JPH03192515A - Magnetic recording medium - Google Patents

Abstract

PURPOSE:To obtain a tough magnetic layer and enough traveling durability by incorporating such a polyurethane resin as a binder component that can be obtained by the reaction of org. diisocyanate, specified long-chain diols, long-chain polyols, etc. CONSTITUTION:The polyurethane resin obtained by effecting the reaction among at least (a) - (d) materials of (a) - (e) materials described below is used as the binder component of a magnetic layer. (a):Org. diisocyanate (b): Long-chain diols having 500 - 5000 mol.wt. (c):Polyols having 4 - 11 carbon number and 3 - 6 hydroxyl groups containing at least one tertiary hydroxyl group, and/or long-chain polyols of 500 - 5000 mol.wt. using the polyols above described and having an end hydroxyl group and at least one tertiary hydroxyl group in the molecular chain (d):Polyols having 2 - 12 carbon number and 2 - 6 hydroxyl groups containing one amino group (e):Diols and/or diamines having 2 - 12 carbon number. By this method, traveling durability of the medium can be adequately improved, and moreover, when an isocyanate crosslinking agent is used with the resin, the crosslinking rate can be increased to suppress genera tion of dropout.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a magnetic recording medium, and more particularly to a magnetic recording medium with excellent running durability.

[Conventional technology]

In general, magnetic recording media are made by applying a magnetic paint consisting of magnetic powder, binder resin, organic solvent, and other necessary components onto a substrate such as a polyester film and drying it. Because of the intense sliding contact, the magnetic layer is required to have little wear and excellent durability.

For this reason, polyurethane resins with excellent wear resistance and toughness have traditionally been used as binder components. It has the disadvantages of poor reactivity, low crosslinking density, and residual unreacted polyurethane resin.As a result, problems such as head clogging and guide ball staining are likely to occur, which impairs running durability. This tendency is particularly noticeable as magnetic recording media become more highly brittle.

Therefore, in order to solve these problems, attempts have been made to use branched polyurethane resins obtained using trifunctional or higher functional polyols such as trimethylolpropane.

[Problem to be solved by the invention]

However, branched polyurethane resins obtained using this type of trifunctional or higher-functional polyols have the disadvantage that they tend to gel during production, and running durability has not yet been sufficiently improved. . Further, the reaction with the polyisocyanate crosslinking agent is not sufficiently carried out, and dropouts occur, making it impossible to sufficiently improve running durability such as still life.

[Means to solve the problem]

This invention was made as a result of various studies in view of the current situation, and includes (a) an organic diisocyanate, (b) a long-chain diol with a molecular weight of 500 to 5,000, and (c) a tertiary diol as a binder component of the magnetic layer. 3 to 6 hydroxyl groups having at least one hydroxyl group,
A long chain polyol (d) amino having a molecular weight of 500 to 500.0, having a polyol having 4 to 11 carbon atoms and/or a terminal hydroxyl group formed using the polyol and having one or more tertiary hydroxyl groups in the molecular chain. 2 to 6 hydroxyl groups containing 1 group, 2 to 6 carbon atoms
By using a polyurethane resin obtained by reacting at least (a), (b), (c), and (d) of 12 polyols (e) diols and/or diamines having 2 to 12 carbon atoms,
It sufficiently improves running durability, and when used in combination with isocyanate crosslinking agents, it increases the reactivity with the crosslinking agent, increases the crosslinking rate, suppresses the occurrence of dropouts, and improves running durability such as still life. This further improves the quality of the product.

The polyurethane resin used in this invention is obtained by reacting at least (a), (b), (c), and (d) of the above-mentioned components (a), (b), (c), (d), and (e). These (a) polyurethane resins are preferably used;
The polyurethane resin obtained by reacting )(b)(c)(d) and the polyurethane resin obtained by reacting (a)(b)(c)(d)(e) have appropriate elasticity. ,
Since it has excellent toughness, when this type of polyurethane resin is used as a binder resin, a strong magnetic layer can be obtained and the running durability can be sufficiently improved.

In addition, this type of polyurethane resin has four or more hydroxyl groups in the molecule and at both ends that can crosslink with a crosslinking agent such as a polyisocyanate crosslinking agent, and among the four or more hydroxyl groups, a third hydroxyl group with particularly excellent crosslinking properties is used. In addition to containing at least one hydroxyl group of the same class, it also contains at least one amino group that strongly crosslinks with a crosslinking agent such as a polyisocyanate crosslinking agent, so when used in combination with a crosslinking agent such as a polyisocyanate crosslinking agent, the reactivity with the crosslinking agent The crosslinking rate increases, the occurrence of dropouts is suppressed, and the running durability is further improved.

