JPH01137427A - Magnetic recording medium - Google Patents

Abstract

PURPOSE:To obtain excellent mechanical strength by using a butadiene polymer contg. an epoxy group and phenoxy resin contg. ternary amine. CONSTITUTION:The butadiene polymer contg. the epoxy group and the phenoxy resin contg. the ternary amine are incorporated into the binder of a magnetic layer. The butadiene polymer consists essentially of a butadiene polymer and is obtd. by copolymerizing the epoxy group introduced to said polymer in order to form a crosslinked structure therein and a monomer having the double bonds copolymerizable with a butadiene compd. The binder having the good crosslinked structure without receiving the influence of moisture at the time of forming the crosslinked structure is thereby 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, and more particularly to a binder contained in a magnetic layer formed on a non-magnetic support. This is related to the improvement of

[Summary of the invention]

The present invention provides a magnetic recording medium in which a magnetic layer mainly composed of ferromagnetic powder and a binder is formed on a non-magnetic support, in which the binder constituting the magnetic layer has an epoxy group as a polar group in the molecule. The present invention aims to provide a magnetic recording medium with excellent durability by using a butadiene-based copolymer having the following properties and a phenoxy resin having a tertiary amine as a binder.

[Conventional technology]

In recent years, magnetic recording media, especially magnetic recording media for VTRs (video tape recorders), are required to have improved magnetic properties, electromagnetic conversion properties, etc. in order to obtain high playback output even when recording at short wavelengths. ing. As a countermeasure, efforts have been made to make the magnetic powder particles finer and to increase the magnetic force, and there is a strong tendency to increase the packing density of the magnetic powder in the magnetic layer, the so-called backing density.

Therefore, the proportion of the binder in the magnetic coating film is extremely small. A magnetic coating containing such a small amount of binder may cause the magnetic layer to peel off when used as a magnetic recording medium, and in order to prevent such deterioration in the strength of the magnetic coating, it is necessary to Need to improve strength.

To this end, it has been proposed to improve the mechanical strength of the magnetic coating by crosslinking the binder in the magnetic coating.

As mentioned above, binders that form a crosslinked structure to increase the mechanical strength of the magnetic coating film include those that form a crosslinked structure using a compound that has an electron IJ adverse bond in the molecule, or Some have been proposed that form a crosslinked structure by utilizing the reaction between the active hydrogen of a hydroxyl group and an isocyanate.

However, for example, a binder made of a compound having an electron beam-sensitive bond as described above requires extremely expensive equipment in order to form a crosslinked structure, and is therefore impractical.

On the other hand, with the above-mentioned binder in which the active hydrogen of the hydroxyl group reacts with an incyanate compound etc. to form a crosslinked structure, the reaction is aimed at 1'NCO+ -01l --:gO, whereas the actual reaction Then -NC
Incyanate reacts with water as shown in O+H□0 → -NHl + Cot, and the amino group created by this reaction reacts with other isocyanates as shown in -NH* 1-NOC--1 deprived-. Therefore, when an incyanate compound is reacted with a hydroxyl group, the -NGO group that is effective is affected by moisture as shown in the above reaction formula, and the amount of -NCOM that contributes to crosslinking decreases, resulting in insufficient crosslinking structure. Since it cannot be formed, it has inferior durability.

[Problem that the invention seeks to solve]

As described above, a crosslinked structure is formed by electron beam sensitive bonding and P! ! Binders that increase the mechanical strength of the coating, or binders that utilize the reaction between incyanate and hydroxyl groups to form a crosslinked structure and increase the mechanical strength of the coating, lack practicality due to equipment problems. In addition, since the reaction itself is susceptible to the influence of moisture and does not form a good crosslinked structure, magnetic recording media using these as a bonding network have the problem that sufficient durability cannot be obtained.

Therefore, the present invention has been proposed to solve the above-mentioned drawbacks in the technical field, and provides a binder that has a good crosslinked structure without being affected by moisture during the reaction to form a crosslinked structure. The purpose of this invention is to provide a magnetic recording medium with excellent durability.

