Foam for mine ventilation control

Abstract

A two component, semi-rigid expanding polyurethane foam that provides adhesion to different surfaces, increased flexibility compared to conventional two component polyurethane foams. The disclosed foam is useful to form a mine seal to close off mine shafts.

Description

Foam For Mine Ventilation ControlField

[0001] The present disclosure relates generally to mine stoppings and seals and materials useful in forming mine stoppings and seals.Brief Description of Related Technology

[0002] Mine shafts are created in the process of tunneling underground in order to extract mineral resources. Once a desired mineral resource has been extracted from a shaft, the shaft may no longer be used for further mining. Shafts are also sometimes abandoned for commercial reasons, such as when the company operating a mine ceases operations in that shaft. Mine shafts which are no longer in use may be sealed for any number of reasons, for example to control and direct the ventilation airflow through underground mines to dilute and render harmless methane, entrained dust, and other contaminants at the working face and other areas of the mine.

[0003] Mine stoppings or mine seals are used to close off mine shafts. Current mine seals are generally formed by creating a support or wall at a desired point in the shaft. The support or wall can be formed from cemented concrete blocks, metal panels, timber, etc. However, these structures will have gaps allowing movement of air, gas and dust.

[0004] These gaps must be sealed. Filling the gaps with cementitious grouts or sealants has been used. Cementitious materials are heavy, require mixing with water before use and skill to apply correctly. Cementitious materials do not expand making it difficult to seal the entirety of an irregularly shaped gap. Even when properly applied when there is shifting and heaving of the mine in the vicinity of the passage (sometimes referred to as a "mine convergence") the cementitious sealant can break or pop off.

[0005] These gaps have also been sealed using rigid polyurethane foam. Conventional consumer spray foams are not suitable for use in mines as they use a flammable propellant; the cured foam is flammable in itself; the one component formula is packaged in containers too small for efficient use in preparing the large area seals needed in mining; and the foam cures to a rigid and brittle state. Two component polyurethane foam kits are available, however some propellants are flammable, the cured foam may beflammable in itself; and the foams cure to a hard, rigid and somewhat brittle state. There are two component polyurethane foam kits sold for use in mines which are stated to be nonflammable. However, users report these foams cure to a hard, rigid and somewhat brittle state Aging will also contribute to foam brittleness. When there is mine vibration, settling or convergence, the current rigid cured foams tend to break away from the surfaces and crack, leading to undesirable leakage of air, gas or dust. This requires weekly inspection of the polyurethane foam at each mine seal and frequent reapplication of new foam at the seals.

[0006] It would be desirable to provide an expandable, lightweight gap sealer that can bond strongly to diverse materials and hardens to a more resilient state than rigid polyurethane foam. Preferably the gap sealer is a polyurethane foam that comprises a nonflammable propellant and cures to a nonflammable product.Summary

[0007] One aspect of the disclosure provides a semi-rigid, expandable, lightweight gap sealer that can bond strongly to diverse materials and hardens to a more resilient state than conventional rigid polyurethane foam.

[0008] It is an object to provide a mine seal having more flexibility than conventional mine seals.Brief Description of the Drawings

[0009] Figure 1 is a graph showing foam compression test results for 4 comparative cured foam samples.

[0010] Figure 2 is a graph showing compression test results for 2 cured foam Examples and 2 cured foam comparative samples.Detailed Description

[0011] The singular forms "a", "an" and "the" include plural referents unless the context clearly dictates otherwise.

[0012] About or “approximately” as used herein in connection with a numerical value refer to the numerical value ± 10%, preferably ± 5% and more preferably ± 1 % or less.

[0013] At least one, as used herein, means 1 or more, i.e., 1 , 2, 3, 4, 5, 6, 7, 8, 9, or more. With reference to an ingredient, the indication refers to the type of ingredient and not to the absolute number of molecules. "At least one polymer" thus means, for example, at least one type of polymer, i.e., that one type of polymer or a mixture of several different polymers may be used.

[0014] The terms “comprising”, “comprises” and “comprised of” as used herein are synonymous with “including”, “includes”, “containing” or “contains”, and are inclusive or open-ended and do not exclude additional, non-recited members, elements or method steps.

[0015] When amounts, concentrations, dimensions and other parameters are expressed in the form of a range, a preferable range, an upper limit value, a lower limit value or preferable upper and limit values, it should be understood that any ranges obtainable by combining any upper limit or preferable value with any lower limit or preferable value are also specifically disclosed, irrespective of whether the obtained ranges are clearly mentioned in the context.

[0016] Preferred and preferably are used frequently herein to refer to embodiments of the disclosure that may afford particular benefits, under certain circumstances. However, the recitation of one or more preferable or preferred embodiments does not imply that other embodiments are not useful and is not intended to exclude those other embodiments from the scope of the disclosure.

[0017] The molecular weights given in the present text refer to number average molecular weights (Mn), unless otherwise stipulated. Molecular weight data can be obtained by gel permeation chromatography (GPC) calibrated against polystyrene standards in accordance with DIN 55672-1 :2007-08 at 35°C, unless otherwise stipulated. The weight average molecular weight Mw can be determined by GPC, as described for Mn. “Polydispersity index” refers to a measure of the distribution of molecular mass in a given polymer sample. The polydispersity index is calculated by dividing the weight average molecular weight (Mw) by the number average molecular weight (Mn).

[0018] As used herein a curable, one component (1 K) composition is a singular formulation that has sufficient commercial stability to be prepared, warehoused and shipped to an end user. The 1 K composition can be used without adding any additionalcomponents and will crosslink or cure when exposed to suitable conditions, for example moisture in the air. As used herein a two component (2K) composition has two or more components. Each of the components is prepared, warehoused and shipped separately from the other components. The components are mixed immediately prior to use. Mixing of the components starts a cure reaction so commercial storage after mixing is not possible.

[0019] As used herein for each of the various embodiments, the following definitions apply:

[0020] Unless otherwise specifically defined, (meth)acrylate refers to at least one of acrylate and methacrylate. A “vinyl group” refers to (CH2=CH-). A "(meth)acryloyl" refers to at least one of acryloyl and methacryloyl, an “acryloyl group” refers to (CH2=CHCO-), and a “methacryloyl group” refers to (CH2=C(CH3)CO-).

[0021] Unless otherwise specifically defined, "acyl" refers to the general formula - C(O)alkyl.

