US 3537121 A
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Nov. 3, 1970 1-. R. M AVOY CLEANING AND BUFFING PRODUCT Filed Jan. 17, 1968 I NVEN TOR. I grownsfifl flvar United States Patent 3,537,121 CLEANING AND BUFFING PRODUCT Thomas R. McAvoy, Stillwater, Minn., assignor to Minuesota Mining and Manufacturing Company, St. Paul, Minn., a corporation of Delaware Filed Jan. 17, 1968, Ser. No. 698,497 Int. Cl. A471 11/40 US. Cl. 15230.12 5 Claims ABSTRACT OF THE DISCLOSURE A soft resilient compressible polishing pad which is superior to lambs wool for buffing aluminum, paint, wax, plastic, and similar surfaces. The pad is essentially a lofty fibrous nonwoven structure bonded by a soft, tough resin containing a finely divided soft mineral filler.
BACKGROUND OF THE INVENTION The invention relates to pads for cleaning (with compounds), bufling, or restoring surfaces.
For decades lambs wool polishing pads or bonnets have been the standard product for use when a painted or waxed surface was to be buffed to bring up its luster. Such pads, which are conformable and soft, have heretofore been superior to any other product for this purpose.
Lambs wool pads do, however, suffer from several inherent drawbacks. They are expensive and, like most natural products, subject to unpredictable variation. The rough surface of wool fibers and their tendency to mat under pressure results in seizing or drag, causing operator fatigue. The presence of even a slight amount of moisture on the surface being bufied, as is often the case, further emphasizes this problem.
The same characteristics also cause lambs wool pads to clog with wax or dirt during use, which in turn aggravates the tendency to seize. Removal of such dirt and Wax is complicated by another characteristic of woolthe presence of a leather face on one side which prevents the ready flow of water or other cleaning solution through the pad. Further, hot water must not be used, lest the wool shrink, kink and distort.
Still another defect of lambs wool is the tendency of a disc formed therefrom to leave swirl marks, perhaps as the result of the wool fibers aligning themselves concentric with the axis of rotation of the driving pad, the local formation of knots, or the collection of dirt spots at the surface. Such marks are visually unattractive, no matter how successful the bufling operation may be in increasing luster.
As might be expected, many attempts have been made to devise a synthetic replacement for lambs wool pads, but prior to the present invention such attempts have not been successful. One obvious substitute for a lambs wool pad is a disc cut from carpeting, but it has essentially the same problems found in lambs wool.
US. Pat. 2,958,593 discloses and claims a nonwoven lofty open mat formed from randomly disposed fibers which are bonded at points where they intersect and contact each other. An adhesive, such as phenolic resin, is used to bind abrasive grains to the fibers, the resultant product being characterized by large voids, through which water and detritus readily pass. Pads formed from such material are compressible, conformable, easy to clean, and low in drag, but they tend to remove a soft surface and/or leave scratch marks, no matter how fine the abrasive particles employed. Even if abrasive grains are omitted, the resin itself leaves scratches in such surfaces, actually removing wax or powdering the ice surfaces of hard synthetic polymer floor finishes, lacquers and similar material. This patent recommends the use of binder resins having a Knoop hardness of 6 or considerably higher (although it indicates somewhat softer binders can be used with some decrease in effectiveness). It has been found that resins having a Knoop hardness as low as 10 cause scratches.
British Pat. 1,006,005 and 1.0l4,297 disclose abrasive articles similar to those in US. Pat. 2,958,593 except that an extremely soft (e.g., Knoop hardness of 1 or 2) adhesive is used to hold the abrasive grains to the fibers, the nonwoven abrasive product being adhered to a support for additional strength. Again, pads formed from such products tend to scratch and remove soft substrates, no matter how fine the abrasive particles. If the abrasive grains are omitted altogether, the problem of scratching is eliminated, but the tendency of the pad to drag exceeds even that exhibited by lambs wool.
SUMMARY OF THE INVENTION The present invention provides products which are comparable to lambs wool in ability to impart luster to butfable waxes and which can be used to clean and restore the surface of hard polymer coatings without powdering. These products do not scratch or abrade the surface being buffed, do not impart swirl marks to the finish, and yet exert a drag far lower than that obtained with lambs wool pads. The novel buffing products resist loading with detritus removed from the surface being buifed, and even those materials which do eventually work their way into the pad can be readily washed free. Both faces of the pad can also be used, thereby effectively increasing its usefulness.
