Note: Descriptions are shown in the official language in which they were submitted.
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COMPOSITIDN FOR PRDDUCING . ~QGI~7L DE~ASI;E S$APED
BC3DIE'S AND ~HDD FOR PRODUCING SUCH A COPiP05ITION
The invention provides a dry mixture and a bakable material
for producing biodegradable moulded items and a process for
producing such a dry mixture or bakable material. The
invention also provides the moulded items produced from
this dry mixture.
Packaging materials accumulate in large amounts in
industry, in trade and in the home environment. In fast-
food chains, for example, large quantities of foods such as
for example hamburgers, chips, sausages etc., and also hot
and cold drinks are sold in plastics packaging such as, for
example packaging based on polyethylene, polypropylene,
polystyrene, etc. Furthermore, packaging based on plastics
is also widely used in the trading sector. Thus, for
example, fruit is offered for sale in pre-set amounts in
plastic trays. Furthermore, for example, apples or peaches
are also transported and sold in trays with hemispherical
indentations. One apple or one peach is placed in each
hemispherical indentation. These trays are increasingly
produced from a plastics material.
The containers mentioned above, made of plastics and in the
shape of beakers, plates, cups, pots, boxes and trays of
all kinds have the advantage that they have a low weight. A
low weight for these containers is an advantage with regard
to the transport costs involved, both when transporting the
empty containers themselves and also when transporting the
goods stored in these containers such as, for example,
fruit .
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Containers made from plastics are generally disposed of as
waste after being used once. As a result of the many
different uses and due to the large numbers in which these
containers are used on a regular basis, these containers
lead to a considerable amount of waste material. The worst
disadvantage is that these containers made from plastics
have extraordinarily long durability. Currently, there are
substantially two processes available for disposing of
these plastics containers.
In the first process, plastics containers contained in any
waste material are incinerated in a refuse incinerator.
This procedure is disadvantageous. On the one hand, the
productibn of plastics containers is based on the
consumption of petroleum oil, i.e. a non-renewable source
of raw materials. Furthermore, this procedure requires the
construction of more refuse incinerators or the more
intense use of refuse incinerators that are already
available. However, as a result of increased public
environmental awareness, the construction of new refuse
incinerators would barely be tolerated at present. To this
extent, there are increasing difficulties in disposal with
regard to the constantly increasing quantities of waste
material being produced.
In the second process, the plastics containers are taken to
further processing as the starting material fbr freshly
produced, plastics containers. However, this procedure
requires firstly the production of single types of plastics
containers and then, after use of the plastics containers,
costly separation of the containers, depending on the
particular type of plastics used. Furthermore, since
plastics containers are used in particular in fast-food
chains, the containers have to be cleansed of food
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residues, fat, ketchup, etc. after use. However, such a
procedure is complicated and cost-intensive so the used
containers are normally incinerated in a refuse incinerator
in accordance with the previously specified process.
With regard to the disadvantages associated with plastics
containers, attempts have been made for same considerable
time to produce biodegradable containers which can be used
as plates, cups, holders, trays, etc. for the uses
mentioned above.
The prior art discloses moulded items based on starch which
are partly or fully biodegradable.
~i
PCT/EP95/00285 (WO 96/23026) discloses a process for
producing moulded items in which a viscous material
consisting of biodegradable fibrous material, water and
starch is baked in a baking tin with the production of a
fibrous material/starch composite. In this case, waste
paper, recycling material yr biodegradable fibrous material
which has previously been pulled apart by shredding is used
as the fibrous material. The proportion of starch to water
in the viscous material is preferably 1:3 to 1:2. The
baking time can be varied between 0.5 and 15 minutes,
wherein it is stated that short cycle times in the range of
1 to 3 minutes are generally sufficient. However, if the
proportion of water in the baking material is' raised, a
baking time between 4 and 12 minutes is required in order
to obtain good results.
The disadvantage is that, in order to produce shorter
baking times, the water content in the baking material has
to be reduced so that ultimately larger amounts of starch
and fibres are used per moulded item produced.
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For economic reasons, mass-produced products, as is the
case with the moulded items in question here, for example
for use in fast-food restaurants, have to be capable of
production at a low price. In this regard, short production
times and a low consumption of material are of critical
importance to a manufacturer in order to be able to promote
his products successfully on the market.
US 5,607,983 discloses a process for producing a
biodegradable moulded item. Short plant fibres, plant fibre
powder, gelling material, water, propellant and auxiliary
substances are stirred to produce a dough and then heated
at a temperature of 150°C to 200°C far 2 to 3 minutes and
then dried for 20 minutes at a temperature of 120°C.
The disadvantages are that, on the one hand this process
requires the use of a propellant and on the other hand the
production time is very long. Neither the additional use of
a propellant nor the production time of altogether 22 to 23
minutes per moulded item can lead to economically viable
production of such moulded items as mass-produced articles.
WO 95/04104 discloses a process for producing a
substantially biodegradable polymer foam, wherein
thermoplastic or destructured starch, a biodegradable
hydrophobic polymer and a biodegradable fibrous or capsule-
like material which has the ability to bind water in
capillaries, are mixed. This process is costly because, in
a first step, firstly thermoplastic starch has to be mixed
with fibres which have been saturated with water, within a
precisely defined temperature and pressure range wherein it
is essential that the water bonded in capillaries in the
fibres is not released. Foam production then takes place in
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a second step, in which both the temperature and the
pressure are increased so that the water bonded in
capillaries in the fibres is released in order to expand
the starch. This process requires a costly process
5 management system with regard to the precise temperature
and pressure range which has to be maintained.
