CN116133794A - Coated abrasive article and method of making the same - Google Patents

Abstract

A coated abrasive article comprising a backing having opposing first and second major surfaces; a make coat disposed on the first major surface At least a portion of and bonds the abrasive grains to the backing; a size coat covering the make layer and at least a portion of the abrasive grains; and a top size layer disposed on the base coat glue layer. The top coat comprises at least partially cured water-based epoxy resin and an organic polymer rheology modifier, and wherein the at least partially cured epoxy resin is present in an amount accounting for the at least partially cured epoxy resin and the organic polymer rheology 75% to 99.99% by weight of the total weight of the modifier. A method of making a coated abrasive article is also disclosed.

Description

Coated abrasive article and method for making the same

Technical Field

The present disclosure relates to abrasive articles including epoxy supersize binder materials and methods of making the same.

Background Art

Abrasive articles generally comprise abrasive grains (also referred to as "abrasive particles") retained in a binder. During the manufacture of various types of abrasive articles, the abrasive grains are deposited on a binder material precursor in an oriented manner (e.g., by electrostatic coating or by some mechanical placement technique). Typically, the most desired orientation of the abrasive grains is substantially perpendicular to the surface of the backing.

For certain coated abrasive articles (e.g., abrasive discs), the backing is a relatively dense planar substrate (e.g., vulcanized fibers or woven or knitted fabrics, optionally treated with an impregnant to increase durability). A primer layer precursor (or primer layer) containing a first binder material precursor is applied to the backing, and the abrasive particles are then partially embedded in the primer layer precursor. In many cases, the abrasive particles are embedded in the primer layer precursor with a certain degree of orientation; for example, by electrostatic coating or by mechanical placement techniques. Then, when a size layer precursor (or size layer) containing a second binder material precursor is covered on the at least partially cured primer layer precursor and abrasive particles, the primer layer precursor is at least partially cured to retain the abrasive particles. Then, if the size layer precursor and primer layer precursor are not fully cured, both are cured to form a coated abrasive article.

In some cases, the supersize layer may be formed from a corresponding supersize layer precursor (size layer).

For thermally cured supersize layer precursors, the coated abrasive product is typically manufactured as a continuous web that is dried and cured in an overhung oven, where the web is draped on a hanger rod that advances through the oven.

Summary of the invention

During curing in an overhead oven, flow of the supersize layer due to gravity can be a problem, especially if the abrasive particles are arranged so that flow is not impeded by the abrasive particles. However, recent trends toward precise placement and/or orientation of abrasive particles have increased the need for solutions to the gravity flow problem described above.

The present disclosure overcomes such problems by using a supersize layer precursor containing a water-based curable epoxy resin and a rheology modifier suitable for making abrasive articles. The rheology modifier includes an organic polymer rheology modifier containing an alkali swellable/soluble polymer. It has now been found that these organic polymer rheology modifiers provide better control over the flow of the supersize layer precursor than previously used techniques.

Organic polymeric rheology modifiers are known to impart pseudoplastic flow properties. In particular, alkali swellable/soluble emulsion (ASE) polymers, hydrophobically modified alkali swellable/soluble emulsion (HASE) polymers, and hydrophobically modified ethoxylated polyurethane (HEUR) polymers have been used in aqueous compositions of latex paints, personal care products, and drilling muds. As used herein, the term "alkali swellable/soluble emulsion (ASE) polymer" specifically excludes hydrophobically modified alkali swellable/soluble emulsion (HASE) polymers.

In a first aspect, the present disclosure provides a method of preparing a coated abrasive article, the method comprising:

Providing a backing having opposing first and second major surfaces, wherein a make layer is disposed on at least a portion of the first major surface and bonds abrasive grains to the backing, and further wherein a size layer is disposed on the make layer and at least a portion of the abrasive grains;

as well as

coating a supersize layer precursor on at least a portion of the size layer, and at least partially curing the supersize layer precursor to provide a supersize layer,

The top glue layer precursor comprises a water-based epoxy resin and an organic polymer rheology modifier,

wherein the organic polymer rheology modifier comprises an alkali swellable/soluble polymer, and wherein the amount of the water-based epoxy resin is 75 wt % to 99.99 wt % based on the total weight of the water-based epoxy resin and the organic polymer rheology modifier.

In a second aspect, the present disclosure provides a coated abrasive article comprising:

a backing having opposing first and second major surfaces;

a make layer disposed on at least a portion of the first major surface and bonding abrasive particles to the backing;

a size layer covering the make layer and at least a portion of the abrasive grains; and

A top glue layer, the top glue layer is arranged on the secondary glue layer,

The super glue layer comprises an at least partially cured epoxy resin and an organic polymer rheology modifier, and the amount of the at least partially cured epoxy resin accounts for 75 wt % to 99.99 wt % of the total weight of the at least partially cured epoxy resin and the organic polymer rheology modifier.

As used in this article:

"Alkali swellable" means capable of at least partially swelling in an aqueous solution of a water-soluble base having a pH greater than 7;

"Alkali-swellable/soluble" means at least one of alkali-swellable or alkali-soluble (i.e., alkali-swellable and/or alkali-soluble);

Unless expressly stated otherwise, "polymer" means an organic polymer; and

"Water-based" means dissolved or dispersed in a liquid medium with water as the main component.

[0026] A further understanding of the features and advantages of the present disclosure will be achieved upon consideration of the detailed description and the appended claims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic cross-sectional side view of an exemplary coated abrasive article 100 according to the present disclosure.

FIG. 2 is a schematic perspective view of an exemplary precisely shaped abrasive particle 200 .

FIG. 3 is a digital photograph of a coated abrasive article prepared using comparative supersize layer precursor CSSR-F.

FIG. 4 is a digital photograph of a coated abrasive article prepared using supersize layer precursor ESSR-5.

It should be understood that numerous other modifications and embodiments can be devised by those skilled in the art that fall within the scope and spirit of the principles of this disclosure.The drawings may not be drawn to scale.

