Patent Application
20070066186
Flexible abrasive articles that have an abrasive layer affixed to a foam backing are used for many abrading applications, including for example, scuffing painted surfaces such as, for example, damaged automotive finishes prior to repairing them. During use, the flexible abrasive articles may be subjected to harsh forces that result in failure of the flexible abrasive article at a time when the abrasive layer is otherwise usable. Such premature failure may occur, for example, by separation of the abrasive layer from the foam backing and/or by damage caused to the foam backing.
In one aspect, the present invention provides a flexible abrasive article comprising:
a compressible backing having first and second opposed major surfaces;
an elastic polyurethane film affixed to at least a portion of the first major surface of the compressible backing; and
an abrasive layer affixed to at least a portion of the polyurethane film, the abrasive layer comprising abrasive particles and a binder.
In some embodiments, the polyurethane film has a treated surface, and the abrasive layer is affixed to at least a portion of the treated surface.
In some embodiments, the flexible abrasive article further comprises an extensible tie layer affixed to at least a portion of the polyurethane film, wherein the abrasive layer is affixed to at least a portion of the extensible tie layer.
In some embodiments, the abrasive layer comprises a plurality of shaped abrasive composites.
In some embodiments, each of the elastic polyurethane film, optional extensible tie layer, and abrasive layer in flexible abrasive articles according to the present invention are foraminous, and there exist a plurality of continuous pores that extend from the second major surface of the backing through the abrasive layer.
In some embodiments, flexible abrasive articles according to the present invention further comprise an attachment system affixed to the second major surface of the compressible backing.
In another aspect, the present invention provides a method of making a flexible abrasive article, the method comprising:
affixing an elastic polyurethane film to a first major surface of a compressible backing which also has an opposite second major surface;
applying a curable composition comprising a polymerizable binder precursor and abrasive particles to the elastic polyurethane film; and
at least partially curing the curable composition to provide an abrasive layer.
In another aspect, the present invention provides a method of making a flexible abrasive article, the method comprising:
affixing an elastic polyurethane film to a first major surface of a compressible backing which also has an opposite second major surface;
affixing an extensible tie layer to the polyurethane film;
applying a curable composition comprising a polymerizable binder precursor and abrasive particles to the extensible tie layer; and
at least partially curing the curable composition to provide an abrasive layer.
In some embodiments, the method further comprises:
imparting a textured surface to the curable composition with a production tool that has a textured surface; and
separating the production tool from the at least partially cured curable composition.
By including an elastic polyurethane film between the abrasive layer and compressible backing, the durability (e.g., useful life) of flexible abrasive articles is typically improved without compromising the flexibility, feel, cut, finish and handling.
As used herein:
“elastic polyurethane film” refers to an elastic film having a polyurethane content greater than about 50 weight percent;
“elastomer” refers to an elastic polymer;
“elastic polyurethane film” refers to a film comprising at least one elastic polyurethane; and
the term “film” refers to a thin layer of material.
An exemplary flexible abrasive article according to the present invention is shown in
Compressible Backing
The compressible backing may comprise any compressible resilient material(s). For example, in some embodiments, the compressible backing may comprise a resilient nonwoven web, optionally in combination with one or more thin synthetic polymeric films affixed thereto. More typically, the compressible backing comprises at least one foam layer, optionally in combination with one or more flexible members (e.g., polymeric films) affixed thereto.
Useful nonwoven webs include, for example, open fiber webs (e.g., lofty open fiber webs) wherein the fibers are bonded together in their mutual contact points by a binder (e.g., formed by drying and/or curing a binder precursor material). The nonwoven web may be made, for example, from an air-supported construction (e.g., as described in U.S. Pat. No. 2,958,593 (Hoover et al.), the disclosure of which is incorporated herein by reference), from a carded and cross-lapped construction, or a meltblown construction. Useful fibers include natural and synthetic fibers, and blends thereof. Useful synthetic fibers include, for example, those fibers made of polyester (for example, polyethylene-terephthalate), high or low resilience nylon (for example, hexamethylene-adipamide, polycaprolactam), polypropylene, acrylic (formed from acrylonitrile polymer), rayon, cellulose acetate, chloride copolymers of vinyl-acrylonitrile, and others. The appropriate natural fibers include those coming from cotton, wool, jute, and hemp.
Fibers diameters may be, for example, less than or equal to 1, 2, 4, 6, 10, 13, 17, 70, 110, 120 or 200 denier, although this is not a requirement. Fiber webs basis weights will depend upon the web thickness and the degree of openness.
Examples of suitable binder precursor materials include latexes (e.g., acrylic latexes or polyurethane latexes), phenolic resins, aminoplast resins, polymer plastisols, and combinations thereof.
The non-woven web is typically formed and then coated with a binder precursor then submitted to a coating procedure in which a curable binder precursor is applied to the web, e.g., by roll coating, dip coating, or spraying.
In general, in those embodiments wherein the compressible backing comprises a foam layer, any foam layer with at least one coatable surface may be used. The foam layer may comprise any compressible foam material. In some embodiments, the compressible foam material is elastic. Useful foams include elastic foams such as, for example, chloroprene rubber foams, ethylene/propylene rubber foams, butyl rubber foams, polybutadiene foams, polyisoprene foams, EPDM polymer foams, polyurethane foams, ethylene-vinyl acetate foams, neoprene foams, and styrene/butadiene copolymer foams. Useful foams also include thermoplastic foams such as, for example, polyethylene foams, polypropylene foams, polybutylene foams, polystyrene foams, polyamide foams, polyester foams, plasticized polyvinyl chloride (i.e., pvc) foams. The foam layer may be of an open cell (e.g., foraminous) or closed cell variety, although typically, if the abrasive article is intended for use with liquids, an open cell foam having sufficient porosity to permit the entry of liquid is desirable. Particular examples of useful open cell foams are polyester polyurethane foams, commercially available from Illbruck, Inc., Minneapolis, Minn. under the trade designations “R 200U”, “R 400U”, “R 600U” and “EF3-700C”.
