Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – From silicon reactant having at least one...
Reexamination Certificate
1999-09-13
2001-05-29
Moore, Margaret G. (Department: 1712)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
From silicon reactant having at least one...
C528S026000, C528S025000, C528S029000, C523S109000, C524S862000
Reexamination Certificate
active
06239244
ABSTRACT:
The present invention relates to polysiloxane materials which have a long shelf life and, after vulcanization, give permanently water-wettable elastomers and the use of said materials as dental impression compounds.
Polysiloxane materials which vulcanize to give elastomers are widely used as impression compounds. The addition-crosslinking systems have proven particularly useful since they set more rapidly and, in contrast to the condensation-crosslinking systems, do not require large amounts of problematic catalyst.
A major disadvantage of silicone impression preparations based on hydrophobic polysiloxanes is due to the fact that it is scarcely possible to take an accurate impression of moist surfaces, such as tissue surfaces, tooth surfaces or surfaces of dentures, in the oral cavity since the moisture contents accumulate in the form of drops between the surface of which an impression is to be taken and the impression compound.
A surface-active impression compound causes the moisture on the surfaces of which an impression is to be taken to spread to give a thin moisture film. As a result, cavities in the impression are avoided and a precise reproduction of the surface structure is achieved.
For example, EP-A-480 238 discloses addition-crosslinking water-wettable silicone impression compounds which contain special alkoxylated fatty alcohol or a methylated or acylated alkoxylated fatty alcohol. However, owing to the poor binding in the impression compounds, the surface-active agents are extracted in contact with aqueous media. Thus, the water wettability is lost through, for example, rinsing with water, disinfection, sterilization, preparation of duplicates with the aid of water-containing impression preparations, such as plaster, before the desired aims of the application, such as reproducible wetting properties of the silicone impression after removal from the moist surface, are achieved.
EP-A-398 745 describes polysiloxane materials which give permanently water-wettable vulcanized products and contain hydrophilic modifiers incorporatable by crosslinking. The hydrophilic modifiers are polysiloxanes which contain hydrophilic alkylene ether groups and either aliphatic double bonds or Si—H groups. The hydrophilic modifiers described in EP-A-398 745 contain a noble metal catalyst as a result of their preparation. In addition, the hydrophilic modifiers preparable to date and containing double bonds have small amounts of Si—H groups and the hydrophilic modifiers preparable to date and containing Si—H groups have small amounts of double bonds.
When used as hydrophilic modifiers, the known copolymers, owing to the deficiencies described above, do not give mixtures having a long shelf life, either with the two-component rubber component (A), which comprises a polysiloxane material having aliphatic double bonds and a noble metal catalyst, or with the component (B) which comprises polysiloxane material having Si—H groups. In all cases, proportions of vulcanized product form during storage.
The separate storage of the hydrophilic modifier is not a satisfactory remedy since a three-component polysiloxane material is too difficult to handle when used in practice.
US-A-5,580,921 likewise describes polysiloxane materials which give permanently water-wettable vulcanized products and have, as hydrophilic modifiers, polysiloxanes incorporatable by crosslinking. The modifier is obtained free of platinum by a very complicated preparation process, in which high-boiling intermediates of the modifier are distilled. The shelf life is improved as a result.
It is the object of the present invention to provide polysiloxane materials which give permanently water-wettable elastomeric vulcanized products and whose components have a particularly long shelf life.
