Fluorinated curable compositions

Details Fluorinated curable compositions Fluorinated curable compositions

2000-09-01

2002-07-02

Dawson, Robert (Department: 1712)

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

Synthetic resins

At least one aryl ring which is part of a fused or bridged...

C524S261000, C525S478000, C525S479000, C528S015000, C528S025000, C528S031000, C528S042000

Reexamination Certificate

active

06414062

ABSTRACT:

This invention relates to fluorinated curable compositions which are effectively vacuum deaeratable and foam breakable, cure into gel products having improved chemical and solvent resistance, and are suited for the potting, sealing and coating of electric and electronic parts.
BACKGROUND OF THE INVENTION
Cured gel products of silicone rubber have good electrically and thermally insulating properties, stable electric properties and flexibility. They are useful as potting and sealing compounds for electric and electronic parts, and coating compounds for protecting control circuit devices such as power transistors, ICs and capacitors from external, thermal and mechanical damages.
Typical silicone rubber composition examples forming such cured gel products are organopolysiloxane compositions of the addition curing type. The organopolysiloxane compositions of the addition curing type are known, for example, from JP-A 56-143241, 62-3959, 63-35655 and 63-33475 as comprising an organopolysiloxane having a vinyl group attached to a silicon atom and an organohydrogenpolysiloxane having a hydrogen atom attached to a silicon atom, wherein crosslinking reaction takes place in the presence of a platinum group catalyst to form a silicone gel.
However, silicon gels resulting from such organopolysiloxane compositions of the addition curing type are prone to degradation or swelling upon exposure to such chemicals as strong bases and strong acids or such solvents as toluene, alcohols and gasoline, often failing to maintain their performance.
As one solution to this problem, JP-A 11-116685 discloses a fluorochemical gel composition comprising a polyfluoro compound having two alkenyl groups and a divalent perfluoroalkylene or perfluorooxyalkylene group in a molecule, an organohydrogenpolysiloxane having a hydrogen atom attached to a silicon atom, and a platinum group catalyst as well as a fluorochemical gel product resulting from curing thereof. This cured fluorochemical gel product exhibits better chemical and solvent resistance as desired than ordinary silicone gels. However, there is a drawback that when the potting compound is fed around an electric or electronic part and kept in vacuum for removing air therefrom, it can spill over the electric or electronic part package due to foaming.
SUMMARY OF THE INVENTION
An object of the invention is to provide a fluorinated curable composition which is effectively vacuum deaeratable and foam breakable and cures into a gel product having improved chemical and solvent resistance.
It has been found that by using a linear polyfluoro compound having at least two alkenyl groups of the following general formula (1) and another linear polyfluoro compound having one alkenyl group of the following general formula (2) as base components and formulating therewith an organosilicon compound having at least two hydrosilyl groups in a molecule, a platinum group catalyst, and a fluorinated organopolysiloxane, there is obtained a fluorinated curable composition which is effectively vacuum deaeratable and foam breakable and cures into a gel product having improved chemical and solvent resistance.
Specifically, the invention provides a fluorinated curable composition comprising as main components, (A) a linear polyfluoro compound of the following general formula (1):
 CH
2
═CH—(X)
a
—Rf
1
—(X)
a
—CH═CH
2
  (1)
wherein X is independently —CH
2
—, —CH
2
O—, —CH
2
OCH
2
— or —Y—NR
1
—CO— wherein Y is —CH
2
— or
and R
1
is hydrogen or a substituted or unsubstituted monovalent hydrocarbon group, Rf
1
is a divalent perfluoroalkylene or perfluorooxyalkylene group, and “a” is independently equal to 0 or 1,
(B) a linear polyfluoro compound of the following general formula (2):
Rf
2
—(X)
a
