US1993821A - Bond for abrasive articles - Google Patents

Description

p 50 binder to afford adequate porosity. This feature sists essentially of adrying operation. The cure Patented 12, 1 35 I 1,993,321

UNITED. STATES rATENT. oFFicE BOND FOR ABRASIVE ARTICLES Baymond C. Benner, Niagara Falls, N. Y., and Garnett H. Porter, Pittsfield, Mass., assignors to The Carborundum Company, Niagara Falls, N. Y., a corporation of Pennsylvania No Drawing. Application October 3, 1931, Serial No. 566,790. Renewed September 14, 1934 8 Claims. (Cl. 51-280) This. invention relates to abrasive materials, amount of bond is more conducive to free cutting. particularly to abrasive materials comprising by the abrasive article. abrasive grains secured by plastic organic bind By varying the amount of bond, the charactering agents, and more specifically to abrasive grains istic which is known as grade, or resistance of bonded by a reversible thermo plastic material. the particles to removal from the composite mass, 5 This application is a continuation in part of our is obtained; ingeneral, the more bond the harder copending application Serial No. 264,568, filed is the grade. In obtaining adequate strength, it March 24, 1928, which has since matured into is sometimes necessary to use a very tough bond. Patent No. 1,825,771 wherein a part of the sub- An alternative, as far as strength is concerned, 10 ject matter of this application is disclosed on page is, to use a large amount of bond, but this reacts 10 2, lines 76 to 127 inclusive, and on page 4, lines 63 against the principle outlined above; namely, that to '70 inclusive. of providing a porous, open structure composed of Abonded abrasive article, obviously, has grinda relatively large amount of abrasive grain and ing characteristics due to the combined effect of a very small amount of binding agent.

the bonding material and the abrasive grains Thus, in practice, some bonds lend themselves 15 used. During the grinding process the amount of to use over only a small-range of grades, whereas work performed by the abrasive article is dependother. bonds might be termed universal grade eat on the ability of the article to clear itself, by range bonds inasmuch as it is possible with these which is meant the progressive exposure of fresh bonds to produce articles varying from the hardest 0 grinding surfaces, and incidentally, the removal to the softest required in practice. The latter of'the worn particles. In general, the types of type is relatively rare, however, and'it is usual materials which afford the qualities necessary in to have each specific bond cover only a limited a satisfactory abrasive are few and; consequently, portion of the whole grade range. the control of the grinding behavior to, produce These bonds may be,classified into organic and the desired results is obtained by selection, proinorganic bonds. The inorganic bonds are repre- 25 portioning and treating of the various bonding sented chiefly by ceramic materials suchas various agents. The various degrees and types of grinding types of clays or other earthy substances. Such action demanded in the art are obtained, for bonds may represent ceramic articles of various the most part, by the choice and the amount of degrees of vitrification including a completely aproper bond suitable for the particular producfused glass-like condition. For certain other 3 tion-demanded. purposes, a porcelain type of bond may be used.

Abrasive articles are required to grind all sorts A further type is one made with water glass or I of materials, both metallic and non-metallic, sodium silicate solution and used either in the and the service demanded of them varies all the condition of partial dehydration or in one of com- 5 way from a very heavy cutting action, such as plete fusion. Such ceramic bonds may be comthe cleaning of fins and gates from castings, to posed of a single clay or more usually of a mixture very light-work on hard tempered steel where of min' a1 ingredients. v

very light, delicate cutting, known as finishing, In t e fabrication of such ceramic articles, the

is required. In any case, it is desirable not to molded article is usually matured by subjecting generate an excessive amount of heat. Such heat it to relatively high temperatures; in general, bewarps, checks, and consequently destroys the tween 8051? F. and 2500 F. The bond usually material being ground. As av result, many types undergoes chemical interaction, and the heat 'of binding agents have been used with a relatreatment is prolonged for periods of from 6 to tively few types of abrasive material to produce 14 days. the necessary characteristics required'of any arti- I Under the classification of organic materials 45 cle for a given purpose. there arev several types; such as, shellac, glue, rub- A further desirable characteristic is that an her, and phenol-aldehyde synthetic resins, such as abrasive product contains a very large amount of Redmanol. v abrasive grain together with a small amount of In the case of glue the curing treatment conis for'the most part influenced by the fact that the for some types of synethetic resins includes a abrasive particles themselves, rather than the transformation of the material to a relativelyinbond, should be presented to the material being fusible or thermo-irreversible condition.- By this ground, inorder that the proper cutting action it is meant that reheating at the initial temperamay be obtained.- Further, the use of a small tures used in molding W111 not produce the same the components are degree of plasticity; a chemical change further, the bond undergoes and consequently, on cooling, not the same as existed originally.