[0022] Unless otherwise specifically defined, "acyloxy" refers to the general formula -O- acyl.

[0023] Unless otherwise specifically defined, "alcohol" refers to the general formula alkyl-OH.

[0024] Unless otherwise specifically defined, "alkenyl" or "lower alkenyl" refers to a linear, branched or cyclic carbon chain having from 1 to about 16 carbon atoms, and advantageously about 1 to about 6 carbon atoms, and at least one double bond between carbon atoms in the chain. Examples include, for example, ethylene, allene, butene, butadiene, hexene, hexadiene, 5, 5-dimethyl-1 -hexene and cyclohexene. Unless otherwise specifically limited an alkenyl group can be unsubstituted, singly substituted, or multiply substituted, with substituent groups in any possible position.

[0025] Unless otherwise specifically defined, "alkoxy" refers to the general formula -0- alkyl.

[0026] Unless otherwise specifically defined, "alkyl" refers to a linear, branched or cyclic alkyl group having from 1 to about 9 carbon atoms including, for example, methyl, ethyl, propyl, butyl, hexyl, octyl, isopropyl, isobutyl, tert-butyl, cyclopropyl, cyclohexyl, cyclooctyl, vinyl and allyl. Unless otherwise specifically defined, an alkyl group can besaturated or unsaturated and substituted or unsubstituted. Unless otherwise specifically limited, a cyclic alkyl group includes monocyclic, bicyclic and polycyclic rings, for example norbornyl, adamantyl and related terpenes.

[0027] Unless otherwise specifically defined, "alkylamino" refers to the general formula - (NH)-alkyl.

[0028] Unless otherwise specifically defined, "di-alkylamino" refers to the general formula -N-(alkyl).sub.2. Unless otherwise specifically limited di-alkylamino includes cyclic amine compounds such as piperidine and morpholine.

[0029] Unless otherwise specifically defined, "alkylmercapto" refers to the general formula -S-alkyl.

[0030] Unless otherwise specifically defined, "alkynyl" or "lower alkynyl" refers to a linear, branched or cyclic carbon chain having from 1 to about 16 carbon atoms, and advantageously about 1 to about 6 carbon atoms, and at least one triple bond between carbon atoms in the chain. Examples include, for example, ethyne, butyne, and hexyne. Unless otherwise specifically limited an alkynyl group can be unsubstituted, singly substituted, or multiply substituted, with substituent groups in any possible position.

[0031] Unless otherwise specifically defined, an aromatic ring is an unsaturated ring structure having about 5 to about 6 ring members and including only carbon as ring atoms. Unless otherwise specifically defined, an aromatic ring can be substituted or unsubstituted.

[0032] Unless otherwise specifically defined, "aryl" refers to an aromatic ring system substituted or unsubstituted, that includes only carbon as ring atoms, for example phenyl, biphenyl or naphthyl.

[0033] Unless otherwise specifically defined, "aroyl" refers to the general formula -- C(=O)-aryl.

[0034] Unless otherwise specifically defined, a carbocyclic ring is a ring structure having about 3 to about 8 ring members, substituted or unsubstituted, that includes only carbon as ring atoms, for example, benzene or cyclohexane.

[0035] Unless otherwise specifically defined, "halogen" refers to an atom selected from fluorine, chlorine, bromine and iodine.

[0036] Unless otherwise specifically defined, a heteroaromatic ring is an unsaturatedring structure having about 5 to about 8 ring members, substituted or unsubstituted, that has carbon atoms and one or more heteroatoms, including oxygen, nitrogen and / or sulfur, as ring atoms. Heteroaromatic rings (or groups) also include fused polycyclic systems in which one or more monocyclic aromatic ring or monocyclic heteroaromatic ring is fused to another heteroaromatic ring. Examples of heteroaromatic rings (or groups) include but are not limited to, furan, thiophene, pyrrole, oxazole, thiazole, isoxazole, pyrazole, imidazole, oxadiazole, triazole, tetrazole, pyridine, pyrimidine, pyrazine, purine, benzothiazole, benzimibazole, benzofurane, indole, quinoline, quinoxaline.

[0037] Unless otherwise specifically defined "heteroaryl" refers to an heteroaromatic ring.

[0038] Unless otherwise specifically defined, a heterocyclic ring is a saturated ring structure having about 3 to about 8 ring members, substituted or unsubstituted, that has carbon atoms and one or more heteroatoms, including oxygen, nitrogen and / or sulfur, as ring atoms. Examples of heterocyclic rings include but are not limited to oxetane, thietane, azetidine, diazetidine, tetrahydrofuran, thiolane, pyrrolidine, dioxolane, oxathiolane, imidazolidine, dioxane, piperidine, morpholine, piperazine, and their derivatives. Unless otherwise specifically limited a heterocyclic ring includes monocyclic, bicyclic and polycyclic rings, for example azaadamantyl and tropanyl.

[0039] Unless otherwise specifically defined, the term "phenacyl" refers to the general formula -phenyl-acyl.

[0040] Room temperature refers a temperature of about 25°C.

[0041] Unless otherwise specifically defined, a spirocycle refers to a ring system wherein a single atom is the only common member of two rings. A spirocycle can comprise a saturated carbocyclic ring comprising about 3 to about 8 ring members, a heterocyclic ring comprising about 3 to about 8 ring atoms wherein up to about 3 ring atoms may be N, S, or 0 or a combination thereof.

[0042] Unless otherwise specifically limited the term substituted means substituted by at least one below described substituent group in any possible position or positions. Substituent groups for the above moieties useful in the disclosed compounds are those groups that do not significantly diminish the biological activity of the disclosedcompound. Substituent groups that do not significantly diminish the biological activity of the disclosed compound include, for example, H, halogen, N3, NCS, CN, NO2, NX1X2, OX3, C(X4)3, OAc, O-acyl, O-aroyl, NH-acyl, NH-aroyl, NHCOalkyl, CHO, C(halogen)3, COOX4, SO3H, PO3H2, SO2NX1X2, CONX1X2, C(O)CF3, alkyl, alcohol, alkoxy, alkylmercapto, alkylamino, di-alkylamino, sulfonamide or thioalkoxy wherein Xi and X2 each independently comprise H or alkyl, or Xi and X2 together comprise part of a heterocyclic ring having about 4 to about 7 ring members and optionally one additional heteroatom selected from 0, N or S, or Xi and X2 together comprise part of an imide ring having about 5 to about 6 members and X4 comprises H, alkyl, loweralkylhydroxy, or alkyl-NXiX2. Unless otherwise specifically limited, a substituent group may be in any possible position or any possible positions if multiply substituted.

