EP0684344A1 - Sealing material against organic liquids - Google Patents

Abstract

The mat for protecting against organic fluid spills has two geo-textile layers between which is packed a layer of an inorganic smektite. This absorbs organic fluids and swells. The protective layer can be improved by adding a proportion of a water absorbing smektite with the ratio between inorganic- and water reactive smektite being betweeen 99:1 to 20:80. The mat can be made of three geo-textile layers with separate layers of smektite. The mat can be made in selected widths with edging which connects to adjacent strips.

Description

The invention relates to a sealing material against organic liquids and the use thereof.

Mixtures of gravel, sand and bentonite swellable in water have already been used to seal landfills, petrol stations and sewage pipes (Greinacher J., G. Piepenbreier, "Glückauf", p. 128 (1992), No. 4, pp. 276-281 ). When water passes through, the bentonite swells, whereby the swelling pressure of the bentonite fills the voids between the grains of sand, which leads to a sealing effect. If it is not a water-carrying pipe, but instead an organic liquid (eg petroleum) is transported in the pipe, the swelling effect of the bentonite swellable in water in contact with organic liquids does not come into play.

Plants for the filling and decanting of water-polluting organic substances are underlaid in the horizontal direction with a mixture of sand and swellable bentonite (EP-A 0 453 619).

The surface is provided with a sand / bentonite mixture, the mixture is compacted and irrigated to swell the bentonite. In this way, the joints of pavers laid on the surface are sealed. The barrier layer obtained has a good sealing effect against water, whereas the passage of organic liquids is not reliably prevented.

When building so-called tank farms, there is a need to protect the surface against the penetration of any leaking organic liquids. Tank farms are above-ground storage facilities for petrol and mineral oils. Large storage tanks are built in a trough on the surface. The trough is covered with a sealing mat, which contains a sealing layer with bentonite swellable in water between the two layers of a geotextile. The geotextile / bentonite mat is overlaid with about 50 cm of gravel / sand. The surface is then watered, causing the bentonite to swell and create a good sealing effect against water. There is no reliable sealing effect against large amounts of flowing organic liquid which does not cause the bentonite to swell.

When installing vertical seals, e.g. landfills, it is state of the art to build sealing walls made of cement, bentonite swellable in water and water (see D. Urban, BBR 3/93, 44 , pp. 102-110; DE -A-3 610 755 and 4 312 570).

Sealing walls with low water permeability are obtained with which can enclose pollutants in order to avoid contamination of the groundwater by leachate. The known mixtures of cement and swellable bentonite do not contain any organophilic bentonite.

Vertical vertical sealing walls are built using the so-called diaphragm wall method. The cavity volume of the cut-off wall is excavated with special grabs, the cavity being filled with a suspension of cement, bentonite swellable in water and water. After the excavation work has been completed, the cement sets hydraulically and a sealing wall with low water permeability is obtained.

However, the sealing effect of these constructions is limited to water and does not reliably extend to organic liquids. There is therefore a need for a method of additional sealing against organic liquids. This can be done by installing an HDPE film web (HDPE = high-density polyethylene) in the vertical direction in the cement-bentonite-water slurry before setting.

DE-A-3 605 252 and EP-B-0 278 348 describe the production of diaphragm walls, into which sealing foils or plates are introduced in the vertical direction before the addition of the bentonite, which sealing edges at the edge areas are provided by tightly closing lock mechanisms (profile locks ) are connected to each other. However, there are no indications of bentonite geotextile mats with a lock mechanism or the use of organophilic clays. There is also the risk of mechanical damage to the film during installation, and the question of long-term durability arises.

DE-A-4 222 969 describes the introduction of a combination of several non-woven fabrics between a waste body (above) and a waterproof HDPE film (below) around the film to protect against mechanical influences in the event of subsidence in the landfill body. Bentonite, which additionally seals against water, can be inserted between the various non-woven fabrics. There is no evidence of the use of organophilic bentonite.

Bentonite geotextile mats are described, for example, in US Pat. Nos. 4,103,499 and 4,565,468 and in DE-A-4,221,329, 4,122,991 and 4,203,861. There is no information on the use of organophilic bentonite.

Another method that is used to prevent the seepage of organic liquids into aquifers is to build oil-resistant barriers with high strength. Examples of this are asphalt concrete or surface waterproofing with bitumen. These sealing systems have the disadvantage that they are not sufficiently elastic under mechanical loads and can crack due to their brittleness, and thus become permanently leaky.

The production of organophilic smectites, i.e. DE-A-3 145 423, 3 145 449, 3 145 452, 3 145 475 describes reaction products of an organic cationic compound and a smectite-type clay with a certain ability to exchange cations, and their use as rheological additives in non-aqueous systems , 3 208 052, US-A-2 531 427, 2 859 234, 2 966 506, 4 664 820 and 5 160 454 and EP-A-0 228 234 and 0 542 266. However, there is no information about the use of these reaction products as sealants against organic liquids.

