Note: Descriptions are shown in the official language in which they were submitted.
PF 61464 CA 02742892 2011-05-05
Recycling of road surfacings
Description
The present invention relates to a process for the production of roads,
tracks, and other
areas used by traffic, by producing a mixture comprising ground road
surfacing, mineral
material, and/or glass, a polymer reaction mixture and, if desired, further
additions, and
applying it to a substrate material, and hardening it. The present invention
further
relates to roads, tracks, and other areas used by traffic, obtainable by a
process of this
type.
Further embodiments of the present invention are found in the claims, in the
description, and in the examples. The abovementioned features of the subject
matter of
the invention, and the features that will be explained below, can of course be
used not
only in the respective stated combination but also in other combinations,
without
exceeding the scope of the invention.
Roads are mostly produced from asphalt, by applying a mineral mixture, mostly
with
bitumen as binder, if appropriate in a plurality of layers, to the substrate.
Road
surfacings using a plastic as binder are also known, for example as described
in
DE 19605990 and DE 19651749.
Bitumen-based roads usually have to be renewed after about 12 to 18 years, as
a
function of quality and loading, and after as little as from 6 to 7 years if
the top layers
have open pores. For this, the old asphalt is removed entirely or to some
extent. Small
amounts of the material removed can, if appropriate, be recycled with the same
grain
size distribution up to a level which is preferably 15% by weight. For this,
the material
must be conveyed to an asphalt mixing plant, where it is mixed at temperatures
of
about 180 C with fresh bitumen and also with mineral material. The resultant
asphalt is
then in turn conveyed from the asphalt mixing plant to the installation site.
This
procedure causes severe environmental pollution, in particular by virtue of
the truck
traffic necessary for this purpose, and also by virtue of the high energy
consumption in
the asphalt mixing plant. A further factor is that asphalt which cannot be
reused, the
binder of which still comprises a proportion of tar, has to be discarded as
special waste,
because tar is toxic.
It was an object of the present invention to provide a process which can
produce roads,
PF 61464 CA 02742892 2011-05-05
2
tracks, and other areas used by traffic, and which reduces pollution of the
environment.
The object of the invention is achieved via a process for the production of
roads, tracks,
and other areas used by traffic, by producing a mixture comprising ground road
surfacing, mineral material, and/or glass, a polymer reaction mixture and, if
desired,
further additions, and applying it to a substrate material, and hardening it.
Roads, tracks, and other areas used by traffic are usually composed of a
plurality of
layers. These have at least one bound top layer at the surface, and also, if
appropriate,
further bound and unbound, deeper, layers. The bound deeper layers are usually
what
are known as the load-bearing layers, and the unbound deeper layers are
usually base
layers composed of rubble and gravel. The usual materials used as binders for
the
bound top layers and load-bearing layers are cement, plastic, or bitumen.
The process of the invention relates here to the production of bound layers.
These can
either be load-bearing layers or top layers. The main difference between the
load-
bearing layers and top layers is the average diameter of the mineral material
used. The
process of the invention preferably relates to the production of top layers.
The
substrate material used can be any desired material, examples being sand,
earth,
loam, concrete, stone. Substrate materials are preferably base layers and/or
load-
bearing layers.
According to the invention, ground road surfacing means either ground or
broken top
layers or else ground or broken load-bearing layers, and ground rubble layers
or
ground gravel layers. The ground road surfacing is preferably ground bound
layers, in
particular ground top layers. The binder for the ground bound layers here is
preferably
a binder based on polymers or based on bitumen, in particular based on
bitumen. This
particularly preferred variant utilizes not only the thermoplastic or
viscoelastic
properties of bitumen but also the high-temperatures of the polymer binder.
The grain
size distribution of the ground road surfacing here can be adjusted in a known
manner
by adapting the grinding conditions or removing undesired grain sizes.
According to the
invention, it is also possible to use pored-asphalt-based top layers as a base
for ground
road surfacing.
The mineral material used here can comprise any known mineral material. By way
of
PF 61464 CA 02742892 2011-05-05
3
example, sand or ground stone, known as broken material, can be used here,
where
sand has a mainly round surface and broken material has edges and fracture
surfaces.
It is particularly preferable that the mineral material used comprises a
material which is
mainly composed of broken material.
The glass used preferably comprises ground or broken glass. Broken glass here
is
preferably colored glass, permitting, for example, application of markings.
Glass can be
used here together with mineral material or instead of mineral material. It is
preferable
to use only mineral material, and no glass.
