DE1769962C3 - Ferromagnetic masses and their use for the production of magnetic recording materials - Google Patents

Description

The invention relates to a mass containing ferromagnetic chromium oxide.

The manufacture of high quality magnetic recording materials has recently been described in U.S. Patent 3,080,319. Such materials, in which the anisotropic chromium oxide particles are highly oriented, are particularly suitable for storing data and information. In all types of information storage it is very desirable to use the magnetic Maintain properties of the recording material over long periods of time under normal storage conditions, so that the entire stored Information can be retrieved at any time.

Although the above-mentioned recording materials were excellent after the first production have good magnetic properties, they slowly deteriorate when stored in a very humid place Atmosphere and at elevated temperatures. Ferromagnetic chromium oxide in the form of dry Powder is stable and can be stored for many years without any noticeable change. Furthermore these powders are not affected by prolonged heating in dry air at elevated temperatures. However, in contact with water suffers Chromium dioxide degrades very slowly, at a rate that is natural other surrounding chemical substances is affected. The one always present in magnetic tapes The tmnaung "w - object of a ferromagnetic oxide * to deliver ferromaoneSS containing mass in contact water and higher temperatures nut no degradation Xe and also to the action _to. chemical substances that give it remains stable.

The subject of the invention is accordingly e.ne ferromagnetic mass, consisting of I 7 to 99 wt .-% of a binder mixture al 1 to 90% by volume of a basic polymer containing a tertiary nitrogen atom, where at least 0.1% by weight of the polymer is present as tertiary amino nitrogen and the part of the polymer containing the tertiary amine has a pKa value of 3 to 11, measured in water from 20 to 35 ° C, W to up to 99 vol .-% other, usually as Binder for ferromagnetic masses containing metal oxides and polymers used. . ^ l j B 1 to 98% by weight of ferromagnetic chromium oxide, which is uniformly dispersed in A, and optionally

C. common modifying additives. The part containing the tertiary amine should preferably comprise 2 to 50% by weight of the basic polymer.

^m ferromagnetic compounds are supplied by the invention, which have improved stability, that is, they retain their excellent magnetic and physical properties for long periods under extreme humidity and temperature conditions. .

Fig. 1 illustrates a recording material in which a plastic tape is ferromagnetic Carries chromium oxide particles distributed in a binder according to the ferromagnetic mass of the invention.

2 shows the ferromagnetic mass of the invention as a uniform recording material, the binder containing the ferromagnetic chromium oxide particles without a plastic base

is required. .... u _L

The tertiary amine-containing basic synthetic polymeric binder can be represented as a polymer are derived from a monomer of the general formula A-B. The meaning of Letters A and B are explained below. The monomers A-B can form a In-house polymers A-B polymerized with themselves are, but preferably made from them by copolymerization with. at least one other copolymerizable comonomers M - explained in detail below - copolymers of A-3 and M. Preferably they are Polymers resistant to oxygen.

In the abovementioned basic monomers A-B, the expression A stands for a part of the molecule of the eye-

my formula

CRi =

the (replacing the group B in which a lower alkyl group, R) in the form of a suitable derivative AR capable of Additionsmischpolymerisation IGT B "shares a tertiary amine-containing moiety is, in the form of the derivative HB (in which hydrogen replaces the group A) a Has a pKa value of 3 to 11 when the corresponding acid is measured in water at 20 to 35 "C.
In the formula

applies to α and b either the number 0 or 1, R ¹ is hydrogen or fluorine, X is hydrogen, an alkyl radical having 1 to 5 carbon atoms, phenyl, fluorine or chlorine, Y is

—O— —SO ₂ - or

SO -

and Z stands for

—O— - S - or

Those polymers are preferred which are obtained from the monomers A-B if, for the MolckUI part A of the formula given above, R ^{1 is} hydrogen, X is methyl, Y is

icrtcs imidazole, for example 1 - methylimidazole, I-substituted benzimidazoles, such as 1-methylbenzimidazole, 1-substituted 1,2,3-triazoles, such as 1-methyl-4-phenyl-1,2,3-triazoles. The tertiary amine-containing part of the molecule B can also consist of secondary dialkyl and alkylarylamines, in which the secondary AminostickstoiT directly to a

Vinyl - (CH ₂ = CH -I group

is bound in the A-part.

One or more such basic groups can be present in the H - B (or A - B) compound. For example, H - B

20th

and Z stands for —O—, where α and b both correspond to the number 11. Corresponding polymers have proven themselves in the same way if the number O applies to R ', hydrogen for X and α and b in both cases, as well as those polymers from monomers AB, where R ^{1 is} hydrogen, X is hydrogen, Y is - O— and α represent the number 1, while for for the number O applies.

The tertiary amine-containing part B can be obtained by various tertiary amines, which the Have the properties listed above. Among the useful tertiary amines that are found in A-B monomers can be transferred include trialkylamines, in which the alkyl radicals I contain to 18 carbon atoms, for example triethylamine, ethyldimethylamine, Tributylamine, Octadecyläthylmethylamin, also dialkylarylamine, in which the Alkyl groups each contain 1 to 18 carbon atoms, e.g., N.N-diethylaniline; belong here too cyclic amines such as N-phenylpipcridine; heterocycli cal tertiary amines such as pyridine; Mono- and Dia'M pyridines, in which the aikyi groups i to iSKohicnitoffatome contain, for example 2-methylpyridine, Quinoline. Acridine, 1,3,5-triazine; next: I-substit-

"

or

CH ₁

CH ₃

CH ₃

40 CH ₃ CH ₂ -N-CH ₂ CH ₂ N-CH ₂ CH ₂ NCh ₃

being.

Particularly preferred H - B compounds, from which the basic monomers A-B are supplied, are triethylamine, ethyldimethylamine, pyridine

and 2-methylpyridine. These come with appropriate Α groups combined to form the copolymerizable basic A — B monomers.

Examples of the special intrinsic polymers obtained from monomers A-B by polymerization and used as polymeric binders in the ferromagnetic compositions of the invention can, are

Poly [2- (N, N-dimethylamino) ethyl methacrylate], poly [2- (N, N-dimethylamino) ethyl vinyl ether], poly [p- (N, N-dimethylamino) styrene] and
Poly [2- (piperidino) ethyl vinyl ether].

Examples of special copolymerizable A — B monomers, which are used for the production of polymeric binders for the purposes of the invention can be the following:

2-methyl-5-vinylpyridine,

2-vinyl pyridine,

4-vinyl pyridine,

3-isopropenylpyridine,

2- (N, N-dimethylamino) ethyl methacrylate,

2- (N, N-dimethylamino) ethy! Methacrylate,

2- (N, N-dimethylamino) ethyl acrylate,

2- (N-methyl-N-phenylamino) -ethyl methacrylate,

2- (N, N-dimethylamino) ethyavinyether,

2 '- (N, N-dimethylamino) -ethyl-1-methy! Vinyl-

ether,

2 '- (Piperidino) -äthy lvinyläthcr,

2- (N-methyl-N-phenylamino) ethyl vinyl ether,

I-vinylimidazole and

p- (N, N-dimethylamino) styrene.

