Note: Descriptions are shown in the official language in which they were submitted.
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The invention relates to a composite material
from parts of a plant origin based on lignocellulose
material, which are bound together with a polymeric com-
pound derived from an original polymer of starting material
'by transformation of the original polymer through actiVatiQn
to active compounds able to react and by crosslinking. The
invention also pertains to a method o manufacturing the
said composite material.
Composite materials based on plant raw materials,
in particular on wooden elements, fibers, chips,~shavings,
' sawdust, and the like, are manufactured at the present by
mixing dry and hydrophobizea particles with various binders,
mainly with thermosetting binders, e.g., with an urea-
formaldehyde resin, and subsequent pressure moulding atI 15 temperature above 130C to the required form of a construc-
tion element, prevailingly;to boards. These materials are
produced in many varieties, which difer from one another
by the type of starting raw material, the type o-f binder,
molding pressure, and temperature. Thelr main common
~20 disadvantage is a long-lasting escape of cleavage products'
o the resinous binder, namely ormaldehyde, oligomers o
urea with formaldehyde, or phenol, which have cancerogenic
or other undesirable~metabolic efects on human organism.
' Because these materials, in particular chip boards, became
recently a still more important construction components of
living houses, the above said disadvantage of the known
; prior art composite materials from plant parts or particles
' became very serious. penetration of these products into
the interior space of buildings should be preven-ted'by
various measures, which increase the building cost.
Bonding of wooden elements is carried out so far
by means of adhesives of various kinds, which are applied
Jon contact surfaces of the bound elements. In addition to
the necessary application o an adhesive layer on the sur-
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face of formed joint, which is performed either in a coldstate or under heating, depending on the type of adhesive
used, the joint should be allowed to rest for a relatively
long time to secure evaporation of water from aqueous
adhesives, or evaporation of solvents from solvent adhesives
to polymerize, in some cases at elevated temperature and
pressure. Some adhesives are harmful to health during their
preparation or also during usage of the adhesivebound parts.
This refers in particular to adhesives containing
formaldehyde, which has cancerogenic or other undesirable
metabolic effects to human. Therefore, the adhesive bonding
of wood and lignocellulose materials is still rather time
consuming and, in many cases, it has also high demands to
energy consumption, in particular in the manufacturing of
composite elements with large interfaces, namely ply-wood and
veneering of wooden bases or bases from lignocellulose
materials.
Another disadvantage of such prior art composite
materials is the complexity of the manufacturing process,
including the preparation of a p.econdensate and a strict
observation of technological process, which is necessary to
attain the required quality of products. Consequently, the
materials do not allow to increase the productivity by
reduction of the production cycle. During the production
process, namely during pressure moulding, harmful reaction
products with a high content of formaldehyde are liberated
in a high concentration from the moulded material. Another
shortcoming is also a high price of articles made from the
said prior art materials, which is caused by relatively
large amounts of the dosed binder, which is present in the
articles in amount of from 10 to 30 weight percent as a
rule.
The invention proposes a new method of
manufacturing a composite material from particles of a
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polymeric lignocellulose material, which method overcomes
-the above mentioned shortcomings.
According to the new method, the individual
particles are bound together with a polymeric compound
derived from the original polymer of the starting
lignocellulose material, by transformation of this original
polymer through activation, to active compounds able to
react, which compounds are -then transferred into a final
polymeric material by crosslinking.
More particularly, the method according to the
invention comprises the steps of:
- contacting surface portions of at least one part of the
lignocellulose matexial particles with an activation agent
selected from the group consisting of concentrated H2S04,
concentrated H3P04, HN03, urea sulfate, NH4HS04, concen-
trated P205 and mixtures thereof, to depolymerize only said
surface portions of said at least one part of the
lignocellulose material and form a monomeric or oligomeric
binding agent therefrom; and
- heating and compressing said lignocellulose material
particles and said monomeric binding agent for a time and
under a temperature and a pressure sufficient to cause the
said surface portions of said at least one part of the
lignocellulose material particles to incorporate the said
A monomeric or oligomeric binding agent therein and
repolymerize to form a hardened mass with cohesion bonds
among particles.
