Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Mixing of two or more solid polymers; mixing of solid...
Reexamination Certificate
2000-01-18
2001-06-26
Dawson, Robert (Department: 1712)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Mixing of two or more solid polymers; mixing of solid...
C524S706000, C524S711000, C524S745000, C524S777000, C524S537000, C524S588000, C528S026000, C528S371000
Reexamination Certificate
active
06252013
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a method for making siloxane copolycarbonates. More particularly, the present invention relates to a melt condensation polymerization method for making siloxane copolycarbonates.
Siloxane copolycarbonates and methods for their production have been studied extensively throughout the years. Siloxane copolycarbonates are well known thermoplastic resins which have good flow and mold release characteristics in injection molding applications. The synthetic method commonly used to make siloxane copolycarbonates is an interfacial phosgenation process.
The interfacial phosgenation process, as described by Phelps et al. in U.S. Pat. No. 5,530,083, involves reacting an aromatic dihydroxy compound, phosgene and catalyst with a hydroxyaryl terminated diorganopolysiloxane. This method successfully integrates siloxane monomers into copolycarbonates. Unfortunately, the interfacial phosgenation process uses chemically hazardous phosgene and an environmentally hazardous chlorinated solvent.
Melt condensation polymerization is a well known process for the production of polymers such as copolycarbonates. This method has yet to be utilized to produce siloxane copolycarbonates. During the typical melt process, severe decomposition of the siloxane chain occurs via siloxane chain scission followed by siloxane depolymerization to give cyclic siloxanes such as dimethylsiloxane cyclic tetramer (D
4
). The degradation of the siloxane chain inhibits the production of siloxane copolycarbonates and thus, this method is not utilized to produce siloxane copolycarbonates.
Due to environmental concerns with the interfacial method and the degradation of the siloxane chain with the melt condensation polymerization method, new methods of synthesizing siloxane copolycarbonates are constantly being sought.
BRIEF SUMMARY OF THE INVENTION
This invention provides a melt polymerization method for preparing a siloxane copolycarbonate comprising the reaction of an aromatic dihydroxy compound, carbonic acid diester, hydroxyaryl terminated polydiorganosiloxane and catalyst with a salt. The salt in aqueous solution at about 0.1 molar has a pH in a range between about 0 and about 7.
DETAILED DESCRIPTION OF THE INVENTION
It has been found that the melt condensation polymerization method can be used in the preparation of siloxane copolycarbonates by use of an acidic or neutral salt. Without the presence of an acidic or neutral salt, the siloxane chain of the hydroxyaryl terminated polydiorganosiloxane typically decomposes. In addition, the siloxane chain of the hydroxyaryl terminated polydiorganosiloxane depolymerizes to produce cyclic silicones. The addition of the salt effectively keeps the siloxane chain intact and a siloxane polycarbonate is successfully prepared.
Salts typically used with the present invention include, but are not limited to, salts of halo-acids as well as salts of non-volatile acids. Salts of halo-acids are an alkali or alkali earth metal salt of hydrochloric acid, hydrobromic acid, or hydroiodic acid. Salts of non-volatile acids are alkali or alkali earth metal salts of phosphorus acid, phosphoric acid, sulfur acid, and lower oxo-acid salts of sulfur acids such as sulfite acid. Salts of non-volatile acids include phosphate salts, phosphite salts, sulfate salts, sulfite salts, and salts of chelating type carboxylic acids such as EDTA. Typical salts used are phosphate salts, cesium salts, sodium salts, halide salts and combinations thereof. The salt in aqueous solution at about 0.1 molar has a pH in a range between about 0 and about 7. Preferably, the salt in aqueous solution at about 0.1 molar has a pH in the range between about 5 and about 6.
Typical catalysts employed in the melt condensation polymerization process include, but are not limited to, alkali metal compounds, alkaline earth metal compounds, quaternary ammonium compounds and combinations thereof.
