1532
INDUSTRIAL AND ENGINEERING CHEMISTRY
material on the tail end of the olefin plateaus. I t would be expected that the diolefins, being more strongly adsorbed than the olefins but less than the aromatics, would appear at the tail end of the olefin plateau. T h e presence of aromatics having a lower viscosity than the olefins is not a satisfactory explanation iri this case, since close-boiling fractions were uaed in all the percolations. Determinations of olefin content on the fractions at the tail end Of the Olefin plateau by the hrolnide-bromate method have given several anSWers substantialllv about 100% and maleic anhydride values as high as 17. The data are sumniarized in Table V.
Vol. 41, No. 7
Diolefins are indicated by bromine numbers as high as 140. Conjugated diolefins are indicated by maleic anhydride valueranging from 11 t o 17. LITERATURE CITED
(1) Dinneen, Bailey, Smith, and Ball, IXD. END.CHEM., AXAL.ED.. 19,992 (1947). (2) Lipkin, Hoffecker,&fartin,and Ledley, Z&j., 20,130 (1948). (3) Mair, B.J.,J.Research Xatl. Bur. Standards, 34, 435 (19451. RECEIVED April 10, 1948.
ANTIFOULING PAINTS Studies in Multiple Pigmentation ALLEN L. ALEXANDER AND R. L, BENEMELIS' .VacaE Research Laboratory, Washington 20, D . C . T h e wartime shortage of cuprous oxide inspired many investigations of substitutes and extenders for this primdry ingredient of so many successful antifouling paints. A s a result, metallic copper flake and powder were used to a degree hitherto considered unsafe on steel hulls for fear of accelerating galvanic corrosion. I n the course of the work reported here, a choice had to be made in the selection of inert pigments to be used with specific toxic ingredients. Zinc oxide appears to provide considerable advantage over more orthodox inerts such as diatomaceous silica for use with cuprous oxide. Similar differences exist but are somewhat less pronounced with respect to metallic copper pigments, while some mercury pigments appear to function equally well with a wide variety of extenders. Experience with metallic extenders, iron and zinc powders, is described with special emphasis on their limitations.
T
HE first article in t,his series ( I ) demonstrated that heavy
pigmentation with metallic copper, in the form of flake or powder, could result in complete inactivation of the protective qualities of antifouling paint when applied t o steel. Some additional evidence is presented here to substantiate this view, Young and others ( I O ) studied the effect of extending antifouling pigments with a n inert material (barytes) and advanced a theory as t o the probable role of such an inert in promot,ing the efficiency of the primary toxic pigment. During the recent war demand for the widely used cuprous oxide greatly exceeded the supply, and resort was made t o other copper pigment's whose ability t o suppress fouling attack had been adequately demonstrated (9). In each of these studies the necessity for close control of pigment-volume relations has been emphasized in order t o avoid serious consequences such as would result from local galvanic couples, a rapid depletion of the store of available toxic, and the complete inactivation of the antifouling film. The Woods Hole, Mass., investigators made a comprehensive study ( 3 ,4, 6, 7 )of the factors governing the action of antifouling paints and showed that matrix and pigment solubilities are critical in the maintenance of adequate leaching rates (8). Leaching rates have been more or less accepted as an accurate measure of ability t o prevent the attachment of fouling organisms. Young, Schneider, and Seagren ( I O ) demonstrated that the substitut,ion of nontoxic pigment for an equal weight of vehicle improved the ant,ifouling qualities of a copper paint. This increase was at,tributed to an increase in the permeability of the film. Thus, if pigment volume is a factor in permeability, its 1
Present address. Sinclair and Valentine Company, Ridgeway, Pa.
