MATERIAU FILTRANT POUR VEHICULES A MOTEUR

FILTER MATERIAL FOR MOTOR VEHICLES

Abrégé anglais

ABSTRACT OF THE DISCLOSURE
An adsorption filter to prevent the emission of hydrocarbons
from the tanks of motor vehicles comprises a highly air-permeable,
substantially stable, three-dimensional bearer structure of wires,
monofilaments or webs to which is secured a layer of granular,
especially bead-structured adsorbent particles with a diameter of 0.1
to 1 mm, whereby the size of the micropores of the adsorbent is reduced
in the direction of flow of hydrocarbons emitted.

Revendications

THE CLAIMS OF THE INVENTION IN WHICH AN EXCLUSIVE PROPERTY OR
PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. Adsorption filter for preventing hydrocarbons from
escaping from motor-vehicle gasoline tanks, characterized by
a highly air-permeable and essentially shape-retaining three-
dimensional supporting skeleton of wire, monofilament, or
webs with a layer of granular and in particular spherical
adsorber particles 0.1 to 1 mm in diameter secured to it.
2. Adsorption filter as claimed in claim 1 wherein the
micropores in the adsorbent decrease in size along the
direction in which the emerging hydrocarbons flow.
3. Adsorption filter as claimed in Claim 2,
characterized in that the micropores decrease incrementally.
4. Adsorption filter as claimed in any one of claims 1
2, or 3, characterized in that the supporting skeleton is a
large-pored reticulated expanded polyurethane.
5. Adsorption filter as claimed in claim 4
characterized in that the expanded polyurethane weighs 20 to
60 g/l and has pores with diameters of 1.5 to 3 mm.
6. Adsorption filter as claimed in any one of claims 1
to 3 or 5, characterized in that the large-pored filter
layer, the first that the emerging hydrocarbons flow through,
contains adsorber particles of one of the following
materials:
a) active carbon with micropores of a diameter of
essentially 10 to 20 and preferably 15 to 20A,
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b) porous organic polymers with pore diameters of 8 to
80A,
c) hydrophobic molecular sieves with a pore diameter
ranging essentially from 8 to 18A.
7. Adsorption filter as claimed in claim 4,
characterized in that the large-pored filter layer, the first
that the emerging hydrocarbons flow through, contains
adsorber particles of one of the following materials:
a) active carbon with micropores of a diameter of
essentially 10 to 20 and preferably 15 to 20A,
b) porous organic polymers with pore diameters of 8 to
80A,
c) hydrophobic molecular sieves with a pore diameter
ranging essentially from 8 to 18A.
8. Adsorption filter as claimed in any one of claims 1
to 3, 5 or 7, characterized in that a fine-pored filter layer
of one of the following materials is positioned downstream of
the large-pored filter layer (preliminary filter) in the
direction traveled by the emerging hydrocarbons:
a) active carbon with micropores with a diameter of
essentially 6 to 10A,
b) polymeric adsorbers with a pore diameter of
essentially 4 to 8 A,
c) hydrophobic molecular sieves with a pore size of 2
to 9 A.
9. Adsorption filter as claimed claim 4, characterized
in that a fine-pored filter layer of one of the following
materials is positioned downstream of the large-pored filter
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layer (preliminary filter) in the direction traveled by the
emerging hydrocarbons:
a) active carbon with micropores with a diameter of
essentially 6 to 10A,
b) polymeric adsorbers with a pore diameter of
essentially 4 to 8 A,
c) hydrophobic molecular sieves with a pore size of 2
to 9 A.
10. Adsorption filter as claimed in claim 6,
characterized in that a fine-pored filter layer of one of the
following materials is positioned downstream of the large-
pored filter layer (preliminary filter) in the direction
traveled by the emerging hydrocarbons:
a) active carbon with micropores with a diameter of
essentially 6 to 10A,
b) polymeric adsorbers with a pore diameter of
essentially 4 to 8 A,
c) hydrophobic molecular sieves with a pore size of 2
to 9 A.
11. Adsorption filter as claimed in any one of claims 1
to 3, 5, 7, 9 or 10, characterized in that the adsorber
particles are attached with an adhesive system that travels
through a viscosity minimum prior to curing.
12. Adsorption filter as claimed in claim 4,
characterized in that the adsorber particles are attached
with an adhesive system that travels through a viscosity
minimum prior to curing.
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13. Adsorption filter as claimed in claim 6,
characterized in that the adsorber particles are attached
with an adhesive system that travels through a viscosity
minimum prior to curing.
14. Adsorption filter as claimed in claim 8,
characterized in that the adsorber particles are attached
with an adhesive system that travels through a viscosity
minimum prior to curing.
15. Adsorption filter as claimed in any one of claims 1
to 3, 5, 7, 9, 10 or 12 to 14, characterized in that the
adhesive system consists of polyurethane prepolymers with
blocked NCO groups and a cross-linker and up to 20% solvent.
16. Adsorption filter as claimed in claim 4,
characterized in that the adhesive system consists of
polyurethane prepolymers with blocked NCO groups and a cross-
linker and up to 20% solvent.
17. Adsorption filter as claimed in claim 6,
characterized in that the adhesive system consists of
polyurethane prepolymers with blocked NCO groups and a cross-
linker and up to 20% solvent.
18. Adsorption filter as claimed in claim 8,
characterized in that the adhesive system consists of
polyurethane prepolymers with blocked NCO groups and a cross-
linker and up to 20% solvent.
19. Adsorption filter as claimed in claim 11,
characterized in that the adhesive system consists of
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polyurethane prepolymers with blocked NCO groups and a cross-
linker and up to 20% solvent.
20. Method of diminishing the escape of hydrocarbons
