DE2921394A1 - GRINDED GLASS SHEET, METHOD OF MANUFACTURING IT AND METHOD OF USING IT - Google Patents

Description

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- 4 Minnesota Mining and Manufacturing Company, St. Paul, Minnesota, V.St.A.

Finely ground glass sheet, process for its manufacture and methods of using the same

The present invention relates to the finishing of the surfaces of vitreous materials. In particular, the present invention relates to a fining sheet, its manufacture and its use.

Grinding and polishing glass surfaces are essential steps in the production of acceptable surfaces on optical components, such as lenses, prisms, mirrors and the like. Such measures are also useful for repairing scratched or otherwise damaged surfaces of utility glass such as window panes, Automotive windshields, windows in railroad cars, display cases and the viewing windows of instruments and others Device types.

While glass may be the main material that is cut and is polished, the processes discussed here also apply to the grinding and polishing of other vitreous materials such as gemstones and the like. The following discussion regarding the surface finishing of glass per se is intended to be different as well, if applicable include such substances.

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The completion of a glass surface basically requires three measures. First, the surface must be rough with a hard Abrasives like diamond roughly ground to the textured shape become - e.g. to a flat surface or in the case of a lens to a desired curvature. The next step, called 'fining', is a preliminary one Finishing the coarse sanded surface to make deep To smooth out scratches, to correct elliptical defects in glass lenses and otherwise an essentially smooth one, but not yet to produce a polished surface. The last step, the polishing, is a fine grinding to remove small scratches and results a smooth finished or - in the case of an optical element, an optically clear surface. The present invention relates to only the fine sanding step.

Prior to the present invention, one conventionally had a slurry suitable abrasive particles in a liquid carrier such as. Water used for fine grinding. It is known that the loose abrasive grains of a fine grinding slurry roll or rotate under the load at the grinding interface and thereby Cut out small pieces from the surface to be sanded, the small craters of a defined musdial-line shape and leave size behind. This is why blocky abrasive grains are used for this purpose in order to create a more even pattern of pits to reach.

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_v ORIGINAL INSPECTED

Such fine-tuning on slurries is done by bps \\ ^r . to the interface between the lens to be machined and the curved metal lapping tool while swinging or rotating at least the lens or the tool while pressing both vigorously together to exert a grinding action on the surface of the lens. Not only is the glass lens ground, but the surface of the lapping tool is also worn, so that it has to be reworked after only a few lenses. Non-abrasive protective covers have been used to prevent this undesirable wear; but longer processing times for the lens had to be accepted.

Grinding glass surfaces with abrasive slurry has numerous disadvantages. For example, large quantities of the slurry are required handled which is inconvenient. Furthermore, the slurry must be kept moving continuously in order to keep the abrasive grains do not settle and an even concentration of the abrasive grains on the sanding surface is guaranteed. Finally are additional equipment is required to prepare, handle and also contain the slurry and to the grinding surface traced back. In addition, one must analyze the slurry in order to maintain its quality and dispersion; this required additional costly hours. In addition, the pump heads, valves, feed lines and lapping tools show and other parts of the feed system that come into contact that come into contact with the slurry experience undesirable wear.

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One has therefore generally unsuccessfully tried to replace the Slurry systems use coated abrasive pads and belts as well as discs with bonded abrasives, as they are used is obviously easier at first. However, the solid abrasive grains of such abrasive elements do not rotate and therefore generate not the required dimple pattern that is required in the fine-tuning step. The prior to the present invention usually The abrasive slurries used lift off more glass per unit of time than abrasive elements with fixed abrasive grains. Slurries also give a more uniform pitted surface that is free from scratches and, just as importantly, no chatter marks or hairline cracks (stress crack lines that often penetrate far into the mass of the machined body) Sanding with bonded or coated abrasives is almost inevitable. Such stress cracks can generally be only recognize when you apply etching solutions, as stress cracks are easily polished over and then the appearance of a perfect polished surface, but then remain as sub-surface imperfections. The flaws where cracks easily arise and become, under external or internal tensions easily propagate as they can arise from mechanical loads, vibrations, heat and other sources. With a number of ground Glass products and in particular safety glasses glasses, safety screens and windows and the like. In which a high Impact resistance is an essential factor, such subsurface imperfections are particularly disadvantageous.

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ORlGiNAL INSPECTED

The points of such fixed abrasive grains wear out very quickly and leave flat spots that not only reduce the glass lift but also scratch the surface. The subsurface imperfections mentioned above often occur when the glass is scratched by these flats. After Polishing such a surface results in a weakened area just below the surface that has numerous flaws contains; as already mentioned, the impact resistance of such products is no longer acceptable.

While with diamond grains contained in arcs or disks at higher contact pressures, a material depreciation is obtained that can be compared With that when sanding with slurries, they still result in surfaces with flaws due to the mechanics of the material being lifted off with fixed grains is based on cutting the surface, not on the formation of the desired shell pits. In addition, diamond-coated grinding tools are very expensive and therefore not economically viable in many applications.