WO-83/01 204 relates to a process for the removal of organic waste, leachate containing organic substances being sorbed on an organophilic clay. Organophiles Clays have a certain sealing effect against organic substances, but this is not sufficient if the organophilic clay is in a loose form which is not enclosed by boundary walls, so that it is not compacted during swelling.

US-A-4 960 740 is concerned with organophilic clays obtained by reacting water swellable bentonite with lecithin. The product is used as an additive for drilling fluids. No other applications are mentioned.

US-A-4 402 881 describes the production of organophilic bentonite, in which dry bentonite a quaternary ammonium compound is added. The mixture is then kneaded and dried. Organophilic bentonite is used for the gelation of oil and drilling fluids containing solvents. There are no indications about the use as a sealing material against organic liquids.

The object of the invention is the development of a sealing material against organic liquids, which adsorbs the organic liquids and creates a barrier layer against incoming organic liquid. The sealing material should have elastic properties and show a "self-healing" effect against any leaks that may occur.

Surprisingly, it has now been found that this object can be achieved in a certain arrangement by using organophilic smectites (optionally in a mixture with smectites which swell in water). The swelling of the organophilic smectite creates an excellent sealing effect.

The invention relates to a sealing material that at least contains a sealing layer between geotextile layers, the sealing layer containing at least one organophilic smectite.

Geotextile layers, which can be designed as a liquid-permeable fabric or nonwoven, are layers of plastic fibers that are not or are difficult to rot, e.g. made of polypropylene, polyethylene, polyvinyl chloride or polyamides (in contrast to easily decomposable textile materials such as cotton, cellulose, etc.). Between the geotextile layers, a sorption and sealing layer with a thickness of about 2-5 mm made of organophilic smectite (powder or granulate) is inserted. The organophilic smectite can be fixed between the geotextile layers by adhesives (e.g. glue) or needling the geotextile layers, the mechanical stability during installation also being improved.

The organophilic smectite swells on contact with organic liquids. The resulting swelling pressure leads to the filling of intermediate spaces in the sealing layer and thus to compaction, which creates a barrier layer that prevents the penetration of organic liquid. Organic compounds occurring in smaller amounts are adsorbed by the barrier layer coated with the organophilic smectite and are thus prevented from groundwater layers. The barrier layer made of organophilic smectite can also be used for vertical sealing walls.

At least one water-swellable smectite can be added to the organophilic smectite, the weight ratio between organophilic smectite and water-swellable smectite being about 99: 1 to 20:80.

According to a further embodiment, the sealing material according to the invention can have at least one further sealing layer contains at least one water-swellable smectite between geotextile layers.

For example, the sealing material can be a geotextile layer in the order given; a sealing layer containing at least one organophilic smectite; optionally a second geotextile layer; a second sealing layer containing a water-swellable smectite; and contain a third geotextile layer.

Furthermore, the organophilic smectite and / or the water-swellable smectite can contain about 20 to 80% by weight of an inert material, wherein the inert material can consist of sand, gravel, earth, ash, slag, low-swelling clay minerals and / or hydraulic binders.

• (a) Anlagen, zum Abfüllen und/oder Lagern von organischen Flüssigkeiten;
• (b) Rohrleitungen für den Transport von organischen Flüssigkeiten und
• (c) vertikalen Dichtwänden.

The invention further relates to the use of the sealing material described above for sealing

• (a) plants for filling and / or storing organic liquids;
• (b) pipelines for the transport of organic liquids and
• (c) vertical sealing walls.

As far as the possible applications are concerned, the pipes are sealed with a geotextile mat which contains the organophilic smectite, optionally mixed with an inorganic smectite which is swellable in water and / or an inert material, for sealing pipes for organic liquids. The sealing material can also be applied as a multi-layer geotextile mat. In the event of pipe leaks, the organic liquid flows into the sealing layer, the organophilic smectite swells, fills the interparticle spaces and a barrier is created to prevent further penetration of the organic liquid. When Any leaks caused by mechanical stress in the sealing layer will automatically close the leaks due to the swelling effect of the organophilic smectite.

The same advantages result if the sealing materials in the form of geotextile mats are used in systems for filling and / or storing organic liquids (e.g. petrol station surfaces and "tank farms").

When creating vertical sealing walls for sealing against organic liquids and for the adsorption of organic constituents in aqueous liquids, the sealing material according to the invention can be installed in the form of a geotextile mat in the vertical direction in the diaphragm wall suspension made of cement, bentonite and water before the cement sets. If the so-called two-phase process is used, the mat is either first installed in the bentonite suspension, whereupon the bentonite suspension is displaced by concrete; or after the bentonite suspension has been displaced by concrete, the mat is inserted vertically into the not yet set concrete.