The grain size distribution of the mixture composed of ground road surfacing
and of
mineral material and/or glass is particularly preferably one based on the
specifications
encountered in bituminous road construction, being a function of the intended
use, for
example for load-bearing layers and top layers, examples being stone-filled
mastic
asphalt or drainable asphalt. The grain size distribution can be adjusted
either via
adjustment of the grain sizes of the ground road surfacing or else via use of
mineral
material with certain grain size distribution, or both. The ground road
surfacing and the
mineral material here can be mixed in any ratio by weight. The proportion of
ground
road surfacing is preferably smaller than 95% by weight, particularly
preferably from 5
to 80% by weight, and in particular from 10 to 70% by weight, based on the
total weight
of the mixture composed of ground road surfacing and of mineral material.
A polymer reaction mixture here means a mixture capable of reacting to give a
polymer. These mixtures encompass those comprising molecules which by way of
example can react to give the polymer via chain-growth reactions, e.g. free-
radical
polymerization, or ionic polymerization, examples being unsaturated compounds,
or
molecules capable of entering into polycondensation reactions, examples being
polyalcohols, or molecules capable of entering into polyaddition reactions,
examples
being polyols and polyisocyanates, or those such as epoxides. Polymer reaction
mixtures of the invention are preferably liquid at 40 C.
The polymer reaction mixture preferably involves a mixture for the production
of an
epoxy resin or of a polyurethane. In particular, it involves a mixture for the
production of
a polyurethane, a polyurethane reaction mixture. The polymer reaction mixture
here
preferably comprises in essence no solvents.
PF 61464 CA 02742892 2011-05-05
4
The polymers obtained from a polymer reaction mixture are preferably compact,
and
this means that they comprise practically no pores. A feature of compact
polymers,
when compared with cellular polymers, is greater mechanical stability. Bubbles
can
occur within the polymer and are mostly not critical. However, they should be
minimized as far as possible. It is moreover preferable that the resultant
polymers are
hydrophobic. This suppresses degradation of the polymers by water.
Polymer reaction mixtures of the invention preferably comprise compounds for
improving adhesion to the recycling material and also to the mineral material.
By way of
example, these are hydroxy- or alkoxyaminosilane compounds of the general
formula
(I)
[x] Si Y (I)
R'
in which
X are, independently of one another, OH, CH3, O[CH2]PCH3;
Y is [CH2]t, [(CH2)rNH(CH2)5]b, [(CH2)rNH(CH2)SNH(CH2)Z]b;
R, R' is H, [CH2]tCH3;
t is0-10;
n is 1 - 3;
p is0-5;
m is4-n;
r, s, b, and z are, independently of one another, 1-10.
The alkoxyaminosilane compound (I) is generally a trihydroxy-, dialkoxy- or
trialkoxyaminosilane compound. Preferred alkoxy radicals X are methoxy and
ethoxy.
The amino group must be an amino group reactive toward isocyanate groups, i.e.
a
primary or secondary amino group. Preferred alkyl radicals R are hydrogen,
methyl,
and ethyl.
The alkoxyaminosilane compound (I) preferably involves a trihydroxyaminosilane
compound or a trialkoxyaminosilane compound, where, in formula (I), X = OH or
PF 61464 CA 02742892 2011-05-05
O[CH2]PCH3, and p = 0, 1.
It is further preferable that the alkoxyaminosilane compound (I) involves an
alkoxydiaminosilane compound, where, in formula (I), Y = [CH2],NH[CH2]s, and r
and s
5 are identical or different, being 1 or 2. Examples are [CH2]3NH[CH2]2,
[CH2]2NH[CH2]2,
[CH2]NH[CH2], [CH2]3NH[CH2]3, [CH2CH(CH3)CH2]NH[CH2]2 and [CH2]2NH[CH2]3.
The alkoxyaminosilane compound (I) in particular involves a
trialkoxydiaminosilane
compound, where, in formula (I), X = O[CH2]PCH3, where p = 0, 1, and Y =
[CH2]rNH[CH2]s, where r and s are identical or different, being 1 or 2.
Particularly preferred alkoxyaminosilane compounds (I) are 3-
triethoxysilylpropylamine,
N-(3-trihydroxysilylpropyl)ethylenediamine, N-(3-
trimethoxysilylpropyl)ethylenediamine,
and N-(3-methyldimethoxymethylsilyl-2-m ethylpropyl)ethylenediamine.
