JPS62262224A - Magnetic recording medium containing polymer dispersant in magnetic layer - Google Patents

Abstract

PURPOSE:To improve dispersibility and productivity by incorporating a compd. which is obtd. from the reaction of the three; a specific compd., aliphat. polyol and di- or triisocyanate and has the carboxy group or carboxy group salt bound on the tertiary carbon into a magnetic layer. CONSTITUTION:The magnetic recording medium provided with the magnetic layer contg. magnetic powder and binder on a base contains the magnetic layer which is obtd. by the reaction of at least the three; the compd. expressed by the formula I, the aliphat. polyol and the di- or triisocyanate and has the carboxy group or carboxy group salt bound on the tertiary carbon in the magnetic layer. In the formula I, R1 and R2 are a bivalent residual hydrocarbon group, R3 is a monovalent residual hydrocarbon group, X1 and X2 are a group reactive with the isocyanate and M denotes a hydrogen atom, alkaline metal atom or alkaline earth metal atom. The magnetic recording medium which has the high output and high S/N and has the magnetic layer formed by using the magnetic coating compd. having the good stagnation stability, hence good productivity is thus obtd.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a magnetic recording medium such as a magnetic tape, a magnetic sheet, or a magnetic disk.

(Prior art) Generally magnetic recording media (hereinafter typically referred to as magnetic tape)
is made by applying a magnetic paint containing magnetic powder, binder, etc. to a support and drying it.

When preparing magnetic paints used in manufacturing such magnetic tapes, various dispersants are used to disperse magnetic powder together with a binder in an organic solvent.

For example, oily or powdered lecithin, saturated or unsaturated fatty acids, salts of these fatty acids, hydrocarbons having polyoxyethylene chains, sulfuric esters or phosphoric esters of higher alcohols, etc. are used to improve the dispersibility of magnetic powder, etc. Various methods have been tried and put into practical use. These dispersants are 0.01 parts by weight per 100 parts by weight of magnetic powder (hereinafter referred to as wt parts).
It is generally used in the range of ~20 Wt parts.

On the other hand, for the preparation of high-density recording and high-performance magnetic tapes that are required in recent years, ultrafine particles of engineering magnetic powder and specific surface area (BET value)
Therefore, it is difficult to obtain magnetic tapes with desired characteristics using conventional dispersants and related technologies.

In addition, the electromagnetic conversion characteristics or tape physical properties are determined by the particle size and specific surface area (BET value: Unit rrX/g
r) K is greatly affected, and the magnetic powder is required to have a large BET value in terms of electromagnetic conversion characteristics and recording density. However, a large BET value brings about great difficulty in dispersing magnetic powder or various fillers. In order to overcome these difficulties or inconveniences, it has a repeating unit of -(CHt CHz O) n-, and the terminal is an (alkyl group) -〇("CH, CH, O)
. - Phosphate esters are well known as dispersants, but as magnetic powder becomes finer and higher densities are required, such phosphoric acid esters are required for magnetic tape performance. The combined use of acid ester or phosphate ester and lecithin also results in insufficient dispersion.

On the other hand, polymer type dispersants are being considered.
It is known that polyimine/polyimine-polyvinyl polymer dispersants are effective in dispersing pigments (Japanese Patent Laid-Open No. 46
-7294), and polyacrylic dispersants are known, but their dispersing power for magnetic powders, especially magnetic powders with a BET value of 30 m"/gr or more, is extremely insufficient, resulting in problems such as output and S/N ratio. cannot give satisfactory performance.

(Objectives of the Invention) The objects of the present invention are: (1) a high-output magnetic recording medium, (2) a high S/N magnetic recording medium, and (3) a magnetic coating material that has good stagnation stability and therefore improves productivity. An object of the present invention is to provide a magnetic recording medium having a magnetic layer using a good magnetic coating.

(Structure of the Invention) The object of the present invention is to provide a magnetic recording medium in which a magnetic layer containing magnetic powder and a binder is provided on a support, at least a compound represented by the following general formula (1), A compound obtained from a three-way reaction of an aliphatic polyol and a di- or tri-isocyanate and having a carboxy group or carboxy group salt bonded to a tertiary carbon (hereinafter referred to as a specific polymer in the present invention), This is achieved by a magnetic recording medium characterized by containing the above magnetic layer.

