JPS61138673A - Magnetic coating compound composition - Google Patents

Abstract

PURPOSE:The titled composition having improved coating performance and orientation properties, providing magnetic recording medium having improved physical properties of dispersibility, durability, and wear resistance of magnetic power, consisting of a binder having a specific pyroxylin containing an unsaturated double bond sensitive to radiation and magnetic powder. CONSTITUTION:The aimed composition comprising (A) a binder having a pyroxylin having 10-55, preferably 10-30 average polymerization degree, containing an unsaturated double bond sensitive to radiation, and (B) magnetic powder as main components. An acrylic double bond is preferably as the unsaturated double bond sensitive to radiation of the component A. An amount of the component A is 1-50wt%, preferably 5-30wt% based on the component B.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a magnetic coating composition used in the manufacture of magnetic tapes, etc., and more particularly, it relates to a magnetic coating composition that has excellent coating properties, orientation properties,
The present invention also relates to a magnetic coating composition that provides a magnetic recording medium with excellent physical properties such as magnetic powder dispersibility, durability, and abrasion resistance.

[Conventional technology]

In conventional magnetic recording media, when forming a magnetic coating film on a non-magnetic medium, a reaction between a crosslinking agent represented by a polyvalent incyanate group-containing compound and a hydroxyl group, an amino group, etc. in a binder is performed. Due to the cross-linking reaction with the functional group, 3
A dimensional network structure is formed. However, in such a crosslinking reaction using heat, the reaction does not proceed easily, so the crosslinking density does not increase, and therefore, there are problems such as an inability to improve wear resistance.

In order to correct the above-mentioned problems, it is possible to instantly cross-link the ingu in the magnetic coating film or dry the low-molecular components without generating heat by radiation irradiation. Magnetic coating compositions have been proposed that form magnetic layers with high density, high modulus, and abrasion resistance.

For example, Japanese Patent Application Laid-Open No. 56-124119 describes as follows.

Chemical properties of magnetic paints and magnetic coatings after coating,
It has high physical stability and is not subject to restrictions in processes such as pot life in the paint state and surface treatment of the paint film until radiation irradiation is performed.

Therefore, it is extremely advantageous to rationalize and automate the production process and ensure quality stability by combining the process of irradiating with radiation after performing the necessary processes.

(B) In the crosslinking and polymerization drying of the radiation-sensitive binder, radicals are generated in the binder by radiation irradiation, and the magnetic coating film is cured and dried by the instantaneous crosslinking and polymerization of these radicals. Therefore, radiation of up to 20 Mrad is instantaneously irradiated only to generate radicals, and the irradiation is performed online in sheet form without causing thermal deformation of polyester film, which is widely used as a base material. A decrease in yield due to glabellar transition of the non-uniform magnetic layer during heat curing after winding in a roll, and a decrease in the 87N ratio in the short wavelength region due to winding and transition of surface roughness on the back side of the base material. This is advantageous in terms of prevention.

(0) (As already mentioned in Bl, the reaction is a radical reaction, and unlike conventional thermosetting chemical reactions, it does not require long-term heating to accelerate the reaction, and the degree of crosslinking, curing, drying and curing due to polymerization is This can be easily controlled by adjusting the radiation dose, making it possible to prevent problems such as sticking due to seepage of low molecular weight components in the magnetic layer.

Therefore, the thermal energy of the thermosetting process can be used to save energy, which is advantageous as an energy saving measure.

Although these proposals have produced some results in terms of physical properties, they are still not in a sufficient state to improve the dispersibility of magnetic particles, the smoothness of the coating film surface, and the durability of the coating film.

In order to improve these drawbacks, for example, Japanese Patent Application Laid-Open No. 57-13
Dispersibility of magnetic powder as disclosed in Publication No. 0231,
For the purpose of improving the smoothness of the coating film surface, radiation-sensitive resins such as vinyl chloride-vinyl acetate-vinyl alcohol copolymer, [hinyl chloride-vinyl acetate-maleic acid copolymer, nitrified cotton, and cellulose diacetate] are used. Techniques have been proposed in which polymers containing polar groups such as -00,1 (groups, -0H groups, etc.) are added, such as cellulose resins such as .

In addition, in the case of magnetic coating compositions made using conventional coating discs, a large amount of solvent is used to adjust the viscosity in order to dissolve the binder, disperse magnetic particles, etc., and improve coating properties and orientation. .

[Problem that the invention seeks to solve]

However, the composition disclosed in JP-A No. 57-130231 is still unsatisfied with coating strength, running durability, and abrasion resistance, and the magnetic coating composition of conventional coating discs is Because a large amount of is used, the coating film becomes porous after the solvent is scattered, and the resulting magnetic recording medium is inferior in surface smoothness, coating strength, magnetic powder packing density, and electromagnetic conversion characteristics. Furthermore, since a large amount of solvent is used, there are disadvantages in terms of energy required for drying the coating film, energy required for recovering the solvent, equipment costs, running costs, etc.

[Means for solving problems]

In order to solve the above-mentioned drawbacks, the present invention has been made as a result of intensive research, in which the binder has an average degree of polymerization of 10 to 55 and is radiation sensitive. We have discovered that by using a nitrification wire having a sexually unsaturated double bond, a magnetic recording medium with excellent physical properties such as dispersibility, surface smoothness, durability, and abrasion resistance, as well as electromagnetic conversion characteristics, can be obtained, and the present invention has been achieved. It is completed.

That is, the present invention provides a magnetic coating composition containing magnetic powder and a binder as main components, wherein the binder has an average degree of polymerization of 10.
55 and containing nitrified cotton having a radiation-sensitive unsaturated double bond.

Nitrified cotton as a raw material used in the present invention has an average degree of polymerization of 10 to 55, more preferably 10 to 30.

If the average degree of polymerization is less than 10, the dispersion stability is poor, and the magnetic powder tends to settle over time, resulting in a short pot life of the magnetic coating composition. Moreover, the durability of the magnetic recording medium obtained from the magnetic coating composition is also poor.

On the other hand, those having an average degree of polymerization exceeding 55 have poor dispersibility and give unsatisfactory results in surface smoothness, orientation ratio, and electromagnetic conversion characteristics of the magnetic recording medium obtained from the magnetic coating composition.