regulation between established limits, whether by the addition of toxic or nontoxic pigment, beconies a significant factor in ant,ifouling effectiveness. The second article in this series ( 2 ) .showed that certain mercury paints containing low volumes of pure toxic are considerably less effective than more highly pigmented paint's containing cven smaller amounts of toxic but increased amounts of inert pigment. Ketchum and Ayers (6') indicated that some differences exist between inert pigments used with certain toxics. This evidence points to the need for determining the more exact role of inert pigments in antifouling paint formulat,ion. Materials considered for this application include, in addition to the usual inerts, zinc oxide, zinc dust, iron pori-der, and many of the prime pigments used in orthodox paint formulations. Primary pigments are referred t,o here as those possessing antifouling or toxic value where hiding qualities are of no consequence. Aside from the solubility characterjstics of toxic pigments, rate of solution is governed by the extent to which they come in contact with sea water. This, in turn, may be a function of the solubility of the matrix, the rate at which it exfoliates (underwater chalking), its porosity, or some combinat,ion of these factors. I n these experiments att,cmpts werc inad(, 60 study the effect of adding graded amounts of inert pigment on t,he ant,ifouling properties of the paint. An endeavor was also made to accelerate exfoliat'ion rate through the addition of corrodible iron and ziiic powders. In other esperiment,s t\vo t,osic pigmenrs were studied in combination. In each experiment direct comparison was made with standard pigmentations for control purposes. EXPOSURE PROCEDURE
Pigment combinations mere dispersed in three matrices of thv following compositions by passing twice through a three-roll mill :
W W rosin Methyl abietate Pliolite 9-1
A 87 12 1
Per Cent by Weight B 75 20 5
c 75 6
20
Vchicle A was pigmented at 12% by volume, B a t Z4YO,and C a i Plym-ood panels were coated with approximately 10 mils of each composition and exposed at Miami Beach, f l a . , for periods up t o 26 months. The panels were inspected monthly and rated with reference to the percentage surface area remaining free from fouling attachment. When a formulation dropped below SO%, it was no longer considered of interest. I n the tables that follow, the figures indicate the total number of months during whicli 36%.
INDUSTRIAL AND ENGINEERING CHEMISTRY
July 1949
TABLE
I.
with formulations containing metallic copper flake and powder. CUPROUS OXIDE-INERT EXTENDER Table 11 gives the results of the exposure of these formulations, Months t o Failure which further demonstrate the economic advantage of using C m O / E x t e n d e ~ 12% PV 24% pv 36% pv extender pigment, although the case in favor of zinc oxide is not 13 17 23 quite so pronounced for metallic copper pigments as with cuprous 45-1 -2 9 17 11 8 oxide. At medium pigmentation zinc oxide shows marked superi2 -4 4 12 5-1 8 11 20 ority. 9 8 4-2 8 COPPERFLAKE.The data for this pigment (Table 111) 2-4 5 4 3 5-1 12 13 26a follow closely those for copper powder with generally increased 4-2 14 14 efficiency for the zinc oxide.
PERFORMANCE O F
Extender Diatomaceous silica Bentonite Zn oxide
2-4
ClllO 100% a Above SOYo a t end of expo8urt'.
TABLE 11.
Extender Diatomaceouq silica Bentonite
Z n oxide
1533
12
6
20
11
16
26a
EXFOLIATING PIGMENTS
Exfoliating paints render toxic pigment continually available a t the paint-water interface by the process of underwater chalking and erosion. By the inclusion of pigments susceptible to oxidation during immersion, this process might be expedited with the result that improved protection could be obtained during the life of such a paint. With this in view a series of paints was prepared, using the same toxic pigments already described progressively diluted with zinc dust from two sources. Table 111 gives the results of exposure of these formulations. These data reveal no improvement in antifouling action, compared to earlier described compositions containing inert pigments. On the other hand, the rapid corrosion of the zinc dust with the resulting opening of the film proceeds a t such a rate that the available store of toxic is used a t an intolerable rate. An earlier paper (1) showed that metallic copper pigment in contact with metals may assume the role of a cathode a t higher pigmentation and thus lose its potency as a fouling deterrent while simultaneously accelerating the corrosion rate of the anodic metal. The data shown in Table I11 on metallic copper pigments further substantiate this ,view. At the higher pigmentation the protection offered by metallic copper in contact with zinc dust is extremely brief or lacking altogether whereas similar high pigmentations with cuprous oxide and zinc dust exhibit equal protection at the lowest pigmentation. Furthermore, the low pigmentations with metallic copper are equal or superior to similar cuprous oxide concentrations. Identical formulations were prepared in which iron powder replaced the zinc dust. I n most cases physical failure, due to accelerated corrosion of the iron particles, occurred so rapidly that exposures were discontinued after three months. However, it does appear highly significant that in each combination containing cuprous oxide and iron powder the panels remained free of fouling, irrespective of pigment-volume. Similarly, at 12 and %yopigment volume, the metallic copper pigments mere also free. I n every case of 36y0 pigment volume with metallic copper, ratings were 0 a t the end of the initial month, lending further evidence to the critical behavior of metallic copper in contact with other metals at higher pigmentations.
