Organic compounds -- part of the class 532-570 series – Organic compounds – Amino nitrogen containing
Reexamination Certificate
1999-08-24
2002-06-25
Barts, Samuel (Department: 1621)
Organic compounds -- part of the class 532-570 series
Organic compounds
Amino nitrogen containing
C564S332000, C564S333000
Reexamination Certificate
active
06410789
ABSTRACT:
The invention relates to a process for preparing aromatic polyamine mixtures from unsubstituted or substituted aniline and formaldehyde or formaldehyde precursors or a condensation product of these compounds.
Unsubstituted or substituted diaminodiarylmethanes are valuable precursors particularly for the preparation of plastics. The unsubstituted diaminodiphenylmethane (frequently called methylenedianiline, MDA), especially, is produced industrially in very great amounts and the majority, after phosgenation to give methylenediphenyl diisocyanate (MDI), is used for the preparation of polyurethanes. Preferably, the 4,4′ isomer is used for this, but the 2,4′ and 2,2′ isomers are also produced in the known preparation processes. In addition, more highly condensed polynuclear compounds are formed. They are generally prepared from aniline and formaldehyde in the presence of catalysts.
In the industrially used processes, inorganic acids in dissolved form are used as homogeneous catalysts. Preferably, aqueous hydrochloric acid is used. This reaction procedure leads, owing to the work-up, to the consumption of equimolar amounts of bases, since the acids still need to be neutralized during the isolation of the desired polyamines. This process is therefore inevitably associated with a production of correspondingly high amounts of salt which must be disposed of or recirculated by complicated means. In addition, the corrosion problems associated with the use of aqueous acids are a considerable disadvantage of this process.
For this reason, great consideration has been given to, and there have been numerous attempts at replacing aqueous homogeneous catalysts by acid heterogeneous catalysts. In addition to acid ion exchangers, the use of acidic synthetic or natural silicon oxides or aluminum oxides, such as zeolites or clay minerals, has been proposed. DE-A-1 230 033, DE-A-1 493 431, U.S. Pat. Nos. 4,071,558, 4,039,580, 4,039,581, and 4,294,987 describe corresponding catalysts.
According to U.S. Pat. No. 4,294,981, in a process of this type, the condensation is carried out in the presence of a strong aqueous acid, after which the acid is removed by solvent extraction. The rearrangement is in turn carried out in the presence of strong acid which is used in a smaller amount. Diatomaceous earth, clay or zeolites can be used in this stage.
According to DE-A-1 230 033, siliceous clay, a synthetic silicon dioxide-aluminum oxide catalyst or a magnesium oxide-aluminum oxide catalyst is used.
According to DE-A-1 493 431, silicon dioxide, silicon dioxide/aluminum oxide or acid-treated aluminum oxide is used as catalyst. Preferably, silica gel or bentonite-like clay, which contains silicon dioxide and aluminum oxide and is preferably acid-activated, is used. However, considerable amounts of higher condensation products are formed in addition to the desired diaminodiarylmethanes.
According to U.S. Pat. No. 4,071,558, an acid-activated clay catalyst, a silicon dioxide-aluminum oxide cracking catalyst or a silicon dioxide-magnesium oxide catalyst is used. Here too, relatively large amounts of 2,4′ isomers and higher molecular weight products are formed when using the clay catalyst.
According to U.S. Pat. Nos. 4,039,580, 4,039,581 and 4,294,987, a mixture of diaminodiarylmethanes and more highly condensed oligomers is obtained in a complicated two-stage process. Apart from aqueous acids, use is also made of diatomaceous earth, clays or zeolites.
According to U.S. Pat. No. 4,294,987, the condensation is carried out in the presence of a strong aqueous acid, after which the acid is removed by solvent extraction. The rearrangement is again carried out in the presence of strong acid which is used in a smaller amount. Diatomaceous earth, clays or zeolites can also be used in this stage.
