US2272874A - Grinding wheel - Google Patents

Description

Patented Feb. 10, 1942 2,272,874 ICE GRINDING WHEEL Samuel S. Kistler, West Boylston, Mass, assignor to Norton Company, Worcester, Mesa, a corporation of Massachusetts No Drawing. Application August 2, 1941,

- Serial No. 405,241

7 Claims. (CI. 51-298) The invention relates to grinding wheels and other abrasive bodies bonded with organic bond.

One object of the invention is to provide an improved dry snagging wheel. Another object of the invention is to provide a grinding wheel or other abrasive body which, in various embodiments, may be substituted for abrasive bodies bonded with shellac, rubber, or phenol formaldehyde, and which will remove a greater amount of metal for a given wheel wear.

Another object of the invention is to provide a resin bond for the manufacture of grinding wheels and other abrasive bodies having a chemical reaction with the work piece to increase the abrading action. Another object of the invention is to provide an ingredient for addition to an aromatic amine-aldehyde polymer which causesspraying acid upon the operator, upon the grinding machine, or corroding the coolant pipes or coolant pump. Other objects will be in part obvious or in part pointed out hereinafter.

The invention accordingly consists in the features of construction, combinations of elements, arrangements of atoms, and in the-several steps and relation and order of each of said steps to one or more of the others thereof, all as will be illustratively described herein, and the scope of the application of which will be indicated in the following claims.

I provide a quantity of abrasive grain, a quantity of a primary aromatic amine, a quantity of aldehyde, and a quantity of a monomeric halogen substituted paraffine hydrocarbon with more than one carbon atom and more than one halogen atom, the halogen being selected from the group consisting of chlorine, bromine and iodine. These monomeric halogen substituted parafline hydrocarbons react with the polymer of the aromatic amine and aldehyde by alkylating it or by migration of the hydrogen halide to the polymer or in both of these ways. According to the present invention I take aniline or other primary aromatic amine andformaldehyde or other aldehyde and condense them in the presence of a strong acid, and then I modify the condensate with a halogen substituted parafilne hydrocarbon. Preferably I first produce a polymer from the reaction of one molecular proportion of aniline with between one and three molecular proportions of formaldehyde in the presence of at least approximately one molecular proportion of acid at least as strong as phosphoric acid. .The polymer thus formed is powdered.

I now take a quantity of abrasive grains, plasticize" them with furfural, for example, then add the aniline formaldehyde polymer together with a halogen substituted parafllne hydrocarbon such as any one of hexa chloroethane, tetra chloropentane, 1,2,diiodoethane (ethylene iodide), 0! beta, butylene bromide. From the mixture "1 mold an abrasive body, press and heat the whole to a temperature capable of causing further reaction and suflicient to fuse the aniline formaldehyde resin. As stated, the preferred aromatic amine useful in my invention is aniline, but other primary aromatic amines may be used, for example,

'diamino diphenyl methane, metaphenylen diamine and meta-.toluidirie. The preferred aldehyde used in my invention is formaldehyde and so far as I now know this gives better results than other aldehydes. Secondly, however, I may use furfural to prepare the aromatic amine resin. A distinction must be made between a furfural aromatic amine resin as such and an abrasive body the abrasive grains of which were plasticized with furfural and the bond of which is modified aromatic amine formaldehyde. I find that as a practical matter to facilitate the use of the dry granular'mix method of making abrasive articles, it is quite desirable to plasticize the abrasive grains with furfural. However, within the scope of the invention the amine-aldehyde resin with abrasive grains and halogenated parafline may be hot pressed, thus dispensing with the use of a liquid plasticizer. Furthermore, it is possible to use other liquid plasticizers.

The invention contemplates the use of any type of abrasive grain desired, for example, fused alumina and other kinds of alumina such as emery or corundum, silicon carbide or other hard carbide, quartz, glass, garnet or diamonds.

