JPS62102420A - Magnetic recording medium - Google Patents

Abstract

PURPOSE:To improve the dispersibility of magnetic powder, the durability of a magnetic layer, etc., by using a thermoplastic polyurethane resin or thermoplastic polyurethane resin and polyisocyanate hardener to constitute a main binder component. CONSTITUTION:The main binder component of a magnetic recording medium consists of the OH group terminated thermoplastic polyurethane resin having the urethane bond obtd. from the reaction of the diol expressed by the formula (n=1-5, R2; CmH2m+1, m=0-6) and diisocyanate and secondary or ternary OH group and/or COOM (M is an alkali metal or hydrogen atom) group as the side chain of the molecule or the thermoplastic polyurethane resin and polyisocyanate hardener. The mol.wt. of the polyurethane resin is preferably 5,000-80,000, more preferably 10,000-60,000. The dispersibility of magnetic powder is improved and the time for preparing a magnetic coating compd. is reduced by using such binder. In addition, the durability, wear resistance, solvent resistance, adhesiveness, etc. are improved.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a magnetic recording medium, and more specifically, a thermoplastic material having a special structure is used as a binder component for the purpose of improving the dispersibility of magnetic powder and the durability of a magnetic layer. O related to positive urethane resins In recent years, due to the expansion of the uses of magnetic recording media and the demand for higher performance, the required performance has become diverse, and in particular, high density, high speed running properties, and long hours under high temperature and high humidity conditions F. There is a need for a magnetic recording medium that provides a magnetic layer that can withstand running. At the same time, improving the productivity of magnetic recording media is also a major issue from the standpoint of energy conservation, and there is a strong demand for reducing the time required to prepare magnetic obstetrics, that is, improving the dispersibility of magnetic powder in the binder. . Although various studies have been made to satisfy these properties, none have been found to be satisfactory in terms of dispersibility, durability, etc. The present inventors have conducted repeated research into a resin with good magnetic powder dispersibility and less deterioration under high temperature and high humidity conditions without impairing the excellent properties of thermoplastic polyurethane resin such as abrasion resistance. result,
As a binder, O11 group-terminated thermoplastic polyurethane tree W
Component I contains a tertiary amino group-containing diol represented by \N-ζ>-R (hereinafter abbreviated as 7i group-containing diol of the present invention), a secondary or tertiary OH group, and C00M, 1, etc. The inventors have discovered that a resin with extremely excellent properties can be obtained by introducing a polar group, and the present invention has been completed.

That is, the present invention has a urethane bond obtained by the reaction of magnetic powder, coagulation, and diisocyanate on a ferromagnetic support, and has a secondary or tertiary OH group and/or cOOM (M is an alkali metal). The present invention relates to a magnetic recording medium characterized by comprising an OH group-terminated thermoplastic polyurethane resin having (or hydrogen atom) group as a side chain of the molecule, or a thermoplastic polyurethane resin and a polyisocyanate curing agent.

This resin contains the alno group-containing diol of the present invention in the molecule, 2
By having polar groups such as primary or tertiary OH groups and C00M groups present in a specific concentration range, the affinity with the magnetic powder is improved, and not only can the dispersibility be improved, but it is also possible to significantly shorten the dispersion time. be.

Furthermore, when polyisocyanate is used as a curing agent, the tertiary 74 group introduced into the molecular chain also acts as a catalyst for the urethane reaction, and the OH group at both ends or the OII group at the side chain and the incyanate ) & reactivity is also increased, and by reducing the crosslinking property, durability such as abrasion resistance can be greatly improved.

The molecular weight of the polyurethane resin of the present invention is 5.000 to so
, ooo preferably 10,000 to 60,000.

If the molecular weight is smaller than this, the strength is low and it cannot be a good binder. Furthermore, if the molecular weight is higher than this, the viscosity becomes higher and a good dispersion cannot be obtained.

In addition to the diol containing tertiary amine 7 groups, the polyurethane resin of the present invention also contains a polyol having a secondary or tertiary OH group in the side chain, a polyol having a -COOM group in the side chain, and a polyol having a side chain thereof. It is formed by a combination of a linear diol etc. that does not have an incyanate group and a diisocyanate, and has an incyanate group of 10
The molar ratio of H groups is obtained by reacting in a range of 0.8 to 1.0.

