Adhesive composition including a polyurethane and isocyanate and related articles and methods

Abstract

An adhesive composition includes a polyurethane with a backbone containing a polyester and 4,4'-diphenylmethane units. The polyurethane has a number average molecular weight of at least 35,000 grams per mole. The adhesive composition further includes a multifunctional isocyanate having at least two isocyanate functional groups. Articles including the adhesive composition or a reaction product thereof such as a belt of flexible sheet material having two ends adhered together with the adhesive composition or a reaction product thereof are also disclosed. Methods of making and using the articles such as a belt, and a method of making the adhesive composition are also disclosed.

Description

[0001] PA102115W002

[0002] ADHESIVE COMPOSITION INCLUDING A POLYURETHANE AND ISOCYANATE AND

[0003] RELATED ARTICLES AND METHODS

[0004] Cross-Reference to Related Application

[0005] This application claims priority to U.S. Provisional Application No. 63 / 683,068, filed August 14, 2024, the disclosure of which is incorporated by reference in its entirety herein.

[0006] Background

[0007] Flexible abrasive articles are available in a wide variety of forms such as endless abrasive belts, tubes, sleeves, discs, and discrete sheets. An endless belt is typically fabricated by joining two free ends of an abrasive sheet together to form a joint, also known as the splice. In some constructions, the splice is held together by a splice adhesive applied to each of the two free ends and optionally splice media overlying the line of juncture and bonded to the splice adhesive.

[0008] These endless abrasive belts are often subjected to rigorous grinding conditions involving high temperatures, such as 200 °C, and high grinding pressures, such as 10 kg / cm2. The splice must be able to withstand such severe grinding conditions so that the abrasive belt remains intact. Thus, the splice adhesive and splice media, if present, each must be sufficiently heat resistant and tough to prevent a failure from occurring at the splice site before it happens in other areas of the abrasive article under severe grinding conditions. If either the splice adhesive or splice media cannot withstand such severe conditions, the splice will break or rupture. This breakage will end the useful life of the abrasive belt and full utilization of the abrasive belt is not achieved.

[0009] In a lap joint, the ends of a segment of coated abrasive material forming the belt overlie, or lap, one another. These overlying ends, or at least one of them, is usually tapered so as to provide a joint approximating the thickness of the coated abrasive material. Moreover, in most cases the abrasive ends are backrubbed to provide for better adhesion. Butt joints, on the other hand, are formed by butting together two free ends or the like of coated abrasive material and thereafter securing these ends together in some fashion, usually by means of an adhesive and, optionally, splice media.

[0010] Polyurethane splice adhesives are described, for example, in U.S. Pat. Nos. 3,763,604 (Malloy), 4,027,435 (Malloy), and 5,595,804 (Korbel). Korbel reports a splice adhesive made from an adhesive obtained from Miles, Inc., under the trade designation “DESMOCOLL 176”, which is an adipic acid / ethylene glycol / polyester, toluene diisocyanate reaction product having hydroxyl functionality.

[0011] Summary

[0012] The present disclosure provides an adhesive composition useful, for example, as a splice adhesive. The adhesive composition includes a polyurethane with a backbone containing a polyester and 4,4 ’-diphenylmethane units, the polyurethane having a number average molecular weight of at least 35,000 grams per mole. Advantageously, and unexpectedly, the adhesive composition can provide more durable belt splices than those including polyurethanes made from toluene diisocyanate and polyurethanes having lower number average molecular weights. The present disclosure further relates to a flexible belt having free ends joined with the adhesive composition.

[0013] In one aspect, the present disclosure provides an adhesive composition that includes a polyurethane with a backbone containing a polyester and 4,4’ -diphenylmethane units. The polyurethane has a number average molecular weight of at least 35,000 grams per mole. The adhesive composition further includes a multifunctional isocyanate having at least two isocyanate functional groups.

[0014] In another aspect, the present disclosure provides an article including the adhesive composition or a reaction product thereof. In some embodiments, the article is an abrasive article.

[0015] In another aspect, the present disclosure provides a belt of flexible sheet material having two ends adhered together with the adhesive composition or a reaction product thereof. In some embodiments, flexible sheet material includes a backing and abrasive grains adhered to the backing.

[0016] In another aspect, the present disclosure provides a process for making the aforementioned belt. The process includes applying the adhesive composition to at least one of the two ends and adhering the two ends together with the adhesive composition.

[0017] In another aspect, the present disclosure provides the use of the adhesive composition as a splice adhesive.

[0018] In another aspect, the present disclosure provides a process for making the adhesive composition. The process includes combining the polyurethane and the multifunctional isocyanate. Before combining, the polyurethane has hydroxyl functional groups.

[0019] In another aspect, the present disclosure provides a method of abrading a workpiece. The method includes providing an article or belt described above, frictionally contacting at least a portion of the abrasive particles with at least a portion of a surface of the workpiece, and moving the workpiece and the abrasive article relative to each other to abrade at least a portion of the surface.

[0020] In this application, terms such as "a", "an" and "the" are not intended to refer to only a singular entity but include the general class of which a specific example may be used for illustration. The terms "a", "an", and "the" are used interchangeably with the term "at least one". The phrases "at least one of and "comprises at least one of followed by a list including the conjunction “or” refers to any one of the items in the list and any combination of two or more items in the list. All numerical ranges are inclusive of their endpoints and integral and non-integral values between the endpoints unless otherwise stated (e.g. 1 to 5 includes 1, 1.5, 2, 2.75, 3, 3.80, 4, and 5). It will be understood that the terms “consisting of ’ and “consisting essentially of’ are subsumed in the term “comprising,” and “comprising” can be replaced with “consisting of’ in any instance herein.

[0021] The term "polymer" refers to a molecule having a structure which includes the multiple repetition of units derived, actually or conceptually, from one or more monomers. The term “monomer” refers to a molecule of low relative molecular mass that can combine with others to form a polymer. The term “polymer” includes homopolymers and copolymers, as well as homopolymers or copolymers that may be formed in a miscible blend, e.g., by coextrusion or by reaction. The term “polymer” includes random, block, graft, and star polymers. The term “polymer” encompasses oligomers.

[0022] A “monomer unit” of a polymer or oligomer is a segment of a polymer or oligomer derived from a single monomer.

[0023] The terms "cure" and “curable” in the present disclosure refer to joining polymer chains together by covalent chemical bonds, usually via crosslinking molecules or groups, to form a network polymer. Therefore, in this disclosure the terms “cured” and “crosslinked” may be used interchangeably. A cured or crosslinked polymer is generally characterized by insolubility but may be swellable in the presence of an appropriate solvent.

[0024] The above summary of the present disclosure is not intended to describe each disclosed embodiment or every implementation of the present disclosure. The description that follows more particularly exemplifies illustrative embodiments. It is to be understood, therefore, that the following description should not be read in a manner that would unduly limit the scope of this disclosure.

[0025] Brief Description of the Drawings

[0026] FIG. 1 is a perspective view of an embodiment of the present disclosure in the form of an endless coated abrasive belt;

[0027] FIG. 2 is a perspective view of the back side of another embodiment of the present disclosure in the form of a coated abrasive article having a butt splice;

[0028] FIG. 3 is a sectional view of another embodiment of the present disclosure in the form of a coated abrasive article having a butt splice;

[0029] FIG. 4 is a sectional view of yet another embodiment of the present disclosure in the form of a coated abrasive article having a lap splice; and

[0030] FIG. 5 is a sectional view of yet another embodiment of the present disclosure in the form of a nonwoven abrasive article having a butt splice.

