US3214378A - Composition for magnetic particle testing - Google Patents

Description

Oct. 26, 1965 4 R. G. HANNEMAN 3,214,373

COMPOSITION FOR MAGNETIC PARTICLE TESTING Filed Sept. l, 1960 Unted States Patent O 3,214,373 CQMPOSITIN FR MAGNETEC PARTTCLE TESTNG Robert Gorden Hannernan, Newbury, Ohio, assigner to The RGH. Company, Inc., Cleveland, Ohio, a corporation of Ohio Filed Sept. 1, 196i), Ser. No. 53,468 1 Claim. (Cl. 252-625) The present application is a continuation-in-part of my copending application Serial No. 502,967, filed April 21, 1955, now abandoned.

This invention relates to a method and compositions for magnetic particle testing.

The presently accepted method for magnetic particle testing is set forth in the Report of the Iron and Steel Division of the Society of Automotive Engineers, adopted January 1941 and revised January 1942. Also see, Military Specification, Inspection Process, Magnetic Particles, MIL-l-6868A, Nov. 6, 1952. As usually practiced, a iine magnetic oxide dispersed in an oily medium is mixed with a light oil to make an inspection. This oxide dispersed in the oily medium is commonly known as No. 7 Black Paste or sometimes by the proprietary name Magnaux paste. The recommended suspensoid is a petroleum distillate of 46 degrees Baume and 4l seconds viscosity (Saybolt) or a maximum of 5.0 centistokes. In the absence of an oil of this character, kerosene is a satisfactory substitute. There is a trend in the aircraft industry to use a lighter suspensoid such as Stoddard solvent. The paste is suspended in the light oil to amount of l or 2 percent solids in the oil. This vehicle or oil bearing the magnetic substance is sprayed or poured over the test piece While the latter is subjected to a suitable direct current of electricity or magnetic field.

A disadvantage of the presently used method is that the oil and grinding assistants in the paste when diluted with the vehicle and spread over the test piece will not evaporate clean and residues are left on the tested specimen which oxidize to a gum. This condition is aggravated by the action of the iron oxide particles to the point where it is almost impossible to remove the residue of the testing process without mechanically scrubbing the specimen in the presence of very strong cleaners. Also, as the suspensoid oil becomes used, particles tend to agglomerate in the machine causing the eciency to drop and causing the machine to plug up so that periodic shut downs occur.

A greater problem than the removal of the above described formation of gum is the removal of the iron oxide particles from the test specimens which have been pressed to the surface by the magnetic force applied thereto as a part of the testing and the resulting rust and corrosion from these particles being in intimate contact with the specimens. In the present invention, the removal of an iron oxide particle with a protective hydrophilic/lipophobic jacket and yet the particle is kept from flocculating with other particles. This jacket can then be removed by water or other solvents which destroys the bond holding the particle to the test piece.

Therefore, the present invention provides a means of removal of the iron oxide particles after testing as well as a means of easily removing the gum formation on the test piece surface.

An object of the present invention is to improve the process of magnetic particle testing so that the tested specimen is readily washed clean after the testing process is concluded. This consists in treating the magnetic oxide with an additive which reduces the interfacial tension of oil against water to a very low degree (approximately 2 dynes per centimeter) and to assist in reducing later oxi- 3,2%,378 Patented ct. 26, i965 fzce dation effects; plus an additive for promoting the oil-water phase transfer and to assist in the oil dispersion; plus a protective colloid to supply a Water soluble film or insulating means between the particles of magnetic iron oxide and the part being tested.

A second main step in the method is the treatment of the suspensoid with additives to lower the surface tension and to aid in emulsification when the specimen is washed after testing and to assist in suspending particles While testing and to permit a large amount of water to be added without occulations of magnetic oxide or effecting the testing procedures.

As a third step, the pre-treated magnetic oxide paste and the pretreated suspensoid oil are then mixed together in the proper proportions to make my improved test solution.