Regarding each component used in producing the polyurethane resin as described in 2, the following are preferably used for each component.

(a) As the organic diisocyanate, tolylene diisocyanate, 4,4'-diphenylmethane diisocyanate, hexamethane diisocyanate, isophorone diisocyanate, etc. are preferably used.

(b) Long-chain diols with a molecular weight of 500 to 5,000 include diols such as ethylenediol, 1,4-butanediol, neopentyl glycol, and 1,6-hexanediol, and dicarboxylic acids such as adipic acid, phthalic acid, and sebacic acid. Preferably used are polyester diols obtained by polycondensation with acids, polylactone diols such as poly ε-caprolactone, and polycarbonate diols such as poly 1,6-hexane carbonate.

(c) Polyols having 3 to 6 hydroxyl groups and 4 to 11 carbon atoms having at least one tertiary hydroxyl group include 1,3
．． 5. -Hydroxy-3-methylpentane, 1,2.3
-Hydroxy-2-methylpropane, 1,2.3-hydroxy-2-ethylpropane, 1,2°4-hydroxy-2-methylbutane, 1,2.5-hydroxy-2-methylpentane, 1,3. Single substances or mixtures of 6-hydroxy-3-methylhexane, 1,2,3,6-hydroxy-2,3-dimethylhexane, etc. are preferably used,
A polyol having a terminal hydroxyl group and having one or more tertiary hydroxyl groups in the molecular chain, with a molecular weight of 500 to 5.
The polyol No. 000 can be produced by polycondensation of the above polyol or a mixture of the above polyol and a diol such as ethylene glycol, 1.4-7' tanediol, neopentyl glycol, and a dicarboxylic acid such as adipic acid, phthalic acid, or sebacic acid. The resulting polyester polyols are preferably used. Furthermore, polycaprolactone polyols obtained by polyadding polylactone diols such as ε-caprolactone to triols, tetrols, pentols, and the above polyols are also preferably used.

(d) 2 to 6 hydroxyl groups, including one amino group, and 2 to 6 carbon atoms
12 polyols include jetanolamine, dibrobanolamine, jetanolamine, 2-aminoethyl-1,4-butanediol, 3-amino-1,2-
Propanediol, tris(hydroxymethyl)aminomethane and the like are preferably used.

(e) As the diol having 2 to 12 carbon atoms, diols such as ethylene glycol, 1,4-butanediol, and neopentyl glycol are preferably used, and -CO
OH, -303M, -P03M! (However, M is H or an alkali metal.) Diols with polar groups such as dimethylolpropionic acid, sodium bis(4-hydroxybutyl)-5-sulfoisophthalate, sodium β-glycerol phosphate, etc. Preferably used. Further, as the diamine, ethylenediamine, tolylene diamine, etc. are preferably used.

These (a), (b), (C), (d), and (e) are made by reacting at least (a), (b), (c), and (d),
If necessary, (e) is further reacted to produce the desired polyurethane resin, and the ratio of (a), (b), (c), and (d) is adjusted as necessary. Methods for producing such polyurethane resins include the one-shot method in which all diols and all polyols are reacted simultaneously with all diisocyanate components, and the isocyanate group-terminated prepolymer obtained by reacting long-chain diols and diisocyanate components in a low-molecular-weight diol, etc. The polyurethane resin used in this invention can be produced by either the one-shot method or the prepolymer method, but in the one-shot method, when a large amount of amino group-containing polyol is used, Since gelation may occur, it is more preferable to use a prepolymer method in which the amino group-containing polyol is added last.

If the average molecular weight of the polyurethane resin produced in this way is smaller than 5,000, it will not be possible to sufficiently improve running durability, and if the average molecular weight is larger than 1,000,000, the solubility of the resin will deteriorate, resulting in electromagnetic The average molecular weight is 5,000 to 100,000 because the properties will deteriorate.
0 is preferably used, and the average molecular weight is 10,000 to 10,000.
50,000 is more preferably used. In addition, the amount used is preferably in the range of 10 to 35% by weight based on the magnetic powder, and in the range of 15 to 30% by weight, in order to exhibit sufficient effects and sufficiently improve running durability. It is more preferable to use it within.

When such a polyurethane resin is used in combination with a polyisocyanate crosslinking agent, the isocyanate groups of the crosslinking agent react with the hydroxyl groups and amino groups contained in the polyurethane resin, resulting in strong crosslinking at a high crosslinking rate.
A strong magnetic layer is formed, the occurrence of dropouts is well suppressed, and running durability is further improved. As the polyisocyanate crosslinking agent, for example, trifunctional low molecular weight isocyanate compounds are preferably used, and specific examples include Coronate L manufactured by Nippon Polyurethane Industries, Desmodinyl manufactured by Bayer, and Takenate D102 manufactured by Takeda Pharmaceutical Company Limited. Can be mentioned.

