DE1260132B - Process for the production of magnetogram carriers - Google Patents

Description

FEDERAL REPUBLIC OF GERMANY

GERMAN

PATENT OFFICE

EDITORIAL

int. Cl .:

C08d

German class: 39 b -5/20

Number: 1260132

File number: B 88243IV d / 39 b

Filing date: July 27, 1966

Open date: February 1, 1968

The invention relates to a method for producing layered magnetogram carriers from or several layers of finely divided magnetizable substances and binders for image, impulse and sound recording.

It is known to produce magnetogram carriers by using a carrier, e.g. B. a film or a Thread or some other body made of plastic or metal, with a dispersion of a magnetizable Coated with which film-forming substances are used as binders. As a binder are z. B. cellulose ethers, cellulose esters, polyesters, polyurethanes, polyvinyl chloride, polyvinylidene chloride, Polyvinyl acetate and copolymers of vinyl chloride, vinylidene chloride and / or vinyl acetate are used been.

It is also known to use copolymers of styrene and acrylonitrile (German Patent 1130194) as well Polyamides (US Pat. No. 2,937,028) can also be used as binders for magnetic layers polymerizable substances, such as mixtures of polyisocyanates and polymers containing hydroxyl groups (Belgian patent 650 663). Copolymers of butadiene and acrylonitrile are also used and hydroxyalkyl methacrylates have been used for this purpose (German Auslegeschrift 1198 859).

However, these binders have disadvantages, such as insufficient stability of the dispersion, inadequate Compatibility with other additives, insufficient abrasion resistance of the magnetic layer, poor mechanical or chemical resistance or poor temperature resistance, excessively strong Shrinkage during production, limited processing time for the binder, insufficient flexibility of the magnetogram carrier, moisture sensitivity and poor surface smoothness.

It has been found that magnetogram carriers can be produced by applying a finely divided magnetic substance, Dispersion containing butadiene copolymers and solvents onto the carrier material and removal of the solvent can advantageously be prepared by using a butadiene copolymer as a Block copolymer consisting of at least three sequences of butadiene and styrene or methylstyrene used whose molecular ends consist of polystyrene or poly-a-methylstyrene blocks.

Such block copolymers can be used in a conventional manner, for. B. exercise according to the information in H 0 - Weyl, Methods of Organic Chemistry, Vol. XIV / 1, pp. 630 ff. And 810.

The block copolymers generally contain 60 to 95 percent by weight of butadiene and 5 to 40 Ge processes for the production of
Magnetogram carriers

Applicant:

Aniline & Soda Factory in Baden

Aktiengesellschaft, 6700 Ludwigshafen

Named as inventor:

Dr. Georg Schnell, 6700 Ludwigshafen;

Dr. Ernst-Günther Kastning, 6701 Assenheim;

Dr. Herman Pankraz Hofmann, 6710 Frankenthal; Dr. Job Werner Hartmann,

Dr. Helmut Christoph, 6700 Ludwigshafen

weight percent styrene and / or «-methylstyrene polymerized. The proportion of polymerized -methylstyrene is generally between 5 and 25 percent by weight and the proportion of polymerized styrene between 10 and 40 percent by weight. Block copolymers of butadiene and styrene are preferred.

Block copolymers in which the polybutadiene blocks are particularly suitable for the process claimed 40 to 70% 1,4-trans structure, 20 to 40% 1,4-cis structure and 5 to 20% 1,2-vinyl structure exhibit. In general, the polybutadiene blocks of the block copolymers have at least 80% 1,4 structure. Your K values (measured according to H. Fikentscher, Cellulose-Chemie, Vol. XIII, P. 58 [1932]) are preferably above 50, and block copolymers with K values between 50 and 70 are preferred.

The butadiene block copolymers suitable as binders for the new process are in conventional solvents, e.g. B. tetrahydrofuran, completely soluble. They generally at temperatures from -80 to + 8O ⁰ C a shear modulus above 10 ⁷ dynes / cm ^2. In addition, the shear modulus changes relatively little in this temperature range. Finally, the block copolymers have glass transition temperatures, which are generally far below 0 ° C and can be up to -8O ⁰ C, especially when the polymerized Polybutadiensequenzen 1,4-cis-structure have. In these properties, the block copolymers differ greatly from random copolymers of a corresponding composition.

