Patent Application
20140100349
Silicic acid (hetero) polycondensates comprising organically polymerisable groups and either sulphonate groups or sulphate groups, organic polymerisates produced therefrom, and a method for producing said polycondensates
The present invention concerns silicic acid (hetero) polycondensates, comprising first groups, bonded by carbon to silicon and comprising at least one polymerizable C═C double bond, as well as second groups, also bonded by carbon to silicon and comprising either sulfonate or sulfate groups, as well as polymers which can be obtained by the polymerization of the afore mentioned double bonds.
Polymerizable organic compounds with acid groups are important components for medical products for achieving desired material properties like wetting, etching effect, complexing, and thereby adhesion on biological interfaces. Dental adhesives are based on such conventional monomeric compounds, but exhibit still some considerable deficits. An essential problem in this context is that the etching effect is often insufficient within the context of self-etch application for realizing the necessary retentive structures required for the adhesion and thus a long-lasting connection between dental tissue and restoration material. Therefore, a prior separate etching step with an etching gel cannot be avoided; this, in turn, increases the susceptibility for errors and the treatment costs. Concerning the increasing demands in regard to biocompatibility (reference is being had to the allergy discussion in connection with dental monomers), the above systems also offer no solution. Since the components of the adhesive in case of a restoration come closest to the tooth roots as well as blood vessels, it is of special interest from a toxicological viewpoint to provide systems that are free of monomers.
In the patent application DE 44 16 857 C1, carboxylic acid-functionalized (meth)acrylate alkoxysilanes are described. They are characterized by a plurality of possibilities for varying or adjusting the properties of the inorganic-organic composite polymers produced therefrom. As a result of the contained carboxylic acid groups, additional reaction possibilities (e.g., glass ionomer reactions) as well as an improved adhesion on inorganic surfaces arise. The etching effect (see self-etch application) of a carboxylic acid group is however nowhere as strong as that of an S—OH functionality. The same holds true for the phosphonic acid-based systems disclosed in EP 1 377 628 B1. Therefore, up to now, it is not possible to obtain with hybrid polymer-based systems a stable enough connection between dental tissue and restoration material in the context of the desirable self-etch application.
For several application purposes, like the stabilization of aqueous silicates or the production of electro-viscous liquids, emulsifiers, detergents or foaming agents, monomeric or condensed silanes containing sulfonate or sulfate groups have been developed. Thus, U.S. Pat. No. 6,777,521 discloses silicone sulfate polymers which are obtainable by the reaction of suitable epoxy compounds with metal sulfate. U.S. Pat. No. 3,328,449 discloses sulfopropylated organo-functional silanes and siloxanes which can be obtained by means of reacting sultones. Organo siloxane sulfosuccinates in which a sulfonated succinic acid ester is bonded by the oxygen atom of the ester group by an alkylene group to a silicon atom are disclosed in U.S. Pat. No. 4,777,277. The preparation of a hydrolytically condensable bis-sulfosuccinate amide of a diaminosilane, obtained by the reaction of the free carboxylic acid of the suitable succinate amide with sodium sulfite, is disclosed in example 1 of U.S. Pat. No. 4,503,242. A silane which carries a sulfonate group and a hydroxyl group at an alkylene oxyalkylene group of the silicon is disclosed in U.S. Pat. No. 5,427,706.
The use of purely organic monomers which carry a terminal sulfonate group as well as an unsaturated olefinic group for concurrent etching and base-coating (“priming”) of teeth is suggested in US 2002/0119426 A1. Also, U.S. Pat. No. 6,759,449 B2 discloses dental adhesive compositions which carry an organically polymerizable (meth)acrylic acid group as well as an acidic group. In this context, no distinction is made between sulfonate groups and phosphonate groups or other acidic groups concerning the usability of the compounds and their properties. The same holds true for US 2003/0055124 A1; only for the (meth)acrylamido phosphonic acids, but not for the also disclosed corresponding sulfonic acids, information is provided for the preparation. Another application, US 2008/0194730, essentially by the same group of inventors, suggests again for dental composites the use of self-etch polymerizable N-substituted (meth)acrylic acid amide monomers which carry additionally an acidic unit, selected from phosphonic acid units and sulfonic acid units. N-methacryloyl aminoalkyl sulfonic acids can be used according to the disclosure of EP 1 421 927 A1 as self-etch primers for dental purposes.
DE 102 06 451 A1 discloses dental adhesive compositions from acidically polymerizable nanoparts in an aqueous phase. The nanoparticles consist of siloxanes having acidic as well as organically polymerizable groups bonded thereto. The acidic groups can be either phosphonate groups or sulfonate groups; individual specific advantages for one or the other group are not specified. The only example of use discloses a specific adhesion value of a dental adhesive from a phosphonic acid-containing material on a tooth surface. A process for producing sulfonate group-containing silanes or siloxane is neither mentioned generally nor in regard to the disclosed compounds.
There is a need for organically polymerizable silicic acid (hetero) polycondensates of superior properties for the application in particular in the dental field. Here, an improved adhesion and/or an improved etching function and/or an adaptation of the optical properties for the cosmetic appearance are especially relevant. To provide a remedy in this context is the object of the present invention.
For solving this object, silicic acid (hetero) polycondensates are provided which have organically polymerizable groups, in particular (meth)acryl groups, as well as sulfate groups or sulfonate groups. In this context, it has been surprisingly found that in all prepared materials the sulfonate group or sulfate group has a substantially stronger etching effect than a phosphonate group in a comparable position.