General formula (1) % formula % In the formula, R8 and R2 represent a divalent hydrocarbon residue (the main chain or @ chain may contain 0.N, S, etc. in addition to C, H), They may be the same or different.

Preferably a divalent fatty #C group having 1 to 10 carbon atoms, more preferably 1 to 3 carbon atoms, and most preferably R
, and R2 are both -CH2-. R3 represents a monovalent hydrocarbon residue, preferably a carbon atom.
Frogs 3 pieces■jisho R deer#〒power, h number, drunkenness 1. ?
1st grade Cff, -.

xl and X represent groups reactive with isocyanate, which may be the same or different; hydroxyl, amino, imino, and mercapto groups are preferred, and hydroxyl is particularly preferred.

M represents a hydrogen atom, an alkali metal atom or an alkaline earth metal atom, preferably a hydrogen atom or K + N
a + L+.

The aliphatic polyol according to the present invention includes glycol (
(e.g. ethylene glycol), glycerin, trimethylol (e.g. trimethylolethane, trimethylolpropane), erythritol.

(For example, pentaeryth + 3) be. Also, the above polyols may be used in combination.

Preferred polyols in the present invention are aliphatic diols, such as ethylene glycol, propylene glycol, diethylene glycol, dipropylene glycol, polypropylene/glycol, polyethylene glycol, 1,4-butanediol, and 1,6-hexane. Examples include diols, and the most preferred among these is polypropylene glycol.

Examples of the incyanate according to the present invention include 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, hexamethylene diisocyanate, diphenylmethane diincyanate, inphorone diincyanate, and the like.

Examples of triinocyanate include adducts of diisocyanate and polyol, such as tolylene diinocyanate or adducts of hexamethylene diisocyanate and trimethylolpropane.

In the present invention, the compound represented by the above general formula (1),
In addition to aliphatic polyols and di- or tri-isocyanates, natural oils such as castor oil, soybean oil, coconut oil, linseed oil, dehydrated castor oil, isomerized safflower oil, or derivatives thereof (
For example, an aliphatic hydrocarbon moiety having 8 to 20 carbon atoms may be introduced into the specific polymer according to the present invention using a monoglyceride) or an adduct of an amine and ethylene oxide derived by hydrogenation of a fatty acid. . In addition, in the polyol, saturated or unsaturated fatty acids and glycerin,
An aliphatic hydrocarbon moiety having 8 to 20 carbon atoms may be introduced as a monoester of trimethylolpropane or trimethylolethane, a monoester or a diester of saturated or unsaturated fatty acids and pentaerythritol.

Regarding the reaction production of the specific polymer according to the present invention, the characteristic of the compound represented by the general formula [13] is that one carbon atom has aliphatic hydrocarbon residues (alkyl groups) arranged on three sides through carbon bonds. , and a carboxylic acid (or its salt). When such a compound is reacted with an aliphatic polyol and inocyanate, under normal reaction conditions, the carboxy group is attacked by the isocyanate group and is preserved as it is without producing acid amide etc. It is known that the group reacts with the inocyanate-reactive group at the end of the alkyl group, and it is also thought that ester bonding between the carboxy group and the hydroxyl group of the polyol in the presence of polycyanate is unlikely.

In the present invention, the specific polymer according to the present invention obtained by reacting the above-mentioned king (preferably at 150°C or lower, more preferably at 130°C or lower) also has a carboxy group bonded to tertiary carbon. are mostly preserved.

Therefore, the specific polymer according to the present invention is preferably a polymer linked by urethane groups specified from the above-mentioned range of compounds, and a polymer in which a carboxy group is bonded to a tertiary carbon.

For the dispersion of the magnetic powder according to the present invention, it seems that the requirement that a carboxyl group or its salt is bonded to the tertiary carbon of the specific polymer is effective, and the BET value of the magnetic powder is 30 m''/gr. The dispersion effect is significantly exhibited when it exceeds 100%, and the Rf output and S/N ratio are significantly improved.

Next, specific examples of the products will be given.

Exemplary product (1) Polypropylene glycol (molecular weight approximately 4oO
) with 2.2-bis-(hydroxymethyl)-propionic acid and hexamethylene diisocyanate:
Amber viscous liquid (2) Polypropylene glycol (molecular weight approximately 400
) and 2.2-bis-(hydroxymethyl)-propionic acid and tolylene diisocyanate: amber viscous liquid.

