Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – From silicon reactant having at least one...
Patent
1995-11-13
1998-04-14
Dean, Ralph H.
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
From silicon reactant having at least one...
528 29, C08G 1838
Patent
active
057392455
DESCRIPTION:
BRIEF SUMMARY
The invention relates to plastics with at least one polyaddition product which contains silane, ether, urethane and urea groups and has a predominantly linear molecular structure with exclusively aliphatically or cycloaliphatically bonded ether, urethane and urea segments and a number-average molecular weight in the range from 800 to 20,000, the polyaddition product having the following features: by weight per 100 parts by weight of polyaddition product; of polyaddition product; of polyaddition product; predominantly linear molecular structure, of the formula III least one of the groups R.sup.1, R.sup.2 and R.sup.3 is a group of the formula V alphamethylvinylcarbonyl or beta-methylvinylcarbonyl group, and in which the remaining groups R.sup.1, R.sup.2 and R.sup.3 are methyl, ethyl or C.sub.1 - to C.sub.4 -alkoxy, if they are not groups of the above definitions, and the plastics furthermore comprising at least one catalyst for condensation of the silane groups.
Further advantageous embodiments of the invention can be seen from the following description and the subclaims.
The plastics of the invention are particularly suitable as impression and modelling compositions, in particular for dental purposes and for mould construction, which have a low tendency to shrink after complete curing.
Plastics based on polyaddition products containing silane, ether, urethane and urea groups mixed with polymerizable compounds are known from EP-A 0 170 865 and EP-A 0 410 199; the polyaddition products as such are described in DE-A 36 36 974; reference is made to the content of these publications.
The alkoxysilyl groups which occur in the plastics which are already known or in the polyaddition products contained in these have a structure according to the above formula III, in which at least one of the groups R.sup.1, R.sup.2 and R.sup.3 is C.sub.1 -C.sub.4 -alkoxy, preferably methoxy or ethoxy, and R.sup.2 and R.sup.3 can have the same meaning as R.sup.1 or are methyl or ethyl groups.
It is preferable if one or two of the groups R.sup.1, R.sup.2 and R.sup.3 in the silyl groups of the formula III are methyl, ethyl or methoxy.
As a result of their content of alkoxysilane groups, these compounds are capable of condensation in the presence of suitable acidic catalysts, elastic, gelatinous polymers being formed as it were as the first stage of curing. Depending on the nature of the polymerizable olefins added, these polymers can then be after-cured to dimensionally stable rigid materials. However, the curing in the first stage specifically leads to unwanted shrinkage processes in impression or modelling compositions, since the condensation products formed during the condensation are incompatible with the polymer material and emerge from the resulting shaped articles, with shrinkage thereof. Thus, products formed during the condensation are incompatible with the polymer material and emerge from the resulting shaped articles, with shrinkage thereof. Thus, for example, in DE-A 36 36 974 a value of 2.2% after 120 minutes is stated for the change in dimensions of the shaped article cured in the first stage for one of the systems mentioned therein; such a material is unusable, in particular, for such dental purposes where extremely high dimensional accuracy is important.
For the plastics known from EP 0 170 865, no data at all have been disclosed on the shrinkage properties during complete curing and on their suitability for dental purposes; furthermore, these plastics have certain disadvantages inasmuch as they are hydrophilic, because of their content of ethyleneoxy groups, and can swell in the presence of water.
The present invention is aimed at plastics of the abovementioned type in which no tendencies to shrink, or considerably reduced tendencies to shrink compared with the prior art, occur after curing and which do not swell on access of water. The invention is based on the finding that the tendencies to shrink can be avoided or reduced if the condensation products liberated in the course of curing are formulated such that they ar
REFERENCES:
patent: 4798878 (1989-01-01), Brinkmann et al.
patent: 5095045 (1992-03-01), Winkel et al.
patent: 5118290 (1992-06-01), Muller et al.
International Search Report.
Lubbers Dierk
Muhlbauer Wolfgang
Dean Ralph H.
Ernst Muhlbauer KG
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