[Means for solving problems]

As a result of long-term intensive research to achieve the above-mentioned objective, the present inventors have found that a binder consisting of a butadiene copolymer having an epoxy group in the side chain and a phenoxy resin having a tertiary amine is excellent. They found that it exhibits durability and completed the present invention.

That is, the present invention provides a magnetic recording medium in which a magnetic layer mainly consisting of ferromagnetic powder and a binder is formed on a non-magnetic support, wherein the binder comprises a butadiene copolymer having an epoxy group and a butadiene copolymer having an epoxy group. It is characterized by containing a phenoxy resin having 3 amines.

The butadiene-based copolymer having an epoxy group used as a binder in the present invention is mainly composed of a butadiene-based copolymer, and the epoxy group introduced therein to form a cross-linked IaIl structure and the butadiene-based copolymer. It is made by copolymerizing a monomer having a double bond that can be copolymerized with a compound.

Here, the butadiene compounds constituting the butadiene copolymer include butadiene rubber mainly composed of 1,3-butadiene, butadiene-styrene rubber (SBR) which is a copolymer of 1,3-butadiene and styrene, .3-
Examples include butadiene-acrylonitrile rubber (NBR), which is a copolymer of butadiene and acrylonitrile. Furthermore, a heptamer copolymerizable with a butadiene compound may be included as a third component.

Examples of the seven polymers copolymerizable with the above butadiene compound include vinyl chloride, vinylidene chloride, vinyl acetate, vinyl alcohol, maleic M, m-hydric maleic acid, acrylic acid,
Examples include methacrylic acid, acrylic ester, methacrylic ester, hydroxyacrylate, hydroxymethacrylate, vinyl propionate, and the like. By selecting one or more of these monomers and copolymerizing them, it is possible to control to some extent the solubility in the solvent, the dispersibility of the ferromagnetic powder, the crosslinkability, etc. of the coating film physical properties.

However, in this case, the proportion of butadiene in the copolymer is preferably in the range of 95 to 50% by weight, and if the content of butadiene is less than 50% by weight, the original characteristics of the butadiene copolymer will be lost. For example, the SN ratio deteriorates.

Further, the number average molecular weight is preferably about 5,000 to 100,000.

In addition, examples of monomers having a double bond copolymerizable with the butadiene compound and having an epoxy group introduced to form a crosslinked structure include unsaturated alcohols such as acryl glycidyl ether and methacryl glycidyl ether. glycidyl ethers of unsaturated acids such as glycidyl acrylate, glycidyl methacrylate, glycidyl p-vinyl benzoate, methylglycidyl itaconate, glycidyl ethyl maleate, glycidyl vinyl sulfonate, glycidyl (meth)allylsulfonate, butadiyl esters of unsaturated acids, butadiene monooxide,
Vinylcyclohexene monooxide, 2-methyl-5
, 6-nipoxyhexene and other epoxide olefins.

The above-mentioned butadiene-based copolymer may have an active hydrogen (for example, a hydroxyl group) in the molecule, and in this case, it may have an epoxy group ring-opened by the catalytic effect of the tertiary amine in the phenoxy resin, which will be described later. The butadiene copolymers react to form a crosslinked structure, and in combination with the crosslinked structure composed of the butadiene copolymer and the phenoxy resin, the mechanical strength of the binder can be increased.

The amount of epoxy groups contained in the above-mentioned butadiene-based copolymer is preferably about 0.02 to 211 mol/i. If the amount of epoxy groups is small, the durability will deteriorate, but if the amount is large, the durability will deteriorate. It becomes difficult to turn it into paint.

On the other hand, the phenoxy resin contained in the binder in the present invention is a phenoxy resin with a tertiary amine introduced into its side chain, and has excellent strength. The basic structure of this phenoxy resin is shown by the following structural formula.

(However, in the formula, n represents an integer of 20 to 20G.) In order to introduce a tertiary amine into the above-mentioned phenoxy resin, it is possible to react with active hydrogen using the hydroxyl group of the side chain of the above-mentioned phenoxy resin. The modification may be performed using a compound having a group and a tertiary amine in the molecule.

The compound having a group capable of reacting with active hydrogen and a tertiary amine in its molecule may be expressed by the following formula (however, in the tertiary amine, R has 1 to 4 carbon atoms.
m represents 2 or 3, respectively. ) and the like.

