Curable compositions

Details Curable compositions Curable compositions

1999-02-23

2001-04-17

Dawson, Robert (Department: 1712)

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

Synthetic resins

From silicon reactant having at least one...

C528S030000, C528S033000, C528S034000, C528S036000, C528S037000, C528S038000, C556S413000, C556S450000, C556S457000, C556S458000, C556S459000, C556S464000

Reexamination Certificate

active

06218499

ABSTRACT:

This invention relates to curable compositions of the condensation curing type which yield fluorine-modified silicone rubber.
BACKGROUND OF THE INVENTION
Silicone rubber compositions of the condensation curing type comprising an organopolysiloxane terminated with Si—OH groups as a base polymer and a silicon compound having a hydrolyzable group such as vinyltriacetoxysilane and vinyltriisopropenoxysilane as a crosslinking agent are used in a variety of applications. Such curable silicone rubber compositions of the one package type cure through the mechanism that condensation reaction takes place between Si—X groups (wherein X is typically acetoxy or isopropenoxy) in the crosslinking agent and Si—OH groups at the terminus of the base polymer to form siloxane bonds and then, excessive Si—X groups undergo hydrolytic condensation reaction under the action of moisture in the ambient atmosphere. In two package type compositions wherein the amount of the crosslinking agent used is equivalent to the amount of Si—OH groups at the terminus of the base polymer, curing can be completed solely by the condensation reaction between Si—OH groups and Si—X groups. In this case, moisture in the ambient atmosphere is not particularly required.
Also known from JP-A 234923/1994 is a fluorine-modified silicone rubber composition of the condensation curing type comprising an oily base polymer in the form of a fluorinated polyether having Si—OCH
3
groups incorporated at its terminus. More particularly, this composition contains a compound of the following formula as the main component and cures through hydrolytic condensation of Si—OCH
3
groups with moisture in the ambient atmosphere.
The resulting fluorine-modified silicone rubber is superior with respect to solvent resistance, chemical resistance, and stain resistance, as compared with prior art silicon rubber based on dimethylpolysiloxane. This silicone rubber, however, has the drawbacks that its moisture permeability is low because it is a polymer having a high fluorine content and that curing to the depth takes a long time because moisture in the ambient atmosphere is requisite for curing.
SUMMARY OF THE INVENTION
An object of the present invention is to provide a novel and improved curable composition of the condensation curing type, typically fluorine-modified silicone rubber composition, which is curable at room temperature without a need for moisture.
We have found that a novel fluorinated polyether having Si—OH groups at both ends is obtained by subjecting a fluorinated polyether having ethylenically unsaturated groups at both ends and an organic silicon compound having at least two Si—H groups in a molecule to addition reaction (or hydrosilylation reaction) in the presence of a catalyst to produce a fluorinated polyether having Si—H groups at both ends, then subjecting the fluorinated polyether having Si—H groups at both ends and H
2
O to dehydrogenation reaction in the presence of a catalyst to convert the Si—H groups to Si—OH groups; or by subjecting a fluorinated polyether having ethylenically unsaturated groups at both ends and an organic silicon compound having both Si—H and Si—X groups in a molecule (wherein X is a hydrolyzable group) to addition reaction to produce a fluorinated polyether having Si—X groups at both ends, then effecting hydrolysis to convert the Si—X groups to Si—OH groups. When the novel fluorinated polyether having Si—OH groups at both ends is used as the base polymer, there is obtained a fluorine-modified silicone rubber composition which is fully curable to the deep interior even in the absence of moisture. The present invention is predicated on this finding.
According to the present invention, there is provided a curable composition comprising (A) a fluorinated organic silicon compound of the following general formula (1), (B) an organic silicon compound of the following general formula (5), (6) or (7), and (C) a condensation accelerator.
Z—R
1
—Rf—R
1
—Z  (1)
In formula (1), Rf is a divalent fluorinated polyether group. R
1
is a substituted or unsubstituted divalent hydrocarbon group which may be separated by at least one atom selected from the group consisting of oxygen, nitrogen, silicon and sulfur atoms, and which may contain an amide or sulfonamide bond. Z is a group of the following general formula (2), (3) or (4):
wherein R
2
, R
3
, and R
4
are independently monovalent organic groups, letters b and c each are equal to 1, 2 or 3, and d is an integer of 0 to 3.
In formulae (5) to (7), Y is a monovalent organic group selected from the group consisting of CH
3
—, C
2
H
5
—, C
3
H
7
—, CF
3
CH
2
—, CH
3
CO—, CH
2
═C(CH
3
)—, CH
3
CH
2
C(CH
3
)═N—,
(CH
3
)
2
N—, (C
2
H
5
)
2
N—, CH
2
═C(OC
2
H
5
)—, and (CH
3
)
2
C═C(OC
8
H
17
)—. R
5
is a monovalent organic group. R
1
and Rf are as defined above. Letter e is equal to 2 or 3, f is equal to 1, 2 or 3, and g is equal to 2 or 3.


REFERENCES:
patent: 4973623 (1990-11-01), Haugsby et al.
patent: 5352752 (1994-10-01), Koike et al.
patent: 5705591 (1998-01-01), Matsuda et al.
patent: 399682 (1990-11-01), None
patent: 745604 (1996-12-01), None
European Search Report dated Oct. 20, 1999.

Affiliated with

Also associated with

Rating

Curable compositions does not yet have a rating. At this time, there are no reviews or comments for this patent.

If you have personal experience with Curable compositions, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Curable compositions will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFUS-PAI-O-2529273