The mixed monomers N, which with the tertiary amine-containing basic monomers A ~ B can be polymerized mixed, include a wciicii range of ethy'onically unsaturated compounds, which are accessible to addition polymerization. Useful monomers M include: Acrylic

acid and methacrylic acid esters of alkanols with 1 to 18 carbon atoms and of / J-polyfluoroalkylethanols and -Hydropolyfluoralkylmethanolen, in which the polyfluoroalkyl group 1 to 17 or 2 to Contains 18 carbon atoms. Example: methyl methacrylate, butyl acrylate, ethyl acrylate, /? - (PoSyfluorpentyl) ethyl methacrylate and "," - trihydropolyfluoropentyl methacrylate; Acrylonitrile and methacrylonitrile, vinyl esters of carboxylic acids having 1 to 18 carbon atoms, e.g .: vinyl acetate, isopropenyl acetate, vinyl trimethyl acetate, vinyl laurate and vinyl benzoate; further Styrene, ring-substituted halogen and alkyl styrenes with 1 to 18 carbon atoms in the alkyl radical and those styrenes which are in the alpha position due to aikyl residues are substituted by 1 to 8 carbon atoms, for example 2,4-dichlorostyrene, 4-methylstyrene, alpha-methylstyrene; Olefins, such as ethylene, Propylene, isobutylene; halogen-substituted olefins such as vinyl chloride, vinyl fluoride, vinylidene chloride, vinylidene fluoride, tetrafluoroethylene and Hexafluoropropylene; Vinyl and halovinyl ethers, for example methyl vinyl ether, methyl isopropenyl ether and perfluoroalkyl perfluorovinyl ether, in which the polyfluoroalkyl radicals contain 1 to 7 carbon atoms.

Particularly preferred mixed monomers M for the copolymerization with the tertiary amine-containing basic monomers A-B of the above type described are the following: methyl methacrylate, butyl methacrylate, 2- (perfluoroalkyl) ethyl methacrylate, Methyl acrylate, butyl acrylate, acrylonitrile, styrene and vinylidene chloride.

Examples of specific copolymers of M with A-B, which can be used as binders for the magnetic Recording materials of the invention have proven their worth are the following:

Vinyl acetate / 2- (N, N-dimethylamino) ethyl

methacrylate,

Styrene / 2-methyl-5-vinylpyridine, Styrene / 2- (N, N-dimethylamino) ethyl methacrylate, Vinylidene chloride / acrylonitrile / 2-methyl-

5-vinylpyridine,

Tetrafluoroethylene / methyl vinyl ether / 2- (N.N-Di-

methyl! amino) ethyl vinyl ether,

Tetrafluoroethylene / 2- {N, N-dimethylamino) -

ethyl acrylate / methyl vinyl ether,

Tetrafluoroethylene / vinyl acetate / 2- (N, N-dimethyl-

amino) ethyl vinyl ether,

Tetrafluoroethylene / vinyl acetate / 2- (N, N-diethyl-

amino) ethyl methacrylate,

Ethylcn / vinyl acetate / 2- (N, N-dimethylamino) -

ethyl methyl acrylate,

Methyl vinyl ether / 2- (N, N-dimethylamino) -

ethyl methacrylate,

Methyl vinyl ether / 2- (N, N-dimethylamino) -

ethyl vinyl ether,

«-Methylstyreneß-methyl-S-vinylpyridine,

Vinyl chloride / methyl methacrylate ^ -Methyl-

5-vinylpyridine,

Methyl methacrylate / vinyl acetate / 2-methyl-

5-vinylpyridine,

1,1-dihydroperfluorobutyl methacrylate / 2- (N, N-Di methylamino) ethyl methacrylate,

Methyl methacrylate / butyl methacrylate / 2-methyl-

5-vinylpyridine and

Butyl methacrylate / butyl acrylate / 2-methyl-

5-vinyl pyridine.

The preparation of the tertiary amine containing Polymers can be carried out by polymerizing the basic monomer A-B via customary methods of addition polymerization, for example by Bulk or solution polymerization, Suspension, emulsion or dispersion using peroxidic, redo »! Or azo initiators or with the help of radiated energy, e.g. B. with ultraviolet light or X-rays as an initiator.

ίο The both M monomers and A — B monomers Copolymers containing are in the same manner via the above-mentioned usual methods accessible, with the desired proportions of M-cotnonomers and A - B comonomers a

is can provide. This includes unsystematic mixed polymers, block polymers or graft polymers.

The manufacture of particularly suitable binders in the ferromagnetic masses of the invention useful polymer is detailed below described.

A 2-1 round bottom flask containing 360 g Methyl methacrylate. 20 g of 2-methyl-5-vinylpyridine, 2.0 g «, <* - azo-diisobutyronitrile and 680 ml of benzene charged. The mixture was stirring on the water bath heated to 80 ° C 15 minutes after reaching a At a temperature of 80 ° C., a solution of 15 g of 2-methyl-5-vinylpyridine in 30 ml of benzene was added while observing the following conditions: Two thirds of the solution were in the course of the following

45 minutes added, after which 0.25 g of "," - azo-diisobutyronitrile in 5 ml of benzene were added; then the remaining third of the solution was added over the course of the next hour, after which another 0.25 g «,! X'-azo-diisobutyronitrile incorporated into 5 ml of benzene

became. After stirring for a further hour at 80 to 81 ° C, the clear solution was at room temperature cooled and 953 g of a yellow solution with 30.6% solids were obtained. From 120 g of this solution the solid polymer was isolated by the

The solution was added to several volumes of cyclohexane with stirring, the precipitated solid was filtered off, re-slurried with cyclohexane, filtered again and dried. Yield: 33.2 g of a white, finely divided, solid polymer. Analysis: 1.15%

Nitrogen corresponds to 9.8% by weight of methylvinylpyridine. The inherent viscosity, measured at a concentration of 0.5% in chloroform at 25 ° C., was 0.24. A 2 l flask was charged with 310 g of methyl acrylate and 12 g of 2-methyl-5-vinyl pyridine under nitrogen

and 630 ml of benzene. The mixture was heated to 80 ° C. with stirring, and 2.0 g of azodiisobutyronitrile, dissolved in 50 ml of benzene, were added. It was then added in portions over the course of an hour 50 ml benzene solution containing 28 g 2-methyl-5-vinyl-

pyridine, added. After stirring for a further I ¹ Z ₄ hours at 80 ° C., the mixture was cooled; 873 g of a yellow, rather viscous solution with a solids content of 27.0% had formed. A 100 g portion of this solution was precipitated by

they were introduced into various parts by volume of hexane, cooling with ice while stirring. The soft one After drying, polymers were redissolved in benzene, after which the benzene solution was in the form of a thin layer on a polytrafluoroethylene film

applied and the thin film was ^{dried in vacuo at 45 0} C for the purpose of removing the solvent. The soft polymer stripped from the polytetrafluoroethylene film weighed 16.2 g.

