Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – From silicon reactant having at least one...
Reexamination Certificate
2002-05-17
2004-06-15
Robertson, Jeffrey B. (Department: 1712)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
From silicon reactant having at least one...
C528S017000, C528S025000, C528S038000, C525S474000, C522S091000, C522S148000, C522S172000
Reexamination Certificate
active
06750309
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to the preparation of a new class of polymers, namely methacrylated urethane/urea copolymers containing moisture curable silicone soft segments in the polymer backbone, and compositions prepared therefrom. More specifically, this invention relates to the preparation of a copolymer derived from a partially methacrylated urethane prepolymer and an amino alkylene dialkoxysilanol terminated silicone prepolymer. These materials therefore have olefinic functionality and alkoxysilane functionality, allowing for cure by means of free radical (photo or anaerobic) mechanisms, as well as by moisture cure.
2. Description of Related Technology
It is known that diisocyanate end-capped urethane, containing both hard block and soft block segments can be prepared by proper control of the stoichiometry and steps in the process. For example, a diisocyanate end-capped hard block segment can be prepared from a diisocyanate and a rigid diol as a first stage or step, followed by a reaction of this diisocyanate end-capped prepolymer with a long chain diol to yield a diisocyanate end-capped polyurethane with soft and hard segments.
U.S. Pat. No. 4,684,538 to Klemarczyk discloses a method to produce acrylate end-capped polysiloxane urethane compositions in which siloxane-carbinol bonds are in the repeat unit of the polymer chain and which are capable of fast UV cure.
U.S. Pat. No. 5,760,155 to Mowrer describes a novel polysiloxane urethane composition in which one of the repeat units in the polymer back bone is comprised of urethane Si bonds, i.e.
The disadvantage of this kind of repeat unit is the inherent hydrolytic instability.
The interest in polysiloxane/polyurethane compositions is further exemplified by U.S. Pat. No. 4,839,443 to Akutus et al., whereby improved surfaces characteristics are alleged. Linear silicone-urethane copolymers are described as providing films of high strength and elasticity when cast from aqueous dispersions.
There is a definite need for a new process which provides polyurethane siloxane copolymers having excellent toughness and adhesive properties. It would be even more advantageous to produce an acrylated end-capped urethane-urea siloxane copolymers without the limitations of prior compositions.
SUMMARY OF THE INVENTION
One aspect of the present invention relates to a new class of (meth)acrylated urethane/urea copolymer compositions having moisture curable silicone segments and photocurable acrylated end-caps. The compositions are particularly useful in a variety of applications such as in the adhesive, coating, caulking and potting areas. These compositions have found to be particularly useful in the electronic, automotive, industrial and consumer fields.
In the synthesis of acrylate end-capped polysiloxane/urethane urea copolymers of the present invention, a process in forming polysiloxane/urethane-urea units was developed to minimize the concentration of available isocynate groups which cause biuret formation. This process, whereby the acrylated polyurethane prepolymer is formed first, and the polysiloxane units are incorporated in a second step, allows for the formation of a dual cured end-capped aminoalkylene dialkoxy silicone/polyurethane material having minimum biuret formation. Moreover, since the polymer is acrylated in the first step of the process it is free of hydroxyalkyl (meth)acrylate, thereby alleviating environmental issues relating to by-products.
In one aspect of the invention there is provided a curable polymer having the structure I:
wherein A and B may be the same or different and have the structure:
(i) wherein Q is
or
a is 2 to 3; R
1
and R
10
may be the same or different and may be a substituted or unsubstituted C
1
-C
10
alkylene group; R is H or CH
3
; and
(ii) wherein R
4
, R
6
, R
7
, R
8
, R
9
and R
11
may be the same or different and are substituted or unsubstituted hydrocarbon radicals; R
11
may also be saturated or unsaturated, for example, it may contain a vinyl group or a (meth)acrylate group; R
2
, R
3
and R
5
may be the same or different and are divalent substituted C
1
-C
40
aliphatic, cycloaliphatic or aromatic hydrocarbon radicals, or a polyol, polyester, or polyalkylidene having a weight average molecular weight from about 200 to about 5,000; n is an integer from 1-1000, desirably 1-10 and more desirably 1-5; p is an integer from 1-1200, desirably 1-200 and more desirably 1-100.
In a further aspect of the invention there is provided a curable polymer which includes the reaction product of:
a) a reactive prepolymer component having a radiation-curable group proximal to one terminus of the prepolymer and an isocyanate group proximal to the other terminus of the prepolymer; and
b) an aminoalkylenedialkoxysilyl-terminated polydiorganosiloxane.
In a still further aspect of the invention there is provided a dual curing composition which includes
a) a (meth)acrylated urethane/urea silicone copolymer which includes the structure:
wherein A and B may be the same or different and have the structure:
wherein R is H or CH
3
; R
1
is a divalent substituted or unsubstituted C
1
-C
40
aliphatic, cycloaliphatic or aromatic hydrocarbon radical; R
2
=R
1
and may be the same or different; R
3
is a polyol, polyether, polyalkylidiene, or polyester having a weight average molecular weight from about 200 to about 5,000; n is an integer from 1-1000; p is an integer from 1-1,200; R
4
is a monovalent substituted or unsubstituted aliphatic, cycloaliphatic or aromatic hydrocarbon radical C
1
-C
40
; R
5
is a substituted or unsubstituted divalent C
1
-C
40
aliphatic, cycloaliphatic or aromatic hydrocarbon radical; R
6
=R
4
and may be the same or different; R
7
=R
6
and may be the same or different; and
b) a cure system for said copolymer.
In still a further aspect of the invention there is provided a method of preparing a curable (meth)acrylated polyurethane/urea silicone co-polymer which includes the step of:
reacting an isocyanate prepolymer having a terminal (meth)acrylate group with an noalkylenedialkoxysilyl-terminated polydiorganosiloxane.
DETAILED DESCRIPTION OF THE INVENTION
In discovering the present invention, it has also been determined that the formation of biuret groups within the backbone structure is also less desirable because it leads to a more rigid structure due to increased crosslinking within the polymer system. The biuret crosslinking reaction occurs when an isocyanate group reacts with intermediate urea groups as shown in the reaction below. The formation of a biuret is schematically shown below:
In contrast to conventional processes for forming polyurethane/acrylates which contain urethane linkages joining the hard and soft segments, the present invention uses a urea linkage to form these segments. This linkage is formed by the reaction of an isocyanate prepolymer with an aminoalkylene dialkoxy-terminated polydimethylsiloxane. The use of secondary amines as opposed to primary amines in this reaction is desirable because it minimizes the formation of biuret by-product. This is because the urea functionality unit formed in the isocyanate/amine reaction is capable of further reaction with available isocyanate group to form a crosslinked biuret structure. This increases the viscosity of the copolymer and limits the processability of the copolymer for further applications such as for adhesives, coatings and sealants. Thus, the present invention provides a process and composition which avoids the formation of biruets.
More particularly, the (meth)acrylated urethane/urea alkylaminoalkenedialkoxy siloxanes of the present invention include those represented by structure I:
wherein A and B may be the same or different and have the structure:
wherein Q is
or
a is 2-3; R
1
and R
10
may be the same or different and may be a substituted or unsubstituted C
1
-C
10
alkylene group; R is H or CH
3
; R
4
, R
6
, R
7
, R
8
, R
9
and R
11
may be the same or different and are substituted
Chu Hsien-Kun
Nakos Steven T.
Bauman Steven C.
Henkel Corporation
Robertson Jeffrey B.
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