US1986849A - Abrading material and process for preparing the same - Google Patents

Description

Jan. 8, 1935.

T. POHL ET AL ABRADING MATERIAL 'AND PROCESS FOR PREPARING THE SAME I Filed Feb. 20, 1932 gwuentoc Eeadorfo/z Z azzzZJaag/JZ- :zezhbz: W' vQm Patented Jan. 8, 1 935 PATENT OFFICE ABRADING MATERIAL AND PROCESS FOR PREPARING THE SAME TheodorPohl, Frankfort-on-the-Main, and Josef Schneider, Oberursel-on-the-Taunus, Germany Application February 20, 1932, Serial No. 594,304

In Germany February 26, 1931 r 11 Claims. ((11,. 51-280) This invention relates to abrading materials for use in abrading and grinding'op'erations.

divided portions of relatively hard materials held together in a suitable working form by a binding agent. Among the abrading materials frequently employed for such purposes arecarborundum, eorun'dum, and finely-ground glass. As binders for the abrading material self-hardening materials such as gypsum, cement, low-melting glass and similar substances have been used and also materials which are not self-hardening themselves but which may be hardened by heating, drying or suitable chemical treatment such as, for example, dextrin, glue, albumins, caseins and similar materials; In certain cases, it has been found desirable and advantageous to use the combination of two or more of the binding agents.

The selection of the particular grinding material In the finished product heretofore known, the

hard particles of the abrading material are compactly held together by the binding materials, the mass containing very irregular and minute pores or spaces which unavoidably developed during the preparation thereof. The abrading composition has been made to' assume many different forms, such as slabs, sticks and wheels in which it may be conveniently utilized; 1

Prior abrading compositions and devices, formed of the materials and in the general manner described, have had the serious disadvantage that after a comparatively short use the attacking power'or the abrading effect on the work being treated rapidly diminishes. This diminution of the abrasive action has been duev to the fact that the fine pores which exist within the composition mass'become clogged and covered with the ma terial removed from the work treated and, as a consequence, the. surface of the abrading ma-,'

terial tends to become smooth and ineffective.

A further disadvantage of prior abrading compositions and devices of the character referred to an abrasive substance which will maintain its cutting and abrading efliciency throughout its life and continuously present an attacking or cutting surface of predetermined power'and effectiveness.

A still further object of the invention is to provide an abrading material which, when formed into grinding discs or wheels, will become very much less heated when rotated at high speeds than grinding discs heretofore known, and which will thereby avoid damage to the material being worked, such as by burning or melt- Another object of the invention is to provide a grinding material and articles formed thereof which has a comparatively coarse cellular formation and in which the particles are spaced a RHSSUW greater distance apart than in those heretofore known.

Still another feature of the invention resides in an, improved ,and novel method for producing abrasive materials and articles made therefrom. These and other features of the invention, and the novel method referred to, will be more fully apparent from the following specification when read in conjunction with-the annexed drawing and will be particularly pointed out in the appended claims.

In the drawing: Fig. l is a side view of an abrading disc formed from the abrading material of this invention. Fig. 2 is a section along line 2--2 of Fig. 1. Figs. -3, 4, 5, 6 and '7 are modified forms of abrading discs constructed in accordance with the particles of the abrading material or to the mixture of the abrading and binding materials are added compounds which act either in conjunction with the liquid employed to render the mass plastic or under the influence of other materials to liberate gases. Suitable compounds which may be added to the abrasive-binder plastic mass for this purpose are aluminum, calcium, magnesium or alloys of these metals, zinc, calcium carbide and bicarbonate. If necessary, certain alkali compounds may also be added to stimulate gas' liberation.

A satisfactory method of obtaining the desired coarse porous cellular structure is to add oxygen bearing compounds .such as hydrogen peroxide (H202) to the mass of grinding and binding materials. The hydrogen peroxide may be used in either liquid or-solid form. Iiibera'tion of the oxygen may be stimulated by the addition of a catalyst, such as manganese dioxide or copper powder, or by suitable chemicals or by heat. An

important advantage of this particular process is that it is possible through it to regulate, or at least greatlyinfluence, the size of the pores or cells which are formed.

