NL8900523A - SOIL-IMPROVING POLYURETHANE-BASED MATERIALS. - Google Patents

Description

Soil-improving polyurethane-based materials

The invention relates to soil improvers, in particular for drainage and hardening, based on divided foam materials, which may or may not be held together by an envelope, depending on the application. It is known to be used in greenhouses, nurseries and the like by plates, pipes and mattresses keep the soil in good condition, because the water balance is favorably influenced. The materials used heretofore have certain drawbacks. If drainage pipes are used, material must be applied above them to prevent siltation, blockage, etc. The use of materials, such as felted PVC foam, again has the drawback that they themselves absorb and retain water and thereby slow down the flow. Furthermore, other properties are also important, such as being able to withstand relatively high temperatures, e.g. occur when steaming soil, as well as a relatively low specific weight.

The invention is directed to a foamed material which requires no maintenance when used as a drainage material and which retains its water-repellent capacity indefinitely. Long-term use is thus possible without clogging and plate formation occurring. The invention is furthermore directed to a foamed material in a divided and whether or not encapsulated form which is resistant to high temperatures such as occur in greenhouses when steaming the soil. In particular, the foamed material consists of a foamed thermosetting polymer that does not melt or shrivel or change shape at the temperatures normally found.

According to the invention there is provided a material for use as a soil improver, in particular as a drainage material or a soil reinforcing material or for other such applications, characterized in that it is built up from a thermosetting polyurethane foam which has been reduced to irregular flakes by a disintegration operation, as defined below.

As is known, polyurethane consists of polymers obtained by the polyaddition of isocyanate group-containing molecules to polyvalent alcohols, acids or amines. By varying the starting materials, polyurethanes with various properties can be obtained.

The invention is based on thermosetting polyurethanes for processing into foam, such as polyester and polyether foam, in which foaming occurs by CO2 or water dosage or by other propellants. The polyurethane foams can be obtained as blocks by foaming in a mold or as plates, the foaming being carried out on a belt. The foams can be flexible or hard depending on the reactions used. In the present invention, dense cell hard polyurethane foams which are thermosetting and do not soften or otherwise lose their good properties upon temperature increase, especially above 140 ° C.

Thus, in particular, thermosetting, closed-cell polyurethane foam is used, which in a disintegration operation is reduced to irregular flakes by means of a known device suitable therefor, such as hammer mills, ball mills, impact mills, vibration mills, etc. A hammer mill provided with a perforated grate with adjustable grate openings with which the flake size can be adjusted appropriately during grinding is particularly suitable. The flakes should have an irregular shape, so that when used, gaps are left between the stacked flakes that are necessary for good drainage.

With a tight packing of the flakes, the danger of plate formation could occur. The most suitable form of irregular flakes is obtained by comminuting the sheet materials in a hammer mill, the grating distance between the grating bars of which is set (square positions) at 20 to 50 nm. The hammers of the mill drive the material through the grating holes, creating very irregular flakes, the average dimensions of which are around the grating distance. If the dimensions of the grid spacing are too small, dust will form and the material will be so small that there is a risk of plate formation during drainage. It is clear that when grating distances are too great, too few mutual channels are created and thus the effect is lost and plate formation can also occur. The flakes can of course also be obtained in a manner other than by the hammer mill treatment, provided that they meet the aforementioned criteria of flake irregularity and flake size.

Thus, the flake material obtained by a hammer mill with said adjustment, starting from shaped foam plates or blocks of various sizes, is considered standard flake material for a definition of its shape.

The invention is in particular advantageous for the processing of polyurethane foam waste which arises during the polyurethane manufacturing process and which is normally no longer usable and is disposed of. For example, in a particular process, the polymerized mixture consisting of the necessary mixed chemicals is sprayed onto a coating layer, which is passed through a continuous rolling belt, while at the same time a covering coating layer is passed through the roller belt. During the passage, the resulting foam is trapped between the laminating layers and adhered, and a continuous foam layer is formed at the exit of the rolled strip. This method inevitably produces waste material when the bales are cut to size. These per se unusable waste pieces are suitable as starting material for the invention. The wrapping of the foam, which may consist of different materials, such as glass fiber, whether or not bituminized, plastic-coated glass fiber, aluminum foil, etc., is not objectionable in itself because only a relatively small amount is present. This material can remain and be processed during the grinding operation; however, it can also be removed if desired.

