Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Cellular products or processes of preparing a cellular...
Reexamination Certificate
1999-03-19
2001-08-07
Foelak, Morton (Department: 1711)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Cellular products or processes of preparing a cellular...
C521S091000, C521S092000, C521S093000, C521S122000, C521S123000, C521S124000, C521S134000, C521S154000
Reexamination Certificate
active
06271271
ABSTRACT:
DESCRIPTION OF ART
The present invention relates to the chemical technology, and in particular to the methods for obtaining the organosilicon compositions being foamed at the expense of gases liberated at chemical reactions of mixture components; the present invention may be used for production of elastomer foams having improved radiation resistance.
Prior Amount
The methods for obtaining foamed organosilicon compositions are well known in the art (U.S. Pat. No. 5,238,967).
Such known methods involved obtaining foamed organosilicon compositions by means of mixing the polymer base, comprising the “&agr;”, “&ohgr;”-dihydroxypolydiorganosiloxanes and foaming agents.
The organosilicon composites obtained by means of the known method are consolidated at room temperature, yet featuring insufficient mechanical strength and thermal resistance.
Such other methods for obtaining hi-strength thermal resistive elastomer materials on the basis of block-copolymers having linear/ladder structure (see High Molecular Compositions, V.XXX, #9, Moscow, 1988, pp. 1832-1836).
Yet the known amount of art does not comprise any data on usage of block-copolymers having linear/ladder structure as a polymer base of foamed organosilicon compositions.
The most close to the present Invention is the method for obtaining the foamed organosilicon compositions, involving the mixing of organosiloxane rubber, organosilicon joining agent and modifier (JP, A, 2-47158).
The known prior method involves usage of: vinyl containing poly organosiloxane as a organosiloxane rubber; polyorganohydridesiloxane with 0.3%-1.6% contents of SiH groups as a joining agent; and compositions containing hydroxyl groups as a modifier.
The known method provides to obtain the foamed organosilicon compositions having improved strength capacity. Yet the material produced according to the known method have high gassing rating at radiation exposure.
It is the basis of the present Invention to resolve a problem to produce light weight and strong organosilicon material resistive to the long-term radiation exposure.
The technical result of the present Invention lies in decrease of radiation gassing of foamed organosilicon compositions, obtained by means of mixing of organosiloxane rubber, organosilicon joining agent and modifier.
To the accomplishment of foregoing technical result and related ends the present Invention, then, consists in that in the method for production of foamed organosilicon compositions, involving the mixing of organosiloxane rubber, organosilicon joining agent and modifier, the polyorganosiloxane block-copolymers are used as organosiloxane rubber, having general formula as follows:
{[R
1
SiO
1.5
]
a
[R
2
(OH)SiO]
b
, [R
3
R
4
SiO]
c
}
n
,
having respective OH groups content from 0.2% to 4.0% and the ratio of R
3
R
4
SiO monomeric units to R
1
SiO
1.5
falling within the range 0.850-10,000, correspondingly, where: R
1
R
2
R
3
R
4
are aliphatic, aromatic radicals having from 1 to 6 atoms carbon; n is an integer from 30 to 360; c=1; a is selected from the 0.019-3.760 interval; b is selected from the 0.008-0.240 interval; or the mixture of the above block-copolymer with the “&agr;”, “&ohgr;”-dihydroxypolydiorganosiloxane in the ratio of (0.05-0.5):1, respectively; while the individual compositions or mixtures of polyorganohydridesiloxanes act as organosilicon joining agent, having a general formula as follows:
R
3
SiO[R
1
(II)SiO]
m
—[R
2
SiO]
n
SiR
3
,
having the weight contents of SiH groups falling within the range (0.35-1.80)%; average numeric value of M molecular mass limited by 50-200, where: R, R
1
is the lowest alkyl radical having from 1 to 6 atoms carbon; m is an integer from 1 to 2; n is an integer from 0 to 19; (m+n) sum equals 20, or at least one substance from the compositions having general formula as follows:
RSiX
3
, where:
R=alkyl radical having from 1 to 6 atoms carbon, CH
2
═CH—, X:—ON═C(CH
3
)
2
, —OC(O)—CII
3
,
and organosilicon amines are used as a modifier, having general formula as follows:
R
1
R
2
N—(CH
2
)
n
—Si(OR
3
)
3
, where:
R
1
═R
2
═H—, CH
3
—, C
2
H
5
—, R
3
═CH
3
—, C
2
H
5
—; n is an integer from 0 to 3, or the mixture of sodium bicarbonate with zinc oxide, or non-organic compound of cobalt with 34% cobalt content,
with the proviso of mass fraction ratio of mixed components as follows:
organosiloxane rubber: 100
organosilicon joining agent: 2-15
modifier: 2-22.
