Process for preparing formed item of aliphatic polyester and formed item prepared by the process

Abstract

The invention provides an aliphatic polyester formed item having transparency and crystallinity in combination by crystallizing, in the course of or after processing, an aliphatic polyester composition comprising aliphatic polyester and one or more transparent nucleating agent selected from the group consisting of aliphatic carboxylic acid amide, aliphatic carboxylic acid salt, aliphatic alcohol and aliphatic carboxylic acid ester having a melting point of 40-300° C.

Description

BACKGROUND OF THE INVENTION AND RELATED ART[0001] 1. Field of the Invention[0002] The present invention relates to a preparation process of a simultaneously transparent and crystallized formed item which comprises an aliphatic polyester and one or more transparent nucleating agent ingredients selected from the group consisting of aliphatic carboxylic acid amide, aliphatic carboxylic acid salt, aliphatic alcohol and aliphatic carboxylic acid ester; and a formed item prepared by the process.[0003] 2. Related Art[0004] Recently, general purpose plastics have led to public issues after use. Disposal of waste plastics increases the amount of refuse. Additionally, these plastics are scarcely degraded under natural environment and thus semipermanently remain under ground even after burial disposal. Further, abandoned plastics have caused problems such as an adverse effect on the beautiful scenery and impairment of living environment for marine organisms.[0005] On the other hand, thermoplas...

AI Technical Summary

Problems solved by technology

Recently, general purpose plastics have led to public issues after use.

Disposal of waste plastics increases the amount of refuse.

Additionally, these plastics are scarcely degraded under natural environment and thus semipermanently remain under ground even after burial disposal.

Further, abandoned plastics have caused problems such as an adverse effect on the beautiful scenery and impairment of living environment for marine organisms.

Further, these polymers begin to degrade within a few weeks in a humid environment such as in soil or in sea water and disappear after an year to several years.

However, PET leads to problems, for example, in uses which require degradability.

At immediately after processing, these processed items are usually amorphous and almost absent from crystals which have a size equal to or larger than the wave length of light beams and result in light scattering.

However, these transparent processed items are usually inferior in thermal resistance due to the amorphous state.

For example, amorphous polylactic acid containers are excellent in transparency and poor in thermal resistance, and thus cannot be used for hot water or a microwave oven.

As a result, the uses of these transparent items have been restricted.

Thus, conventional technique has been difficult like antinomy to simultaneously provide transparency and crystallinity for formed items of aliphatic polyester.

However, in the technical field of aliphatic polyester, technique on crystal has not yet been known to inhibit excess growth in [size], increase in [numbers], accelerate in [crystallization velocity], and thus provide molded items with transparency and crystallinity at the same time.

As a result, each crystal has an overwhelmingly small size.

That is, the amount exceeding 0.05 part by weight leads to mutual slip of pellets and remarkably lowers processing ability.

However, common mold release agents have problems of lowering transparency and strength of the molded articles.

Thus, when the pellets thereof are tried to charge from a hopper to the processing step, softened pellet surfaces are mutually fuse-bonded by heat and pressure in the bottom of the hopper, solidify like a cluster and lead to problems.

When the fuse-bonded pellets are fed as intact to the molding zone of the machine, quality of the molded articles such as processing ability, transparency, strength, flexibility, appearance and smoothness is impaired to cause problems.

As stated above, conventional techniques have been difficult like antinomy to simultaneously provide transparency and crystallinity for aliphatic polyester such as polylactic acid, a copolymer of aliphatic polyhydric alcohol and aliphatic po

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