IL103155A - Liquid permeable element - Google Patents

Abstract

A porous component consists of a number of unsupported segments which are bonded together with a cast elastomer in partic. pref. however with epoxy, polyester or polyurethane resin. [DE4131099A1]

Description

Liquid permeable element BAYER AKTIENGESELLSCHAFT LAUSITZER BRAUNKOHLE AKTIENGESELLSCHAFT (LAUBAG) C. 87030 WATER PROCURING ELEMENTS PRODUCED BY BONDED JOINTS, A PROCESS FOR THEIR PRODUCTION AND THEIR USE This invention relates to liquid-permeable elements which consist of several support-free segments, the individual segments being connected by bonded joints, more particularly using a casting elastomer.

So-called drainage elements are used for draining excavation sites in open cast mining and waste disposal sites and for procuring drinking water. These elements are tube segments, normally in lengths of 1 to 3 m, which are joined to form a tube which is used, for example, to line a drilled well. The basic function of the drainage element is to filter out water and hence to protect the pump situated at the bottom against abrasive contamination. In the procurement of waters of defined quality, for example drinking water, water-impermeable tube segments are used to seal off unsuitable ground water channels at the corresponding drilling depths. The tube segments also have to be firmly joined to prevent any unplanned entry of water. Known techniques include screwthreaded joints of different dimensions and thread types, push-fit joints, socket joints, flanges, bayonet couplings, quick-coupling joints, rubber T sockets, friction welding, fusion or butt welding.

Drainage elements which comprise an impermeable, perforated or slotted thin-walled support as the tube and which are wrapped in textile or textile-like materials as the filter material normally have sufficient flexibility to enable the filter column joined by these techniques to follow any deviations of a drainage bore from the vertical during installation.

Support-free drainage elements of the type described, for example, in DD 109 317 consist of selected particle fractions bonded with thermosets and, for static reasons, have considerable wall thicknesses of 25 to 40 mm. The gravel fractions used may be in the range from 1 to 10 mm and are preferably in the range from 1 to 6 mm. The drainage tube may also have a multilayer construction, i.e. the tube wall consists of layers of different particle sizes incorporating the 0.1 to 1 mm sand layer as outer skin. Suitable fillers are known minerals, such as quartz, silicon carbides, and other minerals which cannot be hydrolytically influenced in natural, broken or edge-rounded form. The binder component is determined by the particular fillers used, but is preferably between 2 and 30% by weight. Accordingly, the elements in question are extremely rigid. With these elements, the necessary flexibility of the filter column is achieved by loose joining of the individual elements which are sealed by a T profile socket of rubber or elastomers.

The natural weight of the tube column presses the end of the elements onto the sealing surfaces and hence provides for sealing. The disadvantage of this arrangement is that hanging installation of the tube column is not pos-sible and, with very small radii of curvature, the joints between the elements open out to such an extent that parts of the external sealing profile can become wedged so that they are unable to perform their function.

Now, the problem addressed by the present invention was to provide joining elements which would not have any of these disadvantages, which could be efficiently produced and which could be used on site. More specifically, the problem addressed by the present invention was to provide adhesive systems which would enable the T sealing profile to be made in situ using an inner mold and an outer mold and which would have short curing times, high flexibility coupled with high strength and good creep behavior and high strength of adhesion to the drainage element.

Accordingly, the present invention relates to a liquid-permeable element consisting of several support-free segments, characterized in that the individual segments are flexibly joined by bonded joints, more particularly using a casting elastomer.

Suitable casting elastomers are those based on unsatu-rated polyesters of phthalic acid, maleic acid, their anhydride, tetrahydrophthalic acid, adipic acid, cumol acid and polyhydric alcohols, such as ethylene glycol, propylene glycol, their dimers and/or trimers, neopentyl glycol, pentaerythritol and solutions thereof in comonomers, such as styrene, o-methyl styrene, vinyl toluene, allyl phthal-ate or trimethylol propane diallyl ether; also epoxy resins as reaction products of epichlorohydrin with bisphenols, novolaks and/or cresols, aniline, cycloaliphatic or aliphatic dicarboxylic acids and monohydric or polyhydric alco-hols and curing agents known per se based on polyamines, polyamidoamines, mercaptans and acid anhydrides.

Preferred casting elastomers are casting resins which combine a minimal tendency to creep and high tensile strength with flexible or medium-flexible tensile behavior. Particularly preferred casting elastomers are polyure-thane-based casting elastomers consisting of polyisocya-nates and polyols or polyamines, preferably polyols.

