JPH04248824A - Production of polyurethane resin and magnetic recording medium using the same - Google Patents

Abstract

PURPOSE:To obtain the subject new resin, excellent in dispersibility of fine magnetic particles and useful as a binder for magnetic recording media by reacting a specific macromonomer as an essential component with an organic polyisocyanate. CONSTITUTION:The objective resin is obtained by radically polymerizing a monomer containing a compound having a metallic sulfonate group and a radically polymerizable group (a copolymer of the aforementioned compound with vinyl chloride, etc.) in the presence of a chain transfer agent (e.g. 1-mercapto-1,1- methanediol) having >=2 OH groups, then reacting the resultant macromonomer (having 5000-500000 molecular weight) having >=2 OH groups in the terminals as an essential component with an organic polyisocyanate (e.g. tolylene diisocyanate) and further reacting the prepared prepolymer with a polyester polyol. The aforementioned resin preferably contains 5-1000 equiv./10<6>g metallic sulfonate therein.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a novel method for producing a polyurethane resin and a magnetic recording medium using the resin as an essential component of a binder.

0002

2. Description of the Related Art Conventionally, magnetic recording media have been manufactured by using polyurethane resin as a binder and dispersing magnetic particles therein, since polyurethane resin has excellent toughness and wear resistance.

However, since polyurethane resin has poor dispersibility of magnetic particles, it is usually used in combination with nitrocellulose, vinyl chloride copolymer, etc., which have excellent dispersibility of magnetic particles.

In recent years, magnetic particles have become increasingly finer to improve the performance of magnetic recording media, and there has been an increasing demand for improving the dispersion performance of polyurethane resins. It has been proposed to introduce functional groups.

[0005]

The present invention further provides a method for producing a polyurethane resin with excellent dispersibility of fine powder magnetic particles, and a magnetic recording medium using the polyurethane resin as an essential component of the binder. purpose.

[0006]

[Means for Solving the Problems] In order to solve the above-mentioned problems, the present inventor has completed the present invention as a result of intensive research into a method for producing a polyurethane resin into which a sulfonic acid metal base is introduced.

That is, the present invention involves radically polymerizing a monomer containing a sulfonic acid metal base and a compound having a radically polymerizable group in the presence of a chain transfer agent having at least two hydroxyl groups. A method for producing a polyurethane resin characterized by reacting two macromonomers as an essential component with an organic polyisocyanate, and a magnetic recording medium in which the polyurethane resin is an essential component of a binder.

The obtained polyurethane resin has extremely excellent dispersibility of fine magnetic particles, and magnetic recording media using the polyurethane resin as an essential binder component have excellent performance, that is, excellent surface smoothness. and has a high squareness ratio.

(Structure) The polyurethane resin of the present invention has a urethane bond in its main chain and a side chain containing a hydrocarbon bond having at least a pendant sulfonic acid metal base. The polyurethane mentioned here may have urea bonds in addition to urethane bonds.

Examples of the compound having a sulfonic acid metal base and a radically polymerizable group of the present invention include vinyl sulfonic acid, methyl vinyl sulfonic acid, allyl sulfonic acid, methallyl sulfonate, styrene sulfonic acid, and acrylic acid.
Examples include alkali metal salts and ammonium salts such as ethyl 2-sulfonate, ethyl methacrylate-2-sulfonate, and 2-acrylamido-2-methylpropanesulfonic acid.

[0011] A compound obtained by copolymerizing a compound having a sulfonic acid metal base and a radically polymerizable group according to the present invention and a monomer having no sulfonic acid group can be used. Examples of these monomers include carboxylic acid vinyl esters such as vinyl acetate and vinyl propionate, methyl vinyl ether, cetyl vinyl ether, and isobutyl vinyl ether.
Vinyl ethers such as ester, vinyl chloride, vinyl halides such as vinyl fluoride, vinylidene halides such as vinylidene chloride and vinylidene fluoride, diethyl maleate, butyl benzyl maleate, dimethyl itaconate,
Unsaturated carboxylic acid esters such as methyl acrylate, ethyl acrylate, butyl acrylate, octyl acrylate, lauryl acrylate, methyl methacrylate, ethyl methacrylate, butyl methacrylate, octyl methacrylate, lauryl methacrylate, ethylene, propylene α-monoolefins such as acrylonitrile, unsaturated nitriles such as methacrylonitrile, styrene, α-
Examples include aromatic vinyls such as methylstyrene and p-methylstyrene. Further examples include glycidyl methacrylate, N,N-dimethylaminoethyl methacrylate or a salt thereof, methacroyloxyethyl acid phosphate or a salt thereof, perfluorooctylethyl methacrylate, and dimethylpolysiloxylpropyl methacrylate. These monomers may be used alone or in combination of two or more. In particular, copolymers with vinyl chloride are useful because they impart hardness to fine powder magnetic particles without impairing their dispersibility.