709 747/592

In the new process, the dispersions of the ferromagnetic substances can be used in a conventional manner getting produced. In general, finely divided ferromagnetic substances are used per 100 parts, preferably rod-shaped γ-iron (III) oxide, 19 to 55 parts of block copolymer and 81 to 220 parts a liquid suitable as a solvent for the block copolymer, e.g. B. tetrahydrofuran or Toluene, and optionally 0.5 to 5.5 parts of dispersant

Greed aids, such as unsaturated or saturated fatty io polyethylene terephthalate film of 24 μ thickness, the acids, as well as their esters, amides and Äthylenoxyd- beforehand with an approximately 0.3 μ thick layer of one

Sequences, with the ends of the molecules representing polystyrene blocks, are made up of 400 parts by volume Agitator ball mill (4 mm steel balls) with 100 parts of acicular y-iron (III) oxide, 2.5 parts Stearic acid and 120 parts of tetrahydrofuran mixed for 2 hours.

The dispersion is pressed through a filter under nitrogen pressure and placed on a casting machine a linear caster of 60 μ wet film thickness to one

additive products. The constituents of the dispersion can be used in a conventional manner, e.g. B. using from agitator ball mills, roller ball mills or bead mills, mixed and homogenized will. The block copolymer used as a binder can be used before the start of grinding, can be added during or after the grinding of the dispersion. Also can the dispersion still small amounts of other additives, such. B. Substances to lower the coefficient of friction the magnetic layer, antistatic agents and antiblocking agents are added.

The finely divided dispersion of the ferromagnetic substances which the block copolymer contains is optionally filtered and then applied to the carrier material in a conventional manner.

As a carrier material z. B. films, tapes and threads made of polyvinyl chloride, polyethylene glycol terephthalate and cellulose triacetate and molded articles made of paper, plastic and non-magnetizable ones Metals into consideration. In some cases, e.g. B. when using films made of polyethylene glycol terephthalate it can be advantageous to improve the adhesive strength of the magnetic layer on the carrier material an intermediate layer, for example based on vinylidene chloride copolymers or saturated Apply polyesters.

The magnetic layer can be applied to the carrier material in a conventional manner, e.g. B. at elevated temperature, preferably between 70 and 150 ⁰ C, are dried.

The new process results in magnetogram carriers that have improved endurance properties, improved flexibility, reduced abrasion and a particularly low sensitivity to temperature and fluctuations in humidity. Band-shaped magnetogram carriers, which after the new methods are particularly suitable for magnetic television recording, for computers as well as instrumentation tapes.

The parts given in the following examples are parts by weight. The volume parts specified therein behave like the liter to the kilogram.

example 1

100 parts of a 20% ig ^en tetrahydrofuran solution of a butadiene-styrene block copolymer made of three

55 commercially available vinylidene chloride-acrylonitrile copolymer had been coated, poured. Drying takes place at 80 to 100 ^° C. for 30 seconds.

The magnetic film is cut to tape format (6.25 mm) and provides audio tapes in which the Magnetic pigment has a density of 1.81 and has particularly good running properties in conventional tape recorders exhibit.

Example 2

In a ball mill with a capacity of 6000 parts by volume (4 mm steel balls), 750 parts of a 20% solution of a block copolymer of butadiene and styrene (three sequences, molecule ends: polystyrene blocks, specific weight 0.94, 200 kg / cm ² tear strength and 1100 % Elongation), 18.5 parts of stearic acid, 18.5 parts of linseed oil fatty acid, 187.5 parts of refined potassium resin, 300 parts of tetrahydrofuran and 300 parts of butyl acetate were weighed out. After 48 hours the dispersion has progressed far enough for the dispersion to be treated further as indicated in Example 1.

The magnetic tapes obtained have a magnetic pigment density of 1.78. You will be on Cut 3.8 mm wide and put into tape cassettes. Such a cassette with 60 m of tape can withstand 50 cycles at 24 ° C and 98% Humidity without discoloration on the erase head, speech head or on the capstan or the pressure roller or deposits occur.

Claims (1)

Claim: Process for the production of magnetogram carriers by applying a finely divided, ferromagnetic Substances, butadiene copolymers and solvents containing dispersion on the Carrier material and removal of the solvent ';, characterized in that one as a butadiene copolymer, a block copolymer consisting of at least three sequences from butadiene and styrene or α-methylstyrene used whose molecular ends consist of polystyrene or poly-Ä-methylstyrene blocks. 709 747/592 1.68 © Bundesdruckerei Berlin