DE 40 09 408 A1 discloses that a dough can be produced from
cellulose-containing and protein-containing materials and
water, which can subsequently be shaped and then baked in
order to provide a degradable, disposable item. The
disposable item produced by this process consists of a
protein lattice in which the cellulose is embedded.
The disadvantage is that the disposable item produced in
this way has to have a wall thickness of about 0.5 cm, for
stability reasons. The production of thin-walled moulded
items, e.g. in the shape of cups, beakers, pots, bowls,
etc., in an acceptable quality, is not possible.
Furthermore, for the stability reasons given above, it is
not possible to provide light-weight trays for fruit such
as e.g. apples, peaches, etc. using this process.
Furthermore, as a result of the thick walls, elevated use
of materials is required. Also, these thick walls require
long baking times of about three to ten minutes and a high
baking temperature of about 250°C. Thus, using the process
disclosed in DE 40 09 408 A1, high-quality moulded items
cannot be produced. Furthermore, this process is unsuitable
for producing low-price, high-quality mass-produced items
due to the high materials input.
EP 0 683 831 B1 discloses a process for dispersing
cellulose-containing fibres in water. This process enables
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the use of cellulose-containing fibres which are bonded
together, such as are present, for example, in paper
materials. With a solids content of up to 80 %,
hydrocolloids such as e.g. starch, plant or animal protein,
are added to an aqueous dispersion of cellulose-containing
fibres under the effects of a strong mechanical force in
order to provide a highly viscous material in which the
cellulose-containing fibres separate and become distributed
in the viscous material. It is necessary to use enough
hydrocolloid for all the water to be bonded. Corn flour is
normally used as the hydrocolloid.
The disadvantage is that a high consumption of material is
associated with the production of a moulded item from the
highly viscous material prepared using this process, due to
the high solids content. Thus, the use of this highly
viscous material does not enable the low-cost production of
moulded items, which is a severe disadvantage in particular
when producing mass-produced items. Furthermore, the
moulded items produced from this viscous material have a
high weight, which ultimately leads to increased transport
costs for the moulded items produced.
The object of the present invention is to provide a
composition far producing a biodegradable moulded item
which enables the reliable and low-cost production of high
quality biodegradable moulded items. In particular there is
a need for a composition which facilitates a reduction in
the production time and a reduction in the amount of
material used. Furthermore there is a requirement for a
process for producing such a composition.
The object of the present invention is achieved by a dry
mixture which contains starch, biodegradable fibrous
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material and protein and optionally additives fvr producing
biodegradable moulded items.
The expression "dry mixture" in the context of the
invention is understood to be a free-flowing composition in
the form, for example, of a powder or granules. It is not
necessary that the dry mixture according to the invention
is absolutely dry. The dry mixture may contain a residual
moisture content of, for example, about 5 to about 14 wt.%,
preferably less than 9 wt.%.
In the context of the invention, the expression "starch" is
understood. to include natural starch, chemically and/or
physical'~ly modified starch, industrially produced or
genetically modified starch and mixtures thereof. Cereal
starches such as, for example, those obtained from maize,
waxy maize, wheat, barley, rye, oats, millet, rice, etc. or
cassava or sorghum can be used as starch. Obviously, the
starch present in leguminosae such as beans or peas or the
starch present in fruit such as, for example, chestnuts,
acorns or bananas can also be used. Furthermore, the starch
present in roots or tubers can be used.
Particularly suitable for the present invention is potato
starch. Potato starch advantageously contains one
phosphorus ester group per 200 to 400 anhydroglucose units.
The negatively charged phosphate groups are linked to the
C6 posita.on in the anhydroglucose unit. When producing a
bakable material from the dry mixture according to the
invention, the negatively charged phosphate groups cause
unravelling of the individual potato amylopectin molecules
via mutual repulsion. Due to mutual repulsion by the
negatively charged phosphate groups, the bends in the
amylopectin molecule are largely unfolded or stretched out.
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This presence of esterified phosphate groups produces a
high viscosity in potato starch/water mixtures.
The expression "biodegradable fibrous material" is
understood to include in particular plant and animal
fibres. Plant fibres used in the context of the invention
are preferably cellulose-containing fibres. Cellulose-
containing fibres are those fibres of any type which
contain cellulose or consist of cellulose. Animal fibres
are understood to be so-called protein fibres such as, for
example, wool, hair or silk.
Particularly preferably, plant fibres are used which can be
present 'with different lengths and widths. In particular,
plant fibres are used which have a length in the range
about 50 ~m to about 3000 Vim, preferably about 100 ~m to
about 2000 Vim, mare preferably about 150 ~m to about
1500 Vim, still more preferably about 200 ~m to about
900 Vim, most preferably 300 ~m to about 600 Vim. The width
of the plant fibres can lie in a range from about 5 ~m to
about 100 Vim, preferably about 10 ~m to about 60 Vim,
particularly preferably about 15 ~m to about 45 Vim. The
fibres are mainly produced from wood, hemp or cotton. Such
fibres can be produced in a known manner by a person
skilled in the art.
