Cross-linkable organopolysiloxane materials formed into...

Details Cross-linkable organopolysiloxane materials formed into... Cross-linkable organopolysiloxane materials formed into...

2000-01-20

2001-09-04

Dawson, Robert (Department: 1712)

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

Synthetic resins

From silicon reactant having at least one...

C528S034000, C528S038000, C556S458000, C556S459000

Reexamination Certificate

active

06284860

ABSTRACT:

TECHNOLOGICAL FIELD
The invention relates to the preparation of organopolysiloxanes containing organyloxy groups by reaction of organopolysiloxanes containing hydroxyl end groups with an alkoxysilane containing a secondary or tertiary amino group in the presence of an acid, and the use of the reaction product as RTV-1-alkoxy compositions.
DESCRIPTION OF THE RELATED ART
In the context of the present invention, the term organopolysiloxanes is to include dimeric, oligomeric and polymeric siloxanes.
Organopolysiloxane compositions which can be stored with exclusion of moisture and on ingress of moisture crosslink at room temperature, alcohols being split off, so-called RTV-1-alkoxy compositions, have already been known for a long time. They essentially comprise an organopolysiloxane with organyloxy end groups and, as further constituents, a crosslinking agent with at least three hydrolysable groups, catalyst and optionally additives. The advantage of these RTV-1-alkoxy systems is that during the crosslinking operation they provide odourless, neutral, eco-alcohols as cleavage products.
An organopolysiloxane with organyloxy end groups is prepared by reactions of an organopolysiloxane with HO end groups with alkoxysilanes. This is described, for example, in U.S. Pat. No. 4,942,211. A disadvantage of this process is that the reaction takes several hours at room temperature. The reaction time is indeed shortened at elevated temperature, but is still so long that it is necessary to wait until RTV-1-alkoxy compositions can be prepared with the organopolysiloxanes formed, having organyloxy end groups, and further constituents. The reaction of an organopolysiloxane with HO end groups with alkoxysilanes in the presence of various catalysts is known. For example, in U.S. Pat. No. 5,196,497 the reaction is carried out in the presence of alkali metal hydroxides. However, deactivation of the catalysts requires a further reaction step.
SUMMARY OF THE INVENTION
The invention is based on the object of preparing RTV-1-alkoxy compositions in the simplest possible manner.
DETAILED DESCRIPTION OF THE INVENTION
The invention relates to a process for the preparation of an organopolysiloxane with organyloxy end groups, in which
(A) an organopolysiloxane with HO end groups is reacted with
(B) an alkoxysilane which has at least two alkoxy groups and a radical which contains at least one secondary or tertiary amino group, which is bonded to the silicon atom via a divalent C
1-12
-hydrocarbon radical, in the presence of
(C) a Brönstedt or Lewis acid.
The process proceeds selectively at an extremely high rate of reaction even at room temperature, so that immediately after components (A), (B) and (C) have been mixed the organopolysiloxane formed, with organyloxy end groups, can be employed ELS an RTV-1-alkoxy composition, optionally after admixing of further constituents.
Another advantage of this process is to be seen in that no side reactions proceed here and, for example, the formation of T and Q units is not observed on a linear organopolysiloxane. The ammonium salts formed do not have to be removed from the reaction product, since they do not cause trouble in RTV-1-alkoxy compositions and even have an accelerating action on the rate of vulcanization. An excess of Brönstedt or Lewis acid (C) causes trouble neither in the organopolysiloxane formed, with organyloxy end groups, nor in the RTV-1-alkoxy compositions.
Linear &agr;,&ohgr;-dihydroxypoly(diorganosiloxanes) of the general formula (I)
HO—[R
2
SiO]
m
—H  (I),
wherein
R denotes monovalent C
1
-C
8
-hydrocarbon radicals which are optionally substituted by fluorine, chlorine, bromine, C
1
-C
4
-alkoxyalkyl or cyano groups and
m denotes values which correspond to a viscosity of the organopolysiloxane (A) with HO end groups of 0.05 to 1000 Pa.s,
