Note: Descriptions are shown in the official language in which they were submitted.
-- 2189319
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LeA 31,319 -US
POLYURETHANE COMPOSITES PRODUCED FROM RECYCLED
POLYOLS AND A PROCFSS FOR THFIR PRODUCTION
BACKGROUND OF THF INVFNTION
The present invention relates to polyurethane composites
(sandwich elements) produced from recycled polyols and to processes for
their production and use.
Composites having a polyurethane core and fiber-reinforced
covering layers made of a different (i.e., non-polyurethane) material are
used in a wide variety of applications. Such composites are used, for
example, in the production of high-quality structural parts for motor
vehicles and motor vehicle body work, particularly in the interior of the
motor vehicle. Two basic methods for the production of composite articles
of this kind are known in the art the filling method and the coating
method. In the filling method, two half shells (covering layers~ are
precast, placed in a mold and the cavity between the shells is filled with a
polyurethane (PU) foam. In the known coating construction method, a
core made of a PU foam is placed in a mold and coated with a suitable
covering material made, for example, of fiber-reinforced plastics such as
epoxy resins or unsaturated polyester resins.
Until now, polyol compositions recovered from polyurethane or
polyurea wasfes (i.e., recycled polyols) have hardly been used in the
production of composites having a polyurethane core.
BACKGROUND OF THF INVENTION
It is an object of the present invention to provide high quality
composite materials having a polyurethane core in which the
polyurethane was produced from recycled polyols.
It is another object of the present invention to provide a process
for the production of high quality composite materials having a
polyurethane core and an outer layer made of a plastic reinforced with
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natural fibers in which the polyurethane core has been produced with a
polyol composition recovered from polyurethane and/or polyurea wastes.
These and other objects which will be apparent to those skilled in
the art are accomplished by forming a polyurethane core from a reaction
5 mixture composed of a polyisocyanate and a recycled polyol. This
recycled polyol is obtained by chemical decomposition of polyurethane
and/or polyurea waste. This recycled polyol must have an OH number of
from about 100 to about 500 mg KOH/g, a water content of up to 5 wt.%
and a viscosity greater than 2,000 mPa s at 20~C. To this polyurethane~0 core is applied a plastic material which is reinforced with natural fibers.
DFTAII Fn DFSCRIPTION OF THF INVFNTION
The present invention relates to composites having a polyurethane
core and at least one covering layer of a fiber-reinforced plastic material.
The polyurethane core is produced by reacting a polyisocyanate with a
15 polyol composition obtained by chemical decomposition of polyurethane
and/or polyurea wastes. The polyol composition has an OH number in
the range of from about 100 to about 500 mg KOH/g, a water content of
from 0 to 5 wt.% and a viscosity of more than 2,000 mPa s (20~C). The
covering or outer layer is made of a plastic material reinforced with
20 natural fibers.
It is surprising that high-quality polyurethane cores for composite
articles can be produced at all using polyol compositions satisfying these
requirements because polyols having a far higher OH number (in most
cases in the range of from 300 to 1,000) and a considerably lower
25 viscosity (in most cases in the range of <2,000 mPa.s (20~C)) have been
used in known processes. The polyol characteristics required for the
practice of the present invention may be achieved by adjusting the
properties of recycled polyols obtained directly by chemical
decomposition of polyurethane and/or polyurea wastes by means of
30 additives described more precisely below.
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The composites of the present invention are in the form of
sandwich elements which contain, in addition to a polyurethane core
formed from a recycled polyol, at least one cove!ing layer made of a
plastic material, preferably an epoxy resin or an unsaturated polyester
5 resin, and natural fibers as reinforcement. The covering layer is
preferably composed of a fiber-reinforced plastic material. Any of the
known fibrous natural fibers, particularly, banana fibers, flax fibers, jute
fibers, hemp fibers, sisal fibers and/or coconut fibers in the form of waste
fiber, knitted fabric and woven fabric are suitable bonded natural fibers.
10 These fibrous materials may reinforce epoxy-unsaturated polyester
resins, polyurethane (PU) resins, melamine resins, vinyl resins or even
thermoplastic powders. These binders can be introduced and applied by
spraying, rolling, coating with a knife, or pouring. When the preferred PU
resins are used, the binders may also contain PU recyclates.
