WO2002091367A1 - Produits de liaison pour supports d'enregistrement magnetiques - Google Patents

Produits de liaison pour supports d'enregistrement magnetiques Download PDF

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Publication number
WO2002091367A1
WO2002091367A1 PCT/US2002/014308 US0214308W WO02091367A1 WO 2002091367 A1 WO2002091367 A1 WO 2002091367A1 US 0214308 W US0214308 W US 0214308W WO 02091367 A1 WO02091367 A1 WO 02091367A1
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WO
WIPO (PCT)
Prior art keywords
adduct
polymerizable
magnetic
isocyanate
group
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PCT/US2002/014308
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English (en)
Inventor
Henri J. M. Gruenbauer
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Dow Global Technologies Inc.
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Publication of WO2002091367A1 publication Critical patent/WO2002091367A1/fr

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    • G—PHYSICS
    • G11—INFORMATION STORAGE
    • G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
    • G11B5/00—Recording by magnetisation or demagnetisation of a record carrier; Reproducing by magnetic means; Record carriers therefor
    • G11B5/62—Record carriers characterised by the selection of the material
    • G11B5/68—Record carriers characterised by the selection of the material comprising one or more layers of magnetisable material homogeneously mixed with a bonding agent
    • G11B5/70—Record carriers characterised by the selection of the material comprising one or more layers of magnetisable material homogeneously mixed with a bonding agent on a base layer
    • G11B5/702—Record carriers characterised by the selection of the material comprising one or more layers of magnetisable material homogeneously mixed with a bonding agent on a base layer characterised by the bonding agent
    • G11B5/7021—Record carriers characterised by the selection of the material comprising one or more layers of magnetisable material homogeneously mixed with a bonding agent on a base layer characterised by the bonding agent containing a polyurethane or a polyisocyanate
    • G11B5/7022—Record carriers characterised by the selection of the material comprising one or more layers of magnetisable material homogeneously mixed with a bonding agent on a base layer characterised by the bonding agent containing a polyurethane or a polyisocyanate containing mixtures of polyurethanes or polyisocyanates with other polymers