PERFORMANCE OF COPPERPOWDER AND FLAKE WITH INERT EXTEPI'DER
Cu/Extender 5-1
4-2 2-4 5-1 4-2 2-4 5-1 4-2 2-4
C u Powder. Mo. t o Failure 12% 2$? 3 3 PV 13 17 12 11 13 15 10 3 11 13 13 2 ISn
12 lRu
Copper 100% 14 a Above SO% a t end of exposure.
9 13 7 22 24 23
12 10 9 12 11 22
13
22
Cu Flake
Mo. t o Failure !&j2 24% 36% PV PV 9
11 10 4
l?
0 12
10 10 5 13 10 9
0 15 15 11
2 8 9 22 17 13
.
12
11
1
9 11 8
16Q
performance remained above 80%. Plywood panels were selected to avoid all influences that niigiit be attributed to a corroding metal panel. COPPER COMPOUNDS
Inasmuch as most successful antifouling paints used in the past contain either copper or mercury, experiments were confined to compounds of these two metals. Cuprous oxide, along with small amounts of copper flake and powder, comprise almost 100% of currently used toxics in U. S. Navy formulations. First consideration is given to these pigments. CUPROUSOXIDE. A series of formulations was prepared in which cuprous oxide was replaced progressively with graded amounts of zinc oxide, diatomaceous silica, and bentonite as indicated in Table I. The number of months to failure (8070 of perfect) is indicated. The superiority of zinc oxide as an extender in conjunction with cuprous oxide is obvious. At a low pigment volume (PV) of 1270 zinc oxide may replace up to 66% of the primary pigment with the maintenance of adequate performance comparable or superior to 100% cuprous oxide. On the other hand, dilutions with bentonite and diatomaceous silica reduce efficiency in direct proportion t o the extent they are substituted. At high pigment volume the role of zinc oxide is most pronounced relative to the other inerts. Replacement of 33% cuprous oxide does not impair performance of the paint. Similar replacements with other inerts examined cause the paint to fail more rapidly and in direct proportion to the extent of substitution. At medium pigmentaTABLE 111. tions (24%) the differences are not so marked, although 33% of the cuprous oxide may be replaced with zinc oxide with no appreciable depreciation of efficiency. COPPER FLAKEAND POWDER.In view of the widespread use of metallic copper pigment as a substitute for the scarce oxide, similar dilution series were prepared, using the inert pigments
Extender Zn dust
*
MERCURY COMPOUNDS
Although compounds of mercury have assumed a minor role in most antifouling formulations used by the Kavy, they cannot
PERFORMANCE O F
Cu/Extender 5- 1 4-2 2-4
'$3 10
7 0
5-1 9 4-2 9 2 -4 3 Cu pigment 100% 11 a Above 80% a t end of exposure.
Zn dust 2
COPPER P I G M E N T S DILUTED WITH
------A
CUP0
20 17 8
36% PV 12 9 2
11 2 2 16
11 7 1 26a
24% PV
Months t o Failure-----------Cu powder 12% 24% 36% PV PV PV 2 10 10 10 6 2 2 4 2 0 13 1 12 1 0 10 1 0 14 15 22
ZIXC
DUST
Cu flake 12% PV 10 6 5
14 10 5 lBa
24% PV 5 0
-3
36% PV 1 0 n
2 1 1
3
..
12
0 0
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
1534
inerts. Again the superiority of mercury pigments is demonstrated even in combination with copper derivatives.
