Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Mixing of two or more solid polymers; mixing of solid...
Reexamination Certificate
1999-10-13
2001-07-03
Dawson, Robert (Department: 1712)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Mixing of two or more solid polymers; mixing of solid...
C525S106000, C526S319000, C526S279000, C526S328500, C526S329700, C523S105000
Reexamination Certificate
active
06255407
ABSTRACT:
The invention relates to a polymeric adhesive according to the main claim, to processes for preparing it and to its use as a medical preparation and for preparing an adhesion promoter for use in the dental field.
Dental prostheses consist in general of a hard polymer; polymethyl methacrylate (PMMA) is used in many cases. In order to improve the accuracy of fit and to avoid pressure points on the oral mucosa, it may be necessary to provide such dental prostheses with relining material which stays permanently soft. Relining materials used include organopolysiloxanes (silicones). However, there are problems in establishing a permanent bond between the polymer of the prosthesis and the silicone relining material.
DE-A-44 14 837 describes an adhesion promoter for producing a bond between PMMA and an organosilicon elastomer. First of all a two-component polyurethane reactive adhesive is applied to the prosthesis polymer and, after a certain curing time, is provided with a film of organohydrogen-silicone fluid. The relining material is applied to this film. Applying a multi-component adhesion promoter of this kind is complex and laborious.
One-component adhesives are disclosed in EP-A-0 632 060 and EP-A-0 826 359. It has been found, however, that the adhesives disclosed therein are sensitive to hydrolysis, and lack stability. Adhesion promoter systems are known, furthermore, from DE-A-195 39 653, EP-A-0 685 547, EP-A-0 384 401, EP-A-0 731 143 and U.S. Pat. No. 5,635,578.
The object of the present invention is to provide an adhesive of the type specified at the outset which is able to produce good adhesion between a polymer and an organosilicone material, is simple and quick to apply, and is chemically stable.
This object is achieved in accordance with the invention by means of an adhesive which comprises a polymer having the following features:
a polymeric backbone,
alkyl, aryl and/or alkenyl groups attached to the backbone by way of ester linkages,
alkyl and/or aryl spacer groups attached to the backbone by way of ester linkages,
an open-chain and/or cyclic silicone group and/or silane group is attached to the spacer by means of an Si—C bond,
an ethylene group is attached to the silicone and/or silane group by means of an Si—C bond,
the ethylene group in turn is connected to a second silicone group which comprises M, D, T and/or Q silicone units and comprises at least one vinyl group attached to Si.
The adhesive of the invention comprises a polymeric backbone. This backbone can, for example, be a poly(alk)acrylate. This terminology includes polyacrylates and polyalkacrylates such as, for example, polymethacrylate.
Alkyl and/or aryl groups (this terminology includes aralkyl groups) are connected as alcohol components to the backbone by way of ester linkages. These alkyl and/or aryl groups may carry additional functional groups such as, for example, hydroxyl groups. The specified alcohol components are preferably esters of methanol, ethanol, propanol, isopropanol, butanol, tert-butanol, pentanol, hexanol, cyclohexanol, octanol, decanol, lauryl alcohol, cetyl alcohol, propynyl alcohol, glycerol, diethylene glycol, triethylene glycol, benzyl alcohol and its derivatives, phenol and its derivatives, 2-hydroxyethoxybenzene and 2-hydroxyethylbenzene, the ester linkage being made with an acid function or acid derivative function on the backbone.
Likewise attached to the backbone by way of ester linkages are branched or unbranched alkyl and/or aryl groups, which act as a spacers. Preferred spacers used are straight-chain, unbranched alkyl chains having a chain length from C
3
to C
18
, with particular preference C
3
and C
6
to C
18
. The spacer may comprise functional groups such as, for example, ester groups, ether functions or additional double bonds.