Definitions

  • the present invention is to a magnetic recording medium having a magnetic layer composed of a magnetic powder and a non-magnetic binder.
  • Coated magnetic recording media are extensively used for a wide variety of applications, including audio recording, video recording, data storage.
  • Coated magnetic recording media typically comprise at least one magnetizable layer coated onto a nonmagnetizable support.
  • the least expensive and most widely used magnetic recording media are particulate media, in which the magnetic layer comprises a magnetic pigment dispersed in a polymeric binder.
  • the binder system in magnetic media must maintain the extremely small magnetic particles in a fixed position; this permits the particles to be subsequently magnetized and demagnetized, and thus impart a strong, modulated magnetic signal over long exposure to a wide range of environmental and mechanical stresses.
  • the binder utilized chemistry which promotes wetting and dispersion of pigments.
  • An object of the present invention is to provide a binder which has enhanced lubrication properties over binder known in the art.
  • the present invention is to a magnetic recording medium having superior lubrication properties and pigment dispersion due to the use of a unique binder.
  • the medium comprises a magnetic layer provided upon the major surface of a substrate, the magnetic layer including at least:
  • a polymeric binder system including a polyurethane-based composition which comprises a polyfunctional liquid polyurethane- containing adduct wherein the adduct contains as a first functional group at least one structo-terminal group per molecule which is polymerizable and at least one second structo-terminal functional group per molecule which is not polymerizable and is selected to impart improved lubricity to the surface of magnetic medium.
  • the present invention is to magnetic media prepared using a polymeric binder containing a liquid polyurethane adduct as described herein.
  • Magnetic media prepared by the present invention have surfaces with improved smoothness, i.e. media with improved lubricity. This enhances mechanical wear performance and facilitates the use of GMR heads.
  • This improvement in lubricating properties is permanent due to the covalent linkage of the lubricating moieties to the binder resin after polymerization. This increases the lifetime of magnetic recording media in comparison to current art using low molecular weight lubricating additives which can leak out or evaporate with time.
  • the polymerization reaction further avoids plasticising effects which are likely to occur when using lubricating additives of the prior art.
  • the magnetic layer includes a magnetic pigment dispersed in the polymeric binder.
  • the magnetic layer may optionally also include one or more conventional additives.
  • the magnetic layer includes approximately 100 parts by weight of magnetic pigment and approximately 5 to 50 parts by weight polymeric binder.
  • the adducts of the present invention generally comprise from 1 to 99 percent by weight of the binder.
  • the binder contains from 5 to 95 percent by weight of the adduct.
  • the polyf ⁇ nctional liquid polyurethane containing adduct has a polyol core which is chain extended with an isocyanate moiety and terminated with at least two functional groups. These functional groups are structo-terminal, that is, they are not pendent, i.e., not branching from the backbone. At least one chain end bears a polymerizable group, and at least one chain end bears a functional group which gives lubrication properties to the final magnetic media.
  • polymerizable group it is understood a moiety that is susceptible to polymerization when exposed to an energy source, optionally in the presence of an initiator.
  • energy sources can be, for example, actinic radiation, ultraviolet or electron-beam radiation, or thermal radiation.
  • radiation polymerizable functionality is ethylenic unsaturation which in general is polymerized through radical polymerization such as can be initiated through exposure to actinic radiation, but can also be polymerized through cationic or anionic polymerization.
  • the functional groups which provide lubricity to the surface of the magnetic medium any compound known to provide such properties. These groups are known to have very low surface tension at the air polymer interface.
  • the adducts of the present invention are derived from NCO terminated prepolymers prepared from a polyol and a polyisocyanate where the prepolymers have a low level of free polyisocyanate monomer, are liquid at 50°C and have a narrow molecular weight distribution.
  • liquid it is meant that the adduct has a pour point of 50°C or less.
  • the adduct has a pour point at a temperature of from 0°C to 40°C.
  • the adduct has an average of from 2 to 8, more preferably from 3 to 8, and yet more preferably from greater than 3 to 6 chain ends per molecule, wherein each chain contains one or more urethane linkages.
  • each chain contains one or more urethane linkages.
  • the adduct contains from 2 to 8 chain ends per molecule; in the case of 8 then from 1 to 7 energy polymerizable moieties per molecule and from 7 to 1 polymerizable moieties are present and in the case of 2 end groups per molecule, statistically there is 1 energy polymerizable moiety and 1 lubricating moiety present.
  • the optimum ratio of polymerizable moieties to lubricating moieties will depend on the intended purpose and surface to be coated and can vary within the ranges of from 1 :7 to 7:1, and preferably from 1 :2 to 2:1.
  • the polyfunctional liquid polyurethanes adducts of the present invention can contain additional functional moieties such as an aryl, alkyl, ester, nitrile, alkene, alkyne, halogen, silyl or combinations thereof.