As the organic diisocyanate that can be used in the present invention, 2.4-) lysine diisocyanate (hereinafter referred to as 2-)
．． 4-TI), 2.6-triL/7 diisocyanate (hereinafter abbreviated as 2.6-TDI) and mixtures thereof, 4,4'-diphenylmethane diisocyanate (hereinafter abbreviated as MDI)%I) -phenylene diisocyanate, m~phenylene diisocyanate, 1.5-
Examples include naphthylene diisocyanate, inphorone diincyanate (hereinafter abbreviated as IPDI), hexamethylene diisocyanate, lysine diisocyanate, xylylene diisocyanate, hydrogenated MDI, Schiff-hexane diincyanate, and mixtures thereof.

Among these, 2.4-TDI, 2.6-TDI, MDI
and mixtures thereof are preferred.

It is represented by the general formula % R1: CmH, m+ 1, where m-0 to 6, which can be used in the present invention.

Examples of diols containing tertiary 71 groups (71 group-containing diols of the present invention) include N,N-bis(2-hydroxyethyl)aniline, N,N-bis(2-human 2xypvir), Examples include aniline, N,N-bis(2-hydroxyethyl)toluidine, N,N-bis(2-hydroxypropyl)toluidine, and the like.

Examples of polyols containing a secondary or tertiary OH group and two primary OH groups that can be used in the present invention include glycerin, l-bis(2-hydroxyethyl)amino-2-boupanol, -methylpropane-1,2
,3-) diol, 3-methylpentane-1,3,5-
Examples include tol, 1,2,6-hexanetriol, and 1 to 10 mole adducts of the above-mentioned ethylene oxides.

The tertiary COOM (M is an alkali metal or hydrogen) group-containing diol introduced in the present invention includes dimethylolpropionic acid (hereinafter referred to as 4PA) or its Na salt; 1) MPA and succinic acid; By reaction with dibasic acids such as maleic acid, adipic acid, glutaric acid, pimelic acid, speric acid, azelaic acid, sebacic acid, phthalic acid, isophthalic acid, terephthalic acid, hexahydro-terephthalic acid, hexahydro-isophthalic acid, etc. Examples include the polyester diols obtained.

The diol containing a 7-mino group of the present invention and the linear diol containing no secondary or tertiary OH group or tertiary cOOM group in the side chain that can be used in the present invention have a molecular weight of 500 to 500 and have a terminal hydroxyl group. 6000 polyether polyols, polyester polyols and low molecular weight glycols. Examples of polyether polyols include polyethylene glycol, polypropylene glycol, polytetramethylene glycol, and the like.

In addition, as polyester polyols, ethylene glycol, 1.2-propylene glycol, 2゜3-butylene glycol, 1.4-butylene glycol, 2.2-butylene glycol,
-dimethyl-1,3-propanediol, diethylene glycol, 1.5-pentamethylene glycol, 1.6
- Glycols such as hexamethylene glycol, 3-methyl-1,5-hentanediol, cyclohexa-so-1,4-diol, cyclohexane-1,4-dimetatool, etc. alone or in mixtures thereof, succinic acid, maleic acid dibasic acids such as divic acid, glutaric acid, pimelic acid, superric acid, azelaic acid, sebacic acid, phthalic acid, isophthalic acid, terephthalic acid, hexahyto-terephthalic acid, hexahydroisophthalic acid, and acid esters thereof , those obtained by polycondensation with acid halides. Further examples include polycaprolactone diols which are subjected to ring-opening addition polymerization in the presence of lactones such as 6-caprolactone and the above-mentioned glycols.

As the low molecular weight glycol, the above-mentioned glycols used in the production of the above-mentioned polyesters can be used alone or in mixtures. Further examples include diols in which 2 to 4 moles of ethylene oxide, propylene oxide, butylene oxide, etc. are added to bisphenol A and hyde μ-quinone.

If necessary, an organic metal compound such as diptyltin dilaurate or a tertiary amine such as N-methylmorpholine or triethylamine may be added as a catalyst during the reaction. Further, in order to increase the stability of the resin, antioxidants, ultraviolet absorbers, hydrolysis inhibitors, etc. may be added.

Furthermore, in producing the above-mentioned thermoplastic polyurethane resin, conventionally known methods can be used, and if desired, after sufficiently mixing the reactants in the presence of a catalyst, the reaction mixture is placed on a flat plate or flat surface. A method of pouring the mixture into an extruder, heating it to 1-1, then crushing it after cooling, a method of injecting the reaction mixture into an extruder, and a method of injecting the reaction mixture into an extruder. A conventional solution reaction method in which the reaction is carried out in an organic solvent such as ethyl acetate or butyl acetate alone or in a mixed solvent system can be used.

