JPH02284911A - Polyurethane resin binder for magnetic recording medium - Google Patents

Abstract

PURPOSE:To obtain the title binder excellent in running durability and long-term storage durability by reaction between a specific polycarbonate polyol, specific chain extender and organic diisocyanate. CONSTITUTION:The objective binder can be obtained by reaction between (A) a polycarbonate polyol with 20-80wt.% of poly(cyclohexane-1,4- dimethanolcarbonate)polyol used as a constituent, (B) a chain extender consisting of a compound having two or more hydroxyl or amino groups, <=1000 in molecular weight (e.g. ethylene glycol, 1,4-butanediol), and (C) an organic diisocyanate (e.g. 2,4-tolylenediisocyanate).

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a polyurethane resin binder for magnetic recording media. C. In detail, the present invention relates to a polyurethane resin binder for magnetic recording media which has excellent running durability and long-term storage durability and is made of a specific polyurethane resin as a binder for a magnetic layer formed on a non-magnetic support.

BACKGROUND ART Generally, magnetic recording media (specifically, magnetic recording media) used in audio equipment, video equipment, computers, etc.

(Used for audio tapes, video tapes, floppy disks, combiator data tapes, etc.) is a magnetic paint containing magnetic powder and a binder, etc. coated on a non-magnetic support such as a polyester film, and then dried to become magnetic. Obtained by forming layers.

As a binder for forming the magnetic layer of such a magnetic recording medium, vinyl chloride resin is generally used.

Polyurethane resin, polyester resin, nitrocellulose resin, epoxy resin, etc. are used.

In recent years, with the expansion of uses for magnetic recording media such as audio tapes, video tapes, and data tapes for computers, the required performance has also become more diverse. ing.

In particular, characteristics such as clear phonetic sounds, high density recording for recording and reproducing images, ability to run at high speed for long periods of time or under conditions of high temperature and humidity, and the ability to withstand long-term storage are particularly required. There is.

As a measure to increase the density, 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, that is, the so-called backing density. However, with the increase in the specific surface area due to the finer particles of magnetic powder and the increase in cohesive force due to higher magnetic force, it is not possible to obtain satisfactory surface properties with conventional binders, and as the surface area of the magnetic powder is increased, The activity of the magnetic powder coating surface has become stronger, and the deterioration of the binder has become a problem because of its influence on the binder that disperses it.

On the other hand, magnetic recording media come into intense contact with magnetic heads, rolls, etc. during recording and reproduction, which causes the magnetic layer to wear out and fall off, resulting in decreased reproduction output, fluctuations, noise generation, increased dropouts, and a decrease in the coefficient of friction. Contamination of the roll due to increased and fallen powder may cause poor running performance, tape squeal, and clogging of the magnetic head.

Furthermore, during use under high temperature and high humidity conditions or during long-term storage, the magnetic layer deteriorates L7, the magnetic layer falls off, the magnetic layer sticks, etc., and improvements are desired.

Problems to be Solved by the Invention In magnetic recording media, a highly durable binder is used that exhibits sufficient running stability even with finely divided magnetic powder, and is capable of being used at high speeds for long periods of time or under high temperature and high humidity conditions. There has been a need for a binder for use in magnetic recording media that has excellent characteristics that can withstand long-term running and long-term storage.

In order to solve the conventional problems, the present inventors conducted extensive research and found that a polyurethane resin with a specific structure was used as a binder to achieve excellent durability and significantly reduce the surface properties of the magnetic layer. The present inventors have discovered that a magnetic recording medium can be obtained, and have completed the present invention.

Means to solve problems That is, the present invention.

A hydroxyl-terminated polyurethane resin binder made by reacting a polycarbonate polyol, a chain extender, and an organic diisocyanate to be used as a binder for magnetic recording media, A) the polycarbonate polyol as a constituent component;
Poly(cyclohexane-1,4-dimethanol carbonate) polyol f: 20 to 80ii is used, and B) the chain extender is a compound containing two or more hydroxyl groups or amino groups with a molecular weight of 1000 or less. It is a binder that is characterized by its adhesive properties.