  • additional functional moieties such as an aryl, alkyl, ester, nitrile, alkene, alkyne, halogen, silyl or combinations thereof.
  • the equivalents of polymerizable and silane moieties and optionally additional functional groups is such that the adduct is substantially free of any isocyanate functionality or any isocyanate-reactive functionality.
  • the adducts of the invention are prepared by reaction of an isocyanate-terminated prepolymer with substances containing the polymerizable group and with substances containing the lubricating moiety.
  • An isocyanate-terminated prepolymer is generally prepared by reacting an excess of an isocyanate with an isocyanate-reactive compound. Materials and processes
  • the isocyanates which may be used in producing a prepolymer include aliphatic, cycloaliphatic, arylaliphatic and aromatic isocyanates.
  • the isocyanates selected are those which have the ability to be removed from crude mixtures through distillation or solvent extraction procedures.
  • Preferred are aromatic and aliphatic polyisocyanates and notably diisocyanates.
  • aromatic and aliphatic isocyanates may also be used in admixture when preparing a prepolymer.
  • aromatic isocyanates examples include the 4,4'-, 2,4' and 2,2'-isomers of diphenylmethane diisocyante (MDI), blends thereof and polymeric and monomeric MDI blends, toluene-2,4- and 2,6-diisocyanates (TDI), m- and p-phenylenediisocyanate, chlorophenylene-2,4-diisocyanate, diphenylene-4,4'-diisocyanate, 4,4'-diisocyanate-3 ,3 '- dimehtyldiphenyl, 3-methyldiphenyl-methane-4,4'-diisocyanate and diphenyletherdiisocyanate and 2,4,6-triisocyanatotoluene and 2,4,4'- triisocyanatodiphenylether.
  • a preferred isocyanate is toluene-2,4- and 2,6-diisocyanates (TDI
  • Suitable aliphatic polyisocyanates include ethylene diisocyanate, 1,6- hexamethylene diisocyanate, 1 ,4-tetramethylene diisocyanate, isophorone diisocyanate, cyclohexane 1 ,4-diisocyanate, 4,4'-dicyclohexylmethane diisocyanate, saturated analogues of the above mentioned aromatic isocyanates and mixtures thereof.
  • Isocyanate-reactive compounds useful in the preparation of the prepolymer include substances bearing a plurality of isocyanate-reactive functional groups per molecule where such functional groups include -OH, -SH, -COOH, -NHR, where R is not reactive towards isocyanate groups, i.e. a Cl to C6 alkane or halogenated alkane. Preferred is when such isocyante reactive functional group is -OH functional.
  • Such isocyanate-reactive materials are collective referred to as being a polyol.
  • the polyol may contain up to 8 such functional groups per molecule, preferably from 2 to 8, more preferably from 3 to 8, and most preferably from greater than 3 to 6 functional groups per molecule.
  • the polyol is a polyether polyol, also known as a polyoxyalkylene polyol.
  • Other polyols include polyester polyols, polycaprolactone polyols, polyalkylene carbonate polyols, polyolefinic polyols and polyphosphate-based polyols.
  • the polyol generally has an equivalent weight of from 100 to 5000.
  • the polyol has an equivalent weight of from 200 or greater, more preferably from 300 or greater.
  • the equivalent weight is less than 3000, more preferably less than 2000, and yet more preferably less than 1500.
  • the polyol is a polyester or polyether polyol.
  • Highly preferred are polyoxyalkylene polyols where the oxyalkylene entity comprises oxyethylene, oxypropylene, oxybutylene or mixtures of two or more thereof.
  • More preferred are oxypropylene-oxyethylene polyols. Processes for making such polyols are known to those in the art.
  • Suitable polyoxyalkylene polyols are exemplified by various commercially available polyols as used in polyurethane, lubricant, surfactancy applications and include polyoxypropylene glycols designated as VORANOLTM P-2000 and P-4000 with respectively equivalent weights of 1000 and 2000; polyoxypropylene-oxyethylene glycols such as DOWFAXTM DM-30 understood to have an equivalent weight of 300 and an oxyethylene content of 65 weight percent, and SYNALOXTM 25D-700 understood to have an equivalent weight of 2750 and an oxyethylene content of 65 weight percent, all available from The Dow Chemical Company; polyoxyethylene triols available under the trademark TERRALOXTM and designated as product WG-98 and WG- 116 understood to have a molecular weight of 700 and 980, respectively, polyoxypropylene-oxyethylene triols designated as NORANOLTM CP 1000 and CP 3055 understood to have respectively a molecular weight of 1000 and 3000, and NORANOLTM CP 3001 understood
  • the polyol used in producing the prepolymer must also be a liquid at 50°C.
  • Cross-linkers and/or chain extenders may also be used in the formulations of the present invention.
  • Such compounds are known in the art.
  • suitable cross- linkers include alkanolamines and other compounds of 200 or lower equivalent weight having from 3 to 8, preferably from 3 to 4, active hydrogen-containing groups per molecule.
  • Such compounds are glycerine and trimethylolpropane, as well as other alkylene triols.
  • alkanolamines include diethanolamine, triisopropanolamine, triethanolamine, diisopropanolamine, adducts of 4-8 moles of ethylene oxide and/or propylene oxide with ethylene diamine, and ammonia.
  • Chain extenders include compounds having two active hydrogen-containing groups per molecule and an equivalent weight of from 31 to 300.
  • Hydroxyl-containing chain extenders include the alkylene glycols and glycol ethers such as ethylene glycol, 1,3-propylene glycol, 1,4-butylene glycol, 1 ,6-hexamethylene glycol, diethylene glycol, triethylene glycol, dipropylene glycol, tripropylene glycol and 1 ,4- cyclohexanedimethanol.