In rubber bonded articles the cure is brought about by means of vulcanization or the reaction of the rubber with a vulcanizing agent, such as sulphur. The resulting components are not the same as in the original mixture. I For this reason, they are classified as thermo-irreversible bonds.

Organic bonds are, in general, of two types; the irreversible and the reversible or thermo-plastic bonds. The irreversible group contains such materials as'urea-formaldehyde and certain phenolaldehyde synthetic resins, and. includes, in particular, some of the irreversible derivatives of the reversible thermo-plasticssuch as phenol and rubber hydrochloride vulcanized with another material such as a halogen compound of sulphur. The other group is identified as the reversible thermo-p'lastics by which it is meant that reheating renders the material plastic within a temperature range used in molding.

This type of bond is exemplifiedby such materials as meta-styrene (a resinous polymer of phenylethylene) and by various reaction products of rubber when used with materials such as the halogens, phenols, and aldehydes.

tough meta-styrol.

This application is particularly concerned with the bonding agent of the reversible type known as metastyrene.

Meta-styrene, a resinous polymer of phenylethylene is produced from the liquid parent substance with the aid of heat or other suitable polymerization agent. The hard glassy resin lends itself readily to plastic molding, especially when used in a powdered condition and rendered plastic at approximately 350 F. The material is considerably ductile when heated and a thread can be pulled out to an extreme length. Bonded abrasive articles have tensile strengths of approproximately 1200 lbs. per sq. in.

Plasticized or modified styrol may be made by any one'of several methods. In general, styrol may be compounded with rubber, gutta percha, balata, and other elastic gums. A preferred practice is to dissolve the rubber or gum, as gutta percha, balata, and the like, in the liquid styrol, (phenyl-ethylene) and polymerize the solutions thus obtained. v

For examplethe gum, such as pale crepe rubber, vulcanized or unvulcanized, is dissolved or swollen in the pure styrol. Polymerization is then brought about, as by heating, to'form a After suitable heat treatment, a solid product results varying in properties'according to the quantity and quality of the gum added. In generaL'the plasticizing gums may be added in amounts of 1 to 10 per cent as desired. Bonded abrasive articles made with modified styrol have shown tensile strengths of 1900 pounds per square inch.

Another example comprises the addition, to as rubber, in a different solvent, such as xylene. This mixtureis polymerized by treatment at for about 60 hours. The solvent may then be removed from the'styrol-rubber mixture by steam distillation or other suitablemethods.

Where good adhesion is required between a pure styrol surface and another surface to which styrol will not adhere readily this polymerized styrol-rubber-xylene solution may be used as a itself priming coating followed by a coating of styrol approximately 275 F.

The resultant product of the plasticizing of styrol gives greater strength and shock resistance than the styrol alone.

By styrol it is understood that homologues are included.

Several methods of making articles in accordance with this invention are possible. The mixture of abrasive grains and bond may be formed into a bonded article by the cold pressed" process whereby the curing of the bond is accomplished subsequent to the compression of the loose mix into the desired shape, or the article may be made by the hot press process in which pressure and heat are applied simultaneously to the mixture of bond and grain.

Modifications of the above general classes of molding may be practised without departing from the spirit of my invention. One of such modifications resides in the manner in which the desired wetness is secured in the mix. Beneficial results are secured'by wetting the grain with the solvent or plasticizer before the binder is added, but it is feasible to mix all of the dry ingredients before the solvent or plasticizer is added.

Variation in the sequence in which the various bond ingredients are added is also within the Particular compositionsof abrading materials.

embodying our invention are given below:

Example I-Hot pressed method 10 parts of pulverized resinous meta-styrene of approximately mesh (to the linear inchl are mixed with parts of abrasive grains of mesh. These materials are moistened with water,

placed in amold, pressed at 2000 pounds per square inch while at 350 F., cooled to about F., and removed from ,the mold in a completed form.

