(Meth)-acrylic acid derivatives of triisocyanates in dentistry

The new (meth)-acrylic acid derivatives of triisocyanates can be prepared by reacting appropriate triisocyanates with hydroxyalkyl (meth)-acrylates. The compounds can be employed as monomers for use in the dental field.

The invention relates to new acrylic acid and methacrylic acid derivatives 
of triisocyanates, called (meth)-acrylic acid derivatives below, and to 
the preparation thereof. The new compounds can be employed as monomers for 
use in the dental field. 
New (meth)-acrylic acid derivatives of triisocyanates, of the formula 
##STR1## 
in which 
R.sup.1 and R.sup.2 are identical or different and represent hydrogen or a 
lower alkyl radical, 
R.sup.3, R.sup.4 and R.sup.5 are identical or different and denote hydrogen 
or methyl, 
Y.sup.1 to Y.sup.3 are identical or different and denote divalent 
straight-chain or branched hydrocarbon radicals, having 2 to 15 carbon 
atoms, which may optionally contain 1 to 3 oxygen bridges and can 
optionally be substituted by 1 to 4 additional (meth)-acryloyloxy 
radicals, and the rings 
A and B are identical or different and can be aromatic or saturated, have 
been found. The (meth)-acrylic acid derivatives can exist as pure isomers 
or as a mixture of isomers. For the use according to the invention of the 
(meth)-acrylic acid derivatives in dental materials, it is particularly 
advantageous to employ the mixtures of isomers since they have a lower 
viscosity than the isomerically pure compounds. 
In the context of the present invention, the substituents can, in general, 
have the following meaning: 
Lower alkyl can denote a straight-chain or branched hydrocarbon radical 
having 1 to about 6 carbon atoms, preferably 1 to 4 carbon atoms. The 
following lower alkyl radicals may be mentioned as examples: methyl, 
ethyl, propyl, isopropyl, butyl, isobutyl, pentyl, isopentyl, hexyl and 
isohexyl. 
Divalent hydrocarbon radicals Y.sup.1 to Y.sup.3 can denote straight-chain 
or branched aliphatic hydrocarbon radicals having 2 to 15 carbon atoms, 
preferably 2 to 10, carbon atoms. The radicals Y.sup.1 and Y.sup.3 can 
optionally contain 1 to 3 oxygen bridges, preferably 1 or 2 oxygen 
bridges. It is also possible for the radicals Y.sup.1 to Y.sup.3 to be 
substituted by 1 to 4, preferably 1 or 2, (meth)-acryloyloxy radicals. The 
following radicals may be mentioned as examples: 
##STR2## 
Ring A represents a benzene nucleus or a cyclohexane radical which contains 
two or three substituents. Ring B represents a benzene nucleus or a 
cyclohexane radical which contains three or four substituents. 
The new (meth)-acrylic acid derivatives are colorless, non-volatile and, 
after polymerization, give transparent plastics having a high wear 
resistance. 
They can be used particularly successfully in dental materials, such as 
dental filling materials and coating agents. The materials thus obtained 
are distinguished by a surprisingly high resistance against physical and 
chemical attack. The hardness and fracture resistance are improved to a 
particular extent compared to conventional materials which are employed 
for this purpose. 
Preferred (meth)-acrylic acid derivatives are compounds of the formula 
##STR3## 
in which 
R.sup.1 represents hydrogen, 
R.sup.2 represents hydrogen or an alkyl radical having 1 to 4 carbon atoms, 
R.sup.3, R.sup.4 and R.sup.5 are identical or different and denote hydrogen 
or methyl, 
Y.sup.1 to Y.sup.3 are identical or different and denote divalent 
straight-chain or branched aliphatic hydrocarbon radicals, having 2 to 10 
carbon atoms, which may optionally contain 1 or 2 oxygen bridges and which 
can optionally be substituted by 1 or 2 additional (meth)-acryloyloxy 
radicals, ring B is aromatic or saturated, and ring A is saturated. 
Particularly preferred (meth)-acrylic acid derivatives are those of the 
formula: 
##STR4## 
in which 
R.sup.1 represents hydrogen, 
R.sup.2 represents hydrogen or methyl, 
R.sup.3, R.sup.4 and R.sup.5 are identical or different and denote hydrogen 
or methyl, 
Y.sup.1 to Y.sup.3 are identical or different and denote divalent 
straight-chain or branched aliphatic hydrocarbon radicals, having 2 to 10 
carbon atoms, which may optionally contain 1 or 2 oxygen bridges and can 
optionally be substituted by 1 or 2 additional (meth)-acryloyloxy 
radicals, and 
rings A and B are saturated. 