A fourth main step in the method, when water is to be used as a cleaning means, is the use of a soaking means to displace and absorb oil remaining on the part tested as Well as on the particles, and to replace it with a water soluble soap. The part may be placed in the soaking liquid while wet with the suspending oil or it may be preferably allowed to dry. This step permits the part to be rinsed clean with water without additional cleaning compounds or mechanical scrubbing.

The drawing shows in diagrammatic form the various steps involved in forming my improved test solution.

The ingredient which I have numbered Iii on the diagram and called magnetic oxide paste may be that which is used in the S.A.E. standard test and known as No 7 Black Paste. This material consists of a line magnetic oxide dispersed in an oily medium which, when mixed with a light oil to make up an inspection bath, shall maintain a satisfactory suspension and must not tend to agglomerate rapidly in suspension. A dispersing agent is incorporated to prevent agglomeration and to disperse the particles in suspension in the oil. The magnetic oxide employed shall consist of at least 85 percent magnetic oxide of iron. The material in paste form shall contain at least percent of solid oxide of iron.

In place of the above, I may take a tine magnetic oxide powder dispersed in oil to a heavy paste consistency and incorporate the ingredient which I have marked 11 on the diagram and indicated there as an additive reducing interfacial tension.

The ingredient which I have marked 11 on the diagram is indicated there as an additive reducing interfacial tension. This is a chemical added to reduce the interfacial tension of the oil against the water in the nal mixture to a very low degree, preferably, 2 dynes per centimeter or less. This also assists in reducing oxidation which normally causes the test material residue to become a varnish-like gum on the specimen. This ingredient 11 may be a proprietary substance sold by Commercial Solvents Corporation and known as Alkaterge-C. This I believe to be a substituted oxazoline with an oxazole content of about 70 percent by weight. I may also use, for this ingredient 11, di(2ethyl hexyl) amine hydrochloride which is sold by Carbide & Carbon Chemicals Company. Sometimes I may -omit ingredient 11 Where the amines in ingredient 15 are suicient to reduce the interfacial tension.

The ingredient which I have marked 12 on the diagram is indicated as an additive promoting oil-Water phase transfer. This is an oil-water soluble quarternary ammonium salt to assist the 0il-water phase transfer and to assist in the oil dispersion. My tests indicate that ionic and non-ionic wetting agents could be mixed with the oil-wetted magnetic oxide paste, but only certain wetting agents in particular quantities give the desired dispersion in the suspending oils. The preferred salt for this purpose is dialkyl-dimethyl ammonium chloride with the alkyl group having about 8 to 18 carbon atoms.

In making the above additions, I take ten parts of ingredient 12 to one `part `of ingredient 11 and mix these together completelyA with 80 or 90 parts of the magnetic oxide and oil paste. The proper combination of materials and mixing time is determined by a resulting stiff consistency following a semifluid state of the material. Also I may add, during the mixing, if desired, a suicient amount of water soluble cellulose solution as a protective colloid. Such water soluble celluloses are methyl cellulose, carboxy methyl cellulose, carboxy methyl hydroxy ethyl cellulose, and the like.

The mixing time for the ingriedients 10 plus 12 or 10 plus 11 plus 12 was determined by observation of the ease of complete dispersion of the mixture in oil and in water. The point of complete mixing of these ingredients 10, 11 and 12 was indicated as that point at which the mixture would go into good dispersion in either oil or water quickly. However, in dening the suspension in water, it should be understood that this is not a complete suspension of the individual magnetic oxide particles in the water but the suspension of very small loosely formed groups of particles sized at the same level of particle size as that of the dialkyl-dimethyl ammonium chloride compound when it is added to oil at 60 degrees F. and given the same agitation.

The additions to the suspensoid oil, now to be described, were selected with various considerations in mind. For instance, it was desired to build a soft jacket around the magnetic oxide particle to keep it from being locked to the tested part by the action of the magnetic eld during testing, and to have a water soluble layer under the particle before, during and after the suspending oil had dried. The additive to the suspensoid oil was also regarded as a means for keeping the particles de-occulated and as a means of achieving instant water dispersions whether the particles were still wet with oil or after the particles had dried.

