Polylactide resin and preparation method thereof

Abstract

The present invention is directed to an organometallic complex and a catalyst composition capable of producing polylactide resins with improved properties at a higher conversion rate, a method of producing the organometallic complex, polylactide resins having enhanced hydrolysis resistance and heat resistance together with superior mechanical properties, a preparation process therefor, and polylactide resin compositions including the same.

Description

BACKGROUND OF THE INVENTION[0001](a) Field of the Invention[0002]The present invention relates to polylactide resins with improved properties, and a preparation process therefor. More specifically, the present invention is directed to an organometallic complex and a catalyst composition capable of producing polylactide resins with improved properties at a higher conversion rate, a method of producing the organometallic complex, polylactide resins having enhanced hydrolysis resistance and heat resistance together with superior mechanical properties, a preparation process therefor, and polylactide resin compositions including the same.[0003](b) Description of the Related Art[0004]Polylactides (or polylactic acids) are a type of resin including a repeating unit of the following General Formula. Unlike conventional petroleum-based resins, the polylactide resins, which are based on biomass, can utilize renewable resources, and their preparation generates less greenhouse gas, CO2, than th...

AI Technical Summary

Benefits of technology

[0014]Thus, the present invention is to provide an organometallic complex and a catalyst composition that can be preferably used as a catalyst in a ring opening polymerization of lactide monomers to produce a polylactide resin with enhanced properties such as mechanical properties, heat resistance, and hydrolysis resistance at a high conversion rate.

[0016]Further, the present invention is to provide a polylactide resin with a higher molecular weight and excellent mechanical properties, wherein the depolymerization or the decomposition in its use is also suppressed so that the resin shows better hydrolysis resistance and heat resistance.

[0017]The present invention is to further provide a process for preparing a polylactide resin, which uses the organometallic complex or the catalyst composition and makes it possible to produce the polylactide resin at a high conversion rate.

Problems solved by technology

However, the polylactide resins tend to biodegrade in and of themselves due to factors such as the catalyst used in their preparation, moisture in the air, and the like, and up to now such drawbacks of their own properties have limited their application.

In this regard, the direct condensation polymerization can produce the polymer at a low cost but it is difficult for the resulting polymers to have a high molecular weight in terms of a weight average molecular weight of 100,000 or more, making it difficult to sufficiently ensure the physical and mechanical properties of the polylactide resins.

Accordingly, the polylactide resin prepared from the ring opening polymerization tends to have a decreased molecular weight, a broadened molecular weight distribution, and an increased amount of remaining monomers, all of which can have an undesirable effect on the polymer properties.

Also, the ring opening polymerization using such catalyst can achieve only a limited level of conversion rate.

Not only do the monomers remaining in the polylactide resin after the polymerization have detrimental effects on the mechanical properties of the resin, but they also tend to be hydrated, causing corrosion at the time of processing, and can accelerate the decomposition via the depolymerization of the resin.

Due to the foregoing drawbacks, even when using the ring opening polymerization previously known in the art, it is difficult to obtain a polylactide resin with a sufficiently high molecular weight and excellent mechanical properties at a high conversion rate because of the depolymerization.

Moreover, in their use, the polylactide resins suffered the decomposition caused by the monomers and the catalyst remaining therein, which in turn brought about serious problems in their properties, such as hydrolysis resistance, heat resistance, and the like.

Such problems have hindered efforts to apply the polylactide resins for a semi-permanent use, such as for exterior materials of the cell phones and interior materials of vehicles.

However, even with this measure, which could prevent the acid from lowering the catalytic activity or causing a hydrolysis of the resin to some extent, it was found that the depolymerization still proceeded and it was difficult to obtain polylactide resins having a high molecular weight and excellent mechanical properties.

However, even with those methods, it was difficult to obtain a polylactide resin with a high molecular weight and excellent mechanical properties at a high conversion rate, and it was difficult to sufficiently prevent the depolymerization or the decomposition of the resin during its use caused by the catalyst or the monomer.

Therefore, the polylactide resins have failed to have a satisfactory level of hydrolysis resistance or heat resistance.

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