The polycarbonate diol constituting the polyurethane resin of the present invention is obtained by a deethanol condensation reaction between a polyhydric alcohol and ethylene carbonate. The polycarbonate diol of the present invention is composed of cyclohexane-1,4-dimetatool <CHDM) and has a number average molecular weight of 500 to 300.
0 poly(cyclohexane-1,4-dimethanol carbonate) polyol containing 20 to 80 weight value, other polycarbonate diols contain 1.6-
Hexanediol, diethylene glycol, propylene glycol, 1゜4-butanediol, 3-methyl-
There are resin group glycols such as 1,5=penta/diol, 1,5-bentanediol, neopentyl glycol, 1,8-octanediol, 1,9-nonanediol, and 1.10-decanediol, and preferred diols are 1,
6-hexanediol. Number average molecule 1500-300 obtained by reaction of these with ethylene carbonate
A polycarbonate diol of 0 is used and has a terminal hydroxyl group. Such polycarbonate diol is
They can be used alone or in combination of two or more.

Further, as the polycarbonate diol, a copolymer of cHDM and another diol can also be used.

In the present invention, the proportion of polycarbonate all consisting of C HD M in the polyol is 20 to 80
% by weight, preferably 30 to 70% by weight.

In this case, if it is less than 20%, satisfactory durability cannot be obtained, and on the other hand, if it exceeds 80%, the Tg (glass transition point) of the resulting resin becomes high, hard and brittle, and it is difficult to improve running performance. Undesirable. In addition, the number average molecular weight of these hydroxyl group-terminated polycarbonate diols is 500 to 300.
0, preferably 700 to 2,500.

In this case, if the molecular weight is less than 500, the urethane group concentration of the resulting polyurethane resin will be too high, resulting in poor flexibility of the resin and poor solubility in solvents, making it unsuitable for use as a binder for magnetic recording media. Undesirable. When the molecular weight is greater than 3000, the urethane group concentration of the resulting polyurethane resin becomes small and the abrasion resistance and heat resistance of the resin decrease. Abrasion resistance and heat resistance are reduced and it cannot be used for high durability purposes.

The chain extender used in the present invention has a molecular weight of 1000
The hydroxyl group te in the following molecule is a compound having at least two or more amine groups, such as ethylene glycol, 1
．． 3-propylene glycol, 1.2-propylene glycol, 1゜4-butitanediol, 1,5-bentanediol, 1.6-hexanediol, 3-mef-1. 5-bentanediol, neopentyl glycol, 1.8-octane glycol, 1°9-nonanediol, diethylene glycol, cyclohexane-1,4
- Diols, glycols such as ethylene oxide or propylene oxide adducts of CHDM or bisphenol A, hexamethylene diamine, xylene diamine, inphorone diamine, monoethanolamine, N
, N#-dimethylethylenediamine and other diamines or amino alcohols, and others include JP-A-61-10
Water and urea, which react with isocyanate groups to form urea bonds as shown in No. 7531, can also be used as chain extenders.

These may be used alone or in combination of two or more.

As the organic diisocyanate used in the present invention, td,
2.4-tolylene diisocyanate, 2.6-toIJ diisocyanate, xylene-1,4-diisocyanate, xylene-1゜3-diisocyanate, 4.4'
-diphenylmethane diinthia, *-), 4.4'-diphenylether diisocyanate, 2-nitrodiphenyl-4,4'-diisocyanate, 2.2'-diphenylpropane-4,4'-diinthia 4-), 3 .3'
-dimethyldiphenylmethane-4,4'-diinocyanate, 4,4'-diphenylglopanediinocyanate, m-phenylene diinocyanate, p-phenylene diinocyanate, naphthylene-1,4-diisocyanate, naphthylene-1,5 -diisocyanate, 3.3'
- Aromatic diisocyanates such as dimethoxydiphenyl-4,4'-diisocyanate, aliphatic diisocyanates such as tetramethylene diisocyanate, hexa, methylene diisocyanate, lysine diisocyanate, inphorone diisocyanate, hydrogenated tolylene diiso7anate, hydrogenated diphenylmethane Diisocyanate, alicyclic diincyanate such as cyclohexane diisocyanate, etc. can be mentioned. These organic diisocyanates may be aromatic, aliphatic, or alicyclic, but
Preferably, it is an alicyclic siaquanate.

