Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – From silicon reactant having at least one...
Reexamination Certificate
2000-01-21
2002-05-21
Dawson, Robert (Department: 1712)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
From silicon reactant having at least one...
C528S421000, C528S418000, C528S032000, C528S033000, C528S041000, C556S458000, C549S215000, C525S477000, C526S279000
Reexamination Certificate
active
06391999
ABSTRACT:
FIELD OF THE INVENTION
The invention relates to epoxy alkoxy siloxane oligomers.
BACKGROUND OF THE INVENTION
In recent years, there has been considerable interest in the photo, e-beam and thermally-induced cationic polymerization of siloxane-containing monomers and oligomers. Such monomers and oligomers have considerable potential in a wide diversity of applications including: non-stick release coatings, adhesives, abrasion resistant coatings for plastics, fiber optic coatings, reinforced composites and optical waveguides. The photopolymerizations of various multifunctional monomers characteristically proceeds only to low conversions due to trapping of residual reactive functional groups within the rigid, crosslinked network as it is formed. In this regard, siloxane containing monomers exhibit anomalous behavior that has been attributed to the conformational flexibility of the siloxane (Si—O—Si) bond and to free volume effects.
Preparation of multifunctional alkoxy siloxanes is difficult to accomplish by prior art methods. While epoxy-functional trialkoxy silanes are commercially available as starting materials, condensation polymerization of multifunctional alkoxy silanes generally results in crosslinked gels. Typically, alkoxy silanes such as tetraethoxysilane (TEOS) are subjected to acid or base catalyzed hydrolysis-condensation in the presence of controlled amounts of water to yield a gel. In most acid catalyzed sol-gel processes, HCl is used, while NaOH and NH
4
OH are often employed as base catalysts. However, it is difficult to reproducibly make intermediate, soluble, low viscosity, fluid oligomers. When such materials are obtained, they exhibit poor pot-lives and they gel on standing, due to further condensation.
In addition, the basic hydrolysis catalysts used in the sol-gel reaction are strong inhibitors for cationic polymerizations, and the traces of basic catalysts that remain in the product inhibit subsequent cationic polymerizations. On the other hand, acid hydrolysis catalysts are not generally useful for the synthesis of epoxy-functional siloxanes, since epoxy groups undergo spontaneous ring-opening reactions with acids.
There is therefore a need for a process for making pure multifunctional alkoxy siloxane oligomers reproducibly and in good yield. There is also a need for alkoxy siloxane oligomers that have long pot-lives and low viscosity and that cure rapidly and completely. There is also a need for oligomers that can be polymerized to polymers having such desirable properties as: exhibiting no glass transition at temperatures below 300° C.; having a relatively low coefficient of thermal expansion (CTE) between 0-180° C.; having a high storage modulus; and remaining stable at elevated temperatures.
SUMMARY OF THE INVENTION
In one aspect, the invention relates to a polymerizable siloxane oligomer comprising a plurality of repeating units of formula A and at least one unit of formula B:
and terminating in a residue R
2
or R
8
. In these formulae FG is a functional group. Each FG may be chosen from
linear, branched and cyclic alkyl residues of 1 of 20 carbons terminating in a 1-alkenyl ether;
linear, branched and cyclic alkyl ether residues of 1 to 20 carbons and 1 to 9 oxygens terminating in a 1-alkenyl ether;
linear, branched and cyclic alkyl residues of 1 to 20 carbons terminating in an acrylate, an alpha-chloroacrylate, an alpha-cyanoacrylate or a methacrylate;
linear, branched and cyclic alkyl ether residues of 1 to 20 carbons and 1 to 9 oxygens terminating in an acrylate, an alpha-chloroacrylate, an alpha-cyanoacrylate or a methacrylate;
linear, branched and cyclic alkyl residues of 1 to 20 carbons substituted with an epoxide;
linear, branched and cyclic alkyl ether residues of 1 to 20 carbons and 1 to 9 oxygens substituted with an epoxide;
arylalkyl residues of 1 to 20 carbons substituted with an epoxide;
arylalkyl ether residues of 1 to 20 carbons and 1 to 9 oxygens substituted with an epoxide; and
epoxy-functional organosiloxane residues of 1 to 20 silicons and 1 to 20 carbons.