13) Polypropylene glycol (molecular weight approximately 400
), 2,2-bis-(hydroxymethyl)-propionic acid and 3-isocyanatomethyl-3,5°5-trimethylcyclohexyl incyanate: viscous liquid.

(4) Polypropylene glycol (molecular weight approximately 400
), propylene glycol, 2,2-bis-(hydroxymethyl)-propionic acid, glycerin, castor oil, and tolylene diinocyanate.

(5) Soybean glyceride and polypropylene glycol produced from 1 mol of soybean oil and 2 mol of glycerin (
400) and a reaction product of 2,2-bis-(hydroxymethyl)-propionic acid and tolylene diisocyanate.

(6) A compound in which 2 moles of ethylene oquinide are added to 1 mole of coconut oil aliphatic amine and 2,2-bis(
Reaction product of hydroxymethyl)-propionic acid and tolylene diisocyanate.

(Polypropylene glycol (molecular weight approximately 400)
and the reaction product of castor oil, 2,2-bis(hydroxymethyl)-propionic acid and tolylene diisocyanate.

The specific polymer according to the present invention is used in an amount of 0.01 to 10 parts by weight, preferably 0.05 to 8 parts by weight, per 100 parts by weight of magnetic powder.

The magnetic powder may be pretreated with a specific polymer.

In the present invention, conventional techniques can be used to form the magnetic layer, back coat layer, or other constituent layers of the magnetic tape of the present invention.

Examples of the magnetic material used for the magnetic layer of the magnetic tape of the present invention include r -Fe2031 Co-containing r -Fe20
3.C.

Deposited 7”-Fe203 #Fe304, Co-containing Fe3O4, Co-deposited Fe3O4+ Co-containing magnetic Fe
dx(''>x>') Oxide magnetic material such as Crow, e.g. Fe*Ni, Co, Fe-N
i alloy, F'@-Co alloy #Fe-AI alloy,
Fe-kl-Ni alloy.

F'e-Ni-P alloy, Fsl-Ni-Co alloy, Fe-Mn-Zn alloy.

Fa -Ni-Zn alloy + Fe-Co-Ni-Cr alloy, F@-Co -Ni-P alloy, Co-Ni alloy, Co-P alloy, Co-Cr alloy, etc.Fe * Ni *
Examples include various ferromagnetic materials such as metal magnetic powder containing Co*Al as a main component. Additives to these metal magnetic materials include Si, Cu lZn + AiP + Mn
* Elements such as Cr or compounds thereof may be included. Hexagonal ferrite such as barium ferrite, iron nitride, and iron carbide are also used.

As the binder used for the magnetic layer, back coat layer, etc. according to the present invention, abrasion-resistant polyurethane can be mentioned. It has strong adhesion to other substances, is mechanically strong to withstand repeated stress or bending, and has good abrasion resistance and weather resistance.

In addition to polyurethane, if K, a cellulose resin, and a vinyl chloride copolymer are also contained, the dispersibility of the magnetic powder in the magnetic layer is improved and its mechanical strength is increased. However, if only the cellulose resin and the vinyl chloride copolymer are used, the layer becomes too hard, but this can be prevented by containing the above-mentioned polyurethane.

Usable cellulose resins include cellulose ether, cellulose inorganic acid ester, and hirulose organic acid ester. The vinyl chloride copolymer described above may be partially hydrolyzed. Preferable examples of the vinyl chloride copolymer include copolymers containing vinyl chloride and vinyl acetate.

Matafenoxy resins can also be used.

Phenoxy resin has advantages such as high mechanical strength, excellent dimensional stability, good heat resistance, water resistance, chemical resistance, and good adhesiveness.

These advantages are complementary to the above-mentioned polyurethane, and also help to significantly improve the stability over time in the physical properties of the tape.

Furthermore, in addition to the above-mentioned binder, 0. Resins generally used in magnetic wiring media, various modified resins with hydrophilic groups (e.g. carboxy groups, sulfo groups, phospho groups), etc., or thermoplastic resins, thermosetting resins, and reactive resins with characteristic behavior. A mixture of resin and electron beam curable resin may be used.

In order to improve the durability of the magnetic layer of the magnetic tape of the present invention, the magnetic paint can contain various curing agents, such as incyanate.

