JP2005097465A - Polyester resin composition, biaxially oriented polyester film and oriented polyester fiber - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a polyester resin composition which, when formed into a molded article such as film and fiber, can give a smooth surface equal to practical use and an enhanced Young's modulus. <P>SOLUTION: The polyester resin composition, in which needle-like iron oxide having a diameter (D) of 0.01-2.5 μm, a length (L) of 0.1-10 μm and an aspect ratio (L/D) of 4-100 is dispersed in an amount of 0.1-20 wt.% based on a weight of the polyester resin composition, is provided. The biaxially oriented polyester film using it is also provided. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a polyester resin composition capable of improving Young's modulus when it is made into a fiber or film by stretching, and a fiber or film having an increased Young's modulus using the same.

  Polyester resins are used in molded products such as films and fibers because they have excellent moldability and mechanical properties. Among these, it is required to reduce the thickness of the magnetic recording medium in the same volume and to increase the recording density by reducing the thickness of the magnetic recording medium using, for example, data storage. In order to satisfy these requirements, it is necessary to provide the base film with a high Young's modulus and excellent surface flatness. Such a requirement has also been required for fibers.

  Therefore, as a method for improving the strength and dimensional stability of a polyester resin, JP-A-6-128466 discloses a polyester resin composition comprising a thermoplastic polyester resin and a specific fibrous wollastonite and a plate-like filler. Proposed. Japanese Patent Application Laid-Open No. 1-144452 proposes a polyester composition obtained by blending polyalkylene terephthalate with glass fibers having a specific fiber length at a high ratio. However, in the polyester resins proposed in these publications, the particle size of the filler to be blended is too large, and the amount to be blended is too large. Therefore, when molded into a film, the surface is not suitable for use as a base film of a magnetic recording medium. There was a problem that was too rough. Japanese Patent Laid-Open No. 2003-82202 proposes the inclusion of carbon nanotubes, but carbon nanotubes are easily entangled due to their structural characteristics, and are difficult to disperse uniformly.

JP-A-6-128466 Japanese Unexamined Patent Publication No. 1-144452 JP 2003-82202 A

  The present invention solves the above-mentioned problems of the prior art, and has a polyester resin composition capable of increasing the Young's modulus when formed into a molded article such as a film or fiber, and has a surface flatness and a higher Young's modulus using the same. The object is to provide a biaxially oriented polyester film or oriented polyester fiber.

  The subject of the present invention is, according to the present invention, a needle having a diameter (D) of 0.01 to 2.5 μm, a length (L) of 0.05 to 10 μm and an aspect ratio (L / D) of 4 to 100. The iron oxide is achieved by a polyester resin composition in which 0.1 to 20% by weight is dispersed based on the weight of the polyester resin composition.

  In the polyester resin composition of the present invention, as a preferred embodiment thereof, (1) the acicular iron oxide is iron oxide having an α-type crystal form, (2) the polyester is polyethylene-2,6-naphthalate, or A polyester resin composition comprising any one of polyethylene terephthalate is also included.

  Moreover, according to the present invention, the object of the present invention is also achieved by a biaxially oriented polyester film or oriented polyester fiber comprising the polyester resin composition of the present invention.

  The biaxially oriented polyester film of the present invention has, as a preferred embodiment thereof, (1) the Young's modulus of either one of the film forming direction and the in-plane direction orthogonal to the film forming direction is in the range of 6 to 20 GPa, (2 ) A biaxially oriented polyester film having a thickness of 2 to 10 μm is also included.

  Furthermore, according to this invention, the oriented polyester fiber which consists of a polyester resin composition of the said invention is also provided.

  According to the present invention, a polyester resin composition capable of increasing the Young's modulus when formed into a molded product such as a film or fiber, and a biaxially oriented polyester film or oriented polyester having a surface flatness and a higher Young's modulus using the same. Fiber is provided.

