Note: Descriptions are shown in the official language in which they were submitted.
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ABRASIVE ARTICLE HAVING REACTION ACTIVATED CHROMOPHORE
TECHNICAL FIELD
This disclosure, in general, relates to abrasive articles and methods for
forming same.
BACKGROUND ART
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
manufacturars 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 fme 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,
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improved abrasive articles and methods for manufacturing abrasive articles
would be
desirable.
DISCLOSURE OF INVENTION
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 einbodiment, ari abrasive article includes a reaction
activated
chromophore.
In an additional exemplary einbodiment, 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.
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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.
MODES FOR CARRYING OUT THE INVENTION
In a particular embodiment, the disclosure is directed to an abrasive article
having a
layer that is forined 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 metliod 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
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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 wliich 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 carboxytenninated 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-
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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 anine 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-
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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-l-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-methylcyclohexyhnethyl-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 otlierwise.
The binder formulation may include another cationically curable component,
such as a
cyclic ether component, a vinyl ether coinponent, 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):
Qj" CQ2 Z-R2
H2C1 CH2
0
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,
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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,
[R,I R-,]+[Qml ~I)
(II)
O
II [LQm]
R3'~ R4
(III)
R5 f,, R7
S [LQm]
I
R6
wherein:
Rl, 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,,; may
also be a
hydroxy group; and m is an integer that corresponds to the valence of L plus
1. An exainple
of a C6-C 18 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, Cl-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;
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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,,; may include BF~
, PF6 , AsF6 ,
SbFb , 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 (N)
[R$(F'eIIRq)c.1d+c1X1c d p (N)
wherein, c is 1 or 2; d is 1,2,3,4 or 5; X is a non-nucleophilic anion, for
example, PF6 , AsFb ,
SbF6 ; CF3SO3 , C2F5SO3 , n-C3F7S03 , n-C4F9S03 , n-C6F13S03 , or n-C8F17S03 ;
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, inethylnaphthalene, or stilbene.
An example of a noimucleophilic anion X- includes FSO3 , an anion of an
organic
sulfonric acid or of a carboxylic acid; or an anion LQ,,;, 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,;. 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-
C8F17S03 , 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.
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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
etliylenic 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 eitlier
the free acid or an
ester. By "acrylic" is meant the group --CH=CRICO2R2, where Rl 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)inethane, 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
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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-cyclohexanedimetlianol.
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)aciylate
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-
triunethylolpropane; 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 40wt %.
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;
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benzyl; benzil ketal, such as benzil dimethyl ketal, or benzil diethyl ketal;
anthraquinones,
such as 2-methylanthraquinone, 2-ethylanthraquinone, 2-tertbutylanthraquinone,
1-
chloroantliraquinone, 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; 1-
hydroxyphenyl
ketones, such as 1-hydroxycyclohexyl phenyl ketone, phenyl (1-
hydroxyisopropyl)ketone or
4-isopropylphenyl(l-hydroxy- isopropyl)ketone; triazine compound, for example,
4"'-methyl
thiophenyl-l-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-l-{4-(2-hydroxyethoxy)phenyl}-2-methyl-1 -propanone, or 2-
liydroxyisopropyl 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- triinethylbenzoyldiphenylphosphine 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. Nos. 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:
R12~ ~R14
/B; D+
R13 R15
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wherein D+ is a cationic dye and R12, R13, R14, and R15 are, eacli
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 liydroxyl-group
material may be a
liquid or a solid that is soluble or dispersible in the remaining coinponents.
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-l,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
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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-cyclohexanedimetharjol 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 polytetrahydrofitran 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 coinponent forms a chromophore in response to
curing of
polymer constituent. In an exeinplary embodiment, the latent coloring
coinponent 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-dimethylaminopheny- 1)-6-
dimethylaminophthalide, 3,3-bis(p-dimethylaminophenyl)phthalide, 3-(p-
dimethylaminophenyl)-3-(1,2-dimethylindole-3-yl)phthalide, 3-(p-
dimethylaininophenyl)-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.
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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-diethylainino-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-
chlorophenylainino)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)xanthen)-3-one), Copikem 14 (a
substituted
phthalide), Copikem 7 (3-{(4Dimethylamino)-phenyl}-3-(1-butyl-2methylindol-
3y1)-6-
dimethyamino)-1(3H )-isobenzofuranone), Copikem 37 (2-(2-Octoxyphenyl)-4-(4-
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dimethylaminophenyl)-6-(phenyl)pyridine), Pergascript Black I-R (6"-
(Dimethylamino)-3"-
methyl-2"-(phenylamino)spiro- (isobenzofuran-1 (311), 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 tliereof. 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 exainple, 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
0.0001wt%
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, magnesiuin 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 (13-
methoxyethoxy)
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silane, vinyltriethoxy silane, vinyltrimethoxy silane, r-
(methacryloxypropyl)trimethoxy silane,
13-(3,4-epoxycyclohexyl)ethyltrimethoxy silane, r-glycydoxypropyltrimethoxy
silane, r-
glycydoxypropylmethyl diethoxy silane, N- 13-(aminoethyl)-r-
aminopropyltrimethoxy silane,
N-13-(aminoethyl)-.gamma.-aminopropylmethyldimethoxy silane, r-
aininopropyltriethoxysilane, 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,
Si02, Ti02,
Zr02, CeO2, Sn02, M003, W03, A1203, In203, La203, Fe203, CuO, Ta2O5, Sb203,
Sb205, or
any combination thereof. A mixed oxide containing different metals may also be
present.