DETAILED DESCRIPTION

An exemplary embodiment of a coated abrasive article according to the present disclosure is shown in FIG1. Referring now to FIG1, the coated abrasive article 100 has a backing 120 and an abrasive layer 130. The abrasive layer 130 comprises abrasive grains 140 secured to a major surface 170 of the backing 120 by a make coat 150 and a size coat 160. A super coat 180 covers the size coat 160.

For example, a coated abrasive article according to the present disclosure may include additional layers such as a backing antistatic treatment layer, and/or an attachment layer if desired.

For example, available backings include backings known in the art for preparing coated abrasive articles. Typically, the backing has two opposing major surfaces, but not necessarily. The thickness of the backing is typically in the range of about 0.02 mm to about 5 mm, advantageously in the range of about 0.05 mm to about 2.5 mm, and more advantageously in the range of about 0.1 mm to about 1.0 mm, but thicknesses outside these ranges may also be used. Generally speaking, the strength of the backing should be sufficient to resist tearing or other damage during the grinding process. The thickness and smoothness of the backing should also be suitable for providing the desired thickness and smoothness of the coated abrasive article; for example, according to the intended application or use of the coated abrasive article.

Exemplary backings include: dense nonwoven fabrics (e.g., needle-punched, melt-spun, spunbonded, hydroentangled or melt-blown nonwoven fabrics), knitted fabrics, stitch-bonded fabrics and/or woven fabrics; scrims; polymeric films; treated forms thereof; and combinations of two or more of these materials.

The fabric backing can be made of any known fiber, whether it is a natural fiber, a synthetic fiber, or a blend of a natural fiber and a synthetic fiber. Examples of available fiber materials include fibers or yarns comprising polyester (e.g., polyethylene terephthalate), polyamide (e.g., hexamethylene adipamide, polycaprolactam), polypropylene, acrylic acid, cellulose acetate, polyvinylidene chloride-vinyl chloride copolymer, vinyl chloride-acrylonitrile copolymer, graphite, polyimide, silk, cotton, linen, jute, hemp or rayon. Available fibers can have natural materials, or have recycled materials or waste materials recovered, for example, from clothing cutting, carpet manufacturing, fiber manufacturing or textile processing. Available fibers can be homogeneous, or composite materials such as bicomponent fibers (e.g., cospun sheath-core fibers). These fibers can be stretched and curled, but can also be continuous filaments, such as those formed by extrusion processes.

The backing may have any suitable basis weight; typically, in the range of 100 grams per square meter to 1250 grams per square meter (gsm), more typically in the range of 450 gsm to 600 gsm, and even more typically in the range of 450 gsm to 575 gsm. In many embodiments (e.g., abrasive belts and abrasive sheets), the backing typically has good flexibility; however, this is not required (e.g., vulcanized fiber disks). To promote adhesion of the binder resin to the backing, one or more surfaces of the backing may be modified by known methods, including corona discharge, ultraviolet light irradiation, electron beam irradiation, flame discharge, and/or roughening.

The primer layer is formed by coating the primer layer precursor on the main surface of the backing and at least partially curing the primer layer precursor. The primer layer precursor comprises a thermosetting/curable composition. The example of suitable thermosetting/curable resins that can be used for the primer layer precursor includes monomers and/or oligomers, epoxy resins, acrylic resins, polyurethane resins, phenolic resins, urea-formaldehyde resins, melamine-formaldehyde resins, amino plastic resins, cyanate resins and combinations thereof that can be polymerized by free radicals. Available binder precursors include thermosetting resins and radiation-curable resins, which can be cured, for example, by heat and/or by being exposed to radiation. According to curable resins, the amount of the catalyst and/or initiator (for example, thermal initiator and/or photoinitiator) usually included is at most 10 weight % of the primer layer precursor. The selection of catalyst and/or initiator is within the capabilities of those of ordinary skill in the art. Additional details regarding make layer precursors can be found in US Pat. No. 4,588,419 (Caul et al.), US Pat. No. 4,751,138 (Tumey et al.), and US Pat. No. 5,436,063 (Follett et al.).

The primer layer precursor and primer layer can be modified by various additives (e.g., fibers, lubricants, wetting agents, surfactants, pigments, dyes, antistatic agents (e.g., carbon black, vanadium oxide and/or graphite), coupling agents (e.g., silanes, titanates, zirconium aluminates, etc.), plasticizers, suspending agents).

In some embodiments, the primer layer precursor comprises a resole phenolic resin and an organic polymer rheology modifier. The organic polymer rheology modifier comprises an alkali swellable/soluble polymer. Based on solids, the amount of the resole phenolic resin accounts for 75% to 99.99% by weight of the total weight of the resole phenolic resin and the organic polymer rheology modifier.

The organic polymeric rheology modifier comprises an alkali swellable/soluble polymer. The amount of the resol phenolic resin is 75 wt % to 99.99 wt % based on the total weight of the resol phenolic resin and the organic polymeric rheology modifier, based on solids.

Generally speaking, phenolic resins are formed by the condensation of phenol and formaldehyde, and are generally classified as resol or novolac phenolic resins. Novolac phenolic resins are acid catalyzed and have a molar ratio of formaldehyde to phenol of less than 1:1. Resole/resol phenolic resins may be catalyzed with an alkaline catalyst and have a molar ratio of formaldehyde to phenol of greater than or equal to one, typically between 1.0 and 3.0, so that hydroxymethyl side groups are present. Alkaline catalysts suitable for catalyzing the reaction between the aldehyde and phenol components of resol phenolic resins include sodium hydroxide, barium hydroxide, potassium hydroxide, calcium hydroxide, organic amines, and sodium carbonate, all as catalyst solutions dissolved in water.

Resols are typically applied as solutions with water and/or organic solvents (e.g., alcohols). Typically, the solution contains about 70% to about 85% solids by weight, but other concentrations may be used. If the solids content is very low, more energy is required to remove the water and/or solvent. If the solids content is very high, the viscosity of the resulting phenolic resin is too high, which typically leads to processing problems.

Phenolic resins are well known and readily available from commercial sources. Examples of commercially available resol phenolic resins that can be used to practice the present disclosure include those sold by Durez Corporation under the trade name VARCUM (e.g., 29217, 29306, 29318, 29338, 29353); those sold by Ashland Chemical Co., Bartow, Florida, under the trade name AEROFENE (e.g., AEROFENE 295); and those sold by Kangnam Chemical Company Ltd. of Seoul, South Korea under the trade name PHENOLITE (e.g., PHENOLITE TD-2207).