The above average degree of polymerization refers to the required amount of sample nitrified cotton (Note 1).
) in an Erlenmeyer flask with a stopper 2 o 0 sLl on a scale and D 30:1 in JIS- adjusted to 20 ± 0.1°C.
4. Add 50 dl of special grade [acetone (reagent)] and make about 16
Let stand for a while. After that, mix gently for about 5 minutes to make a sample solution, and immerse it in water adjusted to 20 ± 0.1 °C.
After allowing the sample solution to stand for 20 minutes or more, the time taken for the sample solution to flow down between the marked lines AB of the capillary of the viscometer is measured. Separately, the flow time of acetone is measured in the same manner as for the sample solution, and the degree of polymerization is determined by the following formula (il, (21, (31)).

Massp = −−1−°1(1) t smile ηsp: specific viscosity t: flow time of sample solution (seconds) flow time of 7 tons of tonia (seconds) where [ma]: intrinsic viscosity 0: Concentration of sample (δ/1) K': 0.315 Km where DP: Average degree of polymerization Km: IIXIQ-' (Note 1) The required amount of viscosity sample to be collected is ysp of 0.1 to 0.
Make it 2.

Nitrified cotton used in the present invention includes, for example, cotton linters,
Nitrified cotton obtained by nitrifying cellulose raw materials such as Utsudonoserp by a known method is heated and depolymerized with water in an autoclave (thus, it is obtained).

The radiation-sensitive nitrified cotton used in the present invention can be obtained by adding a radiation-sensitive unsaturated double bond to the above-mentioned nitrified M t-1fA material.

Typical examples include nitrified cotton with maleic acid double bonds, nitrified cotton with allyl double bonds, nitrified cotton with acrylic double bonds, and nitrified cotton with methacrylic double bonds. and nitrified cotton having a butageno double bond.

In addition, any nitrified cotton having unsaturated double bonds that undergoes cross-linking polymerization upon irradiation with radiation can be used in the present invention.

Radiation is a general term for electromagnetic waves and particles that have the ability to directly or indirectly ionize atoms and molecules. rays, beta rays, electron beams, neutron beams, and their fine particle beams.

Furthermore, the radiation-sensitive unsaturated double bond referred to here refers to a double bond that can be radically polymerized by radiation, and specifically,
Acrylic double bond, methacrylic double bond, maleic acid double bond, acrylic double bond, butadiene 2'
Examples include M-coupling.

Nitrified cotton having a radiation-sensitive unsaturated double bond can be prepared by the reaction in the following example using nitrified cotton having at least one hydroxyl group in the molecule and having an average degree of polymerization of 10 to 55 as a raw material.

(1) A reaction product obtained by adding dicarzenic acid anhydride having a radiation-sensitive unsaturated double bond to nitrified cotton in the presence of a catalyst, such as the hydroxyl group Kal! of nitrified cotton! Nitrified cotton having a maleic acid double bond obtained by reacting maleic anhydride in the presence of a catalyst can be mentioned.

For example, the reaction between a compound having a hydroxyl group in its molecule and a radiation-sensitive dicalic acid anhydride is described in "Wood Chemistry"
Kyoritsu Shuppan (1968) 178.

(11) A reaction product obtained by adding an acid chloride of an organic unsaturated acid having a radiation-sensitive unsaturated double bond to nitrified cotton,
For example, non-nitrified cotton can be obtained by reacting the hydroxyl groups of nitrified cotton with the acid chloride of crotonic acid in the presence of pyridine.

The reaction between a compound having a hydroxyl group in its molecule and an acid chloride of an organic unsaturated acid having radiation sensitivity is described, for example, in "Mokuzai Kagaku", Kyoritsu Shuppan (1968), p. 178.

(iil) A reaction product obtained by adding an aziridine compound having a radiation-sensitive unsaturated double bond to nitrified cotton in the presence of a strong acid catalyst, such as 2-(
Examples include nitrified cotton having an acrylic double bond obtained by reacting 1-aziridinyl)ethyl acrylate.

The reaction between a compound having a hydroxyl group in the molecule and an aziridine compound is described, for example, in "Ethyleneimine and Aza-Aziridine" Academic Press, N.Y. (1969).

(1v) A reaction product of reacting the isocyanate group of a polyincyanate compound with nitrified cotton, and then with one or more molecules of a monomer having a group that reacts with the inquanate group and a radiation-sensitive unsaturated double bond, for example, Nitrified cotton having an acrylic double bond obtained by subjecting the hydroxyl groups of nitrated cotton to a reaction with tolylene diinocyanate and then reacting with 2-hydroxyethyl acrylate can be mentioned.

The polyisocyanate compounds used here include:
2.4-) toluene diisocyanate, 2゜6-toluene diisocyanate, 1,3-xylene diisocyanate, l,4-xylene diinocyanate, m-7 22 diynoquanate, p-7 22 diiso7anate , hexamethylene diisocyanate, inphorondiyne 7anate, Desmodur L%7' Summodur L
(manufactured by Bayer), etc.

Monomers having a group that reacts with incyanate groups and a radiation-sensitive unsaturated double bond include 2- and l'oxyethyl esters of acrylic acid or methacrylic acid;
Esters with hydroxyl groups such as 2-hydroxy 7-propyl ester and 2-hydroxyoctyl ester; Monomers containing 2X bonds; mono- or diglycerides of long-chain resin acids having unsaturated 21i bonds, mono- or diglycerides of mono- or diglycerides of long-chain resin acids having unsaturated 21i bonds, etc., and which have active hydrogen that reacts with incyanate groups, and which are free from radiation. Also included are monomers containing sensitive unsaturated double bonds.

Contrary to the above explanation, the order of introducing radiation-sensitive unsaturated double bonds is to introduce polyincyanate into a monomer having a group that reacts with an incyanate group and a radiation-sensitive unsaturated double bond. It is also possible to react the incyanate groups of the compound and then react the nitrifying M.

As mentioned above, the present invention includes radiation-sensitive unsaturated double bonds such as acrylic double bonds, methacrylic double bonds, allylic double bonds, maleic double bonds, and butadiene double bonds. However, when irradiated with radiation,
Since the acrylic double bond has good sensitivity to radiation, the crosslinking and curing reaction proceeds at low output, which is economical and preferable.

The amount of the nitrified cotton having radiation-sensitive unsaturated double bonds used in the present invention is 1 to 50% by weight, preferably 5 to 30% by weight, based on the weight of the magnetic powder.

