JPS62184621A - Magnetic recording medium - Google Patents

Abstract

PURPOSE:To obtain a magnetic recording medium having excellent dispersibility, packability and orientability of magnetic particles by using a polyester urethane resin which contains the metallic base of sulfonic acid in the molecule and of which the acid value is kept at a specified value or below as at least one component of a binder for the magnetic particles. CONSTITUTION:The polyester urethane resin which contains the metallic base of sulfonic acid at 0.01-2wt% in terms of sulfur content in the molecule and of which the acid value is <=25 equiv/10<6>g is incorporated as the component of the binder into said binder. The polyester urethane resin is obtd. by a general process for producing a polyurethane resin such as prepolymer method or one- shot method using a polyester diol having >=500mol.wt. as an essential component of a long chain diol and using a chain extender having <500mol.wt. according to need.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to magnetic recording media such as magnetic tapes and magnetic disks. More specifically, the present invention relates to a magnetic recording medium using a polyester-urethane resin having excellent properties as a binder for a magnetic layer provided on a non-magnetic support.

(Prior art) Magnetic tape, which is a general-purpose magnetic recording medium, is made by dispersing acicular magnetic particles with a long axis of 1 pm or less in a binder solution together with appropriate additives (dispersants, lubricants, antistatic agents, etc.). The magnetic paint is made by applying it to a polyethylene terephthalate film.The magnetic coating is coated on a polyethylene terephthalate film to improve the dispersibility, filling, and orientation of the magnetic particles, the durability of the magnetic layer, abrasion resistance, heat resistance, and adhesion to the non-magnetic support. Binding agents play a very important role. Conventionally used binders include vinyl chloride/vinegar copolymer, salts (vinyl/vinyl acetate/vinyl alcohol copolymer, vinyl chloride/vinylidene chloride copolymer, polyurethane resin, polyester). Resin, acrylonitrile-butadiene copolymer, nitrocellulose, cellulose acetate-butyrate,
Epoxy resin or acrylic resin is used.

Among these resins, polyurethane resin has superior properties such as toughness and abrasion resistance compared to other resins due to intermolecular hydrogen bonding caused by urethane bonds, but it has a major drawback of poor dispersibility of magnetic particles. be. To improve this dispersibility, Japanese Patent Publication No. 58-41565, Japanese Patent Application Laid-Open No. 57-1988
As seen in Japanese Patent No. 165464, the inventors of the present invention have already discovered that introducing a sulfonic acid metal base into a resin has an excellent effect.

(Problems to be Solved by the Invention) In magnetic recording media, in order to improve the SlN ratio (signal/noise ratio) and increase the alignment density, finer magnetic particles are highly filled in the magnetic layer and highly oriented. This includes measures such as the use of magnetic particles that are difficult to disperse, such as metal particles. Therefore, a binder with better dispersibility is required.

Currently, conventional polyurethane resins cannot meet the requirements of these magnetic recording media, and although it is effective to introduce a sulfonic acid metal base into the resin, it is more difficult to disperse than metal particles. magnetic particles are still insufficient.

In view of the above circumstances, the purpose of the present invention is to improve the dispersibility of magnetic particles,
An object of the present invention is to provide a magnetic recording medium with excellent filling properties and orientation.

(Means for Solving All Problems) The object of the present invention is to use a polyester/urethane resin containing a sulfonic acid metal base in its molecule and having an acid value below a certain limit as at least one component of a binder for magnetic particles. This is achieved by

That is, the present invention provides a magnetic recording medium in which a magnetic material in which ferromagnetic powder is dispersed in a binder is coated on a non-magnetic support, in which a sulfonic acid metal base is contained in the molecule as a component of the binder at a sulfur content of 0. A magnetic recording medium characterized by containing a polyester/urethane resin containing .01 to 2% by weight and having an acid value of 25 equivalents/106 r or less.

The polyester/urethane resin used in the present invention has a molecular ff
l A polyester diol having a molecular weight of 500 or more is used as the main component of a long-chain diol, an organic diisocyanate and, if necessary, a chain extender having a molecular weight of less than 500, using a general manufacturing method for polyurethane resins such as the prepolymer method, the Wanshi II method, and the G method. That's what you get.