Attached to the spacer by means of a stable Si—C bond is an open-chain and/or cyclic silicone group (an organosiloxane) and/or a silane group. The term silicone group includes any group containing at least one siloxane bond (Si—O—Si bond).
Likewise attached to this extended spacer by means of stable Si—C bond is an ethylene group, which in turn is connected to a second silicone group which comprises M, D, T and/or Q silicone units and also at least one ethylenically unsaturated group (vinyl group) attached to an Si atom. The terminology M, D, T and Q to denote silicone units is an international convention (see, for example, ROmpp Chemielexikon, 9th Edition, Vol. 9, p. 4168) and denotes silicone units having the following structures:
The radical R denotes alkyl, aryl or aralkyl groups.
In accordance with the invention, the said second silicone group comprises at least one ethylenically unsaturated group attached to Si. By means of this reactive double bond arranged on the second silicone group, the adhesive is able to establish a chemical bond to the organosilicon elastomer.
The adhesive according to the invention has two essential advantages over the prior art. Firstly, the silicone units of the adhesive include, as the reactive group, ethylenically unsaturated double bonds and no Si—H bonds. Since the Si—H bond is able to react with nucleophiles, the adhesive of the invention is substantially more stable (especially on storage).
Linkage between the backbone and the silicone groups is exclusively by way of stable Si—C bonds, and not by way of hydrolysis-sensitive Si—O—C bonds.
The open-chain and/or cyclic silicone group attached to the spacer has preferably one silane unit and/or from 1 to 10, with particular preference from 1 to 5, silicone units (Si—O units), which can be in a linear, branched and/or cyclic arrangement. Alkyl, aryl and/or aralkyl side groups can be present, preference being given to methyl, ethyl, phenyl and benzyl groups.
The adhesive preferably has the following structural elements:
in which
r is an integer from 1 to 3,
R
1
is identical or different and is H, methyl, ethyl, propyl or butyl,
R
2
is a straight-chain or branched alkyl, aryl, aralkyl and/or alkenyl group,
Z is a straight-chain or branched alkyl or aryl or aralkyl group,
W is an open-chain and/or cyclic silicone group or silane group which is attached by way of Si—C bonds,
X is a second silicone group containing M, D, T and/or Q units, at least one silicone group X containing at least one vinyl group attached to Si.
The said structural elements a) and b) can be arranged in alternation or at random in the backbone. As evident from the formula a), the silicone group W can contain between 1 and 3 second silicone group(s) attached by way of an ethylene group and having at least one vinyl group.
The structural element a) can have the following the composition:
in which R
1
, R
2
, Z and X are as defined in claim
2
, R
3
is a straight-chain or branched alkyl or aryl or aralkyl group and m is an integer from 0 to 2.
The backbone can feature a poly(alk)acrylate, especially poly(meth)acrylate. Where the invention uses the expression acrylate or polyacrylate, this always includes polyalkacrylates which carry an alkyl group, such as for example a methyl group, on the &agr; carbon atom. The poly(alk)acrylate component can have a molecular weight of between 800 and 1,000,000. Preference is given to molar masses of between 5000 and 500,000, with particular preference between 20,000 and 250,000.
Instead of a pure poly(alk)acrylate the backbone can also be a copolymer of (alkyl) acrylates and other unsaturated esters.
The silicone group (X in claim
2
) intended for connection to the organosilicon elastomer preferably has a molecular weight of between 80 and 200,000. Where two or more silicone groups X are attached to the open-chain or cyclic silicone unit (W in claim
2
), the stated molar mass figure relates to one of these silicone groups. Not every silicone group X present in the form of a side chain of the silicone group W need necessarily have a reactive vinyl group, although at least one silicone group X has at least one reactive vinyl group.
The spacer (Z in claim
2
) is preferably a straight-chain, i.e. unbranched, alkyl compound.
The adhesive of the inven
Dawson Robert
Ernst Muhlbauer KG
Morrison & Foerster / LLP
Peng Kuo-Liang
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