The degree of flexibility of the compressible backing will typically vary with the intended use.
In those embodiments wherein the compressible backing comprises a foam layer, the thickness of the compressible foam layer is typically in a range of from 1 to 50 millimeters, however, other thickness may also be used. Typically, the bulk density of the compressible foam layer as determined by ASTM D-3574 is greater than about 0.03 gram per cm3 (2 lbs per ft3), however lower density foam layers may also be used. In some embodiments, the foam layer has a bulk density of about 0.03 to about 0.10 grams per cm3 (1.8-6 lbs per ft3). While thinner or thicker and/or lighter or heavier foams may be useful, they may require special handling because they are somewhat more difficult to process on conventional coating equipment.
The compressible backing is typically in sheet form with substantially parallel major surfaces, but other surface-configurations with one or both major surfaces being planar or other than planar are also useful. For example, in those embodiments wherein the compressible backing comprises a foam layer, the second major surface may be planar to facilitate attachment, while the first major surface may be other than planar, for example, an undulated or convoluted surface. Convoluted foams are disclosed in U.S. Pat. Nos. 5,007,128 and 5,396,737 (both to Englund et al.), the disclosures of which are incorporated herein by reference.
In those embodiments wherein the compressible backing comprises a foam layer, the foam layer may have an elongation in a range of from about 85 to about 150% (i.e., the stretched length of the foam minus the unstretched length of the foam all divided by the unstretched length of the foam and then multiplied by 100 equals 85 to 150%.).
Elastic Polyurethane Film
The elastic polyurethane film may be a uniform film, or it may be a composite film (e.g., having multiple layers produced by coextrusion, heat lamination, or adhesive bonding). In some embodiments, the elastic polyurethane film typically comprises elastic polyurethane (e.g., elastomeric polyurethane). Examples of elastomeric polyurethanes that may be used include, those available under the trade designation “ESTANE” from B.F. Goodrich & Co., Cleveland, Ohio, and those described in U.S. Pat. No. 2,871,218 (Schollenberger); U.S. Pat. No. 3,645,835 (Hodgson); U.S. Pat. No. 4,595,001 (Potter et al.); U.S. Pat. No. 5,088,483 (Heinecke); U.S. Pat. No. 6,838,589 (Liedtke et al.); and RE 33,353 (Heinecke). Useful pressure sensitive adhesive coated polyurethane elastomer films are commercially available from 3M Company under the trade designation “TEGADERM”.
The elastic polyurethane film is generally from about 0.02 to about 6 millimeters in thickness, for example, from 0.02 millimeter to 0.1 millimeter in thickness; however, this is not a requirement.
Typically, the elastic modulus (measured at 1 Hz and 25° C.) of the elastic polyurethane film is between about 2.4×105 and about 7×105 Pascals, for example, between about 3×105 and about 6×105 Pascals, or even between about 4×105 and about 5×105 Pascals, although this is not a requirement.
The elastic polyurethane film is affixed to the compressible backing by a layer of adhesive disposed therebetween.
The elastic polyurethane film may contain fillers, additives, antioxidants, stabilizers, other polymers, and the like.
In some embodiments, the elastic polyurethane film may be made foraminous by perforating the film with an array of needles deployed in a standard needle board installed in a needletacking machine (i.e., needletacking).
In some embodiments, the elastic polyurethane film is affixed to the compressible backing by a layer of an adhesive material such as, for example, glue, hot melt adhesive, or a pressure sensitive adhesive film optionally provided as a transfer tape. In some embodiments, the elastic polyurethane film is in direct contact with the compressible backing.
Adhesion of the Abrasive Layer to the Elastic Polyurethane Film
In some embodiments, an optional tie layer provides good adhesion of the abrasive layer to the elastic polyurethane film.
In some embodiments, the optional tie layer is extensible. Without wishing to be bound by theory, it is believed that the extensible tie layer functions at least in part by relieving stresses that would occur upon stretching between the typically rigid abrasive layer and the elastic polyurethane film.
Examples of suitable extensible tie layers include pressure sensitive adhesives, and elastomeric acrylics (e.g., styrene/acrylic elastomers) whether supplied in bulk or latex form.
Examples of pressure sensitive adhesives that may be used in the tie layer include pressure sensitive adhesives derived from acrylate polymers (for example, polybutyl acrylate), acrylate copolymers (for example, isooctyl acrylate/acrylic acid), vinyl ethers (for example, polyvinyl n-butyl ether), alkyd adhesives, rubber adhesives (for example, natural rubbers, synthetic rubbers and chlorinated rubbers), and mixtures thereof. The adhesive may be provided and applied to the elastic polyurethane film in, for example, bulk, solvent borne, or water-based latex form.
In some embodiments, the optional extensible tie layer is elastic, while in others it is not.
The optional extensible tie layer is generally from about 0.02 millimeter to about 4 millimeters in thickness, for example, from 0.06 millimeter to 2 millimeters in thickness, however this is not a requirement.
Alternatively, or in addition to the optional tie layer the elastic polyurethane film may be surface treated by corona, flame or acid or base priming.
Further, adhesion may be improved in some cases by incorporating at least one of acrylic acid or methacrylic acid into a polymerizable binder precursor used to form the abrasive layer.
