[0001] The invention relates to soil-improving materials, especially for draining purposes,
based on particulate plyurethane foam materials which may be held together by a cover.
It is known to keep the soil in warehouses,nursery-gardens etc in condition by means
of draining pipes and thus advantageously influence the water management. The materials
used thus far all have certain objections.If one uses draining pipes then material
has to be put on top of it to prevent deposition, blocking, which often arises in
connection with the clay layer etc present.The use of materials, like filted PVS-foam
further has the object that they themselves imbibe water and retain it and thus retard
continuous flow. Up to now methyl bromide was used to disinfect the soil.This however
has environmental disadvantages and thus one returns to steaming of the soil. Therefore
still other propertiesare of interest for the present materials, such as resistance
against the relatively high temperatures which occur during steaming of the soil.Further
of course a relatively low weight is of importance.
[0002] The invention is aimed at a foamed material inparticulate form, which during use
as draining materal doen not require maintenance and which indefinitely retains its
water repellant capacity.Thus long term use is possible without occurrence of blocking
or layer formation.
[0003] Furthermore the invention is aimed at a foamed material in particuate and possible
covered form, which is resistant against the relatively high temperatures which may
arise in warehouses when steaming the soil.
[0004] The foamed material especially consists of a famed particulate thermohardable polyurethane
polymer which does not melt or is shrinking of changes shape at the temperatures experienced.
[0005] It is known from German Offenlegungsschrift 2041192 to use polyurethane foam particles
mixed with feed materials and bound together by a binder into a carrier product for
the roots of plants. This publication does not disclose a specific shape of the polyurethane
particles and equally the purpose is different.Furthermore the German Offenlegungsschrift
2213053 describes an apparatus for the detection of draining pipes consisting of an
intermediate layer ofhard foam particles loosely laying on top of each other covered
by an outer layer of fibrous materiaal.
[0006] There is no mention of polyurethane foam flakes and equally not of a specific irregular
shape thereof.The use of polyethylene or polystyrene has objections because of the
temperature sensitivity and also in the course of time deposition may occur.
[0007] According to the invention a material is provided which is used as a soil improving
material, especially as a drain, material or soil strengthening material, which is
characterized in that it is built up of a thermo hardend polyurethane foam,which by
means of a desintegrating process, as defined, is comminuted to irregular flakes.As
is known polyurethane consists of polymers obtained by the polyaddition of isocyanate
containing molecules to polyvalent alcohols, acids or amines.
[0008] By variation of the staring materials polyurethanes with different properties are
obtainable.The invention starts from thermohardenable polyurethanes for processing
into foam, like polyester and polyether foam,wherein foaming occurs by CO₂ or water
dosing or by other foaming gases.The polyurethane foams can be obtained as blocks
by foaming in a mold or as sheets when foaming takes place on a belt.The foams may
be flexible or rigid dependent on the reactions used. In the present invention rigid
polyurethane foams with closed cells are used which are thermo hardable and during
higher temperatures, especially above 140
oC do not soften or otherwise loose their favourite properties .
[0009] Thus especially thermohardend polyurethane foam with dense cells is used, which in
a desintegration process is comminuted to irregular flakes, of which in fact none
has the same shape, by means of for this purpose known apparatuses, like hammer mills,
ball mills, beaters, vibration mills etc.One uses especially a hammer mill provided
with a perforated screen with adjustable screen openings with which the flake size
can be adjusted.The flakes should have an irregular form in such a way that in use
always opening remain between the stacked flakes because of their non-fitting shape.These
opening are of course necessary for a good draining. In case of a dense packing of
the flakes there may arise the danger of layer forming.
[0010] The form most suitable of the irregular flakes is obtained by disintegrating sheet-
or block materials, which are the startingmaterials,in a hammer mill of which the
screen distance between the screen or grid bars is adjusted to 20 mm to 50 mm (square
openings).The material is beaten through the screen openings by the hammers of the
mill so that very irregular shapes of the flakes arise, of which the mean dimensions
are lying about th4 screen distance. It is of course to be understood that no exact
measures can be indicated, such as a mean diameter etc, because the flakes per se
possess too great deviations and may have tortuous forms.However, when the indicated
screen distances are maintained a material is obtained which satisfies the objects
of the invention. The revolutions of the axis with hammers is in the range of 500
to 1100 rpm.The hammers are fixed to one or more axis, according to the type of mill,
which are revolving with the afore mentioned rpm.The hammersgenerally have the shape
of straight metal bars, which in numbers of 2-6 are mounted on the axis. It is to
be understood that variations are possible but that it is decisive that the hammers
are beaten with enough force against the material and that the screen distance is
the determinative factor for the desired form of the flakes.If the dimensions of the
screen are too small dusting takes place and also the material is smaller resulting
in the danger of layer formation during drainage.If the screen distances are too large
too little interrelated channels are formed and thus the draining effect gets lost
and also faster depostion en layer formation is taking place.