Analysis: 1 ^ 83% nitrogen, corresponding to 15.5% by weight methylvinylpyridine in the copolymer. The inherent viscosity, measured at 0.5% concentration in chloroform at 25 ⁰ C, was 0.49

Other polymers suitable for use in the ferromagnetic masses can be formed on the same Paths can be established which, if necessary, can be modified. Accordingly can also different free radical initiators, different solvents, different temperatures, and others Reaction times for the polymerization of the monomers A-B alone or together with others Monomers M be of importance. In the same way, in addition to the solution polymerization of the type described above, there is also block polymerization, Suspension polymerization and emulsion polymerization in question.

In addition to the processes described for preparing the polymers, the tertiary amino group can also be introduced by chemical reaction with a preformed interpolymer, for example by reacting a secondary amine with a halide-containing copolymer according to the following equation:

Polymer — OCH ₂ CHjCl + HNR ₂

-> Polymer — OCH ₂ CH ₂ NR ₂ + HCl

Neber. the addition copolymers described You can also use condensation polymers containing tertiary amino groups as stabilizers in the use ferromagnetic masses. Suitable tertiary amine-containing condensation polymers can be prepared, for example, by reaction of a polyester containing halogen substituents with a secondary amine or by condensation of a dicarboxylic acid with a glycol, the has tertiary amine substituents.

In addition to its stabilizing effect on ferromagnetic masses, the tertiary amine acts containing basic polymeric component of the binder also as a dispersant and as a binder for the chromium oxide particles. All three properties mentioned are generally present simultaneously in the preparations of the masses.

The special structure of the basic polymeric component of the binder is important for ensuring maximum stability of the ferromagnetic mass containing chromium oxide. Polymeric substances that are free of easily oxidizable functional groups are less easy to react with chromium dioxide and therefore represent preferred "backbone" polymers in the binder, ie they form the polymeric component with which the tertiary amine-containing comonomers are copolymerized. It is essential that the amino moiety of the polymer is a tertiary amine; secondary and primary amine containing polymers are not particularly effective in achieving the desired results because these groups can be oxidized _{by CrO 2.} The structural relationships also influence the solubility and dispersing properties of the polymeric binder, as do the physical characteristics of the finished magnetic recording material based on the new ferromagnetic masses.

The basicity of the tertiary amine moiety of the poly

meren binder influences its stabilizing effect. In general, this increases with an increased basicity of the amine. As already mentioned, should the basicity, of the amine portion of the polymer is a pKa S correspond to between 3 and 11 when its conjugate acid is measured in water at 20 to 35 ° C, The measurement of pKa values of organic molecules is reported in: (IJ Ä. A Ib crt and E. P. S e rj e a η t, "Ionization Constants of Acids and Bases",

.ο John Wyley & Sons, Ind., New York, N-Y. (1962), Pp. 140 to 141 and 144 to 145; (2) E.A. Brand and F. C. Nach od, "Determination of Organic Structures by Physical Methods", Academic Press, New York (1955), Chapter 14, "Dissociation Conis stants", p. 567; <3) Y. J ο k a w a, Editor, »Handbook of Organic Structural Analyzes, "W. A. Benjamin Inc., N. Y. (1965), pp. 584-613.

Binders with an amine moiety that has a pKa below 3 generally do a lot less stabilization. The use of binders with an amine part corresponding to a pKa above 11 sometimes has a deleterious effect on the binder. This is how they work, for example very strong basic polymers have a negative effect on the disperser sion of the chromium oxide particles and result in one chen cases to their agglomeration.

The stabilizing effect of the tertiary amine-containing copolymer generally increases with it higher proportions of the basic components A-B within the range of 2 to 50% by weight of the M / A-B interpolymer. In some cases it is the stabilizing effect of type A-B own polymers is lower than that of mixed polymers of the same A-B monomers with additional

Mixed polymers M.

On the other hand, the dispersing effect of the binder tends to be otherwise unchanged Composition drop when the proportion of tertiary amine-containing basic polymers is increased in the binder. The basicity of the amine moiety and the molecular weight and uniformity of the basic polymer are other factors affecting an agglomeration. The general effect of the uniformity of the

meren including the uniform distribution of the amine-containing part in the copolymer to the The stability of the magnetic recording material is generally associated with an increase in the stability with increasing uniformity of the binder. Also

thus an increased uniformity of the polymeric component has a favorable effect on the dispersing effect of the binder.

The molecular weight of the tertiary amine-containing polymer in the binder influences the dispersion

ss greed effect in a characteristic way. As the molecular weight of the polymer decreases, the dispersing effect increases, while on the other hand there is a variation in the molecular weight of the amine-containing Polymers whose stabilizing effect does not

Changed seriously. Makes this an essential one Part of the binder in the ferromagnetic mass, it is generally preferred to use polymers of higher molecular weight. If desired, one can also use mixtures of low molecular weight and

(15 use high molecular tertiary amine-containing polymers in the binder. In this case, the dispersing effect is achieved by the polymer of low molecular weight and by

7W63B / 69

the high molecular weight polymer the binding agent effect '· ■■■' ■■ '■ ■■' ■ '- " '^;'; ^: · ^: ■ · ■■■■. ·'.

The usual dispersants are found in previously known ferromagnetic masses for magnetic tapes in the preparation in amounts of 3 to 6% by weight (or approximately 15 to 30% by volume), based on the magnetic oxide; before. These amounts seem to be enough to keep the oxide surface completely "moist", wherein additional amounts generally do not significantly improve the dispersing effect. It is desirable to incorporate low molecular weight dispersants only in small amounts, as this generally has a deleterious effect on the physical properties of the binder to have. On the other hand, polymeric dispersants can and can be considered as good binders as they are dispersants work in larger quantities.

The tertiary amine-containing polymers

10

Magnetic recording materials can using the ferromagnetic masses of the invention according to those in the art for such Manufacture substances using the usual methods. The one in the U.S. Patent 3,080,319 for the production of coated or uniformly formed tapes can be applied to the production corresponding volume when using tertiary amine-containing basic polymeric binders

■ ο transfer the invention.

The ferromagnetic chromium oxide used in the magnetic recording materials of the invention is preferably in the form of acicular ones Single crystals, the magnetocrystalline aniso tropie with a single slight magnetization have axis that more or less coincides with the needle axis. The production of suitable forms of ferromagnetic chromium oxide is, for example, in U.S. Patents 2885365,

hold up essentially as the usual dispersants 20 2923683,2923684,3034988 and 3278263 described, low molecular weight greases, so that the magnetizable material generally has a minimum concentration in the range of 3 to an intrinsic coercitivity of 6% by weight in general An adequate dispensing of at least 200 oersted ensures a saturation induction per effect. The maximum gram to be used in the range from 70 to 100 Gauss cm ³ / g and concentration depends largely on the remanence ratio of at least about 0.35. added polymers caused physical The Curie temperature of CrO ₂ is 115 to

- "* '» - «- · - <- -: - ■ -ι- 120 ⁰ C, can, however, depending on the present

special modifiers that are 85 to 160 ⁰ C.