Aniline,

in the presence of a strong acid, reacts with formaldehyde, HCHO, to produce a long chain polymer which, when an excess of formaldehyde above the stolchiometric proportions is used. for example 20% excess of formaldehyde, has adjacent chains connected with methylene groups to form a tough, heat resistant, se'mithermoplastic resin. When hexa chloroethane,

ci-r c-t-c or tetra chloropentane,

or -l,2,diiodoethane,

IJHLI 1 1 III or beta butylene bromide,

Br Br H Kiwis ttti invention has particular utility when embodied in snagging wheels the purpose of which is to clean oiT the fins, risers, cores and the lik from rough castings and to smooth billets and the like prior to rolling. snagging involves the removal of much metal and usually in snagging operations Y the des deratum is to remove as much metal as quickly as possibly with a minimum amount of wheel wear. It is my belief that a part of the ir'nproved results in grinding with wheels made according to the present invention is due to the release of hydrogen chloride, hydrogen bromide or hydrogen iodide at the grinding line from the bond, caused by the generation of heat at this line, and the reaction of the thus liberated acid halide with the metal of the work piece. It is my theory that the chips of metal clear themselves from the abrasive grains more readily when their adhesion to the abrasive grains is broken by the presence of an acid. It should be noted that the result is accomplished without the use of any liquid acid and, in fact, without any free acid excepting at the'grinding line. At this point alone is the t mperature high enough to liberate the acid from the molecule and cause its reaction with metal.

Furthermore, as an added advantage, many of the halogenated parafilne hydrocarbons harden the aniline formaldehyde and raise its heat resistance. It is highly desirable to provide strong bonds for snagging wheels. However, the invention may frequently be embodied in grinding wheels or other abrasive bodies other than snagging wheels and for some uses a weaker bond may be desired wherefore those halogenated paraflines which may not increase the hardness or thermal resistance of aniline formaldehyde or other aromatic amine aldehyde resins are still useful because hydrogen halide delivered at the grinding line and only at the grinding line increases the eiilciency of grind semen Example 1 Eight hundred and fifty-eight cubic centimeters of aniline is dissolved in eight liters of water containing nine and three tenths mols of hydrochloric acid. To this is added seven hundred and fifty cubic centimeters of formalin solution containing four tenths gram of formaldehyde per cubic centimeter. After standing for one hour, a quantity of sodium hydroxide is added equivalent to the hydrochloric acid present. The precipitated resin is filtered, washed, dried and ground to a fine powder. Into each ten pounds of this powdered resin I mix two and two tenths pounds of tetra chloropentane. This substituted parafiine appears to give somewhat better results than the others. However, in the usual case the compound may not have an exact formula. It may be a mixture of, for example, tri-chloropentane, tetra-chloropentane and hepta-chloropentane, averaging perhaps tetra-chloropentane. Similarly, instead of using the hexa-chloroethane, I may use tetrachloroethane and tri-chloroethane and mixtures of these and compounds averaging such formulae. As stated, I could also substitute ethylene iodide or beta butylene bromide or other similar compounds. Th invention involve the use of a parafiine hydrocarbon, for some of the carbon atoms of which is substituted chlorine and/or bromine and/or iodine and both straight chain and branch chain paraffine derivatives are included. These compounds may be fully halogenated or they may be only partly halogenated. I find that 20% halogen is sufficient to give practical results.

Twenty-eight and one-tenth pounds of a porous relatively pure grade of fused alumina abrasive,

No. 220 grit size, is now wetwith twenty-three hundredths of a pound of furiural. Fiv and nine-tenth pounds of the above mixture of aniline formaldehyde resin and the halogenated parafline are intimately mixed with the fused alumina wet with furfural, spread in-an eighteen inch mold with a five inch arbor, and hot pressed for one hour and a half at a temperature of C. under a pressure of three tons per square inch. The wheel is then stripped from the mold.

As conducive to a clearer understanding of the present invention, I believe that a structural formula of the resin thus produced is as fol- The above is the modified polymer formed when hexa-chloroethane is used. It will be noted that the nitrogen atoms of the amine groups are connected by the hexa chloroethane. Hydrogen chloride is found attached to each nitrogen atom. However, because of lack of sufficient bonds, Nos. 1 and 2 nitrogen atoms may be connected and Nos. 3 and 4 nitrogen atoms may be connected, but Nos. 2 and 3 in such case will not be connected.