R is alkyl, aryl, haloalkyl or aralkyl of 1 to 10 carbons;
R
1
is R,
R
2
is alkyl, aryl, haloalkyl or aralkyl of 1 to 10 carbons or
R
3
and R
4
are independently alkyl, aryl, haloalkyl, aralkyl, alkoxy or aryloxy of 1 to 10 carbons;
R
5
, R
6
and R
7
are independently FG, alkyl, aryl, haloalkyl, aralkyl, alkoxy or aryloxy of 1 to 10 carbons;
R
8
is alkyl, aryl, haloalkyl, aralkyl, alkoxy or aryloxy of 1 to 10 carbons; m and n are independently 2 to 50; p is 2 to 50 and q is 1 to 50. Note that in this document, variables are defined when introduced and retain that definition throughout.
The foregoing oligomers may also be described in product-by-process terms as polymerizable siloxane oligomers produced by reacting one or more alkoxy silane monomers of formula (RO)
3
SiFG and one or more alkoxy silane monomers of formula R
3
R
4
R
8
SiOR
2a
with 0.5 to 2.5 equivalents of water, in the presence of an ion exchange resin, optionally in the presence of a solvent, and separating the resin from the siloxane oligomer. In these monomers, R
2a
is alkyl, aryl, haloalkyl or aralkyl of 1 to 10 carbons.
In another aspect the invention relates to (1) polymers produced by cationically polymerizing one or more of the foregoing oligomers; and (2) polymers produced by cationically co-polymerizing one or more of the foregoing oligomers with an oligomer of formula:
In another aspect the invention relates to a process for preparing a polymerizable siloxane oligomer comprising reacting one or more alkoxy silane monomers of formula (RO)
3
SiFG and one or more alkoxy silane monomers of formula R
3
R
4
R
8
SiOR
2a
with 0.5 to 2.5 equivalents of water, in the presence of an ion exchange resin, optionally in the presence of a solvent, and separating the resin from the siloxane oligomer. The ion exchange resin is preferably a quaternary ammonium resin.
DETAILED DESCRIPTION OF THE INVENTION
The polymerizable siloxane oligomers of the invention are made up of a plurality of repeating units of formula A and at least one unit of formula B:
The oligomers of the invention may be block oligomers or random oligomers. Preferably the ratio of A to B (or p to q) is from 19:1 to 1:9, most preferably the ratio of A to B is from 1:1 to 3:1. In a preferred embodiment, FG is one or more residues chosen from formulae A-Q:
From among these residues, 2-(3,4-epoxycyclohexylethyl), 3-glycidoxypropyl and 1-propenoxy-2-ethoxyethyl are preferred. In an another preferred embodiment, R
1
is methyl or ethyl; R
2
is
methyl, methoxy, ethyl, ethoxy, phenyl or
R
3
, R
4
and R
8
are chosen independently from methyl, methoxy, ethyl, ethoxy, and phenyl; and
R
5
, R
6
and R
7
are chosen independently from methyl, methoxy, ethyl, ethoxy, phenyl and FG.
As will be apparent to the artisan, the ratios of residues represented by R
5
, R
6
and R
7
in a random oligomer will reflect the ratio and relative reactivities of A to B in the monomer mix from which the oligomer was prepared.
The siloxanes of the invention are straight- or branched-chain oligomers and may additionally contain one or more cyclic structures composed of three monomer units as end groups, as depicted in the formula:
The presence of the ring structure is dependent on the number of equivalents of water employed in the reaction and on reaction conditions, including temperature and time. The oligomer chains are composed of from two to fifty siloxane monomer units, preferably of from two to twenty monomer units.
The effective molecular weight and viscosities of the oligomers of the invention may be varied according to the desired use, both of the oligomer and of the product polymer. For many purposes oligomers in which the sum of p and q is from 4 to 20 are preferred. The rate and extent of the hydrolysis-condensation reaction are dependent on the strength of the catalyst used. Strong acids or bases cause fast hydrolysis and condensation of alkoxysilanes and high conversions to oligomers. The reaction is well controlled with ion exchange resins as catalyst
Heslin Rothenberg Farley & & Mesiti P.C.
Peng Kuo-Liang
Rensselaer Polytechnic Institute
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