BIODEGRADABLE LAMINATED COMPOSITE MATERIAL BASED ON CURED STARCH FOAM AND METHOD FOR PREPARING IT

MATERIAU MIXTE LAMINE BIODEGRADABLE, A BASE DE MOUSSE D'AMIDON RETICULEE; METHODE DE PREPARATION

English Abstract

There is provided biodegradable laminated composite material
based on cured starch foam and a method for preparing it.
During the preparation the starch foam is simultaneously
combined with an additional layer of a further material. The
advantages of the invention include the simple and
cost-efficient method of preparation and the multiple
applications of the composite material.

Claims

7
THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. Laminated composite material comprising at least a
foam layer and at least one additional layer of a material
characterized in that the foam material is cured starch foam
and the layers are biodegradable and interconnected in situ
without a coupling agent.
2. Composite material as defined in Claim 1
characterized in that the starch foam contains native starch.
3. Composite material as defined in any of Claims 1
and 2 characterized in that the starch foam contains modified
starch.
4. Composite material as defined in any of Claims 1 to
3 characterized in that the starch foam is dyed.
5. Composite material as defined in any of Claims 1 to
4 characterized in that the starch foam contains fibers
and/or fillers.
6. Composite material as defined in any of Claims 1 to
characterized in that the additional layer is made of
paper, paperboard, cardboard, textiles from natural and/or
synthetic fibers and/or mixed fabrics, wood veneer, leather,
sheets from synthetic and biopolymeric materials, films from
synthetic and/or biopolymeric materials that are produced in
situ in the preparation of the composite material, as well as
combinations of the aforementioned materials.
7. Composite material as defined in any of Claims 1 to
6 characterized in that the additional layer is combined with
the starch foam unilaterally.

8
8. Composite material as defined in any of claims 1 to 7
characterized in that the additional layer is or can be
printed on.
9. Composite material as defined in any of claims 1 to 8
characterized in that the additional layer is composed
of a plurality of layers.
10. Composite material as defined in claim 9 characterized
in that the starch foam is positioned between the
plurality of layers.
11. Composite material as defined in any of claims 1 to 10
characterized in that it is formed to a plate having
cavities.
12. Composite material as defined in claim 11 characterized
in that the cavities pressed in the plate form hollow
spaces between stacked plates.
13. Packaging material comprising the laminated composite
material as defined in any of claims 1 to 12 especially
for use in packages for sweets.
14. A method for preparing laminated composite material as
defined in any of claims 1 to 12 comprising the steps
of:
a. introducing a starch suspension and at least one
further laminate material in a die,
b. curing the starch foam and simultaneously combining
it with said further material to form laminated
composite material, and
c. removing said laminated composite material from the
mold.

9
15. A method as defined in claim 14 characterized in that
the die is heated prior to step a.
16. A method as defined in claim 14 or 15 characterized in
that an aqueous starch suspension is added in step a.
17 . A method as deffined in claim 14 , 15 or 16 characterized
in that a dyed starch suspension is added in step a.
18. A method as defined in any of claims 14 to 17
characterized in that the starch suspension is injected
in step a.
19. A method as defined in any of claims 14 to 18
characterized in that the starch suspension is
pressure-foamed in step a.
20. A method as defined in any of claims 14 to 19
characterized in that the further material is added
prior to the starch suspension in step a.
21. A method as defined in any of claims 14 to 20
characterized in that the further material is added as
liquid and/or solid, powdery material and a layer is
produced in step a, which layer combined with the starch
foam forms the laminated composite material.
22. A method as defined in any of claims 14 to 21
characterized in that the further material is first
preformed and then introduced in step a.
23. A method as defined in claim 22 characterized in that
the further material is preformed to a shell.