OF MERCURY COMPOUNDS WITH TABLE IV. PERFORMANCE INERT EXTEKDER
HgCI, M o n t h s to Failure
IIgO, LIonths t o Failure ~
Extender Diatomaceous silica
Hg/Extender
12%
24%
PI'
PV
5-1 4-2 2-4
14 14
15 15
11
Bentonite
5-1 4-2 2-4
Zn oxide
5-1 4-2 2-4
Zn dust 1 Zn dust 2
3
3
1pp 3
2;p
1
4
2
3
2
11
15 14 14
16 15 13
26= 26" 2Ga
4 3
3 3 1
26O 21 13
17
14
17
10 19 19
5-1 4-2 2 -4
10 4 5
13 11
17 1 8 11
26a
18
15 16 18
2 2
11 13 17
22 22 15
5-1 4-2 2 -4
14 15 10
19 26"
100% 12 hIercury Above 80% at end of exposure.
13
2fja 26a 25" 2Sa 22 2(ia
22 28"
15
9 10 10
18 21 3
26a 26"
15
20
23
10
3
14
2Sa
hlt.hough the experiments were designed primarily to study the effect of inert pigments in typical antifouling formulations, the data afford some opportunit'y to compare the relative efficacies of' the several toxics studied. Also, the effect of multiple pigmentaLion may be observed. Rlercuric oxide (Table IV) is outstanding in comparison wit,h any of the other pigments at any selected pigment volume. The one instance in which cuprous oxide approaches the same value is when used with zinc oxide (Table I). Some slight differences are apparent between cuprous oxide and copper flake and powder although when averaged ovcr the cnt,ire range these differences are not too well defined. Copper powder demonstrates tt slight superiority over the oxide a t low pigment volume whereas the oxide regains its value at higher pigment concent,rations. Mercurous chloride performs more efficiently than either copper pigment at the higher pigment volume but loses this advantage a t lower concentrations. I n comparing the worth of each pigment the most striking evidence is the invariable consistency of protection afforded by the use of multiple pigmentation (Table V). Even a t low concentrations involving the more expensive mercury pigments, a high level of constant protection is obtained that is lacking in formulations containing single toxics. This suggests additional experiments t o determine the most economical combinations consisting of multiple toxics arid inert pigment combinat,ions that are consistent with acceptable performanre.
26" 20
15
1
RELATIVE MERIT OF SEVERAL TOXlCS
yJ?
2(ia 21 26a
18
be overlooked in any comprehensive study. Their past history as successful toxics is well known, and principally for economic reasons have they been forced to assume a secondary role. Mercuric oxide and mercurous chloride have proved t o be the most versatile of the inorganic derivatives for adaptation to paint films. To understand more fully the extent to which these toxics may be diluted with inert pigments, the same dilutions already described for copper and cuprous oxide were prepared and exposed. Table I V presents the data. These data demonstrate the feasibility of utilizjng inert pigments in conjunction with inorganic derivatives of mercury. Here again, zinc oxide displays a pronounced superiority over diatomaceous silica and bentonite a t lower pigmentations in combination with mercurous chloride. However, similar differences do not hold so obviously for mercuric oxide with which each inert pigment contribut.es almost equally to general performance. The data indicate t,hat mercurous chloride is a highly efficient toxic when included at. higher pigment volume, performing well when diluted with inert pigment. At greater dilution it.s efficiency decreases, but it still remains jn a most favorable position relative to the undiluted product. Zinc dust offers an interesting possibility as a diluent for mercurous chloride, with considerable advantage over diatomaceous silica and bentonite. The data (Table IV) further indicate that mercuric oxide may be supplanted up to 66% by almost any of the inerts investigated. With few exceptions the protection provided by highly diluted mercuric oxide is ample to guarantee adequate protection for extended periods. This not only reaffirms mercuric oxide as a highly efficient toxic, but versatility is demonstrated in that it functions equally well with a wide variety of inert pigments. This is in direct contrast with cuprous oxide and metallic copper pigments. At low and medium pigmentation the mercury paints are not outstandingly different from those containing the copper pigments. On the other hand, the mercury paints at high pigment volume, particularly those with mercuric oxide, demonstrate an outstanding durability over prolonged periods. This is true, whether or not the primary pigment is diluted extensively.