Various modifications may be made in performance of the method, provided the reasonable efforts are taken as follows:
to additionally introduce in the composition tin diethyldicaprylate in amount from 0.3 to 1.5 parts;
to additionally introduce in the composition the filler in amount from 5 to 150 parts;
at least one of the substances acting as a filler might be used from the group as follows: chalk, silica filler, airseal, titan dioxide;
the glass micro-spheres were implemented as a filler;
The aforementioned alternative modifications are unified with single inventory idea, comprising realization of conditions providing to use the block-copolymers having linear/ladder structure on obtaining the radiation resistant foamed organosilicon compositions. In so doing, the block-copolymers of linear/ladder organosiloxanes are used either as polymer base, or as admixture to the linear polyorganosiloxanes.
The process of composition foaming and consolidation occurs at ambient temperature through all the modification variants. The time of foaming and forming of surface film amounts from 1.0 to 40 minutes. The full solidification of foams takes no more 48 hours.
Broadly stated, in accordance with the present Invention, the Method for Obtaining Foamed Organosilicon Compositions consists in the following.
While using under the present method such components as polyorganosiloxanes with silicol terminal groups; type RSiX
3
joining agent and in particular methyltris(acetoxi)silane; and the modifier in a form of mixed sodium bicarbonate with zinc oxide, the process of foaming and consolidation is determined by the following factors.
The acetic acid is evolving resulting from partial interaction of polymer silicol groups and joining agent acetoxi-groups. The acid causes sodium bicarbonate disintegration, proceeding with CO
2
liberation, thus foaming the composition. Disintegration process is catalyzed with zinc oxide.
Attainment of required rates of composition solidification is provided by means of consolidation catalyzers' introduction in a form of tin diethyldicaprylate. On adding such substance, under effect of ambient (air) humidity, the reversible reaction is established, featuring tin diethyldicaprylate hydrolysis followed by formation of hydroxyl derivative tin, in turn reacting with methyltris(acetoxi)silane, further creating the tin organosilicon composition and liberation of additional amount of acetic acid. The reaction of tin organosilicon composition with other silicol polymer groups results in formation of foam elastomer spatial structure.
While using under the present method such components, as polyorganohydridesiloxane as joining agent; and the modifier in a form of non-organic compound of cobalt (with 34% cobalt content), the composition foaming and consolidation is determined by the process as follows.
The polyorganohydridesiloxane/cobalt compound interaction causes formation of non-stable interim complex. Such complex reacting with polymer silicol groups is disintegrated with CO
2
liberation accompanied with formation of transverse joints. Complex ligand comprising CO atoms builds in the joint node. In such a way foaming occurs along with practically simultaneous forming of spatial structure.
Using the combination of joining agent/polyorganohydridesiloxane (or mixture thereof) and a modifier in a form of organosilicon amines (or mixture thereof), the composition foaming is proceeded as follows.
H
2
evolves further to the interaction between rubber silicol groups and joining agent hydride groups. The reaction runs s
Belyaev Spartak Timofeevich
Gulko Piter
Kozodaeva Marina Mikhailovna
Kozodaeva Natalia Mikhailovna
Makarenko Igor Anatol'evich
Foelak Morton
Garrison David L.
Garrison & Associates PS
Obschestvennoe Ob'Edinenie “Euro Asian Physical Society”
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