The invention relates to polysiloxane materials having a long shelf life, giving permanently water-wettable elastomeric vulcanized products and containing the constituents
1. organopolysiloxane having at least two aliphatic double bonds in the molecule,
2. organopolysiloxane having at least two Si—H groups in the molecule,
3. noble metal catalyst and
4. hydrophilic modifier of the general formula I
[H
2
C═CH—A
1
—(A
2
)
m
—X]
n
B (I),
in which
A
1
denotes a divalent C
2
-C
10
-hydrocarbon radical which may be substituted by halogen atoms,
A
2
denotes a divalent C
1
-C
24
-hydrocarbon radical which may be interrupted by non-neighboring oxygen atoms or nitrogen atoms or the groups of the formulae —NR—, —CO— or —CO—NR
1
— and may additionally be substituted by halogen atoms, with the proviso that at least 5 carbon atoms are present per oxygen or nitrogen atom,
x denotes a divalent group —O—, —CO— or —COO—,
B denotes polar radicals which have carbon atoms and at least 2 non-neighboring oxygen atoms, the oxygen atoms being present as ether oxygen or in hydroxyl groups, C
1
—C
4
-acyl groups or C
1
-C
3
-trialkylsilyl groups, with the proviso that not more than 3 carbon atoms are present per oxygen atom,
m denotes the values 0 or 1,
n denotes integral values from 1 to 50,
R and R
1
each denote a monovalent C
1
-C
10
-hydrocarbon radical which may be substituted by halogen atoms.
The polysiloxane material having a long shelf life is very readily water-wettable both before and after vulcanization. The wettability of the vulcanized products remains good even after relatively long contact with aqueous systems, for example after sterilization.
By mixing the constituents 1 to 4, preferably 2 components are prepared, namely the component A which contains the catalyst constituent 3 and all constituents except for constituent 2 and component B which contains all constituents except for constituent 3.
Preferably, all components contain hydrophilic modifiers. In this embodiment, the total amount of hydrophilic modifier in the polysiloxane material having a long shelf life can be considerably increased and hence the hydrophilic properties considerably enhanced without separation occurring. A further advantage of this embodiment is that the hydrophilic modifier may be present in both components homogeneously and in the same concentration. With the use of modern application forms, such as double-chamber cartridges with mounted static mixer, this is very important owing to the very short mixing times.
The divalent C
2
-C
10
-hydrocarbon radical A
1
has a hydrophobic character. It may be saturated, aliphatically unsaturated, aromatic, linear or branched. Preferably, A
1
has 3 to 8 carbon atoms.
The divalent C
1
-C
24
-hydrocarbon radical A
2
has a hydrophobic character. It may be saturated, aliphatically unsaturated, aromatic, linear or branched. The oxygen atoms or nitrogen atoms or groups of the formulae —NR—, —CO— or —CO—NR
1
— may be part of a linear chain or of heterocycles. Preferably, A
2
has 5 to 18 carbon atoms.
—O— and —COO— are preferred as divalent group X, in particular —COO—.
Preferably, B has at least 2, in particular at least 3, oxygen atoms. Preferably, B has not more than 50, in particular not more than 20, oxygen atoms.
The polar radical B is preferably composed of polyethylene glycol units [—CH
2
—CH
2
—O—] with preferably 1-20 alkylene units, in particular with 3-10 alkylene oxide units, or a polyol having 3 to 10 carbon atoms, such as glycerol and sorbitol, or a sugar radical, such as glucose and sucrose. B may contain both free OH groups and acylated, silylated or alkylated OH groups.
The acylated OH groups are preferably acylated with formic or acetic acid. The trialkylsilyl groups are preferably trimethylsilyl groups. The alkylated OH groups are preferably ethoxy or in particular methoxy groups.
n indicates the number of unsaturated units [H
2
C=CH—A
1
—(A
2
)
m
—X] forming a molecular bond with B. n preferably has integral values from 1 to 10.
R and R
1
are preferably alkyl radicals having from 1 to 6 carbon atoms, in particular the methyl, ethyl, n-propyl and isopropyl radicals.
Preferred halogen atoms as substituents of A
1
, A
2
, R and R
1
are fluorine, chlorine and bromine atoms
Bindl Johann
Garhammer Arnold
Kreis Gerhard
Stepp Michael
Brooks & Kushman P.C.
Moore Margaret G.
Wacker-Chemie GmbH
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