The expression "protein" is understood to include
biopolymers based on amino acids. Suitable amino acids are
all the so-called pr~teinogenic amino acids, i.e. the amino
acids which normally contribute to building up proteins,
and also so-called non-proteinogenic amino acids which do
not generally contribute to the structure of proteins.
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The expression "protein", according to the invention, also
includes peptides or polypeptides. Furthermore, in the
context of the invention, the expression "protein" includes
naturally occurring protein, chemically modified protein,
enzymatically modified protein, recombinant protein,
protein hydrolysates or mixtures thereof. The protein may
be of plant or animal origin.
Surprisingly, the dry mixture according to the invention,
which contains starch, biodegradable fibrous material and
protein, facilitates a shortening in baking time of up to
35 %, preferably up to 50 ~. Furthermore, the use of
protein in the dry mixture according to the invention
y
facilitates a reduction of up to 10 wt.% to 20 wt.% in the
materials requirement when producing moulded items.
The dry mixture according to the invention can be stored,
extremely advantageously, for a long period of time without
any marked change in the composition. Advantageously, this
enables pre-preparation and storage of the dry mixture. To
this extent, it is possible, for example, to provide
subcontractors of a manufacturer of biodegradable moulded
items with the dry mixture according to the invention and
thus ensure that the moulded items produced at the
subcontractor's have the desired quality. Since water or
gelatinised starch has to be added to the dry mixture
according to the invention only at the subcontractor's,
transport costs for the dry mixture only are involved, i.e.
the water being added does not have to be transported.
In order to produce biodegradable moulded items, the dry
mixture according to the invention is first blended, with
the addition of water, to give a bakable material or a
dough. The bakable material produced from the dry mixture
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according to the invention differs from the baking
materials known from the prior art in that it is more
creamy, foamy and voluminous and thus has a lower density.
Thus, in order to produce a specific volume of bakable
5 material, use of the dry mixture according to the invention
requires less material than when using a dry mixture which
does not contain protein.
To produce a biodegradable moulded item, a specific volume
10 of bakable material (baking material, dough) is placed in a
baking tin. These baking tins are known from the waffle-
baking industry. Since a specific volume of bakable
material is placed in each of these baking tins, the
increased volume of the bakable material based on the dry
mixture according to the invention thus leads to a
reduction in materials requirement. Since moulded items
produced using the dry mixture according to the invention
are produced in very large numbers, a reduction in
materials requirement of up to 10 wt.% to 20 wt.%
represents an enormous saving in costs.
Furthermore, the use of a bakable material based on the dry
mixture according to the invention leads to a reduction in
the baking time required to produce a moulded item.
"Baking time" in the context of the invention is understood
to be the time between closing the baking tiny, which occurs
after fi3ling the baking tin with bakable material, and
opening the baking tin to remove the baked moulded item.
The baking time is shortened by up to 50 % when using a
bakable material based on the dry mixture according to the
invention. The reason for the reduction in baking time is
not clear. The inventor suspects the following:
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Due to the larger volume of a bakable material produced on
the basis of the dry mixture according to the invention, a
smaller portion by weight of bakable material is placed in
the baking tin. The smaller portion by weight of bakable
material naturally also contains less water which has to be
evaporated during the baking process. It is therefore
assumed that there is a connection between the reduction in
the amount of bakable material being baked and the shorter
baking time.
In addition, the inventor has shown that a moulded item
produced with the dry mixture according to the invention
has large and uniform pores or capillary structures within
the interior of the baked moulded item, i.e. in the
interior of the walls of the moulded item, that is for
example in the base, lid and side regions. These large
pores or capillaries facilitate the easier escape of
water/water vapour than in moulded items which have been
produced using a dry mixture without protein. Therefore, it
is assumed that there is a connection between the large
pores and capillaries and the shorter baking time.
Furthermore, with regard to the large and uniform pore
structure within the walls of conventional moulded items,
there is a weight reduction of up to 20 ~ in the moulded
items produced. A weight reduction of up to 2'0 ~ is
extremely advantageous when transporting the moulded items.
Furthermore, moulded items produced using the dry mixture
according to the invention have a closed surface. A closed
surface is of particular advantage with regard to the
thermal insulation properties of the moulded item.
Furthermore, a closed surface brings about better and more
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reliable repulsion of for example moisture or fat at the
walls or base of the moulded item.
In accordance with a preferred embodiment, starch,
biodegradable fibrous material and/or protein are fixed to
each other in the dry mixture according to the invention.
In the context of the invention, the expression "fixed to
each other" is understood to mean that the components in
the dry mixture according to the invention, i.e. starch,
biodegradable fibrous material, protein and optionally
added additives, adhere to each other with and without the
use of a.banding agent.
~i
Thus, for example, starch and biodegradable fibrous
material can be fixed to each other. Starch and protein or
biodegradable fibrous material and protein can also be
fixed to each other. Starch, biodegradable material and
protein are preferably fixed to each other. Furthermore, it
is possible that the added additives are also fixed within
any of the previously mentioned possibilities. In other
words, according to the invention, all possible fixing
combinations between the components used are possible.
Demixing of the dry mixture according to the invention is
extremely advantageously prevented in this way. For this
purpose, it may be sufficient that only stare and the
biodegradable fibrous material are fixed to each other.
Such demixing can occur, for example, during transport
using heavy goods vehicles or the railway due to regularly
occurring vibrations if, for example, the biodegradable
fibrous material and the starch are not fixed to each
other. The risk of demixing depends strongly on the
particular size of particles and/or fibres used.
