W. P. TER HORST AND E. L. FELIX General Laboratories,
-
U. S.
Rubber Company, Passaic, N. J.
- -
2,3 Dichloro 1 , 4 naphthoquinone has proved t o be a potent and safe fungiclde for both agriculture and textiles. Its effectiveness in t h e control of numerous economic fungi has been demonstrated. In agriculture it m a y be used as a seed treatment or as a foliage spray t o control plant diseases. On textiles 2,3-dichloro1,4=naphthoquinone is a n excellent mildew-proofing agent, has no harmful effect, and resists weathering. It should prove especially valuable in replacing metallic chemicals or in cases where a more suitable fungicide is desired, HE annual fungous damage to agriculture in t h e United States has been estimated at a billion dollars. The annual loss due t o mildew on raw cotton alone is placed at 25 to 75
T
The objectives are to discover chemicals that are highly effective fungicides, are safe to plants, textiles, and man, and can be produced in large quantities from available raw matcrinls. The importance of any chemical t h a t can replace such strategic chemicals as copper and mercury hardly need be mentioned in wartime. 2,3-Dichloro-1,4-naphthoquinoneis outstanding as a fungicide among the many quinone-type chemicals tested. Its effectiveness in the control of twenty-two important and widely divergent fungi has been proved. 1,4-Benzoquinone is not fungicidal except in high dosage. Its further disadvantages are irritation and toxicity t o man, phytotoxicity, high volatility, high chemical reactivity, and fair solubility in water. In 1937 it was discovered (6, 9) that tetrachloro-p-benzoquinone, commonly called “chloranil”, possesses greatly enhanced fungicidal properties without the undesirable features of quinone. Continued research led to the development of 2,3-dichloro-1,4-naphthoquinone which is from four t o eight times more effective on many fungi than tetrachloro-p-benzoquinone. The position of the chlorine atom in the molecule is important and probably critical. Known naphthoquinone structures are the following:
million dopars (1). The importance of mildew-proofing in the 0 war effort cannot be evaluated in terms of money alone. The fields of agriculture and textiles are related, particularly through the economically important cotton crop. Further, the fungus Glomerella goseypii (South.) Edg., causing anthracnose of the cotton plant, attacks and weakens the fibers in the boll (5,7) in the field. These fibers are lost largely at ginning. I n agriculture, sulfur, copper, and organic mercury com1,PNaphthoquinone 1,a-Naphthoq uinone 2,6-Naphthoquinone pounds are extensively used to control pathogenic fungi. While effective in many instances, they have disadvantages. Sulfur, for example, is ineffective in the control of a number of diseases, and during hot weather may burn the foliage. Repeated use increases soil acidity and in the greenhouse may render soil worthless. Elemental sulfur is of restricted value as a seed protector. Copper compounds do not control all diseases and may cause foliage or fruit injury, particularly during a cold spell. They may increase aphid population. As seed protectors, copper compounds arc of limited usefulness. Organic mercury compounds, while often highly effective, are toxic to man and animals. I n the textile industry, fungicides such as copper carbonate, copper naphthenate, and chlorinated phenols are in extensive use. Copper compounds may cause weakening of the fibers as well a s stiffness. Since copper is rubber’s worst enemy, copper compounds cannot be used on rubberized fabrics. I n view of t h e shortcomings of known fungicides, organic Figure 1. Control of Pythium ultimum on Peas w i t h fungicides have been and are being developed 2,3-Dichloro-l,4-naphthoquinone No. 6, t w o rows treated w l t h 0.56 ounce per bushel seed: t h a t will augment and often replace sulfur or No. 7, t w o rows treated w l t h 0.28 ounce per bushel; adlacent metallic fungicides of long standing. .Ingle rows, untreated. Rateofsowing: all rows SOseedseach.
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Vol. 35, No. 12
INDUSTRIAL AND ENGINEERING CHEMISTRY
1256
Others which do not exist, except possibly in derivatives are:
The vapor concentration of 2,3-dichloro-1,4-naphthoquinone at 100’ C. is 0.2 mg. per liter.