The silicic acid (hetero) polycondensates according to the invention encompass first groups, bonded by carbon to silicon and having at least one polymerizable C═C double bond, as well as second groups that are also bonded by carbon to silicon and have either sulfonate groups or sulfate groups. These are, at least formally, co-condensates from at least one silane with a residue, bonded by a carbon atom and carrying an organically polymerizable C═C double bond, in particular a (meth)acryl residue, and at least one silane with a residue bonded by a carbon atom and carrying a sulfonate group or sulfate group, in particular of the formula —(O)d—SO3M with d=0 or 1 and with M=hydrogen or a monovalent metal cation or the corresponding portion of a multi-valent metal cation. Excluded from the claimed subject matter are such co-condensate in which the C═C double bonds are realized exclusively by (meth)acrylic esters which are bonded in the form of a methylene acrylic ester group to the groups that are bonded by carbon to silicon because, firstly, the ester group of the respective methacrylic esters is not stable with respect to hydrolysis so that in an undesirable manner free alcohol molecules can be generated, while at the same time the number of methacrylic acid groups possibly may increase uncontrollably, and, secondly, the double bond is less accessible on account of steric conditions because it is not in the outer region of the silyl unit to which it is bonded so that it cannot be reached as well by its reaction partners. Moreover, an aspect of the invention concerns a very easy incorporation of the optionally present (meth)acryl groups, which can be realized in that they are reacted in the form of the free acid or activated acid, i.e., are bonded to the condensates or their silane precursors. This has the result that the (meth)acryl groups are present in the structures incorporated as (meth)acrylic esters, (meth)acrylic amides or (meth)acrylic thioesters.
The expression “co-condensate” is meant to encompass according to the invention all those condensates which would generate at least two different silanes upon hydrolysis of the Si—O—Si bonds. Supra, they were referred to “formally” as co-condensates because they can be also produced by hydrolytically condensing a single silane and modifying afterwards only some of the groups that are bonded by carbon to the silicon atoms; this will be explained in detail infra.
The organically polymerizable C═C double bond to be employed according to the invention is in several embodiments an activated double bond. As “activated C═C double bonds”, groups are to be understood whose double bonds have in their neighborhood an electron-withdrawing group so that an attack is possible by a NHR group (a nucleophilic attack). Particularly preferred examples of such residues are acrylates and methacrylates which, in accordance with the preceding explanations, are in the form of (meth)acryl silyl esters, (meth)acryl silyl amides or (meth)acryl silyl thioesters, i.e., in a form in which the acryl group is esterified/amidated/thioesterified with the organosilyl group.
Instead of the expression “activated C═C double bonds”, the expression “active C═C double bonds” is also used herein in some places.
As an example of organically polymerizable double bonds that are not active or not activated, the vinyl group, the allyl group as well as double bonds within a ring, such as those in a norbornene group, are to be mentioned here. These groups are sterically also in an external region of the respective silanes so that they are easily polymerized.
The expression “'organically polymerizable” is to be understood as the possibility of polyaddition of the double bonds, on the one hand, but also the polymerization by the addition of residues capable of addition, like thio groups or amino groups, on the other hand. Thus, for example, a norbornene group can be subjected to a thiol-ene addition.
The word or the word part **(meth)acrylic . . . ” is meant to encompass the respective methacryl and acryl compounds alike. The (meth)acryl residues can be in particular a component of a (meth)acrylic acid ester, thioester or amide. (Meth)acrylic acid amide residues are preferred compared with the other (meth)acryl residues because of their better resistance to hydrolysis.
The expression “sulf(on)ate” encompasses the sulfonate group and the sulfate group. The expressions “sulfonate group” and “sulfate group” encompasses the respective acids and salts.
The polycondensates of the invention can be present in many different embodiments and can be producible according to different variants. All variants have in common that they are generated as a rule by the known sol gel process. In this way, silicic acid polycondensates are produced which are often referred to also as ORMOCER®e. The condensation reaction can occur in the presence of additional silanes of the formula SiR*aR**4-a which are known in the art in very large numbers. R* means a hydrolyzable group which enables the incorporation by condensation of the silane into the network, while R** can be any non-condenseable residue. R* can be herein OH or a C1-C10 alkoxy group, more preferred a C1-C4 alkoxy group, and particularly preferred methoxy or ethoxy. However, R* can be, as needed, also a halide like Cl, hydrogen, acyloxy with preferably 2 to 5 carbon atoms, alkylcarbonyl with preferably 2 to 6 carbon atoms, or alkoxycarbonyl with preferably 2 to 6 carbon atoms. In some cases, R* can also be NR2 with R2 being hydrogen, alkyl with preferably 1-4 carbon atoms, or aryl with preferably 6-12 carbon atoms.
In this context, the silanes of both variants are selected in a suitable manner such that the desired condensation level is achievable with them. Thus, up to three residues, optionally only two residues, of the silyl group are selected from hydroxyl groups or—preferred—hydrolyzable groups. Such groups are called generally network formers. Preferably, they are alkoxy groups, aryloxy groups or aralkoxy groups, in particular C1-C10 alkoxy groups, more preferred C1-C4alkoxy groups, and particularly preferred methoxy or ethoxy. However, as needed in special cases, it is possible to select be as hydrolytically condenseable groups in place thereof or partially, in each case independent of each other, halides like Cl, hydrogen, acyloxy with preferably 2 to 5 carbon atoms, alkylcarbonyl with preferably 2 to 6 carbon atoms, or alkoxycarbonyl with preferably 2 to 6 carbon atoms, provided they do not interfere with the reactions which are needed for producing the condensates according to the invention. In individual cases, groups of the meaning NR2 with R2 being hydrogen, alkyl with preferably 1-4 carbon atoms, or aryl with preferably 6-12 carbon atoms can be used instead.
