Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – From reactant having at least one -n=c=x group as well as...
Reexamination Certificate
2002-06-13
2004-12-21
Gorr, Rachel (Department: 1711)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
From reactant having at least one -n=c=x group as well as...
C525S455000, C528S075000, C524S840000, C526S301000, C523S115000, C523S116000, C522S135000, C522S141000, C522S149000
Reexamination Certificate
active
06833425
ABSTRACT:
The invention relates to fillers for plastics formulations based on polyurethane. The invention relates in particular to organic, crosslinked, reactive and radiation-curing plastics fillers based on polyurethane.
Fillers for use as the filler content of plastics formulations for the purpose of improving the physical properties thereof are sufficiently known. Organic fillers have been used for a long time for dental materials, for example, in addition to inorganic fillers such as quartz or glasses. Bead-shaped polymers and copolymers based on methyl methacrylate are a widely used representative for this.
In addition to bead-shaped polymers, for example, precipitation polymers formed from acrylic acid and/or methacrylic acid esters for use in the dental sector are known from EP-B-0 270 915.
Advantageous features of the use of organic fillers are, inter alia, the easy polishability of the composite materials produced therefrom, the favourable price compared with inorganic fillers ground to an ultrafine degree, the high transparency of the polymers obtained and the ash-free combustibility. Because of the wide variability in the composition which organic fillers can have, material properties can also be influenced in a controlled manner, for example the impact strength of dental materials can be influenced favourably by the graft copolymers mentioned in DE-A1-196 178 76.
Bead-shaped polymers and copolymers based on methyl methacrylate show a high tendency to swell. This is necessary in order to enable partial dissolving of the fillers by monomers, since binding of the fillers to the resin matrix becomes possible only by the formation of an interpenetrating network which takes place during the polymerization. However, a constant increase in the viscosity of the compositions formulated with the fillers is caused by this tendency to swell. In the case of prosthesis plastics, which as a rule comprise the highly solubilizing methyl methacrylate as a main constituent of the monomer matrix, these swelling properties determine, for example, the processing time in the pack-press technique (flask technique). The swelling properties can be measured, for example, by measuring the processing time as described in the international standard ISO 1567, a time frame of approx. 30 to 60 minutes being regarded as usable.
DE-C2-197 060 64 describes plastically curable one-component compositions based on PMMA beads and higher molecular weight crosslinking methacrylates. Although storage stabilities of 6 months are claimed, stiffening of the paste nevertheless already occurs within a few days at slightly elevated temperature (36° C.), this being attributable to the increase in viscosity caused by the partial dissolving of the PMMA beads.
Although the precipitation polymers known from EP-B-0 270 915 are not partially dissolved by the conventional (meth)acrylate monomers of dental technology because of their high crosslinking density and therefore also show no changes in viscosity in the course of storage, they are nevertheless not incorporated particularly well into the resin matrix in spite of the residual double bonds present, so that the resulting composite materials have only moderate mechanical properties. The accessibility of the residual double bonds is evidently ensured to only a limited degree.
Other organic fillers, such as plastics powders ground at room temperature or cryogenically, or precipitated polymer powders, show similar problems.
The fillers based on polyethylene, polypropylene, an ethylene-acrylic acid-acrylic acid ester terpolymer or polyurethane which are commercially obtainable under the trade name “Coathylene” result in composite materials with very inadequate mechanical strengths, since no bonding to the resin matrix is possible because of a lack of reaction centres.
There is therefore a considerable demand for fillers on an organic basis which can be polymerized into the matrix and the swelling properties of which in the conventional monomer matrices of dental technology are so low that formulations with stable viscosity properties even at elevated temperature and over a relatively long storage time can be realized.
The object of the present invention is to provide organic fillers which can satisfy the above-mentioned requirements.
This object is achieved by organic, crosslinked, reactive and radiation-curing plastics fillers based on polyurethane.
The fillers according to the invention have a high reactivity, without undergoing severe swelling in conventional dental monomers. They can be polymerized into resin matrices via ethylenic double bonds, are easy and inexpensive to synthesize, and their properties can be adjusted within a wide range by variation of the educts. They can be radiation-cured via the unsaturated functionalities and are therefore particularly suitable for use in the dental sector, but also in other industrial fields where the properties of the fillers according to the invention are of advantage.
The fillers according to the invention are obtainable by reaction of:
(A) 15 to 35 wt. %, preferably 20 to 30 wt. % of one or more radiation-curing (meth)acrylate-based compounds with OH numbers of 40 to 700 mg KOH/g,
(B) 15 to 40 wt. %, preferably 20 to 35 wt. % of one or more polyols with a molecular weight of 500 to 6,000 g/mol,
(C) 0 to 15 wt. %, preferably 0 to 10 wt. % of one or more polyols with a molecular weight of less than 500 g/mol,
(D) 1 to 10 wt. %, preferably 1 to 7 wt. % of at least one compound which is mono- and/or difunctional in the sense of the isocyanate reaction, which additionally contains anionic groups or functional groups which can be converted into anionic groups,
(E) 24 to 69 wt. %, preferably 34 to 55 wt. % of one or more polyisocyanates,
and subsequent chain lengthening or crosslinking of the resulting product from (A) to (E) with
(F) 0.5 to 10 wt. %, preferably 0.5 to 5 wt. %, relative to the total weight of components (A) to (E), of a mixture of one or more diamines with a polyamine of functionality greater than 2,
at least 30 wt. %, preferably at least 50 wt. % of component (F) comprising polyamine of functionality greater than 2.
Radiation-curing but aqueous dispersions of a similar composition are known from the coatings industry. DE-A-195 25 489 and DE-A44 34 554 describe, for example, polyester-(meth)acrylate-urethane dispersions based on polyester-meth)acrylate prepolymers containing hydroxyl groups. These are obtainable by polyaddition of polyester-(meth)acrylate prepolymers containing hydroxyl groups and compounds which are reactive towards isocyanate groups with polyisocyanates and subsequent reaction with polyfunctional amines. These aqueous dispersions form films on drying, and thus no solid particles which can be used as a filler.
Surprisingly, however, it has been found that by reaction of the above-mentioned components (A) to (E) with subsequent crosslinking by component (F), the fillers according to the invention are obtained after stripping off the solvent. It is particularly advantageous here that after the crosslinking with (F) the fillers can be obtained without additional working-up steps.
Component (A) comprises radiation-curing (meth)acrylate-based compounds which have OH numbers from 40 to 700 mg KOH/g according to DIN 53 240. The term (meth)acrylate is used in this specification to represent methacrylate and/or acrylate.
Suitable components (A) are, for example, polyester-(meth)acrylate prepolymers containing hydroxyl groups such as are described in U.S. Pat. No. 4,206,205, DE-OS40 40 290, DE-OS-33 16 592, DE-OS-37 04 098 and in “UV & EB Curing Formulations for Printing Inks Coatings and Paints”, ed. R. Holman and P. Oldring, published by SITA Technology, London (England) 1988, p. 36 et seq. Alternatively, polyepoxy(meth)acrylate prepolymers containing hydroxyl groups which are accessible by reaction of polyepoxides with (meth)acrylic acid, and/or polyurethane-(meth)acrylate prepolymers containing hydroxyl groups can also be used. The use of polyepoxy(meth)acrylate prepolymers containing hydroxyl groups, such
Gangnus Bernd
Hecht Reinhold
Lechner Günther
3M ESPE AG
Gorr Rachel
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