Light-curing ceramic slips for the stereolithographic preparation of high-strength ceramics

Abstract

Slip based on radically polymerizable binder, polymerization initiator and filler, which comprises (A) at least one acidic monomer of general formula I (HG-Y—) a XZ—PG) b   Formula I (B) photoinitiator, and (C) ceramic and/or glass ceramic particles.

1 . Slip based on radically polymerizable binder, polymerization initiator and filler, which comprises the following components:
 A) 1 to 30 wt.-% of at least one acidic monomer of general formula I
   (HG-Y—) a XZ—PG)   Formula I
 
 in which 
 X is not present or is an (a+b)-valent, substituted or unsubstituted, straight-chained aliphatic residue with at least 2 carbon atoms, a branched aliphatic residue with at least 3 carbon atoms, a cycloaliphatic, bi- or tricylic or aromatic residue with 6 to 20 carbon atoms or a combination of these residues, wherein these residues can contain one or more ether groups, 
 PG is a radically polymerizable group; 
 HG is —COOH—, —PO(OH) 2 , —O—PO(OH) 2  or —SO 3 H; 
 Y is not present or is a divalent, straight-chained aliphatic group with 2 to 40 carbon atoms, a branched aliphatic group with 3 to 40 carbon atoms or a cycloaliphatic or aromatic group with 5 to 40 carbon atoms, wherein these groups can contain one or more ether, thioether, amide and/or ester groups; 
 Z is not present or is a divalent, straight-chained aliphatic group with 2 to 40 carbon atoms or a branched aliphatic group with 3 to 40 carbon atoms, wherein these groups can contain one or more ether, thioether, amide and/or ester groups; 
 a is an integer from 1 to 5; and 
 b is 1 or 2; 
   A2) 0 to 50 wt.-% of at least one non-acidic radically polymerizable monomer;   B) 0.001 to 2.0 wt.-% photoinitiator; and   C) 30 to 90 wt.-% ceramic and/or glass ceramic particles;   in each case relative to the total mass of the slip.   
     
     
         2 . Slip according to  claim 1 , wherein the variables of formula (I) have the following meaning:
 X is not present or is an (a+b)-valent, substituted or unsubstituted, straight-chained aliphatic residue with 3 to 15 carbon atoms, a branched aliphatic residue with 3 to 15 carbon atoms, a cycloaliphatic, bi- or tricylic or aromatic residue with 6 to 15 carbon atoms or a combination of these residues, preferably an aromatic or cycloaliphatic C 6  residue and in particular is a straight-chained or branched aliphatic C 3 -C 15  residue, particularly preferably C 3 -C 8  residue, wherein these residues can contain one or more ether groups;   PG is a vinyl (CH 2 ═CH—), allyl (CH 2 ═CH—CH 2 —), allyl ether (CH 2 ═CH—CH 2 —O—), styryl (CH 2 ═CH-phenyl), (meth)acrylate (CH 2 ═C(—H/—CH 3 )—CO—O—) or (meth)acrylamide group (CH 2 ═C(—H/—CH 3 )—CO—NH— or CH 2 ═C(—H/—CH 3 )—CO—NR— with R═C 1 -C 4  alkyl), particularly preferably a (meth)acrylate or (meth)acrylamide group and quite particularly preferably an acrylate (CH 2 ═CH—CO—O—) or acrylamide group (CH 2 ═CH—CO—NH—);   HG is —COOH;   Y is not present or is a straight-chained aliphatic residue with 2 to 10 carbon atoms, a branched aliphatic residue with 3 to 12 carbon atoms, a cycloaliphatic, bi- or tricylic or aromatic residue with 6 to 15 carbon atoms or a combination of these residues;   Z is not present or is a straight-chained aliphatic residue with 2 to 10 carbon atoms, a branched aliphatic residue with 3 to 12 carbon atoms, a cycloaliphatic, bi- or tricylic or aromatic residue with 6 to 15 carbon atoms, a combination of these residues or an oligoethylene glycol (—(CH 2 —CH 2 —O) n —, n=1-5) or an oligopropylene glycol residue (—(CH(CH 3 )—CH 2 —O) n —, n=1-5);   a is 1, 2 or 3; and   b is 1.   
     
     
         3 . Slip according to  claim 2 , wherein the variables of formula (I) have the following meaning:
 X is not present or is an (a+b)-valent, unsubstituted, branched or straight-chained aliphatic residue with 3 to 15, preferably 3 to 8 carbon atoms, which residue can contain 1 or 2 ether groups;   PG is an acrylate or acrylamide group;   HG is —COOH;   Y is a divalent, straight-chained aliphatic group with 2 to 8 carbon atoms or a branched aliphatic group with 3 to 8 carbon atoms, wherein these groups can contain 1 ester group;   Z is a divalent, straight-chained aliphatic group with 2 to 10 carbon atoms or a branched aliphatic group with 3 to 10 carbon atoms, wherein these groups can contain 1 or more, preferably 0 to 3, ether groups;   a is 1, 2 or 3; and   b is 1.   
     