The polymer reaction mixture here generally comprises a concentration of from
0.01 to
10% by weight, preferably from 0.1 to 1 % by weight, based on the total weight
of the
polymer reaction mixture, of the compounds for improving adhesion. The
compound for
improving adhesion here can also have reacted previously with further
constituents of
the polymer reaction mixture, for example by way of any OH group present.
For the purposes of this invention, a mixture for the production of an epoxy
resin
means a mixture which comprises compounds comprising epoxy groups, and
comprises suitable hardeners. The mixtures here are capable, starting from the
compounds comprising epoxy groups, of forming epoxy resins by way of said
epoxy
groups through polyaddition, using suitable hardeners. The invention uses the
expression "a mixture for the production of an epoxy resin" when conversion in
the
reaction, based on the epoxy groups used for the production of the epoxy
resin, is
preferably smaller than 90%, particularly preferably smaller than 75%, and in
particular
smaller than 50%.
Compounds used comprising epoxy groups are preferably compounds which have at
least two epoxy groups and which are liquid at room temperature. Mixtures of
different
compounds comprising epoxy groups can also be used here. It is preferable that
said
compounds are hydrophobic or that the mixtures comprise at least one compound
PF 61464 CA 02742892 2011-05-05
6
which is hydrophobic and which comprises epoxy groups. Hydrophobic compounds
of
this type are by way of example obtained via a condensation reaction of
bisphenol A or
bisphenol F with epichlorohydrin. Said compounds can be used individually or
in the
form of a mixture.
In one embodiment, mixtures are used which are composed of abovementioned
hydrophobic compounds, comprising epoxy groups, with self-emulsifiable
hydrophilic
compounds, comprising epoxy groups. These hydrophilic compounds are obtained
here via introduction of hydrophilic groups into the main chain of the
compound
comprising epoxy groups. Compounds of this type and processes for their
production
are disclosed by way of example in JP-A-7-206982 and JP-A-7-304853.
Hardeners used comprise compounds which catalyze the homopolymerization of the
compounds comprising epoxy groups, or which react covalently with the epoxy
groups
or with the secondary hydroxy groups, examples being polyamines,
polyaminoamides,
ketimines, carboxylic anhydrides, and melamine-urea-phenol adducts and
formaldehyde adducts. It is preferable to use ketimines, obtainable via
reaction of a
compound having a primary or secondary amino group, e.g. diethylenetriamine,
triethylenetetramine, propylenediamine, or xylylenediamine, with a carbonyl
compound,
such as acetone, methyl ethyl ketone, or isobutyl methyl ketone, or to use
aiphatic,
alicyclic, and aromatic polyamine compounds and polyamide compounds. Hardeners
used with particular preference are ketimines or compatible mixtures
comprising
ketimines.
The ratio of reactive groups in the hardener to epoxy groups is preferably
from 0.7:1 to
1.5:1, particularly preferably from 1.1:1 to 1.4:1.
During the production of the epoxy resins, it is also possible to add further
additives,
such as solvents, reactive diluents, fillers, and pigments, alongside the
compounds
comprising epoxy groups, and alongside the hardeners used. Additives of this
type are
known to the person skilled in the art.
A polyurethane reaction mixture is a mixture composed of compounds having
isocyanate groups and compounds having groups reactive toward isocyanates,
where
the reaction conversion, based on the isocyanate groups used for the
production of the
PF 61464 CA 02742892 2011-05-05
7
polyurethane reaction mixture, is preferably smaller than 90%, particularly
preferably
smaller than 75%, and in particular smaller than 50%. The compounds having
groups
reactive toward isocyanates here comprise not only high-molecular-weight
compounds,
such as polyether- and polyesterols, but also low-molecular-weight compounds,
such
as glycerol, glycol, and also water. If the reaction conversion, based on the
isocyanate
group, is greater than 90%, the term polyurethane is used below. A
polyurethane
reaction mixture here can also comprise further reaction mixtures for the
production of
polymers. Examples of further reaction mixtures that can be used for the
production of
polymers are reaction mixtures for the production of epoxides, of acrylates,
or of
polyester resins. The proportion of further reaction mixtures for the
production of
polymers here is preferably less than 50% by weight, based on the total weight
of the
polyurethane reaction mixture. It is particularly preferable that the
polyurethane
reaction mixture comprises no further reaction mixtures for the production of
polymers.