  • Amine chain extenders include, for example, diethyltoluene diamine, phenylene diamine, methylene bis(o-chloroaniline, NaCl-blocked methylene bis)aniline), toluene diamine and aromatic diamines which are substituted for at least one of the carbon atoms adjacent to the amine groups with a lower alkyl group.
  • the cross-linker or chain extenders are used from 0.1 to 20 parts by weight of the polyol component.
  • the isocyanate-terminated prepolymer is generally prepared by the reaction of an excess of polyisocyanate with the polyol under standard conditions known in the art.
  • the polyisocyanate is added at an excess to provide an NCO:OH ratio of greater than 2:1 to 20:1.
  • the NCO:OH ratio is 2.5:1 to 10:1. More preferably the ratio is 3.2:1 to 8:1.
  • the unreacted isocyanate monomer is removed from the prepolymer by distillation or other treatment to a concentration of less than 3 percent, preferably less than 1 percent, more preferably less than 0.5 percent, and yet more preferably less than 0.1 percent by weight of unreacted polyisocyanate in the prepolymer.
  • the temperatures for effecting reaction between the polyisocyanate and polyol are generally 0°C to 120°C.
  • a catalyst may be used. Such catalysts are known in the art and include tertiary amine compounds, amines with isocyanate reactive groups and organometallic compounds.
  • the polyol can be added to the polyisocyanate at a controlled rate, as disclosed in WO 96/34904 to produce prepolymers having a low residual free isocyanate monomer.
  • This controlled addition is done under essentially anhydrous conditions, in the absence of a catalyst and maintained temperature of from 20°C to 80°C.
  • the preparation of prepolymers as described above reduces the formation of higher oligomers or polyol terminated prepolymers.
  • the formation of oligomers rapidly increases the functionality and viscosity of the prepolymer and can lead to gelation. See for example, WO 96/34904 which describes the formation of oligomers.
  • the prepolymer of the invention are characterized in that they have a theoretical isocyanate content of from 1 to 16, preferably from 1 to 10, more preferably from 1 to 7 weight percent. Measured isocyanate contents may be higher depending on residual content of unreacted polyisocyanate.
  • the isocyanate-terminated prepolymer is reacted with isocyanate-reactive substances containing the polymerizable group and with isocyanate reactive substances containing the lubricating group moiety.
  • Isocyanate reactive groups are as defined above and include —OH, -SH, -COOH, -NHR. Preferred is when such isocyanate reactive functional group is -OH functional.
  • the functional group which can polymerize for use in the present invention include the free NCO group and groups which can polymerize under the influence of radiation, such as actinic radiation, ultraviolet or electron-beam radiation.
  • the NCO groups can be provided by the prepolymer when not all of the structo-terminal NCO's of the prepolymer are coupled with another functional group.
  • One type of radiation polymerizable functionality is ethylenic unsaturation which in general is polymerized through radical polymerization such as can be initiated through exposure to actinic radiation, but can also be polymerized through cationic or anionic polymerization.
  • ethylenic unsaturation are groups containing vinylether, vinyl ester (for example, acrylate or methacrylate) or acrylamide functionality.
  • the polymerizable group is vinyl ester group or a vinylether group.
  • the polymerizable group is an acrylate or methacrylate group.
  • the polymerizable vinyl ester can be represented by the following formula:
  • R 1 and the vinyl ether can be represented by the formula
  • R 1 where X is an isocyanate-reactive functional group, such as -OH, -SH, -COOH or -NHR where R is as previously defined; R 1 is a substituent comprising hydrogen, a Cl to C3 alkyl or acyl radicals or a halogen or other groups which will not deleteriously affect the curing of the finished prepolymers, and A is aliphatic or aromatic hydrocarbon segment have 1 to 6 carbon atoms. As it is desirable to have a final product which is a liquid, A and R 1 are selected to give a final product which is a liquid.
  • Hydroxy functional ethylenically unsaturated monomers are preferred.
  • A is a Cl to C4 alkyl. More preferably A is a C2 alkyl.
  • the unsaturated monomer contains vinyl ester, vinyl ether, maleate or fumarate functionality.
  • Examples of the (meth)acrylate having a hydroxyl group used in the present invention include hydroxyethyl acrylate, 2-hydroxylethyl(meth)acrylate, 2- hydroxylpropyl (meth)acrylate, 2-hydroxybutyl (meth)acrylate, 2-hydroxy-3- phenoxypropyl (meth)acrylate, 1,4-butanediol mono (meth)acrylate, 2-hydroxyalkyl (meth) acryloyl phosphate, 4-hydroxycyclohexy (meth)acrylate, 1 ,6-hexanediol mono(meth)acrylate, neopentyl glycol mono(meth)acrylate, trimethylolpropane di(meht)acrylate, trimethylolethane di(meth)acrylate and such like.
  • (meth) acrylates preferred are 2-hydroxyethyl acrylate, 2-hydroxypropyl acrylate, 2-hydroxyethyl methacrylate, 2-hydroxypropyl methyacrylate, diethylene glycol monoacrylate, diethylene glycol monomethyacrylate, glycerine dimethyacrylate, dimethylol propane demethacrylate, and reaction products of polyester glycols with acrylic or methacrylic acid.
  • Such compounds are commercially available or can be produced using standard procedures known in the art.
  • Monomers having vinyl ether functional groups include, for example, 4- hydroxybutyl vinyl ether and triethylene glycol monovinyl ether.
  • Monomers having maleate functional groups include, for example, maleic acid and hydroxy functional maleates.