If the nitrified cotton having the radiation-sensitive unsaturated 2x bonds is less than 1% by weight based on the magnetic powder, sufficient dispersibility cannot be achieved;
Therefore, the magnetic recording medium obtained from the magnetic coating composition has insufficient surface properties, orientation ratio, and electromagnetic conversion characteristics.

Further, if the amount is 50% by weight or more, although the dispersibility is good, the density of the magnetic powder in the magnetic recording medium obtained from the magnetic coating composition becomes too low, resulting in a decrease in recording density.

In addition to the nitrified cotton having a radiation-sensitive unsaturated double bond of the present invention, as a compounding component of the magnetic coating composition, the resins listed below (+11 to (2)) are used as a backbone, and there are It is particularly effective for the purpose of the present invention to mix radiation-sensitive resins or prepolymers into which radiation-sensitive unsaturated double bonds have been introduced by a method.

+13 Polyurethane elastomers, prepolymers and telomers Examples of such urethane compounds include, as isocyanates, 2,4-toluene diisocyanate, 2,6-
Toluene diisocyanate, 1゜3-Chiclene diicanate, 1,4-Chiclene diicanate, l, 5
- Naphthalene diisocyanate, m-7 22 diisocyanate, p-phenylene diisocyanate, 3.3
'-dimethyl-4,4'-diphenylmethane diinocyanate, 4,4'-diphenylmethane diincyanate, 3゜3'-dimethylbiphenylene diincyanate,
Various polyhydric incyanates such as 4゜4'-biphenylene diisocyanate, hexamethylene diisocyanate, in7olone diisocyanate, cyclohexylmethane diisocyanate, Tesmodur L1 Desmodur N, and saturated polyesters (ethylene glycol, diethylene glycol, chrycerin, Polyhydric alcohols such as trimethylolpropane, l,4-butanediol, 1I6-hexanediol, pentaerythritol, nlupitol, neopentyl glycol, 1,4-7 chlorohexanedimethanol, heptalic acid, isophthalic acid , terephthalic acid, succinic acid, adipic acid, polycondensation with saturated polybases such as succinic acid), linear saturated polyethers (polyethylene glycol, polypropylene glycol, polytetramethylene glycol) or polycaprolactone, etc. Polyurethane elastomer, stomer, prepolymer, and telomer consisting of are effective.

+II) Acrylonitrile-butadiene copolymer elastomer An acrylonitrile-butadiene copolymer elastomer having a terminal hydroxyl group, commercially available as PolyBD Liquid Resin manufactured by Sinclair Petrochemical Co., Ltd., or Nippon Zeon Co., Ltd., Hiker 1432J, etc., is particularly suitable for use in butadiene. It is suitable as a di-stomer component whose double bond generates radicals by radiation and undergoes crosslinking and polymerization. Alternatively, those having a terminal hydroxyl group are effective in increasing radiation sensitivity by adding an acrylic unsaturated double bond via diisocyanate or the like.

A prepolymer having a low molecular weight terminal hydroxyl group, such as polybutadiene elastomer PolyBD Liquid Resage 7B-15 manufactured by Sinclair Petrochemical Co., is particularly suitable in view of its affinity with the magnetic powder. R-15
Since the prepolymer has a hydroxyl group at the end of the molecule, it is possible to increase radiation sensitivity by adding an acrylic unsaturated double bond to the end of the molecule, making it even more advantageous as a binder. Also polybutadiene/cyclized product Nippon Synthesis! OBR-M901 manufactured by MU also exhibits excellent performance.

In particular, cyclized polybutadiene has high efficiency in cross-linking polymerization of radicals of unsaturated bonds inherent in polybutadiene by radiation, and has excellent properties as a binder.

Other elastomers such as chlorinated rubber, acrylic rubber, inbutylene rubber and its cyclized products (Nippon Gosei TM OIR?01), epoxy modified rubber, internally plasticized saturated linear polyester (Toyobo Vylon≠300), etc. are also non-radiation sensitive. It is effective for the present invention by introducing a saturated double bond.

Furthermore, the magnetic coating composition according to the present invention may contain known binders listed below as other ingredients.

Yama Vinyl chloride copolymer Chloride-Nyl-vinyl acetate-vinyl alcohol copolymer,
Vinyl chloride-vinyl alcohol copolymer, vinyl chloride-
Vinyl alcohol-propionyl vinyl copolymer, vinyl vinyl-vinyl acetate-marinic acid copolymer, vinyl chloride-vinyl acetate-terminated -OH side chain alkyl group copolymer, such as UCC VBOf (, VYNO, VYMO, VYE
O-X, VYM8-X.

VERR etc. + III Saturated polyester resin 7-talic acid, in-7-talic acid, terephthalic acid, succinic acid, adipi; /1m! % Saturated polybasic acids such as sepacic acid, ethylene glycol, diethylene glycol, glycerin,
trimethylolpropane, 1.2 propylene glycol, 1,3 but/diol, dipropylene glycol, 1
, 4-butanediol, 1.6-hexanediol, pentaerythritol, nrubitol, glycerin, neopentyl glycol, 1,4-cyclohexane dimetatool.
%Oytkg ester resin or a resin that has improved affinity with magnetic powder, which is obtained by modifying these ester resins with -BOs#N8 groups or the like.

(2) Polyvinyl alcohol-based resins such as polyvinyl alcohol, butyral resin, acetal resin, and copolymers of these components.

(Foundation) Epoxy resin, phenoxy resin Epoxy resin produced by the reaction of bisphenol and epichlorohydrin or methyl epichlorohydrin, Shell Chemical Exhibition (Epicote 152.154.828°1001, 1007), Dow Chemical (DFiN431°DBR732, DER)
511, DER331), manufactured by Dainippon Ink and Chemicals (Epicron 4001, Epiclon 800), and high polymerization degree resins of the above Epoki 7 (DKHA, PKHO).

PKHH), copolymer of brominated bisphenol and epichlorohydrin, manufactured by Dainippon Ink & Chemicals (Spiro
:/ 145.152* 153-1120) etc.

(■ Cellulose derivatives nitrified cotton, cellulose acetate butyrate, ethyl cellulose, butyl cellulose, acetyl cellulose, etc.)