In addition, vinyl chloride-vinyl acetate copolymer, vinyl chloride-vinyl acetate-vinyl alcohol co-y1 combination, and vinyl chloride-vinyl acetate-malein M are also commonly used as binder components! combination, polyvinyl butyral resin, acrylic acid ester-acrylonitrile copolymer,
Cellulose acetate butyrate Cellulose derivatives such as nitrocellulose, thermoplastic resins such as polyurethane resins, phenolic resins, epoxy resins, urea resins,
A thermosetting resin such as an alkyd resin may also be used in combination, and depending on the application, a magnetic recording medium with even better characteristics can be obtained by using these binder resins in combination.

The magnetic recording medium of the present invention may be manufactured according to a conventional method. For example, each of the above components (a), (-b), and
), (d), and (e) are mixed and dispersed together with magnetic powder, an organic solvent, and other additives to prepare a magnetic paint, and this magnetic paint is applied onto a substrate such as a polyester film. , applied by any means such as spraying or roll coating, and dried.

At this time, a magnetic layer may be provided on the surface of the substrate, and a back coat layer may be provided on the opposite surface (also, magnetic layers may be provided on both surfaces of the substrate. When providing the back coat layer in this way, The polyurethane resin of the present invention is also suitably used as a binder resin for this back coat layer.

Here, as the magnetic powder used in the magnetic layer, for example, 7FezOs powder, Fe5e4 powder, CQ-containing 7-F
ezO, powder, Co-containing Fe.

In addition to o4 powder, Cry powder, Fe powder, CO powder, C
Various conventionally known magnetic powders such as metal powders such as o-ferrite powder and Ba ferrite powder are widely included.

Further, as the organic solvent, those commonly used in magnetic recording media, such as cyclohexanone, methyl ethyl ketone, methyl isobutyl ketone, toluene, tetrahydrofuran, dioxane, and dimethyl formamide, are used alone or in combination.

Furthermore, as a substrate, polyethylene terephthalate,
Any of those commonly used as substrates, such as various synthetic resin films such as polyamide, polyamideimide, and polyimide, and metal foils such as aluminum foil and stainless steel foil, are preferably used.

In addition, magnetic paint contains myristic acid, stearic acid,
Lubricants such as n-butyl stearate, octyl stearate, isoamyl stearate, silicone oil, paraffin, abrasives such as alumina, Crz03, red iron, etc.
Dispersants such as carbon black or lecithin, etc.
-a and those added to the magnetic paint may be added as necessary.

〔Example〕

Next, embodiments of the invention will be described.

Example 1 4.41-Diphenylmethanedi 50 parts by weight Isocyanate Polybutylene adipate (number 100〃Average molecular weight 1
000) Tin octylate 0.02 Toluene 100 Cyclohexanone
1OO〃 was charged into a reaction vessel equipped with a thermometer, a stirrer, and a reflux condenser, and after reacting at 80''C for 4 hours, 3.6 parts by weight of 1.3.5-hydroxy-3-methane was added. Penkun neopentyl glycol 6.9 Add 8
The reaction was carried out at 0°C for 6 hours. Finally, add 1.4 parts by weight of jetanolamine,
The reaction was carried out at 80°C for 4 hours.

After the reaction, a mixed solvent of cyclohexanone and toluene in a weight ratio of 1:1 was added to make a 20% by weight solution to obtain a polyurethane resin solution. The number average molecular weight of the obtained polyurethane resin was 25,000 in terms of polystyrene by GPC measurement.

Using the polyurethane resin thus obtained, Co-containing 7-Fez0 = powder 100 parts by weight (BET
Specific surface area 40 volts/g, coercive force 650 oersted) Vinyl chloride-vinyl acetate-vinyl alcohol copolymer (U, U.

Manufactured by Company C, VAGH) Polyurethane resin 8 (number average molecular weight 25,000) Carbon black 4" Alumina
5 〃n-butyl stearate 1 〃myristic acid
1 A composition of 120 cyclohexanone and 120 toluene was dispersed in a ball mill for 70 hours, and 5 parts by weight of a trifunctional low molecular weight isocyanate compound (manufactured by Nippon Polyurethane Industries, Ltd.; Coronate L) was added and mixed to prepare a magnetic paint. did. This magnetic paint was applied onto a polyethylene terephthalate film with a thickness of 14 μm so that the thickness after drying would be 4.5 μm, the magnetic particles were oriented through a magnetic field, and after drying, the surface was smoothed to 1/2 A magnetic tape was produced by slitting it into inch width pieces.