The polyurethane reaction mixture can involve what are known as moisture-
curing
systems. These comprise isocyanate prepolymers which form polyurethanes or
polyureas via addition of water or via humidity, mainly by forming urea
groups.
It is preferable to use what are known as two-component systems for the
production of
the polyurethane reaction mixture. For this, an isocyanate component
comprising
compounds having isocyanate groups, and a polyol component comprising
compounds
having groups reactive toward isocyanates are mixed in quantitative
proportions such
that the isocyanate index is in the range from 40 to 300, preferably from 60
to 200, and
particularly preferably from 80 to 150.
For the purposes of the present invention, isocyanate index here means the
stoichiometric ratio of isocyanate groups to groups reactive toward
isocyanate,
multiplied by 100. Groups reactive toward isocyanate here means any of the
groups
which are comprised in the reaction mixture and which are reactive toward
isocyanate,
and this includes chemical blowing agents, but not the isocyanate group
itself.
The polyurethane reaction mixture is preferably obtained by mixing of a)
isocyanates
with b) relatively high-molecular-weight compounds having at least two
hydrogen
atoms reactive toward isocyanate, and also, if desired, c) chain extenders
and/or
crosslinking agents, d) catalysts, and e) other additives. Compounds
particularly
PF 61464 CA 02742892 2011-05-05
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preferably used as components a) and b), and also, if desired, c) to e) are
those which
lead to a hydrophobic polyurethane reaction mixture and to a hydrophobic
polyurethane.
Isocyanates a) that can be used are in principle any of the room-temperature-
liquid
isocyanates having at least two isocyanate groups. Aromatic isocyanates are
preferably used, particularly preferably isomers of tolylene diisocyanate
(TDI) and of
diphenylmethane diisocyanate (MDI), in particular mixtures composed of MDI and
of
polyphenylene polymethylene polyisocyanates (crude MDI). The isocyanates can
also
have been modified, for example by incorporating isocyanurate groups and
carbodiimide groups, and in particular by incorporating urethane groups. The
last-
mentioned compounds are produced via reaction of isocyanates with a
substoichiometric amount of compounds having at least two active hydrogen
atoms
and are usually termed NCO prepolymers. Their NCO content is mostly in the
range
from 2 to 32% by weight. The isocyanates a) preferably comprise crude MDI,
with
resultant increase in the stability of the polyurethane obtained.
In applications of the inventive process where high colorfastness is
important, it is
preferable to use mixtures comprising aliphatic isocyanates and aromatic
isocyanates.
It is particularly preferable to use exclusively aliphatic isocyanates. In one
particular
embodiment, an overlayer composed of polyurethane based on an aliphatic
isocyanate
can be used, in order to protect the top layer based on aromatic isocyanate
from
yellowing. The overlayer here can also comprise mineral material. Preferred
representative aliphatic isocyanates are hexamethylene diisocyanate (HDI) and
isophorone diisocyanate (IPDI). Because the aliphatic isocyanates have high
volatility,
they are mostly used in the form of their reaction products, in particular in
the form of
biurets, allophanates, uretonimines, or isocyanurates.
The isocyanates a) can also be used in the form of their prepolymers. For
this, the
isocyanates a) are reacted in a known manner in excess with compounds reactive
toward isocyanate, for example with the relatively high-molecular-weight
compounds
listed under b), having at least 2 groups reactive toward isocyanate, to give
prepolymers.
The relatively high-molecular-weight compounds b) used, having at least two
hydrogen
PF 61464 CA 02742892 2011-05-05
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atoms reactive toward isocyanate preferably comprise compounds which have, as
group reactive toward isocyanate, hydroxy groups or amino groups. Amino groups
as
groups reactive toward isocyanates lead to formation of urea groups, which in
turn
harden to give a polyurethane which is mostly brittle, but which has very good
hydrolysis resistance and chemicals resistance. The relatively high-molecular-
weight
compounds b) used, having at least two hydrogen atoms reactive toward
isocyanate
preferably comprise polyhydric alcohols, since these generally react more
slowly than
compounds having amino groups and thus permit longer processing times. Given
appropriate high molar masses, for example greater than 1500 g/mol, the use of
polyhydric alcohols moreover gives a relatively elastic material.
The relatively high-molecular-weight, polyhydric alcohols used can by way of
example
comprise polyethers or polyesters. Further compounds having at least two
hydrogen
atoms reactive toward isocyanate groups can be used together with the
compounds
mentioned.