10
24. A method as defined in any of claims 14 to 23
characterized in that a starch suspension comprising
20-45% of granular starch, 0-10% of swelling starch and
water is added in step a, wherein the die is heated to a
temperature of 180-270°C, preferably 200-250°C, and step
c is taken after 30-90 seconds, preferably 45-75
seconds.
25. Use of the composite material as defined in any of
claims 1 to 12 as sorting devices for containers for
packaging goods, in particular chocolates, as foldable
boxes or as padding to avoid transportation damage, as
heat insulation packaging for frozen products or as cups
for cold and hot drinks.

Description

X143432
Biotec Biologische Naturverpackungen GmbH & Co.
Forschungs- and Entwicklungs KG
Emmerich, Germany
Biodegradable Laminated Composite Material Hased on Cured
Starch Foam and Method for Preparing it
The invention relates to biodegradable laminated composite
material based on cured starch foam and a method for
preparing it.
Such composite materials can be used as packaging materials,
as construction materials, for example, for cold, heat or
sound insulation, or for shock absorption.
Conventional foam packaging materials made of polystyrene
(Styrofoam), especially for food stuff, are problematic in
particular in terms of their disposal. Such plastics
virtually do not rot and can only be recycled after sorting.
In a known method a starch suspension is used in place of
plastics. Liquid parts, once introduced in a heated die,
evaporate and cause the suspension to foam or expand. The
material remains in the mold over a particular dwell time
for drying and curing while moisture escapes. Then the mold
is released and the foam part ejected. Foam parts thus
produced rot and are recyclable. Furthermore, they show
cold- and heat-insulating as well as shock-absorbing
properties. However, they have the drawback of exhibiting
relatively low strength unless they are heavyweight or have
fairly thick walls. Furthermore, they are not useful for

2143432
2
certain applications due to their porous surfaces, in
' particular it is difficult to print on them.
By contrast, the object underlying the present invention is
to provide biodegradable laminated composite material
characterized by high strength, a simple and cost-efficient
method of preparation and multiple applications.
This object is achieved by providing the features indicated
in the claims.
In achieving the object, the invention is based on the
concept of foaming and curing starch to form a layer and
simultaneously combining it with an additional layer of a
further laminate material to obtain laminated composite
material. Said further laminate material can be integrated
into the starch foam and/or positioned adjacent to the foam
uni- or bilaterally and serves as support, carrier or
substrate.
The invention has the following advantages.
Starch can be used without further additives. A variety of
materials can be combined with the starch foam to form
laminated composite material. In particular, the laminated
composite material, on account of said further laminate
material; is easy to print on or dye. The laminated
composite material is mechanically stable and exhibits
excellent sound, temperature and electrical insulation
properties due to the porosity of the cured starch foam.
Furthermore, it is effective in absorbing shock. The
invention can most advantageously be used as packaging
material for sweets because the laminated composite material
permits printing for publicity purposes and ensures shock
absorption and heat insulation required for sweets.
The invention is further illustrated below.

zn~34~w
3
' The laminated composite material of the invention comprises
at least a layer of cured starch foam combined with at least
one further material to form laminated composite material.
Preferably, said further material is flat material covered
with starch foam preferably unilaterally.
The method of the invention is based on a starch suspension
which may contain native and/or modified starch. The native
starch may be of any origin in natural or hybrid form and
derived, for example, from potatoes, manioc, rice, corn, wax
corn, corn with high amylose content, grain such as wheat
and fractions prepared therefrom, barley or sorghum. The
modified starch is a physically and/or chemically produced
starch derivative. Preferred are aqueous starch suspensions
that may be mixed with dyes compatible with food stuff.
Furthermore, further laminate material is used in the
method, which material preferably comprises paper,
paperboard, cardboard, textiles, wood veneer, leather,
imitation leather, films from synthetic, biopolymeric and
metallic materials as well as combinations of the
aforementioned materials. Preferably, said further laminate
material is flat material. It is determined by the final
form of the laminated composite material, such as packages,
and can be introduced in the mold either as a blank or in
preformed state. This preferably occurs shortly before the
starch suspension is added.
The starch suspension is preferably introduced in the die by
injection and in measured amounts. In the heated mold the
suspension foams following evaporation and fills the
cavities. During that time and during the drying and
chemicophysical curing processes the starch is combined with
the further laminate material to form a unit that is
subsequently released from the mold as laminated composite
material. These processes are promoted by the increased