In addition, the silanes can also contain groups which are called network modifiers. These are groups which themselves have no influence on the formation of the condensate but can modify its properties. They are preferably alkyl groups, aryl groups, arylalkyl groups, alkylaryl groups or alkylarylalkyl groups that are substituted or unsubstituted, straight-chain, branched or provided with at least one cyclic structure; nevertheless, in individual cases, also corresponding alkenyl groups, arylalkenyl groups or alkenylaryl groups can be present. Preferred are alkyl groups, aryl groups or aralkyl groups, in particular C1-C10 alkyl groups, more preferred C1-C4 alkyl groups, and particularly preferred methyl or ethyl.
In exceptional cases, a single silane can have two groups that are bonded by carbon to the silicon which either both have at least one polymerizable C═C double bond or both have a sulfonate group or sulfate group.
When three hydrolyzable groups/hydroxyl groups are present, a three-dimensional network is generated while silanes with two hydroxyl groups/two hydrolyzable groups from chains and/or rings. Because most of the silanes suitable for the invention have only one group that is bonded by carbon to silicon and that carries either a polymerizable C═C double bond or a sulfonate group or sulfate group, they have, in case of the presence of only two hydrolyzable groups/OH groups, generally one of the afore mentioned groups which are referred to as network modifiers
It can be desirable to provide additional metal compounds for the incorporation by condensation into the inorganic network. For this purpose, in particular hydrolytically condensable compounds of metals of the main groups III and IV as well as of the transition metal groups III to VI are suitable, e.g., of boron, aluminum, titanium germanium, zirconium or tin. These metal compounds are known in large numbers. In these cases, a silicic acid (hetero) polycondensate is generated in which the afore mentioned metal atoms are integrated into the Si—O—Si network. The additional metal compounds are often alkoxy compounds; in specific embodiments of the invention, the other metal compounds themselves can also have reactive groups however. In this context, of special interest for the present invention are complexes which themselves carry (meth)acryl groups because the latter can be integrated by a subsequent organic polymerization into the organic network.
The preparation of the polycondensates can be divided in principle into two groups: According to variant (A), different silanes are provided or generated wherein at least one of them has a sulfonate group or a sulfate group and at least a second one has an organically polymerizable group that has at least one C═C double bond. In contrast to this, according to variant (B), a polycondensate of one or several silanes is generated first which does not yet have all groups necessary for the invention, and then a modification is carried out at the stage of the polycondensate which produces the polycondensate according to the invention.
The variant (A) can be carried out with the aid of a plurality of starting silanes that are partly commercially available, partly can be prepared easily by a person of skill in the art. For example, a methacryl silyl ester can be obtained easily by reaction of a suitable silyl alcohol with methacrylic acid chloride or of a suitable silyl epoxide with methacrylic acid. Other starting silanes are described, for example, in DE 40 11 044 C1 and DE 44 16 857 C1. It is advantageous that also such silanes can be used which have more than one group containing a C═C double bond and/or more than one sulf(on)ate group which are preferably located at the same residue that is bonded by carbon to the silicon. One example for this is following (reaction 7):
The N-methacryl-modified methacrylsilylamide residue used herein can be produced in that a silane with a hydrocarbon group that is bonded by a carbon atom to the Si atom is provided and that carries a primary amino group and a secondary amino group and is reacted with activated methacrylic acid (e.g., methacryloyl chloride or anhydride). Variants can be produced in that instead of the primary amine a hydroxyl group or a thiol group is present and/or in that instead of the secondary amine a side group with a primary amine, a hydroxyl group or a thiol group is present. Examples of suitable aminosilanes are the compounds (aminoethyl aminomethyl) phenylethyl trimethoxysilane, N-(2-aminoethyl)-3-aminopropyl-methyldimethoxysilane, N-(2-aminoethyl-3-aminopropyl) trimethoxysilane, N-2-aminoethyl-3-aminopropyl tris(2-ethylhexoxy)silane, 6-(aminohexylaminopropyl) trimethoxysilane, N-(N′-(2-aminoethyl)aminoethyl)-3-aminopropyl trimethoxysilane, N-(N′-(2-aminoethyl)aminoethyl)-3-aminopropyl methyldimethoxysilane, N-(N′-(2-aminoethyl) aminoethyl)-3-aminopropyl triethoxysilane, N-(N′-(2-aminoethyl)aminoethyl)-3-aminopropyl methyldiethoxysilane, N-(N′-(2-aminoethyl)aminoethyl)-3-aminopropyl trimethylsilane, N-(N′-(2-aminoethyl)aminoethyl)-3-aminopropyl tris(methoxyethoxyethoxy)silane. Analogous compounds with corresponding hydroxyl groups or thiol groups are disclosed in EP 0 779 890 A1 , for example. The hydrocarbon group can also have another configuration than in the examples presented above.
