Two-component preparations containing epoxy compounds

The invention relates to two-component preparations comprising components (I) and (II), wherein at least one component comprises epoxy compounds and the preparations cure by cationic polymerization, initiated by Lewis and/or Br&ouml;nsted acids, after mixing of the two components, the preparations comprising the Lewis and/or Br&ouml;nsted acids in the form of precursor compounds which are suitable for the formation of Lewis and/or Br&ouml;nsted acids.

The invention relates to two-component preparations comprising epoxy compounds, in particular for the preparation of dental compositions. The invention particularly relates to two-component dental compositions which comprise epoxy compounds and are cured by cationic polymerization.

An important parameter of multi-component dental compositions is their processing time. This is understood as meaning the time from the start of setting after mixing of the component to curing of the composition. After mixing the components of the dental composition, the user requires an exactly defined period of time in which he can handle the composition without problems. Directly after this period of time the composition should harden within the shortest time. A slow solidifying of the composition during processing or working is intolerable for the user.

Various systems which attempt to adjust the course of setting of a curing dental composition are known from the prior art.

DE-A-197 53 461 describes, for example, storage-stable cationically polymerizing preparations in which soluble and/or finely divided alkaline earth metal and/or alkali metal compounds allow adjustment of the course of setting. In the case of two-component formulations, the initiator system described there can comprise, inter alia, free Lewis or Br nsted acids. A disadvantage of these preparations is that they allow only a very limited period of time for adjustment of the start of setting, and in addition if the concentration of alkaline earth or alkali metals is increased for the purpose of extending the setting range, they severely delay the end of setting and severely adversely impair the mechanical properties.

DE-A-197 42 980 indeed describes in principle cationically polymerizable compositions, but these are based on ROMP oligomers or polymers, it being possible for epoxy-functional comonomers to be added to the compositions. Free Lewis or Br nsted acids are employed in the catalyst system mentioned. A disadvantage of this system is the fact that the course of setting cannot be adjusted. After the start of the polymerization, this starts to proceed and leads to a hard material with a low volume shrinkage within an extremely short time.

DE-A-195 02 751 describes photocurable model materials for dentistry in which Lewis acids can be formed by a suitable light source. Photocurable materials indeed in principle have a processing time of any desired length, but in practice this property would take effect only in a dark room. In the dental sector, however, work is carried out in without protection in daylight or under an intense artificial light source, which lead to a gradual solidifying of the dental material, as a result of which these initiation systems are not suitable for the preparation of dental materials with a widely adjustable processing time.

Further polymerizable compositions based on epoxides with Lewis or Br nsted acids in free or reactive form as the catalyst or initiator system are known from DE-A-196 48 283. A disadvantage of these compositions in turn is that the setting characteristics cannot be adjusted.

The invention is based on the object of providing dental compositions which do not have the disadvantages from the prior art.

This object is achieved by two-component preparations, wherein at least one component comprises epoxy compounds and the preparations cure by cationic polymerization, initiated by Lewis and/or Br nsted acids, after mixing of the two components, the preparations comprising the Lewis and/or Br nsted acids in the form of precursor compounds which are suitable for the formation of Lewis and/or Br nsted acids and which are formed by chemical reaction during or after mixing of the components.

The advantages of the dental compositions prepared from the preparations according to the invention lie in the exact adjustability of the processing time and in the outstanding physical values of the cured dental compositions.

In particular, when the dental compositions are used as model materials in dentistry for the production of working models, further advantages are found: Compared with gypsum, the compositions according to the invention show increased mechanical values, such as abrasion resistance, tensile strength and compressive strength. The detail reproduction of fine contours and grooves and the dimensional accuracy, which is largely influenced by the lowest possible polymerization shrinkage, are also considerably better. Compared with model materials known to date which are based on plastics and are distinguished by a rather cumbersome handling and/or by too long a setting phase compared with gypsum, the dental compositions according to the invention can be mixed automatically and the setting phase can be adjusted in an outstanding manner. The end of the setting phase determines the earliest possible point in time at which the model can be removed from the mould and worked further.

The preparations are also suitable for other dental applications where low shrinkage is an advantage, for example as materials for the production of temporary crowns and bridges and fixing cements.

The preparations according to the invention comprise two components (I) and (II).

The epoxy compounds and the Lewis and/or Br nsted acids in the form of compounds which are capable of the formation of Lewis and/or Br nsted acids and do not react with the epoxy compounds can be present in component (I) and/or in component (II) in any desired distribution.