It should be understood that alkylation is represented by the connection of nitrogen atoms 1 to2, 3to4,5to 6 ,7to8etce'terabutnot2to3, 4 to 5, or 6 to 7. However, if less than the stoichiometric proportion of the halogenated parafline compound is used (based on the above formula), fewer pairs of nitrogen atoms will be connected by the halogenated parafline hydrocarbon. The compound represented and others like it have the property of giving off hydrogen chloride when heated to a temperature of the order of 500 C. When cooled down far below that point, they no longer give up hydrogen halide.

It will also be observed from the structural formula that occasional pairs of benzene rings are connected with a furyl methylene group. This is derived from furfural which is the aldehyde of furfurane and, furthermore, it is derived from the furfural which is used to wet the abrasive grains. When furfural' issubstituted in whole or in part for formaldehyde for the original condensation process, a furyl group will be found replacing one hydrogen atom'attached to the carbonof some'of the methylene groups con-- nectingthe amino groups to the opposite ring. For example, the following represents a short section of the polymeric structure when furfural instead of formaldehyde is used in the original condensation: C 1

c1- -c1 I H I 0 11/ Cl It will be seen that it is more advantageous to plasticize the abrasive grains with furfural because thereby a number of additional linkages are provided in the polymeric structure, making it stronger. Example II Thirty-seven pounds of 14 mesh fused alumina abrasive is placed in a mixing pan and wet with dive hundred and forty cubic centimeters of fur- .fural.

To this are added nine pounds of the mixture of resin and halogenated paraiilne of Example I and two pounds of cryolite. Mixing is continued and-the mixture thus produced (substantially a dry granular mix) is spread in a sixteen inch mold with a six inch arbor and hot pressed for two hours at a temperature of 160 C. and under a pressure of five hundred tons. Such a wheel will give as good a finish on stainless steel as a rubber wheel but is much more durable.

It may be noted at this point that cold pressing can be resorted to by reason of the plasticizing of the abrasive grains with furfural. However, the results are not as satisfactory as when the hot pressing method is used. Furthermore, the addition of furfural definitely increases the hot pressing.

Example III Nineteen hundred and eighty grams of diamino diphenyl methane are dissolved in eight plasticity and provides a better product when? liters of water containing twenty mols of hydrochloric acid. To this solution is added eight hundred cubic centimeters of formalin solution containing four-tenths gram formaldehyde per cubic centimeter. After standing one hour a quantity of sodium hydroxide is added equivalent to the hydrochloric acid used. The precipitated resin is filtered, washed, dried, and ground to a fine powder.

Eight hundred and eighty-five grams of 60 mesh fused alumina is mixed dry with one hundred and sixty grams of the above powdered resin and forty-nine grams of chlorinated eicosane. This mixture is spread in an eight inch mold and pressed at a temperature of C. under a pressure of one hundred and fifty tons for half an hour. This constitutes a grinding wheel the resin bond of which is hard, tough and heat resistant. This bond likewise during grinding'liberates hydrogen chloride at the grinding line. The structure of such resin bond may be represented as follows:

It will be noted that fully chlorinated eicosane is not shown. Such could be produced but is not readily available. Partially chlorinated eicosane is quite satisfactory for the purpose. Furthermore, the name eicosane has been chosen as the proper chemical name for the product with twenty carbon atoms but the usual commercial variety which can be obtained under the title Chloa'c'osane contains twenty carbonatoms more or less and is probably a mixture of chlorinated high molecular weight paraffines averaging twenty carbon atoms and containing perhaps some molecules with eighteen and some with twenty-two carbon atoms etc. As shown, the chlorine and hydrogen are found more or less at random, there being no particular order of these atoms. The chlorine atoms can and do attach themselves to other chains of the resin and form further linkages. This, however, would be difllcult to show in plan as it is a threedimensional structure.