[0043] The term “alkyl” is meant to mean straight or branched saturated hydrocarbon groups;

[0044] The term “substituted” means substituted with lower alkyl (C1-4), aryl, alkaryl, alkoxy( C 1-4), halo; additionally the term may also include a hetero atom such as 0 or N interrupting the C1-18 alkyl chain.

[0045] The terms “aromatic” or “aryl” means cyclic conjugated hydrocarbon structures (C 1-12) which may optionally be substituted as the term “substituted” is defined herein;

[0046] The terms “halogen,” “halo” or “hal” when used alone or as part of another group mean chlorine, fluorine, bromine or iodine;

[0047] The term “aliphatic” means saturated or unsaturated, straight, branched or cyclic hydrocarbon groups;

[0048] The term “oligomer” means a defined, small number of repeating monomer units such as 10-25,000 units, and desirably 10-100 units which have been polymerized to form a molecule, and is a subset of the term polymer; the term “polymer” any polymerized product greater in chain length and molecular weight than the oligomer, i.e. or degrees of polymerization greater than 25,000.

[0049] “One or more”, as used herein, relates to at least one and comprises 1 , 2, 3, 4, 5, 6, 7, 8, 9 or more of the referenced species. Similarly, “at least one” means one or more, i.e. 1 , 2, 3, 4, 5, 6, 7, 8, 9 or more. “At least one”, as used herein in relation to any component, refers to the number of chemically different molecules, i.e. to the number ofdifferent types of the referenced species, but not to the total number of molecules. For example, “at least one polyol” means that at least one type of molecule falling within the definition for a polyol is used but that also two or more different polyol types falling within this definition can be present but does not mean that only one type of said polyol is necessarily present.

[0050] NCO content refers to the NCO content as determined according to EN ISO 11909.

[0051] Mine seal means a physical barrier in an underground tunnel which contacts the walls, floor, and / or ceiling of the tunnel in order to prevent access to the tunnel, and which preferably limits or prevents the flow of gases from one side of the seal to the other side.

[0052] The disclosed compounds include any and all isomers and stereoisomers. In general, unless otherwise explicitly stated the disclosed materials and processes may be alternately formulated to comprise, consist of, or consist essentially of, any appropriate components, moieties or steps herein disclosed. The disclosed materials and processes may additionally, or alternatively, be formulated so as to be devoid, or substantially free, of any components, materials, ingredients, adjuvants, moieties, species and steps used in the prior art compositions or that are otherwise not necessary to the achievement of the function and / or objective of the present disclosure.

[0053] The word “about” or “approximately” as used herein in connection with a numerical value refer to the numerical value ± 10%, preferably ± 5% and more preferably ± 1 % or less.

[0054] Unless explicitly indicated otherwise, all percentages that are cited in connection with the compositions described herein refer to weight percent (wt.%) with respect to final composition with all components, unless stated otherwise.

[0055] One aspect of this disclosure is use of a semi-rigid two component (2K) polyurethane foam to seal gaps and openings in mine seals. As used herein a semi-rigid foam when cured exhibits a substantially linear modulus with no inflection point or yield point when compression tested. Inflection points or yield points are positions in the test results that show non-linear changes in the modulus curve. Such inflection points or yield points are indicative of undesirable crack formation in the cured foam sample and also predictive that the sample will not fully recover to its original sample shape and / or size.

[0056] The polyurethane foam is a two component composition comprising separate “A” and “B” reactants. The A and B reactants are stable when stored separately and will react at the end of the storage period. Useful stability can be 6 months under normal commercial storage conditions and preferably 1 year or more preferably 24 months. Once mixed they form a foamable mixture that expands and crosslinks into a closed cell semirigid foam. Single component foams are not desirable for mine sealing use for a number of reasons.

[0057] Foamable mixtures are understood to be compositions containing crosslinkable polymers which undergo a volume expansion after application under the influence of a blowing agent and optionally also by chemical reactions and develop gas-filled cell structures. The foams are stabilized by the solidification of the cured polymers and optionally by added foam stabilizers. The foamable mixtures form reaction products having closed cells distributed throughout their entire mass and having a lower bulk density than the as mixed reactants.

[0058] Typically, the mixed A and B reactants will expand to 500% of the initial mixed volume and more preferably 600 to 1000 % of the initial mixed volume. The mixture will crosslink to a tack free state in about 5 minutes or less. A tack free state is when the mixture is dry to the touch of a wooden probe and no stickiness is felt when removing the wooden probe from the surface of the mixed mass and no material is transferred when the probe is removed from the mixed mass. The mixture will have a self supporting state on a vertical wall surface about 5 seconds to 10 minutes after application and preferably will have no sagging or dripping after application to the vertical wall. Once mixed foaming and curing will start. Foaming can continue in some embodiments for up to 5 minutes but is preferably substantially finished in about 1 minute or less, Curing will continue after foaming has finished. The mixed composition can be considered fully cured once it has achieved at least 80% of its final strength.

[0059] Cured reaction products of this polyurethane foam have a closed cell content of 90% or more when tested by ISO 4590. Cured reaction products of this polyurethane foam have an ASTM E162 flame spread index of 25 or lower.

[0060] In one embodiment the B reactant will comprise a polyisocyanate and a propellant. The B reactant mixture is preferably formulated to have an isocyanate functionality ofgreater than 2. Use of an B reactant mixture having an isocyanate functionality of 2 or less is not likely to provide the desired molecular weight and related strength properties. Naturally, the B reactant mixture will be free of materials that are reactive with isocyanate functionality. The B reactant composition is preferably free of flammable solvent; amines and amides.

[0061] The B reactant mixture is preferably formulated to have a viscosity of not greater than about 300 cps (more preferably, not greater than about 200 cps; most preferably, not greater than about 150 cps) at 25 degrees C.

