Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – At least one aryl ring which is part of a fused or bridged...
Reexamination Certificate
1999-02-23
2001-04-17
Dawson, Robert (Department: 1712)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
At least one aryl ring which is part of a fused or bridged...
C524S366000, C524S378000, C524S538000, C524S606000, C524S607000, C524S788000, C524S789000, C524S860000, C524S863000, C524S864000, C524S869000, C523S109000, C528S017000, C528S033000, C528S038000, C206S063500, C206S524100, C106S035000, C106S038300, C106S038350
Reexamination Certificate
active
06218461
ABSTRACT:
The invention relates to a silicone composition curing by condensation at room temperature, composed of a filler and a base paste containing polyorganosiloxane having hydroxy groups, as well as an activator component containing crosslinking agent and a catalyst of an organometallic compound, and the use of the silicone composition.
The invention especially relates to a silicone composition curing by condensation at room temperature composed of a base paste containing filler and a polyorganosiloxane having hydroxy groups, as well as an activator component containing crosslinking agent and a catalyst of an organometallic compound, for use as a dental silicone casting composition.
Silicone stripping compositions are distinguished according whether they are crosslinked by condensation or by addition (R. Marxkors/H. Meiners, Taschenbuch der zahnärzlichen Werkstoffkunde, Munich/Vienna: Carl Hanser Verlag, 1978; Ullmann's Encyclopedia of Industrial Chemistry, 5th ed., Weinheim; New York: VCH, Volume A8, 1987, 288).
The silicone casting compositions in the form of a two-component system consist—if they belong to those which crosslink by condensation—of a base paste containing polydimethyl silanols or other hydroxy-polyorganosiloxanes and fillers as well as activator liquid or activator paste containing crosslinkers and catalyst for the polycondensation. After the two components are mixed shortly before use, the polydimethyl silanols react with the crosslinker consisting usually of silicic acid esters or other alkoxysilanes by condensation with chain lengthening, branching and crosslinking, and rubber-elastic materials very well suited for casting are formed. Silicone impression compositions crosslinking by condensation are disclosed, for example, in DE 1 153 169 B1, DE 26 44 193 A1, DE 34 06 233 A1, DE 36 36 974 Al and DE 43 32 037 A1.
DE 1 153 169 B1 relates to a method of preparing elastomeric castings from two separate compositions in paste form, which are mixed together before curing at room temperature. One of the compositions contains hydroxy terminally blocked diorganopolysiloxane and crosslinkers, for example silicic acid ester or organohydrogen polysiloxanes, the other containing diorganopolysiloxane terminally blocked by triorganosiloxy groups and the condensation catalyst, such as dibutyl tin diacetate. The compositions are used mainly as impression or sealing compositions for technical, artistic or, especially, for dental purposes. It is disadvantageous that the composition containing the hydroxy terminally blocked diorganopolysiloxane and the crosslinker markedly loses its activity in storage.
DE 26 44 193 A1 has disclosed paste compositions for polyorganosiloxanes which can be vulcanized at room temperature, which contain, in addition to crosslinking substances and catalyst (hardening catalysts), 3 to 40 wt.-% of active hydrophilic silicic acid as thickening agent and, in some cases, up to 40 wt.-% of inactive fillers, such as quartz flour or titanium dioxide. Crosslinking substances are esters of silicic and polysilicic acids, alkyl alkoxy silanes, aryl alkoxy silanes or alkylalkanoyl oxysilanes. Their amount is 0.1-10 parts by weight with respect to the polyorganosiloxane. Catalysts are carboxylic acid metal salts, such as dibutyltin dilaurate, tin(II) octanoate, lead laurate, cobalt naphthenate and tetra-isopropyl titanate, or amines or amine salts, such as hexylamine, cyclohexylamine and butyl ammonium acetate. They are used in an amount between 0.1 and 10% of the polyorganosiloxane. The paste compositions are stable when stored in moisture-proof packages, and can, as well as the polyorganosiloxane pastes, be packed in tubes with a select opening diameters and proportioned by the length of the strands pressed from the tubes. The diameters of the tube openings are chosen so as to provide between 3 and 40 parts by weight of the paste compositions for each 100 parts by weight of the polyorganosiloxane pastes.
