Silane-functionalized polyether composition

Details Silane-functionalized polyether composition Silane-functionalized polyether composition

2000-03-20

2002-08-20

Dawson, Robert (Department: 1712)

Synthetic resins or natural rubbers -- part of the class 520 ser

Synthetic resins

From silicon reactant having at least one...

C528S025000, C528S901000, C528S408000, C528S409000, C528S410000, C524S284000, C524S322000, C556S479000

Reexamination Certificate

active

06437071

ABSTRACT:

FIELD OF THE INVENTION
The present invention relates to a curable composition comprising a reactive silicon group-containing polyether oligomer and a plasticizer.
BACKGROUND OF THE INVENTION
Room temperature curing compositions based on a polyether having at least one reactive silicon group per molecule can be utilized, for example, as sealants for architectural and other applications. They are inexpensive and have good performance characteristics. It is desired that they show a proper rate of cure on the occasion of curing. It is also desired that the resulting rubber-like cured products have nonstick surfaces and, as regards tensile characteristics, high elongation and rubber elasticity with good flexibility.
Plasticizers are generally added to room temperature curing compositions not only for the purpose of improving the tensile characteristics which are required of them but also in view of advantages in terms of cost and workability, among others. Some compositions of this type fail to give fully cured products due to formulations thereof and/or curing conditions, so that the product appearance is deteriorated by adhesion of dust and the like due to the residual tack (stickiness) of the cured product surface. Improvements have thus been required.
The present applicant has already proposed, in Japanese Kokai Publication Sho-61-34066 and Japanese Kokai Publication Sho-61-34067, a simple method of producing improvements in the modulus, elongation characteristics and residual tack (stickiness) of a reactive silicon group-containing rubber type organic polymer, which comprises adding a monovalent silanol compound or a derivative thereof.
While the tensile characteristics of such cured products can be improved by the above method, there is still room for improvement with respect to the residual tack (stickiness).
SUMMARY OF THE INVENTION
Accordingly, it is an object of the present invention to provide a curable composition giving cured products improved in residual tack (reduced in stickiness), with the physical properties insuring those tensile characteristics and rubber elasticity required of sealing compositions for general architectural use being retained.
Thus, the present invention provides a curable composition which comprises (I) 100 parts by weight of a reactive silicon group-containing polyether oligomer with the percentage of the number of reactive silicon groups to the number of molecular chain terminals as determined by
1
H-NMR analysis being not less than 85% and (II) 1 to 500 parts by weight of a plasticizer.
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the present invention is described in detail.
The reactive silicon group-containing polyether oligomer (I) to be used in the curable composition of the present invention has a percentage of the number of reactive silicon groups to the number of molecular chain terminals as determined by
1
H-NMR analysis which is not less than 85%.
The reactive silicon group as so referred to herein has at least one hydroxyl group and/or hydrolyzable group bound to a silicon atom and capable of being crosslinked by a mutual condensation reaction to form a siloxane bond. While the above group is not particularly restricted, those groups which are representedby the general formula (1) shown below, for instance, may be mentioned as particularly preferred ones:
—(Si (R
1
2−b
)(X
b
)O)
m
Si(R
2
3−a
)X
a
  (1)
wherein, R
1
and R
2
are the same or different and each represents an alkyl group containing 1 to 20 carbon atoms, an aryl group containing 6 to 20 carbon atoms, an aralkyl group containing 7 to 20 carbon atoms or a triorganosiloxy group of the formula (R′)
3
SiO—, in which the three R′ groups are the same or different and each is a monovalent hydrocarbon group containing 1 to 20 carbon atoms, and when there are two or more R
1
or R
2
groups, they may be the same or different; X represents a hydroxyl group or a hydrolyzable group and, when there are two or more X groups, they may be the same or different; a represents 0, 1, 2 or 3, b represents 0, 1 or 2 and the b's in the m-Si(R
1
2−b
)(X
b
)—O— groups may be the same or different; m represents an integer of 0 to 19; with the condition that the relation of a +&Sgr;b≧1 is satisfied.
As specific examples of R
1
and R
2
in the above general formula (1), there may be mentioned, among others, alkyl groups such as methyl and ethyl, cycloalkyl groups such as cyclohexyl, aryl groups such as phenyl, aralkyl groups such as benzyl, and triorganosiloxy groups represented by (R′)
a
SiO— in which R′ is, for example, methyl or phenyl. Among them, methyl is particularly preferred as R
1
, R
2
and R′.
Among the groups represented by X, the hydrolyzable group is not particularly restricted but may be any known hydrolyzable group. Specifically, there may be mentioned a hydrogen atom, halogen atoms, alkoxy groups, acyloxy groups, ketoximate groups, amino groups, amido groups, acid amide groups, aminooxy groups, mercapto groups, alkenyloxy groups and the like. Among these, alkoxy groups such as methoxy, ethoxy, propoxy and isopropoxy are preferred because of their mild hydrolyzability and ease of handling.
One to three hydroxyl groups and/or hydrolyzable groups may be bound to one silicon atom and the sum (a+&Sgr;b) is preferably 1 to 5. When two or more hydroxyl and/or hydrolyzable groups occur in the reactive silicon group, they may be the same or different.
The number of silicon atoms in the reactive silicon group may be one or two or more. In cases where the reactive silicon group involves silicon atoms joined together via siloxane bonding or the like, the number of silicon atoms may be up to about 20.
Preferred because of their ready availability are those reactive silicon groups represented by the general formula (8):
—Si(R
2
3−a
)Xa  (8)
wherein R
2
, X and a are as defined above in relation to the general formula (1).
The above reactive silicon group may occur as a side chain internally within the polyether molecule chain or at a terminal thereof. For use as sealants or the like for buildings and the like, it is particularly preferred that said group occur at a terminal of said chain. When the reactive silicon group occurs as an internal side chain, the effective size of network bonding of the polyether oligomer component contained in the cured product finally formed becomes small, hence the product tends to become a rubber-like one showing high elasticity modulus and low elongation. On the contrary, when the reactive silicon group occurs in the vicinity of a molecular chain terminal, the effective size of network bonding of the polyether oligomer component contained in the cured product finally formed becomes large, hence the product tends to become a rubber-like one showing high strength, high elongation and low elasticity modulus. Particularly when the reactive silicon group occurs at a terminal of the molecular chain, the effective size of network bonding of the polyether oligomer component contained in the cured product finally formed becomes maximum, and this is particularly favorable for sealant or like use for buildings where rubber elasticity with high elongation characteristics as tensile characteristics and with rich flexibility is desired.
While various methods are conceivable for the measurement of the percentage of introduction of such reactive silicon group, said percentage is determined, in the practice of the present invention, by
1
H-NMR analysis of the reactive silicon group-containing polyether oligomer (I). Thus, the reactive silicon group introduction percentage can be calculated by determining the proportion of the number of reactive silicon groups to the number of molecular chain terminals of polyether oligomer as determined by
1
H-NMR analysis.
From the viewpoint of curability alone of the curable composition, it is sufficient if the number of reactive silicon groups is not less than 50% of the number of polyether oligomer terminals. For achieving improvements i

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