[0062] In one embodiment the A reactant will comprise a mixture of polyol, a plasticizer, a flame retardant, a surfactant, a catalyst, water and optionally a propellant. The A reactant composition is preferably free of flammable solvent; amines and amides. polyisocyanate:

[0063] Useful polyisocyanate components have an average isocyanate functionality of 2 or more. The known aliphatic or aromatic polyisocyanates typically having a molecular mass of less than 500 g / mol are suitable. Exemplary suitable diisocyanates that can be used are ethylene diisocyanate, 1 ,4-tetramethylene diisocyanate, 1 ,4- tetramethoxybutane diisocyanate, 1 ,6-hexamethylendiisocyanat (HDI), cyclobutane-1 ,3- diisocyanate, cyclohexane-1 ,3- and -1 ,4-diisocyanate, bis(2-isocyanato-ethyl) fumarate, 1 -isocyanato-3,3,5-trimethyl-5-isocyanatomethylcyclohexane (isophorone diisocyanate,I PDI), 2,4- and 2,6-hexahydrotoluylene diisocyanate, hexahydro-1 ,3- or -1 ,4-phenylene diisocyanate, benzidine diisocyanate, naphthalene-1 ,5-diisocyanate, 1 ,6-diisocyanato-2.2.4-trimethylhexane, 1 ,6-diisocyanato-2,4,4-trimethylhexane, xylylene diisocyanate (XDI), tetramethyl xylylene diisocyanate (TMXDI), 1 ,3- and 1 ,4-phenylene diisocyanate,2.4- or 2,6-toluylene diisocyanate (TDI) or isomeric mixtures of the TDI, 2,4'- diphenylmethane diisocyanate, 2,2'-diphenylmethane diisocyanate or 4,4'- diphenylmethane diisocyanate (MDI) as well as their isomeric mixtures. Furthermore, partially or completely hydrogenated cycloalkyl derivatives of the MDIs, come into consideration, for example completely hydrogenated MDI (H12-MDI), alkyl-substituted diphenylmethane diisocyanates, for example mono, di, tri or tetraalkyldiphenylmethane diisocyanate as well as their partially or completely hydrogenated cycloalkyl derivatives.Polyisocyanates having an isocyanate functionality greater than 2, such as “polymeric MDI” obtainable as a distillation residue from the distillation of MDI are also usable. Another embodiment uses asymmetric isocyanates that possess NCO groups with a different reactivity towards diols. Exemplary suitable cycloaliphatic asymmetric diisocyanates are 1 -isocyanato methyl-3-iso-cyanato-1 ,5,5-trimethyl-cyclohexane (isophorone diisocyanate, IPDI), 1 -methyl-2,4-diisocyanato-cyclohexane, 1 ,4- diisocyanato-2,2,6-trimethylcyclohexane (TMCDI), or hydrogenated products of the abovementioned aromatic diisocyanates, for example hydrogenated MDI in isomeric pure form, preferably hydrogenated 2,4'-MDI. Exemplary preferred suitable aromatic asymmetric diisocyanates are 2,4- or 2,6-toluylene diisocyanate (TDI), either in isomeric pure form or as the mixture of a plurality of isomers, naphthalene-1 ,5-diisocyanate (NDI), diphenylmethane-2,4'-diisocyanate (MDI) as well as mixtures of the 4,4'- diphenylmethane diisocyanate with the 2,4'-MDI isomers. Combinations of two or more polyisocyanates are also useful. Aromatic diisocyanates such as MDI, mixed isomers of MDI and polymeric MDI provide the best properties and are preferred. The isocyanate functional reaction products of one or more polyols or polyamines with an excess of polyisocyanate (isocyanate prepolymers) should not be used in the B reactant composition. polyol:

[0064] Polyols include compounds having 2 or more OH groups per molecule. The OH groups may be primary or secondary. In some embodiments the polyols have a molecular weight from about 60 to about 10,000 or more.

[0065] One group of useful polyols are low molecular weight polyols having a molecular weight of 600 or less, preferably about 300 or less and more preferably about 150 or less. Some useful low molecular weight polyols include, for example, aliphatic alcohols having from 2 to 4 OH groups per molecule. Examples of suitable aliphatic alcohols include ethylene glycol, propylene glycol, dipropylene glycol, butane-1 ,4-diol, pentane-1 ,5-diol, hexane-1 ,6-diol, heptane-1 ,7-diol, octane-1 ,8-diol and their higher homologs or isomers such as result in a formal sense from a stepwise extension of the hydrocarbon chain by one CH2 group in each case or with the introduction of branches into thecarbon chain. Likewise suitable are higher polyfunctional alcohols having 3 or more OH functional groups such as, for example, glycerol, trimethylolpropane, pentaerythritol and also oligomeric ethers of said substances with themselves or in a mixture of two or more of said ethers with one another.

[0066] Another group of useful polyols include polyether polyols, for example polyethylene glycol and polypropylene glycol. Polyether polyols can be the reaction products of low molecular weight polyfunctional alcohols with alkylene oxides. The alkylene oxides have preferably 2 to 4 carbon atoms. Suitable examples are the reaction products of ethylene glycol, propylene glycol, the isomeric butanediols, hexanediols or ,4'-dihydroxy-diphenylpropane with ethylene oxide, propylene oxide or butylene oxide, or with mixtures of two or more thereof. Also suitable, furthermore, are the reaction products of polyfunctional alcohols, such as glycerol, trimethylolethane or trimethylolpropane, pentaerythritol, sugars or sugar alcohols, or mixtures of two or more thereof, with the stated alkylene oxides to form polyether polyols. Particularly suitable polyether polyols are those having a molecular weight from about 100 to about 10,000, for example from about 200 to about 5,000 and from about 800 to about 5000. Likewise suitable as the polyol component are polyether polyols such as are formed, for example, from the polymerization of tetrahydrofuran.

[0067] Another group of useful polyols include polyether polyols which have been modified by vinyl polymers. Products of this kind are available, for example, by polymerizing styrene or acrylonitrile, or a mixture thereof, in the presence of polyether polyols.

[0068] Another group of useful polyols include polyester polyols. Polyester polyols can be formed by reacting low molecular weight alcohols, especially ethylene glycol, diethylene glycol, neopentyl glycol, hexanediol, butanediol, propylene glycol, glycerol or trimethylolpropane, with caprolactone. Likewise suitable as polyfunctional alcohols for preparing polyester polyols are 1 ,4-hydroxymethylcyclohexane, 2-methyl-1 ,3- propanediol, butane-1 ,2,4-triol, triethylene glycol, tetraethylene glycol, polyethylene glycol, dipropylene glycol, polypropylene glycol, dibutylene glycol and polybutylene glycol.

