AU779419B2

AU779419B2 - Method for strengthening geological formations

Info

Publication number: AU779419B2
Application number: AU26162/02A
Authority: AU
Inventors: Wolfgang Cornely; Oliver Czysollek; Martin Fischer; Petra Samek; Wolfgang Schnorbus
Original assignee: CARBOTECH FOSROC GmbH
Current assignee: CARBOTECH FOSROC GmbH
Priority date: 2001-03-24
Filing date: 2002-03-18
Publication date: 2005-01-20
Anticipated expiration: 2022-03-18
Also published as: PL193085B1; DE10114651C1; PL352956A1; AU2616202A

Description

AUSTRALIA

PATENTS ACT 1990 COMPLETE SPECIFICATION NAME OF APPLICANT(S): CarboTech Fosroc GmbH ADDRESS FOR SERVICE: DAVIES COLLISON CAVE Patent Attorneys 1 Little Collins Street, Melbourne, 3000.

INVENTION TITLE: Method for strengthening geological formations The following statement is a full description of this invention, including the best method of performing it known to me/us:- The invention relates to a method for strengthening geological formations in accordance with the preamble of Claim 1.

From DE 34 33 928 C2 a method is known using polyurethane resin mixtures for strengthening geological formations in black (hard) coal mining. By this method the coal-bearing rock and also the coal are stabilised. In individual cases fires have occurred as a consequence of these applications. These events were found to have been caused since the "reaction heat of the hardening resin created favourable conditions for the spontaneous combustion of the coal. The reaction heat and the reaction 15 temperature in polyurethane resin mixtures is a result of the reaction of the polyisocyanate component B and the OH groups (hydroxyl groups) of the S. polyol component A and by the reaction of the polyisocyanates with water.

Conventional polyurethane resins for strengthening geological formations contain a significant excess of NCO groups. Thus, in accordance with 20 DE34 33 928 C2, reaction mixtures with an isocyanate index of between 120 and 140 are preferred. Temperatures of between 130 and 150'C can occur as reaction temperatures, starting out from approx. 30°C. In the event however that water or hydrous substances are added whereby an isocyanate index of approx. 100 results, i.e. stoichiometric turnover, the temperatures can rise up to 180 0

C.

In order to reduce the reaction temperature, a variety of options are known in principle: One option is to admix low-boiling inert substances, for instance fluorocarbons, which evaporate due to the reaction heat generated and due to the enthalpy of vaporisation contribute to reducing the reaction temperature. In addition a "dilution effect" occurs. When applying this method, a light polyurethane foam is produced which in view of its inferior strength is not suitable for reinforcing rocks.

A further alternative to achieve a reduction in the reaction temperature is the addition of non-volatile inert substances. The easiest method is the addition of liquid inert substances. As a rule, high-boiling plasticisers are used towards this end of the type customarily applied in the chemistry of plastics.

They can be added to both components. The mechanical properties of the polyurethane resin product are however in most cases impaired thereby, in particular the hardness of the resulting end product deteriorates. In higher concentrations, the inert substance tends to exude from the polymer matrix.

This effect results above all in an undesirable impairment of the adhesion properties.

It is also possible to admix solid fillers of the type customarily used in the chemistry of plastics. Whilst the pressure-related mechanical properties are S. generally improved thereby, the tension-related properties deteriorate, in particular the adhesion strength of the resins. In practical applications designed to strengthen rocks, it is of a great disadvantage that the solid 20 fillers have the tendency of settling from the liquid phase. A S. .•homogenisation of such separated systems in situ is not possible as a rule.

To achieve a stable dispersion is difficult above all in view of the low viscosities required in the pumping and injection technology. Liquids with a viscosity of>1000 mPa s cannot be processed with selfpriming pumps of the type customarily used in injection technology.

A further alternative for temperature reduction is the reduction of the number of reactive groups by using components with higher molecular weight. This can be done simultaneously in both components where, on the polyol side, polyols with a lower OH-content or lower OH-number can be used and, on the isocyanate side, prepolymers, i.e. preadducts between polyol and excess isocyanate, can be used. In this way the viscosity is significantly increased on the one hand, and on the other hand the substances become softer so that upon a significant reduction of the reaction temperature they no longer possess the stiffness required for rock reinforcement.

The decisive factor for the enthalpy of reaction generated is the molar turnover relative to the total mass of the components. The molar turnover is limited by that particular component which contains the lowest number of reactive groups. Reactive groups which represent a stoichiometric excess in the other component do not contribute to the heat evolution. In the event the molecular weight of only one component is increased whilst the volume ratio of 1 1 is retained, the stoichiometric ratio, which is expressed by the isocyanate index, is changed. Generally, the isocyanate index in rock strengthening systems is between 120 and 200, i.e. there is an excess of isocyanate, which is either lysed in secondary reactions (allophanate or biuret reaction) or in reactions with water from the environment, if present, or are preserved as unreacted isocyanate group.

In the event the number of reactive groups on the polyol side are reduced, for instance by application of polyols with a lower OH number, and therefore the isocyanate index is increased, this leads to a temperature 20 reduction under laboratory conditions. In practical applications this is however very problematic since the reaction with water from the environment leads to an additional temperature increase. For this reason it is advisable to keep the isocyanate index as low as possible.

If, on the other hand, the number of the reactive groups on the isocyanate side is reduced, for instance by using prepolymers, a reduction of the chemical turnover does not occur and, consequently, also no reduction of the reaction temperature, when starting out from an original isocyanate index of 160 until reaching an isocyanate index of 100 stoichiometric reaction). Only at lower isocyanate indices does a temperature reduction effect occur. The products thereby created are however too soft for rock stabilisation.

It is the object of the invention to provide polyurethane resin mixtures wherein the reaction heat and therefore the reaction temperature are reduced and which react to produce at the same time a polyurethane resin product which is at least equally well suited for the strengthening of geological formations in coal mining, in particular with a view to the adhesion strength, as the traditional polyurethane resin systems. Further aims are easy production, sufficient storage stability as well as easy pumping capability and suitability for application in multiple use container systems customary in coal mining situations.

The object of the invention is achieved by the characteristics of Claim 1.

Further developments are described in the characteristics of the subclaims.

The inventive use of polyether polyols with solid organic fillers which are produced in situ distinguishes itself in that the organic fillers are contained in molecularly disperse distribution. In part, there occurs a covalent linkage with the polyethers.

Due to these chemical compounds, a stable dispersion is obtained. In 20 addition to the filler-containing polyether polyols, a softener must be admixed to the reaction mixtures. Only by way of this combination there are achieved on the one hand low reaction temperatures at simultaneously appropriate viscosities on the one hand; whilst on the other hand high adhesion strength is achieved within a short period, i.e. in less than half an hour.

As filler-containing polyether polyols, polymer polyols are used which are known per se and which are produced by way of radical polymerisation of olefinic monomers with polyethers. The polymer polyols can be admixed to the polyol component in an easy manner and a storage-stable dispersion of a viscosity of between 200 and 600 mPa s (25°C) is obtained which is well suited for applications aimed at strengthening geological formations in coal mining constructions.

Preferably used are polymer polyols with an OH number between 25 and Proven to be particularly suitable are "Desmophen 1920 D" by Bayer AG and "Lupranol 4700" by Messrs. Elastogran. With these polymer polyols a storage-stable dispersion is obtained which, even after several months of storage in multiple-use containers where a subsequent homogenisation is not possible, does not settle.

The polymer polyols can be used in a concentrations of between 5 and 25 as constituents of the polyol component A. During tests it has been found surprisingly that due to the use of polymer polyols not only the reaction temperature can be kept low, i.e. below 100°C, but even by comparison with .i the conventional polyols of the same molecular weight and same hydroxyl number an increase in the mechanical properties is achieved. Thus, when using polymer polyols, a higher adhesion strength at simultaneously lower 15 foam density is achieved which again has a cost-saving effect when using the polyurethane resin mixture.

As filler-containing polyether polyols, polyol dispersions can also be used, wherein polyurea or polyhydrazodicarnoamide are produced by polyaddition of diisocyanates with diamines, alkanolamines or hydrazine in the polyether polyol (PHD-polyether polyols). The polyaddition in this process is executed in a polyether polyol whose OH-groups partially react also with the diisocyanates, whereby the dispersion thus produced obtains its stability. Due to its generally higher viscosity, these polyols are however less preferred compared with the polymer polyols.

As softeners, non-volatile inert liquids are suitable of the type known in the plastics industry. Above all, these are alkyl esters and aryl esters of phosphoric acid, phosphorous acid, and aliphatic and aromatic dicarboxylic acids as well as fatty acid triglycerides and their derivatives, provided that they do not contain any or only negligible amounts of acid hydrogen atoms in the form of hydroxyl groups, amino groups or the like.

By virtue of the admixture of the softeners known per se, the concentration of the reactive groups in the reaction mixture and thereby the turnover and the reaction temperature are reduced. At the same time, the addition of softeners leads however generally to a reduction in the hardness of the reaction mixture produced.

Preferred softeners are triglycerides of fatty acids which in the alkyl chain additionally contain ether functions and/or ester functions, such as for instance soy oil which has been epoxidised and etherified with butyl diethyline glycol or acetylated caster oil.

When using these softeners it has been found surprisingly that the adhesion properties correspond to those of the conventional polyurethane resin systems.

15 The invention is described below by reference to examples.

Examples The following raw materials were used: Polyol 1: trifunctional polyether polyol based on glycerine and propylene oxide with an OH number of 380 and a viscosity (25°C) of 450 mPa s.

Polyol 2 trifunctional polyether polyol based on glycerine, propylene oxide and ethylene oxide with an OH number of 27 and a viscosity (25 0 C) of 1150 mPa s Polyol 3 tetrafunctional polyether polyol based on ethylene diamine and propylene oxide with an OH number of 60 and a viscosity (25 0 C) of 555 mPa s.

Polymer polyol: polyether polyol with approx. 40 solid substance content, grafted with styrene acrylonitrile, an OH number of 29 and a viscosity (25 0

C)

of 5000 mPa s.

glycerine with an OH number of 1810 and a viscosity (20 0 C) of 1400 mPa s Dibutyl tin dilaurate

PMDI

polymeric diphenyl methane diisocyanate with an NCO content of 31.5 by weight and with a viscosity (25°C) of 700 mPa s Softener 1 "RM 11" manufactured by Messrs. Isoelektra with a viscosity (25 0

C)

of 145 mPa s Softener 2 15 acetylated castor oil with a viscosity (25°C) of 250 mPas Softener 3 "Flexaryl 9020" (partially hydrated polyphenyl) with a viscosity 0 C) of 95 mPa s S- Softener 4 20 dioctyl adipate with a viscosity (25 0 C) of 14 mPa s Softener "Neukadur 1014" manufactured by Messrs. Altropol, aliphatic fatty acid ester with a viscosity (25 0 C) of between 5 and 10 mPa s Component Al: 28.8 polyol 1 13.8 polyol 2 46.8 polyol 3 softener glycerine 0.8 dibutyl tin dilaurate 0.8 water\ viscosity (25 0 C) 390 mPa s Component A2: Component B1: Component B2: r 28.8 polyol 1 13.8 polymer polyol 46.8 polyol 3 softener 1.0 glycerine 0.8 dibutyl tin dilaurate 0.8 water viscosity (25°C) 445 mPa s 70.0 PMDI 30.0 softener 1 viscosity (25°C) 365 mPa s 70.0 PMDI 20.0 softener 2 10.0 softener 4 viscosity (25°C) 290 mPa s 70.0 PMDI 20.0% softener 3 viscosity (25°C) 355 mPa s 70.0 PMDI 30.0 softener 4 viscosity (25 oC) 105 mPa s Component B3: Component B4: The polyol components A and the polyisocyanate components B were mixed in a volume ratio 1 1 and the properties of the reaction mixture were determined as follows: Adhesion: A rock prism of the dimensions 160 mm x 40 mm x 40 mm is broken in half and stored for 24 hours at 30 0 C and 80 relative humidity. The fractured surfaces are joined leaving a gap of 3 mm and this gap is sealed with the homogeneous reaction mixtures at a 30°C starting temperature. Following storage at 30 0 C and 80 relative humidity, the bonded prism is subjected to a flexural stress test according to DIN EN 196, Part 1, wherein the load increase is 50 10 N/s. The adhesion strength is measured after 30 minutes and after 7 days.