Attempts have been made in various ways to incorporate fine grinding media into a cohesive layer, the abrasive releases during use, and in this way to grind glass; the success of these attempts was limited. The attempts were on directed to decompose, dissolve or soften the binder and thereby release the abrasive grains, which then

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ORIGINAL! KSFECTcD

roll and spin to create the desired dimple surface in essentially the same manner as when using a slurry can generate. For example, lubricants such as stearic acid, tallow, paraffin wax and similar binders and lubricants are used for this purpose used. Such substances generally decompose too quickly, because their dimensional stability is too low under the load and frictional forces and the resulting frictional heat generally cannot be kept under control.

The present invention provides a fine sanding sheet or pad, which is particularly suitable for fine grinding of coarsely ground glassy and for repairing scratched glassy surfaces, producing a uniformly pitted surface that is equivalent to that or better than what you would get when you fine-tune it with slurries receives; this surface can then be polished immediately and easily in a subsequent polishing step. The fine sanding sheet according to the present invention eliminates the steps required for handling liquids as well as measuring and analysis measures, normally associated with the use of conventional fine sanding slurries.

A small amount of water added to the sanding sheet of the present invention allows the sheet or pad to create its own slurry during sanding while allowing the user to begin work with a clean, easy-to-use dry sheet or pad. The sheet after the previous

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lying invention has a coating that is dry Represents slurry concentrate, which under the conditions of use gradually into an effective mineral slurry dispersed, which is able to fine-grind glass surfaces at least as well as conventional fine-grinding slurries.

The sanding sheet of the present invention is special well suited for fine grinding of coarsely ground glass lenses in conventional fine grinding or polishing machines for glass lenses. The undesirable wear and tear of feed lines, valves, pump heads and other equipment parts that are common with conventional use Fine-tuning slurries is now eliminated. The fine chip sheet of the present invention further protects the texture and curvature of the surface of the lapping tool and substantially eliminates the post processing steps normally required when using conventional slurries are.

The fine grinding sheet according to the present invention has a microcell layer made of water-insoluble Phenolfojrmaldehyd- or Urea-formaldehyde resin binder is formed and in the fine abrasive granules are bound; this layer is applied to a flexible, adaptable underlay sheet. The sanding sheet according to the present invention is produced by the substrate with a composition of the liquid binder, Fine grinding particles and, if necessary, a sufficient amount of one

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\ , ORlGiWAL INSPECTED

compatible solvent coated to form a foamed homogeneous coatable Manufacture composition. The coating agent is prepared applied, dried and cured to form an even, microcellular, manageable, somewhat brittle coating that underneath the conditions of use erodes or degrades and their content increases Releases fine grains in a uniformly controlled manner. The gradually released abrasive grains can rotate freely and therefore create a uniformly pitted surface; in doing so, they leave the area immediately below the surface free of defects back like conventional fine sanding slurries, which can be seen through etching the subsequently polished surface can be confirmed.

In particular, the fine grinding sheet according to the present invention a flexible, adaptable pad on one side with a microcellular resin layer containing abrasives weighing

2
is coated at least 450 g / m 2 and at least 250 / µm (10 mils) thick and capable of degrading uniformly in use. The resinous binder is a thermosetting polymer selected from the group consisting of urea formaldehyde and is modified by adding from about 1 % to about 40 % (preferably from 3 I to 15%) of a thermoplastic polymer modifier consisting of polyamide, polyacrylate, polyacrylonitrile , Polyvinyl ester, polyvinyl alcohol, copolymers with such thermoplastic polymers and their combination existing group can be selected. The fine particles have a Khoop hardness of at least about 1000 and an average particle size of about 15 to 60 μm and are microcellular

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Layer to a volume fraction of the abrasive grains to the binder of about 0.75: 1 to 1.75: 1 included.

The smoothness with which the abrasive grains under the conditions of the The release of the insert is adjustable because, in contrast to the prior art, the release of the abrasive grains does not occur from the Solubility parameters of the binder depends. Rather, the release of the granules from the pad depends on the present invention the gradual, mechanically induced failure and degradation of the coating. The binder of the coating forms a fragile one microcellular matrix which contains fine-grained grains over its entire volume and which are exposed to stress and frictional surface contact in the presence of an aqueous current, it releases its abrasive particles on the surface easily with a rate that one results in effective fine-tuning without unwanted clumps.

The way in which the microcellular layer erodes or degrades or wears out, is a critical factor in determining whether finishing is in a satisfactory and commercial manner can finish acceptable time. For commercial purposes it is very desirable to have a single fine sanding sheet for performing and finishing a be able to use the full fine-tuning process. The fine sanding sheet should degrade so quickly that the required concentration of abrasive grains is reached results at the interface with the object to be ground; nevertheless the blade should not wear out so quickly, that his supply of abrasives is available before the end of the FeinschKfcf-

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ORIGlNAL BATHROOM

Operation is exhausted. The speed with which the sheet or pillow eroded or worn, can be determined with a test in which in simulated use under controlled conditions, the mean volume of the product coating that is lost is determined. at For this test, a weighed disc of the sheet to be tested with a diameter of 114 mm is ground in a normal Taber grinder. The coating is wetted with water and two 13 mm wide normal "Calibrade" grinding wheels of the type H-22 with a diameter of 50 mm are each under a load of 1000 g on the coating surface of the test pad and then the discs with the addition of small amounts of water on the surface of the test disc 100 revolutions long turned. Then the test disc is removed, the loosely ground one Coating washed off, the disk dried and weighed again. The lost decision-making volume, hereinafter referred to as the "erodibility index" is obtained by dividing the weight loss by the specific gravity of the coating. It has been found that useful fine sanding sheets according to the present invention have an erodibility index between about 0.15 cm and about 0.30 cm.

