US20060242910A1

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Publication number: US20060242910A1
Application number: US11/398,848
Authority: US
Inventors: Xiaorong You
Original assignee: Saint Gobain Abrasives Inc
Current assignee: Saint Gobain Abrasives Inc
Priority date: 2005-04-08
Filing date: 2006-04-06
Publication date: 2006-11-02
Also published as: CN101175607A; TW200706368A; MX2007012389A; TWI321099B; CA2602891A1; BRPI0608938A2; WO2006110517A1; EP1877224A1

Abstract

An abrasive article has a layer including an epoxy constituent, a cationic photointiator within the epoxy constituent, and a latent colorant configured to change color in response to activation of the cationic photoinitiator.

Description

CORRESPONDING APPLICATIONS

The present application claims priority from U.S. Provisional Patent Application No. 60/669,413, filed Apr. 8, 2005, entitled “ABRASIVE ARTICLE HAVING REACTION ACTIVATED CHROMOPHORE,” naming the applicant Xiaorong You, which application is incorporated by reference herein in its entirety.

FIELD OF THE DISCLOSURE

This disclosure, in general, relates to abrasive articles and methods for forming same.

BACKGROUND

Abrasive articles, such as coated abrasives and bonded abrasives, are used in various industries to machine workpieces, such as by lapping, grinding, or polishing. Machining utilizing abrasive articles spans a wide industrial scope from optics industries, automotive paint repair industries, to metal fabrication industries. In each of these examples, manufacturing facilities use abrasives to remove bulk material or affect surface characteristics of products.

Surface characteristics include shine, texture, and uniformity. For example manufacturers of metal components use abrasive articles to fine and polish surfaces, and oftentimes desire a uniformly smooth surface. Similarly, optics manufacturers desire abrasive articles that produce defect free surfaces to prevent light diffraction and scattering.

Manufactures also desire abrasive articles that have a high stock removal rate for certain applications. However, there is often a trade-off between removal rate and surface quality. Finer grain abrasive articles typically produce smoother surfaces, yet have lower stock removal rates. Lower stock removal rates lead to slower production and increased cost.

Particularly in the context of fine grained abrasive articles, commercially available abrasives have a tendency to leave random surface defects, such as scratches that are deeper than the average stock removal scratches. Such scratches may be caused by grains that detach from the abrasive article, causing rolling indentations. When present, these scratches scatter light, reducing optical clarity in lenses or producing haze or a foggy finish in decorative metal works. Such scratches also provide nucleation points or attachment points that reduce the release characteristics of a surface. For example, scratches in sanitary equipment allow bacteria to attach to surfaces, and scratches in polished reactors allow formation of bubbles and act as surface features for initiating unwanted reactions.

Loss of grains also degrades the performance of abrasive articles, leading to frequent replacement. Frequent abrasive article replacement is costly to manufacturers. As such, improved abrasive articles and methods for manufacturing abrasive articles would be desirable.

SUMMARY

In a particular embodiment, an abrasive article has a layer including an epoxy constituent, a cationic photointiator within the epoxy constituent, and a latent colorant configured to change color in response to activation of the cationic photoinitiator.

In another exemplary embodiment, an abrasive article includes a polymer matrix, a reaction activated chromophore within the polymer matrix, and particulate abrasive grains.

In a further exemplary embodiment, an abrasive article includes a reaction activated chromophore.

In an additional exemplary embodiment, a method of manufacturing an abrasive article includes initiating a curing process in an abrasive article workpiece. The abrasive article workpiece includes a polymer precursor and a latent colorant. The latent colorant is configured to change color in response to curing. The method also includes determining a target color of the abrasive article workpiece and terminating the curing process when the abrasive article workpiece exhibits the target color.

In another exemplary embodiment, a method of controlling abrasive product quality includes forming an abrasive product comprising a polymeric matrix and a reaction activated chromophore. The reaction activated chromophore is configured to exhibit a color characteristic based on a state of curing. The method also includes inspecting the abrasive product based on the color characteristic and categorizing the abrasive product based on the color characteristic.

In a further exemplary embodiment, an abrasive article includes a layer patterned to form a surface structure. The layer includes a material including a polymeric matrix and a reaction activated chromophore, and includes abrasive grains bonded to the layer.

BRIEF DESCRIPTION OF THE DRAWINGS

The present disclosure may be better understood, and its numerous features and advantages made apparent to those skilled in the art by referencing the accompanying drawings.

FIG. 1 includes an illustration of an exemplary coated abrasive article.

FIG. 2 includes an illustration of an exemplary structured abrasive article

FIG. 3 includes an illustration of an exemplary bonded abrasive article.

The use of the same reference symbols in different drawings indicates similar or identical items.

DESCRIPTION OF THE DRAWING(S)

In a particular embodiment, the disclosure is directed to an abrasive article having a layer that is formed of a polymer matrix. The polymer matrix includes a reaction activated chromophore configured to indicate a state of curing. In one exemplary embodiment, the reactive chromophore includes a latent colorant and a curing byproduct. For example, the curing byproduct may be a byproduct of activating a photoinitiator. The abrasive article may also include particulate abrasive grains.

In another embodiment, the disclosure is directed to a method of manufacturing an abrasive article. The method includes initiating a curing process on a workpiece, determining a target color exhibited by the workpiece and terminating the curing process based on the target color. The curing process may include photo curing or thermal curing.

In a further exemplary embodiment, the disclosure is directed to a method of controlling abrasive product quality. The method includes forming an abrasive product having a polymer matrix and a reaction activated chromophore, inspecting the abrasive product for a color characteristic, and categorizing the abrasive product based on the color characteristic. The color characteristic may, for example, be a target color or color uniformity.

Generally, the abrasive article is formed by curing a binder formulation. The binder formulation typically includes polymer precursors or polymerizable constituents. For example, the binder formulation may include cationically polymerizable constituents or may include radically polymerizable constituents. In addition, the binder formulation includes a catalysts or an initiator, such as a photoinitiator or a thermal intiator, to initiate and facilitate curing. In one particular embodiment, the binder formulation includes a latent colorant. The latent colorant may react with byproduct of the curing, such as species derived from activated initiators, to change color.

The abrasive article also includes abrasive particles. In one embodiment, the binder formulation is used as a compliant layer, a make coat or a size coat in a coated abrasive article. Abrasive grains may be deposited on the make coat and be overcoated with a size coat. In another embodiment, the abrasive grains are mixed with the binder formulation, a mold is filled with the mixture, and the mixture is cured to form a bonded abrasive article.

In an exemplary embodiment, the binder formulation includes a cationically polymerizable constituent. For example, the cationically polymerizable constituent may have epoxy functional groups or oxerane functional groups.

The constituents including epoxy functional groups, also referred to as epoxy constituents, are cationically curable, by which is meant that polymerization or crosslinking of the epoxy group may be initiated by cations. The epoxy constituents can be monomers, oligomers or polymers and are sometimes referred to as “resins.” Such materials may have an aliphatic, aromatic, cycloaliphatic, arylaliphatic, or heterocyclic structure. The epoxy constituents may include epoxy groups as side groups, or the epoxy groups may form part of an alicyclic or heterocyclic ring system. Epoxy groups may also be bound to, for example, siloxane containing backbones.

The epoxy constituent may, for example, include at least one liquid component, such that the combination of materials is a liquid. Thus, the epoxy constituent can be a single liquid epoxy material, a combination of liquid epoxy materials, or a combination of liquid epoxy material(s) and solid epoxy material(s) soluble in the liquid.

An example of a suitable epoxy constituent includes polyglycidyl or poly(methylglycidyl) ester of polycarboxylic acid, poly(oxiranyl) ether of polyether, epoxidised unsaturated fatty acid, or any combination thereof. The polycarboxylic acid can be aliphatic, such as, for example, glutaric acid, adipic acid and the like; cycloaliphatic, such as, for example, tetrahydrophthalic acid; or aromatic, such as, for example, phthalic acid, isophthalic acid, trimellitic acid, or pyromellitic acid; or any combination thereof. The polyether can be poly(tetramethylene oxide). A carboxyterminated adduct, for example, of trimellitic acid or polyol, such as, for example, glycerol or 2,2-bis(4-hydroxycyclohexyl)propane may be used. A suitable epoxidised unsaturated fatty acid may be obtained from, for example, linseed oil or perilla oil.