The invention comprises a lofty nonwoven mat formed essentially from tough strong resilient fibers bonded together at points where they cross and contact each other with a binder comprising a soft resin (e.g., Knoop'hardness of less than 3); to this extent they are similar to products disclosed in the aforementioned British patents. In addition to being soft, the resin in the binder is flexible, tough, resilient and somewhat elastomeric, a particularly preferred resin being a flexible polyurethane. The binder also contains, based on the total volume of binder, from about 10 to about 65% of a finely divided mineral filler which has a Knoop hardness of no more than about 150, and preferably considerably lower. (Crocus, the softest abrasive grain used in coated abrasive products, has a Knoop hardness of about 600, and calcium carbonate, whose Knoop hardness is about 135, is a common extender for adhesives used in the manufacture of coated abrasive products; hence it will be appreciated that the mineral used in this invention truly functions as a filler, not as an abrasive grain.) Suitable fillers include calcium carbonate, kaolin, and talc, which has a Knoop hardness of 12 or less and is presently preferred. The filler desirably constitutes about /6 to /2 the volume of binder, the presently preferred value being about 6.
Synthetic fibers which are not especially affected by moisture are particularly preferred for the practice of this invention fibers of oriented polyethylene terephthalate fibers proving especially suitable. If desired, however, fibers which are not themselves satisfactory may be blended in with fibers of the type just described; for example, rayon fibers may be blended in with polyester fibers. Fibers having a diameter on the order of 10-50 microns may be employed, with fibers in the 2040 micron range being particularly preferred. In general, the finer the fibers, the less open the pad and the less its tendency to impart swirl marks but its greater the tendency to drag. (The open structure of US. Pat. 2,958,593 is based on fibers having a diameter of at least about 25 microns.)
3 BRIEF DESCRIPTION OF THE DRAWING For convenience in visualizing the product of this invention, attention is directed to the accompanying drawing, in which the single figure represents a view in perspective of a polishing pad made in accordance with this invention.
In the drawing, the pad is formed from randomly disposed and interlaced fibers, bonded together at points where they cross and contact each other with a binder which is made up of a soft, tough resin and soft mineral filler, as previously described.
Pads of this type may be driven by a conventional floor surfacing machine, or attached to a inch electric drill or other rotary driving bufling tool. It will be recognized, of course, that rectangular pads can be prepared and used on reciprocating, oscillating, or orbital heads.
Although there is considerable subjectivity involved in evaluating an effective butfing pad, a number of tests are useful in providing an evaluation of performance and other physical characteristics. For example:
Tensile test.-This figure should generally exceed about 15 lbs. per lineal inch in mutually perpendicular directions in the plane of the pad.
60 gloss value-Interim Federal Specification No. P-0040b(GSA-FSS) provides certain standards relating to the preparation and testing of buffable waxes containing a high percentage of Carnauba wax. In accordance with this test, a 4-inch diameter disc of /8-l110h black asphalt tile is covered with a brush coat of 16% solid water emulsion of a butfable wax, allowed to dry for one hour, and adhered to the rigid rotary support of a Schiefer abrasion testing machine. A 4-inch diameter floor surfacing pad is afiixed to a second rotary support and positioned over the tile disc so that slightly over half of the diameters overlap. The disc and pad are then rotated at 250 rpm. for 200 revolutions under an applied force of 5 lbs. The tile is subjected to a 60 gloss measurement in accordance with ASTM Test Specification No. 141. Gloss value should be at least 30.
Abrasive characteristics.A black asphalt 4-inch diameter tile is coated with about 25 milligrams of a hard acrylic polymer finish (e.g., Step Ahead sold by S. C. Johnson and Son, Inc.), and subjected to the Schiefer test described above. The weight of the coated tile is measured before and after testing, visually checked for any appearance of powdered finish. Polymer weight loss should not exceed about 4 milligrams, and little or no white powder should be visible.
Drag.--A 17-inch diameter pad is placed under the driving assembly of a conventional electrically powered floor surfacing machine, in the line circuit of which is connected an ammeter showing a no-load reading of 6.8. The amperage is monitored while the pad being tested is moved over a hard polymer floor surface coating, readings being taken both in level position and when the pad is heeled to move it from place to place. Desirably the amperage should not increase more than about 1.2 when the machine is heeled. In contrast, for example, a machine faced with a lambs wool pad normally draws about 1.3 amperes over no-load when level and 2.6 amperes over no-load when heeled.