[0031] While the above-identified drawings and figures set forth embodiments of this disclosure, other embodiments are also contemplated, as noted in the Detailed Description. In all cases, this disclosure presents the invention by way of representation and not limitation. It should be understood that numerous other modifications and embodiments can be devised by those skilled in the art, which fall within the scope of this disclosure. The figures may not be drawn to scale.

[0032] Detailed Description

[0033] The adhesive composition includes a polyurethane with a backbone comprising a polyester and 4,4 ’-diphenylmethane units. More particularly, the polyurethane comprises the reaction product of a polyester polyol and a polyisocyanate. The polyester polyol may comprise the reaction product of a polyol, for example, a diol, and a polyacid, for example, a dicarboxylic acid. The reaction product is typically obtained by esterifying and polymerizing the polyacid and the polyol, for example, by heating for a few hours with removal of the water formed during the reaction. Examples of suitable diols and diacids include neopentyl glycol, ethylene glycol, propylene glycol, 1,4-butanediol, 1,6-hexanediol, adipic acid, orthophthalic acid, isophthalic acid, and terephthalic acid. Other diols and diacids may be useful, for example, those having 2 to 10 methylene groups.

[0034] In some embodiments, the polyester comprises alkylene groups between ester functional groups, wherein the alkylene groups independently have not more than four carbon atoms. In some embodiments, the polyester comprises alkylene groups between ester functional groups, wherein the alkylene groups independently have not more than 5 carbon atoms in a straight chain. In these embodiments, the polyester tends to have lower crystallinity than polyesters having more than 5 carbon atoms in a straight chain.

[0035] In some embodiments, the polyester polyol useful for making the polyurethane comprises the reaction product of ethylene glycol, neopentyl glycol, orthophthalic acid, and adipic acid. In some embodiments, the polyester polyol useful for making the polyurethane comprises the reaction product of ethylene glycol and adipic acid. Examples of commercially available polyester polyols such as these include those available under the trade designations “DYNACOLL 7110” and “DYNACOLL 7111” from Evonik Corporation, Essen, Germany, polyethylene adipate) polyol with hydroxyl number of 56 obtained under the trade designation “FOMREZ 22-56” from Lanxess, Cologne, Germany, and polyethylene adipate) polyol obtained under the trade designation “STEPANPOL PC-101P-55” from Stepan Company, Northfield, IL, USA.

[0036] In some embodiments, the polyester polyol has a number average molecular weight (Mn) of at least 500 grams per mole (g / mol), in some embodiments, between about 800 g / mol to 10000 g / mol or between 1000 g / mol and 7500 g / mol. If the Mn is below 500 g / mol or above 10000 g / mol, the resultant polyurethane may lack sufficient cohesive strength. In some embodiments, the Mn of the polyester polyol is at least 500 g / mol, 800 g / mol, or 1000 g / mol. In some embodiments, the molecular weight of the polyester polyol is not more than 4000 g / mol, 3000 g / mol, 2500 g / mol, or 1000 g / mol.

[0037] The polyurethane in the adhesive composition of the present disclosure includes 4,4’- diphenylmethane units, which arise from the reaction of diphenylmethane 4,4'-diisocyanate (MDI) with the polyester polyol. Other polyisocyanates which may be useful in combination with MDI to react with the polyester polyol include diphenylmethane-2,4'-diisocyanate, tolylene-2,4-diisocyanate, tolylene-2,6- diisocyanate, naphthylene- 1,5 -diisocyanate, triphenylmethane-4,4',4"-triisocyanate, phenylene-1,3- diisocyanate, phenylene- 1,4-diisocyanate, dimethyl-3,3'-biphenylene-4,4'-diisocyanate, diphenylisopropylidine-4,4'-diisocyanate, biphenylene diisocyanate, xylylene- 1,3-diisocyanate, and xylylene-l,4-diisocyanate. In some embodiments, the polyurethane is free of units of tolylene-2,4- diisocyanate, tolylene-2,6-diisocyanate, phenylene-l,3-diisocyanate, phenylene-l,4-diisocyanate, xylylene-l,3-diisocyanate, and xylylene- 1,4-diisocyanate. In some embodiments, at least 90 mole percent (mol%), at least 95 mol%, at least 97 mol%, at least 98 mol%, at least 99 mol%, at least 99.5 mol% or 100 mol% of the units in the polyurethane arising from polyisocyanates are 4,4 ’-diphenylmethane units.

[0038] Isocyanate -functional derivative(s) of MDI may be used, such as liquid mixtures of the MDI with melting point modifiers (e.g., mixtures of MDI with polycarbodiimide adducts such as that obtained under the trade designation “ISONATE 143L”, from Dow Chemical Company, Midland, MI, USA) and an MDI-polyester prepolymer obtained under the trade designation “RUBINATE 1234” from Huntsman Corporation, The Woodlands, TX, USA.

[0039] In some embodiments of the polyurethane useful for the adhesive composition of the present disclosure, at least 75 mol% of the segments between oxygen atoms of two carbamate functional groups have a molecular weight of at least 500 g / mol. Such segments are represented by R in the general structure shown below. In some embodiments of the polyurethane useful for the adhesive composition of the present disclosure, at least 80, 85, 90, or 95 mol% of the segments between oxygen atoms of two carbamate functional groups have a molecular weight of at least 500 g / mol. In other words, the materials used to prepare the polyurethane include a low level of monomeric or low-molecular-weight diols, which are also referred to as chain extenders. In some embodiments, the materials used to prepare the polyurethane include no chain extenders, which typically have a molecular weight of not more than 250

[0040] As evident from the structure, above, “between oxygen atoms of two carbamate functional groups” refers to the segments derived from diols. Furthermore, “between oxygen atoms of two carbamate functional groups” can be understood as “between oxygen atoms of two adjacent carbamate functional groups”. In some embodiments, R represents the polyester polyol described above in any of its embodiments, and n is a value that provides an Mn of at least 35,000 g / mol as described below.

[0041] The polyurethane useful for the adhesive composition of the present disclosure may be prepared by a variety of techniques known in the art. For example, the polyurethane may be formed by reacting a mixture of the polyester polyol and the polyisocyanate including 4,4 ’-diphenylmethane units in a suitable vessel. Typically, the components are mixed at an elevated temperature (e.g., 30 °C to 120 °C or 50 °C to 100 °C) using conventional mixing techniques under anhydrous conditions. The polyurethane can be prepared without the use of solvent, or one or more solvents (e.g., water-insoluble ethers, esters, branched and straight hydrocarbons, ketones, toluene, xylene, or mixtures thereof) may be employed if desired. The polyurethane may also be prepared in an extruder (e.g., a twin screw extruder) with the starting materials added to various barrels of the extruder. Methods of reactive extrusion are known to those skilled in the art and are described, for example, in Beyer, G. and Hopmann, C. (Eds.). Reactive Extrusion: Principles and Applications . Weinheim, Germany: Wiley-VCH Verlag GmbH & Co. KGaA, 2018 and Janssen, L. P. B. M. Reactive Extrusion Systems. New York: Marcel Dekker, Inc., 2004.