A suitable epoxy constituent may include polyglycidyl or poly(-methylglycidyl) ether obtainable by the reaction of a compound having at least one free alcoholic hydroxy group or phenolic hydroxy group and a suitably substituted epichlorohydrin. The alcohol can be acyclic alcohol, such as, for example, ethylene glycol, diethylene glycol, or higher poly(oxyethylene) glycol; cycloaliphatic, such as, for example, 1,3- or 1,4-dihydroxycyclohexane, bis(4-hydroxycyclohexyl)methane, 2,2-bis(4-hydroxycyclohexyl)propane, or 1,1-bis(hydroxymethyl)cyclohex-3-ene; or contain aromatic nuclei, such as N,N-bis(2-hydroxyethyl)aniline or p,p′-bis(2-hydroxyethylamino)diphenylmethane.

Alternatively, the epoxy constituent may be derived from mono nuclear phenol, such as, for example, from resorcinol or hydroquinone, or may be based on polynuclear phenol, such as, for example, bis(4-hydroxyphenyl)methane (bisphenol F), 2,2-bis(4-hydroxyphenyl)propane (bisphenol A), or on condensation products, obtained under acidic conditions, of phenol or cresol with formaldehyde, such as phenol novolac or cresol novolac.

A suitable epoxy constituent alternatively may include poly(N-glycidyl) compound, which is, for example, obtainable by dehydrochlorination of the reaction product of epichlorohydrin with an amine that comprise at least two amine hydrogen atoms, such as, for example, n-butylamine, aniline, toluidine, m-xylylene diamine, bis(4-aminophenyl)methane or bis(4-methylaminophenyl)-methane. An exemplary poly(N-glycidyl) compound also includes an N,N′-diglycidyl derivative of cycloalkyleneurea, such as ethyleneurea or 1,3-propyleneurea, or a N,N′-diglycidyl derivative of hydantoin, such as of 5,5-dimethylhydantoin.

A further example of a suitable epoxy constituent includes poly(S-glycidyl) compound, which is a di-S-glycidyl derivative, which is derived from dithiol, such as, for example, ethane-1,2-dithiol or bis(4-mercaptomethylphenyl) ether.

An additional example of an epoxy constituent is bis(2,3-epoxycyclopentyl)ether, 2,3-epoxy cyclopentyl glycidyl ether, 1,2-bis(2,3-epoxycyclopentyloxy)ethane, bis(4-hydroxycyclohexyl)methane diglycidyl ether, 2,2-bis(4-hydroxycyclohexyl)propane diglycidyl ether, 3,4-epoxycyclohexylmethyl-3,4-epoxycyclohexane, 3,4-epoxy-6-methylcyclohexylmethyl-3,4-epoxy-6-methylcyclohexanecarboxylate, di(3,4-epoxycyclohexylmethyl)hexanedioate, di(3,4-epoxy-6-methylcyclohexylmethyl)hexanedioate, ethylenebis(3,4-epoxycyclohexanecarboxylate), ethanedioldi(3,4-epoxycyclohexylmethyl)ether, vinylcyclohexene dioxide, dicyclopentadiene diepoxide, .alpha.-(oxiranylmethyl)-.omega.-(oxiranylmethoxy) poly(oxy-1,4-butanediyl), diglycidyl ether of neopentyl glycol, or 2-(3,4-epoxycyclohexyl-5,5-spiro-3,4-epoxy)cyclohexane-1,3-dioxane, or any combination thereof.

An epoxy resin in which the 1,2-epoxy groups are bonded to different heteroatoms or functional groups may also be useful. Such a compound includes, for example, the N,N,O-triglycidyl derivative of 4-aminophenol, the glycidyl ether glycidyl ester of salicylic acid, N-glycidyl-N′-(2-glycidyloxypropyl)-5,5-dimethylhydantoin, 2-glycidyloxy-1,3-bis(5,5-dimethyl-1-glycidylhydantoin-3-yl)propane, or any combination thereof.

In addition, a prereacted adduct of such epoxy resin with a hardener is suitable for epoxy resin. A mixture of epoxy constituents may also be used in the binder formulation.

In a particular embodiment, an epoxy constituent includes cycloaliphatic diepoxide. An exemplary cycloaliphatic diepoxide is bis(4-hydroxycyclohexyl)methane diglycidyl ether, 2,2-bis(4-hydroxycyclohexyl)propane diglycidyl ether, 3,4-epoxycyclohexylmethyl-3,4-epoxycyclohexanecarboxylate, 3,4-epoxy-6-methylcyclohexylmethyl-3,4-epoxy-6-methylcyclohexanecarboxylate, di(3,4-epoxycyclohexylmethyl)hexanedioate, di(3,4-epoxy-6-methylcyclohexylmethyl)hexanedioate, ethylenebis(3,4-epoxycyclohexanecarboxylate), ethanedioldi(3,4-epoxycyclohexylmethyl) ether, 2-(3,4-epoxycyclohexyl-5,5-spiro-3,4-epoxy)cyclohexane-1,3-dioxane, or any combination thereof.

The epoxy constituent can have a molecular weight that varies over a wide range. In general, the epoxy equivalent weight, i.e., the number average molecular weight divided by the number of reactive epoxy groups, is preferably in the range of 60 to 1000.

Typically, the binder formulation includes from about 10% to about 90% by weight of the epoxide constituent. Weight percentages of constituents of the binder formulation are stated relative to the total weight of the curable components of the composition, unless specified otherwise.

