Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – From silicon reactant having at least one...
Reexamination Certificate
2002-10-07
2004-03-16
Moore, Margaret G. (Department: 1712)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
From silicon reactant having at least one...
C528S027000, C528S031000
Reexamination Certificate
active
06706840
ABSTRACT:
BACKGROUND
The invention relates generally to a rapid, direct process for producing pure organosilicon compositions by hydrosilation of olefins and oxirane-containing olefins with silicon hydride groups by using extremely low levels of a platinum catalyst. Generally, hydrosilation catalysts are complexes of platinum, palladium, rhodium, iridium, iron or cobalt. Many of these transition metal hydrosilation catalysts also promote ring-opening polymerization of oxiranes in the presence of silicon hydrides. In this invention the hydrosilation reaction proceeds such that any oxirane rings in both the olefin and organosilicon product remain intact. Furthermore, the invention also relates to curable oxirane-containing siloxane (epoxysiloxane) compositions made by the above method. The ring-opening polymerization reaction during production of an oxirane-containing organosilicon composition may be undesirable as the oxirane polymerization may cause the reaction mixture to gel partially or completely, resulting in the loss of the entire batch and in loss of considerable time in cleanup of the insoluble gelled resin. Partial gelation due to the ring-opening polymerization reaction can occur during hydrosilations such that reproducible batch-to-batch viscosity of the oxirane-containing organosilicon product is difficult to obtain. Such reproducibility in viscosity is highly preferred in commercial applications of oxirane-containing organosilicon compositions and these materials may be used in applications such as coatings, and encapsulents and lens material for high luminosity light emitting diodes.
In some instances product oxirane-containing organosilicon compositions have been found to slowly gel on storage at room temperature in the presence of precious metal hydrosilation catalysts due to the oxirane ring-opening polymerization reaction, thus shortening the product shelf life. While this storage problem can be partially alleviated by deactivating the transition-metal-complex catalyst with an inhibitor, such as dodecyl mercaptan or 2-mercaptobenzothiazole in the case of platinum complexes, it would be preferable to not incorporate this extra component and additional process step into the process of producing the oxirane-containing organosilicon compositions. This storage problem can also be alleviated by ensuring complete consumption of the silicon hydride during the preparative process.
In general, careful control of batch temperature and oxirane-containing olefin feed rate during the synthesis, followed by the above-mentioned inactivation of the catalyst after the completion of the hydrosilation reaction is required in order to minimize the oxirane ring-opening polymerization reaction.
Certain hydrosilation catalysts containing phosphine ligands are known. For example, RhCl(PPh
3
)
3
(Wilkinson's catalyst) efficiently catalyzes the hydrosilation reaction between SiH-containing silanes and siloxanes and vinyl oxiranes. Other rhodium-based catalysts have been reported to selectively promote the hydrosilation reaction without the promotion of an oxirane ring-opening polymerization reaction. A variety of epoxy-functionalized silicone monomers and oligomers have been synthesized using these catalysts. However, most of the catalysts traditionally used in the hydrosilation reaction of oxirane-containing olefins, particularly Pt-containing catalysts, promoted the oxirane ring-opening polymerization reaction, and therefore did not permit the selective preparation of oxirane-containing organosilicon compositions by the hydrosilation route.
It is therefore desirable to provide an efficient method for hydrosilation to prepare organosilicon compositions in the presence of a catalyst in amounts which do not promote the oxirane ring-opening polymerization of either the olefin or the organosilicon product. Such a method will provide a means for preparing an oxirane-containing organosilicon composition having a reproducible viscosity and longer shelf life.
The present invention relates to a method for preparing an organosilicon composition, said method comprising:
preparing a mixture comprising:
at least one olefin;
at least one silicon compound comprising silicon hydride groups, said olefin and said silicon compound being present in amounts such that the mixture comprises at least one reactive double bond per Si—H group;
a hydrosilation catalyst comprising at least one platinum (II) complex having the formula:
PtL
2
X
2
,
wherein each L is independently selected from the group consisting of ER
3
, E(OR)
3
, and E(NR
2
)
3
; each E is independently selected from the group consisting of phosphorus, arsenic, and antimony; each R is independently a hydrocarbyl group; and each X is independently selected from the group consisting of chloride, bromide, and iodide; said hydrosilation catalyst being present in an amount corresponding to an amount of platinum, said amount of hydrosilation catalyst being such that the amount of platinum present in said mixture is in a range between about 1 part per billion to less than 1000 parts per billion relative to a total weight of a product organosilicon composition;
optionally at least one solvent; and
reacting the mixture in the presence of oxygen at a temperature in a range from about ambient temperature to about 300° C., to produce said product organosilicon composition.
In one aspect of the present invention, the amount of hydrosilation catalyst used is such that the amount of platinum present is equivalent to more than about 1 part per billion (ppb) platinum and less than 1000 ppb platinum, the amount of platinum in parts per billion being relative to the total weight of the product organosilicon composition.
In a further aspect, the present invention relates to organosilicon compositions prepared by the method of the invention. In one aspect the present invention relates to stable oxirane-containing organosilicon compositions prepared by the method of the present invention.
DETAILED DESCRIPTION
As used herein, elements of Groups of the Periodic Table are made in reference to the “Periodic Table of the Elements”, as published in “Chemical and Engineering News”, 63(5), 27, 1985, said Table being incorporated herein by reference. In this format, the Groups are numbered 1 to 18.
The present invention may be understood more readily by reference to the following detailed description of preferred embodiments of the invention and the examples included herein. In this specification and in the claims that follow, reference will be made to a number of terms, which are defined to have the following meanings.
The singular forms “a”, “an” and “the” include plural referents unless the context clearly dictates otherwise.
As used herein, the term “olefin” refers to a compound incorporating a carbon-carbon double bond.
As used herein the term “epoxyolefin” refers to an olefin, which also comprises an oxirane ring. Thus, 4-vinyl cyclohexene oxide is both an olefin and an epoxyolefin.
As used herein the term “silicon compound comprising silicon hydride groups” refers to a silicon compound comprising at least one SiH group. An example of a “silicon compound comprising hydride groups” is trimethylsilane (Me
3
SiH). Triphenylsilane is also an example of a “silicon compound comprising SiH groups” as is tetramethydisilane ((HSiMe
2
)
2
).
The term “silicon hydride” when used to describe a complete chemical compound has the same meaning as the term “silicon compound comprising silicon hydride groups”. The term “silicon hydride group” refers to the SiH moiety present in a “silicon compound comprising silicon hydride groups”. For example, trimethylsilane (Me
3
SiH) is a “silicon hydride” which contains a “silicon hydride group”, meaning that it contains an SiH moiety.
As used herein, the term “product organosilicon composition” refers to the product formed in a hydrosilation reaction between at least one “silicon compound comprising silicon hydride groups” as defined herein, and at least one “olefin” as defined herein.
The term “hydrocarbyl group”, as used herein, denotes a monoval
Caruso Andrew J.
General Electric Company
Moore Margaret G.
Patnode Patrick K.
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