JPS62165726A - Magnetic recording medium and binder therefor - Google Patents

Abstract

PURPOSE:To improve the dispersibility of magnetic particles while maintaining the mechanical characteristics which a specific polyurethane resin resin possesses by using said polyurethane resin as a binder for a magnetic recording medium. CONSTITUTION:The polyurethane resin which is produced from the polyketone compd. having at least two hydroxyl groups and expressed by formula I or II as a polyol component is used as the binder for the magnetic recording medium. In formula, n is 1-43 number and m is 1-53 number. The polyketone compd. has preferably 400-6000 number average mol. wt. and more particularly preferably 500-4004000 number average mol. wt. in terms of the flexibility and strong toughness of the resultant polyurethane resin. The number average mol. wt. of the polyurethane resin is 1000-100000, more preferably 5000-50000. The magnetic recording medium is obtd. by providing a magnetic layer formed by dispersing pulverized ferromagnetic powder in such binder on a nonmagnetic base. The specific surface area of the pulverized ferromagnetic powder is preferably <=75m<2>/g.

Description

Detailed Description of the Invention [Field of Industrial Application] The present invention relates to a binder for magnetic recording media and a magnetic recording medium. The present invention relates to a binder for magnetic recording media and a magnetic recording medium.

[Conventional technology]

Conventionally, polyester resins, polyurethane resins, etc. have been widely used as binders for magnetic recording media, but these resins are manufactured by dispersing ferromagnetic fine powder and placing them on a non-magnetic support. These magnetic recording media do not have sufficient magnetic powder dispersibility, surface smoothness, or durability. In particular, among these resins, polyurethane resin has the advantage of high durability, but on the other hand, it has the disadvantage of having a weak affinity with magnetic particles and poor magnetic powder dispersibility and surface smoothness. ing.

Therefore, in order to improve the disadvantage of poor magnetic powder dispersibility of polyurethane resin, SO3M group, C00M group
Polyurethane resin C% each having a polar group such as a group (where M is H, Li, Na or K), etc. Publication), tertiary OH group and SO3
Attempts have been made to use polyurethanes having M groups, or both SO3M and C00M groups.

[Problem that the invention seeks to solve]

However, although the polyurethane resins that have been developed so far have improved affinity and dispersibility for magnetic powder, the effects cannot necessarily be said to be sufficient. The mechanical properties of the resin deteriorate due to the polar groups, so that when a magnetic recording medium is manufactured using the resin, the magnetic recording medium cannot exhibit sufficient durability. For this reason,
It is desired to develop a binder that satisfies all aspects of magnetic powder dispersibility, durability, and flat surface smoothness.

[Means for solving problems]

The present inventors solved the above problems, namely, that polyurethane resins with excellent dispersibility of magnetic particles have not been obtained, and that the polyurethane resins obtained so far do not necessarily have good durability. In view of the fact that satisfactory effects have not been obtained, we have conducted intensive studies with the aim of improving the dispersibility of magnetic particles while maintaining the mechanical properties of polyurethane resins. The inventors have discovered that the above object can be achieved by employing a polyurethane resin manufactured by the inventors, and have completed the present invention.

That is, the present invention provides a binder for a magnetic recording medium made of a polyurethane resin produced using a polyketone compound having at least two hydroxyl groups as a polyol component, and a magnetic layer in which fine ferromagnetic powder is dispersed in the binder. A magnetic recording medium provided on a non-magnetic support is provided.

The polyketone compound having at least two hydroxyl groups used to produce the binder for magnetic recording media of the present invention is preferably produced from acetophenone and/or cyclohexanone and formalin according to a known method, such as the following: It has the structure of

(In the formula C, n represents a number from 1 to 43, and 0 represents a number from 1 to 53.) As a specific method for producing the polyketone compound represented by the formula (1) or (n), an alkali catalyst is used. Examples include a method in which cyclohexane or acetophenone is reacted with an excess of formalin in the presence of cyclohexane or acetophenone.

The polyketone compound used in the present invention is not limited to those produced by the above method, but any compound produced from compounds such as acetone, methyl ethyl ketone, acetophenone, and cyclohexanone can be used. From the point of view, polyketone compounds produced from cyclohexanone as represented by formula (1) are preferred.

