JPS61157516A - Polyurethane resin for magnetic recording medium - Google Patents

Abstract

PURPOSE:The titled resin having improved dispersibility of magnetic powder, by subjecting epsilon-caprolactam to ring opening polymerization in the presence of polytetramethylene ether glycol as an initiator to give a specific polyhydroxy compound, and reacting this compound with a polyisocyanate compound. CONSTITUTION:(A) Polyhydroxy compounds containing two or more active hydrogens in the molecules, including a polycaprolactone having 500-10,000 number-average molecular weight obtained by subjecting epsilon-caprolactam to ring opening polymerization in the presence of a catalyst by the use of polytetramethylene ether glycol as an initiator, and, if necessary, another polyhydroxy compound (e.g., ethylene glycol, etc.), is blended with (B) a polyisocyanate compound (e.g., 2,4-tolylene diisocyanate, etc.), and reacted in the presence of a catalyst (e.g., dibutyltin dilaurate, etc.) under heating, to give the aimed resin. EFFECT:Having improved surface smoothness, heat and moisture properties and physical properties at low temperature.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a polyurethane resin for magnetic recording media, and specifically relates to the dispersibility of magnetic powder.

This invention relates to an improved polyurethane resin for providing a magnetic recording medium with excellent magnetic coating surface smoothness and durability.

[Prior art]

Magnetic recording media are manufactured by coating a magnetic paint consisting of magnetic powder, a binder, an organic solvent, and other additives on a non-magnetic substrate such as polyester film, and drying it. .

In order to obtain excellent electrical properties such as high reproducibility and high signal-to-noise ratio, magnetic recording media are manufactured using pine darts.
A material that requires uniform and fine dispersibility of the magnetic powder and a high degree of smoothness of the magnetic coating surface and has excellent durability is required for a long time of 71.
I'm here.

Therefore, in order to satisfy these performance demands.

Has research been done on various introducing agents? Polyurethane resin has been proposed as a resin for improving the durability of magnetic JD recording media.

Conventionally used thermoplastic polyurethane resins consist of a chain polyol containing hydroxyl groups at both ends, an organic diisocyanate, and a chain extender called a diol, diamine, etc. having a relatively low molecular weight active hydrogen. It is sweetened by reacting with

As such chain polyols having hydroxyl groups at both ends, polyester polyols or polyether polyols are mainly used.

As such polyester polyols, ethylene glycol is generally used.
Examples include polyesters separated from adipic acid and J-cole or/and A-hexane glycol, etc. Polyether thread polyols include polymers or co-electropolymers of ethylene oxide and propylene oxide, and polymers of tetrahydrofuran. Polytetramethylene ether glycol and the like are commonly used.

However, the dispersibility of magnetic powder and the surface smoothness of the magnetic coating film cannot be said to be sufficient in the polyurethane resins used in these polyols, and in the case of polyurethane resins using the above-mentioned polyester polyols. Urethane resin has poor moisture and heat resistance, and 11 urethane resins contain ether bonds and are therefore susceptible to oxidative deterioration.
v.

Also, patent application Sho 5g -/ 3 A' 9 g No. 3 Mei aI
In the book, the polyurethane resin obtained by the reaction of polycaprolactone polyol and an organic diisocyanate compound improves the dispersibility of magnetic powder, the smooth physical properties of the surface of the magnetic layer, and the opacity.

[Purpose of the invention]

In view of the current situation, the present inventors conducted various studies and found that the advantages of the polyether polyol-based polyurethane resin are flexibility and mechanical properties at low temperatures, and the advantages of the polycaprolactone polyol-based polyurethane resin are the magnetic layer. A polyurethane resin that has both surface smoothness and moist heat resistance has an average molecular weight of 500 obtained by polymerizing ε-caglolactone using polytetramethylene ether glycol as an initiator as a polyhydroxy compound having co or more active hydrogens in the molecule. It has been found that it can be obtained by using a compound containing a polycaprolactone polyol of ~10,000 and reacting this with a polydiisocyanate compound. By incorporating the thermoplastic polyurethane resin obtained in this way into the binder, the dispersibility of magnetic powder, the surface smoothness of the magnetic coating film, and the resistance to moisture and heat are improved compared to those using conventional thermoplastic polyurethane resins. The object of the present invention was achieved by discovering that a magnetic recording medium with excellent physical properties at low temperatures can be obtained.

