JPS62185719A - Polyester film for magnetic recording medium - Google Patents

Abstract

PURPOSE:To obtain the titled film having a smooth surface and excellent abrasion resistance and protrusion deformation resistance, by extruding a mixture of a poly(tetramethylene glycol) component with a poly(butylene tetraphthalate) and/or poly(butylene isophthalate) component. CONSTITUTION:A polyester of an intrinsic viscosity >=0.40, obtained by mixing a poly(tetramethylene glycol) component (a) with a poly(butylene terephthalate) and/or poly(butylene isophthalate) component (b) so that the relationships of formulas I-III [wherein A is the wt% of component (a) based on the polyester film and B is the wt% of component (b) based on the polyester film] may be simultaneously satisfied is melt-extruded at 280-300 deg.C to obtain a film. This film is cooled to 70 deg.C or below, stretched in the lengthwise and crosswise directions at an area draw ratio >=4 and heat-treated at 120-250 deg.C to obtain a biaxially stretched polyester film for magnetic recording media, having a centerline average roughness of 0.003-0.023mum.

Description

[Detailed description of the invention]

<Industrial Application Field> The present invention relates to a polyester film for magnetic recording media. Specifically, the present invention relates to a polyester film having a smooth surface, excellent abrasion resistance and ejection deformation resistance, and having few coarse protrusions. More specifically, the present invention relates to a nine-biaxially oriented polyester film which is particularly suitable as a base film for magnetic recording media, and which has such characteristics and extremely excellent workability and productivity during film production. <Prior art and problems to be solved by the invention> Conventional polyester films have excellent properties. In particular, biaxially oriented poly(ethylene terephthalate) film has excellent elastic modulus, flatness, dimensional stability, etc. compared to other films, and is also available on the market at a relatively low price, making it suitable for magnetic recording. It is now indispensable as a base film for media.Nowadays, the progress of magnetic recording media in recent years has been remarkable.For example, magnetic tape, especially video tape, can be used for long periods of time due to higher recording density. Performance improvements such as recording and miniaturization of media are progressing rapidly.Accompanying this, the requirements for modifying the base film have become even more severe. I; ~0.0
/! There is a need for smoothing more than ever before, such as μm. In other words, short wavelength recording methods have been adopted to increase the well-known high recording density, and the thickness of the magnetic layer, which was conventionally around jμm, has been changed to about aμm to reduce output loss. K11JI will be implemented. As this film becomes thinner, the surface shape of the base film will be reflected on the surface of the magnetic layer.In order to improve the electromagnetic conversion characteristics, it is essential to make the surface of the base film even smoother. be. However, as is well known in the past, the smoother the surface of the base film, the worse the coefficient of friction between the films or the friction and abrasion resistance with various base materials. Abrasion particles are likely to be generated during the magnetic layer coating process and the magnetic layer coating process, and this abrasion powder adheres to the film surface and causes the coating to fail when the magnetic layer is coated, causing dropouts. Therefore, in order to achieve base film smoothing on an industrial scale, there are many other challenges that must be overcome.
It was an extremely difficult technique. Under these circumstances, the present inventors have already proposed a method for simultaneously achieving the contradictory film properties of smoothness and abrasion resistance in Japanese Patent Applications Shobo-Co J6-66 and Sho-60-
Ko J! 697 etc. That is, these methods contain poly(alkylene glycol) in polyester.