Gross density The gross density is determined from the foam in the joints, whose volume is 3 mm x 40 mm x 40 mm.

Maximum reaction temperature 15 100 ml of each of the components are homogeneously mixed at 23 °C starting temperature in a 250 ml jar and the temperature change is observed by means of a Ni-Cr-Ni thermo element whose measuring junction is arranged in the centre of the foam and the maximum reaction temperature is determined.

Test results The test recipes were selected such that the stoichiometric ratio of NCO to the OH groups was around 1.45 (isocyanate index 145). The component A2 contains the polymer polyol in accordance with the invention and a softener.

In the component Al the polymer polyol was replaced by a polyol with comparable OH number.

The components B1, B2, B3 and B4 each contain 70 of polymeric diphenylmethane diisocyanate (PMDI) nd 30 softener or softener combinations, wherein the component B1 contains the softeners in accordance with Claim 6 of the invention and the component B2 softeners according to Claim 7.

The tests results are specified in the table below Example Recipe Adhesion at Adhesion at Gross density Max reaction after 30 30'C after 7 of the foam temperature min [Mpa] days [Mpa] [kg/m 3 0

C]

S AI B1 1.2 2.4 320 99 2 A2 B1 1.6 3.1 280 98 3 Al B2 0.7 1.9 320 98 4 A2 B2 1.2 2.6 260 98 Al B3 0.6 1.7 290 98 6 A2 B3 0.9 1.9 260 97 7 Al B4 0.6 1.5 330 98 8 A2 B4 0.9 1.9 300 99 ooooo The tests 2, 4, 6 and 8 were executed in accordance with the S"invention with polymer polyol and softeners in the component A. In the examples 1, 3, 5 and 7 for the purpose of comparison the polymer polyol was replaced by a polyol with comparable OH number. As the table shows, in all reaction mixtures the maximum reaction temperature is below 100 0

C.

10 The gross densities of the foams obtained are lower in the tests in accordance with the invention than in the reference tests. Nevertheless, the adhesion strength is greater. Normally the adhesion strength is reduced with decreasing gross density.

By comparing the examples 2 and 4 with examples 6 and 8, it is found that by using the softeners in accordance with the invention that a higher adhesion strength is obtained.

Throughout this specification and the claims which follow, unless the context requires otherwise, the word "comprise", and variations such as "comprises" and "comprising", will be understood to imply the inclusion of a stated integer or step or group of integers or steps but not the exclusion of any other integer or step or group of integers or steps.

The reference to any prior art in this specification is not, and should not be taken as, an acknowledgement or any form of suggestion that that prior art forms part of the common general knowledge in Australia.

Claims

1. A method for strengthening geological formations in underground black (hard) coal mines by which polyurethane-producing reaction mixtures, which contain a polyol component A and a poly isocyanate component B, are introduced into the formations to be reinforced via previously made boreholes and the reaction mixtures are caused to react, wherein a) the polyol component A contains polyether polyols with solid organic fillers which are produced in situ in the polyether polyol, and b) softeners known per se are admixed to the reaction mixture.

2. A method according to Claim 1, wherein as filler-containing polyether polyols, polyol dispersions are used which are produced by radical polymerisation of olefinic monomers with polyether polyols (polymer polyols).

3. A method according to Claim 2, wherein polymer polyols with an OH number of between 25 and 55 are used.

4. Method according to Claim 2 or 3, wherein the polymer polyols are used at the rate of between 5 and 25% as constituents of the poly component A.

5. Method according to Claim 1, wherein as filler-containing polyether polyols, polyl dispersions are used wherein polyurea or polyhydrazodicarbonamide is produced by polyaddition of diisocyanates with diamines, alkanolamines or hydrazine in the 25 polyether polyol (PHD polyether polyol).

6. Method according to any one of Claims 1 to 5, wherein as softener, fatty acid triglycerides and their derivatives are used. S 30 7. Method according to any one of Claims 1 to 6, wherein as softener, acetylated caster oil is used. P \OPER\Axd\2514408 I spa dm-23/1 1d04

12- 8. A method substantially as hereinbefore described with reference to the Examples. DATED: 23 November, 2004 by DAVIES COLLISON CAVE Patent Attorneys for the Applicant(s): CarboTech Fosroc GmbH