The following (meth)-acrylic acid derivatives may be mentioned as examples: 
##STR5## 
A process has also been found for the preparation of the (meth)-acrylic 
acid derivatives according to the invention which is characterized in that 
a triisocyanate of the formula 
##STR6## 
in which 
R.sup.1 and R.sup.2 are identical or different and represent 
hydrogen or a lower alkyl radical, and rings 
A and B are identical or different and can be 
aromatic or saturated, is reacted with a hydroxyalkyl (meth)-acrylate of 
the formula 
##STR7## 
and/or 
##STR8## 
and/or 
##STR9## 
in which 
R.sup.3, R.sup.4, R.sup.5 and R.sup.6 are identical or different and denote 
hydrogen or methyl, and 
Y.sup.1 to Y.sup.3 are identical or different and denote divalent 
straight-chain or branced aliphatic hydrocarbon radicals, having 2 to 15 
carbon atoms, which may optionally contain 1 to 3 oxygen 
bridges and can optionally be substituted by 1 
to 4 additional (meth)-acryloyloxy radicals. 
Triisocyanates of the formula II are known (DE-A1 3,417,684 and DE-A1 
3,417,683) and can be obtained by phosgenation of appropriate triamino 
compounds. 
Hydroxyalkyl (meth)-acrylates of the formula III to V are commercially 
available or can be prepared in a known fashion by partial esterification 
of appropriate polyols. 
The process according to the invention is generally carried out in a manner 
such that, relative to each isocyanate group of the triisocyanate (II), 
0.9 to 1.1, preferably 1.0 to 1.05 moles of a hydroxyalkyl (meth)acrylate 
of the formula III, IV or V , or mixtures of these compounds, are 
employed, where the sum of all hydroxyl equivalents, relative to each 
isocyanate group of the triisocyanate (II), must give 0.9 to 1.1, 
preferably 1.0 to 1.05. 
The process according to the invention is generally carried out in an inert 
solvent with exclusion of water. Examples which may be mentioned are 
chloroform, tetrahydrofuran, acetone, dioxane, dichloromethane, toluene 
and acetonitrile. Preferred solvents are chloroform, toluene, acetone and 
dichloromethane. 
The process according to the invention is generally carried out in a 
temperature range from 20 to 100.degree. C., preferably from 30.degree. to 
70.degree. C. 
The process according to the invention is generally carried out at 
atmospheric pressure. However, it is also possible to carry out the 
process in the pressure range from 1 to 15 bar. 
The reaction according to the invention for the preparation of urethane is 
preferably carried out with exclusion of water (preferably below 0.1% of 
water). 
In order to accelerte the reaction, tin-containing catalysts, such as 
dibutyltin dilaurate, tin(II) octoate or dibutyltin dimethoxide, are 
preferably used. 
It is also possible to employ compounds having tertiary amino groups, or 
titanium compounds as catalysts. The following catalysts may be mentioned 
as examples: diazabicyclo[2.2.2]octane, triethylamine, N-methylpiperidine, 
tetrabutoxy-titanium (Ullman, Encyclopadie der technischen Chemie 
[Encyclopaedia of Industrial Chemistry], Vol. 19, p. 306 (1981)). 
In general, the catalyst is employed in an amount from 0.01 to 2.5% by 
weight, preferably from 0.1 to 1.5% by weight, relative to the total 
amount of reactants. 
The reaction to form urethane is generally carried out in the presence of 
0.01 to 0.2% by weight of a polymerization inhibitor, for example 
2,6-di-tert.butyl-4-methylphenol. 
The process according to the invention can be carried out as follows, for 
example: 
The reactants are dissolved in the solvent, and the catalyst is added with 
stirring. The course of the reaction with time can be followed, for 
example, by measuring the IR spectra. After complete reaction of the 
isocyanate groups, the reaction products are isolated by removing the 
solvent. Prior purification with the aid of adsorbents, for example 
activated charcoal, bleaching earth, silica gel or aluminum oxide, is, of 
course, also possible. 
The (meth)-acrylic acid derivatives of triisocyanates according to the 
invention can be used as monomers for the preparation of polymeric 
materials. The polymerization can be carried out, in a fashion known per 
se, by free-radical initiation, and produces polymers which have a high 
crosslinking density. 
The (meth)-acrylic acid derivatives of triisocyanates according to the 
invention can be used, in particular, as monomers for dental materials. 
Dental materials which may be mentioned are, for example, filling 
materials for teeth, coating agents for teeth, and components for the 
production of tooth replacements. Depending on the area of application, 
dental materials may contain further auxiliaries. 