  • Compounds providing a reactive terminus with epoxy functionality are, for example, compound having one or more epoxy groups and a hydroxy group that can be reacted with a polyisocyanate, for example, oligomers of bisphenol-A epoxy resins.
  • Compounds providing a reactive terminus for amine-ene or thiol-ene systems can contain an allylic unsaturation, or tertiary amine or thiol groups.
  • the binder can be provided with allylic unsaturation by reaction of an isocyanate with trimethylolpropanediallylether, or the oligomer can be provided with a amine functional group by reaction of the isocyanate with amine functional compounds.
  • the above mentioned isocyanate-reactive substances containing the polymerizable moiety can be also used as a mixture wherein said mixture comprises a blend of two or more such substances.
  • the functional groups which provide lubricity to the surface of the magnetic medium any compound known to provide such properties can be used.
  • functionality moieties which can impart lubricating properties to the magnetic medium include alkane, alkene, fluoro, siloxyl, and silyl.
  • Such functional groups are coupled to the prepolymer via NCO reactive groups as described above.
  • the alkane and alkene compounds can be branched or cyclic and generally contain 2 to 20 carbon atoms. Preferably from 2 to 15 carbon atoms.
  • the fluoro-compounds can be represented by R f X wherein X refers to the isocyanate-reactive functional group as described above.
  • the R f group preferably contains at least 3 carbon atoms, more preferably 3 to 20 carbon atoms, and most preferably 5 to 14 carbon atoms.
  • R f can contain straight chain, branched chain or cyclic fluorinated groups, aromatic fluorinated groups or combinations thereof.
  • Rf can optionally contain heteroatoms such as oxygen, divalent or hexavalent sulfur or nitrogen.
  • Rf contains oxygen. It is preferred that Rf contains 40 to 80 percent fluorine by weight, more preferably 50 percent to 78 percent fluorine by weight.
  • the terminal protion of the R f group is fully fluorinated, preferably containing at least 7 fluorine atoms, for examle CF 3 CF 2 CF 2 -, (CF 3 ) 2 SF 5 , F(CF(CF 3 )CF 2 -O) 4 CF(CF 3 )CH 2 -.
  • Perfluorinated aliphatic groups and perfluorinated ethers are the most preferred embodiments of R f X.
  • fluorochemical agents include, for example, R f containing urethanes, ureas, esters, amines (and salts thereof), amides, acids (and salts thereof), carbodiimides, guanidines, allophanates, biurets, oxazolidinones, and other substances containing one or more R f groups, as well as mixtures and blends thereof.
  • Useful fluorochemical agents can be polymers containing multiple R f groups such as copolymers of fluorochemical acrylate and/or methacrylate.
  • One group of molecules containing silane for use in the present invention can be represented by the general formula X-(CH 2 ) n -O-[(SiO)(CH 3 )2] m -CH 3 where X is an isocyanate reactive group as previously defined; n is an integer from 1 to 20; and m is an integer from 1 to 12.
  • m is an integer from 2 to 15, and more preferably from 3-12.
  • n is an integer from 1 to 10, and more preferably from 2 to 8. M and n are generally selected such that the molecular weight of the siloxane compound is 120 to
  • Siloxane compound are commercially available, as from ABCR GmbH & Co.,
  • silane containing compounds for use as a lubricating moiety include those represented by the general formula G-R 2 SiY'Y 2 Y 3 where R 2 is a divalent linking group having 1 to 8 carbon atoms, which can contain heteroatoms, particularly oxygen; G is HS-, epoxy or H-N-
  • R 3 where R 3 is a C 1 -C 20 organic group or R 2 SiY' Y 2 Y 3 ; Y 1 , Y 2 and Y 3 may be the same or different, represents alkoxyl, carboxy, alkoxy ether, alkyl or aryl; with the proviso that at least one of Y 1 , Y 2 or Y 3 is a silane group which can undergo moisture cure, such as an alkoxy.
  • Y , Y , Y are methoxy, ethoxy, acetoxy, methoxyethoxy or a mixture thereof.
  • Representative examples of R include propyl, butyl, pentyl, or hexyl group.
  • silanes are bis-(gamma-tri methoxysilylpropyl)amine, N-phenyl- gamma-aminopropyltrimethoxysilane, gamma-mercaptopropyltrimethoxysilane, N-(n- butyl)-3-aminopropyltrimethoxysilane, gamma-glycidoxypropyltrimethoxysilane.
  • the adduct of this invention is obtained by capping reaction of the isocyanate- terminated prepolymer with less than a stoichiometric equivalent of the isocyanate- reactive substance containing the polymerizable moiety (for example, OH:NCO is ⁇ 1) and with less than a stoichiometric equivalent of the isocyanate-reactive substance containing the lubricating moiety.
  • the stoichiometry is such to provide for the desired content of moieties.
  • This reaction is generally conducted in a sequential manner where either the isocyanate-reactive substance containing the polymerizable or lubricating moiety is first reacted with the preploymer and then in a subsequent step, the other function group is introduced.
  • the isocyanate-reactivity substance contains a secondary amine
  • silane compounds described above it is necessary that the isocyanate reactive silane-containing moiety is first reacted with the prepolymer and then in a subsequent step the isocyanate-reactive substance containing the polymerizable moiety is introduced.
  • Such a sequence of steps aid in avoiding reaction of an acrylate with the secondary aminosilanes by the Michael addition reaction, resulting in oligomers and eventually gelation.
  • the compounds of the present invention can be represented by the following, for a polyol having a functionality of 2, this can be represented by