In use, the blade of the present invention can be used for civil purposes Lapping tool or another cushion holder and the glassy surface to be finely ground can be introduced. Then you bring pressure in conventional Elevation and agitation with sufficient aqueous current to create a Feinscliliff slurry and material from the surface take off.

Fig. 1 is a top plan view of the sanding sheet of the present invention Invention in the form of a slotted disc for use in a conventional one Lens finishing machine;

Fig. 2 is a partial section through the sheet of Fig. 1 on line 2-2; and FIG. 3 is an exploded side elevational view, partially in section, of a fine lens assembly with a lapping tool on the work surface thereof the cushion of Fig. 1 is applied.

Figs. 1 and 2 of the drawing show a fine grinding sheet for glass lenses in the form of a circular cushion 10 in which a plurality of equally spaced radial slots 11 have been cut. The leaf comprises an abrasive layer 12 containing the fine particles in a microcellular matrix of hardened water-insoluble resin binder contains. This layer is glued to an adaptable, flexible base 13.

A layer 14 of pressure sensitive adhesive can be on top of the other Side of the pad 13 should be provided around the cushion 10 on the work surface of a lens grinding tool. A suitable cover film 15 can also be provided to protect the pressure-sensitive Adhesive layer to protect against soiling during storage and before use.

In use, the sheet material of the present invention is applied j a curved fine-grinding lapping tool 31 is attached to the work surface 30, As shown in FIG. 3, the lens 32 is then made with conventional

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Pressure from the tool 31 pressed against a suitable holding block 33, the contains a recess 34 for receiving the lens. It should be noted that in some devices the lapping tool is pressed against the lens will; Such designs are from the art of fine lens grinding known. In operation, the tool 31 and the block 33 are moved relative to one another rotating or swinging while fresh water or another aqueous solution from a suitable source 35 continuously at a relatively slow rate onto the interface is placed between the lens and the sheet material.

The fine grains and the limited amount of water are added to the Cut surface held to create a slurry covering the lens surface finely grinded. The mineral-resin matrix builds up under the action of load and surface friction in the presence of a water flow gradually releasing the abrasive particles for a period of time sufficient to grind the lens.

During fine grinding, the grinding effect causes additional removal Binder and releasing additional abrasive grains, so that the supply of abrasive grains with relative is refreshed at a steady, controlled speed. The loose abrasive grains are attached to the edge of the lens interface and pillows carried and washed away there with the support of the water current; so it is for the feed during the entire process fresh abrasive granules to the interface.

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The fine sanding sheet can be in any form, how to use them is currently used for lens grinding or polishing - for example, as a disk, as shown in FIG. 1, or as a description of this shape. A disk may or may not be slotted as shown in FIG. 1 to easily conform to the curved work surface of a lapping tool be provided with other openings. Furthermore, the cushion can be in a different shape and, for example, be rectangular, oval or the like; this choice depends on the shape of the lapping tool used. The sheet material can be formed into an endless belt by conventional methods be designed by cutting the adjoining ends of a longer Strips of the sheet material connects together. The preferred fine sanding pad made in accordance with the present invention is shown in Figure 1 and has a plurality of radially directed and equally spaced slots leading from the edge of the pad run its center.

The fine grinding particles used in the present invention have a particle size of the order of 10 to 80 μm and a Knoop hardness of at least 1000 so that the required material removal can take place on the surface of the glass to be fine ground. Grains less than 10 µm generally do not grind hard enough to remove deep scratches in economically acceptable machining time, while grains larger than 90 µm leave deep scratches that are generally not removable by conventional polishing .

Abrasives with adequate hardness can be made from conventional abrasive minerals - e.g. garnet, emery, aluminum oxide, silicon carbide, zirconium oxide and the like ^! As known from slurry grinding, a uniform particle size distribution gives one

Evenly finely ground (or pitted) scratch-free surface. Since the mechanics of grinding with slurries and with the Sdileifblätem according to the present invention primarily by the polishing effect which depends on the sediment granules are form ratios (Adisel length ratio of mineral granules) close to one is preferred. The preferred abrasive grains of the present invention are made from silicon carbide (blocky) in grinding wheel quality and are carefully sieved to a uniform particle size. Much larger particles than the mean value should be avoided as they generally damage or scratch the surface to be sanded.

The binding agent that forms the cohesive microcellular matrix, which binds the fine grinding grains and sticks the abrasive layer to the adaptable backing is made of a water-insoluble resin material educated. The hardened granule is like modified binder should have a Knoop hardness within the range of 15 to 50 and preferably 20 to 40 in order to adequately support the abrasive granules.

The mineral-resin layer can be described as rigid, microcellular Matrix containing tiny cells or cavities, their average Diameters are in a range that is typically the size

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of the abrasive grains does not exceed 50 % , the average hollow space diameter typically being approximately equal to the diameter of the smaller than the average diameter of the abrasive parts. The pitch fraction of the abrasive layer for a useful product according to the present invention has been found to be typically on the order of 0.35 to 0.60. A product with a void fraction of less than 0.2 can no longer be fine-tuned with a commercially acceptable speed.