The polyisocyanates are organic polyisocyanates known per se from polyurethane chemistry. Suitable polyisocya-nates are aliphatic, cycloaliphatic, araliphatic, aromatic and heterocyclic polyisocyanates of the type described, for example, by W. Siefken in Justus Liebigs Anna1en der Chemie, 562, pages 75 to 136, more particularly those corresponding to the following formula Q(NC0)n in which n = 2 to 4 (preferably 2) and Q is an aliphatic hydrocarbon radical containing 2 to 18 (preferably 6 to 10) carbon atoms, a cycloaliphatic hydrocarbon radical containing 4 to 15 (preferably 5 to 10) carbon atoms, an aromatic hydrocarbon radical containing 6 to 15 (preferably 6 to 13) carbon atoms or an araliphatic hydrocarbon radical containing 8 to 15 (preferably 8 to 13) carbon atoms.

Particularly preferred isocyanates are 4,4 '-diisocya-natodiphenyl diphenyl methane, polyisocyanate mixtures of the diphenyl methane series which are obtained in known manner by phosgenation of aniline/formaldehyde condensates and which, in addition to the diisocyanates mentioned, contain varying amounts of higher homologs, 2,4-diisocyanato-toluene and technical mixtures thereof with up to 35% by weight, based on the mixture as a whole, of 2,6-diisocya-natotoluene, hexamethylene diisocyanate, 1-isocyanato-3,3, 5-trimethyl-5-isocyanatomethyl cyclohexane (isophorone diisocyanate) , urethane-, carbodiimide-, isocyanurate-, allophanate- or biuret-modified polyisocyanates based on the unmodified polyisocyanates mentioned or mixtures of the polyisocyanates mentioned by way of example. The corresponding polyisocyanates liquid at room temperature are preferably used. Particularly preferred organic polyisocyanates are the phosgenation products of aniline/formaldehyde condensates.

The polyol component has a hydroxyl value of 50 to 800 and preferably 95 to 600 mg KOH/g. In general, it consists of a mixture of several polyhydroxyl compounds having a molecular weight in the range from 62 to 10,000. The mixture may consist, for example, of the following indi-vidual constituents: Low molecular weight polyols optionally containing ether groups and having a molecular weight of 62 to 400 known as chain-extending or crosslinking agents in polyurethane chemistry, such as ethylene glycol, propylene glycol, the isomeric butanediols, hexane-diols, octanediols, trimethylol propane, glycerol, pentaerythritol and/or sorbitol, polyethylene glycols having a molecular weight in the range mentioned above, propylene glycols having a molecular weight in the range mentioned above, low molecular weight propoxylation products of trimethylol propane having a molecular weight in the range mentioned above or mixtures of these low molecular weight polyols.

Polyether polyols having a molecular weight above 400, preferably up to 10,000 and, more preferably, in the range from 500 to 6000, for example the alkoxylation products of the simple polyhydric alcohols mentioned or even the alkoxylation products of water, polyamines containing at least two NH bonds and/or aminoalcohols containing at least two active hydrogen atoms or mixtures of such polyether polyols having a molecular weight in the range mentioned. Particular preference is attributed to the ethoxylation and/or propoxylation products of the starter molecules mentioned by way of example or of mixtures of the starter molecules mentioned by way of example, ethylene oxide and/or propylene oxide optionally being used in admixture and/or successively in the alkoxylation reaction.

Polyester polyols known per se from polyurethane chemistry, for example of the type obtained by esteri-fication of the simple low molecular weight polyols mentioned above with polybasic acids or anhydrides of polybasic acids. Suitable acid components are, for example, adipic acid, phthalic acid, tetrahydro-phthalic acid and/or hexahydrophthalic acid and their anhydrides.

Casting elastomers may be influenced in their curing rate by addition of suitable catalysts. Suitable catalysts for the particular systems are known per se and include, for example, tertiary amines, organometallic compounds; in the case of epoxides, certain acids (for example salicylic acid) and organic peroxides for the curing of unsaturated polyesters.

The bonded joint is produced by application of a mold consisting of an outer section and an inner section which are sealed by hoses or hose-like elements. These sealing elements may be applied hydraulically, pneumatically or mechanically. The elements or filter tubes are fixed beforehand by spacer pieces, which may be present in the mold, irrespective of whether the elements or filter tubes are fitted together vertically or horizontally. The mold is then filled with the casting elastomer.