The main advantage of the composite material
obtained by the method according to the invention is that
the binder necessary for bonding of individual adjoining
parts is formed directly from the material of these
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particles by means of an activation agent, for example,
sulfuric acid, applied on the surface of the said particles.
Articles made from the composite material according to the
invention contain exclusively the starting material and a
small amount of deactivated
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harmless to health, and, in addition to this, the cost for
preparation of relatively expensive binders is avoided.
Preparation of the material before pressure moulding
proceeds in one step and consists in application of the
S activation agent of the surface of particles of a plant
origin.
Another advantage of the method according to the
invention is the possible utilization of a virtually waste
material, e.g. of bark. At the same time, the content of
water in particles need not to be diminished, in
contradistinction to the known prior art methods, so that
the energy necessary for drying of the starting material is
saved.
Manufacturing of the composite material according
to the invention is achieved by the action of an activation
agent upon a part of the starting material of a plant
origin, to degradate the original high-molecular-weight
polymeric binder of the starting material to a monomer,
followed by neutralization of the excess of activation
agent, if this is desired, and by the action of pressure and
heat on the parts, which are at least in part coated on the
surface with a layer of monomer, to cause polymerization of
the monomer to a polymer derivative, which binds individual
parts of the ma.erial together.
The activation agent is added only to a portion of
parts of the starting material of a plant origin, which
portion is then mixed with the remaining portion of parts.
Then, an article is shaped from this mixture into a cohesive
form.
The starting material used, in this manufacturing
method are parts of a plant origin, which contain
lignocellulose material comprising polysaccharides, lignin,
tannins, essential oils and the like, for example, wooden
elements, chips, flan chaff, sawdust, shavings, corn cobs,
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chopped straw and dry stalks in a crushed form, and various
fibers. The resulting material is cohesive and is pressure
moulded in particular into the shape of boards, blocks,
which strength, other mechanical properties, and other
parameters considerably depend on the starting material and
the manufacturing procedure. The resulting material aan be
used in the form of boards, blocks and other pressed
mouldings for construction parts of buildings or furniture
or insulation purposes.
The hydrolytic effect of acids is used in the
method according to the invention to liberate furylaldehyde
and its derivatives and thus activate the lignocellulose
materials. Monomeric reactive compounds, which are
liberated in this way, are transferred in the reverse way,
in n acid medium and by means of elevated temperature and
pressure, to a crosslinked polymeric material of structure
similar to the original phytomass. The amount of liberated
monomer is controlled by the degree of activation and
determines, together with the moulding pressure, properties
of the product. However, this fact does not exclude the
possible modifications of product properties by addition of
suitable additives, including binders of the furan type.
Another possible procedure consists in adding a
strong mineral acid or a compound liberating such acid,
Lewis acid, or their mixtures to at least one portion of
particles of the starting material. Concentrated sulfuric
acid, gaseous hydrogen chloride, zinc chloride, ammonium
bisulphate, amine sulfates, or mixtures of these compounds
can be added as an activation agent to the said parts.
Lewis acid has to be understood as a compound able to accept
an electron pair. The excess of activation agent in
admixture with the particles, is neutralized, before
pressure moulding, by adding basic agents, in particular
with urea, urea with ammonium sulphate alkaline soaps, Lewis
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bases, or with mixtures thereof. Lewis base should be
understood here as a compound able to render an electron
pair.
The activation agent is applied on particles in
the form of gas, aerosol, or solution, which may be diluted
with inert solvents. The particles of starting material are
left with the same humidity content as they had before pro-
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cessing or, if it is desired, they can be provided on the
surface with a hydrophobic coating.
Prior to pressure mouldingj heat is supplied to
the particles in the amount sufficient to increase their
temperature to 80 - 200C, whereas the particles, contain-
ing the activated monomer at least on a part of their
surface, are then compressed in a mould developing a clos-
ing pressure of 0.2 to 10 MPa. Properties of the resulting
material depend on the moulding pressure and also on the
amount and kind of the activation agent.