It is evident that, instead of a silyl group with two functional groups which can be reacted with (meth)acrylic acid, also one with three or even more such functional groups can be used. The (meth)acrylsilanes which are obtainable, respectively, enable due to their respective available number of (meth)acryl groups an adjustability of the density of the organic network obtainable by the future polymerization. Of course, the number and the chemical structure of the residues RO in reaction 7 can be selected as defined above; the definition “R=Me/Et” in which Me means methyl and Et means Ethyl, are purely exemplary.
The silylsulfonate can be prepared, for example, by reaction of allylsulfonate with a hydridosilane or by reaction of sodium sulfite with an epoxysilane. The sulf(on)ate silane can also be modified arbitrarily. For example, the sulfonic acid group of the corresponding silane can be connected with the silicon atom by means of a carbon chain that is interrupted by oxygen atoms and/or amino groups. Such silanes can be obtained by reaction of an epoxy-containing silane with sodium sulfite, aminoethane sulfonate, methylaminoethane sulfonate or the like, as is evident for example from the reaction 6 discussed infra in which these reactions are carried out, however, only after the hydrolytic condensation of the respective silanes. When sodium sulfate is used instead of sodium sulfite, as for example disclosed in U.S. Pat. No. 6,777,521, a corresponding sulfate is obtained.
According to variant (B), a condensate is prepared either from only one silane which carries however not all invention-relevant groups, wherein afterwards only some of the groups that are bonded by carbon to the silicon are modified with a suitable reaction partner (variant B1), mostly by introduction of a sulfonic acid group or sulfonate group, or two or even more silanes are used for the preparation of the condensate wherein at least one of the silanes is modified afterwards (variant B2), also mostly by introduction of a sulfonic acid group or sulfonate group.
The variant (B1) has the advantage that it is possible to adjust arbitrarily the ratio of the groups with polymerizable double bonds relative to the groups with sulf(on)ate by varying the amount of added sulfonic acid compound. An example of this variant is shown in the following reaction 5:
In the preparation of condensates according to variant (B), already known compounds can also be employed, of course, or known reaction sequences can be used because known (meth)acrylsilanes as well as known sulfonate group-containing silanes can be used. The preparation of condensates as shown in stage 1 of reaction 5 is already known from DE 44 16 857. Afterwards, some of the methacrylate residues are used for attaching a sulfonate group; in the example, a thioalkane sulfonic acid is used for this purpose. In this concrete example, it is important of course that the thioalkane sulfonic acid is used in less than stoichiometric amounts in order to preserve some (meth)acrylate groups. The advantage of a reaction as in this example resides in that the ratio of (meth)acrylate groups to sulfonic acid groups or sulfate groups in the condensate can be selected arbitrarily. Another advantage resides in that the hydroxyl group can be preserved that resulted from the ring opening of the epoxide because it must not be used for the attachment of the (meth)acrylate. Hence, it can be used for other purposes, e.g., for increasing the matrix hydrophilicity of the silicic acid polycondensates or for the attachment of other reactive groups, for example, of a further (meth)acrylate group.
Of course, this reaction can be modified in any manner by an easy exchange of substituents for other substituents, as is known from the art. Accordingly, an aminosilane can be used instead of an epoxysilane, for example, so that the methacryl group is present in the form of the methacrylamide. As described above in relation to variant (A), the silane used as a starting material can contain of course also several reactive groups which can react with activated (meth)acrylic acid, or a silane is used from the start which carries a (non-activated) double bond, for example, a vinyl silane or allyl silane. Another variant is the exchange of the methacrylic acid by a bridged ring system such as a norbornene group which can be obtained by conversion of cyclopentadiene; see the following reaction:
With regard to employable norbornene silane and related compounds, reference is being had to DE 196 27 198 A1. Thus, the norbornene ring shown at the top in the reaction scheme can be optionally substituted, of course; also a bicyclo[2.2.2]octene residue can be present instead of the norbornene residue (i.e., of bicyclo[2.2.1]heptane residue). Furthermore, the double bond-containing five-membered ring of the condensed system can contain an oxygen atom when the (meth)acryl group is reacted with furan instead of cyclopentadiene.
The variant (B2) can be explained by means of the following scheme:
This reaction scheme shows the co-condensation of two silanes wherein one of them carries a (meth)acryl group, the other a strained hetero ring. The hydrolytic condensation can be carried out in a known manner in such a way that the hetero ring remains closed. A sulfonate group is attached after the condensation reaction to the hetero ring. When this is done according to b) by means of the attachment by means of an amino group, the reaction can be carried out easily—and also in known manner—in such a way that the amino group does not attack or does hardly attack the double bond of the methacryl group.
According to the reaction scheme a condensate according to the invention is produced as describe above. With a reaction carried out in this way, the ratio of (meth)acryl groups to sulf(on)ate groups can be determined by the ratio of the employed silanes relative to each other. Incidentally, the same or comparable reaction types as described supra can be also used.
Instead of a methacryl group as shown herein, other C═C double bond-containing groups which are bonded in any manner to the respective silicon atom can be used of course. A small selection is shown in the following scheme:
The use of a silane which was obtained as shown in reaction 5, step 1, by reaction of an epolysilane with methacrylic acid is another alternative. In this alternative, step 2, the hydrolytic condensation, does not follow immediately after the preparation of the silane, as shown in reaction 5, but the methacrylated silane is mixed with additional epoxysilane and the mixture of epoxysilane with methacrylsilane is subjected to the hydrolytic condensation, as shown in reaction 6.