<Polyester resin>
Examples of the polyester resin in the present invention include polyethylene terephthalate, polyethylene isophthalate, polybutylene terephthalate, polyethylene-2,6-naphthalate, polyethylene-α, β-bis (2-chlorophenoxy) ethane-4,4′-cycarboxy. Rate and the like. Among these, polyethylene terephthalate and polyethylene-2,6-naphthalate, which are excellent in moldability and mechanical properties, are preferable, and polyethylene-2,6-naphthalate is most preferable because of its relatively high strength.

  The polyethylene-2,6-naphthalate in the present invention may be used alone, as a copolymer of other polyesters, or as a mixture of two or more kinds of polyesters. Specifically, the repeating structural unit is not limited to substantially ethylene-2,6-naphthalate, but based on the number of moles of the repeating structural unit, 10 mol% or less, preferably 5 mol% or less is the other component. It may be a polyethylene-2,6-naphthalate copolymer and a polymer mixture. Polyethylene-2,6-naphthalate preferably has an intrinsic viscosity of 0.40 or more, and more preferably 0.40 to 0.80. If the intrinsic viscosity is less than 0.4, process cutting may occur frequently. On the other hand, if the intrinsic viscosity exceeds 0.8, productivity during polymerization is lowered, which is not preferable.

  The polyethylene-2,6-naphthalate in the present invention is not limited by its production method. For example, an ester compound of a lower alkyl having 1 to 3 carbon atoms such as dimethyl, diethyl or dipropyl and 2,6-naphthalenedicarboxylic acid is subjected to a transesterification reaction in the presence of ethylene glycol and a transesterification catalyst. It can be produced by polycondensation.

  The above explanation was made for polyethylene-2,6-naphthalate, but the same can be said for other polyesters.

  By the way, the polyester resin constituting the film may contain organic or inorganic inert particles as a lubricant in order to improve the winding property of the film at the time of film formation, the transportability of the film, and the like.

<Needle iron oxide>
The polyester resin composition of the present invention requires that acicular iron oxide is dispersed. According to the study by the present inventors, a film obtained by dispersing a specific acicular iron oxide in a polyester resin and stretching it in a biaxial direction, or a fiber stretched in a uniaxial direction, surprisingly, is acicular oxidation. It has been found that a higher strength is exhibited under the same film forming or yarn forming conditions as compared with a film or fiber made of a polyester resin composition in which iron is not dispersed.

  By the way, as mentioned above, the strength of the polyester resin cannot be improved with any acicular iron oxide, and the diameter (D), length (L), and aspect ratio (L / D) may be in specific ranges. It is necessary and will be described in detail below.

  In the present invention, acicular iron oxide has a diameter (D) of 0.01 to 2.5 μm, a length (L) of 0.05 to 10 μm, and an aspect ratio (L / D) of 4 to 100. Moreover, the ratio in the polyester resin composition of acicular iron oxide is 0.1 to 20 weight%. In addition, the ratio in the polyester resin composition here means the ratio in the polyester resin composition constituting the whole film in the case of a single layer film, and in the case of a laminated film composed of two or more layers, a needle The ratio in the polyester resin composition which comprises the layer containing iron oxide is meant.

  If the diameter (D) of the acicular iron oxide is less than the lower limit, improvement in strength cannot be expected. On the other hand, when the diameter (D) exceeds the upper limit, the film surface becomes rough, and when the magnetic recording medium is obtained, the electromagnetic conversion characteristics of the obtained magnetic recording medium are deteriorated. A preferable diameter (D) of acicular iron oxide is 0.01 to 1 μm, and particularly 0.01 to 0.2 μm when used for a film.

  Further, if the length (L) of the acicular iron oxide is less than the lower limit, improvement in strength cannot be expected. On the other hand, when the length (L) exceeds the upper limit, the film surface becomes rough, and when it is used as a magnetic recording medium, the electromagnetic conversion characteristics deteriorate. A preferable length (L) of acicular iron oxide is 0.05 to 5 μm, and further 0.05 to 1 μm, particularly 0.05 to 0.5 μm when used for a film.

  Furthermore, if the aspect ratio (L / D) of the acicular iron oxide is less than the lower limit, improvement in strength cannot be expected. On the other hand, if the aspect ratio (L / D) exceeds the upper limit, the acicular iron oxide dispersion is likely to be non-uniform, and the improvement in strength cannot be expected. A preferable aspect ratio (L / D) of acicular iron oxide is in the range of 4 to 50, more preferably 5 to 20.

