Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – From silicon reactant having at least one...
Reexamination Certificate
2002-10-31
2004-06-15
Robertson, Jeffrey B. (Department: 1712)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
From silicon reactant having at least one...
C528S012000, C528S025000, C528S032000, C528S037000, C528S041000, C525S474000, C525S479000
Reexamination Certificate
active
06750308
ABSTRACT:
FIELD OF TECHNOLOGY OF THE INVENTION
This invention relates to silicone resin compositions and to molded products of silicone resin that are tridimensionally crosslinked products of said silicone resin compositions. Silicone resin compositions yield transparent materials which are lightweight and highly impact-resistant and are suitable for optical applications such as lenses, optical disks, optical fibers and bases for flat panel displays and for window materials for automobiles and houses.
BACKGROUND TECHNOLOGY
Among heat-curable plastics, silicone resins show excellent resistance to heat, weather and water and possess high potentialities of becoming substitutes for inorganic glasses. In particular, polyorganosilsesquioxanes of a ladder structure are known to be comparable to polyimides in heat resistance.
Examples of polyorganosilsesquioxanes include cage-type octaphenylsilsesquioxane prepared by hydrolyzing phenyltrichlorosilane in an organic solvent to phenyltrihydroxysilane and heating the phenyltrihydroxysilane in a water-free solvent in the presence of an alkaline rearrangement and condensation catalyst to effect polycondensation, phenylsilsesquioxane prepolymers of low intrinsic viscosity prepared by separating said cage-type octaphenylsilsesquioxane and polymerizing it again under heat in the presence of an alkaline rearrangement and condensation catalyst and phenylsilsesquioxane polymers of high intrinsic viscosity prepared by polymerizing the prepolymers again in the presence of an alkaline rearrangement and condensation catalyst and the processes for preparing them are disclosed in JP40-15989 B, JP50-139900 A and J. Polymer Sci. Part C, No. 1, pp. 83-97 (1963).
However, the siloxane linkage in silicone resins including the aforementioned polyorganosilsesquioxanes is highly flexible and, in order for silicone resins to manifest the modulus of elasticity required for structures, the crosslinking density of silicone resins must be increased. Now, an increase in crosslinking density causes a marked increase in curing shrinkage which undesirably renders the molded product brittle. Moreover, the residual stress increases as a result of curing shrinkage and this makes it extremely difficult to mold thick-walled products. For these reasons, silicone resins of high crosslinking density are limited to coatings in their applications and, under existing conditions, it is only silicone rubbers of low crosslinking density that are used for molding applications.
In order to solve the aforementioned problems, copolymerization of silicone resins with acrylic resins of good molding proccessability is proposed. For example, in the case of nonladder-type silicone resins, a technique for copolymerizing an acrylic polymer having alkoxysilyl side chains and an alkoxysilane to form a hybrid composed of an acrylic polymer as organic constituent and polysiloxane as inorganic constituent is disclosed in the Journal of the Chemical Society of Japan, 571-580 (1998). Silicone resins, however, are intrinsically not sufficiently compatible with acrylic resins and there are many cases where optical properties such as light transmission are adversely affected even when the mechanical strength presents no problem.
In order to solve the aforementioned problems in the case of ladder-type silicone resins, polyorganosilsesequioxanes to which reactive functional groups have been introduced as part of side chains are known for the purpose of copolymerizing them with organic compounds having reactive functional groups. Moreover, polyorganosilsesquioxanes in which the hydrogen atoms of the silanol groups are wholly or partly replaced by triorganosily groups are disclosed in EP0516144A1 and elsewhere and the preparation of most of such ladder-type polyorganosilsesquioxanes has a primary objective of improving storage stability by deactivating the terminal silanol groups or controlling the molecular weight of polyorganosilsesquioxanes by adding a silylating agent to terminate the polycondensation of polyorganosilsesquioxanes, that is, a primary objective of end capping.
The end capping is effected in a number of ways as follows: polyorganosilsesquioxane containing the unreacted silanol groups is first synthesized and then treated with a triorganochlorosilane in the presence of an alkaline catalyst such as pyridine to effect dehydrochlorination; similarly, polyorganosilsesquioxane containing silanol groups is treated with a triorganoisocyanatosilane; polyorganosilsesquioxane containing terminal hydroxyl groups is synthesized purposefully and treated with a triorganoalkoxysilane to effect dealkanolation or with a triorganomonochlorosilane to effect dehydrochlorination; hydroxyl-terminated polyorganosilsesquioxane is treated with disilazane. A method for trimethylsilylation based on the reaction of the terminal silanol or alkoxy group of methylsilsesquioxane with hexamethylsilane in the presence of an acid catalyst is described in JP7-70321 A.
As noted above, a variety of methods are known for introducing reactive functional groups as side chain or terminal group to ladder-type polyorganosilsesquioxane and almost all of these methods are based on the prior synthesis of ladder-type polyorganosilsesquioxane having side-chain or terminal hydroxyl groups (silanol groups) followed by the reaction of the hydroxyl groups with compounds containing reactive functional groups such as chlorosilanes, alkoxysilanes, isocyanatosilanes and disilazanes.
However, these ladder-type polyorganosilsesquioxanes, like the aforementioned nonladder-type silicone resins, are poorly compatible with acrylic resins or other organic compounds containing functional groups and, in case the two are copolymerized, deterioration of transparency occurs as a result of phase separation. Consequently, it is difficult to substitute products molded from compositions of the aforementioned polyorganosilsesquioxanes for inorganic glasses. Moreover, the synthesized polyorganosilsesquioxanes contain in their structure a small amount of silanol groups that made no contribution to the polymerization as defect or branched structure and this involves the problems of deterioration of mechanical and heat-resistant properties and loss of storage stability.
It is to be noted that the present applicant has proposed cage-type or ladder-type polyorganosilsesquioxanes containing reactive functional groups and a process for preparing the same in WO98/41566 (U.S. Pat. No. 6,284,858 B1).
DISCLOSURE OF THE INVENTION
Accordingly, an object of this invention is to provide a silicone resin composition which is capable of yielding a silicone resin copolymer of excellent transparency. Another object of this invention is to provide a silicone resin composition comprising a silicone resin and an unsaturated compound which is compatible and copolymerizable with the silicone resin. Still another object of this invention is to provide a silicone resin composition which contains no silanol groups as defect and branched structure and shows good storage stability. A further object of this invention is to provide a silicone resin copolymer which shows excellent heat resistance, transparency, water resistance and mechanical properties and is suitable for use as a substitute for inorganic glass and to provide a molded product thereof. A still further object of this invention is to provide a tridimensionally crosslinked silicone resin copolymer and a molded product thereof.
The silicone resin composition of this invention is formulated from a silicone resin comprising mainly polyorganosilsesquioxane which is represented by formula (1)
[RSiO
3/2
]
n
(1)
(wherein R is an alkyl group containing 1 to 6 carbon atoms or phenyl group) and contains a cage structure in its structural unit and the siloxy (SiO—) groups of which are at least partly linked to a triorganosilyl group represented by the following general formula (2)
(wherein X is a reactive functional group represented by a) —R
1
—OCO—CR
2
═CH
2
, b) —R
1
—CR
2
═CH
2
or c) —CH═CH
2
, R
1
is an alk
Andoh Hideki
Isozaki Masayoshi
Teramoto Takero
Nippon Steel Chemical Co. Ltd.
Rader & Fishman & Grauer, PLLC
Robertson Jeffrey B.
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