The carboxylic acid component of the polyester diol used in the production of the polyester/urethane resin used in the present invention includes aromatic dicarboxylic acids such as terephthalic acid, inphthalic acid, orthophthalic acid, 1.5-naphthalic acid, and p-oxybenzoic acid. acid 1, -(hydroxyethoxy)
Examples include aromatic oxycarboxylic acids such as benzoic acid, aliphatic dicarboxylic acids such as succinic acid, adipic acid, azelaic acid, sebacic acid, and dodecanedicarboxylic acid. Especially terephthalic acid, isophthalic acid, adipic acid,
Sebacic acid is preferred.

In addition, the glycol components of polyester diol include ethylene glycol, propylene glycol, 1.3
-Propanediol, 1,4-butanediol, 1.5
-bentanediol, 1,6-hexanediol, neopentylgusacol, diethylene glycol, dipropylene glycol, 2,2.4-trimethyl-1,3-
Bentanediol, cyclohexane dimetatool, bisphenol - 19 people with ethylene oxide! ITI products and propylene oxy) / included! fil Products include ethylene oxide adducts and propylene oxide adducts of hydrogenated bisphenol^, polyethylene glycol, polypropylene glycol, polytetramethylene glycol, etc.@For the raw material fraction of poly-1 ester diol other than the above, the following is the general formula. (1), (A phosphorus-containing compound represented by Hl can be received.

(In the formula, 1 is a functional group forming ester 1 of 1611i.

1'L2, IL3 are 101 or different groups, selected from the group consisting of 1 carbon @ monovalent hydrocarbon group having 1 to 10 atoms, halogen atom, and ester form of 11d5 + JSE functional group. It will be done. A represents a divalent or trivalent organic residue. Also, jtl is 1 or 2s n2 , n
3 each represents an integer of O to 4) O (in the formula, FL4 is a hydrogen atom, a hydrocarbon group having 1 to 12 carbon atoms that may contain an ester-forming functional group, or M2
O. IIL5 is divalent with 1 to 6 carbon atoms, or 31J
li carbon (arsenic group. R6 is a hydrogen atom, a hydrocarbon group having 1 to 12 carbon atoms even if it contains a hydroxyl group, or M3 s
M2S M2 and M3 are alkali metal atoms. m represents an integer of 0 or 1, and t represents an integer of 1 or 2. ) general formula (13,
When a polyester diol obtained by using the phosphorus-containing compound represented by (II) as at least one component of the raw material is used as a component of the raw material for polyester/urethane resin,
It is effective in greatly improving the drawback of low dispersibility of inorganic pigments and fillers found in conventional polyurethane resins, and when used as a binder in the magnetic layer of coated magnetic recording media, The dispersibility of the magnetic particles is improved, and the properties caused by the dispersibility of the magnetic particles, such as the electromagnetic conversion properties of the magnetic recording medium, are greatly improved.

Other examples of polyester diols include lactone-based polyester diols obtained by complete ring-opening polymerization of lactones such as C-caprolactone.

In addition, some of the raw materials for polyester diol include compounds graded E or higher, such as trimellitic anhydride, glycerin, trimethylolpropane, and pentaerythritol, which impair the organic solvent solubility and coating workability of polyester/urethane resin. It may be used within the range.

The organic diincyanate that can be used in the production of the polyester/urethane resin used in the present invention is 2.
4-) Lylene diisocyanate, 2.6-lylene diisocyanate, p-phenylene diisocyanate, diphenylmethane diisocyanate, m-phenylene diisocyanate, hexamethylene diisocyanate, tetramethylene diisocyanate, 3.31-dimethoxy-4
, 41-biphenylene diisocyanate, 2,4-naphthalene diisocyanate, 3,3'-dimethyl-4,4
'-Biphenylene diisocyanate, 4.4'-diphenylene diisocyanate, 4.4'-diisocyanate diphenyl ether, 1,5-naphthalene diisocyanate, p-xylylene diisocyanate, m-xylylene diisocyanate, 1.3-diisocyanate methylcyclohexane, 1. Examples include 4-diisocyanate methylcyclohexane, 4,4'-diisocyanate cyclohexane, 4,4'-diisocyanate cyclohexitalmethane, and inphorone diisocyanate.