A review discussion of phenolic resins and their manufacture is given in the following reference: Kirk-Othmer, Encyclopedia of Chemical Technology, 4th Ed., John Wiley & Sons, 1996, New York, Vol. 18, pp. 603-644.

In addition to the resol, the curable composition contains an organic polymer rheology modifier, which includes an alkali swellable/soluble polymer. The curable composition includes a resol (usually diluted with water) and an organic polymer rheology modifier, which includes an alkali swellable/soluble polymer. In terms of solids, the amount of the resol accounts for 75% to 99.99% by weight (preferably 82% to 99.99% by weight, and even more preferably 88% to 99.99% by weight) of the total weight of the resol and the organic polymer rheology modifier. Therefore, based on the total weight of the resol and the organic polymer rheology modifier, the curable composition includes 0.01% to 25% by weight, preferably 0.01% to 18% by weight, and more preferably 0.01% to 12% by weight of the organic polymer rheology modifier. If desired, a combination of more than one resole resin and/or more than one organic polymeric rheology modifier may be used.

Alkali swellable/soluble polymers suitable for use as organic polymer rheology modifiers include, for example, alkali swellable/soluble emulsion (ASE) organic polymers, hydrophobically modified alkali swellable/soluble emulsion polymers (HASE), and hydrophobically modified ethoxylated polyurethane polymers (HEUR).

For example, the organic polymeric rheology modifier may be selected from alkali swellable/soluble acrylic emulsion polymers (ASE), hydrophobically modified alkali swellable/soluble acrylic emulsion polymers (HASE), and hydrophobically modified ethoxylated polyurethane (HEUR) organic polymers.

Alkali swellable/soluble emulsion (ASE) rheology modifiers are dispersions of insoluble acrylic polymers in water that have a high percentage of acidic groups distributed throughout their polymer chains. When these acidic groups are neutralized, the salts formed are hydrated. Depending on the concentration of acidic groups, molecular weight, and degree of crosslinking, the salts swell in aqueous solutions or become completely water soluble.

As the concentration of neutralized polymer increases in the aqueous formulation, the polymer chains swell, resulting in an increase in viscosity.

ASE polymers can be synthesized from acid and acrylate comonomers and are typically prepared by emulsion polymerization. Exemplary commercially available ASE polymers include those sold as ACUSOL 810A, ACUSOL 830, ACUSOL 835, ACUSOL 842, and ACRYSOL RM-38.

Hydrophobically modified alkali swellable/soluble emulsion (HASE) polymers are commonly used to modify the rheology of aqueous emulsion systems. Under the influence of alkali, organic or inorganic substances, HASE particles gradually swell and expand to form a three-dimensional network through intermolecular hydrophobic aggregation between HASE polymer chains and/or with emulsion components. This network, combined with the hydrodynamic excluded volume created by the swollen HASE chains, produces the desired thickening effect. The network is sensitive to applied stress, disintegrates under shear, and recovers when the stress is removed.

HASE rheology modifiers can be prepared from the following monomers: (a) an ethylenically unsaturated carboxylic acid, (b) a nonionic ethylenically unsaturated monomer, and (c) an ethylenically unsaturated hydrophobic monomer. Representative HASE polymer systems include those shown in EP 226097B1 (vanPhung et al.), EP 705852B1 (Doolan et al.), U.S. Pat. No. 4,384,096 (Sonnabend), and U.S. Pat. No. 5,874,495 (Robinson).

Exemplary commercially available HASE polymers include those sold under the trade names ACUSOL 801S, ACUSOL 805S, ACUSOL 820, and ACUSOL 823 by Dow Chemical.

ASE and HASE rheology modifiers are pH-triggered thickeners. Whether each emulsion polymer is water-swellable or water-soluble generally depends on its molecular weight. Both forms are acceptable. More details on synthetic ASE and HASE polymers can be found, for example, in U.S. Pat. No. 9,631,165 (Droege et al.).

Hydrophobically modified ethoxylated polyurethane (HEUR) polymers are generally synthesized from alcohols, diisocyanates and one or more polyalkylene glycols. HEURs are water-soluble polymers containing hydrophobic groups and are classified as associative thickeners because the hydrophobic groups associate with each other in water. Unlike HASE, HEURs are nonionic substances and do not rely on bases to activate the thickening mechanism. When their hydrophobic groups associate with other hydrophobic ingredients in a given formulation, they produce intramolecular or intermolecular connections. As a general rule, the strength of the association depends on the number, size and frequency of hydrophobic capping or blocking units. HEURs form micelles like ordinary surfactants. The micelles are then connected between the other ingredients by association with their surfaces. This establishes a three-dimensional network.

Exemplary commercially available HEUR polymers include those sold by Dow Chemical under the trade names ACUSOL 880, ACUSOL 882, ACRYSOL RM-2020, ACRYSOL RM-8W, and ACRYSOL RM-12W.

More details about HEURs can be found, for example, in U.S. Patent Application Publication Nos. 2017/0198238 (Kensicher et al.) and 2017/0130072 (McCulloch et al.) and U.S. Patent Nos. 7,741,402 (Bobsein et al.) and 8,779,055 (Rabasco et al.).

Once the make layer precursor is coated onto the backing, and before curing, the abrasive grains are partially embedded in the make layer precursor. Then, curing of the make layer precursor fixes the abrasive grains in the make layer.

Useful abrasive grains can be the result of a pulverizing operation (e.g., pulverized abrasive grains that have been classified according to shape and size) or the result of a forming operation (i.e., shaped abrasive grains), wherein the abrasive precursor material is shaped (e.g., molded), dried, and converted into a ceramic material. Combinations of abrasive grains produced by pulverizing and abrasive grains produced by a forming operation can also be used. Abrasive grains can be in the form of, for example, single particles, agglomerates, composite particles, and mixtures thereof.

The abrasive particles should have sufficient hardness and surface roughness to function as crushed abrasive particles in the grinding process. Preferably, the abrasive particles have a Mohs hardness of at least 4, at least 5, at least 6, at least 7, or even at least 8.