.As examples of the described method, the following have yielded highly satisfactory results:

Example 1 Nine kg. of powdered'glass of suitable fineness are mixed in a dry condition with 1 kg. of dextrin and sumcient water is added to bring the mixture into a plastic condition. While slowly stir-f To a heated solution of two kg. glue (4 parts glue=3 parts water), 400 cm. of 30% hydrogen peroxide (H202) are rapidly added. The resulting mass is intimately mixed, by stirring, with the catalyzer which may be a mixture of 30 g.

of finely pulverized manganese dioxide in 300 cm. of water. As the development of oxygen begins, the mass is converted into a-tough batch into which is added 9 kg. of powdered glass which has been moistened with water and preheated, the addition taking place during stirring. Thereafter, the mass poured into suitable forms. After cooling, it is removed'from the forms, dried and solidified.

Example 3 Five kg. of a very finely pulverized glass havingan extremely low melting point is stirred with 2.3 litres of water and 150 cm. of 30% hydrogen peroxide (HzQa) and 0.5 litres of ,a 2% soap solution Asa catalyzer, 25 kg. of manganese dioxide dissolved in 250; cm. of. water are added. The addition of the catalyzer causes the development and release of the gas which results in an enlargement of the mass. While the mass is being stirred,

5 kg. of agrinding material suchas ground glass of an extremely high melting point or silicon carbide; are added. The resulting. mixture is poured into" suitable forms and dried... It is then heated until the low melting components of the mixture have sintered.

Example 4 A solution containing 2 kg. of glue is prepared, having the proportions of 2 partsglue to 3 parts water. The solution is heated and cm? of 30% hydrogen peroxide (H202) are added thereto. While this mixture is being stirred, 5 kg. of crystal glass powder which has been moistened with 750 cm. of water are added. To stimulate the development and release of gas, 25 g. of manganese dioxidesuspended in 250 cm. of water to rise. The

are employed. Whenthe gas development has begun, 5 kg. of a grinding material such as powdered carborundum, or corundum, are stirred into the mass. While still warm, the mass is poured into suitable forms, dried and thereafter heated 5 until the glass powder, acting as a binder, has

sintered.

Example. 5

solid bakelite powder which has been previously The batch is" thoroughly mixed and thereafter poured into moistened with 1 litre of water.

suitable forms. After drying, the resulting prodnot is saturated with a solution of bakelite in ace tone After being further dried, the product is preferably heated under pressure to between -170" C.

Example 6 One thousand g. of a suitablegrinding material, such as glass powder, are mixed and stirred with 150 g. df liquid bakelite. Into this mass, 5 cm. .of hydrogen peroxide (30%),, diluted with 10 cm. of acetone, are stirred. 5 g. of manganese dioxide dissolved in 25 cm. of acetone is thenadded and stirred intdthe mixture; The resulting mass is poured into forms where it is allowed mass is thereafter dried and hardened.

Example 7 A solution is made of 2 kg. of glue in the. proportion of 4 parts of glue to 3 parts of water. In this solution is thoroughly mixed 9 kg. of finely ground emery which has been previously mois'-. tened with 1 litre of water. When a uniform mixture has been obtained, 400 cm. of hydrogen peroxide solution (30%) are added and well stirred therewith. A mixture of 30 g. of manganese dioxide in 300 g. of water is next added.

'After swelling of the mass due to the released oxygen, the mass is placed into suitable forms. While still in a wet condition, the formed product is subjected to formaldehyde vapors which causes solidification. The product is then dried. Thereafter, the product may be further treated by dipping'into solutions of. resins or caoutchouc or a bakelite-acetone solution. After a-final drying operation, the product is ready for use.

The coarse cellular or porous formation of the character contemplated by the invention may .also be obtained "by mechanically stirring or beating a plastic mixture of the grinding and binding materials in a violent manner. The result of this agitation is the production of a light foam-like mass which, upon hardening, will have the desired cellular formation. This treatment "may be advantageously improved by the addition of foam-forming compounds.