[0042] A catalyst may be useful for the reaction of the polyester polyol and the polyisocyanate including 4,4 ’-diphenylmethane units. Organometallic compounds, useful for catalyzing the reaction between polyols and isocyanates, include tin catalysts and non-tin catalysts. Examples of suitable tin catalysts include tin(II) octoate (stannous octoate), dibutyltin dilaurate, dibutyl tin diacetate, dibutyl tin mercaptide, dibutyl tin dimaleate, dimethyl tin diacetate, and dimethyl tin dilaurate. Useful "non-tin" catalysts include bismuth and zinc carboxylates, such as bismuth octoate, bismuth neodecanoate, zinc octoate, zinc neodecanoate, and zinc stearate, and ferric acetylacetonate. Further examples of suitable catalysts include tertiary amines such as triethylamine, triisopropylamine, N,N-dimethylbenzylamine, 1,4- diazabicyclo[2.2.2]octane, and mixtures thereof.

[0043] In some embodiments, to make a polyurethane useful in the adhesive composition of the present disclosure, the hydroxyl equivalents are present in the reaction mixture in an amount greater than the isocyanate equivalents. The equivalent ratio of hydroxyl to isocyanate (OH / NCO) can be from about 1.001 / 1 to about 1.2 / 1 and, in some embodiments, no more than 7:6, or from about 1.001 to about 1.17: 1, or from about 1.001 to about 1. 14: 1, or from about 1.005 / 1 to 1.05 / 1. In a stepwise polymerization, including the present preparation of the polyurethane, the Mn of the polymer decreases as the ratio between components increases beyond 1.00.

[0044] The polyurethane useful in adhesive composition of the present disclosure has an Mn of at least 35,000 g / mol. In some embodiments, the polyurethane has an Mn of at least 40,000 g / mol, at least 45,000 g / mol, at least 50,000 g / mol, at least 60,000 g / mol, or at least 65,000 g / mol. As shown in the Examples, below, the durability an adhesive belt increases with increasing molecular weight of the polyurethane. In some embodiments, the polyurethane has an Mn of not more than 100,000 g / mol or 90,000 g / mol. Molecular weights are determined by gel permeation chromatography (GPC) vs. polystyrene standards, in some embodiments, in tetrahydrofuran (THF) solvent at a flow rate of 1.0 mL / min. Conveniently, the GPC method in the Examples, below, can be used.

[0045] While polyurethanes can contain a distribution of compositions and molecular weights as a result of polymerization reactions to make polyesters and polyurethanes, in some embodiments, the polyurethane described herein above comprises at least 90, 95, 96, 97, 98, 99, or 99.5 mole percent of the polyester-diisocyanate based polyurethanes in the composition. The adhesive composition may be free of a reaction product of a poly(tetramethylene glycol) and a polyisocyanate or substantially free of (that is, may contain less than 10, 5, 4, 3, 2, 1, 0.5, or 0.1 weight percent of) a reaction product of a poly(tetramethylene glycol) and a polyisocyanate, based on the total weight of the adhesive composition. The adhesive composition may be free of a polyurethane having polyester units comprising alkylene groups between ester functional groups with more than 5 carbon atoms in a straight chain or substantially free of (that is, may contain less than 10, 5, 4, 3, 2, 1, 0.5, or 0. 1 weight percent of) a polyurethane having polyester units comprising alkylene groups between ester functional groups with more than 5 carbon atoms in a straight chain, based on the total weight of the adhesive composition. The adhesive composition may be free of or substantially free of a polyurethane (that is, may contain less than 10, 5, 4, 3, 2, 1, 0.5, or 0.1 weight percent of a polyurethane) having a Mn molecular weight of less than 35,000 g / mol as evidenced, for example, by a monomodal distribution in the GPC.

[0046] The adhesive composition of the present disclosure includes a multifunctional isocyanate comprising at least two isocyanate functional groups. In some embodiments, the multifunctional isocyanate comprises more than two isocyanate functional groups or at least three isocyanate groups and may be a polyisocyanate, triisocyanate, or tetraisocyanate, for example. In some embodiments, the multifunctional isocyanate is polymeric. In some embodiments, the multifunctional isocyanate is monomeric. Examples of suitable multifunctional isocyanates include polymethylene polyphenylisocyanate obtained under the trade designation “PAPI”, for example, “PAPI 20” and “PAPI 94”, from Dow Chemical Company, a mixture of 4,4 ’-MDI and 2,4 ’-MDI available under the trade designation “MONDUR MLQ” from Covestro, Leverkusen, Germany, a reaction product of trimethylol propane and toluene diisocyanate obtained under the trade designation “MONDUR CB-75” from Covestro, and triphenylmethane-4,4,4-triisocyanate, available, for example, under the trade designation “DESMODUR RE” from Covestro.

[0047] In some embodiments, the multifunctional isocyanate comprising at least two isocyanate functional groups has a molecular weight of not more than 1500 g / mol, 1200 g / mol, or 1000 g / mol. The Mn of the multifunctional isocyanate can be determined by nuclear magnetic resonance (NMR) spectroscopy (e.g., NMR) using techniques known to one skilled in the art. In some embodiments, the multifunctional isocyanate comprising at least two isocyanate functional groups is present in at least 3, 5, or 10 percent by weight, based on the total weight of the adhesive composition excluding any organic solvent that may be present. In some embodiments, the multifunctional isocyanate comprising at least two isocyanate functional groups is present in an amount of up to 30, 25, or 20 percent by weight, based on the total weight of the adhesive composition excluding any organic solvent that may be present. In some embodiments, the multifunctional isocyanate comprising at least two isocyanate functional groups is present in a range from 3 to 30, 5 to 25, or 10 to 20 percent by weight, based on the total weight of the adhesive composition excluding any organic solvent that may be present.

[0048] In some embodiments, during the preparation of the adhesive composition of the present disclosure, the multifunctional isocyanate is mixed with a polyurethane having hydroxyl end groups, described above in any of its embodiments. Before the adhesive composition is applied to a substrate, the hydroxyl groups of the polyurethane can react with a portion of the multifunctional isocyanate. Because the number of isocyanate groups (i.e., in the multifunctional isocyanate) exceeds the number of hydroxyl groups (i.e., in the polyurethane), a significant fraction of the isocyanate groups (i.e., in the multifunctional isocyanate) remain after the hydroxyl groups are consumed by reaction with other isocyanate groups. The resulting adhesive composition includes a polyurethane with a backbone containing a polyester and 4,4 ’-diphenylmethane units and having a number average molecular weight of at least 35,000 grams per mole, the polyurethane now having isocyanate groups.

[0049] The adhesive composition further includes the multifunctional isocyanate having at least two isocyanate functional groups (i.e., the fraction of multifunctional isocyanate that was not reacted with the hydroxyl end groups). In some embodiments of the adhesive composition of the present disclosure, the weight ratio of the polyurethane to the multifunctional isocyanate is in a range from 2: 1 to 30: 1, 3: 1 to 20: 1, or 5: 1 to 10: 1. However, typically the number of isocyanate groups in the multifunctional isocyanate exceeds the number of isocyanate groups in the polyurethane. In some embodiments of the adhesive composition, a ratio of the number of isocyanate groups in the multifunctional isocyanate to the number of isocyanate groups in the polyurethane is at least 10: 1 and, in some embodiments, is up to 100: 1, 50: 1, 25: 1, or 20: 1.

[0050] Compositions, amounts, and ratios in the adhesive composition of the present disclosure can be determined by conventional analytical techniques, for example, nuclear magnetic resonance spectroscopy.