The molar ratio between each component of the present invention is such that the number of moles of the organic diisocyanate is Ne based on the total number of moles of the hydroxyl group-terminated polycarbonate diol and the chain extender.

10H ratio is 0°80 to 1°05, preferably 0°85 to
1°00, which is substantially linear and has hydroxyl groups at both ends, and has a number average molecular weight of 20,000 to 130,000, preferably 30,000 to 60,000.

In this case, if the molecular weight is lower than 20,000, the resin has excellent dispersibility, but the coating film-forming ability of the resin becomes insufficient, resulting in a decrease in performance in terms of durability and surface smoothness. If the number average molecular weight is greater than 130,000, the dispersibility will decrease and the viscosity of the paint will increase, which may cause problems in the mixing, transporting, and coating steps in manufacturing the paint, which is not preferable.

The method for producing the polyurethane resin in the present invention is a known method such as a bulk polymerization (solid reaction) method in which a reaction is carried out in a molten state, a ketone solvent such as methyl ethyl ketone (MEK), methyl imbutyl ketone (MIBK), cyclohexano 7, etc., or ethyl acetate. , ester solvents such as butyl acetate, ether solvents such as dioxane and tetrahydrofuran, glycol ethers known as cellosolve and calpitol, acetic acid glycol ethers such as cellosolve acetate, amide solvents such as dimethylacetamide and dimethylformamide, toluene. , a solution polymerization method in which each component is dissolved and reacted in a solvent such as an aromatic hydrocarbon solvent such as xylene, an alcohol solvent such as methanol, ethanol, or impropatol, etc., alone or in a mixed solvent of two or more. Can be used.

In the production of the hydroxyl-terminated polyurethane resin of the present invention,
Catalysts and stabilizers can be used if necessary. Examples of catalysts include nitrogen-containing compounds such as triethylamine and triethylenediamine, diptyltin dilaurate, and tin octylate.

Examples include organometallic compounds such as zinc stearate.

Stabilizers that can be used in the present invention include ultraviolet absorbers such as substituted benzotriazoles, antioxidants such as phenol derivatives, and hydrolysis inhibitors.

As a binder for the magnetic recording medium according to the present invention, together with the polyurethane resin of the present invention, other commonly used polyurethane resins, vinyl chloride-vinyl acetate copolymers, polybutyl butyral resins, cellulose resins, Thermosetting resins or reactive resins such as polyester resins, epoxy resins and phenoxy resins, acrylonitrile-butane diene copolymers, and unsaturated prepolymers, such as urethane acrylic types, polyester acrylic types, and polyfunctional monomers such as urethane acrylic types. , phosphoric acid ester acrylic type, aryl type, etc. or ultraviolet curable resin can be used in combination.

As the magnetic powder used in the present invention, for example, γ-Fe
Iron oxide magnetic powder such as 2O3, Co-containing -Fe 203, CrO2, hexagonal barium ferrite fine particles, and Fe%Ni, Co, Fe-Ni-Co alloy, Fe
Examples include various ferromagnetic powders such as -Mn-Zn alloys and other metal magnetic powders whose main components are Fe, Ni, and Co.

In addition to magnetic recording media, the t-urethane resin according to the present invention can be used in paints, adhesives, sealants, waterproofing agents, flooring materials, artificial leather, fiber treatment agents, elastic fibers, cushion materials, sheets, belts, films, etc. It can be used for rolls, gears, solid tires, vibration-proofing materials, tubes, backing materials, shoe soles (microcellular), etc.

Function As described above, by containing 20 to 80N41% of polycarbonate polyol consisting of CHD'M in the resin and using a solid polyurethane resin as a binder, the resin can be used for long-time running at high speeds or under high-temperature and high-humidity conditions. It also has excellent properties that can withstand long-term storage, and the surface properties of the magnetic layer are greatly improved.