Abrasive Layer
In some embodiments, the abrasive layer comprises make and size layers and abrasive particles as shown for example, in
In other embodiments, the abrasive layer comprises abrasive particles in a binder, typically substantially uniformly distributed throughout the binder, as shown for example, in
In some embodiments, the abrasive layer comprises a structured abrasive layer, for example, as described in
Structured abrasive layers, useful in practice of the present invention, comprise a plurality of non-randomly shaped abrasive composites and affixed to the elastic polyurethane film. As used herein, the term “abrasive composite” refers to a body that includes abrasive particles and a binder. In some embodiments, shaped abrasive composites may be arranged according to a predetermined pattern (e.g., as an array).
In some embodiments, at least a portion of the shaped abrasive composites may comprise “precisely shaped” abrasive composites. This means that the shape of the abrasive composites is defined by relatively smooth surfaced sides that are bounded and joined by well-defined edges having distinct edge lengths with distinct endpoints defined by the intersections of the various sides. The terms “bounded” and “boundary” refer to the exposed surfaces and edges of each composite that delimit and define the actual three-dimensional shape of each abrasive composite. These boundaries are readily visible and discernible when a cross-section of an abrasive article is viewed under a scanning electron microscope. These boundaries separate and distinguish one precisely shaped abrasive composite from another even if the composites abut each other along a common border at their bases. By comparison, in an abrasive composite that does not have a precise shape, the boundaries and edges are not well defined (e.g., where the abrasive composite sags before completion of its curing). Typically, precisely shaped abrasive composites are arranged on the backing according to a predetermined pattern or array, although this is not a requirement.
Shaped abrasive composites may be arranged such that some of their work surfaces are recessed from the polishing surface of the abrasive layer.
Precisely shaped abrasive composites may be of any three-dimensional shape that results in at least one of a raised feature or recess on the exposed surface of the abrasive layer. Useful shapes include, for example, cubic, prismatic, pyramidal (e.g., square pyramidal or hexagonal pyramidal), truncated pyramidal, conical, frusto-conical, pup tent shaped, and ridged. Combinations of differently shaped and/or sized abrasive composites may also be used. The abrasive layer of the structured abrasive may be continuous or discontinuous.
For fine finishing applications, the density of shaped abrasive composites in the abrasive layer is typically in a range of from at least 1,000, 10,000, or even at least 20,000 abrasive composites per square inch (e.g., at least 150, 1,500, or even 7,800 abrasive composites per square centimeter) up to and including 50,000, 70,000, or even as many as 100,000 abrasive composites per square inch (up to and including 7,800, 11,000, or even as many as 15,000 abrasive composites per square centimeter), although greater or lesser densities of abrasive composites may also be used.
Further details concerning structured abrasive layers having precisely shaped abrasive composites, and methods for their manufacture may be found, for example, in U.S. Pat. No. 5,152,917 (Pieper et al.); U.S. Pat. No. 5,304,223 (Pieper et al.); U.S. Pat. No. 5,435,816 (Spurgeon et al.); U.S. Pat. No. 5,672,097 (Hoopman); U.S. Pat. No. 5,681,217 (Hoopman et al.); U.S. Pat. No. 5,454,844 (Hibbard et al.); U.S. Pat. No. 5,549,962 (Holmes et al.); U.S. Pat. No. 5,700,302 (Stoetzel et al.); U.S. Pat. No. 5,851,247 (Stoetzel et al.); U.S. Pat. No. 5,910,471 (Christianson et al.); U.S. Pat. No. 5,913,716 (Mucci et al.); U.S. Pat. No. 5,958,794 (Bruxvoort et al.); U.S. Pat. No. 6,139,594 (Kincaid et al.); U.S. Pat. No. 6,923,840 (Schutz et al.); and U.S. Pat. Appln. Nos. 2003/0022604 (Annen et al.); the disclosures of which are incorporated herein by reference.
Structured abrasive layers may be prepared by coating a slurry comprising a polymerizable binder precursor, abrasive particles, and an optional silane coupling agent through a screen that is in contact with the elastic polyurethane film, or extensible tie layer). In this embodiment, the slurry is typically then further polymerized (e.g., by exposure to an energy source such as heat or electromagnetic radiation) while it is present in the openings of the screen thereby forming a plurality of shaped abrasive composites generally corresponding in shape to the screen openings. Further details concerning this type of screen coated structured abrasive may be found, for example, in U.S. Pat. No. 4,927,431 (Buchanan et al.); U.S. Pat. No. 5,378,251 (Culler et al.); U.S. Pat. No. 5,942,015 (Culler et al.); U.S. Pat. No. 6,261,682 (Law); and U.S. Pat. No. 6,277,160 (Stubbs et al.); the disclosures of which are incorporated herein by reference.
In some embodiments, a slurry comprising a polymerizable binder precursor, abrasive particles, and an optional silane coupling agent may be deposited on the elastic polyurethane film, or extensible tie layer in a patterned manner (e.g., by screen or gravure printing), partially polymerized to render at least the surface of the coated slurry plastic but non-flowing, a pattern embossed upon the partially polymerized slurry formulation, and subsequently further polymerized (e.g., by exposure to an energy source) to form a plurality of shaped abrasive composites affixed to the elastic polyurethane film, or extensible tie layer. Further details concerning this and related methods are described, for example, in U.S. Pat. Appl. Pub. No. 2001/0041511 (Lack et al.), the disclosure of which is incorporated herein by reference.
Useful polymerizable binder precursors that may be cured to form the above-mentioned binders are well-known and include, for example, thermally curable resins and radiation curable resins, which may be cured, for example, thermally and/or by exposure to radiation energy. Exemplary polymerizable binder precursors include phenolic resins, aminoplast resins, urea-formaldehyde resins, melamine-formaldehyde resins, urethane resins, polyacrylates (e. g., an aminoplast resin having pendant free-radically polymerizable unsaturated groups, urethane acrylates, acrylate isocyanurate, (poly)acrylate monomers, and acrylic resins), alkyd resins, epoxy resins (including bis-maleimide and fluorene-modified epoxy resins), isocyanurate resins, allyl resins, furan resins, cyanate esters, polyimides, and mixtures thereof. Polymerizable binder precursors may contain one or more reactive diluents (e.g., low viscosity monoacrylates) and/or adhesion promoting monomers (e.g., acrylic acid or methacrylic acid).