[0051] In some embodiments, the adhesive composition further comprises a catalyst. The catalyst can be an organometallic compound such as a tin catalyst or non-tin catalyst including any of those described above for the preparation of a polyurethane. In some embodiments, the catalyst is a nitrogen-containing catalyst. In some embodiments, the nitrogen-containing catalyst comprises at least one of a tertiary amine, a urea, an amidine, or an imidazole. Examples of suitable tertiary amines include N-alkyl morpholines, triethylamine, triisopropylamine, N,N-dimethylbenzylamine, quinuclidine, triethylenediamine (l,4-diaza-bicyclo-(2.2.2)-octane), and bis[2-(N,N-dialkylamino)alkyl]ether(s) (sometimes known as "bis ethers"). Further examples of suitable nitrogen-containing catalysts include imidazoles (e.g. hexakis(imidazole) nickel phthalate), imidazolates, tetrahydrobenzimidazoles, ureas, melamines, l,8-diazabicyclo[5.4.0]undec-7-ene (DBU), and l,5-diazabicyclo[4.3.0]non-5-ene (DBN). Further examples of suitable imidazoles include 2-propyl imidazole, 2-butyl imidazole, 2-benzyl imidazole, 2-benzyl-4-methyl imidazole, 2-butyl-4-methyl imidazole, imidazole, 2-methylimidazole, 2- ethyl-4-methylimidazole, 2-phenylimidazole, 1 -benzyl -2 -methylimidazole, 2,4-dimethylimidazole, 2,4,5- trimethylimiazole, and 2-ethylimidazole. Combinations of any of these nitrogen-containing compounds can be used. In some embodiments, the catalyst, which may be a nitrogen-containing catalyst such as any of those described above, is present in an amount of about 0.005 to 2 percent by weight, about 0.01 to about 1 percent by weight, or about 0.05 to 0.5 percent by weight, based on the total weight of the adhesive composition.

[0052] The adhesive composition of the present disclosure may include other ingredients to impart or modify particular characteristics of the composition. These ingredients are typically present in an amount that does not materially adversely interfere with the adhesion of the composition. The adjuvants may comprise up to 50, 40, 30, 25, 20, 15, 10, or 5 weight percent of the composition either individually or in combination. For example, fillers (e.g., carbon black; glass, ceramic, metal, or plastic bubbles; metal oxides such as zinc oxide; and minerals such as talc, clays, silica, and silicates), thermoplastic resins; plasticizers; antioxidants; pigments; UV absorbers; and adhesion promoters such as silanes may be included to modify set time, open time, green strength build-up, tack, flexibility, and adhesion. In some embodiments, the adhesive composition is free of tackifiers or includes not more than 2, 1, 0.5, 0.1, 0.05, or 0.01 percent by weight tackifier, based on the total weight of the adhesive composition. In some embodiments, the adhesive composition is free of chlorinated hydrocarbons (e.g., aliphatic or aromatic chlorinated hydrocarbon) or substantially free of (that is, includes not more than 2, 1, 0.5, 0.1, 0.05, or 0.01 percent by weight) chlorinated hydrocarbons, based on the total weight of the adhesive composition. In some embodiments, the adhesive composition is free of alkylated polystyrene or includes not more than 2, 1, 0.5, 0.1, 0.05, or 0.01 percent by weight alkylated polystyrene, based on the total weight of the adhesive composition.

[0053] In some embodiments, the adhesive composition includes organic solvent. Examples of suitable organic solvents include water-insoluble ethers, esters, branched and straight hydrocarbons, ketones, toluene, xylene, and mixtures thereof. Specific examples of suitable organic solvents include tetrahydrofuran, acetone, methyl ethyl ketone, methyl acetate, ethyl acetate, toluene, and xylene.. These solvents can be used alone or as mixtures thereof. The polyurethane may be combined with the organic solvent in any desirable concentration (e.g., 10 to 90 weight percent, 10 to 50 weight percent, or 10 to 30 weight percent polyurethane in the organic solvent) for ease of handling and then combined with the other components.

[0054] The present disclosure provides an article including the adhesive composition of the present disclosure or a reaction product thereof. In some embodiments, the article is an abrasive article. The article can be a belt. The present disclosure provides a belt of flexible sheet material having two ends adhered together with the adhesive composition of the present disclosure or a reaction product thereof. In some embodiments, flexible sheet material includes a backing and abrasive grains adhered to the backing.

[0055] Examples of abrasive articles of the present disclosure include coated abrasives, lapping coated abrasives, and nonwoven abrasives. In a coated abrasive construction, the abrasive particles are secured to the backing by means of a first binder, commonly referred to as a make coat. Over the make coat and abrasive particles is applied a second binder or size coat which reinforces the abrasive particles. In a lapping coated abrasive construction, the abrasive particles are dispersed in the binder to form an abrasive composite and this abrasive composite is bonded to a backing. For a nonwoven abrasive, the binder bonds the abrasive particles into a nonwoven fibrous substrate.

[0056] Referring to FIG. 1, an embodiment of a belt 11 of the present disclosure is illustrated. The belt has two ends 13, 14 joined together by a splice 12. The machine direction "M" (or central axis) of the endless belt runs parallel to side edge "s". FIG. 2 illustrates perspective view of an abrasive article 22 having two ends 26 and 27 abutting at juncture line 203 and adhered together with adhesive composition or reaction product thereof 28 and optional splice medium 21. The abrasive article 22 comprises flexible backing 29 having a plurality of abrasive particles 24 bonded to front surface 201 of the backing 29 by means of binder in an overlying size coat 25 and an underlying make coat 23. The backing 29 can also have a conventional backsize or backing primer layer preformed as the back surface 202. The ends 26 and 27 of the abrasive article to be spliced can be cut at complementary bias angles in the range of from about 10 degrees to 170 degrees, more typically about 60 degrees to about 120 degrees, relative to the machine direction (parallel to a side edge "s") of the abrasive article. For instance, if end 26 is cut at 65 degrees, the end 27 would be cut a complementary angle of 115 degrees.

[0057] In some embodiments, the back surfaces 202 at the two ends are scuffed or abraded to texture or roughen the surface regions before contact with the adhesive composition 28 and splice medium 21. The adhesive composition 28 is applied to the two ends 26, 27 on the back major surface 202 of the abrasive article (backing 29) before or after the two free ends are brought together. The joined ends 26, 27 and adhesive composition 28 can then be contacted by the optional splice medium 21 arranged over the juncture line 203 to form a butt splice. The term "abutted" encompasses contacting side faces of the two free ends or two free ends in close proximity to each other, contacting or non-contacting, but excludes overlapped or lapped arrangements of the two free ends. The adhesive composition or reactive product thereof 28 can be used to lengthen an abrasive sheet article and / or form an abrasive article into a continuous structure, such as a belt.

[0058] Optional splice medium 21 can include a variety of materials, for example, in the form of monolithic films and fabrics (e.g., wovens and nonwovens). Examples of polymeric materials suitable for the splice medium include polyester, polyamide, polyimide, polypropylene, polyethylene, polyether ketone, polyether sulfone, and poly etherimide. In some embodiments, the slice medium is composed of a polymeric material comprising at least one of polyimide, polyester, polyamide, polyether ketone, polyether sulfone, or polyetherimide. In some embodiments, the splice medium is a semicrystalline polymeric film comprising at least one of a polyimide film, polyester film, or a polyamide film. The polymeric film generally has a thickness of about 5 micrometers to about 80 micrometers, about 10 micrometers to about 75 micrometers, about 10 micrometers to about 50 micrometers, or about 25 micrometers. Optional splice media can also contain plurality of filaments arranged on the splice medium 21 film or fabric to span the juncture line and oriented in a generally parallel direction to the central axis M of the abrasive belt 11, for example. Such filaments are described, for example, in U.S. Pat. No. 5,595,804 (Korbel) and can be made of fiberglass, polyester, steel, cotton, carbon, polyamides, or aramid and can have a length which substantially corresponds to the width dimension "w" shown in FIG. 2. Filaments may be attached to a film or fabric using the adhesive composition of the present disclosure or a fiber adhesive as described in U.S. Pat. No. 5,595,804 (Korbel). In some embodiments, the splice medium in an abrasive article or belt of the present disclosure does not include filaments.

