DE1282700B - Binders for magnetic recording media - Google Patents

Description

FEDERAL REPUBLIC OF GERMANY

GERMAN

PATENT OFFICE

DESIGN SCREEN

Int, α .:

Gilb

German class; 21 al - 37/30

Number: 1282700

File number: P 12 82 700.8-55 (A52527)

Filing date: May 18, 1966

Opening day: November 14, 1968

The present invention relates to a binder for magnetic recording media with a carrier in the form of a tape, a belt, a disk or the like. And with a layer of synthetic Resin binder in which magnetic fine particles are dispersed on this support.

Usually the carrier is made of an organic plastic, although other materials can be used as well. such as paper, glass or metal, can be used. ίο

In many areas of application of magnetic recording media, especially in television and data processing technology, a tape must very often be attached to a recording or playback head walk past, with severe wear and tear on the belt »5.

In the manufacture of magnetic recording tapes heretofore using a thermoplastic Binder incorporated a low molecular weight plasticizer into the binder, ao However, such plasticizers with low molecular weight on the one hand weaken the resin binder very strong and on the other hand lead to instabilities with long signal storage, since the plasticizer tends to wander through the body of the as binder. According to the invention is now instead of a low molecular weight plasticizer along with a vinyl chloride-vinyl acetate copolymer an elastomeric, thermoplastic polymeric material of the polyurethane filament $ o high molecular weight used. It has been found that certain polyurethanes make the vinyl chloride-vinyl acetate copolymer effectively plasticize and moreover in contrast to conventional plasticizers with low molecular weight give the binder strength and long service life, i In addition, such a plasticizing migrates; medium not through the resin binder. In addition, i the wear product of the tape is not sticky, i.e. that is, it does not attach itself to heads or others Playback devices, so that the tape has a long life also from an electrical point of view owns.

The magnetic recording medium according to the invention from a preferably plastic carrier and a layer which adheres to the carrier and consists of a vinyl chloride-vinyl acetate copolymer as a binder with fine particles of magnetic material dispersed therein is thereby characterized in that the binder is a non-reactive, prepolymerized polyurethane as a plasticizer contains.

Binders for magnetic recording media

Applicant:

Ampex Corporation, Redwood City, Calif.
(V. St. A.)

Representative:

Dipl.-Ing. F. Weickmann,

Dipl.-Ing. H. Weickmann

and Dipl.-Phys. Dr. K. Fincke, patent attorneys,

8000 Munich 27, Möhlstr. 22nd

Named as inventor:

Lawrence (NMI) Greybeard, Daly City, Calif.

(V. St. A.)

Claimed priority:

V. St. v. America May 24, 1965 (458479)

In general, the binder for a magnetic recording material according to the invention is carried out Combining the higher molecular weight vinyl chloride-vinyl acetate copolymer with a thermoplastic High molecular weight polyurethane resin associated. The amounts of the two used Resins can vary widely; generally it has been found to be 10 to 75 percent by weight Vinyl chloride-vinyl acetate copolymers can be used with the remainder of the resin composing Settlement consists of a suitable polyurethane.

Suitable vinyl chloride-vinyl acetate copolymers are known per se; they contain about 3 to 38% vinyl acetate, the remainder of the compound consisting of vinyl chloride and vinyl alcohol. A particularly suitable one commercially available vinyl chloride-vinyl acetate copolymer is in trade. It contains approximate

91% vinyl chloride,
3% vinyl acetate,
6% vinyl alcohol.

809 637/1065

This copolymer has an intrinsic viscosity of 0.57 cP and a specific gravity of 1.39 at 20 ⁰ C in cyclohexanone.

Suitable elastomeric polyurethane resins can be prepared by reacting a diisocyanate such as 2,4-toluene diisocyanate, hexamethylene diisocyanate or p-p'-diphenyl diisocyanate, with a 'dibasic Acid, such as adipic or. Phthalic acid, and a polyhydroxy alcohol such as Glycerin, hexanetriol or batanediol can be produced. A particularly suitable polyurethane is made from p-p'-Diphenylmethane diisocyanate, adipic acid and 1,4-butanediol are prepared using the proportions of the components are chosen so that all isocyanate groups react to form a non-reactive polymer. Possess such resins the properties given in the following table:

5701

5702

specific weight

Hardness (Durometer A): ............, - .; ..: ....

Dielectric strength at 23 ⁰ C (psi).> .. · - ··

300% modulus at 23 ° C. (Psi) -. 'V

Abrasion resistance (weight loss b, ei CS-17 spool, 100 g / 500 spool revolutions). *.

1.21 1.19 88 65 5840, 5000 1240 ■ '420

0.0025

0.15

In the following some embodiments of the tie according to the invention are described.

