EP0835239A1 - Ketimine curing agents and rapidly curing magnetic recording media and films prepared with ketimines - Google Patents

Ketimine curing agents and rapidly curing magnetic recording media and films prepared with ketimines

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Publication number
EP0835239A1
EP0835239A1 EP96921736A EP96921736A EP0835239A1 EP 0835239 A1 EP0835239 A1 EP 0835239A1 EP 96921736 A EP96921736 A EP 96921736A EP 96921736 A EP96921736 A EP 96921736A EP 0835239 A1 EP0835239 A1 EP 0835239A1
Authority
EP
European Patent Office
Prior art keywords
group
groups
formula
ketimine
aromatic
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
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Application number
EP96921736A
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German (de)
French (fr)
Inventor
Jeffrey T. Anderson
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
3M Co
Original Assignee
Minnesota Mining and Manufacturing Co
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Filing date
Publication date
Application filed by Minnesota Mining and Manufacturing Co filed Critical Minnesota Mining and Manufacturing Co
Publication of EP0835239A1 publication Critical patent/EP0835239A1/en
Withdrawn legal-status Critical Current

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Classifications

    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08G—MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
    • C08G18/00—Polymeric products of isocyanates or isothiocyanates
    • C08G18/06—Polymeric products of isocyanates or isothiocyanates with compounds having active hydrogen
    • C08G18/28—Polymeric products of isocyanates or isothiocyanates with compounds having active hydrogen characterised by the compounds used containing active hydrogen
    • C08G18/30—Low-molecular-weight compounds
    • C08G18/32—Polyhydroxy compounds; Polyamines; Hydroxyamines
    • C08G18/3225—Polyamines
    • C08G18/3253—Polyamines being in latent form
    • C08G18/3256—Reaction products of polyamines with aldehydes or ketones
    • C—CHEMISTRY; METALLURGY
    • C07—ORGANIC CHEMISTRY
    • C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
    • C07C251/00—Compounds containing nitrogen atoms doubly-bound to a carbon skeleton
    • C07C251/02—Compounds containing nitrogen atoms doubly-bound to a carbon skeleton containing imino groups
    • C07C251/04—Compounds containing nitrogen atoms doubly-bound to a carbon skeleton containing imino groups having carbon atoms of imino groups bound to hydrogen atoms or to acyclic carbon atoms
    • C07C251/06—Compounds containing nitrogen atoms doubly-bound to a carbon skeleton containing imino groups having carbon atoms of imino groups bound to hydrogen atoms or to acyclic carbon atoms to carbon atoms of a saturated carbon skeleton
    • C07C251/08—Compounds containing nitrogen atoms doubly-bound to a carbon skeleton containing imino groups having carbon atoms of imino groups bound to hydrogen atoms or to acyclic carbon atoms to carbon atoms of a saturated carbon skeleton being acyclic
    • C—CHEMISTRY; METALLURGY
    • C07—ORGANIC CHEMISTRY
    • C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
    • C07C251/00—Compounds containing nitrogen atoms doubly-bound to a carbon skeleton
    • C07C251/02—Compounds containing nitrogen atoms doubly-bound to a carbon skeleton containing imino groups
    • C07C251/20—Compounds containing nitrogen atoms doubly-bound to a carbon skeleton containing imino groups having carbon atoms of imino groups being part of rings other than six-membered aromatic rings
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08G—MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
    • C08G18/00—Polymeric products of isocyanates or isothiocyanates
    • C08G18/06—Polymeric products of isocyanates or isothiocyanates with compounds having active hydrogen
    • C08G18/08—Processes
    • C08G18/10—Prepolymer processes involving reaction of isocyanates or isothiocyanates with compounds having active hydrogen in a first reaction step
    • C—CHEMISTRY; METALLURGY
    • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
    • C08G—MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
    • C08G18/00—Polymeric products of isocyanates or isothiocyanates
    • C08G18/06—Polymeric products of isocyanates or isothiocyanates with compounds having active hydrogen
    • C08G18/28—Polymeric products of isocyanates or isothiocyanates with compounds having active hydrogen characterised by the compounds used containing active hydrogen
    • C08G18/30—Low-molecular-weight compounds
    • C08G18/32—Polyhydroxy compounds; Polyamines; Hydroxyamines

Definitions

  • the present invention relates to novel ketimine curing agents.
  • the invention also relates to rapidly curing films prepared using particular ketimine curing agents.
  • the present invention also relates to rapidly curing magnetic recording media prepared using the particular ketimine curing agents. More specifically, the invention relates to rapidly curing magnetic recording media in which the magnetic layer and/or backside coating, if any, ofthe media is prepared by using the particular ketimine curing agent in combmation with an unblocked aromatic isocyanate terminated prepolymer crosslinking agent.
  • Magnetic recording media generally comprise a magnetic coating provided on at least one side of a nonmagnetizable substrate.
  • the magnetic coating comprises a magnetic pigment dispersed in a polymeric binder.
  • the magnetic coating may also include other components such as lubricants; abrasives; thermal stabilizers; antioxidants; dispersants; wetting agents; antistatic agents; fungicides; bacteriocides; surfactants; coating aids; nonmagnetic pigments; and the like.
  • Some forms of magnetic recording media such as flexible magnetic recording tape, also have a backside coating applied to the other side ofthe nonmagnetizable substrate in order to improve the durability, conductivity, and tracking characteristics ofthe media.
  • the backside coating typically comprises a polymeric binder, but may also include other components such as lubricants; abrasives; thermal stabilizers; antioxidants; dispersants; wetting agents; antistatic agents; fungicides; bacteriocides; surfactants; coating aids; nonmagnetic pigments; and the like.
  • the magnetic coating and the backside coating, if any, of a majority of conventional magnetic recording media are derived from materials which require curing in order to provide magnetic recording media with appropriate physical and mechanical properties.
  • the uncured components ofthe magnetic coating or the backside coating are dissolved in a suitable solvent and milled with pigment to provide a homogeneous dispersion.
  • the resulting dispersion is then coated onto the nonmagnetizable substrate, after which the coating is dried, calendered if desired, and then cured.
  • the polymeric binder ofthe magnetic coating or the backside coating is derived from hydroxy functional polymers which rely upon a chemical reaction between the hydroxy functionality and a polyisocyanate crosslinking agent to achieve curing.
  • the polyisocyanate crosslinking agent is typically added to the dispersion just prior to the time that the dispersion is coated onto the substrate.
  • One factor affecting the performance of magnetic recording media is the reactivity ofthe polyisocyanate crosslinking agent. If the cure rate for the polyisocyanate crosslinking agent is too slow, or if its level of cure is too low, then a coating incorporating the agent will tend to have poor green strength until the cure reaction has progressed sufficiently.
  • the coating will be susceptible to damage, e.g., slit edge damage, during subsequent processing unless an inconvenient and expensive time delay to permit a more complete cure is inco ⁇ orated into the manufacturing process.
  • a faster reacting crosslinking agent is desirable.
  • the polyisocyanate crosslinking agent must not react too fast, however. Once the polyisocyanate crosslinking agent is added to a dispersion, the viscosity ofthe dispersion begins to gradually increase as crosslinking reactions take place. If these crosslinking reactions occur too quickly, the viscosity ofthe magnetic dispersion could increase so rapidly that it then would become extremely difficult to filter and coat the dispersion onto a nonmagnetizable substrate. In most formulations, an excess of isocyanate compared to hydroxyl equivalents from the polymers and wetting agents is used to cure the magnetic recording media. The excess isocyanate reacts with water from the atmosphere after being coated. This water reaction forms polyureas which improve the mechanical properties ofthe coating.
  • the polyurea reaction is usually very slow taking weeks or months to complete. During this time, the properties ofthe tape are changing and an inferior product can be the result until the cure is almost complete. An uncured tape can cause many problems in the product such as head clogs, debris, embossing, and manufacturing problems due to low green strength ofthe tape.
  • polyisocyanate crosslinking agent that has been used in magnetic recording media is commercially available under the tradename DESMODUR CB-701 from Bayer, formerly Miles, Inc.
  • DESMODUR CB-701 is commercially available under the tradename DESMODUR CB-701 from Bayer, formerly Miles, Inc.
  • This product is an admixture of adducts formed by end-capping a blend of trimethylolpropane and 1,3 -butane diol with toluenediisocyanate (TDI) in 30 weight % tetrahydrofuran.
  • TDI toluenediisocyanate
  • Certain ketimines have been used as curing agents in polyurethane and epoxy systems. These certain ketimines have been used to accelerate the overall cure rate by reacting with excess NCO groups ofthe polyisocyanate crosslinking agents. These certain ketimines reportedly have good pot lives with aliphatic polyisocyanates and in combination with blocked aromatic polyisocyanates. These two types of polyisocyanates (aliphatic and blocked aromatic), however, are not suitable for use in magnetic coatings.
  • the aliphatic polyisocyanates are not acceptable in that they react too slowly with the hydroxyls from the polymer binder resulting in long cure times whereas the blocked aromatic polyisocyanates require a high temperature treatment (100°C) to unblock the functional group and initiate the cure. This high temperature treatment degrades the magnetic coating and film substrate which is unacceptable.
  • Unblocked aromatic polyisocyanates are used exclusively for curing/crosslinking magnetic coatings and the certain ketimines (not of Formula I disclosed infra) which have been attempted to be used in magnetic coatings do not have good pot lives with unblocked aromatic isocyanates.
  • Various ketimines, ketimines with blocked isocyanates, etc. are disclosed in U.S. Patent Nos. 4,101,497; 4,481,348; 3,267,078; 5,002,830; 4,513,112; 3,420,800; and 4,906,674.
  • Certain film compositions ofthe invention have a cure of at least 80% after 24 hours whereas some conventional film compositions have a cure of about 23% in 24 hours.
  • the coatings prepared using these ketimine curing agents falling within Formula I had better green strength, better cure profiles, improved toughness, and improved slit edge quality as compared to coatings prepared without these ketimines.
  • One aspect ofthe present invention relates to a novel class of ketimine curing agents. These novel ketimines fall within Formula I set forth below.
  • the present invention provides a novel compound comprising a ketimine selected from the group consisting of
  • Another aspect ofthe invention relates to a film forming composition
  • a film forming composition comprising:
  • X is an organic moiety which can optionally comprise one or more atoms selected from the group consisting of N, O, S, Si, and P; Y is selected from the group consisting of aromatic groups and
  • R 3 Rl, R 2 , R3 and R ⁇ are each independently selected from the group consisting of -H, alkyl, aryl, and alkaryl groups;
  • Z is selected from the group consisting of aromatic groups and
  • R 6 ; R4, R5, and R ⁇ are each independently selected from the group consisting of -H, alkyl, aryl, and alkaryl groups; n is a number of at least 2;
  • Y and Z may alternatively form, together with the C- atom to which they are bonded, a cycloalkyl group; when N in Formula I is bonded to an aromatic carbon in X and neither Y nor Z are aromatic groups, no more than four groups selected from the group consisting of
  • R 1 , R 2 , R3, R 4 , _ ⁇ and R 6 can be -H, the remaining groups selected from the group consisting of R*, R 2 , R-* 5 R4 R5 a nd R ⁇ being independently selected from the group consisting of alkyl, aryl, and alkaryl groups; and when N in Formula I is bonded to an aliphatic carbon in X and neither Y nor Z are an aromatic group, no more than three groups selected from the group consisting of Rl, R 2 , R3.
