JPH03227961A - Production of polyaminodiphenylmethane - Google Patents

Abstract

PURPOSE:To efficiently obtain the title compound in high yield useful as a raw material for producing high quality polyisocyanate by nitrating diphenylmethane with a nitrating agent and reducing a prepared mixture consisting essentially of dinitrophenylmethane. CONSTITUTION:Preferably a mixed acid of conc. nitric acid and conc. sulfuric acid as a nitrating agent is gradually dripped into 2-diphenylmethane melt, which is subjected to solventless liquid-phase reaction especially preferably at 40-80 deg.C for 10-180 minutes and nitrated. Then a mixture consisting essentially of dinitrodiphenylmethane shown by the formula readily obtained in high yield is reacted with a metal such as granular tin or a metallic compound and hydrochloric acid as a reducing agent in an inert solvent at 30-70 deg.C preferably for 1-3 hours under reflux by heating and nitro group is reduced into amino group to give the objective compound especially consisting essentially of diaminodiphenylmethane in high yield, industrially and advantageously.

Description

Detailed Description of the Invention (Industrial Application Field) The present invention relates to the production of polyaminodiphenylmethane, especially diaminodiphenylmethane, which is useful as an intermediate for the production of polymethylene polyphenyl polyisocyanate, particularly methylene diphenyl diisocyanate, which is a raw material for polyurethane. Regarding the method.

(Prior art) Polymethylene polyphenyl polyisocyanate is a substance useful as a raw material for the production of polyurethane elastomers and coating materials, and the amount used in this application is limited to that of tolylene, which has a problem of high volatility and strong toxicity. It has now surpassed isocyanate (TDI) and is being mass-produced on an industrial scale. In particular, methylene diphenyl diisocyanate, which is dinuclear, is important because it yields a high quality product.

Conventionally, methylene diphenyl diisocyanate has been produced by condensing aniline (I) and a substance that generates formaldehyde using an acid catalyst such as hydrochloric acid to produce an aromatic polyamine, as shown in reaction formula (A) below. (I
I), and then this polyamine was synthesized according to the following reaction formula (
As shown in B), a common method involves reacting with phosgene in the presence of an inert solvent to convert it into the corresponding polyisocyanate-1-(1).

(1) (n) Kawarachika Shikuchi IB (II) + COCl2 → (I) (Integer from mho to 6) After the reaction with phosgene, the reaction mixture is degassed and the solvent is then recovered to yield the polyisocyanate product. Obtainable. If necessary, the product may be purified by distillation or the like.

In the above - killing (n) and (III), the compound where m = o has two benzene nuclei and is therefore called a dinuclear compound, and the compound with m≧1 and three or more benzene nuclei is called a polynuclear compound. Called.

However, in the method described above, in the reaction of formula (A), m
Since polynuclear bodies with ≧1 are produced in a considerable proportion, it is difficult to obtain methylene diphenyl diisocyanate (m = 0; hereinafter referred to as MDI), which is a desirable dinuclear product, in high yield after the reaction of formula (B). Have difficulty.

As described above, it has not been possible to synthesize diaminodiphenylmethane, which is an intermediate of MDI, with a good yield using conventional methods.

(Problems to be Solved by the Invention) The present invention provides an industrially advantageous method for producing dinuclear polyaminodiphenylmethane, particularly diaminodiphenylmethane, in high yield.

(Means for Solving the Problems) The present inventors have discovered that dinitrodiphenylmethane represented by the following (IV) can be easily synthesized in high yield by nitration of diphenylmethane, and that It has been found that polyaminodiphenylmethane, whose main component is diaminodiphenylmethane, can be obtained in high yield from a mixture whose main component is dinitrodiphenylmethane, by a known reduction reaction of the nitro group.

The gist of the present invention is to nitrate diphenylmethane with a nitrating agent, and reduce the resulting mixture containing dinitrodiphenylmethane as the main component to convert the nitro group to an amino group. A method for producing polyaminodiphenylmethane.

The present invention will be specifically explained below.

According to the method of the invention, diphenylmethane is first nitrated with a nitrating agent.

