US 3309432 A
Description (OCR text may contain errors)
United States Patent 3,309,432 PROCESS FOR UPGRADING THIOPHOSPHATES Jackson Pollard English, Princeton, N.J., assignor to American Cyanamid Company, Stamford, Conn., a corporation of Maine No Drawing. Filed Oct. 23, 1965, Ser. No. 504,182
I 10 Claims. (Cl. 260-989) The present invention relates to a novel process for upgrading pesticidal thiophosphates. More particularly, it relates to a process for upgrading malodorous pesticidal thiophosphates by substantially removing the offensive odor therefrom. Still more particularly, the invention is concerned with a method for treating thiophosphate pesticides with selective aldehydes defined with particularity hereinbelow to obtain storage-stable, odor improved thiophosphates.
In the past, various methods for the elimination or masking of offensive OdOIS in thiophosphate pesticide have been disclosed in the literature. Unfortunately, none has been wholly successful. kor instance, it is known the useful ozonization process for successfully deodorizing malathion, that is, O,( )-dimethyl-S-(1,2-di-' carbethoxyethyl)-phosphorodithioate as succinctly described in US. Letters Patent No. 2,980,723, cannot be universally employed for the treatment of thiophosphate pesticides. Ozonization of illustrative thiophosphates, such as 0,0-dialkyl-S-(alkylthio)alkyl phosphorodithioates causes rapid degradation of such compounds. Moreover, it has been observed that certain masking agents, such as pine and lavender scents are only partially effective for stabilizing odor of particular thiophosphates. Further, they do not achieve the desired level of odor control necessary to classify a treated product as pre- -mium grade. Still others, such as spice scent, can produce an intense odor unlike that of the treated material but equally offensive. If a process whereby a storagestable, deodorized thiophosphate pesticide could be provided eliminating the difficulties of the prior such a process would satisfy a long-felt need.
It is, therefore, a principal object of the invention to eliminate rather than mask the offensive odor generally attributable to thiophosphate pesticides. It is a further object of the invention to provide a relatively simple, effective and economical method for reducing offensive odors in malodorous thiophosphate pesticides having associated therewith small amounts of at least an alkyl mercaptan. It is a still further object of the invention to provide a process for the reduction or prevention of the development of alkyl mercaptans in thiophasphate pesticides. Other objects and advantages will become apparent to one skilled in the art from a consideration of the ensuing description.
To this end, there is provided a relatively straightforward, simple and effective method for attaining a marked improvement in malodorous thiophosphate pesticides. Unexpectedly, the improvement is attained by admixing small amounts of selected aldehydes with the malodorous thiophosphate pesticides. Admixture can take place over a wide range of temperatures, usually between 0 C. and 100 C. Surprisingly, the so-treated malodorous thiophosphate is markedly improved and remains storage-stable with respect to odor over a prolonged period of time.
According to the present invention, any commercially available thiophosphate pesticide can be subjected to the action of an aldehyde in which said aldehyde is at least slightly soluble in the thiophosphate and in which the formed aldehyde-mercaptan derivative is of relatively high boiling point. In general, the addition of from about 0.5% to about 5% by weight of said selective aldepractice,
3,309,432 Patented Mar. 14, 1967 hyde to a malodorous thiophosphate is suflicient to reduce offensive odors of such thiophosphate to a commercially acceptable level. However, when utilizing an amount in excess of 5% of the aldehyde, it is found that the use of such amount is undesirable, since the cost is increased and little, if any, additional advantage either by way of increasing the level, or extending the period, of odor control is attained.
Advantageously, a large variety of thiophosphate pesticides can be treated in accordance with theprocess of the invention. Illustrative of such thiophosphates are:
and equivalents thereof.
Exemplary aldehydes which are characterized as being at least slightly soluble is each of the above thiophosphate pesticides illustrated above and which form mercaptanaldehyde derivatives of relatively high boiling point are: ethyl glyoxylate, acetaldehyde, paraldehyde, benzaldehyde, methylprotocatechuic aldehyde, ethylprotocatechuic aldehyde, p-tolualdehyde, salicylaldehyde, furaldehyde and a-methyl acrylicaldehyde. The preferred aldehydes are ethyl glyoxylate and methylprotocatechuic aldehyde, since the latter readily react without difiiculty with mercapt-ans normally present in thiophosphate pesticides. Significantly, the mercaptan content of the thiophosphate is appreciably reduced, thereby enhansing its odor characteristics.
