Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – From phenol – phenol ether – or inorganic phenolate
Reexamination Certificate
2002-10-16
2004-08-24
Boykin, Terressa (Department: 1711)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
From phenol, phenol ether, or inorganic phenolate
C422S131000, C422S135000, C502S200000, C502S208000, C528S198000, C264S276000, C264S219000
Reexamination Certificate
active
06780961
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates to a method for the interfacial polymerization of oligomeric chloroformates to product polycarbonates. The invention further relates to an efficient process for the continuous interfacial polymerization of oligomeric chloroformates to yield an aromatic polycarbonate.
Polycarbonates, prized for their transparency, toughness and relatively low cost, are produced globally on a scale of well over a billion pounds annually. Given the importance of polycarbonates in the fiercely competitive worldwide materials marketplace it is not surprising that new and more efficient routes to polycarbonates are earnestly sought. Numerous methods for polycarbonate preparation are well known, particularly for aromatic polycarbonates such as bisphenol A polycarbonate. Aromatic polycarbonates have been, and are currently prepared by two principal routes, the “melt” method and the “interfacial” method. The interfacial method is characterized typically by the reaction of a bisphenol with phosgene under interfacial conditions, that is, conditions generally comprising reaction in a water immiscible solvent such as methylene chloride in the presence of an aqueous solution of an acid acceptor such as an alkali metal hydroxide and a catalyst which is typically a tertiary amine such as triethylamine or a tertiary amine in combination with one or more phase transfer catalysts, such as tetrabutylammonium bromide.
One variation on the interfacial approach to polycarbonate preparation has been the bischloroformate method, sometimes referred to as the “BCF” method, in which the chloroformate groups of a low molecular weight oligomeric chloroformate are selectively hydrolyzed under conditions such that, when the chloroformate group is hydrolyzed thereby affording a negatively charged oxygen atom linked to the oligomer, the negatively charged oxygen atom reacts with one of the remaining chloroformate groups at a rate substantially faster that the rate at which the chloroformate groups are undergoing hydrolysis. The result of this rate differential is that the oligomeric chloroformate undergoes chain extension and polycarbonate having sufficient molecular weight to be useful is produced. While substantial research effort has been expended in the development of this “BCF” approach to polycarbonate and impressive achievements brought about, there remain opportunities for further improvement of this process. For example, it would be highly desirable to provide a method in which an oligomeric chloroformate could be continuously converted to high molecular weight product polycarbonate, and, without recourse to resubjecting the product to additional phosgene beyond that employed in the preparation of the oligomeric polycarbonate, afford a product polycarbonate which contained only very low levels of hydroxy groups, starting monomer and chainstopper. Frequently, however, the “BCF” approach affords a product polycarbonate which has an undesirably high level of hydroxy groups, contains high levels of residual monomer and chainstopper, and is generally unsuited for use in the continuous manufacture of polycarbonate. The present invention solves these and other problems which until now have long inhered to the “BCF” approach to polycarbonate manufacture.
BRIEF SUMMARY OF THE INVENTION
In one aspect, the present invention provides a method of making an aromatic polycarbonate, said method comprising contacting under interfacial polymerization conditions a solution comprising an oligomeric chloroformate with an acid acceptor and a catalyst, said oligomeric chloroformate solution having a gross concentration of chloroformate groups, a total concentration of aromatic hydroxyl groups, and a net concentration of chloroformate groups, said net concentration of chloroformate groups being the difference between the gross concentration of chloroformate groups and the total concentration of aromatic hydroxyl groups, said net concentration of chloroformate groups having a value of greater than about 0.04 moles of chloroformate group per liter of said solution.
In another aspect, the present invention relates to polycarbonates prepared by the method of the present invention and articles comprising said polycarbonates.
DETAILED DESCRIPTION OF THE INVENTION
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 which follow, reference will be made to a number of terms which shall be defined to have the following meanings.
The singular forms “a”, “an” and “the” include plural referents unless the context clearly dictates otherwise.
“Optional” or “optionally” means that the subsequently described event or circumstance may or may not occur, and that the description includes instances where the event occurs and instances where it does not.
As used herein the term “polycarbonate” refers to polycarbonates incorporating structural units derived from one or more dihydroxy aromatic compounds and includes copolycarbonates and polyester carbonates.
As used herein, the term “melt polycarbonate” refers to a polycarbonate made by the transesterification of at least one diaryl carbonate with at least one dihydroxy aromatic compound.
“BPA” is herein defined as bisphenol A and is also known as 2,2-bis(4-hydroxyphenyl)propane, 4,4′-isopropylidenediphenol and p,p-BPA.
As used herein, the term “bisphenol A polycarbonate” refers to a polycarbonate in which essentially all of the repeat units comprise a bisphenol A residue.
As used herein, the term “product polycarbonate” refers to a polycarbonate product having a weight average molecular weights, M
w
, greater than 15,000 daltons.
As used herein, “oligomeric” indicates a polymeric species having multiple repeat units and a weight average molecular weights, M
w
, less than 15,000 daltons.
As used herein the term “percent endcap” refers to the percentage of polycarbonate chain ends which are not hydroxyl groups. In the case of bisphenol A polycarbonate prepared from diphenyl carbonate and bisphenol A, a “percent endcap” value of about 75% means that about seventy-five percent of all of the polycarbonate chain ends comprise phenoxy groups while about 25% of said chain ends comprise hydroxyl groups. The terms “percent endcap” and “percent endcapping” are used interchangeably.
As used herein, the terms “chainstopper”, “chainstopping agent”, “endcapping agent” and “endcap” have the same meaning and refer to a monofunctional species such as p-cumylphenol used to control the molecular weight of a product polycarbonate during the polymerization reaction in which the product polycarbonate is formed.
As used herein, the terms “hydroxy group” and “hydroxyl group” have the same meaning and refer to an OH group attached to an organic molecule which may have any molecular weight in a range between the molecular weight of methanol and that of the highest molecular weight polycarbonates achievable. Typically, as used herein, the terms refer to OH groups which are attached to the starting oligomeric chloroformate, or OH groups which are attached to the product polycarbonate.
As used herein the term “aromatic radical” refers to a radical having a valence of at least one and comprising at least one aromatic ring. Examples of aromatic radicals include phenyl, pyridyl, furanyl, thienyl, naphthyl, phenylene, and biphenyl. The term includes groups containing both aromatic and aliphatic components, for example a benzyl group, a phenethyl group or a naphthylmethyl group. The term also includes groups comprising both aromatic and cycloaliphatic groups for example 4-cyclopropylphenyl and 1,2,3,4-tetrahydronaphthalen-1-yl.
As used herein the term “aliphatic radical” refers to a radical having a valence of at least one and consisting of a linear or branched array of atoms which is not cyclic. The array may include heteroatoms such as nitrogen, sulfur and oxygen or may be composed exclusively of carbon and hydrogen. Example
Bui Pierre-Andre
Dardaris David Michel
Fyvie Thomas Joseph
Silva James Manio
Boykin Terressa
Caruso Andrew J.
General Electric Company
Patnode Patrick K.
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