  • the invention also relates to film prepared by curing the film forming composition.
  • prepolymer(s) having at least two unblocked aromatic isocyanate groups is also referred to as an "unblocked aromatic isocyanate terminated prepolymer(s)" herein.
  • stable as used herein with respect to dispersions and compositions refers to dispersions and compositions that have pot lives of at least about 20 minutes.
  • Another aspect ofthe invention relates to a magnetic dispersion for use in magnetic recording media, which dispersion comprises:
  • a pigment selected from the group consisting of magnetizable pigments, non-magnetizable pigments, and mixtures thereof;
  • the invention also relates to magnetic recording media prepared from the magnetic dispersions.
  • the present invention provides a novel film comprising the reaction product of components comprising:
  • the present invention also provides a novel method of making the film ofthe invention, comprising the steps of:
  • composition comprising: (i) a ketimine(s) of Formula I; (ii) a prepolymer(s) having at least two unblocked aromatic isocyanate group(s);
  • the invention also provides a novel magnetic recording medium, comprising at least one coating provided on a nonmagnetizable substrate, wherein each coating independently comprises the reaction product of components comprising:
  • a pigment selected from the group consisting of magnetic pigments, nonmagnetizable pigments, and mixtures thereof;
  • the present invention also provides a novel method of making the magnetic recording medium ofthe invention, comprising the steps of:
  • a binder(s) having at least one hydroxy functional group (iii) a binder(s) having at least one hydroxy functional group; (iv) a non-aqueous solvent; (v) a pigment selected from the group consisting of magnetic pigments, nonmagnetizable pigments, and mixtures thereof;
  • Fig. 1 is a graph illustrating the methylethyl ketone (MEK) soluble ratio for Examples 16-22 and Comparative Example 23.
  • Fig. 2 is a graph illustrating the MEK soluble ratio for Examples 16-22 and Comparative Example 23.
  • the present invention describes particular ketimines (of Formula I) which can su ⁇ risingly be utilized as curing agents to enhance the cure of polymeric systems which inco ⁇ orate unblocked aromatic isocyanate terminated prepolymers as crosslinking agents. These curing agents are particularly useful in magnetic compositions and coatings which use unblocked aromatic isocyanate terminated prepolymers as crosslinking agents.
  • the ketimines usefiil according to the present invention are preferably used to produce stable film forming compositions and stable magnetic recording media dispersions with acceptable pot lives yet provides a resin system which can be cured rapidly once coated upon a substrate.
  • the ketimine curing agents useful according to the present invention are those of Formula I discussed supra. Mixtures of ketimines of Formula I are also useful herein.
  • the group X of Formula I typically has a number average molecular weight of about 25 to about 20,000, preferably about 25 to about 500. Examples of specific groups X can comprise include but are not limited to those selected from the group consisting of hexyl, cyclohexyl, polyethers, polyesters, polyurethanes, polyureas, polycarbonates, diethyl tolyl, phenyl, tris(2-aminoethyl), benzyl, methylene dibenzyl, polymethylenedibenzyl, and the like.
  • the group Y of Formula I typically comprises about 1 to about 20 carbon atoms, preferably about 1 to about 12, and most preferably about 1 to about 9.
  • Examples of specific aromatic groups Y can comprise include but are not limited to those selected from the group consisting of benzyl, phenyl, furfuryl, and the like.
  • R 1 , R 2 and, R ⁇ are each preferably independently selected from the groups consisting of -H, cyclohexyl, methyl, t-butyl, ethyl, propyl, isopropyl, butyl, pentyl, hexyl, cyclopentyl, benzyl, methyl benzyl, and the like.
  • the group Z typically comprises about 1 to about 20 carbon atoms, preferably about 1 to about 12, and most preferably about 1 to about 9.
  • specific aromatic groups Z can comprise include but are not limited to those selected from the group consisting of benzyl, phenyl, furfuryl, and the like.
  • R4, R5, and R ⁇ are each preferably independently selected from the group consisting of -H, methyl, ethyl, propyl, isopropyl, butyl, t-butyl, pentyl, cyclopentyl, hexyl, cyclohexyl benzyl, methylbenzyl and the like.
  • the ketimines of Formula I preferably have a pot life of over 20 minutes when mixed with an unblocked aromatic isocyanate terminated prepolymer crosslinking agents, such as in a dispersion or composition preferably greater than about 3 hours, and most preferably greater than about 24 hours.
  • the coatings and films ofthe invention are coated or otherwise formed before the composition or dispersion from which they are formed gels.
  • Ketimines are typically formed by combining a ketone with an amine.
  • Some representative examples of ketones that can be used to make ketimines of Formula I include but are not limited to those selected from the group consisting of, pinacolone, cyclohexanone, cyclopentanone, diisopropyl ketone, 3-methyl-2-butanone, benzophenone, acetophenone, fenchone, 5-nonanone, 2,4-tetramethyl-3-pentanone, and any other monoketones that are capable of making the ketimine of Formula I.
  • amines that can be used to make the ketimines of Formula I include but are not limited to those selected from the group consisting of 4,4 '-methylenedianiline, 3,5-diethyltoluene-2,4-diamine, 1,4- phenylenediamine, 1,3 -phenylenediamine, xylenediamine, and polyether amines from Texaco Company under the tradename "Jeffamines,” 1,6- hexanediamine, tris(2- aminoethyl)amine, poly 4'-4'methylenedianiline, 4,4'-methylene bis(3-chloro-2,6- diethylaniline), 2,4-toluene diamine, and any other diamine or higher functional amine which are aromatic or aliphatic that can be used to make ketimines of Formula I.
  • the present invention inco ⁇ orates specific ketimines with unblocked aromatic isocyanate terminated prepolymer crosslinking agents in stable film forming compositions and magnetic dispersions.
  • water from the atmosphere hydrolyzes the ketimine to a ketone and an amine.
  • the ketimine hydrolysis is usually complete in about 24 hours. This is much faster than the reaction of atmospheric water with isocyanates and it is why the particular ketimines used in the present invention result in a faster cured product such as a film or magnetic media.
  • the ketone generated from the hydrolysis ofthe ketimine evaporates and the amine reacts readily with the residual isocyanate moieties ofthe unblocked aromatic isocyanate terminated prepolymer crosslinking agent. This fast reaction imparts good physical properties to the product much sooner than which has been observed in conventionally formulated systems. Dispersions and compositions prepared using ketimine curing agents form a tougher product at a much faster rate due to the possible formation of a semi-inte ⁇ enetrating network.
  • Heat may optionally be applied when curing the compositions and/or dispersions ofthe invention.
  • the isocyanate can react directly with the ketimine, crosslinking the system.
  • the reaction of ketimine with isocyanate is as fast or faster then the ketimine hydrolysis reaction and much faster than the atmospheric water/isocyanate reaction.
  • Heat, if applied at all would typically be applied such that the temperature ofthe system is about 25 degrees C to about 60 degrees C. If the temperature is too high degradation ofthe magnetic backing may occur, in the case ofthe preparation of magnetic recording media. See “New Developments in Polyketimine Polyisocyanate Coatings - Their Chemistry and Applications," M. Bock and R. Halpaap, Journal of Coatings Technology. Vol. 59, No. 755, pages 131-135 (1987)
  • the amount of ketimine required varies depending on how much unblocked aromatic isocyanate terminated prepolymer crosslinking agent is present in the formulation. Sufficient unblocked aromatic isocyanate terminated prepolymer and ketimine of Formula I should be present such that the NCO to imine equivalent ratio is 0.5 or greater for films, and preferably about 1.1 to 50 for magnetic recording media.
  • Unblocked aromatic isocyanate terminated prepolymer crosslinking agents are used in combination with the ketimine curing agent of Formula I. These prepolymers are free of hydroxy functionality.
  • unblocked it is meant that the NCO groups have not been reacted with blocking agents such that special conditions are required to liberate the NCO groups.
  • blocking agents such that special conditions are required to liberate the NCO groups.
  • unblocked aromatic isocyanate terminated prepolymers examples include CB-701 from Bayer, formerly Miles Company, Isonate 181 from Dow Chemical, and many other unblocked aromatic isocyanate terminated prepolymers known to those skilled in the art.
  • the useful number average molecular weight of these prepolymers is typically about 100 to 5000, more preferably about 500 to 1500.
  • the unblocked aromatic isocyanate terminated prepolymer is preferably used in an amount such that the equivalent ratio of NCO groups to hydroxy groups is about 0.3 to 10. Sol vents
  • Usefiil non-aqueous solvents according to the present invention are those that will provide compositions and dispersions having good film forming properties.
  • One skilled in the art will be able to select useful non-aqueous solvents for this pu ⁇ ose.
  • useful non-aqueous solvents according to the invention include but are not limited to those selected from the group consisting of acetone, cyclohexanone, xylene, ethyl acetate, tetrahydrofuran, methylisobutyl ketone, mixtures thereof, and the like.
  • Some non-aqueous solvents may contain trace amounts of water (less than 0.1 weight percent based upon the weight ofthe solvent). Trace amounts of water are typically not detrimental to the system ofthe invention.
  • Dispersions and compositions ofthe invention typically comprise less than about 1 weight percent water, more typically less than about 0.5 weight percent, based upon the total weight ofthe dispersions and compositions, respectively.
  • the combination ofthe particular ketimine of Formula I and unblocked aromatic isocyanate terminated prepolymer crosslinking agent may be advantageously used in any application requiring a crosslinking agent with reactive NCO groups
  • the ketimine curing agent and unblocked aromatic isocyanate terminated prepolymer crosslinking agent combination is particularly suitable for use in magnetic recording media.
  • the ketimine curing agent and the unblocked aromatic isocyanate terminated prepolymer crosslinking agent advantageously may be inco ⁇ orated into the magnetic and/or backside coatings of magnetic recording media. These coatings are typically provided on the major surfaces of a nonmagnetizable substrate having first and second opposed major surfaces.
  • the nonmagnetizable substrate may be formed from any suitable substrate material known in the art. Examples of suitable substrate materials include, for example, polymers such as polyethylene terephthalate (“PET”), polyimide, and polyethylene naphthalate (“PEN"); ceramics; glass; metals such as aluminum, or copper; paper; or any other suitable material.