[0011] The flakes may be obtained possibly in another way than by a hammer mill treatment
provided they meet the desired criteria of irregularity of the flakes, shape of the
flakes and size thereof. According to the invention one starts from material having
the shape as obtained by the said hammer mill treatment of plates of blocks thermohardened
pol polyurethane foam, with which material the benefits of the invention can be attained.
[0012] The invention is in particular beneficial for the processing of polyurethane foam
scrap which is formed during the polyurethane manufacturing process and which normally
cannot be used anymore and is disposed off. Thus in a particular process the mixture
to be polymerized, consisting of the needed mixed chemicals, is sprayed on a cover
layer, which is passed through a continuous roller band , there also being passed
a sealing cover layer through the roller band . During the passage the foam made is
confined and adhered between the cover layers and at the exit of the roller band a
continuous foam layer is formed. During this process inevitably there is formed scrap
when the bales are cut into measured pieces. These per se non usable pieces of scrap
are suited as starting material for the invention. The enclosure of the foam, which
may comprise several materials, like glass mat, glass mat covered with plastic etc
is per se not objective because only a relatively small amount is present.
[0013] This material may be present during the mill processing and be processed; if desired
it may be removed.The same holds also for foam obtained in another way, like foam
blocks, in which case mostly no enclosure is present.
[0014] It is important that the endproduct has an irregular shape,by which the water permeability
is increased. water runs smoothly and easily through the irregular ducts in the material
without the material itself taking up water.The ducts must be irregular, not align
with each other and be of sufficient size, because too small ducts may be easily blocked
and the water permeating capacity could become totally lost. As already mentioned
a satisfactory product is obained by the hammer mill treatment as above described.
[0015] In another embodiment for soil improving purposes the foam material according to
the invention is inserted in a water permeable strong enclosure of inert material,
such as plastic so that one obtains mattresses und such forms.These mattresses have
dimensions of e.g. 2-3 meter length and 1,5-2 meter width at a height of 20-25 cm.
They are lightweight and as such easily conveyable. Their bearing capacity is good
and thanks to their water repellent properties no layer forming takes place and the
water is faster removed.
[0016] Owing to their light weight the possibility of settling is minimal and there is also
less setting.It appears that the fragmentation of the foamed blocks or plates has
no adverse effect on the draining properties; i.e. the water take-up of the product
treated is indeed higher because of the pulverisation of the surface cells, but not
that high that as a consequence thereof the draining properties diminish. It has been
found that only at the edges where there are cut open cells there occurs water take-up
of the product.This amounts to not more than 0,5 vol % at 20
oC. Thus the desintegration has no adverse effect and the water permeating properties
are improved. The bulk density of the foamed material is about 32-35 kg/m³. Furthermore
the material has sufficient strength for use for soil improving purposes (tensile
strenght about 2200-2600 kg/m³.
[0017] The flaked polyurethane foam according to the invention is especially suitable for
draining purposes.The material is porous and of light weight and easily transmits
water.Thus it can be used for draining pipes or coils, in which case the flakes are
arranged on top of the pipes or coils.The material as such can be mixed with the soil,
in particular hard soil to improve the draining properties thereof. In a
[0018] In a special embodiment the material is shaped to a mattress, it being enclosed by
a strong,inert and porous material, especially woven materials, like woven plastics.These
mattresses are put in the soil with a soft condition as an underlayer to combat soil
settling and deficient water removal, in particular with a view to the weight. In
comparison sand has a weight of about 1300-1600 kg/m³, just as debris. This has to
be compared with with the about 30 kg/ 30 m³ of the present materials.The material
is for instance brought in the soil to a depth of 20 to 50 cm and then covered with
soil or sand.The condition of the soil appears to be strongly improved owing to the
favorable properties of the mattresses described, i.e. there is practically no soil
setting and the water transport has been improved. As enclosure material a commercially
available polypropylene weaving that has the required properties and works as a filter
is especially suited. The flaked polyurethane foam material has an additional advantage
that it is easily transportable in a loose form and it does not stick to the walls
of the transporting means in contrast with other plastic materials. The flaked polyurethane
foam according to the invention is resistant to fungus and moulds and does not form
a nutrient for micro-organisms. The invention will now be illustrated by the accompanying
drawing, wherein figures 1 and 2 schematically in section through the soil illustrate
a water drain with and without a draining pipe and figure 3 illustrates a similar
section for a draining layer with drain pipe. In the figures 1 denotes the polyurethane
flake material according to the invention that is taken up in an enclosure of permeable
polypropylene material (e.g. Propex
R), reference number 2.In figure 1 a drain pipe (3) is enclosed by the polyurethane
flakes (1). The arrows 4 indicate the groundwater flow,arrows 5 the flow of polyurethane
flakes. A clay layer is indicated by 6. The flakes present prevent the clay layer
from blocking the draining by forming a plate layer.In figure 3 3 again denotes the
drain pipe, above which a continuous layer of polyurethane flakes as defined is arranged,
enclosed by the polypropylene water permeable layer.The arrows denote the water flow.ABove
the flakes a sand layer 8 or another layer (tile path) may be placed.