CONCLUSlON 5
The data indicate that antifouling paint fo~mulationsmay be extended by replacing primary toxic pigment with certain inert materials under specified conditions without materially impairing the paints' ability to prevent fouling attachment. This is in accord with earlier work (10); however, the additional point is made that a n inert must be selected in accordance with its compatibility with the toxic. This appears to be more critical for cuprous oxide than for the other toxic pigments investigated. In this case zinc oxide appears superior, especially a t low (12%) and high (36%) pigmentations. Similarly, copper flake and copper powder may be extended with less marked differences resulting between the several inerts studied, although a slight advantage continues in favor of zinc oxide. The use of extenders with mercury pigments appears to be mandatory j f only for ensuring pro~~
~~
TABLE V. PERFORMANCE OF MULTIPLETOXIC COMBINATIONS 1st Toxic CunO
2nd Toxic HgO
IIgCI C u powder C u flake
IlgO
IIgCl
Cn powder
MULTIPLE TOXIC PIGMENTS
The possible effect of toxic pignlent,s on each other was iivestigated with a view to determining whether their established value for repelling fouling organisms would be cumulative. The formulations described in Table V were prepared and exposed to a fouling environment with the results indicated. The data seem to indicate that each toxic pigment added to a formulation cont,aining cuprous oxide serves to render a more constant protective value. Some improvement is shown in the formulation containing mercuric oxide, which is also charact,eristic whether used alone or with
Vol. 41, No. ?
lZY0 P V 14 13 10
15 13
2GLL 2 1"
1.5
12 16
13 16
22 22 24
5-1 4-2 2-4
15 15 15
17 22 22
10
5-1 4-2 2-4 5- 1 4 -2 2-4
14
17 17 17
23
5-1
4-2 2 -4
Cu flake
HgCl
C u powdcr C u flake
5-1
4-2 2-4
5-1
4-2 2-4
5-1
4-2
2-4 a
Month8 t o Failure 24yc PV 36% P V 12 15 26"
Tonic 1 , Toxic 2 5-1 4-2 2-4 5-1 4-2 2 -4
R a t i n g above 80% a t end of exposure.
15 15 14Q 14 14 14 14 14 14 14 16
20
20 19 19 23 26 16 16 26 23
11
I1
23
12 2GU 26a 26"
26" 24 26" 17 26" 25
185 17 16
.22
2Ga
26" 26" 25
16 15 15
1G 15 25
26u 26" 26''
INDUSTRIAL AND ENGINEERING CHEMISTRY
July 1949
longed protection as well as for economic reasons. The selection of an inert for mercuric oxide does not seem critical inasmuch as it ap ears t o function equally well with any of the types investigateif With mercurous chloride, however, zinc oxide continues to show an advantage. Metallic copper pigments should be avoided in conjunction with other metallic pigments as inerts, owing t o the danger of inactivating the copper, particularly at high pigmentations. Simultaneously accelerated corrosion of the second metal usually results in the complete destruction of the paint film. Metallic powders, such as zinc dust, may be used to fair advantage with mercury and copper oxides and with mercurous chloride. Multiple toxic pigmentation serves to ensure more consistent protection against fouling attack at any pigment-volume ratio. At equal volume concentration, mercuric oxide provides more lasting protection than copper. ACKNOWLEDGMENT
The cooperation of Charles M. Weiss of the Woods Hole Oceanographic Institution is gratefully acknowledged for exposing and reading the panels for the fouling tests a t Miami Beach. Acknowledgment is due to E. F. Carlston, formerly of the Bureau of
1535
Ships, for his interest and suggestions throughout the course of this investigation. LITERATURE CITED
(1) Alexander, A. L.,and Benemelis, R. L., IND.ENG.CHEM.,39, 1028 (1947). (2) Alexander, A. L., King, Peter, and Cowling, J. E., Ibid., 40,461 (1948). (3) Ferry, J. D.,and Carritt, D. E., Ibid., 38, 612 (1946). (4) Ferry, J. D., and Ketchum, B. H., Ibid., 38, 806(1946), (5) Ferry, J. D., and Riley, G. A , , Ibid., 38, 699 (1946). (6) Ketchum, B.H.,and Ayers, J. C., Ibid., 40,2124 (1948). Ferry, J. D., and Burns, A. E., Ibid., 38, 931 (7) Ketchum, B. H., (1946). (8) Ketchum, B.H., Ferry, J. D., Redfield, A. C . , and Burns, A. E., Ibid., 37, 450 (1945). (9) Young, G. H.,Gerhardt, G. W., and Schneider, W . K., Ibid., 35, 432, 436 (1943). Schneider, W. K., and Seagren, G. W.,'Ibid., 46, (10) Young, G.H., 1130,1944. RECEIVED August 14, 1947. Presented before the Division of Paint, Varnish, and Plastics Chemistry at the 112th Meeting of the AMERICAN CHEMICAL New York, N. Y . SOCIETY,
Characteristics and Treatment of Penicillin Wastes H. HEUKELEKIAN Rutgers University, New Brunswick, N . J .