If either ultraviolet radiation or visible radiation is to be used, the polymerizable binder precursor typically further comprises a photoinitiator.
Examples of photoinitiators that generate a free radical source include, but are not limited to, organic peroxides, azo compounds, quinones, benzophenones, nitroso compounds, acyl halides, hydrazones, mercapto compounds, pyrylium compounds, triacrylimidazoles, bisimidazoles, phosphene oxides, chloroalkyltriazines, benzoin ethers, benzil ketals, thioxanthones, acetophenone derivatives, and combinations thereof.
Cationic photoinitiators generate an acid source to initiate the polymerization of an epoxy resin. Cationic photoinitiators can include a salt having an onium cation and a halogen containing a complex anion of a metal or metalloid. Other cationic photoinitiators include a salt having an organometallic complex cation and a halogen containing complex anion of a metal or metalloid. These are further described in U.S. Pat. No. 4,751,138, incorporated herein by reference. Another example of a cationic photoinitiator is an organometallic salt and an onium salt described in U.S. Pat. No. 4,985,340 and European Pat. Appl. Publ. Nos. 306,161 and 306,162; all of which are incorporated herein by reference. Still other cationic photoinitiators include an ionic salt of an organometallic complex in which the metal is selected from the elements of Periodic Group IVB, VB, VIB, VIIB and VIIIB.
The polymerizable binder precursor may also comprise resins that are curable by sources of energy other than radiation energy, such as condensation curable resins. Examples of such condensation curable resins include phenolic resins, melamine-formaldehyde resins, and urea-formaldehyde resins.
The binder precursor and binder may include one or more optional additives selected from the group consisting of grinding aids, fillers, wetting agents, chemical blowing agents, surfactants, pigments, coupling agents, dyes, initiators, energy receptors, and mixtures thereof. The optional additives may also be selected from the group consisting of potassium fluoroborate, lithium stearate, glass bubbles, inflatable bubbles, glass beads, cryolite, polyurethane particles, polysiloxane gum, polymeric particles, solid waxes, liquid waxes and mixtures thereof.
Abrasive particles useful in the present invention can generally be divided into two classes: natural abrasives and manufactured abrasives. Examples of useful natural abrasives include: diamond, corundum, emery, garnet (off-red color), buhrstone, chert, quartz, garnet, emery, sandstone, chalcedony, flint, quartzite, silica, feldspar, natural crushed aluminum oxide, pumice and talc. Examples of manufactured abrasives include: boron carbide, cubic boron nitride, fused alumina, ceramic aluminum oxide, heat treated aluminum oxide (both brown and dark grey), fused alumina zirconia, glass, glass ceramics, silicon carbide, iron oxides, tantalum carbide, chromia, cerium oxide, tin oxide, titanium carbide, titanium diboride, synthetic diamond, manganese dioxide, zirconium oxide, sol gel alumina-based ceramics, silicon nitride, and agglomerates thereof. Examples of sol gel abrasive particles can be found in U.S. Pat. No. 4,314,827 (Leitheiser et al.); U.S. Pat. No. 4,623,364 (Cottringer et al); U.S. Pat. No. 4,744,802 (Schwabel); U.S. Pat. No. 4,770,671 (Monroe et al.) and U.S. Pat. No. 4,881,951 (Wood et al.), all incorporated herein by reference.
The size of an abrasive particle is typically specified to be the longest dimension of the abrasive particle. In most cases there will be a range distribution of particle sizes. The particle size distribution may be tightly controlled such that the resulting abrasive article provides a consistent surface finish on the workpiece being abraded, however, broad and/or polymodal particle size distributions may also be used.
The abrasive particle may also have a shape associated with it. Examples of such shapes include rods, triangles, pyramids, cones, solid spheres, hollow spheres and the like. Alternatively, the abrasive particle may be randomly shaped.
Abrasive particles can be coated with materials to provide the particles with desired characteristics. For example, materials applied to the surface of an abrasive particle have been shown to improve the adhesion between the abrasive particle and the polymer. Additionally, a material applied to the surface of an abrasive particle may improve the adhesion of the abrasive particles in the softened particulate curable binder material. Alternatively, surface coatings can alter and improve the cutting characteristics of the resulting abrasive particle. Such surface coatings are described, for example, in U.S. Pat. No. 5,011,508 (Wald et al.); U.S. Pat. No. 3,041,156 (Rowse et al.); U.S. Pat. No. 5,009,675 (Kunz et al.); U.S. Pat. No. 4,997,461 (Markhoff-Matheny et al.); U.S. Pat. No. 5,213,591 (Celikkaya et al.); U.S. Pat. No. 5,085,671 (Martin et al.) and U.S. Pat. No. 5,042,991 (Kunz et al.), the disclosures of which are incorporated herein by reference.
In some embodiments, for example, those including shaped abrasive composites, the abrasive particles have a particle size ranging from about 0.1 micrometer to about 1500 micrometers, more typically ranging from about 0.1 micrometer to about 1300 micrometers. In some embodiments, the abrasive particles have a size within a range of from JIS grade 600 (18 micrometers at 50% midpoint) to JIS grade 4000 (3 micrometers at 50% midpoint) or even JIS grade 8000 (1.5 micrometers at 50% midpoint), inclusive.
Typically, the abrasive particles used in the present invention have a Moh's hardness of at least 8, more typically above 9; however, abrasive particles having a Moh's hardness of less than 8 may be used.
