Note: Descriptions are shown in the official language in which they were submitted.
CA 02324575 2000-09-19
t ~ , r -,
Biodegradable material for packaging
This invention relates to biodegradable material for
packaging, a process for producing such a material and the
use thereof for the packaging of articles, in particular
foods.
Nowadays one of the greatest problems with regard to the
environment is the avoidance, decrease and disposal of
waste material. This manifests itself particularly clearly
in the case of moulded articles, such as beakers, plates,
cups, bowls, cartons and other containers which are used,
for example, for packaging foods and in fast-food
restaurants. Thus, for example, foods, in particular those
intended for immediate consumption, are often sold in
voluminous packaging. Although such moulded articles are
relatively light, on being disposed of after use they add
to the quantity and volume of durabla_ solid waste material.
Because of this, owing to their considerable volume these
moulded articles take up space in refuse skips and waste-
disposal sites. They are also easily blown away by the
wind. If such moulded articles are thrown away in the open
after the food contained therein has been consumed, over
the years they often disfigure the landscape.
Many of the materials used to date for the production of
the above-mentioned moulded articles are not made from
renewable raw materials either, which also produces
considerable environmental pollution.
From the state of affairs described above, it is clear that
there is a great need for a material which can be used for
moulded articles, in particular packaging, which is
produced,predominantly from renewable raw materials and is
very rapidly biodegradable.
Accordingly, the object of the present invention is to
provide a material which is produced predominantly from
renewable raw materials and is very rapidly biodegradable.
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According to the invention, this is achieved by a
biodegradable packaging material which is distinguished by
having the following components:
(a) 45 to 72 wt.% starch,
(b) 18 to 45 wt.% cellulose-containing fibres,
(c) 0.2 to 10 wt.% fat-containing release agent,
(d) 0.05 to 3.0 wt.% emulsifier and
(e) 2 to 15 wt.% water,
the quantities given in wt.% each being based on the
biodegradable material.
The material according to the invention thus contains
starch as the main component and cellulose-containing
fibres, as well as a fat-containing release agent, an
emulsifier and water as minor constituents. The packaging
material according to the invention may also contain
further additives, for example, fillers, such as chalk,
kaolin, talc, gypsum, alumina, titanium dioxide or
aluminium oxide, fluxing agents, such as magnesium
carbonate, magnesium hydroxide carbonate, sodium hydroxide
solution and ammonium hydroxide, as well as coloured
pigments and food colorants. But the material according to
the invention may also consist only of the stated
components (a) to (e), that is, there may be no additional
components in the material according to the invention apart
from those which are present as the usual accompanying
substances in the components (a) to (e), for example,
contaminants of starch.
In the material according to the invention, the starch and
the cellulose-containing fibres form a starch-fibre
composite which contains the fat-containing release agent,
the emulsifier and the water, this sr_arch-fibre composite
being formed by gelatinisation of the starch. This means
that at least a part of the starch in the material
according to the invention can be present in the form of
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gelatinised starch, and it has been found advantageous that
the greater part to the whole of the starch in the material
according to the invention, and consequently in the starch-
fibre composite, be present in the form of gelatinised
S starch. The term "gelatinised starch" indicates that this
is produced from native starch or from chemically and/or
physically modified starch by first of all heating the
starch in the presence of water and then optionally cooling
it. The fat-containing release agent, the emulsifier and
the water can be evenly distributed in the starch-fibre
composite.
The material according to the invention can be produced
from a dough containing the specified components (a) to (d)
in the proportions required in the material according to
the invention, but with the water content being more than
15 wt.%. This dough is packed, for example, into a closed
baking mould and thus made into the required shape and
subsequently baked. As a result of the baking, part of the
water escapes as steam with a great increase in pressure,
whereby a material according to the invention is obtained.
The steam escapes from the baking mould through openings
specially designed for the purpose. The material according
to the invention thus produced is removed from the baking
mould after the baking process.
The starch present in the material according to the
invention may originate from natural starch, chemically
and/or physically modified starch and mixtures of these.
Examples of the natural starch present in the material
according to the invention are potato starch, maize starch,
rice starch and wheat starch as well as other starches
obtained'from vegetable materials. Potato starch is
preferred, as firstly it is obtainable commercially in
large quantities at an economical price and secondly it
produces materials according to the invention which have
particularly good material properties. In addition, potato
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starch has a large swelling volume, as a result of which
pastes which promote viscosity are obtained, as well as
good adhesive properties.