Examples of the chain transfer agent having at least two hydroxyl groups of the present invention include 1-mercapto-1,1-methanediol, 1-mercapto-1,1-ethanediol, and 3-mercapto-1,2-propane. Diol, 2-
Mercapto-1,2-propanediol, 2-mercapto-2-methyl-1,3-propanediol, 2-mercapto-2-ethyl-1,3-propanediol, 1-
Mercapto-2,2-propanediol, 2-mercaptoethyl-2-methyl-1,3-propanediol, 2
Examples include mercaptan chain transfer agents such as -mercaptoethyl-2-ethyl-1,3-propanediol.

Any known polymerization method can be used to radically polymerize the monomer containing the sulfonic acid metal base of the present invention and a compound having a radically polymerizable group in the presence of a chain transfer agent having at least two hydroxyl groups. However, in view of the solubility of the macromonomer, a solution polymerization method or a suspension polymerization method using a lower alcohol such as methanol or ethanol alone or in combination with deionized water as the polymerization medium is preferred. .

Examples of the polymerization initiator used in the polymerization include lauroyl peroxide, benzoyl peroxide, 3,5,5-trimethylhexyl peroxide, diisopropyl peroxydicarbonate, di-2
-Ethylhexylperoxycarbonate, di-2-ethoxyethylperoxycarbonate, t-butylperoxycarbonate
Oxybibalate, organic peroxides such as t-butylperoxyneodecanoate, 2,2'-azobisisobutyronitrile, 2,2'-azobis-2,4-dimethylvaleronitrile, 4, Examples include azo compounds such as 4'-azobis-4-cyanovaleric acid, and inorganic peroxides such as potassium persulfate, ammonium persulfate, and ammonium perphosphate.

Examples of suspension stabilizers include polyvinyl alcohol, partially saponified polyvinyl acetate, cellulose derivatives such as methylcellulose, hydroxypropylcellulose, and carboxymethylcellulose, polyvinylpyrrolidone, and polyvinylpyrrolidone. Acrylamide, maleic acid-styrene copolymer, maleic acid-methyl vinyl ether copolymer,
Examples include synthetic polymeric substances such as maleic acid-vinyl acetate copolymer, and natural polymeric substances such as starch and gelatin.

Examples of the emulsifier include anionic emulsifiers such as sodium alkylbenzenesulfonate and sodium lauryl sulfate, and nonionic emulsifiers such as polyoxyethylene alkyl ether and polyoxyethylene sorbitan fatty acid partial ester.

[0017] The above-mentioned polymerization initiator, a compound having a sulfonic acid metal base and a radically polymerizable group, other monomers,
Chain transfer agents, suspending agents, emulsifiers, etc. having at least two hydroxyl groups may be added to the polymerization system all at once at the start of polymerization, or may be added in portions during polymerization. Polymerization is usually 3
It is carried out at a temperature of 5 to 80°C with stirring.

The molecular weight of the obtained macromonomer having at least two hydroxyl groups at its terminal is not particularly limited, but is usually from 5,000 to 500,000. The molecular weight of this macromonomer is approximately determined by the amount of the chain transfer agent having at least two hydroxyl groups used relative to the weight of the monomer containing the sulfonic acid metal base and the compound having a radically polymerizable group.