from motor-vehicle tanks, characterized in that the gasoline
vapors forced out when the tank is filled or escaping when
the tank breathes are diverted through an adsorption filter
as claimed in any one of claims 1 to 3, 5, 7, 9, 10, 12 to 14
or 16 to 19 and in that the adsorbed hydrocarbons are
desorbed by fresh air suctioned in by the engine and burned
in the engine.
21. Method of diminishing the escape of hydrocarbons
from motor-vehicle tanks, characterized in that the gasoline
vapors forced out when the tank is filled or escaping when
the tank breathes are diverted through an adsorption filter
as claimed in claim 4 and in that the adsorbed hydrocarbons
are desorbed by fresh air suctioned in by the engine and
burned in the engine.
22. Method of diminishing the escape of hydrocarbons
from motor vehicle tanks, characterized in that the gasoline
vapors forced out when the tank is filled or escaping when
the tank breathes are diverted through an adsorption filter
as claimed in claim 6 and in that the adsorbed hydrocarbons
are desorbed by fresh air suctioned in by the engine and
burned in the engine.
23. Method of diminishing the escape of hydrocarbons
from motor-vehicle tanks, characterized in that the gasoline
vapors forced out when the tank is filled or escaping when
the tank breathes are diverted through an adsorption filter
as claimed in claim 8 and in that the adsorbed hydrocarbons
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are desorbed by fresh air suctioned in by the engine and
burned in the engine.
24. Method of diminishing the escape of hydrocarbons
from motor-vehicle tanks, characterized in that the gasoline
vapors forced out when the tank is filled or escaping when
the tank breathes are diverted through an adsorption filter
as claimed in claim 11 and in that the adsorbed hydrocarbons
are desorbed by fresh air suctioned in by the engine and
burned in the engine.
25. Method of diminishing the escape of hydrocarbons
from motor-vehicle tanks, characterized in that the gasoline
vapors forced out when the tank is filled or escaping when
the tank breathes are diverted through an adsorption filter
as claimed in claim 15 and in that the adsorbed hydrocarbons
are desorbed by fresh air suctioned in by the engine and
burned in the engine.
26. Method of diminishing the escape of hydrocarbons
from motor-vehicle tanks, characterized in that the gasoline
vapors forced out when the tank is filled or escaping when
the tank breathes are diverted through an adsorption filter
comprising a highly air-permeable and essentially shape-
retaining three-dimensional supporting skeleton of wire,
monofilament, or webs with a layer of granular and in
particular spherical particles 0.1 to 1 mm in diameter of an
adsorber with a mean micropore diameter of 3 to 18 A secured
to it and in that the adsorbed hydrocarbons are desorbed by
fresh air suctioned in by the engine and burned in the
engine.
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27. Method as in claimed in claim 20, characterized in
that desorption proceeds in the opposite direction from the
adsorption.
28. Method as in claimed in any one of claims 21 to 26,
characterized in that desorption proceeds in the opposite
direction from the adsorption.
29. Method as claimed in claim 26 or 27, characterized
in that the supporting skeleton is a large-pored reticulated
expanded polyurethane.
30. Method as claimed in claim 28, characterized in
that the supporting skeleton is a large-pored reticulated
expanded polyurethane.
31. Use of an adsorption filter comprising a highly
air-permeable and essentially shape-retaining three-
dimensional supporting skeleton of wire, monofilament, or
webs with a layer of granular and in particular spherical
particles 0.1 to 1 mm in diameter of an adsorber with a mean
micropore diameter of 3 to 18 A secured to it to prevent the
escape of hydrocarbons from motor-vehicle gasoline tanks.
32. Use of adsorption filter as claimed in claim 31,
whereby the supporting skeleton is a large-pored reticulated
expanded polyurethane, for the purposes of claim 31.
33. Use of an adsorption filter as claimed in any one
of claims 1 to 3, 5, 7, 9, 10, 12 to 14 or 16 to 19, whereby
the micropores in the adsorbent decrease in size along the
direction in which the emerging hydrocarbons flow, to prevent
the escape of hydrocarbon from motor-vehicle gasoline tanks.
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34. Use of an adsorption filter as claimed in any one
of claims 1 to 3, 5, 7, 9, 10, 12 to 14 or 16 to 19, whereby
the micropores in the adsorbent decrease in size along the
direction in which the emerging hydrocarbons flow, to prevent
the escape of hydrocarbon from motor-vehicle gasoline tanks.
34. Use of an adsorption filter as claimed in claim 4,
whereby the micropores in the adsorbent decrease in size
along the direction in which the emerging hydrocarbons flow,
to prevent the escape of hydrocarbon from motor-vehicle
gasoline tanks.
35. Use of an adsorption filter as claimed in claim 6,
whereby the micropores in the adsorbent decrease in size
along the direction in which the emerging hydrocarbons flow,
to prevent the escape of hydrocarbon from motor-vehicle
gasoline tanks.
36. Use of an adsorption filter as claimed in claim 8,
whereby the micropores in the adsorbent decrease in size
along the direction in which the emerging hydrocarbons flow,
to prevent the escape of hydrocarbon from motor-vehicle
gasoline tanks.
37. Use of an adsorption filter as claimed in claim 11,
whereby the micropores in the adsorbent decrease in size
along the direction in which the emerging hydrocarbons flow,
to prevent the escape of hydrocarbon from motor-vehicle
gasoline tanks.
38. Use of an adsorption filter as claimed in claim 15,
whereby the micropores in the adsorbent decrease in size
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along the direction in which the emerging hydrocarbons flow,
to prevent the escape of hydrocarbon from motor-vehicle
gasoline tanks.
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Description

