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Polishing pad and method of making the same

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20130012108 patent thumbnailZoom

Polishing pad and method of making the same


The disclosure is directed to polishing pads with porous polishing layers, methods of making such polishing pads, and methods of using such pads in a polishing process. The polishing pad includes a compliant layer having first and second opposing sides and a porous polishing layer disposed on the first side of the compliant layer. The porous polishing layer includes a crosslinked network comprising a thermally cured component and a radiation cured component, wherein the radiation cured component and the thermally cured component are covalently bonded in the crosslinked network. The porous polishing layer also includes polymer particles dispersed within the crosslinked network, wherein the polymer particles comprise at least one of thermoplastic polymers or thermoset polymers. The porous polishing layer typically also includes closed cell pores dispersed within the crosslinked network.
Related Terms: Covalent Polymer

USPTO Applicaton #: #20130012108 - Class: 451 59 (USPTO) - 01/10/13 - Class 451 
Abrading > Abrading Process >Utilizing Nonrigid Tool



Inventors:

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The Patent Description & Claims data below is from USPTO Patent Application 20130012108, Polishing pad and method of making the same.

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CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of U.S. Provisional Application Nos. 61/288,982, filed Dec. 22, 2009, and 61/422,442, filed Dec. 13, 2010, the disclosures of which are incorporated by reference herein in their entirety.

BACKGROUND

During the manufacture of semiconductor devices and integrated circuits, silicon wafers are iteratively processed through a series of deposition and etching steps to form overlying material layers and device structures. A polishing technique known as chemical mechanical planarization (CMP) may be used to remove surface irregularities (such as bumps, areas of unequal elevation, troughs, and trenches) remaining after the deposition and etching steps, with the objective of obtaining a smooth wafer surface without scratches or depressions (known as dishing), with high uniformity across the wafer surface.

In a typical CMP polishing process, a substrate such as a wafer is pressed against and relatively moved with respect to a polishing pad in the presence of a working liquid that is typically a slurry of abrasive particles in water and/or an etching chemistry. Various CMP polishing pads for use with abrasive slurries have been disclosed, for example, U.S. Pat. Nos. 5,257,478 (Hyde et al.); 5,921,855 (Osterheld et al.); 6,126,532 (Sevilla et al.); 6,899,598 (Prasad); and 7,267,610 (Elmufdi et al.). Fixed abrasive polishing pads are also known, as exemplified by U.S. Pat. No. 6,908,366 (Gagliardi), in which the abrasive particles are generally fixed to the surface of the pad, often in the form of precisely shaped abrasive composites extending from the pad surface. Recently, a polishing pad having a multiplicity of polishing elements extending from a compressible underlayer was described in Int. App. Publ. No. WO/2006057714 (Bajaj). Although a wide variety of polishing pads are known and used, the art continues to seek new and improved polishing pads for CMP, particularly in CMP processes where larger die diameters are being used, or where higher levels of wafer surface flatness and polishing uniformity are required.

SUMMARY

The present disclosure provides porous polishing pads with a polishing layer having a thermally cured component and a radiation cured component and methods of making such polishing pads. Pores are incorporated into the polishing layer through the use of polymer particles. The pores in the porous polishing pads disclosed herein are closed cell pores that generally have lower pore size non-uniformity and smaller pore size than the pores of conventional thermally cured polishing pads. The control over pore size and distribution may be advantageous, for example, for the polishing performance of the polishing pad.

In one aspect, the present disclosure provides a polishing pad comprising:

a compliant layer having first and second opposing sides; and

a porous polishing layer disposed on the first side of the compliant layer, the porous polishing layer comprising: a crosslinked network comprising a thermally cured component and a radiation cured component, wherein the radiation cured component and the thermally cured component are covalently bonded in the crosslinked network; polymer particles dispersed within the crosslinked network; and closed cell pores dispersed within the crosslinked network. In some embodiments, the polishing pad further comprises a support layer interposed between the compliant layer and the porous polishing layer.

In another aspect, the present disclosure provides a method of making a polishing pad, the method comprising:

providing a composition comprising a thermally curable resin composition, a radiation curable resin composition, and polymer particles;

forming pores in the composition;

positioning the composition on a support layer; and

forming a porous polishing layer on the support layer by exposing the composition to radiation to at least partially cure the radiation curable resin composition and heating the composition to at least partially cure the thermally curable resin composition. In some embodiments, the method further comprises adhesively bonding a compliant layer to a surface of the support layer opposite the porous polishing layer.