It is not only the hydrogen chloride directly attached to the nitrogen that is available as acid at the grinding line. At the grinding temperature the entire resin breaks down into charcoal, hydrogen chloride which is present as such, and nitrogen. The chlorine atoms will Join with the hydrogen atoms from any part of the resin,

the nitrogen will be liberated as a gas. and the remainder of the resin is carbon in the form of charcoal which, of course, is practically a powder. Such dissociation of the resin clears the abrasive grains for further grinding. Of course, the abrasive itself gradually wears down and this resin will not go to pieces any faster than phenol formaldehyde, for example. Practically all organic bonds dissociate during grinding. According to this invention such bond contains a considerable quantity of halogen and advantage is taken of the dissociation which inevitably releases hydrogen by causing it to combine with halogen atoms to produce an acid which materially assists the abrasive action in clearing the chips of metal and probably also facilitates the actual cutting.

Example IV Ten hundred and eighty grams of metaphenylene diamine is dissolved in eight liters of water containing twenty mols of hydrochloric acid. To this solution is added sixhundred cubic centimeters of formalin solution containing four tenths gram formaldehyde per cubic centimeter..

After standing for one hour a quantity of sodium hydroxide is added equivalent to the hydrochloric acid used. The precipitated resin is filtered, washed, dried, and ground to a fine powder.

Eight hundred and eighty-five grams of 60 mesh fused alumina is mixed dry with one hundred and sixty grams of the above powdered resin and forty-nine grams of beta butylene bromide,

' CHz-CH-CH-CH:

Br Br This mixture is spread in an eight inch mold and pressed at ,a temperature of 175 C. under a pressure of one hundred and fifty tons for half an hour. This wheel has characteristics similar to the wheels of the other examples.

The following is the structural formula of meta phenylene diarnine:

The structure of the brominated resin is as follows w centimeters of furfural.

O H -O);ZZ H M /O U 2. .i. .l

Hydrobromic acid is liberated at the grinding line.

Example V Nine hundred and thirty grams of aniline and two liters of water containing eleven mols of hydrochloric acid are mixed with six hundred and seventy cubic centimeters of furfural and heated to 80 C. overnight. The solid mix resulting is ground and suspended in water containing sodium hydroxide equivalent to the hydrochloric acid used. After neutralization is complete, the powder is filtered, washed and dried.

Eight hundred and eighty-five grams of 60 mesh fused alumina is first wet with thirty cubic centimeters of furfural. Then one hundred and sixty grams of the above powdered resin and twenty grams of ethylene iodide are added. This mixture is spread in an eight inch mold and pressed under a pressure of two hundred tons. It is then stripped from the mold and the green wheel is baked in an autoclave under a pressure of seven atmospheres at a temperature gradually rising to 175 C. and maintained at this temperature for three hours. The structure of the resin may be represented as follows:

CH: CH:

EXAMPLE VI Ten hundred and seventy grams of meta toluidine are dissolved in eight liters of water containing ten and two tenths mols of phosphoric acid. To this solution is added seven hundred and fifty cubic centimeters of formaldehyde solution containing four tenths of a gram of formaldehyde per cubic centimeter. one hour, a quantity of sodium hydroxide is added equivalent to the phosphoric acid used. The precipitated resin is filtered, washed, dried and ground to a fine powder.

Eight hundred and eighty-five grams of 60 mesh fused alumina is first wet with thirty cubic Then one hundred and sixty grams of the above powdered resin and twenty grams of tetra chloropentane are added and mixed to produce a dry granular mix. This mixture is spread in an eight inch mold and pressed under a pressure of two hundred tons at a temperature of C. for one hour. It is then cooled and stripped from the mold, and is found to be a grinding wheel of superior quality.

Interpreting the foregoing diagrams, it must be understood that an approximate condition is what is illustrated. It would be impossible to illustrate all of the linkages. Furthermore, for an absolutely accurate representation a three-dimensional structure would have to be shown.