It is important that the final product has an irregular shape that increases water permeability. The water easily flows through the irregular corridors in the material without the material itself absorbing water. The corridors must be irregular and large because fine corridors are easily clogged and the water permeability could be completely lost.

For soil reinforcement purposes, the foamed divided material is placed in a water-permeable strong casing of inert material, such as plastic, which creates mattresses. These mattresses have e.g. dimensions of 2-3 m length by 1.5-2 m width with a height of 20-25 cm. They are lightweight and therefore easy to move. The load-bearing capacity is good and, thanks to their water impermeability, no plates are formed, while the water is drained faster. Due to the light weight, the chance of subsidence is minimal while little settling occurs. It has been found that the fragmentation of the foam plates or blocks does not adversely affect the water absorption properties; that is, the water absorption of the treated product is increased by the pulverization of the surface cells, but not so high as to deteriorate the drainage properties. It has been found that water absorption of the foam product occurs only at the edges where cut open cells are located. This is no more than 0S5% by volume at 200C. Thus, the disintegration does not adversely affect and the water permeability properties are improved.

The bulk density of the foamed material is approximately 32-35 kg / m. The material is also strong enough to be used for soil improvement purposes (tensile strength approx. 2200-2600 kg / m).

The flocked polyurethane foam is particularly suitable for drainage purposes. The material is porous and lightweight and allows water to pass through easily. It is therefore useful in drainage pipes or hoses, where the flakes are received in the pipes or hoses. The material as such can be mixed with soil, in particular hard soil, in order to improve its drainage capacity. The flakes can also be mixed with potting soil if better water transport is desired. This is also possible for soil embankments, earth walls or noise barriers where water drainage is a problem. In a special application, the material is used in mattress form, which is enveloped by an inert, strong and porous material, in particular woven materials, such as plastic fabrics. Particularly suitable is a commercially available polypropylene fabric which has the required properties and acts as a filter. These mattresses are applied as an underlay in soil with a weak soil condition to combat subsidence and poor water drainage. The material is e.g. inserted to depths of 20 to 50 cm and then covered with soil. The soil condition appears to be greatly improved by the favorable properties of the described mattresses, i.e. that practically no soil subsidence occurs and the water drainage is improved.

The flocked polyurethane foam material has the additional advantage that it is easily transportable in loose form, which, unlike other plastic materials, does not stick to the walls of the means of transport. The flocked polyurethane foam according to the invention is resistant to fungi and fungi and does not form a breeding ground for these micro-organisms. When used in hydroponics instead of the traditional clay granules or as a soil, covered with horticultural cloth as a substrate for pot cultures, no rotting and contamination of e.g. the roots of the plants occur.

Example

Polyurethane material was used as a waste during manufacture. The polyurethane was made by spraying the chemicals onto a belt that was passed through a roll mill after covering by another belt. This material had the following properties.

Heat conductivity coefficient calculated at 20 ° C: 0.020 W / mk. Heat resistance: long-term resistance at 150 ° C.

Linear expansion coefficient: 27 x 10 "6 m / mK in the temperature range from +20 to + 70 ° C.

-2 2

Flexural strength without backing: 38-10 N / mm -2 9

Compressive strength: approx. 17-20.10 N / mm, determined with a deformation of 10¾ (DIN 18164).

Tensile strength: without cladding parallel to the foam direction 35.1 (f 2 N / mm2.

Water absorption: when the foam is immersed in water at a temperature of 20 ° C for 24 hours, the water absorption is only 0.5% by volume. In particular at the edge due to the open cells present at the edge that have arisen during processing. Apart from this edge effect, the water absorption of the foam is zero.