. It was felt that certain amides and amide soaps could be used for this jacket material, especially those that were non-drying in nature, and it was also felt that glycols might help. However, the problem was complicated by the fact that (a) occulation must not occur in the suspension; (b) mixture must be stable; (c) particle flow should not be impeded; (d) the iron oxide particle settling rate must be almost the same as for iron oxide particles in plain oil; and (e) the cost must be moderate.

The vegetable gums were considered and tried but it was found that by themselves, they were worthless, but when used with the finally selected mixture, there were some advantages.

From the evidence of my tests, it was indicated that something having very great particle wetting or dispersive qualities was needed as well as a material to maintain the desired de-flocculation, and a material that would readily allow wetting by oil Vor, water. Tests using various wetting and dispersing agents indicated to me that a balanced combination of anionic, nonionic, cationic materials with the proper hydrophilic/ lipophobic characteristics would be needed. I have found out that the combination of ingredients 13, 14 and 15 as subsequently disclosed herein, was the wetting agent desired and ingredient 16 would take care of the de-occulation. The right amount of ingredients 13 plus 14 plus 15 on the one hand and of ingredient 16 on the other was determined by observing the reaction of these ingredients in the presence of suspensoid oil. The balance point was selected as that which (a) did not cloud the mixture; (b) did not increase the viscosity; and (c) did not cause granulation salting out or instability. This proper ratio is hereinafter disclosed.

The additions to the suspensoid oil are made in several diiferent steps. The ingredient which I have marked 13 on the diagram is indicated as alkyl aryl sodium sulfonate.

The ingredient indicated on the diagramas 14 is there marked alkylated phenol-l-ethylene oxide. This is actually a reaction product of the alkylated phenol plus ethylene oxide. The preferred products for ingredient 14 Iare alkyl phenoxyl polyoxyethylene ethanol or alkyl aryl polyether alcohol.

The ingredient indicated at 15 on the diagram is there designated amine soap. This is an additive for lowering the surface tension and for promoting emulsification. For this ingredient 15 I may use a reaction product of triethanolamine and lauric or oleic. For this ingredient 15 I may also use the reaction product between potassium hydroxide and oleic or lauric acid.

The ingredients 13, 14 and 15 are taken in approximately equal amounts, or I have had good results using the proportions of 2 parts of 13 to one part of 14 to 2 parts of 15. In either case, the ingredients 13, 14 and 15 are mixed and caused to combine and react at a temperature 174 degrees F. or slightly higher, and allowed to pre-cipitate or settle and the precipitate discarded.

For ingredient 16, I use the same ingredient as indicated at 12. 4This as mentioned before is dialkl dimethyl ammonium chloride. I take 57 to 59 percent of ingredients 13 plus 14 plus 15 reacted together, and combine them with 43 to 4l percent of ingredient 16 at approximately degrees F.

Preferably, but not necessarily, I next add sufficient higher fatty acid such as oleic acid or lauric acid to lower the pH of the mixture to 6.5.

The suspensoid oil indicated as ingredient 17 on the diagram may be one of several similar oils. It may be the standard recommended by the S.A.E., namely, on oil of 46 degrees Baume by American Petroleum Institute Standards, 4l seconds viscosity (Saybolt), 165 degrees F. ash point (Tagliabue Open Cup), distillation having an initial point of 390 degrees F. and end point of 490 degrees F. and color 25 on the Saybolt chromorneter. As mentioned previously, it might also be Stoddard solvent. Or it may be a mineral oil such as S.A.E. No. 5 or Sohio Tek No. l5. In any case, I use approximately 97 to 95 percent of the suspensoid oil, ingredient No. 17 on the diagram, and 3 to 5 percent of the additive mixture described above.

The modified suspensoid oil is then thoroughly mixed with the magnetic particles plus their additives 11 and 12 and previously described to make the test solution indicated at 18. This test solution is then flowed over the specimen to be tested while the specimen is subjected to a direct current of the proper amperage or strong magnetic eld.

