Curable composition

Details Curable composition Curable composition

2000-03-27

2002-09-03

Dawson, Robert (Department: 1712)

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

Synthetic resins

From silicon reactant having at least one...

C524S742000, C528S015000, C528S017000, C528S018000, C528S021000, C528S025000, C528S031000, C528S035000, C528S901000

Reexamination Certificate

active

06444775

ABSTRACT:

TECHNICAL FIELD
The present invention relates to a curable composition comprising a reactive silicon group-containing polyether oligomer and a silanol condensation catalyst.
BACKGROUND ART
The room temperature curing composition comprising a reactive silicon group-containing polyether oligomer and a silanol condensation catalyst is known and has been used in the field of sealants, adhesives and so on.
In WO 91/13928, there is disclosed a curable composition comprising a reactive silicon group-containing oxypropylene polymer, a tin(II) organocarboxylate and an organic amine, which is intended for improving reversion characteristic of a cured product.
Japanese Kokai Publication Hei-5-125272 discloses a curable composition comprising a reactive silicon group-containing oxypropylene polymer and an organotin (IV) compound, which is designed for increasing curing rate.
The room temperature curing composition cures as it encounters moisture in the air and if the curing rate is too high, the curing reaction proceeds fast enough in the course of field work to interfere with workability. For improvement in workability, control of the curing rate is important and this control has heretofore been made by changing the catalyst species, increasing or decreasing the amount of the catalyst and/or modifying the terminal reactive silicon group.
However, when the curing rate is lowered by such procedures for improving workability, an excessive reduction in the curing rate results in unsatisfactory curing, such as poor curability and deteriorations in physical properties of the cured product. Thus, workability and curability could hardly be reconciled and adjustment of the curing rate for striking a balance between both properties has so far been made only on a trial-and-error basis.
SUMMARY OF THE INVENTION
The object of the present invention is to provide a curable composition showing a controlled initial curing rate and, hence, offering good workability by introducing a methyl group into the neighborhood of the reactive silicon group within an oligomer to indirectly lower the reactivity of the reactive silicon group within the oligomer.
Thus, the first aspect of the present invention is concerned with a curable composition comprising (A) a reactive silicon group-containing polyether oligomer and (B) a silanol condensation catalyst,
said (A) reactive silicon group-containing polyether oligomer having a partial structure of the following general formula (1) per molecule:
—O—R
1
—CH(CH
3
)—CH
2
—(Si(R
2
2−b
)(X
b
)O)
m
Si(R
3
3−a
)X
a
  (1)
wherein R
1
represents a divalent organic group containing 1 to 20 carbon atoms and one or more constituent atoms selected from the group consisting of hydrogen, oxygen and nitrogen; R
2
and R
3
may be 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—; when 2 or more R
2
or R
3
groups are present, they may be the same or different; R′ represents a monovalent hydrocarbon group containing 1 to 20 carbon atoms and three R′ groups may be the same or different; X represents a hydroxyl group or a hydrolyzable group and when two or more X groups are present, they may be the same or different; a represents 0, 1, 2 or 3; b represents 0, 1 or 2; b may be the same or different over m repeats of (Si(R
2
2−b
)(X
b
)O); m represents an integer of 0 to 19; provided, however, that the relation of a+&Sgr;b≧1 is satisfied.
The preferred embodiment is the above curable composition wherein R
1
in (A) represents CH
2
.
Another preferred embodiment is the above-mentioned curable composition