(To) Other binders include at least one or more thermoplastic polyurethane resins, polyester resins, polyvinylpyrrolidone resins and derivatives (pvp olefin copolymers), polyamide resins, polyimide resins, spiroacetal resins, acrylic esters, and methacrylic esters. Examples include acrylic resins contained as polymerization components. These binders are radiofunctional resins 100! 0 to 400 parts are added to each part.

As the magnetic powder used in the present invention, ferromagnetic iron oxide powder, ferromagnetic chloro dioxide fine powder, ferromagnetic alloy powder, etc. can be used. The acicular ratio of ferromagnetic iron oxide and chromium dioxide is 2
/1 to about 20/1, preferably 5/1 or more, average length is 0
．． A range of 2 to 2.0 μm is effective. The ferromagnetic iron oxide powder referred to here is r F etos *F6304,
Oo doped r-Fe, 0. ．． Oo doped γ
-re, 0s-F clause 304 solid solution, Co-based compound fracture type r-Fe103゜0o-based compound adhering board Fe5O4 (r-
(including the intermediate oxidation state with Fe Snow 03). Also, the C mentioned here
The o-based compounds refer to cases in which the magnetic anisotropy of cobalt, such as cobalt oxide, conomalt hydroxide, conomalt ferrite, and conomalt ion adsorbates, is utilized to improve the coercive force.

The ferromagnetic alloy powder has a metal content of 75% by weight or more, and 80% by weight or more of the metal content is a ferromagnetic metal (ie, Fe, Oo).

Ni, Fe-Co + Fe-Ni, 0o-
Ni, Fe-0o-Ni) with a major axis of approximately 1.0μ
It is a particle of m or less.

Furthermore, single crystal barium ferrite fine powder can also be used.

Furthermore, the magnetic coating composition of the present invention may also contain a dispersant as an additive, a lubricant, an abrasive, an antistatic agent, and the like.

Dispersants used in combination include caprylic acid, capric acid,
Fatty acids having 12 to 18 carbon atoms such as lafric acid, myristic acid, palmitic acid, stearic acid, oleic acid, elaidic acid, linoleic acid, and liluic acid; Esters consisting of said fatty acids and alcohols; The above fatty acids and alkali metals (Lt+Na+, etc.) and alkaline earth metals (
A metal soap consisting of Mg * C1p Ba, etc.), lecithin, etc. are used.

In addition, higher alcohols having 12 or more carbon atoms and their sulfuric esters can also be used.

These dispersants are used in an amount of 0 to 20 parts by weight per 100 parts by weight of the binder.
It is added in a range of parts by weight.

Examples of lubricants include silicone oil, fluorinated oil, carn black, graphite, carn black graphite polymer, molybdenum disulfide, tungsten dioxide, monobasic fatty acids having 12 to 16 carbon atoms, and the number of carbon atoms in the fatty acids. Fatty acid esters (so-called waxes) made of monohydric alcohols having a total of 21 to 23 carbon atoms can also be used. It is added in an amount of 0.2 to 20 parts by weight per 100 parts by weight of these lubricants.

The abrasives used are commonly used materials such as fused alumina, silicon carbide chromium oxide, flundum, artificial corundum, diamond, artificial diamond, garnet, and emery (main ingredients: corundum and magnetite). . These abrasive particles have an average particle size of 0.05 to 5 μm, particularly preferably 0.1 to 2 μm. These abrasives are
It is added in a range of 20 parts by weight.

Antistatic agents used include conductive powders such as graphite, carbon black, and Kazen black graphite polymers; natural surfactants such as Nisaponin; and nonionic surfactants such as alkylene ogicides, glycerin, and glycidol. : Higher alkylamines, No. 4
Cationic surfactants such as ammonium salts, pyridine, other heterocycles, phosphonium or sulfonium; anionic surfactants containing acidic groups such as calzenic acid, sulfo/acid, phosphoric acid, sulfate ester groups, phosphoric ester groups, etc. Ampholytic activators such as diamino acids, aminosulfonic acids, sulfuric acid or phosphoric acid esters of amino alcohols, and the like are used.

These surfactants may be added alone or in combination. Although these are used as antistatic agents, they are sometimes applied for other purposes, such as dispersion, improving magnetic properties, improving lubricity, and as coating aids.

The magnetic coating composition can be obtained by mixing the above composition and, if necessary, an organic solvent, mixing and dispersing the mixture.

The organic solvents used in this case include: ketones such as acetone, methyl ethyl ketone, methyl isobutyl ketone, and cyclohexanone; alcohols such as methanol, ethanol, pronognol, butanol; methyl acetate, ethyl acetate, butyl acetate, and scattered ethyl , esters such as acetic acid glycol monoethyl ether: ethylene glycol monoethyl ether, glycol ethers such as dioxane: aromatic hydrocarbons such as benzene, toluene, silane, etc.: methylene chloride, ethylene chloride, carbon tetrachloride, chloroform, Chlorinated hydrocarbons such as dichlorobenzene can be used.

When preparing the magnetic coating composition of the present invention, the magnetic powder and each of the above-mentioned components are fed into a mixer either simultaneously or individually one after another. At this time, a dispersant may be added together with the magnetic powder.

Various kneaders are used to mix and disperse the composition.

Examples include a two-roll mill, a seel mill, a sand grinder, a die/saw, a high-speed imperani disperser, and a high-speed mixer homogenizer.

To obtain a magnetic recording medium using the thus obtained magnetic coating composition of the present invention, the following method is used, for example.

That is, first, the magnetic coating composition is coated on a non-magnetic support so that the thickness of the magnetic layer is in the range of about 0.5 to 15 .mu.m on a dry thick bed. This dry thickness is used for magnetic recording media,
Determined by shape, standards, etc.

The method for applying the magnetic coating composition onto the support is as follows:
Doctor coat, blade coat, air knife coat,
Squeeze coat, reverse roll coat, gravure coat, etc. can be used.

By such a method, the magnetic layer coated on the support is, if necessary, subjected to a treatment for orienting the magnetic powder in the layer as described below, and then dried.

The orientation treatment can be performed under the following conditions.

Orienting magnetic field is approximately SOO~aooo Qe with alternating current or direct current
That's about it.

The drying temperature of the magnetic layer after orientation is approximately 50 to 120°C, preferably 70 to 100°C, particularly preferably 80 to 90°C, and the air flow rate is 1 to 5 kl/m'', preferably 2 to 90°C.
At 3 Jd/ml, the drying time is about 30 to 10 minutes, preferably 1 to 5 minutes.