[Structure of the invention]

The polyurethane resin used in the present invention has a number average molecular weight of 1 ooo to qoooo, preferably 1 o o o o-5-
It's soooooo. Number average molecule tioo.

Below this, the mechanical properties of the polyurethane resin will be poor and the durability of the magnetic recording medium will be poor. If it is more than 0,000, the dispersibility of the magnetic powder will be poor and the surface smoothness of the magnetic recording medium will be poor.

The method for producing the polyurethane resin used in the present invention is appropriately selected from known manufacturability in consideration of the degree of polymerization of the intended polyurethane resin, the type of raw materials used, and the like. For example, if necessary, a solvent inert to the isocyanate group is usually used, and if necessary, a common urethanization catalyst is used to reduce the temperature from 1O to 0℃, preferably from 0 to 0℃.
A polyhydroxy compound containing active hydrogen is reacted with a stoichiometric excess of a polyisocyanate compound to produce a prepolymer having terminal isocyanate groups, and then a diol as a chain extender, A polyurethane resin containing terminal hydroxyl groups can be obtained by reacting diamines, triols, etc., or a polyhydrochlorinated compound, a chain extender, and a polyisocyanate compound can be simultaneously added in amounts that result in a stoichiometric excess of hydroxyl groups. Examples include a method of reacting to obtain a polyurethane resin having terminal hydroxyl groups. In addition, there is a method for obtaining a polyurethane resin with terminal hydroxyl groups by reacting a polyisocyanate compound and a polyhydric acid compound without using a chain extender, and a method for obtaining a polyurethane resin. It is also possible to adopt a method in which a terminal hydroxyl group is obtained by reacting the polyisocyanate compound, and a polyurethane resin having a terminal hydroxyl group is obtained by further reacting with a polyisocyanate compound.

In the present invention, a polyhydroxy compound having two or more active hydrogens in the molecule (AJ is a ring-opening type of ε-caprolactone using 17 tetramethylene ether glycol as an initiator) with a number average molecule of 500 to 10,000 1] Caprolactone polyol (it is essential to use a compound containing aJ.The number average molecular weight is 1oooo
If it exceeds this value, the dispersibility of the magnetic powder will be poor, which is not preferable.

Polycaprolactone polyol (AJ itself, in accordance with the official seal 1 biography, ε-caprolactone in the presence of a catalyst,
It is obtained by converting polytetramethylene ether glycol having a molecular weight of 300 to too much into a ring-opening type @- as an initiator glycol.

In the present invention, it is essential to contain the above-mentioned polycaprolactone polyol (ILJ) as a polyhydroxy compound having two or more active hydrogens in the molecule, but other polyhydroxy compounds can also be used in combination. As a polyhydroxy compound, usually the molecule t30
~10,000, and are known polyhydroxy compounds generally used for producing polyurethane resins, such as low molecular weight glycols, polyethers, polyesters, polyacetals, polythioethers,
Polybutadiene glycols, silicon-containing polyols,
Phosphorus-containing polyols and the like can be used.

Examples of low molecular weight glycols include methylene 11-col, diethylene glycol, triethylene glycol, fluoropylene gelicol, diethylene glycol, l,3-j tanediol, 'l'-butanediol, pentaethylene glycol, hexamethylene glycol, neopentyl, glycol, and coethyl glycol. /, 3-hexanediol, N-argylgetanolamine, bisphenol A
etc. are used. Furthermore, it is also possible to partially mix and use diols having carboxyl groups such as dimethylalpion heptaic acid, or low molecular weight polyols such as trimethylolpropane.