Example 8 A Nine kgjo'f glass frits which have been moistened with approximately, 1.4 litres of water are thoroughly stirred with a solution of 2 kg. of glue,

containing 4 parts of glue and 3 parts of water. Into this powdered glass-glue mixture, 4 kg. of

kaolin foam are stirred, the kaolin foam used being produced as follows: 4 kg. of kaolin are stirred into a uniform solution with 3.2 kg. of water. To

this solution is added a mixture of 1000 g. of

kaolin or clay and 40 g. of aluminum powder which have been dispersed in 1000 cm. of water,

- kaolin foam with the glass-glue mixture isplaced in forms and subsequently solidified and tempered by treating with a formaldehyde solution or with formaldehyde vapors. If desired the product may then also .be. impregnated with rubber or bakelite solution.

Example 9 A solution is prepared by dissolving 60 g. of, glue in 240 g. of water. The solution is beaten and stirred for a considerable time until a viscous foam has been produced. Into this glue foam are stirred 450 g'. of carborundum powder of seorganic materials, having dimensions corresponding to those of the cells to be produced are added to and thoroughly mixed with the plastic mass which comprises the abrading and grinding materials. After the mass has solidified, either temporarily or finally, the added solid bodies are removed by appropriate treatment and leave the empty cells or pores throughout the mass. The method of removal will of course depend upon the nature of the solid material employed, and also to some extent upon the binding materials used. Thus, if sodium chloride and sugar are employed as the solid to form-the cells, removal is effected by lixiviation with water. Saw dust would be removed by burning. Melting and evaporation may also be resorted to for remov-.

ing solids of other'types.

Example 10 Threehundred and thirty g. of carborundum N0. 46 (with a volume of about 0.01 mm?) are covered with approximately 60 g. of a solution of bakelite so that the carborundum grains become The sugar pearls are then loosened from the mass with hot water, the product dried' and subsequently impregnated with liquid bakelite. The product is then hardened. The hollow cells interspersing the product are approximately" the finishing treatments following the cell-producing steps. It is frequently advantageous to impregnate or saturate the cellular material with such substances as lac, resins, artificial and synthetic resins, such as bakelite, caoutchouc dispersions, caoutchouc solutions and glue, shellac or water glass. As a final step, the material is dried, heated, hardened, chemically treated or vulcanized in accordance with the needs of the material or the nature of the product desired.

The abrading compounds produced by the invention are interspersed with substantial and preferably uniformly formed cells or holes which are separated from each other by solid walls of the abrading mixture; the walls themselves bein substantially free from pores or cells. The cells or holes can be of various shapes, such as, balllike, cylindrical, etc., and the size may vary within a wide range. The form and size of the cells Whatever the method by which they are formed,

and regardless of the size thereof which may vary through a considerable range, it is important that the size of the pores or cells should be either equal to or a multiple of the size of the particles of abrading material used. If this relationship between the cells and the abrading substance is observed, the material removed from the work being treated and the loosened and brokenparti cles of the abrading materialare permitted to escape from the cells and thus leave the latter free and unclogg'ed. As a result, the abrading material at all times presents an active surface consisting of sharp and relatively narrow cutting edges formed by the walls of the cells or pores. j

The following table indicates the various multiples which may be advantageously applied between the volume of the cells and the grinding materials, when the cells are ball-shaped:

(il igitigiiglg Middle vol. Multiple oi tlis gli'gigeigglume of a ball granulation 29 The appended drawing illustrates certain specific forms of cellular formation which may be given to the abrading compositions, the material in each instance being illustrated in the form of a grinding disc. According to Figs. 1 and 2, the grinding disc 2 has a honey-comb formation wherein the hollow cells 4 are uniformly distributed throughout the entire disc, the cells being surrounded by the comparatively thin walls 6 of the selected abrading and binding material. The. cells extend from the periphery of the disc inwardly to the axis opening 8 and from one side to the other. The cells are generally cylindrical or ball-shaped.

In Fig. 3, the grinding disc is characterized by hollow rectangular cells 10 separated from each other by the walls 12 of abrading compositions, the walls andcells forming a general honey-comb formation. The hub 14 of the disc and a central zone 16 are madeof the same abrading composition as the walls 12 but are substantially solid and devoid of cells.