  • Magnetic Pigments Magnetic coatings ofthe present invention typically comprise a magnetic pigment dispersed in a polymeric binder.
  • the magnetic layer may contain 100 parts by weight ofthe magnetic pigment and 5 to 40 parts by weight ofthe polymeric binder.
  • the type of magnetic pigment used in the present invention may include any suitable magnetic pigment known in the art including gamma-Fe 2 O 3 , cobalt-doped gamma-Fe 2 O 3 , Fe 3 O 4 , CrO 2 , barium ferrite, barium ferrite derivatives, metal particles, mixtures thereof, and the like.
  • the magnetic coating ofthe present invention may optionally further comprise one or more conventional additives such as lubricants; abrasives; thermal stabilizers; antioxidants; dispersants; wetting agents; antistatic agents; fungicides; bacteriocides; surfactants; coating aids; nonmagnetic pigments; and the like in accordance with practices known in the art.
  • additives such as lubricants; abrasives; thermal stabilizers; antioxidants; dispersants; wetting agents; antistatic agents; fungicides; bacteriocides; surfactants; coating aids; nonmagnetic pigments; and the like in accordance with practices known in the art.
  • Backside coatings ofthe present invention typically comprise a binder and, optionally, further comprise one or more conventional additives such as lubricants; abrasives; thermal stabilizers; antioxidants; dispersants; wetting agents; antistatic agents; fungicides; bacteriocides; surfactants; coating aids; nonmagnetic pigments; and the like in accordance with practices known in the art.
  • suitable nonmagnetic pigments include but are not limited to those selected from the group consisting of carbon black, Ti ⁇ 2, alumina, alpha-F ⁇ 2 ⁇ 3, mixtures thereof, and the like.
  • polymeric binders suitable for preparing the magnetic coating and/or the backside coating may include any polymer component conventionally used in the magnetic recording art.
  • Polymeric binders useful herein are those having at least one pendant hydroxy, i.e., — OH, group. The — OH groups not only allow the polymer to crosslink with the unblocked aromatic isocyanate terminated prepolymer crosslinking agent but also promote dispersion of the inorganic pigments in the binder, promote the solubility ofthe polymer in solvents, and promote the compatibility ofthe polymer with other polymers.
  • the — OH groups can be primary, secondary, or tertiary, although the use of primary and/or secondary — OH groups is preferred.
  • preferred hydroxyl functional polymers have an — OH equivalent weight in the range from 200 to 20,000, preferably 300 to 5000.
  • the magnetic dispersion may optionally further comprise at least one polymer binder having no pendant — OH groups.
  • One or more ofthe polymer or polymers, if more than one polymer is used, of the binder component may contain one or more other kinds of pendant functional groups to enhance the performance ofthe magnetic recording medium.
  • any binder may contain carbon-carbon double bonds if it is desired to crosslink the binder using both isocyanate and radiation curing techniques.
  • any polymer ofthe binder component may contain a pendant dispersing group in order to facilitate dispersion of magnetic or nonmagnetic pigments in the polymeric binder.
  • the term "dispersing group" means that a group is capable of wetting the magnetic or nonmagnetic pigments to facilitate dispersion of such pigments in the polymeric binder.
  • the dispersing group is a moiety that is ionized or ionizable at a pH in the range from 0 to 10.
  • suitable dispersing groups include quaternary ammonium moieties (e.g., -N(CH 3 ) 3 + C1 " as one example), amines (e.g., -N(CH 3 ) 2 as one example), heterocyclic moieties as described in U.S. Patent No. 5,081,213, sulfobetaines (e.g.,
  • salts or acids based on sulfate e.g., — OSO 3 Na as one example
  • salts or acids based on sulfonate e.g., — SO 3 Na as one example
  • salts or acids based on phosphate e.g., — OPO(OH) 2 as one example
  • salts or acids based on phosphonate e.g., -PO(OH) 2 as one example
  • salts or acids based on carboxyl e.g., — COONa as one example
  • additional resin binders that may be utilized in this invention include but are not limited to non-halogenated vinyl copolymers which contain styrene/acrylonitrile copolymers with ammonium wetting groups (referred to as a "K resin" herein) as described in U.S. Patent No. 5,510,187, assigned to the assignee of the present invention.
  • K resin non-halogenated vinyl copolymers which contain styrene/acrylonitrile copolymers with ammonium wetting groups
  • Vinyl chloride copolymers are useful according to the present invention.
  • Useful vinyl chloride copolymers may or may not contain polar functional group(s).
  • Representative useful vinyl chloride copolymer resins are described in U.S. Patent No. 4,816,683, (assigned to Sekisui Chemical). These are copolymers of vinyl chloride, hydroxypropyl acrylate, methacryloxyethyl trimethylammonium chloride, and methyacryloxyethyl phosphate. These are thought to be similar to or the same as the commercially available "S-LEC E-C" resins (E-C130 and E-Cl 10) made by Sekisui Chemical Co. According to information supplied by Sekisui Chemical Co., these are approximately 84% vinyl chloride, 16% hydroxy acrylic monomer (by weight) and contain a fraction of a percent of other monomers, including a quaternary ammonium monomer.
  • UCARMAG binder 528 from Union Carbide which contains carboxyl groups (about 56100 g/mole) and hydroxy groups (850 g/mole) and is described in U.S. Patent No. 4,985,314.
  • Vinyl chloride copolymers containing no polar functionality are also useful.
  • An example is VAGH from Union Carbide which contains vinyl chloride and hydrolyzed vinyl acetate such that the hydroxyl equivalent weight is about 750 g/mole.
  • polyurethane resins examples include but are not limited to polyurethanes containing multidentate chelating functional groups pendent from the polymer backbone (referred to as "B resin" herein) as described in U.S. Patent No. 5,498,685, assigned to the assignee ofthe present invention.
  • B resin multidentate chelating functional groups pendent from the polymer backbone
  • Other useful polyurethanes are the vinyl sulfonated and non-sulfonated hydroxy functional polyurethane copolymers prepared from macromonomer diols as described in U.S. Patent No. 5,384,362.
  • the magnetic coating can be coated onto a nonmagnetizable substrate in a variety of ways.
  • a process for applying the magnetic coating onto a nonmagnetizable substrate the components ofthe magnetic coating are combined and mixed with a suitable solvent to form a substantially homogeneous dispersion, except that the ketimine curative and unblocked aromatic isocyanate terminated crosslinking agent are preferably combined and mixed with the other components ofthe magnetic dispersion just prior to coating (but in any case at a time sufficiently prior to coating such that the dispersion does not gel before coating).
  • the dispersion is then coated onto the nonmagnetizable substrate, which may be primed or unprimed.
  • the dispersion may be applied to the substrate using any conventional coating technique, such as gravure or knife coating techniques.
  • the coated substrate may then be passed through a magnetic field to orient the magnetic pigment after which the coating is dried, calendered if desired, and then allowed to cure.
  • the films ofthe invention can be prepared from the unblocked aromatic isocyanate terminated prepolymers, optionally an organic polymer(s) having at least one hydroxy functional group, and ketimine(s) of Formula I.
  • useful organic polymers having at least one hydroxy group include but are not limited to those selected from the group consisting of polyurethanes, polycarbonates, polyesters, polyethers, vinylchloride polymers, acrylic polymers, styrenic polymers, polyvinyl acetates, polyvinyl alcohols, polyvinyl butyral, mixtures thereof, and the like.
  • the composition from which the films are formed and thus the films themselves may optionally further comprise an additive selected from the group consisting of inorganic fillers, lubricants, surfactants, catalysts, leveling agents, mixtures thereof, and the like.
  • Films ofthe present invention can be used for the following pu ⁇ oses: top coats, adhesives, protective coatings, sealants, inorganic filled coatings, and the like.
  • the films ofthe present invention typically are tougher than conventional films cured without the ketimine curing agents of Formula I. Also the films ofthe present invention typically cure faster than such conventional films.
  • MEK methylethyl ketone
  • MDI methylene diphenyldiisocyanate
  • Examples 1-3 disclose the preparation of novel ketimines ofthe invention which also fall within Formula I.
  • Example 1 disclose the preparation of novel ketimines ofthe invention which also fall within Formula I.
  • Examples 4 and 5 disclose the preparation of ketimines which are known but which fall within Formula I. It has been discovered that these ketimines are su ⁇ risingly usefiil as curing agents with an unblocked aromatic isocyanate terminated prepolymer.
  • Comparative Examples 6 and 7 disclose the preparation ofknown ketimines which fall outside Formula I and cannot be used as curing agents with unblocked aromatic isocyanate terminated prepolymers according to the present invention.
  • the PHPU used herein was prepared as follows:
  • the Resin B used herein was prepared as follows:
  • the Resin K used herein was prepared as follows:
  • a nonhalogenated vinyl copolymer was prepared from the following ingredients: 161.25 pbw styrene, 50.0 pbw acrylonitrile, 37.5 pbw hydroxypropylacrylate, 1.25 pbw methacryloxyethyl trimethyl ammonium chloride, 0.5 pbw mercaptopropane diol, 3.75 pbw methyl ethyl ketone, and 1.25 pbw 2,2'-azobisisobutyronitrile.
  • the ingredients were charged into a 1 liter amber reaction bottle.
  • the resultant admixture which contained some undissolved methacryloxyethyl trimethyl ammonium chloride, was purged with N2 for 7 minutes at 1 liter per minute, after which the bottle was sealed.
  • the sealed bottle and its contents were tumbled in a constant temperature bath, at 65°C or 70°C for 80 hours.
  • the product was a clear, homogeneous solution containing a nonhalogenated vinyl copolymer.
  • the inherent viscosity ofthe sample in MEK was measured according to the procedure described in F. Rodriguez, "Principles of Polymer Systems," Chemical Engineering Series, 2nd Edition (McGraw-Hill), pages 181-185. Tg was also measured. The inherent viscosity was 0.30 to 0.33. The Tg was 79°C.
  • Resins (B and K), isocyanate crosslinking agent (CB-701) and ketimine were combined according to Table II below to prepare polymer films.
  • Handspread coatings were made from a 40% solids solution ofthe components in methylethyl ketone (MEK). The handspreads were coated to a thickness of 10 mils (wet) on a polypropylene backing, then dried in an oven for 15 minutes at 60° Celsius. The polymer film was then peeled away from the polypropylene backing. The degree of cure, appearance, toughness and modulus of these films were measured and are reported in Table III below.
  • the modulus and toughness data was acquired using a half inch wide by 4 inch long (1.25 by 10.0 cm.) strip of film and a Model 1122 Instron. The numbers were generated by the data collected from the stress strain curve produced by the Instron.
  • the % cure results were obtained by soaking the films in methylethyl ketone (MEK) for two hours and weighing the undissolved material.
