Curable organopolysiloxane materials

Details Curable organopolysiloxane materials Curable organopolysiloxane materials

2000-08-11

2002-03-19

Moore, Margaret (Department: 1712)

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

Synthetic resins

From silicon reactant having at least one...

C502S152000, C502S158000, C502S262000

Reexamination Certificate

active

06359098

ABSTRACT:

TECHNICAL FIELD
The present invention relates to silicone materials crosslinkable by addition of Si-bonded hydrogen at an aliphatic carbon-carbon multiple bond, processes for their preparation, platinum catalysts used for this purpose and the use of the crosslinkable materials.
BACKGROUND ART
Addition-crosslinking silicone materials crosslink by reaction of aliphatically unsaturated groups with Si-bonded hydrogen (hydrosilylation) in the presence of a catalyst, typically a platinum compound. Owing to the fact that the crosslinking reaction starts as soon as the essential constituents are simultaneously present, addition-crosslinking silicone materials have thus far been prepared almost exclusively as two-component formulations, the composition of the individual components being such that all three essential constituents are simultaneously present only after the individual components have been mixed together. Usually, one of the components contains the polyorganosiloxane having alkenyl functional groups and the platinum catalyst, and the other component contains the crosslinking agent having SiH functional groups, if necessary, in combination with further polyorganosiloxane having alkenyl functional groups. After mixing of the individual components, complete curing to give the silicone elastomer can be effected at room temperature, but is usually carried out at elevated temperature.
The use of two-component addition-crosslinkable silicone materials is associated with numerous disadvantages, such as, for example, logistics, the high risk of contamination by traces of platinum, and the necessity for an additional mixing step. Although a ready-to-use material is obtained after mixing of the components, it has only a limited pot life at room temperature. This necessitates, on the one hand, processing quickly following mixing, and, on the other hand, frequent cleaning of the storage container, metering units, processing machines, etc., since the material remaining, for example, through back-mixing or adhesion to the container walls, ultimately gels.
Because of these disadvantages, there have been many attempts to provide addition-crosslinking silicone materials as a one-component formulation (1C system). Since in the case of a 1C system all constituents required for the crosslinking are present together, the problem of suppressing premature crosslinking, which usually also takes place at room temperature, must be addressed. Possibilities for specifically controlling (increasing) the pot life of an addition-crosslinking material are sufficiently well known, for example through the use of inhibitors which are capable of considerably reducing the activity of the platinum catalyst at room temperature, such as, phosphorus compounds in combination with peroxides according to U.S. Pat. No. 4,329,275, or azodicarbonyl compounds according to EP-A-490 523. Although the pot life per se can be increased as desired through the type and content of such inhibitors, a disadvantageous effect on the crosslinking behavior is also inevitably associated with increasing pot life, particularly when the pot life is extended to several months by high inhibitor contents. Higher initiation temperatures and low crosslinking rate as well as undercrosslinking are the result in such cases.
A further possibility fundamentally differing from the use of inhibitors consists of encapsulating the platinum catalyst in a finely divided material which does not release the platinum until an elevated temperature has been reached. This can be effected, for example, by microencapsulation of the platinum catalyst with a thermoplastic silicone resin or an organic thermoplastic, as described, for example, in EP-A-363 006, which, however, is relatively expensive.
A third possibility consists in selecting, as the catalyst, specific platinum complexes whose activity is such that the hydrosilylation reaction takes place sufficiently rapidly at elevated temperature but to such a small extent at room temperature that pot lives of several months are achieved. Such addition-crosslinking materials containing platinum complexes were described, for example, in EP-A-583 159 and DE -A-36 35 236. Although the materials described have substantially improved pot lives with, in some cases, sufficiently high crosslinking rates, there is still a need for improving the pot life and crosslinking rate of addition-crosslinking materials formulated as a single component through use of more efficient platinum catalysts, without having to accept the abovementioned disadvantages.
DISCLOSURE OF INVENTION
The present invention provides addition-crosslinkable compositions containing aliphatically unsaturated compounds and Si-H-functional organopolysiloxanes together with unique platinum complexes which allow for extended shelf life as one-component addition-curable organopolysiloxanes, and extended pot life for two-component addition-curable organopolysiloxanes, without compromising crosslinking rates or levels.
BEST MODE FOR CARRYING OUT THE INVENTION
The present invention thus relates to curable organopolysiloxane materials containing
(A) compounds which have radicals having aliphatic carbon-carbon multiple bonds,
(B) organopolysiloxanes having Si-bonded hydrogen atoms or, instead of (A) and (B) or in addition thereto,
(C) organopolysiloxanes which have SiC-bonded radicals having aliphatic carbon-carbon multiple bonds and Si-bonded hydrogen atoms, and
(D) a platinum catalyst selected from the group consisting of compounds of the formula
and/or oligomeric or polymeric compounds which are composed of structural units of the general formula
and optionally chemically bonded structural units of the general formula
R
9
r
SiO
(4−r)/2
  (VI)
in which
R
2
denotes an optionally substituted diene which is linked by at least one &pgr;-bond to platinum and represents a straight or a branched chain having 4 to 18 carbon atoms or a cyclic ring having 6 to 28 carbon atoms,
R
3
is identical or different and denotes a hydrogen atom, a halogen atom, —SiR
4
3
, —OR
6
or monovalent, optionally substituted hydrocarbon radicals having 1 to 24 carbon atoms, with the proviso that, in the compounds of the formula (III), at least one radical R
3
denotes —SiR
4
3
,
R
4
is identical or different and denotes hydrogen, a halogen atom, —OR
6
or monovalent, optionally substituted hydrocarbon radicals having 1 to 24 carbon atoms,
R
6
is identical or different and is a hydrogen atom, —SiR
4
3
or a monovalent, optionally substituted hydrocarbon radical having 1 to 20 carbon atoms,
R
7
is identical or different and denotes a hydrogen atom, a halogen atom, —SiR
4
3
, —SiR
4
(3−t)
[R
8
SiR
9
s
O
(3−s)/2
]
t
, —OR
6
, or monovalent optionally substituted hydrocarbon radicals having 1 to 24 carbon atoms, with the proviso that, in formula (V), at least one radical R
7
denotes —SiR
4
(3−t)
[R
8
SiR
9
s
O
(3−s)/2
]
t
,
R
8
is identical or different and denotes oxygen or divalent, optionally substituted hydrocarbon radicals having 1 to 24 carbon atoms, which may be bonded to the silicon via an oxygen atom,
R
9
is identical or different and denotes hydrogen or an organic radical,
r is 0, 1, 2 or 3,
s is 0, 1, 2 or 3 and
t is 1, 2 or 3.
Within the scope of the present invention, the term organopolysiloxane is intended to include polymeric, oligomeric and dimeric siloxanes.
If R
2
is a substituted diene or the radicals R
3
, R
4
, R
5
, R
6
, R
7
and R
8
are substituted hydrocarbon radicals, preferred substituents are halogen atoms such as F, Cl, Br and I, cyano radicals, —NR
6
2
, heteroatoms such as O, S, N and P, and groups —OR
6
, in which R
6
has the abovementioned meaning.
The compositions according to the invention may be one-component organopolysiloxane materials as well as two-component organopolysiloxane materials. In the latter case, the two components of the materials according to the invention may contain all constituents in any desired combination, in general with the proviso that one component does not simultan

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