The starch is present in the material according to the
invention in a quantity of 45 to 72 wt.%, preferably 58 to
66 wt.% and particularly preferably 64 to 66 wt.%, in each
case based on the material according to the invention.
These quantities of starch in the material according to the
invention produce a starch-fibre composite which is
mechanically particularly stable as well as a very rapid
biodegradability.
The material according to the invention contains cellulose-
containing fibres which, together with the starch which is
also present, form the starch-fibre composite described in
more detail above, which constitutes the basic structure of
the material according to the invention. The term
"cellulose-containing fibres" indicates fibres of any type
which contain cellulose or consist of cellulose. In a
preferred embodiment, the cellulose -containing fibres are
pulp fibres, i.e. fibres which can be obtained from pulp.
Pulp is a term for the finely fibrous composition,
consisting predominantly of cellulose, obtained on the
decomposition of wood or other fibrous plants.
The term "fibres" used in the present Application indicates
fine, thin structures of limited length, with the length
being greater than the width. They may be in the form of
single fibres or bundles of fibres. Such fibres can be
produced in the manner known to the person skilled in the
art, and here it has proved to be particularly advantageous
if in the production of the fibres the cellulose-containing
material is crushed, for example, by means of a hammer
mill.
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In a preferred embodiment of the material according to the
invention, the length of the cellulose-containing fibres is
in the range of 0.1 to 3.0 mm; the width of the cellulose-
containing fibres is preferably in the range of 0.01 to
5 0.06 mm.
The quantity of cellulose-containing fibres in the material
according to the invention is 18 to 45 wt.%, preferably 20
to 30 wt.%, particularly preferably 21 to 24 wt.% and most
preferably approximately 24 wt.%, in each case based on the
material according to the invention. These quantities of
cellulose-containing fibre in the material according to the
invention, in a particularly advantageous way, enable the
material according to the invention to have a good
mechanical stability and an excellent biodegradability.
The ratio of starch to fibre in the material according to
the invention can be so adjusted that it is 1:1 to 4:1,
preferably 3:1 to 2.5:1, for example, approximately 2.7:1.
As already explained above, the material according to the
invention contains a fat-containing release agent, which is
present in a quantity of 0.2 to 10 wt.%, based on the
material. The quantity of fat-containing release agent is
preferably 0.2 to 2.5 wt.% and particularly preferably 0.6
to 1.3 wt.%, in each case based on the material according
to the invention.
The term "fat-containing release agent" covers compositions
of any type which contain a fat or several different fats
and facilitate the release of the material according to the
invention from the baking mould after the baking process.
Fats are triglycerides, i.e. esters of glycerol, wherein
the three hydroxyl groups are esterified by fatty acids.
Here the fatty acids in a fat molecule can be identical or
different. The fat may be a synthetic or naturally-
occurring fat, such as a vegetable fat or animal fat. The
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fat may moreover be partially or completely hardened;
completely hardened fats have an excellent stability in
storage and do not become rancid. In addition, it is an
advantage if the fat-containing release agent has a good
S stability in storage and a high separation efficiency, and
is physiologically safe. It is also useful if the melting
point of the fat is above room temperature (approximately
18°C), for example, 40°C or higher, as a better water
repellency of the material according to the invention is
thereby achieved.
In a preferred embodiment of the fat-containing agent used
in the material according to the invention, this agent
contains mainly fat. The quantity of fat in the fat-
containing agent is advantageously at least 90 wt.%,
preferably at least 94.5 wt.% and particularly preferably
at least 98 wt.%, in each case based on the fat-containing
agent. The fat-containing agent may also consist entirely
of fat .
Besides the fat or fats, the fat-containing release agent
may contain small quantities of other constituents such as,
for example, oil or wax, neither of which should be fats,
or lecithin.
The fat-containing agent preferably has the following
composition, the data in wt.% being based on the fat-
containing agent: approximately 64.5 wt.% vegetable fat,
approximately 30.0 wt.% animal fat and approximately
5.5 wt.% of a mixture of lecithin and a wax, preferably
beeswax. This fat-containing agent is distinguished by
having an excellent stability in storage, a good separation
efficiency and by being physiologically safe. It is
accordingly most suitable for an agent according to the
invention.
