Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B24—GRINDING; POLISHING
  • B24D—TOOLS FOR GRINDING, BUFFING OR SHARPENING
  • B24D3/00—Physical features of abrasive bodies, or sheets, e.g. abrasive surfaces of special nature; Abrasive bodies or sheets characterised by their constituents
  • B24D3/34—Physical features of abrasive bodies, or sheets, e.g. abrasive surfaces of special nature; Abrasive bodies or sheets characterised by their constituents characterised by additives enhancing special physical properties, e.g. wear resistance, electric conductivity, self-cleaning properties
  • B24D3/346—Physical features of abrasive bodies, or sheets, e.g. abrasive surfaces of special nature; Abrasive bodies or sheets characterised by their constituents characterised by additives enhancing special physical properties, e.g. wear resistance, electric conductivity, self-cleaning properties utilised during polishing, or grinding operation

Definitions

• This invention relates to abrasive sheet material, and particularly to an improved abrasive sheet material suitable for fine-grinding and polishing soft, non-ferrous metals such as copper, aluminum, and their soft alloys.
• abrasive sheet material covers paper and fabric sheets and belts coated with abrasive grains which are bonded to the fibrous, flexible base by a layer of binder material.
• abrasive sheet material When such abrasive sheet material is employed for removing sur* face layers of soft, particularly non-ferrous metal, the metal tends to drag and to load the abrasive sheet, that is, particles of the soft metal tend to clog the interstices between the abrasive grains on the surface of the flexible base. It is impractical to remove the metal from the abrasive sheet, and it is not unusual to discard abrasive belts or flat sheets before much of the abrasive material is lost from the base.
• This invention is concerned primarily with improving abrasive sheet material in which the abrasive grains have a size smaller than 100 grit, but its advantages are available, at least to some extent, in coarser abrasive sheets.
• Polytetrafluoroethylene has been proposed as a lubricant coating for abrasive material in US. Pat. No. 3,042,508, and has been shown to provide greatly improved grinding efficiency, but it is not practical to apply a continuous and coherent fluorocarbon layer to abrasive grains on a fibrous substrate such as paper or cloth because the fluorocarbon layer must be consolidated at temperatures well beyond the decomposition temperature of the usual flexible base materials.
• the object of the invention is the provision of an improved grinding or polishing material of the type in which one of the major faces of a flexible base of sheet material carries a layer of binder material, and a multiplicity of abrasive grains are secured to the base by the binder material.
• the improved grinding or polishing material of the invention includes an exposed covering layer covering the abrasive grains and essentially consisting of an intimate mixture of a second binder material and wax.
• the wax is present in the mixture in the form of particles having an average size of less than 500 microns, and the second binder material is solid and shape-retaining at least at 25C when traveling at 10,000 ft/min. in a circular path of 4 inch diameter.
• the weight ratio between the second binder material to the wax in the mixture is between 1:5 and 2:1, and preferably between 1:1 and 2:3.
• wax is employed herein according to modern usage, as defined by l-llackhs Chemical Dictionary (McGraw-l-lill Book Company, New York, 1969), to encompass substances characterized by a crystalline to microcrystalline structure, the capacity of acquiring gloss when rubbed, the capacity to produce pastes or gels with suitable solvents or when mixed with other waxes, a low viscosity at just about the melting point, and low solubility in solvents for fats at room temperature.
• a wax for the purpose of this invention, thus may be a mineral wax, an animal or vegetal wax, or a synthetic wax. Beeswax, carnauba wax, ouricuri wax, paraffin, ceresin, polyolefin waxes, and amide waxes are merely representative of suitable waxes.
• the binder materials employed for securing the abrasive grains to the flexible base are conventional and include synthetic resin compositions, but also water soluble glue, such as hide glue.
• the second binder material which is mixed with the wax in the covering layer must be strong enough to prevent loss of wax by centrifugal force generated typically when an abrasive belt travels at 10,000 ft./min. in a circularly arcuate path about a pulley 4 inches in diameter, but greater strength, of course, is desirable as far as it is consistent with the necessary flexibility of the abrasive sheet material.
• Binder materials combined with the wax particles in the covering layer thus may be synthetic resin compositions including phenolic, urea, epoxy, polyester, polyurethane, and alkyd resins, but. also water soluble glue.