  • X ' represents the divalent radical formed between an isocyanate and the isocyanate reactive moiety of the polyol; where X represents the divalent radical formed between an isocyanate and the isocyanate reactive group of the polymerizable moiety or the isocyanate reactive group of the lubricating moiety;
  • ISO represents a moiety derived from a polyisocyanate component having 2 isocyanate reactive groups
  • POLYOL represents a moiety derived from a polyol component comprising a compound having 2 isocyanate reactive functional group, such a polyol can have more than 2 isocyanate reactive functional groups as described herein, for a polyol with a functionality of 3 the formula would contain a third -X 1 -ISO-X 2 -Z, etc; Z represents a moiety derived from a polymerizable moiety or a lubricating moiety having at least one isocyanate reactive group.
  • the viscosity of the reactants, process or final adduct it may be desirable to control the viscosity of the reactants, process or final adduct. This can be achieved by introducing a "reactive diluent" to the process. Such diluent can be introduced at any stage of the process after formation of the -NCO terminated prepolymer.
  • reactive diluent it is understood a liquid substance which is able to undergo polymerization when exposed to the previously mentioned energy sources yet does not undergo reaction with the isocyanate-terminated prepolymer nor with the isocyanate-reactive substances.
  • Suitable reactive diluents are compounds comprising acrylate or methacrylate functionality and those characterized by absence of an isocyanate-reactive functionality.
  • Preferred diluents include, N-vinyl pyrrolidone and dipropyleneglycoldiacrylate (DPGDA).
  • the amount of reactive diluent added is sufficient to give a viscosity of the final adduct solution of between 500 to 2,000 cps. It may also be desirable for viscosity control to include an adduct-inert solvent that is not energy polymerizable, such as isopropylacetate.
  • the process temperature is chosen for convenience of reaction time and can be greater than 80°C. In general, exposure to a temperature greater than 100°C should be minimized for the purpose of avoiding undesirable side reactions.
  • the reaction of the isocyanate- terminated prepolymer with a polyfunctional substance can, if desired, be accelerated by use of a suitable urethane-promoting catalyst.
  • a suitable urethane-promoting catalyst include tertiary amine compounds and organotin compounds as used when preparing, for example, polyurethane foam by reaction of a polyisocyanate with a polyol. It is to be noted that use of a catalyst in this can lead to final adducts having a higher viscosity than those prepared in the absence of catalyst.
  • the magnetic pigment can be selected from any of the magnetic pigments known in the art. These include, for example, gamma-iron(III) oxide, finely divided magnetite, ferromagnetic undoped or doped chromium dioxide, cobalt-modified gamma-iron(III) oxide, Fe 3 O 4 , barium ferrites or ferromagnectic metal particles, and metal particles.
  • the ratio of magnetic material to binder is from 1 to 10, in particular from 3 to 8 parts by weight of magnetic material to one part by weight of the binder mixture.
  • the nonmagnetizable substrate may be any suitable substrate materiel known in the art.
  • suitable substrate material include, for example, polyesters such as polyethylene terephthalate (PET); polyolefins such as polypropylene; cellulose derivatives such as cellulose triacetate or cellulose diacetate; polymer such a polycarbonate, polyvinyl chloride, polyimide, polyphenylene sulfide, polyacrylate, polyether sulphone, polyether ether ketone, polyetherimide, polysulphone, aramid film, polyethylenene 2,6-naphthalate film, fluorinated polymer, liquid crystal polyesters, polyamide, or polyhdyric acid; metals such as aluminum, or copper; paper; or any other suitable material.
  • PET polyethylene terephthalate
  • polyolefins such as polypropylene
  • cellulose derivatives such as cellulose triacetate or cellulose diacetate
  • polymer such a polycarbonate, polyvinyl chloride
  • the liquid polyurethane-containing adduct present in the magnetic layer is generally not used alone, but, in order to achieve optimum properties, is mixed with further suitable conventional binders known in the art.
  • the amount of the liquid polyurethane-containing adduct in the polymeric binder is from 5 to 55 (had stated 30 earlier), preferably from 10 to 30 percent by weight.
  • the binder forms a chemically crosslinked network, for example, through radiation curing or through reaction of pendant hydroxy groups with a polyfunctional isocyanate crosslinker.
  • Additional polymers present in the binder matrix are in general polyvinyl formals, polyurethane elastomers, mixtures of polyisocyanates and relatively high molecular weight polyhydroxy compounds, nitrocelluloses, linear saturated polyester resins of terephthalate or isophthalic acid and ethylene glycol, vinyl chloride polymers having more than 60 percent of vinyl chloride building blocs, vinyl chloride copolymers with one or more unsaturated carboxylic acids of 2 to 5 carbon atoms as comonomers or hydroxyl-containing vinyl chloride copolymers which can be prepared by hydrolysis of vinyl chloride/vinyl ester copolymers or direct copolymerization of vinyl chloride with hydroxyl-containing monomers, such as allyl alcohol or 4-hydroxybutyl or 2- hydroxyethyl (meth)acrylate, the polymers being soluble in conventional solvents.
  • hydroxyl-containing monomers such as allyl alcohol or 4-hydroxybutyl or 2- hydroxyethyl (meth)acrylate
  • Mixtures of one or more polyurethane elastomers with polyvinyl formals, phenoxy resins, linear saturated polyester resins and vinyl chloride copolymers having the composition stated above are also sutiable as binders.
