Classifications

• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
  • C08J5/00—Manufacture of articles or shaped materials containing macromolecular substances
  • C08J5/18—Manufacture of films or sheets
• • G—PHYSICS
  • G11—INFORMATION STORAGE
  • G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
  • G11B5/00—Recording by magnetisation or demagnetisation of a record carrier; Reproducing by magnetic means; Record carriers therefor
  • G11B5/62—Record carriers characterised by the selection of the material
  • G11B5/73—Base layers, i.e. all non-magnetic layers lying under a lowermost magnetic recording layer, e.g. including any non-magnetic layer in between a first magnetic recording layer and either an underlying substrate or a soft magnetic underlayer
  • G11B5/739—Magnetic recording media substrates
  • G11B5/73923—Organic polymer substrates
  • G11B5/73927—Polyester substrates, e.g. polyethylene terephthalate
  • G11B5/73929—Polyester substrates, e.g. polyethylene terephthalate comprising naphthalene ring compounds, e.g. polyethylene naphthalate substrates
• • G—PHYSICS
  • G11—INFORMATION STORAGE
  • G11B—INFORMATION STORAGE BASED ON RELATIVE MOVEMENT BETWEEN RECORD CARRIER AND TRANSDUCER
  • G11B5/00—Recording by magnetisation or demagnetisation of a record carrier; Reproducing by magnetic means; Record carriers therefor
  • G11B5/62—Record carriers characterised by the selection of the material
  • G11B5/73—Base layers, i.e. all non-magnetic layers lying under a lowermost magnetic recording layer, e.g. including any non-magnetic layer in between a first magnetic recording layer and either an underlying substrate or a soft magnetic underlayer
  • G11B5/739—Magnetic recording media substrates
  • G11B5/73923—Organic polymer substrates
  • G11B5/73927—Polyester substrates, e.g. polyethylene terephthalate
  • G11B5/73931—Two or more layers, at least one layer being polyester
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08J—WORKING-UP; GENERAL PROCESSES OF COMPOUNDING; AFTER-TREATMENT NOT COVERED BY SUBCLASSES C08B, C08C, C08F, C08G or C08H
  • C08J2367/00—Characterised by the use of polyesters obtained by reactions forming a carboxylic ester link in the main chain; Derivatives of such polymers
  • C08J2367/02—Polyesters derived from dicarboxylic acids and dihydroxy compounds