The geotextile layers are usually needled with one another, so that the organophilic smectite arranged between them is compressed and presses even more against the geotextile layers during swelling. However, the organophilic smectite does not initially swell during installation in the diaphragm wall because work is carried out in an aqueous environment at this stage. The cement then sets hydraulically and a sealing wall is created which contains a sealing layer made of organophilic smectite. If organic contaminants penetrate the sealing wall, they are first adsorbed on the organophilic smectite. If larger amounts of the organic liquid reach the sealing layer, the organophilic smectite swells and forms a barrier layer for the organic liquid. Thus, an adsorption layer builds up first and then a sealing layer.

The organophilic smectite is the reaction product of an inorganic smectite with a cationic organic compound, preferably a quaternary ammonium compound, and can be prepared in a manner known per se (cf. the publications mentioned at the outset).

In dieser Formel haben die Substituenten folgende Bedeutung:
R₁ ist eine gesättigte oder ungesättigte aliphatische Kohlenwasserstoffgruppe mit 10 bis 20 C-Atomen, R₂ und R₃, welche gleich oder voneinander verschieden sein können, sind gesättigte oder ungesättigte aliphatische Kohlenwasserstoffgruppen mit 1 bis 20 C-Atomen oder Aralkylgruppen mit 7 bis 10 C-Atomen. R₄ ist eine Alkylgruppe mit 1 bis 6 C-Atomen oder eine Aralkylgruppe mit 7 bis 10 C-Atomen. Das Anion X^⊖ kann OH⁻, Cl⁻, Br⁻, CH₃SO₄⁻ oder CH₃CO₂⁻ sein.Suitable quaternary ammonium compounds can be represented by the following formula:

In this formula, the substituents have the following meanings:
R₁ is a saturated or unsaturated aliphatic hydrocarbon group with 10 to 20 C atoms, R₂ and R₃, which may be the same or different, are saturated or unsaturated aliphatic hydrocarbon groups with 1 to 20 C atoms or aralkyl groups with 7 to 10 C atoms . R₄ is an alkyl group with 1 to 6 C atoms or an aralkyl group with 7 to 10 C atoms. The anion X ^⊖ can be OH⁻, Cl⁻, Br⁻, CH₃SO₄⁻ or CH₃CO₂⁻.

Examples of suitable compounds are dimethylditallow ammonium chloride, the tallow alkyl radical being in hydrogenated form, or benzyl tallow dimethylammonium chloride.

The amount of organic cation required for the reaction should be between 30 and 120 mVal / 100 g smectite.

The cationic compound is fixed to the inorganic smectite by cation exchange, hydrophobization and a layer widening of the smectite taking place. In the simplest case, the cationic organic compound is added to the smectite under shear, dried and ground. Alternatively, the smectite can be dispersed in the water and separated from non-swellable impurities by cleaning with hydrocyclones. The cationic organic compound is added to this purified suspension, after which the organophilic bentonite floats on the water. Then it is filtered and dried.

The starting material for the organophilic smectite or the inorganic smectite is preferably selected from the group of montmorillonites, beidellite, hectorites and saponites. The ion exchange capacity should be at least 30 mVal / 100 g.

The sealing material according to the invention can be designed as a geotextile mat in the form of a web which has a locking mechanism on each side edge for sealingly connecting the web to another web which has a complementary locking mechanism on each side edge.

The lock mechanism may have profiles attached to the side edges of the webs, the profiles of one web engaging the profiles of the other web. Here, the profiles can be (a) self-sealing or (b) sealable with sealant. These lock mechanisms are described in the simultaneously filed German patent application P 44 18 629.0, which is intended to be part of the present description as a reference.

The invention is illustrated by the following examples, describe the model tests for sealing materials with geotextile layers.

Example 1 (comparison)

A non-woven fabric made of polypropylene fibers is placed on a glass suction filter with porosity 1 (diameter 5.5 cm filter area 23.75 cm²). 10 g of water-swellable bentonite (sodium bentonite; commercial product Montigel® F from Süd-Chemie AG) are spread over this geotextile layer (layer thickness about 3-4 mm). This layer is covered with a second layer of a polypropylene nonwoven. Then xylene is added. The bentonite shows no swelling effect in the presence of xylene, which is why the xylene runs immediately.