The nanoparticle, for exainple, may comprise a particle selected from the
group consisting of
ZnO, Si02, Ti02, Zr02, Sn02, A1203, 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, US 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.
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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 embodiinent, the
particulate filler
has an average particle size about 3 nm to about 200 nm, such as about 3 iun
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 1Ø The
half-width of the
distribution is the widtli 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
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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 otlier 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 Si02 concentration 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
higlier. In
contrast with traditional fillers, the solution formed nanocomposites exhibit
low viscosity and
improved processing characteristics at higlier 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
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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, zirconialaluinina
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, einery, alumina nitride, or a blend thereof. Particular embodiments
have been created by
use of dense abrasive grains coinprised 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 weiglit 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
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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 coated abrasive article 100,
which
includes abrasive grains 106 secured to a backing or support member 102.
Generally, the
abrasive grains 106 are secured to the backing 102 by a make coat 104. The
make coat 104
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 coated abrasive article 100 may further include a size coat 108 overlying
the make
coat 104 and the abrasive grains 106. The size coat 108 generally functions to
further secure
the abrasive grains 106 to the backing 102 and may also provide grinding aids.
The size coat
108 is generally forined 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 abrasive 100 may also, optionally, include a back coat 112. The
back coat
112 functions as an anti-static layer, preventing abrasive grains from
adhering to the back side
of the backing 102 and preventing swarf from accumulating charge during
sanding. In
another example, the back coat 112 may provide additional strength to the
backing 102 and
may act to protect the backing 102 from environmental exposure. In another
example, the
back coat 112 can also act as a compliant layer. The compliant layer may act
to relieve stress
between the make coat 104 and the backing 102.
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
fihn, cellulose
ester film, metal foil, mesh, foam (e.g., natural sponge material or
polyurethane foam), cloth
(e.g., cloth made from fibers or yams 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.
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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.
Nos. 5,108,463 (Buchanan et al.); 5,137,542 (Buchanan et al.); 5,328,716
(Buchanan); and
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
wliich 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
exainple, 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 coated abrasive article 100 of FIG. 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.
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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 forinulation 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
fonnulation 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 exeinplary embodiment of an engineered or structured abrasive is
illustrated in
FIG. 2. The structured abrasive includes a backing 202 and a layer 204
including abrasive
grains. The backing 202 may be formed of the materials described above in
relation to the
backing 102 of FIG. 1. Generally, the layer 204 is patterned to have surface
structures 206.
The layer 204 may be formed as one or more coats. For example, the layer 204
may
include a make coat and optionally, a size coat. The layer 204 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 the backing 202. Optionally, a
functional powder
may be applied over the layer 204 to prevent the layer 204 from sticking to
the patterning
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tooling. The binder of the make coat or the size coat may include latent
colorant. The
structured abrasive article 200 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 the abrasive article 300 illustrated in
FIG. 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
as article 300,
includes the abrasive grains bound by nano-coinposite 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 forinulation may be applied
over the abrasive
grains to form a size coat. In another example, the binder forinulation 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
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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 witli 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
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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
liunit. Positive
a* is typically red and negative a* is typically green. Positive b* is
generally yellow and
negative b* is generally blue. For example, wlien 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.
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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 detertnining 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
anopox XP 22/0314 72.02 Epoxy
4,8-bis(hydroxymethyl)
tricyclo[5.2.1.0)decane 14.40 Polyol
Chivacure 184 0.48 Photoinitiator
Chivacure 1176 2.88 Photoinitiator
Nanocryl XP 21/0954 9.60 Ac late
S ecial Blue 1 0.40 additive
BYK A-501 0.02 additive
Silwet L 7600 0.20 additive
Totals: 100.00
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EXAMPLE 2
Sample binder formulations are prepared and cured. The color of the cured
samples
are tested using a HunterLab ColorQuest 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 300W D bulb/600W 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 IJV-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 fiu-ther 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(M), acrylate precursor (SR 399, a
dipentaerythritol
pentaacrylate available from Atofina-Sartomer, Exton, PA), and dye (specialty
bluel,
available from Noveon Hilton Davis, Inc., 2235 Langdon Farms Rd., Cincinnati,
OH 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 uicreasing 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)
tricyclo(5.2.1.0)decane 13.50 13.50 13.50 13.50
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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 forinulations.
The above-disclosed subject matter is to be considered illustrative, and not
restrictive,
and the appended claims are intended to cover all such modifications,
eiihancements, and
other embodiments, which fall within the true scope of the preseirt 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.
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