[0059] FIG. 3 is a sectional view of another embodiment of the present disclosure in the form of a coated abrasive article having abrasive grains 34 adhered to a backing 39 and having a butt splice. In FIG. 3., abrasive ends 36, 37 are seen to be closely abutted together. The ends 36, 37 may be cut at a suitable angle as described above. Adhesive composition or reaction product thereof 38 fills the juncture line 303. Adhesive composition or reaction product thereof 38 also adheres to and may penetrate splice medium 31, which may be a woven or nonwoven material. In FIGS. 2 and 3, splice medium 21, 31 overlaps and is adhered to the two ends with the adhesive composition or the reaction product thereof 28, 38.

[0060] In FIG. 4, adhesive composition 48 is shown being used to join together surfaces 406, 407 of the two ends 46, 47 respectively, of a strip of abrasive material 41. In the illustrated embodiment, the two ends 46, 47 are overlapped and adhered together. Abrasive material 41 comprises a backing 49 and abrasive grains 44 adhered to the backing 49 by means of a make coat 43. In the illustrated embodiment, surfaces 406, 407 are beveled by skiving and abrading, respectively, resulting in narrowing of the two ends 46 and 47. This preparatory treatment can improve adhesion and decrease joint thickness. In general, skiving the upper surface 406 of end 46 may be carried out to remove substantially all the adhesive layer 43. A taper, as shown, of 50 to 75 micrometers from the trailing edge of the skived area to the leading edge thereof may be useful. The lower surface 407 of end 47 can be, for example, back rubbed, wire brushed, or sand blasted to provide an abraded surface area matching with the skived surface 406 on end 46.

[0061] FIG. 5 is a sectional view of an embodiment of the abrasive article or belt of the present disclosure in the form of a nonwoven abrasive article 51 having a butt splice. The butt splice 111 comprises the first end 107 and the second end 109 of the nonwoven abrasive web 101 that abut each other, an adhesive composition of the present disclosure or the reaction product thereof 115 disposed in a seam 117 between the first end 107 and the second end 109, splice medium 119 disposed on the second major surface 105 of the nonwoven abrasive web opposite, and a layer of adhesive composition 121 disposed between the splice medium 119 and the second major surface 105. The adhesive composition 115 disposed in the seam can be separate or integral with the adhesive composition 121 that adheres the splice medium to the second side of the nonwoven abrasive web. The adhesive composition 115 can be the same as, or different from, the adhesive composition 121. Both may be the adhesive composition of the present disclosure or a reaction product thereof independently as described above in any of its embodiments. The nonwoven abrasive web comprises a nonwoven web of fibers 123, abrasive particles 125, and a polymeric binder composition (not shown), wherein the abrasive particles are adhered to the fibers with the polymeric binder composition. In the illustrated embodiment, the nonwoven abrasive includes a reinforcing scrim material 127.

[0062] An abrasive article of the present disclosure, which may be a belt, typically comprises a backing having a plurality of abrasive particles bonded to the backing by means of one or more resins. Examples of typical backings include polymeric film, primed polymeric film, cloth, paper, vulcanized fiber, nonwovens, treated versions thereof, and combinations thereof. Examples of typical resins include phenolic resins, aminoplast resins, urethane resins, epoxy resins, acrylate resins, acrylated isocyanurate resins, urea-formaldehyde resins, acrylated urethane resins, acrylated epoxy resins, and mixtures thereof.

[0063] A variety of abrasive particles are useful in the articles and methods disclosed herein. Examples of useful abrasive particles include fused aluminum oxide, heat treated aluminum oxide, ceramic aluminum oxide, white fused aluminum oxide, black silicon carbide, green silicon carbide, titanium diboride, boron carbide, tungsten carbide, titanium carbide, diamond, cubic boron nitride, garnet, fused alumina zirconia, sol gel abrasive particles, silica, iron oxide, chromia, ceria, zirconia, titania, silicates, metal carbonates (such as calcium carbonate (for example, chalk, calcite, marl, travertine, marble and limestone), calcium magnesium carbonate, sodium carbonate, magnesium carbonate), silica (for example, quartz, glass beads, glass bubbles and glass fibers) silicates (for example, talc, clays, (montmorillonite) feldspar, mica, calcium silicate, calcium metasilicate, sodium aluminosilicate, sodium silicate) metal sulfates (for example, calcium sulfate, barium sulfate, sodium sulfate, aluminum sodium sulfate, aluminum sulfate), gypsum, aluminum trihydrate, graphite, metal oxides (for example, tin oxide, calcium oxide), aluminum oxide, titanium dioxide) and metal sulfites (for example, calcium sulfite), metal particles (for example, tin, lead, copper), plastic abrasive particles formed from a thermoplastic material (for example, polycarbonate, poly etherimide, polyester, polyethylene, polysulfone, polystyrene, acrylonitrile-butadiene-styrene block copolymer, polypropylene, acetal polymers, polyvinyl chloride, polyurethanes, nylon), plastic abrasive particles formed from crosslinked polymers (for example, phenolic resins, aminoplast resins, urethane resins, epoxy resins, melamine-formaldehyde, acrylate resins, acrylated isocyanurate resins, urea-formaldehyde resins, isocyanurate resins, acrylated urethane resins, acrylated epoxy resins), and combinations thereof. Useful abrasive particles also encompass individual abrasive particles bonded together to form an abrasive agglomerate. Abrasive agglomerates are further described in U.S. Pat. Nos. 4,652,275 (Bloecher) and 4,799,939 (Bloecher).

[0064] Abrasive particles useful for practicing the present disclosure may be crushed or may have regular or irregular shapes. Examples of suitable shaped abrasive particles include those produced by molding a sol-gel, drying, and sintering the dried sol-gel to obtain shaped ceramic abrasive particles as described in U.S. Pat. Nos. 5,201,916 (Berg), 5,984,988 (Berg), Re. 35,570 (Rowenhorst), 8,034,137 (Erickson), 8,123,828 (Culler), 8,142, 531 (Adefris), 8,142,891 (Culler), 8,142,532 (Erickson), and 8,764,865 (Boden), and in U.S. Pat. Appl. Pub. Nos. 2010 / 0319269 (Erickson) and 2015 / 0052825 (Adefris). Shaped abrasive agglomerate particles may also be useful for practicing the present disclosure, for example, agglomerates including various abrasive particles in a ceramic matrix such as those disclosed in U.S. Pat. Nos. 5,975,988 (Christianson), 6,319,108, 6,702,650, and 6,951,504 (each to Adefris), 11,607,776 and 11,478,899 (each to Lukowski), 12,006,464 (Skorina), and in Int. Pat. Appl. Pub. No. WO2015 / 088953 (Kasai) and agglomerates including shaped abrasive particles in an organic resin matrix such as those disclosed in U.S. Pat. Appl. Pub. No. 2014 / 0080393 (Ludwig).