These compounds are synthesized as follows.

Specific examples of these compounds include the following.

When a compound having a group capable of reacting with active hydrogen and a tertiary amine in its molecule is reacted with a phenoxy resin, the 1NGO group remaining in the former and the 10H in the phenoxy resin are reacted.
A phenoxy resin into which a tertiary amine has been introduced is obtained.

The specific reaction formula is as follows.

It can also be synthesized by the following method.

That is, a compound containing a tertiary amine and chlorine in the molecule,
A phenoxy resin having a polyfunctional OH group is dissolved in a solvent such as dimethylformamide or dimethyl sulfoxide in which the blue component is soluble, and amines such as pyridine, picoline, triethylamine, epoxy compounds such as ethylene oxide, propylene oxide, etc. The following reaction formula shows a method of introducing a tertiary amine by a dechlorination reaction between an 10H group and chlorine in the presence of a dehydrochlorination agent.

In the phenoxy resin synthesized as described above, the amount of tertiary amine introduced is 0.01 to 1. Q rrt mo
Preferably l/g, introduction amount is 0.01m+w
If it is less than ol/g, the crosslinking property will be decreased and the dispersibility of the non-magnetic powder will be poor. Ommol/
If it is more than g, the solubility in the solvent will deteriorate and the moisture resistance of the coating film will deteriorate.

In addition, the number average molecular weight of the above phenoxy resin is preferably within the range of 5,000 to 100,000 when preparing a paint. If this molecular weight is less than 5,000, durability will be poor, and if it is more than 100,000, it will not be resistant to solvents. Solubility deteriorates.

In the present invention, by combining the butadiene copolymer having the epoxy group and the phenoxy resin having the tertiary amine, the tertiary amine contained in the phenoxy resin can be converted into the epoxy group contained in the butadiene copolymer. promotes the ring-opening reaction of Therefore, a crosslinked structure is developed between the butadiene copolymer and the phenoloxy resin or between the butadiene copolymer, resulting in a coating film with excellent durability. 1. The ratio of the butadiene copolymer to the phenoxy resin 1 is preferably from 2/8 to 8/2 of the butadiene copolymer/phenoxy resin.
A tertiary amine compound may be added alone as a crosslinking promoter to the binder used in the magnetic recording medium of the present invention. By using this tertiary amine compound in combination, the butadiene copolymer The ring-opening reaction of the epoxy group contained can be further promoted.

Furthermore, the binder used in the magnetic recording medium of the present invention includes:
It is also possible to form a crosslinked structure by adding polyisocyanate as a curing agent and utilizing the reaction between this polyisocyanate and the hydroxyl group in the butadiene copolymer or the hydroxyl group in the phenoxy resin. By using it in combination with the structure, a magnetic coating film with even more excellent strength can be obtained.

The above-mentioned epoxy group-containing butadiene copolymer and tertiary amine-containing phenoxy resin may be used in combination with other binders.

As such other binders, those conventionally used as binders for magnetic recording media can be used, such as vinyl chloride-vinyl acetate copolymer.

vinyl chloride-vinyl acetate-vinyl alcohol copolymer,
Vinyl chloride-vinylacetate-maleic acid copolymer, vinyl chloride-vinylidene chloride copolymer, vinyl chloride-acrylonitrile copolymer, acrylic ester-acrylonitrile copolymer, acrylic ester-vinylidene chloride copolymer, methacrylic acid Ester-vinylidene chloride copolymer, methacrylic acid ester-styrene copolymer, thermoplastic polyurethane resin, polyvinyl fluoride, vinylidene chloride-acrylonitrile copolymer, butadiene-acrylonitrile copolymer, acrylonitrile-butadiene-methacrylic acid copolymer Coalescence, polyvinyl butyral, cellulose derivatives, styrene-butadiene copolymers, polyester resins, phenolic resins, epoxy resins, thermosetting polyurethane resins, urea resins, melamine resins, alkyd resins,
Examples include urea-formaldehyde resins and mixtures thereof. Among them, polyurethane resin and polyester resin are said to impart flexibility.

