JPH03214426A - Production of magnetic recording medium - Google Patents

Abstract

PURPOSE:To obtain good electromagnetic conversion characteristics and traveling durability by mixing and dispersing a solvent in a kneaded material having a specified composition, adding fatty acid and polyisocyanate thereinto and then forming a magnetic layer. CONSTITUTION:The kneading process is devided into several stages. First, 100 pts. wt. of ferromagnetic powder, 10 - 60 pts.wt. of solvent, and polyurethane and/or polyester are kneaded so as to obtain good dispersibility, into which magnetic powder is dispersed. Then 3 - 15 pts.wt. of vinyl choloride resin is added for further kneading, and successively 150 - 300 pts.wt. of solvent is added for kneading and dispersing. Then 0.5 - 5 pts.wt. of fatty acid having 10 - 30 carbon number and 2 - 10 pts.wt. of polyisocyanate are added to this dispersion, which is applied on a supporting body 1 to form the magnetic layer 2. By this method, the components of the coating material are sufficiently mixed without causing hardening reaction. Thus, the obtd. magnetic layer 2 has excellent electromagnetic conversion characteristics and traveling durability.

Description

[Detailed description of the invention] a. INDUSTRIAL APPLICATION FIELD The present invention relates to magnetic recording media such as magnetic tapes and magnetic disks.

mouth. BACKGROUND OF THE INVENTION Generally, magnetic recording media such as magnetic tapes are manufactured by applying a magnetic paint made of ferromagnetic powder, a binder, etc. onto a non-magnetic support and drying it.

In recent years, there has been a demand for higher recording densities in magnetic recording media, especially video magnetic recording media that require short wavelength recording, and ferromagnetic powder has also become finer to meet the demands for higher recording densities. In addition, powders with high coercive force and a specific surface area of 45 rrr/g or more are being used.

However, as ferromagnetic powder becomes finer and has a higher coercive force, the cohesive force of individual particles becomes stronger, and as a result, the dispersibility necessary to obtain high playback output and good S/N ratio for short wavelength recording becomes weaker. and surface smoothness will not be fully satisfied. This tendency is particularly noticeable in ferromagnetic metal powders. In addition, in magnetic recording media containing ferromagnetic powder that is not sufficiently dispersed, the magnetic powder, etc. contained in the coating film is likely to fall off during recording and reproduction, resulting in undesirable development such as clogging of the ζB air hand. This causes deterioration of running durability.

Conventionally, various methods have been used to evaluate such dispersibility, as shown in the table below.
It is proposed to summarize them in 1.

In most of these, kneading is performed in two stages to prepare the magnetic paint (however, "metal" refers to metal magnetic powder, and "salt-vinyl acetate" refers to vinyl chloride-vinyl acetate copolymer). (represents union).

(The following is a blank space) These conventional methods have the problems described in (1) to (7) below.

(1). If kneading with 21 Gu is not done in the second stage,
Dispersibility becomes insufficient, leaving problems in electromagnetic conversion characteristics and running durability.

(2). Even if polyurethane is kneaded in the first step, if a lubricant or abrasive is added at the same time as the binder mono-vinyl acetate used in the second step, the dispersibility will deteriorate.

Further, since the polyurethane used in the first stage has a low adsorption power to the metal magnetic powder, the kneading effect deteriorates, and the desired electromagnetic conversion characteristics and running durability cannot be obtained.

Similarly, salt-vinyl acetate added in the second stage gives the same results as polyurethane. (Unexamined Japanese Patent Publication No. 56-167771~
(3) 6 Even if polyurethane is kneaded in the first stage, unless salt to vinyl acetate are kneaded in the second stage, the salt-vinyl acetate will not be able to be sufficiently adsorbed to the metal magnetic powder, and the dispersion will be difficult. The coating liquid lacks stability and the electromagnetic conversion characteristics deteriorate. (Japanese Unexamined Patent Publication No. 57141026) (4) If the binder (polyurethane, mono-vinyl acetate) is kneaded at the same time without separating it into the first and second stages, the viscosity of the paint after dilution and dispersion will be high and the gloss will be high. , the electromagnetic conversion characteristics and running durability of the tape are poor.

(5). Adding an abrasive during kneading may adversely affect the dispersion of the magnetic powder (damage to the magnetic powder: because the abrasive has a high hardness), or may cause poor dispersion of the abrasive due to differences in the appropriate point of dispersion of the abrasive itself. Therefore, after the magnetic coating is formed, it tends to fall off, resulting in dropouts.

(Japanese Unexamined Patent Application Publication No. 58-200423) (6). If the binder used during kneading is a chloride-vinyl acetate resin and the binder added during dispersion is polyurethane, the polyurethane will be insufficiently dispersed and the running durability and electromagnetic characteristics of the tape will deteriorate. (Unexamined Japanese Patent Publication No. 60138732, No. 61-872
Publication No. 6) (7). If fatty acids are added before the third stage, the adsorption of polyurethane, polyester, and vinyl chloride resin to the magnetic powder will be hindered, resulting in an increase in the viscosity of the paint and deterioration of the magnetic and electrical properties after tape formation.