The casting elastomer mixture is prepared in known manner by mixing the casting resin components in batches in two-component metering and mixing units which consist of piston or gear pumps, static and/or dynamic mixers and vacuum generators for degassing and which may contain means for applying pressure to promote transport and also stirrers and temperature-control systems.

The casting elastomers may be cured at ambient temper-ature or, to accelerate curing, at elevated temperature or by a combination of both methods, i.e. by pre-curing at ambient temperature and full curing at elevated temperature after demolding. To this end, the mold fittings used may be of a heatable design to facilitate processing, even at relatively low temperatures.

Basically, the cure time of the casting elastomers may be freely selected, but is preferably in the range from 30 seconds to 2 minutes.

The bonded joint is preferably established in such a way that the stability of several, preferably at least 6 to 8, filter tube or element joints (segments) is guaranteed both for transport and for installation; the flexibility of the joined filter columns is guaranteed to a certain extent. To this end, a flexibility zone is formed by the casting resin between the filter tubes to be joined; the flexibility zone ensures that the filter column is able to follow any deviations of a drainage bore from the vertical during assembly and during installation; columns of filter tubes can be continuously produced with perfect seals at the filter joints so that there is no danger of the well silting up; the filter columns can be installed in any position (horizontal/vertical) . Accordingly, the filter columns can also be used as drainage tubes and for raising and diverting media from waste disposal sites and the like.

According to the invention, the elements or filter tubes thus produced are used, for example, as drainage elements in mining, preferably in open-cast mining, in waste management and in agriculture, building construction and forestry. In the procurement of drinking water, the casting elastomers used must of course be of a type from which no physiologically harmful substances can be eliminated or dissolved out.

For special applications, it may be useful or necessary to bond a limited number of individual segments to one another and then loosely to apply an elastic T socket. It is also possible in this case to bond the T socket with the casting elastomer.

It is also possible in accordance with the invention to use partly impermeable segments instead of liguid-permeable segments (for example for sealing against certain ground water channels) .

The invention is illustrated by the following Examples.

Examples Starting component a) is a polyether mixture consisting of: 35 parts by weight consisting of 1 mol propylene glycol, 87 parts by weight propylene oxide, 13 parts by weight ethylene oxide; OH value 28 - 30 parts by weight consisting of 1 mol trimethylol propane, 87 parts by weight propylene oxide, 13 parts by weight ethylene oxide; OH value 35 25 parts by weight consisting of 1 mol trimethylol propane, 82.5 parts by weight propylene oxide, 17.5 parts by weight ethylene oxide; OH value 35 7.7 parts by weight ethylene glycol; OH value 1806 5 parts by weight zeolite powder; OH value 165, viscosity at 25eC 1000 mPa.s, density at 20*C 1.03.

Starting component b) is a diphenyl methane diisocya-nate mixture predominantly containing 4,4-isomers and, in smaller amounts, polymers of higher functionality and prepolymers based on tripropylene glycol. It has an isocyanate content of 28.5% and a viscosity at 25'C of 140 mPa. s.

Starting component c) : diazabicyclooctane (accelerator) .

These starting components may be processed as follows: 100 Parts by weight polyol corresponding to starting component a) , 38 parts by weight isocyanate corresponding to starting component b) and 0.3 part by weight accelerator corresponding to starting component c) are mixed by means of a dynamic mixer at 25'C in a low-pressure two-component machine. The gel time is 40 s. After 3 minutes, the test specimen can be demolded. Hardness after complete curing: 65 Shore A.

Determination of bond strength: Concrete bending prisms (measuring 4 x 4 x 16 cm, DIN 1048) were made in accordance with DD 109 317. Silicone oil/siloxane mixtures were used as the release agent. The binder component was 5% by weight for the 2 to 8 mm grain fraction and 5% by weight for the 2 to 4 mm grain fraction. In the four-point bending test, a breaking force of 5816 N was determined for the 2 to 8 mm grain test specimens. The test specimens were each halved to a length of 8 cm and joined by free pressureless casting at their ends coated with release agent in accordance with Example 1. A poly-urethane mixture corresponding to Example 1 was applied in a layer thickness of 10 mm as the casting elastomer. Casting was carried out in such a way that a T-shaped profile was formed, overlapping the sides of the test specimen by 10 mm. Four-point bending strength was tested after curing for 24 h at approx. 22 "C.