Acrylonitrile butadiene copolymer and the like are preferred.

The above epoxy group-containing butadiene copolymer or the third
A hydrophilic polar group may be introduced into the amine-containing phenoxy resin or other binder used in combination for the purpose of further improving dispersibility.
SOJ group, -0505M group, PO(OM')! group, -C
00M group, -NGsJ group (where M represents a hydrogen atom or an alkali metal atom, M' represents a hydrogen atom, an alkali metal atom or a hydrocarbon atom, G represents an alkyl group, and J represents a halogen, respectively.

) etc.

In the magnetic recording medium of the present invention, the magnetic layer is formed by coating the surface of the non-magnetic support with a magnetic paint prepared by, for example, dispersing ferromagnetic powder in the above-mentioned binder and dissolving it in an organic solvent.

Here, the material for the non-magnetic support may be any material that is normally used in this type of magnetic recording medium, such as polyesters such as polyethylene terephthalate, polyolefins such as polyethylene, polypropylene, etc. cellulose derivatives such as cellulose triacetate, cellulose diacetate, and cellulose acetate butyrate; vinyl resins such as polyvinyl chloride and polyvinylidene chloride; plastics such as polycarbonate, polyimide, polyamide, and polyamideimide;
Examples include paper, metals such as aluminum and E, light alloys such as aluminum alloys and titanium alloys, ceramics, and single crystal silicon. Examples of the forms of this non-magnetic support include film and tape.

It may be a sheet, disk, card, drum, etc.

Moreover, any ordinary ferromagnetic powder can be used as the ferromagnetic powder used in the magnetic layer. Therefore, ferromagnetic powders that can be used include ferromagnetic iron oxide particles,
Examples include ferromagnetic chromium dioxide, ferromagnetic alloy powder, hexagonal barium ferrite fine particles, iron nitride, and the like.

The above-mentioned ferromagnetic iron oxide particles are those whose X value is in the range of 1.33≦X≦1.50 when expressed as general 2Fe0m, that is, magnetite Cr-Fe0. XW1.50)
, magnetite (F e O, x = 1.33) and their solid solutions (F e O,, 1,33< x <1
．． 50). Furthermore, cobalt may be added to these ferromagnetic iron oxides for the purpose of increasing coercive force. There are two types of cobalt-containing iron oxide: doped type and deposited type.

The above-mentioned ferromagnetic chromium dioxide may include CrOt or Ru for the purpose of improving coercive force.

3n, Te, Sb, Fe, Ti, V, Mn, etc. can be used.

Examples of the ferromagnetic alloy powder include Fe, Co, and Ni.

Fe-Co, Fe-Ni, Fe-Co-Ni.

Co-NL, Fe-Co-B, Fe-Co-Cr-B,
Mn-B1. Mn-AJ, Fe-Co-V, etc. can be used, and in order to improve various properties, Aj, Si
, Ti, Cr, Mn, Cu.

A metal component such as Zn may also be added.

In addition to the binder and ferromagnetic powder, the magnetic layer also contains additives such as a dispersant, a lubricant, an abrasive, an antistatic agent,
These dispersants, lubricants, etc. may be added with rust preventive agents, etc.
As the Ken F110%, antistatic agent, and rust preventive agent, any conventionally known ones can be used.

The constituent materials of the magnetic layer described above are prepared as a magnetic paint by dissolving it in an organic solvent and coated on a non-magnetic support.The solvent for the magnetic paint may be acetone, methyl ethyl ketone, methyl isobutyl ketone, cyclohexanone, etc. Ketone solvents, methyl acetate, ethyl acetate, butyl acetate,
Ethyl lactate.

Ester solvents such as acetic acid glycol monoethyl ether, glycol ether solvents such as glycol dimethyl ether, glycol monoethyl ether, dioxane, etc.
Aromatic hydrocarbon solvents such as benzene, toluene and xylene, aliphatic hydrocarbon solvents such as hexane and heptane, methylene chloride, ethylene chloride, carbon tetrachloride,
Examples include organic chlorine compound solvents such as chloroform, ethylene chlorohydrin, and dichlorobenzene.