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Further explanations with regard to performing the fixing
procedure are given in the details for the process for
producing the dry mixture according to the invention.
The dry mixture according to the invention is preferably
present as granules.
The expression "granules" is understood to be an
accumulation of granular grains. A granular grain (pellet)
is an asymmetric aggregate of powder particles. It does not
have a harmonic, geometric shape. The shape of a sphere, a
rod, a cylinder, etc. is produced only approximately and by
suggestifon. The surface is generally uneven and jagged, in
many cases the material is fairly porous. The so-called
fluidised bed process is often used to produced granules.
Provision of the dry mixture according to the invention as
granules advantageously enables simple packing and handling
of the dry mixture according to the invention. In
particular a dry mixture according to the invention, when
present as granules, is very easy to meter out, which is
extremely advantageous when automating a process for
producing biodegradable moulded items.
The starch present in the dry mixture according to the
invention is preferably native starch. Native'starch is
obtained, in granular form by the wet milling of starch-
containing raw materials such as e.g. cereals, tubers and
roots. Since the starch is then already present as
granules, production of the dry mixture according to the
invention as granules is very simple.
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According to a preferred embodiment, the protein is chosen
from the group which consists of naturally occurring
protein, chemically modified protein, enzymatically
modified protein, recombinant protein, protein hydrolysates
and mixtures thereof.
Preferably, about 0.5 to about 12 wt.%, particularly
preferably about 2 to about 10 wt.~ and most preferably
about 4 to about 8 wt.°s of protein is present in the dry
mixture according to the invention.
However, the amount of protein present in the dry mixture
according to the invention can vary with the protein used
or the protein mixture used. Furthermore, however, it is
also possible to determine an optimum amount for each dry
mixture of the particular protein being added by means of a
few trials within the ranges stated above.
Examples of proteins which may be used are proteins of
animal origin such as, for example, actin, myoglobin,
myosin, haemoglobin, collagen, elastin, immunoglobulins,
keratins, fibroin, conchagene, ossein, albumins, casein,
FPC (fish protein concentrate).
Proteins of plant origin which may be used are prolamines
such a e.g. gliadin, secalin, hordein, zein and maize and
soya protein.
Plant proteins such as e.g. soya, maize, pea, lupin, millet
protein, have proven to be very suitable for the purposes
of the invention. Soya protein is particularly preferably
used. Soya protein is extremely advantageously available in
large amounts at low prices.
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In accordance with a further development of the invention,
hydrophobic proteins are used as proteins. Hydrophobic
proteins are characterised by a high proportion of
uncharged amino acids in the amino acid sequence. In
5 particular, these proteins contain high proportions of
glycine, alanine, valine, leucine, isoleucine,
phenylalanine, tryptophan, proline and methionine, wherein
these provide the protein overall with a hydrophobic
character.
It is obvious to a person skilled in the art that the
proteins listed above represent only an example of the
selection in order to illustrate the invention. Obviously,
r
other proteins or protein mixtures can also be used. The
essential criterion is that, with regard to the very large
numbers of moulded items being produced, the price of the
protein or protein mixture being used is low.
In accordance with a preferred embodiment of the present
invention, the protein is chosen from the group which
consists of casein, alkali metal caseinate, alkaline earth
metal caseinate, casein hydrolysate and mixtures thereof.
Extremely advantageously, casein and caseinates are
available in large amounts at an acceptable price. With
regard to the large numbers of biodegradable moulded items
being produced from the dry mixture according~to the
invention, it is essential that the protein used in the dry
mixture according to the invention has a low price. Thus,
about 1 kg of casein can be obtained from 30 1 of skimmed
milk.
The casein is used in the form normally isolated from milk.
Naturally, it is also possible to use the a-,(3- and y- sub-
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units of casein separately or in specific combinations
thereof .
In the context of the invention, casein is obtainable
commercially as acid casein from BMI-Landshut.
Preferably, about 1 to about 10 wt.%, particularly
preferably about 2 to 8 wt.% and most preferably about 3 to
about 7 wt.% of casein is present in the dry mixture
according to the irnrention.
Plant protein is also preferably present in the dry mixture
according to the invention, preferably soya protein in an
amount off about 0.5 to about 10 wt.%.
The casein can be used as such or as an alkali metal
caseinate or alkaline earth metal caseinate. Calcium
caseinate has proven to be especially useful.
Calcium caseinate which can be used in the context of the
invention is available commercially as Caseinato Di Calcio
from BMI-Landshut.
Preferably about 1 to about 10 wt.%, particularly
preferably about 2 to about 8 wt.% and most preferably
about 3 to about 7 wt.% of calcium caseinate is present in
the dry mixture according to the invention.
In accordance with another preferred embodiment of the
invention, the dry mixture according to the invention may
contain further additives. Using these additives, it is
possible to have an effect on the properties of the
biodegradable moulded items produced from the dry mixture
according to the invention. Examples of additives which may
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be present in the dry mixture are hydrvphobising agents,
whitening agents, foodstuffs colorants, flavourings, etc.