The chain extender used as necessary during the production of the polyester/urethane resin used in the present invention preferably has a molecular weight of less than 500, contains two active hydrogens in one molecule, and has a @adjusted concentration of urethane groups or urea groups in the resin. However, it has the effect of improving the toughness characteristic of polyurethane resins. Specific compounds include linear glycols such as ethylene glycol, 1,3-propylene glycol, 1,6-hexanediol, cyclohexane dimetatool, xylylene glycol, diethylene glycol, triethylene glycol, and ethylene oxide adducts of bisphenols. ,
Propylene glycol, neopentyl glycol, 1.
2-butanediol, 1,3-butanediol, 2,2
．． Branched glycols such as 4-4-limethyl-1,3-bentanediol, propylene oxide adducts of bisphenols, amino alcohols such as monoethanol, amine, N-methylethanolamine, ethylenediamine, hexamethylenediamine, isophoronediamine, piperazine Examples include diamines such as, water, and the like.

The polyurethane resin used in the present invention contains a sulfonic acid metal base in the molecule, and the metal atoms include lithium,
Examples include alkali metal atoms such as sodium and potassium.

Examples of methods for introducing a sulfonic acid metal base into a polyurethane resin include the following methods.

(2) A method in which a compound having a sulfonic acid metal base is used as a part of the dicarboxylic acid component or diol component of the polyester diol used as the long-chain diol component.

(2) A method in which at least one component of the chain extender is a compound containing a sulfonic acid metal group in the molecule.

■ Incyanate-terminated prepolymer, H2NOH2
0H2SO3H, HOOH20H2SO3H, H2NO
Examples include a method of reacting with a sulfonic acid group or a compound containing a sulfonic acid metal base, such as H20H2SO3Na, and neutralizing the sulfonic acid group with sodium hydroxide, potassium hydroxide, or the like.

Among these methods, a method in which a polyester diol containing a sulfonic acid metal base is used as at least one long-chain diol component is preferred in view of solubility in general-purpose organic solvents, stability of production, and the like. Examples of the sulfonic acid metal salt-containing compound used to produce the sulfonic acid metal salt-containing polyester diol include 5-sodium sulfoisophthalic acid, 5-potassium sulfoisophthalic acid, sodium sulfoterephthalic acid, and 2-sodium sulfo-1,4- Examples include butanediol, 2,5-dimethyl-3-sodium sulfo-2,5-hexanediol, and the like.

The content of sulfonic acid metal base in polyurethane resin is
Ion content of 0.01-2% by weight, preferably
0.01-1.5% by weight, particularly preferably 0.05
~1.0% by weight, with a sulfur content of 0.0% by weight.
If the content is less than 0.01% by weight, no effect of containing the sulfonic acid metal base is observed, and if it exceeds 1.5% by weight, the solution viscosity will greatly increase, the solubility in general-purpose organic solvents will decrease, and the physical properties will change due to humidity. can be seen. This is particularly noticeable when the content exceeds 2% by weight.

The polyester/urethane resin used in the present invention has an acid value of 25 or less equivalents per 106 grams of resin, preferably 20 equivalents/10 grams or less, and 0 equivalents/1.
0 grams or more. Acid value is 25 equivalentffi/10'
If it exceeds gram, the dispersibility of finely divided magnetic powder or metal magnetic powder will decrease, and as a result, the electromagnetic conversion characteristics of the magnetic recording medium will deteriorate.

The acid value of the polyurethane resin varies depending on the acid terminal in the polyester diol used as a raw material or the acid-containing impurities in the glycol in the hs reaction using glycol as a chain extender.