This nitration step consists of diphenylmethane (melting point 26-2
It is preferable to carry out the reaction as a solvent-free liquid phase reaction by gradually dropping the nitrating agent into the melt at 7°C.
Other reaction methods can also be employed.

As the nitrating agent, a mixed acid of concentrated nitric acid and concentrated sulfuric acid is preferred, but fuming nitric acid may be used instead of concentrated nitric acid. The amount of the nitrating agent used is about 1.0 to 20.0 times in molar ratio to diphenylmethane.

The reaction temperature is preferably in the range of 20 to 150°C, particularly 40 to 80°C. When the reaction temperature exceeds 150°C, the amount of by-products such as trinitrodiphenylmethane increases,
The yield of the target dinitrodiphenylmethane decreases, and the reaction proceeds rapidly, making it difficult to control the reaction. 2
If the temperature is below 0°C, the reaction will be difficult to proceed and the reaction time will be too long.

The reaction time varies depending on the reaction temperature, the type of nitrating agent, the dropwise addition rate, etc., but the reaction is usually terminated by stirring the reaction mixture for about 10 to 180 minutes after the completion of the dropwise addition. As mentioned above, nitration is usually carried out without a solvent, but if necessary, an inert solvent such as acetic acid can be used as a nitration agent.

After the reaction is completed, the reaction mixture is washed with water to remove excess nitrating agent, and the nitrated product is recovered by dehydration and drying. Preferably, an organic solvent that dissolves the nitration product is added to the reaction mixture to extract the product into the organic phase, and the nitration agent is separated from the aqueous phase by separation. Then, the aN of this product
The liquid is washed with water as described above, and after drying, the solvent is evaporated and the desired nitrated product is isolated.

Nitration of diphenylmethane produces dinitrodiphenylmethane in high yield, and a mixture of borini-1-rodiphenylmethane containing dinitrodiphenylmethane as a main component is obtained as a reaction product. The content of each isomer of 2,2″-dinitrodiphenylmethane, 2,4dinitrodiphenylmethane, and 4,4″-dinitrodiphenylmethane in the product varies depending on the reaction conditions, but usually the majority is 4,4′-dinitrodiphenylmethane.
- isomers, and the amounts of the 2.2''- and 2,4''-isomers produced are small.

This reaction product may be directly subjected to the next nitro group reduction step, but if necessary, it may be purified by a conventional method such as distillation or recrystallization before being subjected to the next step.

The nitration product obtained in the nitration step is then reduced to convert the nitro groups into amino groups, thereby obtaining the desired polyaminodiphenylmethane whose main component is diaminodiphenylmethane.

This reduction can be carried out according to any known reduction reaction capable of reducing the nitro group of an aromatic nitro compound to an amino group. Usually, this reduction is carried out with a reducing agent consisting of an acid and a metal. As the reducing agent, for example, metals or metal compounds such as zinc, iron, tin, tin chloride, and hydrochloric acid can be used.

Reduction of the nitro group with metal/hydrochloric acid can be carried out by slowly adding hydrochloric acid to the mixture of the above nitration product and metal in an inert solvent. Here, the amount of the metal used is usually in the range of 0.1 to 10 times, preferably 0.5 to 2 times, in weight ratio to the di-I to B-compounded product. The amount of hydrochloric acid to be used varies depending on the concentration of hydrochloric acid used, but is usually in the range of 0.8 to 100 times, preferably 2 to 10 times, the weight ratio of the 21-ro conversion product.

This reduction reaction of the nitro group is carried out at a reaction temperature of room temperature to 90°C, preferably 30 to 70°C. If the reaction temperature exceeds 90°C, undesirable side reactions occur and the reaction progresses rapidly, making it difficult to control the reaction. As the inert solvent, aromatic hydrocarbons such as benzene and toluene, lower carbonic acids such as acetic acid, and alcohols such as ethanol can be used. After the hydrogen generation due to the addition of hydrochloric acid has subsided, the reaction is completed by further heating and refluxing for 0.1 to 10 hours, preferably 1 to 3 hours.