It has proven especially beneficial to introduce an
additive or several additives adhering to the starch in
order to have an effect on the product properties of the
moulded item. Application of the additive as adhering to
starch advantageously prevents possible demixing of the
additive and starch during transport of the dry mixture
according to the invention. The dry mixture according to
the invention preferably contains up to 10 wt.%, preferably
0.3 to 5 wt.%, particularly preferably 0.9 to 1.8 wt.% of
additive.
,I
The expression "additive" in the context of the invention
includes any compounds which are suitable for affecting the
product properties of the moulded item. These additives are
preferably fully or substantially fully biodegradable.
Preferred examples of these additives are hydrophobising
agents, whitening agents, colorants, foodstuffs colorants,
flavourings, etc.
Hydrophobising agents are constituents which provide the
moulded item produced from the dry mixture according to the
invention with hydrophobic properties. Whitening agents are
compounds which are used to lighten the colour of the
moulded item. Examples of colorants which are'used are blue
colorants which are used, for example, for colouring fruit
boxes or fruit trays. The following blue colorants may be
used, for example: natural colorants or lacquer colorants.
Green colorants, for example, may also be used for
colouring pots for holding plants. The following green
colorants may be used, for example: natural colorants or
lacquer colorants.
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Foodstuffs colorants are colorants used for the design of
coloured packaging for foodstuffs. Flavourings in the
context of the invention are any, in particular
biodegradable, flavourings which provide, for example, the
moulded item produced from the dry mixture according to the
invention with a certain odour and/or taste.
A particularly preferred example of a hydrvphobising agent
is fluoroalkyl polymers, wherein the expression
"fluoroalkyl polymers" indicates that they are polymers
which are built up in particular from repeating alkyl
units, wherein one or more, optionally even all, of the
'i
hydrogen'atoms can be replaced by fluorine atoms. For
example, a hydrophobising agent based on a perfluoroalkyl
acrylate copolymer can be used.
The whitening agent can be a compound with at least one
disulfone group. Such compounds are well known to a person
skilled in the art and engaged in this industrial field. An
example of such a disulfone compound is 4,4'-bis-(1,3,5-
triazinylamino)-stilbene-2,2'-disulfonic acid.
Furthermore, the object underlying the invention is
achieved by a bakable material which contains starch,
biodegradable fibrous material, protein and water and
optionally additives.
The expression "bakable material" is understood to be a
baking material or dough which can be baked in baking
devices known from waffle technology such as e.g. baking
tongs with the formation of a moulded item. The bakable
material is placed, for example, in a heated baking tin for
such a baking device, wherein the bakable material is
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distributed in the baking tin and this is filled
completely. The bakable material present in the baking tin
emits water or water vapour when subjected to heat and this
emerges from the baking tin through the escape channels
provided. During this process, solidification of the
bakable material takes place with the production of the
desired moulded item.
The bakable material can be prepared from the dry mixture
according to the invention by adding water and optionally
additives, if these are not already present in the dry
mixture, by blending such as, for example, by stirring or
kneading.
The bakable material preferably contains about 3 wt.% to
about 15 wt.%, preferably about 5 wt.% to about 10 wt.%,
most preferably 7.8 wt.% to about 9.8 wt.% of biodegradable
fibrous material, preferably cellulose-containing fibres.
Furthermore, the bakable material preferably contains about
6 wt.% to about 30 wt.%, preferably about 10 wt.% to about
20 wt.%, most preferably about 16.1 wt.% to about 20.05
wt.% of native starch.
Furthermore, the bakable material preferably contains about
2 wt.% to about 10 wt.%, preferably about 4 wt.% to about 8
wt.%, most preferably about 5.4 wt.% to about~6.8 wt.% of
pregelatinised starch.
Furthermore, the bakable material preferably contains about
45 wt.% to about 90 wt.%, preferably about 60 wt.% to about
80 wt.%, more preferably about 60 wt.% to about 75 wt.%,
most preferably about 63 wt.% to about 71 wt.% of water.
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Protein is present in the bakable material according to the
invention in an amount of up to 10 wt.%, preferably up to
about 5 wt.%, more preferably up to about 3 wt.% protein,
most preferably up to about 2 wt.%.
5
The bakable material preferably contains 0.5 to 10 wt.% of
plant protein. Plant proteins such as e.g. soya, maize,
peas, lupins, millet protein have proven to be particularly
suitable far the purposes of the invention. Soya protein is
10 particularly preferably used. Soya protein is extremely
advantageously available in large amounts at a low price.
More preferably, the bakable material preferably contains 1
to 2 wt.% of plant protein, preferably soya protein.
15 The preceding data given as percentages by weight are each
given with respect to the total weight of the bakable
material.
Pregelatinised starch can be produced from about 90 to
20 about 99.9 wt.% water and about 0.1 to about 10 wt.% of
native starch, more preferably from about 95 wt.% water and
about 5 wt.% native starch. A starch suspension is first
produced from these two components. This starch suspension
can then be heated and subsequently cooled in order to
produce pregelatinised starch.
Heating preferably takes place at a temperature at which
the aqueous suspension of starch granules turns into a
sticky form. This temperature is also known as the Kofler
gelatinisation temperature. The Kofler gelatinisation
temperature for potato starch is between 56 and 66°C and for
maize starch is between 62 and 72°C. The suspension is held
within this temperature range, for example, for a period of
about 10 minutes. Then the pregelatinised starch is cooled.
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21
The temperature to which it is cooled is preferably about
50°C or lower.