By incorporating a small amount of , it is possible to significantly improve abrasion resistance, ejection deformation resistance, and even scratch resistance.This is an especially excellent formulation for base films for magnetic recording media that aim to improve performance. However, even in this invention for producing a film having such excellent properties, when the film manufacturing aspects such as productivity and workability are reviewed, there still remain aspects that require improvement. That is, in the normal base film manufacturing process, when converting a molten polymer into an amorphous sheet, the so-called electrostatic cooling method is preferably employed, but poly(
When a molten polymer containing a relatively large amount of alkylene glycol is extruded, for example, JP-A-Sho! As described in Japanese Patent No. t-/773/R, it is a known fact that the adhesion of the bath-melted polymer to the cooling drum decreases, resulting in poor productivity. The invention provided above is no exception; for example, the amount of poly(ethylene glyco-/I/) most preferably used in this invention is O,OS~O,
It was found that the problem was the worst in the JWT area, and the company was forced to take measures by reducing production speed. Adoption of such electrostatic application cooling method is now an indispensable prescription in magnetic recording media applications where quality requirements for thickness unevenness are particularly strict.Improving adhesion is also necessary and important from the viewpoint of productivity. That was the case. Conventionally, it has been known that as a method of improving such adhesion, it is necessary to lower the specific resistance of the polyester composition when it is melted, as described in, for example, Japanese Patent Publication No. 7-440-31. In order to lower the specific resistance, alkali metals, alkaline earth metals, or compounds thereof are contained in polyester. Furthermore, Japanese Patent Application Laid-Open No. 69-3333/1989 provides a formulation in which a metal compound and a phosphorus compound coexist in a polyester composition containing poly(alkylene glycol) to lower the resistivity during melting. In any case, a method is used in which a metal compound is dissolved in polyester. However, when these methods are applied to increase productivity, it is necessary to add a large amount of metal compounds in order to sufficiently lower the resistivity. This method is not necessarily suitable for use in magnetic recording media because it is precipitated as coarse particles in polyester, and when formed into a film, many coarse protrusions are formed on the surface, causing dropouts. Thus, a base film for magnetic recording media,
A polyester with a low resistivity during melting and few coarse particles in a formulation containing a small amount of poly(alkylene glycol) that has a smooth surface with an Ra of 0.00 j to 0.0 / , t μm and has abrasion resistance. If a composition can be obtained, its industrial value in terms of productivity is extremely large. Means for Solving Problems> In view of the above circumstances, the present inventors have developed a biaxially oriented polyester film for magnetic recording media, which is a film that is smooth and has wear resistance, and that reduces the electrostatic charge during film formation. As a result of extensive research on methods for increasing productivity using applied cooling, we have discovered a poly(alkylene glycol) compounding system that has low specific resistance when melted, and have arrived at the present invention. That is, the gist of the present invention is to combine poly(tetramethylene glycol) component (A) and poly(butylene terephthalate) and/or poly(butylene isophthalate) component CB) so as to simultaneously satisfy the following formulas (1) to (I). The present invention relates to a biaxially oriented polyester film for magnetic recording media, which is characterized in that it is blended with the following. o, oos≦A≦j 11@611
1111@@11 (1) o, ooz≦ B≦
lQ 1III fist...@ number・ (lI)lIde ≦A/B≦9/7 ・・・−・・・・ (ffl)
The present invention will be explained in more detail below. The polyester as used in the present invention is a product obtained by polycondensing aromatic dicarboxylic acids such as terephthalic acid, isophthalic acid, naphthalene, and 6-dicarboxylic acid or their esters with glycols such as ethylene glycol, diethylene glycol, and neopentyl glycol. It is a polyester manufactured by These polyesters are produced by directly reacting aromatic dicarboxylic acids and glycols, or by transesterifying alkyl esters of aromatic dicarboxylic acids and glycols, followed by polycondensation, or by reacting aromatic dicarboxylic acids with glycols. It can also be produced by methods such as diglycol ester polycondensation. Typical examples of such polymers include poly(ethylene terephthalate) and poly(ethylene-λ,6-naphthalate). This polymer may be a homopolymer or may be a copolymer of a third component. In any case, in the present invention, ethylene terephthalate units and/or ethylene-J,
A-Naphthalate unit is more than 0m01es, preferably? Polyester having an Omo content of 1% or more is preferred. Furthermore, in the present invention, if the degree of polymerization of the polyester is too low, the mechanical properties will deteriorate, so the intrinsic viscosity of the polyester is O0.
3 or more, preferably O, j O to O, de O1, more preferably O, jj to o, trz. In the present invention, a biaxially oriented film is produced using such polyester as a raw material, and the method is as follows. That is, polyester is extruded at 0 to 300°C.