In a further aspect, the present disclosure provides a method of polishing comprising:

contacting a surface of a substrate with the porous polishing layer of the polishing pad according to the present disclosure; and

relatively moving the polishing pad with respect to the substrate to abrade the surface of the substrate.

Exemplary embodiments of polishing pads according to the present disclosure have various features and characteristics that enable their use in a variety of polishing applications. In some embodiments, polishing pads of the present disclosure may be particularly well suited for chemical mechanical planarization (CMP) of wafers used in manufacturing integrated circuits and semiconductor devices. In some embodiments, the polishing pad described in this disclosure may provide some or all of the following advantages.

For example, in some embodiments, a polishing pad according to the present disclosure may act to better retain a working liquid used in the CMP process at the interface between the polishing surface of the pad and the substrate surface being polished, thereby improving the effectiveness of the working liquid in augmenting polishing. In other exemplary embodiments, a polishing pad according to the present disclosure may reduce or eliminate dishing and/or edge erosion of the wafer surface during polishing. In some exemplary embodiments, use of a polishing pad according to the present disclosure in a CMP process may result in improved within wafer polishing uniformity, a flatter polished wafer surface, an increase in edge die yield from the wafer, and improved CMP process operating conditions and consistency. In further embodiments, use of a polishing pad according to the present disclosure may permit processing of larger diameter wafers while maintaining the required degree of surface uniformity to obtain high chip yield, processing of more wafers before conditioning of the pad surface is needed in order to maintain polishing uniformity of the wafer surfaces, or reducing process time and wear on the pad conditioner.

In this disclosure:

“Pore size non-uniformity” refers to the standard deviation of the pore size mean divided by the mean pore size multiplied by 100.

The term “polyurethane” refers to a polymer having more than one urethane linkage (—NH—C(O)—O—), urea linkage (—NH—C(O)—NH— or —NH—C(O)—N(R)—, wherein R can be hydrogen, an aliphatic, cycloaliphatic or aromatic group), biuret, allophanate, uretdione, or isocyanurate linkage in any combination.

The term “(meth)acrylate” refers to acrylates and methacrylates, which can include urethane acrylates, methacrylates and combinations of acrylates and methacrylates.

The term “polymeric” refers to a molecule having a structure that includes the multiple repetition of units derived from molecules of low relative molecule mass. The term “polymeric” includes “oligomeric”.

Terms such as “a”, “an” and “the” are not intended to refer to only a singular entity, but include the general class of which a specific example may be used for illustration. The terms “a”, “an”, and “the” are used interchangeably with the term “at least one”.

The phrases “at least one of” and “comprises at least one of” followed by a list refers to any one of the items in the list and any combination of two or more items in the list.

All numerical ranges are inclusive of their endpoints and non-integral values between the endpoints unless otherwise stated.

Various aspects and advantages of exemplary embodiments of the disclosure have been summarized. The above Summary is not intended to describe each illustrated embodiment or every implementation of the present disclosure. The Drawings and the Detailed Description that follow more particularly exemplify some embodiments of the disclosure.

BRIEF DESCRIPTION OF DRAWINGS

Exemplary embodiments of the present disclosure are further described with reference to the appended figures, wherein:

FIGS. 1A and 1B are micrographs of a cross-section and top view, respectively, of a porous polishing pad in the prior art;

FIG. 2 is a schematic side view of one embodiment of a polishing pad according to the present disclosure;

FIG. 3 is a side view of a polishing pad having projecting polishing elements according to another embodiment of the present disclosure;

FIG. 4 is a side view of a polishing pad having projecting polishing elements according to yet another embodiment of the present disclosure;

FIGS. 5A and 5B are micrographs of a cross-section and top view, respectively, of the cured composition of Example 2 useful for forming polishing layers according to the present disclosure;

FIGS. 6A and 6B are micrographs of a cross-section and a top view, respectively, of the cured composition of Comparative Example 3;

FIGS. 7A and 7B are micrographs of a cross-section and top view, respectively, of the cured composition of Example 15 useful for forming polishing layers according to the present disclosure; and

FIG. 8 is a micrograph of a cross-section view of the cured composition of Example 11 useful for forming polishing layers according to the present disclosure.

Like reference numerals in the drawings indicate like elements. The drawings herein as not to scale, and in the drawings the components of the polishing pads are sized to emphasize selected features.

DETAILED DESCRIPTION

Typical CMP pads are constructed from thermoset (e.g., polyurethane) materials having pores. The pores can be generated using a variety of methods such as microballoons, soluble fibers, gas entrapment (e.g., in-situ or ex-situ generated), and physical air entrapment. Control of the pore size, pore volume, and pore distribution through the pad can be challenging when using these methods due to temperature gradients created during polymerization, skin/core effects resulting from molding operations, distribution of the fibers, dissolving rate of the soluble fibers, and polishing chemistry.