Further possible procedure consists in the
deposition of particles, having at least a part of the
surface activated, into layers, whereas at least two layers
contain deposited particles mixed with different amounts or
kinds of the activation agent or the neutralization agent.
The method according to the invention
permits to form an adhesive bonding of wooden or ligno-
cellulose elements without using a special adhesive,
because the necessary bonding structure is created directly
on aontact surfaces or the joined elements from the
material of these elements. Wooden and lignocellulose
materials contain polysaccharides, lignin, tannins, essen-
tial oils, and the like. By initiating a superficial hydro-
lysis with acid agents or enzymatically on the surface of
wood or similar materials, there are generated adhesive
compounds present in the wood, which enable to form an
integral joint because they create, after application of
pressure, passing-through molecules of a new-formed polymer,
which are partly in the joint and partly anchored in the
original parts in a structural network of both joined
elements.
Expensive or harmful adhesives are not needed
for the formation of an adhesive bond, which then contains
exclusively compounds of virtually the same composition as
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had the original material. The main advantage is a great
facilitation, lower cost, and acceleration of the produc-
tion process.
The method according to the invention can serve
for manufacturing of plywood, sticking of veneers on various
lignocellulose bases, and formation of various articles
from laminated wood. Such performance of a laminated
article is especially advantageous, where a central core
is formed from pressure moulded particles of wood bound
together with a regenerated polymeric material and where
the central core is jacketed from both sides with a wooden
veneer or plywood stuck also with the regenerated active
material.
Pressure moulding of the particles with binding
compounds, based on a furan binder and on activated binding
compounds of phytomass, proceeds at the particle tempera-
ture of 12CC to 200C in the mould, which closing pressure
is 1 to 10 MPa. Properties-of final products depend on the
moulding pressure and on the amount of binder on the con-
tact surfaces of moulded particles and may be the same inthe whole thickness of product or may change in various
layers of the product. The resulting products from the
compos-te material acquire mainly the shape of boards,
blocks, and other moulded articles and may be used as
2~ various construction, insulation, or other-purpose partsO
The method according to the invention permits
produce useful products also from materials which are
virtually wastes from the production of furylaldehyde from
plant parts. After hydrolysis of wood particles and separa-
tion of furylaldehyde, residues with residual binding com-
ponents can be pressure moulded to obtain a useful product.
To attain better properties, further furan binder or
further activated particles of a plant origin can be added
to the residual material. In this way, furylaldehyde is
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obtained from the whole volume of each particle, a small
part of which is returned into the composite material in
the form of a component of furan binder applied to the sur-
face of remaining particles. Mutual connection of the
binder with the original material of untreated particles is
advantageously achieved by formation of linkages between
the active ends of original structure and the chains of
newly formed polymer from the binder. The furan binder has
to be understood as a binder based in particular on furyl-
alcohol or furylacetone which contains furylaldehyde at
least in a small amount.
The binding effect of the binder generated from
a lignocellulose material may be increased by addition of
some derivative of phenol, which partly gives the rise to
a furylaldehyde resol curable by heating to resin.
Pressure moulding of products from the particles
is carried out in such a way, that the particles are com-
pressed together by the moulding pressure of 0.2 to 10 MPa
at temperature of 80C to 200C, whereas the moulding
pressure acts for 5 to 300 seconds.
The method according to the invention can be
advantageously adapted by applying a catalyst, which
facilitates the hydrolysis of original material, on the
contact surfaces. Such catalysts are, e.g., potassium
permanganate, aluminium, zinc, metallic hydrides.
The composition and manufacturing of the com-
posite material according to the invention is illustrated
by means of the following examples, which, however, do not
limit the scope of invention by any means.
Example 1
To prepare a product from the composite material
according to the invention, 100 weight parts of spruce-wood
chips was fed into a drum blender and a fog of concentrated
sulfuric acid in air was applied on the chips by means of a
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spraying equipment. Total amount ox applied sulfuric acid
was 3 weight parts. Then, 6 weight parts of powdered urea
was added and mixed with the chips and sulfuric acid to
form a moulding mixture. The original polymer on the sur-
face of chips was activated or transferred to a monomer by
action of sulfuric acid and the excess of sulfuric acid
was neutralized in the subsequent step by the added powdered
urea. The moulding mixture was then pressure moulded at
temperature of 180C and closing pressure of 8.0 MPa for
5 minutes. The product which was removed from a press
after 5 minutes exhibited bending strength of 12.0 MPa and
volume weight of 950 kg/m3.
