JPS5828844B2 - Method for stabilizing carbamates - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for stabilizing carbamates, and more particularly to a method for improving the thermal stability of carbamates.

The following general formula CI, 1 (wherein A is an alkyl group having 1 to 5 carbon atoms or a phenyl group optionally substituted with a halokene atom, or α
Carbamate compounds represented by -naphthyl group and R1 represents an alkyl group having 1 to 4 carbon atoms are widely used as agricultural chemicals.

This carbamate compound can usually be easily produced from incyanate and alcohol or phenol, but generally carbamate compounds are unstable to heat, for example, when heated above their melting point, a portion of the carbamate compound is It has the disadvantage of decomposing into isocyanate and alcohol or phenols.

Therefore, for example, when producing a carbamate compound that is solid at room temperature, the carbamate is usually processed in a molten state from the time it is produced until it is powdered. , there is a problem that a pungent odor of incyanate is generated.

In addition, in order to use powdered or liquid carbamate as a pesticide,
Agrochemicals are prepared by mixing with various compounding agents, but there is a similar problem in that the carbamate decomposes when heat treatment is performed in this preparation process as well.

Several methods have been proposed to overcome these problems, but none have yet been found to be satisfactory.

In view of the above circumstances, the present inventors conducted various studies on methods for improving the thermal stability of the carbamate compound of the general formula CI, 10, and found that the thermal stability was significantly improved by blending a certain specific compound. The present invention was completed based on the findings.

That is, the gist of the present invention is to add the following general formula Cn to a melt of a carbamate compound represented by the general formula CI, l.
) ~ (IV, 1 (wherein, R2 represents a phenyl group optionally substituted with an alkyl group having 1 to 8 carbon atoms, a halogen atom, or an alkyl group having 1 to 4 carbon atoms) Alternatively, there is provided a method for stabilizing carbamates, which comprises blending at least one compound selected from phosphite esters.

The present invention will be explained in detail below.

The carbamate compounds of the general formula [■] that are the object of the present invention include, for example, m-cresol, 0-ethylphenol, p-iso-7"ropylphenol, o-5e
c-butylphenol, on-pentylphenol,
Phenol substituted with an alkyl group having 1 to 5 carbon atoms such as 3,5-dimethylphenol, 0-chlorophenol, p-chlorophenol, o-7''romphenol
Phenol or α- substituted with lunatonohalogen atom
Alcohol or phenol components such as naphthol and, for example, methyl isocyanate, ethyl isocyanate, n
-7" carbamates synthesized from incyanate components such as lopylisocyanate, 1so-butyl isocyanate, and n-butyl isocyanate. Specific examples include 0-secondary-butylphenyl-N-methyl carbamate, m- tert -butylphenyl-N
-methylcarbame), o-1so-furobylphenyl-N-methylcarbamate, m-tolyl-N-methylcarbamate, 3,5-dimethylphenyl-N-methylcarbamate, o-chlorophenyl-N-methylcarbamate, Examples include 0-n-butylphenyl-N-ethylcarbamate, p-chlorophenyl-N-n-furobylcarbamate, and α-naphthyl-N-butylcarbamate.

On the other hand, examples of the phosphoric acid ester or phosphite of advance general formula [■] ~ (IV, l) include dimethyl phosphate, diethyl phosphate, di-n-butyl phosphate, di-n-hexyl phosphate. , phosphoric acid diesters such as di-n-octyl phosphate, diphenyl phosphate, di-m-tolyl phosphate, monomethyl phosphate, monoethyl phosphate, monopropyl phosphate, mono-n-pentyl phosphate, monophosphate -n-
Phosphate monoesters such as heptyl, monophenyl phosphate, mono-m-tolyl phosphate, mono-p-chlorophenyl phosphate, monomethyl phosphite, monoethyl phosphite,
Mono-n-butyl ring phosphate, mono-n-octyl phosphite, monophenyl phosphite, mono-o-see phosphorous acid
Examples include phosphorous acid monoesters such as -butylphenyl.

Phosphate triesters such as triphenyl phosphate and triethyl phosphate, phosphite diesters such as dimethyl phosphite and diethyl phosphite, or phosphorous triesters such as ring triphenyl phosphate and triethyl phosphite are used. In this case, the thermal stability of the carbamate cannot be sufficiently improved.

The blending ratio of the phosphoric esters of the present invention described above is usually:
The amount is from 0.01 to 3% by weight, preferably from 0.02 to 1% by weight, based on the carbamate compound.

If this blending ratio is too small, the thermal stability of the carbamate cannot be sufficiently improved; conversely, if it is too large, there is no difference in the effect (not only does the purity of the carbamate decrease, but it is also economically unfavorable). .

In the present invention, two or more of the above phosphoric esters,
They may be used in combination, and may also be mixed with other heat stabilizers and various additives for preparing agricultural chemicals.

☆Y As a method of blending a phosphoric acid ester with a carbamate compound, the phosphoric acid ester is mixed into a liquid (molten state) carbamate and stirred to form a uniform mixture.

In the case of a compound that is solid at room temperature, if a predetermined amount of phosphoric acid ester is added immediately after the production of the carbamate in a molten state, even if the carbamate is heated and melted in the subsequent transfer process and powdering process, Even if heat treatment is performed during the preparation of the agricultural chemical, decomposition of the carbamate is significantly suppressed, which is preferable.

As described above, in the present invention, the thermal stability of carbamate is greatly improved, so that no irritating odor is generated during heat treatment of carbamate, and the working environment is improved and practical.

Next, the present invention will be explained in more detail with reference to examples, but the present invention is not limited to the following examples unless it exceeds the gist thereof.

Example 1 A composition in which each of the phosphoric acid esters shown in Table 1 was blended with 500 liters of o-see-butylphenyl-N-methylcarbamate (melting point 28°C) was prepared in 11 closed molds equipped with a stirrer and a heating device. After charging the mixture into a container and heating it to 80°C to melt the carbamate and holding it for 15 hours while stirring, the concentration of methyl isocyanate (produced by decomposing the carbamate) in the melt was measured by gas chromatography. The results shown in Table 1 were obtained.

Example 2 In Example 1, a composition was prepared in which the compound shown in Carbamay was mixed with 0.2 wt% of di-n-★★butyl phosphate in Table 2, and the heating temperature was set at 100°C. Thermal stability tests similar to those in Example 1 were conducted and the results shown in Table 2 were obtained.

Example 3 A similar thermal stability test was carried out in Example 2 using the compounds shown in Table 3 as carbamates, but with the heating temperature kept at 150° C., and the results shown in Table 3 were obtained.

Reference Example In Example 1, a similar test was conducted using the compounds shown in Table 4 outside the scope of the present invention as phosphoric acid esters, and the results shown in Table 4 were obtained.

From the above results, the carbamate composition obtained according to the present invention shows significantly less decomposition of carbamate even after heat treatment.
It can be seen that the amount of methyl isocyanate produced is low.

On the other hand, when phosphoric esters are not added, or when phosphoric esters other than those of the present invention are used, it can be seen that the concentration of methyl isocyanate is also high because the amount of carbamate decomposition is large.

Claims (1)

[Scope of Claims] 1 General formula CI below 4) is added to the melt of the carbamate compound represented by the following general formula (
II, l~(IV, l] (wherein, R2 has 1 to 8 carbon atoms
represents an alkyl group or a phenyl group optionally substituted with a halogen atom or an alkyl group having 1 to 4 carbon atoms)
1. A method for stabilizing carbamates, which comprises blending at least one compound selected from phosphoric acid esters and phosphite esters represented by: