AU2001260175B2 - Polyurethane foams with reduced exothermy - Google Patents

Description

WO 01/79321 PCT/EP01/03714 In -1-

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Polyurethane foams of low exothermicitv The invention relates to polyurethane foam systems of low exothermicity and to their use for consolidating geological formations in underground mining, in tunnel Q 5 construction and in civil engineering.

NO Two-component polyurethane foam systems are employed to a large extent in underground coal mining for consolidation of rock and coal and for sealing off Sagainst inflowing waters. The formation of polyurethane from polyisocyanates and polyols is exothermic in principle. Under adverse circumstances ignition of coal dust may occur as a consequence of the high reaction temperatures which arise in the foamed body. When the reaction mixture flows in to relatively large hollow spaces in particular, the core temperature of the polyurethane foam can increase to such an extent that self-ignition of the polyurethane and consequently burning of coal in situ can occur.

To avoid this disadvantage of polyurethane systems, EP-A 167 002 proposed the use of reaction products of isocyanates with aqueous alkali metal silicate solutions. EP- A 636 154 discloses production by reaction of polyisocyanates, aqueous alkali metal silicate solutions and cement. However, these systems have not found acceptance in practice.

It has now been found that by combination of certain polyisocyanate prepolymers with selected polyols and suitable fillers, the exothermicity of the polyurethane formation can be lowered to the extent that risk of fire no longer occurs during consolidation of rock.

The invention therefore relates to foams which contain polyurethane groups and are obtained by reaction of WO 01/79321 PCT/EP01/03714 -2- 1. a polyisocyanate component with an NCO content of 20 to 30 wt.%, preferably 23 to 28 which comprises at least 50 wt.% of a prepolymer containing isocyanate groups with an NCO content of 20 to 28 wt.%, 2. a polyol component with an OH number of 120 to 350, preferably 180 to 300, 3. a solid filler which is dispersed in the polyol component b) or the prepolymer preferably in the polyol component and has an average particle size of 4 to 100 pm, preferably 4 to 25 in particular 10 to 25 lm, 4. water, optionally catalysts, 6. optionally additional additives.

According to the invention, the isocyanate component a) contains 20 to 30 wt.%, preferably 23 to 28 of NCO groups and comprises at least 50 wt.% of a prepolymer containing 20 to 30 preferably 23 to 28 of isocyanate groups. This prepolymer is preferably prepared by reaction of isocyanates of the diphenylmethane series with polyether polyols with a functionality of 3 to 8 and an OH number of 350 to 1,000 and a number-average molecular weight of 150 to 1,000. Suitable prepolymers are also described in EP-A 550 901. Isocyanates of the diphenylmethane series which are employed are di-nuclear diphenylmethanediisocyanates, such as and/or 2,4'-diphenylmethane-diisocyanate or higher homologues thereof or mixtures of diphenylmethane-diisocyanates with two or more nuclei, for example polyphenylene-polymethylene-polyisocyanates, such as are prepared by aniline-formaldehyde condensation and subsequent phosgenation ("crude MDI") or the polyisocyanates with a functionality higher than 2.0 which are obtainable industrially under the name "polymeric diphenylmethane-diisocyanate".

WO 01/79321 PCT/EP01/03714 -3- Products which comprise 75 to 95 wt.% of di-nuclear isomers are preferred, in particular those in which the content of the 2,4'-isomer in the di-nuclear isomers is to 40 wt.% and the content of 2,2'-isomer is 2 to 10 wt.%.

In addition to the prepolymer, the isocyanate component a) can comprise up to wt.% of further isocyanates of the diphenylmethane series. This is preferably polymeric MDI. However, monomeric MDI can also be employed, or MDI types which are modified, e.g. contain biuret, allophanate or isocyanurate groups, as long as the viscosity of the isocyanate component a) does not thereby rise too much.

To ensure a good processability of the isocyanate component its viscosity is preferably established in a range from 200 to 6,000 mPas, particularly preferably 500 to 3,000 mPas. Such isocyanate components can be conveyed and injected into the rock mass formations without problems using the piston or gear pumps conventionally used for consolidating rock mass.

The polyol component b) has an OH number of 120 to 350, preferably 180 to 300.

The polyol component preferably comprises polyoxyalkylene polyols which have functionalities of 2 to 8, preferably of 2 to 4, and are obtained by polyaddition of alkylene oxides, such as, for example, ethylene oxide, propylene oxide, butylene oxide, decyloxirane or phenyloxirane, preferably ethylene oxide and/or propylene oxide, on to starter compounds with active hydrogen atoms. Starter compounds which are employed are compounds with two or more hydroxyl end groups, such as, for example, water, triethanolamine, 1,2-ethanediol, 1,2-propanediol, 1,3propanediol, diethylene glycol, dipropylene glycol, triethylene glycol, tripropylene glycol, 1,2-butanediol, 1,3-butanediol, 1,4-butanediol, 1,2-hexanediol, 1,3hexanediol, 1,4-hexanediol, 1,5-hexanediol, 1,6-hexanediol, glycerol, trimethylolpropane, pentaerythritol or sorbitol. The starter compounds can be used by themselves or as mixtures.

WO 01/79321 PCT/EP01/03714 -4- One or more polyester polyols can also be co-used in the polyol component b) in amounts of up to 10 wt.% of the total amount of component Suitable polyester polyols have number-average molecular weights of 200 to 6,000 g/mol, preferably 200 to 2,400 g/mol, and are obtainable from aromatic and/or aliphatic dicarboxylic acids and polyols which contain at least two hydroxyl groups. Examples of dicarboxylic acids are phthalic acid, isophthalic acid, terephthalic acid, fumaric acid, maleic acid, azelaic acid, glutaric acid, adipic acid, suberic acid, sebacic acid, malonic acid and succinic acid. The pure dicarboxylic acids and any desired mixtures thereof can be used. Instead of the free dicarboxylic acids, the corresponding dicarboxylic acid derivatives, such as e.g. dicarboxylic acid mono- or diesters of alcohols having one to four carbon atoms, can also be employed. Such esters are formed, for example, in the recycling of polyester waste. Dicarboxylic acid anhydrides, such as phthalic anhydride or maleic anhydride, can also be employed as the acid component. The following are preferably used as the alcohol component for the esterification: ethylene glycol, diethylene glycol, tetraethylene glycol, 1,2-propanediol, 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, 1,6hexanediol, 1,10-decanediol, glycerol, trimethylolpropane, pentaerythritol or mixtures thereof. It is also possible to use polyester polyols from lactones, e.g. scaprolactone, or hydroxycarboxylic acids, e.g. co-hydroxycarboxylic acids. The polyol component can also comprise polyether-ester polyols, such as are obtainable e.g. by reaction of phthalic anhydride with diethylene glycol and subsequent reaction with oxirane.

In the preparation of the foams according to the invention, a solid filler with an average particle size of 4 to 100 rtm, preferably 4 to 25 pm, in particular 10 to pm, is employed as component Storage-stable dispersions with a viscosity suitable for processing can be obtained with such fillers. Suitable fillers are, for example, aluminium trihydroxide, urea-formaldehyde resins (condensation products of urea and formaldehyde, see Houben-Weyl, "Methoden der organischen Chemie", vol. XIV, 1963, p. 319-402), rock powder or pyrogenic silica; aluminium trihydroxide is preferred. For the preparation of the foams according to the WO 01/79321 PCT/EP01/03714 invention, the filler is dispersed or suspended in the polyol component b) or the prepolymer preferably in the polyol component The filler is preferably employed in an amount of 30 to 55 particularly preferably 35 to 50 wt.%, based on the amount of the suspending agent.

If the filler is dispersed in the polyol component the viscosity of the fillercontaining polyol component should preferably be not more than 6,000 mPas, so that it can be conveyed via a low-pressure pump. The viscosities of the isocyanate component and filler-containing polyol component are particularly preferably adjusted to approximately the same value, in order to facilitate processing, in particular uniform mixing of the components.

For the preparation of the foams according to the invention, water is added as the blowing agent preferably in an amount of 0.1 to 1 particularly preferably 0.6 to 0.9 based on the polyol component The amount of water is very particularly preferably chosen such that a foaming factor of 2 to 6 is achieved, i.e.

the volume of the foam prepared is two to six times the total volume of the starting components.

Catalysts e) which accelerate the reaction between the isocyanate component and the polyol component can optionally be added during the preparation of the foams according to the invention. Examples of suitable catalysts are organotin compounds, such as tin(II) salts of organic carboxylic acids, e.g. tin(II) acetate, tin(II) octoate, tin(H) ethylhexoate and tin(I) laurate, and the dialkyltin(IV) salts, e.g. dibutyltin diacetate, dibutyltin dilaurate and dioctyltin diacetate. Further examples of suitable catalysts are amines, such as dimethylaminopropylurea, dimethylaminopropylamine, bis(dimethylaminopropyl)amine, diazabicyclooctane, dimethylethanolamine, triethylamine, dimethylcyclohexylamine, dimethylbenzylamine, pentamethyldiethylenetriamine, N,N,N'N'-tetramethylbutanediamine, Nmethylmorpholine, bis(dimethylaminoethyl) ether and tris(dialkylaminoalkyl) -shexahydrotriazines.

WO 01/79321 PCT/EP01/03714 -6- Examples of suitable catalysts for producing polyisocyanurate structures are potassium salts, such as potassium acetate or potassium octoate. A combination of several catalysts can also be used.

Further additives f) are optionally also used for the preparation of the foams according to the invention, for example pigments, dyestuffs or plasticizers, such as dioctyl phthalate. These are usually added to the polyol component in amounts of 0 to 10 parts by weight, preferably 0 to 5 parts by weight.

Flameproofing agents are optionally also added, preferably those which are liquid and/or soluble in one or more of the components employed for the preparation of the foam. Commercially available phosphorus-containing flameproofing agents are preferably employed, for example tricresyl phosphate, tris-(2-chloropropyl) phosphate, tris-(2,3-dibromopropyl) phosphate, tris-(1,3-dichloropropyl) phosphate, tetrakis-(2-chloroethyl)ethylene diphosphate, diethylethane phosphonate and diethanolaminomethylphosphonic acid diethyl ester. Halogen- and/or phosphoruscontaining polyols which have a flameproofing action are also suitable. The flameproofing agents are preferably employed in an amount of not more than particularly preferably not more than 20 based on component b).

The invention also provides the use of the foams according to the invention for consolidation of rock in mining and civil engineering, for example for consolidation of coal and surrounding rock, and for sealing off against inflowing waters in underground hard coal mining.

Due to geological fault zones and the hollow spaces caused by extraction, outbursts of rock from the hanging sides are forever occurring, leading to serious interruptions in production and to a considerable danger to the persons working underground.

During consolidation of the rock mass, the polyurethane foams according to the invention are forced via bore holes by means of suitable injection pumps into the WO 01/79321 PCT/EP01/03714 4 -7rock mass formation to be consolidated. The expanding reaction mixture cements Sthe filled gaps and cracks and thus leads to a re-establishment of the system strength O of the geological formation; caving in of rock or of coal is reliably prevented.

The preparation of the foams according to the invention is preferably carried out by Smixing, in a volume ratio of 1:1, the isocyanate component a) and a mixture r comprising components e) and An NCO/OH ratio of 130 to 300 is Spreferably established here, particularly preferably 180 to 260.

The recipe for the foams according to the invention is preferably chosen such that the temperature which the reaction mixture reaches during the polyurethane formation does not exceed a maximum of 120'C. Recipes in which the maximum reaction temperature does not exceed 1 10°C are particularly preferred.

In order that the invention may be readily understood and put into practical effect, particular preferred embodiments will now be described by way of the following, non-limiting Examples.

WO 01/79321 PCT/EP01/03714 -8- Examples The following starting components were employed for the following examples: Formulation A Polyol mixture of OH number 239 mg KOH/g, comprising: 1) 20.9 pt. by wt. of a polyether of OH number 190, which has been obtained by reaction ofpropylene glycol with ethylene oxide, 2) 78 pt. by wt. of a polyether of OH number 255 mg KOH/g, which has been obtained by reaction of trimethylolpropane with ethylene oxide and propylene oxide, 3) 0.9 pt. by wt. of water as the blowing agent and 4) 0.2 pt. by wt. of dibutyltin dilaurate as the catalyst.

Formulation B Polyol mixture of OH number 111 mg KOH/g, comprising: 1) 98.9 pt. by wt. of a polyether of OH number 112, which has been obtained by reaction ofpropylene glycol with propylene oxide, 2) 0.9 pt. by wt. of water as the blowing agent and 3) 0.2 pt. by wt. of dibutyltin dilaurate as the catalyst.

Formulation C Polyol mixture of OH number 381 mg KOH/g, comprising: WO 01/79321 PCT/EP01/03714 -9- 1) 98.9 pt. by wt. of a polyether of OH number 385, which has been obtained by reaction of trimethylolpropane with propylene oxide, 2) 0.9 pt. by wt. of water as the blowing agent and 3) 0.2 pt. by wt. of dibutyltin dilaurate as the catalyst.