C. OBJECTS OF THE INVENTION An object of the present invention is to provide a method for manufacturing a magnetic recording medium that is excellent in both electromagnetic conversion characteristics and running durability.

two. Structure of the Invention The present invention provides a method for manufacturing a magnetic recording medium having a magnetic layer containing ferromagnetic powder and a binder, which includes (a). 100 parts by weight of ferromagnetic powder, 3 to 15 parts by weight of polyurethane and/or polyester, and 10 to 60 parts by weight of solvent.
(b). 3 to 15 parts by weight of a vinyl chloride resin is added to the kneaded material obtained in this first kneading step, preferably 0.05 parts by weight.
A second kneading step of further kneading under a power consumption load of ~0.5 KW (per kg of ferromagnetic powder), a scattering step, (d). The dispersion obtained in this second kneading step is subjected to an addition step of adding 0.5 to 5 parts by weight of a fatty acid having 10 to 30 carbon atoms and 10 to 10 parts by weight of a fatty acid having 10 to 30 carbon atoms. The present invention relates to a method for manufacturing a magnetic recording medium.

In the present invention, in the first kneading step, a power consumption load of 0.05 to 0.5 KW (per 1 kg of magnetic powder) is applied to the mixture containing the ferromagnetic metal powder, polyurethane and/or polyester, and a solvent. The above object can be more than fully achieved by applying the mixture to a kneading device for 120 minutes, adding vinyl chloride resin in the second kneading step, and kneading under the same conditions as in the first kneading step. Further, it is desirable that the atmosphere at this time has an oxygen concentration of 5% or less in order to prevent oxidation of the ferromagnetic metal powder, which is particularly susceptible to oxidation, and to improve electromagnetic conversion characteristics and dispersibility. It is preferable to use this atmosphere in the first kneading step as well.

Examples of the kneading apparatus used at each stage of the first and second kneading steps include an open kneader, a pressurized continuous kneader, a plastic kneader, a two-roll mill, and a three-roll mill. Next, in the third step, a solvent is added and second kneading is performed, and examples of the second kneading device at this time include a sand mill, a ball mill, a sand grinder, a Kobol mill, an attriter mill, and the like. In the fourth step, it is preferable to add a saturated or unsaturated fatty acid having 10 to 30 carbon atoms and a polyisocyanate, and further coat this liquid on a non-magnetic support in the fifth step.

As the ferromagnetic powder in the present invention, those commonly used as ferromagnetic powders for magnetic recording media can be used. Examples of ferromagnetic powders include γ-Fe203, C
O-containing 7-Fe. O. , Co-coated T Fez Os,
Fe3 o4, Co-containing Fe304, Co-coated Fe
x 04 , Co-containing magnetic Fe OX (3/2>
x>4/3), and oxide magnetic materials such as Crow. Hexagonal ferrites such as barium ferrite and iron nitride are also used.

Examples of ferromagnetic metal powders include Fe, Ni, Co, Fe-Al series, Fe-Al-Ca series, Fe-Al-N
i-based, Fe-Al-Zn-based, Fc-Al-Co-based, Fe
-Ni series, Fe-Ni-Al series, Fe-Ni-Co series,
Fe-Ni-Si-AI! ．． -Mn-based, Fe-Ni -
Si-Al-Zn system, Fe-AR-Si system, Fe-A
Il-Co series, Fe-Ni-Zn series, Fe-Ni-Mn
system, Fe-Ni-Si system, Fe-Mn-Zn system, FeC
Examples include o-Ni-P type, Co-Ni type, and other ferromagnetic powders such as metal magnetic powders containing Fe, Ni, CO, etc. as main components. Among these, Fe-based metal powders have excellent electrical properties, and are especially suitable for Fe-Al-based and Fe-Al- based metal powders in terms of corrosion resistance and dispersibility.
Ca-based, Fe-AffiNi-based, Fe-AN-Zn-based,
Fe-AlCO system, Fe-Ni system, Fe-Ni -Aj
2 system, Fe-Ni-Zn system, Fe-Ni-Af-
Si-Zn system, Fe-Ni-Aj2-Si-Mn
Fe-based metal powders such as FeNi-Co and FeNi-Co are preferred.

Further, a preferred structure of the ferromagnetic metal powder is such that the content ratio of Fe atoms to Al atoms contained in the ferromagnetic metal powder is an atomic ratio of Fe:AI! -100:1-10
0:20, and the ESCA of the ferromagnetic metal powder
Fe present in the surface area less than 100 people at the analysis depth by
The content ratio of atoms and Al atoms is the atomic ratio F e :
Af! =30:70 to 70:30. Alternatively, Fe atoms, Ni atoms, Al atoms, and Si atoms are contained in the ferromagnetic metal powder, and further, at least one of Zn atoms and Mn atoms is contained in the ferromagnetic metal powder, and the content of Fe atoms is 90%. Ni atom content is 1 atom % or more, less than IO atom %, Aj2 atom content is 0.1 atom % or more, less than 5 atom %, Si atom content is 0.1 atom % or more. , less than 5 at%, the content of Zn atoms and/or the content of Mn atoms (however, if it contains both Zn atoms and Mn atoms, this total amount) is 0
．． Fe atoms, Ni atoms, A1 atoms, Si atoms, Zn atoms and/or Mn atoms present in a surface area of 1 atomic % or more and less than 5 atomic % and less than 100 at the analysis depth by ESCA of the ferromagnetic metal powder. The content ratio of atoms is F in terms of atomic number ratio.
e :Ni:Aj2:Si: (Zn and/or Mn
) = 100: (4 or less): (10 to 60)
Examples include ferromagnetic metal powder having a structure of: (10-70) : (20-80).