From the point of view of an optimal combination of stability, magnetic and physical Properties are preferably used binders in which the tertiary amine-containing polymers

" _R 10 to 50% by volume. Such amounts

The amount of particular binder chosen allows for the incorporation of other polymeric binders and the physical properties of the medium which are often desired in order to make the magnetic

To give recording material special properties. So in some cases it is desirable

Effects on the finished recording material, since the stabilization is generally higher Amounts of tertiary amine containing polymers increases. This particular constituent will generally be used in the maximum possible proportions which can be used in the range of the optimum physical properties desired for the total mass. In each individual case it depends

Polymer additive from. For example, in some cases it is necessary or desirable to use the tertiary amine containing polymers in the minimum amounts of

incorporate other polymers in order to ensure special strength properties of up to 6% by weight, based on chromium oxide, or to

increase surface uniformity and smoothness, etc. Such polymeric substances, which are preferably to be incorporated into the binders, can be commercially available

Be polymers that are generally used in the

effectively supplies and also uses certain desired 45 position of magnetic tapes, you can physical properties greatly improved. However, these also represent polymers that are produced by addition polymerization or condensation polymerization

i i obtained commercially available monomers

set, while in other preparations increasing the amount of the tertiary amine-containing Polymers up to 50 vol .-%, based on the total binder, a considerable increase in stabilizer

Optimum valuable properties can generally be achieved if the tertiary amine-containing polymer constituent amounts to from 10 to Makes up 50% by volume of the total organic solids present in the composition.

In those special cases in which the dispersing Effect of the binders of the invention is not present to the desired extent, can also known low molecular weight dispersants are introduced into the binder. Under these circumstances the basic polymer component acts primarily as a stabilizer and binder, while the dispensing effect is mainly tion in will.

A particularly suitable type of polymeric components that are expediently added is preformed polyester / polyurethane / elastomer bandages average; Example: A soluble polyester-polyurethane resin based on diphenylmethane diisocyanate, Adipic acid and an alkanediol having 2 to 4 carbon atoms. Such binders can also use Crosslinking agents, such as with trifunctional polyisocyanates, have been crosslinked. Example: 2,4-toluene diisocyanate / trimethylolpropane (3: 1), 4,4'-methylene

yypp

by the incorporated dispersant of nicd- ⁽ >"bis-cyclohexyl isocyanate) etc. lih lif id I di fill D tiä Ai h

rigcm molecular weight is supplied. In these cases the stabilizing effect achieved is generally lower than in those cases in which only a tertiary amine-containing basic polymer is present in the dispersant. The actual stability of such magnetic masses depends largely on the stability of what is added usual dispersants.

The tertiary amine-containing binder of the invention can be used as a coating on tapes of conventional polymeric substances are applied using the methods known in the art, for example by solution coating, coating the melt or dispersion coating. Preferably, the coating compositions are a shear Subjected to action, as eic by the known

dispersing milling devices, for example Sand mills, ball mills or roller mills are achievable; Suitable sand mills are in the U.S. Patent Nos. 2581414 and 2855156. The tertiary amine-containing binder of Invention can also be formulated for the manufacture of unitarily formed ribbons, i.e. H. from Tapes in which the mass consisting of chromium oxide and binding agent without a strip on the back is used to form a complete magnetic recording material.

A common method of making magnetic tapes for comparison is as follows: One certain amount of a solution of a tertiary amine-containing basic polymer dissolved in a suitable solvent and sufficient to have a content of at least 0.1% amino nitrogen to yeasts, is placed in a container and a certain amount of acicular ferromagnetic chromium oxide particles and 2 to 3 times, based on the oxide weight, added to Ottawa sand. The container is closed and grinding the ingredients in slurry form for about 45 minutes by mounting the container in a commercially available paint conditioner which is, for example, 10000 vibrations / min, oscillates. The contents of the container are then placed in a larger container containing a solution of the contains other polymeric binders incorporated into the binder mass in such amounts should be that ultimately a binder is present which contains 35 to 41 vol .-% of chromium oxide particles. This mixture is then milled in the dye conditioner for several minutes. The mixture is then removed from the container and filtered under pressure through a nylon pad that is placed on a metal sieve with a Transmittance was 2 microns; (i.e. 98% of the material with a particle size above 2 microns not pass) to remove the sand. If desired, other ingredients, z. B. other dispersants or other modifying agents such as crosslinking agents, lubricants, etc. be introduced into the coating solution at various points in the milling process after the tertiary amine-containing basic polymer has been milled with the chromium oxide particles is.

The dispersions prepared as described are then uniformly coated onto a carrier film, for example one on polyethylene terephthalate, and smoothed with the aid of a doctor blade Placing on a suitable plate brought to the desired coating thickness. The wet films will in time passed through opposing magnets, one for aligning the magnetic Particles in parallel form have sufficient orienting field strength. The coated tape containing the oriented chromium oxide particles becomes then left to dry under cover overnight at room temperature. The obtained coated Tapes have now been aged under various conditions to test their stability. When the tapes are to be assessed for their magnetic properties, they will be the first kalandricrt at elevated temperatures and pressures, with the exact temperature and pressure of dor special composition of the coating and the Band carrier is dependent. Include the magnetic Masses of the belts are crosslinking agents, so they will be exposed at normal or elevated temperatures cured for such periods of time that are sufficient to ensure crosslinking in the polymer of the masses.

The effectiveness of the tertiary amine: containing basic binders with regard to their stabilizing effect can be determined by mar

■ ο certain magnetic and physical properties measures after the tapes have been subjected to various accelerated aging conditions Samples of the tapes are enclosed in special vessels that contain a humidistat

> s that sets the desired humidity conditions; the samples are then placed in a circulating air oven at the desired location Temperatures. Such treaters are used at 65 ° C and 50% relative humidity performed using a mixture of 2 vol. water with 1 vol. conc. Sulfuric acid al Humidistat. In this very accelerated aging test, the specified he increased temperatures the effect of damp Decomposition is generally great. The height the faster decomposition occurs, the faster the moisture.

Aging effects can best be monitored by the decrease in the remaining intrinsic flux density Φ, each 1.27 cm on five pieces of tape of 5.08 cm Edge length is observed and the slow increase in the coercive force iHc of the tape is measured. Although the losses of Φ and the growth of iHc door represent the intended purpose, they do not provide any precise information the goodness of the tape. The output signal (£ <,) or the signal voltage from peak to peak normally grows with the increase in iHc, and this largely compensates for losses of Φ,. Furthermore, a loss of

4c 10% at Φ, only about a decrease of 1 dB; 1 dti roughly represents the smallest measurable change in the belt characteristic. The accelerated tests show that the decrease is initially rapid, and that the speed is then due to the training a protective layer on the surface of the oxide decreases. Changes in Φ are reported as: time, measured in days, in which there is a 10% decrease in the initial Φ . This loss of the remaining intrinsic flux density is referred to as the f, _{0 value} net. When comparing two I ₁₀ values of different tapes, it should be taken into account that the percentage loss of Φ of a tape generally depends on the coercive properties and the degree of dispersion of the chromium oxide in the binder.