The polyketone compound used in the present invention preferably has a number average molecular weight of 400 to 6000, particularly 5
00 to 4000 is desirable.

When producing the polyurethane resin which is the binder for magnetic recording media of the present invention, in addition to the above-mentioned polyketone compound, commonly known high molecular weight polyols used for producing polyurethane can also be used. Generally known high molecular weight polyols have a number average molecular weight of t500~
Those in the range of 6,000 are preferable, and examples thereof include polyether polyols and polytetramethylene ether glycols obtained by adding alkylene oxides such as ethylene oxide and propylene oxide to low-molecular polyols or amine compounds; Condensation polymers with polyhydric alcohols/L-colds such as glycol, propylene glycol, and 1,4-butanediol, and polybasic acids such as phthalic acid, maleic acid, malonic acid, succinic acid, adipic acid, and terephthalic acid. 1. Polyester polyols, polycaprolactone polyols, polycarbonate polyols, acrinopolyols, and polyacetals having hydroxyl groups at the ends. Examples include mustard oil and tall oil. Furthermore, liquid rubbers having active hydrogen groups such as hydroxyl groups, amino groups, imino groups, carboxyl groups, and mercapto groups at the molecular terminals and mixtures thereof can also be used.

Furthermore, a secondary or tertiary hydroxyl group, a sulfonic acid group represented by -8O, and a carboxylic acid group represented by -COOM (in each case, M is a hydrogen atom or 1).

It is also possible to use high molecular weight polyols having -P-1 (M' indicates M or a hydrocarbon), ammonium salts and/or amine salts of carboxyl groups, and the like.

When producing the polyurethane resin which is the binder for magnetic recording media of the present invention, a generally known chain extender used for producing polyurethane can also be used, if necessary. Generally known chain extenders preferably have a number average molecular weight in the range of 1,150 to 500, such as ethylene glycol, 1,2-propylene glycol, 1,3-propylene glycol, 1,3-butanediol, 1. +--f Tanediol, neopentyl glycol, diethylene glycol, 1,5-pentamethylene glycol, 1,6-hexane glycol, cyclohexane-1,4-diol, cyclohexane-1,4-
Low molecular weight products such as dimethatol, bis-β-hydroxyethylhydroquinone, J-coal, ethylenediamine, etc.
1.2-propylenediamine, 1,3-propylenediamine, 1゜4-phcundiamine, 1,6-hexanediamine, 4.4'-methylenebis-2-chloroaniline, 4゜4'-methylenebis-2-diamine Chylaniline, 4
, 4'-methylenebisdiphenylamine, inphorone diamine, 2,4-diaminotoluene, 2,6-diaminotoluene, and mixtures thereof can also be used. In addition, a secondary or tertiary hydroxyl group in the molecular chain, a sulfonic acid group represented by -803M,
A carboxylic acid group represented by -COOM (M in each case represents a hydrogen atom or a metal atom such as Li, Na, K, etc.), a phosphoric acid group (M') represented by a carboxyl group or -P + OM')2 A chain extender having a polar group such as M or a hydrocarbon can also be used.

Examples of the organic polyinsyanate used in producing the polyurethane resin which is the binder for magnetic recording media of the present invention include hexamethylene diincyanate, lysine diincyanate, inphorone diincyanate, quinlene diincyanate, cyclohexane diincyanate, and toluidine diincyanate. cyanide), 2.4-) lylene diocyanate, 2.6-) lylene di incyanate, 4
゜4'-diphenylmethane diincyanate, p-phenyl diincyanate, tn-phenylene diincyanate, 1,5-naphthylene diincyanate, 4,4
'-Biphenyl diincyanate, 3゜3'-dimethylbiphenyl-4,41-diincyanate, 3,3'-
Examples include dimethoxybiphenyl-4,4'-diincyanate, and water additives and mixtures of these aromatic incyanates. Among these, 4,4'-diphenylmethane diincyanate, 2,4- and 2,6- are particularly preferably used in the present invention from the viewpoint of the strength of the polyurethane resin left behind.
dry dilene cyanate and mixtures thereof.

