Preparation of amino-functional siloxanes

Details Preparation of amino-functional siloxanes Preparation of amino-functional siloxanes

2001-10-05

2003-03-18

Dawson, Robert (Department: 1712)

Synthetic resins or natural rubbers -- part of the class 520 ser

Synthetic resins

From silicon reactant having at least one...

C528S033000, C528S037000, C556S407000, C556S410000, C556S412000, C556S413000, C556S425000

Reexamination Certificate

active

06534615

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to a process for preparing amino-functional siloxanes using cyclic silazanes. Aminoalkylpolysiloxanes and aminoalkyl silicone resins can be used in many fields, including the preparation of polyimides and polyetherimides. However, the commercial use of these compounds on a large scale is hindered by a relatively expensive production process.
2. Background Art
A known process for the preparation of amino-functional siloxanes is the base-catalyzed equilibration of octamethylcyclotetrasiloxane with bisaminopropyltetramethyldisiloxane, as described, for example, in U.S. Pat. No. 5,512,650. This reaction has the disadvantage that expensive bisaminopropyltetramethyldisiloxane is used as starting material. In addition, the long reaction times required by the equilibration reaction, sometimes more than 10 hours, are disadvantageous.
U.S. Pat. No. 3,146,250 describes a further process which has hitherto not been employed industrially and begins with from specific cyclic silanes of the formula I which can react with HO—Si groups at the end of a silicone chain.
In this formula, R′ is a carbon chain having at least 3 and not more than 6 carbon atoms, R″ is a hydrocarbon radical, and the radical R on the nitrogen is either hydrogen, a hydrocarbon radical or an organosilyl radical of the formula (halogen-R
1
—) Y
2
Si—, where Y and R
1
are hydrocarbon radicals. If the radical R is hydrogen, the compound is an unsubstituted cyclic silazane which can be used for functionalizing hydroxy-terminated silanols. However, a disadvantage of these unsubstituted cyclic silazanes is that they can be synthesized only in very poor yields or by starting with expensive starting materials. The syntheses frequently employ very toxic allylamine, whose use is subject to particularly strict safety precautions.
Of greater interest is the synthesis of N-substituted silazanes which can frequently be prepared in better yields. However, if the N-silyl-substituted silazane described in U.S. Pat. No. 3,146,250 is used, the reaction with hydroxy-terminated siloxanes gives undesired by-products as indicated in the following reaction scheme
In these formulae, Y and X are, for example, methyl, R is propyl, and Hal is halogen, for example chlorine. The proportions of the respective products can be derived from simple probability calculations.
If the N-substituted silazanes of the formula II
where R for example, is a propyl group, are used, as described in DE 3546376, undesired by-products are likewise obtained in considerable amounts:
SUMMARY OF THE INVENTION
The invention provides a process for preparing an amino-functional organosiloxanes of the formula III,
(SiO
{fraction (4/2)}
)
k
(R
1
SiO
{fraction (3/2)}
)
m
(R
1
2
SiO
{fraction (2/2)}
)
p
(R
1
3
SiO
½
)
q
[O
½
SiR
1
2
—R—NH
2
]
s
[O
½
H]
t
  (III)
which comprises reacting an organosiloxane of the formula IV
(SiO
{fraction (4/2)}
)
k
(R
1
SiO
{fraction (3/2)}
)
m
(R
1
2
SiO
{fraction (2/2)}
)
p
(R
1
3
SiO
½
)
q
[O{fraction (
1
/
2
)}H]
r
  (IV)
with a cyclic silazane of the formula V
where
R is a divalent Si—C—and C—N—bonded, unsubstituted or cyano- or halogen-substituted C
3
-C
15
-hydrocarbon radical in which one or more non-adjacent methylene units may be replaced by —0—, —CO—, —COO—, —OCO— or —OCOO—, —S— or —NRX
x
—groups and in which one or more non-adjacent methine units may be replaced by —N ═, —N ═N— or —P═ groups, where at least 3 and not more than 6 atoms are located between the silicon atom and the nitrogen atom of the ring,
R
X
is hydrogen or a C
1
-C
10
-hydrocarbon radical which may be unsubstituted or substituted by —CN or halogen,
R
1
is a hydrogen atom or a monovalent Si—C—bonded C
1
-C