In some embodiments, at least one of the compressible backing, elastic polyurethane film, extensible tie layer, and abrasive layer is foraminous. This may be accomplished by a suitable means, including, for example, die cutting or perforating, needlepunching, or any or all of the aforementioned components of the flexible abrasive article; or, for example, as in the case of the abrasive layer by providing the abrasive layer with openings by a suitable coating method, such as described in U.S. Pat. No. 6,923,840 (Schutz et al.), the disclosure of which is herein incorporated by reference.
In some embodiments, it may be desirable to thermally emboss flexible abrasive articles according to the present invention. For example, channels may be embossed into at least the abrasive layer to facilitate fluid transport and/or swarf removal. U.S. Publ. Pat. Appl. No. 2003/0150169 A1 (Annen), the disclosure of which is incorporated herein by reference, describes such embossing techniques.
For example, the compressible backing, elastic polyurethane film, extensible tie layer, and abrasive layer may be foraminous and interrelated such that there exist a plurality of continuous pores that extend from the second major surface of the compressible backing through the abrasive layer.
In some embodiments, flexible abrasive articles according to the present invention may be embossed, for example, to create a pattern of higher and lower areas that would facilitate swarf removal during use.
Attachment System
Flexible abrasive articles according to the present invention may be secured to a support structure, commonly referred to as a backup pad. The flexible abrasive article may be secured by means of, for example, a pressure sensitive adhesive, hook and loop attachment, or some other mechanical means.
Accordingly, flexible abrasive articles according to the present invention may further comprise an attachment system affixed to the second major surface of the compressible backing. The attachment system is typically designed to secure the flexible abrasive article to a tool (optionally having a back up pad mounted thereto) such as, for example, a rotary sander.
In some embodiments, the attachment system comprises a layer of pressure sensitive adhesive, typically made by applying a layer of pressure sensitive adhesive to the second major surface of the compressible backing. Useful pressure sensitive adhesives for this layer include, for example, acrylic polymers and copolymers (e.g., polybutyl acrylate), vinyl ethers, e.g., polyvinyl n-butyl ether, vinyl acetate adhesives, alkyd adhesives, rubber adhesives, e.g., natural rubber, synthetic rubber, chlorinated rubber, and mixtures thereof. One preferred pressure sensitive adhesive is an isooctyl acrylate:acrylic acid copolymer. The pressure sensitive adhesive may be coated out of organic solvent, water or be coated as a hot melt adhesive.
In some embodiments, the attachment system comprises a quick connect mechanical fastener such as, for example, those described in U.S. Pat. No. 3,562,968 (Johnson et al.); U.S. Pat. No. 3,667,170 (Mackay, Jr.); U.S. Pat. Nos. 3,270,467; and 3,562,968 (Block et al.); and in commonly assigned U.S. Ser. No. 10/828,119 (Fritz et al.), filed Apr. 20, 2004; the disclosures of which are incorporated herein by reference.
In some embodiments, the attachment system comprises a loop substrate. The purpose of the loop substrate is to provide a means that the flexible abrasive article can be securely engaged with hooks from a support pad. The loop substrate may be laminated to the coated abrasive backing by any conventional means. The loop substrate may be a chenille stitched loop, a stitchbonded loop substrate or a brushed loop substrate (e.g., brushed nylon). Examples of typical loop backings are further described in U.S. Pat. Nos. 4,609,581 and 5,254,194 (both to Ott), the disclosures of which are incorporated herein by reference. The loop substrate may also contain a sealing coat to seal the loop substrate and prevent subsequent coatings from penetrating into the loop substrate.
In some embodiments, the attachment system comprises an intermeshing attachment system. An example of such an attachment system may be found in U.S. Publ. Pat. Appln. No. 2003/0143938 (Braunschweig et al.), the disclosure of which is incorporated herein by reference.
Likewise, the back side of the abrasive article may contain a plurality of hooks; these hooks are typically in the form of sheet like substrate having a plurality of hooks protruding therefrom, for example, as described in U.S. Pat. No. 5,672,186 (Chesley et al.), the disclosure of which is incorporated herein by reference. These hooks will then provide the engagement between the coated abrasive article and a support pad that contains a loop fabric. This hook substrate may be laminated to the coated abrasive backing by any conventional means.
Method of Making
Flexible abrasive articles according to the present invention may generally be made by: providing a compressible backing with first and second opposed major surfaces; affixing an elastic polyurethane film to at least a portion of the first major surface of the compressible backing; and affixing an abrasive layer to the elastic polyurethane film, wherein the abrasive layer comprises abrasive particles in a binder. The surface of the elastic polyurethane film may be surface treated to enhance adhesion as discussed hereinabove.
In those embodiments including an extensible tie layer, flexible abrasive articles according to the present invention may generally be made by affixing the extensible tie layer to the elastic polyurethane film, and then affixing the abrasive layer to the extensible tie layer.
Affixing the various components may be accomplished by any suitable means such as, for example, an adhesive (e.g., hot melt or pressure sensitive), glue, mechanical fasteners, coextrusion, by heat and/or pressure laminating, or any other suitable method.
Useful adhesives include, for example, acrylic pressure sensitive adhesive, rubber-based PSA, waterborne lattices, solvent-based adhesives, and two-part resins (e.g., epoxies, polyesters, or polyurethanes). Examples of suitable pressure sensitive adhesives include acrylate polymers (for example, polybutyl acrylate), acrylate copolymers (for example, isooctyl acrylate/acrylic acid), vinyl ethers (for example, polyvinyl n-butyl ether), alkyd adhesives, rubber adhesives (for example, natural rubbers, synthetic rubbers and chlorinated rubbers), and mixtures thereof. An example of a pressure sensitive adhesive coating is described in U.S. Pat. No. 5,520,957 (Bange et al.), the disclosure of which is incorporated herein by reference.