—CH═CH
2
  (2)
wherein X and “a” are as defined above, and Rf
2
is a monovalent perfluoroalkyl or perfluorooxyalkyl group,
(C) an organosilicon compound having at least two hydrosilyl groups in a molecule,
(D) a platinum group catalyst, and
(E) a fluorinated organopolysiloxane.
DESCRIPTION OF THE PREFERRED EMBODIMENT
In the fluorinated curable composition of the invention, component (A) is a linear polyfluoro compound of the following general formula (1).
CH
2
═CH—(X)
a
—Rf
1
—(X)
a
—CH═CH
2
  (1)
Herein X is independently —CH
2
—, —CH
2
O—, —CH
2
OCH
2
— or —Y—NR
1
—CO— wherein Y is —CH
2
— or
and R
1
is hydrogen or a substituted or unsubstituted monovalent hydrocarbon group. Rf
1
is a divalent perfluoroalkylene group or divalent perfluorooxyalkylene group. Letter “a” is independently equal to 0 or 1.
In formula (1), Rf
1
is a divalent perfluoroalkylene group or divalent perfluorooxyalkylene group. The preferred divalent perfluoroalkylene groups are of the formula: —C
m
F
2m
— wherein m is an integer of 1 to 10, preferably 2 to 6. The preferred divalent perfluorooxyalkylene or
perfluoropolyether groups are of the following formulae:
wherein Y is F or CF
3
, p, q and r are integers satisfying p≧1, q≧1, 2≦p+q≦200, especially 2≦p+q≦110, and 0≦r≦6;
wherein r, s and t are integers satisfying 0≦r≦6, s≧0, t≧0, 0≦s+t≦200, especially 2≦s+t≦110;
wherein Y is F or CF
3
, u and v are integers satisfying 1≦u≦100 and 1≦v≦50;
—CF
2
CF
2
&Parenopenst;OCF
2
CF
2
CF
2
&Parenclosest;
w
OCF
2
CF
2
—
wherein w is an integer in the range of 1≦w≦100.
Illustrative examples of Rf
1
are given below.
—C
4
F
8
—, —C
6
F
12
—,
—CF
2
CF
2
OCF
2
(CF
2
)
2
CF
2
OCF
2
CF
2
—,
—CF
2
(OCF
2
CF
2
)
n
(OCF
2
)
m
OCF
2
—{overscore (n)}=1~100, {overscore (m)}=1 to 100,
—CF
2
CF
2
(OCF
2
CF
2
CF
2
)
n
OCF
2
CF
2
—{overscore (n)}=5 to 100
In formula (1), X is independently —CH
2
—, —CH
2
O—, —CH
2
OCH
2
— or —Y—NR
1
—CO—. Herein Y is —CH
2
— or a group of the following formula.
R
1
is hydrogen or a substituted or unsubstituted monovalent hydrocarbon group. The monovalent hydrocarbon groups preferably have 1 to 12 carbon atoms, more preferably 1 to 10 carbon atoms. Illustrative are unsubstituted monovalent hydrocarbon groups, for example, alkyl groups such as methyl, ethyl, propyl, butyl, hexyl, cyclohexyl and octyl, aryl groups such as phenyl and tolyl, and aralkyl groups such as benzyl and phenylethyl, and substituted monovalent hydrocarbon groups obtained by replacing some or all of the hydrogen atoms in the foregoing groups by halogen atoms such as fluorine.
The alkenyl groups in formula (1) are preferably vinyl, allyl and analogous groups having a —CH═CH
2
structure at the end. The alkenyl groups may be bonded to opposite ends of the backbone directly or via divalent linkage groups represented by X.
In formula (1), letter “a” is independently equal to 0 or 1.
Component (B) is a linear polyfluoro compound of the following general formula (2).
Rf
2
—(X)
a
—CH═CH
2
  (2)
Herein X and “a” are as defined above, and Rf
2
is a monovalent perfluoroalkyl group or monovalent perfluorooxyalkyl group.
In formula (2), Rf
2
is a monovalent perfluoroalkyl group or monovalent perfluorooxyalkyl group. The preferred monovalent perfluoroalkyl groups are of the formula: C
m
F
2m+1
— wherein m is an integer of 1 to 20, preferably 2 to 10. The preferred monovalent perfluorooxyalkyl or perfluoropolyether groups are of the following formulae:
wherein p is an integer of at least 1, and
wherein q is an integer of at least 1.
Illustrative examples of Rf
2
are given below.
C
4
F
9
—, C
8
F
17
—,
In formula (2), X and “a” are as defined in formula (1). It is understood that X and “a” in formula (1) may be identical with or different from X and “a” in formula (2), respectively.
Like component (A), the alkenyl group in formula (2) is preferably a vinyl, allyl or analogous group having a —CH═CH
2
structure at the end. The alkenyl group may be bonded to the backbone directly or via a divalent linkage group represented by X.
The composition of the invention should preferably have an appropriate flow and maintain adequate physical properties upon

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