[0069] Further suitable polyester polyols are preparable by polycondensation. For instance, difunctional and / or trifunctional alcohols can be condensed with a sub stoichiometric amount of dicarboxylic acids and / or tricarboxylic acids, or their reactive derivatives, to form polyester polyols. Examples of suitable dicarboxylic acids are adipic acid or succinic acid and their higher homologs having up to 16 carbon atoms, unsaturated dicarboxylic acids such as maleic acid or fumaric acid, and also aromatic dicarboxylic acids, particularly the isomeric phthalic acids, such as phthalic acid, isophthalic acid or terephthalic acid. Examples of suitable tricarboxylic acids are citric acid or trimellitic acid. These acids may be used individually or as mixtures of two or more thereof. Particularly suitable in the context of the invention are polyester polyols formed from at least one of said dicarboxylic acids and glycerol which have a residual OH group content. Other suitable alcohols are hexanediol, ethylene glycol, diethylene glycol or neopentyl glycol or mixtures of two or more thereof.

[0070] In one embodiment the polyester polyols have a molecular weight from about100 to about 10,000. Polyester polyols of such molecular weight include, for example, the reaction products of polyfunctional alcohols, preferably difunctional alcohols (together where appropriate with small amounts of trifunctional alcohols) and polyfunctional carboxylic acids, preferably difunctional carboxylic acids. Instead of free polycarboxylic acids use may also be made (if possible) of the corresponding polycarboxylic anhydrides or corresponding polycarboxylic esters with alcohols having preferably 1 to 3 carbon atoms. The polycarboxylic acids may be aliphatic, cycloaliphatic, aromatic or heterocyclic or both. They may where appropriate be substituted, by alkyl groups, alkenyl groups, ether groups or halogens, for example. Examples of suitable polycarboxylic acids include succinic acid, adipic acid, suberic acid, azelaic acid, sebacic acid, phthalic acid, isophthalic acid, terephthalic acid, trimellitic acid, phthalic anhydride, tetrahydrophthalic anhydride, hexahydrophthalic anhydride, tetrachlorophthalic anhydride, endomethylenetetrahydrophthalic anhydride, glutaric anhydride, maleic acid, maleic anhydride, fumaric acid, dimer fatty acid or trimer fatty acid or mixtures of two or more thereof. Where appropriate, minor amounts of monofunctional fatty acids may be present in the reaction mixture.

[0071] The polyester polyols may, where appropriate, contain a small fraction of carboxyl end groups. Polyester polyols obtainable from lactones, 6-caprolactone for example, or hydroxy-carboxylic acids, co-hydroxycaproic acid for example, may likewise be used.

[0072] Another group of useful polyols include polyacetal polyols and polyester ether polyols. Polyacetal polyols are compounds obtained from glycols reacted with aldehydes, for example, diethylene glycol or hexanediol or a mixture thereof condensed with formaldehyde. Polyacetal polyols can also be obtained by the polymerization of cyclic acetals.

[0073] Another group of useful polyols include polycarbonate polyols. Polycarbonate polyols can be obtained, for example, by reacting diols, such as propylene glycol, butane- 1 ,4-diol or hexan-1 ,6-diol, diethylene glycol, triethylene glycol or tetraethylene glycol, or mixtures of two or more thereof, with diaryl carbonates, for example, diphenyl carbonate, or phosgene.

[0074] Another group of useful polyols include polyacrylates which have OH groups. These polyacrylates are obtained, for example, by polymerizing ethylenically unsaturated monomers which carry an OH group. Monomers of this kind are obtainable, for example, by esterifying ethylenically unsaturated carboxylic acids and difunctional alcohols, the alcohol generally being present in a slight excess. Examples of ethylenically unsaturated carboxylic acids suitable for this purpose are acrylic acid, methacrylic acid, crotonic acid or maleic acid. Corresponding esters carrying OH groups are, for example, 2- hydroxyethyl acrylate, 2-hydroxyethyl methacrylate, 2-hydroxypropyl acrylate, 2- hydroxypropyl acrylate, 2-hydroxypropyl methacrylate, 3-hydroxypropyl acrylate or 3- hydroxypropylmethacrylate or mixtures of two or more thereof.Propellant:

[0075] Flammable propellants such as propane have been used in polyurethane foams. Flammable propellants are undesirable for preparing mine sealings as they introduce flammable gas into the mine and increase fire hazard. Hydrofluorocarbon (HFC) propellants such as in the Freon family have been used in various foams. HFC propellants are undesirable as they contribute to global warming, are legislatively bannedin some countries and can be extremely expensive. Potential low Global Warming Potential (GWP) replacements for hydrofluorocarbon blowing agents include hydrofluoroolefin (HFO) blowing agents. In one embodiment the Solstice® Gas Blowing agent (GBA, HFO-1234ze, trans 1 ,3, 3, 3 tetrafluoropropene) produced by Honeywell has been proposed as a blowing agent for low pressure systems. Attractive properties of HFO-1234ze include a low boiling point (-19° C.) and favorable kauri-butanol solubility (12.5 compared to 9.2 for HFC-134a). In addition, HFO-1234ze has an ODP of zero, is volatile organic carbon (VOC) exempt, and has a GWP of less than 1 due in part to its low atmospheric lifetime ("18 days) compared with HFC-134a (13.4 years). Another option is use of HFO-1234zd liquid blowing agent. Attractive properties of HFO-1234zd include a boiling point (19° C.) and also has an ODP of zero. For higher viscosity compositions such as the A reactant a combination of the HFO liquid blowing agent and HFO gas blowing agent may be better suited for forcing the composition out of a container and expanding that composition. For low viscosity compositions such as the B reactant use of only the gas HFO blowing agent may be sufficient.