Because of their high hydrolysis resistance, polyether alcohols are preferred
as
relatively high-molecular-weight compounds b) having at least two hydrogen
atoms
reactive toward isocyanate. These are produced by conventional and known
processes, mostly via an addition reaction of alkylene oxides onto H-
functional starter
substances. The functionality of the polyether alcohols used concomitantly is
preferably
at least 2, their hydroxy number being at least 10 mg KOH/g, preferably at
least 15 mg
KOH/g, in particular in the range from 20 to 600 mg KOH/g. They are produced
in a
conventional manner via reaction of at least difunctional starter substances
with
alkylene oxides. Starter substances used can preferably comprise alcohols
having at
least two hydroxy groups in the molecule, examples being propylene glycol,
monoethylene glycol, diethylene glycol, dipropylene glycol, tripropylene
glycol. Starter
substances of relatively high functionality can preferably be glycerol,
trimethylolpropane, pentaerythritol, sorbitol, and sucrose. Alkylene oxides
used
preferably comprise ethylene oxide and propylene oxide, in particular
propylene oxide.
The reaction mixtures of the invention preferably comprise compounds having
hydrophobic groups. These particularly preferably involve hydroxy-
functionalized
compounds having hydrophobic groups. These compounds having hydrophobic groups
have hydrocarbon groups preferably having more than 6, particularly preferably
more
PF 61464 CA 02742892 2011-05-05
than 8 and less than 200, and in particular more than 10 and less than 100,
carbon
atoms. The compounds having hydrophobic groups can be used as a separate
component or as a constituent of one of components a) to e), for the
production of the
reaction mixture. The hydroxy-functionalized hydrophobic compounds preferably
5 involve compounds which comply with the definition of the relatively high-
molecular-
weight compounds b) having at least two hydrogen atoms reactive toward
isocyanates.
Component b) here can comprise hydroxy-functionalized hydrophobic compounds or
can preferably be composed thereof.
10 The hydroxy-functionalized hydrophobic compound used preferably comprises a
hydroxy-functionalized compound known from oleochemistry, or a polyol known
from
oleochemistry.
A number of hydroxy-functional compounds that can be used are known in
oleochemistry. Examples are castor oil, oils modified using hydroxy groups,
e.g.
grapeseed oil, black cumin oil, pumpkin seed oil, borage seed oil, soybean
oil,
wheatgerm oil, rapeseed oil, sunflower oil, peanut oil, apricot seed oil,
pistachio oil,
almond oil, olive oil, macadamia nut oil, avocado oil, sea buckthorn oil,
sesame oil,
hazelnut oil, evening primrose oil, wild rose oil, hemp oil, thistle oil,
walnut oil, fatty acid
esters modified using hydroxy groups and based on myristoleic acid,
palmitoleic acid,
oleic acid, vaccenic acid, petroselinic acid, gadoleic acid, erucic acid,
neuronic acid,
linoleic acid, linolenic acid, stearidonic acid, arachidonic acid, timnodonic
acid,
clupanodonic acid, or cervonic acid. It is preferable here to use castor oil
and its
reaction products with alkylene oxides or with ketone-formaldehyde resins. The
last-
named compounds are marketed by way of example by Bayer AG as
Desmophen 1150.
Another group of polyols which are known in oleochemistry and whose use is
preferred
can be obtained via ring-opening of epoxidized fatty acid esters with
simultaneous
reaction with alcohols and, if need be, subsequent further transesterification
reactions.
Incorporation of hydroxy groups into oils and fats occurs primarily via
epoxidization of
the olefinic double bond comprised in these products, followed by reaction of
the
resultant epoxy groups with a mono- or polyhydric alcohol. The product here of
the
epoxy ring is a hydroxy group or, in the case of polyhydric alcohols, a
structure having
a relatively high number of OH groups. Since oils and fats are mostly glycerol
esters,
PF 61464 CA 02742892 2011-05-05
11
parallel transesterification reactions proceed with the abovementioned
reactions. The
molar mass of the resultant compounds is preferably in the range from 500 to
1500
g/mol. These products are supplied by way of example by Henkel.
In one particularly preferred embodiment of the inventive process, the
relatively high-
molecular-weight compound b) having at least two hydrogen atoms reactive
toward
isocyanate comprises at least one polyol known in oleochemistry and at least
one
phenol-modified aromatic hydrocarbon resin, in particular one indene-coumarone
resin.
Polyurethane reaction mixtures based on said component b) have a level of
hydrophobic properties which is sufficiently high that in principle they can
even be
hardened under water, or installed during rainfall.