The 7-mino group-containing diol, secondary or tertiary OH group of the present invention, present in the molecular chain of the thermally 1TWi polyurethane resin obtained by the method of the present invention,
The effect of the and C00M group and the preferable range of each concentration are that the main group-containing diol of the present invention has the effect of increasing the glass transition point of the thermoplastic polyurethane resin to be produced, and the side dO
H groups, terminal OH groups, and reactive groups (OH groups) of nitrocellulose, vinyl chloride, vinegar, vinyl alcohol copolymers, polyvinyl butyral, etc., used in combination as necessary, and incyanate groups used as curing agents. It has the effect of having a catalytic effect that increases the reactivity with secondary or tertiary OH.
The tertiary C00M group has the effect of improving durability and solvent resistance by forming crosslinks through reaction with a curing agent, and because of the inclusion of these hydrophilic polar groups, the binder is adsorbed to the magnetic powder and the bond between the magnetic powder and the magnetic powder increases. This is thought to have the effect of increasing affinity and increasing dispersibility.

The appropriate concentration of the 71 group-containing diol of the present invention is 0, 10 to
5.0 mmol/g, preferably 0.5-2.0
mrno 1/g. If it is less than 0.01 mmol/g, the effect of raising the glass transition point and the urethanization catalyst effect will be small.On the contrary, if it is higher than 0.01 mmol/g, the benzene nucleus concentration will increase and the flexibility, which is a characteristic of urethane resin, will be lost. However, it becomes inferior in terms of wear resistance and durability.

Surprisingly, in the case of ordinary polyurethane resin skeletons, when the urethane group concentration is increased to increase the hardness of the resin,
It is difficult to dissolve in methyl ethyl ketone, ethyl acetate, cyclohexanone, etc., but when the 7-mino group-containing diol of the present invention is used as a chain extender to increase the urethane group concentration, the solubility in these solvents is improved. to

Furthermore, it is noteworthy that while ordinary polyurethane resins are difficult to dissolve in methyl isobutyl getone, the urethane resins having the amino group-containing diol structure of the present invention are easily dissolved therein.

The appropriate concentration of secondary or tertiary OH groups and tertiary COOM groups is 0.01 to 1.0 as the total concentration of these hydrophilic polar groups.
mml/g, preferably (0.10 to 0.50 mml/g as 11M 011 group, 0.01 to 0.50 mml/g as C00M group)
O, (If it is less than 11 mmol/g, there is no effect on the dispersion tendency -H, and if it is less than the appropriate concentration of each polar group -L, the magnetic paint tends to aggregate, which is not suitable.

In addition, when using a curing agent, adding 3 to 50% by weight to the thermoplastic polyurethane resin will improve the mechanical strength, abrasion resistance, heat resistance, solvent resistance, and adhesion of the magnetic layer to the base material. It is possible to greatly improve the performance by [1].

If necessary, the binder may contain thermoplastic polyurethane resins, vinyl chloride-vinyl acetate copolymers, fiber resins, polyvinyl butyral resins, which are commonly used as binder components for magnetic recording media. Thermoplastic polyester resin, vinyl chloride-vinyl propionate copolymer,
By using commercially available products such as epoxy resin and phenoxy resin in combination, the dispersibility of the magnetic powder and the flatness of the surface of the magnetic layer can be improved! # It can also be used to improve sex.

Other hydrophilic polar groups, such as ether groups (-0-), sodium sulfonate groups (5O4Na), epoxy groups, compounds, vinyl chloride copolymers, and epoxy resins may also be used in combination.

Magnetic powder is dispersed in the binder thus obtained l2,
A magnetic layer is formed by dissolving it in an organic solvent and coating it on a nonmagnetic support.

Furthermore, in addition to the binder and magnetic powder described above, additives such as a dispersant, a lubricant, an abrasive, an antistatic agent, and a rust preventive may be added to the magnetic layer.

Incidentally, examples of the polyisocyanate compound used as a curing agent include Coronate L1, Coronate HL, Coronate EH, Coronate 2030, and -Ronate 3030.
, Coronate 4048, =Ronate 4190, Coronate) 4192 (all manufactured by Nippon Polyurethane Industries), etc. can be used.

By using the binder according to the present invention, the dispersibility of magnetic powder is improved, the preparation time of magnetic paint can be shortened, and durability, abrasion resistance, solvent resistance, adhesion, etc. are improved. I can do it.

Furthermore, the thermoplastic polyurethane resin of the present invention can be applied as an adhesive for film lamination, an ink binder, a surface treatment agent for plastics, etc., other adhesives, and a coating agent.

Next, the present invention will be explained in more detail with reference to Examples.