  Further, if the amount of acicular iron oxide added is less than the lower limit, improvement in strength cannot be expected. On the other hand, if the addition amount exceeds the upper limit, the effect of acicular iron oxide becomes saturated, and further, the film formation and the yarn making process become unstable. The addition amount of acicular iron oxide is preferably in the range of 0.1 to 10% by weight, more preferably 0.1 to 5% by weight.

The acicular iron oxide is not particularly limited as long as it satisfies the above-mentioned characteristics, but is preferably α-type or γ-type iron (III) (Fe ₂ O ₃ ), particularly α-type oxidation. Iron (III) (Fe ₂ O ₃ ) is preferred.

  Such a polyester resin composition of the present invention is applied to a biaxially oriented polyester film or oriented polyester fiber, that is, needle-shaped iron oxide having a specific shape is selected and stretched biaxially or uniaxially. As a result, strength and dimensional stability can be expressed to a higher degree.

  The method for dispersing acicular iron oxide in the polyester is not particularly limited. For example, a method in which acicular iron oxide is dispersed in ethylene glycol as a slurry is added in the polyester production process, uniaxial or biaxial kneading extrusion A method of directly adding acicular iron oxide to the polyester obtained by polycondensation using a machine and kneading and dispersing it, creating a high concentration acicular iron oxide-containing polyester by any of the above methods, A method of mixing and kneading with a polyester not containing particles using a biaxial kneading extruder to obtain a polyester composition having an arbitrary concentration can be preferably used.

  Particularly preferred is the ability to uniformly disperse acicular iron oxide, so that a high concentration of acicular iron oxide-containing polyester can be mixed and kneaded with a polyester not containing particles using a uniaxial or biaxial kneading extruder at any concentration. This is a method for obtaining a polyester composition.

<Biaxially oriented polyester film>
Next, a film using the polyester resin composition of the present invention will be described. Although acicular iron oxide may be contained in the whole film, when a film is a laminated film of two or more layers, at least one layer should just contain acicular iron oxide. For example, a two-layer structure of a layer containing no acicular iron oxide and a layer containing acicular iron oxide (acicular iron oxide-containing layer), acicular iron oxide-containing layers and both surfaces containing acicular iron oxide Three-layer structure in which layers that are not to be laminated, three-layer structure in which acicular iron oxide-containing layers are laminated on both surfaces of a layer that does not contain acicular iron oxide, and these layer structures further contain acicular iron oxide The layer structure of 3 or more layers which provide the layer which does not carry out or a needle-like iron oxide content layer can be mentioned.

  When the biaxially oriented polyester film of the present invention is used as a base fill of a magnetic recording medium, the surface roughness (Ra) of at least one exposed surface of the film is 0.1 to 10 nm, more preferably 0.5 to 5 nm. Preferably there is. When the surface roughness exceeds 10 nm, when a magnetic layer is provided on the surface to form a magnetic tape, the surface of the magnetic layer is roughened and electromagnetic conversion characteristics are deteriorated. On the other hand, when the surface roughness is less than 0.1 nm, the slipping property between the film and the film is lowered, and the winding property of the film is deteriorated.

  As a means for providing the biaxially oriented polyester film of the present invention with such a surface roughness, in addition to adjusting the type, shape, size and amount of acicular iron oxide contained in the biaxially oriented polyester film, The inert particles can be added, and the inert particles can be adjusted depending on the type, shape, size and addition amount of the inert particles. Moreover, it can adjust also by the surface treatment which forms a fine unevenness | corrugation in at least one surface of the biaxially-oriented polyester film of this invention, for example, the coating process of a slippery coating agent. As the inert fine particles, for example, inorganic fine particles (for example, kaolin, alumina, titanium oxide, calcium carbonate, silicon dioxide, etc.) containing the elements of Periodic Tables IIA, IIB, IVA, and IVB, silicone resins, crosslinks Examples thereof include fine particles made of a polymer having high heat resistance such as polystyrene. When inert fine particles are contained, the average particle size of the fine particles is preferably 0.05 to 1.0 μm, more preferably 0.1 to 0.8 μm. The content of the inert fine particles is preferably 0.05 to 0.5% by weight (based on the polymer), more preferably 0.1 to 0.3% by weight (based on the polymer). Moreover, you may use together two or more types of inert particles from which a kind, a shape, or a size differs.