Examples of the organic polyisocyanate of the present invention include aromatic diisocyanates such as tolylene diisocyanate, diphenylmethane diisocyanate, naphthalene diisocyanate, and phenylene diisocyanate, hexamethylene diisocyanate, lysine diisocyanate, cyclohexane diisocyanate, isophorone diisocyanate, dicyclohexylmethane diisocyanate, and xylylene diisocyanate. Isocyanate, aliphatic or alicyclic diisocyanate such as tetramethylxylylene isocyanate, triphenylmethane triisocyanate, polyphenylpolymethylene polyisocyanate, polyisocyanate with carbodiimide group, polyisocyanate with allophanate group, isocyanurate group Examples include polyisocyanates having

[0020] In the present invention, the compound containing an oligomer having at least two hydroxyl groups at the end and reacting with the organic polyisocyanate includes, for example, one or more of polyester polyols, polyether polyols, polyester ether polyols, etc. Mixtures may be mentioned.

Examples of the polyester polyol of the present invention include ethylene glycol, 1,2-propylene glycol, 1,3-propylene glycol, 1,3-butylene glycol, 1,4-butylene glycol, and 2,2-propylene glycol.
-dimethyl-1,3-propanediol, 1,6-hexanediol, 3-methyl-1,5-pentanediol, 1,8-octanediol, diethylene glycol,
Triethylene glycol, dipropylene glycol, tripropylene glycol, cyclohexane-1,4-diol, cyclohexane-1,4-dimethanol, glycerin, trimethylolpropane, trimethylolethane, hexanetriol, pentaerythritriol,
One or more polyhydric alcohols such as sorbitol and methyl glycoside and succinic acid, adipic acid, glutaric acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, phthalic acid, isophthalic acid, terephthalic acid, and trimellitic acid. , phthalic anhydride, tetrahydrophthalic anhydride,
These include condensates with one or more polybasic acids or acid anhydrides such as glutaric anhydride, maleic acid, maleic anhydride, and hexahydroisophthalic acid. Furthermore, γ-butyrolactone, ε-
Also included are ring-opening polymers such as caprolactone. Furthermore, polycarbonate diols such as poly(hexamethylene carbonate) diol may also be mentioned.

The polyether polyol of the present invention includes one or two of the polyhydric alcohols and polyamines mentioned above.
These include ring-opening polymers of ethylene oxide, propylene oxide, butylene oxide, styrene oxide, tetrahydrofuran, etc. alone or in combination of two or more kinds, using one or more species as an initiator.

The polyester ether polyol of the present invention may be one or two of the above polyester polyols.
These include ring-opening polymers of ethylene oxide, propylene oxide, butylene oxide, styrene oxide, tetrahydrofuran, etc. alone or in combination of two or more kinds, using one or more species as an initiator.

The molecular weight of the polyester polyol, polyether polyol, polyester ether polyol, etc. of the present invention is not particularly limited, but is usually 500 to 5,000.

[0025] In addition to polyester polyols, polyether polyols, and polyester polyether polyols, the polyurethane resin obtained in the present invention may be a low-molecular compound having two or more groups that react with isocyanate groups. Examples of these low molecular weight compounds include ethylene glycol, 1,2-propylene glycol, 1,3-propylene glycol, 1,3-butylene glycol, 1,4-butylene glycol, 2,2-dimethyl-1,3- Propanediol, 1,6-hexanediol, 3-methyl-1,5-pentanediol, 1,
8-octanediol, diethylene glycol, triethylene glycol, dipropylene glycol, tripropylene glycol, cyclohexane-1,4-diol, cyclohexane-1,4-dimethanol, glycerin, trimethylolpropane, trimethylolethane, hexanetriol, penta Polyols such as erythriol, sorbitol, methyl glycoside, ethylene diamine, 1,3-propylene diamine, 1,2-propylene diamine, hexamethylene diamine, hydrazine,
Examples include one or a mixture of two or more polyamines such as piperazine, N,N'-diaminopiperazine, 2-methylpiperazine, 4,4'diaminodicyclohexylmethane, isophoronediamine, diaminobenzene, diphenylmethanediamine, and methylenebisdichloroaniline. It will be done.