A suitable binder composition arises from thermosetting urea or phenol-formaldehyde polymer materials, which are preferably obtained by adding about 1 % by weight to about 40% by weight , preferably 3 % by weight to about 15% by weight a thermoplastic polymer modifier to improve cohesion. Such resins offer good adhesion to the surface of the backing and only poor adhesion to the surface of the abrasive granules. While unmodified phenol-formaldehyde resins can be used, some of them result in a very brittle mineral-resin matrix that breaks easily when handled.

The thermoplastic polymeric modifiers can be selected from among a variety selected from polymers, for example polyamides, polyacrylates, polyacrylonitriles, polyvinyl esters !, polyvinyl alcohols, their copolymers and combinations. The preferred modifier is a ι as "Hycar 1571" from B.F. Goodrich Chemical Company Nitrile rubber latex.

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The modifiers are preferably added to the coating composition as a solution in a compatible solvent, as latex or other partial, chendispersion in a liquid carrier such as. Water added.

Such resin coatings can be cured by heating them to a suitable temperature for a long enough time that the solvent goes off and the resin cures completely - e.g. about eight hours at about 115 C. Shorter treatment times are of course sufficient at higher temperatures if the substrate can withstand them. The preferred curing temperature is 100 ⁰ C to 130 ⁰ C.

The weight ratio of the fine grinding granules to the binder resin in the Abrasive coating should be in the range of about 6: 1 to about 2: 1, and preferably 4: 1 to 3: 1 when the abrasive is SiC is to achieve the filling of abrasive particles that is required is to provide an effective slurry with an ever-wearing binder. The mineral * resin ratio can be better to define as volume ratio, whichever is used Loops, ttelart is in the range from 0.75: 1 to 1.75: 1.

The preparation of the microporous mineral-binder layer requires the preparation of a coating material that allows the formation of tiny closed cells or hollow spaces that occur during coating and Hardnesses are retained. Most of the usable abrasive grains result by their very nature such tiny cells, each of them being tiny one or more such cells are assigned and the size of each

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α * .λ

Cell typically does not significantly exceed the size of the granule. The granules and the binding agent must be carefully selected so that this cell formation also occurs; the use of substances that hinder this effect should be avoided. Since it is necessary to adjust the coating composition to optimize the cell formation effect, the addition of solvents, viscosity aids and fillers may be desirable in some cases. The applied application technique should be controlled in such a way that an accumulation of binder on the uppermost surface of the microcellular layer is avoided. For example, the viscosity of the mineral-resin coating composition can be adjusted to the performance of the application machine used in the individual case with compatible solvents such as, for example, water or ethylene glycol monoethyl ether (available under the name 'Ethyl Cellosolve ¹ from Union Carbide Company) or combinations thereof Coordinate the setting of the desired consistency of the coating. The preferred coating composition has a viscosity greater than 60,000 cP.

The coating weight of the abrasive layer should be at least 450 g / m with a minimum coating thickness of 250 µm (10 mils) im Be dry so that the abrasive grains are present in a layer thickness to complete a conventional lens fine cut to be able to.

Conventional mixing and application methods and equipment can be used to make the article of the present invention. The preferred mixer is a slow speed stirrer or kneader and the application is preferably made with a blade.

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An inner fine grinding using the fine grinding cushion according to the present invention takes less than 10 minutes, typically 3 to 6 minutes, if a conventional spectacle lens of 65 mm diameter with moderate curvature (6 diopter curve) is placed under a load of 9 ^ kg (20 lbs) fine sanded. Under these conditions raises sheet material according to the present invention is typically at least 0.5 g of glass, and usually about 0.75 g t> ^is about 1.30 g of glass from.

The adaptable flexible pad can consist of a suitable Material that is compatible with the coating components and remains stable under the curing conditions; it can be permeable or impermeable materials Act. If an impermeable backing material is used, it may be necessary to reduce the viscosity of the coating compound and adjust the drying process accordingly to avoid the formation of large bubbles upon drying and such a large loss on cells to prevent the Erodxerbarkextsxndex from shifting to a value that is no longer acceptable. The preferred one Backing material is a spun bonded ("spun bond") Polyester web, as sold as "Lanapress No. 00-4219-02" from West Point Pepperell Company, Palatine, Illinois, V.St.A., or as "Reemay" from E.I. duPont Company is; however, other tracks of a similar structure can also be used use.

The when using the fine sanding sheet or cushion after the The aqueous flow applied to the present invention preferably consists largely of water, but can also include others Have ingredients typically found in slurry finishing solutions or conventional Surface treatment with abrasive coatings can be used. These can be water-soluble oils, emulsifiable Act oils, wetting agents and the like. J

The water supply to the interface between the fine sanding pad and the line to be sanded should be relatively weak ^ on the order of about 1.0 to 50 ml / min and preferably 2 to 20 ml / min. Too little or too much water reduces the grinding effect · The water supply should be adjusted in this way that the amount of glass lifted from the lens surface is maximal.

