Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B24—GRINDING; POLISHING
  • B24D—TOOLS FOR GRINDING, BUFFING OR SHARPENING
  • B24D11/00—Constructional features of flexible abrasive materials; Special features in the manufacture of such materials
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08K—Use of inorganic or non-macromolecular organic substances as compounding ingredients
  • C08K5/00—Use of organic ingredients
  • C08K5/04—Oxygen-containing compounds
  • C08K5/06—Ethers; Acetals; Ketals; Ortho-esters

Definitions

• the present invention relates to flexible coated abrasive sheets. More particularly, this invention relates to abrasive sheet structures such as coated abrasive belts and similar articles which are especially suitable for use in leather sanding operations.
• abrasive sheet structures are employed mainly to even off the surface of the leather and to prepare a uniform surface for the subsequent absorption of colors in the preparation of leather articles. Such structures are also widely used to provide a suede surface on leather.
• difficulty often is encountered in these and other leather sanding operations in that abrasive sheet structures ordinarily are readily filled or clogged by leather particles abraded and removed from the leather surface. This is true even though the active abrading surface of the abrasive sheet or belt is continuously brushed or otherwise mechanically scrubbed, as an integral part of the operation, in an effort to keep the sheet as unfilled and unclogged as possible.
• an abrasive sheet of improved fill-resistance might be obtained by applying increased amounts of abrasive binder, thereby raising the total binder to abrasive mineral ratio Well over that normally employed for an abrasive structure of the type, grit size, etc. to be used.
• the basis of this approach lies in filling to a high degree the spaces or valleys between the abrasive grains, so the latter would not protrude, relatively, as far from the sheet. This approach of raising the binder:mineral ratio has fallen far short of a practical and successful solution.
• binder herein, we are referring to part or all the glue, adhesive, and/r resin materials which serve to bond the abrasive mineral to the sheet, including the so-called make-coat, sand-size coats, etc.
• a novel flexible coated abrasive sheet which is highly fill-resistant to leather is produced by employing a special binder composition at the abrading surface of the sheet.
• the special binder composition is not singly what produces the desired feature in our structures.
• the special binder composition is utilized in a particular physical relationship to the abrasive mineral grains of the sheet, all as more particular- 1y described hereinafter. Indeed, We have found it is not sufficient to employ the special binder composition in the manner in which abrasive binders generally are utilized in abrasive sheets of conventional type.
• glycols such as ethylene glycol, propylene glycol, trimethylene glycol, hexylene glycol, and octylene glycol
• ether alcohols such as polyethylene glycol, .diethylene glycol, polypropylene gloycol, and butylcarbitol
• other polyhydric alcohols such as sorbitol, pentaerythritol, triethanolamine, polyvinyl alcohol, and glycerol
• cyclohexanepolyols such as 1,3,5- cyclohexanetriol, and inositol
• various ether and ester derivatives of polyethers such as alkylphenyl-ethers of polyethylene glycol and .dilaurate esters of polyethylene glycols.
• the oxy-cornpounds in the abrasive binder of our structures are present at the surface of the sheet structure. They may be presentat the surface only, such as where the oxy-containing binder composition is applied as the sandsize over some standard make-coat, or even as a super-size applied over a conventional sandsize. If desired, theentire abrasive binder may contain the oxycompound. In the interest of economy, however, we ordinarily prefer to employ the oxy-compound' only in the surface portion of the binder, i.e., in a sandsize, or supersize; since experience has shown very little of the abrasive binder is worn away from the abrasive sheet in leather sanding operations before. the abrasive mineral grains are dulled beyond practical usefulness.
• our novel abrasive sheet structures When employed in leather sanding operations, and other abrading operations presenting similar difiiculties, such as plastic sanding and, to a somewhat lesser extent, wood sanding operations, our novel abrasive sheet structures are extremely fill-resistant. They can be employed for long periods, in many instances without necessity of being periodically brushed or otherwise mechanically cleaned, all the while remaining effective in producing the desired finish. Even where some filling or clogging ultimately results (as it inevitably must as the sheet wears out), our structures are readily cleaned, ordinarily by briefly wiping with a brush. In fact, after such brushing it is usually not even visually evident that the sheet had been filled; and to the untrained eye not even evident that the sheet had been used at all.