For use as monomers for dental filling materials or coating agents (dental 
varnishes) in the dental field, the (meth)-acrylic acid derivatives of 
triisocyanates according to the invention can be mixed with comonomers 
which are known per se. Thus, for example, the viscosity can be matched to 
the application. These monomer mixtures generally have a viscosity in the 
range 60 to 10,000 mPa.s. 
The following comonomers may be mentioned as examples: triethylene glycol 
dimethacrylate, tetraethylene glycol dimethacrylate, 1,12-dodecanediol 
dimethacrylate, 1,6hexanediol dimethacrylate, diethylene glycol 
dimethacrylate, 
2,2-bis[p-(2'-hydroxy-3'methacryloyloxypropoxy)phenyl]propane and 
2,2-bis[p-(2'-methacryloyloxethoxy)phenyl]propane. Also of advantage are 
comonomers having urethane groups, for example the known products of the 
reaction of 1 mol of a diisocyanate, for example hexamethylene 
diisocyanate, trimethylhexamethylene diisocyanate or isophorone 
diisocyanate, with 2 mols of a hydroxyalkyl (meth)acrylate, for example 
glycerol dimethacrylate, 2-hydroxypropyl acrylate, etc. 
Further examples of comonomers are: trimethylolpropane tri(meth)-acrylate, 
bis-(meth)acryloyloxyethoxymethyl)tricyclo[5.2.1.0.sup.2.6 ]decane 
(according to DE-A 2,931,925 and 2,931,926), 
1,3-di((meth)acryloyloxypropyl)-1,1,3,3-tetramethyl-disiloxane and 
1,3-bis(3(meth)acryloyloxyethylcarbamoyloxy-propyl)-1,1,3,3-tetramethyl-di 
siloxane. In particular, conomomers are preferred which have a boiling 
point above 100.degree. C. at 13 mbar. 
In the context of the present invention, it is likewise preferred that 
mixtures of different (meth)acrylic acid derivatives according to the 
invention be employed. 
The proportion of (meth)-acrylic acid derivatives of triisocyanates 
according to the invention in the monomer mixtures is generally 10 to 90% 
by weight, preferably 20 to 75% by weight. 
It is also possible to employ monomer mixtures which contain several 
comonomers. 
The (meth)-acrylic acid derivatives of triisocyanates according to the 
invention, if appropriate as a mixture with the known monomers, can be 
cured to form crosslinked polymers using methods which are known per se 
(G.M. Brauer, H. Argentar, Am. Chem. Soc., Symp. Ser. 212, pp. 359-371 
(1983). For so-called redox polymerization, a system comprising a 
peroxidic compound and a reducing agent, for example based on tertiary 
aromatic amines, is suitable. Examples of peroxides are: dibenzoyl 
peroxide, dilauroyl peroxide and di-4-chlorobenzoyl peroxide. 
Tertiary aromatic amines which may be mentioned are, for example, 
N,N-dimethyl-p-toluidine, 
bis-(2-hydroxyethyl)-p-toluidine,bis-(2-hydroxyethyl)-3,5-dimethylaniline 
and N-methyl-N-(2-methyl-carbamoyloxypropyl)-3,5-dimethylaniline, 
described in DE-A 2,759,239. 
The concentration of the peroxide or of the amine is advantageously 
selected so that it is 0.1 to 5% by weight, preferably 0.5 to 3% by 
weight, relative to the monomer mixture. The peroxide- and 
amine-containing monomer mixtures are stored separately until used. 
Polymerization of the monomers according to the invention can also be 
induced by irradiation with UV light or visible light (for example in the 
wavelength range 230 to 650 nm). Suitable initiators for the 
photoinitiated polymerization are, for example, benzil, benzil dimethyl 
ketal, benzoin monoalkyl ether, benzophenone, p-methoxybenzophenone, 
fluorenone, thioxanthone, phenanthrenequinone and 2,3-bornandione 
(camphorquinone), if appropriate in the presence of synergistically acting 
photoactivators, such as N,N-dimethylaminoethyl methacrylate, 
triethanolamine or 4-N,N-dimethyl-aminobenzenesulphonic acid 
bisallylamide. 
The execution of the photopolymerization process is described, for example, 
in DE-A 3,135,115. 
Besides the initiators described above, light-screening agents and 
polymerization inhibitors which are known per se for this application can 
be added to the (meth)-acrylates according to the invention. 
The light-screening agent and the polymerization inhibitor are each 
generally employed in an amount from 0.01 to 0.50 part by weight, relative 
to 100 parts by weight of the monomer mixture. The monomer mixtures can be 
employed, without addition of fillers, as coating agents for teeth (dental 
varnishes). After polymerization, a scratch-resistant coating on the 
substrate is obtained. 