The phenol-modified aromatic hydrocarbon resin used having a terminal phenol
group
preferably comprises phenol-modified indene-coumarone resins, and particularly
preferably industrial mixtures of aromatic hydrocarbon resins. These products
are
commercially available and are supplied by way of example by Rutgers VFT AG as
NOVARES .
The OH content of the phenol-modified aromatic hydrocarbon resins, in
particular the
phenol-modified indene-coumarone resins, is mostly from 0.5 to 5.0% by weight.
The polyol known from oleochemistry and the phenol-modified aromatic
hydrocarbon
resin, in particular the indene-coumarone resin, are preferably used in a
ratio by weight
of from 100:1 to 100:50.
Production of an inventive polyurethane reaction mixture can use a chain
extender c).
However, the chain extender c) can also be omitted here. However, the addition
of
chain extenders, crosslinking agents, or else, if desired, a mixture of these
can prove
successful for modification of mechanical properties, e.g. hardness.
If low-molecular-weight chain extenders and/or crosslinking agents c) are
used, the
production of polyurethanes can use known chain extenders. These are
preferably low-
molecular-weight compounds having groups reactive toward isocyanates whose
molar
mass is from 62 to 400 g/mol, examples being glycerol, trimethyloipropane,
known
glycol derivatives, butanediol, and diamines. Other possible low-molecular-
weight
PF 61464 CA 02742892 2011-05-05
12
chain extenders and/or crosslinking agents are given by way of example in
"Kunststoffhandbuch, Band 7, Polyurethane" [Plastics Handbook, volume 7,
Polyurethanes], Carl Hanser Verlag, 3rd edition 1993, chapter 3.2 and 3.3.2.
The polyurethanes used can in principle be produced without the presence of
catalysts
d). Catalysts d) can be used concomitantly to improve hardening. The catalysts
d)
selected should preferably be those that maximize reaction time. It is thus
possible that
the polyurethane reaction mixture remains liquid for a long period. These
catalysts are
known to the person skilled in the art. It is also possible in principle, as
described, to
work entirely without catalyst.
Other conventional constituents can be added to the polyurethane reaction
mixture,
examples being conventional additives e). These comprise by way of example
conventional fillers. The fillers used are preferably the conventional,
organic and
inorganic fillers, reinforcing agents, and weighting agents known per se.
Individual
examples that may be mentioned are: inorganic fillers, such as silicatic
minerals, e.g.
phyllosilicates, such as antigorite, serpentine, hornblendes, amphiboles,
chrysotile,
metal oxides, such as kaolin, aluminum oxides, titanium oxides, and iron
oxides, metal
salts, such as chalk, barite, and inorganic pigments, such as cadmium sulfide,
zinc
sulfide, and also glass. It is preferable to use kaolin (China clay), aluminum
silicate,
and coprecipitates composed of barium sulfate and aluminum silicate, and also
natural
and synthetic fibrous minerals, such as wollastonite, metal fibers of various
lengths,
and in particular glass fibers of various lengths, which may, if desired, have
been
coated with a size. Examples of organic fillers that can be used are: carbon
black,
melamine, rosin, cyclopentadienyl resins, and graft polymers, and also
cellulose fibers,
polyamide fibers, polyacrylonitrile fibers, polyurethane fibers, polyester
fibers based on
aromatic and/or aliphatic dicarboxylic esters, and in particular carbon
fibers.
If the abovementioned inorganic fillers are used as additives e), their
mineral substance
constitution preferably differs from that of the mineral material, and they
are ignored
when determining the grain size distribution of the mineral material.
The inorganic and organic fillers can be used individually or in the form of a
mixture,
and their amounts comprised in the reaction mixture are preferably from 0.5 to
50% by
weight, particularly preferably from 1 to 40% by weight, based on the weight
of
PF 61464 CA 02742892 2011-05-05
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components a) to e).
The polyurethane reaction mixture should also comprise dryers, such as
zeolites.