Some commercially available CMP pads have an open cell pad construction generated during thermal curing of an isocyanate resin. FIG. 1 shows cross-section and top views of a commercially made open cell CMP pad available from PPG Industries, Pittsburgh, Pa., under the trade designation “S7”. As shown in FIG. 1, the size, shape, and distribution for the pores in this pad is not controlled.

The present disclosure is directed to improved porous polishing pads, in which typically closed cell pores are formed with controlled size and uniformity. Various exemplary embodiments of the disclosure will now be described. Exemplary embodiments of the present disclosure may take on various modifications and alterations without departing from the spirit and scope of the disclosure. Accordingly, it is to be understood that the embodiments of the present invention are not to be limited to the following described exemplary embodiments, but are to be controlled by the limitations set forth in the claims and any equivalents thereof.

Referring now to FIG. 2, the porous polishing pad 2a comprises a compliant layer 10a and a porous polishing layer 12a disposed on one side of (that is, one major surface of) the compliant layer. Interposed between the porous polishing layer 12a and the compliant layer 10a is optional support layer 8a, which is useful for some embodiments of the porous polishing pad and method of the present disclosure. The porous polishing layer comprises a crosslinked network, polymer particles dispersed within the crosslinked network, and closed cell pores dispersed within the crosslinked network. In contrast to polishing pads and methods in which a component of the polishing pad is removed during polishing to form voids (e.g., by erosion or dissolution) the polishing pads according to the present disclosure are porous before the polishing process begins.

Exemplary polymer particles in the polishing layer can include thermoplastic polymer particles, thermoset polymer particles, and mixtures thereof. The term “thermoplastic polymer” refers to a polymeric material that is essentially not crosslinked and essentially does not form a three-dimensional network. The term “thermoset” refers to a polymer that is at least substantially crosslinked wherein said polymer has essentially a three-dimensional network. In some embodiments, the polymer particles can be chosen such that there is minimal sintering of the particles upon heating (i.e., there is minimal plastic flow at the boundary of the polymer particles, and little to no coalescence between the particles of the polymer particles in the polishing pad of the present disclosure). In some embodiments, when the polymer particles of the pad comprises particulate thermoplastic polymer, the polishing pad can be prepared below the melting or sintering point of the particulate thermoplastic polymer. In other embodiments, the polymer particles comprise thermoset polymers.

Polymer particles useful for practicing the present disclosure can be prepared by various methods (e.g., a condensation reaction, a free radical initiated reaction, or combinations thereof). In yet other embodiments, the polymer can include an interpenetrating polymer network formed by stepwise or simultaneous condensation and free radical polymerization reactions. In this disclosure, the term “interpenetrating polymer network” (IPN) refers to a combination of two polymers both in network form, at least one of which is synthesized or crosslinked in the immediate presence of the other. Typically in IPNs, there are no induced covalent bonds between the two polymers. Thus, in addition to mechanical blending and copolymerization, IPNs represent another mechanism by which different polymers can be physically combined.

The polymer particles can be prepared by various methods. In some embodiments, bulk polymers can be cryogenically ground and classified into desired particle size ranges. The shape of the polymer particles can be regular or irregular, and can include the following shapes: sphere, fiber, disk, flake, and combinations or mixtures thereof. In some embodiments, the polymer particles are substantially spherical. The term “substantially spherical” refers to a particle having a sphericity of at least 0.75 (in some embodiments, at least 0.8, 0.85, 0.9, 0.95, 0.96, 0.97, or 0.98). In some embodiments, the polymer particles are fibers. Fibers useful for practicing the present disclosure typically have an aspect ratio (that is, longest dimension over shortest dimension) of at least 1.5:1, for example, at least 2:1, 3:1, 4:1, 5:1, 10:1, 25:1, 50:1, 75:1, 100:1, or more. Fibers useful for practicing the present disclosure may have an aspect ratio in a range from 2:1 to 100:1, 5:1 to 75:1, or 10:1 to 50:1.

In some embodiments, the polymer particles can have an average particle size of at least 5 (in some embodiments, at least 7, 10, 15, 20, 25, 30, 40, or 50) microns. In some embodiments, the polymer particles can have an average particle size of up to 500 (in some embodiments, up to 400, 300, 200, or 100) microns. The particle size generally refers to the diameter of the particle; however, in embodiments when the particles are not spherical (e.g., fibers), the particle size can refer to the largest dimension of the particle. The average particle size of the polymer particles can be determined by conventional methods. For example, the average particle size of the polymer particles can be determined using light scattering techniques, such as a Coulter LS particle size analyzer which is manufactured and commercially available from Beckman Coulter Incorporated. As used herein and in the claims, “particle size” refers to the diameter or largest dimension of the particle based on volume percent as determined by light scattering using a Coulter Counter LS particle size analyzer. In this light scattering technique, the size is determined from a hydrodynamic radius of gyration regardless of the actual shape of the particle. The “average” particle size is the average diameter of the particle based on volume percent. In some embodiments, particularly in embodiments where the particles are fibers, the fibers have a maximum particle size of up to about 600, 500, or 450 microns (30, 35, or 40 U.S. Mesh) as determined by conventional screening techniques. For example, in some embodiments, at least 97, 98, or 99 percent of the fibers pass through a screen having openings of 600, 500, or 400 microns (30, 35, or 40 U.S. Mesh).

In some embodiments, the polymer particles have a high degree of uniformity. In some embodiments, the non-uniformity of the size of polymer particles is up to 75 (in some embodiments, up to 70, 65, 60, 65, or 50) percent. Particle size non-uniformity refers to the particle size standard deviation divided by the average particle size multiplied by 100.

In some embodiments, the polymer particles are substantially solid. As used herein, the term “substantially solid” means that the particulate polymer is not hollow, for example, the polymer particles are not in the form of hollow microcapsules. However, in some embodiments, the substantially solid polymer particles can contain entrapped gas bubbles.

Suitable polymer particles include polyvinylchloride, polyvinylfluoride, polyethylene, polypropylene, nylon, polycarbonate, polyester, poly(meth)acrylate, polyether, polyamide, polyurethane, polyepoxide, polystyrene, polyimide (e.g., polyetherimide), polysulfone and mixtures thereof. In some embodiments, the polymer particles can be chosen from poly(meth)acrylate, polyurethane, polyepoxide and mixtures thereof.

In some embodiments, the polymer particles comprise water-soluble particles. Exemplary useful water soluble particles include particles made of saccharides (e.g., polysaccharides such as dextrin, cyclodextrin, starch, mannitol, and lactose), celluloses (e.g., hydroxypropylcelluloses and methylcelluloses), protein, polyvinyl alcohol, polyvinyl pyrrolidone, polyacrylic acid, polyethylene oxide, water-soluble photosensitive resin, sulfonated polyisoprene, sulfonated polyisoprene copolymer, and any combination of these. In some embodiments, the polymer particles comprise a cellulose. In some of these embodiments, the polymer particles comprise methylcellulose. Even though in these embodiments, the polymer particles comprise water-soluble particles, the polymer particles can form pores in the polishing layer when the polishing layer is formed. A working liquid that can dissolve the particles during polishing is not required to form pores.

In some embodiments, the polymer particles comprise a polyurethane, which can be prepared, for example, from a resin comprising at least two isocyanate groups, and/or a capped isocyanate reactant having at least two capped isocyanate groups; and a second resin that has at least two groups that are reactive with isocyanate groups.

In some embodiments, the first and second resins can be mixed together and polymerized or cured to form a bulk polyurethane, which can then be ground (e.g., cryogenically ground), and optionally classified. In some embodiments, the polymer particles can be formed by mixing the first and second resins together, slowly pouring the mixture into heated deionized water under agitation (optionally in the presence of an organic cosolvent and/or surfactant), isolating the formed particulate material (e.g., by filtration), drying the isolated particulate material, and optionally classifying the dried particulate polyurethane. In another embodiment, the isocyanate and hydrogen materials can be mixed together in the presence of an organic solvent (e.g., alcohols, water-insoluble ethers, branched and straight hydrocarbons, ketones, toluene, xylene and mixtures thereof).

In some embodiments, the first resin comprising at least two isocyanate groups can be chosen from isocyanate functional monomers, isocyanate functional prepolymers and combinations thereof. Exemplary suitable isocyanate monomers include aliphatic polyisocyanates; ethylenically unsaturated polyisocyanates; alicyclic polyisocyanates; aromatic polyisocyanates wherein the isocyanate groups are not bonded directly to the aromatic ring, for example, alpha,alpha′-xylene diisocyanate; aromatic polyisocyanates wherein the isocyanate groups are bonded directly to the aromatic ring, for example, benzene diisocyanate; halogenated, alkylated, alkoxylated, nitrated, carbodiimide modified, urea modified, and biuret modified derivatives of these polyisocyanates; and dimerized and trimerized products of these polyisocyanates.

Exemplary aliphatic polyisocyanates include ethylene diisocyanate, trimethylene diisocyanate, tetramethylene diisocyanate, hexamethylene diisocyanate, octamethylene diisocyanate, nonamethylene diisocyanate, 2,2′-dimethylpentane diisocyanate, 2,2,4-trimethylhexane diisocyanate, decamethylene diisocyanate, 2,4,4,-trimethylhexamethylene diisocyanate, 1,6,1-undecanetriisocyanate, 1,3,6-hexamethylene triisocyanate, 1,8-diisocyanato-4-(isocyanatomethyl)octane, 2,5,7-trimethyl-1,8-diisocyanato-5-(isocyanatomethyl)octane, bis(isocyanatoethyl)-carbonate, bis(isocyanatoethyl)ether, 2-isocyanatopropyl-2,6-diisocyanatohexanoate, lysinediisocyanate methyl ester, lysinetriisocyanate methyl ester and mixtures thereof.

Exemplary suitable ethylenically unsaturated polyisocyanates can include butene diisocyanate and 1,3-butadiene-1,4-diisocyanate. Exemplary suitable alicyclic polyisocyanates include isophorone diisocyanate, cyclohexane diisocyanate, methylcyclohexane diisocyanate, bis(isocyanatomethyl)cyclohexane, bis(isocyanatocyclohexyl)methane, bis(isocyanatocyclohexyl)-2,2-propane, bis(isocyanatocyclohexyl)-1,2-ethane, 2-isocyanatomethyl-3-(3-isocyanatopropyl)-5-isocyanatomethyl-bicyclo[2.2.1]-heptane, 2-isocyanatomethyl-3-(3-isocyanatopropyl)-6-isocyanatomethyl-bicyclo[2.2.1]-heptane, 2-isocyanatomethyl-2-(3-isocyanatopropyl)-5-isocyanatomethyl-bicyclo[2.2.1]-heptane, 2-isocyanatomethyl-2-(3-isocyanatopropyl)-6-isocyanatomethyl-bicyclo[2.2.1]-heptane, 2-isocyanatomethyl-3-(3-isocyanatopropyl)-6-(2-isocyanatoethyl)-bicyclo[2.2.1]-heptane, 2-isocyanatomethyl-2-(3-isocyanatopropyl)-5-(2-isocyanatoethyl)-bicyclo[2.2.1]-heptane, 2-isocyanatomethyl-2-(3-isocyanatopropyl)-6-(2-isocyanatoethyl)-bicyclo[2.2.1]-heptane and mixtures thereof.

Exemplary aromatic polyisocyanates wherein the isocyanatc groups are not bonded directly to the aromatic ring include bis(isocyanatoethyl)benzene, alpha, alpha, alpha′, alpha′-tetramethylxylene diisocyanate, 1,3-bis(1-isocyanato-1-methylethyl)benzene, bis(isocyanatobutyl)benzene, bis(isocyanatomethyl)naphthalene, bis(isocyanatomethyl)diphenyl ether, bis(isocyanatoethyl)phthalate, mesitylene triisocyanate, 2,5-di(isocyanatomethyl)furan and mixtures thereof.

Exemplary suitable aromatic polyisocyanates having isocyanate groups bonded directly to the aromatic ring include phenylene diisocyanate, ethylphenylene diisocyanate, isopropylphenylene diisocyanate, dimethylphenylene diisocyanate, diethylphenylene diisocyanate, diisopropylphenylene diisocyanate, trimethylbenzene triisocyanate, benzene triisocyanate, naphthalene diisocyanate, methylnaphthalene diisocyanate, biphenyl diisocyanate, ortho-tolidine diisocyanate, 4,4′-diphenylmethane diisocyanate, bis(3-methyl-4-isocyanatophenyl)methane, bis(isocyanatophenyl)ethylene, 3,3′-dimethoxy-biphenyl-4,4′-diisocyanate, triphenylmethane triisocyanate, polymeric 4,4′-diphenylmethane diisocyanate, naphthalene triisocyanate, diphenylmethane-2,4,4′-triisocyanate, 4-methyldiphenylmethane-3,5,2′,4′,6′-pentaisocyanate, diphenylether diisocyanate, bis(isocyanatophenylether)ethyleneglycol, bis(isocyanatophenylether)-1,3-propyleneglycol, benzophenone diisocyanate, carbazole diisocyanate, ethylcarbazole diisocyanate, dichlorocarbazole diisocyanate and mixtures thereof.