Dental compositions obtained from the preparations according to the invention comprise, distributed over components (I) and (II), the following constituents:

(B) 0.01 to 20 wt. %, preferably 0.1 to 10 wt. %, of compounds which are capable of formation of Lewis or Br nsted acids, and optionally free Lewis and/or Br nsted acids,

Epoxy compounds according to constituent (A) can be cycloaliphatic and/or aromatic and/or aliphatic epoxy compounds with at least two and/or at least four epoxy groups.

Cycloaliphatic epoxides can be, for example, the epoxides known from DE-A-196 48 283, which correspond to the following general formulae:

in which the symbols have the following meanings:

Z an aliphatic, cycloaliphatic or aromatic radical having 0 to 22, preferably 0 to 18 C atoms, or a combination of these radicals, it being possible for one or more C atoms to be replaced by O, C O, O(C O) , SiR 2 and/or NR, wherein R is an aliphatic radical having 1 to 7 C atoms, it being possible for one or more C atoms to be replaced by O, C O and/or O(C O) ,

A an aliphatic, cycloaliphatic or aromatic radical having 1 to 18, preferably 1 to 15 C atoms or a combination of these radicals, it being possible for one or more C atoms to be replaced by O, C O, O(C O) , SiR 2 and/or NR, wherein R is an aliphatic radical having 1 to 7 C atoms, in which one or more C atoms can be replaced by O, C O and/or O(C O) ,

B 1 , B 2 , D, E independently of one another, an H atom or an aliphatic radical having 1 to 9, preferably 1 to 7 C atoms, it being possible for one or more C atoms to be replaced by O, C O, O(C O) , SiR 2 and/or NR, wherein R is an aliphatic radical having 1 to 7 C atoms, in which one or more C atoms can be replaced by O, C O and/or O(C O) ,

X CH 2 , S or O,

n 2 to 7, preferably 2 to 5,

m 1 to 10, preferably 1 to 7,

p 1 to 5, preferably 1 to 4, and

Low-viscosity epoxides such as are described in DE-A-196 48 283 can also be employed.

Combinations of aliphatic, cycloaliphatic or aromatic epoxides are possible. Cycloaliphatic epoxy compounds with at least two epoxy groups, cycloaliphatic epoxy compounds with at least four epoxy groups or the combination of cycloaliphatic epoxy compounds with two epoxy groups and cycloaliphatic epoxy compounds with at least four epoxy groups are preferably employed.

The Lewis and/or Br nsted acids according to constituent (B) are formed by chemical reactions of selected constituents of the two components during or after mixing thereof. Free Lewis and/or Br nsted acids such as are known from conventional systems can also be employed.

In the case where free Lewis or Br nsted acids are additionally used, it has proved expedient to add the acids to that component which comprises no epoxy compounds. Where appropriate, to adjust the processing time it is expedient also to employ the substances for delaying cationic polymerization known from DE-A-197 53 461 which has not yet been published at the time of this Application.

Both components of the dental compositions according to the invention can additionally comprise certain contents of so-called photoinitiators which form Br nsted or Lewis acids when irradiated with light of the wavelength range from 200 to 650 nm. Typical classes of compounds for these photoinitiators are onium salts, such as diazonium, sulphonium, iodonium and ferrocenium salts with complex anions of low nucleophilicity. These include, for example, diazonium compounds (U.S. Pat. No. 3,205,157), sulphonium compounds (U.S. Pat. No. 4,173,476) and iodonium compounds (U.S. Pat. Nos. 4,264,703, 4,394,493). In the examples mentioned, instructions are given to use ultraviolet light.

Derivatives of cyclopentadienyl-iron-arene complexes (EP-A-0 094 915, WO-96/03453, EP-A-0 661 324) can also be used. It is also possible to add -dicarbonyl compounds, for example camphorquinone, which act as sensitizers in the visible range. Combined preparations of camphorquinone and iodonium compounds are known from U.S. Pat. Nos. 5,554,676 and 4,828,583.

To produce the Br nsted and/or Lewis acids, the components comprising photoinitiators are irradiated, before mixing, by lamps which emit light of the required wavelength range.

The photoinitiators are preferably employed in a component which comprises no epoxy compounds.

The Br nsted and/or Lewis acids are produced by selected constituents which are stored separately in the two components and which react chemically with one another during or after mixing of the two components.

Typical examples of those reactions which can lead to the acids necessary for initiation of the polymerization of epoxy compounds are redox reactions using bisaryliodonium salts, reducing agents and copper complexes, and the dehalogenation of alkyl halides assisted by metal salts.

In the case of these latent initiation systems, it is possible to add the particular reaction partner both to the components comprising epoxy compounds and to the component which comprises no epoxy compounds.

In general, the distribution of the constituents of the latent initiation systems over the two components is undertaken such that premature polymerization of the epoxy compounds during storage of the two-component materials is reliably avoided.