The silicic acid (hetero) polycondensates according to the invention can carry other functional groups which can impart to them advantageous properties for special applications. Foremost, carboxylic acid group and hydroxyl groups are to be named in this context. Examples of the presence of hydroxyl groups are found in the preceding reactions 5, 6 and in the scheme concerning the variant B2. They can be obtained, for example, in that an additional silane carrying such a group is co-condensed with the remaining starting silanes. Instead, a silane can be used which has, in addition to this group, a polymerizable C═C double bond and/or a sulf(on)ate group, namely optionally at the same group that is bonded by carbon to the silicon. Suitable silanes will be described infra.
All silicic acid (hetero) polycondensates according to the invention, independent of whether prepared according to variant (A) or one of the variants (B), can be produced additionally with use of at least one silane having a residue that is bonded by carbon to the silicon and has an organically polymerizable C═C double bond as well as a sulf(on)ate group. This silane can be represented, for example, by the formula (I)
R1aR2bSiZ4-a-b (I)
wherein R1 is a hydrolytically condensable residue; R2 an alkyl, aryl, arylalkyl, alkylaryl or alkylarylalkyl that is substituted or unsubstituted, straight-chain, branched or has at least one cyclic structure, as an exception it can be instead a corresponding alkenyl or can encompass an alkenyl whose carbon chain in all cases optionally can be interrupted by —O—, —S—, —NH—, —S(O)—, —C(O)NH—, —NHC(O)—, —C(O)O——C(O)S, —NHC(O)NH— or C(O)NHC(O) groups which can optionally be oriented in both possible directions; Z is a residue in which are present at least one (meth)acryl group and at least either a sulfonate group or a sulfate group that are bonded directly or indirectly by an unsubstituted or substituted hydrocarbon group to the silicon atom; a is 1, 2 or 3; b is 0, 1 or 2; and a+b together are 2 or 3. In particular, it is preferred that the residues Z furthermore have in each case at least one hydroxyl group or a carboxylic acid group or an ester derived therefore or a corresponding salt.
In several preferred embodiments, the silanes of the formula (I) can be represented by the following formula (Ia):
wherein:
R1 is a hydrolytically condensable residue,
R3 is an alkylene that is unsubstituted or substituted with a functional group, straight-chain, branched or has at least one cyclic structure,
A is a linking group,
R4 is an alkylene that is optionally interrupted by O, S, NH or NR8 and/or optionally functionally substituted,
M is hydrogen or a monovalent metal cation or the corresponding portion of a multi-valent metal cation, preferably selected from alkali cations and alkaline earth cations, in particular from Na, K, ½ Ca, ½ Mg, or ammonium is,
R5 and R6, independently of each other, either have the meaning of R1 or are alkyl, aryl, arylalkyl, alkylaryl or alkylarylalkyl, substituted or unsubstituted, straight-chain, branched or having at least one cyclic structure, or can be instead in exceptions also a corresponding alkenyl, arylalkenyl or alkenylaryl,
R7 is a hydrocarbon group, as has been defined supra, bonded by a carbon atom to the silicon atom,
R8 is C1-C6 alkyl or (meth)acryl,
B is vinyl, 2-allyl or, in case of e>1, an organic residue with e vinyl groups present in each case bonded to a group located in the curly brackets,
Y is a nitrogen atom, —O—CH═, —S—CH═ or —NH—CH═, and in each case the oxygen atom, the sulfur atom or the NH group has a bond to the neighboring C(O) group,
b is=0 or 1,
c is=0 or 1,
with the proviso that, for the combination of Y being a nitrogen atom, b=0, c=0, and d=0, the residue R3 is ethylene, and with proviso that, for the combination of Y being a nitrogen atom, b=0, c=1, and d=0, the residue R4 is an alkylene that is interrupted by O, S, NH or NR8 and optionally functionally substituted,
d is=0 or 1, and
e is=1, 2 or 3.
The linking group A in the formula (la) is preferably selected from (read from the left to the right in the formula la) C(O)NH, NHC(O), NR8C(O), C(O)O, and OC(O), and R8 is defined as above. In special cases, the linking group A can have these groups oriented however in a direction opposite to the reading direction and can be selected additionally from NHC(O)O, NR8C(O)O, NHC(O)NH, C(O)NHC(O), and C(O)S. The residue R4 is substituted in specific embodiments with at least one hydroxyl group and/or with a residue R9COOM, wherein R9 is a chemical bond or a C1-C6 alkylene residue and M is hydrogen or a monovalent metal cation or the corresponding portion of multi-valent metal cation, preferably selected from alkali cations and alkaline earth cations, in particular from Na, K, ½ Ca, ½ Mg, or ammonium.
With few exceptions, the syntheses for the preparation of the silanes of the formula (I) or (Ia) are controlled such that for the addition of the sulfonic acid group or sulfate group to the molecule that already contains a (meth)acryl group a C═C double bond is available. As desired, to the latter either sodium sulfite or a sulfonic acid with a residue that is easily reacted by addition, such as hydroxyl, thio or aminoalkane sulfonic acid, can be added. Alternatively, the attachment of the sulfonic acid group can also be carried out by the reverse principle in that hydroxyl, thio or aminoalkylsilane is reacted with an alkylene sulfonic acid. With this process, a chain length extension by the carbon atoms of the alkylene group is of course inevitable, which is the reason why the first variant is preferred over the second. Finally, there is still the possibility to cause ring opening of a strained hetero ring, in particular of a three-membered ring, with sulfite or a hydroxyl, thio or aminoalkane sulfonic acid. This variant has the advantage that the ring opening reaction generates another reactive group which can be used for the subsequent attachment of the activated (meth)acrylic acid. The three-member ring can be opened alternatively also by means of a sulfate; in these cases, a sulfate group-containing product is obtained.