Suitable abrasive particles include, for example, crushed abrasive particles comprising: fused alumina, heat treated alumina, white fused alumina, ceramic alumina materials (such as ceramic alumina materials commercially available from 3M Company, St. Paul, Minnesota as 3M CERAMIC ABRASIVE GRAIN), brown alumina, blue alumina, silicon carbide (including green silicon carbide), titanium diboride, boron carbide, tungsten carbide, garnet, titanium carbide, diamond, cubic boron nitride, garnet, fused alumina-zirconia, iron oxide, chromium oxide, zirconium oxide, titanium dioxide, tin oxide, quartz, feldspar, flint, corundum, sol-gel prepared ceramics (e.g., alpha alumina), and combinations thereof. Examples of sol-gel prepared abrasive particles and methods of preparing the same from which the abrasive particles can be separated can be found in U.S. Pat. Nos. 4,314,827 (Leitheiser et al.); 4,623,364 (Cottringer et al.), 4,744,802 (Schwabel), 4,770,671 (Monroe et al.), and 4,881,951 (Monroe et al.). It is also contemplated that the abrasive particles may include grinding agglomerates such as, for example, those described in U.S. Pat. Nos. 4,652,275 (Bloecher et al.) or 4,799,939 (Bloecher et al.). In some embodiments, the abrasive particles may be surface treated with a coupling agent (e.g., an organosilane coupling agent) or other physical treatment (e.g., iron oxide or titanium oxide) to enhance the adhesion of the crushed abrasive particles to the binder. The abrasive particles may be treated before they are combined with the binder, or they may be surface treated in situ by including the coupling agent in the binder.

Preferably, the abrasive particles (and in particular the abrasive particles) comprise ceramic abrasive particles, such as, for example, polycrystalline alpha alumina particles prepared by a sol-gel process. Ceramic abrasive particles composed of microcrystals of alpha alumina, magnesium aluminum spinel, and rare earth hexaaluminate can be prepared using sol-gel alpha alumina particle precursors according to the methods described in, for example, U.S. Pat. No. 5,213,591 (Celikkaya et al.) and U.S. Published Patent Application Nos. 2009/0165394A1 (Culler et al.) and 2009/0169816A1 (Erickson et al.). Further details regarding methods of preparing sol-gel derived abrasive particles can be found, for example, in U.S. Pat. Nos. 4,314,827 (Leitheiser), 5,152,917 (Pieper et al.), 5,435,816 (Spurgeon et al.), 5,672,097 (Hoopman et al.), 5,946,991 (Hoopman et al.), 5,975,987 (Hoopman et al.), and 6,129,540 (Hoopman et al.), and U.S. Published Patent Application No. 2009/0165394 Al (Culler et al.).

In some preferred embodiments, useful abrasive particles (particularly in the case of abrasive particles) may be shaped abrasive particles, which can be found in U.S. Pat. Nos. 5,201,916 (Berg), 5,366,523 (Rowenhorst (Re 35,570)), and 5,984,988 (Berg). U.S. Pat. No. 8,034,137 (Erickson et al.) describes aluminum oxide abrasive particles that have been formed into a specific shape and then crushed to form fragments that retain a portion of their original shape features. In some embodiments, the abrasive particles are precisely shaped (i.e., the shape of the particles is at least partially determined by the shape of the cavity in the production tool used to prepare them). Details about such abrasive particles and methods of making them can be found, for example, in U.S. Pat. Nos. 8,142,531 (Adefris et al.), 8,142,891 (Culler et al.), 8,142,532 (Erickson et al.), 9,771,504 (Adefris), and U.S. Patent Application Publication Nos. 2012/0227333 (Adefris et al.), 2013/0040537 (Schwabel et al.), and 2013/0125477 (Adefris). A particularly useful precisely shaped abrasive particle shape is a sheet shape having three side walls, any of which can be straight or concave, and can be vertical or inclined relative to the sheet base; for example, shapes such as those described in the references cited above. FIG. 2 shows an exemplary such precisely shaped abrasive particle 200.

The surface coating on the abrasive particles can be used to improve the adhesion between the abrasive particles and the binder material, or to facilitate the electrostatic deposition of the abrasive particles. In one embodiment, the surface coating described in U.S. Patent No. 5,352,254 (Celikkaya) can be used in an amount of 0.1% to 2% of the surface coating relative to the weight of the abrasive particles. Such surface coatings are described in U.S. Patent Nos. 5,213,591 (Celikkaya et al.), 5,011,508 (Wald et al.), 1,910,444 (Nicholson), 3,041,156 (Rowse et al.), 5,009,675 (Kunz et al.), 5,085,671 (Martin et al.), 4,997,461 (Markhoff-Matheny et al.) and 5,042,991 (Kunz et al.). In addition, the surface coating can prevent the shaped abrasive particles from being capped. "Capping" is a term that describes the phenomenon whereby metal particles from the workpiece being abraded become welded to the tops of the abrasive particles. Surface coatings that perform the above functions are known to those skilled in the art.

In some embodiments, the length and/or width of the abrasive particles may be selected to be in the range of 0.1 micrometers to 3.5 millimeters (mm), more typically in the range of 0.05 mm to 3.0 mm, and more typically in the range of 0.1 mm to 2.6 mm, although other lengths and widths may be used.

Abrasive grains may be selected to have a thickness ranging from 0.1 micrometers to 1.6 millimeters, more typically 1 micrometer to 1.2 millimeters, although other thicknesses may also be used. In some embodiments, the abrasive grains may have an aspect ratio (ratio of length to thickness) of at least 2, 3, 4, 5, 6 or more.