Useful alkali metal compounds as catalysts include sodium hydroxide, potassium hydroxide, lithium hydroxide, sodium hydrogencarbonate, potassium hydrogencarbonate, lithium hydrogencarbonate, sodium carbonate, potassium carbonate, lithium carbonate, sodium acetate, potassium acetate, lithium acetate, sodium stearate, potassium stearate, lithium stearate, sodium borohydride, lithium borohydride, sodium borophenolate, sodium benzoate, potassium benzoate, lithium benzoate, disodium hydrogenphosphate, dipotassium hydrogenphosphate, dilithium hydrogenphosphate, disodium, dipotassium and dilithium salts of biphenol A and sodium, potassium, and lithium salts of phenol.
Useful alkaline earth metal compounds as catalysts include calcium hydroxide, barium hydroxide, magnesium hydroxide, strontium hydroxide, calcium hydrogen carbonate, barium hydrogencarbonate, magnesium hydrogencarbonate, strontium hydrogencarbonate, calcium carbonate, barium carbonate, magnesium carbonate, strontium carbonate, calcium acetate, barium acetate, magnesium acetate, strontium acetate, calcium stearate, barium stearate, magnesium stearate, and strontium stearate.
Useful quaternary ammonium compounds as catalysts include tetraalkylammonium compounds such as tetramethylammonium hydroxide and tetraethylammonium hydroxide.
Preferred catalysts include tetramethylammonium hydroxide, sodium hydroxide and mixtures thereof.
The salts are typically added in the beginning stages of the melt condensation polymerization process. Most typically, the salts are added before the temperature of the reactor reaches about 100° C. due to the degradation of the siloxane chains above this temperature. The salts can be added in any convenient forms, such as in the form of a solution or in the form of a solid.
Carbonic acid diesters are of the general formula, R
2
(CO
3
) wherein R is an alkyl or aryl group. Typical examples of carbonic acid diesters include, but are not limited to, diphenyl carbonate, ditolyl carbonate, bis(chlorophenyl) carbonate, m-cresyl carbonate, dinaphthyl carbonate, diethyl carbonate, dimethyl carbonate, dibutyl carbonate, dicyclohexyl carbonate and combinations thereof. The carbonic acid diester most typically used is diphenyl carbonate.
Some of the hydroxyaryl terminated polydiorganosiloxanes which can be used in the practice of the invention, are phenol-siloxanes included within formula I,
where R is selected from hydrogen, and wherein each R is independently the same or different radical selected from halogen, C
(1-8)
alkoxy, C
(1-8)
alkyl and C
(6-13)
aryl, R
1
is a C
(2-8)
divalent aliphatic radical, R
2
is independently selected from the same or different C
(1-13)
monovalent organic radicals, and n is an integer in a range between about 1 and about 100 inclusive and has an average value in a range between about 10 and about 100 inclusive. Preferably, n has a value in a range between about 5 and about 75, and more typically, n has a value in a range between about 10 and about 60.
The hydroxyaryl terminated polydiorganosiloxane can be made by effecting a platinum catalyzed addition between a siloxane hydride of formula II,
and an aliphatically unsaturated monohydric phenol where R
2
and n are as previously defined. Examples of a similar procedure is disclosed in U.S. Pat. No. 5,357,022 and U.S. Pat. No. 5.530,083.
Some of the radicals included within R in the formula I are halogen radicals, such as bromo, and chloro; alkyl radicals such as methyl, ethyl and propyl; alkoxy radicals such as methoxy, ethoxy and propoxy; aryl radicals such as phenyl, chlorophenyl, and tolyl. Radicals included within R
1
are, for example, dimethylene, trimethylene, and tetramethylene. Radicals included within R
2
are, for example, C
(1-8)
alkyl radicals, haloalkyl radicals such as trifluoropropyl and cyanoalkyl radicals; and aryl radicals such as phenyl, chlorophenyl and tolyl. R
2
is preferably methyl, or a mixture of methyl and trifluoropropyl, or a mixture of methyl and phenyl.
Some of the aliphatically unsaturated monohydric phenols, which can be used to make the hydroxyaryl terminated polydiorganosiloxanes are, for exam
Banach Timothy Edward
Davis Gary Charles
McCloskey Patrick Joseph
Smigelski, Jr. Paul Michael
Bennett Bernadette M.
Dawson Robert
General Electric Company
Ingraham Donald S.
Zimmer Marc S.
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