Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Mixing of two or more solid polymers; mixing of solid...
Reexamination Certificate
2002-02-06
2003-11-18
Seidleck, James J. (Department: 1711)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Mixing of two or more solid polymers; mixing of solid...
C525S191000, C525S244000
Reexamination Certificate
active
06649695
ABSTRACT:
The present invention relates to the use of block copolymers comprising polymer blocks A which are essentially composed of isobutene and polymer blocks B which are essentially composed of units which-are derived from vinylaromatic monomers, as resilient sealing materials.
Flexible sealing materials, also referred to as sealing compounds, are used, for example, for sealing joints. Typical sealing compounds consist of polysulfide, butyl rubber, silicones or resilient polyurethanes. Depending on the use, the sealing materials must fulfill stringent requirements. They may not lose their resilience under extreme temperature variations and may not become brittle, especially at low temperatures. At the same time, high mechanical strength is often desired. Furthermore, the sealing materials should be stable to the effects of weathering and/or to chemicals, for example to household cleaners. For a number of applications, in particular extremely low gas permeability, in particular to air, argon and water vapor, is required.
For example, sealing materials having high resilience and mechanical strength in combination with low gas permeability are required for the production of insulation glass windows. Insulation glass windows consist as a rule of two or more glass panes which are kept apart by spacers, for example by aluminum rails or hollow aluminum profiles. The space between the individual glass panes is as a rule filled with a gas, for example argon or sulfur hexafluoride, for better insulation. The joints between the individual glass panes, in particular the joints between the aluminum profiles and the glass panes, must be sealed with a sealing material which, on the one hand, prevents the escape of the insulating gas and, on the other hand, prevents penetration of atmospheric humidity, i.e. air and water vapor, into the space between the glass panes.
The prior art solves the problem by adhesively bonding the aluminum profiles acting as spacers to the glass panes by means of a layer of polyisobutene which simultaneously acts as a sealing compound. In this way, high gastightness is achieved. However, this type of seal does not result in sufficient mechanical strength of the composite pane and is sensitive to mechanical damage. In the prior art, this structure is therefore covered with a further sealing compound having higher mechanical strength. For example, cold-crosslinkable or hot-crosslinkable sealing materials comprising polysulfide, butyl rubber, silicones or polyurethanes are suitable for this purpose. The use of two sealing materials makes the application of such seals more expensive and thus increases the production costs for insulation glazing. In addition, such sealing materials have only insufficient gas impermeability.
It is an object of the present invention to provide a flexible sealing material which is impermeable to gases such as argon or water vapor and at the same time has high resilience in combination with sufficient mechanical strength.
We have found that this object is achieved and that, surprisingly, these requirements set for sealing materials are fulfilled by block copolymers which contain at least one polymer block A which is composed of isobutene units and at least two further polymer blocks B which are composed of units which are derived from vinylaromatic monomers.
The present invention accordingly relates to the use of linear or star block copolymers which have at least one polymer block A which is essentially composed of isobutene units and at least two polymer blocks B which are essentially composed of units which are derived from vinylaromatic monomers, as resilient sealing material.
Block copolymers based on isobutene and vinylaromatic monomers and processes for their preparation are known from the prior art (cf. for example U.S. Pat. No. 4,946,899 and literature stated therein).
Both linear block copolymers, for example of the type B-A-B or (A-B-)
k
A, where k≧2, and star block copolymers are suitable for the use according to the invention. Among these, those block copolymers which have a central polymer block which is essentially composed of isobutene units are preferred. Such block copolymers having a central polyisobutene block are of the formula I
where
A is a polymer block A according to the above definition,
B is a polymer block B according to the above definition,
n is 0, 1 or 2 and
X is a single bond or an n+2-valent hydrocarbon radical of up to 30 carbon atoms.
