Organic compounds -- part of the class 532-570 series – Organic compounds – Heterocyclic carbon compounds containing a hetero ring...
Reexamination Certificate
2001-03-30
2002-05-07
Owens, Amelia (Department: 1625)
Organic compounds -- part of the class 532-570 series
Organic compounds
Heterocyclic carbon compounds containing a hetero ring...
C562S580000, C562S587000
Reexamination Certificate
active
06384241
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a purified salt of &bgr;-hydroxyethoxy acetic acid, which is a precursor of a purified 2-p-dioxanone.
The present invention relates to a manufacturing method of a purified salt of &bgr;-hydroxyethoxy acetic acid, which is a precursor of a purified 2-p-dioxanone.
The present invention relates to a manufacturing method of a purified 2-p-dioxanone obtained from a purified salt of &bgr;-hydroxyethoxy acetic acid.
The present invention relates to a method of manufacturing a purified 2-p-dioxanone in an industrially advantageous manner.
The present invention also relates to a purified 2-p-dioxanone having a function to produce a polyparadioxane having a high molecular weight and a narrow molecular weight distribution characterized by not having a carboxyl group at the molecule end, after a polymerization reaction.
The present invention relates to a purified 2-p-dioxanone having a function to produce a polyparadioxane having a high molecular weight and a narrow molecular weight distribution characterized by not detecting a peak in 8.1 ppm attributable to a proton of a carboxyl group by nuclear-magnetic-resonance spectrometry (NMR, measured at 25 ° C.).
2. Description of the Related Art
[Technical Background of a Salt of &bgr;-hydroxyethoxy Acetic Acid]
It has conventionally been said to be a common sense by so-call those skilled in the art that purified salts of &bgr;-hydroxyethoxy acetic acid are oily, not crystalline, and that a fusion peak-top temperature is not detected by differential scanning calorimetry (DSC). No literature describes melting points of salts of &bgr;-hydroxyethoxy acetic acid.
[Investigation on Salts of &bgr;-Hydroxyethoxy acetic acid by the Present Inventors]
The present inventors have thus conducted investigations eagerly and obtained a novel finding that in the course of purification of salts of &bgr;-hydroxyethoxy acetic acid, they change from an oily state to crystalline and the fusion peak-top temperature gradually becomes measurable by differential scanning calorimetry (DSC).
According to the novel finding by the present inventors, the fusion peak-top temperature is preferably 205 to 208° C., more preferably 206 to 207° C., further preferably 206.5±0.2° C.
[Technical Background of 2-p-dioxanone]
2-p-Dioxanone is a compound useful as a raw material for a biodegradable and absorbable polymer used in a medicine etc.
[Investigation on 2-p-Dioxanone by the Present Inventors]
In the course of eager investigation on the technology for manufacturing a polydioxane having a narrow molecular weight distribution, the present inventors have obtained a finding that hydrochloric acid and acid chlorides among impurities present in 2-p-dioxanone inhibit manufacturing of a polydioxane having a narrow molecular weight distribution.
In other words, the present inventors have obtained a finding that hydrochloric acid and acid chlorides, if present in 2-p-dioxanone, would generate undesirable impurities due to their high reactivity, and the undesirable impurities involves such a critical problem that even if only a trace amount remains, they promotes ring-opening, cleavage, and degradation of 2-p-dioxanone.
The present inventors have found that if such ring-opening, cleavage, and degradation occur, undesirable impurities having a carboxyl group at ends are produced, which in turns inhibit a ring-opening polymerization reaction, suppress an increase in molecular weight, induce production of undesirable oligomers, and widen a molecular weight distribution as well.
According to the findings of the present inventors as described above, such an empirical rule has been obtained that a molecular weight distribution is wide when a large amount of carboxyl groups are present at molecular ends of a polymer, while a molecular weight distribution is narrow when no carboxyl group is present at molecular ends of a polymer, that is, an amount of carboxyl groups at molecular ends of a polymer is an index of molecular weight distribution.
