Stock material or miscellaneous articles – Composite – Of epoxy ether
Reexamination Certificate
2001-11-28
2003-09-02
Dawson, Robert (Department: 1712)
Stock material or miscellaneous articles
Composite
Of epoxy ether
C424S423000, C433S222100, C433S228100, C433S229000, C428S414000, C523S455000, C528S098000
Reexamination Certificate
active
06613437
ABSTRACT:
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 Brönsted 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 Brönsted 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 Brönsted 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 Brönsted acids, after mixing of the two components, the preparations comprising the Lewis and/or Brönsted acids in the form of precursor compounds which are suitable for the formation of Lewis and/or Brönsted 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 Brönsted acids in the form of compounds which are capable of the formation of Lewis and/or Brönsted 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:
(A) 10 to 80 wt. %, preferably 10 to 60 wt. %, of epoxy compounds,
(B) 0.01 to 20 wt. %, preferably 0.1 to 10 wt. %, of compounds which are capable of formation of Lewis or Brönsted acids, and optionally free Lewis and/or Brönsted acids,
(C) 10 to 89.99 wt. %, preferably 30 to 89.99 wt. %, of diluents,
(D) 0 to 79.99 wt. %, preferably 15 to 59.99 wt. %, of modifiers.
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
q 1 to 5, preferably 1 to 4.
Low-viscosity epoxides such as are described in DE-A-196 48 283 can also be employed.
The epoxides known from U.S. Pat. Nos. 2,716,123, 2,985,667, 2,750,395, 2,863,881, 3,187,018, 5,085,124, EP-A-0 449 027 and EP-A-0 574 265 are also suitable, in particular epoxides of the following structural formulae
Combinations of aliphatic, cycloaliphatic or aromatic epoxides are possible. Cycloaliphatic epoxy compounds with at least two epoxy groups, cycloaliph
Eckhardt Gunther
Fuehrer Cornelia
Gangnus Bernd
Weinmann Wolfgang
3M ESPE AG
Aylward D.
Birch & Stewart Kolasch & Birch, LLP
Dawson Robert
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