According to U.S. Pat. No. 4,039,580, a condensation of aniline and formaldehyde is carried out in the absence of a catalyst and the condensation product is reacted in the presence of diatomaceous earth, clays or zeolites. The diamine content of the product is from 44 to 50%. U.S. Pat. No. 4,039,581 describes similar reactions. However, owing to their high prices, their insufficient activities or unsatisfactory catalyst operating lives, these catalysts have not been able to become established in the industry. High proportions of 4,4′ isomers and very low contents of more highly condensed products cannot be obtained in these processes. Relatively large proportions of 2,4′ or 2,2′ isomers are always obtained.
For this reason, there continues to be a demand for heterogeneous catalysts which are inexpensive, have a high activity and a long operating life, are environmentally compatible and lead to high yields of 4,4′ isomers with small amounts of more highly condensed products.
It is an object of the present invention to provide catalysts which have the abovementioned properties, and to provide a process for preparing aromatic polyamine mixtures.
We have found that this object is achieved by a process for preparing aromatic polyamine mixtures which contain compounds of the formula (I)
H
2
N—A—CH
2
—B—NH
2
(I)
where A and B are 1,4-phenylene radicals each of which independently of one another can have from 1 to 4 substituents selected from C
1-20
alkyls and halogens,
by reacting a compound of the formula (IV)
H—A—NH—CH
2
—HN—B—H (IV)
and/or a compound of the formula (V)
H—A—NH—CH
2
—B—NH
2
(V)
where A and B are substituted as above,
at from 20° C. to 200° C. in the presence of a heterogeneous inorganic catalyst selected from the group consisting of
a) one or more oxides of elements of group 3 to group 10, preferably group 4 to group 6, of the Periodic Table of the Elements, which can be acid-activated,
b) a catalyst comprising a clay which is doped with at least one oxide of elements of groups 2 to 13 or the lanthanides of the Periodic Table of the Elements and can be acid-activated or
c) a catalyst comprising one or more sheet silicates which may be acid-activated and have an acidity below pK
a
=1.5 of more than 0.05 mmol/g of catalyst.
In this process, the compound of the formulae (IV) and/or (V) can be obtained by reacting aniline, which is unsubstituted or substituted at the aromatic ring in the o- or m-position with from 1 to 4 substituents selected from C
1-20
alkyls or halogens, with formaldehyde or formaldehyde precursors.
In addition, the object is achieved by a process for preparing aromatic polyamine mixtures which contain compounds of the formula (I)
H
2
N—A—CH
2
—B—NH
2
(I)
where A and B are 1,4-phenylene radicals each of which independently of one another can have from 1 to 4 substituents selected from C
1-20
alkyls and halogens,
by reacting anilines, which are unsubstituted or substituted at the aromatic ring in the o- or m-position with from 1 to 4 substituents selected from C
1-20
alkyls and halogens, with formaldehyde or formaldehyde precursors at from 20° C. to 200° C. in the presence of a heterogeneous catalyst selected from the group consisting of
a) one or more oxides of elements of group 3 to group 10, preferably group 4 to group 6, of the Periodic Table of the Elements, which can be acid-activated,
b) a catalyst comprising a clay which is doped with at least one oxide of elements of groups 2 to 13 or the lanthanides of the Periodic Table of the Elements and can be acid-activated, or
c) a catalyst comprising one or more sheet silicates which may be acid-activated and have an acidity below pK
a
=1.5 of more than 0.05 mmol/g of catalyst.
Catalyst a)
It has been found according to the invention that oxides of elements of group 3 to group 10, preferably group 4 to group 6 of the Periodic Table of the Elements or their mixtures may be used highly advantageously as catalysts in the abovementioned reactions. The division into groups of the Periodic Table is in accordance with the new notation, see Cotton and Wilkinson, Advanced Inorganic Chemistry, 5th edition, John Wiley & Sons.
Preferably, oxides of
Becker Rainer
Eller Karsten
Hesse Michael
Langensiepen Hans-Werner
Barts Samuel
BASF - Aktiengesellschaft
Keil & Weinkauf
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