Examples of the polyethers include polymeric polymers or copolymers of ethylene oxide, propylene oxide, tetrahydrofuran, and the like. Also usable are polyethers or mixed ethers obtained by condensation of the above-mentioned low-molecular-weight glycols, and products obtained by adding and superimposing ethylene oxide or aggravated propylene to these polyethers and the above-mentioned low-molecular-weight glycols.

As the polythioether, it is particularly preferable to use thioglycol alone or a condensation product of thioglycol and other glycols.

For example, polyacetals! , dabutanediol and formaldehyde, or @, Q'-dioxyethoxydiphenyldimethylmethane and formaldehyde.

Examples of polyesters include polyesters obtained from low-molecular-weight glycols and dibasic acids by dehydration wire reaction, and lactone polyols obtained by ring-opening polymerization of lactones such as ζ-caprolactone in the presence of the above-mentioned low-molecular glycols. can give.

Moreover, it is also possible to mix and use a part of trifunctional or higher functional polyol as the polyhydroxylated adduct.

In the present invention, polycaprolactone polyol (the content of a) is a polyhydroxy compound having two or more active hydrogens in the molecule (at least tot
It is desirable that the lid s contains polycaprolactone polyol (a).
Moisture heat resistance and low temperature characteristics cannot be fully expressed, which is not preferable.

In the present invention, the polyisocyanate compound (B) used to produce a polyurethane resin by reacting with a polyhydroxy compound includes co, 4-tolylene diisocyaner),
J, lh-tolylene diisocyanate, g, lt'-diphenylmethane diisocyanate, naphthalene-7,3
-Diisocyanate, toridine diisocyanate, xylylene diisocyanate, inphorone diisocyanate, hexamethylene diisocyanate, lysine ethyl ester diincyanate, a, 4t'-methylenebis(cyclohexyl isocyanate), ω, ωl- Organic diisocyanate compounds such as diisocyanate dimethylcyclohexane and companions of these organic diisocyanate compounds and polyhydric alcohols can be used.

Among these organic diisocyanates, excellent results have been obtained in the case of urethane resins using organic diisocyanates containing cyclohexyl group-containing diisocyanates, particularly those containing isophorone diisocyanate. Urethane resins using diisocyanate are particularly excellent in dispersion of magnetic powder and surface smoothness of the magnetic layer.

The chain extensions used in the production of polyurethane resin include ethylene glycol, propylene glycol, /, 4
-butanediol, /, 6-hexyl? -:y C#
Glycols with aromatic rings such as bisphenol A1 hydroquinone bis(euhydroxyethyl ether J, P-xylylene glycol, bis(β-human C7-?shetylinophthalate) , ethylenediamine, propylenediamine, hydrazine, piperazine, isophoronediamine, metaphenylenediamine, Q, lA
Diamines such as '-diaminodiphenylmethane and j,J'-cycloLμ'-aminodiphenylmethane can be used.

It is also possible to use the aforementioned polyhydroxy compounds as chain extenders.

In the present invention, solvents for producing polyurethane resins are usually ketones such as methyl ethyl ketone, methyl isobutyl ketone, and cyclohexanone that are inert to isocyanate groups, esters such as ethyl acetate and butyl acetate, and aromatic compounds such as toluene and benzene. A hydrocarbon solvent such as tetrahydrofuran is used.

As a catalyst for producing a polyurethane resin, a tin-based, iron-based, or tertiary amine-based catalyst, which is a usual urethanization reaction catalyst, is used.

Examples of tin-based catalysts include dibutyltin dilaurate, dioctyltin dilaurate, dibutyltin dioctoate,
Stanus octoate, etc.

Examples of iron-based catalysts include iron acetylacetonate and ferric chloride.

Examples of tertiary nitrogen catalysts include triethylamine and triethylenediamine.

The magnetic layer of a magnetic recording medium is prepared by mixing a magnetic coating agent, a magnetic powder, and, if necessary, each separated component with an appropriate π-organic solvent to prepare a magnetic paint, which is coated on the surface of a non-magnetic support. , is formed by drying.