The description given above for producing pregelatinised
starch is understood to be simply an example of a method of
production. Obviously other processes for producing
pregelatinised starch are known to a person skilled in the
art and these may be used for the present invention. For
example, the starch suspension or slurry can also be
gelatinised with steam in a so-called jet-cooker.
According to an advantageous further development, the
biodegradable fibrous material consists of cellulose-
containing fibres. Furthermore, it is preferable that the
starch is native starch. Moreover, the bakable material
preferably contains protein which is chosen from the group
which consists of naturally occurring protein, chemically
modified protein, enzymatically modified protein,
recombinant protein, protein hydrolysates and mixtures
thereof. The protein is preferably chosen from the group
which consists of casein, alkali metal caseinate, alkaline
earth metal caseinate, casein hydrolysate and mixtures
thereof. The alkaline earth metal caseinate calcium
caseinate is particularly preferred.
For further details, appropriate reference is made to the
particular specifications for the dry mixture according to
the invention.
The bakable material according to the invention can
obviously also be produced without using the dry mixture
according to the invention. The relevant individual
components, i.e. starch, biodegradable fibrous material,
protein and optionally additives can be mixed in any
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22
sequence with water to produce the bakable material
according to the invention. For example, a dough can first
be produced from starch, biodegradable fibrous material and
water, to which are then added protein and optionally
additives.
The object underlying the invention is also achieved by
using protein to produce a dry mixture or a bakable
material in order to produce biodegradable moulded items.
Furthermore, the object is achieved by a moulded item which
has been produced using the dry mixture according to the
invention or the bakable material according to the
invention.
The dry mixture according to the invention is outstandingly
suitable for producing biodegradable moulded items.
Water is added to the dry mixture according to the
invention, which contains starch, biodegradable fibrous
material and protein and optionally other additives, and
mixed until a bakable material is obtained.
A bakable material is preferably characterised by a
homogeneous distribution of all the constituents and has a
viscosity which is required for the particular purpose. The
viscosity of the bakable material can be adjusted by the
proportion of water added to the dry mixture consisting of
starch, biodegradable fibrous material and protein and
optionally additives. The preferred viscosity of the baking
material required for the particular moulded item being
produced can be determined using a few trials. It may be
advantageous to adjust the viscosity of the baking mixture,
depending on the shape, the size and the particular wall
thickness of the moulded item being produced and on the
~
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size of the particular baking tin being used to bake the
moulded item.
The bakable material produced is then baked. For this
purpose, the bakable material is placed in a baking tin and
heated in a closed baking tin at a temperature of
preferably about 100°C to about 200°C, particularly
preferably at about 150°C.
l0 The baking tin is designed as a function of the shape of
the desired end product, for example in the shape of a pot
or a beaker. The baking tin can be formed from at least two
baking sheets, i.e. an upper and a lower baking sheet,
which are held in baking tongs, wherein the inner surfaces
of the baking sheets are held at a distance when the baking
tin is in a closed, locked condition, with the formation of
a mould cavity. The mould cavity is then filled with the
bakable material. The baking tin has specially designed
evaporation openings for the escape of water vapour. A
plurality of baking tongs may also be used for the
simultaneous production of a plurality of moulded items.
Such devices for baking are based on the technology for
waffle baking which is known per se.
The duration of the baking process is substantially
determined by the size of the moulded item being baked and
also by the particular wall thickness chosen~for the
moulded'item. The baking time is normally between 10 s and
about 100 s, preferably about 30 s to about 80 s, more
preferably 60 s to 70 s:
The object of the invention is also achieved by a process
for producing the dry mixture according to the invention
(first embodiment), wherein
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a) starch, biodegradable fibrous material and protein are
mixed;
b) an aqueous solution is sprayed on during mixing; and
c) the mixture obtained in accordance with step b) is
dried.
Furthermore, the object of the invention is achieved by a
process for producing the dry mixture according to the
invention (second embodiment), wherein
a) starch and biodegradable fibrous material are mixed;
b) an aqueous protein-containing solution is sprayed on
during mixing; and
c) the mixture obtained in accordance with step b) is
dried.
The expression "aqueous solution" is understood according
to the invention to be water or a solution based on water
such as, for example, a protein-containing aqueous
solution, pregelatinised starch, protein-containing
pregelatinised starch, an additive-containing aqueous
solution, etc.
In this process, additional pregelatinised starch is
preferably sprayed on in step b) during mixing.
The fixing of, for example, starch and biodegradable
fibrous material to each other can be achieved by, for
example, spraying water on during mixing of the starch,
biodegradable fibrous material and protein and drying the
mixture. The water preferably evaporates shortly after it
has come into contact with the starch, biodegradable
fibrous material and protein; i.e. the water is added in an
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amount and over a sufficient time for the surface of the
starch particles or grains to be made slightly tacky. The
biodegradable fibrous material, for example cellulose
fibres, and the protein then remain adhering to the surface
5 of these starch particles which have been "made tacky".
Naturally, it is also possible for the protein to act as a
kind of adhesive as soon as it comes into contact with
water and fix the starch and biodegradable fibrous material
to each other. Naturally, the two effects may also occur at
10 the same time.
According to the second embodiment, an aqueous protein-
containing solution is sprayed on instead of water during
the mixing of starch and biodegradable fibrous material.
15 Fixing of the starch, biodegradable fibrous material and
protein to each other is also achieved in this second
process. Fixing the components to each other is performed
using the same effects as described for the first
embodiment.