These are preferably added, prior to production of the inventive reaction
mixture, to the
compounds b) having at least two hydrogen atoms reactive toward isocyanate, or
to
the component which comprises the compounds b) having at least two hydrogen
atoms
reactive toward isocyanate. Addition of the dryers avoids any increase in the
concentration of water in the components or in the reaction mixture, and thus
avoids
formation of foamed polyurethane. Additions preferred for water adsorption are
aluminosilicates, selected from the group of the sodium aluminosilicates,
potassium
aluminosilicates, calcium aluminosilicates, cesium aluminosilicates, barium
aluminosilicates, magnesium aluminosilicates, strontium aluminosilicates,
sodium
aluminophosphates, potassium aluminophosphates, calcium aluminophosphates, and
mixtures thereof. It is particularly preferable to use mixtures of sodium
aluminosilicates,
potassium aluminosilicates, and calcium aluminosilicates in castor oil as
carrier
substance.
To improve the long-term stability of the inventive top layers, it is moreover
advantageous to add agents to counter attack by microorganisms. Addition of UV
stabilizers is also advantageous, in order to avoid embrittlement of the
moldings. These
additives are known, and examples are given in "Kunststoffhandbuch, Band 7,
Polyurethane" [Plastics Handbook, volume 7, Polyurethanes], Carl Hanser
Verlag, 3rd
edition 1993, chapter 3.4.
It is preferable that the components c), d), and e) are added to the compounds
having
at least two hydrogen atoms reactive toward isocyanate groups. This blend is
often
referred to in industry as polyol component.
The ratio in which the isocyanates are combined with the compounds having at
least
two hydrogen atoms reactive toward isocyanate groups should preferably be such
that
a stoichiometric excess of isocyanate groups is present.
In one preferred embodiment of the invention, polyurethane reaction mixtures
are used
which lead to hydrophobic, substantially compact polyurethanes. A polyurethane
is
termed compact polyurethane if it is substantially free from gas inclusions.
The density
PF 61464 CA 02742892 2011-05-05
14
of a compact polyurethane is preferably greater than 0.8 g/cm3, particularly
preferably
greater than 0.9 g/cm3, and in particular greater than 1.0 g/cm3.
Examples of materials that can be used as further additions are those which
inhibit run-
off of the binder from the mineral material. Examples of additions of this
type that can
be added are organic fibers, such as cellulose fibers. It is moreover possible
to add
polymers which are nowadays used in the bitumen-based systems used. These are
especially neoprenes, styrene-butadiene-styrene, block copolymers, or a
mixture of
these, or else any of the other known rubbers or a mixture of these. The
additions can
either be added directly to the mineral mixture in the form of powder or
granules, or
else can be dispersed in one of the polyurethane components.
There is no restriction on the production of mixtures of the invention,
comprising ground
road surfacing, mineral material, and a polymer reaction mixture, and also, if
used,
further additions. They can by way of example be produced in mixers into which
the
ground road surfacing and the mineral material is introduced, and the starting
components for the production of the polyurethane reaction mixture are
introduced, for
example by spraying. Additions to be added here, if desired, are preferably
added to
the mixture at the respective advantageous juncture. By way of example,
therefore,
these may be in solution or dispersion in one of the components of the
reaction
mixture, for example in one of components a) to e), and may be added with
these to
the mixture. The additions can also be separately added to the mixture. By way
of
example, cellulose fibers can be added at a juncture such that these are
present in
homogeneous dispersion in the mixture for the production of top layers, but
are not
irreversibly damaged by the mixing procedure. The inventive mixture here can
by way
of example be produced by the process described in DE 196 32 638. It is
likewise
possible, for example, to begin by producing the polyurethane reaction mixture
and
then to mix this with the mineral material and, if used, with the further
additions. In
another embodiment, the mineral material can, if desired, first be mixed with
some of
the components of the reaction mixture, for example with components b) and, if
present, c) to e), and then the components not yet present, for example
component a),
can be added in a mixer. The mixture of the invention, comprising ground road
surfacing, can be produced by a mobile method at the installation site.
Transport to a
central plant is not necessary.
PF 61464 CA 02742892 2011-05-05
The hydrophobic polyurethane reaction mixtures whose use is preferred feature
particularly good processability. By way of example, said polyurethane
reaction
mixtures, and the polyurethanes obtained therefrom, feature particularly good
adhesion. Because of the hydrophobic nature of the system, the polyurethane
reaction
5 mixture hardens despite the presence of water, e.g. rain, to give a
practically compact
product.
When the mixture of the invention is applied to the substrate material, it is
not
necessary that the substrate material is dry. Surprisingly, even when
substrate material
10 is wet, good adhesion is obtained between the load-bearing layer or the top
layer and
the substrate material.