The Eigenkoerzitivkraft iHc and the remaining intrinsic flux density Φ are measured with a ballistic DC ammeter, which is slightly modified from that of Davis and Hartenheim in the Review of Scientific Instruments, 7, 147 (1936).

the device. The following is used as a measure of the square shape of the magnetization curve and thus the magnetization properties of a strip: ratio of peak voltage to sattol tension PjW. In general, a tape for magnetic fret

The higher the PjW value, the more suitable it is for recording. The Pj W ratio is taken as the first derivative of one with an electrical alternating current of 60 H; generated hysteresis curve measured. The Derivation «

.ti

13 ^{14 r}

curve is obtained as an oscillographic image with methyl isobutyl ketone. The vessel with its contents became a normal, commercially available β / H measuring device, such as a further 30 minutes on the color mill, e.g. the model 651 B from Scientific Atlants. The shakes, after which the contents go through under pressure P / W value represents the ratio of the peak voltage filter pad that was filtered on a metal screen the derivation curve for which the field freedom was 5 with a 2 micron permeability range. the the resulting saddle voltage of the derivative curve. The viscosity of the filtrate was then, if necessary, The output voltage of the above determined by dilution with tetrahydrofuran to about Magnetic tapes treated in the manner described can be set to 7 poise (corresponding to No. 4 Spmdel of Brookfieldin commercial magnetic tape recorders with 30 kHz viscometer). This dispersion can Saturation can be measured without bias. So then for the purpose of coating a carrier foil When it can be seen that the output signal is the production of a magnetic recording tape is almost the same as that used by others.

common types of magnetic tape. A dispersion prepared as described was used

If the strips are then sprayed onto a 0.038 mm thick carrier film made of poly- tic compounds of the type described under 1-ethylene terephthalate and with the aid of a ferromagnetic strip circuit of certain cleaning processes produced squeegee set a layer thickness of 0.076 mm, are, they show a significantly improved (dimensions of the carrier film: 101.6 χ 8.25 cm). the The initial voltage compared to the conventional film lay flat on a glass plate. The damp film Ribbons. was then by two opposite one another

Recording materials that have been produced with the ferromagnetic 20 magnets with a magnetic orientation field masses of the invention, guided by about 900 Gauss to the chromium oxide are characterized by high quality and unusual surfaces, after which the oriented film is stable and can Glass cover can be used overnight at room temperature for which the magnetic cover has been left to dry. The dry tapes is an option. For example, one can then evaluate the magnetic properties for radio and television recordings and, at the desired temperature changes, continue to age for measuring instrument equipment, temperatures and humidities. The devices to be assessed in terms of data centers and in different types of regulation of output voltage and smoothness. Get improved stability of the invention, recording 30 19643 kg / m prepared with the tapes were kakndriert before aging initially at about 110 ⁰ C and masses. The material is characteristic of these and makes the test results of this example particularly suitable for applications in which Table I below shows the materials over long periods of time at high temperatures ο ie 1 e 2 to 22

Temperature and high humidity "

have to. 35 Table I also shows the test results.

The ferromagnetic masses of the invention are carried out with others, in the same way as in the tapes produced by the following examples were determined in detail from Example 1, illustrative. AUe quantities are, unless nothing but the specified quantity of the same or otherwise noted, to be regarded as weight information. another methylmeacrylate / methylvmylpyri-

40 din copolymers or another methyl vinyl

B ei game 1 pyridine-containing polymers in place of the

3.4% MMA / MVP (90/10) mixed polymers of the two

A glass vessel with a capacity of about 60 ml was placed with game 1. Loaded in table I and the following substances: the tables show the proportions of the various mixed

45 monomers, expressed in% by weight of the mono-

0.5 g of a copolymer of 90% methyl mers, indicated, which is used to produce the mixed

methacrylate and 10.2% 2-methyl-5-vinyl polymers have served. In Examples 16-18

pyridine, including lies the polyester-polyurethane resin and

29.6 ml of tetrahydrofuran, the vinylidene chloride / acrylic acid ifrfl copolymers

10.0 g of ferromagnetic chromium oxide with a 50 in a weight ratio of 40:60 instead of

Self- coercive force iHc of 382 Oersted, 50:50, as in Examples 1 to 15 and 19

an n _r of 37.4 Gauss cm ³ / g and one up to and including 22 as well as in the comparative examples

1, value of 82.0 Gauss cm ³ / g, is the case. Table I also lists the test results for

30 ml Ottawa sand (particle size: 0.59 to two comparison bands where the tertiary

0.84 mm). 55 amine-containing copolymers were omitted,

while on the other hand a common dispersing

The vessel was closed and the ingredients were worked in, as was a verals sludge for 1 hour by shaking the vessel. In these comparative experiments known device shaken with about 60 as a dispersant soy lecithin and a fatty alcohol / 1000 revolutions / min. The content of the amine sulfate applied

The vessel was then placed in another glass vessel from The examples show that increasing stability

about 120 ml volume and also 11.3 g usually with the use of increasing amounts of a 15% solution of the polyester-polyurethane to tertiary amine-containing copolymers par resin of biphynylmethane diisocyanate / adipic acid / 65 aiiei and that also the use of BiUandiol in Tetrahydrofuran is added, and mixed polymers which have increasing amounts of the tertiary 5.6 g of a 30% solution of a vinylidene chloride / amine-containing component lead to he-acrylonitrile (VC1 ₂ / AN) (80/20) mixed polymers with greater stability. In addition, the two

Games that the tertiary amine-containing copolymers as well as acting as a dispersing agent as a stabilizer and that the ^D olyrneren of low molecular weight tend to have a better dispersing action, compared to their stabilizing effect. Example 9 shows that the good stabilizing effect of the tertiary amine-containing copolymer is transferred to magnetic tapes which have been produced on a continuous experimental scale coating apparatus.

Examples 23 to 32

The procedure of Example 1 was repeated with the exception that the particular vinylpyridine-containing polymers characterized in Table II below were substituted for the 2-methyl-5-vinylpyridine copolymer of this example in the amounts indicated. In Examples 23 to 30 and in the comparative examples, the proportions of ester urethane resin and VCl ₂ / AN binder correspond to those of Example 1, ie they are in a ratio of 50:50, in Examples 31 and 32 inclusive these two binders, however, in a weight ratio of 40:60.

The test results of magnetic tapes made in the same manner as described in Example 1 were produced are also given in Plate II. The examples explained here show also that increased stability is often achieved by using such polymers which have a higher Have proportion of the tertiary amine-containing part of the molecule.