According to Fig. 5, the grinding disc is pro;

vided'with transverse bores 22 arranged parallel to the axis and extending through the. entire thickness 01 the disc from one side to the other.

- The center of the disc is formed by the solid zone 24. The bores are arranged generally in circles, the circumference of which becomes larger as the distance from the axis of the disc increases.

In Fig. 6, the disc is formed with radially extending prismatic bores 28 generally similar to those of Fig. 4, and has a solid area of abrasive composition 28 similar to the disc of Fig. 3. Fig. 7 illustrates a' grinding disc in which the cells 30 vary insize and formation but are relatively' large as compared with the grains of the abrading material of the surroundingcomposk tion 32.

The cells of thediscs may be formed by 'any of the methods hereinbefore described, while bores of the type, shown in Figs. 4, 5 and 6 may be formed by punching or boring while the disc is in plastic or semi-plastic conditionand prior to the setting or hardening of. the material.

An 'abrading disc formed in accordance with the present invention has many advantages over previous grinding discs. As the abrading compounds wear away, new hollow cells continucusly open. In this manner, new and fresh cutting edges are continuously presented. As the hollow spaces or cells are substantially large as compared with the grindingparticles removed from thematerial being treated, they do not become clogged but, on the contrary, are always free of extraneous matter. Thejgrinding efllciency or attacking powerof the disc does not diminish with With an abrading device constructed in accordance with the invention it is possible to grind and .abrade many materials which heretofore could be treated only by means of fresh sand, or emery paper, or cloth. Thus, it is now possible to grind'eifectively materials such as wood,-

cork, and leather. Other materials. which may be effectively treated by the abrading device of this invention are, ebonite, galalith, celluloid, glass, ceramic materials, such as chamottes, porcelain and the like, molten magnesia, aluminum oxide, and metals and metal alloys such as,"

brass, bronze, steel and the like.

Having thus described the invention what we claim as new and desire to secure byLetters Patent of the United States is: 1. As an article of manufacture, a grinding body of cellular structure consisting of abrading and binding materials and having hollow spaces uniformly interspersed throughout, said hollow spaces being larger than the grains of the abrading material used.

p ployed.

2. As an article of manufacture, a grinding bodyotbellular structure consisting of abrading nd binding materials'and having hollow spaces uniformly interspersedthroughout, said hollow spaces being of substantially uniform size and larger than the grains of the abrading material 3.'As an article of manufacture, a grinding body of cellular structure consisting of abrading .and binding materials and having hollowspaces uniformly interspersed throughout, the avera'ge uniformly interspersed throughout, said hollow spaces being larger than the grains of the abradmaterial .used, the individual cells forming saidhollow spaces being spaced from each other.

by thin walls consisting of the grinding and binding materials.

5.-As an article of manufacture, a grinding body of cellular structure consisting of abrading and binding materials andhaving hollow spaces uniformly interspersed throughout, said hollow spaces being larger than the grains of the abrading material employed, the individual cells forming said hollow spaces being partially separated from each other. 6. A grinding body consisting of abradingrmaterial and binding medium, and having therein pores of greater size than the grains of the abradingmaterial, said pores comprising 50% or more of the total volume of the grinding body.

7. A grlndingbody consisting of abrasive ma-' terial and binding medium which, by being uniformly interspersed with hollow spaces, has a cellular structure, and the number and size of the hollow spaces is such that the total volume of the hollow spaces, inclusive of any pores which maybe present in the walls, is 50% or more of the total volume of the grinding body or the part of the grinding body which is interspersed by hollow spaces and the average size of the hollow spaces is at least equal to the average size of the ains of abrasive material. Q

B. Grinding body according to claim 7 in which the total volume of the hollow spaces amounts to 60 to 80% of the total volume of the grinding body or of the part of the grinding body inter-e spersed by artificial hollow spaces.

9. Grinding body according to claim 7, in which nected by openings. I THEODOR POHL. JOSEF SCHNEIDER.

the size of the grinding grains

Images