Abrasive particles may be independently sized according to specified nominal grades recognized by the abrasives industry.Exemplary abrasives industry recognized grading standards include those promulgated by ANSI (American National Standards Institute), FEPA (European Abrasive Manufacturers Federation), and JIS (Japanese Industrial Standards). Such industry-recognized grading standards include, for example: ANSI 4, ANSI 6, ANSI 8, ANSI 16, ANSI 24, ANSI 30, ANSI 36, ANSI 40, ANSI 50, ANSI 60, ANSI 80, ANSI100, ANSI 120, ANSI 150, ANSI 180, ANSI 220, ANSI 240, ANSI 280, ANSI 320, ANSI 360, ANSI 400, and ANSI 600; FEPA P8, FEPA P12, FEPA P16, FEPA P24, FEPA P30, FEPA P36, FEPA P40, FEPA P50, FEPA P60, FEPA P80, FEPA P100, FEPA P120, FEPA P150, FEPA P180, FEPA P220, FEPA P240, P320, FEPA P400, FEPA P500, FEPA P600, FEPA P800, FEPA P1000, FEPA P1200; FEPA F8, FEPA F12, FEPA F16 and FEPA F24; and JIS 8, JIS 12, JIS 16, JIS 24, JIS 36, JIS 46, JIS 54, JIS 60, JIS 8 0. JIS 100, JIS 150, JIS 180, JIS 220, JIS 240, JIS 280, JIS320, JIS 360, JIS 400, JIS 600, JIS 800, JIS 1000, JIS 1500, JIS 2500, JIS 4000, JIS6000, JIS 8000 and JIS 10,000. More typically, the crushed alumina particles and seedless sol-gel alumina-based abrasive particles are independently sized to ANSI 60 and 80 or FEPA F36, F46, F54 and F60 or FEPA P60 and P80 classification standards.

Alternatively, the abrasive particles can be sieved using a test sieve that meets the U.S. standard, which is formulated according to ASTM E-11 "Standard Specification for Wire Cloth and Sieves for Testing Purposes". ASTM E-11 specifies the design and construction requirements for test sieves that use the media of a wire mesh woven sieve cloth mounted in a frame to classify materials according to a specified particle size. -18+20 is a typical designation, which means that the shaped abrasive particles can pass through a test sieve No. 18 that meets the ASTM E-11 specifications, but can be retained on a test sieve No. 20 that meets the ASTM E-11 specifications. In one embodiment, the shaped abrasive particles have a particle size such that most of the particles pass through an 18-mesh test sieve and can be retained on a 20-mesh, 25-mesh, 30-mesh, 35-mesh, 40-mesh, 45-mesh, or 50-mesh test sieve. In various embodiments, the shaped abrasive particles can have a nominal screen grade including: -18+20, -20+25, -25+30, -30+35, -35+40, -40+45, -45+50, -50+60, -60+70, -70+80, -80+100, -100+120, -120+140, -140+170, -170+200, -200+230, -230+270, -270+325, -325+400, -400+450/-450+500, or -500+635. Alternatively, a custom mesh size such as -90+100 can be used.

The size layer is generally formed by coating and at least partially curing a size layer precursor comprising a thermosetting/curable composition on the at least partially cured make layer and abrasive particles, and at least partially curing the size layer precursor. Suitable size layer precursors/size layers may have the same or different compositions as those contained in the make layer precursors/make layers described above.

In some embodiments, the size layer precursor comprises a resole resin and an organic polymeric rheology modifier, as described above in the context of the make layer precursor/make layer.

The supersize layer precursor comprises a water-based epoxy resin and an organic polymer rheology modifier as described above.

Exemplary water-based epoxy resins and their precursors (e.g., water-dispersible epoxy resins) include epoxy resins sold by Hexion, Columbus, Ohio, such as EPI-Rez Resin WD-510 water-dispersible liquid resin, and epoxy resins sold under the trade names EPI-REZ Resin 3510-W-60 and EPI-REZ Resin 7510-W-60, EPI-REZ Resin 3515-W-60, EPI-REZ Resin 3520-WY-55, EPI-REZ Resin 6520-WH-53, EPI-REZ Resin 7520-WD-52, EPI-REZ Resin 3522-W-60, EPI-REZ Resin 3540-WY-55, EPI-REZ Resin 6540-WH-53, EPI-REZ Resin 7540-WD-53, EPI-REZ Resin 3542-W-60, EPI-REZ Resin 3543-W-60, EPI-REZ Resin 3544-WY-55, EPI-REZ Resin 3545-WY-55, EPI-REZ Resin 3546-WY-55, EPI-REZ Resin 3547-WY-55, EPI-REZ Resin 3548-WY-55, EPI-REZ Resin 3549-WY-56, EPI-REZ Resin 3550-WY-56, EPI-REZ Resin 3551-WY-56, EPI-REZ Resin 3552-WY-56, EPI-REZ Resin 3553-WY-56, E 3546-WH-53, EPI-REZ Resin 5520-W-60, EPI-REZ Resin 5522-WY-55, EPI-REZ Resin 5003-W-55, EPON Resin RSW-2801, EPI-REZ Resin 5108-W-60, and EPI-REZ Resin 6006-W-68; epoxy resins sold under the trade names D.E.R. 900, D.E.R. 913, D.E.R. 915, D.E.R. 916, and D.E.R. 917 by Olin Corp., Clayton, Missouri; and BECKOPOX VEP from Allnex Corp., Frankfurt, Germany. 2381W/55WA epoxy resin. Some preferred water-based epoxy resins include diglycidyl ether of bisphenol A.

In some embodiments, the top glue layer is formed by a composition containing a water-based epoxy resin, a nonionic emulsifier, water, an imidazole curing agent, a potassium tetrafluoroborate grinding aid and a dispersant. Once the epoxy dispersion is applied to the coated abrasive product, it can be heated to cause the polymerization of the epoxy resin. The heating is usually carried out at a temperature of about 80°C to about 130°C, preferably about 105°C to about 115°C for a period of about 10 minutes to about 250 minutes, preferably about 20 minutes to about 50 minutes. More details about water-based epoxy resins and top glue layers containing them can be found in, for example, U.S. Patent No. 5,556,437 (Lee et al.).

Typically, the supersize layer also contains at least one grinding aid, but this is not required.

