Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – From reactant having at least one -n=c=x group as well as...
Reexamination Certificate
1999-11-24
2001-04-24
Seidleck, James J. (Department: 1711)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
From reactant having at least one -n=c=x group as well as...
C528S061000, C528S062000, C528S064000, C528S028000, C528S073000
Reexamination Certificate
active
06221998
ABSTRACT:
TECHNICAL FIELD
This invention relates to a one-part moisture curable composition which has excellent storage stability and high curing rate once taken out of the container, and use of this composition enables production of a cured product of high flexibility without using any plasticizer. The one-part moisture curable composition of the present invention is useful as an adhesive or a sealant in the fields of coating, civil engineering and architecture.
BACKGROUND ART
An isocyanate compound is known to react with a curing agent such as an amine to form urethane bond, and a cured compound is readily formed by such reaction.
When such isocyanate compound is stored with an amine as a mixture, the mixture undergoes gelation, curing, and the like during the storage and the mixture was not at all storage stable. Therefore, the isocyanate compound has been generally used as a two-part composition, and the isocyanate compound and the curing agent were mixed in time of its use.
A curable composition in the form of a one-part curable composition has been awaited. The one-part curable compositions that are currently in use require use of a plasticizing agent such as dioctyl phthalate (DOP). The plasticizing agent, however, bleeds out after curing, and has raised a problem as environmental hormones. Of the room temperature-curable compositions, development of an isocyanate-based one-part curable composition is highly demanded since the flexibility of such composition is superior to that of the composition containing an epoxy compound as its main component.
Use of a blocked (capped) amine as a latent curing agent has been investigated for the purpose of solving the problems of odor and toxicity of the amine curing agents and improving the handling convenience. One technique known for such amine blocking is use of a ketimine which is an amine blocked with a ketone, and known ketimines include those synthesized from an alkylenediamine and a ketone such as methyl isobutyl ketone or methyl ethyl ketone. Ketimine is a compound stable in the absence of water. Ketimine, however, easily undergoes hydrolysis in the presence of water to become an active amine, and therefore, ketimine acts as a curing agent in the presence of moisture in the air.
However, use of such known universal ketimine for the latent curing agent of an isocyanate compound was associated with the problem of insufficient storage stability such as gelation during the storage of the mixture.
In addition, isocyanate compounds had insufficient adhesion to mortar and the like, and a tackifier such as an epoxy resin was often added to the isocyanate compound at the sacrifice of the flexibility.
In view of the situation as described above, there is a strong demand for a one-part, room temperature, moisture-curable composition which cures at an accelerated speed at room temperature by the moisture in the air, which exhibits improved adhesion to mortar and the like, and which cures into a flexible product even without using any plasticizer.
DISCLOSURE OF THE INVENTION
An object of the present invention is to provide an isocyanate-based one-part moisture curable composition which has excellent storage stability, which cures at a high rate once taken out of the container, and which cures into a highly flexible product without using any plasticizer.
Through investigation of the production of one-part moisture curable compositions containing an isocyanate compound, the inventors of the present invention found that a one-part isocyanate-based moisture curable composition having a high storage stability can be produced by using an isocyanate compound having a bulky group at &agr; position of the isocyanate group and a ketimine having a bulky group at &agr; position of the ketimine bond (C═N) for the latent curing agent; and that the thus produced composition also cures at a high speed to form a cured product having a high flexibility without using any plasticizer. The present invention has been completed on such findings.
In view of the situation as described above, the one-part moisture curable composition of the present invention comprises
(A) an isocyanate compound having a structure wherein all of the isocyanate (NCO) groups in the molecule have secondary or tertiary carbon bonded thereto, and
(B) a ketimine having ketimine (C═N) bond derived from a ketone or an aldehyde and an amine having a structure wherein &agr;-position of at least one of the carbon or the nitrogen of the ketimine bond has a branched carbon atom or a ring member carbon atom bonded thereto.
The isocyanate compound (A) is represented, for example, by formula (1):
wherein R
c
and R
a
are independently an organic group which may contain O, S, or N; R
b
is hydrogen atom or said organic group; and p is an integer of at least 1.
The isocyanate compound (A) is preferably a polyisocyanate having two or more said isocyanate groups in the molecule.
Alternatively, the isocyanate compound (A) may be a urethane prepolymer derived from a polyisocyanate and a polyol.
The urethane prepolymer may be an adduct of said polyisocyanate and trimethylol propane.
Also, the urethane prepolymer may be a urethane prepolymer derived from said polyisocyanate and polypropylene glycol.
Also, the urethane prepolymer may be a urethane prepolymer derived from said polyisocyanate and a polyol having a bisphenol skeleton.
The ketimine (B) is preferably a ketimine wherein &agr;-position of the ketimine carbon has a branched carbon atom or a ring member carbon atom bonded to. The branched carbon atom of the ketimine may be introduced from a ketone or an aldimine represented by formula (2):
wherein
R
1
is a C
1-6
alkyl group;
R
2
is methyl group or ethyl group;
R
3
is hydrogen atom, methyl group, or ethyl group; and
R
4
is hydrogen atom or methyl group.
In the ketimine wherein a branched carbon atom or a ring member carbon atom is bonded to the ketimine carbon, the ketimine nitrogen preferably has methylene group bonded thereto.
The ketimine (B) of such structure usually has two or more ketimine bonds in one molecule.
It is also preferable that the ketimine (B) is a silicon-containing ketimine or a polycondensate thereof wherein the ketimine carbon has a branched carbon atom or a ring member carbon atom bonded thereto, and wherein the ketimine contains an amine component derived from an aminoalkoxysilane represented by formula (4):
wherein
R
6
is a C
1-6
alkyl group, a C
1-6
alkoxy group, or a monovalent siloxane derivative;
R
7
is a divalent hydrocarbon group which may contain nitrogen;
R
8
is an alkoxy group; and
m is 1, 2 or 3.
Such ketimine (B) may further contains a group derived from an epoxy group-containing alkoxysilane, and have epoxy group and an alkoxysilyl group in one molecule.
The one-part moisture curable composition according to the present invention may further contain an epoxy resin.
BEST MODE FOR CARRYING OUT THE INVENTION
The present invention is hereinafter described in further detail.
The one-part moisture curable composition of the present invention comprises an isocyanate compound (A) of particular structure and a ketimine (B) of particular structure as described below.
First, such components contained in the moisture curable composition of the present invention are described.
(A) Isocyanate compound.
The isocyanate compound used in the present invention has a structure wherein all of the isocyanate (NCO) groups in the molecule have secondary or tertiary carbon bonded thereto. The groups other than the NCO group bonding to the secondary or the tertiary carbon are not limited, for example, in terms of the number of carbon atoms, bulkiness, inclusion of hetero atoms such as O, S and N, and the like. The two groups bonding to the tertiary carbon may be either the same or different from each other.
Such isocyanate compounds is typically represented by formula (1):
In the formula, R
c
and R
a
are independently an organic group which may contain O, S, or N; R
b
is hydrogen atom or said organic group; and p is an integer of at least 1.
Exemplary such organic gr
Adachi Naoya
Okuhira Hiroyuki
Bagwell Melanie D.
Finnegan Henderson Farabow Garrett & Dunner L.L.P.
Seidleck James J.
The Yokohama Rubber Co. Ltd.
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