The molecular weight of the polyester/urethane resin used in the present invention is preferably in the range of 5,000 to 5,000 on average molecular weight. When the molecular weight is less than 5,000, the mechanical strength of the polyurethane resin decreases, and when it exceeds s, o, or ooo, the dissolution viscosity becomes too high and may be difficult to handle.

The polyaddition reaction of the polyurethane resin used in the present invention involves the simultaneous reaction of all components.1. Finally, there is a prepolymer method in which a diisocyanate compound is first reacted with a long-chain diol under conditions where the diisocyanate compound is in excess, and the resulting incyanate group-terminated prepolymer is further polymerized using a chain extender. In the case of the polyurethane resin used in the present invention, both the one-shot method and the prepolymer method can be used for manufacturing. Examples of the reaction method include a method in which the raw materials are carried out in a molten state, and a method in which the raw materials are dissolved in a solution.

As a reaction catalyst, tin-octylate, dibutyltin dilaurate, triethylamine, etc. may be used. In addition, ultraviolet absorbers, hydrolysis inhibitors, acid inhibitors, etc. may be added before, during, or after the production of polyurethane resin. May be added.

In the present invention, in addition to the polyurethane resin used in the present invention, other resins are added and/or reacted with the polyurethane resin for the purpose of adjusting flexibility, improving cold resistance, heat resistance, etc. It is desirable to mix a compound that crosslinks with the resin. Other resins include vinyl chloride resins, polyester resins, cellulose resins, epoxy resins, phenoxy resins, polyvinyl butyral, acrylonitrile-butadiene copolymers, and the like.

On the other hand, as compounds that crosslink with polyurethane resins, there are polyisosiapho 816 compounds, epoxy resins, melamine resins, urea resins, etc. Among these, polyisosiapho 816 compounds are particularly desirable.

The ferromagnetic particles used in the magnetic layer of the magnetic recording medium of the present invention include r-Fe203, r-Pe203 and Fe3O4 crystals, 0r02, :I balt-coated j-Fe203 or Fe3O4, barium ferrite, and Fa- Examples include ferromagnetic alloy powders such as 0o, FeCoNi, and the like.

In particular, the polyester/urethane resin of the present invention is effective for finely divided magnetic powder with a surface area of BgT40m/V or more, or magnetic powder with poor dispersibility such as metal or alloy powder. If necessary, plasticizers such as dibutyl phthalate and triphenyl phosphate, dioctyl sulfonodium succinate, t-butylphenol-polyethylene ether, ethylnaphthalene sodium sulfonate, dilauryl succinate, zinc stearate, soybean oil lecithin, Lubricants such as silicone oil and various antistatic agents can also be added.

(Function) The polyurethane resin used in the present invention contains a sulfonic acid metal base in the molecule and has an acid value of 25 equivalents of 7102 or less, and has improved dispersibility of magnetic particles.

Although the mechanism by which a small amount of acid value affects dispersibility has not been clearly elucidated, the dispersibility of magnetic particles can be improved due to the intermolecular interaction of the polyurethane resin adsorbed to the magnetic particles due to the highly polar gold sulfonate group. It is believed that the higher the arsenic oxidation, the greater the interaction between the adsorbed polyurethane resins, resulting in a lower dispersibility.

(Examples) Hereinafter, the present invention will be specifically illustrated by examples. In the examples, the term "part" simply indicates the weight.

It was titrated with

The number average molecular weight was measured by gel permeation chromatography using THP as a solvent in terms of standard polystyrene. Solution viscosity was measured at 25°C using MgK/l-luene 1/1 (volume ratio) as a solvent with a solid concentration of 30%.
It was held at

Example 1 Using the polyester/urethane resin (■) listed in Table 1, a composition with the following blending ratio was placed in a ball mill and dispersed for 48 hours.
30 (manufactured by Nippon Polyurethane Industry Co., Ltd.) was added as a curing agent in an amount of 5 parts, and the mixture was further mixed for 1 hour to obtain a magnetic paint. This was applied onto a polyethylene terephthalate film having a thickness of 12p while applying a magnetic field of 2,000 Gauss so that the thickness of the dry TE was 5μ. After being left at 50°C for 2 days, it was slit into 1/2 inch pieces to obtain a magnetic tape.