EXAMPLES Next, the present invention will be explained in more detail with reference to examples. In addition, "part" and "part" in examples, comparative examples, application examples, etc.
%" means "parts by weight" and "% by weight" unless otherwise specified.

Example 1 A polycarbonate polyol CCH consisting of CHDM was placed in a reaction vessel equipped with a thermometer, a stirrer, and a condenser.
D M P CD ) Number average molecular weight (Mn) 2000
Polycarbonate polyol (HG-P CD) consisting of 400 parts of 1,6-hexane glycol (Urn
Add 1,600 parts of 2,000 parts, 58 parts of CHDM, 1,100 parts of cyclohexanone, and 0.4 parts of urethanation catalyst diptyltin dilaurate (DBTDL) and mix at 50°C. After that, inphorone diisocyanate total R (NCO10H ratio)
Add 0.98 parts (approximately 261 parts) and react at 80°C. As the viscosity increases with time, it is diluted with cyclohexanone and MEKK, and the final amount of MEK is 2164 parts and the amount of cyclohexanone is 3247 parts (MEK/cyclohexanone =
2/3. 9) and synthesized to a solid content of 30%. This polyurethane resin (transparent pale yellow liquid)
PU-1) solution has a solid content of 30.1% and a viscosity of 3000c.
At p/25°C, the number average molecular weight was 30,000.

Example 2 In Example 1, CHDM PCD (Mn=2000
) 1000 copies, )(G PCD (Mn=2000
) was used in the same manner as in Example 1, except that 1000 parts of polyurethane resin (PU) was used. -2) A solution was obtained.

Example 3 In Example 1, CHDM-PCD (Mn=2000)
1400 copies, 6 HG-PCD (Mn=2000)
The raw materials, amount used, reaction conditions, etc. were all the same as in Example 1 except that 0.00 parts were used, and the result was a pale yellow liquid with a solid content of 29.0 parts.
5%, viscosity 2800cp/25℃ polyurethane resin (
Next, obtain the PU-3) solution.

Example 4 In Example 1, 500% of CHDM-PCD (Mn=1000) and 500% of @%HG-POD (Mn=1000)
The same procedures as in Example 1 were carried out except that the raw materials, amount used, and reaction conditions were all the same as in Example 1. A pale yellow liquid, a polyurethane resin (PU-
4) A solution was obtained.

Example 5 In Example 1, CHD M −P CD (Mn =
700) t-1000 copies, HG-PCD (Mn=100
The raw materials, amount used, reaction conditions, etc. were all the same as in Example 1 except that 700 parts of 0) were used. Solid content 30.4chi,
A pale yellow liquid polyurethane resin (PU-5) solution with a viscosity of 2400 cp/25°C was obtained.

Example 6 CHDM-PCD (Mn=2500) in Example 1
i 1000 copies, HG-P CD (Mn=IQOO)
Raw materials and amounts used, except for the use of 1000 parts.

All the reaction conditions etc. were the same as in Example 1 [synthesized, solid content 30.
A pale yellow liquid polyurethane resin (PU-6) solution with 0% viscosity and 3800 cp/25° C. was obtained.

Example 7 50% each of CHDM and 1,6-hexane glycol
Polycarbonate polyol-/I/(Mn
=2000) to 2000 copies, CHDM to 58 copies:
The total R of inphorone diisocyanate is 0.98.
The reaction was carried out in the same manner as in Example 1 to obtain a pale yellow liquid polyurethane resin (PU-7) having a solid content of 29.9% and a viscosity of 3100 cp/25°C.

Comparative Example 1 HG-PCD (M
The reaction was carried out in the same manner as in Example 1 except that 2000 parts (n=2000) was used, and the reaction was carried out in the same manner as in Example 1, resulting in a pale yellow liquid with a solid content of 29.8
A polyurethane resin (comparison-1) having a viscosity of 2500 cp/25° C. was obtained.

Comparative example 2 Actual m Example i K
= 2000) to 200, HG-PCD (Mn = 2000
) t-1so.

A pale yellow liquid polyurethane resin (Comparison-2) having a solid content of 30.1% and a viscosity of 2900 cp/25° C. was obtained in the same manner except that the same amount was used.