P
USE AS A G R I C U L T U R A L F U N G I C I D E
0 2,3-Naphthoquinone 1,5-Naphthoquinone 1,7-Naphthoquinone
Of these six naphthoquinone structures, sixty-six possible dichloro isomers can be drawn. The literature (4, 6, 10, I S , 14, 19, $0)describes only six dichloronaphthoquinones:
0
Cl
8
c1 0
2,3-Dichloro- 1,4naphthoquinone
5,8-Dichloro-l,4naphthoquinone
0
0
I
I
5,6-Dichloro-1,4naphthoquinone
0
0
0
dl 3,4-Dichloro-1,2naphthoquinone
b
c1
1,5-Dichloro-2,6naphthoquinone
2,6-Dichloro-1,4naphthoquinone
2,3-Dichloro-1,4-naphthoquinoneis not a new material. I t s preparation was recorded by Graebe (IO) in 1867 and described by Carstanjen (4) the following year. It is quite soluble (4 per cent) in xylene and o-dichlorobenzene; fairly soluble in dioxane, acetone, benzene, and diethyl ether; and slightly soluble in glacial acetic acid, ethyl alcohol, carbon tetrachloride, Skellysolve B, Cellosolve, Stoddard solvent, gasoline, cod oil, cottonseed oil, castor oil, and Nujol. The solubility in water a t pH 7.0 is in the order of 1 to 10,000,000, which is 2500 times less soluble than 1,4naphthoquinone with a solubility of 1 t o 4 0 0 0 .
TABLE I.
The high fungicidal potency of 2,3-dichloro-1,4-naphthoquinone has been demonstrated repeatedly. It was determined first on the regularly employed test fungus, Pythium ultimum Trow, on peas in the greenhouse. Maximum control of Pythium (90 t.o 94 per cent plant stand) under the most favorable conditions for disease development was obtained at a dosage of 0.56 to 1.12 ounces per bushel of seed. Practical control was obtained at 0.28 ounce per bushel, equal to 1/32 per cent by seed weight (Figure 1). The average pea stand at a dosage of 0.28 ounce per bushel oi seed in twelve experiments was 80 per cent compared t o 24 in the untreated, a significant mean difference of 56 per cent. Corresponding mean height of plants after about 10 days was 5.97 em. for the treated and 4.67 for the untreated, a mean difference of 1.30 em., which was highly significant with odds of 10,000 to 1. Analysis of variance on results from the twelve expcriments in which the four dosages (2.24, 1.12, 0.56, and 0.28 ounce of 2,3dichloro-1,4-naphthoquinone per bushel of seed) were employed showed no significant differences in plant height between dosages. The chemical was applied also a t dosages of 4.48 and 8.96 ounces per bushel of pea seed to determine any tendency to injure seed. The results were not significantly different from those obtained with a dosage of 1.12 ounces, showing the chemical to be safe on seed. The material appears to be noninjurious t o foliage also and offers considerable promise as a plant spray against leaf diseases. The chemical is not compatible with nitrogen-fixing bacteria. 2,3-Dichloro-1,4-naphthoquinonehas given good results also on Lima beans at 0.2 ounce per bushel and on corn (field and sweet) a t 0.25 ounce per bushel. I t s toxicity to Ustilago sp. in slide tests indicates possible value in the control of cereal smuts. It has given fair control of the fungi causing cotton dampingoff. The results obtained against Rhizoctonia and anthracnose damping-off in the greenhouse are shown in Table I. 2,3-Dichloro-1,4-naphthoquinone appreciably reduced both Rhizoctonia and Glomerella infection at a dosage of 0.5 ounce of active material per bushel of cottonseed applied just before planting. The percentage of anthracnose infection in the untreated seedlings always was high, although the percentage of actual damping-off from this disease was never exceptionally high, as in peas. Anthracnose control with the chemical may be observed in both criteria but is most striking in the percentage of healthy plants obtained. 2,3-Dichloro-1,4-naphthoquinonecompletely prevents germination of cotton anthracnose spores at 1 p. p. m. or less in slide tests. Test tube cultures of treat,ed and untreated cottonseed highly infested with anthracnose revealed that 6 ounces per
CONTROL O F COTTON
DISEASES WITH 2,3-DICHLORO-1,4-NAPHTHOQUINONE Individual Tests against:
7
Anthrarnnsnb ..-. ~
75
Concentration
Dosage, Ounces per Bu. Total Active
Rhizoctoniaa % Stand _ _ Treated
u n-
treated
0
Figure 2. Prevention of Chaetomi u m Mildew on Duck w i t h 2, 3-Dichloro-I, 4-naphthoquinone Lower half treated, upper half u n t r e a t e d .