The polyurethane resin used in the present invention may have either an incyanate group at both ends of the molecule, a hydroxyl group at both ends, or an incyanate group at one end and a hydroxyl group at the other end. . Further, the number average molecular weight of the polyurethane resin is 1.000 to 100.000.
, preferably 5, OOO to 50,000. When the number average molecular weight of the polyurethane resin is less than 1.000, the mechanical properties, abrasion resistance, and heat and humidity resistance of the resin are insufficient. In addition, the number average molecular weight is 100,
If it exceeds 000, these performances will improve, but the dispersibility of the magnetic powder will be very poor.
When dissolving polyurethane resin in a solvent to make a paint,
In many cases, it is difficult to make the paint into a paint. Number average molecular weight is 5, OOO~50. The OOO one is
In particular, it is convenient for exhibiting the magnetic powder dispersibility and durability required of the binder for magnetic recording media of the present invention.

In producing the polyurethane resin that is the binder for magnetic recording media of the present invention, conventionally known methods can be used. For example, after thoroughly mixing the reactants, the reaction mixture is poured onto a flat plate or vat and heated. , followed by cooling and then crushing, or a single or mixed organic solvent such as dimethylformamide, toluene, xylene, benzene, dioxane, tetrahydrofuran, cyclohexanone, methyl ethyl ketone, methyl isobutyl ketone, ethyl acetate, butyl acetate, etc. A manufacturing method such as a solution reaction method in which the reaction is carried out in a liquid can be adopted. At this time, should the reaction temperature be reduced or the reaction time? A reaction catalyst can also be added to shorten the time. Specific examples of reaction catalysts include amine compounds and salts thereof such as triethylenediamine, tetramethylethylenediamine, and tetramethylhexanediamine, and organic metals such as dibutyltin dilaurate, tin octylate, lead octylate, and manganese octylate. Compounds and mixtures thereof can be mentioned. Further, for the purpose of increasing the stability of the polyurethane resin, antioxidants, ultraviolet absorbers, hydrolysis inhibitors, etc. may be added alone or in combination.

Further, the magnetic recording medium of the present invention is prepared by dispersing ferromagnetic fine powder in the binder for magnetic recording media obtained as described above to form a magnetic layer, and disposing this on a non-magnetic support. be done.

The blending ratio of binder and ferromagnetic fine powder during manufacturing is determined from the viewpoint of mechanical strength and wear resistance of the magnetic layer.
Ferromagnetic fine powder 100! 10 to 1 binder for part f
A range of 0.00 parts by weight is preferred, and a range of 15 to 60 parts by weight is particularly preferred.

Ferromagnetic fine powders that can be used in the present invention include r -Fe2O3,1-Fe2O3 and Fe3O4.
Examples include mixed crystals with CO, r-Fe coated with CO, 03, CO-modified iron oxide, Crow.iron, etc., and fine alloy powders containing the base iron as a main component can be preferably used. Regarding the shape of these ferromagnetic fine powders, any shape such as needle, plate, or spherical shape can be used. In addition, the specific surface area of these ferromagnetic fine powders is preferably in the range of 75 m''/y or less as measured by the BET method from the viewpoint of reproduction output, and particularly preferably 40 m''/y or less. The ferromagnetic fine powder used in the invention is made of commonly known silane-based, titanium-based, aluminum-based coupling agents, and surfactants having polar groups such as phosphoric acid groups, sulfone groups, and carboxyl groups. It may be surface-treated.

Furthermore, aluminum oxide, chromium oxide, and silicon oxide may be added as reinforcing agents to the magnetic layer consisting of the binder and ferromagnetic fine powder, and plasticizers such as dibutyl phthalate and triphenyl phosphate, zinc stearate, and silicon may be added as reinforcing agents. A lubricant such as oil, a dispersant such as soybean oil lecithin, various antistatic agents such as carbon black, etc. can also be added.

These materials constituting the magnetic layer are dissolved in an organic solvent to prepare a magnetic coating, and a magnetic recording medium is manufactured by coating this on a support. Solvents for preparing magnetic paints include ketones such as acetone and methyl ethyl ketone, alcohols such as methanol and ethanol, esters such as ethyl acetate and butyl acetate, ethers such as dioxane and tetrahydrofuran, and benzene and toluene. Examples include aromatic hydrocarbon solvents and aliphatic hydrocarbon solvents such as hexane.