The binder formulation may include another cationically curable component, such as a cyclic ether component, a vinyl ether component, a cyclic lactone component, a cyclic acetal component, a cyclic thioether component, a spiro orthoester component, an oxetane-functional component, or any combination thereof. In a particular embodiment, an oxetane is a component comprising one or more oxetane groups, i.e. one or more four-member ring structures according to formula (5):
The binder formulation may also include a cationic photoinitiator. Generally, a cationic photoinitiator that, upon exposure to actinic radiation, forms cations that initiate reactions of the epoxy constituents can be used. Such a photoinitiator includes, for example, an onium salt with anions of weak nucleophilicity. An example includes halonium salt, iodosyl salt or sulfonium salt, such as are described in published European patent application EP 153904 and WO 98/28663, sulfoxonium salt, such as described, for example, in published European patent applications EP 35969, 44274, 54509, and 164314, diazonium salt, such as described, for example, in U.S. Pat. Nos. 3,708,296 and 5,002,856, or any combination thereof. Another cationic photoinitiator includes metallocene salt, such as described, for example, in published European applications EP 94914 and 94915. An additional suitable onium salt initiator or metallocene salt can be found in “UV Curing, Science and Technology”, (Editor S. P. Pappas, Technology Marketing Corp., 642 Westover Road, Stamford, Conn., U.S.A.) Or “Chemistry & Technology of UV & EB Formulation for Coatings, Inks & Paints”, Vol. 3 (edited by P. K. T. Oldring). In a particular example, a cationic photoinitiator includes a compound of formula I, II or III below,
wherein:
R1, R2, R3, R4, R5, R6, and R7 are, independent of each other, a C6-C18 aryl-group that may be unsubstituted or substituted by suitable radicals; L is boron, phosphorus, arsenic, or antimony; Q is a halogen atom or some of the radicals Q in an anion LQ_m⁻ may also be a hydroxy group; and m is an integer that corresponds to the valence of L plus 1. An example of a C6-C18 aryl group includes a phenyl, a naphthyl, an anthryl, or a phenanthryl group. A suitable radical includes alkyl, for example, C1-C6 alkyl, such as methyl, ethyl, n-propyl, isopropyl, n-butyl, sec-butyl, iso-butyl, tert-butyl, or various pentyl or hexyl isomers; alkoxy, for example, C1-C6 alkoxy, such as methoxy, ethoxy, propoxy, butoxy, pentyloxy, or hexyloxy; alkylthio, such as C1-C6 alkylthio, such as methylthio, ethylthio, propylthio, butylthio, pentylthio, or hexylthio; halogen, such as fluorine, chlorine, bromine, or iodine; amino; cyano; nitro; arylthio, such as phenylthio; or any combination thereof. An example of a halogen atom Q includes chlorine or fluorine. An anion LQ_m⁻ may include BF₄⁻, PF₆⁻, AsF₆⁻, SbF₆⁻, SbF₅(OH)⁻, or any combination thereof. In a particular example, the photoinitiator includes a compound of formula III wherein R5, R6, and R7 are aryl, such as phenyl, biphenyl, or any combination thereof.
In another example, the photoinitiator includes a compound of formula (IV)
[R₈(Fe^IIR₉)_c]_d^+c[X]_c^−d, (IV)
wherein, c is 1 or 2; d is 1,2,3, 4 or 5; X is a non-nucleophilic anion, for example, PF₆⁻, AsF₆⁻, SbF₆⁻, CF₃SO₃⁻, C₂F₅SO₃⁻, n-C₃F₇SO₃⁻, n-C₄F₉SO₃⁻, n-C₆F₁₃SO₃⁻, or n-C₈F₁₇SO₃⁻; R8 is a pi-arene; and R9 is an anion of a pi-arene, such as a cyclopentadienyl anion. An example of a pi-arene or an anion of pi-arene is found in published European patent application EP 94915. An additional example of a pi-arene includes toluene, xylene, ethylbenzene, cumene, methoxybenzene, methylnaphthalene, pyrene, perylene, stilbene, diphenylene oxide, diphenylene sulfide, or any combination thereof. In a particular example, the pi-arene is cumene, methylnaphthalene, or stilbene.
An example of a nonnucleophilic anion X− includes FSO₃⁻, an anion of an organic sulfonric acid or of a carboxylic acid; or an anion LQ_m⁻, as defined above. In particular, an anion may be derived from a partially fluoro or perfluoroaliphatic or a partially fluoro or a perfluoro aromatic carboxylic acid, or in particular, from a partially fluoro or perfluoroaliphatic or a partially fluoro or perfluoroaromatic organic sulfonic acid, or is an anion LQ_m⁻. A further example of an anion X⁻ includes BF₄⁻, PF₆⁻, AsF₆⁻, SbF₆⁻, SbF₅(OH)⁻, CF₃SO₃⁻, C₂F₃SO₃⁻, n-C₃F₇SO₃⁻, n-C₄F₉SO₃⁻, n-C₆F₁₃SO₃⁻, n-C₈F₁₇SO₃⁻, C₆F₅SO₃⁻, phosphorus tungstate, silicon tungstate, or any combination thereof. In particular, an anion is PF₆⁻, AsF₆⁻, SbF₆⁻, CF₃SO₃⁻, C₂F₃SO₃⁻, n-C₃F₇SO₃⁻, n-C₄F₉SO₃⁻, n-C₆F₁₃SO₃⁻, n-C₈F₁₇SO₃⁻, or any combination thereof.
A metallocene salt can also be used in combination with an oxidizing agent. Such a combination is described in published European patent application EP 126712.
In a particular embodiment, the binder formulation includes from about 0.1 wt % to about 20 wt %, such as about 0.2 wt % to about 10 wt %, of cationic photoinitiator, based on the total weight of the binder formulation.
To increase the light efficiency, or to sensitize the cationic photoinitiator to specific wavelengths, such as for example specific laser wavelengths or a specific series of laser wavelengths, a sensitizer may be used, depending on the type of initiator. An exemplary sensitizer includes a polycyclic aromatic hydrocarbon, an aromatic keto compound, or any combination thereof. A specific example of a sensitizer is mentioned in published European patent application EP 153904. An exemplary sensitizer includes benzoperylene, 1,8-diphenyl-1,3,5,7-octatetraene, or 1,6-diphenyl-1,3,5-hexatriene, as described in U.S. Pat. No. 5,667,937. An additional factor in the choice of sensitizer is the nature and primary wavelength of the source of actinic radiation.
In an embodiment, the binder formulation may include a radically polymerizable constituent. For example, the binder formulation may include a compound having at least one ethylenic unsaturation which can be polymerized with radicals. An example of a suitable ethylenic unsaturation is a group, such as acrylate, methacrylate, styrene, vinylether, vinyl ester, N-substituted acrylamide, N-vinyl amide functionalities, maleate ester, fumarate ester, or any combination thereof. In particular embodiments, the ethylenic unsaturation is provided by a group containing acrylate, methacrylate, N-vinyl, or styrene functionality. For example, the binder formulation may include one or more compounds having one or more (meth)acrylate functionalities.
The free-radical polymerizable acrylic material that may be used in the binder formulation has, on average, at least one acrylic group which can be either the free acid or an ester. By “acrylic” is meant the group—CH═CR1CO₂R2, where R1 can be hydrogen or methyl and R2 can be hydrogen or alkyl. By “(meth)acrylate” is meant an acrylate, methacrylate, or any combination thereof. An acrylic material typically undergoes a polymerization or a crosslinking reaction initiated by a free radical. The acrylic material can be a monomer, an oligomer, a polymer, or any combination thereof. Typically, the acrylic material is a monomer or an oligomer.
An acrylic constituent includes, for example, diacrylate of cycloaliphatic or aromatic diol, such as 1,4-dihydroxymethylcyclohexane, 2,2-bis(4-hydroxycyclohexyl)propane, 1,4-cyclohexanedimethanol, bis(4-hydroxycyclohexyl)methane, hydroquinone, 4,4-dihydroxybiphenyl, bisphenol A, bisphenol F, bisphenol S, ethoxylated or propoxylated bisphenol A, ethoxylated or propoxylated bisphenol F, or ethoxylated or propoxylated bisphenol S, and any combination thereof.
A useful aromatic tri(meth)acrylate includes, for example, a reaction product of triglycidyl ether of trihydric phenol, or phenol or cresol novolac having three hydroxy groups with (meth)acrylic acid. In a particular embodiment, the acrylic material includes 1,4-dihydroxymethyl-cyclohexane diacrylate, bisphenol A diacrylate, ethoxylated bisphenol A diacrylate, or any combination thereof.
In a particular embodiment, the binder formulation may include an acrylate of bisphenol A diepoxide, such as Ebecryl 3700® from UCB Chemical Corporation, Smyrna, Ga., a mixed acrylate/epoxy compound of bisphenol A such as Ebecryl 3605®, or an acrylate of 1,4-cyclohexanedimethanol.
In addition to or instead of the aromatic or cycloaliphatic acrylic material, other acrylic materials can be useful. A poly(meth)acrylate having functionality of greater than 2, where appropriate, may be used in the binder formulation. Such a poly(meth)acrylate can be, for example, a tri, tetra, or pentafunctional monomeric or oligomeric aliphatic (meth)acrylate.
A suitable aliphatic polyfunctional (meth)acrylate includes, for example, a triacrylate or a trimethacrylate of hexane-2,4,6-triol, glycerol, or 1,1,1-trimethylolpropane; ethoxylated or propoxylated glycerol; or 1,1,1-trimethylolpropane or a hydroxy group-containing tri(meth)acrylate which is obtained by the reaction of triepoxy compound, such as, for example, triglycidyl ether of the mentioned triol, with (meth)acrylic acid. In addition, pentaerythritol tetra-acrylate, bistrimethylolpropane tetra-acrylate, pentaerythritol monohydroxytri(meth)acrylate, or dipentaerythritol monohydroxypenta(meth)acrylate, or any combination thereof may be useful.
In another embodiment, hexafunctional urethane (meth)acrylate is useful. Such urethane (meth)acrylate can be, for example, prepared by reacting a hydroxy-terminated polyurethane with acrylic acid or methacrylic acid, or by reacting an isocyanate-terminated prepolymer with hydroxyalkyl (meth)acrylate to follow the urethane (meth)acrylate. Also useful are an acrylate or a methacrylate, such as tris(2-hydroxyethyl)isocyanurate triacrylate.
Typically, the amount of radically polymerizable constituent is, for example, between about 0.1 wt % and about 60 wt %, such as between about 5 wt % and about 60 wt % or between about 10 wt % and about 40 wt %.
The binder formulation may include a radical initiator, such as a radical photoinitiator, especially in combination with radically polymerizable constituent. A photoinitiator that forms free radicals when irradiated can be used. Typical a photoinitiator includes benzoin, such as benzoin; benzoin ether, such as benzoin methyl ether, benzoin ethyl ether, or benzoin isopropyl ether; benzoin phenyl ether; benzoin acetate; acetophenone, such as acetophenone, 2,2-dimethoxyacetophenone, 4-(phenylthio)acetophenone, or 1,1-dichloroacetophenone; benzyl; benzil ketal, such as benzil dimethyl ketal, or benzil diethyl ketal; anthraquinones, such as 2-methylanthraquinone, 2-ethylanthraquinone, 2-tertbutylanthraquinone, 1-chloroanthraquinone, or 2-amylanthraquinone; triphenylphosphine; benzoylphosphine oxides, such as, for example, 2,4,6-trimethylbenzoyidiph-enylphosphine oxide (Lucirin TPO); benzophenone, such as benzophenone, or 4,4′-bis(N,N′-dimethylamino)benzophenone; thioxanthones or xanthones; acridine derivative; phenazene derivative; quinoxaline derivative; I-phenyl-1,2-propanedione-2-O-benzoyloxime; I-aminophenyl ketones; I-hydroxyphenyl ketones, such as I-hydroxycyclohexyl phenyl ketone, phenyl(1-hydroxyisopropyl)ketone or 4-isopropylphenyl(1-hydroxy-isopropyl)ketone; triazine compound, for example, 4′″-methyl thiophenyl-1-di(trichloromethyl)-3,5-S-triazine, S-triazine-2-(stilbene)-4,6-bistrichloromethyl or paramethoxy styryl triazine, or any combination thereof.
