Manufacturing process for aminoalkyl silanes

Details Manufacturing process for aminoalkyl silanes Manufacturing process for aminoalkyl silanes

2001-11-26

2002-07-23

Shaver, Paul F. (Department: 1621)

Organic compounds -- part of the class 532-570 series

Organic compounds

Silicon containing

Reexamination Certificate

active

06423858

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a process for manufacturing aminoalkylsilanes.
2. Description of the Background
A method for manufacturing aminoalkylsilanes, of which 3-aminopropyltriethoxysilane (AMEO) is an example, is known, wherein a chloroalkylsilane, such as 3-chloropropyltriethoxysilane (CPTEO), reacts in batches with an excess of ammonia or an organic amine in liquid phase, for example, with ammonia at T=90° C., p=50 bar abs. and time=6 h. The product is then evaporated or concentrated and the pressure is reduced, at which point excess ammonia escapes and ammonium chloride is yielded in crystalline form. The evaporation process generally requires a period of time of over 10 hours. The ammonium chloride is usually separated from the crude product by filtration. The crude product is then distilled (DE-OS 27 49 316, DE-OS 27 53 124). However, a distinct disadvantage of this process is that, when the pressure is reduced over the product mixture, instances of caking occur, involving cakes of ammonium chloride or aminohydrochlorides. These cakes appear on the wall of the synthesis reactor, as well as on the stirring apparatus, and have a negative influence on heat transfer during the evaporation process. The deposits and caking require the plant to be at a frequent standstill, in which case the synthesis reactor has to be shut down, emptied, opened, filled with water in order to dissolve the ammonium salt crust, or freed of the cakes by mechanical means, then dried and closed.
EP 0 849 271 A2 also discloses the manufacture of 3-aminopropyltrialkoxysilanes from 3-chloropropyltrialkoxysilanes and ammonia by continuous operation. However, the disadvantage of this process is that even with a 100 fold excess of ammonia in relation to chloropropyltrialkoxysilane and an additional secondary reaction at 120° C., a 95% maximum yield of crude silane mixture is only obtained from primary, secondary and tertiary aminosilanes.
Apart from the distillation and separation of precipitated ammonium chloride, additional pressure extraction is required for product separation. A need, therefore, continues to exist for an improved process of manufacturing 3-aminopropylalkoxysilanes.
SUMMARY OF THE INVENTION
Accordingly, one object of the invention is to provide an improved and more efficient process for manufacturing amninoalkylsilanes, particularly for the manufacture of 3-aminopropylalkoxysilanes.
Briefly, this object and other objects of the present invention as hereinafter will become more readily apparent can be attained by a process for the manufacture of aminoalkylsilanes of formula I:
R
1
R
2
N—(CH
2
)
y
—Si(OR
3
)
3−n
R
4
n
  (I)
wherein R
2
and R
2
are each independently, identical of different, hydrogen, aryl, arylalkyl or C
1-4
-alkyl; R
3
and R
4
are each independently, identical or different, C
1-8
-alkyl or aryl; y is 2, 3 or 4 and n is 0 or 1, 2 or 3, comprising:
reacting an organosilane of formula II:
X—(CH
2
)
y
—Si(OR
3
)
3−n
R
4
n
  (II),
wherein X is Cl, Br, I or F; and R
3
, R
4
, y and n are each as defined above with ammonia or an organic amine compound of the formula:
HNR
1
R
2
  (III),
 wherein
R
1
and R
2
are each as defined above with at least one of R
1
and R
2
not being hydrogen in a liquid phase;
evaporating ammonia or organic amine under reduced pressure while ammonium chloride or aminohydrochloride by-products, produced in the reaction of the first step, remains dissolved in the liquid phase;
transferring the product mixture after said evaporation to another vessel operated at a lower pressure level of than the second stage, and allowing ammonium chloride or aminohydrochloride to crystallize;
separating the crystalline ammonium chloride or aminohydrochloride from the crude product; and
distilling the crude product to produce purified aminoalkylsilane product.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