  • MEK methylethyl ketone
  • the best results for toughness and cure occur when there is a small excess of isocyanate equivalents as is the case with Examples 10, 12, 14, and 15.
  • Examples 8 and 9 have a 1 to 1 equivalent ratio of imine to isocyanate and are tougher but not cured as extensively as the Comparative Examples 11 and 13 with no ketimine present.
  • the hazy coatings in Examples 8-10 are, it is theorized, were most likely due to the 4,4'-methylenedianiline crystallizing in the film.
  • Examples 16-22 and Comparative Example 23 contained magnetic particles, were prepared from the same dispersion composition except for varying amounts of isocyanate and ketimine.
  • the dispersion composition was as follows: 100 parts barium ferrite pigment, ( ⁇ T 50130 from Toda) 5 parts alumina head cleaning agent, 9.6 parts hydroxyl containing binders (4.8 parts EC-130 vinyl chloride resin from Sekisui Chemical and 4.8 parts PHPU polyurethane the preparation of which is described previously and in U.S. Patent No.
  • Example CB 701 70% Ketimine 72% NCO/Ketimine eq. solids solids Ex. 3 ratio

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Abstract

The present invention provides novel ketimine curing agents. The present invention also provides rapidly curing magnetic recording media prepared using certain ketimine curing agents. More specifically, the invention provides rapidly curing magnetic recording media in which the magnetic layer and/or backside coating, if any, of the media is prepared by using a ketimine curing agent in combination with an aromatic isocyanate terminated prepolymer cross-linking agent. The invention also provides dispersions for magnetic media and a method of making magnetic recording media. The invention also provides rapidly curing films prepared using certain ketimine curing agents, film forming dispersions, and a method of making films.

Description

KETIMINE CURING AGENTS
AND RAPIDLY CURING MAGNETIC RECORDING MEDIA
AND FILMS PREPARED WITH KETTMINES
FIELD OF THE INVENTION
The present invention relates to novel ketimine curing agents. The invention also relates to rapidly curing films prepared using particular ketimine curing agents. The present invention also relates to rapidly curing magnetic recording media prepared using the particular ketimine curing agents. More specifically, the invention relates to rapidly curing magnetic recording media in which the magnetic layer and/or backside coating, if any, ofthe media is prepared by using the particular ketimine curing agent in combmation with an unblocked aromatic isocyanate terminated prepolymer crosslinking agent.
BACKGROUND OF THE INVENTION Magnetic recording media generally comprise a magnetic coating provided on at least one side of a nonmagnetizable substrate. For particulate magnetic recording media, the magnetic coating comprises a magnetic pigment dispersed in a polymeric binder. The magnetic coating may also include other components such as lubricants; abrasives; thermal stabilizers; antioxidants; dispersants; wetting agents; antistatic agents; fungicides; bacteriocides; surfactants; coating aids; nonmagnetic pigments; and the like.
Some forms of magnetic recording media, such as flexible magnetic recording tape, also have a backside coating applied to the other side ofthe nonmagnetizable substrate in order to improve the durability, conductivity, and tracking characteristics ofthe media. The backside coating typically comprises a polymeric binder, but may also include other components such as lubricants; abrasives; thermal stabilizers; antioxidants; dispersants; wetting agents; antistatic agents; fungicides; bacteriocides; surfactants; coating aids; nonmagnetic pigments; and the like. The magnetic coating and the backside coating, if any, of a majority of conventional magnetic recording media are derived from materials which require curing in order to provide magnetic recording media with appropriate physical and mechanical properties. To prepare such magnetic recording media, the uncured components ofthe magnetic coating or the backside coating, as appropriate, are dissolved in a suitable solvent and milled with pigment to provide a homogeneous dispersion. The resulting dispersion is then coated onto the nonmagnetizable substrate, after which the coating is dried, calendered if desired, and then cured.
Curing can be achieved in a variety of ways. According to one approach, the polymeric binder ofthe magnetic coating or the backside coating is derived from hydroxy functional polymers which rely upon a chemical reaction between the hydroxy functionality and a polyisocyanate crosslinking agent to achieve curing. The polyisocyanate crosslinking agent is typically added to the dispersion just prior to the time that the dispersion is coated onto the substrate. One factor affecting the performance of magnetic recording media is the reactivity ofthe polyisocyanate crosslinking agent. If the cure rate for the polyisocyanate crosslinking agent is too slow, or if its level of cure is too low, then a coating incorporating the agent will tend to have poor green strength until the cure reaction has progressed sufficiently. As a result, the coating will be susceptible to damage, e.g., slit edge damage, during subsequent processing unless an inconvenient and expensive time delay to permit a more complete cure is incoφorated into the manufacturing process. Thus, in order to obtain a coating with good green strength, a faster reacting crosslinking agent is desirable.
The polyisocyanate crosslinking agent must not react too fast, however. Once the polyisocyanate crosslinking agent is added to a dispersion, the viscosity ofthe dispersion begins to gradually increase as crosslinking reactions take place. If these crosslinking reactions occur too quickly, the viscosity ofthe magnetic dispersion could increase so rapidly that it then would become extremely difficult to filter and coat the dispersion onto a nonmagnetizable substrate. In most formulations, an excess of isocyanate compared to hydroxyl equivalents from the polymers and wetting agents is used to cure the magnetic recording media. The excess isocyanate reacts with water from the atmosphere after being coated. This water reaction forms polyureas which improve the mechanical properties ofthe coating. The polyurea reaction is usually very slow taking weeks or months to complete. During this time, the properties ofthe tape are changing and an inferior product can be the result until the cure is almost complete. An uncured tape can cause many problems in the product such as head clogs, debris, embossing, and manufacturing problems due to low green strength ofthe tape.
One commercially available polyisocyanate crosslinking agent that has been used in magnetic recording media is commercially available under the tradename DESMODUR CB-701 from Bayer, formerly Miles, Inc. This product is an admixture of adducts formed by end-capping a blend of trimethylolpropane and 1,3 -butane diol with toluenediisocyanate (TDI) in 30 weight % tetrahydrofuran. This admixture is relatively slow to react. Coatings prepared from this material tend to have a slow cure profile, poor green strength, and are susceptible to slit edge damage when substrates bearing such coatings are slit into appropriate widths to form magnetic recording tape.
Certain ketimines (however, not those of Formula I described infra) have been used as curing agents in polyurethane and epoxy systems. These certain ketimines have been used to accelerate the overall cure rate by reacting with excess NCO groups ofthe polyisocyanate crosslinking agents. These certain ketimines reportedly have good pot lives with aliphatic polyisocyanates and in combination with blocked aromatic polyisocyanates. These two types of polyisocyanates (aliphatic and blocked aromatic), however, are not suitable for use in magnetic coatings. The aliphatic polyisocyanates are not acceptable in that they react too slowly with the hydroxyls from the polymer binder resulting in long cure times whereas the blocked aromatic polyisocyanates require a high temperature treatment (100°C) to unblock the functional group and initiate the cure. This high temperature treatment degrades the magnetic coating and film substrate which is unacceptable. Unblocked aromatic polyisocyanates are used exclusively for curing/crosslinking magnetic coatings and the certain ketimines (not of Formula I disclosed infra) which have been attempted to be used in magnetic coatings do not have good pot lives with unblocked aromatic isocyanates. Various ketimines, ketimines with blocked isocyanates, etc., are disclosed in U.S. Patent Nos. 4,101,497; 4,481,348; 3,267,078; 5,002,830; 4,513,112; 3,420,800; and 4,906,674.
Thus, in the manufacture of magnetic recording media, a need exists for a curing agent that will facilitate a complete cure ofthe magnetic coating within a week without adversely affecting the pot life ofthe magnetic dispersion used to make the coating.
SUMMARY OF THE INVENTION We have discovered certain novel ketimines. We have discovered that these novel ketimines as well as certain particular known ketimines which have a particular formula (Formula I disclosed infra) which previously have not been used for such a purpose, can, surprisingly, when used in combination with unblocked aromatic isocyanate terminated prepolymer crosslinking agents, provide films as well as magnetic and backside coatings which achieve a greater degree of cure within 24 hours than what is observed with conventional coatings. These ketimine curing agents that are useful according to the present invention were not observed to have any adverse effect on the dispersion pot lives particularly with respect to viscosity build up. Certain film compositions ofthe invention have a cure of at least 80% after 24 hours whereas some conventional film compositions have a cure of about 23% in 24 hours. The coatings prepared using these ketimine curing agents falling within Formula I had better green strength, better cure profiles, improved toughness, and improved slit edge quality as compared to coatings prepared without these ketimines.
One aspect ofthe present invention relates to a novel class of ketimine curing agents. These novel ketimines fall within Formula I set forth below. The present invention provides a novel compound comprising a ketimine selected from the group consisting of
Another aspect ofthe invention relates to a film forming composition comprising:
(a) a ketimine(s) of Formula I:
Z
X-(-N=C )n (Formula I)
I
Y wherein
X is an organic moiety which can optionally comprise one or more atoms selected from the group consisting of N, O, S, Si, and P; Y is selected from the group consisting of aromatic groups and
R1
C-R2
R 3 Rl, R2, R3 and R^ are each independently selected from the group consisting of -H, alkyl, aryl, and alkaryl groups;
Z is selected from the group consisting of aromatic groups and
R4 I
-C-R5
I
R6 ; R4, R5, and R^ are each independently selected from the group consisting of -H, alkyl, aryl, and alkaryl groups; n is a number of at least 2;
Y and Z may alternatively form, together with the C- atom to which they are bonded, a cycloalkyl group; when N in Formula I is bonded to an aromatic carbon in X and neither Y nor Z are aromatic groups, no more than four groups selected from the group consisting of
R1, R2, R3, R4, _\ and R6 can be -H, the remaining groups selected from the group consisting of R*, R2, R-*5 R4 R5 and R^ being independently selected from the group consisting of alkyl, aryl, and alkaryl groups; and when N in Formula I is bonded to an aliphatic carbon in X and neither Y nor Z are an aromatic group, no more than three groups selected from the group consisting of Rl, R2, R3. R R5 an£j R6 can ]_Q _JJ tf>e remaining groups selected from the group consisting of R*, R2, R- , R^, R$ and R^ being independently selected from the group consisting of alkyl, aryl, and alkaryl groups;
(b) a prepolymer(s) having at least two unblocked aromatic isocyanate groups;
(c) optionally a non-aqueous solvent; and
(d) optionally an organic polymer(s) having at least one hydroxy functional group, the organic polymer(s) being dispersible in the non-aqueous solvent if present. The invention also relates to film prepared by curing the film forming composition. The term "prepolymer(s) having at least two unblocked aromatic isocyanate groups" is also referred to as an "unblocked aromatic isocyanate terminated prepolymer(s)" herein.