After the reaction, the inert solvent is removed, the residue is made strongly alkaline with an alkali such as sodium hydroxide, and the produced amino compound is extracted with a water-immiscible inert organic solvent.

As the extraction solvent, methyl ethyl kene, diethyl ether, dichloromethane, butanol, chloroform, etc. can be used.

After the extraction, the extraction solvent is recovered using a trapping trap to obtain the desired polyaminodiphenylmethane product whose main component is diaminodiphenylmethane.

The product thus obtained can be used for the production of polyisocyanates with phosgene, usually as is or, if necessary, after a purification step such as distillation, thereby producing a high-quality MDI-based aroma. A group polyisocyanate is obtained.

(Example) The present invention will be explained below with reference to Examples.

300 with reflux cooling pipe, thermometer and dropping funnel
Put 10g of diphenylmethane into a sterile flask,
It was heated to 50°C. While stirring, add mixed acid (70% by weight nitric acid, 796% by weight sulfuric acid) in a dropping funnel at a weight ratio of 8/1.
35g of the mixture in step 1) at a reaction temperature of 50 to 60°
The mixture was gradually added dropwise at a rate within the range of C. After the dropwise addition was completed, the mixture was further stirred at 60°C for 30 minutes. After the reaction, 100 ml of toluene was added, the aqueous layer was separated, the organic layer was washed with water and dried, and the toluene solution was analyzed by high performance liquid chromatography.

As a result, unreacted diphenylmethane was not detected, and 2
, 2′-dinitrodiphenylmethane, 2,4′-diaminodiphenylmethane, and 4,4′-dinitrodiphenylmethane, the yields of each isomer were 7.6, IQ, and 3, respectively.
and 68.8 mol%. Trinitrodiphenylmethane and mononitrodiphenylmethane were detected as by-products.

Actual difference flame I (reduction of nitro group) Toluene was recovered from the toluene solution obtained in Example 1 using an evaporator, and a solid substance containing residual dinitro diphenylmethane as a main component was obtained. A round bottom flask equipped with a reflux condenser, a stirrer, a dropping funnel, and a thermometer was charged with 2.0 g of the above solid, 15 ml of ethanol, and 4 g of granular tin, and 10 m2 of concentrated hydrochloric acid was added from the dropping funnel until the reaction temperature was 60°C. It was added gradually at a rate that did not exceed °C.

After the reaction had subsided, heating and stirring on a steam bath was continued for 1 hour. The reaction solution was cooled to room temperature, and while cooling with ice, 30 mft of aqueous alkaline solution containing 7 g of sodium hydroxide was gradually added to make the reaction solution strongly alkaline. Then, after recovering the ethanol by distillation, the residue was distilled to approximately 50 mp
.

The mixture was extracted with diethyl ether. Diethyl ether was removed from the extract by distillation, and the extract was further purified by vacuum distillation to recover 1.6 g of a polyaminodiphenylmethane product containing diaminodiphenylmethane as a main component.

When this product was analyzed by gas chromatography, 2,2'-diaminodiphenylmethane, 2,4'-diaminodiphenylmethane and 4
, 4'-diaminodiphenylmethane, the content of each isomer is 7.2, 9.7 and 69.
0% by weight, and triaminodiphenylmethane and monoaminodiphenylmethane were detected as by-products.

(Effects of the Invention) According to the method of the present invention, polyaminodiphenylmethane containing diaminodiphenylmethane as a main component can be efficiently obtained in high yield using diphenylmethane as a raw material.

Moreover, it is possible to produce only dinuclear polyaminodiphenylmethane, with almost no production of polynuclear polyamines as seen in conventional methods for producing aromatic polyamines, so it can be used as a raw material for producing high-quality polyisocyanates. A useful polyaminodiphenylmethane is obtained.

Claims (1)

[Claims] (1) Polyaminodiphenylmethane containing diaminodiphenylmethane as the main component, which is characterized by nitrating diphenylmethane with a nitrating agent and reducing the resulting mixture containing dinitrodiphenylmethane as the main component to convert the nitro group into an amino group. manufacturing method.