KR810001698B1 - Process for the preparation of diphenylmethane dicarbamates and polymethylene polyphenyl carbamates - Google Patents

Abstract

Diphenylmethane dicarbamates and polymethylene polyphenyl carbamate homologs and derivatives of these compounds are porduced by the condensation of N-aryl carbamic acid esters, such as ethyl phenyl carbamate, with formaldehyde, para-formaldehyde or trioxane in the presence of an organic sulfonic or halogenated organic sulfonic acid which has an acid concentration of at least 75 %, at temperatures of from ambient to about 175≰C, and optionally in the presence of an inert solvent.

Description

Diphenylmethane dicarbamate and polymethylene poly phenyl carbamate production process

The present invention relates to the preparation of aromatic carbamic acid esters, in particular diphenylmethane dicarbamate and related higher homologs and derivatives, by condensing N-aryl carbamic acid esters with carbonyl compounds in the presence of organic or halogenated organic sulfonic acids.

Carbamic acid esters (polyurethanes), polymers such as dimenylmethane dicarbamate and the higher homologs thereof, polymethylene polyphenyl carbamate, are of increasing value as important products, in particular US Pat. Nos. 3,962,302 and 3,919,279 It is used to prepare a valuable diisocyanate and polyisocyanate mixture and diphenylmethane diisocyanate as commodity by decomposing the aromatic carbamic acid ester as a polymer in a suitable solvent as shown.

At present, there is no method for successfully producing a polymerizable aromatic ester of carbamic acid directly. Commercially valuable diphenylmethane diisocyanates and polyisocyanates are prepared by phosgenation of a mixture of polyamines and diamines, most of which are made by condensing aniline and formaldehyde in the presence of a catalyst such as an inorganic acid. That's an example.

Conventional methods for preparing polymerizable aromatic carbamic acid esters (polyurethanes) include, for example, US Pat. No. 2,946,768 and UK Pat. No. 461,352. According to the patent, aldehydes and ketones in condensation media of diluted inorganic acids Condensation of the same carbonyl compound and arylcarbamic acid ester.

In this process, carbonyl compounds such as formaldehyde belong to the undesirable N- (alkoxycarbonyl) -phenylaminomethylphenyl compounds containing dimers, trimers, tetramers, etc. in response to the nitrogen of the carbamate salts. Although the amount of polyurethane is different, it generally produces about 15-50 wt%. This compound is called N-benzyl compound, which is fully described in US Patent Application No. 905,705 (filed May 5, 1978). have. N- (alkoxycarbonyl) phenyl amino methylphenyl impurities, although efforts have been made to prepare diisocyanates and polyisocyanates or to use compounds containing polyurethanes which cannot be converted to isocyanates by pyrolysis, but which contain these unnecessary compounds and polyurethanes. Since there is no way to separate the polyurethane from it, there are various problems.

The present invention condenses formaldehyde, paraformaldehyde or trioxane and N-arylcarbamic acid esters in the presence of an organic sulfonic acid with an acid-concentration of at least 75% to diphenylmethane dicarmate and polymethylene polyphenyl carbamate homologues. And it is possible to avoid the various problems and the generation of such impurities as described above by the present invention as a derivative of the compound.

Organic sulfonic acids used in the process of the invention are excellent catalysts for condensing N-arylcarbamate for a variety of reasons. That is to say, (1) since it has an organic substitution factor, sulfonic acid is generally much more soluble in carbamate solution than inorganic acid, so it proceeds single phase reaction at working concentration, and (2) considerably strong acid. Phosphorus organosulfonic acid eliminates the formation of N- (alkoxycarbonyl) phenylaminomethylphenyl impurities during condensation, and (3) unnecessary side reactions such as chlorination, which is the reaction of sulfuric acid with hydrochloric acid, and sulfonation of N-arylcarbamate, It is not. Since these side reactions can be suppressed, the higher-quality diphenylmethane dicarbamate and polymethylene polyphenyl carbamate products are thermally decomposed into polymerizable aromatic isocyanates, resulting in much higher yields of isocyanates.