For the acid used in condensing the resin, be-

After standing for sides hydrochloric and phosphoric, the following acids may also be used:

Hydriodic acid Trl-chloro acetic acid Di-chloro acetic acid Maleic acid Oxalic acid Picric acid Sulphuric acid The requirement is that the acid should be at least as strong as phosphoric acid to give the best results.

Every example of the invention constitutes abrasive grains bonded with a halogenated primary aromatic amine-aldehyde resin. Usually the chlorinated paraiflne hydrocarbons will be used because they are cheaper and give the results. As shown, however, iodine substituted and bromine substituted paraffines may be used. Fluorine compounds are rejected because they are too stable, and therefore will not alkylate.

I always use a parafline derivative from ethane up, that is, having two or more carbon atoms, and there should be at least two halogen atoms substituted for hydrogen in this hydrocarbon. It should be understood that the substituted paraffines may attach to the amino groum at carbon atoms other than (as well as) the end carbon atoms. In the diagrams of structure, straight chains have been shown but branched chain parailine derivatives can be employed. In fact,

commercial Chlorcosane (which I have used) contains branch chains. While I have mentioned specific curing temperatures, it should'be understood that any temperature between 130 C. and 190 C. may be used for curing any of the resins with the halogenated parafllne.

It will thus be seen that there has been provided by this invention a composition of matter, an article of manufacture, and an art in which the various objects hereinabove set forth together with many thoroughly practical advantages are successfully achieved. As various possible embodiments might be made or the mechanical features of the above invention and as the art herein described might be varied in various parts, all without departing from the scope of the invention, it is to be understood that all matter hereinbefore set forth is to be interpreted as illustrative and not in a limiting sense.

I claim:

1. An abrasive body comprising abrasive grains bonded with the condensation product of one molecular proportion of primary aromatic amine and between one and three molecular proportions of aldehyde selected from the group consisting of formaldehyde and furfural, condensed in the presence of at least approximately one molecular proportion of acid at least as strong as phosphoric acid and reacted by heating at resin curing temperatures with a monomeric halogen substituted parafiine hydrocarbon with more than one carbon atom and more than one halogen atom, the halogen being selected from the group consisting of chlorine, bromine and iodine.

2. An abrasive body comprising abrasive grains bonded with the condensation product of one molecular proportion of aniline and between one and three molecular proportions of aldehyde selected from the group consisting of formaldehyde and furfural, condensed in the presence of at least approximately one molecular proportion of acid at least as strong as phosphoric acid, and reacted by heating at resin curing temperatures with a monomeric halogen substituted parafiln hydrocarbon with more than one carbon atom and more than one halogen atom, the halogen being selected from the group consisting of chlorine, bromine and iodine.

3. An abrasive body comprising abrasive grains bonded with the condensation product of one molecular proportion of primary aromatic amine and between one and three molecular proportions of formaldehyde, condensed in the presence of at least approximately one molecular proportion of acid at least as strong as phosphoric acid and reacted by heating at resin curing temperatures with a monomeric halogen substituted parafline hydrocarbon with more than one carbonatom and more than one halogen atom, the halogen being selected from the group consisting of chlorine, bromine and iodine.

4. An abrasive body comprising abrasive grains bonded with the condensation product of one molecular proportion of aniline and between one and three molecular proportions of aldehyde consisting at least in part of formaldehyde, condensed in the presence of at least approximately one molecular proportion of acid at least as strong as phosphoric acid, and reacted by heating at resin curing temperatures with a monomeric halogen substituted parafflne hydrocarbon with more than one carbon atom and more than one halogen atom, the halogen being selected fromthe group consisting of chlorine, bromine and iodine.

5. An abrasive body according to claim 1 in which the halogen substituted parafline body is a poly chloroethane.

6. An abrasive body according to claim 1 in which the halogen substituted parafllne is a poly chloropentane.

'7. An abrasive body according to claim 1 in which the halogen substituted parafllne hydrocarbon is approximately a poly chloroeicosane.

SAMUEL S. KISTLER.