  In the biaxially oriented polyester film of the present invention, the Young's modulus in one of the film forming direction (longitudinal direction) and the width direction (lateral direction) is preferably 6 GPa or more, more preferably 8 GPa or more, and particularly preferably 10 GPa or more. If the Young's modulus in the longitudinal direction and the transverse direction are both less than 6 GPa, dimensional stability is impaired due to changes in tension and changes in temperature and humidity when tapes are used, and problems such as track misalignment tend to occur. Moreover, the effect by adding acicular iron oxide becomes difficult to express. The upper limit of the Young's modulus in the film forming direction (longitudinal direction) and the width direction (transverse direction) is not particularly limited, but it is usually preferably 20 GPa or less because sufficient Young's modulus can be imparted also in the orthogonal direction. The sum of the Young's modulus in the vertical direction and the horizontal direction is preferably 12 GPa or more, more preferably 15 GPa or more, and particularly preferably 17 GPa or more. Such a high Young's modulus can be obtained by addition of acicular iron oxide at a lower magnification than conventional films not containing acicular iron oxide. The upper limit of the sum of Young's moduli in the film forming direction (longitudinal direction) and the width direction (lateral direction) is not particularly limited, but is usually at most 30 GPa.

  The Young's modulus in the longitudinal direction is preferably 6 GPa or more, more preferably 8 GPa or more, and particularly preferably 10 GPa or more because the dimensional change in the width direction due to the tension change in the longitudinal direction of the tape can be suppressed. On the other hand, the Young's modulus in the lateral direction is preferably 6 GPa or more, more preferably 8 GPa or more, and particularly preferably 10 GPa or more, since the change in the width direction of the tape due to temperature and humidity changes can be suppressed.

  The thickness of the biaxially oriented polyester film of the present invention is not particularly limited, but when used for a base film of a magnetic recording medium, it is preferably 2 to 10 μm, more preferably 3 to 8 μm, and particularly preferably 4 to 6 μm. If the thickness is less than the lower limit, the tape strength is insufficient, the tape width shrinks due to the tension at the start of running, etc., the track and the magnetic head shift, and recording reproduction errors are inevitable. If the thickness exceeds the upper limit, the tape length stored in the cartridge is shortened, and a desired storage capacity cannot be obtained.

<Film forming method>
The biaxial polyester film of the present invention can be produced, for example, according to the following method.

  First, pellets of polyester resin containing a high concentration of acicular iron oxide and polyester resin pellets not containing acicular iron oxide are mixed at a predetermined ratio, and after drying, for example, the polyester is polyethylene-2,6-naphthalate. In this case, an unstretched film can be prepared by extrusion through a T die from an extruder at a melting temperature of 280 ° C. to 330 ° C., casting on a cooling drum, and cooling and solidifying. In the case of polyethylene-2,6-naphthalate, this unstretched film is stretched at a temperature of 100 to 170 ° C. at a magnification of 3 to 8 times, and then at a temperature of 115 to 180 ° C. in the direction perpendicular to the stretching direction. Stretch at a magnification of ~ 7 times. Alternatively, longitudinal and lateral stretching may be divided into two or more stages as necessary (longitudinal multistage stretching, longitudinal-horizontal-longitudinal three-stage stretching, longitudinal-horizontal-vertical-horizontal four-stage stretching, etc.). . Moreover, you may implement by simultaneous biaxial stretching. Thus, the total draw ratio is preferably 10 to 60 times, more preferably 20 to 50 times as the area draw ratio. The biaxially oriented film is preferably heat-set at a temperature of 180 to 250 ° C., more preferably 200 to 230 ° C., and the heat setting time is preferably 1 to 60 seconds.