  • Particularly preferred organic polymers are mixtures of polyurethane elastomers with phenoxy resins, polyurethane elastomers with polyvinyl formals, polesterurethanes with vinyl chloride polymers or linear polyester resins and low molecular weight OH-containing polyureaurethanes.
  • the additional additives are selected to include a combination of hard and soft resins.
  • the soft resin typically comprises a polyurethane backbone formed by the reaction of one or more polyols with one or more polyisocyanates, while examples of hard resins include polymers and copolymers of vinyl chloride, vinyl acetate, styrene, acrylonitrile, acrylate and methacrylate esters, etc.
  • the binder may include pendant polar groups capable of wetting the pigment particles as assisting the dispersion of the pigment particles.
  • groups include carboxylic, sulphonic, phosphoric and phosphonic acids (and their corresponding salts), quaternary ammonium salts, phosphate esters and phosphonate esters. Examples of such compounds are disclosed in U.S. Patents 5,491,029, 5,491,029, and 5,501,903.
  • the magnetizable layer of the present invention may also comprise one or more conventional additives such as lubricants, abrasives, thermal stabilizers; crosslinking agents, head cleaning agents, thermal stabilizers, antioxidants, dispersants, wetting agents, antistatic agents, fungicides, bactericides, surfactants, coating aids, nonmagnetic pigments, etc, in accordance with practices known in the art.
  • additives such as lubricants, abrasives, thermal stabilizers; crosslinking agents, head cleaning agents, thermal stabilizers, antioxidants, dispersants, wetting agents, antistatic agents, fungicides, bactericides, surfactants, coating aids, nonmagnetic pigments, etc, in accordance with practices known in the art.
  • the components of the magnetizable layer are usually combined with a suitable solvent to prepare a dispersion which is then coated onto the nonmagnetizable substrate.
  • suitable solvents may include ketones such as acetone, methyl ethyl ketone, methyl isobutyl ketone, or cyclohexanone; alcohols such as methanol, ethanol, propanol, or butanol; esters such as methyl acetate, ethyl acetate, butyl acetate, ethyl lactate, or glycol diacetate; monoethyl ether or the like; water-based systems; tetrahydrofuran; glycol ethers such as ethylene glycol kimethyl ether, or ethylene glycol monoethyl ether; dioxane or the like; aromatic hydrocarbons such as benzene, toluene, or xylene; aliphatic hydrocarbons such as
  • the magnetic recording media using a binder containing an adduct of the present invention may be manufactured by conventional methods.
  • the dispersion is typically coated on a continuous web substrate by methods such as roller coating, slot coating, graminister coating, etc.
  • the coated web is passed through a series of permanent or solenoidal magnets and drying ovens to align the magnetic pigments and to dry and cure the coating.
  • Binders containing unsaturated groups are cured by E-bean or radiation curing. If two or more layers are to be coated on the same side or opposite sides of the substrate, said layers may be applied simultaneously or sequentially.
  • the coated web is typically calendered then converted to the final product (for example, tapes or discs) by conventional processes such as slitting and die cutting.
  • T-80 is an 80/20 mixture of the 2,4 and 2,6 isomers of toluene diisocyante.
  • S-3000 is a sorbitol initiated polyoxypropylene polyol with an approximate molecular weight of 3,000.
  • S-l 800 is a sorbitol initiated polyoxypropylene polyol with an approximate molecular weight of 1,800.
  • NORANOL *CP 260 is glycerine inititated polyoxypropylene with a molecular weight of approximately 260, available from The Dow Chemical
  • NORANOL P-2000 is a polyoxypropylene diol having a molecular weight of approximately 2,000, available from The Dow Chemical
  • NORANOL RN482 is a sorbitol initiated polyoxypropylene polyol prepared from 9 moles of propylene oxide per mole of sorbitol, available from The
  • DETDA diethyl toluenediamine
  • MDIPA is methyl-bis-diisopropylaninline.
  • *NORANOL is a trademark of The Dow Chemical Company.
  • Isocyanate terminated prepolymers were prepared by reacting the polyols listed in Table 1 with and excess of T-80 (greater than 2:1 molar ratio of isocyanate to hydroxyl). The excess TDI was removed by distillation to give a final isocyanate-terminated stripped prepolymer with a free TDI content of ⁇ 0.1 weight percent.
  • the indicated prepolymer was added to a reactor and then a stoichiometric amount of lH,lH,2H,2H-perfluoroactane-l-ol, from Apollo Scientific Ltd., to end cape 50 percent of the isocyanate groups was added over 50 minutes. The mixture was then stirred for an additional hour and an infrared spectrum showed there was no free isocyanate.
  • the control prepolymers were used directly after the stripping step.
  • the prepolymers were reacted with various crosslinkers, as indicated in the table, at an index of 1 without the addition of catalyst.
  • Contact angles to give an indication of the surface free energy, were determined with the sessile drop method using a copouter aided KRUSS G2/G40 contact angle measuring system. Measuring values of contact angels are obtained automatically after a drop of a test liquid is deposited on the surface. For each droplet, ten pair of contact angles were measured. For each samle surface at least 3 droplets of each formulation were applied.
  • the surface free energy values were calculated according to the method of Wu, J. Polym. Sci. C34, 19 (1971). According to this method, the total surface free energy is given as the sum of a dispersive component.
  • Table 1 'Ex' refers to examples of the present invention and 'ref is the reference or control sample.