The sanding sheet of the present invention is attached to the work surface of a lapping tool in a conventional manner. In some cases it may be desirable to have a layer of conventional pressure sensitive adhesive on the back to make it easier to hold the fine sanding sheet on the surface. Suitable pressure sensitive adhesive compositions include those of the rubber-resin types and acrylates; rubber-resin pressure sensitive adhesives are preferred. If a pressure-sensitive adhesive layer has been applied to the sanding sheet, it may be desirable to use a protective film as well

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to apply which the adhesive surface of the pressure sensitive Adhesive layer protects against contamination during storage and handling before use. Such protective films can made of silicone-treated paper, non-stick plastic films or any material known for this purpose.

Examples

The invention is illustrated by the following examples will.

example 1 Composition; the coating Components parts by weight

1. Alkali-catalyzed resole-phenol-formaldehyde resin with 53 - 57 ^ pesticides; Viscosity 200-400 cP at 25 ⁰ G; Gel time 29 - 36 min at 100 ⁰ O; pH 9.0-9.4 (available from Ashland Chemical Company as

"Arofene 72155") 54-

2. Reactive low-melting polyamide resin with 100% pesticide; spec. Weight 0.97; Amine value 275-325; Amine equivalent weight 180; Viscosity 31,000 - 48,000 cP at 25 ⁰ G (available as Versamid 125 from Pirma General Mills Chemical Company)

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~ 24 -

3. Alkali-catalyzed resole phenol-formaldehyde resin with 75 - 77 ? Ό solids; Viscosity 1600-2500 cP at 25 ⁰ G; Gel time 50-58 min at 100 ⁰ C; relationship
Formaldehyde: phenol 1.75: 1 »00; number average molecular weight 168; spec. Weight 1.2 23

Fine grains

Silicon carbide in sham quality, 400 mesh,

spec. Weight 3.18; Knoop hardness 2480

(average particle size 20 µm) 275

The above-mentioned components of the coating were used in the specified proportions mixed into a homogeneous mixture in which the abrasive grains and 20 parts by weight of ethylene glycol monoethyl ether were mixed into an applicable mass. The resulting ratio (dry) mineral: resin is 4: 1 (Weight) or 1.5: 1 (volume).

This composition was then bladed to a thickness of 0.64 mm on a spunbond nonwoven polyester sheet with

ρ
a weight of about 85 g / m and a thickness of about 254 279 / µm (available as 'Lanapress Style No. 0042-19-02' from West Point Pepperell Company, Palatine, Illinois, V.St.A.) brushed on, the coated sheet then placed in a compressed air oven at about 115 ⁰ O and held there for about eight hours. A sham-shaped sample was made from this sheet to the one shown in Fig.

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F ""

- 25 -

cut out shape shown with a diameter of 76 mm, to make a "fine-tuning pillow".

Prepared according to the procedure described in this example, j Fine polishing pads were compared to standard slurries from the technique of lens processing as well as conventional coated ones Abrasive sheets evaluated. The grinding results of a laboratory evaluation to compare the effective grinding rate the slurries, the coated abrasives, and the cut-in sheet according to the present invention are summarized in Table 1. The standard alumina abrasive slurry a particle size of 12 µm, which is common in the lens processing art, was found in three concentrations evaluated, i.e. 7 »3» 16.0 and 36.4 grams of abrasive per 100 grams of slurry. The standard abrasive sheet material included 15 µm silicon carbide abrasive grains in a 1: 1 weight ratio to binder «These abrasive articles were on a coarsely ground glass lens with a diameter of 65 well rated and moderate curvature; the glass was removed by weighing at one-minute intervals of the lens before and after grinding. The slurry was continuously on the interface of a smooth cast iron Lapping punch and the glass lens were flooded with a circulating pump cut the same contact area as the pad according to the present invention and the interface between this sheet

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material and the machined lens are flooded with water. The | Interface between the cushion of the present invention!

and the glass lens to be ground was water of about 2.5 emv;

min fed. In each case, the load between the lapping punch and the lens was varied from 4.5 to 13.5 kg (10 to 30 lbs.), as indicated in Table I. The table also shows the total lifted during each time interval and the total after four minutes removed amount of glass.

As can be seen, the pad of the invention was as good or better than a conventional slurry under loads of 4.5 to 13 j 5 kg (10 to 30 lbs.). Conventional coated Abrasive articles were found to be completely inadequate.

The surface quality of the treated glass lenses was determined by measuring the roughness and the surface profile on a "Bendix Proficorder" determined. The recorded CLA values (center line average) - also known as AA values (arithmetic mean) - describe the standard deviation of the peaks and Valleys from the mean. The average peak height (KPH) describes the average height between the peak and the valley. "Max NPH" denotes single deep scratches.