The term "stable" as used herein with respect to dispersions and compositions refers to dispersions and compositions that have pot lives of at least about 20 minutes.
Another aspect ofthe invention relates to a magnetic dispersion for use in magnetic recording media, which dispersion comprises:
(a) a prepolymer(s) having at least two unblocked aromatic isocyanate groups;
(b) a ketimine(s) of Formula I; (c) a binder(s) having at least one hydroxy functional group;
(d) a non-aqueous solvent;
(e) a pigment selected from the group consisting of magnetizable pigments, non-magnetizable pigments, and mixtures thereof;
(f) optionally a head cleaning agent; (g) optionally a wetting agent; and
(h) optionally a lubricant.
The invention also relates to magnetic recording media prepared from the magnetic dispersions.
The present invention provides a novel film comprising the reaction product of components comprising:
(a) optionally an organic polymer(s) having at least one hydroxy functional group;
(b) a prepolymer(s) having at least two unblocked aromatic isocyanate group(s); and (c) a ketimine(s) of Formula I.
The present invention also provides a novel method of making the film ofthe invention, comprising the steps of:
(a) forming a composition comprising: (i) a ketimine(s) of Formula I; (ii) a prepolymer(s) having at least two unblocked aromatic isocyanate group(s);
(iii) optionally a non-aqueous solvent; and (iv) optionally an organic polymer(s) having at least one hydroxy ftinctional group;
(b) forming a coating ofthe composition;
(c) allowing the coating to cure by exposure ofthe coating to atmospheric moisture.
The invention also provides a novel magnetic recording medium, comprising at least one coating provided on a nonmagnetizable substrate, wherein each coating independently comprises the reaction product of components comprising:
(a) a binder(s) having at least one hydroxy functional group;
(b) a prepolymer(s) having at least two unblocked aromatic isocyanate group(s); and (c) a ketimine(s) of Formula I;
(d) a non-aqueous solvent;
(e) a pigment selected from the group consisting of magnetic pigments, nonmagnetizable pigments, and mixtures thereof;
(f) optionally a head cleaning agent; (g) optionally a wetting agent; and
(h) optionally a lubricant.
The present invention also provides a novel method of making the magnetic recording medium ofthe invention, comprising the steps of:
(a) forming at least one dispersion each dispersion independently comprising: (i) a ketimine(s) of Formula I;
(ii) a prepolymer(s) having at least two unblocked aromatic isocyanate group(s);
(iii) a binder(s) having at least one hydroxy functional group; (iv) a non-aqueous solvent; (v) a pigment selected from the group consisting of magnetic pigments, nonmagnetizable pigments, and mixtures thereof;
(vi) optionally a head cleaning agent; (vii) optionally a wetting agent; and (viii) optionally a lubricant.
(b) forming a coating(s) ofthe dispersion (s) on a nonmagnetizable substrate;
(c) allowing the coating(s) to cure by exposure ofthe coating(s) to atmospheric moisture.
BRIEF DESCRIPTION OF THE DRAWINGS
Fig. 1 is a graph illustrating the methylethyl ketone (MEK) soluble ratio for Examples 16-22 and Comparative Example 23.
Fig. 2 is a graph illustrating the MEK soluble ratio for Examples 16-22 and Comparative Example 23.
DETAILED DESCRIPTION OF THE INVENTION The present invention describes particular ketimines (of Formula I) which can suφrisingly be utilized as curing agents to enhance the cure of polymeric systems which incoφorate unblocked aromatic isocyanate terminated prepolymers as crosslinking agents. These curing agents are particularly useful in magnetic compositions and coatings which use unblocked aromatic isocyanate terminated prepolymers as crosslinking agents. The ketimines usefiil according to the present invention are preferably used to produce stable film forming compositions and stable magnetic recording media dispersions with acceptable pot lives yet provides a resin system which can be cured rapidly once coated upon a substrate.
Ketimine Curing Agents
The ketimine curing agents useful according to the present invention are those of Formula I discussed supra. Mixtures of ketimines of Formula I are also useful herein. The group X of Formula I typically has a number average molecular weight of about 25 to about 20,000, preferably about 25 to about 500. Examples of specific groups X can comprise include but are not limited to those selected from the group consisting of hexyl, cyclohexyl, polyethers, polyesters, polyurethanes, polyureas, polycarbonates, diethyl tolyl, phenyl, tris(2-aminoethyl), benzyl, methylene dibenzyl, polymethylenedibenzyl, and the like.
The group Y of Formula I typically comprises about 1 to about 20 carbon atoms, preferably about 1 to about 12, and most preferably about 1 to about 9. Examples of specific aromatic groups Y can comprise include but are not limited to those selected from the group consisting of benzyl, phenyl, furfuryl, and the like.
When Y is not aromatic then R1, R2 and, R^ are each preferably independently selected from the groups consisting of -H, cyclohexyl, methyl, t-butyl, ethyl, propyl, isopropyl, butyl, pentyl, hexyl, cyclopentyl, benzyl, methyl benzyl, and the like.
The group Z typically comprises about 1 to about 20 carbon atoms, preferably about 1 to about 12, and most preferably about 1 to about 9. Examples of specific aromatic groups Z can comprise include but are not limited to those selected from the group consisting of benzyl, phenyl, furfuryl, and the like. When Z is not an aromatic group, R4, R5, and R^ are each preferably independently selected from the group consisting of -H, methyl, ethyl, propyl, isopropyl, butyl, t-butyl, pentyl, cyclopentyl, hexyl, cyclohexyl benzyl, methylbenzyl and the like.
The ketimines of Formula I preferably have a pot life of over 20 minutes when mixed with an unblocked aromatic isocyanate terminated prepolymer crosslinking agents, such as in a dispersion or composition preferably greater than about 3 hours, and most preferably greater than about 24 hours. The coatings and films ofthe invention are coated or otherwise formed before the composition or dispersion from which they are formed gels.
Ketimines are typically formed by combining a ketone with an amine. Some representative examples of ketones that can be used to make ketimines of Formula I include but are not limited to those selected from the group consisting of, pinacolone, cyclohexanone, cyclopentanone, diisopropyl ketone, 3-methyl-2-butanone, benzophenone, acetophenone, fenchone, 5-nonanone, 2,4-tetramethyl-3-pentanone, and any other monoketones that are capable of making the ketimine of Formula I.
Some representative examples of amines that can be used to make the ketimines of Formula I include but are not limited to those selected from the group consisting of 4,4 '-methylenedianiline, 3,5-diethyltoluene-2,4-diamine, 1,4- phenylenediamine, 1,3 -phenylenediamine, xylenediamine, and polyether amines from Texaco Company under the tradename "Jeffamines," 1,6- hexanediamine, tris(2- aminoethyl)amine, poly 4'-4'methylenedianiline, 4,4'-methylene bis(3-chloro-2,6- diethylaniline), 2,4-toluene diamine, and any other diamine or higher functional amine which are aromatic or aliphatic that can be used to make ketimines of Formula I.
The present invention incoφorates specific ketimines with unblocked aromatic isocyanate terminated prepolymer crosslinking agents in stable film forming compositions and magnetic dispersions. After coating the dispersion or composition onto a substrate, water from the atmosphere hydrolyzes the ketimine to a ketone and an amine. The ketimine hydrolysis is usually complete in about 24 hours. This is much faster than the reaction of atmospheric water with isocyanates and it is why the particular ketimines used in the present invention result in a faster cured product such as a film or magnetic media.
The ketone generated from the hydrolysis ofthe ketimine evaporates and the amine reacts readily with the residual isocyanate moieties ofthe unblocked aromatic isocyanate terminated prepolymer crosslinking agent. This fast reaction imparts good physical properties to the product much sooner than which has been observed in conventionally formulated systems. Dispersions and compositions prepared using ketimine curing agents form a tougher product at a much faster rate due to the possible formation of a semi-inteφenetrating network.
Heat may optionally be applied when curing the compositions and/or dispersions ofthe invention. When heat is applied, the isocyanate can react directly with the ketimine, crosslinking the system. When heat is applied, the reaction of ketimine with isocyanate is as fast or faster then the ketimine hydrolysis reaction and much faster than the atmospheric water/isocyanate reaction. Heat, if applied at all, would typically be applied such that the temperature ofthe system is about 25 degrees C to about 60 degrees C. If the temperature is too high degradation ofthe magnetic backing may occur, in the case ofthe preparation of magnetic recording media. See "New Developments in Polyketimine Polyisocyanate Coatings - Their Chemistry and Applications," M. Bock and R. Halpaap, Journal of Coatings Technology. Vol. 59, No. 755, pages 131-135 (1987)
The amount of ketimine required varies depending on how much unblocked aromatic isocyanate terminated prepolymer crosslinking agent is present in the formulation. Sufficient unblocked aromatic isocyanate terminated prepolymer and ketimine of Formula I should be present such that the NCO to imine equivalent ratio is 0.5 or greater for films, and preferably about 1.1 to 50 for magnetic recording media.
Unblocked Aromatic Isocyanate Terminated Prepolymer Crosslinking Agents
Unblocked aromatic isocyanate terminated prepolymer crosslinking agents are used in combination with the ketimine curing agent of Formula I. These prepolymers are free of hydroxy functionality. By "unblocked" it is meant that the NCO groups have not been reacted with blocking agents such that special conditions are required to liberate the NCO groups. One skilled in the art would be able to distinguish between blocked and unblocked prepolymers. Examples of unblocked aromatic isocyanate terminated prepolymers that can be used include CB-701 from Bayer, formerly Miles Company, Isonate 181 from Dow Chemical, and many other unblocked aromatic isocyanate terminated prepolymers known to those skilled in the art. There are no limitations regarding the isocyanates, diols and triols that are used to prepare the unblocked aromatic isocyanate terminated prepolymer. The useful number average molecular weight of these prepolymers is typically about 100 to 5000, more preferably about 500 to 1500.
The unblocked aromatic isocyanate terminated prepolymer is preferably used in an amount such that the equivalent ratio of NCO groups to hydroxy groups is about 0.3 to 10. Sol vents
Usefiil non-aqueous solvents according to the present invention are those that will provide compositions and dispersions having good film forming properties. One skilled in the art will be able to select useful non-aqueous solvents for this puφose. Examples of useful non-aqueous solvents according to the invention include but are not limited to those selected from the group consisting of acetone, cyclohexanone, xylene, ethyl acetate, tetrahydrofuran, methylisobutyl ketone, mixtures thereof, and the like. Some non-aqueous solvents may contain trace amounts of water (less than 0.1 weight percent based upon the weight ofthe solvent). Trace amounts of water are typically not detrimental to the system ofthe invention. Dispersions and compositions ofthe invention typically comprise less than about 1 weight percent water, more typically less than about 0.5 weight percent, based upon the total weight ofthe dispersions and compositions, respectively.