When used as dental filling materials, fillers are generally added to the 
monomer mixtures obtained. In order to be able to achieve a high filler 
content monomer mixtures which have a viscosity in the range 60 to 10,000 
mPa.s are particularly advantageous. Inorganic fillers can advantageously 
be added to the monomer mixtures containing the compounds of the formula I 
according to the invention. Examples which may be mentioned are mountain 
crystal, quartzite, crystobalite, quartz glass, highly disperse silicic 
acid, aluminum oxide and glass ceramics, for example Lanthanum- and 
zirconium-containing glass ceramics (DE-A 2,347,591). 
Inorganic fillers are preferably treated with an adhesion promoter in order 
to improve bonding to the polymer matrix of the polymethacrylate. The 
adhesion promotion can be achieved, for example, by treatment with 
organosilicon compounds (E.P. Pleuddemann, Progress in Organic coatings, 
11, 297 to 308 (1983)). 3-Methacryloyloxypropyltrimethoxysilane is 
preferably employed. 
The fillers for the dental filling materials according to the invention 
generally have an average particle diameter of 0.01 to 100 .mu.m, 
preferably from 0.05 to 50 .mu.m, particularly preferably 0.05 to 5 .mu.m. 
It can also be advantageous to employ alongside one another several 
fillers which have different particle diameters and different degrees of 
silanization. 
The proportion of filler in the dental filling materials is generally 5 to 
85% by weight, preferably 50 to 80% by weight. 
For the preparation of dental filling materials, the components are 
processed using commercially available compounders. 
The proportion of the (meth)-acrylic acid derivatives according to the 
invention in the filling materials is generally 5 to 90% by weight, 
preferably 10 to 60% by weight, relative to the filling material. The 
curing of the dental filling materials to form a molded element ocurs in 
the tooth cavity using the abovementioned methods. As a consequence of the 
high wear resistance of the dental filling obtained, dental filling 
materials which contain the compounds according to the invention in 
polymerized form are particularly suitable for use in the posterior 
region. 
The (meth)-acrylic acid derivatives of triisocyanates according to the 
invention can also be employed as components in the production of tooth 
replacements. 
In this case, the monomers according to the invention are combined with the 
conventionally used components which are known per se. The monomers are 
preferably employed as a mixture with alkyl methacrylates, such as methyl 
methacrylate. In addition, bead polymers which are known per se can also 
be added. In order to adjust the tooth color known inorganic and organic 
color pigments and opacifiers can be added. The use of stabilizers and 
light-screening agents is also possible. 
Plastic teeth are produced by free-radical polymerizatin of the dental 
materials with shaping. Processing is possible both by injection processes 
and compression processes and is generally carried out according to 
conventional production methods for teeth based on poly(methyl 
methacrylate), for example by thermal polymerization using polymerization 
initiators which are known per se, for example based on peroxides and azo 
compounds, such as dibenzoyl peroxide, dilauroyl peroxide, cyclophexyl 
percarbonate and azoisobutyrodinitrile. Mixtures of polymerization 
initiators having various decomposition temperatures are also highly 
suitable.

EXAMPLE 1 
Preparation of the adduct of dicyclohexylmethane triisocyanate and glycerol 
dimethacrylate 
45.45 g (0.15 mol) of dicyclohexylmethane triisocyanate (isomer mixture 
having an NCO content of 41.5% by weight) are dissolved in 100 ml of 
chloroform. 57 mg of 2,6-di-tert.-butyl-4-methyl-phenol and 100 mg of 
tin(II) octoate are added to this mixture. 102.6 g (0.45 mol) of glycerol 
dimethacrylate (isomer mixture of 1,3and 1,2-bis-methacryloyloxy-propanol) 
are added dropwise at 30.degree. C. with stirring. When the addition is 
complete, the mixture is stirred at 50.degree.-60.degree. C. until the 
isocyanate groups have completely reacted. 
The conversion is followed by measuring the IR spectra (isocyanate bands at 
.about.2200 cm.sup.-1). 
The reaction mixture is cooled, stirred with activated charcoal, filtered 
through Celite.RTM. and freed of solvent in a water-pump vacuum. 
The residue is concentrated in a high vacuum to constant weight. 
IR (film on KBr) [cm.sup.-1 ]: .nu.(N-H): 3400 
(C=O): 1690-1750 (ester and amide I) .nu.(C=O): 1000-1530 
(amide II) 
.nu.(C=C): 1638 cm.sup.-1. 