The surface of the coating film may be smoothed before drying. As this method, methods such as magnet smoothing, smoothing coil, smoothing blade, smoothing blanket, etc. are applied.

The materials for the support include polyesters such as polyethylene terephthalate and polyethylene-2,6-naphthalate; polyolefins such as polyethylene and polypropylene; cellulose conductors such as cellulose triacetate; polycarbonate; Aluminum, copper, tin, zinc, or non-magnetic metals containing these, depending on other uses of plastics such as reimide and polyamide-imide;
Paper materials such as paper and paper coated or laminated with polyolefins can also be used.

In addition, the form of the non-magnetic support is film, tape, sheet,
It may be a disk, card, drum, etc., and various materials are selected depending on the form as necessary.

Further, the surface of the nonmagnetic support opposite to the side on which the magnetic recording layer is provided may be coated with a so-called back coat for the purpose of preventing static electricity, preventing transfer, and the like.

Similarly, it is also possible to add a lubricant as a top coat on the magnetic layer in order to improve the running characteristics of the magnetic recording medium.

It is preferable to apply the magnetic coating composition having the above-mentioned structure onto a non-magnetic support by a known method, dry it, and then irradiate it with radiation, but smoothing treatment may be performed before, after, or during the irradiation. You can also do that.

For smoothing the surface of the magnetic layer, a calendaring process using a mirror roll and a mirror roll or a calendaring process using a mirror roll and an elastic roll is used.

For example, a metal roll can be used as the specular roll, and a cotton roll or a synthetic resin roll (such as nylon or polyurethane) can be used as the elastic roll.

Calendar conditions are approximately 25~I G Okl/cm”
(fD C1-ring pressure, at a temperature of about 10 to 150°C, particularly preferably 10 to 70°C, 5 to 200 m/m
It is preferable to carry out 1 to 30 stages at a processing speed of 1 to 30 in. If the temperature and pressure exceed these upper limits, the magnetic layer may peel off, the support may be deformed, or other adverse effects may occur. Further, if the processing speed is less than about 5 m/min, the surface smoothing effect cannot be obtained, and if it is more than about 200 m/min, the processing operation becomes difficult.

As the radiation used for crosslinking the magnetic coating film of the present invention, an electron beam using an electron beam accelerator as a radiation source is particularly advantageous for the reasons described below. However, in addition, r-rays B using 006G as a radiation source, β-rays using 110 as a radiation source, and X-rays using an X-ray generator as a radiation source are also used.

As an irradiation source, electron beams are used because of the control of absorbed dose and the ease of connection with 7-can control equipment for self-containing ionizing radiation introduced into the manufacturing process line. The use of accelerators is advantageous. Various types of electron beam accelerators have been put into practical use, mainly due to differences in the method of obtaining high voltage, such as Kotskucroft type, bump graph deaf type, resonant transformer type, iron core insulation transformer type, and linear accelerator type. is a bump grout that is relatively inexpensive and provides high output.
It is a 7-store curtain beam system.

As for electron beam characteristics, acceleration voltage is IQOKV ~ 1000
KV % preferably 150-300 KV, absorbed dose 0.5-20 Mrad, preferably 2
~10 Mrad. When the accelerating voltage is less than 100 KV, the amount of energy transmitted is insufficient, and when it exceeds 100 OKV, the energy efficiency used for polymerization decreases, which is not economical.

If the absorbed dose is less than 0.5 Mrad, the curing reaction will be insufficient and the strength of the magnetic layer will not be obtained, and if it is more than 20 Mrad, the energy efficiency used for curing may decrease.
This is not preferable because the object to be irradiated generates heat and the plastic support in particular deforms.

In a low accelerating voltage accelerator, the cost of the system itself is reduced, but it is further advantageous in terms of the power of the ionizing radiation shielding equipment.

In addition, during radiation crosslinking, it is important to irradiate the recording medium with radiation in a stream of inert gas such as nitrogen gas or helium gas. Because it is porous, ink that is irradiated with radiation in the air inhibits the radicals generated in the polymer from effectively working on the crosslinking reaction due to the influence of ozone, etc. generated by radiation irradiation during crosslinking of the binder component. do.

Since the surface of the magnetic layer is naturally porous, the inside of the coating film is also affected by the crosslinking inhibition of the binder. Therefore, it is important to maintain the atmosphere of the area to be irradiated with active energy rays in an inert gas atmosphere such as nitrogen gas, helium gas, carbon dioxide gas, etc., with an oxygen concentration of at most 1%, preferably 300 ppm or less.

Specific examples of such systems include the low-voltage TIG electron beam accelerator (electrocurtain system) manufactured by Energy Sciences (ESI) in the United States, and the self-closed scanning type low-voltage type manufactured by West German Polymer Physics. Electron beam accelerators are preferred.

〔effect〕

The magnetic coating composition of the present invention contains, as a binder, nitrified cotton having an average degree of polymerization of 10 to 55 and having a radiation-sensitive unsaturated 231F bond, so it has excellent dispersibility, durability, and abrasion resistance. This provides a magnetic recording medium with excellent surface smoothness and, in turn, excellent electromagnetic conversion properties.

〔Example〕

The present invention will be explained below with reference to Examples. In addition, in the example “
``part'' means ``rxt part''.

(Synthesis of Nitrified Cotton Having Radiation Sensitive Unsaturated Double Bonds) Synthesis Example-1 Synthesis of Nitrified Cotton Having Niacrylic Double Bonds Nitrified cotton having an average degree of polymerization of 20 was dried and dissolved in methyl ethyl ketone (MEK). A 25% by weight solution was prepared.

On the other hand, iso7anatoethyl methacrylate (Im) (
(manufactured by Dow Chemical Company) was dissolved in 400 parts of a mixed solvent of methyl ethyl ketone and toluene (3N), and 12.4 parts of hydroquinone (manufactured by Dow Chemical Company) were dissolved in 400 parts of a mixed solvent of methyl ethyl ketone and toluene (3N), and 12.4 parts of hydroquinone (manufactured by Dow Chemical Co.
After adding part s and heating to 60°C, the above nitrified wire melt T4
After mixing 00 parts, the mixture was reacted at 60° C. until the NOO reaction rate reached 95% or more.