In the present invention, a ferromagnetic powder having a specific surface area of 45 rrr/g or more by the BET method is preferably used in accordance with the increase in recording density.

The specific surface area of the ferromagnetic powder in the present invention is measured by a specific surface area measurement method called the BET method, and is expressed as the surface area per unit duram in square meters. This specific surface area and its measurement method are described in "Powder Measurement J (J. M. Dallave
lle, Clydeorr Jr. Co-authored by Benta and others; translated by Sangyo Toshosha), it is described in detail, and also in ``Chemistry Handbook,'' Applications, p. 1170-117l (edited by the Chemical Society of Japan; published by Maruzen, April 30, 1966). Are listed. To measure the specific surface area, for example, the powder is heat-treated at around 105°C for 13 minutes while being degassed to remove what is adsorbed to the powder, and then introduced into the measuring device to set the initial pressure of nitrogen. Set to 0.5kg/rrf,
Adsorption measurements were carried out using nitrogen at a liquid nitrogen temperature (-105''C) for IO minutes.A counter soap (manufactured by Yuasa Ionics ■) was used as the measuring device.

The binder in the present invention is polyurethane, polyester, or vinyl chloride resin, and preferably these resins are -SO. M, -0SO. +M, COOM and one PO(O
Contains a repeating unit having at least one polar group selected from the group consisting of M'h (where M represents a hydrogen atom or an alkali metal atom such as NaSK, Li, etc., and M' is a hydrogen atom, (These are alkali metal atoms such as Na, K, Li, etc. or alkyl groups.) The above polar groups have the effect of improving the dispersion of the magnetic powder, and their content is 0.1 to 0.
8.0 mol% (more preferably 0.5 to 6.0 mol%
). When the content is less than 0.1 mol%, the dispersibility decreases, and when it is more than 8.0 mol%, the magnetic paint tends to gel. In addition, the weight average molecular weight is preferably 15,00
0 to 50,000.

The content of the binder in the magnetic layer is usually 10 to 40 parts by weight (preferably 15 to 3 parts by weight) per 100 parts by weight of the ferromagnetic powder.
0 parts by weight). In this case, polyu? The ratio of tan and/or polyester to vinyl chloride resin is usually within the range of 90:10 to 10:90 (preferably 70:30 to 30:70) by weight.

Next, the synthesis of the vinyl chloride copolymer in the present invention will be described.

In the present invention, the vinyl chloride copolymer used as a binder is a copolymer containing an OH group, such as a vinyl chloride rubinyl alcohol copolymer, which contains the following polar groups and chlorine atoms. It can also be synthesized by addition through reaction with a compound.

C f C H■CH. So, M, C I C Hz C Hz O SO: + M, C
lCH2PO (OM')Z, CICH2 COOM Among these, taking C i CHgCllzSOJa as an example, (CHzCH) + Cl (CTo)z SO
JaOH → one (CH2CH) − +
}ICE1 0 (CHz) z SOJa.

Alternatively, there is a method of copolymerizing all of them as copolymerizable monomers. That is, a predetermined amount of a reactive heptanomer having an unsaturated bond into which a repeating unit containing a polar group is introduced is poured into a reaction vessel such as an autoclave, and a general polymerization initiator such as BPO (penzoyl peroxide) or AIBN is added.
Polymerization can be carried out using a polymerization initiator such as a radical polymerization initiator such as (abbisisobutyronitrile), a redox polymerization initiator, an anionic polymerization initiator, or a cationic polymerization initiator. For example, specific examples of reactive monomers for introducing sulfonic acid or its salts include vinyl sulfonic acid,
Unsaturated hydrocarbon sulfonic acids such as allyl sulfonic acid, methacryl sulfonic acid, and p-styrene sulfonic acid, and salts thereof can be mentioned.

Furthermore, sulfoalkyl esters of acrylic acid or methacrylic acid such as 2-acrylamido-2-methylpropanesulfonic acid, (meth)acrylic acid sulfoethyl ester, (meth)acrylic acid sulfoprobyl ester and salts thereof, or acrylic acid. Examples include ethyl acid-2-sulfonate.

When introducing carboxylic acid or its salt (introduction of COOM), (meth)acrylic acid, maleic acid, etc. are used, and when phosphoric acid or its salt is introduced, (meth)acrylic acid-2-phosphate ester is used. good.