DESCRIPTION OF PRESENTLY PREFERRED EMBODIMENTS Although considerable latitude is permissible in constructing products in accordance with this invention, it is believed that understanding will be facilitated by referring to the following illustrative but nonlimiting examples. Parts are by weight, unless otherwise indicated.
EXAMPLE 1 A lofty nonwoven Web was formed on a Rando-Webber machine from 15 denier (approximately 40-micr0n diameter) l /z-inch crimped oriented polyethylene terephthalate fibers. The web was approximately 2 inches thick and weighed approximately 68 grams per 24 square inches of web.
A mineral-filled binder, containing about 30% soft mineral filler by volume, was prepared by blending and curing the following components:
Parts by weight Ethylene glycol monoethylether acetate 400 Liquid polyester resin, having a molecular weight of 1800-2000, an equivalent weight of about 900, and a hydroxyl number of about 63 (commercially available from Rohm & Haas, under the trade designation Paraplex U-148) Moderately branched OH-terminated polyester, formed by reacting adipic acid, hexane triol, and butylene glycol, commercially available from Mobay Chemical Co. under the trade designation Multron R-12 Finely divided silica viscosity-builder, commercially available from Godfrey L. Cabot, Inc., under the trade designation Cab-O-Sil M-5 75% solids ethyl acetate solution of the reaction product of 1 mol of trimethylolpropane and 3 mols of toluene diisocyanate, commercially available from Mobay Chemical Co. under the trade designation Mondur CB-75 Talc, 46-micron, maximum Knoop hardness about 12 Ethylene glycol monoethylether acetate, sufiicient to lower viscosity to 2600, cps., viz
The fibrous web described in the preceding paragraph was then passed between a pair of 8-inch diameter knurled rubber rolls set with negative clearance, the lower roll rotating in a pan of the liquid (2600 cps.) composition just described, approximately 177 dry grains per 24 square inches being applied. The coated web was heated for about 15 minutes at 320 F. toreact the isocyanate adduct with the polyester and form an elastomeric polyurethane, the final thickness of the web being about 1% inches. (When the talc was omitted and the composition formed into a patty and cured in the same manner, the tensile strength of the cured composition was found to be 5,360 psi. at an ultimate elongation of 35%, the Knoop hardness being less than 1.) Tensile strength of the web was found to be 78 lbs. per inch of width in the lengthwise direction and 62 lbs. per inch of width in the cross direction.
A 17-inch diameter pad was diecut from the cured bonded web and tested in comparison with a conventional lambs wool pad in the buffing of a standard buifable floor wax. It was found that the appearance of the buffed wax was similar in each case. The amount of drag exhibited by the product of this example was, however, significantly less than that of the lambs wool pad, the amperage increase over no-load being respectively 0.2 and 0.8 for level and heeled positions. Further, when the pad eventually picked up enough wax to detract from its eifectiveness, it could be washed and cleaned easily. In contrast, the lambs wool pad was extremely'difiicult to clean, and exposure to water tended to make it mat even worse than it had before.
EXAMPLE 2 A nonwoven lofty web was formed from 6-denier (approximately 25-micron) l /z-inch crimped oriented polyethylene terephthalate fibers in the manner described in Example 1. The web was approximately 1% inches thick and weighed 41 grains per 24 square inches.
A soft mineral-filled binder composition was formed by blending the following components:
I Parts by weight Ethylene glycol monoethyl ether acetate 8 Saturated polyester, having an OH number of 47, commercially available from Mobay Chemical Co.
under the trade designation Multron R-68 15 1,2,6 hexane triol 0.8 Mondur CB-75, as in Example 1 13.1 Xylol 8 Talc, as in Example 1 25.5 Cab-O-Sil M-S, as in Example 1 0.5
The web described in the preceding paragraph was bonded with the foregoing binder composition in the manner described in Example 1, a total of 99 dry grains per 24 square inches being applied. The binder was cured in the manner described in Example 1, the final thickness being /2 inch.
