Issue 02/2019

By:
Barry Dean,
Naperville, Illinois, USA
Bioplastic Patents
new
series
U.S. Patent 9,914,832 (March 13, 2018), ”Articles Produced
By Thermoforming”, Maximillian Lehenmeier, Gabriel
Skupin, Martin Bussmann, (BASF SE, Ludwigshafen DE)
Ref: EP 2015/059301
The patent illustrates and teaches thermoforming
compositions that improved impact strength based on
blending compositions comprising a biodegradable polyester
from succinic acid and 1,3 propanediol or 1,4 butanediol,
an aliphatic-aromatic polyester from C6 – C18 dicarboxylic
acid and terephthalic acid based on 1,3 propanediol or 1,4
butanediol, polylactic acid and at least one mineral filler,
e.g. talc. The ratio of the degradable polyester from succinic
acid and the diol to the polylactic acid component is from
2.5 – 3.1. The improved impact strength is taught to be a
function of the level of the aliphatic-aromatic polyester
used at levels of 5 to 14 percent.
Thermoforming is a process where a sheet is heated
a temperature to enable pliable forming of a shape (e.g.,
tray, cup, lids, containers etc). Polymer composition
consistency and viscosity stability are key for shape
integrity, reproducibility and scrap recycle. The performance
feature taught in the above patent, improved impact is
also dependent of polymer composition consistency and
viscosity stability.
The thermoforming compositions have polymeric content
that is compostable and offers options for recycling.
This section highlights recently granted patents
that are relevant to the specific theme/focus of
the Bioplastics Magazine issue. The information
offered is intended to acquaint the reader with
a sampling of know-how being developed to
enable growth of the bioplastics markets.
U.S. Patent 9,687,585 (June 27, 2017), “Thermoformed
Poly-4-Hydroxybutyrate Medical Implants”, Matthew
Bernasconi, Dennis Connelly, Said Rizk, David Martin,
Simon Williams (Tepha, Inc Lexington, MA, USA)
This patent teaches methods for producing thermoformed
articles or precursors from poly-4-hydroxy alkanoate (P4HB)
for medical applications. For example a film or sheet based
on P4HB is thermoformed into a laminate from film and
a mesh. The laminate can be used for a variety of devices
directly implanted in the body for soft and hard tissue repair
(wound management, reconstructive surgery, orthopaedic
surgery). The inherent improved toughness of P4HB (Tg
= - 45 to – 65 C) relative to other polyhydroxyalkanoates
is taught as key for preventing breakage during the
implantation and for part integrity during the healing
process in vivo. The thermoformed parts can be further
machined to produce the desired implant shape. Physical
properties of the thermoformed mesh and mesh laminate
show no detrimental effects from sterilization cycles.
Viscosity consistency and control is key as with other
materials in thermoforming processes; this technology
calls out the need for intrinsic viscosity of < 3.5 dL/g but >
0.35 dL/g
44 bioplastics MAGAZINE [02/19] Vol. 14