Magnetic Recording Media
Although the combination ofthe particular ketimine of Formula I and unblocked aromatic isocyanate terminated prepolymer crosslinking agent may be advantageously used in any application requiring a crosslinking agent with reactive NCO groups, the ketimine curing agent and unblocked aromatic isocyanate terminated prepolymer crosslinking agent combination is particularly suitable for use in magnetic recording media.
Nonmagnetizable Substrates
The ketimine curing agent and the unblocked aromatic isocyanate terminated prepolymer crosslinking agent advantageously may be incoφorated into the magnetic and/or backside coatings of magnetic recording media. These coatings are typically provided on the major surfaces of a nonmagnetizable substrate having first and second opposed major surfaces. The nonmagnetizable substrate may be formed from any suitable substrate material known in the art. Examples of suitable substrate materials include, for example, polymers such as polyethylene terephthalate ("PET"), polyimide, and polyethylene naphthalate ("PEN"); ceramics; glass; metals such as aluminum, or copper; paper; or any other suitable material.
Magnetic Pigments Magnetic coatings ofthe present invention typically comprise a magnetic pigment dispersed in a polymeric binder. Typically, the magnetic layer may contain 100 parts by weight ofthe magnetic pigment and 5 to 40 parts by weight ofthe polymeric binder. The type of magnetic pigment used in the present invention may include any suitable magnetic pigment known in the art including gamma-Fe2O3, cobalt-doped gamma-Fe2O3, Fe3O4, CrO2, barium ferrite, barium ferrite derivatives, metal particles, mixtures thereof, and the like.
Magnetic Media Additives
In addition to the polymeric binder and the magnetic pigment, the magnetic coating ofthe present invention may optionally further comprise one or more conventional additives such as lubricants; abrasives; thermal stabilizers; antioxidants; dispersants; wetting agents; antistatic agents; fungicides; bacteriocides; surfactants; coating aids; nonmagnetic pigments; and the like in accordance with practices known in the art. Backside coatings ofthe present invention typically comprise a binder and, optionally, further comprise one or more conventional additives such as lubricants; abrasives; thermal stabilizers; antioxidants; dispersants; wetting agents; antistatic agents; fungicides; bacteriocides; surfactants; coating aids; nonmagnetic pigments; and the like in accordance with practices known in the art. Examples of useful nonmagnetic pigments include but are not limited to those selected from the group consisting of carbon black, Tiθ2, alumina, alpha-Fβ2θ3, mixtures thereof, and the like.
Magnetic Media Binders
The terms "polymeric binders", "binders", "binder component", and "magnetic media binders", are used interchangably herein. Polymeric binders suitable for preparing the magnetic coating and/or the backside coating may include any polymer component conventionally used in the magnetic recording art. Polymeric binders useful herein are those having at least one pendant hydroxy, i.e., — OH, group. The — OH groups not only allow the polymer to crosslink with the unblocked aromatic isocyanate terminated prepolymer crosslinking agent but also promote dispersion of the inorganic pigments in the binder, promote the solubility ofthe polymer in solvents, and promote the compatibility ofthe polymer with other polymers. The — OH groups can be primary, secondary, or tertiary, although the use of primary and/or secondary — OH groups is preferred. Generally, preferred hydroxyl functional polymers have an — OH equivalent weight in the range from 200 to 20,000, preferably 300 to 5000. The magnetic dispersion may optionally further comprise at least one polymer binder having no pendant — OH groups.
One or more ofthe polymer or polymers, if more than one polymer is used, of the binder component may contain one or more other kinds of pendant functional groups to enhance the performance ofthe magnetic recording medium. For example, any binder may contain carbon-carbon double bonds if it is desired to crosslink the binder using both isocyanate and radiation curing techniques. As other examples of pendant functional groups, any polymer ofthe binder component may contain a pendant dispersing group in order to facilitate dispersion of magnetic or nonmagnetic pigments in the polymeric binder. The term "dispersing group" means that a group is capable of wetting the magnetic or nonmagnetic pigments to facilitate dispersion of such pigments in the polymeric binder. Preferably, the dispersing group is a moiety that is ionized or ionizable at a pH in the range from 0 to 10. Representative examples of suitable dispersing groups include quaternary ammonium moieties (e.g., -N(CH3)3 +C1" as one example), amines (e.g., -N(CH3)2 as one example), heterocyclic moieties as described in U.S. Patent No. 5,081,213, sulfobetaines (e.g.,
— N+(CH3)2(CH2CH2CH2SO3 ")), salts or acids based on sulfate (e.g., — OSO3Na as one example), salts or acids based on sulfonate (e.g., — SO3Na as one example), salts or acids based on phosphate (e.g., — OPO(OH)2 as one example), salts or acids based on phosphonate (e.g., -PO(OH)2 as one example), salts or acids based on carboxyl (e.g., — COONa as one example), mixtures thereof, and the like. Examples of additional resin binders that may be utilized in this invention include but are not limited to non-halogenated vinyl copolymers which contain styrene/acrylonitrile copolymers with ammonium wetting groups (referred to as a "K resin" herein) as described in U.S. Patent No. 5,510,187, assigned to the assignee of the present invention.
Vinyl chloride copolymers are useful according to the present invention. Useful vinyl chloride copolymers may or may not contain polar functional group(s). Representative useful vinyl chloride copolymer resins are described in U.S. Patent No. 4,816,683, (assigned to Sekisui Chemical). These are copolymers of vinyl chloride, hydroxypropyl acrylate, methacryloxyethyl trimethylammonium chloride, and methyacryloxyethyl phosphate. These are thought to be similar to or the same as the commercially available "S-LEC E-C" resins (E-C130 and E-Cl 10) made by Sekisui Chemical Co. According to information supplied by Sekisui Chemical Co., these are approximately 84% vinyl chloride, 16% hydroxy acrylic monomer (by weight) and contain a fraction of a percent of other monomers, including a quaternary ammonium monomer.
Another class of useful vinyl chloride copolymers are the sulfonated vinyl "MR" resins (MR-110, MR-113, MR-120, and others) commercially available from Nippon Zeon Co. Polymers of this type are described in U.S. Patent Nos. 4,707,410 and 4,707,411 (assigned to Nippon Zeon).
Another useful vinyl chloride copolymer is UCARMAG binder 528 from Union Carbide which contains carboxyl groups (about 56100 g/mole) and hydroxy groups (850 g/mole) and is described in U.S. Patent No. 4,985,314.
Vinyl chloride copolymers containing no polar functionality are also useful. An example is VAGH from Union Carbide which contains vinyl chloride and hydrolyzed vinyl acetate such that the hydroxyl equivalent weight is about 750 g/mole.
Examples of polyurethane resins that may be utilized in this invention include but are not limited to polyurethanes containing multidentate chelating functional groups pendent from the polymer backbone (referred to as "B resin" herein) as described in U.S. Patent No. 5,498,685, assigned to the assignee ofthe present invention. Other useful polyurethanes are the vinyl sulfonated and non-sulfonated hydroxy functional polyurethane copolymers prepared from macromonomer diols as described in U.S. Patent No. 5,384,362.
Other examples of binders that can be used in this invention include all polymers that are known to those skilled in the art of magnetic recording media.
Magnetic Dispersions and Coatings
The magnetic coating can be coated onto a nonmagnetizable substrate in a variety of ways. As one example of a process for applying the magnetic coating onto a nonmagnetizable substrate, the components ofthe magnetic coating are combined and mixed with a suitable solvent to form a substantially homogeneous dispersion, except that the ketimine curative and unblocked aromatic isocyanate terminated crosslinking agent are preferably combined and mixed with the other components ofthe magnetic dispersion just prior to coating (but in any case at a time sufficiently prior to coating such that the dispersion does not gel before coating). The dispersion is then coated onto the nonmagnetizable substrate, which may be primed or unprimed. The dispersion may be applied to the substrate using any conventional coating technique, such as gravure or knife coating techniques. The coated substrate may then be passed through a magnetic field to orient the magnetic pigment after which the coating is dried, calendered if desired, and then allowed to cure.
Free Films
The films ofthe invention can be prepared from the unblocked aromatic isocyanate terminated prepolymers, optionally an organic polymer(s) having at least one hydroxy functional group, and ketimine(s) of Formula I.
Examples of useful organic polymers having at least one hydroxy group include but are not limited to those selected from the group consisting of polyurethanes, polycarbonates, polyesters, polyethers, vinylchloride polymers, acrylic polymers, styrenic polymers, polyvinyl acetates, polyvinyl alcohols, polyvinyl butyral, mixtures thereof, and the like. The composition from which the films are formed and thus the films themselves may optionally further comprise an additive selected from the group consisting of inorganic fillers, lubricants, surfactants, catalysts, leveling agents, mixtures thereof, and the like.
Films ofthe present invention can be used for the following puφoses: top coats, adhesives, protective coatings, sealants, inorganic filled coatings, and the like. The films ofthe present invention typically are tougher than conventional films cured without the ketimine curing agents of Formula I. Also the films ofthe present invention typically cure faster than such conventional films.
Examples
The following non-limiting examples are presented to demonstrate the utility of the present invention. All parts, percentages, ratios, etc. in the Examples and elsewhere throughout are by weight unless indicated otherwise.
Abbreviations
The following abbreviations are used herein:
Ex. = example rt = room temperature 25°C Comp. = comparative eq. = equivalent pbw = parts by weight
MEK = methylethyl ketone
App. = appearance Tough .= toughness
Mod. = modulus
MDI = methylene diphenyldiisocyanate
Examples 1-3 Examples 1-3 disclose the preparation of novel ketimines ofthe invention which also fall within Formula I. Example 1
Preparation of 4,4'-methylenedianiline/cyclohexanone ketimine
To a 250 ml flask was added 52.5 grams (0.530 equivalent) 4,4'- methylenedianiline and 125 grams cyclohexanone. The reaction was mixed and refluxed at 155°C for 2 hours and 10 mis of water was collected in a trap. There was no amine peak in the infrared spectrum. The ketimine (shown below) was 71% solids in cyclohexanone.
Example 2
Preparation of 4,4'-methylenedianiline/pinacolone ketimine
To a 250 ml flask was added 54.7 grams (0.552 equivalent) 4,4'- methylenedianiline and 132 grams pinacolone. The reaction was mixed and refluxed at
110°C for 16 hours and 10 mis of water was collected in a trap. There was no amine peak in the infrared spectrum. The ketimine (shown below) was 60% solids in pinacolone.
Example 3
Preparation of 3, 5-diethyltoluene-2,4-diamine/cyclohexanone ketimine
To a 250 ml flask was added 52.7 grams (0.592 equivalent) of 3,5- diethyltoluene-2,4-diamine and 135 grams cyclohexanone. The reaction was mixed and refluxed at 155 degrees C for 24 hours and 11 mis of water was collected in a trap. There was no amine peak in the infrared spectrum. The ketimine (shown below) was 72% solids in cyclohexanone.