Synthesis Example 2 Synthesis of Nitrified Cotton Having Niacrylic Double Bond t Nitrified cotton having an average degree of polymerization of 20 is dried and dissolved in MEK to obtain 2
5] [31% solution. On the other hand, 13.9 parts of tolylene diisocyanate (TDI) was added to 2 tons of 4
After heating to 80°C in a two-cell flask, 9.3 parts of 2-hydroxyethyl acrylate (2-HBA), 015 parts of tin actylate, and 0.015 parts of hyroquinone were added until the temperature in the reaction vessel was 80°C. The mixture was added dropwise while controlling the temperature to 85°C, and after the addition was completed, the reaction was completed by stirring at 80°C for 3 hours. Next, 400 parts of the above nitrified cotton solution was added to the above TDI,
2-The temperature inside the reaction vessel in the HE person 1/1 adduct is 75~
The solution was added dropwise while controlling the temperature to 85°C, and after the completion of the dropwise addition, the reaction was allowed to proceed at 80°C until the NCO reaction rate reached 95% or more.

Synthesis Example 3 Synthesis of Nitrified Cotton Having Niacrylic Double Bond Nitrified cotton having an average degree of polymerization of 20 was dried and dissolved in methyl ethyl ketone to make a 25% by weight solution. On the other hand, polynato 2 methylene ether glycol (molecular weight approximately 1000) with trilene sulfate (incyanate content 6)
% by weight) was dissolved in 134 parts of a mixed solvent of methyl ethyl ketone and toluene (3N), parts of dibutyltin dilaurate O and OS were added, and 2H
9.3 parts of BA were mixed and stirred at 60°C for 3 hours to complete the reaction. This solution was mixed with 400 parts of the above nitrified cotton solution and stirred at 30° C. for 48 hours to react until the NOO reaction rate reached 95% or more.

Synthesis Examples 4 to 8 Synthesis of Nitrified Cotton Having Niacrylic Double Bond Nitrified cotton having an average degree of polymerization of 5, 10, 30, and 55.70 was dried and dissolved in methyl ethyl ketone (Ml!iK) to give 25.
It was made into a heavy tχ solution. Thereafter, iso7anate ethyl methacrylate (IBM) was reacted in the same manner as in Synthesis Example 1 to synthesize nitrified cotton having an acrylic double bond. Synthesis example-4 using nitrified cotton with an average polymerization degree of 5, Synthesis example-5 using nitrified cotton with an average polymerization degree of 10, Synthesis example-6 using nitrified cotton with an average polymerization degree of 30. , average degree of polymerization 5
Synthesis example-7 using nitrified cotton of No. 5, average degree of polymerization 70
Synthesis example 8 was prepared using the following.

Synthesis Example 9: Synthesis of Nitrified Cotton Having Maleic Acid Double Bond Nitrified cotton having an average degree of polymerization of 2G was dried and dissolved in methyl ethyl ketone (MEK) to form a 25% by weight solution.

400 parts of the above nitrified cotton solution was heated to 80°C, and 7.9 parts of maleic anhydride, 0.05 part of sulfuric acid, and 0.015 parts of isopropyl titanate were added to it until the temperature in the reaction vessel was 80-85.
℃ while controlling the dropwise addition, and after the completion of the dropwise addition, stirred at 80℃ for 3 hours to complete the reaction.
Nitrified cotton with double bonds was synthesized.

Synthesis Example - 1 O Nitrified cotton having an average degree of polymerization of 20 was dried and dissolved in methyl ethyl ketone (MEK) to make a 25% by weight solution.

400 parts of the above nitrified cotton solution was heated to 80°C, and 2-
(1-aziridinyl)ethyl acrylate), 0.1 part of hydroquinone, and 0.3 parts of sulfuric acid were added dropwise while controlling the temperature in the reaction vessel to be 80 to 85°C, and after the completion of the dropwise addition, the temperature was 80°C. The mixture was stirred for 4 hours to complete the reaction, and nitrified cotton having an acrylic double bond was synthesized.

Synthesis Example 11: Nitrified cotton having a crotonic acid-based double bond Nitrified cotton having an average degree of polymerization of 20 was dried and dissolved in methyl ethyl ketone (MEK) to make a 25% by weight solution.

400 parts of the above nitrified cotton solution was heated to 80°C, and 8.4 parts of croton acid chloride and 70.02 parts of pyridine were added dropwise thereto while controlling the temperature in the reaction vessel to be 80 to 85°C. After the dropwise addition was completed, the mixture was stirred at 80° C. for 3 hours to complete the reaction, and nitrified cotton having a crotonic acid double bond was synthesized.

Example 1 Acicular γ-Pesos (long axis 0.4μ,
Short axis o, osμ, Hc 6000e)
120 parts by weight Car RGN Black (for antistatic use, Mitsubishi Black MA-600J si
t part α-person 1.0. Powder (0.5μ granules) 2
Part by weight dispersant (dog bean oil split lecithin) 3 parts by weight Solvent (methyl ethyl ketone/toluene = 5 Q 150
) 100 parts by weight The above composition was mixed in a ball mill for 3 hours to thoroughly wet the acicular magnetic iron oxide with the dispersant.

Next, nitrified cotton with acrylic double bonds (synthesis example-1)
10 parts by weight Acrylic double bond-introduced urethane elastomer (US) 15 parts by weight Solvent (methyl ethyl ketone) 200 parts by weight Lubricant (higher fatty acid modified silicone oil) 4 parts M (telephone pole) Acrylic double bond introduced urethane elastomer is one in which an acrylic double bond is introduced into a polyurethane skeleton consisting of adipic acid, ethylene glycol, and tolylene diyne heptaanate. (Journal of
Applied Polymer Science, To-o, 23゜p
3227-3242 (1979)) was put into the ball mill and mixed and dispersed again for 42 hours to obtain a magnetic coating composition. This magnetic coating composition was applied onto a 20 μm polyethylene terephthalate support using a doctor blade to a dry film thickness of 4 μm, oriented using a cobalt magnet (1600 Gauss), and then heated with hot air. The solvent was dried (90°C, 1 minute). After this, smoothing treatment is performed using a five-stage calender consisting of a group of flat rolls and mirror-finished rolls (roll temperature 4
0℃, pressure 100 kg/cry? ), using an EaI electrocurtain type electron beam accelerator, electron beam irradiation was carried out under the conditions of acceleration voltage 200 KV, electrode current 10 mA, and total irradiation dose 4 Mrad in a nitrogen gas atmosphere with a residual oxygen gas concentration of 300 ppm. Polymerization, drying and curing reactions of magnetic coatings were carried out.

