DE1774163A1 - Flexible ferrite keeper for magnetic thin-film storage and process for the production of the material for the ferrite keeper - Google Patents

Description

SIEMENS AKTIENGESELLSCHAFT Munich 2, '~ - ^{l! Jcb} Berlin and Munich Wittelsbacherplatz 2

P 17 74 163.8-53 VPA 68/2362

Flexible ferrite keeper for magnetic thin-film storage and process for the production of the material for the ferrite

Keeper

The invention relates to a flexible ferrite molded body for a keeper for magnetic thin-film memory a plastic component as a binding agent for the ferrite material and a method for producing the material for such a ferrite molded body.

What is to be understood by a ferrite keeper includes, among other things. from IBM Journal, March 1966, pages 130-134. In IBM Technical Disclosure Bulletin, Volume 8, May 1966, pages 1827 to 1828, a ferrite keeper is given in which the originally powdery ferrite component is solidified with silicone rubber as a hardening binder.

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The object of the invention is to provide a flexible, highly compressed ferrite molded body made from powder material with a smooth surface and high permeability, which is suitable as a ferrite keeper. One Another object is to develop a method for producing the material for a press-ready, to specify flexible ferrite molded bodies that can be used as perrit keepers. Subsequent deformation of the Moldings that have already been produced by a subsequent pressing process should not be excluded.

These objects are achieved by a ferrite molded body which, according to the invention, is characterized in that the plastic material is predominantly polyisobutylene and the molded body is produced by pressing the ferrite-plastic mixture. According to a further development of the invention, the material is prepared for a colchen ferrite shaped bodies by a process that initially a 10 to 30 ° / o polyisobutylene solution is prepared having one to about 100 ⁰ C vaporizable solvent for polyisobutylene, and in particular with benzene, then this solution is mixed with ferrite powder with a particle size smaller than 100 to 200 μm, then the liquid product is dried until the liquid is practically completely evaporated and then the drying product is granulated and sieved to a largely uniform particle size so that it is shaped into the desired shape According to a further development of the invention, further additives such as polyethylene and / or bitumen such as "lexphalt" are added to the plastic component.

Instead of bitumen, resins or waxes with comparable properties can also be used.

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The following considerations led to the invention:

In the manufacturing process of a molded body as specified above from a powdery substance with a binder, it is advantageous if, as in the present case, the manufacturing process is not is determined by technically conditioned, restrictive time sequences, the properties of the substances used are based. Such time sequences would be e.g. the pot life and the setting time of a hardening binder »Zum On the one hand, the manufacturing process is made much easier. On the other hand, they are in terms of manufacturing products manufactured using a time-independent process also more uniform in their physical properties, as the initial conditions for the production of the individual pieces are each equivalent.

Further details of the invention may include the specific and particularly preferred embodiments described below be taken according to the invention =

A nickel-zinc-ferrite powder with a grain size of 80 μm and smaller and a 30% solution of Oppanol B 50 in light gasoline in a weight ratio of about 6.5: 1 are mixed well with one another. Oppanol B 50 is i ⁿ 'commercially available polyisobutylene having a molecular weight in the order of 50 000. This mixture of ferrite and Oppanol solution is allowed to dry for as long as is practically completely evaporated to the gasoline. If necessary, the mixture is warmed up a little, but it should be noted that the temperature remains so low that no change in the magnetic properties of the ferrite can occur. The resulting rather solid mixture of ferrite and oppanol is then crushed into granules with a largely uniform grain size and sieved. In the manner indicated, a starting material is obtained, which may be used with additional

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also moderate temperature increase with high pressure can be pressed into bodies of the desired shape. The pressed moldings have, despite the very low, The proportion of plastic made up of only a few percent of the total mass is by far sufficient Strength and flexibility and, on the other hand, precisely because of the low proportion and also because of the relatively high proportion Compaction has a high permeability. The permeability measured on toroidal cores at 25 kHz is between 17 and 26. The ring permeability of the ferrite material used was in the form of a sintered body Values between 1100 and 1500.

Another exemplary embodiment of the invention is that the following:

It will be a nickel-zinc-ferrite powder and a 30% Oppanol B 50 / bitumen solution in light petrol in the ratio from about 6 parts of ferrite to 1 part of solution mixed together. The bitumen used in the exemplary embodiment uses a product which cannot be further defined and is available under the name "I.Iexphalt 25", which is available in the solution in a ratio of 30: 100 parts by weight Oppanol B 50 is contained. The compound as stated and a well mixed mixture is dried again as in the example described above and granulated and can then be pressed into the shape of the finished body.