100 parts of a solution of polyester/urethane resin ■ listed in Table 1 (solid content concentration 3
0%, MFiK/ ) Luene 171 solution) Ferromagnetic metal powder (re-Oo-Ni18F!T 59m /f
3120 parts olive oil 1 part cyclohexanone 50 parts toluene
10010Os
50@is Examples 2 to 10, Comparative Example 1
~7 Instead of the polyester-urethane resin ■ used in Example 1, polyester-based urethane resin ~ [phase] and the second
A magnetic tape was obtained in the same manner as in Example 1 using the resins listed in the table.

Table 2 shows the characteristics of the magnetic tapes of the above examples and comparative examples.

The polyester diol used in the examples has the following composition.

Polyester terephthalic acid/15-sodium isophthalate sulfoisophthalate l ethylene glycol/neopentyl glycol-6 molar ratio) Molecular weight 2000 Polyester ■ 15-sodium acyphthalate sulfoisophthalate//1
．． 6-hexanediol/neopentyl glycol-9
7/3/70/30 (Mole ratio) Polyester with a molecular weight of 2000 ◎ 15-sodium adipic acid Neopentyl glycol sulfoisophthalate - 80/20/100 (Mole ratio)
Molecular weight 1000 Polyester ■ Terephthalic acid/Isophthalic acid l Ethylene glycol/Neopentyl glycol - 60/40/60/40 (Mole ratio) Molecular weight 2000 The abbreviations used in the examples indicate the following 1H anastomosis.

PBA: Polybutylene adipate, molecular weight 100O
NPG: Neopentyl glycol 1.6-HD: 1,6-hexanediol HP Sweet: Neopentyl glycol monohydroquineparade ME
λ: Seven ethanolamine MDI: 4.4'-diphenylmethane diincyanate IPDI: Isophorone diisocyanate MEK
: Methyl ethyl ketone DMP : 2,2-dimethylolpropionic acid In Table 1, (X) represents the solution viscosity using MEK/toluene/dimethylformamide as the solvent.

Table 2 Table 3
Surface squareness ratio 0.60 0.58 0.65 0.63 0.60 0.63 ■ Adipate type polyurethane 2 Nippon Polyurethane Co., Ltd. “Niraporan 2304J ■■ Nitrified cotton: Daicel Co. r ns 2 Jido Co., Ltd. r VA
GHJ Magnetic layer gloss: Measure the 60 degree gloss of the magnetic layer surface. The higher the gloss value, the better the dispersibility of the magnetic particles, and as a result, the squareness ratio,
Properties that affect the electromagnetic conversion properties of the magnetic tape, such as filling properties, orientation, and surface smoothness, are improved.

Example 11, Comparative Example 8 Polyester listed in Table 1 was used as a binder for the magnetic layer.
00-y-Fe using urethane resin ■ as magnetic particles
A magnetic tape was obtained in the same manner as in Example 1 except that 2O2 (surface area, BET 5Qm/r) was used.

However, the acid value of the polyester/urethane resin was changed by adjusting the acid value of the raw material.

FIG. 1 shows the relationship between the acid value of the polyester/urethane resin and the 60 degree gloss of the magnetic layer.

(Effect of the invention) Polyester containing a sulfonic acid metal base in the molecule.
By suppressing the acid value of the urethane resin within the range of the present invention, it is clear from the Examples and Comparative Examples that the magnetic recording medium of the present invention has improved electromagnetic performance due to the dispersibility of the magnetic particles.

[Brief explanation of drawings]

Figure 1 shows the relationship between acid value and gloss of polyester/urethane resin.

Claims (1)

[Claims] In a magnetic recording medium in which a magnetic material in which ferromagnetic powder is dispersed in a binder is coated on a non-magnetic support, a sulfonic acid metal base is contained in the molecule as a component of the binder at a sulfur content of 0.0% per polymer. 1. A magnetic recording medium comprising a polyester/urethane resin containing 01 to 2% by weight and having an acid value of 25 equivalents/10^6 g or less.