The material is resistant to chemicals apart from highly concentrated alkali and inorganic acids and is further resistant to fungi and fungi. The material obtained as such was processed in a hammer mill, the grate of which was adjusted to square openings with a size of 3 cm. Only the flakes that passed through the sieve were collected. The flakes obtained in this operation had very irregular shapes and practically none of the same in shape. During the grinding operation, almost all of the trapped propellant gas was released. The product obtained was made into mattresses by encapsulating it in inert plastic films. It was used for this

R

polypropylene fabric, commercially available as Propex, which is water-permeable and has sufficient strength. The fabric structure acts as a filter and prevents fine soil particles from entering the mattress. It is not affected by acids or bases.

The thickness was 1 mm. Of course, a similar fabric of other plastics with similar properties can be used. These mattresses were applied as a bottom layer in a soil with a limp condition to combat subsidence and inadequate water drainage. The material was introduced into the soil at depths of 20 to 50 cm and then covered with soil. The soil condition appears to have been greatly improved by the favorable properties of the described mattresses, i.e. practically no subsidence occurred anymore and the water drainage was thereby also improved.

The material can also be used in road construction or paving as an underlay instead of sand or other soil stiffeners.

It is clear that various types of rigid polyurethane foams (thermo-hardened PUR foam) obtained depending on the selected starting materials and additives are useful for the present purposes, if subjected to the disintegration step to obtain irregularly shaped, angular flakes. for the hard foam are low (volume) weight, good strength, low water absorption and high resistance, in particular against steam temperatures. Due to the disintegration operation, the trapped propellant (such as, for example, halohydrocarbons) is almost completely removed.

It is furthermore clear that the dimensions of the flakes can be adjusted by changing the grating distance of the hammer mill so as to obtain somewhat coarse flakes. When using the flakes in potting soil, the grating distance will preferably be set at 30 mm, use as drainage material at 40 mm. The grid of the bars should have rectangular openings to give the flakes an angular shape. Round openings would create too much dust and the flakes would remain too small or too round. Of course, any other grinding machine can be used, provided that the same irregular and angular shapes are obtained as according to the defined hammer mill.

Polyurethanes are well-known polymers obtained by the stepwise polymerization of alcohols (HO- (GH2) n-OH) and isocyanates (0 = C = NRN = C = 0), which have proven to be of particular importance as hard and soft foams. The functionality of the raw materials depends on whether thermoplastics or thermosets are obtained. For the present purposes, thermosetting polyurethane foams are important. To obtain hard foams, blowing agents are often used, which build up the macromolecular foam mass in gaseous form, eg halogenated hydrocarbons. Since the methods of preparation of polyurethane foams are well known, a detailed description of these products, which are the starting materials of the present applications, is considered superfluous »7 -

Claims (10)

Soil improvement material based on flocked, foamed polymers which may be held together by an envelope, characterized in that thermo-cured, closed cell polyurethane foam is reduced to irregular flakes obtained as defined. 2. The material according to claim 1, characterized in that it is reduced to irregular flakes obtained by treatment with a hammer mill with grating distance of 20-50 mm. 3. Material according to claims 1-2, characterized in that it is reduced in such a way that the trapped propellant is almost completely removed. 4. Material according to claims 1-3, characterized in that thermo-hardened foamed polyurethane with closed cells with a bulk density of 30-35 kg / m3 and a compressive strength of 17-20 10 "N / mm2 is used, the water absorption of which immersion in water at a temperature of 20 ° C for 24 hours does not exceed 0.5% by volume at the edges. A material according to claim 4, characterized in that it originates from the waste material obtained in the manufacture of foamed polyurethane. 6. Material as claimed in claims 1-5, characterized in that it is put in the form of a mattress, enveloped by a water-permeable, inert fabric of plastic or another synthetic or natural material. Use of the material according to claims 1-6, as a drainage material in a drainage pipe, mattress or as a layer. Use of the material according to claims 1-6 as a flake material for hydroponics. 9. Use of the material according to claims 1-6, as filler material for drainage pipes, potting soil and as support for planters and pothooks. Use of the material according to claims 1-6 as a drainage material in soil that is exposed to high steam temperatures.