This invention relates to a method for the production of a compound
material, in particular of a biodegradable or compostable compound material, according
to the preamble of claim 1. Furthermore, this invention relates to a compound material
according to the preamble of claim 15, which comprises lignin and at least one
Methods for the production of a compound material comprising lignin
and at least one additive as well as compound materials of this type are known
in the prior art. In this contents the term "lignin" describes either pure lignin
or derivatives thereof, for example alkali-lignin, ligninsulfonates, Kraft lignin,
lignosulfonic acid, hydrolysis lignin, organosolv-lignin, acetosolv-lignin, milox-lignin,
steam explosion lignin or other lignin derivatives.
In the following, the terms melting, melted or melt is used in accordance
with practice in the plastic processing industry. It means that the viscosity of
the material has been reduced sufficiently to process the material. It does not
necessarily mean that crystalline matter actually have melted, but just that viscosity
is reduced by any physical or chemical transformation of the material
In the known production methods lignin which was decomposed from
biomass and isolated, is mixed with at least one additive or additional component
From EP-B-0 720 634, for example, a compound material comprising
lignin and a protein derivative as well as a method for the production thereof
are known. In the known compound material due to the combination of lignin and
the protein derivative as additive the physical properties and characteristics
of the compound material are highly improved.
In EP-A-0 687 711 a fiber compound material and a method for the
production thereof are disclosed. For the production of the compound material natural
fibers are added to melted lignin.
From WO 98/06785 it is known to melt lignin and to add to the melted
lignin a protein which reacts with the lignin. Afterwards, at least one additive
is added to the melt of lignin and protein wherein after the hardening the additive
is bound in the lignin-protein-matrix.
All these known methods have in common that a dry and isolated lignin
or a dry and isolated lignin derivative is used as initial substance and blended
with additives. Afterwards the blend is melted. Due to the melting of the lignin
the technical efforts during their production are high so that the production of
these compound materials is expensive.
Furthermore, the physical properties, such as the E-module or the
impact strength, are only slightly improved. If for example fibers are used as
additive, there is only a low effect on the tensile strength and the E-module,
because of a non-optimal contact and a non-optimal adhesion and/or cohesion between
the fibers and the lignin-matrix. Also there are only minor effects, for example
on impact strength, when an additive like an elastomer is used since also in this
case there is only a non-optimal contact and adhesion between the elastomer and
the lignin-matrix. Furthermore, there is only a non-homogeneous distribution and
a low-degree of dispersion of the additive in the lignin-matrix. Additionally,
these non-compound materials have a high melt viscosity and an unusual melt behavior
so that they are not easy to handle.
As a result, there is a demand for compostable or biodegradable compound
materials which are easy to produce, which can be composted after their use without
polluting the environment, and which have mechanical properties comparable to those
of synthetic compound materials.
It is an object of the present invention to provide a method
for the production of a compound material comprising lignin and at least one additive
as well as a compound material of this type, in which the physical properties of
the compound material are further improved in a simple way.
This object is achieved by a method having the features of claim
1. Furthermore, this object is achieved by a compound material having the features
of claim 15.
Usually lignin is decomposed from biomass, for example from wood,
straw or comparable materials, by degrading the biomass. Also in this content
the term "lignin" describes either pure lignin or lignin derivatives. The decomposing
of the lignin can for example be carried out by dissolving said lignin bound in
the biomass in a solvent, by hydrolysis of the biomass or by other known methods
for decomposing lignin from biomass, for example enzymatic processes. The intermediate
product is produced by dissolving and/or dispersing lignin in a solvent. According
to the invention it is then proposed to add the additive or additional component
to said lignin while said lignin is still dissolved and/or dispersed in said solvent.
Afterwards, the lignin and the additive are together separated from the solvent
as compound material.
Due to the blend of the additive with the still dissolved and/or
dispersed lignin and the subsequent separation of the additive together with the
lignin the additive is very homogeneously distributed in the compound material.
Thereby, the physical properties of the final compound material can
be directly influenced and improved in a very early stage during the production
of the compound material, since the additive is continuously distributed and suspended
in the solvent during the formation of the compound material.
Further preferred embodiments of the invention can be taken from
the following specification, the claims and the drawing.
Preferably, the intermediate product which contains said dissolved
and/or dispersed lignin in a solvent is product during the degrading process of
the biomass for the production of said lignin. Thereby, both, the production of
the lignin and the production of the compound material, can be carried out at the
same place and in the same production plant so that a transportation of the solvent
or the lignin is not necessary anymore.
Alternatively, it is also possible to constitute the intermediate
product by dissolving or dispersing lignin, which has already been precipitated
or dried, in a solvent.