• Example I To one side of a Web of 130 lb. neoprene-treated cylinder paper was applied a 38% solution of hide glue at a wet coating weight of 10 grains per 4" x 6 (4 inch by 6 inch) sheet. The glue coated sheet was then electrostatically coated with 22 grains by weight of Grade 240 aluminum oxide mineral per 4" x 6" sheet. The coated web was then festooned in a 100 F. oven maintained at a relative humidity of 47 percent for 10 minutes to dry the glue make-coat. The web was then passed through squeeze rolls by which a sandsize composition was applied at a wet coating weight of 22 grains per 4" x 6" sheet.
• the sandsize adhesive previously had been prepared by blending 86.5 parts of a solution of an A stage base-catalyzed phenol-formaldehyde resin having 81% non-volatiles with 30 parts of glycerine, and 7.6 parts of water, all by weight.
• the viscosity of this sandsize composition was approximately 360 cps. at 125 F. as measured by a Brookfield Viscometer.
• the web was then again hung in festoons and the sandsize precured by heating in an oven for 18 minutes at 160 F., 108 minutes at 200 F., and 18 minutes at 190 F.
• the procured material was taken down from the festoons and wound into drum form with two layers of cheese cloth interposed between the convolutions.
• Final cure of the coated abrasive web was then effected by heating the drum for 1 hour at 150 F., 2 hours at 175 F., and 5 hours at 200 F.
• the ratio of abrasive binder to abrasive mineral in the sheet structure of the present example is 3.16: 1.
• the abrading surface of the resulting sheet material was found not to be receptive to or readily wet by neats-foot oil, the oil forming in small droplets on the surface at a very high contact angle.
• An endless belt having a width of 50 inches and a length of 103 inches was formed from the cured coated abrasive sheet material, and used on a belt sander conventionally employed in leather finishing operations.
• the contact cylinder over which the belt passed was made of 45 durometer rubber having serrations /8 inch wide spaced inch apart and extending at an angle of 25 to the side of the contact drum.
• the belt travelled at a rate of 5200 feet per minute, and leather sides were fed through the machine at a rate of 60 feet per minute. No noticeable filling of the belt by the abraded leather particles occurred for more than 4 hours, during which aoaaevs over 2200 leather sides had been processed. When some filling ultimately did occur, the dust was easily removed With a compressed air blast.
• a coated abrasive sheet having the same mineral grade composed of conventional materials of conventional total binderzmineral ratio was found to have filled and clogged in only 4 minutes after processing only 30 sides.
• the total binder:mineral ratio of such a conventional structure is in the order of 1.32:1.
• a structure formed of materials identical to those of the present example, except for the omission of the glycerine, and containing a total binder:mineral ratio of 3.6 :1 also quickly fills with leather particles and is unsatisfactory.
• This procedure involves a reflectance test by which the degree to which the abrasive binder fills around the abrasive grains can be determined. It is noted that the man at the abrasive maker has, for many years, held abrasive sheets at an angle to light, and in this way qualitatively determined, by the glossiness of the sheet, whether approximately the correct amount of binder, for his purpose, is present.
• ASTM test D523-5 1 entitled standard method of test for 60DEG specular gloss.
• ASTM test D523-5 1 entitled standard method of test for 60DEG specular gloss.
• a beam of light rays is directed toward the sheet to be measured at an angle of 60 to a line perpendicular to the sheet.
• a photoelectric cell also at an angle of 60 to the perpendicular, measures the amount of light which is reflected from the sheet and received by the cell.
• An ideal completely reflecting perfect mirror is assigned a value of 1000. Reflection apparently occurs primarily -from the upper surface of the sandsize adhesive, and the greater the resin:mineral ratio for any specific type of sheet the greater the reflectance.
• Measuring the reflectance integrates the finished characteristics of the sheet, taking into consideration the various dififerences necessitated by the particular raw materials employed and the manner in which they are associated. By and large it makes little difierence in the resultant reflectance value of an abrasive sheet whether the binder or sandsize is filled or unfilled, or whether it is one type of resin or glue as opposed to another. Thus the refiectance of the sheet is essentially independent of whether the binder contains the oxy compounds we employ in the structures hereof.
• the 60 specular gloss value for the coated abrasive sheet of this example was 10.5 units.
• the total binderzmineral ratio should at least equal a level exhibiting a gloss value of about 5 units.
• the ratio of total binder to mineral should not be so great as to flood the sheet or to bury the abrasive mineral grains to an extent where the useful aggressiveness of the abrasive surface of the sheet is lost.
• sheet structures hereof, wherein the abrasive binder to mineral ratio is at a level demonstrating a gloss value of 30*33 are useful though we generally prefer to employ the binder at somewhat lower levels.
• the gloss value in sheets containing the coarser grades of mineral employed in leather-sanding, e.g., grade 120, We prefer the gloss value to be in the range of about 6-12.
• a gloss value in the range of about 9-18 is preferred.