• the preferred amide waxes are derivatives of ethylenediamine in which two acyl radicals of fatty acids, particularly of stearic, palmitic, and oleic acid, are attached to at least one amine nitrogen, and more specifically the distearoylethylenediamines.
• the commercial products which are nominally distearoylethylenediamines are mixtures of the N,N- and N,N'-isomers, and may contain minor amounts of impurities. The specific location of the acyl groups and the presence of minor amounts of impurities have not been found significantly to affect the performance of the amide waxes.
• the effectiveness of a covering layer in the abrasive sheet material of the invention is not impaired by the presence of a pulverulent, inorganic or organic filler which is softer than the abrasive grains employed if it does not amount to more than 60 percent of the weight of the covering layer.
• Calcium carbonate is typical of inexpensive filler materials readily available.
• the weight of the covering layer may vary between 5 and 1,000 g/m and will be selected according to the mesh or grit of the abrasive grains. Coarse abrasive generally requires a heavier covering layer than finer abrasive grain. For abrasive grains smaller than 100 grit, which benefit most from the improvement of this invention, a covering layer of 5 to g/m is adequate.
• EXAMPLE 1 An endless belt of cotton twill having two major faces 50 mm wide and 3,500 mm long was coated on a roller coater with a commercial, water-bearing, A-stage phenol formaldehyde resin composition having a nominal viscosity of 800 cp to 1,000 cp, a pH of 8.0 to 9.0, and a density of about 1.25 at C. The resin composition was capable of conversion to the B-stage in about 5 minutes at 120C without significant loss of formaldehyde;
• the coated base of textile sheet material was covered with 120-grit emery grains from an electrostatic spray gun, and the abrasive grains were bonded to the base by heating to 90C until the resin layer solidified.
• the grains then were covered with a surface layer prepared by dispersing 10 parts micronized amide wax and 4 parts calcium carbonate powder in 20 parts of another commercial, A-stage phenol formaldehyde composition and depositing the mixture by means of a roller coater, all parts herein being by weight unless stated otherwise.
• the amide wax was Hoechst Wax C, a commercial product essentially consisting of di-octadecanoylethylenediamine, the stearoyl groups being bound to the nitrogen atoms of the diamine.
• the wax employed had a nominal dropping point of 139 to 144C, an acid number of 3 7, a saponification number of 3 10, a density of 0.99 1.01 at 20C, and was free from measurable amounts of ash.
• the A-stage phenolic resin employed as a binder material in the covering or surface layer had nominal properties of 900 to 1,100 cp viscosity, a pH of 8.0 to 8.5, a density of 1.26 at 20C, and it converted to the B-stage in about 10 minutes at 120C.
• the laminar belt structure so obtained was cured in an oven at a temperature gradually raised to 120C, and held at 120C for 2 hours.
• Additional belts were prepared from otherwise the same materials employing 220, 320, and 400 grit emery.
• a second set of four abrasive belts was prepared for comparison purposes without the amide wax under otherwise identical conditions.
• the belt so prepared was tested as described in Example 1. It removed 30 g aluminum from a test body in the standard testing period of 60 minutes, and did not contain wax in a covering layer.
• EXAMPLE 3 A belt prepared as in Example 2 was further coated with a covering layer prepared by intimately mixing 134 parts micronized Hoechst Wax C with 100 parts of a liquid epoxy resin composition containing a hardener, and curing the covering layer.
• the amount of aluminum removed by the modified belt from a test body under conditions otherwise identical with those used in Example 2 increased from 30 g to 227 g.
• EXAMPLE 4 In the otherwise unchanged procedure of Example 3, Hoechst Wax C was replaced by an equal amount of an amide wax commercially available as Glockem Wax D2S, chemically closely similar to Hoechst Wax C, and having a similar range of physical properties including a dropping point of 142 147C, an acid number of 2 6, a saponification number of less than 6, a density of 0.997 at 20C, and an ash content of 0.018 percent.
• the belt so prepared removed 207 g aluminum from the test body.
• EXAMPLE 5 It removed 207 g aluminum from the standard test body.
• EXAMPLE 6 134 Parts paraffin was dissolved in benzene, and the benzene solution was mixed with the liquid, catalyzed epoxy resin composition employed in Examples 3 and 4 by means of a high speed mixer which caused small paraffin particles to be uniformly dispersed in the resin composition. The mixture so obtained was applied to a belt prepared as in Example 2, and the coated belt was stored until the resin was fully cured.
• the belt When polypropylene wax was substituted for the paraffin, the belt was capable of removing 162 g aluminum in the standard test.