In some embodiments, the first resin comprising at least two isocyanate groups is selected from the group consisting of alpha, alpha′-xylene diisocyanate, alpha, alpha, alpha′, alpha′-tetramethylxylene diisocyanate, isophorone diisocyanate, bis(isocyanatocyclohexyl)methane, toluene diisocyanate, 4,4′-diphenylmethane diisocyanate, and mixtures thereof.

In some embodiments, the first resin having at least two isocyanate groups can comprise an isocyanate functional polyurethane prepolymer. Isocyanate functional polyurethane prepolymers can be prepared by various conventional techniques. In some embodiments, at least one polyol such as a diol, and at least one isocyanate functional monomer such as a diisocyanate monomer, can be reacted together to form a polyurethane prepolymer having at least two isocyanate groups. Exemplary suitable isocyanate functional monomers include the aforementioned isocyanate functional monomers.

Suitable isocyanate functional polyurethane prepolymers useful for practicing the present disclosure can have molecular weights that vary within a wide range. In some embodiments, the isocyanate functional polyurethane prepolymer can have a number average molecular weight (Mn) of from 500 to 15,000, or from 500 to 5000, as determined, for example, by gel permeation chromatography (GPC) using polystyrene standards.

Exemplary polyols useful for preparing isocyanate functional polyurethane prepolymers include straight or branched chain alkane polyols, such as 1,2-ethanediol, 1,3-propanediol, 1,2-propanediol, 1,4-butanediol, 1,3-butanediol, glycerol, neopentyl glycol, trimethylolethane, trimethylolpropane, di-trimethylolpropane, erythritol, pentaerythritol and di-pentaerythritol; polyalkylene glycols, such as di-, tri- and tetraethylene glycol, and di-, tri- and tetrapropylene glycol; cyclic alkane polyols, such as cyclopentanediol, cyclohexanediol, cyclohexanetriol, cyclohexanedimethanol, hydroxypropylcyclohexanol and cyclohexanediethanol; aromatic polyols, such as dihydroxybenzene, benzenetriol, hydroxybenzyl alcohol and dihydroxytoluene; bisphenols, such as 4,4′-isopropylidenediphenol (bisphenol A); 4,4′-oxybisphenol, 4,4′-dihydroxybenzophenone, 4,4′-thiobisphenol, phcnolphthlalcin, bis(4-hydroxyphenyl)methane (bisphenol F), 4,4′-(1,2-ethenediyl)bisphenol and 4,4′-sulfonylbisphenol; halogenated bisphenols, such as 4,4′-isopropylidenebis(2,6-dibromophenol), 4,4′-isopropylidenebis(2,6-dichlorophenol) and 4,4′-isopropylidenebis(2,3,5,6-tetrachlorophenol); alkoxylated bisphenols, such as alkoxylated 4,4′-isopropylidenediphenol having one or more alkoxy groups, such as ethoxy, propoxy, alpha-butoxy and beta-butoxy groups; and biscyclohexanols, which can be prepared by hydrogenating the corresponding bisphenols, such as 4,4′-isopropylidene-biscyclohexanol, 4,4′-oxybiscyclohexanol, 4,4′-thiobiscyclohexanol and bis(4-hydroxycyclohexanol)methane.

Further examples of suitable polyols useful for preparing isocyanate functional polyurethane prepolymers include higher polyalkylene glycols, such as polyethylene glycols having a number average molecular weight (Mn) of from 200 to 2000 grams per mole; hydroxyl-bearing acrylics, such as those formed from the copolymerization of (meth)acrylates and hydroxy functional (meth)acrylates, such as methyl methacrylate and hydroxyethyl methacrylate copolymers; and hydroxy functional polyesters, such as those formed from the reaction of diols, such as butane diol, and diacids or diesters, such as adipic acid or diethyl adipate. In some embodiments, the polyol useful for practicing the present disclosure can have a number average molecular weight (Mn) of from 200 to 2000 grams per mole.

In some embodiments, an isocyanate functional polyurethane prepolymer can be prepared by reacting a diisocyanate such as toluene diisocyanate, with a polyalkylene glycol such as poly(tetrahydrofuran).

In some embodiments, an isocyanate functional polyurethane prepolymer can be prepared in the presence of a catalyst. In some embodiments, the amount of catalyst used can be less than 5 percent by weight, or less than 3 percent by weight, or less than 1 percent by weight, based on the total weight of the polyol and isocyanate functional monomer. In some embodiments, exemplary suitable catalysts include a stannous adduct of an organic acid, such as stannous octoate, dibutyl tin dilaurate, dibutyl tin diacetate, dibutyl tin mercaptide, dibutyl tin dimaleate, dimethyl tin diacetate, dimethyl tin dilaurate, 1,4-diazabicyclo[2.2.2]octane, and mixtures thereof. In other embodiments, the catalyst can be zinc octoate, bismuth, or ferric acetylacetonate. Further exemplary suitable catalysts include tertiary amines such as triethylamine, triisopropylamine and N,N-dimethylbenzylamine.