EXAMPLE 2 
The adduct of triisocyanato-dicyclohexylmethane and glycerol dimethacrylate 
is prepared as described in Example 1. When the reaction is complete, 
however, the reaction mixture is cooled, stirred with activated charcoal 
and filtered through Celite.RTM., and 95.95 g of triethylene glycol 
dimethacrylate are added. The mixture is concentrated in vacuo to constant 
weight. A color less monomer mixture, which can be employed directly as a 
monomer solution for the preparation of dental materials, is obtained. The 
content of (meth)-acrylic acid derivative according to the invention is 
60.7% by weight. 
EXAMPLE 3 
Preparation of the adduct of triisocyanato-methyldicyclohexylmethane and 
glycerol dimethacrylate 
38.9 g (0.1227 mole) of triisocyanato-methyldicyclohexylmethane (isomer 
mixture having an NCO content of 37% by weight0 are dissolved in 200 ml of 
chloroform, and 53.7 mg of 2,6-di-tert. butyl-4-methylphenol and 100 mg of 
dibutyltin dilaurate are added. 83.9 g (0.368 mol) of glycerol 
dimethacrylate (isomer mixture of 1,3and 1,2-bismethacryloyloxypropanol) 
are slowly added dropwise at 50.degree. C. with stirring. The mixture is 
stirred at 50.degree.-60.degree. C. until complete conversion (IR check) 
of the isocyanate groups. The product is isolated as described in Example 
1. The trisurethanehexamethacrylate obtained is no longer pourable at room 
temperature. 
Dilution with triethylene glycol dimethacrylate to a content of 65% by 
weight of the (meth)-acrylic acid derivative according to the invention 
gives a usable monomer mixture having a viscosity of about 1 Pa.s. 
EXAMPLE 4 
Preparation of the adduct of triisocyanatodicyclohexylmethane with 
2-hydroxypropyl acrylate 
30.3 g (0.1 mol) of triisocyanato-dicyclohexylmethane (NCO content 41.5% by 
weight), 35 mg of 2,6-di-tbutyl-4-methylphenol and 0.1 g of tin(II) 
octoate are dissolved in 100 ml of chloroform. 39 g (0.3 mol) of 
2hydroxypropyl acrylate are added dropwise at room temperature. The 
mixture is stirred at 60.degree. C. until complete conversion of the NCO 
groups. The reaction mixture is worked up analogously to Example 1. IR 
(film on KBr) [cm.sup.-.sup.1 ]: 
.nu.(N-H): 3400, U (C=O): 1690-1760, 
(C=O) (amide II): 1500, U (C=C): 1620, 1640 
EXAMPLE 5 
Preparation of the adduct of triisocyanato-dicyclohexylmethane and 
2-hydroxypropyl methacrylate 
30.3 g (0.1 mol) of triisocyanato-dicyclohexylmethane (NCO content 41.5% by 
weight), 37 mg of 2,6-ditert.-butyl-4-methylphenol and 0.1 g of tin-(II) 
octoate are reacted in 100 ml of chloroform at 60.degree. C. with 43.2 g 
(0.3 mol) of 2-hydroxypropyl methacrylate. The product is isolated 
analogously to Example 1. 
EXAMPLE 6 
Production of a dental filling material 
198.3 parts by weight of a monomer mixture from Example 2, comprising 60.7% 
by weight of the adduct of triisocyanato-dicyclohexylmethane and glycerol 
dimethacrylate and 39.3% by weight of triethylene glycol dimethacrylate, 
0.4 part by weight of camphorquinone, 0.25 part by weight of benzil 
dimethyl ketal and 1.0 part by weight of 4-N,N-dimetylaminobenzene 
sulphonic acid bisallylamide are processed into a monomer solution under 
exclusion of light. This solution cures under the action of visible light 
and/or UV light at an exposure duration of 60 seconds to form a plastic 
which has a high mechanical stability. 
For the preparation of a dental filling material, 38 parts by weight of the 
abovementioned monomer solution and 62 parts by weight of a pyrogenic 
silicic acid (Aerosil OX 50), silanized with 5% by weight of 
3-methacryloyloxypropyl-trimethoxysilane, are processed at room 
temperature in a commercially available compounder to for a paste. A test 
element produced from this paste and cured using a commercially available 
dental lamp (Translux.RTM.) according to DIN 13922, exhibits a very high 
modulus of flexion, very high flectional strength and improved abrasion 
resistance. 
It is understood that the specification and examples are illustrative but 
not limitative of the present invention and that other embodiments within 
the spirit and scope of the invention will suggest themselves to those 
skilled in the art.