The tested specimen may then be cleaned in a standard vapor degreaser or further steps of my invention may be utilized to aid in iinally cleansing the specimen.

The soaking or cleaning step will next be described. This is the point in my process where one of several methods might be used. For instance, (l) the oil might be incorporated in or become a part of a soap, or (2) the oil might be displaced or emulsied by Water and a detergent, or (3) the oil might be coupled with the water by means of an alcohol or other coupling agent, or (4) the oil might be eliminated from the tested piece and the associa-ted magnetic oxide particles by a combination of (1) and (2), or (5) a combination of (l), (2) and (3). mentioned herein. For practical reason-s, the 4th solution was Selected.

The reasons for this choice were: (a) the cost of the material, (b) the conditions of the suspensoid oil remain-` ing on the tested part are never the same in any two operations since more or less draining and drying time is allowed and this will vary the amount of oil to be replaced or otherwise moved or changed, (c) the single agents mentioned in (l), (2) and (3) above are not quite as good as a slightly unstable combination of these agents for the accomplishment of the cleaning tasks due to the short cleaning time allowance usually encountered in a production testing operation, and (d) the use of these multiple agents allows selective work to be done, namely, coupling the oil to a detergent and water combination, making a soap with the oil, and replacing and enlarging the particle jacket as pre-formed in the testing solution, with a completely water soluble covering. The agen-t indicated at (l) above for incorporating the oil in a soap, in my preferred form, is oleic acid plus an amine or other powerful emulsifying soap. The agent (2) above for displacing the oil by use of water and a detergent is the ingredients 13 plus 14 plus 15, mixed together as described previously. The agent (3) mentioned above may be diethylene glycol monoethyl ether, diethylene glycol monoethyl ether, or a combination of both for coupling the soap to water. This has a flash point of approximately 205 to 240 degrees F. and is a mutual solvent for all of the materials used in my process.

This preferred cleaning step comprises soaking the tested specimen for one to three minutes in a specially prepared bath utilizing approximately 1 pound of ingredients 1 3 plus 14 plus 15 as mixed together and previously described, plus 1 pound of either form of ingredient 15, namely, the reaction product of triethanolamine with oleic Or other f the fatty acids mentioned above, or potassium hydroxide reacted with oleic acid as mentioned in connection with ingredient 15. To this mixture I add 18 grams of alkaline builder such as sodium pyrophosphate or sodium carbonate or trisodium phosphate and these materials are added to each gallon of water in the soaking bath preferably maintained at 160 to 180 F. for more rapid action. After the one to three minute soaking period, I prefer to rinse the specimen utilizing the previously described mixture of ingredients 13 plus 14 plus 15 at the rate of one part to 8000 to 12,000 parts of water which will then have a surface tension of about 34 dynes per sq. cm. so that the test piece can be dried without Water spotting.

Preferably, for economic reasons, the specimen should be dry before cleaning, but my cleaning process will operate Well in any case.

The advantage of using my invention over the previously used standard procedure of the Society of Automotive Engineers results in (l) better dispersion of the magnetic particles, (2) easier addition of the magnetic particle paste to the suspensoid oil, (3) elimination of clogging of equipment, (4) longer lasting suspension of the magnetic particles in the oil, (5) aids in the better wetting of the tested specimen as the test solution Hows over it, and therefore an oil with greater viscosity and higher flash point can be used with no sacrice in etdc-iency, (6) improves the travel of the magnetic particles to faults or cracks in the specimen, (7) improves the cleaning of the tested specimen by either a vapor degreaser or by water or by oil, (8) reduces the oxidation of the suspensoid oils during and after use, (9) reduces cleaning time for the specimen and eliminates approximately two-thirds of the cleaning of the testing machine, (l0) inhibits rusting of the specimen, (11) produces a cleaner specimen part after the operation is completed, and (l2) improves the action of a vapor-degreaser if such is used.

The following example Iillustrates the preparation of my additive for a suspensoid oil, the coating of iron `oxide particles to form an iron oxide paste and the use of the additive and paste in preparing a Itest solution for detecting flaws in metal articles.