Example 2 In the synthesis of polyurethane resin in Example 1, polyester diol (adipic acid/neopentyl glycol/1.3.5-
The molar ratio of hydroxy-3-methylpentane is 50/40
/10, molecular weight 2000), 1.
3.5-hydroxy-3-methylpentane and jetanolamine were omitted, the amount of neopentyl glycol used was changed from 6.9 parts by weight to 9.5 parts by weight, and tris(hydroxymethyl)aminomethane was newly added to 2 parts by weight. A polyurethane resin was obtained in the same manner as in Example 1, except that .2 parts by weight were added. The number average molecular weight of the obtained polyurethane resin is G
It was 31,000 in terms of polystyrene by PC measurement.

The polyurethane resin thus obtained was used in Example 1.
A magnetic tape was produced in the same manner as in Example 1, except that the same amount of polyurethane resin was used in place of the polyurethane resin used in the composition of the magnetic paint in Example 1.

Comparative Example 1 In the synthesis of polyurethane resin in Example 1, the amount of neopentyl glycol used was changed from 6.9 parts by weight to 11 parts by weight.
．． A polyurethane resin was obtained in the same manner as in Example 1, except that the amount was changed to 0 parts by weight and 1.3.5-hydroxy-3-methylpentane and jetanolamine were omitted. The number average molecular weight of the obtained polyurethane resin was 28,000 in terms of polystyrene by GPC measurement.

The polyurethane resin thus obtained was used in Example 1.
A magnetic tape was produced in the same manner as in Example 1, except that the same amount of polyurethane resin was used in place of the polyurethane resin used in the composition of the magnetic paint in Example 1.

Comparative Example 2 In the synthesis of the polyurethane resin in Example 1, the amount of neopentyl glycol used was varied from 6.9 parts by weight to 9.9 parts by weight.
6 parts by weight, omitting 1,3.5-hydroxy-3-methylpentane, and reducing the amount of jetanolamine used to 1.
Example 1 except that the amount was changed from 4 parts by weight to 1.6 parts by weight.
A polyurethane resin was obtained in the same manner as above. The number average molecular weight of the obtained polyurethane resin was 21,000 in terms of polystyrene by GPC measurement.

The polyurethane resin thus obtained was used in Example 1.
A magnetic tape was produced in the same manner as in Example 1, except that the same amount of polyurethane resin was used in place of the polyurethane resin used in the composition of the magnetic paint in Example 1.

Regarding the magnetic tapes obtained in each example and comparative example,
Chroma S/N ratio, dropout and still life were tested and measured using the following methods.

<Chroma S/N ratio> A chroma signal was recorded on each obtained magnetic tape using a VH3 type VTR, and the noise portion of the reproduced signal was measured at the initial stage and after 10 repeated runs using a chroma noise measuring device. The chroma S/N ratio was determined. The chroma S/N ratio was expressed as a relative value with the magnetic tape of Comparative Example 1 as a reference (OdB).

<Dropout> Record the color bar signal on the obtained magnetic tape and
The number of dropouts was measured after repeated runs. The number of dropouts is 1.5X with the dropout counter.
The number of times in which the playback output level decreased by 16 dB or more for a period of 10 seconds or more was expressed in 15 minutes.

<Still Life> Color bar signals were recorded on each of the obtained magnetic tapes and reproduced in still mode, and the time until the reproduced signal level decreased by 6 dB was measured.

Table 1 below shows the results.

Table 1 [Effects of the Invention] As is clear from Table 1 above, the magnetic tapes obtained in Examples 1 and 2 were both Chroma S /N ratio is high, the number of dropouts is small, and the still life is long, which indicates that the magnetic recording medium obtained by the present invention has good electromagnetic conversion characteristics and excellent running durability.

Claims (1)

[Claims] 1. As a binder component: (a) an organic diisocyanate (b) a long-chain diol with a molecular weight of 500 to 5,000 (c) a hydroxyl group having at least one tertiary hydroxyl group and a carbon number of 3 to 6; 4 to 11 polyols and/or terminal hydroxyl groups formed using the polyols, and one or more tertiary hydroxyl groups in the molecular chain, with a molecular weight of 500 to 50.
00 long chain polyol (d) 2 to 6 hydroxyl groups containing one amino group, 2 to 6 carbon atoms
12 polyols (e) A magnetic material having a magnetic layer containing a polyurethane resin obtained by reacting at least (a), (b), (c), and (d) of diols and/or diamines having 2 to 12 carbon atoms. recoding media