[0065] The present disclosure provides a process for making a belt. The process includes applying the adhesive composition to at least one of the two ends and adhering the two ends together with the adhesive composition. In some embodiments, the abrasive sheet material is first cut to the desired length. Typically, the length can be anywhere from 15 cm to 1000 cm, for example, between 30 cm and 500 cm. In some embodiments, each of the two ends of the coated abrasive is cut through its width at an angle anywhere between 10 to 170 degrees or 35 to 155 degrees relative to the central axis or machine direction of the belt. The two ends are cut such that the angles add up to 180 degrees, for example, one angle can be 65 degrees, and the other angle can be 115 degrees.

[0066] In some embodiments, after the material is cut, the two ends are textured or roughened as described above. Roughening of the two ends can be accomplished, for example, with a wire brush, sandblasting, or sandpaper. The roughening is employed to increase the surface area to be coated by the adhesive composition and the roughened topography enhances the anchoring of the adhesive to the article surface, as opposed to a smooth surface.

[0067] Applying the adhesive composition to at least one of the two ends of the belt in the process of the can be carried out by such techniques as spraying, brushing, roll coating, knife coating, or die coating over the optionally roughened or scuffed area. In some embodiments, the adhesive composition is applied as a solution in organic solvent and allowed to dry. The adhesive composition may soak into the backing somewhat upon application. The amount of adhesive composition applied can be in the range, for example, from 0.35 to 200 mg / cm2, in some embodiments from 1.75 to 30 mg / cm2.

[0068] After the adhesive composition is applied, the two ends are adhered together with the adhesive composition. In some embodiments, the two ends are overlapped and adhered together. In some embodiments, the two ends are brought together juxtaposely at the faces of their ends in a flush relationship with no gap or only a minimal gap to form a butt splice. In some embodiments, the two ends are brought together before the adhesive composition is applied to at least one of the two ends. In some embodiments, splice media as described in any of its embodiments is placed over the two ends. A roller may be used to force the splice media into the adhesive composition to obtain and ensure intimate contact between the two.

[0069] The adhesive composition of the present disclosure is typically cured to provide a reaction product thereof. In some embodiments, the curing reaction requires the introduction of water that subsequently reacts with the isocyanate and leads to the formation of urea linkages in the cured adhesive. The curing can be accomplished, for example, with heat and pressure. In some embodiments, curing is carried in a heated press. The pressure applied can be in the range of 24 kg / cm2to 184 kg / cm2along the splice. The temperature is selected to initiate the curing of the adhesive composition, but not too high to degrade the splice media or coated abrasive backing. In some embodiments, the temperature is in a range from 30 °C to 200 °C, from 50 °C to 175 °C, or from 75 °C to 150 °C. Heat and pressure may be applied in the press, for example, from 5 to 50 seconds or from 10 to 40 seconds.

[0070] Splicing can be carried out on a full width coated abrasive material and then, if desired, the full width material can be slit longitudinally in the machine direction of the belt to convert the spliced abrasive material into any desired smaller width belts.

[0071] The present disclosure provides a method of abrading a workpiece. The method includes providing an article or belt described above in any of its aspects, frictionally contacting at least a portion of the abrasive particles with at least a portion of a surface of the workpiece and moving the workpiece and the abrasive article relative to each other to abrade at least a portion of the surface. Generally, an endless abrasive belt can traverse over at least one idler roll and a platen or contact wheel. The hardness of the platen or contact wheel is adjusted to obtain the desired rate of cut and workpiece surface finish. The abrasive belt speed depends upon the desired cut rate and surface finish and generally ranges anywhere from about 20 to 100 surface meters per second, typically between 30 to 70 surface meter per second. The belt dimensions can range from about 0.5 cm to 100 cm wide or 1.0 cm to 30 cm wide, and from about 5 cm to 1,000 cm long or from 50 cm to 500 cm long.

[0072] The abrasive article can be used to abrade a workpiece. The workpiece can be any type of material such as metal, metal alloys, exotic metal alloys, ceramics, glass, wood, wood like materials, composites, painted surface, plastics, reinforced plastic, stones, and combinations thereof. The workpiece may be flat or may have a shape or contour associated with it. Examples of workpieces include glass eye glasses, plastic eye glasses, plastic lenses, glass television screens, metal automotive components (e.g., clutch plates and other flat automotive components), stainless steel coils, plastic components, particle board, painted automotive components, magnetic media, tubing, plates, hydraulic rods, and elevator shafts.

[0073] During abrading, the abrasive article and the workpiece are moved relative to each other such that the abrasive article abrades the workpiece. The abrasive article is moved relative to the workpiece, or vice versa. Depending upon the application, the force at the abrading interface can range from about 0. 1 kg to over 1000 kg. Typically, this range is between 1 kg to 500 kg of force at the abrading interface. In addition, abrading may occur under wet conditions. Wet conditions can include water and / or a liquid organic compound. Examples of typical liquid organic compounds include lubricants, oils, emulsified organic compounds, cutting fluids, and soaps. These liquids may also contain other additives such as defoamers, degreasers, and corrosion inhibitors. The abrasive article may oscillate at the abrading interface during use, which may result in a finer surface on the workpiece being abraded.

[0074] Various embodiments of the present disclosure are described below.

[0075] In a first embodiment, the present disclosure provides adhesive composition comprising a polyurethane with a backbone comprising a polyester and 4,4 ’-diphenylmethane units, the polyurethane having a number average molecular weight of at least 35,000 grams per mole and a multifunctional isocyanate comprising at least two isocyanate functional groups. In a second embodiment, the present disclosure provides the adhesive composition of the first embodiment, wherein the polyurethane has a number average molecular weight of at least 40,000, grams per mole, at least 45,000 grams per mole, at least 50,000 grams per mole, at least 55,000 grams per mole, or at least 60,000 grams per mole. In a third embodiment, the present disclosure provides the adhesive composition of the first or second embodiment, wherein the multifunctional isocyanate comprises more than two isocyanate functional groups.

[0076] In a fourth embodiment, the present disclosure provides the adhesive composition of any one of the first to third embodiments, further comprising a catalyst. In a fifth embodiment, the present disclosure provides the adhesive composition of any one of the first to fourth embodiments, further comprising a nitrogen-containing catalyst. In a sixth embodiment, the present disclosure provides the adhesive composition of any one of the first to fifth embodiments, further comprising at least one of a tertiary amine catalyst, a urea catalyst, an amidine catalyst, or an imidazole catalyst.

[0077] In a seventh embodiment, the present disclosure provides adhesive composition of any one of the first to sixth embodiments, wherein the polyester comprises alkylene groups between ester functional groups, wherein the alkylene groups independently have not more than five carbon atoms in a straight chain. In an eighth embodiment, the present disclosure provides the adhesive composition of any one of the first to seventh embodiments, wherein the polyester comprises alkylene groups between ester functional groups, wherein the alkylene groups independently have not more than four carbon atoms. In a ninth embodiment, the present disclosure provides the adhesive composition of any one of the first to eighth embodiments, wherein at least 75 mole percent of the segments between oxygen atoms in two carbamate functional groups have a molecular weight of at least 500 grams per mole. In a tenth embodiment, the present disclosure provides the adhesive composition of any one of the first to ninth embodiments, wherein at least 90 mole percent of the units in the polyurethane arising from polyisocyanates are 4,4 ’-diphenylmethane units.