On the one hand a sticking together of starch particles and
biodegradable fibrous materials is achieved by spraying on
an aqueous protein-containing solution. Moreover, the
spraying on of an aqueous protein-containing solution means
that the starch particles and the biodegradable fibrous
material become coated with the protein-containing solution
and thus the starch particles and biodegradable fibrous
material act as support materials for the protein.
Furthermore, pregelatinised starch as an aqueous solution
can also be sprayed on instead of water and thus achieve
fixing of the starch, biodegradable fibrous material and
protein. The pregelatinised starch preferably has a
temperature of less than 50°C. Obviously both water and
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pregelatinised starch may be sprayed on in sequence or at
the same time.
In the secand embodiment of the process according to the
invention, it is possible to spray on an aqueous protein-
containing solution and pregelatinised starch in sequence
or at the same time. Furthermore, it is also possible to
introduce the protein directly into the pregelatinised
starch and then spray on the protein-containing,
pregelatinised starch during mixing of the biodegradable
fibrous material and starch.
Drying the mixture to produce the dry mixture according to
the invention can take place, for example, in a warm
environment such as e.g. a warm stream of air. However,
other drying techniques which have long been familiar to a
person skilled in the art may also be used.
Mixing during the process according to the invention
(embodiment 1 or 2) in accordance with step b) and drying
in accordance with step c) are preferably performed in a
single step by fluidising in a fluidised bed in a warm
stream of air.
Particularly preferably, the spraying on of aqueous or
aqueous protein-containing solution and optionally of
pregelatinised starch is performed in a fluidised bed unit
in which starch and biodegradable fibrous material are
fluidised in a warm stream of air. Here again, the
pregelatinised starch can be sprayed in before or after or
at the same time as the aqueous or aqueous protein-
containing solution. Obviously, a previously prepared,
optionally protein-containing pregelatinised starch can
also be sprayed into the fluidised bed here. The solutions
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are preferably sprayed on using spray nozzles located above
the fluidised bed.
The use of a fluidised bed reactor in which the starch,
biodegradable fibrous material and optionally protein are
fluidised in a warm stream of air is especially
advantageous when the dry mixture according to the
invention is intended to be provided as dry granules.
Within the fluidised bed produced by the warm stream of
air, the water introduced with the aqueous or aqueous
protein-containing solution and the optionally sprayed on
pregelatinised starch evaporates very rapidly. Fixing of
the biodegradable fibrous material, starch particles and
protein'to each other takes place in the fluidised bed as
the water evaporates. Thus, extremely advantageously, a dry
mixture according to the invention is produced in which
demixing of starch, biodegradable fibrous material and
protein cannot occur.
The temperature of the warm steam of air in the fluidised
bed unit is preferably about 40°C to about 90°C, preferably
about 50°C to about 70°C. As mentioned above, the aqueous or
aqueous protein-containing solution and optionally
pregelatinised starch can be sprayed on via spray nozzles
located above the fluidised bed.
Furthermore, the additives mentioned above can be sprayed
on in the form of aqueous solutions. The additives can be
made up appropriately, depending on the properties of the
moulded item being produced, and sprayed on at the same
time as or in sequence with the aqueous or aqueous protein-
containing solution and optionally the pregelatinised
starch.
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Furthermore, it is possible to spray on a fat-containing
mould release agent with the pregelatinised starch sprayed
on at a temperature of about 50°C. The fat-containing mould
release agent may consist, for example, largely of fat and
also contain at least one component which is chosen from
the group consisting of oil, wax and lecithin. Beeswax is
preferably used as a wax.
Obviously, commercially available fat-containing mould
release agents such as, for example, Premix, may also be
used. Premix is a mixture of fully or partly unhardened
plant fats and can be obtained from I.C.L. van der Zon in
Essen ur~der the reference number HC 2000.
In general, plant fats and oils have proven suitable as
mould release agents. However, synthetic fats and oils may
also be used. The mould release agent is preferably chosen
from the group consisting of Soya bean oil, palm fat and
mixtures thereof. The concentration of mould release agent
is preferably 0.05 to 0.7 wt.%, more preferably 0.1 to 0.2
wt.%, each with respect to the bakable material. These
mould release agents can be sprayed on together with the
pregelatinised starch and/or protein-cr~ntaining solution,
for example as a Soya protein solution.
However, the fat-containing mould release agent may also be
added in a separate working step to the bakable material
itself or during preparation of the bakable material from
the dry mixture according to the invention. Obviously,
however, it is also possible to place the fat-containing
mould release agent directly in the baking tin immediately
before the baking process.
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The following examples are used to further illustrate the
invention.
To produce a bakable material, native starch and cellulose
fibres were placed in a fluidised bed unit on a Conidur
base with an area of 1862 cm2 (26.6 cm x 70.0 cm). The depth
of the bed was a total of about 225 mm. Potato starch (as a
powder) with a moisture content of about 16 wt.% was used
as native starch. Cellulose fibres with a length of about
600 ~.m and a width of about 30 ~,m were used as
biodegradable fibraus material.
The native potato starch and cellulose fibres were mixed
dry in a fluidised bed. Warm air with a temperature of
about 70°C and a volume flow of 480 m3/h was passed through
the starch/cellulose fibre mixture, from below the base, in
order to produce a fluidised bed.