Grinding aid is a material that significantly affects the chemical and physical processes of grinding and improves performance. Grinding aids cover a variety of different materials and can be inorganic or organic. Examples of chemical groups of grinding aids include waxes, organic halide compounds, halide salts, metals and their alloys, and stearates and metal salts of stearates. Organic halide compounds will usually decompose during grinding and release halogen acids or gaseous halides. Examples of such materials include chlorinated paraffins, such as tetrachloronaphthalene, pentachloronaphthalene, and polyvinyl chloride. Examples of halide salts include sodium chloride, potassium cryolite, sodium cryolite, ammonium cryolite, potassium tetrafluoroborate, sodium tetrafluoroborate, silicon fluoride, potassium chloride, and magnesium chloride. Examples of metals include tin, lead, bismuth, cobalt, antimony, cadmium, iron, and titanium.

Other miscellaneous grinding aids include sulfur, organic sulfur compounds, graphite, and metal sulfides. Combinations of different grinding aids may be used, and in some cases this may produce a synergistic effect.

Grinding aids are particularly useful in coated abrasives. In coated abrasive articles, grinding aids are typically used in a topsize layer, which is applied above the surface of the size layer. However, grinding aids are sometimes added to the size layer. Typically, the amount of grinding aid incorporated into a coated abrasive article is about 50 to 800 grams per square meter (g/m ^{2 )} , preferably about 80 to 475 g/m ² , but not necessarily.

The top size layer typically has a basis weight of 5 grams per square meter to 1100 grams per square meter (gsm), preferably 50 gsm to 700 gsm, and more preferably 250 gsm to 600 gsm, but not necessarily. The basis weights of the make, size, and optional top size layers typically depend, at least in part, on the abrasive grit grade and the specific type of abrasive article.

The base layer, the size layer, and the supersize layer are formed by at least partially curing the corresponding precursors (ie, the base layer precursor, the size layer precursor, and the supersize layer precursor).

The primer layer, the double layer and the top layer and their precursors may also contain additives, such as fibers, lubricants, wetting agents, surfactants, pigments, dyes, antistatic agents (e.g., carbon black, vanadium oxide and/or graphite, etc.), coupling agents (e.g., silanes, titanates and/or zirconium aluminates, etc.), plasticizers, suspending agents, etc. The amounts of these optional additives are selected to provide preferred characteristics. Coupling agents can improve adhesion to abrasive particles and/or fillers. The curable composition may be heat-cured, radiation-cured or a combination thereof.

The base coat, the top coat and the top coat and their precursors may also contain filler materials, diluting abrasive particles (e.g., as described below) or grinding aids, usually in the form of particulate materials. Usually, the particulate materials are inorganic materials. Examples of fillers that can be used in the present disclosure include: metal carbonates (e.g., calcium carbonate (e.g., chalk, calcite, marl, travertine, marble and limestone), calcium magnesium carbonate, sodium carbonate, magnesium carbonate), silicon dioxide (e.g., quartz, glass beads, glass bubbles and glass fibers) silicates (e.g., talc, clay, (montmorillonite) feldspar, mica, calcium silicate, calcium metasilicate, sodium aluminate, sodium silicate) metal sulfates (e.g., calcium sulfate, barium sulfate, sodium sulfate, sodium aluminum sulfate, aluminum sulfate), gypsum, vermiculite, wood flour, aluminum trihydrate, carbon black, metal oxides (e.g., calcium oxide (lime), aluminum oxide, titanium dioxide) and metal sulfites (e.g., calcium sulfite).

Further details regarding coated abrasive articles and methods of making them can be found, for example, in U.S. Pat. Nos. 4,734,104 (Broberg), 4,737,163 (Larkey), 5,203,884 (Buchanan et al.), 5,152,917 (Pieper et al.), 5,378,251 (Culler et al.), 5,436,063 (Follett et al.), 5,496,386 (Broberg et al.), 5,609,706 (Benedict et al.), 5,520,711 (Helmin), 5,961,674 (Gagliardi et al.), and 5,975,988 (Christianson).

Coated abrasive articles according to the present disclosure can be used, for example, to grind a workpiece. Such methods may include: bringing abrasive particles according to the present disclosure into frictional contact with a workpiece surface, and moving at least one of the coated abrasive particles and the workpiece surface relative to the other to grind at least a portion of the workpiece surface. Methods for grinding with coated abrasive articles according to the present disclosure include, for example, rough grinding (i.e., high pressure and high cutting) to polishing (e.g., polishing medical implants with coated abrasive belts), wherein the latter is typically completed with abrasive particles of finer grades (e.g., ANSI 220 and finer grades). The size of abrasive particles for a particular grinding application will be apparent to those skilled in the art.

Grinding can be done by dry or wet methods. For wet grinding, the introduced liquid can be provided in the form of a light mist to a full stream. Examples of common liquids include water, water-soluble oils, organic lubricants, and emulsions. These liquids can be used to reduce the heat associated with grinding and/or be used as lubricants. The liquid can contain trace additives, such as bactericides, defoamers, etc.

Examples of workpieces include aluminum metal, carbon steel, mild steel (e.g., 1018 mild steel and 1045 mild steel), tool steel, stainless steel, hardened steel, titanium, glass, ceramics, wood, wood-like materials (e.g., plywood and particle board), paint, painted surfaces, and organic-coated surfaces, etc. The force applied during grinding is typically in the range of about 1 to about 100 kilograms (kg), but other pressures may be used.

Selected Embodiments of the Disclosure

In a first embodiment, the present disclosure provides a method of making a coated abrasive article, the method comprising:

Providing a backing having opposing first and second major surfaces, wherein a make layer is disposed on at least a portion of the first major surface and bonds abrasive grains to the backing, and further wherein a size layer is disposed on the make layer and at least a portion of the abrasive grains;

as well as

coating a supersize layer precursor on at least a portion of the size layer, and at least partially curing the supersize layer precursor to provide a supersize layer,

The top glue layer precursor comprises a water-based epoxy resin and an organic polymer rheology modifier,

wherein the organic polymer rheology modifier comprises an alkali swellable/soluble polymer, and wherein, based on solids, the amount of the water-based epoxy resin is 75 wt % to 99.99 wt % based on the total weight of the water-based epoxy resin and the organic polymer rheology modifier.

In a second embodiment, the present disclosure provides a method according to the first embodiment, wherein the at least partially curing the supersize layer precursor is performed in an overhung oven.

In a third embodiment, the present disclosure provides a method according to the first or second embodiment, wherein the supersize layer precursor has a basis weight of 5 to 1100 grams per square meter.