Aromatic incyanates that can be used include, for example, tolylene diincyanate (TDI) and adducts of these incyanates and active hydrogen compounds, and those with an average molecular weight in the range of 100 to 3,000 are preferable. .

Examples of the aliphatic isocyanate include hexamethylene diinocyanate (HMDI) and adducts of these incyanates and active hydrogen compounds. Among these aliphatic incyanates and adducts of these incyanates and active hydrogen compounds, those having a molecular weight in the range of 100 to 3,000 are preferred. Among the aliphatic incyanates, non-alicyclic incyanates and adducts of these compounds with active hydrogen compounds are preferred.

The magnetic paint used to form the above-mentioned magnetic layer may contain additives other than the specific polymer according to the present invention, such as dispersants, lubricants, abrasives, other fillers, and antistatic agents, if necessary. It may be included.

Examples of the dispersant include lecithin, phosphoric acid ester, amine compound, alkyl sulfate, fatty acid amide, higher alcohol, polyethylene oxide, sulfosuccinic acid, sulfosuccinic acid ester, known surfactants, and salts thereof. Salts of polymeric dispersants having organic groups (eg carboxy, phospho, sulfo groups) can also be used. These dispersants may be used alone or in combination of two or more. These dispersants are added in an amount of 1 to 20 parts by weight per 100 parts by weight of the binder. These dispersants may be used to pre-treat the magnetic powder in advance.

In addition, as lubricants, silicone oil, fluorine oil, graphite, carbon black graft polymer,
Molybdenum disulfide, tungsten disulfide, lauric acid,
Fatty acids having 6 or more carbon atoms such as myristic acid, fatty acid esters consisting of fatty acids and alcohols, etc. can also be used. These lubricants are 0.2 to 2 OM per 100 parts by weight of binder.
It is added within the range of fE.

As the polishing agent, alumina (preferably α-alumina)
, silicon carbide, titanium oxide, chromium oxide, silicon nitride,
Boron nitride, aluminum nitride, corundum, artificial corundum, diamond oxide, artificial diamond, garnet, emery (main ingredients: corundum and magnetite), etc. are used. These 17F abrasives have an average particle diameter of 0.05 to 5 μm, particularly preferably 0.1 to 211 μm.
It is. These abrasives are added in an amount of 1 to 20 parts by weight based on 100 parts by weight of the binder.

As the fins (which may have the same effect as the abrasive), organic powders or inorganic powders can be used individually or in combination.

As the organic powder used in the present invention, acrylic styrene resin, benzoguanamine resin powder, melamine resin powder, and phthalocyanine pigment are preferable, but polyolefin resin powder, polyester resin powder, polyamide resin powder, and polyimide are preferred. type resin powder, polyfluoroethylene resin powder, etc. can also be used, and inorganic powders include silicon oxide, titanium oxide, aluminum oxide, calcium carbonate, barium sulfate, zinc oxide, tin oxide, aluminum oxide, chromium oxide, silicon carbide, and calcium carbide. , α-Fe
203. Examples include talc, kaolin, calcium sulfate, boron nitride, zinc fluoride, and molybdenum dioxide.

Antistatic agents include carbon black, graphite, conductive powders such as tin oxide-antimony oxide compounds, titanium oxide-tin oxide-antimony oxide compounds, natural surfactants such as saponin, alkylene oxides, and graphite. IJ Nonionic surfactants such as 4-phosphorus and glycidol; Cationic surfactants such as higher alkyl amines, primary ammonium salts, pyridine, other heterocycles, phosphonium or sulfonium: carboxylic acids, sulfonic acids , anionic surfactants containing acidic groups such as phosphoric acid, sulfuric acid ester groups, and phosphoric ester groups; amphoteric surfactants such as amino acids, aminosulfonic acids, and sulfuric or phosphoric esters of amino alcohols.

Solvents to be added to the above paint or diluting solvents during application of this paint include ketones such as acetatone, methyl ethyl ketone, methyl isobutyl ketone, and cyclohexanone; alcohols such as methanol, ethanol, propatool, and butanol; acetic acid. Methyl, ethyl acetate, butyl acetate,
Esters such as ethyl lactate and ethylene glycol monoacetate; ethers such as glycol dimethyl ether, glycol sonoethyl ether, dioxane, and tetrahydrofuran; and aromatic hydrocarbons such as benzene, toluene, and xylene can be used.