The method for producing the polyurethane resin of the present invention is carried out by reacting a macromonomer having at least two terminal hydroxyl groups with an organic polyisocyanate as an essential component. The reaction order is not particularly limited. For example, an organic polyisocyanate may be added to a mixture of a macromonomer, a polyol such as a polyester polyol, and a low-molecular compound and reacted, or an organic polyisocyanate may be added and reacted to a mixture of a macromonomer and a polyol such as a polyester polyol. A low-molecular compound may be added to a prepolymer to react, or a polyol such as a polyester polyol and a low-molecular compound may be added to a prepolymer obtained by adding an organic polyisocyanate to a macromonomer and reacting. Furthermore, macromonomers, polyols such as polyester polyols, low molecular weight compounds, and/or organic polyisocyanates may be added in portions.

The ratio of the organic polyisocyanate to the macromonomer, polyol such as polyester polyol, and low molecular weight compound is not particularly limited, but the ratio of the group that reacts with the isocyanate group to the isocyanate group is usually 2:1 to 2:1. It is done in a ratio of 1:2.

The reaction can be carried out without a solvent, in an organic solvent or in water, but it is usually carried out in an organic solvent at 20°C.
It is carried out at a temperature of -120°C, preferably 30-100°C. Examples of the organic solvent include one or a mixture of two or more of ethyl acetate, butyl acetate, cellosolve, cellosolve acetate, acetone, methyl ethyl ketone, cyclohexanone, toluene, xylene, dimethylformamide, dimethylacetamide, isopropanol, and the like. These organic solvents can be added at the beginning, middle, end, and each stage of the reaction.

In producing the polyurethane resin of the present invention, a tertiary amine catalyst and/or an organometallic catalyst may be used at the beginning and/or during the reaction, if necessary.

Furthermore, when producing the polyurethane resin of the present invention, alcohols such as methanol, ethanol, and propanol, and/or amine compounds such as dimethylamine, diethylamine, dipropylamine, and dibutylamine are added at the beginning of the reaction. It can be added during and/or at the end of the reaction.

[0031] A monomer containing the sulfonic acid metal base of the present invention and a compound having a radically polymerizable group is radically polymerized in the presence of a chain transfer agent having at least two hydroxyl groups, and the obtained terminal has at least two hydroxyl groups. The content of the metal sulfonic acid salt in the polyurethane resin obtained by reacting the oligomer with the organic polyisocyanate as an essential component is not particularly limited, but is preferably 5 to 1,000.
Equivalents/106 grams, more preferably 5 to 200 equivalents/106 grams.

[0032] If it is less than 5 equivalents/106 grams,
The dispersibility of fine powder magnetic particles is poor, 1000 equivalents/10
If it exceeds 6 grams, the solvent solubility of the polyurethane will be poor and it will be impractical.

The molecular weight of the polyurethane resin obtained in the present invention is not particularly limited. For example, when the molecular weight of the polyurethane resin of the present invention is low, it can be used after being crosslinked with a curing agent such as an organic polyisocyanate. Alternatively, if the molecular weight is large, it can be used without crosslinking.

[0034] Antioxidants, ultraviolet absorbers, hydrolysis inhibitors, dyes, pigments, fillers, etc. can be added to the polyurethane resin of the present invention, if necessary. The magnetic recording medium of the present invention uses the above polyurethane composition as an essential binder component.

As the binder for the magnetic recording medium of the present invention, in addition to the polyurethane composition of the present invention, resins compatible with the polyurethane composition of the present invention, such as polyurethane resins other than the present invention, vinyl chloride resins, polyester resins, etc. A mixture of resins, polyvinyl butyral resins, epoxy resins, phenoxy resins, polyamide resins, cellulose resins, etc. can be used.

A crosslinking agent can be used in the binder of the magnetic recording medium of the present invention. Examples of the crosslinking agent include a phenol-formaldehyde initial condensate, a urea-formaldehyde initial condensate, a melamine-formaldehyde initial condensate, and a polyisocyanate compound. Among these, polyisocyanate compounds are particularly preferred.

The fine powder magnetic particles used in the magnetic recording medium of the present invention include, for example, γ-Fe2O3, Fe3O4
, reduced iron, CrO3, Co-containing γ-Fe2O3, Co-containing Fe3O4, and the like.

The magnetic recording medium of the present invention may further contain a plasticizer such as dibutyl phthalate and triphenyl phosphate, dioctyl sulfonodium succinate, sodium ethylnaphthalene sulfonate, dilauryl succinate, zinc stearate, and soybean oil. Lubricants such as lecithin and silicone oil and various antistatic agents may be added.