Furthermore, it is proposed to add additional precipitated or dried
lignin to the intermediate product, which already contains dissolved and/or dispersed
lignin in a solvent, in order to set the lignin-concentration in the solvent to
a predetermined value.
Lignin is very often decomposed during the cellulose processing of
the paper production. For this purpose the lignin contained in the cellulose of
the biomass is dissolved in the solvent. The resulting solvent contains dissolved
lignin and further biomass constituents, for example hemicellulose, cellulose and/or
In a preferred embodiment of practicing the method according to the
invention it is therefore proposed to separate these biomass constituents contained
in the solvent before the additive is added for the production of the compound
material to the solvent. As a consequence, two different agents can be produced
in on process. On the one hand, the cellulose separated from the biomass can be
used for the paper production while, on the other hand, lignin dissolved in the
solvent can be used for the production of the compound materials.
If, however, the compound material to be produced shall also contain
biomass constituents, for example cellulose fibers, in order to strengthen the
structure of the compound material, it is also possible to separate only a part
of the biomass constituent from the solvent so that a predetermined amount of the
biomass constituent remains in the solvent. Afterwards, the additive is added
to the solvent containing lignin and biomass constituents so that a compound material
also comprising biomass constituents can be produced.
When said lignin received after the degrading of the biomass is dissolved
and/or dispersed in said solvent it is preferred to use an additive which is soluble
or dispersable in said solvent. By using a soluble or dispersable additive a very
homogenous distribution of the additive with respect to the lignin dissolved and/or
dispersed in the solvent can be achieved.
Furthermore, it is proposed to use a polymeric elastomer as additive,
whereby a component material can be produced which has an above average dispersability.
Additionally, it is proposed to use as additive a colloidal dispersion
of polymers in a hydrous agent. This colloidal dispersion, e.g. latex, can contain
different types of synthetic or natural polymers, polychloroprenes, styrine butadiene
copolymers, natural rubber or synthetic rubber. When adding such a dispersion
to the dissolved and/or dispersed lignin the lignin and the polymers contained
in the dispersion will co-precipitate whereby a compound material results which
can easier be processed, has a higher machineability and superior mechanical properties
compared to known compound materials comprising lignin and comparable polymers.
In a still further embodiment of practicing the method according
to the invention celluloseacetates, polycarbonates, shellac and/or other natural
resins are added to the dissolved and/or dispersed lignin as additive wherein also
in this embodiment the respective additive added to the decomposed lignin is embedded
into the lignin-matrix during the precipitation or conversion of the lignin from
soluble form to powder. Thereby desired properties of the compound material can
be adapted for example a high tensile strength or a thermal non-deformability in
a comparable high temperature range of, for example, 150 to 180°C.
By using additives by means of which lignin ethers are obtained,
so that hydroxyethylated, hydroxypropylated or hydroxybutyrated lignin derivatives
result, compound materials can be produced which are more compatible to react with
thermoplastic blend components when the compound material is used in thermoplastic
materials. A copolymerization with polyethylenglycol results in less rigid products
since the polyethylenglycol acts as soft segment in the compound material.
In another embodiment of practicing the method according to the invention
it is suggested to use natural fibers and/or synthetic fibers and/or inorganic
fibers as additives which are added to the decomposed lignin. The use of fibers
has the advantage that in particular the mechanical properties of the object formed
from the compound material can be increased since the fibers are able to resist
loads acting on the object. Preferably, short single fibers are used since they
show a very homogeneous distribution in the compound material. If fiber bundles
are supplied to the solvent, it is proposed to additionally treat them mechanically
so that the fibers are homogeneously dispersed in the solvent.
If natural fibers, for example coir, flax, hemp, or other bast fibers,
are used for the compound material the compound material becomes compostable or
biodegradable so that a recycling of products produced by the compostable compound
material is not necessary anymore. This is in particular interesting for the production
of parts used in the interior of cars, airplanes and the like.
Furthermore, it is possible to use synthetic fibers as additives
which are particularly characterized by superior mechanical properties. As synthetic
fibers, fibers can be used which are made of polymers, for example polyamide, polytetrafluorethylene,
aramide, polyester, polyvinyl chloride, polyvinylidene chloride, polyethylenes
and the like. Also inorganic fibers like glass fibers or carbon fibers can be
used as additive.
Furthermore, it is proposed to add a further additive to the compound
material, after the compound material has been separated from the solvent. For
example, softeners, plastilizers, natural fibers, synthetic or inorganic fibers,
or the like, can be added to the compound material, wherein for the addition of
the further additive the compound material can, for example, be melted or can
be dissolved in another solvent.