0 5
b
_
% _Stand _ -- u n-
Healthy
-_n-
% of Eme&ed ~U
Treated
treated
Treated
treated
..
..
..
..
..
..
Machine-delinted seed planted in Mississip i cotton soil. Fuzzy seed highly infested naturally and p k n t e d immediately after treatment.
..
INDUSTRIAL AND ENGINEERING CHEMISTRY
December, 1943
bushel of the 12.5 per cent chemical (that is, 0.75 ounce of active material per bushel) completely kill Glomerella gossypii when applied 3 months in advance of planting. Possibly higher dosage would accomplish this in a shorter time.
NHiNOs KiHPOa
1257 2.0 2.8
grams erems
Stachybotrys was grown on potato dextrose agar. Ond tenth per cent ultrafiltered orange juice was added to the spore suspension t o stimulate germination on the slide, although its necessity for either fungus was not determined. Metarrhizium, except for the smallness of its spores, is admirably suited t o slide work, since spores capable of 100 per cent germination are produced in profusion. The L D 5 0 and L D 9 5 values on Metarrhizium thus are found t o be as follows: Chemical
LD50
P. p . m. 2,3-Dichloro-1,4-naphthoquinone Tetraohloro-p-benzoquinone
Figure 3. Soil Adherence in 2,3-Dichloro-I, 4-naphthoquinone Treated (left) a n d Untreated (right) Fire Hose upon Removal f r o m Sol1 21 Days after Burial
0.37 2.5
LD95 P. p . m. 0.56
4.00
The results show the potency of 2,3-dichloro-l,4-naphthoquinone, the L D 5 0 as well as the L D 9 5 values being only one eighth those of tetrachloro-p-benzoquinone. The LD50 value for 2,3-dichloro-1,4-naphthoquinoneon Stachybotrys is about 1.3 p. p. m., the LD95, 2.5 p. p. m. The ascospores of C h a e t m i u m globosum Kze. failed to germinate satisfactorily for slide tests. The wholly submerged formation of mature perithecia by this fungus on plain agar is unusual and suggests possible internal fructification in fabric under certain conditions. E F F E C T O N S T R E N G T H OF C O T T O N F A B R I C I N ABSENCE OF M I L D E W
USE AS A M I L D E W P R E V E N T I V E
The armed forces need mildew prevention on numerous items. The ideal textile fungicide possesses the following properties: Effectiveness against both fungi and bacteria (for which property the term “bacterifungicide” is proposed) ; effectiveness a t low temperatures; resistance to weathering, leaching, and heat; ease of application; no odor; no objectionable color alteration; no change in “feel’’ of fabric; no tendering; no undesirable effect on dyeing; nontoxicity and noncorrosiveness; no increase in flammability; inexpensiveness and availability. 2,3-Dichloro-1,4-naphthoquinonehas proved in laboratory and soil burial tests to be a highly effective mildew-proofing agent for cotton fabrics against such molds as Chaetomium, Metarrhizium, Stachybotrys, Aspergillus, Penicillium, and others employed in u. s. Department of Agriculture test procedures for mildew preventives. Stachybotrys spp. (probably S. atra Corda and S. cylindrospora Jensen) were important in the destruction of cotton fabrics in some of the soil burial tests. It has been demonstrated experimentally that S. cylindrospora is an active cellulose destroyer on cotton batting, absorbent cotton, and ashless filter paper (16). S. papyrogena Sacc. is destructive to cotton also ( l a ) . The occurrence and destructiveness of Stachybotrys spp. and related genera on paper has been known for a long time @,8, 17). SLIDE
The effects of 2,3-dichloro-1,4-naphthoquinoneon cotton fabric in the absence of mildew was determined by 60-hour exposure of the originally treated uninoculated and unincubated sample t o the combined action of iiltraviolet light, water spray, and heat (80”C.). The average bursting strengths of a sample of &ounce duck, originally testing 202 pounds, thus exposed in a n accelerated weathering unit, was 6 2 pounds for the acetone-treated check and 79 pounds for the 2,3-dichloro-l,4-naphthoquinone treated (1per cent in acetone). Thus no greater loss of strength over the check, due to the chemical, is indicated in controlled en-
TESTS
The toxicity of 2,3-dichloro-1,4-naphthoquinoneto Metarrhizium and Stachybotrys was determined in slide tests, following the procedure of McCallan and co-workers ( 1 4 , later adopted by the Committee on Standardization of Fungicidal Tests, American Phytopathological Society. Spores were from 4-7 day old cultures. Metarrhizium (N. R. R. L. No. 1875) was grown on strips of filter paper extending into a liquid medium suggested by Greathouse (11). This medium, of about pH 3.7, proved excellent for the production of spores in both Metarrhizium and Glomerella gossypii, and has the composition which follows.