The mixture of the invention here preferably comprises from 1 to 20% by
weight,
particularly preferably from 2 to 15% by weight, and in particular from 4 to
10% by
15 weight, of polymer reaction mixture, based on the total weight of the
mixture of the
invention, comprising ground road surfacing, mineral material, and a polymer
reaction
mixture, and also, if desired, further additions.
The bond between mineral material and binder of the invention is very strong.
Furthermore, particularly if hydroxy-functional compounds having hydrophobic
groups
are used, there is practically no hydrolytic degradation of the polyurethanes,
and the
durability of the top layers produced by the process of the invention is
therefore very
high. Top layers of the invention have particularly good load-bearing
properties and are
therefore suitable for all roads, tracks, and areas used by traffic,
particularly for
runways and for roads subject to relatively high loads in construction class V
to I,
particular III to I, and runways, where roads of construction class V are
access roads,
and roads of construction class I are motorways and highways. The mineral
material
used here preferably comprises the materials recommended for the respective
construction class.
Surprisingly, and particularly when hydrophobic reaction mixtures are used,
there is
very little frost damage. A further advantage of top layers of the invention
is low repair
cost. It.is sufficient, for example, that the mixture for the production of a
top layer is
produced, without heating, in small amounts in situ, and is applied to the
damaged site
and compacted. Furthermore, the mechanical properties of the top layers of the
PF 61464 CA 02742892 2011-05-05
16
invention do not change over a period of a number of years. A further
advantage of top
layers of the invention is improved wet slip resistance, in particular in the
case of top
layers with high polyurethane content in comparison with top layers with high
bitumen
content.
It is preferable that the mixture comprising ground road surfacing, mineral
material, and
a polymer reaction mixture, and also, if desired, further additions is
compacted after
application to a substrate material. The intensity of compaction here depends
on the
desired application, by way of example, only a little compaction is used for
the
production of drainable asphalt, which can dissipate moisture, but a higher
degree of
compaction is used for the production of asphalt that can withstand high
loadings. The
degree of compaction needed also depends on the composition of the rock.
The process of the invention is preferably used for the renovation of roads.
The ground
road surfacing here is preferably obtained directly at the usage location by
surface
grinding to remove material from the road requiring renovation. The material
obtained
by the grinding process is preferably broken, ground, and/or sieved, in order
to obtain a
preferred grain size distribution. This recycling material is mixed with
binder and with
further mineral material and preferably reinstalled onto the road in situ, as
load-bearing
layer or top layer. For this, the appropriate substrate is preferably
pretreated with
familiar adhesion-promoter systems, for example with polyurethane-based spray
adhesives. This serves to give an even greater improvement in the adhesion
between
the layers and to compensate any stresses arising, caused by high loading, for
example heavy traffic load or caused by differences in coefficients of thermal
expansion between substrate and load-bearing layer or top layer. The materials
here
are installed using equipment conventional in road construction. The
installation
equipment used here preferably has an antiadhesive coating, or has been wetted
with
a, preferably biologically based, release agent. It is preferable that the top
layer
installed is then provided with a coating of scattered fine-grain mineral
material (e.g.
sand), in order to give an even greater improvement in the good wet slip
properties.
In comparison with the conventional process in which the new asphalt is
obtained only
in stationary asphalt plants, the process of the invention can save time and
energy, by
omitting the truck transport which is otherwise needed. A further feature of
inventive
tracks, roads, and areas used by traffic is very high durability, in
particular when
PF 61464 CA 02742892 2011-05-05
17
subject to frost-thaw cycles, and high elasticity, and exceptionally high
strength. Top
layers of the invention thus combine the favorable properties of bitumen-based
top
layers with top layers based on polymer reaction mixtures, e.g. polyurethanes
or
epoxides.
The invention is illustrated by the example below:
Polyurethane reaction mixture 1:
100 parts by weight of the polyol component of the Elastan 6551/101 system and
50 parts by weight of lsoPMDl 92140, a formulation comprising diphenylmethane
diisocyanate (MDI) were mixed with one another.
10 parts by weight of polyurethane reaction mixture 1 are mixed with 90 parts
by weight
of a mixture composed of 90 parts by weight of mineral mixture (grain size
2/5,
Piesberger) and with 10 parts by weight of a broken bitumen-based standard
recycling
material from an asphalt top layer, charged to a mold of dimensions 100 x 100
x100 mm, compacted using 8.5 N/mm2, and hardened.
The compressive strength of the resulting specimen was determined after more
than
24 hours of storage, being 7.0 N/mm2. This value shows that it is possible to
produce
top layers from this type of material.
