Resin composition, molded article, and production methods thereof

Abstract

There are provided a resin composition comprising a polylactic acid which (i) comprises a poly-L-lactic acid (component B-1) and a poly-D-lactic acid (component B-4), (ii) has a weight ratio of the component B-1 to the component B-4 (component B-1 / component B-4) of 10 / 90 to 90 / 10, and (iii) shows a proportion of melt peaks at 195° C. or higher to all melt peaks in a temperature rising process in measurement by a differential scanning calorimeter (DSC) of at least 20%; a molded article of the resin composition; and methods for producing the resin composition and the molded article.

Description

FIELD OF THE INVENTION[0001]The present invention relates to a resin composition and a molded article that contain a polymer obtained from biomass resources. More specifically, it relates to a resin composition that contains a specific polylactic acid and has excellent heat resistance and hydrolysis resistance, and a molded article of the resin composition.BACKGROUND OF THE ART[0002]Thermoplastic resins have excellent heat resistance, mechanical properties, impact resistance and dimensional stability and are widely used in fields such as an office automation equipment field, automobile field and electric / electronic part field. On the other hand, however, the thermoplastic resins also have an aspect that most of raw materials thereof rely on oil resources.[0003]In recent years, in view of fear of exhaustion of the oil resources and a problem of increase of carbon dioxide in air that causes global warming, carbon-neutral biomass resources that do not rely on oils for raw materials and...

AI Technical Summary

Benefits of technology

[0011]An object of the present invention is to provide a resin composition and a molded article that use a biomass-derived polylactic acid and cause small burdens on the environment. Another object of the present invention is to provide a resin composition which comprises a thermoplastic resin (component A) and a polylactic acid (component B) and has excellent hydrolysis resistance. Still another object of the present invention is to provide a resin composition having excellent heat resistance and chemical resistance. Still another object of the present invention is to provide a molded article having excellent heat resistance, mechanical properties, hydrolysis resistance and chemical resistance.

[0012]The present inventors have found that a molded article having excellent heat resistance, mechanical properties, hydrolysis resistance and chemical resistance is obtained by molding a resin composition that comprises a thermoplastic resin (component A) and a polylactic acid having a high stereocomplex crystal content, the polylactic acid being obtained by melt-kneading a polylactic acid containing at least 90% of L-lactic acid unit and a polylactic acid containing at least 90% of D-lactic acid unit at high temperatures, and have completed the present invention based on this finding.

[0015]An object of the present invention is to provide a resin composition and a molded article that use a biomass-derived polylactic acid and cause small burdens on the environment. Another object of the present invention is to provide a resin composition comprising a polylactic acid (component B) and having excellent hydrolysis resistance. Still another object of the present invention is to provide a resin composition having excellent heat resistance and chemical resistance. Still another object of the present invention is to provide a molded article having excellent heat resistance, mechanical properties, hydrolysis resistance and chemical resistance.

[0016]The present inventors have found that a molded article having excellent heat resistance, mechanical properties, hydrolysis resistance and chemical resistance is obtained by molding a resin composition that comprises a polylactic acid (component B) having a high stereocomplex crystal content, the polylactic acid being obtained by melt-kneading a polylactic acid containing at least 90% of L-lactic acid unit and a polylactic acid containing at least 90% of D-lactic acid unit at high temperatures, and have completed the present invention based on this finding.

Problems solved by technology

However, the properties of the polylactic acids such as mechanical properties and heat resistance are unsatisfactory in order for the polylactic acids to be used as industrial materials in fields in which thermoplastic resins are used.

Further, the polylactic acids have a problem that they show significantly low hydrolysis resistance when used under wet and hot conditions because they have biodegradability.

However, when this stereocomplex polylactic acid is produced by an industrially advantageous melt-extrusion process, it is very difficult to achieve stereo-complexification to a sufficient level.

When stereo-complexification is insufficient, the stereocomplex polylactic acid cannot exhibit good heat resistance that is a characteristic thereof.

Further, although the stereocomplex polylactic acid has a tendency of showing a higher crystallization rate than the poly-L-lactic acid or poly-D-lactic acid, it is still insufficient to produce the stereocomplex polylactic acid efficiently by injection molding.

As described above, even the stereocomplexpolylactic acid still has a number of problems in order to be used in wide applications.

However, it is the current situation that a problem of decrease of hydrolysis resistance that is derived from a characteristic of the polylactic acids has not yet been solved and hinders the above materials from being used as industrial materials in various fields.

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