In some embodiments, for polyurethanes useful for making polymer particles, the first resin having at least two isocyanate groups includes a capped isocyanate compound having at least two capped isocyanate groups. The term “capped isocyanate compound” refers to a monomer or prepolymer having terminal and/or pendent capped isocyanate groups which can be converted to decapped (i.e., free) isocyanate groups and separate or free capping groups. Any of the aforementioned examples of suitable isocyanate compounds can be capped. Exemplary nonfugitive capping groups of the capped isocyanate include 1H-azoles, such as 1H-imidazole, 1H-pyrazole, 3,5-dimethyl-1H-pyrazole, 1H-1,2,3-triazole, 1H-1,2,3-benzotriazole, 1H-1,2,4-triazole, 1H-5-methyl-1,2,4-triazole and 1H-3-amino-1,2,4-triazole; lactams, such as ε-caprolactam and 2-pyrrolidinone; morpholines such as 3-aminopropyl morpholine; and N-hydroxy phthalimide. Exemplary fugitive capping groups of the capped isocyanate compound include alcohols, such as propanol, isopropanol, butanol, isobutanol, tert-butanol and hexanol; alkylene glycol monoalkyl ethers, such as ethylene glycol monoalkyl ethers (e.g., ethylene glycol monobutyl ether and ethylene glycol monohexyl ether), and propylene glycol monoalkyl ethers (e.g., propylene glycol monomethyl ether); and ketoximes, such as methyl ethyl ketoxime.

While not intending to be bound by any theory, it is believed that the inclusion of capped isocyanate material in the first resin having at least two isocyanate groups can result in the formation of covalent bonds: (a) between at least a portion of the particulate polyurethane particles; and/or (b) between at least a portion of the particulate polyurethane and at least a portion of the crosslinked network. In some embodiments, the capped isocyanate compound can be present in an amount such that the first resin capped isocyanate groups in an amount of at least 5 mole percent, or at least 10 mole percent, or less than 40 mole percent, or less than 50 mole percent, based on the total molar equivalents of free isocyanate and capped isocyanate groups.

The second resin that has at least two groups that are reactive with isocyanate groups can be chosen from a wide variety of materials. In some embodiments, the second resin has functional groups chosen from hydroxyl, mercapto, primary amine, secondary amine and combinations thereof. Exemplary suitable second resins include the aforementioned polyols.

In some embodiments, the second resin which can have at least two groups that are reactive with isocyanate groups includes a polyamine. Exemplary polyamines include ethyleneamines such as ethylenediamine (EDA), diethylenetriamine (DETA), triethylenetetramine (TETA), tetraethylenepentamine (TEPA), pentaethylenehexamine (PEHA), piperazine, diethylenediamine (DEDA), and 2-amino-1-ethylpiperazine. Further exemplary suitable polyamines include one or more isomers of dialkyl toluenediamine, such as 3,5-dimethyl-2,4-toluenediamine, 3,5-dimethyl-2,6-toluenediamine, 3,5-diethyl-2,4-toluenediamine, 3,5-diethyl-2,6-toluenediamine, 3,5-diisopropyl-2,4-toluenediamine, 3,5-diisopropyl-2,6-toluenediamine and mixtures thereof. In some embodiments, the polyamine can be chosen from methylene dianiline, trimethyleneglycol di(para-aminobenzoate), and amine-terminated oligomers and prepolymers.

In some embodiments, suitable polyamines can be chosen from those based on 4,4′-methylene-bis(dialkylaniline) (e.g., 4,4′-methylene-bis(2,6-dimethylaniline), 4,4′-methylene-bis(2,6-diethylaniline), 4,4′-methylene-bis(2-ethyl-6-methylaniline), 4,4′-methylene-bis(2,6-diisopropylaniline), 4,4′-methylene-bis(2-isopropyl-6-methylaniline), 4,4′-methylene-bis(2,6-diethyl-3-chloroaniline) and mixtures thereof.

In some embodiments, preparation of a particulate polyurethane from a first resin comprising at least two isocyanate groups and a second resin comprising at least two groups that are reactive with an isocyanate can be carried out in the presence of a catalyst. Suitable catalysts include those listed above for the preparation of an isocyanate functional polyurethane prepolymer.