Figure 4. Prevention of Stachybotrys M i l d e w w i t h 2, 3-Dichloro-1, 4-naphthoquinone on Fire Hose Buried 3 Weeks in Greenhouse Soil L e f t : Untreated hose. original tensile strength 29 Ib./sq. In., final 0. R i g h t : Hose treated Aith 1 per cent ohemioal in acetone; original tensilostrength 29 lb./sq. i n . , f i n a l 25
INDUSTRIAL AND ENGINEERING CHEMISTRY
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Vol. 35, No. 12
The 2,3-dichloro-1,4-napbthoquinone uptake by cotton duck from immersion in 1 per cent acetone solution is 1.5t o 1.7 per cent of the original duck weight. Bursting strength deterniinations on cotton sheeting before and after 3-week soil burial follow:
Figure 5. Prevention of Stachybotrys Mildew (Dark Areas) and Bacteriosis (Holes) w i t h 2, 3-Dichloro1, 4-naphthoquinone on Cotton Duck Buried 3 Weeks in Greenhouse Soil Left:
Untreated
duck; original bursting strength 202 pounds, final 0 .
R i g h t : Duck treated w i t h 1 per cent chemical i n acetone: original bursting strength 205 pounds, final 215.
vironment, equivalent to several months of natural aging. The increase in strength over the check is probably due to shrinkage of the fabric. FABRIC INOCULATION TESTS
Laboratory tests were conducted with Metarrhizium sp. or Chaetomium gZobosum as recommended by Thom et al. (18). The fabric under test was impregnated with a solution of 2,3-dichloro-1,4-naphthoquinoneof known concentration and allowed to dry. Duplicate tests were made on dried treated samples, unwashed and washed for 16 to 24 hours in running tap water to determine resistance to leaching. Artificial inoculation with the desired mildew and 30-day incubation under optimum conditions for mildew development ensued. Fungicidal evaluation was based on visual observation and tensile and bursting strength determinations. The effectiveness of 2,3-dichloro-1,4naphthoquinone in the control of Chaetomium is shown strikingly in Figure 2, in which the entire sample was inoculated and incubated after part of i t had been treated and dried. The tests on leached and unleached duck are shown in Table 11. SOIL B U R I A L T E S T S
.
In the soil burial tests, samples were buried horizontally l / d to inch deep in good greenhouse soil of p H 7.2, using natural fungous flora as inocula. Soil moisture and other environment were kept at optimum conditions for mildew growth. Period of burial was 21 days. It is noteworthy that well mildew-proofed fabrics can be removed from the soil relatively clean, whereas untreated or poorly protected fabrics are covered with a layer of soil held b y the mildew mycelia (Figure 3). Mildewed and mildew-proofed fire hose and duck after burial and soil removal are shown in Figures 4 and 5 , together with some tensile and bursting strength figures. Further bursting strengths in treated and untreated duck, before and after 3-week soil burial, follow:
192 211 205 208
0 0 0 0
...
..
Av. 202
0
132 0
150
M E T H O D S OF A P P L I C A T I O N
2,3-Dichloro-1,4-naphthoquinonemay be applied to fabric or leather in one of four ways: in organic solvent, in aqueous suspension, in a lacquer, or by vapor. Solutions of the chemical are best prepared in such .solvents as acetone, benzene, Cellosolve, Stoddard solvent, o-dichlorobenzene, or mineral, vegetable, and animal oils. Recommendations for light cotton sheeting are 0.1 per cent and for heavy fabrics, duck, etc., 0.5 to 1 per cent. Only simple immersion with subsequent drying is required. Aqueous suspensions of p H 4 to 5 , containing 20 per cent active chemical and the necessary protective agents, ball-milled, may be employed. Application is made from a dilution containing 1 per cent active ingredient, padding, and drying.