Example 2
Crushed residues of dry corn stalks were fed into
a drum blender in the amount of 100 weight parts and 5
weight parts of 96 sulfuric acid was added by spraying
homogeneously as much as possible on the surface of stalks.
Then, 7 weight parts of powdered urea was admixed and the
prepared mixture was pressure moulded at temperature of
160C and closing pressure of 8.0 MPa. Final properties
were attained after 4 minutes under pressure, when the
activated monomer crosslinked on the particle surface giving
virtually the same kind of polymer as was the polymer of
starting material; i.e. the bending strength of at least
1.2 MPa at the volume weight 700 kg/m3.
Example 3
A mixture of wood chips and saw dust in the ratio
3:1 was charged into a drum blender in the total amount of
100 weight parts. Sulfuric acid was evenly applied on the
surface of particles in the form of aerosol in the amount
of 4 weight parts. Then, 6 weight parts of powdered urea
was added and the mixture was thoroughly mixed. The mould-
ing mixture was pressure moulded in a press under final
pressure of about 2.0 MPa at temperature of 170C for 6
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minutes. The product attained bending strength of at
least 10 MPa at the volume weight above 800 kg/m3.
Example 4
Chips of birch wood (100 wt. parts) were mixed
S in a blender with 8 wt. parts of powdered urea. Then,
6 wt. parts of 80 phosphoric acid was dispersed by means
of a spraying equipment. The prepared mixture was pressure
moulded at temperature of 170C and pressure of 8 MPa for
6.5 min. The resulting product had density of 0.65 g/cm3
and bending strength of at least 1.5 MPa.
Example 5
Chips of coniferous wood (100 wt. parts) were
mixed with 6.25 wt. parts of powdered urea and then 6.25
parts of 65 nitric acid was spread in the mixture. The
material resulting from pressure moulding of the mixture
at pressure of 8 MPa and temperature of 170C for 7 min.
had density of 0.65 g/cm3 and tensile and bending strengths
o at least 1.5 MPa.
Example 6
Chips of spruce wood (100 wt. parts) were mixed
in a blender with 4 wt. parts of powdered urea and 3 wt.
parts of potassium permanganate as a catalyst which accel-
erates the activation of binding compounds. Then, 4 wt.
parts of 96 % sulfuric acid was added to the mixture as a
fine fog with air. The mixture was pressure moulded at
temperature of 150C and pressure of 10 MPa for 2 min. The
product had density of 0.95 g/cm3 and bending strength of
15 MPa. ''
Example 7
The same mixture as in example 1 was pressure
moulded under the same pressure at temperature of 80C for
10 min. Properties of the product were the same.
Example 8
The surface of veneers, which form layers of a
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manufactured plywood, were coated by brush or spraying with
a concentrated or diluted acid, particularly sulfuric acid,
to initiate superficial hydrolysis of wood on the contact
surface of veneers, which gives arl active monomer by
hydrolytic degradation of the original polymer. To neu-
tralize the excess of sulfuric acid, if any, powdered urea
was dusted on the contact surface of veneers. The veneers
were then laminated, inserted into a press, and loaded with
pressure of 2.0 MPa at temperature~of 160C for 15 seconds.
The active monomer was transformed by pressure and heat
into a regenerated polymer, the macromolecules of which are
linked together, on one hand, and anchored in the original
material of veneers, on the other. A strong-mutual bonding
of contact surfaces occurs in this way and the product is
finished after removing from the press.