Table 2 summarizes the profile values for finished lenses in different Phases of the fine-tuning process together, i.e. (1) for the rough lens surfaces before grinding, (2) die resulting lens surface after fine grinding with appropriate

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- of the invention (after i 1 g / 100 g slice) 36.4 damn.
Grinding example a standard 12 i
example 1 16.0 0.160 middle 0.190 - 27 Slurry, and (3) the finished lenses t
/ Um-alumina- Conventional slurry 0.163 0.138 0.022 0.142 neither after a fine-tuning pillow conventional 1-3 after polishing with (cone. 0.153 0.134 0.002 0.133 manufactured) or / um geroxide slurries. 7.3 0.130 0.131 0.001 0.139 0.150 0.133 0.563 0.001 0.604 Pressure time Tabel 0.130 0.579 0.326 0.006 0.330 (kg) (min) 0.063 0.213 0.271 0.008 0.232 4.5 1 0.027 0.122 0.157 0.006 0.193 2 0.390 0.099 0.112 0.003 0.110 3 0.139 0.083 0.866 0.003 0.865 4th 0.087 0.517 0.286 0.020 0.325 total 0.060 0.192 0.187 0.012 0.271 9 1 0.073 0.085 0.131 0.008 0.348 2 0.359 0.076 0.096 0.003 0.295 3 0.108 0.057 0.700 0.004 1,239 4th 0.072 0.410 0.027 total 0.031 13.5 1 0.009 2 0.220 3 4th in total

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Table 2

Assessment of the glass lens surface (/ um)

(1) Before fine-tuning:

(2) After the fine-tuning:

GLA

avg. Center height

maximum center height

(3) After polishing:

GLA

avg. Center height

maximum center height

CLA

avg. Sp.-H.

max.sp.-height

example 1

1.5
5.0
7.5

example 1

0.10

0.17
0.22

5.0 10.0 25.00

AufSChlänmrimg

, 5

7.5

On sludge

0.10 0.16 0.23

The accuracy of the optical curvature of the finished lens was determined by measuring the number of diopters (focal length) and the optical axis on a lensometer commonly used in optical laboratories certainly. The lenses machined by both methods had the desired optical accuracy.

Example 2 Coating

Components

1. Phenol-formaldehyde resin with 53-57 % solids content; "Arofene 72155" (as in example 1)

2. 75-77 # solids phenol-formaldehyde resin; (as in example 1 described)

Parts by weight (wet)

50

lomo / 0670

3. Nitrile rubber latex with 42-44 % solids; as "Hycar 1571" ν. from BF Goodrich Chemical Corp. available 9

Abrasive granules

Silicon carbide in. Disc quality, 400 mesh (such as

described in example 1) 218

The above-described components of the coating were in mixed in the specified proportions to form a homogeneous mixture that contains the abrasive grains and about 20 parts by weight of water were added to an application mass. The resulting mineral / resin dry ratio was 3 »5: 1 (weight) or 1.4: 1 (volume). The mass was spread onto the nonwoven web with the blade, hardened and finally to the in Example 1 described fine grinding cushion further processed. The grinding results are summarized in Table 3.

Example 3 Coating

Component parts by weight (measure)

1. Phenol-formaldehyde resin with 53 - 57 ° / ° solids content; Trade name

"Arofene 72155" (as in Example 1) 37.5

2. phenol-formaldehyde resin with 75-77 % solids content; (as described in example 1) 58

909180/007 ©

j 3. Acrylic latex with 48 - 52 JIi solids content

'(as "Hycar 2679" by B.F. Goodrich

Chemical Corp. available) 4.5

Fine grains

Silicon carbide, disc quality, 400 mesh

(as described in example 1) 270

The ingredients of the coating and the mineral were mixed and the viscosity adjusted with water, as described in Example 2. The resulting mineral / resin dry ratio was 4: 1 (weight) or 1.6: 1 (volume).

The mass was spread with the blade on an impermeable, non-woven web, hardened and processed further to form the fine sanding pads described in Example 1. The saturated nonwoven web was the spunbond polyester web of Example 1 impregnated with 3.7 mg / cm of a 1: 1 mixture (solids basis) of the phenol-formaldehyde resin ( 75-77% solids) with the acrylic latex described above.

The grinding results are summarized in Table 3.

Example 4 Coating Ingredients parts by weight (wet)

1. Phenol formaldehyde with 53 to 57 ° / o solids content; "Arofene 72155" (as in

Example 1 described) 26

2. Phenol-formaldehyde resin with a solids content of $ 75-77 (as described in example 1) 4-1

3. Nitrile rubber latex with 42-44 # solids; "Hycar 1571" (as described in Example 2) 11

4 ·. Aqueous polyvinyl alcohol solution, $ 5 solid content, made from polyvinyl alcohol powder "Elvanol", fully hydrolyzed, by the company EGG. duPont Corp. 22nd

Fine grains

Silicon carbide, grinding wheel quality, 4-00 mesh

(as described in example 1) 204-

The ingredients and mineral were mixed and then mixed as in Examples 1 to 3 above to a mineral / resin weight ratio of 4: 1 (volume ratio 1.56: 1) applied.

The fine-grinding cushions made from this were tested; the The results are summarized in Table 3.

Example 5
Ba layering

Components Parts by weight (wet)

1. Phenolforealdehyde resin with 53-57 % solids; ¹¹ ArOf «ne 72155" (as described in Example 1) 50

IOmO / 0670

2921334

2. Phenol-formaldehyde resin with $ 75- $ 77 solids

share (as described in example 1) 41.5

\ 5. Nitrile rubber latex with 42-44 # solids content; "Hycar 1571 (as described in Example 2) 8.5

Fine polished grains

Aluminum oxide, disc quality, 400 mesh, specific gravity of 3.95, Knoop hardness about 2100 269

■ The ingredients and the mineral were mixed and then applied, as described in Examples 1-4. The dry mineral / resin ratio was 4.3: 1 (weight) and 1.37: 1, respectively ! (Volume), which is comparable to a ratio of 3 »5: 1 for the less dense silicon carbide material.