Landscapes

  • Paints Or Removers (AREA)
  • Polyurethanes Or Polyureas (AREA)

Abstract

L'invention concerne un support d'enregistrement magnétique possédant des propriétés de lubrification et une dispersion des pigments supérieures grâce à l'utilisation d'un unique produit de liaison. Ce support comprend une couche magnétique formée sur la surface principale d'un substrat, cette couche magnétique comprenant au moins: (1) un pigment magnétique et (2) un système de produit de liaison polymérique comprenant une composition à base de polyuréthanne qui contient un produit d'addition comprenant du polyuréthanne liquide, ce produit d'addition contenant en tant que premier groupe fonctionnel au moins un groupe structurel terminal par molécule polymérisable, et au moins un second groupe fonctionnel structurel terminal par molécule non polymérisable. Ce produit d'addition est choisi pour conférer un pouvoir lubrifiant amélioré à la surface du support magnétique.
PCT/US2002/014308 2001-05-07 2002-05-07 Produits de liaison pour supports d'enregistrement magnetiques WO2002091367A1 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
US28919901P 2001-05-07 2001-05-07
US60/289,199 2001-05-07

Publications (1)

Publication Number Publication Date
WO2002091367A1 true WO2002091367A1 (fr) 2002-11-14

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Country Status (1)

Country Link
WO (1) WO2002091367A1 (fr)

Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0592905A1 (fr) * 1992-10-12 1994-04-20 BASF Magnetics GmbH Milieu d'enregistrement magnétique
WO1996034904A1 (fr) * 1995-05-01 1996-11-07 The Dow Chemical Company Produit d'addition contenant de l'urethane liquide
US5679752A (en) * 1995-03-15 1997-10-21 Minnesota Mining And Manufacturing Company Magnetic recording medium incorporating fluorine-containing, solvent-soluble vinyl copolymer having no vinyl chloride or vinylidene chloride components
WO1998020060A1 (fr) * 1996-11-01 1998-05-14 The Dow Chemical Company Composition contenant de l'urethane liquide polyfonctionnel

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0592905A1 (fr) * 1992-10-12 1994-04-20 BASF Magnetics GmbH Milieu d'enregistrement magnétique
US5679752A (en) * 1995-03-15 1997-10-21 Minnesota Mining And Manufacturing Company Magnetic recording medium incorporating fluorine-containing, solvent-soluble vinyl copolymer having no vinyl chloride or vinylidene chloride components
WO1996034904A1 (fr) * 1995-05-01 1996-11-07 The Dow Chemical Company Produit d'addition contenant de l'urethane liquide
WO1998020060A1 (fr) * 1996-11-01 1998-05-14 The Dow Chemical Company Composition contenant de l'urethane liquide polyfonctionnel

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