In a fourth embodiment, the present disclosure provides a method according to any one of the first to third embodiments, wherein the organic polymer rheology modifier is selected from the group consisting of alkali swellable/soluble acrylic polymers, hydrophobically modified alkali swellable/soluble acrylic polymers, hydrophobically modified ethoxylated polyurethane polymers, and combinations thereof.

In a fifth embodiment, the present disclosure provides a method according to any one of the first to fourth embodiments, wherein the amount of the water-based epoxy resin is 85 wt % to 99.99 wt % based on the total weight of the water-based epoxy resin and the organic polymer rheology modifier.

In a sixth embodiment, the present disclosure provides a method according to any one of the first to fifth embodiments, wherein the abrasive particles comprise shaped abrasive particles.

In a seventh embodiment, the present disclosure provides a method according to the sixth embodiment, wherein the shaped abrasive particles comprise precisely shaped abrasive particles.

In an eighth embodiment, the present disclosure provides a method according to the sixth embodiment, wherein the shaped abrasive particles comprise precisely shaped triangular flakes.

In a ninth embodiment, the present disclosure provides a coated abrasive article comprising:

a backing having opposing first and second major surfaces;

a make layer disposed on at least a portion of the first major surface and bonding abrasive particles to the backing;

a size layer covering the make layer and at least a portion of the abrasive grains; and

A top glue layer, the top glue layer is arranged on the secondary glue layer,

The top glue layer comprises an at least partially cured epoxy resin and an organic polymer rheology modifier, and the amount of the at least partially cured epoxy resin accounts for 75 weight percent to 99.99 weight percent of the total weight of the at least partially cured epoxy resin and the organic polymer rheology modifier.

In a tenth embodiment, the present disclosure provides a coated abrasive article according to the ninth embodiment, wherein the organic polymer rheology modifier is selected from the group consisting of alkali-swellable/soluble acrylic polymers, hydrophobically-modified alkali-swellable/soluble acrylic polymers, hydrophobically-modified ethoxylated polyurethane polymers, and combinations thereof.

In an eleventh embodiment, the present disclosure provides a coated abrasive article according to the ninth or tenth embodiment, wherein the at least partial epoxy resin is present in an amount of 85 wt % to 99.99 wt % based on the total weight of the at least partially cured epoxy resin and the organic polymeric rheology modifier.

In a twelfth embodiment, the present disclosure provides a coated abrasive article according to any one of the ninth to eleventh embodiments, wherein the abrasive particles comprise shaped abrasive particles.

In a thirteenth embodiment, the present disclosure provides a coated abrasive article according to the twelfth embodiment, wherein the shaped abrasive particles comprise precisely shaped abrasive particles.

In a fourteenth embodiment, the present disclosure provides a coated abrasive article according to the twelfth embodiment, wherein the shaped abrasive particles comprise precisely shaped triangular flakes.

Objects and advantages of this disclosure are further illustrated by the following non-limiting examples, but the particular materials and amounts thereof recited in these examples, as well as other conditions and details, should not be construed to unduly limit this disclosure.

Example

Unless otherwise stated, all parts, percentages, ratios, etc. in the examples and the rest of the specification are by weight. Table 1 below reports the materials used in the examples.

Table 1

Resin preparation

Comparison of top coat precursor CSSR-A

A 3 liter plastic container was charged with 438 g ER, 173 g water, 8.7 g ADD4, 55.1 g ADD 5, 13.8 g ADD 6, 18.1 g SF1, 1.9 g SF2, and 319.4 g LR and mixed for 10 minutes with an overhead mechanical stirrer. Next, 1972 g FIL2 was added over a 15 minute period. The resulting mixture was stirred for 15 minutes with an overhead stirrer.

Comparison of topcoat precursors CSSR-B , CSSR-C , CSSR-D and CSSR-E

99.5 grams of CSSR-A and 0.25 grams of FIL1 were charged into a 118 ml glass jar. The mixture was stirred for 5 minutes with an overhead stirrer to prepare a comparative supersubstrate precursor CSSR-B. Comparative supersubstrate precursors CSSR-C, CSSR-D and CSSR-E were prepared in a similar manner and the formulations are described in Table 2.

Top coat precursors ESSR-1 and ESSR-2

To a 118 ml glass vessel was added 99.5 grams of CSSR-A and 0.5 grams of ADD 2. The mixture was stirred for 5 minutes with an overhead stirrer to prepare Supersize Layer Precursor 1 (ESSR-1). Exemplary Supersize Layer Precursor 2 (ESSR-2) was prepared in a similar manner and the formulation is described in Table 2.

Top coat precursors ESSR-3 and ESSR-4

To a 118 ml glass jar was added 99.5 grams of CSSR-A and 0.5 grams of ADD. The mixture was stirred for 5 minutes with an overhead stirrer to prepare supersize layer precursor ESSR-3. Supersize layer precursor ESSR-4 example was prepared in a similar manner and the formulation is described in Table 2 below.

Table 2

Inclined Plane Flow Test

The inclined plane flow test involves placing a 0.1 gram drop of resin on a horizontally placed glass slide at a specified temperature and then rapidly tilting the slide on a tilting device set at a 48.7° angle for 1 minute (see Figures 1, 2 and Tables 2, 3). The distance the resin travels in one minute is recorded in millimeters (mm). The smaller the distance, the less likely the resin will overflow and cause bottom loop puddling in an overhang cure oven. Analysis of the data (Figures 1, 2 and Tables 2, 3) clearly illustrates the thixotropic nature of ESSR-1, 2, 3 and 4. In fact, these examples show a 10-fold to 20-fold improvement over the comparative examples (CSSR-A, B, C and D) on a 100% solids weight basis.

Table 3 below shows the inclined plane flow test results for various resins at room temperature (RT) and 41°C.

Table 3

Primer resin MR

A primer resin was prepared by charging 7812 g PF, 6823 g FIL1 and 364 g water into a 17 liter bucket. The resin was mixed at room temperature for 30 minutes using an overhead stirrer.

Resin SR1

To a 17 liter bucket was added 11100 g PF, 5800 g FIL1, 5800 g FIL1, 420 g ADD5 and 2000 g water to prepare the resizing resin. The resin was mixed at room temperature for 30 minutes using an overhead stirrer.