The fine-grinding cushions made from this were tested; the The results are summarized in Table 3.

Example 6 Components parts by weight (wet)

1. Urea-formaldehyde resin with 63-66 % solids content, pH 7 »6; spec. Density 1.296; available as "Durite AL-8401"

from Borden Chemical Co.) 86

2. Nitrile rubber latex with 42-44 % solids content; available as "Hycar 1571" 14

9G98B0 / 067Ö

3-25% aqueous solution of ammonium chloride NH.C1 as a catalyst for the ureaff ormaldehydhar ζ

4. fine grinding granules, silicon carbide, Disc quality, 400 mesh (as described in Example 1)

186

^: These ingredients and the abrasive particles were mixed and then applied as described in Examples 1-5

The fine-grain cushion made from this was tested; the The results are summarized in Table 3.

Table 3

Summary of the grinding tests Amount of glass lifted (g)

Machine: Coburn Ro. 506, cylindrical lens polishing machine Conditions: pressure 9 kg (20 lbs); 4 min

lifted

Ex. mineral Weight ratio
Mineral ϊ resin 1 Resin type Amount of glass
(G) 1 SiG 4: : 1 Phenol / polyamide 0.865 2 SiC 3.5 1 Phenol / rubber 1.194 3 SiG 4: 1 Phenol / acrylic 1,392 4th she 4: : 1 Phenol / rubber / PVA 1.036 5 Al ₂ O ₃ 4.3 1 Phenol / rubber 0.935 6th SiC 3: Urea form
aldehyde / gum 0.864 Comparison: On sludge
Al ₂ O ₃ 0.866

ΘΟ9β.6Ο / σβ7Ο

Comparison:

damn. Abrasive material

SiC 1: 1 phenol 0.020

Examples 7 to 15 and Comparative Examples A to D

Comparative Examples A to D and Examples 7 to 13 were used prepared and evaluated according to the methods described for Examples 1-6. The ingredients used in these examples were the following:

Explanation of the components

. "Phenolic resin I" was obtained from an alkali-catalyzed ßesol-i Phenol-formaldehyde resin with a pesticide content of 75 - 77 ^ j i

a viscosity from 1600 to 2500 cP at 25 ⁰ C, a gelling time: 50-58 minutes at 100 ⁰ C, a ratio of formaldehyde to phenol! of 1.75: 1 »an average numerical molecular weight! j of 168 and a specific gravity of 1.2.

j "phenolic resin II" was obtained from alkalikatalysiertem resol phenol-formaldehyde resin having 53-57% solids, a viscosity of 200-400 cP at 25 ⁰ O, a gelation 29-36 min at 100 ⁰ C and a pH from 9.0 to 9 , 4 (available as "Arofene 72155" from Ashland Chemical Company).

"Nitrile rubber" was obtained from a nitrile rubber latex containing 42-44 % solids (available as "Hycar I57I").

109 8 60/0670

"Polyamide" was obtained from a reactive, low-melting polyamide resin with 100 % solids, a specific weight of 0.97 »an amine number of 275-325» an amine equivalent weight of 180, a viscosity of 31,000 to 48,000 at 25 ^° C. (as " versamid 125 "available from General Mills Chemical Company).

Compositions (parts by weight, dry) Parts Example 7 64 30th Binder: phenolic resin I. 6th Phenolic resin II 400 Nitrile rubber Abrasive: SiC, 400 mesh 50 Example 8 44 Binder: phenolic resin I. 6th Phenolic resin II 400 mesh 500 Nitrile rubber Abrasives: aluminum oxide / zirconium oxide, 50 Example 9 44 Binder: phenolic resin I. 6th Phenolic resin II 400 Nitrile rubber ' Abrasive: Al ₂ O ₅ , 400 mesh 50 Example 10 44 Binder: phenolic resin I. 6th Phenolic resin II 400 Nitrile rubber Abrasive: Al ₂ O ₅ , 400 mesh

56 -

Example 11

Binder: phenolic resin I 35

Phenolic resin II 32.5

Polyamide 32.5

Abrasive: SiC, 4-00 mesh 400

Example 12

Binder: phenolic resin I 56.5

Phenolic resin II 11

, Polyamide 32.5

Abrasive: SiC, 400 mesh 4-00

Example 13

Binder: phenolic resin I 67

Phenolic resin II 32

Nitrile rubber 1

Abrasive: SiC, 400 mesh 400

Comparative example A.

Binder: phenolic resin I 64

Phenolic resin II 30

Nitrile rubber 6

Abrasive: SiC, 400 mesh 400

Comparative example B

Binder: phenolic resin I 64

Phenolic resin II 30

Nitrile rubber 6

Abrasive: Alumina / Zirconia, 400 mesh 400

9098S0 / QS7Q

-3V--

Comparative Example C

Binder: phenolic resin I 50

; Nitrile rubber 50

j Abrasive: SiC, 400 mesh 400

Comparative Example D.