[0078] In an eleventh embodiment, the present disclosure provides the adhesive composition of any one of the first to tenth embodiments, wherein the adhesive composition is substantially free of a reaction product of a poly(tetramethylene glycol) and a polyisocyanate. In a twelfth embodiment, the present disclosure provides the adhesive composition of any one of the first to eleventh embodiments, wherein the adhesive composition is substantially free of a polyurethane having polyester units comprising alkylene groups between ester functional groups with more than 5 carbon atoms in a straight chain, based on the total weight of the adhesive composition. In a thirteenth embodiment, the present disclosure provides the adhesive composition of any one of the first to twelfth embodiments, wherein the adhesive composition is substantially free of a polyurethane having a Mn molecular weight of less than 35,000 grams per mole.

[0079] In a fourteenth embodiment, the present disclosure provides the adhesive composition of any one of the first to thirteenth embodiments, wherein the multifunctional isocyanate is monomeric. In a fifteenth embodiment, the present disclosure provides the adhesive composition of any one of the first to thirteenth embodiments, wherein the multifunctional isocyanate is polymeric. In a sixteenth embodiment, the present disclosure provides the adhesive composition of any one of the first to fifteenth embodiments, wherein the multifunctional isocyanate comprises at least three isocyanate functional groups. In a seventeenth embodiment, the present disclosure provides the adhesive composition of any one of the first to sixteenth embodiments, wherein the molecular weight of the multifunctional isocyanate is not more than 1500 grams per mole. In an eighteenth embodiment, the present disclosure provides the adhesive composition of any one of the first to seventeenth embodiments, further comprising organic solvent. In a nineteenth embodiment, the present disclosure provides the adhesive composition of any one of the first to eighteenth embodiments, wherein the multifunctional isocyanate is present in the adhesive composition in an amount of at least 3 weight percent, at least 5 weight percent, at least 10 weight percent, at most 30 weight percent, at most 25 weight percent, at most 20 weight percent, or a combination thereof, based on the total weight of the adhesive composition excluding any organic solvent that may be present. In a twentieth embodiment, the present disclosure provides the adhesive composition of any one of the first to nineteenth embodiments, wherein the adhesive composition is substantially free of chlorinated hydrocarbons.

[0080] In a twenty-first embodiment, the present disclosure provides an article comprising the adhesive composition of any one of the first to twentieth embodiments or a reaction product thereof. In a twenty- second embodiment, the present disclosure provides the article of the twenty-first embodiment, wherein the article is an abrasive article. In a twenty-third embodiment, the present disclosure provides a belt of flexible sheet material having two ends adhered together with the adhesive composition of any one of the first to twentieth embodiments or a reaction product thereof. In a twenty-fourth embodiment, the present disclosure provides the belt of the twenty-third embodiment, wherein the flexible sheet material comprises a backing and abrasive grains attached to the backing. In a twenty-fifth embodiment, the present disclosure provides the belt of the twenty-third or twenty-fourth embodiment, wherein the flexible sheet material comprises a nonwoven. In a twenty-sixth embodiment, the present disclosure provides the belt of any one of the twenty-third to twenty-fifth embodiments, wherein the two ends are overlapped and adhered together. In a twenty-seventh embodiment, the present disclosure provides the belt of any one of the twenty-third to twenty-sixth embodiments, wherein the two ends are abutting. In a twenty-eighth embodiment, the present disclosure provides the belt of any one of the twenty-third to twenty-seventh embodiments, further comprising a splice medium overlapping and adhered to the two ends with the adhesive composition or the reaction product thereof.

[0081] In a twenty-ninth embodiment, the present disclosure provides a process for making the belt of any one of the twenty-third to twenty-eighth embodiments, the process comprising applying the adhesive composition to at least one of the two ends and adhering the two ends together with the adhesive composition. In a thirtieth embodiment, the present disclosure provides the process of the twenty-ninth embodiment, further comprising heating the adhesive composition. In a thirty-first embodiment, the present disclosure provides the process of the twenty-ninth or thirtieth embodiment, further comprising curing with adhesive composition with heat and pressure. In a thirty-second embodiment, the present disclosure provides the process of any one of the twenty-ninth to the thirty-first embodiments, wherein applying the adhesive composition comprises applying the adhesive composition as a liquid. In a thirty- third embodiment, the present disclosure provides the process of any one of the twenty-ninth to thirty- second embodiments, wherein the adhesive composition comprises solvent when it is applied. In a thirtyfourth embodiment, the present disclosure provides use of the adhesive composition of any one of the first to twentieth embodiments as a splice adhesive.

[0082] In a thirty-fifth embodiment, the present disclosure provides a process for making the adhesive composition of any one of the first to twentieth embodiments, the process comprising combining the polyurethane and the multifunctional isocyanate, wherein before combining, the polyurethane has hydroxyl functional groups. In a thirty-sixth embodiment, the present disclosure provides the process of the thirty-fifth embodiment, wherein before combining, a ratio of polyester units to the 4,4’- diphenylmethane units is not higher than 7:6.

[0083] In a thirty-seventh embodiment, the present disclosure provides a method of abrading a workpiece, the method comprising providing the article or belt of any one of the twenty-second to twentyeighth embodiments, frictionally contacting at least a portion of the abrasive particles with at least a portion of a surface of the workpiece, and moving at least one of the article or the workpiece relative to the other to abrade at least a portion of the surface. In a thirty-eighth embodiment, the present disclosure provides the method of the thirty-seventh embodiment, wherein the workpiece comprises at least one of stainless steel, carbon steel, or titanium.

[0084] In order that the present disclosure can be more fully understood, the following examples are set forth. It should be understood that these examples are for illustrative purposes only and are not to be construed as limiting this disclosure in any manner. For example, the particular materials and amounts thereof recited in these examples, as well as other conditions and details, should not be construed to unduly limit this disclosure.

[0085] EXAMPLES

[0086] Unless otherwise noted, all parts, percentages, ratios, etc. in the Examples and the rest of the specification are by weight. Unless stated otherwise, all other reagents were obtained, or are available from fine chemical vendors or may be synthesized by known methods.

[0087] In the Examples, "wt%" stands for weight percent, "g" for grams, and "mg" for milligrams. Molecular weights are expressed in "g / mol" for grams per mole. Volumes are measured in "mL" for milliliters and "L" for liters. Lengths are given in centimeters, denoted by “cm”, and millimeters, denoted by “mm”. Rotational speed is indicated by "RPM," which stands for revolutions per minute. Temperature is measured in degrees Fahrenheit, represented by "°F" or degrees Celsius, represented by "°C". Force is given in pounds-force, abbreviated as "Ibf." Time is measured in seconds, abbreviated as "s," and minutes, abbreviated as "min." Mnrefers to number average molecular weight, and Mwrefers to weight average molecular weight.

