US2272875A - Grinding wheel - Google Patents

Description

Patented Feb. 10, 1942 GRINDING WHEEL Samuel S. Kistler, West Boylston, Mass., assignor to Norton Company, Worcester, Mass., a corporation of Massachusetts No Drawing. Application August 2, 1941, Serial No. 405,242

8 Claims. (01. 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 causes additional curing thereof when heated.

Another object of the invention is to improve an aniline formaldehyde polymer. Another object of the invention is to improve an aniline formaldehyde bonded grinding wheel or other abrasive body.

Another object of the invention is to get an acid to the surface of the work piece being ground without spreading it all over the work piece, thereby increasing the effectiveness of the grinding operation without etching the work piece or causing it to rust or otherwise detrimentally affecting it and without such disadvantages as spraying 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 an aliphatic halo aldehyde and condense them in the presence of a strong acid, and then I modify the condensate with a straight or branched chain halo hydrin as above defined. 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 the aliphatic halo hydrin. From the mixture I mold an abrasive body, press'and heat the whole to a temperature capable of causing further reaction and sumcient to fuse the aniline formaldehyde resin.

The invention contemplatesthe 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, or diamonds.

The invention contemplates the use of any primary aromatic amine. Aniline is the preferred example but I may also use metaphenylene diamine or meta toluidine or diamino diphenyl methane. 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 Hydrochloric acid Phosphoric acid Trichloro acetic acid Dichloro acetic acid Maleic acid Oxalic acid Picric acid Sulphuric acid Hydriodic acid For plasticizing the abrasive'grains I may as aforesaid use furfural or any other suitable plasticizer or none at all. When furfural is used the furyl methylene group substitutes for the 3. Ethylene chlorohydrin H H Cl-JJ-JJ-Oll I I I I 4. Alpha butylene chlorohydrin n n n it 5. Beta butylene chlorohydrin 6. Propylene chlorohydrin n n ll lat (k-(Ln '7. 1,2,amylene chlorohydrin 8. 2,3,amylene chlorohydrin 9. 3,4,amylene chlorohydrin 10. 2 methyl butylene 1,2chlorohydrin cm 11 n c-'( :-cn=

c Cl l I n on 11. 2 methyl, butylene 2,3chlorohydrin cm H on, on c1 12. 2 methyl, butylene 3,4chlorohydrin C'll-CllOll-Cl.'2Cl

Clla

It is to be understood that in most of the above formulae the hydroxyl group and the halogen atom may change places and that in most cases both isomers will be obtained.

When the halohydrin is made from hypohalous acid, the hydroxyl group and the halogen group will be found on adjacent carbon atoms. It will be noted that I have mentioned the chlorine and and raise its heat resistance.

bromine products only. The fluorine compounds are believed to be too stable to alkylate the resin satisfactorily. The iodine compounds can be used in this invention although they are expensive. Accordingly the halohydrins that are useful in my invention are those that contain chlorine, bromine or iodine. I will usually use the chlorine compounds because theyare cheaper and quite as satisfactory.

Aniline,

in the presence of a strong acid, reacts with formaldehyde, HCHO, to produce a long chain polymer, which when an excess of formaldehyde of above the stoichiometric proportions is used, for example 20% excess of formaldehyde, has adjacent chains connected with methylene groups to form a tough, heat resistant, semi-thermoplastic resin. When any one of the halohydrins is added in the polymer formed from aniline and formaldehyde and the mixture is heated to between C. and C., the halohydrln alkylates the aniline formaldehyde attaching itself to the secondary amine groups. When such a resin is used for the bond of a grinding wheel, I find that superior results in grinding can be achieved. The invention has particular utility when embodied in snagging wheels the purpose of which is to clean off the fins, risers, cores and the like 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 the desideratum is to remove as such metal as quickly as possible with a minimum amount of wheel wear. It is my belief that the improved results in grinding with wheels made according to the present invention are due to the release of hydrogen chloride or hydrogen bromide 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 temperature high enough to liberate the acid from the molecule and cause its reaction with metal.

Furthermore, as an added advantage, these halohydrins harden the aniline-formaldehyde 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 halohydrins 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 efliciency of grinding without spraying the work piece generally or the operator or the machine with "acid.

Considering now certain specific examples of the manufacture of grinding wheels in accordance with the present invention, I may proceed as follows:

aavasvs l hydrin be substituted tor the ethylene chloro- Example I Eight hundred and fifty-eight cubic centimeters of aniline is dissolved in eight liters of water containing nine and three-tens 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 ethylene chlorohydrin.

