A Revolution in Blow Molding


Successful Injection Blow Molding of 100% Polylactic Acid

 

A revolution in injection blow molding

In 2017, Bioworks succeeded in making plastic bottles 100% made from commercial polylactic acid with a conventional PET mold by adding about 5% of our proprietary additive.

This made it possible to produce plastic bottles that are 100% bio-based, biodegradable, and compatible with hot water and microwaving on a commercial scale. For the future, we look to cooperate with major beverage and cosmetic manufacturers for distribution of the bottles on a larger scale to make a contribution to the global environment.

 

Issues in conventional polylactic acid molding

◇ When heated, the preform gets deformed and bent and/or inner walls sticks together.

injectionblow

◇ Crystallization cannot be controlled during blowing and stretching, and uneven stretch results in rupture.

Crystallization occurs due to stretching and leads to whitening.

injectionblow

<Addition of Bioworks additive>

① Controls crystallization and eliminates deformation during heating.

②Structurally regulates flux and eliminates rupture at the time of blowing.

③ Eliminates whitening due to appropriate nucleating process design.

PLA 透明 ボトル

※Transparent heat-proof bottle 100% made from polylactic acid

 

 

■What is injection blow molding?

First, a hollow preform is injection-molded and then is sandwiched by top and bottom molds. When the preform is heated and softened, air is blown into it to inflate the preform, pressing it to the inner walls of the molds. When the item is cooled and solidified, the molds are opened and it is taken out.


 

Successful Direct Blow Molding of 100% Polylactic Acid

 

A revolution in direct blow molding
With conventional polylactic acid, extruded resin is stretched to a bar shape, and this made direct blow molding technically very difficult.
In 2017, Bioworks succeeded in direct blow molding of commercial polylactic acid with conventional resin molds (e.g. PP) by adding a small amount of our plant-derived additive. For the future, we plan to work on and commercialize the molding of larger products such as automotive air ducts.

 

 

 【Issues in conventional polylactic acid molding】

 

Extremely low viscosity during fusing causes extruded tube-shaped resin to sag, making inner walls stick together.

This prevents air blowing into the preform. Thus, polyester resins, including PET resin and polylactic acid resin, were not appropriate for direct blow molding.

<Addition of Bioworks additive:>

This successfully increases viscosity by altering the molecular structure of polylactic acid and inhibiting its basic physical properties. This enables extrusion while retaining a hollow state without drawdown.

 

ポリ乳酸 マネキン
100% polylactic acid mannequin (Source: Nanasai Co., Ltd.)

ポリ乳酸 ボトル
100% polylactic acid bottles

 

■What is direct blow molding?
Direct blow molding is a technique to form a hollow item (e.g. a container) by blowing compressed air into extruded soft resin in a tube shape, sandwiched by molds.