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Surprisingly, it has now been found that these fat-
containing release agents, in particular in the quantities
used, have no adverse effect on the structural properties
of the material according to the invention. The excellent
mechanical stability of the packaging material is thus not
adversely affected either. Furthermore, the odorous
properties of the material are not adversely affected
either, despite the high quantities of fat which are
introduced into the material according to the invention via
the fat-containing release agent; that is, the packaging
material does not smell unpleasant, even on prolonged
storage. Furthermore, it is not necessary to grease the
baking mould used for the production of the material
according to the invention and the material can still be
easily removed from the baking mould. It is thereby
possible to dispense with the greasing of the baking mould
with a liquid release agent, which is otherwise necessary
in the production of biodegradable materials for packaging,
and thus firstly the production is made more economic and
secondly there is no ensuing encrustation of the baking
mould by the liquid release agent. Moreover, it has been
found that the material according to the invention is also
rendered water-repellent by the above fat-containing
release agent.
As already explained above, the material according to the
invention contains an emulsifier. Here the term
"emulsifier" covers compounds of any type which are
amphiphilic, i.e. which contain a lipophilic and a
hydrophilic group in the molecule, the emulsifier not being
a fat. The emulsifier advantageously has a melting point
higher than room temperature, for example, approximately
40°C or higher. The emulsifier brings about a homogeneous
distribution of the fat-containing release agent which is
also present in the material according to the invention. It
has also been found advantageous, especially when the
material according to the invention is used as packaging
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for food, that the emulsifier be permitted under the food
laws. The emulsifier is preferably a mono- or diglyceride
of edible fatty acids, which is esterified with a
carboxylic acid, such as citric acid, mono- and
S diacetyltartaric acid, lactic acid or acetic acid and
tartaric acid. These emulsifiers are classified under EEC
Number 472. The term "edible fatty acids" is a common term
in the field of fats, so that the person skilled in the
relevant art knows which fatty acids can be used. The
emulsifier can also be a fatty alcohol ether sulfate, a
fatty alcohol sulfate, in each case preferably with a
higher fatty alcohol (from 12 C atoms), an alkali metal
salt of a higher fatty acid (fatty acid with 12 or more
carbon atoms), for example, sodium stearate. The emulsifier
may also be a mixture of two or more of the above
emulsifiers.
The quantity of the emulsifier in the material according to
the invention is 0.2 to 3.0 wt.%, preferably O.OS to
0.8 wt.% and particularly preferably 0.2 to 0.4 wt.%, in
each case based on the material according to the invention.
In this connection, it was surprising that with such small
quantities, even large quantities of fat-containing agent
can be introduced homogeneously into the material according
to the invention.
Surprisingly, the water-repellency of the material
according to the invention is improved by the emulsifier.
In addition, the separation efficiency can also be improved
with the emulsifier, that is, after the dough which
constitutes the material according to the invention has
been baked, the material according to the invention can be
removed from the baking mould even more easily.
In addition, water is present in the material according to
the invention in a quantity of 2 to 1S wt.%, preferably 6
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to 12 wt.°s, in each case based on the material according to
the invention.
Preferred materials according to the invention are shown in
Table 1 below.
Table 1: Composition of materials according to the invention (in wt.%)
Type of Z1 Z2 Z3 Z4 Z5 Z6 Z7 ZS Z9 Z10 Z11
raw material
Starch 65.5 65.465.1 64.864.4 65.1 64.864.5 64.262.9 59.5
Fibre 24 24 24 24 24 23 23 23 23 22 21
Fat 0.2 0.3 0.6 0.9 1.3 1.6 1.9 2.2 2.5 4.8 9.2
Emulsifier0.3 0.3 0.3 0.3 0.3 0.3 0.3 0.3 0.3 0.3 0.3
Water 10 10 10 10 10 10 10 10 10 10 10
Type of Z12 Z13 Z14 Z15 Z16 Z17 Z18 Z19 Z20 Z21 Z22
raw material
Starch 65.75 65.5 65.264.8 64.364.9 64.5 64.163.7 61.657.1
Fibre 24 24 24 24 24 23 23 23 23 22 21
Fat 0.2 0.3 0.6 0.9 1.3 1.6 1.9 2.2 2.5 4.8 8.9
Emulsifier0.05 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 1.6 3.0
Water 10 10 10 10 10 10 10 10 10 10 10
Starch: potato starch
Fibre: pulp fibre
Fat: mixture of 64.5 wt.% vegetable fat, 30 wt.% animal fat and 5.5 wt.%
lecithin and
beeswax
Emulsifier: monoglyceride citrate
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The material according to the invention excels in having a
multitude of advantages. Firstly, it has a high mechanical
stability, which is still very high even where the
thicknesses (wall thicknesses) of the material are small,
5 i.e. approximately 2 mm. This excellent mechanical
stability is achieved in particular through the high
content of cellulose-containing fibres, which may be to up
to 45 wt.~. At the same time the flexibility of the
material according to the invention is very high, which is
10 particularly surprising, as cooled starch is very brittle.