• the present example illustrates the use of a monomeric polyhydric alcohol as the oxy-compound in the binder. Many other polyhydric compounds are equally suitable, the various aliphatic glycols being especially suitable. The following example illustrates the use of higher monomolecular weight polymeric ether alcohols as the oxycompound.
• Example 11 An adhesive was prepared by blending 86.5 parts of A stage phenolic resin containing 81% non-volatile material, 30 parts of polyethylene glycol having an average molecular weight of 1540, and 7 parts of water, all by weight.
• a conventional Grade 280 aluminum oxide coated abrasive sheet material having a hide glue bond make coat on a 130-lb. neoprene-treated cylinder paper backing and a phenolic resin sandsize (total binderzmineral volume ratio of 1.32:1) was supersized with the adhesive com-. position described in the preceding paragraph at a wet coating weight of 14 grains per 4" x 6" sheet.
• the said coated abrasive sheet material (without the supersize) is sold commercially by the Minnesota Mining and Mannfacturing Company, St. Paul, Minnesota under the trade designation Production Resinite Paper, E-Weight.
• the thus suspersized sheet material was precured in festoons for 4 hours at 175 F., and finally cured in festoons for 1 hour at 150 F, 2 hours at 175 F, and 5 hours at 200 F.
• the cured product was then taken down from the festoons and flexed to render it more flexible.
• the final ASTM glossmeter value obtained using the test previously described, ranged from to 12' units.
• the adhesivezmineral volume ratio of the structure was 3.48:1.
• An endless belt having a width of 11 inches and a length of 65 inches was fabricated from the material described in the preceding paragraph and mounted on a belt sander similar to that employed in leather sanding operations.
• the contact roll over which the belt passed was identical to that described in Example I and was driven at 2850 surface feet per minute.
• a conveyor belt mounted beneath the contact roll was used to transport leather test pieces through the machine at a rate of 40 feet per minute, the aperture between the surface of the abbrasive belt and the surface of the conveyor belt being set at .065 inch.
• a welting leather strip 6 inches x 47 inches x .128 inch was fed through this machine ten times. The surface of the leather was then observed to be uniformly napped, color-receptive, and extremely attractive. The small amount of leather detritus which adhered to the surface of the belt was readily brushed away.
• a Grade 280 belt identical with that of the present example but containing no supersize treatment, was found undesirably to burnish the leather irregularly after only three passes. -By this time the sheet filled or clogged, and the leather particles which adhered to the surface of the belt could not be brushed free.
• a conventional belt which was resized with unmodified phenolic resin to a reflectance comparable to that of the product described in the preceding 6 paragraph performed no better than the conventional sheet.
• polyethylene glycols of all known molecular weights are extremely soluble in Water, and can be employed in structures of the present invention
• various other of the fill-retarding oxy-compounds are only sparingly soluble in water, if soluble at all.
• solvents other than water preferably are used for incorporating the oxy-compound into the binder composition, care being taken to employ a solvent or dispersant which is compatible with the binder composition, solvent vehicle for the latter, and/ or the solution of the binder composition, as the case maybe.
• the vehicle for the oxy-compound also can be the same as that for the-binder.
• ethylene glycol monoethyl ether (Cellosolve) is employed as a common solvent for the oxy-compound and the phenol-aldehyde binder composition.
• Example 111 A special binder composition was'prepared by employing an ether derivative of a polyether. Ten parts of Tergitol Non-ionic NP35 (an alkyl phenyl ether of polyethylene glycol manufactured and sold by Union Car-- bide), 2 parts of water, and 111 parts of liquid A stage. phenolic resin containing 81% non-volatile material, all by weight, were blended together.
• Tergitol Non-ionic NP35 an alkyl phenyl ether of polyethylene glycol manufactured and sold by Union Car-- bide
• a commercial Grade 240 aluminum oxide coated abrasive sheet material having a pound neoprene treated cylinder paper backing, a hide glue bond adhesive and a phenolic resin sandsize adhesive (total adhesive: mineral volume ratio of 1.19: 1) was supersized with the composition described in the preceding paragraph at a wet coating weight of 15 grains per 4" x 6" sheet. Curing conditions were identical to those described in the preceding example, except that the final cure was made in roll form. The ASTM glossmeter reflectance of this material was 17, and the adhesive:mineral volume ratio was about 3.04: 1.
• the product of this example was flexed by passing it over a 1 inch steel bar while supporting the face of the material with a rubber roll. Endless belts were fabricated and tests conducted in the same manner described in the preceding example. After 10 passes of a strip of welting leather, no burnishing had occurred, and the leather strip was uniformly downy and color-receptive. The few leather particles which superficially adhered to the surface of the belt could be readily brushed oif.