Grain fraction 2 - 8 mm: 5807 N Grain fraction 2 - 4 mm: 6150 N In both types of test specimen, fracture occurred both in the test material of the drainage segment and also partly at the interface with the connecting element. The test arrangement consisted of supports arranged at a dis-tance of 100 mm and pressure cutters arranged at a distance of 45 mm. The connecting element was positioned centrally between the pressure cutters. The T-shaped overlap was situated in the tensile zone.

Example 1 Drainage elements according to DD 109 317 consisting of a 2 to 4 mm gravel fraction and a binder component of 5% by weight with an external diameter of 414 mm and a wall thickness of 32 mm are arranged one above the other and fixed by means of a supporting ring mold consisting of 1 mold half for the inside and another mold half for the outside of the tube in such a way that a gap of 10 mm is formed.

This gap is filled by free pressureless casting as described above. After standing for 10 minutes, the mold halves are removed. The drainage element joint showed the desired properties.

Example 2 25 cm long segments of the drainage elements described in Example 1 were joined to one another in pairs in accordance with Example 1. On this occasion, however, the tube segments were arranged horizontally for casting. The mold assembly of Example 1 was completed by a cover plate so that a closed mold was formed. The mold cavity was filled through a bore in the upper peak of the mold ring by free casting for 1.25 minutes using a two-component metering and mixing machine. After standing for 10 minutes, the two mold halves could be removed.

Example 3 The test arrangement was the same as in Example 2, except that the mold cavity was filled in 2 minutes from the lower peak of the mold ring through a replaceable hose. The two mold halves could again be removed after 10 mins.

Example 4 Segments from Example 2 joined together in pairs were subjected to long-term testing under pressure. A vertical load of 5 t was applied. The compression in the elastic connecting element was less than 0.1% after 1000 hours.

Example 5 Segments from Example 2 joined together in pairs were tensile-tested by applying load to the bonded joint. The maximum tensile stress to failure was 12 KN.

Example 6 A drilled well was lined with support-free drainage segments by the methods described above.

Figure 1 shows a drilled well lined with support-free well tubes 2 produced in accordance with the invention, lost base plates 5, a UWM (underwater motor) pump 3 with a riser 4 and a gravel-filled annular space.

Vertically installed low-tensile gravel filters according to Example 1 are used as the well tubes 2. Six individual segments 1 meter in length were joined to one another at their end faces 1 by the method according to Example 2. After curing of the adhesive, the run-in pipe was guided through the tube section 6 and screwed to the base plate 5 so that tube section 6 can be lowered vertically into the prepared bore hole on the base plate 5. The tube column is propped by supports above the tube section on the run-in pipe.

The further lining of the well may then be carried out as follows: The next tube section 6 and all tube sections 6 are fitted together and bonded as already described, a run-in plate being used instead of the base plate 5. The tube section 6 is positioned over the well and supported by the lowermost filter tube. The run-in pipe is released and screwed to the pipe already present in the well. The two tube sections are joined in situ as in Example 1. The tube column is lowered into the bore hole and propped by the pipe via the last filter tube, this operation being repeated until the final stage is reached.

During running in, the tube sections 6 form stable running-in units which provide for efficient operation. Displacement of the filter tubes from the perpendicular is minimized although the filter column remains movable so that the tube column is able to follow any irregularities in the bore and any subsequent shifting of the rock. Squeezing forces and hence additional stressing are avoided. 103155/2

Claims (9)

1. A liquid-permeable element consisting of several support-free segments, characterized in that the individual segments are flexibly joined by bonded joints, more particularly using a casting elastomer.

2. An element as claimed in claim 1, characterized in that the individual segments have a circular cross-section and consist of a mineral filter material bonded with epoxy, unsaturated polyester or polyurethane casting resins.

3. An element as claimed in claim 1 or 2, characterized in that polyurethanes are used as the casting elastomers or casting resins.

4. An element as claimed in any of claims 1 to 3 , characterized in that several bonded elements are joined by an elastic T socket.

5. An element as claimed in any of claims 1 to 4, characterized in that the individual segments consist of a mixture of gravel and polyurethane casting resin.

6. An element as claimed in any of claims 1 to 5, characterized in that elements for creating a gap are present between the individual segments.

7. An element as claimed in any of claims 1 to 6, characterized in that partly impermeable segments are present instead of liquid-permeable segments.

8. The use of the elements claimed in any of claims 1 to 7 for drainage and for well sinking.

9. The use of the elements claimed in any- one of claims 1 to 7 for drainage in mines. For the Applicants,