The resulting tape was cut into % inch width pieces to obtain video tapes. The surface gloss and amount of powder falling off of this tape were measured. The results are shown in Table-1.

Comparative Example 1 Cobalt-coated needle-like 1-pe203 (long axis 0.4 μ, short axis Q, 05 x, Hc 6000e)
120 parts by weight Carzen Black (for antistatic use, Mitsubishi Black MA-600) 5 parts by weight α-At20. Powder (0.5μ granules) 2]U
Partial dispersant (soybean oil refined lecithin) 3 parts by weight Solvent (methyl ethyl ketone/toluene = 5015 G)
10 parts by weight The above composition is mixed in a ball mill for 3 hours to thoroughly wet the acicular magnetic iron oxide with the dispersant.

Next, polyvinyl butyral resin (BM8 manufactured by Sekisui Chemical Co., Ltd.
) 10 parts by weight of acrylic double bond-introduced urethane elastomer ((USA): described in the notes of Example-1) 15 parts by weight Solvent (methyl ethyl ketone) 240 parts by weight Lubricant (Rice fatty acid modified silicone oil) 4 parts by weight The thoroughly mixed and dissolved solution was put into the Zeel mill and mixed and dispersed again for 42 mm to obtain a magnetic coating composition.

This magnetic coating composition was coated, oriented, dried with a solvent, smoothed, and irradiated with radiation in the same manner as in Example 1.

The resulting tape was cut into % inch width pieces to obtain video tapes. Regarding this tape, the surface glossiness and amount of powder falling off were measured in the same manner as in Example 1. The results are shown in Table-1.

Example 2 Cobalt-coated acicular γ-pesos (major axis 0.4μ, short axis 0.05μ, Hc 6000e)
100 parts by weight of nitrified cotton having acrylic double bonds (Synthesis Example-2) 10 parts by weight of polyester polyurethane with acrylic double bonds introduced (molecular weight approximately 30,000, acrylic based on the reaction product of butanediol adipic acid and phenylmethane diincyanate) Double bond introduction) 10 parts by weight Ester acrylate oligomer (Acronix M6100, Toagosei) 4 parts by weight Hexamethylene dibacrylate 3 parts by weight Solvent (methyl ethyl ketone) 240 parts by weight Dispersant (stearic acid) 1.2 parts by weight Dispersant (Butyl stearate) 1.2 parts by weight of the above composition was mixed and dispersed in a Zeel mill for 42 hours to obtain a magnetic coating composition. This magnetic coating composition was coated, oriented, dried with a solvent, smoothed, and irradiated with radiation in the same manner as in Example 1.

The resulting tape was cut into t-% inch width to obtain a videotape. Surface gloss, amount of powder falling off, dropout, and still durability time were measured for this tape. Table 1 shows the measurement results of surface gloss and amount of powder falling off, and Table 2 shows the measurement results of derotsuzo out and still durability time.

Comparative Example 2 Cobalt-coated acicular γ-Fe2es (long axis 0.4μ, short axis o, osμ, Hc 6000e)
120 parts by weight Nitrified cotton H% (manufactured by Asahi Kasei Industries, Ltd.)
10 parts by weight Acrylic double bond-introduced polyester polyurethane (molecular weight approximately 30,000, acrylic double bond introduced into the reaction product of butanediol adipic acid and phenylmethane diiso7anate) 10 parts by weight Ester acrylate oligomer
Mar (Toa Synthetic Aronics M6100)
4 parts by weight of xamethylene diacrylate
3 parts by weight of solvent (methyl ethyl ketone) 3 parts by weight of dispersant (stearic acid) 1.2 parts by weight of dispersant (butyl stearate) 1.2 parts by weight The above composition was mixed and dispersed in a Zeel mill for 42 hours to obtain a magnetic coating composition. Ta. This magnetic coating composition was coated, oriented, dried with a solvent, smoothed, and irradiated with radiation in the same manner as in Example 1.

The resulting tape was cut into % inch width pieces to obtain video tapes. This tape was measured for surface gloss, amount of powder falling off, dropout, and still durability time. Table 1 shows the measurement results of surface gloss and amount of powder dropout.
Table 2 shows the measurement results of still durability time.

Table 1 Hata: Surface glossiness was measured by the amount of reflected light of light incident at an incident angle of 6G' using a commercially available gloss meter (ODI-80H-GV4 manufactured by Ska Shun Co., Ltd.) , and a large value indicates that the glossiness of the crosspiece surface has deteriorated.

#12: Powder removal property is 30 cm in length and 3 inches in width (approximately 1
．． Apply a load of 50S' to one end of the tape cut to 2crn) and use 1000 grit sandpaper to sand it to 2.5cy++/
Shedding was carried out 10 times at a speed of seconds, and the amount of wear was measured from the change in weight before and after shedding.

Example 3 Cobalt-coated acicular γ-Fe203 (long axis 0.4 μ, short axis o, os μ, Hc 6000e)
120 parts by weight Carbon black (for antistatic use, Mitsubishi Kazen Black MA-6100) 5 parts by weight α-At 10 g powder (o, s μ particles) 2 parts by weight Powder (sorbitan monooleate) 3 parts by weight mi
agent (methyl ethyl ketone/toluene = 50/s o )
Too parts by weight The above composition is mixed in a ball mill for 3 hours to thoroughly wet the magnetic iron oxide with the dispersant.

Next, “nitrified cotton with acrylic double bonds (synthesis example-3)”
15 parts by weight Polybutadiene elastomer with acrylic double bond introduced (acrylic double bond introduced into Sinclair Petrochemical's low molecular weight terminal hydroxyl group polybutadiene polybutadiene BD liquid resin 7R-15 using tolylene diisocyanate) 15
Part by weight TiW agent (methyl ethyl ketone/toluene = 5 Q
150) A solution in which 100 parts by weight of a lubricant (fluorinated oil, 4 parts by weight of DuPont Light Tsuxun, manufactured by DuPont) was thoroughly mixed and dissolved was placed in the ball mill and mixed and dispersed again for 42 hours to obtain a magnetic coating composition.

The obtained magnetic coating composition was coated, oriented, dried with a solvent, smoothed, and irradiated with radiation in the same manner as in Example 1.

