Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – From phenol – phenol ether – or inorganic phenolate
Reexamination Certificate
2000-12-14
2003-06-10
Boykin, Terressa M. (Department: 1711)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
From phenol, phenol ether, or inorganic phenolate
C528S198000, C528S202000
Reexamination Certificate
active
06576739
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates to a general method of polycarbonate preparation applicable to the manufacture of polycarbonates from sterically hindered bisphenols and provides a means for preparing either high molecular weight polycarbonates or low molecular weight polycarbonate oligomers. In addition, the method further relates to a method of making symmetrical diaryl carbonates from sterically hindered phenols.
The preparation of polycarbonates via interfacial polymerization of a bisphenol upon treatment with phosgene is practiced commercially on a world wide basis. The major polycarbonate so produced is that prepared from bisphenol A. Polycarbonate is obtained upon treatment a mixture of bisphenol A in a water immiscible solvent, such as methylene chloride, with a slight excess of phosgene in the presence of an amine catalyst, such as triethylamine, and sufficient aqueous sodium hydroxide to complete the conversion of essentially all of the intermediate chloroformate groups to carbonate groups. Bisphenol A polycarbonate possesses many outstanding properties such as transparency, high impact strength and excellent molding properties but lacks many of the attributes of polycarbonates prepared from bisphenols more sterically hindered than bisphenol A. Such attributes include the high glass transition temperature and hydrolytic stability of polycarbonate prepared from 2,2-bis(3,5-dimethyl-4-hydroxyphenyl)propane (TMBPA), and the flame retardancy of polycarbonate prepared from bis(3,5-dibromo-4-hydroxyphenyl)propane (TBBPA). The hydroxyl groups of Bisphenol A are relatively unhindered and as a consequence bisphenol A reacts readily under interfacial conditions to form polycarbonate without recourse to the use of a large excess of phosgene. The importance of steric hindrance becomes apparent in situations in which the preparation of a polycarbonate from a bisphenol having sterically hindered hydroxyl groups is attempted. Thus, sterically hindered bisphenols such as TMBPA or TBBPA afford only very low molecular weight materials when subjected to interfacial polymerization conditions which successfully convert bisphenol A into high molecular weight polycarbonate. Higher molecular weight polycarbonates may be obtained from sterically hindered bisphenols through the use of interfacial polymerization conditions which employ a large excess of phosgene and long reaction times, but molecular weights of the product polymers are still limited with respect to molecular weights attainable in the interfacial polymerization reaction of bisphenol A and phosgene.
There exists a need for methods to effect the preparation of polycarbonates from sterically hindered bisphenols wherein the molecular weight of the product polycarbonate may be controlled to produce either high or low molecular weight materials and in which method the use of excess phosgene and long reaction times is minimized.
BRIEF SUMMARY OF THE INVENTION
In one aspect the present invention relates to a process for making a polycarbonate comprising structural units I
wherein R
1
-R
8
are independently hydrogen, halogen, C
1-
C
20
alkyl, C
6-
C
20
aryl, C
7-
C
21
aralkyl or C
5-
C
20
cycloalkyl;
W is a bond, an oxygen atom, a sulfur atom, a SO
2
group, a C
6
-C
20
aromatic radical, a C
6
-C
20
cycloaliphatic radical or the group
wherein R
9
and R
10
are independently hydrogen, C
1-
C
20
alkyl, C
6-
C
20
aryl, C
7-
C
21
aralkyl or C
5-
C
20
cycloalkyl, or
R
9
and R
10
together form a C
4-
C
20
cycloaliphatic ring which is optionally substituted by one or more C
1-
C
20
alkyl, C
6
-C
20
aryl, C
5-
C
21
, aralkyl, C
5-
C
20
cycloalkyl groups or a combination thereof;
said method comprising:
(A) admixing a solvent, water, optionally one or more phase transfer catalysts and optionally one or more chain stoppers, with at least one bisphenol having structure II
(B) adding phosgene and sufficient aqueous base to maintain a pH in a range between about 5 and about 14; said phosgene being added incrementally in an amount equivalent to between about 1.01 and about 1.75 equivalents based upon the amount of bisphenol used in step (A);
(C) adding a catalyst in an amount corresponding to between about 0.001 and about 0.10 equivalents based upon the amount of bisphenol used in step (A), said catalyst having structure III
wherein each R
11
and R
12
is independently a C
1
-C
18
alkyl group, a C
3
-C
18
cycloalkyl group, or R
11
and R
12
together form a C
4-
C
20
cycloaliphatic ring which may be substituted by one or more C
1-
C
20
alkyl, C
6-
C
20
aryl, C
5-
C
21
aralkyl, C
5-
C
20
cycloalkyl groups or a combination thereof; and
(D) agitating the mixture formed by steps (A), (B) and (C) at a pH in a range between about 8 and about 14 until said mixture is free of chloroformate groups.
Another aspect of the present invention relates to high and low molecular weight polycarbonates formed from sterically hindered bisphenols. The invention further relates to articles formed from said polycarbonates. The present invention further relates to the preparation of symmetrical diaryl carbonates of sterically hindered phenols.
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.
“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.
“Mesitol” is herein defined as 2,4,6-trimethylphenol.
As used herein the term “aromatic radical” refers to a radical having a valence of at least one comprising at least one aromatic group. Examples of aromatic radicals include phenyl, pyridyl, furanyl, thienyl, naphthyl, phenylene, biphenyl. The term includes groups containing both aromatic and aliphatic components, for example a benzyl group.
As used herein the term “aliphatic radical” refers to a radical having a valence of at least one comprising 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. Examples of aliphatic radicals include methyl, methylene, ethyl, ethylene, hexyl, hexamethylene and the like.
As used herein the term “cycloaliphatic radical” refers to a radical having a valance of at least one comprising an array of atoms which is cyclic but which is not aromatic. The array may include heteroatoms such as nitrogen, sulfur and oxygen or may be composed exclusively of carbon and hydrogen. Examples of cycloaliphatic radicals include cyclcopropyl, cyclopentyl cyclohexyl, tetrahydrofuranyl and the like.
As used herein the term “solvent” refers to a single pure solvent such as methylene chloride, or in the alternative to mixtures of solvents such as a mixture of methylene chloride and toluene.
In one aspect the instant invention provides a method for the preparation of both high and low molecular weight polycarbonates incorporating repeat units I via interfacial polymerization of bisphenols II with phosgene. In some instances, a mixture of bisphenols is interfacially polymerized to afford a copolycarbonate which may include repeat units I derived from one or more hindered phenols, such as 2,2-bis(3,5-dibromo-4-hydroxyphenyl)propane, as well as repeat units I derived from relatively unhindered bisphenols, such as 2,2-bis(4-hydroxyphenyl)propane.
Accordingly, in step (A) at least one bisphenol II is combined with a water immiscible solvent, water and optionally a chain stopper, and optionally a phase transfer catalyst. Prior to the introduction of phosgene, sufficient aqueous base is added to raise the pH of the reaction mixture to a range between about 9 and about 14, preferably between about 11 and about 13.5. In step (B) the mixture is stirred and about 1.01 to about 1.75 equivalents, prefer
Brunelle Daniel Joseph
Phelps Peter David
Shanklin Elliott West
Boykin Terressa M.
Caruso Andrew J.
General Electric Company
Johnson Noreen C.
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