Hardenable mass with silane dendrimers

Details Hardenable mass with silane dendrimers Hardenable mass with silane dendrimers

2000-02-03

2002-01-01

Dawson, Robert (Department: 1712)

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

Synthetic resins

From silicon reactant having at least one...

C424SDIG001, C525S477000, C525S478000, C528S015000, C528S031000

Reexamination Certificate

active

06335413

ABSTRACT:

This application is the national phase under 35 U.S.C. §371 of PCT International Application No. PCT/EP98/05319 which has an International filing date of Aug. 21, 1998, which designated the United States of America.
The invention relates to curable compositions which contain highly-branched molecules on a silane base and are particularly suitable as dental materials.
For dental materials, there is a high demand for materials with high end hardness for the most varied indications. Materials for bite registration, temporary and permanent filling materials, crown and bridge materials as well as cement and enamel can be named as examples. The end hardness plays an important role in all of these uses, for example it determines the dimensional stability, cuttability and castability of impression materials.
Normally, to increase the end hardness of curable materials, the filler content of the materials or the functionability level of reactive monomers is increased or the chain length for the reactive monomers is decreased.
Polymerisable compositions which have a high filler content and are suitable as dental materials are described for example in The International Encyclopaedia of Composites (S. M. Lee, Ed., Vol. 2, VCH Publishers, New York 1990, page 182) and by L. Ehrnford (Swed. Dent. J. Suppl. 18, 1983). Highly-filled materials are known from EP-A-0 480 472, which can only be processed however when acted on by ultrasonic transmissions.
Furthermore, short-chain vinyl end-stopped polydimethyl siloxanes of the general formula:
CH
2
═CH—R
2
SiO—(SiR
2
O)
n
—SiR
2
—CH═CH
2
are know from DE-A-2 646 726 where R is the same or different univalent, optionally substituted hydrocarbon radical free from aliphatic multiple bonds and n is 0 or an integer from 1 to 6. These compounds are used as inhibitors to regulate the cross-linking speed of addition cross-linked silicon impression materials.
DE-A-4 122 310 discloses on the other hand that compounds of the same general formula in which however n is an integer between 10 and 20 have no inhibitory effect whatsoever, but rather can be used to increase the end hardness of the cross-linked rubbers.
Thus it emerges from these documents that at least 22 chain links (i.e., wherein n is greater than or equal to 20 in the above mentioned general formula) must lie between two terminal C—C double bonds in molecules of the general formula stated in order to increase the hardness of the rubber; smaller intervals between the C—C double bonds inhibit cross-linking. This circumstance is also known from DE-A-4 324 685 in which diallyl maleinate and 1,3-divinyl-1,1,3,3-tetramethyldisiloxane can be named as examples of polymerization inhibitors, among others. Similarly, such molecules with more than 42 chain links (i.e., wherein n is greater than 40 in the above-mentioned formula) between the terminal double bonds are not imputed with any cross-linking properties.
There is a high demand for cross-linking monomers which increase the end hardness of a curable material but do not adversely affect the remaining properties, in particular the viscosity of the material.
The object of the present invention is to provide curable materials with increased end hardness and a viscosity suitable for processing in the dental field.
The object is achieved by a curable material containing:
(A) optionally organopolysiloxanes with at least two unsaturated groups in the molecule,
(B) organohydrogenpolysiloxanes with at least 3 SiH groups in the molecule,
(C) optionally organopolysiloxanes without reactive groups;
(D) catalyst
(E) optionally hydrophilizing agents,
(F) fillers and
(G) optionally standard dental additives, adjuvants and colorants,
characterized in that they additionally
(H) contain at least one silane dendrimer with terminal alkenyl groups.
Surprisingly, it has been ascertained that adding silane dendrimers to curable materials increases the end hardness of these materials considerably, but simultaneously acts against the increase in viscosity of the non-cured materials, although the silane dendrimers, at least in the first generation, have a considerably smaller double-bond interval as is regarded as strictly necessary in the prior art in order to have no inhibitory effect. Furthermore, with neighbouring double bonds, there is always the danger of complexing the catalyst, and thus an inhibitory effect is also to be observed. Successful polymerization using the silane dendrimers according to the invention is thus all the more astonishing.
Diorganopolysiloxanes with terminal triorganosiloxy groups of which at least one of the three organic groups is a vinyl group are preferred as component (A) Preferred diorganosiloxanes of this structure are represented by the following formula:
in which R represents a non-substituted or substituted monovalent hydrocarbon group with 1 to 6 C atoms, which is preferably free from aliphatic multiple bonds and n is chosen so that the viscosity lies between 4 and 50,000 mPas. At least 50% of the R radicals preferably consist of methyl groups, and examples for other R groups are ethyl, vinyl and 3,3,3-trifluoropropyl groups. Such molecules are described in U.S. Pat. No. 4,035,453, the disclosure of which should be included here. Component (A) is prepared according to standard procedures which are portrayed e.g. in W. Noll, “Chemie und Technologie der Silikone”, Verlag Chemie Weinheim 2. edition 1964, pages 162-206 or J. Burghardt, Chemie und Technologie der Polysiloxane in “Silikone, Chemie und Technologie”, Vulkan Verlag, Essen, 1989, pages 23-37.
Linear polydimethylsiloxanes of the above structure with the specified viscosity ranges for which the end groups consist of dimethylvinylsiloxy units and the other R substituents in the chain consist of methyl groups are particularly preferred.
Component (B) is preferably an organopolysiloxane with at least 3 Si-bonded hydrogen atoms per molecule. This organopolysiloxane preferably contains 0.01 to 1.7 wt.-% silicon-bonded hydrogens. The silicon valencies which are not saturated with hydrogen or oxygen atoms are saturated with monovalent hydrocarbon radicals which are free from aliphatic multiple bonds. The hydrocarbon radicals can be substituted or non-substituted. At least 50%, preferably 100% of the hydrocarbon radicals which are bonded to silicon atoms consist of methyl radicals. Such components are also described in the literature mentioned above with regard to structure and preparation.
The quantity ratios of components (A), (B) and (H) are preferably chosen so that 0.5 to 10 mol SiH units of component (B) is present per mol of unsaturated double bond of components (A) and (H). The sum of the components (A), (H), and the component (B) are in the range from 5 to 70 wt.-% relative to the total weight of all components. Preferably, they are in the range from 10 to 60 wt.-% and particularly in a range from 15 to 50 wt.-%.
Suitable components (C) are polymer organosiloxanes without reactive substituents as are described e.g. in W. Noll “Chemie and Technologie der Silikone”, Verlag Chemie Weinheim, 1968, pages 212 ff. These are preferably linear, branched or cyclical organopolysiloxanes for which all silicon atoms are surrounded by oxygen atoms or monovalent hydrocarbon radicals, the hydrocarbon radicals being able to be substituted or non-substituted. The hydrocarbon radicals can be methyl, ethyl, C
2
-C
10
aliphatics, trifluoropropyl groups as well as aromatic C
6
-C
12
substituents. The component (C) contributes only to thinning and expanding the rubber network and acts as a plasticizer for the cured material. As it is a relatively cheap component, it contributes to the reduction of the preparation costs of the dental materials according to the invention.
Polydimethylsiloxanes which have trimethylsiloxy end groups are particularly preferred as component (C). The quantity of component (C) is 0 to 40 wt.-%, preferably 0 to 20 wt.-%, particularly preferably 0.1 to 10 wt.-%.
Component (D) is preferably a platinum complex which was prepared from hexachloroplatinum acid by reduction w

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