Examples 4-5
Examples 4 and 5 disclose the preparation of ketimines which are known but which fall within Formula I. It has been discovered that these ketimines are suφrisingly usefiil as curing agents with an unblocked aromatic isocyanate terminated prepolymer.
Example 4
Preparation of 1,6-hexanediamine/pinacolone ketimine To a 250 ml flask was added 41.4 grams (0.714 equivalent) of 1,6- hexanediamine and 164 grams pinacolone. The reaction was mixed and refluxed at 110°C for 3 hours and 12 mis of water was collected in a trap. There was no amine peak in the infrared spectrum. The ketimine (shown below) was 58% solids in pinacolone.
Example 5
Preparation of 1,6-hexanediamine/benzophenone ketimine
To a 250 ml flask was added 45.4 grams (0.783 equivalent) of 1,6- hexanediamine, 98.7 grams benzophenone, 0.05 gram titanium butoxide catalyst and 100 grams toluene solvent. The reaction was mixed and refluxed at 125°C for 16 hours and 10 mis of water was collected in a trap. There was no amine peak in the infrared spectrum. The ketimine (shown below) was 58% solids in toluene.
Comparative Examples 6 and 7
Comparative Examples 6 and 7 disclose the preparation ofknown ketimines which fall outside Formula I and cannot be used as curing agents with unblocked aromatic isocyanate terminated prepolymers according to the present invention.
Comparative Example 6
Preparation of 1,6-hexanediamine/cyclohexanone ketimine
To a 250 ml flask was added 42.0 grams (0.725 equivalent) of 1,6- hexanediamine and 151 grams cyclohexanone. The reaction was mixed and refluxed at 155°C for 3 hours and 13 mis of water was collected in a trap. There was no amine peak in the infrared spectrum. The ketimine (shown below) was 63% solids in cyclohexanone.
Comparative Example 7
Preparation of 1,6-hexanediamine/methylethyl ketone ketimine
To a 500 ml flask was added 63.4 grams (1.094 equivalent) of 1,6- hexanediamine and 386 grams methylethyl ketone. The reaction was mixed and refluxed at 85°C and 200 grams of methylethyl ketone and 20 mis of water was collected in a trap. There was no amine peak in the infrared spectrum. The ketimine (shown below) was 60% solids in MEK.
Pot Lives of Ketimines of Examples 1-5 and Comparative Examples 6-7 with Aromatic Isocyanate Terminated Prepolymer
The pot lives for the ketimines of Examples 1 -5 and Comparative Examples 6-7 with an unblocked aromatic isocyanate terminated prepolymer (CB-701 discussed above) were each evaluated by combining each ketimine with sufficient unblocked aromatic isocyanate terminated prepolymer such that a 1 : 1 equivalent ratio of imine to isocyanate was present. The time observed to gel (pot life) is recorded below.
Table I
Ketimine Example Time to gel
1 3 hours
2 over 3 weeks
3 24 hours
4 0.5 hour
5 over 2 months
Comp. 6 5 minutes
Comp. 7 few seconds
Comparative Examples 6 and 7 cannot be used in magnetic dispersions due to their short pot lives. Phosphonated Polyurethane (PHPU
The PHPU used herein was prepared as follows:
To a 1 -liter flask were added 67.9 grams Ravecarb™ 106 polycarbonate diol available from EniChem Company (OH eq. weight = 1000; 0.068 eq.), 20.8 grams of neopentyl glycol (0.400 eq.), 11.8 grams of fyrol 6 diol available from Akzo Chemical
(0.093 eq.) and 127 grams MEK. Then 84.5 grams diphenylmethane diisocyanate (0.676 eq.) and 0.1 grams dibutyltin dilaurate were added. The mixture was heated at 80 degrees Celsius for 2 hours. Then 46.6 grams TONE™ 0305 polycaprolactone triol available from Union Carbide Coφoration (OH eq. weight = 180; 0.254 eq.) and 69.5 grams MEK were added. The reaction mixture was heated at reflux for 1 hour. The inherent viscosity ofthe resultant polyurethane polymer in tetrahydrofuran was 0.302 dl/g. The polymer was calculated to have a hydroxyl equivalent weight of 1500 and a phosphonate equivalent weight of 5000.
Resin B - 20.000 Equivalent Weight Mercaptosuccinic Acid Polyurethane
The Resin B used herein was prepared as follows:
To a 25 gallon kettle were added 7.5 kg TONE™ 0210 (17.7eq) polycaprolactone diol from Union Carbide Coφoration, 1.9 kg neopentyl glycol (36.7 eq), and 27 kg MEK. Then 10.2 g dibutyltin dilaurate and 8.9 kg MDI (71.2 eq) were added. The mixture was heated at 80 degrees Celsius for 2 hours. Then 195.8 g mercaptosuccinic acid (1.5 eq), 6.6 kg TONE™ 0305 polycaprolactone triol (36.7 eq), and 9 kg MEK were added. The reaction mixture was heated at reflux for 3 hours. An additional charge of 590 g MDI (4.72 eq), was added and held at reflux for 3 hours. Final inherent viscosity = 0.28 dl/g. Calculated mercaptosuccinic acid equivalent weight = 19,600. Calculated hydroxyl equivalent weight = 1425.
Resin K
The Resin K used herein was prepared as follows:
A nonhalogenated vinyl copolymer was prepared from the following ingredients: 161.25 pbw styrene, 50.0 pbw acrylonitrile, 37.5 pbw hydroxypropylacrylate, 1.25 pbw methacryloxyethyl trimethyl ammonium chloride, 0.5 pbw mercaptopropane diol, 3.75 pbw methyl ethyl ketone, and 1.25 pbw 2,2'-azobisisobutyronitrile.
The ingredients were charged into a 1 liter amber reaction bottle. The resultant admixture, which contained some undissolved methacryloxyethyl trimethyl ammonium chloride, was purged with N2 for 7 minutes at 1 liter per minute, after which the bottle was sealed. The sealed bottle and its contents were tumbled in a constant temperature bath, at 65°C or 70°C for 80 hours. The product was a clear, homogeneous solution containing a nonhalogenated vinyl copolymer. The inherent viscosity ofthe sample in MEK was measured according to the procedure described in F. Rodriguez, "Principles of Polymer Systems," Chemical Engineering Series, 2nd Edition (McGraw-Hill), pages 181-185. Tg was also measured. The inherent viscosity was 0.30 to 0.33. The Tg was 79°C.
Free Film Examples 8-10. 12. 14-15 and Comparative Examples 11 and 13
Resins (B and K), isocyanate crosslinking agent (CB-701) and ketimine were combined according to Table II below to prepare polymer films. Handspread coatings were made from a 40% solids solution ofthe components in methylethyl ketone (MEK). The handspreads were coated to a thickness of 10 mils (wet) on a polypropylene backing, then dried in an oven for 15 minutes at 60° Celsius. The polymer film was then peeled away from the polypropylene backing. The degree of cure, appearance, toughness and modulus of these films were measured and are reported in Table III below.
Table II
Example Resin K Resin B CB-701 Ketimine
8 37.6% 37.6% 14.6% 10.2% Ex. 1
9 34.7% 34.7% 18.0% 12.6%Ex. 2
10 37.6% 37.6% 17.7% 7.1% Ex. 1
Comp. 11 37.6% 37.6% 24.8%
12 37.6% 37.6% 17.7% 7.1% Ex. 3
Comp. 13 37.6% 37.6% 24.8%
14 37.6% 37.6% 18.0% 6.8% Ex. 3
15 37.6% 37.6% 15.6% 9.2% Ex. 3 Table III
Ex. NCO/Ketimine Cure App. Tough. Mod. eq. ratio MPa MPa
Comp. 11 73% 4 days rt Clear 28 22830
8 1: 1 29% 4 days rt Hazy 184 11440
9 1: 1 39% 4 days rt Hazy 182 11930
10 1.7:1 71% 4 days rt Hazy 272 14480
12 1.7:1 86% 4 days rt Clear 508 27030
Comp. 13 21% l day rt Clear 14430
14 1.9:1 82% 1 day rt Clear 238 11430
15 1.2:1 81% 1 day rt Clear 225 10570
The modulus and toughness data was acquired using a half inch wide by 4 inch long (1.25 by 10.0 cm.) strip of film and a Model 1122 Instron. The numbers were generated by the data collected from the stress strain curve produced by the Instron.
The % cure results were obtained by soaking the films in methylethyl ketone (MEK) for two hours and weighing the undissolved material. The best results for toughness and cure occur when there is a small excess of isocyanate equivalents as is the case with Examples 10, 12, 14, and 15. Examples 8 and 9 have a 1 to 1 equivalent ratio of imine to isocyanate and are tougher but not cured as extensively as the Comparative Examples 11 and 13 with no ketimine present. The hazy coatings in Examples 8-10 are, it is theorized, were most likely due to the 4,4'-methylenedianiline crystallizing in the film.
Examples 16-22 and Comparative Example 23
Examples 16-22 and Comparative Example 23, contained magnetic particles, were prepared from the same dispersion composition except for varying amounts of isocyanate and ketimine. The dispersion composition was as follows: 100 parts barium ferrite pigment, (ΣT 50130 from Toda) 5 parts alumina head cleaning agent, 9.6 parts hydroxyl containing binders (4.8 parts EC-130 vinyl chloride resin from Sekisui Chemical and 4.8 parts PHPU polyurethane the preparation of which is described previously and in U.S. Patent No. 5,498,685) 3 parts myristic acid lubricant, 1.4 parts butyl myristate lubricant and 278 parts of a 60:20:20 ratio of methylethyl ketone, toluene, cyclohexanone solvents. Added to 100 grams ofthe above 30% solids dispersion was the isocyanate and ketimine in amounts specified in Table IV below.
Table IV
Example CB 701 70% Ketimine 72% NCO/Ketimine eq. solids solids Ex. 3 ratio
16 l.Olg 0.05 27.1
17 0.95g 0.10 g 13.2
18 0.90g 0.15g 6.3
19 0.85g 0.21g 3.9
20 0.80g 0.26g 2.8
21 0.74g 0.31g 2.1
22 0.69g 0.36g 1.6
Comp. 23 1.06g O.OOg oo
Handspreads ofthe dispersions of Exs. 16-22 and Comp. Ex. 23 were coated on a six inch (15.24 cm) wide polyester backing. A six by six inch piece of this coating and backing was cut out and placed in a vial. About 20 grams of methylethyl ketone was added to the vial and the vial was placed on a shaker for 2 hours. The methylethyl ketone soluble portion was separated from the coating and backing and the solvent was evaporated. The weight ratio ofthe MEK soluble portion to the original coating and backing was determined and is plotted in Figs. 1 and 2. This ratio is an indication ofthe degree of cure in the coating. Higher ratios indicate less cure.