Further, it is preferable that an epoxy group is introduced into the vinyl chloride copolymer. Introduction of epoxy groups improves the thermal stability of vinyl chloride copolymers. When introducing an epoxy group, the content of repeating units having epoxy groups in the copolymer is preferably 1 to 30 mol% (more preferably 1 to 20 mol%). Glycidyl acrylate is preferably used as the monomer for introduction.

Regarding the introduction of polar groups into vinyl chloride copolymers, please refer to JP-A-57-44227 and JP-A-58-108052.
No. 59-8127, No. 60-101161, No. 60-235814, No. 60-238306,
6 (No. 1-238371, No. 62-121923,
There are descriptions in publications such as No. 62-146432 and No. 62-146433, and these can also be used in the present invention.

Next, the synthesis of polyester and polyurethane in the present invention will be described.

Polyesters are generally obtained by the reaction of polyols and polybasic acids. Utilizing this known method, a polyester (boliol) having a polar group can be synthesized using a polybasic acid having a polar group as part of the polybasic acid.

Examples of polybasic acids include phthalic acid, isophthalic acid, terephthalic acid, adipic acid, azelaic acid, sebacic acid, maleic acid, and the like.

Examples of polybasic acids having polar groups include 5-sulfoisophthalic acid, 2-sulfoisophthalic acid, 4-sulfoisophthalic acid, 3-sulfophthalic acid, 5-dialkyl sulfoisophthalate, 2-dialkyl sulfoisophthalate, and 4-sulfoisophthalic acid. Examples include dialkyl sulfoisophthalate, dialkyl 3-sulfophthalate, and their sodium and potassium salts. Examples of polyols include trimethylolpropane, hexanetriol, glycerin, trimethylolethane, neopentyl glycol, pentaerythritol, ethylene glycol, propylene glycol, 1,3-butanediol, 1,4-butanediol, 1,6- hexanediol, diethylene glycol,
Examples include cyclohexanedimethanol.

Further, polyesters having other polar groups introduced therein can also be synthesized by known methods.

Furthermore, for the synthesis of polyurethane, a reaction between a polyol and a polyisocyanate, which is a commonly used method, can be used. As the polyol component, generally used is a polyester polyol obtained by a reaction between a polyol and a polybasic acid. Therefore, by using the above polyester polyol having a polar group as a raw material, a polyurethane having a polar group can be synthesized. Examples of polyisocyanate components include diphenylmethane-4,4'-diisocyanate (MDI)
, hexamethylene diisocyanate (HMDI), tolylene diisocyanate (TD■), 1,5-naphthalene diisocyanate (NDI), tolidine diisocyanate (TODI), lysine isocyanate methyl ester (LD[), and the like.

Further, as another method for synthesizing polyurethane, it can be synthesized by addition by reaction of polyurethane having an OH group with the following compound containing a polar group and a chlorine atom.

C1. CI12CH, So. M, CICH. CH20SO, M, C I
C t{z P O (OM')! ,C1CH,C
OOM Regarding the introduction of polar groups into polyurethane, please refer to Japanese Patent Publication Nos. 58-41565, 57-92422, 57-92423, 59-8127, 59-5423, and 59-5424. No. 62-
There are descriptions in publications such as No. 121923, and these can also be used in the present invention.

In addition to the above resin, the binder is 20% by weight of the total binder.
The following resins can be used below.

Examples include weight average molecular weights of 10,000 to 20
0,000, vinyl chloride-vinylacetate copolymer, vinyl chloride-vinylidene chloride copolymer, vinyl chloride-acrylonitrile copolymer, butadiene-acrylic nitrile copolymer, polyamide resin, polyvinyl butyral, cellulose derivative (nitrile). (cellulose, etc.), styrene-butadiene copolymers, various synthetic rubber resins, phenol resins, epoxy resins, urea resins, melamine resins, phenoxy resins, silicone resins, acrylic resins, urea formamide resins, and the like.

In order to improve the durability of the magnetic layer of the present invention, it is preferable to include polyisocyanate.

Examples of aromatic polyisocyanates that can be used include adducts of tolylene diisocyanate (TDr) and active hydrogen compounds. In addition, as the aliphatic polyisocyanate, hexamethylene diisocyanate (HMD
There are adducts of active hydrogen compounds and the like. The weight average molecular weight of the polyisocyanate is 100 to 3.0
A value in the range of 00 is preferred.

To form the magnetic layer, additives such as a dispersant, a lubricant, an abrasive, an antistatic agent, and a filler may be included as necessary.

Dispersants include caprylic acid, capric acid, lauric acid,
Fatty acids having 10 to 30 carbon atoms such as myristic acid, valmitic acid, stearic acid, and oleic acid, and their alkali metal salts or alkaline earth metal salts or amides thereof; polyalkylene oxide alkyl phosphate esters; lecithin ; Trialkyl polyolefin oxy quaternary ammonium salt; Ab-based compounds having a carboxyl group and a sulfonic acid group, etc. are used. These dispersants are preferably added in an amount of 0.5 to 5% based on the ferromagnetic powder.

The lubricant may contain fatty acids and/or fatty acid esters having 10 to 30 carbon atoms.

