Method of making N-[2-aminoethyl]...

Details Method of making N-[2-aminoethyl]... Method of making N-[2-aminoethyl]...

2002-02-11

2002-09-17

Shaver, Paul F. (Department: 1621)

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

Organic compounds

Silicon containing

Reexamination Certificate

active

06452033

ABSTRACT:

TECHNICAL FIELD
This invention relates to the preparation of &ohgr;-[N-(2-aminoethyl)]aminoalkylalkoxysilanes. More specifically, this invention relates to the preparation of such silanes by reaction of &ohgr;-chloroalkylalkoxysilane with excess ethylenediamine utilizing a recycled ethylenediamine hydrochloride salt phase stream.
BACKGROUND OF THE INVENTION
As is well known, &ohgr;-[N-(2-aminoethyl)]aminoalkylalkoxysilanes have the general formula,
R
1
R
2
NCH
2
CH
2
NR
3
R
4
in which R
1
, R
2
, and R
3
independently are a member selected from the group consisting of a hydrogen atom or an alkoxysilane of the formula:
R
5
Si(R
6
)
3−a
(OR
7
)
a
 in which R
5
, R
6
, and R
7
are each independently C
1-8
alkyl (including straight chain or branched alkyls) and a as 1, 2, or 3. R
4
is a said alkoxysilane. The &ohgr;-[N-(2-aminoethyl)]aminoalkylalkoxysilanes are widely used as silane coupling agents and are effective for various polymer property modification purposes, for example, improving adhesion at an organic-inorganic interface.
These compounds are synthesized by reacting &ohgr;-chloroalkylalkoxysilanes with ethylenediamine to form &ohgr;-[N-(aminoethyl)]aminoalkylalkoxysilanes. Stoichiometrically, this method uses one mole of &ohgr;-chloroalkylalkoxysilane and two moles of ethylenediamine for synthesizing one mole of &ohgr;-[N-(2-aminoethyl)]aminoalkylalkoxysilane, with one mole of ethylenediamine monohydrochloride being formed at the same time, as shown by the following reaction scheme.
ClR
5
Si(R
6
)
3−a
(OR
7
)
a
+2NH
2
CH
2
CH
2
NH
2
→NH
2
CH
2
CH
2
NHR
5
Si(R
6
)
3−a
(OR
7
)
a
+NH
2
CH
2
CH
2
NH
3
+
Cl
−
In the above equation R
5
is any alkyl group and each of R
6
and R
7
is an alkyl radical having 1 to 8 carbon atoms and a is equal to 1, 2, or 3.
In reality, the end product &ohgr;-[N-(2-aminoethyl)]aminoalkylalkoxy-silane further reacts with the starting reactants &ohgr;-chloroalkylalkoxysilane and ethylenediamine to form poly-alkylated products as shown below.
ClR
5
Si(R
6
)
3−a
(OR
7
)
a
+NH
2
CH
2
CH
2
NHR
5
Si)
(R
6
)
3−a
(OR
7
)
a
+NH
2
CH
2
CH
2
NH
2
→NH
2
CH
2
CH
2
N[R
5
Si(R
6
)
3−a
(OR
7
)
a
]
2
{or (OR
7
)
a
(R
6
)
3−a
SiR
5
NHCH
2
CH
2
NHR
5
Si(R
6
)
3−a
(OR
7
)
a
}+NH
2
CH
2
CH
2
NH
3
+
Cl
−
This di-alkylated ethylenediamine continues to react with &ohgr;-chloroalkylalkoxysilane and ethylenediamine to form the tri-alkylated product as shown below:
NH
2
CH
2
CH
2
N[R
5
Si(R
6
)
3−a
(OR
7
)
a
]
2
{or (OR
7
)
a
(R
6
)
3−a
SiR
5
NHCH
2
CH
2
NHR
5
Si(R
6
)
3−a
(OR
7
)
a
}+ClR
5
Si(R
6
)
3−a
(OR
7
)
a
+NH
2
CH
2
CH
2
NH
2
→(OR
7
)
a
(R
6
)
3−a
SiR
5
NHCH
2
CH
2
N[R
5
Si(R
6
)
3−a
(OR
7
)
a
]
2
+NH
2
CH
2
CH
2
NH
3
+
Cl
−
Theoretically, this process continues until a hexa-alkylated ethylenediamine product is formed, but in actuality only the mono-, di-, and tri-alkylated products are seen in detectable levels using gas chromatography analysis.
In general, a present method for preparing &ohgr;-[N-(2-aminoethyl)]aminoalkyl-alkoxysilanes in a continuous flow process is as follows.
An ethylenediamine stream is co-fed to a reactor with an &ohgr;-chloroalkylalkoxysilane stream of the formula:
ClR
5
Si(R
6
)
3−a
(OR
7
)
a
as defined above, at a feed ratio of 3-20 moles of ethylenediamine per mole of &ohgr;-chloroalkylalkoxysilane. The optimum molar feed ratio of ethylenediamine to alkoxysilane is dependent upon the specific alkoxysilane used. Typically the molar feed ratio just inside the single phase region is optimum, but also depends upon the desired level of polyalkylated ethylenediamines in the product.