In DE 34 06 233 A1, finely divided fillers intended for silicone compositions in paste form which cure at room temperature by condensation or addition are described, whose particles are coated with paraffin oil, have an average particle size between 1 and 25 micrometers and can consist of calcium carbonate, cristobalite or quartz flour. The silicone compositions contain 30-90 weight-percent of the fillers and are used preferably in molding materials for dental purposes, a distinction being made between systems which crosslink by condensation and those which crosslink by addition. In the former case the liquid or paste activator components contain a carboxylic acid metal salt and a silicic acid ester, and the silicone compositions contain polyorganosiloxanes with two or more hydroxy groups in the molecule.
In DE 43 32 037 A1, a condensation-crosslinking silicone for molding in dentistry is proposed whose principal and secondary components are mixed in a 1:1 ratio and can be packaged in chambers of double cartridges in a 1:1 ratio by volume. The principal component consists of hydroxypolysiloxane, pyrogenic silicic acid, calcium carbonate, water and dibutyltin dilaurate, the secondary components consist of cristobalite, silicone oil and paraffin oil. This silicone, however, contains no crosslinking agent and therefore does not harden to a rubber-elastic material.
While in the case of addition-crosslinking silicone molding compositions, two-component systems in the form of pastes with good shelf life are known, which can be proportioned by weight or by volume, preferably in a 1:1 ratio (see, for example, EP 0 219 660 B1), this type contains no systems of crosslinking agents which are to be added to it and have good shelf life in the condensation-crosslinking silicone molding compositions.
The invention is therefore addressed to the problem of finding a silicone composition of the above-described kind which cures by condensation at room temperature and consists of both the paste and the activator component, wherein both components are stable in storage, can be proportioned in the desired ratio of admixture with one another and can be uniformly mixed together in any ratio. The activator component is to have a fluid-to-pasty consistency and is to permit the silicone composition to be offered in tubes, in tubular bags which are intended for use together with cartridges and are disclosed, for example, in DE 296 02 111 U1, and preferably in double cartridges. The silicone composition is to be suitable especially for use as a dental molding composition.
Double cartridges are two-chamber devices of the kind described, for example, in EP 0 378 806 B1 for mixing reactive components with one another and dispensing the paste mixtures obtained. Before use the stopper originally sealing the double cartridges is removed and inserted with the open dispensing end foremost into a static mixer. With double cartridges the correct ratio of admixture of the components and the uniformity of the mixed pastes can be achieved in a simple manner.
The silicone composition constituting the solution of the problem is characterized according to the invention in that the activator component additionally contains a polyaddition product with at least two alkoxysilyl groups in the molecule.
The term, polyaddition products, in the meaning of the invention are the products obtained as a result of a polyaddition. Polyaddition is a polymerization reaction in which polymers are built up by the frequently repeated addition of bisfunctional or polyfunctional educts or monomers (Römpp Chemie Lexikon, 9th ed., Stuttgart, New York: Georg Thieme Verlag, vol. 5, 3508).
The silicone composition according to the invention has proven especially valuable if the polyaddition product is one that contains ether, urethane, urea and alkoxysilyl groups, with a mainly linear molecular structure, exclusively aliphatically or cycloaliphatically bound ether, urethane and urea segments, and an average molecular weight of 800 to 20,000,
a) a content of 25-90 wt.-% polyether groups,
b) a content of 0.5-10 wt.-% urethane grou
Freckmann Michael
Nehren Klaus-Dieter
Schwabe Peter
Dawson Robert
Heraeus Kulzer GmbH & Co. KG
Norris & McLaughlin & Marcus
Robertson Jeffrey B.
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