It is an advantage that the process of the present invention eliminates the need for considerable specialized equipment and utilizes relatively inexpensive equipment operable over a wide temperature range. In general, the aldehyde can be added prior to, during or subsequent to the preparation of the thiophosphate being treated. Deodorization is attained upon the addition of the selective aldehyde within a relatively short period of time, usually from about fifteen minutes to about three hours.
The invention will be illustrated in conjunction with the following examples which are to be taken as illustrative only and not by way of limitation.
Example 1 The reduction of methyl mercaptan in malathion by treatment with small amounts of a selective aldehyde is demonstrated by utilizing twelve individual compositions of malathion containing methyl mercaptan. To each individual composition is added from about 0.1% to about 2% by weight of diverse selective aldehydes. The product is then analyzed particularly for mercaptan retention.
The determination of the amount of methyl mercaptan in each composition is made by heating treated samples to 56 C. for two hours and then collecting the vapors above the samples. These vapors are chromatographed at 30 C. on a six-foot column containing 10% of a mixture of cyanoethylmethyland cyanodimethyl 3 in Table I below. Untreated malathion is employed as the control.
Added by partitioning from saturated aqueous sodium sulfate solution. [Theoretical: 2%.]
Example 2 The effectiveness of ethyl glyoxylate for deodorizing malathion (O,'O-dimethyl phosphorodithioate of diethyl mercaptosuccinate) is demonstrated by utilizing from to 1.5% by weight of ethyl glyoxylate.
Several samples of technical grade malathion having a" rather strong offensive mercaptan odor are mixed with the treating aldehyde. Such samples are placed on a water bath maintained at 56 C. for a period of 34 days and periodically analyzed for methyl mercaptan, a particularly malodorous component.
Determination of the amount of methyl mercaptan present in untreated malathion is accomplished by means of gas-liquid chromatography. The malathion samples are heated at 56 C. for two hours. Vapors above the samples are collected and chromatographed at 30 C. on a six-foot column containing 10% of a mixture of cyanoethylmethyland .cyanodimethyl silicone gum. Each determination is accomplished with a flame ionization detector. The amount of methyl mercaptan present in each sample is reported in Table 11 below.
TABLE II 20 time, is N('N-1).
temperature held at either 34 C. or 60 C. for either 15 or 41 days. Untreated samples of each material stored under identical conditions are employed as controls. After storage for 15 or 41 days, the samples are 5 evaluated by the known Scheffes method of paired comparisons. The comparisons are randomized amongst a panel of judges with each observation or comparison of a sample pair being made by a different judge. To eliminate a possible bias due to the desensitization of the 01- factory nerves by the first sample prolfered, thereby causing a preference for the second, both orders of presentation for each sample pair are obtained for evaluation. In addition, all panels have been run in duplicate, and the degree of reproducibility has been good.
From a statistical point of view, to determine the relative preference of N samples, each sample is compared with each of the other (N-l) samples. With both orders of presentation -for each pair of samples, the number of permutations or combinations for N samples, two at a Preferences are scored on an arbitrary numerical scale, 12 for a higher preference, and 0 for no preference. The sign of the score depends upon whether the preference is for the first or second sample proffered. The preferred sample receives a positive score when it is proffered first and negative score when proifered second. In the absence of a desensitization effect and random or systematic error, the sum of the scores for both orders of presentation for each sample pair would be zero. When there is no preference for either sample, a 0 score is entered for the sampled proffered first.
A scoring box is made up with the row scores pertaining to the preference of samples proffered first and column scores pertaining to the preference of samples proffered second. The total score for each sample is obtained by making a sign change when adding the column scores to the row scores. After the rows and columns have been added, and allowing for the necessary sign changes, the sample with highest positive score will be the most preferred and the other samples can be ranked in descending order. The results of the above tests are presented in Table III below.