In addition, as a support, polyethylene terephthalate,
Examples include polyesters such as polyethylene-2,6-naphthalate, polyolefins such as polypropylene, cellulose derivatives such as cellulose triacetate and cellulose diacetate, plastics such as polyamide and polycarbonate, metals such as Cu, AI, and Zn, and glass. , BN e Si carbide, porcelain, ceramics such as earthenware, etc. can also be used.

The thickness of these supports is about 3 to 100 μm in the case of a film or sheet, preferably 5 to 50 μm,
In the case of a disk or card, it is approximately (9) μm to 10J1 m, and in the case of a drum, it is used in a cylindrical shape, and the shape can be devised depending on the recorder used.

Coating methods for forming the magnetic layer on the support include air doctor coating, blade coating, air knife coating, squeeze coating, impregnation coating, reverse roll coating, transfer roll coating, gravure coating, kiss coating, cast coating, Spray coats and the like can be used, but are not limited to these.

(Example) The present invention will be specifically explained using examples.

Examples 1 to 5 and comparative example group (5) A magnetic paint was prepared according to the formulation shown in Table IK below.

After preparing the prescription components shown in Table IK in a ball mill and dispersing them, this magnetic paint was filtered through a 1 μm filter, 5 parts of polyfunctional isocyanate was added, and the mixture was coated on a support to a thickness of 5 μm and supercalendered. One copy was slit to a width of 2 inches to prepare a videotape (corresponding to the numbers of each example and comparative example). However, the numbers after the M2 column in Table 1 represent parts by weight, and "actual" in the second and subsequent columns represent examples, and "ratio" represent comparative examples.

In addition, the comparative examples corresponding to the examples are grouped with the same number.

*l Polypropylene glycol (molecular weight approximately 400)/
2, 2-bis-(hydroxymethyl)-7', ropionic acid/tolylene diisocyanate = 1.570.6
/ 1.7 molar ratio of reaction product Book 2 Polypropylene glycol (molecular weight approximately 400) / Castor oil / 2, 2-
Reaction product with a molar ratio of bis-(hydroxymethyl)-propionic acid/tolylene diincyanate = 210.4/1/2.9 *3 Polypropylene glycol (molecular weight approximately 400)/2.2-bis-(hydroxymethyl )-propionic acid/soybean monoglyceride/tolylene diincyanate = 1/1.7/1.3/3.20
Table 2 shows the videotape performance of each of these reaction products.

The tapes of the examples have the S of the corresponding tapes of the comparative examples.
Table 2 As is clear from Table 2, all of the examples are Lumi S/N,
Both Rf output has improved, and the winding appearance has also been improved.

A good rolling appearance indicates stable running performance.

In addition, when observed from the viewpoint of productivity, the viscosity of the coating paint of Example 4 in the 24-hour stagnation test (room temperature) K without the addition of a curing agent was slightly above 24 poise from added voids. In the paint of Comparative Example (4), under the same conditions, the edge voids significantly increased from the additive voids, and the lack of stagnation stability caused problems in productivity. The same was true for the other Examples to Comparative Examples.

(Effect of the invention) The polymer dispersant according to the present invention exhibits excellent dispersion power in a range of BET values of 60 i/gr Ic, and provides a direction in the dispersion technology of ultrafine magnetic powder after precipitation. .

Furthermore, it is an industrially valuable dispersant that has a favorable effect on productivity, and a medium using it has a particularly high ng'
This shows an excellent customization of a magnetic recording medium whose magnetic layer contains magnetic powder having an r value.

Claims (1)

[Scope of Claims] A magnetic recording medium in which a magnetic layer containing magnetic powder and a binder is provided on a support, at least a compound represented by the following general formula (1), an aliphatic polyol, and a di- or A magnetic recording medium characterized in that the magnetic layer contains a compound obtained from a three-way reaction of tri-isocyanate and having a carboxy group or a carboxy group salt bonded to a tertiary carbon. General formula (1) ▲There are mathematical formulas, chemical formulas, tables, etc.▼ [In the formula, R_1 and R_2 are divalent hydrocarbon residues, R_3
represents a monovalent hydrocarbon residue, and X_1 and X_2 represent a group reactive with isocyanate. M represents a hydrogen atom, an alkali metal atom, or an alkaline earth metal atom. ]