This object is achieved, for example, by using components which cannot be polymerized by acids and which comprise the particularly critical constituent of the particular latent initiation system.

In the case of the formation of acids by redox reactions from bisaryliodonium salts, reducing agents and copper compounds, for example, it has thus proved expedient to store the bisaryliodonium salts and the reducing agents in a component which comprises no epoxy compounds. A further component then comprises the copper compounds together with the epoxy compounds.

The iodonium salts are present in the components to the extent of 0.01 to 20 wt. %, preferably 0.2 to 10 wt. %, based on the weight of the mixed material, the reducing agents also necessary are present to the extent of 0.01 to 10 wt. %, preferably 0.05 to 5 wt. %, based on the weight of the mixed material, and the copper compounds are present to the extent of 0.005 to 10 wt. %, preferably 0.01 to 5 wt. %, based on the weight of the mixed material.

Diaryliodonium compounds, which are known, inter alia, from DE-A-197 36 471, are particularly preferred. They have the following structure:

Ar 1 and Ar 2 independently of one another can be different, substituted or unsubstituted, fused or non-fused aromatic systems having 4 to 20 C atoms, such as, for example, phenyl, tolyl, cumyl, anisyl, chlorophenyl, nitrophenyl, naphthyl, thienyl, furanyl and pyrazolyl, wherein R 1 and R 2 are identical or different and independently of one another denote an H atom, an aliphatic radical having 1 to 19, preferably 1 to 9 C atoms, it being possible for one or more C atoms to be replaced by O, C O, O(C O) , F, Cl, Br, SiR 3 3 and/or NR 3 2 , wherein R 3 is an aliphatic radical having 1 to 7 C atoms, in which one or more C atoms can be replaced by O, C O and/or O(C O) , and a and b independently of one another can be 1 to 5. The aromatics Ar 1 and Ar 2 can be bonded to one another via R 1 and/or R 2 .

The counter-anion Y is an anion of low nucleophilicity of the following structure:

K x L y

wherein K is an element of main group IIII, V or VII, such as B, Al, P, Sb, As or I, and x can assume numerical values from 1 to 4. The L independently of one another denote aromatic, aliphatic, araliphatic or cycloaliphatic radicals having 1 to 25 C atoms, in which one or more C atoms can be substituted by F, Cl, Br or I, and y can assume numerical values from 0 to 6.

Reducing agents for carrying out the redox reaction for formation of acids are organic or inorganic compounds or polymers which are capable of lowering the charge of the heteroatom within the diaryliodonium salt. Compounds which are worth mentioning are ascorbic acid and derivatives thereof, in particular the palmitate, oleate and acetate. Tin(II) compounds can also be employed, for example Sn 2 carboxylates, in particular tin octoate, tin stearate, tin laurate, tin citrate, tin oxalate and tin benzoate. Among the organic compounds there may be mentioned -hydroxy compounds, for example ketones, in particular acyloins and benzoins. Also included are iron(II) compounds, for example ferrocenes, FeBr 2 and FeCl 2 , reducing sugars, such as glucose, fructose and galactose, phenols, such as thiophenol, silanes and organosiloxanes.

Alkyl halides which are suitable for the dehalogenation of alkyl halides assisted by metal salts are described in Makromol. Chem. 178, 2139-2140 (1977) and in Die Makromolekulare Chemie 156 (1972) 325-328.

Compounds of the type R 3 C X, wherein X represents a halogen, preferably Cl and Br, and R represents any desired substituted or unsubstituted aliphatic or cycloaliphatic radical with a chain length of 1 to 15 C atoms, preferably 1 to 8 C atoms, or an aromatic radical substituted in any desired manner, are suitable in particular. Compounds with up to three different substituents on the central C atom can also be used.

Metal salts are understood as meaning inorganic or organic metal salts which are capable of abstracting the halogen from the compounds of the abovementioned type. Possible salts are those such as AgBF 4 , Ag SbF 6 , AlCl 3 , ZnCl 2 and also BF 3 . Lewis acid compounds of the type M(III)X 3 , M(II)X 2 , M(V)X 5 and possible adducts thereof with AgX are generally suitable. X here represents a halogen, preferably F, Cl or Br, and M represents a metal from the main or sub-group in question, preferably from main groups III and V, and in these preferably B, Al, Sb or As, and from sub-groups I, II, IVa and VIIIa, and in these preferably Cu, Ag, Zn, Fe, Co, Ni and Ti.

Diluents as flow improvers as constituent (C) are present in at least one of the two components of the preparations according to the invention. Diluents which are usually used as plasticizers can advantageously be employed.

