Organic compounds -- part of the class 532-570 series – Organic compounds – Carboxylic acids and salts thereof
Reexamination Certificate
2002-01-10
2002-12-24
Rotman, Alan L. (Department: 1625)
Organic compounds -- part of the class 532-570 series
Organic compounds
Carboxylic acids and salts thereof
C562S400000
Reexamination Certificate
active
06498271
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates to the preparation of branched polycarbonates. More particularly, it relates to new tricarboxylic acid branching agents and the polycarbonates derived therefrom.
Polycarbonate resins are a well known class of synthetic polymeric resins which may be prepared by various methods including the reaction of a dihydroxy compound, preferably a dihydroxyaromatic compound, with a carbonate precursor; see for example U.S. Pat. No. 3,028,365. For certain purposes such as blow molding, branched polycarbonates are superior to the linear polymers by reason of their melt rheology behavior. In particular, they exhibit high melt elasticity and high melt strength. Melt elasticity is the recovery of the elastic energy stored within the melt from distortion or orientation of the molecules by shearing stresses. Melt strength may be simply described as the tenacity of a molten strand and indicates the ability of the melt to support a stress. These advantageous properties of the branched resins are in large part a result of their non-Newtonian flow characteristics.
In the typical preparation of branched polycarbonates, a linear polycarbonate or its precursor undergoes reaction with a branching agent. Commonly employed branching agents include 1,1,1-tris(4-hydroxyphenyl)ethane (THPE) and trimellityl trichloride (TMTC). However, THPE is very expensive, partly by reason of its method of preparation in which an essential reactant is the expensive 4-hydroxyacetophenone. Branched polycarbonates prepared with TMTC are photochemically unstable.
It is of interest, therefore, to provide new branching agents which are relatively inexpensive. In one embodiment of the present invention, aliphatic branching agents are produced by a series of reactions which can include a biosynthesis step. This series of reactions has potential for being very inexpensive to conduct. The product is an aliphatic tricarboxylic acid which is capable of being used to produce branched polycarbonates having excellent properties.
SUMMARY OF THE INVENTION
One aspect of the invention is aliphatic tricarboxylic acids having the formula
wherein each of R
1
and R
2
is independently a divalent aliphatic hydrocarbon radical containing about 5-10 carbon atoms.
Another aspect of the invention is a process for making an aliphatic tricarboxylic acid having the formula
wherein each of R
1
and R
2
is independently a divalent aliphatic hydrocarbon radical containing about 5-10 carbon atoms, which comprises the steps of
(a) converting an olefinic monocarboxylic acid to an olefinic dicarboxylic acid by biotransformation in the presence of a yeast, such as strains of
Candida tropicalis;
and
(b) carboxylating the olefinic dicarboxylic acid to a tricarboxylic acid with carbon monoxide and water in the presence of a catalyst.
Still another aspect of the invention is branched polycarbonates comprising structural units of the formula
wherein each A is independently a divalent aliphatic, alicyclic or aromatic radical, and branching units of formula III derived from at least one compound of formula I:
wherein R
1
and R
2
are as previously defined.
DETAILED DESCRIPTION; PREFERRED EMBODIMENTS
The R
1
and R
2
radicals in the tricarboxylic acids of this invention are divalent aliphatic hydrocarbon radicals containing about 5-10 carbon atoms. Most often, each of R
1
and R
2
is a straight chain alkylene radical. In preferred embodiments R
1
is —(CH
2
)
7
— and R
2
is —(CH
2
)
8
—. Thus, the preferred tricarboxylic acid is 9-carboxy-1,18-octadecanedioic acid, hereinafter sometimes designated “CODDA”.
The tricarboxylic acids of the invention may be prepared from olefinic monocarboxylic acids, preferably oleic acid, by a two-step reaction sequence. The first step is the biotransformation of the olefinic monocarboxylic acid to the corresponding olefinic dicarboxylic acid, preferably 1,18-octadec-9-enedioic acid. This biotransformation occurs in the presence of various strains of yeast, including strains of
Candida tropicalis,
as disclosed in U.S. Pat. Nos. 5,620,878 and 5,962,285, the disclosures of which are incorporated by reference herein. As noted in those patents, a preferred strain of
C. tropicalis
for this purpose is designated AR40 and that strain was deposited Mar. 9, 1990, with the American Type Culture Collection as ATCC 20987.