wherein said (A) reactive silicon group-containing polyether oligomer has a partial structure of the following formula per molecule:
—O—CH
2
—CH(CH
3
)—CH
2
—Si(CH
3
)(OCH
3
)
2
A still another preferred embodiment is the above-mentioned curable composition
wherein said (A) reactive silicon group-containing polyether oligomer is obtainable by reacting a polyether oligomer having an unsaturated bond of the following general formula (2):
—O—R
1
—C(CH
3
)═CH
2
  (2)
R
1
is as defined above,
with a reactive silicon group-containing compound represented by the following general formula (3):
H—(Si(R
2
2−b
)(X
b
)O)
m
Si(R
3
3−a
)X
a
  (3)
R
2
, R
3
, a, b, m and X are as defined above,
in the presence of a catalyst and a sulfur compound in an oxygen-containing atmosphere.
A still another preferred embodiment is the above-mentioned curable composition
wherein said (A) reactive silicon group-containing polyether oligomer has a partial structure of the following formula:
—O—CH
2
—CH(CH
3
)—CH
2
—Si(CH
3
)(OCH
3
)
2
said (A) being obtainable by reacting a polyether oligomer having an unsaturated bond of the following formula:
—O—CH
2
—C(CH
3
)═CH
2
with a reactive silicon group-containing compound represented by the following formula:
H—Si(CH
3
)(OCH
3
)
2
in the presence of a catalyst and a sulfur compound in an oxygen-containing atmosphere.
A further preferred embodiment is the above-mentioned curable composition
wherein, in the reactive silicon group-containing polyether oligomer, the number of reactive silicon groups is not less than 85% of the number of molecular chain terminals.
DETAILED DESCRIPTION OF THE INVENTION
The present invention is now described in detail. The reactive silicon group-containing polyether oligomer for use as the component (A) in the present invention may be any polyether oligomer having a polyether main chain and, in a side chain thereof or in a terminal position thereof, at least one partial structure of the following general formula (1):
—O—R
1
—CH(CH
3
)—CH
2
—(Si(R
2
2−b
)(X
b
)O)
m
Si(R
3
3−a
)X
a
  (1)
wherein R
1
represents a divalent organic group containing 1 to 20 carbon atoms and one or more constituent atoms selected from the group consisting of hydrogen, oxygen and nitrogen; R
2
and R
3
may be 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—; when 2 or more R
2
or R
3
groups are present, they may be the same or different; R′ represents a monovalent hydrocarbon group containing 1 to 20 carbon atoms and three R′ groups may be the same or different; X represents a hydroxyl group or a hydrolyzable group and when two or more X groups are present, they may be the same or different; a represents 0, 1, 2 or 3; b represents 0, 1 or 2; b may be the same or different over m repeats of (Si(R
2
2−b
)(X
b
)O); m represents an integer of 0 to 19; provided, however, that the relation of a+&Sgr;b≧1 is satisfied.
The reactive silicon group-containing oligomer heretofore in use has a reactive silicon group bound to an oligomer main chain through a straight-chain alkyleneoxy group such as —O—CH
2
—CH
2
—CH
2
— and, as such, tends to be too rapid in curing to provide for sufficient workability. In the present invention, the reactive silicon group is bound to the oligomer main chain through —O—R
1
—CH(CH
3
)—CH
2
—, a group having a side-chain methyl group. By providing a methyl side-chain in this manner, the curing rate can be controlled to provide a curable composition of improved workability.
R
1
represents a divalent organic group containing 1 to 20 carbon atoms and one or more constituent atoms of the group consisting of hydrogen, oxygen and nitrogen. As said divalent organic group, there can be mentioned —CH
2
—, —C
2
H
4
—, —C
3
H
6
—, —C
4
H
8
—, —C
5
H
10
—, —C
6
H
4
—, —C
6
H
12
—, —C
7
H
14
—, —C
8
H
16
—, —C
9
H
18
—, —C
10
H
20
—, —CH(CH
3
)—, —CH
2
—CH(CH
3
)—, —CH
2
—CH(CH
3
)—CH
2
—, —C
2
H
4
—CH(CH
3
)—, —CH
2
—C
6
H
4
—, —CH
2
—C
6
H
4
—CH
2
—, —C
2
H
4
—C
6
H
4
—, —C(O)—, —C(O)—CH
2
—, —C(O)—C
6
H
4
—, —C(O)—NH—, —C(O)—NH—CH
2
—, —C

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