In this case, the amount of fatty acid added is 0.0% relative to the ferromagnetic powder.
2 to 10% by weight is good, and 0.5 to 5% by weight is even better.

When the fatty acid content is less than this range, running properties tend to deteriorate, and when it exceeds this range, the fatty acid tends to seep out and output decreases. Further, the amount of fatty acid ester added is preferably 0.2 to 10% by weight, and even more preferably 0.5 to 5% by weight, based on the ferromagnetic powder. If the amount of fatty acid ester is less than this range, the running performance tends to deteriorate, and if it is more than this range, the fatty acid ester tends to seep out or a decrease in output is likely to occur. Moreover, in order to improve the above effects, the weight ratio of fatty acid and fatty acid ester is preferably 10:90 to 90:10.

Fatty acids may be monobasic acids or dibasic acids,
The number of carbon atoms lθ to 30, more preferably 12 to 22. Examples of fatty acids include caproic acid, cabrylic acid, cabric acid, lauric acid, myristic acid, palmitic acid, stearic acid, isostearic acid, linolenic acid, linoleic acid,
Examples include oleic acid, elaidic acid, behenic acid, malonic acid, succinic acid, maleic acid, glutaric acid, adivic acid, pimelic acid, azelaic acid, sebacic acid, 1,12-dodecanedicarboxylic acid, and octanedicarboxylic acid.

Examples of fatty acid esters include oleyl oleate, isocetyl stearate, dioleyl maleate, butyl stearate, butyl palmitate, butyl myristate,
Octyl myristate, octyl palmitate, pentyl stearate, pendyl palmitate, isobutyl oleate, stearyl stearate, lauryl oleate, octyl oleate, isobutyl oleate, ethyl oleate, isotridecyl oleate, to 2-ethyl xyl stearate, ethyl stearate, 2-ethylhexyl palmitate, isoprobyl palmitate, isoprobyl myristate, butyl laurate, cetyl-2-ethyl hexalate, dioleyl adipate, dienalazibet, diisobutyl adipate, diisodecyl adipate, Examples include oleyl stearate, 2-ethylhexyl myristate, isopentylbalmitate, isobentyl stearate, diethylene glycol-monobutyl ether palmitate, diethylene glycol-monobutyl ether palmitate, and the like.

In addition to the fatty acids and fatty acid esters mentioned above, other lubricants such as silicone oil, graphite, carbon fluoride, molybdenum disulfide, tungsten disulfide, fatty acid amide, α-olefin oxide, etc. may be added to the magnetic layer. good.

Examples of abrasives include alpha alumina, fused alumina, chromium oxide, titanium oxide, alpha iron monoxide, silicon oxide, silicon nitride, silicon carbide, molybdenum carbide, tungsten carbide, boron carbide, corundum, zirconium oxide, zinc oxide. , cerium oxide, magnesium oxide, boron nitride, and the like.

The average particle diameter of the abrasive is preferably 0.05 to 0.6 μm, more preferably 0.1 to 0.3 μm.

Antistatic agents include conductive powders such as carbon black and graphite; cationic surfactants such as quaternary amines; anionic surfactants containing acidic groups such as sulfonic acid, sulfuric acid, phosphoric acid, phosphate ester, and carboxylic acid. agent; amphoteric surfactant such as aminosulfonic acid; natural surfactant such as saponin; etc. are used. The above antistatic agent is preferably added in an amount of 0.01 to 40% by weight based on the binder.

Examples of solvents blended into the paint forming the magnetic layer include ketones such as acetone, methyl ethyl ketone, methyl isobutyl ketone, and cyclohexanone; aromatic hydrocarbons such as benzene, toluene, and xylene; methanol, ethanol, propanol, and butanol. Alcohols such as methyl acetate, ethyl acetate, butyl acetate; cyclic ethers such as tetrahydrofuran; halogenated hydrocarbons such as methylene chloride, ethylene chloride, carbon tetrachloride, chloroform, dichlorobenzene, etc. Can be mentioned.

The magnetic paint used in the present invention is produced by kneading and dispersing ferromagnetic powder, a binder, a dispersant, a lubricant, an abrasive, an antistatic agent, etc. in a solvent.

Examples of kneading and dispersing machines used for kneading and dispersing magnetic paints include two-roll mills, three-roll mills, ball mills, tron mills, vebble mills, cobol mills, sand mills,
Sand grinder, Szegveri attritor,
High-impeller classifiers, high-speed impact mills, high-speed stone mills, dispersers, high-speed mixers, homogenizers, ultrasonic dispersers, open kneaders, continuous doublers, pressure doublers, planetary kneaders, and the like are included. In particular, 0
．． Dispersing machines that can provide a power consumption load of 0.05 to 0.5 KW (per kg of magnetic powder) are a pressurized 21 goo, an open kneader, a continuous kneader, a two-roll mill, and a three-roll mill.

In the above-mentioned kneading and dispersion steps, kneading is carried out in multiple stages (two stages) based on the present invention.