Gasoline-powered motor vehicles are highly significant
sources of hydrocarbons that pollute the air. That poorly
tuned engines emit considerable levels of incompletely
burned fuel is known. Approximately 50,000 tons of
hydrocarbons, however, are released into the environment in
the Federal Republic of Germany every year just from adding
gasoline to fuel tanks. The space inside the tank not
occupied by liquid fuel is saturated with hydrocarbon gas, a
lot of which is expelled when gasoline is added.
There are basically two ways today of preventing these
vapors from escaping into the atmosphere.
1. A recirculation system can be integrated into the
gasoline pump. This approach entails significant
investment, and means that the gasoline-pump nozzle has to
fit every gasoline-tank opening.
2. An active-charcoal filter can be accommodated in
the vehicle for the expelled vapors to travel through and be
absorbed in for later resorption into fresh air suctioned in
by the engine and combustion within the engine.
The second solution is of advantage in that it not only
requires significantly less investment but can be introduced
step by step and will also handle any vapors that escape

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during the ~ank's normal oscillations (breathing) in
temperature and pressure The currently available filters
of course have a number of drawbacks that make the
automotive industry hesitant to install them.
Cylindrical filter canisters similar to the classical
particle jilters are beginning to be used in the United
States. They accommodate two kilograms of compressed carbon
compacted under slight pressure. Compressed carbon,
however, does not resist abrasion very well, and the
vehicles' inherent jolting and vibration leads to abrasion
and hence obstruction. Local compacting creates channels
and regions of high resistance, entailing non-unifor~
exploitation of the carbon and fracturing. Since only a
slight loss of pressure is acceptable, the particles of
active carbon must be really large. Their size means
extensive distances for the material being adsorbed or
desorbed to travel when penetrating them, and the kinetics
of the process are poor. Finally, the rather large and
rigid canisters are difficult to accommodate in a passenger
vehicle, every spare cubic inch of which is being exploited
nowadays, and the attempt to provide room often means total
reorganization.
The object of the present invention is accordingly to
improve adsorption of the hydrocarbons that oc,cur while a