For a ferrite keeper, a mixture of ferrite - preferably nickel-zinc ferrite and a binder made of Oppanol B 50 and Lup ° Ten _o The Oppanol-Lupolen solution required for this is produced in a special way as follows: im ratio of about 1:12 is Lupolen 1800 S in. light petrol dissolved at about 12O ⁰ C. This still warm solution is then, with slow stirring, about 5 to 6 times the amount of a 3O ⁰ ZoIgOj ₁ oppanol-

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Solution added, whereby the Lupolen flocculates. These Oppanol-Lupolen solution is now provided with the Ferrite powder mixed in the ratio given above and for the purpose of evaporation of the solvent dried. From the granulated dry product you can the desired moldings can be produced again.

For a ferrite keeper it is important that the essentially plate-shaped body is still somewhat flexible, It is also important that the surface is not only mechanically smooth, but also with regard to its magnetic or electromagnetic properties homogeneous, namely homogeneous with respect to the size of the individual Memory cells, is. On the other hand, the highest possible permeability is required, which among other things is greater, the larger the grain size of the deodorant content is. These two Requirements give the person skilled in the art sufficient information for the selection of the most suitable one for a ferrite keeper Range of the grain size of the ferrite powder.

It is also of very special importance that a ferrite keeper has the lowest possible coercive field strength which could cause permanent magnetization. Apart from that, of course, made of a ferrite material it is to be assumed that from 3ich there is already only a low coercive field strength, is in the selection of the material also ensure that the subsequent processing operations, especially during Milling the ferritic does not cause a coercive field strength that is too great. If necessary, the Powder, taking into account a suitable atmosphere in each case perform. When selecting the method according to the invention, it is advantageous to use it it must be ensured that these can only cause a slight increase in the coercive field strength by themselves.

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Due to the special selection of the individual substances is achieved that the pressed according to the invention Moldings are still quite flexible and have a smooth surface despite the very low proportion of binder to have.

Instead of the substances specified here for the binding agent, e.g. instead of Oppanol, Lupolen, des You can use "Mexphalto" as well as dec gasoline as a solvent within the scope of the invention also corresponding comparable ones Substances are used.

It has proven to be particularly advantageous to apply the pressure jerk to be used when pressing the shaped bodies to alternately decrease several times during the actual Preßvorjfanges and each time again to the maximum value to increase. This process step designed as indicated has the advantage that the subsequently produced molded bodies, in particular plates, have smooth surfaces. By this measure it was also avoided that the surface has a structure in the manner of being distinguishable from one another Has districts that were not excluded from a single press.

9 claims

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Claims (9)

PA 9/491/1170 - 7 - claims 1. Flexible ferrite molded body for a keeper for magnetic Thin-film storage with a plastic component as a binder for the ferrite material, thereby characterized in that the plastic component for predominant portion is polyisobutylene and the shape 'Body made by pressing the ferrite-plastic mixture is. 2. Ferrite molded body according to claim 1, characterized in that the plastic component additionally polyethylene contains. 3. Ferrite molded body according to claim 1 or 2, characterized in that that in the plastic component in addition a bitumen such as "Mexphalt 25" is included. 4. A method for producing a ferrite molded body according to one of the claims 1 to 3, characterized in that that a solution of the plastic component is prepared in an evaporable solvent, the solution well mixed with the powdery ferrite material, then dried, granulated, sieved and pressed into bodies of the desired shape. 5. The method according to claim 4, characterized in that the material is produced for the ferrite-form body by a 10 to 30 ° / o polyisobutylene solution is prepared having one to about 100 ⁰ C vaporizable solvent for polyisobutylene, then this solution with Ferrite powder with a grain size smaller than 100 to 200 μm is mixed, then the microfabric is dried until the solvent content has practically evaporated and then the drying product is granulated and sieved to a largely uniform grain size. 109861/1403 " ⁸ " BAD ORIGINAL Today's documents <αλ. ι% ι From ₆ .2 No. 1 sau 3 dee Ämtorune · «· * ν. α. ₉ . ie «, /} PA 9/491/1170 - 8 - 6. The method according to claim 5, characterized in gelcennzeich.net, that the solvent is gasoline. 7. The method according to claim 4, characterized in that the material for the ferrite molded body is produced by an approximately 10 ° / ° ig ^G polyethylene solution and a 10 to 30% polyisobutylene -! ^ - solution is each made in gasoline , then the polyisobutylene solution is added in portions to the polyethylene solution up to a ratio of polyethylene to polyisobutylene of 5: 100, so that the polyethylene flocculates finely, then this mixture of the two solutions is mixed with ferrite powder with a particle size of less than 100 to 200 '/ um, then the mixed product is dried until practically complete evaporation of the gasoline content and the drying product is granulated and sieved to a largely uniform grain size. 8. The method according to claim 4 or 5, or 6 or 7, characterized in that the polyisobutylene solution has a bitumen such as I.Iexphalt in a ratio of about 100 parts of polyisobutyl is mixed with 30 parts of bitumen. 9. The method according to any one of claims 1 to 8, characterized characterized in that the pressing pressure is increased and decreased alternately several times during the pressing process will. 109851 / U03 BATH ORIGINAL