The support to which the magnetic paint is applied may be any non-magnetic material, such as polyesters such as polyethylene terephthalate, polyolefins such as polypropylene, cellulose derivatives such as cellulose triacetate, polycarbonate, polyvinyl chloride, polyimide, polyamide,
Examples of the material include metals such as aluminum.

The polyurethane resin used in manufacturing the magnetic recording medium of the present invention can also be used in combination with other generally known polyurethane resins or other resins.

For example, resins used in combination include nitrocellulose,
Cellulose derivatives such as cellulose acetate and cellulose acetate phthalate; vinyl chloride/vinyl acetate copolymers,
Vinyl chloride/vinyl acetate/vinyl alcohol copolymer,
Salt vinyl acetate resins such as vinyl chloride/vinyl acetate/maleic acid copolymers; vinylidene chloride resins such as vinylidene chloride/vinyl chloride copolymers, vinylidene chloride/acrylonitrile copolymers; polyester resins such as alkyd resins and linear polyesters ; Acrylic resins such as (meth)acrylic acid/acrylonitrile copolymer and methyl (meth)acrylate/acrylonitrile copolymer; Acetal resins such as polyvinyl acecool and polyvinyl butyral; Phenoxy resins and epoxy resins.

Examples include polyamide resin, butadiene/acrylonitrile copolymer, styrene/butadiene copolymer, and the like. These resins may be used alone or in combination.

Further, in the present invention, in order to improve the durability of the polyurethane resin, it is preferable to use the polyurethane resin after curing it with a suitable curing agent.

Curing agents that can be used in the present invention include:
Examples include low-molecular polyinsyanate having two or more incyanate groups, and compounds in which a polyisocyanate compound is reacted with a low-molecular-weight polyol to form an incyanate group at the end of the molecule, and the molecular weight thereof ranges from 150 to 7.
A value of about 000 is preferable. Among these, low molecular weight polyincyanates having two or more incyanate groups are particularly preferred.

Examples of the low molecular weight polyisocyanate having two or more incyanate groups include a reaction product of 3 moles of diincyanate such as tolylene diisocyanate and hexamethylene diincyanate and 1 mole of trimethylolpropane, modified diphenylmethane diincyanate, polyphenylmethane polyinocyanate, etc. Polyfunctional incyanate compounds such as cyanate can be mentioned. These compounds are manufactured by Nippon Polyurethane Corporation Kara 1 Coronate LJ, ``Coronate Hshi'', ``Coronate 2030J,'' Millionate MRJ.
, 1 Million One MTLj and other product names from Sumitomo Bayer Urethane ■ [Desmodule LJ, rDesmodule N], [Desmodule ILJ, [Desmodule HLJ, [Desmodule RJ, rDesmodule RF]]
Takenate D-1 is produced by Takeda Pharmaceutical under the trade name J.
02J, “Takenate D-110NJ, “Takene~”
D-202'' and other trade names.

[Effect]

The reason why the polyurethane resin as the magnetic recording N-body binder of the present invention has suitable performance is considered as follows.

The ester bonds of polyester polyols conventionally used in polyurethane resins exist on the main chain of the molecular chain, resulting in severe steric hindrance, making it relatively difficult for them to interact with the polar groups on the surface of magnetic powder. On the other hand, since the polyketone compound used in the present invention has a carbonyl group pointing outward from the molecular chain, it is considered that there is less steric hindrance in interaction with magnetic powder, making the interaction easier.

In addition, for the purpose of improving magnetic powder dispersibility, SO3M group, C0
In the method of introducing polar groups such as 0M groups (M has the same meaning as above) into polyurethane resin, these polar groups are superior to the carbonyl of the polyketone compound in terms of their ability to interact with magnetic powder. However, when these polar groups are introduced into polyurethane resin, the solubility in solvents is extremely reduced, so it is not possible to introduce the necessary amount of polar groups to obtain sufficient magnetic powder dispersibility. This is the current situation. However, since the polyurethane resin produced using the polyketone compound of the present invention inherently has excellent solubility in solvents, a large number of carbonyl groups can be introduced by using this resin, and as a result, magnetic powder and It is thought that excellent dispersibility can be obtained because the interaction with the binder is strong, and as a result, the binder and magnetic powder are strongly bonded, so that the powder generated when the magnetic layer is rubbed by a magnetic head etc. It is thought that there will be less falling off and high durability will be achieved.