That is, in the l-th kneading step, the above-mentioned ferromagnetic metal powder 10
0 parts by weight and 3 to 3 parts of polyurethane and/or polyester
15 parts by weight and 10 to 60 parts by weight of solvent, preferably 5 parts by weight.
Knead for ~120 minutes. In this step, it is possible to sufficiently knead the ferromagnetic metal powder and the polyurethane and/or polyester, which are difficult to disperse in particular by normal methods, and the magnetic powder can be well dispersed in the binder. In this case, if the binder has the above-mentioned polar group, the dispersion can be further improved. The amount of binder should be between 3 and 15 parts by weight as mentioned above; less than 3 parts by weight has no effect as a binder (binding of magnetic powder), and more than 15 parts by weight is actually too much. This prevents uniform dispersion of the magnetic powder, and the amount of magnetic powder becomes too small. The amount of binder is further preferably 6 to 12 parts by weight, more preferably 7 to 11 parts by weight. Regarding solvents,
You can choose from the ones mentioned above, but the amount is 10 to 6
It should be 0 parts by weight. If it is less than 10 parts by weight, it is too small and kneading is difficult, and if it exceeds 60 parts by weight, the viscosity decreases too much and kneading is also difficult. The amount of the solvent is preferably 20 to 55 parts by weight, and more preferably 30 to 50 parts by weight.

In addition, in the second kneading step, the vinyl chloride resin 3
~15 parts by weight are added and further kneaded, preferably for 10 to 120 minutes. This allows the polyurethane and/or
Alternatively, in addition to the improvement in abrasion resistance due to the polyester, the dispersibility of the magnetic powder is improved due to the vinyl chloride resin, and its mechanical strength is increased. However, if the vinyl chloride resin alone is used, the layer becomes too hard, but this can be prevented by containing polyurethane, and the adhesion to the support or base layer is improved. In this second kneading step, since the magnetic powder has already been sufficiently dispersed in the first kneading step, the vinyl chloride resin can be further kneaded well while maintaining this state. The amount of vinyl chloride resin added should be within the above range; if it is less than 3 parts by weight, there will be no effect;
If the amount exceeds 1 part by weight, the above-mentioned drawback (the layer becomes hard) will occur. The amount added is preferably 6 to 12 parts by weight, more preferably 7 to 11 parts by weight. This vinyl chloride resin preferably has the above-mentioned polar group.

Regarding the entire binder composition, the ratio of the above-mentioned polyurethane and other resins (total amount of vinyl chloride resin) is preferably 90/10 to 40/60 by weight.
, 85/15 to 45/55 are more desirable.

Outside this range, if the amount of polyurethane is too large, dispersion tends to be poor, and if the amount of other resins is too large, the surface properties tend to be poor, and especially if it exceeds 60% by weight, the physical properties of the coating film become less favorable overall.

In the case of vinyl chloride-vinyl acetate, it can be mixed with polyurethane with a considerable degree of freedom, and preferably polyurethane has a
It is 75% by weight.

In the present invention, after the second kneading step, as a third step, a solvent of 150 to 30% is added to the kneaded material obtained in the second kneading step.
A second kneading step is performed in which 0 part by weight is added and the second kneading is carried out. During this second kneading, a dispersion having an appropriate viscosity can be prepared using a solvent without adding fatty acids. It is essential to use at least 150 parts by weight of the solvent in order to ensure sufficient coating properties for the final magnetic coating material.

However, if it exceeds 300 parts by weight, it will be too much and a desired dispersion will not be obtained. This amount of solvent is further 160 to 28
It is preferably 0 parts by weight, and more preferably 170 to 260 parts by weight.

Next, as a fourth step, 0.5 to 50% of a fatty acid having 10 to 30 carbon atoms is added to the dispersion obtained in the second kneading step described above.
An addition step of adding 10 to 10 parts by weight and 10 to 10 parts by weight of carbon atoms is performed. This addition step is preferably carried out immediately before the next application of the magnetic paint onto the non-magnetic support, but fatty acids (the above-mentioned saturated or unsaturated fatty acids with 10 to 3 carbon atoms) must be added in the same addition step. Since polyurethane is added, at that point, polyurethane,
Polyester and vinyl chloride resin are sufficiently adsorbed to the magnetic powder. Therefore, by adding fatty acids at this stage, unnecessary adsorption of fatty acids to the magnetic powder can be prevented, and the paint components can be sufficiently stirred and mixed, and the polyisocyanate, which is a curing agent, has been added sufficiently. It can be applied without any curing reaction occurring before the coating is applied.

The number of carbon atoms in the fatty acid used should be IO-30, but if it is less than 10, it will be too small and the lubrication or dispersion effect will be poor, and if it exceeds 30, it will be too large and the lubricity will deteriorate. The number of carbon atoms is preferably 12 to 22, more preferably 14 to 2.
2 is better. If the amount added is less than 0.5 parts by weight, there will be no effect, and if it exceeds 5 parts by weight, the amount will be too large, causing blooming and deteriorating the magnetic properties. The amount added is preferably 0.5 to 4 parts by weight, and even more preferably 0.5 to 3 parts by weight.