[Effect]

By using an epoxy group-containing butadiene copolymer and a tertiary amine-containing phenoxy resin together, the tertiary amine in the phenoxy resin exerts a catalytic effect, promoting the ring-opening reaction of the epoxy group in the butadiene copolymer. A crosslinked structure is developed between the active hydrogen of the butadiene copolymer or the active hydrogen of the phenoxy resin.

Further, the crosslinking reaction due to the action of the tertiary amine described above proceeds almost unaffected by moisture. Therefore, a good crosslinked structure is formed and the binder has excellent durability.

〔Example〕

Hereinafter, specific examples of the present invention will be described, but the present invention is not limited to these examples.

Table 1 shows the butadiene copolymer used as the binder in this example, and Table 2 shows the phenoxy resin used as the binder.

Table 1 Table 2 Magnetic recording media were prepared using the butadiene copolymers shown in Table 1 above and the phenoxy resins shown in Table 2 as binders.

Co coated r-Fe on 11 spots! 03 100 parts by weight (
Specific surface area: 40nr/g) Butadiene copolymer A-112 parts by weight Phenoxy resin B-112 parts by weight Carbon blank (antistatic agent) 2 parts by weight Cr
*Os (abrasive) 2 parts by weight dimethyl silicone (n lubricant) 1 part by weight butyl stearate (lubricant) 1 part by weight methyl ethyl ketone 100 parts by weight toluene
60 parts by weight cyclohexanone
60 parts by weight of the above composition in a ball mill
After mixing for 4 hours and filtering with a 3 μm filter, this was coated on a 14 μm thick polyethylene terephthalate film so that the film thickness after drying was 6 μm.
After performing magnetic field orientation treatment, it was dried and rolled up.

After further supercalendering, an additional 80
A sample tape was prepared by heating at ℃ for 24 hours and cutting into a width of 172 inches.

2 to 4 In the composition of the magnetic coating, the butadiene copolymer is one of the butadiene copolymers shown in Table 1, the phenoxy resin is one of the phenoxy resins shown in Table 2, and the type thereof is A sample tape was prepared in the same manner as in Example 1 except for the changes shown in Table 3.

In the composition of the main magnetic paint, the butadiene copolymer is any of the butadiene copolymers shown in Table 1, and the phenoxy resin is any of the phenoxy resins shown in Table 2. Sample tapes were prepared in the same manner as in Example 1 except that the types were changed as shown in Table 3.

Table 3 shows the types of butadiene copolymers and phenoxy resins used in Examples 2 to 4 and Comparative Examples 1 to 3.

Table 3: Still characteristics and powder fall-off were measured for each of the sample tapes obtained.

The above still characteristics are based on 4.2MH2 sample tape.
The video signal was recorded, and the time until the playback output attenuated to 50% was taken as the time. In addition, powder falling off was evaluated by visually observing the amount of falling powder on the head drum, guide, etc. after running the shuttle 100 times for 60 minutes, and using a point deduction method (-5 to 0). 4th result
Shown in the table.

Table 4 As is clear from the above Table 4, each of the sample tapes according to the present invention not only had less powder falling off, but also had significantly improved still characteristics.

〔Effect of the invention〕

As is clear from the above description, in the present invention,
By using a butadiene copolymer containing an epoxy group and a phenoxy resin containing a tertiary amine, the ring-opening reaction of the epoxy group in the butadiene copolymer is promoted by the action of the tertiary amine in the phenoxy resin. A crosslinking reaction occurs between the butadiene copolymer and the phenoxy resin, resulting in a binder with excellent mechanical strength.

Furthermore, since this reaction proceeds almost unaffected by moisture, the binder can have very good durability.

Therefore, by using this binder, a magnetic recording medium with excellent durability can be provided without deteriorating the electromagnetic conversion characteristics.

Patent applicant: Sony Corporation Agent Patent Attorney Mi Koike Episode Sakae Tamura Same as Masaru Sahara

Claims (1)

[Claims] A magnetic recording medium in which a magnetic layer mainly composed of ferromagnetic powder and a binder is formed on a non-magnetic support, the binder comprising a butadiene copolymer having an epoxy group; A magnetic recording medium comprising a phenoxy resin having a tertiary amine.