Example 9
To form an adhesive binding of two wooden and/or
lignocellulose elements with the thickness of 5 to lO mm,
for example, of a mortise-and-tenon joints, halved friezes,
or corner connections of dovetail males, a concentrated
acid, in particular sulfuric acid, was applied on the
contact surface of linked parts by brush or spraying, to
generate an activated monomer on the contact surfaces of
joined parts from their material by acid hydrolysis. The
contact surfaces were then put together, the joined elements
were inserted into a press where the contact surfaces were
compressed by pressure of 6.0 MPa at temperature of 180C
for 180 seconds. The joint was finished after removing
from the press.
Example lO
In the manufacturing of jacketed chipboard, chips
of spruce wood were first prepared, then charged into a
drum blender in the amount of lO0 weight parts, and there
coated with 5 weight parts of 96 % sulfuric acid by means
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of a spraying equipment. To neutralize the excess of
unreacted sulfuric acid, 7 weight parts of powdered urea
was spread into the mixture. The mixture prepared in this
way was transferred into a mould with one of jacket layers,
e.g., a wooden veneer or plywood or a fibreboard, placed
on its bottom. The surface of this layer was previously
furnished also with a coating of sulfuric acid to induce
the superficial hydrolysis. An upper jacket layer, e.g.
also wooden veneer, plywood or fibreboard, the contact
surface of which was furnished with a coating of sulfuric
acid, was then placed on the surface of layer of the
activated wooden chips. The mould was then closed and the
content was moulded at the closing pressure of 8.0 MPa at
temperature of 180C, which were kept for 5 minutes. The
laminated board with a chipboard core was thus made in a
single process and had volume weight of 950 kg/m3 and
bending strength higher than 12.0 MPa.
Example 11
Wooden chips (300 g) were mixed in a drum blender
with 10 g of phosphorus pentoxide added. This mixture was
pressure moulded at pressure of 1 MPa and temperature of
1~0C for 2 min. The obtained material in the form of a
board has bending strength of 11.0 MPa.
Example 12
Wooden chips (300 g) were mixed in a drum blender
with 30 g of ammonium hydrogensulfate. The mixture was
pressure moulded at temperature of 180C for 7 min. The
resulting material in the form of a board exhibited bending
strength of 18.0 MPa.
Example 13
A fog of 80 % aqueous solution of urea sulfate
was applied in the amount of 38 g on the surface of 300 g
wooden chips in a drum blender. The mixture was pressure
moulded at temperature of 180C for 3 minutes and gave the
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product in the form of a board, which attained bending
strength of 18,6 MPa.
Example 14
Wooden chips (250 g) with applied acid catalyst
were mixed in a drum blender with the mixture comprising
150 g of wooden chips
34 g of urea sulfate
20 g of furylalcohol
10 g of furylaldehyde.
The mixture was moulded by pressure of 0,80 MPa
at temperature of 80C for 8 hours. The resulting material
in the form of a cube exhibited compression strength of
44,5 MPa.
Example 15
Sawdust (300 g) and 14 g of ammonium hydrogen-
sulfate were mixed in a drum blender and then 20 g of furyl-
alcohol and 10 g of furylaldehyde were applied on this
mixture. The blend was moulded under pressure of 0,8 MPa
at temperature of 80C for 8 hours. The moulding, having
the form of a cube, exhibited compression strength of
23,8 MPa.
Example 16
To the same mixture as in example 1 was added 5
weight parts of emulsion polyvinylchloride and then the
mixture was pressure moulded at temperature of 180C and
pressure of 2 MPa for 5 minutes. The resulting material
had flexural strength of 21,96 MPa and it was water-resis-
tant without change of its volume.
Example 17
To a mixture as in example 1, neutralized by a
mixture of urea and ammoniumsulphate was added a powder
mix of polyvinylchloride and chlorinated polyethylene in
the weight ratio of 1:1. The resulting blend was pressure
moulded at temperature of 180C and pressure of 6 MPa for
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six minutes. The resulting material had flexural strength
of 19,6 MPa and it was water-resistant without change of
its volume.
' Example 18
To as mixture as in example 3 was added powdered
polypropylene and it was pressure moulded at temperature of
180C and pressure of 1,9 MPa for 5 minutes. Resulting
composite material had flexural strength of 22,3 MPa and
good water-resistance.