In some embodiments, the molar equivalent ratio of isocyanate groups and optional capped isocyanate groups to isocyanate-reactive groups useful for preparing particulate polyurethanes is from 0.5:1.0 to 1.5:1.0, e.g., from 0.7:1.0 to 1.3:1.0 or from 0.8:1.0 to 1.2:1.0. In some embodiments, a crosslinked polyurethane can be prepared by using less than the stoichiometrically required amount of the second resin such that the urethane or urea linkages will react with remaining isocyanates. In other embodiments, the partial replacement of difunctional by trifunctional compounds will result in more thermally stable chemical crosslinks.

Some useful particulate polyurethanes are commercially available, for example, from Dainichiscika Color & Chemicals Mfg. Co., Ltd. Advanced Polymers Group, Tokyo, Japan, under the trade designation “DAIMIC-BEAZ” in grades “UCN-5350D”, “UCN-5150D”, and “UCN-5070D”; polyurethane particles available from Negami Chemical Industrial Co., Ltd., Nomi-city, Japan, under the trade designation “ART PEARL”; and aliphatic polyether-based thermoplastic polyurethanes available, for example, from Bayer Corporation under the trade designation “TEXIN”.

In some embodiments, suitable polymer particles useful for practicing the present disclosure include particulate polyepoxides. A particulate polyepoxide can be prepared, for example, from a reaction product of a first resin having at least two epoxide groups; and a second resin having at least two groups that are reactive with the epoxide groups of the epoxide.

In some embodiments, the first resin comprising at least two epoxide groups and the second resin can be mixed together and polymerized or cured to form bulk polyepoxide, which then can be ground (e.g., cryogenically ground), and optionally classified. In some embodiments, the particulate polyepoxide can be formed by mixing the epoxide functional and hydrogen functional materials together, slowly pouring the mixture into heated deionized water under agitation, isolating the formed particulate material (e.g., by filtration), drying the isolated particulate material, and optionally classifying the dried particulate polyepoxide.

In some embodiments, suitable epoxide functional materials useful for practicing the present disclosure include epoxide functional monomers, epoxide functional prepolymers and combinations thereof. Exemplary suitable epoxide functional monomers can include aliphatic polyepoxides, such as 1,2,3,4-diepoxybutane, 1,2,7,8-diepoxyoctane; cycloaliphatic polyepoxides, such as 1,2,4,5-diepoxycyclohexane, 1,2,5,6-diepoxycyclooctane, 7-oxa-bicyclo[4.1.0]heptane-3-carboxylic acid 7-oxa-bicyclo[4.1.0]hept-3-ylmethyl ester, 1,2-epoxy-4-oxiranyl-cyclohexane and 2,3-(epoxypropyl)cyclohexane; aromatic polyepoxides, such as bis(4-hydroxyphenyl)methane diglycidyl ether; hydrogenated bisphenol A diepoxide and mixtures thereof. Epoxide functional monomers that may be useful in the present disclosure are typically prepared from the reaction of a polyol and an epihalohydrin, for example, epichlorohydrin. Polyols that may be used to prepare epoxide functional monomers include those recited previously herein with regard to the preparation of the isocyanate functional prepolymer. A useful class of epoxide functional monomers include those prepared from the reaction of a bisphenol and epichlorohydrin (e.g., the reaction of 4,4′-isopropylidenediphenol and epichlorohydrin to make 4,4′-isopropylidenediphenol diglycidyl ether).

In some embodiments, an epoxide functional prepolymer useful for preparing particular epoxides can be prepared by reacting a polymeric polyol and epichlorohydrin. Exemplary suitable polymeric polyols can include polyalkylene glycols, such as polyethylene glycol and polytetrahydrofuran; polyester polyols; polyurethane polyols; poly((meth)acrylate) polyols; and mixtures thereof.

In some embodiments of the present disclosure, the epoxide functional prepolymer can include an epoxy functional poly((meth)acrylate) polymer which can be prepared from a (meth)acrylate monomer and an epoxide functional radically polymerizable monomer (e.g., glycidyl (meth)acrylate). Suitable epoxide functional prepolymers can have a wide range of molecular weight. In some embodiments, the molecular weight of the epoxide functional prepolymer can be from 500 to 15,000 grams per mole, or from 500 to 5000 grams per mole, as determined, for example, by gel permeation chromatography (GPC) using polystyrene standards.



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stats Patent Info
Application #
US 20130012108 A1
Publish Date
01/10/2013
Document #
13518475
File Date
12/20/2010
USPTO Class
451 59
Other USPTO Classes
451539, 451532, 451529, 51296
International Class
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Drawings
6


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Abrading   Abrading Process   Utilizing Nonrigid Tool