Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – From carboxylic acid or derivative thereof
Reexamination Certificate
2000-07-12
2002-02-26
Acquah, Samuel A. (Department: 1711)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
From carboxylic acid or derivative thereof
C528S274000, C528S302000, C524S700000, C524S783000
Reexamination Certificate
active
06350850
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a process for producing a polyester, in particular, an aliphatic polyester. More particularly, the present invention relates to a process for producing a polyester by which a high polymerization degree polymer can be easily obtained and which is industrially effective.
2. Prior Art
An aromatic polyester, a representative of which is polyethylene terephthalate, is widely used in a fiber material, a film, a container and an engineering plastic. On the other hand, an aliphatic polyester is utilized as a suture. In addition, since an aliphatic polyester is biodegradable and is easily recycled and degraded, its utility tends to extend year by year in view of the problems on recent plastic waste.
As a process for producing a polyester, a process is generally performed in which a dicarboxylic acid component and a diol component are polycondensed using as a catalyst a proton acid such as sulfuric acid or a metal compound such as titanium alkoxide. However, since an equilibrium constant for a polyesterification reaction is around 1 to 10, in order to obtain a high polymerization degree polymer, it is necessary to remove as much produced water as possible and shift the equilibrium towards a product side. The necessity of this dehydration procedure is a factor of rendering high polymerization degree polyester synthesis difficult.
As a process for synthesizing a polyester that improves such problems and which is industrially applied, there is a process for production with a microorganism and a process for polymerization in a high boiling point solvent. However, in the synthesis with a microorganism, large scale synthesis is difficult and, additionally, it is difficult to obtain a pure polymer by removing a microorganism. In addition, in the process for polymerization using a high boiling point solvent, a remaining solvent in a polyester article becomes problematic. Also, because hydrolysis occurs more easily in a aliphatic polyester than in an aromatic polyester, removal of water in the polymerization system becomes a great problem and there are many problems for industrialization such as increase in plant investment and complication in the polymerization process.
DESCRIPTION OF THE PRESENT INVENTION
An object of the present invention is to provide a process for producing a polyester which can easily afford a high polymerization degree polymer without the use of a high boiling point solvent and dehydration procedure under reduced pressure.
In order to attain the aforementioned object, the present inventors studied intensively and, as a result, found that a high polymerization degree polyester can be obtained without the use of high a boiling point solvent and dehydration procedure under reduced pressure by using a distannoxane catalyst, which resulted in the completion of the present invention.
That is, the present invention is a process for producing a polyester from a dicarboxylic acid and a diol which comprises polycondensing the dicarboxylic acid and the diol in the presence of a distannnoxane catalyst.
Also, the present invention is a process for producing a polyester from the dicarboxylic acid and the diol, which comprises melt polycondensation of the carboxylic acid and the diol under normal pressure in the presence of the distannoxane catalyst and also in the presence of an organic solvent which does not dissolve any of the dicarboxylic acid, the diol and the polyester produced from the carboxylic acid and the diol and, as a result, in the presence of mainly two phases.
As used herein, “normal pressure” refers to the usual atomospheric status without application of reduced pressure and pressurization.
In the present invention, as a distannoxane catalyst used, there is a distannoxane catalyst represented by the following formula (1):
wherein R
1
, R
2
, R
3
and R
4
are the same or different and denote alkyl group, and X and Y are the same or different and denote isothiocyanate group, halogen atom, hydroxy group, alkoxy group, or acyloxy group.
Examples of the alkyl group in R
1
, R
2
, R
3
and R
4
in the aforementioned formula (1) are straight or branched alkyl groups having a carbon number of 1 to 10 such as methyl, ethyl, propyl, isopropyl, n-butyl, isobutyl, s-butyl, t-butyl, pentyl, hexyl, heptyl and octyl group. Inter alia, alkyl groups having a carbon number of 1 to 6 are preferable. In particular, C
4
alkyl group such as n-butyl group is preferable.