Referring to Fig. 1, after 24 hours at about 25 degrees Celsius, the ratio shows that all ketimine containing examples were cured to a greater degree than the Comparative Ex. 23, which did not have any ketimine.
Referring to Fig. 2, after 9 days at about 25 degrees Celsius, all ofthe examples (16-22 and Comparative 23) show a greater degree of cure than what was observed after 24 hours. Examples 17 and 18, however, indicate that further improvement in the degree of cure can be achieved through formulation optimzation with ketimines. Other embodiments of this invention will be apparent to those skilled in the art upon consideration of this specification or from practice ofthe invention disclosed herein. Various omissions, modifications, and changes to the principles described herein may be made by one skilled in the art without departing from the true scope and spirit ofthe invention which is indicated by the following claims.

Claims

CLABVIS:
1. A compound comprising a ketimine selected from the group consisting of
2. A film forming composition comprising:
(a) a ketimine(s) of Formula I: Z
I
X-(-N=C )n (Formula I)
I
Y wherein
X is an organic moiety which can optionally comprise one or more atoms selected from the group consisting of N, O, S, Si, and P; Y is selected from the group consisting of aromatic groups and
R1
I -C-R2 I
R3 ;
Rl, R2, R3 and R4 are each independently selected from the group consisting of -H, alkyl, aryl, and alkaryl groups;
Z is selected from the group consisting of aromatic groups and R4
I
-C-R5
R6 ; R4, R5? and R^ are each independently selected from the group consisting of -
H, alkyl, aryl, and alkaryl groups; n is a number of at least 2 ;
Y and Z may alternatively form, together with the C- atom to which they are bonded, a cycloalkyl group; when N in Formula I is bonded to an aromatic carbon in X and neither Y nor Z are aromatic groups, no more than four groups selected from the group consisting of Rl, R2, R3, R4, R5? and R^ can be -H, the remaining groups selected from the group consisting of R*, R2, R3, R4, R5 and R^ being independently selected from the group consisting of alkyl, aryl, and alkaryl groups; and when N in Formula I is bonded to an aliphatic carbon in X and neither Y nor Z are an aromatic group, no more than three groups selected from the group consisting of R1, R2, R3, R4, R5, and R6 can be -H, the remaining groups selected from the group consisting of R , R2, R3, R4, R5 and R^ being independently selected from the group consisting of alkyl, aryl, and alkaryl groups; (b) a prepolymer(s) having at least two unblocked aromatic isocyanate groups;
(c) optionally a non-aqueous solvent; (d) optionally an organic polymer(s) having at least one hydroxy functional group, the organic polymer(s) being dispersible in the non-aqueous solvent if present; and
(e) optionally an additive selected from the group consisting of inorganic fillers, lubricants, surfactants, catalysts, leveling agents, and mixtures thereof.
3. The composition of claim 2 having a pot life of greater than about 3 hours.
4. The composition of claim 2 wherein the ketimine(s) of Formula I is the reaction product of a ketone selected from the group consisting of pinacolone, cyclohexanone, cyclopentanone, diisopropyl ketone, 3-methyl-2-butanone, benzophenone, acetophenone, fenchone, 5-nonanone, 2,4-tetramethyl-3-pentanone, and an amine selected from the group consisting of 4,4'-methylenedianiline, 3,5-diethyltoluene-2,4- diamine, 1,4-phenylenediamine, 1,3 -phenylenediamine, xylenediamine, a polyether amine, 1,6 hexanediamine, tris(2-aminoethyl)amine, poly 4'-4'methylenedianiline, 4,4'- methylene bis(3-chloro-2,6-diethylaniline) and 2,4-toluene diamine.
5. The composition of claim 2 wherein the organic polymer(s) having at least one hydroxyl group is selected from the group consisting of polyurethanes, polycarbonates, polyesters, polyethers, vinylchloride polymers, acrylic polymers, styrenic polymers, polyvinyl acetates, polyvinyl alcohols, polyvinyl butyral, and mixtures thereof.
6. A magnetic recording medium comprising at least one coating provided on a nonmagnetizable substrate, wherein each coating independently comprises the reaction product of components comprising:
(a) a binder(s) having at least one hydroxy functional group;
(b) a prepolymer(s) having at least two unblocked aromatic isocyanate group(s); and (c) a ketimine(s) of Formula I:
Z
I
X-(-N=C )n (Formula I) I
Y wherein
X is an organic moiety which can optionally comprise one or more atoms selected from the group consisting of N, O, S, Si, and P; Y is selected from the group consisting of aromatic groups and
R1
I
-C-R2
I R3 ;
Rl, R2, R3 and R4 are each independently selected from the group consisting of -H, alkyl, aryl, and alkaryl groups;
Z is selected from the group consisting of aromatic groups and
R4
-C-R 5
R6
R4, R , and R^ are each independently selected from the group consisting of - H, alkyl, aryl, and alkaryl groups; n is a number of at least 2 ;
Y and Z may alternatively form, together with the C- atom to which they are bonded, a cycloalkyl group; when N in Formula I is bonded to an aromatic carbon in X and neither Y nor Z are aromatic groups, no more than four groups selected from the group consisting of
R1, R2, R3, R4, R5, and R6 can be -H, the remaining groups selected from the group consisting of R1, R2, R3, R4, R5 and R6 being independently selected from the group consisting of alkyl, aryl, and alkaryl groups; and when N in Formula I is bonded to an aliphatic carbon in X and neither Y nor Z are an aromatic group, no more than three groups selected from the group consisting of Rl, R2, R3, R4, R5, and R^ can be -H, the remaining groups selected from the group consisting of Rl, R2, R3, R4, R^ and R^ being independently selected from the group consisting of alkyl, aryl, and alkaryl groups;
(d) a non-aqueous solvent;
(e) a pigment selected from the group consisting of magnetic pigments, nonmagnetizable pigments, and mixtures thereof;
(f) optionally a head cleaning agent; (g) optionally a wetting agent; and
(h) optionally a lubricant.
7. The magnetic recording medium of claim 6 wherein the ketimine(s) of Formula I is the reaction product of a ketone selected from the group consisting of pinacolone, cyclohexanone, cyclopentanone, diisopropyl ketone, 3-methyl-2-butanone, benzophenone, acetophenone, fenchone, 5-nonanone, 2,4-tetramethyl-3-pentanone, and an amine selected from the group consisting of 4,4'-methylenedianiline, 3,5- diethyltoluene-2,4-diamine, 1,4-phenylenediamine, 1,3 -phenylenediamine, xylenediamine, a polyether amine, 1,6 hexanediamine, tris(2-aminoethyl)amine, poly 4'-4'methylenedianiline, 4,4'-methylene bis(3-chloro-2,6-diethylaniline) and 2,4- toluene diamine.
8. A film comprising the reaction product of components comprising:
(a) optionally an organic polymer(s) having at least one hydroxy functional group;
(b) a prepolymer(s) having at least two unblocked aromatic isocyanate groups; and (c) a ketimine(s) of Formula I:
Z
I
X-(-N=C )n (Formula I) I
Y wherein
X is an organic moiety which can optionally comprise one or more atoms selected from the group consisting of N, O, S, Si, and P; Y is selected from the group consisting of aromatic groups and
R1
-C-R
R
RΪ, R2, R3 and R4 are each independently selected from the group consisting of -H, alkyl, aryl, and alkaryl groups;
Z is selected from the group consisting of aromatic groups and
R4
C-R5
R6
R4, R , and R^ are each independently selected from the group consisting of - H, alkyl, aryl, and alkaryl groups; n is a number of at least 2 ;
Y and Z may alternatively form, together with the C- atom to which they are bonded, a cycloalkyl group; when N in Formula I is bonded to an aromatic carbon in X and neither Y nor Z are aromatic groups, no more than four groups selected from the group consisting of
Rl, R2, R3, R4, R5, and R^ can be -H, the remaining groups selected from the group consisting of R*, R2, R3, R4, R^ and R^ being independently selected from the group consisting of alkyl, aryl, and alkaryl groups; and when N in Formula I is bonded to an aliphatic carbon in X and neither Y nor Z are an aromatic group, no more than three groups selected from the group consisting of R1, R2, R3, R4, R5, and R6 can be -H, the remaining groups selected from the group consisting of R , R2, R3, R4, R^ and R > being independently selected from the group consisting of alkyl, aryl, and alkaryl groups; and
(d) optionally an additive selected from the group consisting of inorganic fillers, lubricants, surfactants, catalysts, leveling agents, and mixtures thereof.
9. The film of claim 8 wherein the ketimine(s) of Formula I is the reaction product of a ketone selected from the group consisting of pinacolone, cyclohexanone, cyclopentanone, diisopropyl ketone, 3-methyl-2-butanone, benzophenone, acetophenone, fenchone, 5-nonanone, 2,4-tetramethyl-3-pentanone, and an amine selected from the group consisting of 4,4'-methylenedianiline, 3,5-diethyltoluene-2,4- diamine, 1,4-phenylenediamine, 1, 3 -phenylenediamine, xylenediamine, a polyether amine, 1,6 hexanediamine, tris(2-aminoethyl)amine, poly 4'-4'methylenedianiline, 4,4'- methylene bis(3-chloro-2,6-diethylaniline) and 2,4-toluene diamine.
10. The film of claim 8 wherein the organic ρolymer(s) having at least one hydroxy group is selected from the group consisting of polyurethanes, polycarbonates, polyestέrs, polyethers, vinylchloride polymers, acrylic polymers, styrenic polymers, polyvinyl acetates, polyvinyl alcohols, polyvinyl butyral, and mixtures thereof.
EP96921736A 1995-06-28 1996-06-20 Ketimine curing agents and rapidly curing magnetic recording media and films prepared with ketimines Withdrawn EP0835239A1 (en)

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US3267078A (en) * 1963-12-16 1966-08-16 Wyandotte Chemicals Corp Polyether urethane coating composition cured with a di-imine
DE1694237B2 (en) * 1968-01-02 1974-08-22 Bayer Ag, 5090 Leverkusen Process for the production of crosslinked plastics, including sheet-like structures, by the isocyanate polyaddition process
DE2630013A1 (en) * 1976-07-03 1978-01-12 Schering Ag Bonding plasticised vinyl chloride (co)polymer - using polyester-urethane adhesive soln. contg. aromatic polyisocyanate, Schiff's base and/or enamine
DE3631842A1 (en) * 1986-09-19 1988-03-24 Basf Ag INNER MOLD RELEASE AGENTS, THE USE THEREOF FOR THE PRODUCTION OF MOLDED BODIES BY THE POLYISOCYANATE POLYADDITIONAL PROCESS AND METHOD FOR THE PRODUCTION OF THE MOLDED BODIES
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