Example A magnetic iron oxide paste `component `for a test solution for magnetic particle testing was prepared by adding and mixing parts by weight of a dialkyl dimethyl ammonium chloride and one part by weight of a substituted oxazoline with an yoxazole content of about 70 percent by Weight with 85 parts by weight of No 7 Black Paste,

Alkyl Groups No. of Car- Percent by bon Atoms Wt.

8 8 10 9 Dodecyl 12 47 Tetradecyl. 14 18 Hexadeeyl 16 8 Octadecyl 18 l0 The substituted oxazoline, added to reduce interfacial tension of the lm of oil around the iron oxide particle against Water in the final mixture to be described later, was a nonvolatile cationic surface active agent having a specic `gravity at (25/ 25 C.) of 0.92 to 0.93, a nitrogen `content (Kjeldahl) of 3.8 to 4.11%, a color on the Gardner scale (19233) of 15 maximum, a viscosity of 25 C. of 122 centipoises, an oxazoline content of 70 percent and a molecular weight of approximately 350. A suitable oxazoline (2methyl4,4dioctyl-2-oxazoline), having the above desired properties, may be prepared by reacting approximately equal moles of 2-amino-2-dioctyl-l-undecanol and acetic acid. The above ingredients, the quaternary ammonium salt, the substituted Ioxazoline, and magnetic particles were mixed by grinding in a ball mill for about 5 minutes at room temperature until the resultant treated particles could be dispersed quickly into either oil or water. This dispersing quality 'was checked by taking a small aliquot portion of the mixture and checking its dispersion at about 2 percent by Weight in both oil and Water solutions.

In mixing the quaternary ammonium salt, the substituted oxazoline, and the magnetic particles, 'other equipment and mixing times may `be used to thoroughly disperse the same. By grinding the ingredients in a mill, Iusually only 3 or 4 minutes are necessary; by paddle mixing at high speeds, generally from about 8 to 48 hours are required.

An additive for the suspensoid oil was prepared by mixing y2 parts by Weight of decyl benzyl sodium sulfonate, one part of a nonionic surfactant which is: a reaction product of one mole of octyl phenol and three moles of ethylene oxide, and two parts by weight of an amine soap which is a reaction product of about equal moles of triethanol amine and lauric acid. After the three ingredients, correspondingto ingredients 13, 14 and 15 in the ilow sheet, were mixed, the mixture was` heated with intermittent stirring to a temperature of 174 F. for 3 hours to cause a reaction between the three ingredients. The reaction batch was cooled. A precipitate formed and was allowed to settle and then ltered. The liquid filtrate was then used as a major portion of the additive for the suspensoid oil.

To `complete preparation of an additive for the suspenlsoid oil, 58 parts `by weight lof the above described reaction product of 13, 14 and 15 were mixed with 42 parts by weight of the same dialkyl dimethyl ammonium chloride described in preparing the magnetic oxide component. The above ingredients were mixed at F., the liquid mixture :becoming slightly turbid `but quickly clearing with no other indication of a reaction evident.

A suspensoid loil (ingredient 17 on the flow sheet), the same oil used in the magnetic oxide paste, and having a F. ash point (Tagliabue Open Cup), va viscosity of 41 seconds and a Baum of 46 degrees was used to suspend the oxide particles in the testing solution. Four parts yby weight of the above described liquid mixture of ingredients 16 and the reaction product of 13, 14 and 15 were -added to 496 parts yby weight of the s-uspensoid oil to provide a modified suspensoid oil component. Three parts :by `weight of oleic acid was added to the modiiied suspensoid oil to bring the pH down to about 6.5.