In addition, the material according to the invention is
resistant to cold water for up to 1 hour. Furthermore,
articles produced from the material according to the
invention, for example, a container and an accompanying
lid, can be bonded together by moistening with water, with
a very good adhesion of the two articles to one another
being achieved. The material according to the invention is
also virtually completely biodegradable within 28 days, in
accordance with DIN 54900. Moreover, the material according
to the invention is stable in storage for a long period,
i.e. during storage there is no change in the material
according to the invention. The material also consists
predominantly of biologically occurring raw materials and
can therefore be referred to as "biological" material.
Finally, the material according to the invention need not
be adjusted to a specific water content by means of a
special conditioning step.
The material according to the invention can consequently be
used extremely well as material for moulded articles (i.e.
articles which have a definite shape) of any type, for
example, as disposable tableware, as fast-food packaging
(containers for hamburgers and chips), as packaging for
foods, for example, dry, moist, paste-like and fried food.
After a biodegradable barrier layer has been applied to the
material according to the invention, this can then be used
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as a receptacle for liquid foods, such as hot beverages and
soups.
The moulded articles can assume any shape, for example, the
shape of a bowl, a plate, a beaker, a dish. Further
examples of moulded articles which can be produced with the
material according to the invention are shown in Figures 1
to 4.
In addition, the moulded articles may have the shape of an
urn, of the type used for cremations, or the shape of a
rocket, as used for fireworks.
The present invention also provides a process for producing
a material for packaging, in particular of the type
described above, wherein first of all a baking composition
is prepared by mixing 7 to 22 wt.% cellulose fibres, 18 to
36 wt.% starch, 0.1 to 4.6 wt.% fat-containing release
agent, 0.1 to 1.5 wt.% emulsifier and 50 to 60 wt.% water,
in each case based on the baking composition, and then
baking this composition, with the formation of a.moulded
article.
The term "baking composition" indicates compositions of any
type which can be baked, i.e. expanded by steam. The baking
composition which is used in the process according to the
invention can be described as soft, semisolid dough.
After the baking process, a product (material) of the
following composition can be obtained:
(a) 45 to 72 wt.% starch,
(b) 18 to 45 wt.% cellulose-containing fibres,
(c) 0.2 to 10 wt.% fat-containing release agent,
(d) 0.05 to 3.0 wt.% emulsifier and
(e) 2 to 15 wt.% water.
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It can, therefore, be the packaging material according to
the invention described in more detail above. Consequently,
it is advantageous if the starch, the cellulose-containing
fibres, the fat-containing release agent and the emulsifier
used in the process according to the invention are the
components used above in connection with the material
according to the invention.
A preferred quantity of starch used in the process
according to the invention is 30 to .32 wt.%, based on the
baking composition.
In a preferred embodiment of the process according to the
invention, the quantity of cellulose-containing fibre is 10
to 12 wt.%, based on the baking composition.
The fat-containing release agent in the baking composition
is preferably 0.1 to 1.2 wt.%, with 0.3 to 0.6 wt.% being
particularly preferred.
The preferred quantity of emulsifier used in the baking
composition in the process according to the invention is
0.03 to 0.4 wt.%, particularly preferably 0.1 to 0.2 wt.%.
The water may be present in the baking composition in the
process according to the invention in a quantity preferably
of 54 to 58 wt.%.