Resin SR2

To a 17 liter bucket was added 11100 g PF, 5800 g FIL1, 5800 g FIL1, 420 g ADD5, 118 g ADD3 and 2000 g water to prepare the resizing resin. The resin was mixed at room temperature for 30 minutes using an overhead stirrer.

Top coat precursor ESSR-5

Exemplary supersize layer precursor ESSR-5 was prepared by charging 18180 grams of CSSR-A, 92 grams of ADD2, 92 grams of ADD3, and 614 grams of water into a 17 liter bucket and mixing for 30 minutes with an overhead mechanical stirrer.

Coated Abrasive Comparison Top Gel CSSR-F

The coated abrasive examples and comparative examples were prepared by roll coating a 30.48 cm wide continuous polyester backing (as described in Example 12 of Thurber et al., U.S. Pat. No. 6,843,815) with a coating weight of 210 g/m2, followed by electrostatic coating of mineral SAP1 at a weight of 605 gsm. The coated material was cured at 90°C for 90 minutes and at 102°C for 60 minutes. The resulting material was then roll coated with a coating weight of 567 g/m2 (gsm) with a size resin SR1. The material was cured at 90°C for 60 minutes and at 102°C for 60 minutes. The resulting material was then roll coated with a comparative top coat precursor CSSR-A at a coating weight of 567 g/m2 (gsm). The material was finally cured at 90°C for 60 minutes, at 102°C for 12 hours, and at 109°C for 1 hour.

Example of coated abrasive top size ESSR-5

The coated abrasive examples and comparative examples were prepared by roll coating a 30.48 cm wide continuous polyester backing (as described in Example 12 of Thurber et al., U.S. Pat. No. 6,843,815) with a coating weight of 210 gsm by roll coating a primer resin MR, followed by electrostatic coating of a mineral SAP1 at a weight of 605 gsm. The coated material was cured at 90° C. for 90 minutes and at 102° C. for 60 minutes. The resulting material was then roll coated with a size resin SR2 at a coating weight of 567 gsm. The material was cured at 90° C. for 60 minutes and at 102° C. for 60 minutes. The resulting material was then roll coated with a comparative top coat precursor ESSR-5 at a coating weight of 567 gsm. The material was finally cured at 90° C. for 60 minutes, at 102° C. for 12 hours, and at 109° C. for 1 hour.

Comparison of top size precursors for coated abrasives

As shown in Figures 3 and 4, the coated abrasive article prepared using the comparative supersize layer precursor CSSR-F (shown in Figure 3) exhibited a bottom loop pick-up problem, while the same coated abrasive article except that the supersize layer precursor ESSR-5 (shown in Figure 4) was used did not have this problem.

All cited references, patents, and patent applications incorporated by reference in this application are incorporated in a consistent manner. In the event of inconsistencies or conflicts between the incorporated references and the present application, the information in the present application shall prevail. The foregoing description, which is given to enable one of ordinary skill in the art to practice the present disclosure protected by the claims, should not be construed as limiting the scope of the present disclosure, which is defined by the claims and all equivalents thereof.

Claims (14)

1. A method of making a coated abrasive article, the method comprising:

providing a backing having opposed first and second major surfaces, wherein a make layer is disposed on at least a portion of the first major surface and bonds abrasive particles to the backing, further wherein a size layer is disposed on at least a portion of the make layer and the abrasive particles; and

coating a make layer precursor on at least a portion of the size layer, and at least partially curing the make layer precursor to provide a make layer,

wherein the make coat precursor comprises a water-based epoxy resin and an organic polymer rheology modifier, wherein the organic polymer rheology modifier comprises an alkali-swellable/soluble polymer, and wherein the amount of the water-based epoxy resin is from 75 wt% to 99.99 wt% of the total weight of the water-based epoxy resin and the organic polymer rheology modifier on a solids basis.

2. The method of claim 1, wherein the at least partially curing the top coat precursor is performed in a pendant oven.

3. The method of claim 1, wherein the top coat precursor has a basis weight of 5 grams to 1100 grams per square meter.

4. The method of claim 1, wherein the organic polymeric rheology modifier is selected from the group consisting of alkali swellable/soluble acrylic polymers, hydrophobically modified ethoxylated polyurethane polymers, and combinations thereof.

5. The method of claim 1, wherein the amount of the water-based epoxy resin is 85 to 99.99 weight percent based on solids based on the total weight of the water-based epoxy resin and the organic polymer rheology modifier.

6. The method of claim 1, wherein the abrasive particles comprise shaped abrasive particles.

7. The method of claim 6, wherein the shaped abrasive particles comprise precisely-shaped abrasive particles.

8. The method of claim 6, wherein the shaped abrasive particles comprise precisely-shaped triangular flakes.

9. A coated abrasive article comprising:

a backing having opposed first and second major surfaces;

a make layer disposed on at least a portion of the first major surface and bonding abrasive particles to the backing;

A size layer overlying the make layer and at least a portion of the abrasive particles; and

a top adhesive layer arranged on the compound adhesive layer,

wherein the top coat comprises an at least partially cured epoxy resin and an organic polymer rheology modifier, and wherein the amount of the at least partially cured epoxy resin is from 75 wt% to 99.99 wt% of the total weight of the at least partially cured epoxy resin and the organic polymer rheology modifier.

10. The coated abrasive article of claim 9 wherein the organic polymeric rheology modifier is selected from the group consisting of alkali swellable/soluble acrylic polymers, hydrophobically modified ethoxylated polyurethane polymers, and combinations thereof.

11. The coated abrasive article of claim 9, wherein the amount of the at least partially epoxy resin comprises 85 wt% to 99.99 wt% of the total weight of the at least partially cured epoxy resin and the organic polymeric rheology modifier.

12. The coated abrasive article of claim 9, wherein the abrasive particles comprise shaped abrasive particles.

13. The coated abrasive article of claim 12 wherein the shaped abrasive particles comprise precisely-shaped abrasive particles.

14. The coated abrasive article of claim 12 wherein the shaped abrasive particles comprise precisely-shaped triangular flakes.

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