It has now been discovered, surprisingly, that aminoalkylsilanes can be manufactured simply and economically by reacting an alkylarylsilane, such as 3-chloropropyltriethoxy silane (CPTEO), in a first process stage with an excess of ammonia or an organic amine used in excess in a liquid phase, and then evaporating ammonia or organic amine in a second process stage under reduced pressure, wherein a substantial portion of excess ammonia or organic amine escapes and ammonium chloride or predominantly aminohydrochloride remains, appropriately fully dissolved in a liquid phase. The product mixture from the second process stage is then transferred to a vessel, operated at a lower level of pressure than in the evaporation step, and ammonium chloride or aminohydrochloride crystallizes. The crystalline ammonium chloride or aminohydrochloride is separated from the crude product and finally the crude product is processed by distillation to provide purified aminoalkylsilane product.
The present invention, in particular, provides an effective method of producing aminoalkylsilanes having formula I above by the reaction of an organosilane having formula II shown above with ammonia or a nitrogen compound having formula III shown above.
Preferred suitable 3-chloralkylalkoxysilanes include 3-chloropropyltriethoxysilane, 3-chloropropyltrimethoxysilane, 3-chloropropylmethyldimethoxysilane and 3-chloropropylmethyldiethoxysilane as the organosilane of formula II. However, other chloralkylalkoxysilanes, such as, for example, 3-chloropropyldiethylmethoxysilane or 3-chloropropylethylpropylethoxysilane, can also be employed in the present process.
In the process of the present invention ammonia, methylamine, ethylamine or diethylamine is preferably used as nitrogen containing constituent having formula III.
Examples of products of the present invention which can be manufactured simply and economically include 3-aminopropyltriethoxysilane, 3-aminopropyltrimethoxysilane, 3-aminopropylmethyldiethoxysilane and N-methyl-3-aminopropyltrimethoxysilane, to name but a few.
In the process of the present invention organosilanes of formula II and ammonia or an organic amine of formula III in liquid form are usually fed to a pressure reactor, in which case it is suitable to set the molar ratio of chloralkylalkoxysilane to ammonia or organic amine compound at 1:10 to 1:50. In the first process stage conversion generally takes place at a pressure of 25 to <100 bar abs. and at a temperature of 50 to <110° C., wherein conversion is almost complete. In addition, the almost complete portion of ammonium chloride or aminohydrochloride by-product remains dissolved in the liquid phase. Preferably more than 99%, in particular preferably 99.9% to 100%, of the ammonium chloride or aminohydrochloride resulting from the reaction remains dissolved in the liquid phase of the first stage. The resulting product mixture is then transferred to the second process stage, in which case the second process stage is performed at a substantially lower pressure than the first process stage. In the process, considerable quantities of ammonia are flashed removed, for example, 50% to 80% by weight of the excess ammonia or organic amine. This removal of excess reactant is effected by using an operating procedure in which the pressure transitions from 50 to 15 to 20 bar abs.
The second evaporative stage is normally performed at pressures of >10 to <50 bar abs., preferably 11 to 35 bar abs., more preferably 13 to 25 bar abs., and most preferably 15 to 20 bar abs., and at a temperature of >10 to <110° C., preferably 20° C. to 95° C., more preferably 30° C. to 85° C., and most preferably 35° C. to 80° C., so that ammonium chloride or aminohydrochloride remains almost completely dissolved in a liquid phase This procedure enables problems which arise from the accumulation of solids to be prevented as desired. In general, the evaporation times result from the excess quantities of ammonia and amine of the reaction and the available evaporation apparatus, evaporator surfaces and the like as we

Affiliated with

Also associated with

Rating

Manufacturing process for aminoalkyl silanes does not yet have a rating. At this time, there are no reviews or comments for this patent.

If you have personal experience with Manufacturing process for aminoalkyl silanes, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Manufacturing process for aminoalkyl silanes will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFUS-PAI-O-2816406