All together, three basic variants for the production of the silanes with the formula (I) are available according to the invention as follows:
An example of the preparation of such a silane according to variant (i) is shown below in an exemplary way by means of the reaction 1:
A reaction according to variant (ii) is shown below in an exemplary way by means of the reaction 3:
A conversion according to variant (iii) is shown below in an exemplary way by means of the reaction 4;
The preceding reaction examples show conversions to suifonates. By the use of sulfates, as disclosed in U.S. Pat. No. 6,777,521, instead of sulfites in the reactions according to variant (ii), the corresponding sulfate compounds can be obtained.
The syntheses for producing the silicic acid (hetero) polycondensates according to the invention are characterized in all variants by the simplicity of the reaction control, a low number of working steps, and good yields.
As partially already mentioned above, in specific embodiments of the invention a hydrocarbon residue bonded to a silicon atom can be substituted with more than one sulfonic acid group or sulfuric acid group and/or with more than one (meth)acryl group. By the presence of more than one (meth)acryl group the network which forms upon polymerization of the condensates can become even more fine-meshed. In this connection, is should be noted that by the contents of polymerizable double bonds the modulus of elasticity of the future organically polymerized polymer can be adjusted in such a way that the polymer becomes more or less flexible and thereby less hard or harder. By the presence of more than one sulfonic acid group or sulfuric acid group the etching effect of the condensate is further increased.
The inventors have surprisingly found that already with low sulfonic acid contents an enormous etching effect on the dental tissue can be observed. This can be demonstrated by means of a comparison of the average roughness of the enamel surface: Polished enamel has an average roughness of about 0.21 μm, measured with an optical profilometer of the company UBM. With a phosphonic acid-functionalized silicic acid polycondensate of glycerin-l-methacryloyl-2-(siloxypropyl) carboxymethyl phosphonic acid, roughness in the range of 0.33 can be achieved. With condensates of the compounds according to the invention, the roughness is within the range of more than 0.45 μm. Dental enamel images are shown in the
The versatility and the specific adaptation possibility to the respective purpose of the silicic acid (hetero) polycondensates according to the invention and the polymers configured or formed therefrom are based quite substantially on the indicated preparation possibilities. Hence, the use of additional monomers, e.g., the use of reactive diluting agents with the goal of a sufficient organic crosslinking of the polymers, can therefore often be dispensed with. This is an advantage in particular when the condensates according to the inventions and the polymers available therefrom are to be used in the medical field, e.g. dental field. For it is known from the increasing public discussion of the subject matter, that (meth)acrylate-based monomers are suspected of triggering allergies.
The inventors, moreover, were surprised by the fact that the silicic acid polycondensates according to the invention are generally water-soluble, even through they carry a large number of (meth)acrylate groups and have an inorganically condensed structure. This has great advantages for many applications, wherein medical applications are to be mentioned foremost. For the condensates can be applied in aqueous medium, i.e. can be applied in any form without the use of a non-aqueous solvent being required. But also for industrial applications water-based reactions are always advantageous, namely already for reasons of occupational safety and the environmental compatibility.
The possibility of forming other reactive groups in the silanes besides the sulfonic acid functional group opens up additional possibilities. Thus, sulfonic acid groups have a stronger etching effect than carboxyl groups while the latter have complexing properties. Should there be additional hydroxyl groups, these can be used either for improving wetting at the base surface or for further reactions which can further modify the silicic acid (hetero) polysiloxanes according to the invention. One example is complexing or reacting with a dicarboxylic acid (which can be caused, e.g., by means of appropriately activated acid molecules).
In addition to degree of polymerization and etching effect, the groups and residues located according to the invention on the polycondensates of the invention have further properties which are favorable for several intended purposes: The sulfonate group or sulfate group is a charge carrier for which reason uses are possible as electrophoresis gels, as materials for the electrophoretic coating or as materials that modify conductivity or antistatic properties. Moreover, the group can serve as an acidic catalyst, namely, on the one hand, for the sol gel process (a later separation step to the catalyst separation can then be dispensed with) and, on the other hand, in respect to the future use (an example are the mesoporous membranes with sulfonic acid groups which can serve as catalyst for chemical processes). The group provides furthermore a good solubility in polar media. Particularly for dental purposes, but not exclusively for this purpose, it serves as an adhesion promoting group for inorganic, organic as well as hybrid surfaces. Like carboxylic acid groups, it can also form ionic bonds by means of which e.g., alkali, earth alkali, ammonium, Ti, Zr, Sn, Ca and other suitable cations can be incorporated in the form of their salts into the polycondensate network. In this way, several modification or material-specific adjustments, e.g., concerning the X-ray opacity, the refractive index or the contact toxicity, can be achieved. By the sulfonate groups or sulfate groups in the material, the material is moreover imparted with an antimicrobial effect. But the invention can be applied also in quite different fields because e.g. proton-conducting membranes, e.g., for fuel cells, can be formed with sulfonate group-containing or sulfate group-containing materials. Further, the materials are suitable e.g. as an ion exchanger, as a pseudo-static phase in the electrokinetic chromatography or as substances with interfacial tension lowering action (detergent).