[0088] Table 1 : Materials used in the Examples

[0089] Gel Permeation Chromatography (GPC)

[0090] Samples of polymer were dissolved in tetrahydrofuran at a concentration of 5 mg / g and then subjected to GPC analysis. The GPC equipment consisted of a 1260 Infinity II liquid chromatography system (comprised of isocratic pump, autosampler, column compartment and variable wavelength UV / vis detector) from Agilent Technologies (Santa Clara, CA, USA) operated at a flow rate of 1.0 mL / minute. The GPC column set was comprised of two PLgel 5 micrometer MIXED-C (300 mm length x 7.5 mm internal diameter) and a PLgel 5 micrometer guard column (50 mm length x 7.5 mm internal diameter) all from Agilent Technologies. The detection consisted of a miniDAWN 3 angle Light Scattering detector and an OPTILAB differential refractive index detector, both from Wyatt Technology Corporation (Santa Barbara, CA, USA). Data were collected and analyzed using software ASTRA version 8 from Wyatt Technology Corporation. The column compartment, UV / vis detector, and differential refractive index detector were set to 40 °C. The solvent and eluent (or mobile phase) consisted of tetrahydrofuran (THF) (stabilized with 250 parts per million of butylated hydroxytoluene) OMNISOLV grade from EMD Millipore Corporation, Burlington, MA.

[0091] Preparatory Example 1 Polyurethane

[0092] Polyol (82.05 wt%), Catalyst (0.01 wt%), and Isocyanate Prepolymer (17.94 wt%) were mixed in a twin-screw extruder and formed into pellets using conventional reactive extrusion techniques to form a polyurethane with a backbone comprising a polyester and 4,4 ’-diphenylmethane units. A sample was dissolved in THF at 5 mg / g and analyzed by GPC to give an MN value of 78,400 g / mol and an Mw value of 159,800 g / mol. Preparatory Example 2 Polyurethane

[0093] Polyol (81.77 wt%), Catalyst 8 (0.01 wt%) and Isocyanate Prepolymer (18.22 wt%) were mixed in a twin-screw extruder and formed into pellets using conventional reactive extrusion techniques a polyurethane with a backbone comprising a polyester and 4,4 ’-diphenylmethane units. A sample was dissolved in THF at 5 mg / g and analyzed by GPC to give an MN value of 105,900 g / mol and an Mw value of 230,400 g / mol.

[0094] Example 1

[0095] A sample of the Preparatory Example 1 polyurethane was dissolved in 2-butanone (MEK) at a level of 20 wt% solids. A reactive solution was prepared with a mixture of 33.2 grams of this polymer solution, 0.032 grams of DABCO, and 1.16 grams of Polyisocyanate. A portion of this reactive mixture was painted onto the areas within 0.75 inch (1.9 cm) of each end of a strip of abrasive material (24 inches (61 cm) long by 2.5 inches (6.35 cm) wide) obtained under the trade designation “SCOTCH-BRITE Surface Conditioning Low Stretch Belt”, SC-BL, A / O, from 3M Company, St. Paul, MN. The total reactive mixture applied to each belt sample was 2.4 mb. An additional 1.2 mb of this solution was applied to a 2.5-inch (6.35-cm) long strip of woven polyester tape 1.5 inch (3.8 cm) wide. The coatings were allowed to dry for 40 minutes at ambient temperature. The two ends of the strip were butted together to form a belt, and the coated tape was placed over the dried adhesive on the belt. That assembly was pressed with 6000 Ibf (27000 Newtons) for 30 seconds between a platen at 300 °F (149 °C) (contacting the polyester tape) and a platen at 200 °F (93 °C) (contacting the working surface of the belt). This process was repeated to produce a second, replicate belt sample.

[0096] Illustrative Example 2

[0097] A sample of Polyurethane was dissolved in THF at 5 mg / g and analyzed by GPC to give an MN value of 53,800 g / mol and an Mw value of 118,300 g / mol. Another sample of Polyurethane was dissolved in MEK at a level of 20 wt% solids. A reactive solution was prepared with a mixture of 33.2 grams of this polymer solution, 0.032 grams of DABCO, and 1.16 grams of Polyisocyanate. This reactive solution was used to prepare two belt samples using the same process as Example 1.

[0098] Illustrative Example 3

[0099] Polyol (33.03 grams) and Isocyanate Prepolymer (6.98 grams) were mixed in a plastic cup. 15 mb of this reactive mixture was charged to a microcompounder (MC-15 available from Explore). This was mixed for 29 minutes at a temperature of 180 °C and a screw speed of 100 RPM. The resulting polymer was then dispensed onto a polyester liner and allowed to cool. Samples of each polymer were dissolved in THF at a concentration of 5 mg / g and analyzed by GPC to give an MN value of 30,700 g / mol and an Mw value of 59,200 g / mol. Another sample of this polyurethane was dissolved in MEK at a level of 20% solids. A reactive solution was prepared with 16.6 grams of polymer solution, 0.016 grams of DABCO, and 0.58 grams of Polyisocyanate. This reactive solution was used to prepare two belt samples using the same process as Example 1. Belt Life Testing Under Free Spin Condition

[0100] Each sample from Example 1, Illustrative Example 2, and Illustrative Example 3 was cut into four smaller belts, 0.5 inch (1.27 cm) wide. These belts were tested to failure under free spin conditions using a file belt sander (product number 28366 from 3M Company, St. Paul, MN). The average belt life for the eight specimens (four replicate specimens from each pair of replicate samples) was 184 seconds for Example 1, 152 seconds for Illustrative Example 2, and 114 seconds for Illustrative Example 3.

[0101] This disclosure is not limited to the above-described embodiments but is to be controlled by the limitations set forth in the following claims and any equivalents thereof. This disclosure may be suitably practiced in the absence of any element not specifically disclosed herein.

Claims

What is claimed is:

1. An adhesive composition comprising: a polyurethane with a backbone comprising a polyester and 4,4 ’-diphenylmethane units, the polyurethane having a number average molecular weight of at least 35,000 grams per mole; and a multifunctional isocyanate comprising at least two isocyanate functional groups.

2. The adhesive composition of claim 1, further comprising a catalyst.

3. The adhesive composition of claim 1 or 2, further comprising a nitrogen-containing catalyst.

4. The adhesive composition of any one of claims 1 to 3, wherein the polyester comprises alkylene groups between ester functional groups, wherein the alkylene groups independently have not more than five carbon atoms in a straight chain.

5. The adhesive composition of any one of claims 1 to 4, wherein the polyester comprises alkylene groups between ester functional groups, wherein the alkylene groups independently have not more than four carbon atoms.

6. The adhesive composition of any one of claims 1 to 5, wherein multifunctional isocyanate has a molecular weight of no more than 1500 grams per mole.

7. The adhesive composition of any one of claims 1 to 6, wherein multifunctional isocyanate is present in an amount ranging from 3 percent by weight to 30 percent by weight, based on the total weight of the composition, excluding any organic solvent.

8. The adhesive composition of any one of claims 1 to 7, wherein at least 75 mole percent of the segments between oxygen atoms of two carbamate functional groups have a molecular weight of at least 500 grams per mole.

9. A belt of flexible sheet material having two ends adhered together with the adhesive composition of any one of claims 1 to 8 or a reaction product thereof.

10. The belt of claim 9, wherein the flexible sheet material comprises a backing and abrasive grains adhered to the backing.

11. The belt of claim 9 or 10, wherein the flexible sheet material comprises a nonwoven.

12. The belt of any one of claims 9 to 11, wherein the two ends are overlapped and adhered together.

13. The belt of any one of claims 9 to 11, wherein the two ends are abutting.

14. The belt of any one of claims 9 to 13, further comprising a splice medium overlapping and adhered to the two ends with the adhesive composition or the reaction product thereof.

15. A process for making the belt of any one of claims 9 to 14, the process comprising: applying the adhesive composition to at least one of the two ends; adhering the two ends together with the adhesive composition; and optionally, heating the adhesive composition.

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