  Moreover, the laminated biaxially oriented polyester film of the present invention uses two extruders, and at least one of them is fed with a pellet containing acicular iron oxide, melted, extruded from a two-layer or multilayer die, and thereafter The treatment may be performed by repeating the same operation as the biaxially oriented polyester film of the present invention.

<Magnetic recording medium>
The biaxially oriented polyester film and laminated biaxially oriented polyester film of the present invention have excellent Young's modulus, dimensional stability, flatness, slipperiness, winding property, etc., and are high density magnetic recording media, particularly digital recording. It is preferably used as a base film for a magnetic recording medium.

  In the magnetic recording medium using the biaxially oriented polyester film or laminated biaxially oriented polyester film of the present invention, a magnetic layer is applied to one side surface (or the flat side surface in the case of lamination), or vacuum deposition, sputtering, ion plating. And the like, and a ferromagnetic metal thin film layer made of iron, cobalt, chromium, or an alloy or oxide containing these as a main component is formed on the surface thereof. ) And the like, and a fluorine-containing carboxylic acid-based lubricating layer are sequentially provided, and a backcoat layer is provided on the surface opposite to the magnetic layer.

Hereinafter, the present invention will be further described based on examples. The various physical property values and characteristics in the present invention are measured and defined as follows.
(1) Young's modulus Using a tensile tester “Tensilon” manufactured by Toyo Baldwin Co., Ltd., the film was placed in a room adjusted to a temperature of 20 ° C. and a humidity of 50%. The length of the film was cut to 15 cm, the chuck was 100 mm, the film was pulled in the film forming direction and the width direction at a charting speed of 10 mm / min, and the chart speed was 500 mm / min. The Young's modulus in the film forming direction and the width direction is calculated.
(2) Diameter and length of acicular iron oxide The diameter and length are observed with a transmission electron microscope (TEM), and 100 acicular iron oxides are measured and averaged.
(3) Average particle diameter of inert particles Measured using a CP-50 type Centrifugal Particle Size Analyzer manufactured by Shimadzu Corporation. The particle size corresponding to 50 mass percent is read from the cumulative curve of the particle size and the abundance of each particle size calculated based on the centrifugal sedimentation curve obtained, and this value is taken as the average particle size. To do.
(4) Surface roughness of the film (centerline average roughness: Ra)
The center line average roughness (Ra) is measured according to JIS-B601. In the present invention, a stylus type surface roughness meter (SURFCORDER SE, 30C) manufactured by Kosaka Laboratory Ltd. is used for measurement under the following conditions.
(A) Stylus tip radius: 2 μm
(B) Measurement pressure: 30 mg
(C) Cutoff: 0.08mm
(D) Measurement length: 8.0 mm
(E) How to summarize data: The same sample is repeatedly measured 6 times, the largest value is removed, and the center line average roughness (Ra) is obtained as an average value using the remaining five data.
When the surface roughness (Ra) of the center line exceeds 10 nm, the surface is too rough, and it is determined that it cannot be used as a magnetic recording medium.

[Example 1]
Polyethylene-2 having an intrinsic viscosity (orthochlorophenol, 35 ° C.) of 0.60 containing 3.0% by weight of acicular iron oxide (α-Fe ₂ O ₃ ) having an average diameter of 0.02 μm and an average length of 0.10 μm , 6-Naphthalate is dried at 180 ° C. for 5 hours, then fed to an extruder hopper, melted at 300 ° C., and a T-type extrusion die is used to maintain a surface finish of 0.3 S and a surface temperature of 60 ° C. The film was rapidly cooled and solidified to obtain an unstretched film.

The unstretched film thus obtained was preheated at 120 ° C., and further heated by an infrared heater with a surface temperature of 830 ° C. from above 14 mm between low-speed and high-speed rolls and stretched 5.4 times. After quenching, it was supplied to a stenter and stretched 4.8 times in the transverse direction at 125 ° C. Subsequently, the film was heat-fixed at 225 ° C. for 3 seconds to obtain a biaxially oriented polyester film having a thickness of 4.5 μm. The Young's modulus of the obtained biaxially oriented polyester film was 10 GPa in the vertical direction and 7 GPa in the horizontal direction.
Table 1 shows the properties of the obtained polyester resin composition and biaxially oriented polyester film.