     
         4 . Slip according to  claim 1 , which further comprises
 D) 0.001 to 1.0 wt.-% inhibitor, relative to the total mass of the slip.   
     
     
         5 . Slip according to  claim 1 , which further comprises
 0 to 20 wt.-% debinding accelerator (E),   0 to 20 wt.-% plasticizer and   0 to 70 wt.-% solvent,   in each case relative to the total mass of radically polymerizable components.   
     
     
         6 . Slip according to  claim 1 , which further comprises
 F) 0.00001 to 2.0 wt.-% coloring components, relative to the mass of component (C).   
     
     
         7 . Slip according to  claim 1 , which comprises as component (C) glass ceramic particles or ceramic particles based on pure ZrO 2 , pure Al 2 O 3 , pure ZrO 2 —Al 2 O 3 , ZrO 2  which is stabilized with HfO 2 , CaO, Y 2 O 3 , CeO 2  and/or MgO, ZrO 2 —Al 2 O 3  which is stabilized with HfO 2 , CaO, Y 2 O 3 , CeO 2  and/or MgO or non-oxide ceramics. 
     
     
         8 . Slip according to  claim 1 , wherein the particles of component (C) are surface-modified with a linear or branched carboxylic acid, in particular formic acid, acetic acid, propionic acid, octanoic acid, isobutyric acid, isovaleric acid or pivalic acid; an acidic phosphoric acid ester, in particular dimethyl, diethyl, dipropyl, dibutyl, dipentyl, dihexyl, dioctyl or di(2-ethylhexyl)phosphate; a phosphonic acid, in particular methyl, ethyl, propyl, butyl, hexyl, octyl or phenyl phosphonic acid; or a silane, in particular propyltrimethoxysilane, phenyltrimethoxysilane, hexyltrimethoxysilane, octyltrimethoxysilane, trimethylchlorosilane, trimethylbromosilane, trimethylmethoxysilane or hexamethyldisilazane, wherein the surface-modification agent does not contain radically polymerizable groups. 
     
     
         9 . Slip according to  claim 1 , wherein the particles of component (C) have a particle size in the range from 20 nm to 50 μm. 
     
     
         10 . Slip according to  claim 5 , which comprises as debinding accelerator (E)
 a chain transfer agent, in particular a mercaptan, a disulphide or a photoiniferter, preferably lauryl mercaptan, a dithiourethane disulphide, tetramethylthiuram disulphide or isopropylxanthogenic acid disulphide; and/or   a comonomer which has one or more thermally labile groups, in particular one or more peroxide, azo or urethane groups; and/or   a comonomer with a ceiling temperature of −10 to 150° C., in particular α-methylstyrene, polytetrahydrofuran (PTHF), or a telechel with radically polymerizable groups, in particular a PTHF di(meth)acrylate telechel.   
     
     
         11 . Slip according to  claim 6 , which comprises as coloring component (F) a transition metal compound, in particular an acetyl acetonate and/or a carboxylic acid salt of the elements iron, cerium, praseodymium, terbium, lanthanum, tungsten, osmium, terbium and manganese, in particular iron (III) acetate or iron (III) acetyl acetonate, manganese (III) acetate or manganese (III) acetyl acetonate, praseodymium (III) acetate or praseodymium (III) acetyl acetonate or terbium (III) acetate or terbium (III) acetyl acetonate. 
     
     
         12 . Slip according to  claim 1 , which further comprises at least one further component from the group of dispersants, defoaming agents, and antiskinning agents. 
     
     
         13 . Slip according to  claim 1 , which comprises at most 40 wt.-% of multifunctional monomers relative to the total mass of radically polymerizable components. 
     
     
         14 . Process of using the slip according to  claim 1  for the preparation of ceramic or glass ceramic shaped articles. 
     
     
         15 . Process according to  claim 14 , wherein the ceramic shaped article is a dental restoration, such as an inlay, onlay, veneer, crown, bridge or framework. 
     
     
         16 . Process for the preparation of a ceramic or glass ceramic shaped article, wherein
 (a) a green body is prepared by curing a slip according to  claim 1  by local introduction of radiation energy with formation of the geometric shape of the green body,   (b) the green body is then subjected to a heat treatment to remove the binder (debinding), in order to obtain a white body, and   (c) the white body is sintered.