A suitable free-radical photoinitiator alternatively includes acetophenone, such as 2,2-dialkoxybenzophenone; a 1-hydroxyphenyl ketone, for example 1-hydroxycyclohexyl phenyl ketone, 2-hydroxy-1-{4-(2-hydroxyethoxy)phenyl}-2-methyl-1-propanone, or 2-hydroxyisopropyl phenyl ketone (also called 2-hydroxy-2,2-dimethylaceto-phenone), or 1-hydroxycyclohexyl phenyl ketone. Another class of free-radical photoinitiators comprises a benzil ketal, such as, for example, benzil dimethyl ketal. An alpha-hydroxyphenyl ketone, benzil dimethyl ketal, or 2,4,6-trimethylbenzoyldiphenylphosphine oxide is also useful as a photoinitiator.
Another class of suitable free radical photoinitiators includes an ionic dye-counter ion compound, which is capable of absorbing actinic rays and producing free radicals that can initiate the polymerization of an acrylate. As such, an ionic dye-counter ion compound can thus cure using visible light in an adjustable wavelength range of 400 to 700 nanometers. An additional ionic dye-counter ion compound and its mode of action are, for example, found in European patent application EP 223587 or U.S. Pat. No. 4,751,102,4,772,530 or 4,772,541. A further example of an ionic dye-counter ion compound includes an anionic dye-iodonium ion complexe, an anionic dye-pyryllium ion complexe or a cationic dye-borate anion compound of the following formula:
wherein D⁺ is a cationic dye and R12, R13, R14, and R15 are, each independently of the others, alkyl, aryl, alkaryl, allyl, aralkyl, alkenyl, alkynyl, an alicyclic or saturated or unsaturated heterocyclic group. An additional example of a radical R12 to R15 can be found, for example, in published European patent application EP 223587.
In a particular embodiment, the binder formulation may include about 0.01 wt % to about 20 wt % of free-radical photoinitiator, such as about 0.01 wt % to about 15 wt % of free-radical photoinitiator, based on the total weight of the composition.
A hydroxyl-group containing material may be used in the binder formulation. For example, the hydroxyl-group material may include liquid organic material having a hydroxyl functionality of at least 1, and preferably at least 2. The hydroxyl-group material may be a liquid or a solid that is soluble or dispersible in the remaining components. Typically, the material is substantially free of a group that substantially slows down the curing reaction. Often, the organic material contains two or more primary or secondary aliphatic hydroxyl groups (i.e., the hydroxyl group is bonded directly to a non-aromatic carbon atom). A monomer, an oligomer, or a polymer can be useful. The hydroxyl equivalent weight, i.e., the number average molecular weight divided by the number of hydroxyl groups, is typically in the range of 31 to 5000.
A representative example of a suitable organic material having a hydroxyl functionality of 1 includes alkanol, monoalkyl ether of polyoxyalkyleneglycol, monoalkyl ether of alkyleneglycol, or any combination thereof.
A representative example of a useful monomeric polyhydroxy organic material includes alkylene and arylalkylene glycol or polyol, such as 1,2,4-butanetriol, 1,2,6-hexanetriol, 1,2,3-heptanetriol, 2,6-dimethyl-1,2,6-hexanetriol, (2R,3R)-(−)-2-benzyloxy-1,3,4-butanetriol, 1,2,3-hexanetriol, 1,2,3-butanetriol, 3-methyl-1,3,5-pentanetriol, 1,2,3-cyclohexanetriol, 1,3,5-cyclohexanetriol, 3,7,11,15-tetramethyl-1,2,3-hexadecanetriol, 2-hydroxymethyltetrahydropyran-3,4,5-triol, 2,2,4,4-tetramethyl-1,3-cyclobutanediol, 1,3-cyclopentanediol, trans-1,2-cyclooctanediol, 1,16-hexadecanediol, 3,6-dithia-1,8-octanediol, 2-butyne-1,4-diol, 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 1,7-heptanediol, 1,8-octanediol, 1,9-nonanediol, 1-phenyl-1,2-ethanediol, 1,2-cyclohexanediol, 1,5-decalindiol, 2,5-dimethyl-3-hexyne-2,5-diol, 2,7-dimethyl-3,5-octadiyne-2-7-diol, 2,3-butanediol, 1,4-cyclohexanedimethanol, or any combination thereof.
A representative example of a useful oligomeric or polymeric hydroxyl-containing material includes polyoxyethylene or polyoxypropylene glycol or triol of molecular weights from about 200 to about 10,000; polytetramethylene glycol of various molecular weights; copolymer containing pendant hydroxy groups formed by hydrolysis or partial hydrolysis of a vinyl acetate copolymer, polyvinylacetal resin containing pendant hydroxyl groups; hydroxy-terminated polyester or hydroxy-terminated polylactone; hydroxy-functionalized polyalkadiene, such as polybutadiene; aliphatic polycarbonate polyol, such as an aliphatic polycarbonate diol; hydroxy-terminated polyether, or any combination thereof.
A hydroxyl-containing monomer includes 1,4-cyclohexanedimethanol or aliphatic or cycloaliphatic monohydroxy alkanol, or any combination thereof.
A typical hydroxyl-containing oligomer or polymer includes a hydroxyl or a hydroxyl/epoxy functionalized polybutadiene, 1,4-cyclohexanedimethanol, polycaprolactone diol or triol, ethylene/butylene polyol, monohydroxyl functional monomer, or any combination thereof. An example of polyether polyol is polypropylene glycol of various molecular weight or glycerol propoxylate-B-ethoxylate triol. Another example includes a linear or a branched polytetrahydrofuran polyether polyol available in various molecular weights, such as for example 250, 650, 1000, 2000, and 2900 MW.
In a particular embodiment, the binder formulation may include up to 60 wt % of polyol. For example, the binder formulation may include about 0.1 wt % to about 60 wt % polyol, such as between about 3 wt % and about 20 wt %.
The binder formulation includes a latent coloring component. In a particular embodiment, the latent coloring component forms a chromophore in response to curing of polymer constituent. In an exemplary embodiment, the latent coloring component forms color or changes color on contact with a photochemically generated photoacid. In a particular embodiment, the latent coloring component is a triaryl methane-, diphenyl methane-thiazine-, spiro-, lactam-, fluoran or isobenzofuranone-based color former. An example of triarylmethane-based color former includes 3-3-bis(p-dimethylaminophenyl)-6-dimethylaminophthalide, 3,3-bis(p-dimethylaminophenyl)phthalide, 3-(p-dimethylaminophenyl)-3-(1,2-dimethylindole-3-yl)phthalide, 3-(p-dimethylaminophenyl)-3-(2-methylindole-3-yl)phthalide, 3,3-bis(1,2-dimethylindole-3-yl)-5-dimethylaminophthalide, 3,3-bis(1,2-dimethylindole-3-yl)-6-dimethylaminophthalide, 3,3-bis(9-ethylcarbazole-3-yl)-6-dimethylaminophthalide, 3,3-bis(2-phenylindole-3-yl)-6-dimethylaminophthalide, 3-p-dimethylaminophenyl-3-(1-methylpyrrole-3-yl)-6-dimethylaminophthalide, etc., or triphenyl methane e.g., Crystal Violet Lactone, or any combination thereof.
A typical diphenylmethane-based latent colorant component includes 4,4′-bis-dimethylaminobenzhydryl benzyl ether, N-halophenyl-leucoauramine, N-2,4,5-trichlorophenyl-leucoauramine, or any combination thereof. An exemplary thiazine-based color former includes benzoyl-leucomethylene blue, p-nitrobenzoyl-leucomethylene blue, or any combination thereof. An exemplary spiro-based color former includes 3-methyl-spiro-dinaphthopyran, 3-ethyl-spiro-dinaphthopyran, 3-phenyl-spirodinapthopyran, 3-benzyl-spiro-dinaphthopyran, 3-methyl-naphtho-(6′-methoxybenzo)spiropyran, 3-propyl-spiro-dibenzopyran, or any combination thereof. A lactam-based color former includes rhodamine-b-anilinolactam, rhodamine-(p-nitroanilino) lactam, rhodamine-(o-chloroanilino)lactam, or any combination thereof. A fluoran-based color former includes 3,6-dimethoxyfluoran, 3,6-diethoxyfluoran, 3,6-dibutoxyfluoran, 3-dimethylamino-7-methoxyfluoran, 3-dimethylamino-6-methoxylfluoran, 3-dimethylamino-7-methoxyfluoran, 3-diethylamino-7-chlorofluoran, 3-diethylamino-6-methyl-7-chlorofluoran, 3-diethylamino-6,7-dimethylfuoran, 3-(N-ethyl-p-toluidino)-7-methylfluoran, 3-diethylamino-7-(N-acetyl-N-methylamino)fluoran, 3-diethylamino-7-N-methylaminofluoran, 3-diethylamino-7-dibenzylaminofluoran, 3-diethylamino-5-methyl-7-dibenzylaminofluoran, 3-diethylamino-7-(N-methyl-N-benzylamino)fluoran, 3-diethylamino-7-(N-chl-oroethyl-N-methylamino)fluoran, 3-diethylamino-7-diethylaminofluoran, 3-(N-ethyl-p-toluidino)-6-methyl-7-phenylaminofluoran, 3-(N-ethyl-p-toluidino)-6-methyl-7-phenylaminofluoran, 3-diethylamino-7-(2-carbomethoxy-phenylamino)fluoran, 3-(N-ethyl-N-isoamylamino)-6-methyl-7-phenylaminofluoran, 3-(N-cyclohexyl-N-methylamino)-6-methyl-7-phenylaminofluoran, 3-pyrrolidino-6-methyl-7-phenylaminofluoran, 3-piperidino-6-methyl-7-phenylaminofluoran, 3-diethylamino-6-methyl-7-xylidinofluoran, 3-diethylamino-7-(o-chlorophenylamino)fluoran, 3-dibutylamino-7-(o-chloro-phenylamino)fluoran, 3-pyrrolidino-6-methyl-7-p-butylphenylaminofluoran, or any combination thereof.
Latent colorant components permitting the production of a wide range of colors are described, for example, by Peter Gregory in High-Technology Applications of Organic Colourants, Plenum Press, pages 124-134.
In particular, a latent coloring component includes an isobenzofuranone-based color former or a color former that is available under the tradenames of Copikem and Pergascript. An example of such a coloring component inlcudes Copikem 20 (3,3-Bis(1-butyl-2-methyl-H-indol-3-yl)-1-(3H)-isobenzofuranone), Copikem 5 (2′-Di (phenylmethy)amino-6′-(diethylamino)spiro(isobenzofuran-1 (3H), 9′-(9H)xanthem)-3-one), Copikem 14 (a substituted phthalide), Copikem 7 (3-{(4Dimethylamino)-phenyl}-3-(1-butyl-2methylindol-3yl)-6-dimethyamino)-1-(3H)-isobenzofuranone), Copikem 37 (2-(2-Octoxyphenyl)-4-(4-dimethylaminophenyl)-6-(phenyl)pyridine), Pergascript Black I-R (6″-(Dimethylamino)-3″-methyl-2″-(phenylamino)spiro-(isobenzofuran-1(3H), 9″(9H)xanthem-3-one), or Pergascript Color Former (like diamiofluoran compound, bisaryl carbazolyl methane compound, phthalide compound, bisindolyl phthalide compound, aminofluoran compound, or quinazoline compound), or any combination thereof. While the above examples are presented for illustrative purposes, use of various other exemplary colorants can be envisaged based on the disclosure herein.