In all examples, "a single dispersion" is used first made from a mixture of magnetic iron oxide in suitable solvents and additives, in which the mixture for several hours in one Ball mill. "In a separate vessel a resin solution is prepared * which with the dispersion is mixed together. This mixture is in a ball mill for several hours ground. The relative amounts of. Dispersion and the resin solution are selected so that, after removal of the solvents, the final coating - · ■ * composition approx. 70 to 80 percent by weight magnetic iron oxide; containsi ■ ·: ■ · »«: ■ \ -i; The resulting dispersion is seen as a thin <over-

layer with a knife coater on a 2.54 · 10 ^ ³ to 1.27 -10- * cm thick polyester

'■ applied to the carrier. The nasseSchichtwirdineiaeniDrei 'zone oven at about 79 ° C (175 ⁰ F) in the first zone and at about-167 ° C (225 ° F) in the second and third

Zone dried. The pulling speed is 30.5 m / min .; Die'-drying time in the oven ■ * is about 35 to 40 seconds'. -The tapes are rolled up immediately after leaving the oven and tested later. '- ■ ^. ■ ■ - · ■ ■ '

The following table shows the specific weight percentages:

Beisjuel ·! Parts by weight example 2

Example 3

Dispersion
Magnetic oxide.

soot

Additions*)

Methyl ethyl ketone. ':.
Methyl isobutyl ketone
toluene

Resin solution

PVC

Polyurethane ........

Methyl ethyl ketone ...
Methyl isobutyl ketone
toluene

*) Additives: lecithin, silicone oil and mercury phenyl oleate.

100.0% 100.0%

30.0% 2.9%

l, v / o

5.8%

7.9%

11.7%

4.8 ° /, 4.1% 16.6 % 4.8% 9.8%

.100.0%

The finished tapes were tested physically and magnetically and found to be good. The test results given in the table below are typical of the results obtained. '' ■■■ -

example 1 Example 2 Example 3

Belt abrasion test, number of kilometers run ¹ )

Layer-to-Layer Adhesion

Photo detachment ² )

Output power ³ ) at 800 bpi (bits per inch), 200%

saturation

Pulse width, microseconds ⁴ )

Resistance, ohms per inch

Approximation to rectangular hysteresis, ratio BrJBs

(Remanence induction / saturation induction)

*) During the failure test, the tape was tested until it no longer provided satisfactory digital information. The tapes were still up to 100,000 revolutions good, while known commercially available tapes failed after 30,000 to 40,000 revolutions in the same tests.

*) In computer applications, a light mark is placed on certain parts of the back of the tape, with the tape being scanned by a photocell. Does the mark come off the back of the 100.00+ tape during storage
no
no

+2.5

30th
4.3 x 10 ^s

0.755

100.00+
no
no

+3.5

30th
1.8 · 10 «

0.770

100.00+
no
no

+2.5

30th
1.8 · 10 ·

0.756

and adheres to the adjacent magnetic layer, showing that the binder is sticky and off is unsuitable for this reason.

*) This experiment gives the percentage increase in output power compared to known commercial computer tapes.

·) A small pulse width shows good responsiveness short wavelengths. The values found are three to four times as high as with known commercial ones Ribbons.

The present invention makes a magnet »5 tape with high efficiency and long service life, which is particularly useful for video and computer applications is suitable.

Claims (4)

Patent claims: 1. A magnetic recording medium comprising a preferably plastic support and a Adhering to the carrier layer, which consists of a vinyl chloride-vinyl acetate copolymer consists as a binder with fine particles of magnetic material dispersed therein, characterized in that the binder as a plasticizer is a non-reactive, Contains prepolymerized polyurethane. 2. Recording medium according to claim 1, characterized in that the proportion of the Vinyl chloride-vinyl acetate copolymer makes up 10 to 75 percent of the binder resin. 3. Recording medium according to claim 1 and 2, characterized in that the layer contains about 70 to 80 percent by weight of magnetic particles, with the remainder of the layer is formed by the resin. 4. Recording medium according to claim 1, 2 or 3, characterized in that the resin from a mixture of 10 to 75 percent by weight vinyl chloride-vinyl acetate copolymer and 25 to 90 percent by weight of elastomeric polyurethane with a specific weight of about 1.19 to 1.21, with the vinyl chloride-vinyl acetate copolymer about 91% vinyl chloride, about 3% Contains vinyl acetate and approximately 6% vinyl alcohol. Considered publications: German Auslegeschrift No. 1130612;
U.S. Patent No. 2,909442. 809 637/1065 11.68 O Bundesdruckerei Berlin