Adhesives may be applied by any suitable means including, for example, roll coating, brushing, extrusion, spraying, bar coating, and knife coating.
The abrasive layer may be affixed to the optional extensible tie layer or elastic polyurethane film by coating and curing an abrasive layer precursor thereon. Details concerning such procedures are discussed hereinabove.
In one embodiment, a structured abrasive layer is affixed to either of the optional extensible tie layer or elastic polyurethane film according to the procedures of U.S. Pat. No. 6,929,539 (Schutz et al.), the disclosure of which is incorporated herein by reference.
Briefly, the procedure involves applying a curable composition comprising abrasive particles and a polymerizable binder precursor. The curable composition is capable of being cured by radiation energy (e.g., ultraviolet or visible light, or e-beam radiation). The polymerizable binder precursor can polymerize, for example, via a free radical mechanism or a cationic mechanism.
During the manufacture of the shaped, handleable structure, radiation energy is transmitted through the production tool and into the mixture to at least partially cure the curable composition. The phrase “partial cure” means that the binder precursor is polymerized to such a state that the resulting mixture releases from the production tool. The binder precursor can be further cured once it is removed from the production tool by any energy source, such as, for example, thermal energy or radiation energy. The binder precursor can also be further cured before the shaped, handleable structure is removed from the production tool.
Useful sources of radiation energy for this invention include, for example, electron beam, ultraviolet light, and visible light. Other sources of radiation energy include infrared and microwave. Thermal energy can also be used. Electron beam radiation, which is also known as ionizing radiation, can be used at a dosage of about 0.1 to about 10 Mrad, preferably at a dosage of about 1 to about 10 Mrad. Ultraviolet radiation refers to non-particulate radiation having a wavelength, within the range of about 200 to 400 nanometers, preferably within the range of about 250 to 400 nanometers. It is preferred that ultraviolet radiation be provided by ultraviolet lamps operating in a range of 100 to 300 Watts/cm. Visible radiation refers to non-particulate radiation having a wavelength within the range of about 400 to about 800 nanometers, for example, within the range of about 400 to about 550 nanometers.
Typically, radiation energy is transmitted through the production tool and directly into the mixture. It is desirable that the material from which the production tool is made not absorb an appreciable amount of radiation energy or be degraded by radiation energy. If ultraviolet radiation or visible radiation is used, the production tool material should transmit sufficient ultraviolet or visible radiation, respectively, to bring about the desired level of cure.
The production tool should be operated at a velocity that is sufficient to avoid degradation by the source of radiation. Production tools that have relatively high resistance to degradation by the source of radiation can be operated at relatively lower velocities; production tools that have relatively low resistance to degradation by the source of radiation can be operated at relatively higher velocities. In short, the appropriate velocity for the production tool depends on the material from which the production tool is made.
The production tool can be in the form of a belt, e.g., an endless belt, a sheet, a continuous sheet or web, a coating roll, a sleeve mounted on a coating roll, or die. The surface of the production tool that will come into contact with the mixture has a topography or pattern. This surface is referred to herein as the “contacting surface.” If the production tool is in the form of a belt, sheet, web, or sleeve, it will have a contacting surface and a non-contacting surface. If the production tool is in the form of a coating roll, it will have a contacting surface only. The topography of the abrasive article formed by the method of this invention will have the inverse of the pattern of the contacting surface of the production tool. The pattern of the contacting surface of the production tool will generally be characterized by a plurality of cavities or recesses. The opening of these cavities can have any shape, regular or irregular, such as a rectangle, semicircle, circle, triangle, square, hexagon, octagon, etc. The walls of the cavities can be vertical or tapered. The pattern formed by the cavities can be arranged according to a specified plan or can be random. The cavities can butt up against one another.
Thermoplastic materials that can be used to construct the production tool include polyesters, polycarbonates, poly(ether sulfone), poly(methyl methacrylate), polyurethanes, polyvinylchloride, polyolefins, polystyrene, or combinations thereof. Thermoplastic materials can include additives such as plasticizers, free radical scavengers or stabilizers, thermal stabilizers, antioxidants, and ultraviolet radiation absorbers. These materials are substantially transparent to ultraviolet and visible radiation. One type of production tool is described in U.S. Pat. No. 5,435,816 (Spurgeon et al.). Examples of materials forming the production tool include polycarbonate and polyester. The material forming the production tool should exhibit low surface energy. The material of low surface energy improves ease of release of the abrasive article from the production tool. Examples of materials suitable include polypropylene and polyethylene. In some production tools made of thermoplastic material, the operating conditions for making the abrasive article should be set such that excessive heat is not generated. If excessive heat is generated, this may distort or melt the thermoplastic tooling. In some instances, ultraviolet light generates heat. It should also be noted that a tool consisting of a single layer is also acceptable, and is the tool of choice in many instances. A thermoplastic production tool can be made according to the procedure described in U.S. Pat. No. 5,435,816 (Spurgeon et al.), the disclosure of which is incorporated herein by reference.
Abrasive Articles
Flexible abrasive articles according to the present invention may be manufactured to have any form. For example, the flexible abrasive article may have the form of a circular abrasive pad (e.g., shown as 300 in
In some embodiments that are useful, for example, as sanding cloths, the compressible backing comprises a multiplicity of separated resilient bodies connected to each other in a generally planar array in a pattern, which provides open spaces between adjacent connected bodies, each body having a first and second opposed surfaces.
Such compressible backings 610 may be formed, for example, by dipping a scrim into a liquid, which is curable to form a foam, and curing by placing the dipped scrim in an oven, which causes the composition to expand and solidify.
The scrim may be made of natural or synthetic fibers, which may be either knitted or woven in a network having intermittent openings spaced along the surface of the scrim. The scrim need not be woven in a uniform pattern but may also include a nonwoven random pattern. Thus, the openings may either be in a pattern or randomly spaced. The scrim network openings may be rectangular or they may have other shapes including a diamond shape, a triangular shape, an octagonal shape or a combination of these shapes.
