Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – From carboxylic acid or derivative thereof
Patent
1997-06-03
1999-03-16
Troung, Duc
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
From carboxylic acid or derivative thereof
528354, 528357, C08G 6356
Patent
active
058832220
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to a process for producing polyhydroxycarboxylic acids, specifically, those having a weight-average molecular weight of 50,000 or above. Said polyhydroxycarboxylic acids are useful as biodegradable plastics for food-wrapping films, beverage bottles, drug delivery systems, etc.
BACKGROUND ART
Some methods are known as the methods for producing polyhydroxycarboxylic acids of a high molecular weight by the use of Lactides; for example, a method which comprises polymerizing, in the presence of polyvalent heavy metal oxide such as lead oxide, a lactide which is obtained by heating lactic acid (U.S. Pat. No. 2,703,316), a method for producing copolymers of lactic acid and glycolic acid having an average molecular weight of 72,000 by copolymerizing, in the presence of stannous octanoate, a mixture of lactide and glycolide respectively obtained by dehydration condensation of lactic acids and glycolic acid (Japanese Published Examined Patent Application No. 14688/81), and a method for producing polylactic acids having a molecular weight of 100,000 by polymerizing DL-lactide in the presence of stannous octanoate (Japanese Published Unexamined Patent Application No. 69553/90). However, these methods, in which Lactides of high purity are necessary, require purification steps of crude lactides such as recrystallization and distillation, and thus have various problems for industrial utilization due to a number of complicated.
DISCLOSURE OF THE INVENTION
The present invention relates to a process for producing polyhydroxycarboxylic acids, specifically, those having a weight-average molecular weight of 50,000 or above by polymerizing Lactides in the presence of an inorganic solid acid catalyst carrying silica and/or a light metal.
The polyhydroxycarboxylic acids include polymers and copolymers of lactides.
The Lactides include lactide and glycolide. As the Lactides, besides commercially available ones, Lactides which are synthesized from the corresponding hydroxycarboxylic acids such as lactic acid and glycolic acid according to the ordinary method may be used without purification. If necessary, these synthesized Lactides may be used after being purified by recrystallization (Japanese Published Unexamined Patent Application No. 279435/94) and distillation (PCT National Publication No. 503490/95).
The Lactides can be used in combination with lactone. The lactone include .gamma.-butyrolactone and .epsilon.-caprolactone. The lactone is preferably used in an amount of 20 wt % (hereinafter % means wt %) or below based on the amount of Lactide.
Among various kinds of inorganic solid acid catalysts, inorganic solid acid catalysts carrying silica and/or a light metal as the constituting component are used in the present invention.
The light metal includes alkali metals such as lithium, sodium, and potassium, and alkaline earth metals such as magnesium and calcium, and aluminum.
An inorganic acid addition salt of the alkali metal and the alkaline earth metal such as carbonates or bicarbonates thereof, hydroxycarboxylates thereof such as lactate or glycolate thereof, an organic acid addition salt of the alkali metal and the alkaline earth metal such as acetates, oxides, or hydroxides thereof may be used as the alkali metal and the alkaline earth metal.
The inorganic solid acid catalyst carrying silica and/or a light metal includes aluminum silicate, zeolite, acid clay, activated clay, bentonite, kaolin, talc, magnesium silicate, aluminum borate, and silicate. Usually, commercially available ones are used.
When the combination of an inorganic solid catalyst and an alkali metal or an alkaline earth metal is employed, an inorganic solid acid catalyst as mentioned above is treated according to the following methods to prepare a catalyst. carbonates, bicarbonates or hydroxides of an alkali metal compound catalyst or an alkaline earth metal compound catalyst to obtain an inorganic solid acid catalyst carrying an alkali metal compound catalyst or an alkaline earth metal compound catalys
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Murayama Toshikazu
Tsukazi Nobuko
Yanagisawa Norio
Yokomori Yorozu
Kyowa Hakko Kogyo Co. Ltd.
Troung Duc
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