One part of the magnetic oxide paste component and 99 parts 'by IWeight of the modified `suspensoid oil were thoroughly mixed to provide a test solution. The resultant test solution was used to check metal surfaces for daws and cracks by the magnetic particle testing technique as set forth in the Rep-ort of the Iron and Steel Division of The Society of Automotive Engineers, adopted January 1941 and revised January 1942 in which the solution is poured over the test piece while the piece is subjected to a strong magnetic held. The test solution was excellent in all respects, the magnetic oxide particles remained deooculated during the test and were removed easily from the test pieces and did not clog the machine.

ySeveral test pie-ces lwere checked, one of which was cleaned in a vapor degreaser employing trichlorethylene. Another test piece `was thoroughly and easily cleaned by soaking the piece in a bath of 1 part by weight of the reaction product of 13, 14 and I15 and 1 part by weight of ingredient 15 (the reaction product of triethanol amine and lauric acid), 0.04 part yby lweight of sodium carbonate and 8.3 parts by weight of water. After soaking in the above bath, the test piece was rinsed in a bath of 1 part of the reaction product of 13, 14 and 15 in 10,000 parts of water.

In the above example, .good results can be obtained by using Arquad 2C, a dialkyl dimethyl ammonium chloride having alkyl groups of 8 to 18 carbon atoms, sold by Armour and Company, Chicago, Illinois, as the ingredients y12 and `16. Likewise, the particular dialkyl dimethyl ammonium chloride used in the example can be substituted for in whole or part by other water insoluble dialkyl dimethyl ammonium chlorides having alkyl groups of about 8 to 18 carbon atoms suc-h las octyl, nonyl, decyl, dodecyl, tetrad-ecyl, hexadecyl, octadecyl, octadecenyl, and iso octyl including 'Z-ethyl hexyl. Als-o, the substituents yon the disubstituted dimethyl ammonium chlorides may also include in addition to alkyl groups, other aliphatic hydrocarbon groups such :as alkenyl groups having about 8 to -18 carbon atoms and groups sometimes termed coco which are derived from coconut oil and Ialso have 8 to 18 carbon atoms in their molecular chain.

Surprisingly, however, the above quaternary ammonium chloride is the only cationic wetting agent that can be used in the present invention, it having been found that other wetting agents including mono-alkyl trimethyl ammonium chlorides upset the delicate physical and chemical balance :of the system and deocculation of dispersed magnetic-oxide particles cannot be maintained. In addition dispersal of the magnetic oxide particles and their subsequent complete removal also cannot be accomplished.

In the above example and, in particular, the preparation of the reaction product of ingredients 13, 14 and 15; other alkyl phenol/alkylene oxide reaction products can be substituted in whole or part for the octyl phenol/ ethylene oxide reaction product used. Suitable alkyl phenol/ethylene oxide reaction products are those prepared by reacting preferably about one equivalent weight of octyl phenol or other alkyl phenols having about to 14 carbon atoms including pentyl phenol, hexyl phenol, 2-ethy1 hexyl phenol, nonyl phenol, decyl phenyl and duodecyl phenol with about 2 to 12 equivalent weights of ethylene oxide. In some cases, while it is preferred that ethylene oxide be used, and be the major portion of the alkylene oxide component, part or even all of the ethylene oxide may be substituted for by propylene oxide; in a similar manner, at least a minor portion of the alkylene 8 oxide may be propylene oxide-1,2; propylene oxide-1,3; or butylene-1,4-oxide.

Again referring to the reaction product of ingredients 13, 14 and 15, the reaction product (15) of triethanol amine and lauric acid may be substituted in whole or part by another water soluble amine soap such as the reaction product of (l) about one equivalent weight of a basic -component such as an alkali metal hydroxide including sodium hydroxide, potassium hydroxide, ammonium hydroxide, an amine compound containing an oxygen atom as an ether atom or Ias an :atom in a Ihydroxyl group such as triethanol amine, diethanol amine, monoethanol amine, and other amino hydroxy compounds having an amino group, a hydroxyl group, three to four carbon atoms and a molecular weight preferably between 89 and 106 including 2amiuo-lbutanolg and 2-amino-2- methyl-l-propanol with (2) about .9 to 1.1 equivalent weights of an aliphatic hydrocarbon acid having about 3 to 18 carbon atoms such as saturated aliphatic acids including propionic, n-butyric, valeric, caproic, caprylic, capric, lauric, myristic and palmitic and unsaturated aliphatic hydrocarbon acids inclu-ding undecylenic, linoleic, linolenic, and oleic. Surprisingly, stearic acid, a saturated aliphatic acid having 18 carbon atoms does not Work while oleic acid with 18 carbon atoms does work. However, stearic acid reacts with an amine to form a Iwater insoluble salt and is therefor unsuitable for use as an aliphatic acid for reaction with a base to prepare the necessary Water soluble amine soap.