[Example 2]
Polyethylene-2,6-naphthalate for layer A containing 3.0% by weight of acicular iron oxide (α-Fe ₂ O ₃ ) having an average diameter of 0.02 μm and an average length of 0.10 μm, an average particle size of 0.1 μm B-layer polyethylene-2,6-naphthalate containing 0.01% by weight of spherical silica particles was dried at 180 ° C. for 5 hours, then fed to another extruder hopper and melted at a melting temperature of 300 ° C. Layer A and layer B were laminated using a manifold-type coextrusion die, and rapidly cooled and solidified on a casting drum maintained at a surface finish of 0.3 S and a surface temperature of 60 ° C. to obtain a laminated unstretched film. The thickness of each layer is 60% for the A layer and 40% for the B layer.

The laminated unstretched film thus obtained was preheated at 120 ° C., and further heated by an infrared heater having a surface temperature of 830 ° C. from above 14 mm between low-speed and high-speed rolls and stretched 5.9 times. Then, it was rapidly cooled, then supplied to a stenter, stretched 4.5 times in the transverse direction at 125 ° C., further 1.15 times in the transverse direction at 170 ° C., and stretched 5.2 times in total. Subsequently, the film was heat-fixed at 225 ° C. for 3 seconds to obtain a laminated biaxially oriented polyester film having a thickness of 4.5 μm. The Young's modulus of the obtained film was 11 GPa in the vertical direction and 8 GPa in the horizontal direction.
Table 1 shows the properties of the obtained polyester resin composition and biaxially oriented polyester film.

[Examples 3 to 5]
Except changing acicular iron oxide and its addition amount as shown in Table 1, the same operation as Example 1 was repeated. Table 1 shows the properties of the obtained polyester resin composition and biaxially oriented polyester film.

[Comparative Example 1]
Polyethylene-2,6-naphthalate containing 0.02% by weight of calcium carbonate particles having an average particle diameter of 0.6 μm and 0.2% by weight of silica particles having an average particle diameter of 0.1 μm without adding acicular iron oxide Was dried at 180 ° C. for 5 hours and then supplied to an extruder hopper to obtain a biaxially oriented film having a thickness of 4.5 μm in the same manner as in Example 1. Table 1 shows the properties of the obtained polyester resin composition and biaxially oriented polyester film.

[Comparative Examples 2 to 5 and Example 6]
A biaxially oriented film having a thickness of 4.5 μm was obtained in the same manner as in Example 1 except that the acicular iron oxide was changed as shown in Table 1. Table 1 shows the properties of the obtained polyester resin composition and biaxially oriented polyester film.

  PEN in Table 1 indicates polyethylene-2,6-naphthalate, and the content indicates the particle content in the resin composition. In addition, the diameter of calcium carbonate and silica showed an average particle diameter, and the shape was substantially spherical.

Claims (6)

  Acicular iron oxide having a diameter (D) of 0.01 to 2.5 μm, a length (L) of 0.1 to 10 μm, and an aspect ratio (L / D) of 4 to 100 is the weight of the polyester resin composition. A polyester resin composition characterized by being dispersed by 0.1 to 20% by weight as a reference.   The polyester resin composition according to claim 1, wherein the acicular iron oxide comprises iron oxide having an α-type crystal form.   The polyester resin composition according to claim 1, wherein the polyester resin is polyethylene-2,6-naphthalate or polyethylene terephthalate.   Acicular iron oxide having a diameter (D) of 0.01 to 2.5 μm, a length (L) of 0.05 to 10 μm, and an aspect ratio (L / D) of 4 to 100 is the weight of the polyester resin composition. A biaxially oriented polyester film comprising a polyester resin composition dispersed as a reference in an amount of 0.1 to 20% by weight.   The biaxially oriented polyester film according to claim 1, wherein the Young's modulus of either the film forming direction or the in-plane direction orthogonal to the film forming direction is in the range of 6 to 20 GPa.   The biaxially oriented polyester film according to claim 1, which has a thickness of 2 to 10 µm.