• EXAMPLE 7 A belt prepared as in Example 2 was coated with a covering layer initially consisting of an intimate mixture of 100 parts liquid epoxy resin composition containing a hardener and identical with the composition employed in Examples 3 and 4, 134 parts micronized Hoechst Wax C, and parts calcium carbonate powder.
• the belt when tested after complete cure of the resin, removed 24] g aluminum from the test body.
• the improvement apparently due to the presence of the filler material cannot be fully explained at this time.
• EXAMPLE 8 In a procedure otherwise unchanged from that of Example 7, the calcium carbonate in the covering layer was replaced by 10 parts powdered cryolite (Na AlF The aluminum removed in the standard test of Example 1 amounted to 231 g.
• Example 9 The procedure of Example 2 was repeated using 320 grit emery and a correspondingly reduced layer of glue (see Table 1). The thickness of the phenolic resin layer applied over the abrasive grains also was reduced to g/m The belt so prepared removed 4 g aluminum from the test body in the standard grinding test of Example 1.
• Example 3 Application of a covering layer of epoxy resin composition and amide wax, as in Example 3, improved the test result to 36 g aluminum.
• EXAMPLE 10 A twill belt was coated with a first binder layer of A-stage phenolic resin composition and with grit emery as in Example 1. After partial curing of the first binder layer, the grit was covered with enough additional A-stage phenol-formaldehyde resin to make the second or intermediate layer 50 g/m after curing. As a covering or surface layer, the: mixture of epoxy resin composition and amide wax described in Example ,3 was applied. A control sample lacking the covering layer was also prepared.
• a test block of structural steel having a tensile strength between 37 and 45 kplmm a carbon content of less than 0.20 percent, a phosphorous content of less than 0.06 percent, and a sulfur content of less than 0.05 percent was ground on a commercial belt grinder at a speed of 6,000 ft./min. and at a pressure of 6 kg by means of the two belts.
• the control belt removed 306 g steel and lost 3.5 g of its abrasive grains after 30 minutes grinding.
• the belt according to the invention removed only 269 g steel and lost 6.1 g abrasive material, being thus clearly inferior to the control.
• Additional belts were prepared from 220 grit emery with correspondingly reduced thicknesses of bonding material and covering layer, and employed in tests on bodies of the above-mentioned mild structural steel, an austenitic stainless steel, commercial aluminum (99 percent Al), brass (58 percent Cu), phosphorbronze, copper, melamine formaldehyde resin, and nylon 6.
• the belt according to this invention was superior to the control belt in grinding aluminum, copper, nylon, stainless steel, melamin resin, and brass, in that order, and inferior to the control belt on the harder metal of the structural steel and phosphorbronze.
• binder materials being members of the group consisting of phenol formaldehyde resin, urea formaldehyde resin, epoxy resin, polyester resin, polyurethane resin, alkyd resin, and water soluble glue.
• the weight ratio of said second binder material to said wax being between 1:1 and 2:3.
• said covering layer containing up to 60 percent by weight of a solid, particulate filler having a hardness substantially smaller than the hardness of said grains.
• said first binder material essentially consisting of water-soluble glue
• said Second binder material being a cured epoxy resin composition
• said wax is an amide of a fatty acid.
• the size of said abrasive grains being smaller than 100 grit.
• said second binder material being a cured epoxy or phenol formaldehyde resin
• said wax being an amide of a fatty acid
• wax being a member selected from the group consisting of beeswax, carnauba wax, ouricouri wax, paraffin, ceresin, polyolefin wax, and amide wax.

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• Engineering & Computer Science (AREA)
• Mechanical Engineering (AREA)
• Polishing Bodies And Polishing Tools (AREA)

Applications Claiming Priority (1)

Publications (1)

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Family Applications (1)

Country Status (8)

Cited By (6)

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Citations (7)

• 1973
  • 1973-03-10 DE DE2312052A patent/DE2312052A1/de active Pending
• 1974
  • 1974-03-01 CH CH295474A patent/CH576312A5/xx not_active IP Right Cessation
  • 1974-03-04 US US447789A patent/US3926585A/en not_active Expired - Lifetime
  • 1974-03-04 IT IT12504/74A patent/IT1005632B/it active
  • 1974-03-06 FR FR7407688A patent/FR2220349B1/fr not_active Expired
  • 1974-03-08 BE BE141818A patent/BE812076A/xx unknown
  • 1974-03-08 NL NL7403140A patent/NL7403140A/xx not_active Application Discontinuation
  • 1974-03-11 GB GB1067574A patent/GB1468238A/en not_active Expired

Patent Citations (7)

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