[0039]

EXAMPLES Next, examples will be shown, but the present invention is not limited to these examples. In the text, "part" is based on weight.

<Production example of macromonomer> In a polymerization vessel, 150 parts of methanol, 150 parts of deionized water, 0.7 part of 3-mercapto-1,2-propanediol, and methyl cellulose were added.
After charging 0.6 parts of water and 0.2 parts of polyoxyethylene sorbitan fatty acid partial ester, the can was sealed, and after degassing under reduced pressure, 3 parts of sodium styrene sulfonate, 100 parts of vinyl chloride, and 10 parts of vinyl acetate were added and stirred at 50°C. did. After that, 2,
0.6 part of 2,5-trimethylhexanoyl peroxide was charged to start polymerization, and the pressure in the polymerization vessel was 2 kg/cm.
When the temperature reached 2, it was cooled. After collecting unreacted vinyl chloride, it was dehydrated, washed and dried to obtain macromonomer A. The hydroxyl value of this macromonomer A is 6mg/gKOH
Met.

Example 1 100 parts of the above macromonomer, 100 parts of polybutylene adipate diol having a molecular weight of 2000, and 5 parts of butylene glycol were dissolved in 940 parts of cyclohexanone, and after adding 0.2 part of dibutyltin dilaurate, diphenylmethane was dissolved. 28 parts of diisocyanate was added and reacted at 70°C for 10 hours to obtain a polyurethane solution with a resin concentration of 20%.

Example 2 The polyurethane solution of Example 1 was blended with the following composition and kneaded in a sand mill for 2 hours, after which 10 parts of a polyisocyanate curing agent (Burnock D-750, manufactured by Dainippon Ink and Chemicals Co., Ltd.) was added. In addition, after kneading for an additional 5 minutes, a filtration operation was performed to prepare a magnetic paint.

[0043] Blended Co-containing γ-Fe2O3
200 parts polyurethane solution
200 parts soybean oil lecithin
1 part toluene
100
This magnetic paint was applied onto a polyester film having a thickness of 12 microns so that the film thickness after drying would be 5 microns, and dried after orientation. Next, it was mirror-finished by calendering. The surface smoothness of this coated surface was measured using a gloss meter with a reflection angle of 60° C., and the reflectance was 96%. Further, as a result of measurement using a magnetic property measuring device, the squareness ratio was 0.82.

[0044]

Effects of the Invention The polyurethane resin obtained in the present invention has excellent dispersibility of fine powder magnetic particles, and can be used as a binder for magnetic recording media to improve the quality of magnetic recording media, such as providing smooth surfaces and high squareness ratios. It is useful as

Claims (5)

[Claims] Claim 1: A monomer containing a sulfonic acid metal base and a compound having a radically polymerizable group is radically polymerized in the presence of a chain transfer agent having at least two hydroxyl groups, and the resulting product has at least two hydroxyl groups at its terminal end. A method for producing a polyurethane resin, which comprises reacting a macromonomer with an organic polyisocyanate as an essential component. 2. A monomer containing a compound having a sulfonic acid metal base and a radically polymerizable group is a compound having the sulfonic acid metal base and a radically polymerizable group, a carboxylic acid vinyl ester, a vinyl halide, a vinylidene halide, Unsaturated carboxylic acid ester, unsaturated nitrile, aromatic vinyl, glycidyl methacrylate, N,N-dimethylaminoethyl methacrylate or its salt, methacroyloxyethyl acid phosphate or its salt, per- The method for producing a polyurethane resin according to claim 1, wherein the polyurethane resin is a copolymer with one or a mixture of two or more selected from fluorooctylethyl methacrylate and dimethylpolysiloxylpropyl methacrylate. . 3. The method for producing a polyurethane resin according to claim 2, wherein vinyl chloride is used as the vinyl halide. 4. The method for producing a polyurethane resin according to claim 1, wherein the sulfonic acid metal salt is contained in the polyurethane resin in an amount of 5 to 1000 equivalents/10 6 grams. 5. A magnetic recording medium using a polyurethane resin as an essential binder component.