Pregelatinised starch was sprayed on from above the
fluidised bed at a spray rate of 65 g/min for 5 minutes,
via two nozzles, each with a nozzle diameter of 0.8 mm and
a spray pressure of 1.2 bar. The temperature of the sprayed
on solution of pregelatinised starch was less than 50°C.
The product obtained consisted of granules in which starch
and cellulose fibres were uniformly banded together. (The
product temperature was 42°C and the product moisture
content was 8.6 wt.%).
The granules obtained in this way were mixed with water in
order to adjust to the following concentration ranges:
Cellulose fibres 9.72 wt.% - 7.84 wt.%
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Potato starch 20.05 wt.% - 16.17 wt.%
Pregelatinised starch 6.79 wt.% 5.48 wt.%
-
Water 63.43 wt.% - 70.51 wt.%
The bakable material mentioned above was portioned out and
the corresponding proportion of protein, i.e. casein or
calcium caseinate, was added as cited below. The protein
5 was homogeneously distributed in the bakable material, in
the proportions cited below, by mixing.
To determine the reduction in baking time, moulded items
were then baked in the same baking tins, wherein the
10 bakable~material or dough was used with and without the
addition of protein. The baking time was determined by
determining the time from closing the baking tin, after the
bakable material had been placed in the baking tin, up to
opening the baking tin in order to remove the baked moulded
15 item.
The amount of casein added in wt.% is given with respect to
100 wt.% of the bakable material mentioned above. The
reduction in baking time as a percentage was calculated
20 with reference to the time by which the baking time was
shortened in absolute terms as compared with the baking
time for the comparison mixture without the addition of
protein.
25 The following results were obtained:
Table 1: Casein added to the dough (bakable material)
Casein added in wt.% Reduction in baking time as
-age
0.5 % 10
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31
1 . 0 -s 2 0 %
2.0 % 30 ~
>2.0 % 30
up to 10 % 30 %
Table 2: Calcium caseinate added to the dough (bakable
material)
Calcium caseinate in wt.% Reduction in baking time as
%-age
0.5 % 15
1.0 % . 25 %
2.0 % 35
>2.0 % 35
% 35
The data in wt.% for added calcium caseinate and the data
with respect to reduction in baking time were determined as
described above.
It can be seen that a clear reduction in baking time can
again be achieved by using calcium caseinate.
Since the moulded items are produced as mass-produced
items, a reduction in baking time of, for example, 25
when adding 1.0 wt.% of calcium caseinate isfa very
significant improvement in the process with regard to the
economic aspects. Furthermore, since not only is the baking
time reduced to a considerable extent but also the
materials requirement is reduced by 10 wt.% to 20 wt.%, the
invention represents a significant advance in the field of
producing biodegradable moulded items.
o, CA 02396982 2002-07-10
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32
When using soya protein instead of casein or caseinate,
comparable advantageous effects are produced. Since soya
protein is cheaper than casein or caseinate, soya protein
is preferably used as added protein when producing large
quantities of biodegradable moulded items. The bakable
material preferably contains 0.5 to 10 wt.%, more
preferably 1 to 2 wt.%, of soya protein.
In addition, biodegradable moulded items produced with the
addition of protein have better thermal insulation
characteristics with a more uniform pare structure.
After the baking process, the biodegradable moulded items
produced using this process have a residual moisture
content of about 6, wt.%, which may rise to about 10 wt.%
after storage of the moulded items at ambient humidity.
Adjusting the residual moisture content to about 10 wt.%
has proven to be advantageous with regard to the
flexibility of the moulded items produced. In fact, it has
been shown that a residual moisture content of about 10
wt.% makes the moulded items more flexible.
The biodegradable moulded items according to the invention
produced from the dry mixture according to the invention
can be produced extremely advantageously at a low cost,
with a clear reduction in baking time and a reduction in
the materials requirement. Furthermore, the biodegradable
moulded'items produced using the dry mixture according to
the invention have outstanding characteristics with regard
to breaking strength, elasticity, insulation properties and
surface quality.
The closed surface on moulded items according to the
invention also facilitates the reliable application of
~
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33
moisture- and grease-repellent barrier layers, for example
in the form of biodegradable films. These films of
polyester, polyesteramide or polylactic acid may be applied
to the baked moulded item. It has been shown that the
adhesive properties of the moulded items produced using the
dry mixture according to the invention are improved when
applying barrier layers in the form of films, for example
using the thermoforming process.
When using the dry mixture according to the invention or
the bakable material according to the invention, cheap,
high-quality, biodegradable moulded items can be produced.
For example, moulded items according to the invention have
a wall thickness of about 1.6 to 1.8 mm. Obviously, moulded
items with thinner walls, such as for example about 0.8 to
about 1.4 mm, or thicker walls such as for example about
2.0 to about 3.2 mm can also be produced.
The moulded items are produced extremely advantageously
from renewable raw materials and can biodegrade completely
or substantially completely. To this extent, the dry
mixture or bakable material according to the invention is
not subject to the "Green Point" system created in Germany
for the waste disposal of packaging. That is, a producer of
the previously mentioned moulded items in the form of
packaging material does not have to pay the conventional
packaging duty to the "Green Point" waste disposal system.
The moulded items produced from the dry mixture or bakable
material according to the invention are almost fully
biodegraded, in a pit or in a compost heap, within 10 to 14
days.
