic anhydride 1.42 22.3 43.5 64.7
Treated Pigment
Grains” Water 200 600
600 600
Sonvolatile Vehicle
I
.
AQCEOVS RED LEAD-PHTHALIC SYSTEMS Heating Time, hr. 48 3 3 3
Compn.
Temp.,
C.
80 85 85 95
Pb804 95.5 42.0 6.6 0.0
.
2.7
of
ACID
Residue?
Lead phthalate 4.3 48.0 76.5 85.0
Te
PhOl 0 00 10 0 16.9 15.0
100 grams of red lead in each experiment.
Table VI11 is a compilation of results on a commercial paint sample which was almost three years old. Even after storage for this length of time the phthalic anhydride content of the pigment has not increased beyond the amount shown by the laboratory-prepared 97% grade red lead paint the day it was made. Together with the other data, this shows that in 97y0 grade red lead paint no lead phthalate is formed during storage. Other data in Table VI11 indicate the effect of heat and moisture on the reaction. Even a t elevated temperatures and with moisture present in the paint, the reaction to form lead phthalate does not take place with the true red lead. Tables I and I1 compare the Navy and the modified Kappelmeier methods of analysis. By the Navy method, duplicate samples of the same pigment do not check. With the Kappelmeier method, duplicate samples gave checks within a few hundredths per cent. The range of amounts of phthalic anhydride which can be determined accurately by the modified Ilappelmeier method varies from 0.3 to 35%. The data of Tables I11 and IV show the difficulties that arise in an attempt to determine the phthalic anhydride in an extracted vehicle. The Kappelmeier method is precise in that check results on duplicate determinations are easily obtained.
April, 1945
INDUSTRIAL AND ENGINEERING CHEMISTRY
The difficulty lies in the determination of volatile and the subsequent translation of the phthalic anhydride values to a nonvolatile basis. Various methods of test for percentage of volatile were tried, but they were not sufficiently accurate to use as the basis for determination of the phthalic anhydride content of the extracted vehicle solids. On a straight alkyd resin varnish, which had not been made into a paint and to which no drier had been added, two different operators, working some 5 months apart, obtained the same value for the phthalic anhydride content. With the methods of analysis now available, no definite conclusion can be drawn from the change in the phthalic anhydride content of the extracted vehicle. In other words, a change of a few tenths per cent in the phthalate content of the extracted vehicle cannot be determined, and therefore a study of the vehicle does not show the possible formation of lead phthalate or other phthalate reaction products. CONCLUSIONS
1. No reaction takes place between true red lead (PbsOJ and
alkyd resin. Reaction takes place only between the free litharge (PbO) and the alkyd resin vehicle. Red lead pigments containing 92% or more PbaO*do not react with alkyd resin vehicles to form lead phthalate. The evidence of formation of lead phthalate in the case of red lead of 85% true red lead content is not conclusive. 2. The phthalate found in the extracted red lead pigments was present as unextracted alkyd resin retained on the pigment. 3. After long storage, red lead-alkyd resin paints, in which the pigment is 97% true red lead, show no change in'paint film flexibility.
403
4. The phthalate content of the vehicle extracted from red lead paints cannot be determined accurately with present methods of analysis. 5. The method established for determining the phthalate content of the extracted pigment, as set forth, is quantitative and reliable. ACKNOWLEDGMENT
The authors desire to acknowledge the assistance of the staff of the National Lead Company Research Laboratories for many suggestions which materially contributed to the work reported in this paper. LITERATURE CITED
(1) Am. Soc. for Testing Materials, Standards, Part 11, D154-38, p890 (1942). (2) Ibid., Part 11,D522-41, p, 938 (1942). (3) Ibid., Part 11,D563-40T, p. 1362 (1942).
(4) Federal Specification, TT-P-141A. (5) Fonrobert and Munchmeyer, FarbenZtg., 41,747 (1936). (6) Goldberg, A. I., IND. ENO.CHIIM.,ANAL.ED.,16, 198 (1944). (7) Iowa State Highway Comm., Specification 41-59-7, Shop Coat (July 15,1941). (8) Naval Aircraft Specification ST-15c (July, 1938). (9) Sanderson, J. M., A.S.T.M. Bull., 107, 15 (1940). (10) Sheiton,J. G., Metal Finishing, 39, 703 (1941). (11) Taylor, J. J., Paint, Oil Chem. Rev., 105, No. 10, 10 (1943). (12) Toeldte, W., Farben Ztg., 45, 67 (1940). (13) U. 5. Maritime Comm. Specification 52-MC-23 (Aug. 28, 1943). (14) Ibid., M C 52-A-1, Class XXII (June 6,1939). (15) U.S. Treasury Dept. Specification 358 (July 8, 1939). PRESENTED before the Division of Paint, Varnish, and Plastics Chemistry at t h e 108th meeting of the AMERICANCHmirrcAL SOCIETY, New York, N. Y.
Compatibility of DDT with Insecticides, Fungicides, and Fertilizers ELMER E. FLECK AND H. L. HALLER Bureau of Entomology and Plant Quarantine, U . S . Department of Agriculture, Beltsuilb, M d .
T
HE indicated widespread use of DDT as an insecticide ( I , 4)
and its known instability in the presence of certain catalysts ( 2 ) make it desirable to have information as to the possible cata-
lytic effect of other insecticides, fungicides, fertilizer materials, and accessories with which it may be applied. DDT is a rather stable compound by itself. Long periods of exposure to the air have caused no appreciable change. Irradiation of the solid material, spread in a thin layer, for 35 hours with a 100-watt General Electric mercury vapor lamp, type AH-4, caused the melting point of DDT to be lowered by only 2' C. Similarly, an alcoholic solution of pure D D T showed no change after exposure to sunlight for over a year.
Some of the more common insecticides, fungicides, and fertilizers have been tested for catalytic action in the dehydrochlorination of DDT. Materials used for diluents have been shown to vary in their activity as catalysts for the decomposition of DDT. The anhydrous chlorides of iron, aluminum, and chromium are active dehydrohalo-
In contrast to this stability in the neutral state, it has been shown that DDT in alcoholic solution readily reacts with alkalies in accordance with the following reaction (3):
c1 I Cl-c-cl 1
+ KaOH
C-H
60 Cl
c1
-
c1 c1-
t:II 4-NaCl f H2O
C
$0 c1
c1
genation catalysts for DDT. The catalytic action of anhydrous ferric chloride has been shown to be promoted by solution in naphthalene, chloronaphthalene, chlorobenzene, 0- and p-dichlorobenzenes, and nitrobenzene, and inhibited by various hydrocarbon and fatty oils, alcohols, ketones, acids, and anhydrides.