As the binder, in addition to the polyurethane resin obtained in the present invention and the low molecular weight polyisocyanate compound, vinyl chloride, which is commonly used as a binder component, can be used.
It is also possible to use a mixture of vinyl acetate copolymer, nitrocellulose, epoxy resin, phenoxy resin, thermoplastic polyurethane resin, and the like.

Examples of low molecular weight polyisocyanate compounds include adducts of inocyanate compounds containing one or more inocyanate groups (adducts with divalent or trivalent polyhydric alcohols,
- adducts such as polymers, triplexes, adducts with water, etc.)
can be used.

As such a low molecular weight polyisocyanate compound, for example, DES module L1 (trade name) manufactured by Bayer AG
DeSmodule N1 Nippon Polyurethane Industries ■Product name of the jacket Coronate L, Coronate HL, Mytic GP10 manufactured by Mitsubishi Chemical Industries @3! rA, -r ITEC NY-nof
A (registered trademark of Mitsubishi Chemical Industries, Ltd.), etc.

These low molecular weight polyisocyanate compounds account for 3~! of the total amount of binder! rOc weight i)%.

The magnetic powder conveniently used in the magnetic recording medium of the present invention includes known ones that have been conveniently used in the past, such as γ-
Iron oxide, cobalt-coated r-iron oxide, cobalt-doped γ-
Examples include iron oxide, 0r02, alloy magnetic powder, metal magnetic powder, and the like.

In addition, when forming the magnetic layer of a magnetic recording medium, various commonly used additives such as antistatic agents, carbon black, lubricants, non-magnetic inorganic pigments, etc. may be added as necessary. You can also do it.

As the non-magnetic support, polyester (for example, polyethylene ester, boria, polyolefin, cellulose derivative, non-magnetic metal, paper, etc.) is used.
Its shape may be a film, tape, sheet, card, disk, etc.

Furthermore, the polyurethane resin of the present invention can be made into a polyurethane resin that is cured by electron beam or ultraviolet light by introducing an acrylic group or a methacrylic group, and can be used as a binder for electron beam-curable or ultraviolet-curable magnetic recording media. Any type of acrylic or methacrylic group that causes a curing reaction with electron beams or ultraviolet rays may be introduced, but for example, when an equimolar reaction product of diinocyanate and human O-P dialkyl acrylate is used with the polyurethane resin of the present invention, Examples include a method of reacting.

In addition, although the case where the polyurethane resin of the present invention is used as a magnetic layer of a magnetic recording medium has been described above, the polyurethane resin of the present invention can be used not only for the magnetic layer but also for magnetic recording &! It can also be applied to the so-called top coat layer (the upper surface of the magnetic layer), the back coat layer (the lower layer of the base film), and the undercoat layer (the intermediate layer between the magnetic layer and the film).

〔Example〕

Next, the present invention will be explained in more detail with reference to Examples, but the present invention is not limited to the following Examples unless the gist of the present invention is exceeded.

Example 1 (1) Production of polyurethane resin A four-lobe flask was equipped with a thermometer, stirrer, dropping funnel, and condenser with a drying tube. , $'-diphenylmethane diisocyanate 1009 and 3 g of methyl ibutyl ketone lI were charged, and the internal temperature was brought to 0° C. and stirred. PTMG for this
/ 000 (Polycaprolactone polyol with a number average molecular weight of 1zoo obtained by ring-opening polymerization of ε-caprolactone using polytetramethylene ether glycol with a number average molecular weight of *1000 as an initiator, a bifunctional polyol of yoog and a number average molecular weight of !SO Caprolactone polyol (Plaxel-o: Daicel Chemical Industries ■'4K) g3fi was added dropwise from the dropping funnel. After the addition was completed, a heating reaction was carried out at go°C for one hour to produce a greborimer having an incyanate group at the end. This reaction was continued. The mixture was dropped into a mixed solution of 4-butanediol r, ay and methyl ibutyl ketone sop. After the dropwise addition, a heating reaction was carried out at gO ℃ for 3 hours to obtain a polyurethane resin.The reaction was completed. What we did is here in the infrared absorption spectrum!; o cm-
This was confirmed by the disappearance of the isocyanate group absorption of '.