If X is an n+2-valent hydrocarbon radical, this is a consequence of the preparation and results from the respective polymerization initiator. Together with the polymers blocks A surrounding it, it forms the central polymer block which is essentially composed of isobutene units.
According to the invention, the block copolymer contains at least one polymer block A which is essentially composed of isobutene units. Some of the isobutene units in the polymer blocks may also be replaced by monoolefinically unsaturated monomers having silyl groups. Typical silyl groups are trialkoxysilyl groups in which the alkoxy radical has, as a rule, 1, 2, 3 or 4 carbon atoms and may in turn be substituted by C
1
-C
4
-alkoxy. Examples of such radicals are trimethoxysilyl, triethoxysilyl, tri-n-propoxysilyl and tri(methoxyethyl)silyl. The polymer blocks A then preferably contain up to 20, for example from 0.1 to 20, in particular from 0.5 to 10, % by weight, based on the total weight of all polymer blocks A in the block copolymer, of such monomers as polymerized units. Examples of monoolefinically unsaturated monomers having trialkoxysilyl groups are in particular C
2
-C
10
-monoolefins which are substituted by a tri-C
1
-C
4
-alkoxysilyl group: these include trialkoxysilyl-substituted ethene, propene, n-butene, isobutene, n-pentene, 2-methyl-1-butene or 2-methyl-1-pentene. Examples of such monomers are: 1-(trimethoxysilyl)ethene, 1-(trimethoxysilyl)propene, 1-(trimethylsilyl)-2-methyl-2-propene, 1-(tri(methoxyethoxy)silyl)ethene, 1-(tri(methoxyethoxy)silyl)propene, 1-(tri(methoxyethoxy)silyl)-2-methyl-2-propene. Styrene derivatives which have one of the abovementioned trialkoxysilyl groups, for example 2-, 3- or 4-trimethoxysilylstyrene, or compounds of the type CH
2
═CH—C
6
H
4
—Q—Si(OCH
3
)
3
, where Q is a bifunctional radical, for example a C
1
-C
10
-alkylene group, which may be interrupted by one or more, nonneighboring oxygen atoms or imino groups, e.g. —CH
2
—NH—C
2
H
4
—NH—C
3
H
6
—, are also suitable. Such monomers derived from styrene may also be used for modifying the styrene block.
According to the invention, the block copolymer contains at least one further polymer block B which is composed of units which are derived from vinylaromatic monomers. Suitable vinylaromatic monomers are: styrene, &agr;-methylstyrene, C
1
-C
4
-alkylstyrenes, such as 2-, 3- and 4-methylstyrene and 4-tert-butylstyrene, and 2-, 3- or 4-chlorostyrene. Preferred vinylaromatic monomers are styrene and 4-methylstyrene and mixtures thereof. A very particularly preferred vinylaromatic monomer is styrene, which may be replaced by up to 20% by weight of 4-methylstyrene.
In the formula II, X is preferably a 2- or 3-valent hydrocarbon radical of up to 30, preferably 5 to 20, carbon atoms. X links the polymer blocks A surrounding it and composed of isobutene to a central polymer block which is essentially composed of isobutene units. X is preferably one of the following radicals:
where m is 1, 2 or 3
The number-average molecular weight of the central polyisobutene block corresponds approximately to the sum of the number-average molecular weights of all polymer blocks A in formula I. This is as a rule from 20,000 to 100,000, preferably from 25,000 to 90,000, very particularly preferably from 30,000 to 80,000 daltons. The ratio of the total weight of all polymer blocks A to the total weight of all polymer blocks B is as a rule from 1:1 to 9:1, preferably from 1.2:1 to 4:1, in particular from 3:2 to 7:3.
In the interest of mechanical strength, it has proven advantageous if the polymer block or polymer blo
Knoll Konrad
Lange Arno
Mach Helmut
Rath Hans Peter
Asinovsky Olga
BASF - Aktiengesellschaft
Keil & Weinkauf
Seidleck James J.
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