Depending from the polymerization of the lignin in the compound material
the compound material can be separated from the solvent for example by filtering,
decantation, evaporation, spray drying or vacuum drying.
If, however, the compound material is also dissolved in the solvent,
it is also possible to precipitate the compound material from the solvent. For
this purpose, a precipitating agent, for example sulfuric acid or carbondioxide,
can be supplied to the solvent after a predetermined time after the additive has
been added to the solvent.
According to another aspect of the present invention, the invention
relates to a compound material comprising lignin and at least one additive, wherein
the compound material has been constituted by blending said additive with said
lignin, while said lignin was dissolved and/or dispersed in a solvent, and by separating
the compound material from the solvent containing said lignin and said additive.
In a preferred embodiment of this compound material said lignin is
selected from a group comprising alkali-lignin, Kraft lignin, ligninsulfonates,
lignosulfonic acid, organosolv-lignin, acetosolv-lignin, hydrolysis lignin, milox-lignin
or steam explosion lignin. These are the main lignin derivatives which are used
as initial substance for the constitution of the compound material.
Additionally, in order to provide compound materials having advantageous
mechanical properties, for example a comparable high tensile strength, it is additionally
proposed that the compound material comprises natural fibers, for example coir,
hemp etc., and/or synthetic fibers, for example polyamide fibers, polyvinylchloride
fibers, and/or inorganic fibers, for example glass fibers and carbon fibers.
In another preferred embodiment of the compound material according
to the invention the compound material contains one or a combination of polymeric
elastomers from a group comprising polychloroprenes, styrene butadiene copolymers,
natural rubber and synthetic rubber. If the compound material has been constituted
by adding one of the aforesaid additives to the decomposed lignin the added polymere
co-precipitates with the decomposed lignin.
Thereby a compound material is constituted which has improved mechanical
properties compared to compound material comprising lignin and a comparable polymer
which has been produced by using a method known in the prior art.
Preferably, the compound material is a thermoplastic compound material
so that the compound material can be heated and deformed into each desired shapes.
Such a thermoplastic compound material can for example be used for the production
of interior parts for cars and airplanes.
In the following a preferred embodiment of practicing the method
according to the invention will be explained in detail with reference to the accompanying
drawing. Therein the only Figure shows a flow-chart of an embodiment according
to the invention of practicing a method for the production of a compound material.
At the beginning in step S 100 an intermediate product containing
dissolved and/or dispersed lignin in a solvent is decomposed by degrading biomass.
The produced lignin may be any lignin from ligninosulfonates from sulfide pulping,
Kraft lignin from Kraft pulping, alkali-lignins from alkali pulping, other lignins
from other pulping processes, hydrolysis lignin from hydrolysis of biomass or
dissolved waste produced from sugar production or other agricultural waste products.
Alternatively, it is also possible in step 100 to constitute the
intermediate product by dissolving or dispersing lignin, which has already been
precipitated or dried, in a solvent.
In step S 200 biomass constituents, like hemicellulose, cellulose,
sugar or the like, can optionally be removed. In a preferred embodiment according
to the invention it is proposed, that a predetermined amount of such biomass constituents,
for example cellulose, is left in the solvent whereby the structure of the compound
material to be produced can be strengthened.
In step S 300 at least one additive is blended with the lignin dissolved
and/or dispersed in the solvent. For example, synthetic aramide fibers can be used
as additive which are supplied to the solvent. Additionally, further additives,
for example softeners or the like, can also be supplied to the solvent if necessary.
After a predetermined period of time the lignin derivative contained
in the solvent starts to precipitate wherein the aramide fibers are evenly distributed
in the precipitating lignin whereby the compound material is generated.
In order to accelerate and/or to start the precipitation a precipitating
agent, for example carbondioxide, can be supplied to the solvent, so that the
compound material can be removed from the solvent for example by filtering. The
resulting compound material may afterwards be dried, so that the compound material
can be provided in powder form. Spray drying or vacuum drying may also be processes
for conversion of the soluble lignin compound to powder form.
In step S 500 it is further proposed to optionally dry blend said
compound material with at least one further additive.
The compound material produced by the method according to the invention
shown in the figure is a thermoplastic material which can be heated and formed
into desired shapes, as it is proposed in the figure as further step S 600. Such
a thermoplastic compound material can for example be used for the production of
interior parts for cars.
When using natural fibers like core, flax fibers or hemp fibers instead
of synthetic fibers the products produced with the compound material are compostable
so that an expensive recycling of the products is not necessary anymore.