• Example IV A coated abrasive sheet like that described in connection with Example I was prepared except only four parts of glycerine were incorporated into the sandsize composition. The sheet was then coated with the sandsize composition and cured as described in Example I. The cured sandsize composition of the resulting sheet thus contained only about 5 percent by weight of the oxy-compound. The resulting structure was found to be a satisfactory fillresistant sheet in leather sanding operations.
• the amount and type of oxy-compound usedv preferably is selected so that no reaction occurs between; it and the binder to produce a reactionproduct having;
• a substantial amount of the oxy-compound incorporated with the binder composition ordinarily is extractable by solvent extraction procedures indicating that much of the oxy-compound exists in the sheet substantially in an unreacted state.
• abrasive sheet materials hereof containing abrasive grains in the intermediate grade ran es this is because in the leather sanding industry, to which the examples hereof are especially directed, abrasive sheets are normally used which have grade sizes within range of from about Grade 120 through 320 and finer.
• the present invention is not limited either to these ranges; for it also has marked utility in the coarser grade ranges, and also in the very fine grade ranges, particularly in other industrial fields.
• a flexible coated abrasive sheet which is highly fillresistant to leather and similar materials comprising a flexible backing and abrasive grains firmly bonded thereto by a total binder present in a high binder to mineral ratio at a gloss value of 'at least about units, said binder comprising a synthetic resin including uniformly distributed therein at least at the exposed surface thereof an oxycontaining compound compatible with the remaining binder constituents and selected from the class consisting of aliphatic polyhydric alcohols and aliphatic polyethers.
• a flexible coated abrasive sheet which is highly fillresistant to leather and similar materials comprising a flexible backing and abrasive grains firmly bonded there- .to by a totalbinder present in a high binder to mineral ratio at a gloss value of at least about 5 units, said binder at the surface thereof comprising a hardened phenol-aldehyde resin having uniformly distributed therein an oxycontaining compound compatible with the remaining binder constituents and selected from the class consisting of aliphatic polyhydric alcohols and aliphatic polyethers.
• a flexible coated abrasive sheet which is highly fillresistant to leather and similar materials comprising a flexible backing and abrasive grains firmly bonded thereto by a total binder present in a high binder to mineral ratio at a gloss value within the range of about 6l8 units, said binder at the surface thereof comprising a hardened phenol-aldehyde resin having uniformly distributed therein an oxy-containing compound compatible with the remaining binder constituents and selected from the class consisting of aliphatic polyhydric alcohols and aliphatic polyethers.
• a flexible coated abrasive sheet which is highly fill-resistant to leather and similar materials comprising a flexible backing and abrasive grains of grade range of from about to 400' finnly bonded thereto by a total binder present in a high binder to mineral ratio at a gloss value within the range of about 6-18 units, said binder at the surface thereof comprising a hardened phenol-aldehyde resin having uniformly distributed therein an oxycontaining compound compatible With the remaining binder constituents and selected from the class consisting of aliphatic polyhydric alcohols and aliphatic polyethers.
• a flexible coated abrasive sheet which is highly fillresistant to leather and similar materials comprising a flexible backing and abrasive grains firmly bonded thereto by a total binder present in a high binder to mineral ratio at a gloss value of at least about 5 units, said sheet having a surface size coat comprising a hardened phenol-aldehyde resin having glycerine distributed therein.
• a flexible coated abrasive sheet which is highly fillresistant to leather and similar materials comprising a flexible backing and abrasive grains firmly bonded thereto by a total binder present in a high binder to mineral ratio at a gloss value of at least about 5 units, said sheet having a surface size coat comprising a hardened phenol-aldehyde resin having an aliphatic glycol distributed therein.

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• Chemical & Material Sciences (AREA)
• Health & Medical Sciences (AREA)
• Chemical Kinetics & Catalysis (AREA)
• Medicinal Chemistry (AREA)
• Polymers & Plastics (AREA)
• Organic Chemistry (AREA)
• Engineering & Computer Science (AREA)
• Mechanical Engineering (AREA)
• Polishing Bodies And Polishing Tools (AREA)

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Cited By (7)

Citations (3)

• 1958
  • 1958-11-17 US US774099A patent/US3043673A/en not_active Expired - Lifetime
• 1959
  • 1959-11-13 ES ES0253405A patent/ES253405A1/es not_active Expired
  • 1959-11-16 DE DE1494174A patent/DE1494174C3/de not_active Expired
  • 1959-11-16 GB GB38773/59A patent/GB912905A/en not_active Expired
  • 1959-11-16 CH CH8065059A patent/CH403536A/de unknown

Patent Citations (3)

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