(2) Manufacture of magnetic recording media Polyurethane resin-t, 100 parts Nitrocellulose tro part [Daicel Chemical Industry Co., Ltd.]
F'M-2'00) Vinyl chloride-vinyl acetate copolymer ro part (Kikagaku Kogyo@mtoooaKT) Lecithin 70 parts Carbon Bragg μθ part co-containing W 7
'Fe2O37'' θ parts Methyl ethyl ketone 920 parts Methyl isobutyl ketone 310 parts Cyclohexanone
310 parts After kneading for 6 hours in a sand grind mill with the above composition, Mytic G was added as crosslinking sample 1.
0 parts of P/(7j-A (manufactured by Mitsubishi Chemical Industries, Ltd.: TDI and trimethylolpropane reactant) were mixed and filtered to obtain a magnetic paint.

This magnetic paint was applied onto polyethylene terephthalate film f-shim so that the film thickness after drying was approximately 10 μm, and the solvent was
After removing the lice using a dryer, the surface was smoothed using a calender. Thereafter, the magnetic recording medium was subjected to raw heat treatment at 60° C. for a short period of time to obtain a magnetic recording medium.

The results of measuring the surface reflectance of the magnetic coating film of the obtained magnetic recording medium are shown in Table No.

Example 1 (1) Production of polyurethane resin-2 In the same apparatus as in Example 1, inholonodiinocyanate tq J, methyl isobutyl ketone soqg, and dibutyltin dilaurate o, osg were charged, and the internal temperature was adjusted to gθ℃. and stirred. Using PTMGg, tO (polytetramethylene ether glycol with a number average molecular weight g5Q) as an initiator, this is subjected to ring-opening polymerization of ε-calactone, resulting in a caprolactone polyol with a number average molecular weight of 1·l and θ0.
i was added dropwise. After the dropwise addition was completed, a heating reaction was carried out at 0° C. for a period of time to produce a prepolymer having isocyanate groups at the terminals. This reactant is then converted into a eufunctional cablactone poly, t-ru 2 g ji, ) I of number average molecular Rzso.
It was added dropwise to a mixed solution of J methylolpropane/3I and sqqg of methyl isobutyl ketone. , 10 after completion of dripping
A heating reaction was carried out at °C for 3 hours to obtain a polyurethane resin.

(2) Manufacture of magnetic recording medium A magnetic recording medium was prepared in the same manner as in Example 1, except that polyurethane resin-1 was used instead of polyurethane resin-7 in Example 1.

□ Table 7 shows the results of measuring the surface reflectance of the magnetic coating film of the obtained magnetic recording medium.

Comparative Example 1 (1) Production of Polyurethane Resin-3 Into the same apparatus as in Example 1, gqg of inphorone diisocyanate, 2g2fi of methyl isobutyl ketone, and o, o, yg of dibutyltin dilaurate were charged, and the internal temperature was adjusted to 10°C. Stirred. A cofunctional polycaprolactone polyol 19Jji with a number average molecule *rro was added dropwise to this. After finishing dropping gO
A heating reaction was carried out at ℃ for 1 hour to produce a prepolymer with terminal or incyanate groups. Subsequently, this reactant was added to 71
μm butanediol z, tIi and methyl isobutyl ketone/! It was added dropwise to the mixed solution with Ofl. After completion of dripping
A heating reaction was carried out at 0°C for 3 hours, and polyurethane resin-3
I got it.

(2) Manufacture of magnetic recording medium A magnetic recording medium was manufactured in the same manner as in Example 1, except that polyurethane resin-3 was used in place of polyurethane resin-3 in Example 1.

The results of measuring the surface reflectance of the magnetic coating film of the obtained magnetic recording medium are shown in Table No.