〔Example〕

The present invention will be fully explained below with reference to Examples and Reference Examples.
The present invention is not limited to these examples. In addition, in the following examples and the like, all "parts" indicate "parts by weight."

Reference Example Manufacture of polyketone compound: Cyclohexanone 1058F and formalin (36%) 820F were placed in a reaction bath equipped with a stirrer, a thermometer, and a dropping funnel.
F and 30% sodium hydroxide solution IQ was added dropwise from the dropping funnel at 60° C. while stirring to adjust the pH of the reaction solution to 8. After 6 to 7 hours of reaction, the reaction is stopped when the formaldehyde odor in the reaction solution disappears, and the sodium hydroxide is neutralized with dilute sulfuric acid. Then, unreacted cyclohexanone and water were removed by concentrating under reduced pressure to obtain a pale yellow transparent ketone resin with a molecular weight of 000.

Example 1 Production of polyurethane resin: (Production Example 1) In a reaction vessel equipped with a thermometer, a stirrer, and a reflux condenser, 227 parts of the polyketone compound with a molecular weight of 81,000 obtained in Reference Example, 451 parts of methyl ethyl ketone, and 4.4 '-Diphenylmethane diincyanate (68.3 parts) was added, and 1
Allowed time to react. Then 1,4-butanediol 5.1
After reacting at 80°C for 1 hour, 0.6 parts of dibutyltin dilaurate was added as a catalyst, and the mixture was further aged at 80°C for 12 hours to obtain a polyurethane resin with molecules t3o and ooo.

(Production Example 2) In a container similar to Production Example 1, 120 parts of a polyketone compound with a molecular weight of 2 o o o, 18.6 parts of ethylene glycol, 2
, 4- and 2.6-drilene diincyanate mixture (
! Amount ratio 80/20) 61 parts, methyl ethyl ketone 300
of the mixture was added and reacted at 60C for 3 hours. Next, 0.4 part of dibutyltin dilaurate was added as a catalyst, and 80 parts of dibutyltin dilaurate was added as a catalyst.
A polyurethane resin having a molecular weight of 20,000 was obtained by aging at C for 12 hours.

(Production Example 3) The molecule fl O used in Production Example 1 was placed in the same container as Production Example 1.
208 parts of a polyketone compound of Q O, 45 os of methyl ethyl ketone, and 77.9 parts of 4,4'-cy72nylmethane diincyanate were added, and the mixture was reacted at 60°C for 1 hour. Next, 9.3 parts of 1,4-butanediol and 5.1 parts of 0.0-diethyl-N,N-bis(2-hydroxyethyl)amine methylphosphonate were added, and after reaction at 80°C for 1 hour, dibutyltin diol was added as a catalyst. lauray) was added and further aged at 80°C for 12 hours to obtain a polyurethane resin having a molecular weight of 15,000 and having one -PO(OCzHa)2 group in one polymer molecule.

(Production Example 4) Molecule n1oo used in Production Example 1 in the same container as Production Example 1.
139 parts of polyketone compound of O, 3 parts of methyl ethyl ketone
00 parts, 52.1 parts of 4,4'-diphenylmethane diincyanate were added, and the mixture was reacted at 60°C for 1 hour. Next, 63 parts of 1,4-butanediol and 2.7 s of dimethylolpropionic acid were added, and after reaction at 80°C for 2 hours, 0.4 part of dibutyltin dilaurate was added as a catalyst.
Aging was performed at ℃ for 12 hours, and Coo was added to each polymer molecule.
A polyurethane resin of -1toooo molecules having one t(group) was obtained.

(Production Example 5) Molecule f100 used in Production Example 1 was placed in the same container as Production Example 1.
112 parts of a polyketone compound of
After heating for an hour, 5-radium sulfobis-β-hydroxyethyl inphthalate and methyl ethyl keto 71
A mixture of 60 parts and 160 parts of xanone was gradually added to the cyclo. After adding the solvent, 0.4 parts of dibutyltin dilaurate was added as a catalyst, and the mixture was aged at 80° C. for 10 hours to obtain a polyurethane resin with a molecule t8000 having one SO3Na group in one polymer molecule.