Tests were conducted using various resins in clear film durability evaluation examples and comparative examples.

Clear film creation; polyiso-
Add 10 parts of Coronanate (Coronate: trade name manufactured by Nippon Polyurethane Industries) (in terms of solid content). Apply on release paper using a knife coater to a dry film thickness of 100 μm. After processing at 60℃ for 15 minutes, apply at 120"C for 30 minutes. After the treatment, it was cured and dried at 25° C. for 3 days to provide a sample for durability evaluation.

Durability test: A test piece of clear film cut with a JI 84 tambell was placed in a constant temperature and humidity chamber at 70°C x 95SRH, left for 5 weeks, and the retention rate of the film's physical properties was determined according to the test method of JISK-6301. Table 1 shows the results.
Shown below.

Retention rate: (TB after test (6 or IB)/TB after test
(or EB))
Evaluation of magnetic paint and magnetic layer Application example 1 Using the polyurethane'/MMCPU-1 obtained in Example 1, a composition for magnetic recording media was prepared on a table using a dog grind mill (manufactured by Igarashi Kikai KK) for 8 hours. The magnetic paint obtained by dispersion was dried on a polyethylene terephthalate film having a thickness of 12 μm, and then coated with KW1 cloth to a thickness of 5 μm, dried, and the glossiness of each film was examined (Table 3). In addition, Coronate-L (manufactured by Nippon Polyurethane Industries) was added as a polyisocyanate to the magnetic paint obtained by dispersing for 8 hours, and 10vt% of the polyurethane resin (A) was added as a curing agent in terms of resin content.
After further mixing for 1 hour, it was coated on a polyethylene terephthalate film with a thickness of 12 μm to a thickness of 5 μm after drying while applying a magnetic field of 2000 Gauss.
A magnetic tape was obtained after being left at 60°C for one day. The results are shown in Table 2.

Compound composition for magnetic recording media Co-γ-Fe2O3 100 parts Polyurethane resin (PU-1) (Resin content)
25 parts lecithin 2 parts toluene 110 parts MEK
110 parts cyclohexanone
70 parts application examples 2-7. Comparative Application Examples 1 to 2 Instead of the polyurethane resin (PU-1) used in Application Example 1, the polyurethane resins obtained in Examples PU-2 to 7 and Comparative Examples 1 to 2 (Comparison-1, Comparison-2) were used. Example 1
The running characteristics of magnetic tape were evaluated and compared using the same prescription. The results are shown in Table 2.

Change in friction during running: Changes in dynamic friction coefficient during a running test at 60° C. x 95% RH for 4 weeks were measured using a surface property measuring device (New Scientific Instruments Method HE IDON-14).

Observe the amount of decrease in adhesion after storage at 60°C, 95% RH, and 4 weeks and the deterioration (extracted amount) by Soxhlet extraction test.

durability: Table 2 Notes to Table 2 The symbols are as follows.

O: Rate of change 5 or less O: Rate of change 5% to 10 Δ: Rate of change 101 to 20 H: Rate of change 20% or more As is clear from the results in Tables 1 and 2, polycarbonate polyol from CHDM It can be seen that the polyurethane resin produced using polycarbonate and the magnetic recording medium in which this resin is used as a binder for the magnetic layer have excellent durability and running stability.

Effects of the Invention The hydroxyl-terminated polyurethane resin of the present invention has a molecular weight of 500.
~3,000 Polycarbonate Polyols Composed of chain extenders organic polyisocyanates, polycarbonate polyols contain cyclohexane-
By containing 20 to 80 units of 1,4-dimethatool, the durability of the resulting polyurethane resin, as well as the durability and running stability of the magnetic recording medium using this as a binder for the magnetic layer, are extremely excellent. .

Claims (1)

[Scope of Claims] A hydroxyl-terminated polyurethane resin binder prepared by reacting a polycarbonate polyol, a chain extender, and an organic diisocyanate used as a binder for magnetic recording media, comprising: A) the polycarbonate polyol as a constituent component;
B) The chain extender is a compound containing two or more hydroxyl groups or amino groups with a molecular weight of 1000 or less. A binder characterized by