Pads diecut from the bonded web of this example proved outstanding in cleaning polymethylmethacrylate (Plexiglas) airplane windows effectively without scratching using conventional cleaning and buffing agents. Used similarly, these pads also cleaned up oxidized and discolored aluminum aircraft bodies. Conventional rubbing compounds could also be used with these pads to rub down automobile lacquer finishes, and the pad itself was extraordinarily efiective in bringing up a high luster without imparting the swirl marks characteristic of finishes made using lambs wool pads.
EXAMPLE 3 Example 1 was repeated substituting calcium carbonate (Knoop hardness of about 135) for the tale. The pad felt both harsher and stiffer than the pad of Example 1, but performance was comparable.
EXAMPLE 4 Example 1 was repeated, increasing the amount of talc so that it constituted 65% of the total binder volume. The product was extremely effective in bufling and showed a lower drag than any of the products described above. The tensile strength, however, was somewhat lower than is considered desirable.
When the amount of tale is reduced to of the total binder volume, the tendency to drag increases beyond that which is considered desirable, and ability to impart satisfactory gloss to a bufiable wax is decreased.
EXAMPLE 5 Example 1 was repeated, replacing the talc with kaolin clay (Knoop hardness about 60) in which 12-18% of the particles had an average diameter above 5 microns and 62-68% had a diameter of less than 2 micron. The product felt similar to that of Example 3, and performance results were comparable.
EXAMPLE 6 Example 1 was repeated, substituting -denier nylon for the 15-denier polyethylene terephthalate fibers. The cured bonded web was less lofty than that of Example 1, and pads die-cut therefrom felt harsh and were somewhat stiffer.
EXAMPLE 7 Example 1 was repeated, replacing the polyurethane resin in the binder with a comparable amount of -a 44.5% aqueous emulsion of a thermosetting self-crosslinking hard acrylate polymer (Rhoplex HA-24, commercially available from Rohm and Haas); a patty formed from this polymer has a Knoop hardness of about 1.3 after 6 cure. The pad was suitable for bufling but lacked the durability of pads made in accordance with Example 1.
Numerous modifications can be made of the invention described hereinabove without departing from the spirit of the foregoing disclosure. For example, the strength of a nonwoven web can be increased by needle tacking prior to bonding thereby compacting the web and reducing both the openness and percentage void space of the final product. Similarly, different treatments can be applied to the web, for example to achieve a product having a function for both bufling with a cleaning compound and imparting a final luster. To enhance the amount of cleaning compound which one face of the pad can hold, it is likewise possible to adhere flock fibers thereto. To increase the hydrophilic nature of a pad which is to be used with aqueous emulsions of polishing compounds, it is likewise contemplated to treat one face with modified polyvinyl alcohol.
What is claimed is:
1. A soft, resilient, compressible buifing pad which is capable of imparting a high luster to surfaces of aluminum, paint, wax, plastic and the like and of cleaning polymethylmethacrylate sheets, all at low drag and without scratching the surface, removing significant amounts of substrate or leaving swirl marks therein, said pad comprising in combination:
a lofty, nonwoven mat having an extremely high void volume and consisting essentially of crimped tough, strong, synthetic organic resilient fibers having a diameter on the order of 10-50 microns,
said fibers being bonded together at points where they cross and contact each other with a filled binder which comprises:
a flexible polyurethane resin having a Knoop hardness of no more than about 3, and
based on the total volume of binder, about 10% to of a finely divided mineral filler having a Knoop hardness of no more than about 150.
2. The pad of claim 1 wherein the synthetic fibers consist essentially of oriented polyethylene terephthalate.
3. The pad of claim 2 wherein the mineral is present in an amount constituting about /3 of the volume of said binder.
4. The pad of claim 3 wherein the filler is talc.
5. The product of claim 1 wherein one surface of the pad is provided with means to enhance its receptivity to aqueous emulsions of bufling compounds.
References Cited UNITED STATES PATENTS 2,958,593 11/ 1960 Hoover et al. 51295 3,026,190 3/ 1962 McMahon et a1. 51-295 3,075,222 1/ 1963 Miller 15230.12 XR 3,171,151 3/1965 Sickle et al. 15-118 3,175,331 3/1965 Klein 51-402 XR 3,232,729 2/ 1966 Holland 51-298 3,431,689 3/1969 Schnabel 51400 DANIEL BLUM, Primary Examiner US. Cl. X.R. 51295, 296