TABLE11. TENSILESTRENGTH(POUNDS)OF TREATED AND UNTREaTED DUCKAFTER 30-D-kY INCUBATION FOLLOWING INOCULATIOX WITII Chaetomium globosum" Untreated Check Warp Filling
6
19 2
13 16 Av.11.2
21 15 20 20
..
19
'
Benzene Check W a r p Filling
2,3-Dichloro-l,4-naphthoquinone 0.1% i n 0.5% in Benzene Benzene W a r p Filling Warp Filling
Duck Unwashed before Incubstion 8 6 94 89 89 88 4 28 10 29 95 76 2 20 102 86 13 94 .. 94.8 8 4 . 7 7.5 20.7
Duck Waahed 35 32 8 28 26 33 2 28 15 .. Av.17.2 30.2
..
93 86 84 93 93 89.8
78 76 86 87
..
81.7
24 Hour5 in Running Water befoie Incubation 2 18 93 81 87 80 99 90 95 90 7 12 12 14 15
30 26
10
21.6
Original teneile strength:
..
92 97
..
85 86 87
95.2 85.8
87 99
78 82
..
85
92.0
83.0
warp 97, filling 71.
1 7 2 3-Dichloro-1 4-naphh o h u i n o n e i n Abetone Before burial After burial
0
197
Lb./Sq. In.
Cotton sheeting, as well as fire hose and duck, was rendered mildew-proof by 2,3-dichloro-1,4-naphthoquinone,as shown by visual examination and tensile and bursting strength determinations. Both Chaetomium and Stachybotrys mildews were controlled effectivelyin soil burial tests. The apparent increase in strength due to treatment is attributed to shrinkage in the course of the tests. 2,3-Dichloro-1,.i-naphthoquinone retains its fungicidal effectiveness at average temperatures of 50" F. or lower. A considerable degree of fungicidal compatibility with lime is indicated, provided somewhat above minimum effective concentrations are employed.
a
Acetone Check Before burial After burial
Fabric Treatment Untreated, unburied Untroated, buried 0 17" 2,3-dichloro-l,4-naphthoquinone, buried
207
218
2,3-Dichloro-1,4-naplithoquinone can be applied to surfaces other than cotton, such as wood, rubber, etc., by painting with a lacquzr containing the chemical. The chemical can be applied easily and economically by exposure of the fabric to the vapor at 125' C. for a t least one hour.
INDUSTRIAL AND ENGINEERING CHEMISTRY
December, 1943
ACKNOWLEDGMENT
Grateful acknowledgment is made t o E. C. Ladd, R. J. Norton, and J. L. Kurlychek of these laboratories for their part in the development of this fungicide, and to the management for permission to publish this paper. Anthracnose-infected cottonseed was kindly supplied by C. H. Arndt, Clemson Agricultural College. LITERATURE CITED
1259
(9) Felix, E. L., Phytopathology, 32, 4 (1942). (10) Graebe, C., Ber., 1, 36 (1867). (11) Greethouse, G. A., personal c o m m u n l c a t l o n to J. L. Kurlychek, 1943. (12) Greathouse, G. A., Klemme, Dorthea, and Barker, H . D., IND. ENQ.C H ~ MANAL. ., ED., 14, 614 (1942). (13) Guareschi, J., Ber., 19, 1184 (1886). (14) Hellstroem, P., Ibid., 21, 3269 (1888). (15) McCallan, 8. E. A., et al., Contrib. Boyce Thompson Inst., 4, 233 (1932); 9, 249 (1938); 10, 329 (1939); 12, 49 (1941); 12, 431, 461 (1942); Phytopathology, 33, 627 (1943) (16) Paine, F. S., M ~ o o l o g i a ,19,248 (1927). (17) Smith, G., “Industrial Mycology”, London, Edward Arnold & Co., 1938. (18) T h o m , C., Humfield, H., a n d Holman, H. P., -4m. Dyestuf Reptr., p, 3, Oct. 22, 1934. (19) Willstaetter, R., and Parnas, J., Ber., 40, 3975 (1907). (20) Zincke, T h . , Ibid., 19, 2499 (1886). I
(1) Anonymous, Oil, P a i n t , and Drug Reptr., p. 41, July 1, 1940. (2) Bakhtin, V. S., J . All-Rum. Congr. Bot., Leningrad, 1928, 169 (1928). (3) Barre, H. W., S. C. Agr. Expt. Sta., Rept. 22, 89-118 (1909). (4) Carstanjen, E., Ber., 2, 633 (1868). (5) Claus, Ad., and Mueller, P. F., Ibid., 18, 3073 (1885). (6) Cunningham, H. S., and Sharvelle, E. G . , Phytopathology, 30,4-5 (1940). (7) Edgerton, C. W., La. Agr. Expt. Sta., BUZZ.137 (1912). (8) Engler, A., and Prantl, K., “Die naturlichen Pflanrenfamilien”, Vol. 11, p. 460 (1900).