I
N THE production of
Laboratory work on waste from two plants during more This paper summarizes laboratory work during more than 1.5 years was designed to survey and develop possible penicillin the most comthan 1.5 years, designed to methods of treating wastes from penicillin production. mon raw material has been The spent broth and wash water from penicillin producsurvey and develop possible corn steep liquor, fortified tion are similar in character and may be treated separately methods of treating these with variable quantities of wastes. Catch samples of or together by the same processes. Amyl acetate and lactose and other sugars and wastes from two plants were mycelium affect performance. Chemicals such as chloromineral salts. The broth is obtained and some of these form, formaIdehyde, phenylacetamide, butyl alcohol, aerated in large tanks after and acetone increase the B.O.D. at certain concentrations were subjected to more or inoculation with pure cultures less complete analysis (results and inhibit biological activity at higher concentrations. of species of Penicillium. not included). B.O.D. (bioPlain sedimentation and chemical treatment do not After the growth of the Peniremove appreciable amounts of B.O.D. Anaerobic digeschemical oxygen demand) cillium sp. a residual unoxition, properly regulated, reduces B.O.D. about 80%. values of all the samples dized portion of the broth Aeration in the absence of flocculent growths but inocuwere determined and are remains and is wasted. lated with liquor containing dispersed growths, produces given as averages, The spent Usually the mycelial growth broth was obtained after amyl after 24 hours B.O.D. reductions varying from 70 to 90%' is vacuum filtered and diswithin the initial 1000 to 4000 p.p.m. B.O.D. range of acetate recovery, but usually posed of separately. waste. Sand mtration as a final treatment produces an a residual amount remained In the extraction of penieffluent suitable for discharge into streams. With loadin varying concentrations. cillin the most common solings not in excess of 1000 pounds per acre per day, B.O.D. The p H values of the samples vents are amyl acetate and were adjusted a t the plant or reduction of about 90% was obtained. chloroform. The solvent is in the laboratory to bring usually recovered and reused, them within the oDtimum for although residual quantities biological treatment. The methods of treatment studied were: remain in the waste. Phosphoric or sulfuric acid added in the exneutralization and chemical treatment, anaerobic digestion, aeratraction process constitutes one of the main inorganic constituents tion in the absence of flocculent growths, and sand filtration. [All of the waste. Small amounts of other chemicals such as formaldeB.O.D. determinations were made according to methods of the hyde may also be present. The p H value of the waste spent broth American Public Health Association ( I ). ] is between 2.0 and 2.5, because of the large quantities of acid used. Another source of waste is wash water, derived from washing B.O.D. OF ANTIBIOTIC WASTES of tanks, filters, centrifuges, stills, and floors. Occasionally a contaminated batch of fermented liquor containing the mycelium The B.O.D. values of a number of antibiotic wastes obtained may be discharged into the wash water. The waste cannot be from two plants are given in Table I. Plant A produced 14,000 gallons of spent broth and used 35,000 gallons of wash water per expressed volumetrically on the basis of units of penicillin proday. The average of 12 samples of stripped lactose broth from the duction, because improvements in the process have increased the production of penicillin a t plant A had a B.O.D. of 4380 p.p.m. yield without an increase in volume.