The material is melted at a temperature in the range of about 7.degree. C., extruded into a sheet from a die, cooled to a temperature of about 7.theta. Next, the sheet-like material is stretched in the longitudinal and transverse directions to an area magnification of 9 times or more, preferably 9 times or more to obtain a biaxially oriented polyester film, and the film is further heat-treated at a temperature of 10S-2Sθ°C. Especially manufactured. In this way, the biaxially oriented polyester film of the present invention is produced, and the centerline average roughness (Ra) of the film is o, oo3 to O6θ, Jμm1, preferably O8
θOA; ~0.0/! μQ, more preferably 0.00 μm to o, oi, y μm. If Ra is less than 0.007 μm, the film surface will be too smooth, and even if the special formulation of the present invention is applied, the handling workability in the film manufacturing process and magnetic layer coating process cannot be adequately addressed, and the film surface will be too smooth for bank coating, etc. It is difficult to put it into practical use unless special treatment is performed. On the other hand, Ra is 00013μm
If you use a videotape or magnetic disk,
The electromagnetic conversion characteristics are poor, and it becomes difficult to achieve high recording density. In the present invention, the following method may be employed to obtain a film that provides such surface roughness. That is, a method in which fine inert particles are blended in advance with the polyester that is usually used for the film is simple and preferably employed. There are two main ways to do this. One of them is the additive particle method, which uses kaolin, talc,
Calcium carbonate, magnesium carbonate, barium carbonate, calcium sulfate, barium sulfate, lithium phosphate, calcium phosphate, magnesium phosphate, aluminum oxide,
In this method, silicon oxide, titanium oxide, or a polymer compound having a crosslinked structure is crushed and classified as necessary, and then added and blended at any stage from the polyester manufacturing process to the melt extrusion process during film formation. This method is suitable for use in the present invention because the particle size can be easily adjusted and a film with the desired surface roughness can be easily designed, but the manufacturing process is complicated and the precipitated particle method described below is Compared to this, it has the disadvantage that coarse particles are easily mixed in. Another method is the precipitated particle method, in which metal compounds such as lithium compounds, calcium compounds, and magnesium compounds that are soluble in ethylene glycol or polyester oligomers are added to polyester during polyester production, and then the mixture is produced in the presence of phosphorus compounds or This is a method in which fine particles are precipitated in the absence of carbon dioxide. It goes without saying that if these metal compounds are added at the beginning of the transesterification reaction, they can also serve as catalysts. Although it is not necessarily easy to control K to a desired particle size in this method, the particle size distribution of the particles is extremely sharp and therefore there is little co-existence of coarse particles, so it is preferably employed in the present invention. Furthermore, since the specific resistance of the polyester resin obtained by this method during melting is generally higher than that of the polyester resin obtained by the additive particle method, the effects of the present invention are remarkable and it is particularly preferably adopted. The method for producing polyester resin using the precipitated particle method used in the present invention will be exemplified below. That is, the transesterification reaction in polyester production is carried out in the presence of a lithium compound and a calcium compound,
After completion of the transesterification reaction, one or more compounds selected from the group of phosphoric acid, phosphorous acid, or their fullyl esters or aryl esters are added in an amount of o, b to 3 times equivalent, preferably 0. υ can be obtained by adding 1-1 times equivalent, preferably 0.9 to /j times equivalent, and then carrying out a multi-fringe reaction. The lithium compound and the lithium compound used in this case may be any compound as long as it dissolves in the transesterification product. The equivalent ratio of the phosphorus compound to the metal compound is expressed by the following formula (% formula %) (wherein PsOa and Ll represent the number of moles of the phosphorus compound, calcium compound and j-tium compound, respectively). By using a metal compound and a phosphorus compound in combination as described above, a resin in which particles containing a metal element and a phosphorus element are precipitated in polyester can be obtained. In the present invention, particles for developing the specific surface roughness necessary for the present invention are blended into polyester by such a method, but it is not possible to adopt either the additive particle method or the precipitated particle method. Also, the particle amount is 0.001 to Jwt%, preferably 0.0/Jwt% based on the polyester.
~0. tvtt, more preferably 0. θ/~o, 5
It is best to select from the wt96 range. Further, the average particle diameter of such particles is usually 0.00 to 2 μm, preferably 0.00 μm.
It is selected from the range of 7 to -μm. Note that, naturally, in the present invention, one of the above methods may be used in combination. Next, the formulation is related to improving the main attributes and workability when using the electrostatic cooling method without impairing the wear resistance and ejection deformation resistance that are the main focus of the present invention. A specific amount of poly(tetramethylene glyco-/I/) component (A) and poly(butylene terephthalate) and/or poly(butylene isophthalate) component CB) are made to coexist in a polyester film having such surface roughness. It is essential that both component (A) and component (13) be contained, and the conditions for their coexistence must also be within a certain range. That is, the present invention adds a poly(tetramethylene glycolone component) to the finally obtained polyester film.
A) The child is o, oos~5wt, preferably θ, θ~
If the weight is low, the poly(butylene terephthalate) and/or poly(butylene isophthalate) component CB) is o, oos~10wt, preferably o, os~, t
Component (A) and component CB contained in wt% and coexisting
) content ratio A/B must be //9 to 9//. The content of such component (A) and component CB) is o, oos
When wtt is less than 6, almost no improvement effect on wear resistance and ejection deformation resistance is observed, and component (A) fik!