[0076] Although HFO blowing agents like HFO-1234ze meet requirements for the Kyoto Protocol (GWP<150)and are cleared for use under SNAP 21 , the short lifespan of the molecule has led to challenges with the product shelf life of foam systems. Two component foam systems contain A-side (isocyanate) and B-side (resin) components stored separately under pressure. Both contents require propellants to fully dispense these mixtures. HFO-1234ze and other HFO blowing agents tend to break down and interact with moieties in the B-side. HFO molecules are believed to react with amine catalysts, for example, via nucleophilic substitution. This reaction is believed to produce hydrofluoric acid, which in turn attack surfactants and polyols. Such phenomenon has been observed via nuclear magnetic resonance (NMR) and gas chromatography-mass spectrometry. These undesirable reactions yield a significant reduction in foam properties, particularly gelation and tack-free times, foam appearance, cell structure, and mechanical properties among others. Consequently, a simple 1 :1 substitution of an HFC blowing agent with an HFO blowing agent in a polyurethane foam system can reduce shelf life from one year or greater to a commercially unusable life of weeks or days. Therefore, replacement of one propellant with an HFO propellant is not a simple matterand conventional spray foam systems based on HFCs must undergo modifications in order to meet the demand of shelf life stability and superior foam properties. Any formulated HFO propellant adhesive must emulate the spray characteristics and general physical properties of the current-HFC blown two-component products currently on the market while maintaining commercially acceptable storage stability.Flame retardant:

[0077] The composition will typically comprise one or more flame retardants. The flame retardant can be selected from the group of the halogenated (especially brominated) ethers of the "Ixol" type from the Solvay company; 3,4,5,6-tetrabromo-, 2-(2- hydroxyethoxy)ethyl-2-hydroxypropyl ester); organic phosphates such as diethyl ethane phosphonate, triethyl phosphate, dimethyl propyl phosphonate, diphenyl cresyl phosphate; chlorinated phosphates such as tris-(2-chloroethyl)phosphate, tris-(2- chloroisopropyl)phosphate, tris(1 ,3-dichloroisopropyl)phosphate, tris(2,3- dibromopropyl)phosphate and tetrakis(2-chloroethyl)ethylene diphosphate or their mixtures. It is preferable to select flame retardants that do not possess hydroxyl groups to avoid interaction of the flame retardant with reactive NCO groups of the polyisocyanate. Solid flame retardant materials are preferably not used.Catalyst:

[0078] The composition will preferably also comprise one or more polymer cure catalysts. Some useful catalyst compounds include titanates such as tetrabutyl titanate and tetrapropyltitanate; tin carboxylates such as dibutyltin dilaurate (DBTL), dibutyltin diacetate, tin octoate; tin oxides such as dibutyltin oxide, and dioctyltin oxide; organoaluminum compounds such as aluminum trisacetylacetonate, aluminum trisethylacetoacetate; chelate compounds such as titanium tetra acetylacetonate; amine compounds such as triethylenediamine, guanidine, diphenylguanidine, 2,4,6- tris(dimethylaminomethyl)phenol, morpholine, N-methylmorpholine, 2-ethyl-4- methylimidazole, and 1 ,8-diazabicyclo-(5,4,0)-undec-7-ene (DBU), 1 ,4- diazabicyclo[2,2,2]octane, N,N-dimethylpiperazine, 1 ,8-diazabicyclo[5.4.0]undec-7-ene, dimorpholinodimethyl ether, dimorpholinodiethyl ether (DMDEE) or their mixtures.Blowing agent:

[0079] The composition will comprise one or more blowing agents. The blowing agent forms a gas when part A and part B are mixed that helps form the mixture into a foam. Solid blowing agents such as azides that decompose to a gas when heated are not useful in this application as there is insufficient heat during application. Liquid blowing agents that form a gas during mixing can be used. One useful blowing agent is water.Additives:

[0080] The composition according to the invention can also optionally comprise additives that are known for foam production as the foam precursor. These can be for example plasticizers, stabilizers, adhesion promoters, catalysts, biocides, cell stabilizers, similar adjuvants and combinations thereof. In such a case it is advantageous to maintain as low as possible the fraction of ingredients that are not reacted in the polymer, such as plasticizers or solvents. In some embodiments one or more of these additives may be avoided.

[0081] Stabilizers are understood to mean antioxidants, UV-stabilizers, hydrolysis stabilizers or foam stabilizers. Examples of these are the commercial sterically hindered phenols and / or thioethers and / or substituted benzotriazoles and / or amines of the HALS type (Hindered Amine Light Stabilizer). It is preferred if a UV stabilizer is employed that carries a silane group and becomes attached to the end product during crosslinking or curing. Furthermore, benzotriazoles, benzophenones, benzoates, cyanoacrylates, acrylates or sterically hindered phenols can also be added.

[0082] Exemplary foam stabilizers are polyether siloxanes, such as copolymers of ethylene oxide and propylene oxide bonded to a polydimethylsiloxane group, polysiloxane-polyoxyalkylene copolymers branched through allophanate groups, other organopolysiloxanes, such as dimethylpolysiloxanes; oxyethylated alkylphenols, oxyethylated fatty alcohols, and / or paraffin oils. Furthermore, for improving the emulsifying action, the cell structure and / or stabilization, oligomeric polyacrylates containing polyoxyalkylene and fluoroalkane groups as the side chain groups are suitable.

[0083] Organofunctional silanes, such as hydroxy-functional, (meth)acryloxy-functional, mercapto-functional, amino-functional or epoxy-functional silanes can optionally be used as adhesion promoters.Compositions:

[0084] Developing a two component, semi-rigid, closed cell foam composition having acceptable reactant viscosities and cured foam flexibility, good adhesion, and low shrinkage is difficult. Long chain higher molecular weight polyols favor flexibility of the cured foam. However, such polyols have a high viscosity and are difficult to dispense and mix at the proper ratio with polyisocyanates. Shrinkage is affected by the isocyanate to polyol ratio; the choice of gelling catalyst, the choice of blowing catalyst, the amount of blowing catalyst; presence of cell opener, cell stabilizer and surfactant, amount of heat generated when part A and part B are mixed. Different propellants have different chemical structures and different compatibilities with the other components in part A and part B so a drop in change from one composition component such as propellant to another with no other changes is not usually possible.

[0085] In one embodiment the A reactant will comprise a mixture of different polyols, for example a polyether polyol having a molecular weight of 800 or more, a polyether polyol having a molecular weight of 600 or less and a polyester polyol having a molecular weight of 200 to 5000. The high molecular weight polyether polyol provides the cured foam with flexibility while the lower molecular weight polyether polyol reduces the viscosity of the A reactant. The polyester polyol enhances structural integrity of the cured foam. The polyols are in a ratio of polyester polyol : polyether polyol of 1 :4 to 4:1 , more preferably 1 :3 to 3:1 to balance properties of the cured foam.