In general, the latent colorant or latent coloring component may react with or change color in response to byproducts or chemical changes associated with curing of the binder formulation. For example, the latent colorant may change color in response to activation of a cationic photoinitiator. In another example, the latent colorant may change color in response to a concentration of photoacid. In a further example, the latent colorant may change color in response to changes in concentration of monomeric constituents, solvents, or byproducts of the polymerization of monomers. In an additional example, the latent colorant may change color in response to generation of cations or the concentration of cations, in particular, cations, such as H⁺ cations, which may be expressed as pH in particular binder formulations and solvents.
In a particular embodiment, the binder formulation includes between about 0.0001 wt % and about 2.0 wt %, such as about 0.0005 wt % to about 1.0 wt %, latent coloring component.
The binder formulation may also include a filler. In an embodiment, an inorganic substance is used and provided for water-resisting capabilities and mechanical properties. An example of an inorganic filler includes silica, glass powder, alumina, alumina hydrate, magnesium oxide, magnesium hydroxide, barium sulfate, calcium sulfate, calcium carbonate, magnesium carbonate, silicate mineral, diatomaceous earth, silica sand, silica powder, titanium oxide, aluminum powder, bronze, zinc powder, copper powder, lead powder, gold powder, silver dust, glass fiber, titanic acid potassium whiskers, carbon whiskers, sapphire whiskers, verification rear whiskers, boron carbide whiskers, silicon carbide whiskers, silicon nitride whiskers, or any combination thereof.
The condition of the surface of the particles of the filler used and the impurities contained in filler from the manufacturing process can affect the curing reaction of the resin composition. In such a case, the filler particles may be washed with an appropriate primer.
The inorganic filler also may be surface-treated with a silane coupling agent. An exemplary silane coupling agent includes vinyl triclorosilane, vinyl tris(β-methoxyethoxy) silane, vinyltriethoxy silane, vinyltrimethoxy silane, r-(methacryloxypropyl)trimethoxy silane, β-(3,4-epoxycyclohexyl)ethyltrimethoxy silane, r-glycydoxypropyltrimethoxy silane, r-glycydoxypropylmethyl diethoxy silane, N-β-(aminoethyl)-r-aminopropyltrimethoxy silane, N-β-(aminoethyl)-.gamma.-aminopropylmethyldimethoxy silane, r-aminopropyltriethoxysilane, N-phenyl-r-amino propyl trimethoxy silane, r-mercaptopropyl trimethoxysilane, and r-chloropropyltrimethoxy silane, or any combination thereof.
The above inorganic filler may be used singly or in combination of two or more. In a particular embodiment, the binder formulation includes about 0.01 wt % to about 95 wt % filler relative to the total weight of the composition. For example, the binder may include about 10 wt % to about 90 wt %, or about 20 wt % to about 80 wt % filler.
In a further particular embodiment, the particulate filler may be formed of inorganic particles, such as, for example, metals (such as, for example, steel, Au or Ag) or a metal complex, such as, for example, metal oxide, metal hydroxide, metal sulfide, metal halogen complex, metal carbide, metal phosphate, inorganic salt (like, for example, CaCO₃), ceramics, or any combination thereof. An example of a metal oxide includes ZnO, CdO, SiO₂, TiO₂, ZrO₂, CeO₂, SnO₂, MoO₃, WO₃, Al₂O₃, In₂O₃, La₂O₃, Fe₂O₃, CuO, Ta₂O₅, Sb₂O₃, Sb₂O₅, or any combination thereof. A mixed oxide containing different metals may also be present. The nanoparticle, for example, may comprise a particle selected from the group consisting of ZnO, SiO₂, TiO₂, ZrO₂, SnO₂, Al₂O₃, co-formed silica alumina, or any combination thereof. The nanometer sized particle may also have an organic component, such as, for example, carbon black, highly crosslinked/core shell polymer nanoparticle, or an organically modified nanometer-size particle, or any combination thereof. Such a filler is described in, for example, U.S. Pat. No. 6,467,897 and WO 98/51747, hereby incorporated by reference.
Particulate filler formed via a solution-based processes, such as sol-formed or a sol-gel formed ceramic, are particularly well suited for use in the composite binder. A suitable sol is commercially available. For example, a colloidal silica in aqueous solution is commercially available under such trade designations as “LUDOX” (E.I. DuPont de Nemours and Co., Inc. Wilmington, Del.), “NYACOL” (Nyacol Co., Ashland, Ma.) or “NALCO” (Nalco Chemical Co., Oak Brook, Ill.). Many commercially available sols are basic, being stabilized by alkali, such as sodium hydroxide, potassium hydroxide, or ammonium hydroxide. An additional example of a suitable colloidal silica is described in U.S. Pat. No. 5,126,394, incorporated herein by reference. A well-suited particle includes sol-formed silica and sol-formed alumina. The sol can be functionalized by reacting one or more appropriate surface-treatment agents with the inorganic oxide substrate particle in the sol.
In a particular embodiment, the particulate filler is sub-micron sized. For example, the particulate filler may be a nano-sized particulate filler, such as a particulate filler having an average particle size about 3 to 500 nm. In an exemplary embodiment, the particulate filler has an average particle size about 3 nm to about 200 nm, such as about 3 nm to about 100 nm, about 3 nm to about 50 nm, about 8 nm to about 30 nm, or about 10 nm to about 25 nm. In a particular embodiment, the average particle size is not greater than about 500 nm, such as not greater than about 200 nm, less than about 100 nm, or not greater than about 50 nm. For the particulate filler, the average particle size may be defined as the particle size corresponding to the peak volume fraction in a small-angle neutron scattering (SANS) distribution curve or the particle size corresponding to 0.5 cumulative volume fraction of the SANS distribution curve.
The particulate filler may also be characterized by a narrow distribution curve having a half-width not greater than about 2.0 times the average particle size. For example, the half-width may be not greater than about 1.5 or not greater than about 1.0. The half-width of the distribution is the width of the distribution curve at half its maximum height, such as half of the particle fraction at the distribution curve peak. In one particular embodiment, the particle size distribution curve is mono-modal.
The particulate filler is generally dispersed in an external phase. Prior to curing, the particulate filler is colloidally dispersed within the binder formulation and forms a colloidal composite binder once cured. For example, the particulate material may be dispersed such that Brownian motion sustains the particulate filler in suspension. In general, the particulate filler is substantially free of particulate agglomerates. For example, the particulate filler may be substantially mono-disperse such that the particulate filler is dispersed as single particles, and in particular examples, has only insignificant particulate agglomeration, if any.
In a particular embodiment, the particles of the particulate filler are substantially spherical. Alternatively, the particles may have a primary aspect ratio greater than 1, such as at least about 2, at least about 3, or at least about 6, wherein the primary aspect ratio is the ratio of the longest dimension to the smallest dimension. The particles may also be characterized by a secondary aspect ratio defined as the ratio of orthogonal dimensions in a plane generally perpendicular to the longest dimension. The particles may be needle-shaped, such as having a primary aspect ratio at least about 2 and a secondary aspect ratio not greater than about 2, such as about 1. Alternatively, the particles may be platelet-shaped, such as having a primary aspect ratio at least about 2 and a secondary aspect ratio at least about 2.
In a particular embodiment, the particulate filler is prepared in an aqueous solution and mixed with the external phase of a suspension. The process for preparing such suspension includes introducing an aqueous solution, such as an aqueous silica solution; polycondensing the silicate, such as to a particle size of 3 nm to 50 nm; adjusting the resulting silica sol to an alkaline pH; optionally concentrating the sol; mixing the sol with constituents of the external fluid phase of the suspension; and optionally removing water or other solvent constituents from the suspension. For example, an aqueous silicate solution is introduced, such as an alkali metal silicate solution (e.g. a sodium silicate or potassium silicate solution) with a concentration in the range between 20% and 50% by weight based on the weight of the solution. The silicate is then polycondensed to a particle size of from 3 nm to 50 nm, for example, by treating the alkali metal silicate solution with acidic ion exchangers. The resulting silica sol is adjusted to an alkaline pH (e.g. pH>8) to stabilized against further polycondensation or agglomeration of existing particles. Optionally, the sol can be concentrated, for example, by distillation, typically to SiO₂concentration of about 30% to about 40% by weight. The sol is mixed with constituents of the external fluid phase. Thereafter, water or other solvent constituents are removed from the suspension. In a particular embodiment, the suspension is substantially water-free.
The fraction of the non-filler constituents in the pre-cured binder formulation, generally including the organic polymeric constituents, as a proportion of the binder formulation can be about 20% to about 95% by weight, for example, about 30% to about 95% by weight, and typically from about 50% to about 95% by weight, and even more typically from about 55% to about 80% by weight. The fraction of the dispersed particulate filler phase can be about 5% to about 80% by weight, for example, about 5% to about 70% by weight, typically from about 5% to about 50% by weight, and more typically from about 20% to about 45% by weight. The colloidally dispersed and submicron particulate fillers described above are particularly useful in concentrations at least about 5 wt %, such as at least about 10 wt %, at least about 15 wt %, at least about 20 wt %, or as great as 40 wt % or higher. In contrast with traditional fillers, the solution formed nanocomposites exhibit low viscosity and improved processing characteristics at higher loading. The amounts of components are expressed as weight % of the component relative to the total weight of the composite binder formulation, unless explicitly stated otherwise.