214~43~
4
internal pressure in the die and preferably conducted while
controlling pressure and temperature.
It is surprising that the relatively high molding
temperature does not affect the further laminate material
when the method is conducted properly. This also applies for
any printing done to the further laminate material,
especially paper, paperboard or cardboard, prior to
introduction in the die and subsequent deformation. In
particular, if the starch suspension is applied to the
further laminate material unilaterally, the print appears on
one side of the laminated composite material upon release
from the mold. In the case of unilateral application of the
starch suspension, recycled cardboard material can be used
for packaging food stuff which material does not come into
contact with the food stuff at the outside of the packages.
To obtain several printable or smooth surfaces and to
enhance strength, a plurality of layers of the further
laminate material can be introduced in the die. In this case
the starch suspension is mainly introduced between the
layers of said further laminate material.
By proper design of the die, structures can be molded into
the laminated composite material, such as, e.g., openings,
cavities, webs or ribs. This might make sense for packaging
and strength reasons. After removal from the die, the
material can be further processed by deforming, stamping,
punching and/or formating.
A preferred application of the method is the production of
packaging material. In this case the further laminate
material can be preformed to a packaging shell.
The combination of further laminate material and starch foam
results in the finished articles having much higher strength
than its individual components or addition thereof without

21434 ~'~
intimate bonding. The laminated composite material has low
specific weight and relatively thin walls. Moreover, it
exhibits considerably improved cold- and heat-insulating as
well as shock-absorbing properties in comparison to
conventional plastics and is antistatic.
The combination of, for instance, flat material and starch
foam requires no additives such as hot or cold glue or
plastics, etc. As a result, the laminated composite material
can be easily recycled in addition to being biodegradable
and compostable because it can be disposed of as
monomaterial and at very low cost. In particular, if paper,
cardboard or paperboard is used as the flat material, the
laminated composite material can be recycled in the paper,
cardboard or paperboard production.
The properties of the laminated composite material of the
invention permit a multitude of applications other than
packaging. For example, the material can be used in
construction, electronics and the automobile manufacture for
insulation purposes. Furthermore, it can be used for fashion
articles having fairly high stability, such as furniture
which must be recyclable due to their short life.
Using an example, the method of the invention will be
described in more detail below.
In a continuous process a starch suspension is prepared
wherein liquid and solid adjuvants are automatically
measured, finely dispersed in a homogenization step and
reacted. Potato starch, corn swelling starch and water are
present in the suspension in a weight ratio of 100:5.2:106.
Furthermore, a temperature- and pressure-controlled
expansion molding apparatus having a similar construction as
a waffle iron and comprising a mold made of cast iron in the
form of a packaging shell is heated to 220°C. The die of the

21.43432
6
molding apparatus is made of two parts. A preformed shell is
placed as flat cardboard material in the lower mold part.
Then 21.5 g of starch suspension is poured into the shell
and the two-part die is closed. The starch suspension is
foamed, dried, cured and thereby solidly combined with the
cardboard shell. After a dwell time of about 70 seconds, the
finished packaging shell in the form of laminated composite
material is removed.
The expansion molding apparatus can be rearranged for the
production of a multitude of surface structures for plate-
like laminated composite materials. This merely requires
replacement of the mold made of cast iron. Thus, a variety
of sorting devices for containers to store assortments of
small parts (e.g., screws or small household articles) or to
store pressure-sensitive and perishable food stuff (e. g.,
chocolates or eggs) can be produced, for example.
The shell has a specific weight of 190 kg/m3 and excellent
packaging properties. It combines high strength and low
weight, exhibits cold- and heat-insulating, shock-absorbing
and antistatic properties. It is readily biodegradable and
compostable as well as excellently recyclable in the paper
industry.