The composites of the present invention are suitably of sandwich
construction comprising a covering or coating layer A composed of a
plastic material reinforced with natural fibers, a core layer B composed of
a polyurethane foam formed from a recycled polyol, and if desired, an
additional layer which is either composed of the same material as layer A
20 or composed of a different material. Decorative materials such as films,
molded skins, textiles or carpet may then be applied to the outer layer.
This application may be conducted in a separate operation or even in a
single production step (one-step method) or by pressing behind in known
manner (direct coating) directly onto the external surfaces of the covering
25 layer(s). In multilayer sandwich structures, additional layers of different
materials may also optionally be included.
Any of the common reaction products of an isocyanate and the
commonly used diols and/or polyols (e.g., polyesters or polyethers) may
be used as the polyurethane or polyurea wastes which are decomposed
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to produce the polyol compounds used in the practice of the present
invention.
The present invention also provides a process for the production of
composites (sandwich elements) having a polyurethane core and at least
5 one fiber-reinforced covering layer. In this process, a polyisocyanate is
reacted with a polyol composition obtained by chemical decomposition of
polyurethane and/or polyurea waste and optionally other auxiliary
substances and additives. The polyol composition must have an OH
number in the range of from about 100 to about 500, preferably from
10 about 200 to about 450, most preferably from about 250 to about 400 mg
KOH/g, a water content of from 0 to about 5 wt.%, preferably from about
0.2 to about 2 wt.%, most preferably from about 0.5 to about 1 wt.% and
a viscosity at 20~C of more than 2,000 mPa s, preferably from about
3,000 to about 20,000 mPa s, most preferably from about 5,000 to about
10,000 mPa s. At least one covering layer of a plastic material reinforced
with natural fibers is applied to the polyurethane core.
In the process of the present invention, any of the known auxiliary
substances and additives may be used. Examples of such auxiliary
substances and additives include: release agents, blowing agents, fillers,
20 catalysts and flameproofing agents.
The process of the present invention may be carried out by the
filling (deposit) method or by the coating method. Both the filling
construction and the coating construction methods are known to those
skilled in the art. In the filling method, two half shells (for example,
25 covering layers made of a plastic material reinforced with natural fibers)
are precast and placed in a mold. The cavity between the shells is filled
using the PU foam produced in accordance with the present invention. In
the coating construction method, a core made of PU foam produced in
accordance with the present invention is placed in the mold and then
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coated with a covering material reinforced with natural fibers such as an
epoxy resin or polyester resin reinforced with natural fibers.
The composites of the present invention containing a foamed PU
core are preferably produced by the coating construction method using
recycled polyols. Any of the known conventional blowing agents and
auxiliary substances (e.g., release agents) may be added. If no external
release agent is added during the production of the composites of the
present invention by the coating construction method in a mold, then a
particularly strong adhesive bond between the polyurethane core material
and the coating material is achieved without any need for finishing or
preparing the coating and/or core layer. Any of the known plastic
materials reinforced with natural fibers may be used as the coating layer
n such a process.
The polyols used in the practice of the present invention may be
obtained by chemical decomposition of any polyurethane and/or polyurea
wastes. Even the decomposition products of polyurethane and/or
polyurea composite materials may be used. These composite
materials may be composed of PU and other materials such as
thermoplastics. Where the non-PU material is a thermoplastic, the
thermoplastic material should be separated from the polyurethane to a
large extent before recycling the PU. Such a composite material may be,
for example, an automobile control panel made of a glass-fiber reinforced
PU support, a soft-textured PU foam as back-filling material or an
aliphatic PU skin as a decorative and covering layer.
Methods for chemically decomposing polyurethane and/or polyurea
wastes into polyol compounds are known. Examples of such known
processes include aminolysis, alcoholysis and glycolysis. These methods
have already been described in detail in the prior art. See, for example,
W. Ra~hofer, Recycling von Polyurethan-Kunsl~torren, Huthig-Verlag,
Heidelberg 1994.