The binder formulation including an external phase comprising polymeric or monomeric constituents and optionally including dispersed particulate filler may be used to form a make coat, size coat, compliant coat, or back coat of a coated abrasive article. In a exemplary process for forming a make coat, the binder formulation is coated on a backing, abrasive grains are applied over the make coat, and the make coat is cured. A size coat may be applied over the make coat and abrasive grains. In another exemplary embodiment, the binder formulation is blended with the abrasive grains to form abrasive slurry that is coated on a backing and cured. Alternatively, the abrasive slurry is applied to a mold, such as injected into a mold and cured to form a bonded abrasive article.
The abrasive grains may be formed of any one of or a combination of abrasive grains, including silica, alumina (fused or sintered), zirconia, zirconia/alumina oxide, silicon carbide, garnet, diamond, cubic boron nitride, silicon nitride, ceria, titanium dioxide, titanium diboride, boron carbide, tin oxide, tungsten carbide, titanium carbide, iron oxide, chromia, flint, emery, or any combination thereof. For example, the abrasive grains may be selected from a group consisting of silica, alumina, zirconia, silicon carbide, silicon nitride, boron nitride, garnet, diamond, cofused alumina zirconia, ceria, titanium diboride, boron carbide, flint, emery, alumina nitride, or a blend thereof. Particular embodiments have been created by use of dense abrasive grains comprised principally of alpha-alumina.
The abrasive grain may also have a particular shape. Examples of such shapes include rods, triangles, pyramids, cones, solid spheres, hollow spheres and the like. Alternatively, the abrasive grain may be randomly shaped.
The abrasive grains generally have an average grain size not greater than 2000 microns, such as not greater than about 1500 microns. In another example, the abrasive grain size is not greater than about 750 microns, such as not greater than about 350 microns. For example, the abrasive grain size may be at least 0.1 microns, such as from about 0.1 microns to about 1500 micron, and more typically from about 0.1 microns to about 200 microns or from about 1 micron to about 100 microns. The grain size of the abrasive grains is typically specified to be the longest dimension of the abrasive grain. Generally, there is a range distribution of grain sizes. In some instances, the grain size distribution is tightly controlled.
In a blended abrasive slurry including the abrasive grains and the binder formulation, the abrasive grains provide from about 10% to about 90%, such as from about 30% to about 80%, of the weight of the abrasive slurry.
The abrasive slurry may further include a grinding aid to increase the grinding efficiency and cut rate. Useful grinding aids can be inorganic based, such as halide salts, for example sodium cryolite, potassium tetrafluoroborate, etc.; or organic based, such as chlorinated waxes, for example, polyvinyl chloride. A particular embodiment includes cryolite and potassium tetrafluoroborate with particle size ranging from 1 micron to 80 microns, and most typically from 5 microns to 30 microns. The weight percent of grinding aid ranges is generally not greater than about 50 wt %, such as from about 0 wt % to about 50 wt %, and most typically from about 10 wt % to about 30 wt % of the entire slurry (including the abrasive grains).
FIG. 1 illustrates an exemplary embodiment of a coatedabrasive article100, which includesabrasive grains106 secured to a backing orsupport member102. Generally, theabrasive grains106 are secured to thebacking102 by amake coat104. Themake coat104 includes a binder, which is typically formed of a cured binder formulation including latent colorant. When the binder formulation is cured the latent colorant reacts to form reaction activated chromophores that impart color to the binder or change the color of the binder.
The coatedabrasive article100 may further include asize coat108 overlying themake coat104 and theabrasive grains106. Thesize coat108 generally functions to further secure theabrasive grains106 to thebacking102 and may also provide grinding aids. Thesize coat108 is generally formed from a cured binder formulation that may be the same or different from the make coat binder formulation and may include a second latent colorant.
The coated abrasive100 may also, optionally, include aback coat112. Theback coat112 functions as an anti-static layer, preventing abrasive grains from adhering to the back side of thebacking102 and preventing swarf from accumulating charge during sanding. In another example, theback coat112 may provide additional strength to thebacking102 and may act to protect the backing102 from environmental exposure. In another example, theback coat112 can also act as a compliant layer. The compliant layer may act to relieve stress between themake coat104 and thebacking102.
The backing may be flexible or rigid. The backing may be made of any number of various materials including those conventionally used as backings in the manufacture of coated abrasives. An exemplary flexible backing includes a polymeric film (including primed film), such as polyolefin film (e.g., polypropylene including biaxially oriented polypropylene), polyester film (e.g., polyethylene terephthalate), polyamide film, cellulose ester film, metal foil, mesh, foam (e.g., natural sponge material or polyurethane foam), cloth (e.g., cloth made from fibers or yarns comprising polyester, nylon, silk, cotton, poly-cotton or rayon), paper, vulcanized paper, vulcanized rubber, vulcanized fiber, nonwoven materials, any combination thereof, or any treated version thereof. A cloth backing may be woven or stitch bonded. In a particular example, the backing is selected from a group consisting of paper, polymer film, cloth, cotton, poly-cotton, rayon, polyester, poly-nylon, vulcanized rubber, vulcanized fiber, metal foil, or any combination thereof. In another example, the backing includes polypropylene film or polyethylene terephthalate (PET) film.
The backing may, optionally, have at least one of a saturant, a presize layer or a backsize layer. The purpose of these layers is typically to seal the backing or to protect yarn or fibers in the backing. If the backing is a cloth material, at least one of these layers is typically used. The addition of the presize layer or backsize layer may additionally result in a “smoother” surface on either the front or the back side of the backing. Other optional layers known in the art may also be used (e.g., tie layer; see, e.g., U.S. Pat. No. 5,700,302 (Stoetzel et al.), the disclosure of which is incorporated by reference).
An antistatic material may be included in any of the above cloth treatment materials. The addition of an antistatic material can reduce the tendency of the coated abrasive article to accumulate static electricity when sanding wood or wood-like material. Additional details regarding antistatic backings and backing treatments can be found in, for example, U.S. Pat. No. 5,108,463 (Buchanan et al.); U.S. Pat. No. 5,137,542 (Buchanan et al.); U.S. Pat. No. 5,328,716 (Buchanan); and U.S. Pat. No. 5,560,753 (Buchanan et al.), the disclosures of which are incorporated herein by reference.
The backing may be a fibrous reinforced thermoplastic, such as described, for example, in U.S. Pat. No. 5,417,726 (Stout et al.), or an endless spliceless belt, as described, for example, in U.S. Pat. No. 5,573,619 (Benedict et al.), the disclosures of which are incorporated herein by reference. Likewise, the backing may be a polymeric substrate having hooking stems projecting therefrom, such as that described, for example, in U.S. Pat. No. 5,505,747 (Chesley et al.), the disclosure of which is incorporated herein by reference. Similarly, the backing may be a loop fabric, such as that described, for example, in U.S. Pat. No. 5,565,011 (Follett et al.), the disclosure of which is incorporated herein by reference.
In some examples, a pressure-sensitive adhesive is incorporated onto the back side of the coated abrasive article such that the resulting coated abrasive article can be secured to a pad. Exemplary pressure-sensitive adhesives include latex crepe, rosin, acrylic polymer or copolymer, including polyacrylate ester (e.g., poly(butyl acrylate)), vinyl ether (e.g., poly(vinyl n-butyl ether)), alkyd adhesive, rubber adhesives (e.g., natural rubber, synthetic rubber, chlorinated rubber), or any mixture thereof.
An exemplary rigid backing includes a metal plate, a ceramic plate, or the like. Another example of a suitable rigid backing is described, for example, in U.S. Pat. No. 5,417,726 (Stout et al.), the disclosure of which is incorporated herein by reference.
A coated abrasive article, such as the coatedabrasive article100 ofFIG. 1, may be formed by coating a backing with a binder formulation or abrasive slurry. Optionally, the backing may be coated with a compliant coat or back coat prior to coating with the make coat. Typically, the binder formulation is applied to the backing to form the make coat. In an embodiment, abrasive grains are applied with the binder formulation, wherein the abrasive grains are blended with the binder formulation to form abrasive slurry prior to application to the backing. Alternatively, the binder formulation is applied to the backing to form the make coat and the abrasive grains are applied to the make coat, such as through electrostatic and pneumatic methods. The binder formulation is cured such as through thermal methods or exposure to actinic radiation, causing a color change in the latent colorant.
Optionally, a size coat is applied over the make coat and abrasive grains. The size coat may be applied prior to curing the make coat, the make coat and size coat being cured simultaneously. Alternatively, the make coat is cured prior to application of the size coat and the size coat is cured separately. Latent colorants in the size coat may change color during curing.
The binder formulation forming the make coat, the size coat, the compliant coat or the back coat may include colloidal binder formulation. The colloidal binder formulation may include sub-micron particulate filler, such as nano-sized particulate filler having a narrow particle size distribution. In a particular embodiment, the colloidal binder formulation is cured to form the size coat. In another embodiment, the colloidal binder formulation is cured to form the make coat. Alternatively, the colloidal binder formulation may be cured to form the optional compliant coat or the optional back coat.
In a particular embodiment, the coats and abrasive grains may be patterned to form structures. For example, the make coat may be patterned to form surface structures that enhance abrasive article performance. Patterns may be pressed or rolled into the coats using, for example, a rotogravure apparatus to form a structured or engineered abrasive article.
An exemplary embodiment of an engineered or structured abrasive is illustrated inFIG. 2. The structured abrasive includes abacking202 and alayer204 including abrasive grains. Thebacking202 may be formed of the materials described above in relation to thebacking102 ofFIG. 1. Generally, thelayer204 is patterned to havesurface structures206.