(Comparative Production Example 1) A polyurethane resin was produced in the same manner as Production Example 1 except that polybutylene adipate having a molecule of f1000 was used instead of the polyketone compound.

(Comparative Production Example 2) A polyurethane resin was produced in the same manner as Production Example 2 except that polybutylene adipate having a molecular weight of -12000 was used instead of the polyketone compound.

Example 2 Evaluation of magnetic powder dispersibility: A magnetic recording binder having the composition shown below was prepared, and its dispersibility was evaluated. The evaluation was carried out by mixing each composition in a sand mill for 4 hours, applying the resulting magnetic paint onto a polyethylene terephthalate base film with a thickness of 75 microns, and measuring the surface reflectance of the film. The results are also shown in Table 1.

(Composition) Polyurethane resin solution (non-volatile content: 40%) 125 parts C
o Fig r-Fe203 10
0 parts Methyl ethyl ketone 278 parts Cyclohexanone 139 parts Soybean oil lecithin 0 or 2.4 parts (Results) Table 1: Gloss values (incident angle 60°/acceptance angle 60°) using a variable angle gloss meter manufactured by Murakami Color Research Institute It was measured.

Example 3 Durability evaluation of magnetic disk: Magnetic disk 14m with the composition shown below! L, its durability was evaluated. The magnetic disk was manufactured as follows. First, the following composition was kneaded in a sand mill for 4 hours, 10 parts of a curing agent (Coronate L manufactured by Nippon Polyurethane Co., Ltd.) was added, kneaded for 10 minutes, and then filtered to obtain a magnetic paint. Next, the obtained magnetic paint was coated to a thickness of 75 mm.
It was coated on a micron polyethylene terephthalate base film using an applicator so that the thickness after drying would be 2 microns. After drying, it was given a mirror finish by calendering and then aged to obtain a magnetic disk. Furthermore, the durability of the magnetic disk was determined by mounting the magnetic disk in a drive and measuring the time until the playback output decreased to 50% of the input. The results are shown in Table 2.

(Composition) Polyurethane resin solution (non-volatile content 40%) 75
Part vinylite VAGH (manufactured by Union Carbide, USA; vinyl chloride-vinyl acetate copolymer) 20 parts Soybean oil lecithin 0 or 2.4 parts Co-coated r
-Fe20g 100 parts Carbon black 3 parts Lubricant
2 parts methyl ethyl keto 7
200 parts cyclohexanone 10
0 parts (results) Table 2 [Effects of the invention] As specifically shown in the examples, the binder of the present invention uses a polyurethane resin that inherently has a highly dispersible polyketone compound, so it has excellent properties. It exhibits excellent interaction with magnetic powders as well as fractional effects. In addition, the lack of towability and strong resin properties of polyketone compounds was improved by using polyurethane resin, resulting in high durability. Therefore, the magnetic recording medium using the highly dispersible and highly durable polyurethane resin of the present invention can meet the demand for a magnetic recording medium that has excellent electromagnetic conversion characteristics and high durability.

that's all Procedural amendment (voluntary) May 14, 1986

Claims (1)

[Scope of Claims] 1. A binder for magnetic recording media comprising a polyurethane resin produced using a polyketone compound having at least two hydroxyl groups as a polyol component. 2. The binder for magnetic recording media according to claim 1, wherein the polyketone compound has a molecular weight in the range of 400 to 6,000. 3. A polyketone compound is represented by the following formula (I) or (II) ▲ There are mathematical formulas, chemical formulas, tables, etc. ▼ (In the formula, n represents a number from 1 to 43, m represents a number from 1 to 53) A binder for magnetic recording media according to claim 1. 4. A magnetic layer obtained by dispersing ferromagnetic fine powder in a binder for magnetic recording media made of a polyurethane resin produced using a polyketone compound having at least two hydroxyl groups as a polyol component is provided on a non-magnetic support. A magnetic recording medium. 5. The number average molecular weight of the polyurethane resin is 1,000~
Claim 4 is in the range of 100,000.
Magnetic recording medium described in Section 1. 6. The blending ratio of polyurethane resin and ferromagnetic fine powder is
5. The magnetic recording medium according to claim 4, wherein the weight ratio is in the range of 10 to 100 parts of the polyurethane resin to 10 parts of the ferromagnetic fine powder.