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The polyol compositions used in the practice of the present
invention are preferably obtained by glycolysis of polyurethane and/or
polyurea wastes in known manner. Coarsely ground or finely
comminuted polyurethane and/or polyurea wastes are reacted at
temperatures of from 160 to 240~C with glycols, preferably diethylene
glycol, in the weight ratio of waste:glycol of from 10:1 to 1:2, preferably
from 5:1 to 1:1. After stirring for from about 0.5 to 10 hours, a liquid
product having the following characteristics is obtained: OH number in
the range of from 20 to 1,070 mg KOH/g, water content in the range of
from 0 to 5 wt.%, viscosity at 20~C of ~2,000 mPa-s. At very high OH
numbers, the viscosity may also be below 2,000 mPa-s. (20~C).
Since the polyol compositions obtained directly from the chemical
decomposition of polyurethane and/or polyurea wastes do not generally
satisfy the requirements of a polyol suitable for use in the practice of the
present invention, the OH number, water content and/or viscosity of the
decomposition product are usually adjusted by incorporating additives.
For this purpose, mixtures of known additives such as cross-linking
agents, cell stabilizers, flow-promoting agents, release agents, catalysts,
blowing agents, etc. are added in amounts which total from about 2 to 50
wt.%, based on the weight of the recycled polyol used. The mixtures of
additives generally have an OH number of from 300 to 1,050 mg KOH/g,
a viscosity of from 100 to 5,000 mPa s (at 20~C), a water content of from
0 to 10 wt.% and an acid number of from 0 to 100 mg KOH/g.
It is surprising that polyols satisfying the OH number, water
content and viscosity requirements of the present invention that are
obtained by chemical decomposition of polyurethane and/or polyurea
wastes are suitable at all for the production of high-quality polyurethane
composites having a sandwich structure, because generally when new
(i.e., non-recycled) polyols are used in such processes, those polyols
have considerably higher OH numbers (500 to 1,000). The viscosity of
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polyol compounds used in the prior art is also generally considerably
lower (mostly in the viscosity range of <2,000 mPa s (20~C)). It was not
therefore to be expected that polyol compositions obtained from
polyurethane and/or polyurea wastes could be processed into high quality
polyurethane composites notwithstanding their far higher viscosity and
their lower OH number (reduced activity).
The polyurethane composites of the present invention are useful
for the production of high-quality structural components for a variety of
applications. The production of these composites makes it possible to
use materials generated from waste in an advantageous manner without
sacrificing the mechanical properties of the composite product.
The polyols obtained from the chemical decomposition of
polyurethane and/or polyurea wastes can be reacted with any of the
known polyisocyanates. Suitable polyisocyanates include: aliphatic,
cycloaliphatic, araliphatic, aromatic and heterocyclic polyisocyanates.
Such polyisocyanates are described, for example, by W. Siefgen in
Justus Liebigs Annalen der Chemie, 362, pages 75 to 136. Useful
polyisocyanates include those represented by the general formula
Q(NCO)n
in which
n represents 2 to 5, preferably 2 to 3, and
Q represents an aliphatic hydrocarbon radical having from 2 to 18
(preferably 6 to 10) carbon atoms, a cycloaliphatic hydrocarbon
radical having from 4 to 15 (preferably 5 to 10) carbon atoms, or
an aromatic hydrocarbon radical having from 6 to 15 (preferably 6
to 13) carbon atoms.
Examples of such polyisocyanates are given in German Offenlegungs-
schrift 2,832,253, pages 10 to 11.
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Particularly preferred are the commercially available polyiso-
cyanates such as 2,4- and 2,6-toluene diisocyanate, and any mixtures of
these isomers ("TDI"); diphenylmethane diisocyanate ("MDI") and
polyphenylpolymethylene polyisocyanates which are prepared by aniline-
5 formaldehyde condensation and subsequent phosgenation; as well aspolyisocyanates possessing carbodiimide groups, urethane groups,
allophanate groups, isocyanurate groups, urea groups or biuret groups
("modified polyisocyanates"). Modified polyisocyanates which are derived
from 2,4- and 2,6-toluene diisocyanate or 4,4'- and/or 2,4'-diphenyl-
10 methane diisocyanate are particularly preferred.
