Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Polymers from only ethylenic monomers or processes of...
Reexamination Certificate
1999-12-20
2003-10-14
Teskin, Fred (Department: 1713)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Polymers from only ethylenic monomers or processes of...
C526S095000, C526S102000, C526S104000, C526S106000, C526S226000, C526S240000, C526S241000, C526S279000, C526S908000, C525S326500, C525S372000, C525S373000, C522S066000, C528S014000, C528S016000, C528S017000, C528S018000, C528S019000, C528S323000, C528S326000, C528S409000, C528S411000, C528S414000, C528S416000, C528S417000, C528S423000
Reexamination Certificate
active
06632897
ABSTRACT:
The present invention relates to the use of nanoscale metal oxide particles as polymerization catalysts. Particularly, the present invention relates to the use of nanoscale metal oxide particles as catalysts which can replace the conventional catalysts for the thermal and photochemical polymerization of (e.g. radically) polymerizable species such as, e.g., peroxides, azo compounds and the conventional UV polymerization initiators. This allows the manufacture of inorganic-organic composite materials containing or consisting of an inorganic network which does not contain any residues derived from said conventional polymerization initiators.
It is already known to crosslink silicon containing polycondensates or heteropoly-condensates wherein, for example, an epoxy group or a methacrylic group is covalently bonded to a silicon atom in the presence of thermally or photochemically active catalysts by means of said functional organic groups. Moreover, it is known that by using nanoscale fillers which are homogeneously dispersed in an inorganic-organic matrix transparent molded articles and coatings may be produced.
According to the present invention it has sursprisingly been found that it is possible to effect a polymerization or crosslinking by means of certain polymerizable groupings even without the above-mentioned conventional catalysts if nanoscale particles (in the following sometimes referred to as nanoparticles) of certain substances are mixed with (e.g. dispersed in) said species which are to be polymerized or crosslinked, respectively and which show said polymerizable groupings, and the resulting mixture is treated thermally and/or irradiated (with UV light). This makes it possible, for example, to thermally and/or photochemically effect the polymerization of species (monomers, oligomers and polymers including polycondensates) having (meth)acrylate groups, as well as the polyaddition of species having an epoxide ring in the sole presence of said nanoparticles as catalysts. It is believed that the catalytic action of said nanoparticles is primarily due to the presence of (numerous) Lewis acid or Lewis base centers, respectively, on the surface thereof.
Although it is known that, e.g., aluminum alkyls catalyze polymerization reactions of double bonds according to the Ziegler-Natta process, similar catalytic effects of particles have not as yet been known.
Accordingly the present invention provides a process for the thermal and/or photochemical polymerization or crosslinking of species (monomers, oligomers and polymers including polycondensates) having at least one polymerizable carbon-carbon multiple bond and/or at least one carbon containing ring capable of undergoing a ring opening polymerization, said ring preferably containing at least one heteroatom selected from the group consisting of oxygen, nitrogen and sulfur as ring atom, wherein said process is characterized in that as (preferably sole) thermal and/or photochemical polymerization catalyst nanoscale particles of at least one metal oxide (including mixed oxides of metals) is used.
Said process makes it possible to produce, e.g., (highly transparent) molded articles and coatings, particularly for optical purposes, said molded articles and coatings being also an object of the present invention.
Among the advantages of the present invention is the fact that the conventional polymerization and polyaddition catalysts may be dispensed with and as a result thereof no corresponding decomposition products are present in the final polymer (e.g. molded article or coating) and that the polymerization catalysts employed according to the present invention are not subject to inhibition by oxygen, which constitutes a problem with many of the conventionally used (particularly UV) initiators.
In the following the process according to the present invention will be explained in more detail.
The species to be polymerized or crosslinked may be both purely organic species and mixed inorganic-organic species.
In the present description and the appended claims the term “organic species” is meant to denote species which in addition to carbon and hydrogen as mandatory components may optionally contain only elements selected from the group consisting of oxygen, nitrogen, sulfur and halogen (i.e., fluorine, chlorine, bromine and iodine). On the other hand, “inorganic-organic species” is to denote those species which in addition to the just mentioned elements may optionally contain further elements, particularly and preferably silicon, but also other elements such as, e.g., metals like aluminum, titanium and zirconium (preferably in addition to silicon).
According to the present invention preferred inorganic-organic species are (monomeric) hydrolyzable silicon compounds which in addition to one or more hydrolyzable groups (e.g. alkoxy groups) contain at least one non-hydrolyzable radical having a polymerizable carbon-carbon multiple bond (preferably a double bond) or a carbon containing ring capable of undergoing a ring opening polymerization (polyaddition) (preferably an epoxide ring) as well as precondensates (oligomers) and polycondensates derived from said monomeric silanes. Said precondensates or polycondensates, respectively, may in turn be those which are derived from one or more of the just described hydrolyzable silanes having a polymerizable carbon-carbon double bond or a ring capable of undergoing a ring opening polymerization as well as optionally, in addition thereto, from one or more other hydrolyzable silanes (without the just mentioned groups) and one or more hydrolyzable compounds of other elements cocondensable with said hydrolyzable silanes, for example those of aluminum, titanium and zirconium. It is, however, preferred that such precondensates and polycondensates are derived exclusively from hydrolyzable silanes.
The hydrolyzable silanes having a polymerizable group (in the following the term “polymerizable group” is meant to comprise not only polymerizable carbon-carbon multiple bonds but also carbon containing rings capable of undergoing a ring opening polymerization) are preferably compounds having 2 or 3, preferably 3, hydrolyzable radicals and 1 or 2, preferably 1, non-hydrolyzable radicals featuring a polymerizable group (preferably (meth)acrylate group or epoxide ring). Examples of hydrolyzable radicals are halogen (F, Cl, Br and 1, particularly Cl and Br), alkoxy (particularly C
1-4
alkoxy such as, e.g., methoxy, ethoxy, n-propoxy, i-propoxy and butoxy), aryloxy (particularly C
6-10
aryloxy such as phenoxy), acyloxy (particularly C
1-4
acyloxy such as acetoxy and propionyloxy) and alkylcarbonyl (e.g. acetyl). Particularly preferred hydrolyzable radicals are alkoxy groups, especially methoxy and ethoxy.
Said polymerizable groups are bonded to the silicon atom preferably in the form of a group R—O—(CH
2
)
n
—Si, wherein R represents the group comprising the polymerizable entity and n has a value of from 1 to 10, preferably from 2 to 6. A particularly preferred linking group between R and Si is the oxypropyl group.
Hydrolyzable silicon compounds featuring a polymerizable group which are particularly preferred according to the present invention are those of the general formula
X
3
SiR′
wherein the groups X, the same or different from each other (preferably the same), represent a hydrolyzable group (preferably C
1-4
alkoxy and particularly methoxy and ethoxy) and R′ represents a glycidyloxy C
1-6
alkylene or methacryloxy C
1-6
alkylene radical.
It also is possible that in the above formula one or two radicals X, preferably one radical X, is replaced by a non-hydrolyzable radical without polymerizable group such as, e.g., an alkyl or aryl group, for example methyl, ethyl and phenyl.
Additional examples of hydrolyzable silanes having a polymerizable group are, e.g., those having a vinyl or allyl group directly bonded to the silicon.
Specific examples of hydrolyzable silanes to be employed as species to be polymerized or crosslinked, respectively (or as starting materials therefor) according to the present
Geiter Elisabeth
Schmidt Helmut
Ehrman Heller
Institut Für Neue Materialien gemeinnützige
Teskin Fred
White & McAuliffe LLP
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