Typical representatives are the esters of phthalic acid, such as di-2-ethylhexyl phthalate, or the esters of polybasic aliphatic acids, such as dioctyl adipate or acetyl tributylcitrate.

In addition, aliphatic and aromatic hydrocarbons with 6 to 30 C atoms which can be branched or unbranched are very suitable. Typical examples are polypropylene oils or polyisobutylene oils. Advantageously, aromatic hydrocarbons such as polyphenylene compounds, dibenzyltoluene and dibenzylphenyl methane are used.

Polyester polyols which can be prepared for example by polycondensation from low-molecular polyols and polycarboxylic acids and/or their anhydrides can also be used.

Typical representatives of this class are marketed by H ls under the name Dynacoll. Preferably, polyester polyols whose molar masses are between 1000 and 5000 g/mol and hydroxyl equivalent masses of 500 to 2000 are used.

Particularly preferably, polyester polyols as they can be obtained through catalysed reactions of caprolactone with different starting alcohols can be used.

Typical representatives of this compound class are marketed by UCC under the name Tone or by Daicel under the name Placcel.

Polycaprolactone triols with molar masses of 200 to 1000 g/mol and polycaprolactone diols with molar masses of 300 to 2000 g/mol can be used.

Furthermore, polycarbonate diols with molar masses of 400 to 2000 g/mol and the general structure

can be used as diluents, X and Y being able to be identical or different and, independently of each other, mean alkylene, arylene, alkarylene, polyoxyalkylene and p can assume values between 1 and 50.

Furthermore, partly epoxidated polybutane diols can optionally be used which represent homopolymerisates of butadiene, which are terminated with OH groups, have molar masses of 1000 to 5000 g/mol and possess a high content of double bonds, which, through epoxidation, can optionally be partly converted to central aliphatic epoxide groups. Representatives of this compound class are marketed by Atochem under the name Poly bd .

Finally, polyether polyols of the general structure:

can also be used, m meaning an integer of 20 to 150, n an integer of 1 to 5 and R hydrogen or C1-C4 alkyl.

Preferably, mixed polyether polyols which are composed of propylene oxide units and/or ethylene oxide units and/or tetrahydrofurane units, are used.

Alkoxy-extended polyols such as for example ethoxylated Bisphenol A or propoxylated trimethylol propane can also advantageously be used.

To adjust the properties, it can be expedient to use mixtures of polyols of different average molar mass and different structure.

By modifiers are meant for example fillers. Fillers can be for example quartz, quartz powder, ground or reactive glasses, fragment polymerisates, silica gels as well as pyrogenic silicic acid or their granules, customary in the dental field. But other fillers such as for example finely-distributed metal or plastic powder, barium sulphate, titanium dioxide or in general finely-ground minerals are suitable. For better incorporation into the polymer matrix, it can be advantageous to hydrophobize the fillers. Hydrophobizing agents are silanes, for example glycidyloxypropyltrimethoxysilane. The maximum particle size of the inorganic fillers is 100 m, preferably 20 m.

As further modifiers, such as dyes or thixotropic agents, the substances customary in the dental engineering field can be used.

The two components of the preparations according to the invention can be stored separately, for example in double-chamber cartridges, and be mixed internally before use by eduction via a static or dynamic mixer. Hand-mixing variants are also possible.

The ratio between the component containing no epoxy compounds and the component containing epoxy compounds can be 1:10 to 1:1 and preferably 1:5 to 1:2.

EXAMPLES

The invention is described in more detail below by examples from the model material sector, which are in no case intended to limit the scope of the invention. The substances used in the course of these examples can be obtained from the following manufacturers:

The substance LM used as a stabilizer was prepared in accordance with DE-A-197 53 461, example 1.

The base pastes and catalyst pastes characterized in the following examples with the aid of their compositions were prepared in 3-finger kneaders on a 100 g scale. After achieving a homogeneous state of mixing, the pastes were evacuated and then introduced into 4:1 double-chamber cartridges.

Comparison Example 1

Millable after Flexural strength Can be mixed Material min Mpa automatically Comparison 30 105 14 Yes example 1 Example 1 45 65 6 Yes Example 2 45 99 7 Yes Example 3 30 62 5 Yes Example 4 45 34 3 Yes Example 5 45 41 1 Yes Comparison 30-60 16 2 No example 2 Comparison 360-480 43 2 No example 3 In comparison example 1, in which only free acid was employed as the initiator, the processing time of 60 seconds was too short. A super-hard gypsum of the Fujirock (GC) brand is used as comparison example 2, and a conventionally curing epoxy resin of the Blue Star type E (Girbach) brand is used as comparison example 3.