Examples 33 to 37

The procedure of Example 1 was repeated, replacing the methylvinylpyridine copolymer this example now dialkylaminoethyl methacrylate copolymers in the following Table III amounts to be taken have been applied. The corresponding test results are listed in Table III. The examples show that there is increased stabilization in use of increasing proportions of another tertiary amine-containing copolymer.

Examples 38 to 40

The procedure of Example 1 was repeated with the exception that instead of the 2-methyl-5-vinylpyridine copolymers In this example, special tertiary amine-containing polymers are used in the amounts shown in Table IV became. The test results are also given in Table IV. It can be seen that own polymers of tertiary amine-containing monomers act as stabilizers, but that they do less are effective as the copolymers of the same tertiary amine containing monomer with methyl methacrylate.

Particularly high quality magnetic recording materials can be produced by a lightweight Modification of the procedure of Example 1. These are described in Examples 41 and 42.

Example 41

10 g of magnetic chromium oxide with an Eigenkoerzitivkraft iHc of 438 Oersted, an a _r of 82.6 Gauss cm ² / g and an a _r of 38 Gauss cm ² / g were slowly with stirring in a nitrogen atmosphere to a solution of 0.7 g of a Methyl acrylate / 2-methyl - 5 - vinylpyridine - (84/16) - copolymers in 1.375 g of methyl isobutyl ketone and 26.6 g of tetrahydrofuran (THF). An equal volume of Ottawa sand with a particle size of 0.59-0.84 mm was added and the dispersion was stirred using a disk stirrer at 36,576 cm / min. Stirred for 30 minutes, adding THF in such amounts to maintain the viscosity.

to obtain. The resulting dispersion was added 0.04 g of stearic acid amide, and also 1.20 g of one 10% solution of polyisocyanate, made from 2,4-toluene diisocyanate / trimethylolpropane (3/1) in Tetrahydrofuran, and finally 17.86 g in one

15% solution of a soluble polyester-polyurethane resin of diphenylmethane diisocyanate / adipic acid / butanediol in THF. With continued stirring (30 min. At 36,576 cm / min.), The dispersion was pressure filtered through a sieve with a flow width of 5 microns. The filtered dispersion had a viscosity of 7.2 poise, a ß _P / ß _s of 0.89 and a PI W of 29.2.

The dispersion described was applied to a 0.038 mm thick carrier film made of polyethylene terephthalate

sprayed and set a layer thickness of 0.076 mm with a doctor blade. Although the coating is still was flowing, the film was passed through two opposing magnets that created a magnetic field of about 900 gauss to align the chromium oxide particles; subsequently became on air dried. The dry film was calendered twice at 110 ° C./19,643 kg / m 2. The calendered Tape was cured at 55 ° C for two days. The glossy film obtained was very good Wear resistance, it showed a total abrasion of 0.16 μ cm / min., Compared to the 0.39 μ cm / Min. Value for the total abrasion of common standard high-performance belts. The tape also had good frequency fidelity and low noise floor

(AC and DC), good stability (Φ _Γ ί ₁₀ at 10.6 days and 65 ° C at 50% relative humidity), also low friction (μ = 0.27 against brass in a standard friction meter).

Example 42

The preparation and the procedure described in Example 41 were used with the exception that the toluene diisocyanate / trimethylolpropane resin was replaced by 0.12 g of 4,4'-methylenebis (cyclohexyl isocyanate) as a crosslinking agent. The calendered tape was cured at 65 ° C for about 22 hours. The tape obtained is smooth and adheres well. It showed a total abrasion of 0.32 μcm / min, and excellent frequency fidelity with low AC noise and a Φ _Γ ί ₁₀ of 7.3 days at 65 ° C and 50% relative humidity.

Examples 42 to 63

In these examples, the procedure of Example I was modified to include in some cases the vinylidene chloride / acrylonitrile mixed polymer was omitted from the binder mass and that the special tertiary amine-containing copolymers in the proportions shown in Table V are used became. The proportion of chromium oxide particles in the coating compositions was as in the previous examples up to 41% of the total volume of solids. These examples show that tertiary amine

containing copolymers are effective as stabilizers and binders in such preparations, which contain polyester / polyurethane binders alone, but also in the same way in preparations containing mixtures of these binders with vinylidene chloride / acrylonitrile copolymers contain.

As indicated above, mixtures of tertiary arain containing polymers work together with conventional dispersants has a beneficial effect on the stability of the magnetic tapes. The action of Combinations of dispersants with two different binder masses containing chromium oxide Ribbons are illustrated in Examples 64-66.

Examples 64 to 66

Coated tapes were made using the procedure of Example 1 with the exception that vinylidene chloride / acrylonitrile mixed polymer alone and

15th

Polyester-polyurethane resin alone were used for the 50/50 mixtures of these binders in the example mentioned, and methyl methacrylate / 2-methyl-5-vinylpyridine (90/10) copolymer alone or in a mixture with equal volumes of soy lecithin was used as a dispersant would. The total volume of dispersants used was 16% of the volume of CrO _{2 used} , corresponding to 3.3 to 4.0% by weight of CrO ₂ , depending on the density of the particular dispersant used. The test results obtained with the tapes of these examples are summarized in Table VI, together with the test results on comparative tapes which did not contain a tertiary amine-containing polymer.

Special preparations that are particularly useful in the formation of magnetic recording materials Invention are important, either with a plastic carrier tape (Fig. 1) or without (Fig. 2) are given in Table VII.

Panel I.

Stabilization of chromium oxide containing magnetic tapes with 2-methyl-5-vinylpyridine copolymers

(CrO ₂ = 41% by volume of the solid; binder = EU / VC1 ₂ -AN 50/50 in Examples 1 to 15 and 19 to 22; 40/60 in Examples 16 to 18)