The present invention relates to a carbonyl compound selected from formaldehyde, paraformaldehyde or trioxane or mixtures thereof in the presence of an organic sulfonic acid catalyst medium having an acid concentration of at least 75% in alkanesulfonic acid, halogenated alkanesulfonic acid and aromatic sulfonic acid. A method of condensing N-arylcarbamic acid esters to produce polymethylene polyphenyl carbamate, which is a diphenylmethane dicarbamate and a high molecular weight homologue.

By the method of the present invention, diphenylmethane dicarbamate and related polymethylene polyphenyl carbamate can be produced in high yield by condensing carbonyl compound and N-arylcarbamic acid ester in the presence of organic sulfonic acid. The reaction by the organosulfonic acid catalyst can generally be carried out in a suitable reactor equipped with a stirring device and a temperature controller. As a general method of advancing the reaction, N-arylcarbamic acid ester and a solvent are added to the reaction vessel depending on the circumstances, and at the same time, a carbonyl compound and a sulfonic acid catalyst, such as formaldehyde, are added to the required reaction temperature for a predetermined time. Or cool as needed.

A heating or cooling device is used inside or outside the reactor to maintain the temperature in the required range. The reaction can be batch, semi-continuous or continuous and the order in which the materials are added varies depending on the particular apparatus used. The reaction product is recovered and treated in a conventional manner, that is, the acid component is extracted as water or neutralized with an appropriate inert base, and then each phase is separated and distilled to remove the solvent used. Among the N-arylcarbamic acid esters used as reactants in the condensation reaction with an acid catalyst, at least one carbamic acid ester group, that is, -NHCOCR group (where R is an alkyl group, an aryl group, or an alkyl substituted element having up to 8 carbon atoms) Up to 4 alkyl-substituted aryl groups). Likewise, the N-aryl groups of the carbamic acid esters may have substituents such as alkyl groups, alkoxy groups, halogens, etc. in the ring. Preference is given to using lower alkyl esters, ie ethyl esters such as ethylphenyl carbamate.

N-arylcarbamic acid esters used in the present invention can be prepared according to the method of US Pat. No. 3,895,054 to zajacek et al. Carbamic acid esters (urethanes) are prepared by reacting at a constant temperature and pressure in the presence of a base or water, or according to known aromatic carbamate production methods.

Carbonyl compounds that can be used in the process of the invention are formaldehyde or paraformaldehyde and trioxane, which are those which can form formaldehyde monomers in the presence of acid.

The amount of carbonyl compound relative to the N-arylcarbamic acid ester used in the reaction depends on the degree of condensation or polymerization required in the reaction product. In general, the molar ratio of the N-aryl carbamic acid ester to the carbonyl compound in the form of free formaldehyde in the reaction mixture is about 1.5 to 8: 1. In the higher range, the dimer carbamate production is overwhelming, while in the lower range the higher polymerizable polymethylene polyphenyl carbamate is overwhelming.

Organic sulfonic acid media suitably used in the present invention as condensation reaction catalysts include halogenated alkanesulfonic acids or aromatic sulfonic acids having up to 10 carbon atoms in the alkanesulfonic acid or alkyl group. Mixtures of sulfonic acid catalysts may be used but each acid catalyst is preferred to reduce the problems associated with recovery.

Representative organic sulfonic acid catalysts that can be particularly suitably used in the present invention include sulfonic acid, trifluoromethane sulfonic acid, trichloromethane sulfonic acid, P-toluene sulfonic acid, benzenesulfonic acid and the like of methane, ethane and butane. . The general use concentration of the organosulfonic acid is about 0.1 to 75% of the N-arylcarbamate used, preferably 5.0 to 50 wt%.