Thelayer204 may be formed as one or more coats. For example, thelayer204 may include a make coat and optionally, a size coat. Thelayer204 generally includes abrasive grains and a binder. In one exemplary embodiment, the abrasive grains are blended with a binder formulation to form an abrasive slurry. Alternatively, the abrasive grains are applied to the binder after the binder is coated on thebacking202. Optionally, a functional powder may be applied over thelayer204 to prevent thelayer204 from sticking to the patterning tooling. The binder of the make coat or the size coat may include latent colorant. The structuredabrasive article200 optionally may include compliant and back coats (not shown). These coats may function as described above.
In a further example, a binder formulation including latent colorant may be used to form bonded abrasive articles, such as theabrasive article300 illustrated inFIG. 3. In a particular embodiment, binder formulation and abrasive grains are blended to form abrasive slurry. The abrasive slurry is applied to a mold and the binder formulation is cured, causing a change in color of the latent colorant. The resulting abrasive article, such asarticle300, includes the abrasive grains bound by nano-composite binder in a desired shape.
In a particular embodiment, the abrasive article is formed by blending nanocomposite precursors with other polymeric precursors and constituents. For example, a nanocomposite epoxy precursor, including nano-sized particulate filler and epoxy precursor, is mixed with acrylic precursor to form a nanocomposite binder formulation. The binder formulation is applied to a substrate, such as a backing or to a mold. Abrasive grains are also applied to the substrate and the binder formulation is cured.
When the nanocomposite binder forms a make coat for a coated abrasive article, the nanocomposite binder formulation may be applied to a backing and abrasive grains applied over the formulation. Alternatively, the binder formulation may be applied over the abrasive grains to form a size coat. In another example, the binder formulation and the abrasive grains may be blended and applied simultaneously to form a make coat over a substrate or to fill a mold. Generally, the binder formulation may be cured using thermal energy or actinic radiation, such as ultraviolet radiation.
In a particular embodiment, the binder formulation includes an epoxy constituent, a cationic photoinitiator within the epoxy constituent, and a latent colorant configured to change color in response to activation of the cationic photoiniator. The binder formulation may include about 10 wt % to about 90 wt %, such as about 65 wt % to about 80 wt %, of the epoxy constituent and may include about 0.1 wt % to about 20 wt %, such as about 0.1 wt % to about 4.0 wt %, of the cationic photoinitiator. The epoxy constituent may include nano-sized particulate filler, such as filler having particle size not greater than about 100 nm, such as not greater than about 50 nm.
The binder formulation may include an acrylic constituent and a radical generating photoinitiator. The binder formulation may include about 0.1 wt % to about 60 wt %, such as about 5 wt % to about 15 wt %, of the acrylic constituent and may include about 0.01 wt % to about 20 wt %, such as about 0.1 wt % to about 4 wt %, radical generating photoinitiator. The acrylic constituent may include nano-sized particulate filler, such as filler having particle size not greater than about 100 nm, such as not greater than about 50 nm. The binder formulation may also include a polyol constituent in an amount of about 0.1 wt % to about 60 wt %, such as about 10 wt % to about 17 wt %.
The latent colorant may exhibit a specific color based on curing of the epoxy constituent. In an example, the latent colorant reacts with byproducts of the cationic photoinitiator to change color. The binder formulation may include one or more colorants. For example, the binder formulation may further include a second latent colorant. The second latent colorant may change to a second color based on the curing. In another example, the second colorant changes color in response to a different reaction, such as activation of a radical generating photoinitiator.
In an exemplary embodiment, the latent colorant and the second latent colorant may together change to appear as a desirable color. For example, a first reaction activated chromophore associated with the first latent colorant may have a first electromagnetic energy absorption profile and a second reaction activated chromophore associated with the second latent colorant may have a second electromagnetic energy absorption profile. In an example, the first electromagnetic energy absorption profile is different from the second electromagnetic energy absorption profile. In a further example, the first electromagnetic energy absorption profile and the second electromagnetic energy absorption profile appear as a desired color.
In an alternative embodiment, a latent colorant may be selected for addition to a binder formulation to provide color coding of binder formulations. For example, a first binder formulation may include a first latent colorant and a second binder formulation may include a second latent colorant. In such an embodiment, the color of a cured abrasive product may aid in identifying the binder formulation used to form the cured abrasive product. In a further example, each coat, such as a make coat or a size coat, may be formed from a different binder formulation and each of the different binder formulations may include a different latent colorant.
The binder formulation may be cured to form an abrasive product, such as a layer of a coated abrasive product. Latent colorants become chromophores through reactions associated with curing of the polymer components. Generally, the latent colorants and chromophores are organic, not to be confused with inorganic pigments. Typically, the binder formulation and resulting abrasive product are free of particulate pigment. In some examples, particulate pigment can interfere with curing through actinic radiation, causing defects in resulting abrasive products.
In another embodiment, the disclosure is directed to a method of manufacturing an abrasive article. The method includes initiating a curing process on a workpiece, determining a target color exhibited by the workpiece, and terminating the curing process based on the target color. The target color may represent partial curing or full curing. The curing process may include photo curing or thermal curing. In an example, a make coat is applied to the abrasive article workpiece prior to curing. In another example, an uncured size coat is applied to the workpiece prior to curing. In a further example, a mold is filled to form the workpiece. A second curing process may be initiated after terminating the curing process, a second target color may be determined and the second curing process terminated based on the second target color.
In a further exemplary embodiment, the disclosure is directed to a method of controlling abrasive product quality. The method includes forming an abrasive product having a polymer matrix and a reaction activated chromophore, inspecting the abrasive product for a color characteristic, and categorizing the abrasive product based on the color characteristic. The color characteristic may, for example, be a target color or color uniformity. Categorizing the abrasive product may include rejecting the abrasive product, accepting the abrasive product or grading the abrasive product. Grades may be associated with abrasive product usage conditions. The product may be further cured after categorizing.
Measurement of color can be performed with a chromameter. When the resin composition is opaque, for example, due to the presence of a filler, the color of the resin and the article is measured with a chromameter on the article or resin. In an example, a chromameter provides three values in the L*a*b color scale (CIELAB). The CIELAB color scale is an approximate uniform color scale. In a uniform color scale, the differences between points plotted in the color space correspond to visual differences between the colors plotted. The CIELAB color space is organized in a cube form. The L* axis runs from the top to bottom. The maximum L* is 100, which represents a reflecting diffuser. The minimum L* is zero, which represents black. The a* and b* axis have no specific numerical limit. Positive a* is typically red and negative a* is typically green. Positive b* is generally yellow and negative b* is generally blue. For example, when a* is −60, it represents green and when a* is +60, it represents red. The b* represents blue when it is −60 and yellow when it is +60. Articles having a* and b* value between −20 and 20 typically have a grey appearance. Articles having a* and b* values between −20 and −60 or between 20 and 60 are generally more colorful.
Typically, conventional resin compositions with and without fillers but without latent colorant exhibit large L* values of between 90 and 100. In contrast, embodiments of articles, for example, formed by UV-curing of a resin including latent colorant exhibit a different color than the uncured resin. Such a color may be expressed as a change in L* value, a* value, or b* value relative to the resin. In an example, the L* value may change at least about 10 units, such as at least about 20 units. Typically, the a* or b* values of an article change by at least about 10 units after cure of the resin. For instance, the a* or b* value may change by at least about 20 units. In an exemplary embodiment, the L* value may not change substantially, but the color may change, for example, from red to blue. In such an embodiment, the a* or b* value may change at least about 20 units, such as at least about 30 units. In another embodiment, the L* value of the article changes relative to the resin, so that cured articles have L* values of between 0 and 85, such as between 20 and 75. In an example, the a* or b* value of the cured articles may stay the same as the values of the resin when the L* value changes.
In a particular embodiment, the L* value of a binder formulation or an abrasive article workpiece may change by at least about 10%, such as at least about 20% or at least about 30%. In another example, the a* value or the b* value may change by at least about 10%, such as at least about 20% or at least about 30%. When determining a target color, the method may include determining a target L* value or a change in L* value. Alternatively, the method may include determining a target a* value or a target b* value or changes in the a* value or the b* value.