In the process according to the invention, the cellulose-
containing fibres are preferably used in the form of a non-
woven fabric. For this, the cellulose-containing fibres are
first of all processed to form a non-woven fabric in the
conventional manner. A non-woven fabric composed of
cellulose-containing fibres can be produced, for example,
by crushing webs of pulp with a hammer mill (unravelling
them), individual fibres thus being obtained. These
individual pulp fibres are then processed to form a
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non-woven fabric, as is conventional, for example, in the
hygiene industry for producing cotton wool for sanitary
towels. In the additional steps of the process according to
the invention, the non-woven fabric can be spread out flat,
S for example, on a conveyor belt. The remaining components
(a) and (c) to (e) are then applied to the non-woven fabric
on this non-woven fabric spread out on the conveyor belt.
Here the conveyor belt can serve to transport the non-woven
fabric to the positions at which the addition of the
remaining components takes place.
In a preferred embodiment of the process according to the
invention, the starch consists partly of native starch and
partly of boiled starch (starch which has been heated in
water (boiled)). The favourable proportion of native starch
to boiled starch is in the range of 1.0:1 to 4.0:1,
preferably 2.5:1 to 3.5:1, particularly preferably
approximately 3:1. The boiled starch can contain the entire
water content of the dough as well as the emulsifier, the
fat-containing agent and optionally other additives. The
native starch and the chemically and/or physically modified
boiled starch can be added separately to the cellulose-
containing fibres.
For the separate addition of the native starch and the
boiled starch, it has been found particularly advantageous
to proceed in the following manner:- A mixture is prepared
in a boiler by mixing together the water, the fat-
containing agent, the emulsifier, optionally other
additives and a portion of the starch in the form of native
starch and heating for 10 minutes to 1 hour, preferably 20
minutes to 40 minutes, at a temperature of 60°C to 80°C,
preferably 64°C to 68°C. As a result of heating the starch-
containing mixture in the boiler, the originally added
native starch is converted into gelatinised starch (boiled
starch). Ultimately, this means that the cellulose-
containing fibres are mixed both with the gelatinised
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starch in the form of the mixture described above and with
the native starch, namely, the remaining portion of all the
starch.
It is possible to add first of all the boiled starch and
then the native starch to the cellulose-containing fibres.
However, the native starch can first of all be added, and
then the boiled starch. If the cellulose-containing fibres
are in the form of a non-woven fabric, for example, on a
conveyor belt, then the mixture containing the boiled
starch described above can first of all be applied to the
non-woven fabric, whereby a two-layered structure is
obtained, to which the native starch is then applied, for
example, by trickling or scattering. Surprisingly, it has
now been found that this procedure ensures that a precise
composition in small volume elements, which can then be
easily processed into a baking composition, is achieved.
After having been combined, the above-mentioned components
are mixed. Here the components can be mixed in a
conventional manner, for example, by kneading with a
kneader, such as a continuous kneader. In the course of
kneading there may be a resulting reduction in volume of
approximately 7:1, because the fibres have a very low
density. The kneading process is considerably facilitated
through the addition of the precise composition in small
volume elements.
The baking composition obtained is then baked. For this,
the baking composition is placed (metered) into a baking
mould and heated in the closed baking mould for 0.5 minutes
to 15 minutes, preferably 1 minute to 3 minutes and
particularly preferably 1.5 minutes, at a temperature of
I00°C to 300°C, preferably 150°C to 220°C and
particularly
preferably 190°C to 200°C. The baking mould is fashioned
according to the shape of the required end product, for
example, in the shape of a bowl. The baking mould can be
CA 02324575 2000-09-19
formed by at least two baking plates, i.e. an upper and a
lower baking plate, which are held in baking tongs, the
internal surface of the baking plates being kept apart
while the baking mould is maintained in the closed position
5 by bolts, with the formation of a mould cavity, and the
mould cavity is filled with the baking composition. The
baking mould has specially shaped openings for release of
the steam. A large number of baking tongs can also be used
for the simultaneous production of a large number of
10 moulded articles. The baking composition can be metered
into the baking mould by compressed air, spiral conveyors,
pumps or by application of a vacuum, the use of compressed
air being preferred. The metering can be carried out at a
temperature of up to 80°C.
Such devices for baking are based on the known per se
technology of waffle baking.