[0086] In some embodiments the following A reactant compositions are useful. Amounts are in wt.% by weight of the A reactant composition.Propellant also served as a blowing agent for this embodiment. Propellant is added to the mixed A reactant composition in an amount of 2 - 40%, preferably 5-40% by weight of mixed A reactant composition.In some embodiments the following A reactant compositions are useful. Amounts are in wt.% by weight of the A reactant composition.the mixed A reactant composition in an amount of 2 - 40%, preferably 5-40% by weight of mixed A reactant composition.

[0091] In some embodiments the following B reactant compositions are useful.Amounts are in wt.% by weight of the B reactant composition.Propellant can be added to the mixed part B composition. Propellant also served as a blowing agent for this embodiment. Propellant is added to the mixed B reactant composition in an amount of 0 - 45%, preferably 2-35% by weight of mixed A reactant composition.

[0087] The A and B reactants should have a number of properties for successful application as a mine sealant. The separate components should be stable during storage for 6 months to 24 months or more. The A reactant should have a viscosity of 50 to 2,000 cps, preferably 50-500 ops and more preferably 50-300cps at 25°C and the B reactant should have a viscosity of not greater than about 500 cps, preferably not greater than about 300 cps; and more preferably 50 - 150 cps at 25°C to provide ease of mixing and flow through application equipment.

[0088] The A and B reactants are each packaged separately in a pressurizable container and stored separately. Each container can be pressurized with an inert gas, such as dried nitrogen to help with dispensing. Typically, the containers are pressurized to 100to 300 psi. During use, each part is separately connected via a feed hose to a handheld trigger and mixing nozzle. When the trigger is pressed the A composition and B composition separately flow under pressure to the nozzle where they are mixed and expelled from the nozzle onto a surface. Once the two parts are mixed foaming and a curing reaction are started. Since the containers and feed hose are separate there is no mixing of the A and B reactants or curing in these areas allowing reuse. The nozzle is replaceable so if cured material impedes flow the nozzle can be replaced. The mixed composition sets up to a non-movable gel or solid in minutes and fully cures within 24 hours.

[0089] The ratio of part A composition to part B composition is predetermined by the chemical compositions of part A and part B and / or by the dispensing equipment. In preferred embodiments the weight ratio of part A to part B is in the range of 1 : 2 to 2 : 1 and preferably about 1 : 1. This should provide an isocyanate to OH functionality ratio of 1.0 : 1 to 1.8 : 1 and preferably 1 .1 : 1 to 1 .6 : 1 .

[0090] In preferred embodiments the composition can have one or more of the following properties for use as a mine sealant. The A reactant and B reactant can each have a suitably low viscosity to allow ease of flow from the storage tank through the mix equipment and to encourage adequate mixing of the two reactants. The mixed reactants when sprayed onto a generally vertical wall can foam in place with little observable sagging or dripping from the application point The cured foam can have minimal shrinkage to allow the cured foam to form a seal lessening or preventing movement of air, gas and dust through the seal. The cured foam can have a substantially linear modulus with no inflection point or yield point to provide a semi-rigid foam. This allows the cured foam seal to withstand movement of the support structure with no cracking. The cured foam can have a linear modulus of 0.1 to 0.5, preferably 0.15 to 0.5. The cured foam can have an ASTM E162 flame spread of 25 or less, preferably 20 or less so as to limit combustibility of the cured foam seal in the event of a mine fire.

[0091] The following examples are included for purposes of illustration so that the disclosure may be more readily understood and are in no way intended to limit the scope of the disclosure unless otherwise specifically indicated.Measurement of viscosity

[0092] Viscosity was tested using a Brookfield viscosimeter with a #27 spindle at 5 - 10 rpm and 25 °C.Measurement of tack free time

[0093] Parts A and B were mixed. The mixed composition was gently touched with a wood probe. The time when there was no mixed composition transferred to the probe was recorded as the tack free time.

[0094] Measurement of flame spreadCured reaction products of the mixed A and B parts were tested for flame spread according to ASTM E162.

[0095] Measurement of Compression ForceCompression testing was done following ASTM D3574. Briefly, a 8 mm diameter steel rod is push into the foam sample at a rate of 1 mm per second to a depth of 5mm. The force at each depth is measured and recorded.

[0096] Measurement of Foam Cracking During CompressionAny discontinuity or drop in the force reading in the Compression test graph is indicative of a crack forming in the foam sample. See the small drop areas for Sample D in Figures 1 and 2.

[0097] Measurement of Foam ShrinkageSpray a sample of mixed A and B reactants into a transparent cup and measure height at full cure, which happens in about 2 minutes. Wait 24 hours and take a second height measurement. A slight change is 5%. Anything less than 10% is acceptable.

[0098] Measurement of modulusModulus is calculated from the compression data.Example 1A 2 component curable composition was prepared as shown below. The components of each part are added to that part and mixed. All amounts have been rounded to one decimal place.1. Polyether polyol, mixture of Multranol 4012 and Arcol PPG-1000 from Covestro AG at 5:12 ratio2. Polyester polyol, mixture of Voranol 360 from Dow Chemical, and Terate 5350 from Stepan Company at 8:6 ratio3. polyol, Saytex RB-9170 from Albermarie4. Flame retardant, mixture of Levagard TEP-Z from Lanxess and TCPP from M Chemical at 10:30 ratio5. Catalyst, mixture of DABCO TMR-20, DABCO T-120, Polycat 204 from Evonik at 2: 1.5:1 ratio.6. Surfactant, Vorasurf DC193 from Dow1 Mondur MR-light2 TCPPParts A and B were separately placed in pressurized containers. The components were sprayed at a 1 : 1 weight ratio onto a surface to form a sample. The sample was allowed to cure at room temperature for 24 hours.Example 2A 2 component curable composition was prepared as shown below. The components of each part are added to that part and mixed. All amounts have been rounded to one decimal place.1. Polyether polyol, mixture of Multranol 4012 and Arcol PPG-1000 from Covestro AG at 5 to 12 ratio2. Polyester polyol, mixture of Voranol 360 from Dow Chemical, and Terate 5350 from Stepan Company at 8 to 6 ratio3. Flame resistant polyol, Saytex RB-9170 from Albermarie4. Flame retardant, mixture of Levagard TEP-Z from Lanxess and TCPP from M Chemical at 11 :35 ratio5. Catalyst package, mixture of DABCO TMR-20, DABCO T-120, Polycat 204 from Evonik at 1 :1 .5:1 ratio6. Surfactant, Vorasurf DC193 from Dow1 Mondur MR-light2 TCPPParts A and B were separately placed in pressurized containers. The components were sprayed at a 1 : 1 weight ratio onto a surface to form a sample. The sample was allowed to cure at room temperature for 24 hours.