Within a halogen atom in X and Y are included chlorine, bromine and iodine. Inter alia, a preferable halogen atom is chlorine and bromine atom, in particular chlorine atom.
Examples of the alkoxy group in X and Y are alkoxy groups having a carbon number of 1 to 10 (preferably a carbon number 1 to 6 ) such as methoxy, ethoxy, propoxy, isopropoxy, butoxy, isobutyloxy, s-butyloxy, t-butyloxy, pentyloxy, hexyloxy and octyloxy group. These alkoxy groups may have hydroxyl group. Within such alkoxy group having hydroxy group are included 2-hydoxyethoxy group, 2-hydoxypropoxy group, 3-hydoxypropoxy group and 4-hydroxybutoxy group.
Examples of the acyloxy group in X and Y are aliphatic acyloxy groups having a carbon number of 2 to 10 (preferably, a carbon number of 2 to 5) such as acetoxy, propionyloxy, butyryloxy, valeryloxy and hexanoyloxy group. These acyloxy groups may have carboxyl group.
Within such acyloxy group having carboxyl group are included carboxyacetyloxy, 2-carboxypropionyloxy, 3-carboxypropionyloxy and 4-carboxybutyryloxy group.
Among the distannoxanes represented by the formula(1), those compounds are preferable in which R
1
, R
2
, R
3
and R
4
are each n-butyl group, X and Y are isothiocyanate group, halogen atom (for example, chlorine and the like), hydroxy group, alkoxy group (for example, alkoxy group having a carbon number of 1 to 6 optionally having hydroxy group) and acyloxy group (for example, acyloxy group having a carbon number of 2 to 5 optionally having carboxyl group). Representative examples of such the compounds are 1-chloro-3-hydroxy-1, 1, 3, 3-tetra n-butyldistannoxane, 1, 3-dichloro-1,1,3,3-tetra n-butyldistannoxane, 1, 3-diisothiocyanate-1,1,3,3-tetra n-butyldistannoxane, and 1-hydroxy-3-isothiocyanate-1,1,3,3-tetra n-butyldistannoxane.
The above distannoxanes have the advantages that they are cheap and easily synthesized and, in spite of an inorganic skeleton, they are soluble in almost all organic solvents. Further, while other metal catalysts generally simply reduce the activation energy of a forward reaction and an inverse reaction in a reaction of synthesizing a polyester by polycondensation of a diol and a dicarboxylic acid and, thus, have no effect on an equilibrium constant, the distannoxane catalysts do not cause a reverse reaction, that is, hydrolysis due to the presence of water in the reaction system. This is presumed to be due to the two-layer structure of distannoxanes. That is, it has been made clear that distannoxane takes a ladder-like dimer structure by the interaction similar to an ionic bond between an electron-excessive functional group (X, Y) such as oxygen atom and an electron-deficient tin atom as shown by, for example, the following formula:
wherein R
1
, R
2
, R
3
, R
4
, X and Y are as defined above. It is considered that this dimer structure is formed also in a solution and re-access of produced water to a reaction point is prevented by the hydrophobic action of alkyl groups (R
1
~R
4
) which surround the circumference of this distannoxane skeleton. For this reason, when distannoxane is used as a catalyst for synthesizing a polyester by polycondensation of a diol and a dicarboxylic acid, a high polymerization degree polyester can be simply obtained under the mild conditions at a lower temperature and normal pressure without raising the temperature and performing dehydration procedure under reduced pressure. Therefore, distannoxane is useful for synthesizing an aliphatic polyester which easily undergoes hydrolysis. In the process of the present invention, by using the above distan
Hayakawa Teruaki
Takahashi Hiroyuki
Teranishi Tadashi
Ueda Mitsuru
Acquah Samuel A.
Daicel Chemical Industries Ltd.
Oppenheimer Wolff & Donnelly LLP
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