The obtained tape was cut into h-inch width to obtain a videotape. Regarding this tape, the dropout and still durability times were measured in the same manner as in Example 2. Table the results.
Shown in 2.

Comparative Example 3 Cobalt-coated acicular γ-Fe, 0. (Long axis 0.4μ, short axis 0.05μ, Hc 6000e) 1
20 g Carnon Silk (for antistatic use, Mitsubishi Carzen Black MA-6100) 5 parts by weight α-At 03 powder (0.5μ particles) 2 parts by weight Dispersant (sorbitan monooleate) 3 parts Solvent (methyl ethyl ketone/ Toluene = 507'5o) 10
0 parts by weight The above composition is mixed in a ball mill for 3 hours to thoroughly wet the magnetic iron oxide with the dispersant.

Next, 15 parts by weight of nitrified cotton with an average degree of polymerization of 20, an acrylic double bond-introduced polybutadiene elastomer (low molecular weight terminal hydroxyl group polybutadiene manufactured by Sinclair Petrochemical Co., Ltd., polyBD Liquid Resin R-15, using tolylene diinocyanate) Acrylic double bond introduced) 15 parts by weight solvent (methyl ethyl ketone/toluene = 50150)
2oo-4 parts lubricant (
Fluorinated oil, DuPont Kleitxun
A solution obtained by thoroughly mixing and dissolving the four production parts was put into the mail mill and mixed and dispersed again for 42 hours to obtain a magnetic coating composition.

The obtained magnetic coating composition was coated, oriented, dried with a solvent, smoothed, and irradiated with radiation in the same manner as in Example 1.

The resulting tape was cut into a 3-inch width to obtain a videotape. Regarding this tape, the dropout and still durability times were measured in the same manner as in Example 2. Table the results.
Shown in 2.

Table 2 [3: Dropout is the number of dropouts per minute when so-called 3-step waves are recorded and played back using Matsushita Electric Industrial Co., Ltd.'s VH8.

IM4 Nistil durability time is the time required until the playback screen becomes completely invisible when still playback is performed using the same deck and signal (measurement conditions: 40℃, 80%RH)
).

Examples 4 to 6 The same operation as in Example 1 except that the nitrified cotton produced in Synthesis Examples 5 to 7 was used in place of the nitrified cotton having an acrylic double bond (Synthesis Example 1) of Example 1. The tape was manufactured.

The obtained tape was cut into % width pieces to obtain video tapes.

(The example using nitrified cotton in Synthesis Example 5 is called Example 4, the example using nitrified cotton in Synthesis Example 6 is called Example 5, and the example using nitrified cotton in Synthesis Example 7 is called Example 6. ), and the average degree of polymerization, surface light, magnetism, and amount of powder falling off of this tape were measured.

The results are shown in Table-3.

Comparative Examples 4 to 5 Tapes were produced in the same manner as in Example 1, except that the nitrified cotton of Synthesis Examples 4 and 8 was used in place of the nitrified cotton having an acrylic double bond (Synthesis Example 1) of Example 1. did. (Comparative Example 4 was an example using nitric cotton from Synthesis Example 4, and Comparative Example 5 was an example using nitrified cotton from Synthesis Example 8.) Got the tape.

The average polymerization, surface gloss, and amount of powder falling off of this tape were measured. The results are shown in Table-3.

Table 3 Examples 7 to 9 The same operation as in Example 1 except that the nitrified cotton of Synthesis Examples 9 to 11 was used in place of the nitrified cotton having an acrylic double bond (Synthesis Example 2) of Example 2. So I got the tape. (In addition, the example using nitrified cotton of Synthesis Example-9 is Example 7, Synthesis Example-10
Example 8 was an example using the nitrified cotton of Synthesis Example 11, and Example 9 was an example using the nitrified cotton of Synthesis Example-11. ) The obtained tape was cut into % width pieces to obtain video tapes.

The surface glossiness and amount of powder falling off of this tape were measured. The results are shown in Table 4.

Table-4 Patent applicant Asahi Kasei Industries, Ltd. Procedural amendment (voluntary) January 18, 1985 Manabu Shiga, Commissioner of the Patent Office1, Indication of the case 1982 Patent Application No. 2593722, Name of the invention Magnetic paint Composition 3, Relationship with the case of the person making the amendment Patent applicant 1-2-6-4 Dojimahama, Kita-ku, Osaka-shi, Osaka Prefecture, Contents of the amendment in the "Detailed Description of the Invention" column of the specification subject to the amendment (11 On page 5, line 6 of the specification, ``Magnetic is used for dispersing powder, etc.''
Correct J to "For dispersion of magnetic powder, etc."

(2) Replace “nitrification line” on page 6, line 6 with “nitrified cotton”.
Correct to.

(3) “C: Sample concentration (δ/l)” on page 8, line 6
"C: Concentration of sample (g/j) Correct to J.

(4) "Acrylic" on the bottom line of page 9 has been corrected to "allylic".

(5) Replace “resin acid mono” on page 13, line 2 with “
Corrected to "Fatty acid mono".

(6) “Because I have good sensitivity” on page 13, line 17.
should be corrected to "Because I am highly sensitive."

(7) "In the molecule" on page 14, line 14 is corrected to "in the molecule."

(8) rso, Na group, etc. on page 19, line 4 of the same page.
be corrected to ``r-3OJa5, etc.''.

(9) On page 20, line 14, "ferromagnetic chlorine dioxide fine powder" is corrected to "ferromagnetic chromium dioxide fine powder."

αω Change “(rice)” from the bottom line to the fifth line on page 36 of the same page to “
(*) Corrected to J.

(11) In the second line from the bottom of page 38, “((US): Notes in Example-1 @) J” was corrected to “((*): Notes in Example 1)” do.

that's all ”

Claims (1)

[Scope of Claims] 1. A magnetic coating composition containing magnetic powder and a binder as main components, wherein the binder has an average degree of polymerization of 10 to 55 and contains a radiation-sensitive unsaturated double bond. Magnetic coating composition 2 characterized in that it contains nitrified cotton having a radiation-sensitive unsaturated double bond, and the degree of polymerization of the nitrified cotton having a radiation-sensitive unsaturated double bond is 10 to 30.Claim 1 Magnetic coating composition 3, the magnetic coating composition according to claim 1 or 2, wherein the radiation-sensitive unsaturated double bond is an acrylic double bond.