r wt%, and component CB)-jft/Ow
If the amount exceeds t%, the effect of improving the film properties reaches a saturated state, and the thermal stability during drying or melting in the film manufacturing process deteriorates, which may even affect the mechanical properties of the polyester film. This is not desirable. In addition, in the present invention, it is essential that the component CA) and the component (E) coexist, and the content ratio A/B is /9
~? When // is outside the range, strangely, no improvement effect on wear resistance and ejection deformation resistance is shown. The molecular weight of the component (A) used in the present invention, that is, poly(tetramethylene glycol) is not particularly limited, but is usually 300 to t, σ00, preferably da00 to b,
000. More preferably 00~. y, ooo. In addition, component CB used in the present invention, that is, poly(butylene tere-7-thaleton) and/or poly(butylene in-7-thalerate) is produced by polycondensing terephthalic acid, isophthalic acid and its ester, and/or Hiro-butanediol. This polyester is produced by directly reacting terephthalic acid and/or isophthalic acid with 1.darptanediol, and can also be produced by directly reacting terephthalic acid and/or isophthalic acid with 1.darptanediol. It can also be produced by polycondensation after transesterification, or by polycondensation of ditetramethylene glycol ester of terephthalic acid and/or isophthalic acid.This polyester may be a homopolymer, or a third component or by copolymerizing antioxidants,
It may also contain additives such as antistatic agents and ultraviolet absorbers. In any case, in the present invention, the amount of butylene terephthalate and/or butylene inphthalate units is 10 mol or more, preferably 10 mol or more. It is preferable to have Omob% or more. Further, the intrinsic viscosity of the component (B) is preferably 00 or more, preferably o, ro-o, de0, and more preferably O, ZS to o, rs. The method of blending is not particularly limited, but it is preferable to blend component (A) and component CB) in advance, considering the small amount of them blended. . To blend component CB) in advance, add component (CB) during melt polycondensation.
It may be carried out in the presence of A), or a triblend method using an extruder or the like may be used. That is, component (A) and component (B) may be separate, or (A) and (B) may be copolymerized. If the amount of each component is even smaller, a so-called masterbatch method may be used to manufacture a master chip in which predetermined amounts of component (A) and component CB) are blended with polyester. The magnetic recording medium referred to in the present invention refers to magnetic tapes for video, audio, digital audio, computer memory, etc. for consumer use or broadcasting stations, magnetic disks for floppies, Mavica (still electrophotography), etc. Refers to cards, etc. <Effects of the Invention> A specific range of poly(tetramethylene glycol) component (A) and poly(butylene tre-7-thaletone and/or poly(butylene isophthalate) component C) obtained in this way
If a polyester composition co-containing B) is subjected to a film manufacturing process that employs an electrostatic cooling method, the adhesion to the cooling drum, which was the biggest drawback of poly(alkylene glycol) alone blended systems, can be improved. An excellent film can be obtained without any deterioration. In other words, such a decrease in adhesion is caused by, for example,
l! 13 Da S Publication and Tokukai Sho! ; As described in IO No. 7-/900', this leads to a phenomenon called bound bubbles in which air bubbles are drawn into the gap between the polyester composition sheet and the cooling drum, resulting in a significant deterioration in film quality. These trapped bubbles are a phenomenon that occurs when the rotational speed of the cooling drum is increased, and therefore, a decrease in adhesion is a factor that directly controls the production rate, so the method of the present invention does not cause a decrease in adhesion. has great industrial value, and its added value for base films for magnetic recording media is extremely large. It goes without saying that the present invention has excellent film properties such as abrasion resistance and anti-protrusion deformation in the recent trend toward smoothing base films for magnetic recording media. A base film for magnetic recording media that eliminates the formation of a large amount of metal compounds that were intentionally added to the polyester composition in order to adopt the electrostatic cooling method, and therefore has extremely few coarse protrusions when made into a film. It turned out to be of extremely high quality. In other words, as mentioned earlier, the formation of coarse protrusions on the film surface is a factor directly related to the dropout of the magnetic recording medium.
, a reduction in their number leads to a significant improvement in quality. As detailed above, the present invention simultaneously improves film properties, film quality, and productivity for magnetic recording medium base films, and has great industrial value. <Examples> Hereinafter, the present invention will be explained in more detail with reference to Examples.