Definitions

• This invention relates to the use of a high melting, high strength biaxially oriented PENBB copolyester film for the manufacture of superior performing magnetic recording disks, and the disks made therefrom
• PENBB copolyester biaxially oriented film as a base for magnetic recording disks.
• PENBB resin may be extruded and formed into film using conventional biaxial orientation systems.
• the film product is higher melting than polyethylene terephthalate film, has a higher glass transition temperature, and higher inherent modulus and tensile properties.
• PENBB as mentioned herein is a copolyester containing acid- derived units of which at least 25 mole percent are bibenzoate units.
• the remainder of the acid-derived units are difunctional units such as 2,6- dicarboxy naphthalate, which is preferred or terephthalate, isophthalate, adipic acid or poly-functional units such as trimellitic acid, pyromellitic acid, and p- hydroxy benzoic acid .
• the diol units of the copolyester may be chosen from ethylene glycol, diethylene glycoi, propylene glycol, neopentyl glycol, 1 ,4-cyclohexane dimethanol, and p-xyiene glycol.
• the preferred copolyester would contain 4,4'-bibenzoate as acid derived units in the range 40 to 60 mole percent and 2,6-dinaphthoic acid in the range 60 to 40 percent.
• the dioi component preferably comprises at least 80 mole percent ethylene glycol- ⁇ e ⁇ ved units by weight, more preferably 95 to 100 percent.
• U.S. Patent No. 3,008, 934 c iscloses copolyesters containing as acid derived units 4,4'-bibenzoate and a host of other dicarboxylates including 2, 6- naphthalic dicarboxylate. It also discicses oriented fibers and films prepared from these copolyesters, however, oiaxially oriented PENBB films are not disclosed or envisioned In particular, those films with improved stiffness (tensile modulus) and tensile strength in both MD and TD as well as thermostability. UV stability, hydrophobicity, dimensional stability and impermeability toward gases in comparison to PET film are not disclosed in U.S. Patent No. 3,008,934.
• the copolyester is obtained by polycondensation of the corresponding diacid or lower dialkyl diester and the corresponding diol. Both components should normally be employed in equimolar ratios. It may, however, be advantageous to employ one of the components — especially the diol — in excess during the synthesis, for instance in order to influence the reaction kinetics or to serve as a solvent
• the polycondensation is carried out according to known processes used, e.g., in the production of polyethylene terephthalate (PET) . Usually about 1 00 mole percent of the dicarboxylic acid or dialkyldicarboxylate mixture are mixed with > 100 mole percent of the corresponding d ⁇ ol(s) .
• This mixture is then heated to about 200 ° C, preferably in the presence of a transeste ⁇ fication catalyst, until sufficient lower alkyl alcohol or water has been removed from the mixture via distillation.
• This reaction yields an oligomer or a low molecular weight polyester, which is subsequently subjected to polycondensation, preferably in the presence of a stabilizer and/or catalyst
• Useful stabilizers and catalysts can be polyphosphates, t ⁇ organyl phosphates, antimony t ⁇ oxide or tetraalkoxy t ⁇ tanate(IV) or mixtures of t ⁇ phenylphosphate and antimony t ⁇ oxide.
• a preferred process for the production of such copolyesters is described in U.S Patent Application Serial No.
• the polymer melt is extruded through a die onto a chill roll where it solidifies, biaxially oriented, heat set, optionally post treated, and then wound on a roll.
• the solidified film as extruded on the chill roll should be obtained in an essentially amorphous state.
• the melt film must be pinned to the chill roll by a known method such as electro ⁇ static pinning, vacuum, air knife or the like.
• the biaxial orientation of the film is achieved by stretching the film at elevated temperature in the machine direction (MD) and transverse direction (TD) .
• This stretching can be either simultaneous or sequential.
• the first stretching step can be in either MD or TD, followed by stretching in the other direction.
• the orientation in MD can also be achieved in several steps, either one after another prior to stretching in TD, or before and after the TD stretching.
• Preferred temperatures for stretching lie between the glass transition temperature and about 30 ° C above the cold crystallization temperature of the PENBB copolymer composition in use (both temperatures can easily be measured on amorphous films by DSC) .
• Suitable total stretch ratios in MD and TD lie between 1 to 2 and 1 to 1 0, preferably between 1 to 2.5 and 1 to 5.
• the product of the MD and TD total stretch ratios should be between 1 and 30 preferably between 5 and 20.
• Biaxial drawing is performed such that the birefringeance is ⁇ 0.2, preferably ⁇ 0.1 to ensure adequately isotropic properties.
• Birefringeance as mentioned herein is the absolute value of the difference between the maximum and minimum refractive indices in the plane of the film, as measured on common instruments such as Abbe refractometer, optical bench or compensators.
• the modification may include one or more of the following techniques: Inclusion of fine particles within the polymer. Such particles may be added during the polymer manufacturing process, formed by precipitation of catalyst residues during polymerization, and/or added in heavily loaded master batches to the extrusion melt stream.
• coatings applied to the base film may provide surface protrusions, or combinations of protrusions and depressions, sufficient to provide good slip and handleability without negatively impacting electronic records properties.
• These coatings may also contain inert paniculate matter to provide the proper surface character.
• Such multilayers may be all of PENBB or may contain layers of other polymers such as polyethylene terephthalate, PEN, etc. It is preferred that at least one of these layers contain means to provide a surface rough enough to provide good ship. This may be achieved by added particles or by coatings. At least one surface should be smooth to provide an excellent base for the magnetic susceptible layer. It is preferred that any protrusions on this surface be less than 0.75 This may be best achieved by having at least one layer of the PENBB either free from added particles or only containing particles that are very small. For example, a slip coating could be applied to only one surface layer of the disk whereas the other surface layer has no such coating and is smooth enough for magnetic recording.
• the biaxially oriented PENBB film of the instant invention is characterised by a heat shrinkage of ⁇ 0.5 % in both machine (MD) and transverse (TD) direction when measured at 1 50 ° C for 30 minutes. Its tensile modulus is in the range of about 5 to 1 0 GPa in both machine (MD) and transverse (TD) direction as measured at 20 ° C. The equilibrium water pick up is less than 0. 1 % at 50% relative humidity and 23 ° C. A film exhibiting the above described desirable combination of parameters is unique and was hitherto unknown .
• Biaxially oriented film is produced from a PENBB copolyester made from
• Example 1 except that: a master batch of 3% silica (Syloblock 44 from Grace GmbH, Worms, Germany), produced by adding the silica to the reaction mixture according to Example 1 after transesterification, is added to the PENBB co-polymer to give a diluted concentration of about 2000 ppm of silica in the extruded film.
• the biaxial orientation and heat setting are carried out under the same conditions as in Example 1 to give a film of substantially the same physical properties. However, it was found that this product had good slip and could readily be handled.
• EXAMPLE 3 To produce a suitable base for magnetic recording disks, an A/B type co-extrusion of the filled (cf. Example 2) and un-filled (cf. Example 1 ) resins is made.
• the filled polymer layer is 25 % by weight of the total film weights; the unfilled polymer layer is 75 % by weight.
• the filler particles in the filled polymer layer do not protrude through the surface of the unfilled layer. This film shows good slip, and has excellent smoothness on the unfilled surface which is suitable for a magnetic susceptible coating.
• EXAMPLE 4 Film from Example 1 is coated in-line between the forward draw stage and the transverse draw stage with a latex containing methyl methacrylic- ethyl acrylate-methacrylamide terpolymer and stearamidopropyl-dimethyl-B- hydroxy-ethylammonium nitrate, as described in U.S. Patent No. 4,302,506 at a coating weight of 1 5 mg/cm 2 .
• This product has sufficient slip to be readily processable through magnetic coating equipment.

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• Chemical & Material Sciences (AREA)
• Engineering & Computer Science (AREA)
• Manufacturing & Machinery (AREA)
• Materials Engineering (AREA)
• Health & Medical Sciences (AREA)
• Chemical Kinetics & Catalysis (AREA)
• Medicinal Chemistry (AREA)
• Polymers & Plastics (AREA)
• Organic Chemistry (AREA)
• Magnetic Record Carriers (AREA)
• Manufacture Of Macromolecular Shaped Articles (AREA)

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• 1992
  • 1992-12-09 EP EP93901394A patent/EP0671993A1/de not_active Withdrawn
  • 1992-12-09 WO PCT/US1992/010687 patent/WO1994013470A1/en not_active Application Discontinuation

Patent Citations (4)

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