The ethylenediamine and &ohgr;-chloroalkylalkoxysilane react as described above. A single phase effluent stream from the reactor (continuous stirred tank reactor, plug flow reactor, or combination of the two), which is a mixture of ethylenediamine, alcohol, &ohgr;-[N-(2-aminoethyl)]aminoalkylalkoxysilane, and ethylenediamine monohydrochloride, is passed to a stripping and/or distillation column. In the stripping column enough ethylenediamine is removed overhead to induce a phase separation in the material remaining in the column into two liquid phases.
The alcohol mentioned above is generated in a side reaction between extraneous water impurity that enters with both the ethylenediamine and the alkoxysilane feeds. The side reaction is shown below, where b is equal to or less than a and a is equal to 1, 2, or 3.
~
Si(R
6
)
3−a
(OR
7
)
a
+b*H
2
O→
~
Si(R
6
)
3−a
(OR
7
)
a−b
(OH)
b
+b*R
7
OH
The two-phase effluent stream from the distillation column is passed to a phase separator (gravity, mechanical, electrical, etc.) where the denser phase which is a mixture of ethylenediamine and ethylenediamine monohydrochloride is removed.
The lighter silane phase effluent stream from the phase separator which is mainly a mixture of ethylenediamine, alcohol, and 3-[N-(2-aminoethyl)]aminoalkylalkoxysilane, is passed to a second distillation column where the aminoethylaminoalkylalkoxysilane is purified. The ethylenediamine and alcohol are removed from the top of the column and recycled to an ethylenediamine purification column that may also treat incoming ethylenediamine. The aminoethylaminoalkoxysilane stream is sometimes further purified in a stripping, distillation, or flash system to reduce the level of poly-alkylated ethylenediamine.
The ethylenediamine overhead stream and new ethylenediamine are also directed to the ethylene purification distillation column where alcohol is removed.
While producing a high yield of high quality alkylated ethylenediamines the prior process requires, as described above, that the contents of the reactor, the reaction mixture, be passed through a distillation column for removal of a substantial amount of ethylenediamine. The distillation operation was required before the residual reaction mixture could be separated into a product rich phase for product isolation and purification. It would be more efficient and economical to have a process in which the reaction mixture comprises two phases so that the product rich phase could be obtained without a preliminary distillation step and use of distillation equipment for that purpose. It is an object of this invention to provide such a process.
SUMMARY OF THE INVENTION
The reaction between two moles of ethylenediamine and one mole of a suitable &ohgr;-chloroalkylalkoxysilane produces an &ohgr;-[N-(2-aminoethyl)]aminoalkylalkoxysilane and a mole of ethylenediamine hydrochloride. As stated above a considerable excess of ethylenediamine is used to suppress the formation of polysilane, i.e., poly-alkylated ethylenediamine, containing products. Therefore, in a continuous process utilizing this practice, the excess ethylenediamine must be separated from the product stream and recycled to the reactor. In accordance with this invention, the byproduct ethylenediamine hydrochloride salt is also recycled to the reactor in sufficient quantity to produce two liquid phases in the reactor and in the stream flowing from it.
The two liquid phase effluent from the reactor is a mixture of &ohgr;-[N-(2-aminoethyl)]aminoalkylalkoxysilane, ethylenediamine, ethylenediamine hydrochloride, and extraneous alcohol. The stream is first conducted to a phase separation vessel rather than to a distillation column. Upon phase separation, the top bulk phase contains predominantly silane and ethylenediamine. The heavier bulk phase contains predominantly ethylenediamine hydrochloride and ethylenediamine. The heavier phase is recycled to the reactor in sufficient quantity to maintain the two phase system in the reactor and used to control the degree of polyalkylation. The balance of the heavier phase is removed from the process.
The lighter phase is transferred to a

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