The second step is the carboxylation of the olefinic dicarboxylic acid to the acid of formula I. Such carboxylation may be effected by reaction of the olefinic dicarboxylic acid, preferably 1,18-octadec-9-enedioic acid, with carbon monoxide and water in the presence of a catalyst, typically one comprising a transition metal or a noble metal and a ligand, such as palladium chloride-triphenylphosphine. A typical reaction is disclosed in Frankel et al.,
J. Am. Oil Chem. Soc.,
50, 39-43 (1973), the disclosure of which is incorporated herein by reference. Following preparation, the tricarboxylic acid product may be isolated by conventional means.
The tricarboxylic acids of the invention may also be prepared by catalytic carboxylation of oleic acid, followed by biotransformation. It is believed, however, that the preferred method employs biotransformation as the first step.
The A value in the branched polycarbonates of this invention, occurring in the structural units therein having formula II, may be the same or said polycarbonates may contain two or more different units of that formula. Said A values may be aliphatic, alicyclic, aromatic or mixed; those which are aliphatic or alicyclic generally contain up to about 8 carbon atoms. Suitable A values include ethylene, propylene, trimethylene, tetramethylene, hexamethylene, dodecamethylene, 1,4-(2-butenylene), 1,10-(2-ethyldecylene), 1,3-cyclopentylene, 1,3-cyclohexylene, 1,4-cyclohexylene, m-phenylene, p-phenylene, 4,4′-biphenylene, 2,2-bis(4-phenylene)propane, benzene-1,4-dimethylene and similar radicals such as those which correspond to the dihydroxy compounds disclosed by name or formula (generic or specific) in U.S. Pat. No. 4,217,438, the disclosure of which is incorporated by reference herein. Also included are radicals containing non-hydrocarbon moieties. These moieties may be substituents such as chloro, nitro, alkoxy and the like, and also linking radicals such as oxy, thio, sulfoxy, sulfone, ester, amide, ether and carbonyl. Most often, however, all A radicals are hydrocarbon radicals.
Preferably at least about 60% and more preferably at least about 80% of the total number of A values in the mixtures, and most desirably all of said A values, are aromatic. The aromatic A radicals preferably have the formula
(IV) —A
1
—Y—A
2
—,
wherein each of A
1
and A
2
is a monocyclic divalent aromatic radical and Y is a bridging radical in which one or two atoms separate A
1
from A
2
. The free valence bonds in formula IV are usually in the meta or para positions of A
1
and A
2
in relation to Y.
The A
1
and A
2
values may be unsubstituted phenylene or substituted derivatives thereof, illustrative substituents (one or more) being alkyl, alkenyl, halo (especially chloro and/or bromo), nitro, alkoxy and the like. Unsubstituted phenylene radicals are preferred. Both A
1
and A
2
are preferably p-phenylene, although both may be o- or m-phenylene or one o- or m-phenylene and the other p-phenylene.
The bridging radical, Y, is one in which one or two atoms, preferably one, separate A
1
from A
2
. It is most often a hydrocarbon radical and particularly a saturated radical such as methylene, cyclohexylmethylene, 2-[2.2.1]-bicyclohep-tylmethylene, ethylene, isopropylidene, neopentylidene, cyclohexylidene, cyclopentadecylidene, cyclododecylidene or adamantylidene, especially a gem-alkylene (alkylidene) radical. Also included, however, are unsaturated radicals and radicals which contain atoms other than carbon and hydrogen; for example, 2,2-dichloroethylidene, carbonyl, phthalidylidene, oxy, thio, sulfoxy and sulfone. For reasons of availability and particular suitability for the purposes of this invention
Amaratunga Mohan Mark
Lobos John Henry
Mobley David Paul
Brown S. Bruce
General Electric Company
Johnson Noreen C.
Reyes Hector M.
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