Even if the process according to the invention is carried out in the presence of a solvent at a high reaction temperature of 60 ° C. or higher, it should be a chemically inert and safe solvent or solvent mixture with respect to the components of the reaction system and when used, it should generally be considered as the viscosity of the condensation reaction product. Appropriate amount of solvent is generally in the range of 0-50 wt.%, Based on the reaction mixture, and suitable solvents include nitrated and halogenated aromatic hydrocarbons having up to 12 carbon atoms, and examples thereof include nitrobenzene, nitrotoluene, chlorobenzene, and dibro. Parent alkenes and substituted alkanes and alkanes having up to 16 carbon atoms, which belong to n-heptane, isopentane, n-hexane, 2-methylpentane, n-pentane, 2,4-dimethylhexane Lower aliphatic acids having up to 8 carbon atoms, including 2-methylhexane, 2-ethylpentane, cyclopentane, cyclohexane, methylchlorohexane, ethylcyclopentane, cyclooctane, chloroform, carbon tetrachloride, dichloroethane, etc. Examples: acetic acid, propionic acid) and lower aliphatic alcohols with up to 8 carbon atoms (e.g. methanol, ethanol, propanol, butanol, etc.). Nitrobenzene and florobenzene are good solvents to use. Although the amount of solvent used may be large, it is generally not necessary to consider the burden on recovery. Although solvent mixtures may be used as described above, it is preferable to use individual solvents to avoid problems in recovery.

The reaction according to the present invention proceeds at a temperature from practical to 170 ° C. In general, it is preferable to proceed with the reaction at a temperature of about 50 ° ~ 130 ° C to obtain a convenient reaction rate.

Although high pressures can be used to react at high temperatures, the process according to the invention is generally carried out at atmospheric pressure. If necessary, the process may be carried out at negative pressure. The reaction time generally depends on the reaction temperature of N-arylcarbamate and the amount and type of the sulfonic acid catalyst used. The reaction time also varies depending on whether the reaction is continuous or discontinuous, but the general reaction time is about 2 minutes. It ranges from a few hours to a few hours.

In the examples that follow, the reaction is carried out in a 300 ml or three necked reaction flask with a suitable volume equipped with a mechanical stirrer, reflux cooler and thermometer.

After adding the reaction to the reaction flask, the flask is immersed in a constant temperature oil bath. At the end of the reaction, water is added to the flask to quench the reaction and extract the sulfonic acid catalyst medium. The condensate can be washed with additional water or INNaOH solution is added to neutralize the remaining acid and solvent. The conversion of the added N-arylcarbamate, the yield of the condensation product, and the distribution of the polymer are determined by high performance liquid chromatography.

Example 1

To a mixture of 120 g ethylphenylcarbamate, 120 g nitrobenzene and 25 g trifluoromethane sulfonic acid, add 12.1 g of trioxane to 24.2 g of nitrobenzene over 25 minutes. External cooling is allowed to maintain the temperature at 25 ° C. during trioxane addition. The reaction mixture is again stirred at 25 ° C. for 20 minutes and then heated to 70 ° C. over 45 minutes. The final product only contains a trace (<1%)-N-alkoxycarbonyl) terylaminomethylphenyl as an impurity. The product is a mixture of diphenylmethane dicarbamate (-50%) and the high polymer carbamade (polymethylene polyphenyl carbamate). The isocyanate product, which is separated after pyrolysis of carbamate, contains 31 wt% of isocyanate groups.

Example 2-15

As shown in the table, up to Examples 2-15 are repeated following the general method of Example 1 using various N-arylcarbamate sulfonic acid catalysts, solvents and reaction conditions.

In Examples 2, 3 and 4, an acid catalyst was initially added at 25 ° C. over 20 minutes, 10 minutes and 5 minutes, respectively, to a mixture of carbonyl compound, carbamate and solvent. In Examples 5-15, both the reactant solvent and the acid are mixed, and the exothermic reaction mixture generated at this time is controlled at the reaction temperature for the required time.

TABLE 1

(1) EPC-ethylphenylcarbamate

(2) BPC-1-butyl-N-phenylcarbamate

(3) EMPC-ethyl-O- (2-methylphenyl) carbamate

(4) MPC-methyl-N-phenylcarbamate

The title of each column

Claims (1)

N- and carbonyl compounds selected from formaldehyde, paraformaldehyde or trioxane or mixtures thereof in the presence of an organic sulfonic acid catalyst medium having an acid concentration of at least 75% in alkanesulfonic acid, halogenated alkanesulfonic acid and aromatic sulfonic acid. A method for producing diphenylmethane dicarbamate and polymethylene polyphenyl carbamate by reacting an aryl carbamic acid ester to recover the required carbamate.