In addition, 2 parts by weight of polyisocyanate should be added as a curing agent, but if it is too large, the layer will become too hard and the adhesive properties will deteriorate, so the amount should be 10 parts by weight or less, and 1 to 9 parts by weight. parts by weight is preferred, and 2 to 8 parts by weight is even better.

As described above, the kneading can be divided into two stages and the kneading can be carried out under the optimum conditions for each stage, so that all of the problems (+) to (7) of the conventional method described above can be solved. especially,
Sufficient kneading is possible by performing kneading at each stage at 0.05 to 0.5 KW (per 1 kg of ffi powder). This power consumption is the driving power supplied to the above-mentioned kneading machine, and if it is less than 0.05 KW, it will be too small and the kneading will be insufficient, and if it exceeds 0.5 KW, the kneading will become uneven and the power consumption will tend to increase. There is. This power is preferably 0.05 to 0.4KW, and 0.07 to 0.4KW.
KW is even better.

In the present invention, after the second kneading step, the second kneading step using a solvent is performed to adjust the viscosity to an appropriate level, and then fatty acids and curing agents are added while maintaining the viscosity of the paint. can be done well. Note that the abrasive may be added in the second kneading step, but may also be added after the addition step.

Examples of non-magnetic supports used in the present invention include:
Polyethylene terephthalate, polyethylene-2.6-
Examples include polyesters such as naphthalate; polyolefins such as polypropylene; cellulose derivatives such as cellulose diacetate and cellulose triacetate; polycarbonate and polyamide.

As shown in the drawings, the magnetic recording medium of the present invention has a magnetic layer 2 on a non-magnetic support 1 such as polyethylene terephthalate, and if necessary, a back coat layer ( BC layer) 3 is provided. Further, an overcoat layer (OC layer) may be provided on the magnetic layer 2.

Further, an undercoat layer (UC layer) may be provided between the magnetic layer and the support. Furthermore, the nonmagnetic support 1 may be subjected to a corona discharge treatment.

Examples of coating methods for forming the magnetic layer on the non-magnetic support include air doctor coating, air knife coating, blade coating, squeeze coating, impregnation coating,
Examples include transfer coat, reverse roll coat, kiss coat, gravure coat, cast coat, and spray coat.

The magnetic layer coated on the non-magnetic support is dried while being subjected to magnetic field orientation treatment. Next, surface smoothing processing is performed by calendaring. Thereafter, slitting is performed by performing burnishing or blade processing as necessary.

Note that the present invention is applicable to magnetic tapes as well as magnetic disks.

Ho. Example Hereinafter, the present invention will be explained with reference to specific examples.

The ingredients, proportions, order of operations, etc. shown below may be changed in various ways without departing from the spirit of the invention. <Example-1> 100 parts by weight of ferromagnetic metal powder? Sodium sulfonate group-containing polyurethane (UR-8300 manufactured by Toyobo Co., Ltd.) 8 parts by weight Cyclohexanone 10 parts by weight Methyl ethyl ketone 20 parts by weight Toluene
20 parts by weight of the above composition was added so that the actual load on the motor was 0.25 KW/kg magnetic powder, and 0.2 parts by weight.
The mixture was kneaded for 40 minutes using a pressurized 21-glue under N2 such that the amount of the mixture was 5% or less (first stage). Next, a sodium sulfonate group-containing vinyl chloride resin (M
RIIO) 8 parts by weight was added so that the actual load on the motor was 0.07 KW/kg - magnetic powder, and 0 parts by weight.
The mixture was kneaded for 60 minutes in a pressurized furnace in N2 so that the amount of the mixture was 5% or less (second stage).

Next, this kneaded material was taken out to a sand mill, the following materials and glass beads were further added, and the mixture was heated for 2 hours (3rd
step).

Kneaded product 170 parts by weight Cyclohexanone 40 parts by weight Methyl ethyl ketone 80 parts by weight Toluene
80 parts by weight α-alumina
7 parts by weight putyl stearate
1 part by weight of the above magnetic paint was filtered through a 0.5 μm filter, and 1 part by weight of stearic acid and 5 parts by weight of a polyisocyanate compound (CoroFut L, manufactured by Nippon Polyurethane Co., Ltd.) were added and mixed by stirring (fourth stage). ). Thereafter, it was coated on a non-magnetic support, dried while being oriented in a magnetic field, and supercalendered to give a magnetic layer thickness of 2.5 μm. Thereafter, a back coat paint having the following composition was put into a ball mill, kneaded and dispersed for 70 hours, filtered through a lμm filter, and 20 parts by weight of a polyisocyanate compound (Coronate L manufactured by Nippon Polyurethane Co., Ltd.) was added to prepare the Apply this to the opposite side of the magnetic layer by 0.5
A 8 mm videotape was prepared by applying the film to a thickness of μm and slitting it into 8 cylinder widths.