The use in the medical sector (specifically dental field), e.g., as an adhesive promoting agent (monomer-free bonding) and as a matrix component for cements, is in particular favored by the combination of the sulfonate groups or sulfate groups and optionally additionally by the —CO2H groups with polymerizable/polyadditive double bonds in a molecule.
The quantitative proportion of C═C double bond-containing silane to sulf(on)ate-containing silane in the condensate according to the invention is basically not critical. Thus, the number of the C═C double bond-containing residues that are bonded by carbon to silicon to the number sulf(on)ate-containing residues bonded by carbon to silicon can be, for example, in the range of 10:1 to 1:10. Particularly preferred is a ratio of 3:1 to 1:1, and often a ratio of about 1:1 will be selected. Ratios in which the number of the C═C double bond-containing residues predominates in comparison to the number of sulf(on)ate-containing groups are preferred in several cases because then an especially tight organic network can be generated. The same goal can be achieved of course also in that those groups are used that are bonded by carbon atoms to the silicon and that carry more than one C═C double bond.
By use of any fillers (particles, fibers), as the particles described for example in DE 196 43 781, DE 198 32 965, DE 100 18 405, DE 104 10 38, DE 10 2005 018 351, DE 10 2005 061 965 as well as in DE 10 2005 053 721, or of SiO2 particles in combination with the silicic acid (hetero) polycondensates according to the invention, the corresponding composites are obtained. SiO2 particles, for example, can be obtained by known sol gel processes; they can have a very narrow diameter distribution. These or also differently composed nanoparticles can be modified on their surface, e.g., silanized, in order to adapt their surface properties to those of the matrix.
The composites can be plastically processed and are characterized by very high filler concentrations that are possible (see nanohybride composites) in combination with an excellent processibility. Therefore, different properties can be adjusted in wide ranges for the resultant silanes, resin systems, matrix systems as well as for the filled systems (composites) and adapted to the requirements.
Particularly preferred is the use of the invention in the dental field, i.e., as an adhesive, for example. In this context, the silicic acid (hetero) polycondensate obtained by hydrolytic condensation from the silanes according to the invention can be mixed with one or several additives and/or fillers, in particular for the production by dental composites, before organic curing. An essential component in this regard are nanoparticulate fillers or a combination of such fillers of different size or different composition, as mentioned above, optionally in combination with other known fillers like particulate dental glasses, e.g., Ba—Sr aluminum borosilicates.
The filler can be added according to the desired field of application in very different total quantities. Thus, adhesives need only relatively small filler amounts. Also, fissure sealers, coatings for the neck of the tooth, and the like contain in general a proportion of less than 50 wt. %, e.g., 1-50 wt. % and preferably from approx. 1 to 20 wt. % of a filler. In other cases, the filler can be present optionally e.g. in a proportion of 50 wt. % of the composite, or even clearly above that, and in particular in a proportion of 70 to 90 wt. % of the composite when higher filled or highly filled composites are needed, e.g., for fillings and the like.
In accordance with the intended special purpose of use, suitable additives can be added to the silicic acid (hetero) polycondensates or the composite of the invention, such as initiators, coloring agents (dyes or pigments), oxidation inhibitors, polymerization inhibitors (for avoiding a premature polymerization), leveling agents, UV absorber, stabilizers, microbiocidal active ingredients or the like, as is known to a person of skill in the art. Examples of polymerization initiators are initiators for radical polymerization, namely for thermal curing like peroxides (e.g., benzoyl peroxide) or photo initiators like benzophenone, camphorquinone or combinations of a-diketones with amine as a reducing agent, as for example disclosed in DE 199 03 177 C2. For the dual curing of radically and cationically polymerizable systems, in particular diaryl iodonium or triaryl sulfonium salts can be added for which the aforementioned publication also provides examples.
The filled dental composite (i.e. the organically not yet crosslinked filled resin), after it has been applied for the intended purpose, can be crosslinked in suitable manner organically and thus be cured. Above all, an organic polymerization of the (meth)acrylate groups is used for this purpose. This is a radical polymerization that usually occurs with addition of radical starters like the above mentioned ones and optionally known activators, with exposure to e.g. visible light (blue light; dental irradiator), i.e. photochemically, thermally or redox-induced, but also occurs within the scope of 2-component reactions or anaerobically. The combination of self curing action with e.g. photo-induced or thermal curing is also possible.
However, the use of the silicic acid (hetero) polycondensates according to the invention applies not only to composites adapted for dental purposes, but inter alia also to the use in the form of bulk materials, (dental) cements, adhesives, potting compounds, coating materials, adhesion promoters, binding agents for ceramic particles (ceramic shaping processes), producing or priming of fillers and fibers, use in reaction extruders and the like for most different purposes (in particular for medical, but also for (micro)optical and (micro)electronic applications). The condensates can be converted by means of a large number of processes into structured surfaces or bodies, for example, by silk screen printing, inkjet printing, direct laser writing, photo lithography or two-photon or multi-photon polymerization.
Below, the invention will be explained with the aid of examples in more detail.
To a solution of 3.4 g (0.01 mol) N,N′ dimethacryloyl-3-(2-aminoethylamino)-propylmethyl dimethoxysilane in acetone/water (ratio 1:1), 2.5 g (0.01 mol) 3-trimethoxysilylpropyl sulfonic acid were added and stirred at 40° C. until the condensation was complete. Afterwards the volatile components were removed under vacuum.