A PRELIMINARY paper on the same subject was presented before t h e Division of Agricultural and Food Chemistry a t the 105th Meeting of the A N ~ R I C A N CHEMICAL S O C I E T Y , Detroit, Mlah.
FLEX LIFE AND CRYSTALLIZATION OF
SYnthetic Rubber J. H. FIELDING The Goodyear Tire & Rubber Company, Akron, Ohio
Natural rubber and Butyl B are similar in under some conditions not sufof stretchednatural rubber that stretching produces fibering; their ficient to make i t tear all the has been the subject of way across. Again, if the strip flex life is good and high tensile gum stocks were stretched before cutting, much experimental work in the are possible. GR-s and Buns lack there was a certain degree of past. A great deal of this has semblance of fibering. Gum stocks have been devoted to the more theoelongation, somewhat less than retical aspects such as x-ray low tensile and, in -general, flex life is poor. the ultimate, a t which the strip had to be cut three quarters of patterns, thermal effects, and volume change. It is now its width in order to produce complete rupture; a t lower elongations a much smaller cut was known that neither Buna h-nor GR-S has a fiber diagram when sufficient. This same phenomenon of semiracking was used to exstretched and that Butyl B and neoprene do have such patterns. plain the knotting of a carbon black stock, where the tear has a Since the industry is now in the process of changing from natural rubber to GR-S, it is of interest to see just what this lack of strong tendency to go at right angles t o any chosen direction crystallinity means from a compounding and performance standof tear. A totally different approach but equally effective was used by point. It is possible that many of our ideas based on rubber must Cadwell (8). Rubber was flexed from various starting elongachange, that GR-S must be considered a n e x material, and that radical changes in formulation and construction must be made. tions greater than zero, with the result that flex life improved tremendously as elongation T+ as increased and passed through a maximum a t a point somewhat below the ultimate elongation. PHYSICAL EFFECTS OF CRYSTALLIZATION This ability t o resist rupture in the direction of strain is thought When natural rubber is stretched, an alignment and fitting to be one of the greatest contributing factors to the toughness of together of adjacent molecules or parts takes place which has vulcanized natural rubber. The object of this paper is to search many of the theoretical aspects of crystallization. The physical for a similar behavior in synthetic rubber. result is that the rubber bekomes fibrous. It becomes stronger as it is stretched. I t s resistance to rupture or tear is increased TEARING EXPERIMENTS by the very force or deformation that tends to rupture it. At the Four typical compounds were made up (Table I) and were subsame time it becomes weaker in a direction a t right angles to this. The result is that tensile strength is high whether or not a reinjected qualitatively to a tear test designed to reveal any tendency forcing pigment is used, and rubber may be said to be reinforced toward fibering. Wide dumbbell picces were cut with a razor by its own crystallization. longitudinally and stretched in a Cooey machine, and an attempt Tearing behavior of rubber was covered extensively some years made to continue the split by tearing manually. Other pieces ago by Busse ( I ) . His work involved determining the relation were stretched, then razor cut longitudinally, and tearing was between the depth of a transveree cut and the force required to attempted. Still other pieces were stretched, then punctured rupture the strip. It was shown that, because of “semiracking”, with a pin, and an attempt made t o force the pin along the strip the force required to make a cut grow part way across a strip was longitudinally and thereby split it.
T
HE crystalline structure