The polyurethane composites (sandwich elements) of the presentinvention are useful in motor vehicle construction, furniture construction,
machine construction and the construction of apparatus. These
polyurethane composites are advantageously used in motor vehicle
15 construction, particularly in the interior of the motor vehicle. In addition to
possessing low weight with high strength, the sandwich elements of the
composites of the present invention have a particularly low content of
emittable and extractable substances. In the motor vehicle sector, these
composites can be employed, for example, as two- and/or three-
20 dimensional moldings such as concealable panels or coverings, insidedoor panels, control panel supports, dashboard supports, air ducts, cable
coverings, cable ducts and luggage boot linings. They can also be
processed to form housings and covers for housings, pallets, supports for
light loads, coverings, vertical and horizontal structural components,
25 bulkhead walls, inlaid floors, et cetera. In the furniture sector, the
polyurethane composites of the present invention can also be used as a
substitute for tropical wood, particularly in the form of imitation plywood.
The following Examples are intended to illustrate the invention
without, however, limiting the scope thereof.
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FxAMpLEs
Example 1 (Chemical decomposition of polyurethane wastes by
glycolysis)
A granular material having a maximum particle size of 8 mm and
composed of glass-fiber reinforced polyurethane urea having a density of
1.26 g/cm3 was subjected to glycolysis. 4 kg of diethylene glycol were
placed in a 20 I vessel equipped with stirrer and heating jacket, covered
with nitrogen and preheated to 220~C. 8 kg of granulated polyurethane
urea were introduced in portions into the hot mixture under a layer of
nitrogen. The addition was carried out at a rate such that at any time a
stirrable mixture was present. When addition of the granular material was
complete, the mixture was stirred at 200-210~C for a period of 90 min,
cooled to 160~C, then mixed with 0.2 kg of ethyl acetoacetate and stirred
at this temperature for one hour. A liquid product composed of recycled
polyols was obtained, which on standing formed two phases. The product
had the following properties:
OH number = 353 mg KOH/g
NH number = 33 mg KOH/g
Acid number = 0.07 mg KOH/g
Viscosity = approx. 20,000 mPa-s (20~C)
Example 2 (Production of a foamed polyurethane core for a composite in
accordance with the present invention)
To the recycled polyols obtained by glycolysis in Example 1 was
added a mixture of additives. This mixture of additives was used in an
25 amount which was 25 wt.%, based on the total weight of polyol. The
mixture of additives had the following properties:
OH number = 400 mg KOH/g
Water content = 2.6 wt.%
Viscosity = 1,500 mPa s (20~C)
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The resultant polyol formulation had the following properties:
OH number = approximately 380 mg KOH/g
Water content = approximately 1 wt.%
Viscosity = approximately 3,500 mPa s (20~C)
This polyol formulation was reaction injected molded with
polyisocyanate (crude MDI) in known manner to produce a foamed
polyurethane molding. An external release agent was not used. A
polyurethane molding having a bulk density of 400 kg/m3 was obtained.
Example 3 (Production of a composite (sandwich element) in accordance
with the present invention)
Example 3a
Outside the mold, coconut fiber mats having a substance weight of
600 g/m2 were impregnated and coated with a PU matrix material
(commercially available under the name Baypreg~ from Bayer AG) by
15 spraying in known manner.
A mold (steel, 120~C, 300 x 300 x 8 mm) was covered with a
covering coconut fiber reinforced PU layer produced as described above,
a polyurethane core produced as described in Examplé 2 and an
additional covering layer of the coconut fiber reinforced PU. The mold
was then closed. After 2 minutes at 120~C and a pressure of 50 bar, a
sandwich element bonded by adhesion was released.
Example 3b
A composite was produced in the same manner as described in
Example 3a) with the exception that a decorative film of PVC/ABS was
laid onto one of the covering layers before the mold was closed. After 2
minutes at 120~C and at a pressure of 50 bar, a sandwich element
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bonded by adhesion and having an additional decorative layer was
released.
All sandwich elements produced in accordance with the present
invention exhibited a very good adhesive bonding between core and
5 covering layer, good dimensional stability and strength.
Although the invention has been described in detail in the
foregoing for the purpose of illustration, it is to be understood that such
detail is solely for that purpose and that variations can be made therein
by those skilled in the art without departing from the spirit and scope of
10 the invention except as it may be limited by the claims.