Back coat layer coating liquid composition: Carbon blank (A) (average particle size 30 nm) Carbon black (B) (average particle size 60 rv+) Nitrocellulose polyurethane resin cyclohexanone methyl ethyl ketone toluene <Example-2> Ferromagnetic of Example-1 The composition of the metal powder is such that the overall atomic abundance ratio is Fe:Ni:Affi:Si:Zn=95
:2:l:l:1, and the abundance ratio of atoms on the surface is Fe:Ni:Af! :Si:Zn=39:0:17:2
An 8III1 videotape was produced in the same manner except that the video tape was changed to 0:24.

30 parts by weight 70 parts by weight 30 parts by weight 200 parts by weight 200 parts by weight 200 parts by weight <Examples 3 to 10 and 12 to 16, Comparative Examples 1-12, 14 to 19> Shown in Table 2 below 8M video tapes were produced in the same manner except that each component was changed.

Example 11, Comparative Example 13> A 2-inch VHS tape was produced in the same manner as in Example 1 except that the slit width was η inches.

Comparative Example 20> An 8au videotape was produced in the same manner except that all the materials added in the first to third stages of Example 1 were dispersed at the same time using a sand mill.

Then, the following performance evaluations were performed on each of the above tapes, and the results are shown in Table 3 below.

Glossiness: The glossiness of the coated sample film (without calender treatment) was measured at an incident angle of 60° perpendicular to the coating direction, and expressed as 100% for the standard plate.

Head wear amount: 8kaku video deck CCD-V900 (manufactured by Sony Corporation)
The amount of head wear was measured for each sample after repeated running for 200 hours at 5''C and 20% RH.

Head stain: After running for 200 hours, the condition of the head was visually observed.

○・・・・・・Almost no dirt Δ・・・・・・Some dirt ×・・・・・・Significant dirt Still life: Reproduction output of still images decreased by 2 dB Indicates the time in minutes. The conditions were 40''C, 20% RH. Coefficient of dynamic friction: was determined by measuring the tape tension at the inlet and outlet of the head cylinder.

Y-output (out): The output at 7MHz was measured using a modified 8ffII1 video deck.

From this result, based on the present invention, kneading was carried out 2 times under the specified conditions.
It can be seen that good performance can be achieved in all aspects by carrying out the process in stages, followed by the second kneading process using a solvent and the addition process of fatty acids and curing agents.

F. Effects of the Invention As described above, in the present invention, lH kneading is carried out in multiple stages, and in the first kneading step, 100 parts by weight of ferromagnetic metal powder, 3 to 15 parts by weight of polyurethane and/or polyester, and a solvent are added. Since 10 to 60 parts by weight are kneaded, the ferromagnetic metal powder, which is difficult to disperse by normal methods, and polyurethane and/or polyester can be sufficiently kneaded, and the magnetic powder can be well dispersed in the binder. In addition, in the second kneading step, 3 to 15 parts by weight of vinyl chloride resin is added to the kneaded product obtained in the first kneading step and further kneaded, so that the magnetic powder is sufficiently dispersed. Because of this, the vinyl chloride resin can also be kneaded well while maintaining that state.

In addition, a solvent of 150 to 3
Since the second kneading step of adding 0.00 parts by weight and kneading is performed, it is possible to prepare a dispersion liquid with a suitable viscosity using the solvent. Furthermore, as a fourth step, the dispersion obtained in the above-described second kneading step is added with a carbon atom number of 10 to
30 fatty acid 0.5 to 5 parts by weight, and 10 carbon atoms
Since we are performing an addition process that adds ~10 parts by weight,
At that point, the polyurethane, polyester, and vinyl chloride resin have already been sufficiently adsorbed to the magnetic powder in the first and second kneading steps, so adding fatty acids at this time will increase the amount of fatty acids into the magnetic powder. Unnecessary adsorption is prevented, the paint components are sufficiently stirred and mixed, and the curing agent polyisocyanate is also added sufficiently, allowing the paint to be applied without causing a curing reaction before the next paint is applied. . As a result, a magnetic recording medium with excellent electromagnetic conversion characteristics and running durability can be provided.

[Brief explanation of drawings]

The drawing is an enlarged cross-sectional view of an example of the magnetic recording medium of the present invention. In addition, in the symbols shown in the drawings, 1...Support 2...Magnetic layer 3...Back coat layer (BC layer) be.

Claims (1)

[Claims] 1. In a method for manufacturing a magnetic recording medium having a magnetic layer containing ferromagnetic powder and a binder, when forming the magnetic layer, (a) 100 parts by weight of ferromagnetic powder; 3 to 15 parts by weight of polyurethane and/or polyester and 10 to 60 parts by weight of solvent
a first kneading step of kneading parts by weight; (b) a second kneading step of adding 3 to 15 parts by weight of a vinyl chloride resin to the kneaded product obtained in the first kneading step and further kneading; (c) ), solvent 15 was added to the kneaded material obtained in this second kneading step.
(d) A mixing and dispersing step of adding and mixing and dispersing 0 to 300 parts by weight of a fatty acid having 10 to 30 carbon atoms and 0.5 to 5 parts by weight of a fatty acid having 10 to 30 carbon atoms, to the dispersion obtained in this mixing and dispersing step. 1. A method for producing a magnetic recording medium, comprising an addition step of adding 2 to 10 parts by weight of isocyanate.