20
-hydrocarbon radical which may be unsubstituted or substituted by —CN, —NCO, —NR
x
2
, —COOH, —COOR
x
, -halogen, -acryl, -epoxy, —SH, —OH or —CONR
x
2
or is a C
1
-C
15
-hydrocarbonoxy radical in which one or more non-adjacent methylene units may be replaced by —O—, —CO—, —COO—, —OCO— or —OCOO—, —S— or —NR
X
— groups and in which one or more non-adjacent methine units may be replaced by —N ═, —N ═N— or —P ═ groups,
s is at least 1,
r is at least 1,
s+t is equal to r and
k+m+p+q is at least 2.
The cyclic silazanes of the formula V used can be prepared simply and in high yields. In addition, they react with hydroxy-functional siloxanes of the formula IV without use of special catalysts and without the formation of by-products.
In the cyclic silazane of the formula V, R may be aliphatically saturated or unsaturated, aromatic, linear or branched. R is preferably an unbranched C
3
-C
6
-alkylene radical which may be substituted by halogen atoms, in particular fluorine and chlorine. It is preferred that 3 atoms are located between the silicon atom and the nitrogen atom of the ring.
The C
1
-C
20
-hydrocarbon radicals and C
1
-C
20
-hydrocarbonoxy radicals R
1
may be aliphatically saturated or unsaturated, aromatic, linear or branched. R
1
preferably has from 1 to 12 atoms, in particular from 1 to 6 atoms, preferably only carbon atoms, or one alkoxy oxygen atom and otherwise only carbon atoms. R
1
is preferably a linear or branched C
1
-C
6
-alkyl radical. Particular preference is given to the radicals methyl, ethyl, phenyl, vinyl, and trifluoropropyl.
Preference is given to preparing the compounds of the formula III in which R is a propylene radical and R
1
is methyl, ethyl, phenyl, vinyl or trifluoropropyl.
The amino-functional organosiloxane of the formula III can be linear, cyclic or branched. The sum of k, m, p, q, s and t is preferably in the range from 2 to 20,000, in particular from 8 to 1000. To make a reaction between the organosiloxane of the formula IV and the silazane possible, r has to be >0, i.e. the organosiloxane of the formula IV must contain hydroxy groups.
Preferred variants of branched organosiloxanes of the formula III are organosilicone resins. These may comprise a plurality of units, as indicated in the formula III, with the molar percentages of the units present being given by the indices k, m, p, q, r, s and t. The proportion of units r is preferably from 0.1 to 20%, based on the sum of k, m, p, q and r. At the same time, k+m also must be >0. In the case of organosiloxane resins of the formula III, s must be >0 and s+t must be equal to r.
Preference is given to resins in which 5% <k+m <90%, based on the sum of k, m, p, q, r, s and t, and t is preferably 0. In a particularly preferred case, the radical R is a propylene radical and R
1
is a methyl radical.
If resins which have a specified amine content are to be prepared, the stoichiometric ratio of resin to cyclic silazane is selected so that the desired amine content is achieved. Remaining Si—OH groups may, if appropriate, remain unreacted in the product.
A further preferred variant of an amino-functional organosiloxanes of the formula III is a linear organosiloxane of the formula VI,
 [H]
u
[H
2
N—R—SiR
1
2
]
v
O(SiR
1
2
O)
n
SiR
1
2
—R—NH
2
  (VI)
which is prepared from an organosiloxane of the formula VII
HO(R
1
2
SiO)
n
R
1
2
SiOH  (VII)
by reaction with a cyclic silazane of the formula V above, where
u is 0 or 1,
v is 1−u and
n is from 1 to 20,000, and wherein
u is preferably 0, and
n is preferably from 1 to 20,000, in particular from 8 to 2000.
If a mixture of starting compounds of the formula VII is used, the value of n is the average degree of polymerization of the silanols of the formula VII present.
The linear organosiloxanes of the formula VI prepared in this way can be characterized essentially by 3 different parameters:
-viscosity (or molecular weight)
-amine content
-degree of amino-functionality of the end groups.
However, only two of these parameters can be varied independently in the case of a linear organosiloxane of the formula VI, i.e. at a given viscosity and functiona

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