Example II-Cold pressed method with solvent or plasticizer added before binder 1000 grams of 36 mesh crystalline alumina abrasive grain are moistened with 10 cubic centimeters of furfural. 100 grams of a mixture of equal parts meta styrol and a thermally reversible phenolic condensation product resin of the type known to the trade as Novolak" are then added to the moistened grain and thoroughly mixed therewith. The resulting mixture is then placed in a suitable mold, pressed at approximately 2000 pounds per square inch, removed from'the mold, and put into an oven, the initial temperature of which may be about 200 F. The temperature of the oven is then increased at the rate of about 25 F. per hour up to about 350 F. and this temperature is maintained for about 12 hours. The temperature is then reduced in a period of 5-10 hours to about ,F. when the finished article may be removed. 7

Alternatively, the abrasive grain may be moistened with other suitable liquids such as a liquid phenolic condensation product resin of the thermally irreversible type (in which case the resin becomes an intermediate bond) or other respect to the mold proper.

suitable liquid, or other bonds may be substituted for the mixture of meta styrol and solid phenolic resin of this example, such as meta styrol alone,

meta styrol and shellac, meta styrol and coumarone resin, etc.

izromple III-Hot pressed method with intermediets head so grams of the polyhasic acid resin known to the trade as No. 1359 Glyptal are dissolved in 15 cubic centimeters of iurfura'l and this'solution is mixed with lace gra ns of 100 mesh silicon carbide abrasive grains. so grams of metastyrol, which have heeri passed through a loo mesh screen, are then added to the moistened grain and thoroughly mixed therewith. The mixture is placed in a mold and pressed in a hot pressf or conventional type between platens, the temperature of which is raised to 287 F. by the application of to pounds steam pressure. article is pressed at about 20cc pounds per suuare inch until heated throughout when the tempera ture can be reduced to set the bond and the article may be removed from the mold. a

Another method of making a hot pressed article consists in mining the abrasive grain and the bond (metastyrol either alone or mixed with other suitable bond such as shellac or a synthetic resin); heating the mixture until the bond flows, coating the grain; coolina; disintegrating the mix; and pressing the mix while heating as just described Example ZV- fifldldififid hot press method with mified bond 1000 grams of 400 mesh crystalline alumina abrasive grain are mixed with so grams of shellac and 50 grams of metastyrol in powdered term. The dry mixture is placed in a suitable mold and pressed to approximately 1000 pounds per square inch, whereuponqhe movable" part of the mold (the plunger) is clamped into place by a suitable device which prevents motion or the plunger with The clamped mold is then placed in an oven, the temperature of which is maintained at about 300 F., left in the oven until it is thoroughly heated to lose the bond, and then removed. After cooling below the softening point or the bondthe article may be removed. 1

The intermediate bond referred to in the examples provides a convenient method of varying the grindingproperties of the bonded abrasive article. By choosing as the intermediate-bond (for example, in the cold pressedv process illustrated in Example II) a material which adheres readily to abrasive grain, a relatively tough article is secured, while converselythe use of a poorly adherent intermediate bond makes a com-z paratlvely "sow." article. Instead of the liquid resin in Example 11 we may use, for example, a

solution or a synthetic resin or mixture of resins The in a'suitable solvent. So-caued solvent rubber (rubber swollen by a liquid such as bcnzol) an aqueous dispersion of rubber (either natural or artificial), or the metastyrol (either alone or mixed with another suitable bond) may be dissolved and used as the intermediate bond, the main bond (the powder bond) being or any suitable material in all these cases.

ing agents are: the various resins cited in the examples, plasticizers such as dibutyl phthalate or tricresyl phosphate, and inert fillers. such as wood-flour or pulverized flint. Y

The principal features of the invention which are deemed novel are embraced in the iollovring claims.

We claim: c

1. An abrasive article comprising abrasive grains and a bond consisting of metastyrol and a plasticizer.

2. An grains and a resinous bond, said bond containing a major proportion of metastyrol and a minor proportion of a modifying agent.

3.'An abrasive article comprising abrasive a major proportion of metastyrol and a minor proportion of shellac,

abrasiveesticle comprising ahrasive grains and a resinous bond, said bond containing 4. An abrasive article comprising elirasive I grains and a resinous bond, said bond containing amajorproportion oi metastyrol and a minor proportion of a thermally reversible condensation product resin. v

5. An abrasive article comprising coated abrasive grains and a bond containing a substantial proportion of plasticized metastyrol, the coating on the abrasive grains consisting for the most part or synthetic resin. a

6. An abrasive article'comprlsing coated abrasive grains and a bond containing a substantial proportion of plastlcized metastyrol, the coating on the abrasive grains consisting for the most part of heat hardenable resin.

7. An abrasive article comprising coated abra sive grains and a bond containing a substantial proportion of 'plasticized metastyrol, the coating on the abrasive grains. consisting for the most part of a phenolic condensation product resin.-

- 8. An abrasive article "comprising abrasive grainsa d a bond containing a substantial proportion t' plasticlzed metastyrol.

' RAYMOND C. BENNER.

.GARnETr H. roman.