Example
[0019] On starts from polyurethane foam material which arose as scrap during the production.The
polyurethane was prepared by means of spraying of the chemicals on a band which after
covering by another band was conveyed through a roll mill.This material had the following
properties: Heat conduction coefficient calculated at 20
0C: 0,020 W/km.
Heat resistance: during a long time resistant against 15
oC.
Linear expansion coefficient: 27 x 10⁻⁶ m/mK in the tmeperature range of + 20 to +
70
oC.
Bending strength withour cover: 38.10⁻² N/mm².
Strength: about 11-20.10⁻²N/mm²,determinded at a deformation of 10% ( DIN 18164).
Tensile strength: without cover parallel to the foam direction 35.10⁻² N/mm².
Water take-up:when immersing the foam in water at a temperature of 20
0C during 24 hours the water absorption is about 0.5 vol %. Especially at the edges
where there are open cells which were formed during the processing.Apart form this
boundary effect the water absorption is zero. The material is resistant against chemicals
apart from very concentrated alkaline materials and inorganic acids and it is further
resistant against moulds and fungus. the material as obtained was processed in a hammer
mill of which the screen was adjusted to square openings with a dimension of 3 cm.
All flakes passing through the sieve were collected.The flakes obtained after this
processing had very irregular ,tortuous shapes and none of them has substantially
the same shape. The product obtained was processed into mattresses by enclosing it
in an inert, water permeable plastic foil.For this purpose use was made of polypropylene
weave material, commercially available as Propex
R, which possesses sufficient strenght. As a consequence of the woven structure it
acts like a filter and thus is water permeable. It is not attacked by acids and bases.
The thickness was about 1 to 2 mm. Of course another similar woven material of other
plastics within similar properties may be used. These mattresses were put in a soil
with soft condition as a lower layer to combat soil settleing and deficient water
transport.The material was put in the soil to a depth of 20-50 to 80 cm and then covered
by soil or sand.It appeared that the condition of the soil was strongly improved by
the favourable properties of the matresses as described, relating to the lower weight
compared with the raw material,i.e. there was substantially no settling of the soil
and thus the water removal was improved as well.
[0020] The material is also applicable in road building or in streets as an under layer.
It is to be understood that various types of hard polyurethane foams (thermoset PUR-foam),
obtained dependent on the chosen starting materials and additives, are suitable for
the present purposes,provided they are subjected to the desintegration step to get
irregularly formed angular flakes.The properties of the utmost importance for the
hardened foam are a low (volume) weight, a good strength, a low water absorption and
a high resistance, especially against steam temperatures. As a consequence of the
desintegration step the enclosed pressure gas,if any, is substantially removed.
[0021] The general dimensions of the flakes can be adjusted by changing the screen distance
of the hammer mill.For use as a draining material the screen distance (square) is
set at about 40 mm. The rectangular shape of the screen is op importance to give the
flakes an angular form.
[0022] Polyurethanes are well known polymers obtained by the stepwise polymerisation of
alcohols (HO-(CH₂)-OH) and isocyanates (O=C=N-R-N=C=O), which are appear to be important
as hard and soft foams. For the present purposes the thermosetting polyurethane foams
are of interest. Because of the fact that the preparation processes of these foams
are generally known a further description is regarded as superfluous.
1. Soil improving material based on flaked, foamed polymers which possible are hold
together by an enclosure, wherein one starts from a thermoset polyurethane foam with
closed cells, which is comminuted to irregular flakes, as defined.
2. Material according to claim 1, wherein this is comminuted to irregular flakes by
a treatment with a hammer mill with a screen distance of 20-50 mm.
3. Material according to claim 1-2, wherein one starts from thermoset foamed polyurethane
with closed cells with a bulk density of 30-35 kg/m³ and a pressure resistance of
11-20 10⁻² N/mm, of which the water absorption when immersed in water of a temperature
of 200C during 24 hours is not more than 0,5 vol % at the edges.
4. Material according to claim 3,wherein this originates from scrap material obtained
during the preparation of foamed polyurethane.
5. Material according to claims 1-4, wherein thsi has the shape of a mattress, enclosed
by a water permeable inert woven material of plastic or another synthetic or natural
woven material.
6. Use of a material according to claims 1-5, as draining material on a draining pipe
or as a mattress.
7. Use of a material according to claims 1-5, as draining material in soil which is
exposed to high steam temperatures during sterilization.