AS previously indicated, ingredient 15 may also be di(2- ethyl hexyl) amine hydrochloride or other dialkyl amine hydrochloride having preferably alkyl groups of about 6 to 10 carbon atoms such as hexyl, octyl, nonyl and decyl.

Continuing to describe the reaction product of 13, 14 and 15 and, in particular, the ingredient 13, other alkyl aryl sodium sulfonates such as dodecyl benzyl sodium sulfonate, polypropyl benzene sodium sulfonate, octyl benzyl sodium s'ulfonate, tetradecy'l benzyl sodium sulfon- :a-te, and octadecyl benzyl sodium .salt are useful and are the preferred substitutes. Also suitable for use as ingredient 13 are alkali metal salts of sulphonic acids derived from petroleum sources and having an average molecular weight of generally about 250 to 750 and preferably about 400 to 520. In general, while the ysodium salt is preferred, alkali metal soaps of potassium are of some use in the present invention.

The sulfonic acids used to form the alkali metal soap may be derived from either petroleum or alkyl aromatic acids. Suitable alkyl aryl sulphonic acids are polypropyl benzene sulfonic acid, didodecyl toluene sulfonic acid, octadecyl naphthalene sulfonic acid and octadecyl benzene sulfonic acid. As previously indicated the alkali metal soaps of these acids may have an average molecular weight of about 250 to 750.

The above described reaction product of ingredients 13, 14, and 15 is preferably prepared by reacting two parts of 13 to one part of 14 to two parts of 15, although good results are obtained using equal amounts of all these ingredients. Also suitable are the ranges of 2O to 60 parts by weight of 13, 10 to 50 parts by weight of 14, and 20 to 60 parts by weight of 15. Likewise, while the preferred temperature of the reaction is about to 185 degrees, temperatures of 15() to 200 degrees may be used if the reaction is not prolonged at the higher temperatures, say for more than 2 hours and, also, if the time of reaction is extended to 5 to 8 hours at the low temperature. In any event, the resultant product has been found to be anionic in nature so that, surprisingly, even where it is mixed with a cationic wetting agent ('16), it provides unusual results.

While it is not completely understood, the major portion and preferably about 2/3 of the reaction product is anionic while the balance, usually about l or in the range of 1A to 2/s lof the product, is nonionic, apparently some of the nonionic portion of the starting ingredients remaining unchanged.

While the reaction product of 13, 14 and 15 was combined with ingredient 16 at 120 F. in the example, the same can be mixed effectively at a temperature preferably above normal room temperature, say 90 F. to a temperature of as high as 180 F. before a reaction occurs between the two components-one anionic and one cationic-and renders the mixture useless in the present invention.

Just after adding the above amonio-cationic mixture to the suspensoid oil, the pH of the former is lowered to about to 7 and preferably 6.4 to 6.8 with a long chain aliphatic fatty acid having about 6 to 24 carbon atoms that is compatible with the hydrocarbon materials above described. While oleic acid is preferred to adjust the pH, other aliphatic acids such as hexyl, decyl, lauric, stearic and palmitic may be used. While acid materials such as hydrochloric acid, acetic acid etc. could drop the pH of the mixture, the resultant suspensoid oil would not keep the magnetic oxide particles deflocculated.

Further considering the mixture of the anionic reaction product of 13, 14 and 15 and the cationic dialkyl dimethyl `ammonium chloride (16), the preferred amounts of each ingredient are 57 to 59 parts by weight of the reaction product and 41 to 43 parts of the quaternary ammonium chloride although generally about 55 to 65 parts of the reaction product can be mixed with 35 to 45 parts of the chloride to provide a satisfactory modifying component for the suspensoid `oil. When the above ranges ingredients are used, generally from about 1 to 10 parts of oleic acid are used to acidify 100 parts of the modifying additive mixture to balance the same.