Synthesis Example of Resin, 1 ゛Molecular weight 60
0 polybutylene adipate (hereinafter abbreviated as PBA) 60
0g% 15ONOLC-100 [manufactured by Kasei Ampuji Nikko Co., Ltd., N,N-bis(2-hydroxybouyl)aniline] 418g, 1.4-butylene glycol (hereinafter referred to as 1.
48G) 27 g, I) MPA 10 g, core a*-) T-100 (made in Japan d (11 Uta 7 Engineering 91),
TDI) 582g and methyl ethyl ketone (hereinafter ME
3,040 g of dibutyltin dilaurate (hereinafter referred to as DBTl) as a catalyst were charged, and after reacting at a reaction temperature of 75 to 80°C for 5 hours,
Upon cooling, a homogeneous and transparent polyurethane solution was obtained.

The obtained solution has a solid content of 35%, a viscosity of 5000 cp/25'C number average molecule 1 it (by GPC, the same applies hereinafter), and a concentration of 4.3'>N-Q- group, C0OH group (calculated value). (same below) C) N-G] = 1.22 mmol/g, (COOH:
] =0,04 6 mmol/g Example 2 Using the same apparatus and reaction conditions as in Example 1, the molecule t 10
00 PBA 700g, l5ONOLC-10029
2.6g, 1.48G 18.9g, DMPA 1
1.3g.

MDI599.0g and MEK3010g, catalyst and t7
3 g of DBTDLo was charged and reacted to obtain a homogeneous and transparent polyurethane solution.

The obtained solution had a solid content of 35%, a viscosity of 7,000 cp/25°C number average min.
CC00H) = 0.0 smmol/g Example, 3 Using the same equipment and reaction conditions as Example 1, the molecular weight was 2000.
800g of polyprolactone diol.

Neopentyl glycol 41.6 g, I5O
NOL C-100251g,:3-methylpentane-
1,3,5-triol 25.8g, Coronae) T-8
0 (Japan Polyurethane Industry [, TDI) 372g and M
1,390 g of EK and 71,390 g of EK were reacted to obtain a homogeneous and transparent polyurethane solution.

The obtained solution had a solid content of 35%, a viscosity of 3000 cp/25°C, and a number average molecular weight of 30,000 C>N−C−]=0.80 mmol/g as shown below.

[Side &A OH) = o, 1a mmol/g Example, 4 Example 2 and Example 2 except that 1.3.1 g of Na salt of DMPA was used, in which the C0OH group of DMPA in Example 2 was neutralized with caustic soda. A homogeneous and transparent polyurethane solution was obtained by reacting under the same conditions.

The obtained solution had a solid content of 35%, a viscosity of 9000 cp/250, and a number average molecular weight of 42,000 (>N-Q-) = 0. s 6 mmol/g%
(COONa)' = 0.05 mmol/g Example,
5 Using the same equipment and reaction conditions as in Example 1, the molecular weight was 2000.
polyhexane adipate) (hereinafter abbreviated as P+■A) t mol,! = Polyester diol containing tertiary COOH in the side chain obtained by transesterification of 1 mole of DMPA (
OH value = 105.2, acid value: 52.6) 100g and PHA with molecular weight 1000 600g%N, N-bis(2-human-xyethyl)aniso 7250g, I Pr) 1225
．． 6 g of 1 MDI254, 0 g and 2655 g of MEK were charged and reacted to obtain a homogeneous transparent polyurethane solution.

The obtained solution had a solid content of 35%, a viscosity of a o o OCp/25°C, a number average molecular force ()N-Q-) = o, 84 mmol/g -(
C00H) = 0.066 mmol/g Examples 6-1
0 side in Example 5 @ polyester diol containing C0OH groups, P HA and N, N of molecule jllo00
- C00H group concentration in polyurethane resin by changing the ratio of bis(2-human-xyethyl)aniline and >N-C>-
The concentration of groups was varied and reacted to obtain a homogeneous clear polyurethane solution. (Examples 6 to 10) Concentration of C0OH group and >No- group in each example (mm
ol/g) is as follows C0OHN-Q Example, 6 0.01 0.84 Example, 7 0.07 1.30 8 0.10 0.8090.10
1.70 10 0.30 0.80, 11 Using the same equipment and reaction conditions as in Example 1, the molecular weight was 2000.
Polycaprolactone diol 1000g 1 neopentyl glyco i' 52 gs 15ONOLC-100
313g, 3-methylpentane-1゜3.5 tri*-
32.2g of T-80, 1730g of toluene and 1740g of MEK were reacted to obtain a homogeneous and transparent polyurethane solution.