Typically, the scrim comprises a first set of rows of separated fibers deployed in a first direction and a second set of fibers deployed in a second direction to provide a grid including multiple adjacent openings wherein resilient bodies are located in alternate openings with openings between resilient bodies being devoid of resilient bodies, although this is not a requirement. The scrim may also comprise an open mesh selected from the group consisting of woven or knitted fiber mesh, synthetic fiber mesh, natural fiber mesh, metal fiber mesh, molded thermoplastic polymer mesh, molded thermoset polymer mesh, perforated sheet materials, slit and stretched sheet materials and combinations thereof.
The composition of the resilient bodies may either be foamed or non-foamed and may be composed of any of a variety of elastomeric materials including, but not limited to, polyurethane resins, polyvinyl chloride resins, ethylene vinyl acetate resins, synthetic or natural rubber compositions, acrylate resins, and/or other suitable elastomeric resin compositions.
In this embodiment, the compressible backing is characterized by having openness between resilient bodies to provide a cumulative openness as compared to the total area of the resilient body on the order of about 20% to about 80%, more typically, between about 30% to about 60%.
The compressible backing may have a sufficient thickness to make it convenient for being hand held. The thickness is measured between the highest point of the first major surface of the resilient body to the second surface of the resilient body. The thickness typically is between about 1 millimeter and about 15 millimeters, more typically about 3 millimeters to about 10 millimeters, although other thicknesses may also be used.
While a square or rectangular shape of the resilient body is often desirable, the body may be any convenient geometric shape including, but not limited to, square, rectangular, triangular, circular, and in the shape of a polygon. The resilient bodies are typically uniform in shape, but they need not be. The resilient bodies may be aligned in rows longitudinally and in a transverse direction but for some applications it may be preferable that they not be aligned because in sanding operations where the abrasive product is moved in only one direction, for example, the longitudinal direction, longitudinally aligned abrasive covered resilient bodies could produce an unwanted scratch pattern in the surface being abraded.
The dimensions of the resilient bodies may vary from about 2 millimeters to about 25 millimeters, more typically from 5 millimeters to 10 millimeters. When referring to the dimensions of the resilient body, the dimensions are intended to include the widths in the longitudinal or transverse direction or the maximum dimension of the body when measured from one side to the other notwithstanding any direction.
In this embodiment, the openings in the compressible backing are generally individually smaller than the adjacent resilient body and may have dimensions on the order of about 2 millimeters to about 25 millimeters, preferably of about 5 millimeters to about 10 millimeters. The openings may be somewhat rectangular, if the resilient bodies are rectangular or they may take any other configuration depending on the shape of the adjacent resilient bodies. The shape of the openings is typically defined by the shape of the edges of the resilient bodies. The resilient bodies and the openings are generally uniformly distributed throughout the entire area of the flexible abrasive product of the invention but this is not necessary in all cases.
Exemplary compressible backings according to this embodiment are well known, for example, as commercially available under the trade designations “OMNI-GRIP”, “MAXI-GRIP”, “ULTRA GRIP”, “EIRE-GRIP”, and “LOC-GRIP” from Griptex Industries, Inc. of Calhoun, Ga., or made according to U.S. Pat. No. 5,707,903 (Schottenfeld), the disclosure of which is incorporated herein by reference.
In this embodiment, each the elastic polyurethane film, extensible tie layer, and abrasive layer may form continuous uninterrupted layers or may having openings therethrough, the openings in the film generally corresponding in position to openings in the compressible backing.
Further details concerning flexible abrasive articles according to this embodiment such as, for example, the compressible backing and the abrasive layer, may be found in U.S. Pat. No. 6,613,113 (Minick et al.), the disclosure of which is incorporated herein by reference.
Method of Using
Flexible abrasive articles may be used, for example, by hand or in combination with a power tool such as for example, a rotary sander or belt sander.
Flexible abrasive articles according to the present invention are useful for abrading (including finishing) a workpiece by a method that includes: providing a flexible abrasive article according to the present invention; frictionally contacting at least one abrasive particle with a workpiece; and moving at least one of the abrasive particle and the workpiece relative to the other to abrade at least a portion of the surface of the workpiece. For example, the abrasive article may oscillate at the abrading interface during use.
The workpiece can be any of a variety of types of material such as painted substrates (e.g., having a clear coat, base (color) coat, primer or e-primer), coated substrates (e.g., with polyurethane, lacquer, etc.), plastics (thermoplastic, thermosetting), reinforced plastics, metal, (carbon steel, brass, copper, mild steel, stainless steel, titanium and the like) metal alloys, ceramics, glass, wood, wood-like materials, composites, stones (including gem stones), stone-like materials, and combinations thereof. The workpiece may be flat or may have a shape or contour associated with it. Examples of common workpieces that may be polished by the abrasive article of the invention include metal or wooden furniture, painted or unpainted motor vehicle surfaces (car doors, hoods, trunks, etc.), plastic automotive components (headlamp covers, tail-lamp covers, other lamp covers, arm rests, instrument panels, bumpers, etc.), flooring (vinyl, stone, wood and wood-like materials), counter tops, and other plastic components.
During abrading processes it may be desirable to provide a liquid to the surface of the workpiece and/or the abrasive layer. The liquid may comprise water, an organic compound, additives such as defoamers, degreasers, liquids, soaps, corrosion inhibitors, and the like, and combinations thereof.
Objects and advantages of this invention 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 invention.
Unless otherwise noted, all parts, percentages, ratios, etc. in the examples and the rest of the specification are by weight, and all reagents used in the examples were obtained, or are available, from general chemical suppliers such as, for example, Sigma-Aldrich Company, Saint Louis, Miss., or may be synthesized by conventional methods.