In the above example, referring to the magnetic oxide paste component, other substituted oxazolines may be employed. Suitable substituted oxazolines are Z-rnethyl- 4,4-dialkyl-2-oxazoline in which the alkyl radical has from about 1 to 10 carbon atoms such as methyl, ethyl, propyl, hexyl, octyl, nonyl and decyl although alkyl groups of 7 to 9 are highly preferred unless the methyl group on the 2 position is substituted for by a higher alkyl group, preferably ethyl or propyl so that the molecular weight of the oxazoline is preferably about 325 to 375.

Also referring to the oxide particle component, generally about 1 to 20 parts by weight of dialkyl dimethyl ammonium chloride are used -per 80 to 99 parts by weight magnetic oxide particles. Likewise, about .l to 3 parts by weight are used with the above amounts of oxide particles and chloride. In general then the above oxide particle mixture, moistened with about 3 to 20 parts by weight of oil, is used in an amount of generally 1/10 to 5 parts and, preferably 1/2 to 2 parts, by weight per 95 to 99 9/10 parts by weight of the modified suspensoid oil previously described.

In turn, as previously indicated, the modified suspen- 10 soid oil is made by using to 991/2 parts by fweight of the oil and about 1/2 to 10 parts (and preferably 3 to 5 parts) by weight of the balanced wetting agent additive-namely the mixture of the liquid reaction product of 13, 14 and 15 and the ingredient 16.

What is claimed is:

A composition consisting essentially of (l) about 1/16 to 5 parts by weight of a mixture of (A) about 80 to 99 parts by weight of a mixture of about 90 parts by Weight of fine magnetic iron oxide .particles and l0 parts by weight of a light oil of about 46 Baume having a Tagliabue Open Cup Hash point of yabout F. and a viscosity of about 41 seconds (Saybolt) and (B) about 1 to 20 parts by weight of a dialkyl dimethyl ammonium chloride in which the alkyl group has about 8 to 18 carbon atoms and (2) about 95 to 99%@ parts by weight of a modified suspensoid oil consisting essentially of about 90 to 991/2 parts by weight of said light oil and about 1/2 to 10 parts by weight of an additive comprising (a) 55 to 65 parts by weight of a mixture obtained by heating at about 90 F. to F., about 2O to 60 parts by weight of dodecyl benzene sodium sulfonate, about l0 to 50 parts by weight of a reaction product of lauric acid and triethanol amine and about 20 to 60 parts by weight of a reaction product of about one equivalent weight of an alkyl phenol in which the alkyl group has about 5 to 1-4 carbon atoms and about 2 to 12 equivalent weights of an alkylene oxide, and (b) about 35 to 45 parts by weight `of a dialkyl dimethyl ammonium chloride in which the alkyl group has about 8 to 18 carbon atoms.

References Cited by the Examiner UNITED STATES PATENTS 1,962,733 6/34 Davidson 252-62.5 2,106,882 2/38 Betz 252-62.5 2,365,253 12/44 De Forest 324-38 2,428,471 10/47 Pruitt 324-38 2,461,494 2/49 De Forest 324-38 2,478,951 8/49 Stakely 252-408 2,560,839 7/51 Ayo et al. 252-110 2,577,773 12/51 Lambert.

2,663,809 12/53 Winslow 252-625 XR 2,675,356 4/54 Woodworth et al 252-110 2,676,487 4/ 54 Clarke 252-408 XR 2,713,033 7/55 Cardwell et al. 252-148 2,723,239 11/55 Harvey 252-62.5 2,751,352 6/56 Bondi 252-62.5 2,754,266 7/56 Stegemeier et al. 252-9 FOREIGN PATENTS 642,820 6/62 Canada.

JULIUS GREENWALD, Primary Examiner.

LLOYD MCCOLLUM, JAMES W. LAWRENCE,

Examiners.

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