Untreated, Technical 0,0-Dimethyl Phosphorodithioate of DiethylMercaptosuccinate MethylMercaptan (p.p.m.) Days in 56 C. Bath Technical plus 0% ethyl glyoxylate 81 1,300 622 6, 300 Technical plus 0.5% ethyl glyoxylate. 0 0 0 2, 560 Technical plus 1.0% ethyl glyoxylate. 0 0 0 44 Technical plus 1.5% ethyl glyoxylate 0 0 1.9 0
Example 3 Deodorization of 0,0- diethyl S- (ethylthio)methyl phosphorodithioate is demonstrated by the following procedure wherein 2.0% by weight of ethyl glyoxylate is mixed with samples of the technical grade material and with distilled technical grade material and stored at a 75 various aldehydesi The data also show that the addition of 1.5%
TABLE III [Odorpreierence scores of 0,0-diethyl S-(ethylthiomethyDphos horodithioatc [Thimet] containing 2.0% ethyl glyoxylated by wei ght] O Oripr PanebScore,
ven a s Thimet Sample Temp, y m ven Technical 84 6 3 Technical plus Ethyl Glyoxylate 34 4 1 0 D stilled 34 0 7 Distilled plus Ethyl Glyoxylate 34 10 11 Example 4 In this example, the marked odor control capacity of n the treatment of phosphorodithioates is demonstrated by the following tests wherein 0,0-dimethyl phosphorodithioate of diethyl mercaptosuccinate, O,()-diethyl S-(ethylthiomethyl) phosphor-odithioate and 0,0-diethyl S-(N-methylcarbarnoylmethyl)phosphorodithioate are treated with from about 1% to about 4% by weight of a variety of aldehydes and mixtures of such al dehydes. In these tests, the technical grade phosphorodithioatesare admixed with aldehyde, permitted to stand for about 24 hours, and then sniffed to determine the level of odor control achieved by the various treatments. Untreated technical grade material is used as a control. The results of the tests appear in Table IV below.
3. A process according to claim 1 wherein the aldehyde present ranges between about 1% and about 4%, by weight.
4. A method according to claim 1 wherein the aldehyde is ethyl glyoxylate.
. 5. A method according to claim 1 wherein the aldehyde is methylprotocatechuic aldehyde.
6. A method according to claim 1 wherein the aldehyde is ethy-lprotocatechuic aldehyde.
7. A process according to claim 1 in which the malodorous thiophosphate is 0,0-dimethyl phosphorodithioate of diethyl mercaptosuccinate.
TABLE IV Sample Additive Percent Odor Control Added 0,0-dimethyl phosphorodithioate of diethyl mer- Benzaldehyde 1 Good, ahnond-like odor.
D Ethyl glyoxylate 2 Good, little or no odor.
Methylprotocatechuic aldehyde. 1 Good, slight vanilla odor. Ethylprotocatechuie aldehyde 1 Good, slight vanilla odor.
Control no additive Benzal ehyde Methylprotoeateehuie aldehyde Ethylprotocateehuie aldehyde Poor, malodorous. Good, strong almond odor.
4 Good, vanilla odor.
4 Good, vanilla odor.
2 Good, Slight vanilla odor. 2
Benzaldehyde Good, slight almond odor. Methylprotoeatech e aldehyd Good, slight almond odor. Salieylaldehyde Good, nitrobenzene-like odor. D Control, no additive Poor, malodorous. Op-diethyl S-(N-methylcarbamoylmethyDphos- Ethylprotocatechuic aldehyde 1 Good, vanilla odor.
Do Control, 110 additive Poor, malodorous.
I laim; 8. A process according to claim 1 in Which the mal- 1. A method for the upgrading of an untreated, malodorous thiophosphate is 0,0-diethyl S-(ethylthiomethyl) odorous, mercaptan-containing thiophosphate pesticidev phosphorodithioate.
9. A process according to claim 1 in which the malodorous thiophosphate is 0,0-dimethyl S-(N-methylcarbamoylmethyl) phosphorodithioate.
10. A method according to claim 1 in which the treating temperature is maintained between about 0 C. and about C.
No references cited.
CHARLES E. PARKER, Primary Examiner.
BERNARD BILLIAN, FRANK M. SIKORA,