example Tertiary amine containing polymers Own on Wt .-%, Methyl methacrylate. Diphenyl methylene diisocyanate, properties of the tape Stability, Butanediol. Mixed polymers (proportions) viscosity related to Methyl acrylate. 80/20. iHc, PI W (, 0 at 0.49 CrO ₂ Butyl methacrylate. Oersted 65 ° C / 50% Lauryl methacrylate. rel. Wet. 0.15 0.28 5.0 2-methyl-5-vinyl pyridine. 26.3 1 MMA / MVP (90/10) 0.27 3.6 2-vinyl pyridine. 370 21.2 19.5 2 MMA / MVP (90/10) 0.27 7.2 2,4-toluene diisocyanate (3/1). 368 22.3 > 20 (fc, = 20) 3 MMA / MVP (90/10) 0.31 3.4 Preformed polyester-polyurethane resin from 371 24.6 9.1 4th MMA / MVP (98/2) 0.14 5.0 Vinylidene chloride / acrylonitrile mixed polymer 363 17.7 19.2 5 MMA / MVP (80/20) 0.29 3.4 364 23.4 17.0 6th MMA / MVP (50/50) 0.08 5.0 360 18.0 9.8 7th MMA / MVP (15/85) 2.54 5.0 364 16.7 19.6 δ MMA / MVP (90/10) 0.24 6.0 382 9.8 25.0 9 *) MMA / MVP (90/10) 5.0 364 31.7 19.2 10 MMA / MVP (90/10) (+ XL-I; 5.8% by weight binder 372 29.5 + Stearic acid amide, 1% rel. Binder) MA / MVP (90/10) 5.0 14.6 11th MA / MVP (50/50) 5.0 354 24.6 16.6 12th BMA / MVP (80/20) 5.0 370 17.9 10.2 13th BA / MVP (80/20) 5.0 355 30.7 7.5 14th LMA / MVP (80/20) 5.0 365 16.1 8.8 15th 2-VP / MVP (50/50) 4.0 370 28.1 7.5 16 *) With this special tape, the mass of Example 3 was continuously measured with the aid of a 364 16.1 working test coating device applied a carrier film made of Polyäthylcnterephthalat. MMA = MA = BMA = LMA = MVP = 2VP = XL-I = E-U = Adipic acid and VCl ₂ -AN =

(I.

continuation

example Tertiary amine containing polymers SMA / MVP (95/5) Weight%, Properties of the bandet PI W Stability, Mixed polymers (proportions) P.igen- Styrene / MVP (50/50) related to iHc I ₁₀ at viscous MMA / BA / MVP (42/42/16) CrO ₂ Oersted 65 "C / 50% MMA / HEMA / MVP (85/5/10) rel. Wet. MA / HEMA / MVP (73/8/19) 4.0 24.6 5.8 17th BA / HEMA / MVP (73/8/19) 4.0 354 38.3 36.0 18 **) 5.0 364 26.1 17.7 19th 5.0 370 22.7 22.7 20th Soy lecithin 5.0 370 23.0 21.3 21 Fatty acid alcohol amine sulfate 5.0 370 27.9 13.8 22nd No dispersant 370 Comparison attempt 5.0 26.8 1.8 A. 5.0 370 21.0 3.7 B. - 370 17.6 4.5 C. This tape contains vinylidene chloride / acrylonitrile existing binders 360 also some methyl methacrylate. **) The end = Methyl methacrylate. MMA = = Methyl acrylate. MA = = Stearyl methacrylate. SMA = = Hydroxyl methacrylate. HEMA = = 2-methyl-5-vinylpyridine. MVP =

Plate II

Stabilization of chromium oxide containing magnetic tapes with 2-vinyl and 4-vinyl pyridine copolymers

(CrO _? = 41% by volume of the solid; binder = EU / VC1 ₂ -AN 50/50 in Examples 23 to 30; 40/60 in Examples 31 to 32)

example Tertiary amine containing polymers crowd properties the tapes Stability, Mixed polymers (proportions) CrO ₂ iHc PW Ίο. b ^ei in% by weight Oersted 65 ° C / 50% rel. Wet. 3.4 9.5 23 MMA / 2-VP (98/2) 3.4 360 15.0 10.7 24 MMA / 2-VP (95/5) 3.4 364 18.4 13.0 25th MMA / 2-VP (90/10) 3.4 364 16.3 12.7 26th MMA / 2-VP (80/20) 3.4 368 16.6 26.0 27 MMA / 2-VP (50/50) 5.0 360 17.7 14 ,? 28 MMA / 4-VP (90/10) 5.0 372 16.7 14.8 29 MMA / 4-VP (80/20) 5.0 365 17.3 12.8 30th MMA / 4-VP (50/50) 4.0 365 14.7 6.9 31 BMA / 2-VP (95/5) 4.0 354 24.6 15.0 32 VCl ₂ / AN / 2-VP 4.0 354 27.4 3.0 Comparative experiment D Soy lecithin 3.3 360 34.7 3.2 Comparative experiment E Fatty alcohol amine sulfate 364 25.4

MMA = methyl methacrylate. BMA = butyl methacrylate.

2-VP = 2-vinyl pyridine.

4-VP = 4-vinyl pyridine.

VCl ₂ = vinylidene chloride. AN = acrylonitrile. E-U = Preformed polyester / polyurethane resin made from diphenylamine diisocyanate, adipic acid and bulanili oil. VCl ₂ -AN = vinylidene chloride / acrylonitrile (80/20) mixed polymers.

Plate III

Stabilization of chromium oxide-containing magnetic tapes with dialkylaminoethyl methacrylate own polymers

(CrO ₂ = 41% by volume of the solid) (binder = E-IWCl ₂ -AN, 50/50)

example Tertiary amine containing polymers

Comparative experiment D

Comparative experiment E

Comparative experiment F

BMA / DEAM (98/2) BMA / DEAM (90/10) BMA / DEAM (80/20) MMA / DEAM (80/20) MMA / DMAM (90/10) soy lecithin fatty alcohol amine sulfate MMA / MVP (90/10)

ilymerc crowd
CrO ₂
in% by weight properties
IHc,
Oersted the tapes Stability,
Ίο at
65 "C / 5O%
rel. Wet. 3.6 371 27.3 8.2 5.0 370 21.4 13.2 5.0 370 18.2 19.4 5.0 370 19.5, St. 5.0 370 21.0 14.2 4.0 360 34.7 3.0 3.3 364 25.4 3.2 3.6 368 22.3 19.5

MVP = 2-methyl-S-vinyl pyridine.

2-VP = 2-vinyl pyridine.

4-VP = 4-vinyl pyridine.

E-U = Preformed polyester-polyurethane resin made from diphenyl methylene diisocyanate, adipic acid and butanediol. VCI ₂ -AN = vinylidene chloride-acrylonitrile (& 0/20) mixed polymers.

Plate IV

Stabilization of chromium oxide-containing magnetic tapes with tertiary amine-containing polymers (CrO ₂ = 41% by volume of the solid; binder = E-IVVCl ₂ -AN, 50/50)

example Tertiary amine containing polymers crowd
CrO,
in weight% Traits the tapes Stability,
Ίο at
65 "C / 50%
rel. Wet 4.0 (Hc,
Oersted P / W 8.2 38 Poly (MVP) 4.0 354 11.9 8.6 39 Poly- (2-VP) 3.4 *) 364 10.8 ~ 7-9 40 Poly (4-VP) 4.0 354 18.4 3.0 Comparative experiment D Soy lucithin 3.3 360 34.7 3.2 Comparative experiment E Fatty alcohol sulphate 364 25.4

*) Polymer is not completely soluble in the binder.

MVP · ■ - 2-methyl-5-vinylpyridine,

2-VI ¹ = 2-vinyl pyridine.

4-VP 4-vinyl pyridine.

! • ■ II = pre-formed polyurethane mixture of diphynylmcthiindlisocylinal, adipic acid and thinnediol

VCl ₁ -AN - Viiiylidenchlorid-Acrylonitril- (ao / 20) -MiBchpolymcres.