The obtained solution had a solid content of 35%, a viscosity of 2500 cp/25°C, and a number average molecular weight of 3,20,000 (>N-<IΣ) = o, a o t mmol/
g 1 [side chain OH) = 0.129 mmol/g Example 12.13 3-methylpentane in Example 11 1.3.5 The ratio of triol was changed, and Example 12 had a side chain OH concentration of 0.2
0 mmol/g s In Example 13, a solution with a side fI40H concentration of 0.05 mmol/g was obtained.

Comparative Example, 1 Except for l5ONOLC-100 in Example, 2,
>N-ζ under the same conditions except that 1.48G14f1g
〉-A polyurethane solution without groups was obtained.

This resin is insoluble in MEK and cannot be synthesized.
/cyclohexanone=1/1 (IijHt) The solution had titanium properties.

The obtained solution was as follows: tR1fj min 35% (MEK/cyclohexane-finished) Viscosity 30,000 (Titanium AQ) Number average molecular weight 35,000 (>N-◇-]=0, CC00tI)=( 1.05mm
o + 4 mm side, 2 real M (Ml, 3-methylpentane-1,3 in 11
,5) 1.4 B G 21.6 instead of diol
A polyurethane solution free of 1ilII chain OH groups was obtained as g.

The obtained solution had a solid content of 35% and a viscosity of 6000 cp/25°C number average molecular weight as shown below. O million()N-<Isa:] = 0.87 mmo 1/g(
Side chain 0H) = 0 Comparative example, 3 PHA (molecular weight 1000) instead of polyester diol containing side chain C0OH group in Example, 5
The reaction was carried out under the same conditions as in Example 5, except that a homogeneous and transparent polyurethane solution was obtained.

The concentration of >N-C=- group and C00H group in the obtained solution is as follows [>N-〇-) = 0.84 mmo 17 g (C0
0H)=Q Dispersibility of Magnetic Powder The fractional properties of magnetic powder were evaluated using the polyurethane solutions of Examples 1 to 13 and Comparative Examples 1 to 3.

Compounded polyurethane solution 100 parts by weight Co-γ-
F, 0. 300 parts by weight toluene
3501 MEK 350# Cyclohexanone 230 l The above mixture was dispersed in a Pall mill for 15 hours, 25 hours, and 45 hours, and the resulting magnetic paint was coated on a polyethylene terephthalate base film with a thickness of 15 μm to a film thickness of 10 μm after drying. The dispersibility of the magnetic powder was evaluated by applying a gloss test (according to JIS Z 8741) and observing the surface condition of the magnetic layer under a microscope (50 times magnification). The results are shown in Table 1.

Wear Resistance of Magnetic Tape A wear resistance test of magnetic tape was conducted using the polyurethane solutions of Examples 1 to 13 and Comparative Examples 1 to 4.

Compounded polyurethane solution 60 parts by weight
AGH40# (vinyl chloride vinyl acetate copolymer, manufactured by U, C, C) = 22- C(') -γ-Fe201 400 61
11 parts cyclohexanone 600 1MEK
60ON Lubricant (stearic acid) 8 After dispersing the mixture in G-F for 25 hours in a ball, add 25 parts of Fronate polyisocyanate curing agent made by Nippon Polyurethane Industries, and mix for an additional hour. The obtained magnetic paint was applied to a polyethylene terephthalate base film E having a thickness of 15 μm so that the film thickness after drying was 10 μm to obtain a magnetic tape. Wear resistance test (taper set H-1
01,10100O and evaluated. The results are shown in Table 2.

Table, 1 0 Excellent Δ normal × Inferior Same below Table, 2

Claims (1)

[Claims] In a magnetic recording medium formed by forming a coating layer mainly composed of magnetic powder and a binder on a non-magnetic support, the main binder component is (1) ▲ mathematical formula, chemical formula, table, etc. There is ▼ [▲ There are mathematical formulas, chemical formulas, tables, etc. ▼ or ▲ There are mathematical formulas, chemical formulas, tables, etc. ▼ However, n = 1 to 5, R_2: CmH_2m + 1 However, m = 0 to 6] Reaction of diol and diisocyanate Urethane bonds and secondary or tertiary OH groups obtained from COOM
A magnetic recording medium comprising an OH group-terminated thermoplastic polyurethane resin having (M is an alkali metal or a hydrogen atom) group as a side chain of the molecule, or (2) the thermoplastic polyurethane resin and a polyisocyanate curing agent.