Stage 1: 3.93 g (0.015 mol) triphenyl phosphine and 0.316 g (0.06 wt. %) butylhydroxyl toluene were dissolved in 377.8 g (1.521 mol) diethoxy(3-glycidyloxypropyl) methylsilane. Afterwards, the solution was heated to 85° C. and 142.05 g (1.65 mol) methacrylic acid added dropwise during 1.5 h. After 24 h at reflux, the product was dissolved in ethyl acetate and was adjusted with 1N hydrochloric acid to pH 1-2. After 3 d, the solution was washed with 1 N sodium hydroxide solution up to a pH value of 12 and, afterwards, the volatile components removed under vacuum.
Stage 2: To a solution of 7.78 g (0.008 mol) product of the stage 1, 0.68 g NaOH in 40 ml ethanol, 1.33 g (0.008 mol) sodium 2-mercaptoethane sulfonate in 40 ml H2O was added dropwise at 50° C. After 19 h, ethanol was removed at 40° C. under vacuum, and the aqueous solution was purified twice with ethyl acetate. The aqueous phase was treated with a cation exchanger and, afterwards, the volatile components were removed under vacuum. The product can be redissolved in water.
Average roughness Ra=0.45 μm (on enamel)
Stage 1: To a solution of 2.2 g (0.01 mol) methacryloxypropyl trimethoxysilane in 50 ml ethyl acetate, 2.2 g (0.01 mol) 3-glycidoxypropyl methyldimethoxysilane were added. After addition of a well-established catalyst, as for example ammonium fluoride, the reaction mixture was stirred at 40 ° C. until the condensation was complete. After usual work-up, e.g., extraction with water, the volatile components were removed under vacuum.
Stage 2: The co-condensate of stage 1 was dissolved in 20 ml ethanol and was heated to 80° C. A solution of (0.01 mol) sodium bisulfite in 20 ml water was added dropwise and the reaction mixture was stirred under reflux for 4 h. After evaporation of ethanol, the aqueous phase was purified with ethyl acetate, treated with a cation exchanger, and afterwards the volatile components were removed under vacuum.
Stage 1: 5.11 g (0.024 mol) N-(2-aminoethyl)-3-aminopropyl methyldimethoxysilane was dissolved in 5.21 g triethylamine and 30 ml toluene and was cooled to 0° C. Afterwards, 5.0 ml (0.051 mol) methacrylic acid chloride in 30 ml toluene were added dropwise. The reaction mixture was stirred for 3 h at room temperature. The mixture was centrifuged, and the obtained solution adjusted with 1N hydrochloric acid to pH 1-2. After 24 h, the volatile components were removed under vacuum.
Stage 2: 3.92 g (0.013 mol) of the product of stage 1 were dissolved in 30 ml ethanol, the solution adjusted with sodium hydroxide to pH 10, and heated to 60° C. Afterwards, 1.93 g (0.015 mol) sodium 2-mercaptoethane sulfonate dissolved in 40 ml H2O were added dropwise, followed by stirring for 4 h. Ethanol was removed under vacuum and the aqueous solution treated with a cation exchanger. The volatile components were removed under vacuum. The product is a water-soluble solid.
Average roughness Ra=0.58 μm (on enamel)
Stage 1: 8.69 g (0.042 mol) N-(2-aminoethyl)-3-aminopropyl methyldimethoxysilane were dissolved in 50 ml ethyl acetate and heated to 50° C. A solution of 4.23 g (0.043 mol) maleic acid anhydride in 30 ml ethyl acetate was added dropwise, followed by stirring for 19 h. The mixture was centrifuged and the residue was purified twice with ethyl acetate and was dried under vacuum.
Stage 2: 6.06 g (0.021 mol) of the product of the stage 1 were dissolved in 5 ml water and 1.72 g NaOH and cooled to 0° C. 2.1 ml (0.021 mol) methacrylic acid chloride were slowly added dropwise with strong stirring action, followed by stirring for 5 h at 50° C. Afterwards the volatile components were removed under vacuum.
Stage 3: 9.82 g (0.021 mol) of the product of the stage 2 were dissolved in 20 ml water and heated to 60 ° . Afterwards, 2.61 g (0.021 mol) sodium sulfite were added dropwise under stirring, followed by stirring for 24 h. The aqueous solution was treated with a cation exchanger and the volatile components were removed under vacuum. The product can be redissolved in water.
Average roughness Ra=0.48 μm (on enamel)
Stage 1: 5.04 g (0.040 mol) sodium sulfite were dissolved in 30 ml H2O and heated to 80° C. A solution of 9.96 g (0.040 mol) 3-glycidoxypropyl methyldiethoxysilane in 10 ml ethanol was added dropwise and stirred for 3 h under reflux.
After evaporation of ethanol the aqueous phase was purified with ethyl acetate, and the volatile components were removed under vacuum.
Stage 2: 5.04 g (0.016 mol) of the product of the stage 1 was dissolved in 10 ml water and 2.79 g (0.070Ehiol) NaOH and cooled to 0° C. Afterwards, 4.0 ml (0.016 mol) methacrylic acid chloride were added dropwise, and the reaction mixture was stirred for 4 h at 30° C. The solution was purified with ethyl acetate, the aqueous phase treated with a cation exchanger, and the volatile components removed afterwards under vacuum. The product is water-soluble.
| Number | Date | Country | Kind |
|---|---|---|---|
| 10 2011 050 672.1 | May 2011 | DE | national |
| 11167853.8 | May 2011 | EP | regional |
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/EP2012/060031 | 5/29/2012 | WO | 00 | 11/27/2013 |