Example 2

The procedure of Example 1 is repeated with the difference that, instead of the bentonite swellable in water, 10 g of a bentonite treated with 50 mVal quaternary ammonium compound (ditallow dimethylammonium chloride) are used per 100 g of bentonite. The arrangement is overlaid with xylene. The xylene does not penetrate and the organophilic bentonite swells. After a swelling time of 3 hours, the organophilic bentonite has swelled out. A water jet vacuum is then applied and 10 ml / h of xylene pass through the assembly. This example is a model example for a geotextile mat with only weakly (for example by gluing) interconnected outer geotextile layers.

Example 3

The procedure of Example 2 is repeated with the difference that 10 g of a bentonite treated with 90 meq of ditallow dimethylammonium chloride per 100 g of bentonite are used. The organophilic bentonite slowly swells in the xylene, but the xylene does not pass through the layer. After 32 hours, the organophilic bentonite swelled. After applying a water jet vacuum, it was found that 3 ml of xylene passed through the arrangement per hour.

According to Examples 2 and 3, the organophilic bentonite was able to swell freely because the geotextile layer only loosely rested on the sealing layer. If the sealing layer swells against the pressure of a load, as is the case in an analogous manner with sealing mats, in which the geotextile layers are needled with one another, the sealing properties improve even further, as can be seen from the following examples:

Example 4

A polyethylene fabric with a mesh size of approximately 0.1 mm was placed on a glass filter with a filter area of 63.6 cm² and a porosity of 0. A sealing layer of 26.8 g of the organophilic bentonite from Example 2 was applied thereon. A second polyethylene fabric was placed on top, with a load of 22.8 kg. Then the assembly was filled with xylene.

The sealing layer now took 38 hours to fully swell. After the sealing layer had swelled completely, the xylene was pressed onto the sealing layer with an excess pressure of 1 bar. After 2 h, xylene passed through the sealing layer for the first time. The arrangement was changed from 4 ml xylene / h flows through.

Example 5

The procedure of Example 4 was repeated with the difference that 26.8 g of the organophilic bentonite from Example 3 were used. The swelling time was 48 hours. No breakthrough of the xylene was found until the experiment was stopped after 5 days.

Examples 6 to 11

Mixtures of sand and the organophilic bentonite according to Example 2 were produced. The mixing ratio of organophilic bentonite / sand was 1: 9 (example 6), 2: 8 (example 7), 3: 7 (example 8), 4: 6 (example 9), 5: 5 (example 10) and 6: 4 (Example 11). The mixtures were processed and examined as indicated in Example 2. The time was measured until the xylene was completely penetrated by the sealing layer. A water jet vacuum was then applied and the amount of xylene that flowed through the sealing layer was measured. The results are shown in the table below.

Examples 12 to 17

The experiments were carried out analogously to Examples 6-11, but using the organophilic bentonite from Example 3.

The results are summarized in the table below.

The arrangements according to Examples 6 to 11 showed sufficient impermeability to the toluene. The orders according to Examples 12 to 17 already showed a good seal with a minimum weight ratio of 3 parts organophilic bentonite / 7 parts sand.

Claims (11)

Sealing material against organic liquids, containing at least one sealing layer between geotextile layers, the sealing layer containing at least one organophilic smectite. Sealing material according to Claim 1, characterized in that at least one smectite which is swellable in water is admixed with the organophilic smectite, the weight ratio between organophilic smectite and smectite swellable in water being 99: 1 to 20:80. Sealing material according to claim 1 or 2, characterized in that it is a geotextile layer in the order given; a sealing layer containing at least one organophilic smectite; optionally a second geotextile layer; a second sealing layer containing a water-swellable smectite; and contains a third geotextile layer. Sealing material according to one of claims 1 to 3, characterized in that the organophilic smectite and / or the water-swellable smectite contains about 20 to 80% by weight of an inert material. Sealing material according to claim 4, characterized in that the inert material consists of sand, gravel, earth, ash, slag, low-swelling clay minerals and / or hydraulic binders. Sealing material according to one of claims 1 to 5, characterized in that the organophilic smectite is the reaction product of an inorganic smectite with a cationic organic compound, preferably a quaternary ammonium compound. Sealing material according to one of claims 1 to 6, characterized in that the starting material for the organophilic or inorganic smectite is selected from the group of montmorillonites, beidellite, hectorites and saponites. Sealing material according to one of Claims 1 to 7 as a geotextile mat in the form of a web which has a locking mechanism on each side edge for sealingly connecting the web to another web which has a complementary locking mechanism on each side edge. Sealing material according to claim 8, characterized in that the lock mechanism has profiles attached to the side edges of the webs, the profiles of one web engaging the profiles of the other web. Sealing material according to claim 9, characterized in that the profiles (a) are self-sealing or (b) or can be sealed by sealing means. Use of the sealing material according to one of claims 1 to 10 for sealing (a) plants for filling and / or storing organic liquids; (b) pipelines for the transport of organic liquids and (c) vertical sealing walls.