The following abbreviations are used throughout the Examples:
A layer of transfer adhesive, commercially available under the trade designation “HS300LSE” from 3M Company, St. Paul, Minn., was applied to one surface of a 2.3 mm thick open cell polyurethane foam, commercially available under the trade designation “R600U” from Illbruck, Inc., Minneapolis, Minn. A polypropylene-laminated loop material, part of a hook and loop mechanical fastener system was then laminated to the transfer adhesive with the loops outwardly disposed. Another layer of the transfer adhesive was applied to the opposing surface of the foam and a 0.8 mil (203 micrometer) thick polyurethane elastomeric transfer film, commercially available under the trade designation “TEGADERM”, from 3M Company, was laminated to the transfer adhesive. The release layer was removed from the TEGADERM film, exposing the adhesive surface.
An abrasive slurry was made by mixing until homogeneous, at 20° C., 14.0 parts of AS1, 14.0 parts of AS2, 4.0 parts of AS3, 3.0 parts of AS4, 1.0 parts of AS5, 7.0 parts of AS6, and 57.0 parts of AS8. The slurry was applied via knife coating to a polypropylene production tool having a uniformly distributed array of three-sided pyramids with a peak height of 178 micrometers, shown in
Example 2 was carried out according to the method described in Example 1, except that the flexible abrasive material was subsequently perforated by needle-tacking with a punch density of 53 perforations per square inch (8.2 perforations per cm2) using needles designated as “15×18×25×3.5 RB” available from Foster Needle Co., Inc., Manitowoc, Wis. The perforations were made from the abrasive side down through the attachment system.
Flexible abrasive discs were made according to the method described in Example 1, except the TEGADERM film was replaced with a 0.8 mil film of ESTANE 58309NAT022 polyurethane resin (B.F. Goodrich, Cleveland, Ohio), and the abrasive slurry composition was: 13.7 parts of AS1, 13.7 parts of AS2, 3.9 parts of AS3, 2.9 parts of AS4, 1.0 parts of AS5, 6.8 parts of AS6, 2.4 parts of AS7, and 55.6 parts of AS8.
Flexible abrasive discs were made according to the method described in Example 3, except the slurry formulation was: 13.3 parts of AS1, 13.3 parts of AS2, 3.8 parts of AS3, 2.9 parts of AS4, 1.0 parts of AS5, 6.7 parts of AS6, 4.8 parts of AS7, and 54.2 parts of AS8.
Flexible abrasive discs were made according to the method described in Example 3, except the slurry formulation was: 13.0 parts of AS1, 13.0 parts of AS2, 3.7 parts of AS3, 2.8 parts of AS4, 0.9 parts of AS5, 6.5 parts of AS6, 7.0 parts of AS7, and 53.0 parts of AS8.
A 6-inch (15.2 cm) abrasive foam disc, commercially available under the trade designation “443SA TRIZACT HOOKIT II BLENDING DISC P1000” from 3M Company. Comparative Example A is similar to Example 2, except the attachment layer is the hook component of a hook and loop mechanical fastener system, and it does not have does it have a polymeric transfer film.
Cut and Finish Testing
Abrasive performance testing was performed using 18 inches by 24 inches (45.7 cm by 61 cm) clear coated black painted cold roll steel test panels, obtained from ACT Laboratories, Inc., Hillsdale, Mich., as the sanding substrate. Sanding was performed using a random orbit sander, model number “59025” obtained from Dynabrade, Inc., Clarence, N.Y., operating at a line pressure of 40 pounds per square inch (258 kilopascals (kPa)). For testing purposes, flexible abrasive discs prepared according to Examples 1 through 5 were attached to a 6-inch (15.2 cm) interface pad, which was then attached to a 6-inch (15.2 cm) backup pad, both commercially available under the trade designations “HOOKIT INTERFACE PAD, PART NO. 05251” and “HOOKIT BACKUP PAD, PART NO. 05876”, from 3M Company. Comparative Example A was similarly attached to a 6-inch (15.2 cm) “HOOKIT II” type interface pad and backup pad, part numbers “05774” and “05274”, respectively.
Each test panel was divided into four 18″ (45.7 cm) long lanes, each lane being 6 inches (15.2 cm) wide. Each abrasive disc was tested by damp-sanding (with water) for 30 seconds in a single lane. The test panel was weighed before and after sanding of each lane. The difference in mass is the measured cut, reported as grams per 30 seconds. After sanding, the average surface finish (Rz) in micrometers (μm) of each lane was measured using a profilometer available under the trade designation “SURTRONIC 3+ PROFILOMETER” from Taylor Hobson, Inc., Leicester, England. Rz is the average of 5 individual measurements of the vertical distance between the highest point and the lowest point over the sample length of an individual profilometer measurement. Five finish measurements were made per lane. Four abrasive discs were tested per Lot and the results are reported as average of all four abrasive discs, such that the reported cut is the average of four measurements and the reported finish is the average of 20 measurements.
The sanding results are reported in Table 1 (below).
Durability Testing
Test panels were damp sanded by hand, using finger-point pressure to contact the abrasive disc to the test panel, using abrasive discs of Examples 1 and 2, and Comparative A. The sanding action was linear. After 23 seconds of sanding, Comparative A developed a hole, approximately 0.5 inches (12.7 mm) in diameter, in the abrasive and foam backing. Upon further sanding, this hole continued to expand. However, after 60 seconds of sanding, neither Example 1 nor Example 2 showed any degradation or wear.
Various modifications and alterations of this invention may be made by those skilled in the art without departing from the scope and spirit of this invention, and it should be understood that this invention is not to be unduly limited to the illustrative embodiments set forth herein.