Twenty-eight and one-tenth pounds of a porous, relatively pure grade fused alumina abrasize, No. 20 grit size, is now wet with twentythree hundredths of a pound of iurfural. vF'ive and nine-tenths pounds of the above mixture of aniline formaldehyde resin and the ethylene chloro hydrin are intimately mixed with the fused alumina wet with furiural, spread in an eighteen inch mold with a five inch arbor, and

-hot pressed for one hour and a half at a temperature of 160 C. under a pressure of three tons per square inch. Thewheel is then stripped from the mold.

As conducive to a clearer understanding of the present invention, I believe that .the structural formula of the resin thus produced is as follows:

The above is the modified polymer formed when ethylene chlorohydrin is used. It will be noted that the nitrogen atoms of the secondary amine groups are connected by the ethylene chlo rohydrin. Hydrogen chloride is found attached to some of the secondary amine groups. Other secondaryamine groups have water attached to them. Furyl methylene groups are shown connecting some of the points on the benzene rings ortho to the secondary amine groups. These furyl groups were derived from the furfural used to plasticize the abrasive grain. Naturally if enough furfural is used all of these ortho points will be connected, while if less than the sat urating amount is used, only some of the ortho hydrin approximately the following structure will @t/ I E ,H Cl Thus it will be seenthat if ethylene bromohydrin is used (in sumcient quantity) one-hall. of the secondary amine groups will have hydrogen bromide attached to them and the other half of the secondary amine groups will have elements of of water attached to them. Also in the case of iii) points will be connected. These furyl groups As a'sub example within the general framework of Example I if glycerol alpha gamma dichlorothese last named compounds the connecting halohydrin groups will be branched because the amino groups react with the carbon atoms having halogen attached and also having hydroxyl attached.

These compounds have the property of giving ofi hydrogen chloride (or hydrogen bromide) when heated to a temperature of 500 C. When heated to a temperature tar below that point they no longer give up the hydrogen halide.

. Erample II Thirty-seven pounds of No. 14 mesh fused alumina abrasive is placed in. a mixing pan and wet with five hundred and forty cubic centimeters of furfural. To this are added nine pounds of the resin and halohydrin mixture of Example I and two pounds of cryolite. Further mixing is caused and then the mixture thus produced (which is substantially what is called 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 C. and under a pressure of five hundred tons. Such a wheel will give as good a finish on stainless steelas on 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 plasticity of the mix and provides a better product when hot pressed.

Example III Nineteen hundred and eighty grams of diamino diphenyl methane are dissolved in eight 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 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 amylene chlorohydrin. 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 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:

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 propylene chlorohydrin are added and mixed to produce a dry granular mix. This mixture is spread in an eight inch mold and pressed under a pressure H C! II Cl\ n I -C @rQ s-Q t l H I i I n-cccm CH7CC-H cm on;

H-C-CHa CHa- H H i l 0* N I I EE....9E; 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 six 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 wet with twenty-two cubic centimeters of furfural. To the thus wet abrasive grain is added on hundred and sixty grams of the above powdered resin and fifty grams of ethylene bromo hydrin. 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. tural formula of meta phenylene diamine:

Following is the strucof two hundred tons, then stripped from the mold and the green wheel is baked in an autoclave at a pressure of seven atmospheres at a temperature gradually rising to C. and maintained at this temperature for three hours. The structure of the resin may be represented as 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. After standing for 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 centimeters of furfural. Then one hundred and sixty grams of the above powdered resin and twenty grams of ethylene chlorohydrin 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 Hydriodic acid Tri-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 halohydrins will be used because they are cheaper and give the results. As shown, however, bromine substituted halohydrins may also be used. While I have mentioned specific curing temperatures, it should be understood that any temperature between C. and C. may

be used for curing any of the resins with the halohydrins.

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 of 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 01 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 halohydrin selected from' the group consisting of the chlorhydrins, bromhydrins and iodhydrins.

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 halohydrin selected from the group con sisting of the chlorhydrins, bromhydrins and iodhydrins.

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 halohydrin selected from the group consisting of the chlorhydrins, bromhydrins and iodhydrins.

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 halohydrin selected from the group consisting of the chlorhydrins, bromhydrins and iodhydrins.

5. An abrasive body according to claim 1 in which furyl methylene groups connect some of the benzene rings of the resin polymer ortho to the amino groups thereof.

6. An abrasive body according to claim 2 in which furyl methylene groups connect some of the benzene rings of the resin polymer ortho to the amino groups thereof.

'7. An abrasive body according to claim 3 in which furyl methylene groups connect some of the benzene rings of the resin polymer ortho to the amino groups thereof.

8. An abrasive body according to claim 4 in which furyl. methylene groups connect some of the benzene-rings of the resin polymer ortho to the amino groups thereof.

SAMUEL S. KISTLER.