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gasoline tank is being filled or while the tank is brea-thing -
and to prevent their escape.
The filter employed in accordance with the invention
consists ox a highly air-permeable and essentially shape-
retaining three-dimensional supporting skeleton with a layer
of granular adsorber particles 0.1 to 1 mm in diameter
secured to it. Filters with such a supporting framework and
granular adsorbers are described for example in German OS 3
813 563.
Highly air-permeable filters in the present sense are those
with an impedance of less than 100 and preferably between 10
and 30 Pa to air flowing through a filter 1 cm thick at a
speed of 1 m~sec. Motor vehicles in the sense of the
present invention are not only automobiles and trucks but
also any boats and aircraft powered by internal-combustion
engines employing gasoline as a fuel.
One particularly appropriate filter is made of a reticulated
expanded polyurethane with a pore count of 5 to 25 and
preferably 10 to 20 pores per inch (ppi) and with spherules
ox active carbon 0.1 to 1 mm in diameter adhering to its
inner and outer surfaces. The small and extremely hard
spherules do not rub against one another and there is
accordingly no abrasion. The large apertures ,in the matrix

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ensure very little loss of pressure and a very uniform flow.
A filter material of this type can be of any desired shape--
sheet, cylinder, slab, etc.-- and completely irregular. It
can ev2n be packed into tubing. Essentially, any available
space can be exploited. The very extensive outer surface of
the spherules and the short distances for the adsorbate to
travel ensure optimal utilization of their capacity, making
it possible to use much less-- approximately 50~ less--
active carbon than i5 used in known filtexs. When a filter
has to be replaced, all of the materiai is removed from the
framework in one piece with no possibility of contamination.
It is as easy to replace as a video cassette.
Gasolines have a mean boiling range of 30 to 200 C and
consist primarily of hydrocarbons with 4 to 12 carton atoms.
To adsorb the volatile constituents requires relatively
small micropores. To desorb the higher boiling-point
constituents again, however, requires relatively large
micropores. The resulting contradiction cannot always be
satisfactorily resolved.
To allow optimal desorption of the higher and lower boiling
point constituents of the fuel, distributing the adsorbents
throughout the filter with the size of their micropores
decreasing in the direction the emerging hydrocarbons are
flowing in has been recommended. The decrease in the

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diameter of the granules of adsorber attached to the air-
permeable support can be continuous or incremental. The
filter will accordingly comprise two or more layers
containing adsorbents with regions of different micropore
diameter.
The complete filter package in one preferred en~odiment of
the invéntion is in at least two sections, with the first
section trapping the less volatile constituents, which would
poison the fine-pored adsorber. This initial filter layer,
which could also be called a preliminary filter, contains
adsorbers with large micropores. Although it intercepts
only a small portion of the volatile constituents, it does
adsorb all the higher boiling-point constituents.
It is predominantly the more volatile constituents, butanes
and pentanes for example, that are adsorbed in the second
and directly adjacent section, which contains adsorbers with
small micropores. The higher boiling-point constituents,
which it would be impossible to desorb from the small
micropores, have already precipitated in the first section.
Since desorption with fresh air occurs in the opposite
direction, it is impossible for the small micropores to clog
up with "high boilers." Full capac1ty is accordinyly
maintained.

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When the adsorption filter to be employed in accordance with
the invention only contains adsorbers with a specific range
of micropores, adsorbers with pore diameters essentially
ranging from 3 to 18 A (0.3 to 1.8 nm) are recommended. In
this event the adsorption filter will have only one section
with one type of adsorbing granules.
Appropriate adsorbers constitute
a3 Active carbon with a micropore diameter
essentially in the vicinity of 6 + 14 I;
b) Polymeric adsorbers, especially those based on
divinyl benzene, with a micropore diameter essentially
ranging from 5 to 15 A.
c) Hydrophobic molecular sieves with a pore diameter
of 3 to 18 A.
These various types of adsorber with a relatively wide range
of micropore diameter can be attached to the matrix in the
form of conceivable mixtures or the filter can consist of
layers of adsorbents a), b), or c) from essentially the same
range of micropores at a right angle to the flow of emerging
hydrocarbons.
The following adsorbents can be employed for the larger-pore
filter layer (preliminary filter), which the hydrocarbon
vapor that occurs flows through first:

a) Active carbon with micropores of a diameter of
essentially 10 to 20 and preferably 15 to 20 A. Such large-
pored active carbons are commercially available for
purifying water for example. Their inner surface is usually
800 to 1~00 mZ/g.
b) Polymeric adsorbers, also called organic molecular
sieves, which are essentially porous organic polymers based
on styrene-and divinyl benzene with pore diameters of
essentially 8 to 80 A. Such adsorbers have inner surfaces
of 600 to 1600 m2/g. They are commercially available under
the brand Bonopore~R) for example.
c) Hydrophobic molecular sieves with a pore diameter
ranging essentially from 8 to 18 A. These have the
crystalline structure of normal zeolitic molecular sieves,
although they adsorb organic molecules and hardly any water
vapor. Water intake is extremely slight, even in the
presence of relatively much moisture. Zeolite of this type
are sold under the designation hydrophohic zeolite by the
firm of Munters Zeol AB for example. Similar conventional
zeolite called DAY ("de-aluminized Y") zeolite are available
from Degussa AG.
It is practical to position a filter layer with smaller
micropores made of one of the following materials downstream
of such a large-pore filter layer (preliminary filter):
a) Active carbon with a micropore diameter of

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essentially B 2 A.
b) Polymeric adsorbers with micropores with a
diameter ranging from 4 to 8 A, liXe those commercially
available under the brand Sorbathene. These have inner
surfaces of approximately 1400 to 160Q m2/g.
c) Hydrophobic molecular sieves with a pore size of 2
to 9 A. Their characteristics are those of the hydrophobic
molecular sieves employed in the pxeliminary-filter layer.
Active-carbon spherules with coal-tar p;tch, petroleum
pitch, or asphalt as a starting material are preferred. The
spherules of pitch are rendered infusible by oxidation, and
then carbonized and activated. The inner surfaces range
from 600 to 1600 , depending on the extent of activation.
Another appropriate starting material is spherules deriving
from the copolymerization of styrene and divinyl benzene.
The spherules of active carbon obtained therefrom by
pyrolysis with or without additional activation are
characterized by a hard shell, numerous micropores in the
range of 5 to 10 A, and satisfactory transport pores. The
micropores occupy as much as 0.5 ml/g of the active carbon
for example.
It is also possible to use, instead of the aforesaid
spherules of active carbon, more or less spherlcal

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agglomerates of milled active carbon and an appropriate
binder obtained by pelleting as descrihed for example in
German A 3 510 209. The advantage of this process is that
various types of active carbon and different adsorbents can
be employed, and specific adsorptive properties can be
purposefully demanded.
The preferred adhesive compounds, binders, and binder
dispersions employed in accordance with the invention to
attach the granules of adsorber to the matrix are those that
cure subject to heat.
Preferred are adhesive compounds of polymers that can be
cross linked but travel through a viscosity minimum before
doing so. Such adhesive systems as Bayer's high-solid
polyurethane-reactive Imprim~R) products for example are
initially highly viscous, meaning that they exhibit
satisfactory initial adhesion when the supporting skeleton
is sprinkled with particles of adsorber. They exhibit a
severe decrease in viscosity as temperature increases,
resulting in improved wetting of the adsorber particles and
hence particularly satisfactory adhesion subsequent to
cross-linkage curing. Small constrictions occur at the
points of contact between the supporting skeleton and the
adsorber particles while the viscosity minimum is being
traveled through. Due to the practically punctate

attachment of the particles of adsorber, almost their whole
surface will be available to the gas being purified
subsequent to curing.
The binders or adhesion systems must be resistant to
hydrocarbon, meaning that they must neither dissolve nor
expand when they come into contact with the liquid
hydrocarbons or their vapors.
The aforesaid adsorbers, supports, and adhesives are
examples that do not exclude other systems with basically
the same function. Depending on the shape of the filter's
housing, it is also possible to employ more than two filter
sections with adsorbers that have incrementally decreasing
micropore diameters. The vapors will always initially
contact the filter layer with the larger micropores and exit
the filter by way of the layer with the smallest micropores,
whereas desorption will occur subject to fresh air in the
opposite direction.