It is deduced from the above described findings of the present inventors that removal of hydrochloric acid and acid chlorides from 2-p-dioxanone solves the problems of the prior art.
The present inventors have then found that it is quite difficult to remove hydrochloric acid and acid chlorides efficiently from 2-p-dioxanone by purification measures such as distillation and the like.
Then, the present inventors have found that it is quite easy to purify a salt of &bgr;-hydroxyethoxy acetic acid, a precursor of 2-p-dioxanone, and reached to consider whether a purified 2-p-dioxanone, which has been purified and requires no further purification, might be readily obtained from a purified precursor, and thus preceded eager investigation.
[Prior Art for Process of Manufacturing 2-p-Dioxanone]
The following prior art can be mentioned with respect to processes of manufacturing 2-p-dioxanone.
(1) Process of Synthesis from 2,3-Dichloro-p-dioxanone
J. Am. Chem. Soc. Vol. 80, 604-608 (1958) discloses a process of manufacturing 2-p-dioxanone in which trans-2,3-dichloro-p-dioxane is reacted with an acid chloride represented by formula (3) to obtain 2-carboxy-3-chloro-p-dioxane (4) represented by the following formula (4), and then 2-carboxy-3-chloro-p-dioxane is subjected to heat treatment to obtain 2,3-dichloro-p-dioxanone.
where R represents p-C
6
H
4
Cl, CH
3
, and H.
This manufacturing process has such a problem that hydrochloric acid and acid chlorides are produced as byproducts, however.
The byproducts, hydrochloric acid and acid chlorides, are highly reactive with an object, 2-p-dioxanone, to produce undesirable impurities. The undesirable impurities involve such a critical problem that even if only a trace amount remains, they promote ring-opening, cleavage, and degradation of 2-p-dioxanone.
When such ring-opening, cleavage, and degradation occur, undesirable impurities having a carboxyl group at ends are produced.
These undesirable impurities in turns inhibit a ring-opening polymerization reaction, suppress an increase in molecular weight, and induce production of undesirable oligomers, and widen a molecular weight distribution as well.
As described above, such an empirical rule has been obtained that a molecular weight distribution is wide when a large amount of carboxyl groups are present at molecular ends of a polymer, while a molecular weight distribution is narrow when no carboxyl group is present at molecular ends of a polymer, that is, an amount of carboxyl groups at molecular ends of a polymer is an index of molecular weight distribution.
In addition, the raw material, 2,3-dichloro-p-dioxanone, also generates hydrochloric acid and acid chlorides as byproducts in its manufacturing process and has problems similar to those described above.
In addition, 2,3-dichloro-p-dioxane, a raw material of this synthetic route, is generally synthesized by a reaction of dioxane with sulfuryl chloride, but each 2 equivalents of HCl and SO
2
gases are generated, treatment of which gases is industrially problematic.
(2) Process of Synthesis from Diol Using Catalyst
There have been a great number of reports concerning a method in which diethylene glycol is subjected to a dehydrogenation reaction by heating to a high temperature using a corresponding quantity of a catalyst to obtain 2-p-dioxanone. For example, Japanese Patent Application Laid-Open No. 4-505321 discloses a method of manufacturing 2-p-dioxanone by a catalytic dehydrogenation reaction of dialkylene glycol comprising the step of contacting dialkylene glycol with an effective amount of a dehydrogenation catalyst containing catalytically effective amounts of copper compounds, zinc compounds, and co-catalyst compounds. The selectivity rates in the examples are 73.7 to 99%.
Japanese Patent Application Laid-Open No. 10-120675 describes a process of manufacturing 2-p-dioxanone in which diethylene glycols are contacted with a catalyst comprising copper on a carrier with acid s
Akieda Hideyuki
Ishitoku Takeshi
Matsumoto Takuji
Nakahara Yoshinori
Nakatani Satoru
Burns Doane Swecker & Mathis L.L.P.
Mitsui Chemicals Inc.
Owens Amelia
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