Formulation D Polyol mixture of OH number 242 mg KOH/g, comprising: 1) 98.9 pt. by wt. of a polyether of OH number 245, which has been obtained by reaction of glycerol with propylene oxide, 2) 0.9 pt. by wt. of water as the blowing agent and 3) 0.2 pt. by wt. of dibutyltin dilaurate as the catalyst.

Isocyanate I Isocyanate prepolymer with an NCO content of 25.6 wt.% (Desmodur® VP.PU 28HS07, Bayer AG, D-51368 Leverkusen); reaction product of a polyisocyanate with a content of 60 wt.% 4,4'-diisocyanatodiphenylmethane and 22 wt.% 2,4'diisocyanatodiphenylmethane, and 3 wt.% 2,2'-diisocyanatodiphenylmethane, with a polyether polyol of OH number 865, which has been obtained by reaction of trimethylolpropane with propylene oxide, in a ratio of amounts of 92.5 wt.% wt.% polyol.

WO 01/79321 PCT/EP01/03714 Isocyanate II Polyisocyanate with an NCO content of 31 wt.% (Desmodur® 44V70 L, Bayer AG, D-51368 Leverkusen), which comprises diisocyanatodiphenylmethane isomers to the extent of approx. 31 of which approx. 89 wt.% is 4,4'diisocyanatodiphenylmethane and approx. 11 wt.% is 2,4'diisocyanatodiphenylmethane.

Aluminium hydroxide with an average particle size of 15 25 pim (Martinal® ON- 320, Martinswerk GmbH, D-50127 Bergheim) was employed as the filler.

These components were tested in a known manner in the laboratory: approx. 200 grams of the components were mixed together at a volume ratio of isocyanate to polyol of 1:1 and raw material temperatures of 23°C. The reaction temperature was then measured in the middle of the test specimen. After about four hours, the test specimens were cut and the foam structure evaluated.

The test results are summarized in table 1.

WO 01/79321 PCT/EP01/03714 -11- Table 1 Example 1 2* 3* 4 5 16* 7* 8 Polyol component A [pt. by wt.] 55 I 75 100 55 B [pt. by wt." C [pt. by wt.] D [pt. by wt.] 55 Isocyanate component I [pt. by wt.] 90 90 90 90 90 90 II [pt. by wt.] 90 OH number of the polyol 239 111 381 242 239 239 239 239 component [mg KOH/g] NCO content of the iso- 25.6 25.6 25.6 25.6 25.6 25.6 31.0 28.1 cyanate component

AI(OH)

3 45 45 45 45 25 0 45 Foam structure A C A A A A C A Maximum reaction 105 68 131 103 115 121 97 99 temperature Comparison example not according to the invention A: acceptable, C: collapse Throughout this specification and the claims which follow, unless the context requires otherwise, the word "comprise", or variations such as "comprises" or "comprising", will be understood to imply the inclusion of a stated integer or group of integers or steps but not the exclusion of any other integer or group of integers or steps.

P:\WPDOCS\CRN\SETSpc\7742610.doc-30/06/05 c -lla- The reference to any prior art in this specification is not, and should not be taken as, San acknowledgement or any form of suggestion that the prior art forms part of the common general knowledge in Australia.

Persons skilled in the art will appreciate that numerous variations and modifications N will become apparent. All such variations and modifications which become Sapparent to persons skilled in the art, should be considered to fall within the spirit

C

and scope that the invention broadly appearing before described.

Claims (4)

1. Foams containing polyurethane groups, obtained by reaction of a) a polyisocyanate component with an NCO content of 20 to 30 wt.% which comprises at least 50 wt.% of a prepolymer containing isocyanate groups with an NCO content of 20 to 28 wt.%, CI b) a polyol component with an OH number of 120 to 350, c) a solid filler which is dispersed in the polyol component b) or the prepolymer a) and has an average particle size of 4 to 100 pm, d) water, e) optionally catalysts, f) optionally additional additives.

2. Process for the preparation of foams according to claim 1 containing polyurethane groups, in which the isocyanate component a) is reacted in a volume ratio of 1:1 with a mixture comprising components d) and optionally e) and f).

3. Use of the foams according to claim 1 for consolidation of rock in mining and civil engineering. P:\WPDOCS\CRN\SEThSp.\7742610.doc-30/6/5 -13-

4. Foams containing polyurethane groups, obtained by the reaction as defined in o claim 1, and use thereof, substantially as hereinbefore described, with reference to the accompanying, non-comparative Examples. DATED this 30th day of June, 2005 O BAYER AKTIENGESELLSCHAFT AND CARBOTECH FOSROC GMBH O Sby their Patent Attorneys DAVIES COLLISON CAVE