While the baking composition is in the process of being
baked, the water contained in this composition is removed.
Here it is advantageous to design the baking process in
such a way that the residual water content in the material
obtained after baking is less than 5 wt.o. Through the
removal of the water, the composition is expanded and the
starch contained in the composition is gelatinised, whereby
the previously described material according to the
invention having the starch-fibre composite structure can
be obtained. In storage or in normal use, the material
according to the invention can take up water from the
environment, so that the water content is ultimately 5 to
15 wt.%, preferably 6 to 12 wt.%, based on the baking
composition.
The process according to the invention has a number of
advantages. Owing to the special composition of the baking
composition, the flowability of the baking composition used
in the process according to the invention is distinctly
CA 02324575 2000-09-19
16
improved, so that the per se highly viscous baking
composition can be accurately metered by metering pumps. It
is thereby possible to carry out the process according to
the invention continuously. Furthermore, it is not
necessary to grease the baking mould. All moulded articles
produced by the process according to the invention were
able to be produced quickly, economically and with
excellent material properties as regards stability of form,
fracture strength and elasticity, density of structure and
surface condition. Owing to the special composition, the
material according to the invention, with a water content
of less than 5 wt.%, immediately after baking is already so
outstandingly stable that it can be further processed or
used straightaway.
Short description of the Figures:-
Figures 1 to 4 show examples of moulded articles which can
be produced with the material according to the invention.
Figure 1 shows an article of moulded packaging 1 which has
a base and cover section 2,3, connected by a hinge 4, and
is suitable for use, for example, as a closable receptacle
for food, even in the hot state. Owing to the high
elasticity, the hinge 4 produced from the material
according to the invention can be repeatedly opened and
closed. This is all the more amazing, as materials based on
starch are usually extremely brittle and fracture easily.
Figure 2 shows a moulded article l in the form of an open
rectangular container, which can also be combined with a
corresponding counter moulded article to form a completely
closed package. The tray-shaped moulded article 1 has a
multiplicity of semicylindrical indentations 5, each of
these being subdivided into a longer segment 6 and a
shorter segment 7; this arrangement is repeated
symmetrically on the other side of the moulding, separated
CA 02324575 2000-09-19
17
by a central crosspiece 8. Lateral "feet" 9 increase the
stability of the shape and improve the support and stacking
properties of the moulded packaging. Such a packaging
container can be used, for example, as a receptacle for
ballpoint pens, lipsticks, cosmetic articles, pencils,
writing implements, or in pharmacy, for example, as a
receptacle for packaging tubes.
Figures 3 and 4 show relatively deep moulded articles 1, of
the type which can be used, for example, as flowerpots,
seedboxes or for other packaging or covering purposes.
The following Examples illustrate the invention.
Examples 1 to 22: Production of materials according to
the invention
Baking compositions (doughs), the composition of which is
given in Table 2, were prepared as follows:-
The given quantities of water, emulsifier, fat-containing
agent and the proportion of native patato starch indicated
in Table 2 as being boiled starch were placed in a boiler
and heated at approximately 65°C for approximately 30
minutes, with stirring. Boiled starch which also contained
the emulsifier and the fat-containing agent was thus
obtained.
A pulp non-woven fabric was produced in conventional manner
from pulp fibres of 0.1 mm to 3.0 mm in length and 0.01 to
0.06 mm in width.
The pulp non-woven fabric was then spread out flat. To this
pulp non-woven fabric was then applied first the boiled
starch described above, so that a layer of boiled starch
containing an emulsifier and fat-containing agent was
formed on the pulp non-woven fabric. The quantity of native
CA 02324575 2000-09-19
18
starch given in Table 2 was then scattered onto the layer
of boiled starch. The composition thus obtained was
subsequently introduced into a kneader and therein
thoroughly kneaded in order to blend the components,
whereby a baking composition (dough) was obtained.
The dough was then placed in a baking mould and baked at
approximately 195°C for approximately 90 seconds.
Materials according to the invention, which were produced
predominantly from renewable raw materials and were rapidly
biodegradable, were thus obtained. Moreover, these
materials had a high mechanical stability at a wall
thickness of approximately 2 mm, accompanied by good
flexibility, and were resistant to cold water for up to 1
hour.
CA 02324575 2000-09-19
19
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