[0099] Samples of inventive foams 1 and 2 and four comparative samples were tested. The results are shown below and in Figures 1 and 2.2 comparative sample B is TITE foam big gap 1 K polyurethane foam from Henkel Corporation.3 comparative sample C is Silent Seal 2K foam from ICP Building Solutions Group4 comparative sample D is Tiger Foam 2Kfoam from Commercial Thermal Solutions, Inc.

[0100] Compression testing clearly shows the difference between a flexible foam vs a hard foam. As shown in Figure 1 , cured samples of four commercially available foams were tested. Samples A and B are one component spray foams. The one component spray foam typically showed desirable flexibility when cured. This is believed due to a longer polymer chain and lower crosslink density.

[0101] Samples C and D are commercially available two component hard spray foams. Two component foams cure to a hard state and both samples C and D exhibited the typical two component foam hardness.

[0102] Figure 1 shows two significant differences in cured samples of these commercially available foams. Samples A and B are one component spray foams. Samples C and D are commercial 2 component hard spray foams sold for mine seal use. One component foam samples A and B show a lower slope suggesting they have a lower modulus than two component foam samples C and D. Secondly foam samples A and B show a smooth, generally linear curve through the compression test, while both of foam samples C and D exhibit bends and dips in the curve. The bends and dips indicate discontinuities and cracks in the cured foam sample during compression testing.

[0103] Comparative example B, a one component spray foam, showed desirable flexibility due when cured. However, the uncured composition has a viscosity too high to use in a 2 component spray foam for mine seal use. Comparative sample C and comparativesample D are commercially available two component spray foams used to make mine seals. Both of these samples show a high modulus and irregular compression curves indicating crack formation in the cured foam.

[0104] Figure 2 shows compression test results for Examples 1 and 2 and commercially available samples B (TITE foam big gap) and D (Tiger foam). Examples 1 and 2 show a lower modulus and a smooth curve, indicating few or no cracks in the cured foam. Cured foam of comparative example B, a one component spray foam, showed desirable flexibility when cured. However, the uncured composition has a viscosity too high to use in a two component spray foam for mine seal use. Cured foam of sample D again shows a high modulus and irregular compression curves indicating crack formation in the cured foam.

[0105] Examples 1 and 2 have a low viscosity suitable for use as a two component foam. Cured samples of Examples 1 and 2 are soft and resilient. Compression tests of Examples 1 and 2 show a low modulus as well as a smooth curve, indicating few or no cracks in that cured foam sample. Examples 1 and 2 exhibit properties superior to commercially available products for two component mine seal use.

Claims

WHAT IS CLAIMED:1 . A two component, reactive composition for producing a mine seal, comprising an A composition and a B composition: the A composition comprising: polyether polyol; polyester polyol; flame retardant; blowing agent; propellant; and optionally comprising catalyst; surfactant; and additives; wherein the polyether polyol and polyester polyol have a ratio of 1 :4 to 4:1 ; and the B composition comprising: polyisocyanate; propellant; and optionally flame retardant and additives; wherein mixing the A composition and B composition initiates a cure reaction and cured reaction products of the mixture has an ASTM E162 flame spread of 25 or less and a substantially linear modulus with no substantial inflection point or yield point to provide a semi-rigid foam.

2. The two component, reactive composition for producing a mine seal of claim 1 , wherein the A composition has a viscosity of 50 to 2,000 cps, preferably 50-500 cps and more preferably 50-300 cps at 25°C and / o the B reactant has a viscosity of not greater than about 500 cps, preferably not greater than 300 cps and more preferably 50-150 cps at 25°C.

3. The two component, reactive composition for producing a mine seal of claim 1 or 2, wherein A composition and the B composition are mixed at a weight ratio of 1 :2 to 2:1.

4. The two component, reactive composition for producing a mine seal of any one of claims 1 to 3, wherein A composition and the B composition are mixed at an isocyanate functionality : OH functionality of 1 .0:1 to 1 .8 : 1 , preferably 1.1 : 1 to 1.6:1.

5. The two component, reactive composition for producing a mine seal of any one of claims 1 to 4, wherein cured reaction products of the mixed A composition and B composition have a modulus of 0.1 to 0.5, preferably 0.15 to 0.3.

6. The two component, reactive composition for producing a mine seal of any one of claims 1 to 5, wherein cured reaction products of the mixed A composition and B composition have a compression force of 1600 grams or less.

7. The two component, reactive composition for producing a mine seal of any one of claims 1 to 6, wherein the A composition comprises 0-20% low molecular weight polyol; 10-80% polyether polyol; 1 -25% polyester polyol; 10-70% flame retardant; 1-5% catalyst; 10-30% blowing agent and 15-25% propellant, the amounts being wt.% and equaling 100 for the A composition and / or the B composition comprises 60-100% polyisocyanate; 0-40% flame retardant and 1-15% propellant, the amounts being wt.% and equaling 100 for the B composition.

8. The two component, reactive composition for producing a mine seal of any one of claims 1 to 7, wherein the B composition polyisocyanate comprises polymeric MDI.

9. Cured reaction products of the two component, reactive composition for producing a mine seal of any one of claims 1 to 8.

10. Use of the two component, reactive composition of any one of claims 1 to 8 to form a mine seal.

11. A method of sealing a shaft in a mine, comprising: identifying the shaft to be sealed; building a support across the shaft to be sealed; providing an A composition comprising: polyether polyol; polyester polyol; flame retardant; blowing agent; propellant; and optionally comprising catalyst; surfactant; and additives;wherein the polyether polyol and polyester polyol have a ratio of 1 :4 to 4:1 ; and providing a B composition comprising: polyisocyanate; propellant; and optionally flame retardant and additives; mixing the A composition and B composition as they move through a nozzle to initiate a cure reaction in the mixture; spraying the mixture over the support; expanding the mixture over the support to seal gaps in the support and minimize movement of air, gas or dust through the support; and curing the mixture, wherein cured reaction products of the mixture have an ASTM E162 flame spread of 25 or less and a substantially linear modulus with no inflection point or yield point to provide a semi-rigid foam.

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