Comparative Example 2 (1) Production of polyurethane resin (μ'-diphenylmethane diisocyaner) in the same equipment as in Example 1.
/oo9 and methyl isobutyl ketone ttsog
was charged, the internal temperature was raised to 10°C, and the mixture was stirred. To this/, 4
Polyester diol Jhoy having a number average molecular weight of 1000 and consisting of t-butanediol and adipic acid was added dropwise.

After the completion of the dropwise addition, a thermal reaction was carried out at 710° C. for 11 hours to produce a prepolymer having inocyanate groups at the terminals. Subsequently, add this reactant to l, 4! -butanediol z, tIg
and methyl isobutyl ketone 33! It was added dropwise to the mixed solution with i. After the dropwise addition was completed, a thermal reaction was carried out at 0°C for g hours.
Polyurethane resin-μ was obtained.

(2) Manufacture of magnetic recording medium A magnetic recording medium was manufactured in the same manner as in Example 1, except that tlK polyurethane resin-q of polyurethane resin-z of Example 1 was used.

Table 7 shows the results of measuring the surface reflectance of the magnetic coating film of the obtained magnetic recording medium.

Furthermore, Example 11, Comparative Example 1. - Add Mytic GP I as a crosslinking agent to 100 parts of the polyurethane resin obtained in
QjA (Mitsubishi Kahin Kogyo Co., Ltd.) / A 100μ thick film obtained by applying a 1 part diluted solution and leaving it at room temperature for 30 minutes, then drying it at 0°C for 4 hours. Mechanical properties and λ under moist heat at 70°C and 93% relative humidity
The mechanical properties of the cured film were measured after a week had passed.

The results are shown in the table.

Furthermore, the cured film obtained by drying at 0° C. for 4 hours was left in a cold room at 5° C. for one week, and the turbidity of the coating film was observed. Table 3 shows the results.

Furthermore, Example/1 J, Comparative Example 1. The magnetic recording medium obtained in - was cut to a width of '2.7111, and the length was -rr o.
o Wit magnetic tape is made, and it is attached to a drum-shaped f
A Repeated 9 rubbing tests were carried out with a given weight in contact with the rubbing body at 5°C and a humidity of ttθ%, and the first kinetic friction coefficient μl
The coefficient of kinetic friction μ when the same location is repeatedly slid 500 times. . was measured. The results are shown in Table 4.

Table l Urn surface reflectance: Measurement of glossiness (incident angle 1t!r°/acceptance angle as') using a digital bending angle Motosawa meter (Suga Test Instrument ■iJ) Table l Physical properties of polyurethane resin (*IJ Moist heat test conditions: Tabai Constant Temperature and Humidity Tester Temperature 70℃, Relative Humidity T!I, - Weeks (Qin 2) Tensile Test: Measured by Tensilon Test Piece: Length 8!rOw, Width" *xs J'Jsa1
00A measurement environment: temperature 23°C, relative humidity 60% Table 3 Transparency of cured film Example from the results in Table 7! It can be said that the magnetic recording medium using the polyurethane resin of - has high gloss and excellent dispersibility of magnetic powder. Also, from the results of Tables 1, 3, and q, Example 1. It can be seen that the polyurethane resin of - is also excellent in heat and humidity resistance and mechanical properties at low temperatures.

〔Effect of the invention〕

The polyurethane resin for magnetic recording media of the present invention is a resin obtained by the reaction of a polyinocyanate compound and the above-specified polyhydrogycin compound, and has better dispersibility of magnetic powder, surface smoothness, and heat-and-moisture properties than conventional products. , which is recognized to have excellent effects on physical properties at low temperatures,

Claims (1)

[Claims] (1) In a polyurethane resin obtained by the reaction of a polyhydroxy compound (A) having two or more active hydrogens in the molecule and a polyisocyanate compound (B), the polyurethane resin has two or more active hydrogens in the molecule. Hydroxy compound (A
) is a polyurethane for magnetic recording media, characterized in that a compound containing a polycaprolactone polyol having a number average molecular weight of 500 to 10,000 obtained by ring-opening association of ε-caprolactone using polytetramethylene ether glycol as an initiator is used. resin