Binder: phenolic resin I 100

■ Abrasives: SiC, 400 mesh 150

Table 4 gives both the erodibility factor and the. Glass lift on. The method according to which the erodibility factor is loading _;

i was correct, is explained above, while the glass lift on the! ' Same manner as in Example 1 with a load of 9 kg (20 lbs) _;

I. ■ ■ Ϊ

j was determined. ;

309850/0678

Table 4

game mineral Epodability Glass lift (g) at SiC factor (cm3) in 4 min 1 SiC 0.189 0.865 2 SiC 0.204 1.194 3 SiC 0.220 1,392 4th Al ₂ O ₃ 0.196 1.036 5 SiC 0.260 0.935 6th SiC 0.177 0.864 7th Al-0xid / Zr-0xid 0.251 1.160 8th Al ₂ O ₃ 0.208 1,100 9 Al ₂ O ₃ 0.192 0.908 10 SiC 0.214 1,140 11 SiC 0.167 0.940 12th SiC 0.252 0.997 13th SiC 0.167 0.940 A. Al oxide / Zr oxide 0.115 0.407 B. SiC 0.090 0.376 C. SiC 0.471 0.173 D. 0.006 0.020

$ 09860/0670

Claims (6)

(nachoereicht] BERLIN MÖNCHEN patent attorneys ρ. ρ, ιςρη ^ ρ ο DADTMPR patent attorneys Dr.-Ing.Hans Ruschke Ul. nUOOni \ C. Ot ΓΑΠ I INCH Dlpl.-Ing.Hans E. Ruschke Dipl.-lng. Olaf Ruschke ΡΑΤΕΝΤΔΝ WÄ LT E Dlpl.-Ing.Jürgen Rost Auguste-Viktoria-Strasse 65 PienzenaueretraBe Berlin 33 BERLIN-MUNICH 8000 Munich Telephone: (0 30) 8 28 38 95 Telephone: (0 89) 98 03 (030 8284481 (089) 987258 Τ · 1.χ: 1Μ7Κ (089) 98 88 Cable: Quadratur Bariin Telex: S 22 767 Cable: Quadratur Munich M 4100 Patent Claims 1. iFeinschliffblatt with a coating of a resin binder containing abrasive grains on a flexible base, characterized in that the coating is a 2 microcellular layer weighing at least 450 g / m and at least 250 µm (10 mils) thick, consisting of Ca) a hardened modified resin binder with a Khoop hardness in the range of 15 to 30 which is selected toffformaldehyd from the urine and group phenolformaldehyde existing and modified is thermoplastic having from about 1 part by weight of l to about 40 wt .-% of a thermoplastic polymer-Madifiziermittels, which is selected from the polyamide, polyacrylate, polyacrylonitrile, polyvinyl esters, polyvinyl alcohol, and copolymers with these Polymerizing agents and combinations thereof, and (b) fine grind granules having a Khoop hardness of at least about 1,000 and an average particle size of about 1 to 60 µm, to a volume ratio of abrasive granules to binder in the range of about 0.75: 1 up to 1.75: 1, whereby the fine grinding sheet can form a fine grinding slurry if there is water flow, exposed to pressure and counteracted SWAOHGEREtCHT | ! 921394 abrasive glassy material is applied. 2. Fine grinding sheet according to claim 1, characterized in that it is in the form of a circular disk with radially directed blades which, starting at the edge of the disk, extend towards the center of the disk, but do not reach them. 3. Fine grinding sheet according to claim 1, characterized in that it is in the form of an endless belt. 4. Fine sanding sheet according to claim 1, further characterized by a pressure-sensitive adhesive on the opposite side of the flexible substrate provided with the abrasive. 5. Process for the production of a fine sanding sheet by mixing a hardenable resin and abrasive granules, applying the mixture to a flexible base and drying and hardening the coating, characterized in that (1) a hardenable resin composition of about 99 wt . -I to about 60% by weight of a thermosetting material selected from the group consisting of urea-formaldehyde and phenol-formaldehyde and about 1 % to about 40 % of a thermoplastic polymer modifier in a suitable liquid carrier with fine ground granules having an average particle size of 15 to 60, to a volume ratio of the abrasive granules to the resin in the order of 0.75: 1 to 1.75: 1 to form a cellular viscous mass, (2) in the I WAKE UP [ Carrying step the viscous mass on an adaptable flexible Applying sheet to a substantially uniform coating thickness of at least 250 / µm (10 mils) after drying, and (3) in the drying and curing step, a temperature less than about 140 C applies to a rigid microcellular matrix To form soap pellets and resin. 6. Process for fine grinding glassy surfaces by application a fine sanding agent on the surface to be sanded in one liquid carrier under pressure, characterized in that the fine grinding medium is obtained by (1) a fine grinding sheet according to claim 1 on a glassy surface to be finely sanded, and (2) the sanding sheet relative to the glassy surface Surface under pressure and rotating and / or vibrating Movement moves while holding the sanding sheet in a continually freshened watery environment long enough to keep Abrasive particles loosen from the sheet in an amount and concentration of time to cause a slurry of abrasive particles to separate forms and remains, which can fine-grind the glassy surface. 9098E0 / 0670