are preferably employed as the organopolysiloxane (A) with HO end groups.
Examples of hydrocarbon radicals R are linear and cyclic saturated and unsaturated alkyl radicals, such as the methyl radical, aryl radicals, such as the phenyl radical, alkaryl radicals, such as tolyl radicals, and aralkyl radicals, such as the benzyl radical.
Unsubstituted hydrocarbon radicals having 1 to 6 carbon atoms are preferred as radical R, the methyl radical being particularly preferred.
The organopolysiloxanes (A) preferably have a viscosity of 100 to 1,000,000 mPa.s, in particular 20,000 to 350,000 mPa.s, in each case measured at 23° C.
Alkoxysilanes of the general formula (II)
(R
1
O)
n
SiR
2
(3−n)
R
3
  (II),
in which
R
1
and R
2
each denote monovalent C
1
-C
10
-hydrocarbon radicals which are optionally substituted by fluorine, chlorine, bromine, C
1
-C
4
-alkoxyalkyl or cyano groups,
n denotes the values 2 or 3,
R
3
denotes a monovalent radical of the general formula (III)
H
p
R
4
(2−p)
N[—R
5
—NR
6
]
q
—(CH
2
)—R
5
—  (III),
R
4
denotes monovalent C
1
-C
10
-alkyl radicals which are optionally substituted by fluorine, chlorine, bromine, C
1
-C
4
-alkoxyalkyl or cyano groups,
R
5
denotes divalent C
1
-C
12
-alkylene radicals which are optionally substituted by fluorine, chlorine, bromine, C
1
-C
4
-alkoxyalkyl or cyano groups,
R
6
denotes a hydrogen radical or monovalent C
1
-C
10
-alkyl radicals which are optionally substituted by fluorine, chlorine, bromine, C
1
-C
4
-alkoxyalkyl or cyano groups,
p denotes the values 0 or 1 and
q denotes the values 0, 1, 2 or 3, are preferably employed as the alkoxysilane (B).
R
1
and R
2
preferably denote in each case unsubstituted C
1
-C
6
-hydrocarbon radicals, in particular methyl, ethyl and propyl radicals.
R
4
preferably denotes linear and cyclic saturated C
1
-C
10
-alkyl radicals, in particular C
1
-C
8
-alkyl radicals.
R
5
preferably denotes linear and branched saturated C
1
-C
10
-alkyl radicals, in particular C
1
-C
8
-alkyl radicals. In particular, the radicals R
5
are unsubstituted.
R
6
preferably has a hydrogen radical and the preferred meanings of R
4
. The hydrogen radical is particularly preferred.
p preferably has the value 1.
Examples of Brbnstedt or Lewis acids (C) which can be employed are mineral, carboxylic and sulphonic acids and metal compounds, metal salts and metal complex salts which function as Lewis acids. Examples of Lewis acids are BF
3
, AlCl
3
, TiCl
3
, SnCl
4
, SO
3
, PCl
5
, POCl
3
, FeCl
3
and hydrates thereof and ZnCl
2
. Examples of Brönstedt acids are boric, tetrafluoroboric and nitric acid, nitrous acid, phosphoric acid, phosphorous acid, hypophosphorous acid, acidic phosphoric esters, acidic polyphosphoric esters, sulphuric acid, sulphurous acid, peroxosulphuric, hydrochloric, hydrofluoric, hydroiodic, hydrobromic, perchloric and hexachlorophosphoric acid, and benzenesulp.,.onic, p-toluenesulphonic, methanesulphonic, trifluoromethanesulphonic and carboxylic acids, such as chloroacetic, trichloroacetic, acetic, acrylic, benzoic, trifluoroacetic, citric, crotonic, formic, fumaric, maleic, malonic, gallic, itaconic, lactic, tartaric, oxalic, phthalic and succinic acid.
Compounds which hydrolyse with water and form Brönstedt acids can also be employed in the process. In this case, as much water as is necessary to form the Brönstedt acids must be employed at the same time. For example, hydrolysis-sensitive carboxysilanes, such as methyltriacetoxysilane, or siloxaness can be employed. The water required for the hydrolysis can also be adsorbed on solids, such as fillers.
Particularly preferred Brönstedt acids (C) are acidic phosphoric esters of the general formula (IV)
(HO)
a
OP(—O—R
7
)
(3−a)
  (IV)
in which
R
7
denotes a monovalent C
3
- to C
50
-hydrocarbon radical which is optionally substituted by hydroxyl, fluorine, chlorine, bromine, C
1
-C
10
-alkoxyalkyl or cyano groups and can be interrupted by radicals, bonded to carbon atoms on both sides, from the group consisting of —O—, —COO—, —OOC—, —CONR
2
—, —NR
2
CO— and —CO— and
a denotes the values 1 or 2.
The reaction products of the acidic phosphoric esters of the general formula (IV, stabilize the organopoly

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