23

24

Plate V

Stabilization of chromium oxide as a binder stabilizer

containing magnetic tapes with tertiary amine-containing copolymers

(CrO ₂ = 41% by volume of total solids)

Example composition of the binder

Polymers

1: 1

61 62

ratio

by E-U

or

E-U

+ VCl ₂ -AN

to the

basic

Polymers

E-U + MMA / MVP (90/10) 9.4:

EU + MMA / MVP (90/10) 4.7 ^:

E-U + MMA / MVP (90/10) U = J E-U + MMA / MVP (90/10) U.l

f + XL-1.8.1% by weight binder + stearic acid amide, 0.9% by weight based on binder)

EU + MMA / MVP (90/10) (+ DC 200, l, 0% by weight CrO ₂ ) EU + MMA / MVP (95/5) EU + MMA / MVP (80/20) EU + MMA / MVP ( 50/50) EU + MMA / MVP (15/85) EU + MMA / 2-VP (95/5) 'EU + MMA / 2-VP (80/20) EU + MMA / 2-VP (50/50 ) EU + MMA / 4-VP (90/10) EU + MMA / 4-VP (50/50) EU + BMA / MVP (80/20) EU + BMA / MVP (80/20) (+ stearic acid amide, 0 , 3% by weight based on oxide EU + MMA / DEAM (90/10) EU + MMA / DEAM (80/20)

/ + XL-I 2.2% by weight, based on oxide) _E tu χ MMA / MVP / HEMA (85/10/5)

EU + VCl ₂ -AN (50/50) (+ MMA / DMAEVE (94/6) EU + VCl ₂ -AN (50/50)

(+ 1-VIm (94/6)

Comparative

sample C E-U + soy lecithin 6.7: 1

6.7: 1

9.4: 1

basic polymer, wt .-% CrO ₂

3.3

6.6

14.6

14.6

16.2

16.2

16.2

16.2

16.2

16.2

16.2

16.2

16.2

16.2

16.2

16.2

16.2 16.2

16.2 5.0

5.0

Properties of the tape

iHc, Oersted

Stability at 65 ° C / 5O% rel. Wet.

364 355 364 364

372

361

357

357

365

361

364

361

360

355

368

372

375 400

382 370

372 364

23.0 26.6 19.6

23.7

26.4

21.9

20.4

23.3

17.9

22.0

25.4

23.9

25.0

16.9

35.0

29.5

33.5 12.4

30.2 21.8

17.8

12.6 20.4 37.0 16.6

32.5

21.3

21.2

21.0

14.1

20.2

21.5

33.8

18.2

13.3

17.5

17.3

14.5 11.6

20.8 19.0

15.4

E-U -

VCIi-AN - vinyiiueuw · "« ·· - · - MMA - methyl methacrylate. BMA - ButylmethacryUt. HEMA - "DEAM -

DMAEVE - uimeinyiwn »'" "" ·' "·." ' MVP - fromM «thyl-3.» TaylHJ! Mta · 2-VP - 2-vinyl pyridine.

XL-I -I-VTm -DC-200 - of Diphenylmcthundiisocyunal, adipic acid

33.8 2.2

and butanediol.

700639/69

25th

26th

Plate VI

Stabilization of chromium oxide-containing magnetic tapes with tertiary amine-containing copolymers and dispersants

(CrO ₂ = 41% by volume of total solids)

example binder Dispersants Vol%
CrO ₂ Properties of the P / W Tapes iHc, Stability, Oersted tiobei 65 "C / 50% 22.7 rel. Wet. 64 VCl ₂ -AN MMA / MVP (90/10) 16.0 371 64.5 65 VCl ₂ -AN (Soy lecithin) 8.0 32.3 (MMA / MVP (90/10)) 8.0 368 37.6 9.5 Comparative experiment H VCl ₂ -AN Soy lecithin 16.0 364 23.0 2.7 43 E-U MMA / MVP (90/10) 16.0 364 12.6 66 E-U [Soy lecithin] 8.0 25.9 [MMA / MVP (90/10)] 8.0 364 33.8 4.7 Comparative experiment G E-U Soy lecithin 16.0 364 2.2 VCl ₂ -AN = vinylidene chloride-acrylonitriHgO / aoj mixed polymer.

yH / jpy

wwV »Τ?!? ^p ° ¹ y ^ester - ^po 'y ^uretha nha «of diphenylmethane diisocyanate, adipic acid and butanediol MMA = methylmetnacrylate. MVP = 2-methyl-5-vinylpyridine.

Plate VI

Masses for magnetic tapes

Masses that contain the ferromagnetic composition chromium oxide of the binder

(Wt .-%)

(Wt .-%)

Preparation a ferromagnetic chromium oxide

preformed polyester-polyurethane resin from diphenylmethane diisocyanate, adipic acid and butanediol

Methyl acrylate ^ -Methyl-S-vinylpyridine copolymer

2,4-toluene diisocyanate / trimethylolpropane (3/1): crosslinking 0.2-1 5 medium ' '

70-80 (35-45% by volume)
14-25

2-7.5

Stearic acid amide to lubricant Preparation B

ferromagnetic chromium oxide preformed polyester-polyurethane resin of diphenylmethane diisocyanate, adipic acid and butanediol / vinylidene chloride-acrylonitrile (80:20) mixed polymers 60 / 40-40 / 60 Methyl methacrylate ^ -Methyl-S-vinylpyridine (90/10) 2,4-toluene diisocyanate / trimethylolpropane (3/1) Stcarinsüurcamid

0.1-0.4

70-80 (35-45% by volume) 13-26

2-7.5

0.2-3.0

0.1-0.4

1 sheet of drawings

69-88

10-25 1-5

0.6-1.3

64-88

10-25

1-10

0.6-1.3

Claims (3)

Patent claims: 1. Ferromagnetic mass, consisting of A. 2 to 99% by weight of a binder mixture> out a) 1 to 90% by volume of a basic polymer containing a tertiary nitrogen atom, at least 0.1% by weight / o of the polymer as a tertiary ammo .ο nitrogen and the tertiary Amine-containing part of the polymer has a pKa value of 3 to 11, measured in water from 20 to 35 ° C, b) 10 to 99% by volume of others, usually as a binder for ferromagnetic masses containing metal oxides used polymers and B. 1 to 98% by weight of ferromagnetic chromium oxide evenly dispersed in A, as well as, if applicable C. common modifying additives. 2. Ferromagnetic mass according to claim 1, characterized in that the basic polymeric material is a mixed polymer of 2-methyl 5-vinylpyridine and at least one other polymerizable, ethylenically unsaturated monomer. 3. Use of the ferromagnetic masses according to claims 1 and 2 for the production of magnetic recording materials. However, like the formation of aluminum, the formation of an aluminum delays the degradation of magnetic recording materials, which is also influenced in the opposite sense by the polymers which are present in the binder of the recording materials and which have been set to desirable mechanical