EXAMPLE 1

An example binder formulation includes:



INGREDIENT	Wt. %	Description

Nanopox XP 22/0314	72.02	Epoxy
4,8-bis(hydroxymethyl)	14.40	Polyol
tricyclo[5.2.1.0)decane
Chivacure 184	0.48	Photoinitiator
Chivacure 1176	2.88	Photoinitiator
Nanocryl XP 21/0954	9.60	Acrylate
Specialty Blue 1	0.40	additive
BYK A-501	0.02	additive
Silwet L 7600	0.20	additive
Totals:	100.00

EXAMPLE 2

Sample binder formulations are prepared and cured. The color of the cured samples are tested using a HunterLab Color Quest XE chromameter in reflectance test mode with a D65 illuminant and at an angle of 10°. The color of the samples is represented in the CIELAB color scale. A white backing medium is used during measurement.

Effect of dye concentration on binder color is determined by testing binder formulations in a standardized abrasive article configuration (4 inch length and 10 inch width). The binder formulations at different dye concentrations are used as a size coat over abrasive grains and a make coat. Film samples that have size coatings at different dye concentration are UV cured at 300 W D bulb/600 W H bulb at a line speed 50 feet/minute. The abrasive grains are 80 micron heat-treated semi-friable aluminum oxide from Treibacher (BFRPL) P180 grit and the make coat is formed of UV-curable epoxy/acrylate resins. The abrasive grains and make coat overlie a polyester backing. The effect of dye concentration on the value L*, a*, b* is determined. Size coats on sample abrasive articles are formed from binder formulations including Nanopox XP A610 available from Hanse Chemie, an epoxy resin including 3,4-epoxy cyclohexyl methyl-3,4-epoxy cyclohexyl carboxylate and 40 wt % colloidal silica particulate filler. The binder formulations also include UVR 6105, which includes 3,4-epoxy cyclohexyl methyl-3,4-epoxy cyclohexyl carboxylate and no particulate filler. The binder formulations further include a polyol (4,8-bis(hydroxymethyl) tricyclo(5.2.1.0)decane), a cationic photoinitiator (Chivacure 1176), a radical photoinitiator (Irgacure 2022, available from Ciba®), acrylate precursor (SR 399, a dipentaerythritol pentaacrylate available from Atofina-Sartomer, Exton, Pa.), and dye (specialty blue 1, available from Noveon Hilton Davis, Inc., 2235 Langdon Farms Rd., Cincinnati, Ohio 45237-4790).

Table 1 illustrates the concentration of components in the binder formulations and the resulting value of L*, a*, and b*. Generally, increasing the concentration of Specialty Blue 1 dye causes a reduction in L* for the cured binder formulation. In addition, b* changes in a negative direction with increasing Specialty Blue 1 dye in the binder formulation.

TABLE 1


INGREDIENT	A	B	C	D

Nanopox A610	60.00	60.00	60.00	60.00
UVR 6105	19.92	19.92	19.92	19.92
4,8-bis(hydroxymethyl)	13.50	13.50	13.50	13.50
tricyclo(5.2.1.0)decane
Irgacure 2022	0.48	0.48	0.48	0.48
Chivacure 1176	1.50	1.50	1.50	1.50
SR 399	4.60	4.60	4.60	4.60
Specialty Blue 1	0	0.1	0.2	0.4
L*	72.05	61.61	52.61	44.58
a*	−0.76	−7.52	−7.75	−2.36
b*	4.16	−10.96	−22.19	−30.11

Exemplary embodiments of the above described binder formulations and abrasive articles formed from the binder formulation may advantageously be useful in quality control, end product coloration, characterization of the product, and process control. Absence of particulate pigments advantageously leads to improved curing for actinic radiation curable binder formulations.

The above-disclosed subject matter is to be considered illustrative, and not restrictive, and the appended claims are intended to cover all such modifications, enhancements, and other embodiments, which fall within the true scope of the present invention. Thus, to the maximum extent allowed by law, the scope of the present invention is to be determined by the broadest permissible interpretation of the following claims and their equivalents, and shall not be restricted or limited by the foregoing detailed description.