The present invention is not limited to the following examples unless it exceeds the gist thereof. In addition, the measurement method of the strength characteristics in the present invention was carried out by the following method. Further, parts shown in the examples mean parts by weight. (1) Center line average roughness Ra (μrrL) Koita Institute ■
*Surface roughness measuring instrument 8111-. Using Type 7F', the test was carried out according to the method described in J. In addition, as detailed conditions, stylus diameter: μm, stylus pressure: 3
0■, cutoff value; 0. The Dttms measurement length was 3, the number of measurements was 1, and the average value of 70 points after cutting the maximum and minimum values was taken as the Ra value. (2) Evaluation of abrasion resistance Using the tape abrasion evaluation machine shown in Fig. 7, a polyester film with a width of 10 mm was run over a length of 11 mm, and a fixed bin shown in (1) in the figure [61 tI 1 house, The amount of abrasion powder adhering to the hard chrome plated 0.2S finish was visually judged and evaluated according to the following ranks. In addition, the film running speed is tom1 minute, and (If) in the figure
The initial tension detected by the tension pickup shown in was set to 3θott, and the angle θ of the film winding around the fixing pin (1) in the figure was set to / j j'. Rank ◎; Adhering wear particles are not observed at all. Rank ○: There is very little adhering abrasion powder, and there is no practical problem at all. Rank Δ: There is some adhering wear powder, which may be a problem when used for a long time. Ranks: There is an extremely large amount of attached abrasion powder, which poses a practical problem. (3) Evaluation of protrusion deformation resistance When winding the film, a certain amount of particles of approximately jμm are intentionally sandwiched between the films, and the number of turns required for the partial ring-shaped bulge in the film to disappear is counted, and A , B
The evaluation was divided into three ranks: , O. The one with the least number of windings, that is, the one with excellent anti-protrusion deformation properties, was ranked A. (4) Number of coarse protrusions The film surface was vacuum ablated with aluminum, and the number was measured using a two-beam method using an interference microscope. The number of protrusions exhibiting third-order or higher interference fringes was measured over 100 ctd at the measurement wavelength o and sq μm, and the coarse protrusion value was determined. (5) Specific resistance of polymer when melted (Ω・crrL)
According to the method described in JP-A No. 67-190090, the melting temperature of one polymer was set to 2 s'C, and the DC voltage was 100
The value immediately after applying V was taken as the specific resistance value at the time of melting. (6) Determination of the limit speed at which the electrostatic application cooling method can be applied Between the gold and the cooling drum surface, a diameter of 0.7
A tungsten wire electrode of Im is provided, and a DC voltage of A is applied.
kV is applied to impart an electrostatic charge to the molten sheet flowing between the wire and the cooling drum, causing it to adhere tightly to the cooling drum, thereby obtaining a substantially amorphous sheet. Then vertically J, 6x, horizontally 1
f(Q, Q times the stretching and heat treatment at 10°C to form a film. At this time, the rotational speed of the cooling drum was adjusted while adjusting the extrusion amount so that the final film thickness was 1-μm. As the speed is gradually increased, when the speed exceeds a certain level, a phenomenon called so-called bound bubbles enters the gap between the extruded sheet and the surface of the cooling drum. When these bound bubbles begin to enter By examining the rotational speed of the cooling drum, the limit speed for application of the electrostatic cooling method to the polyester composition was determined. (7) Evaluation of electromagnetic conversion characteristics First, the following magnetic paint was applied to the polyester film and dried. The magnetic layer was formed to have a film thickness of μm. That is,
1-Fe, O, 200 parts by weight, polycrethane resin JO parts by weight, nitrocellulose 10 parts by weight, salt-vinyl acetate copolymer 1
0 parts, lecithin St parts, cyclohexanone 100 parts
1 part of methyl inbutyl ketone, 100 parts of methyl imbutyl ketone, and 3001 parts of methyl ethyl ketone were mixed in a ball mill.
After mixing and dispersing for t hours, the polyincyanate compound j'' was added to form a magnetic coating, which was coated on a polyester film, magnetically oriented before the coating was sufficiently dry, and then dried. It was calendered and slit into a 772-inch width to make a videotape.The videotape thus obtained was manufactured by Matsushita Electric's NV-J.
Various electromagnetic conversion characteristics were regularly evaluated using a tOO video deck. That is, the VTR head output was measured using a synchroscope, and the VTR head output was measured at a measurement frequency of 1.5 megahertz, and the TG was measured using a scalar video noise measuring device (9-type 3R// manufactured by Sibank).
-7 type U? Video signal noise (13/N) when using the OA//noise unit was measured, and the relative value was expressed in decibels (dB) with the sample of Comparative Example 1 in Table 1 as θ decibels (aB). In addition, we played back the videotape that recorded the Hiro and Hiro megahertz signals, and counted the number of dropouts at 1S μsec -206B for about 20 minutes at the back dropout counter of Daeken Industry ■, and calculated the number of dropouts per minute. /=]<The converted value is shown. Comparative Examples 1 to 3 (Manufacture of polyester) 100 parts of dimethyl terephthalate, 70 parts of ethylene glycol, 0.0 parts of lithium acetate. / part and calcium acetate -
Charge 0.09 parts of aqueous salt into a transesterification reactor, and
The methanol was successively removed by increasing the temperature from °C to 7 °C, and the transesterification reaction was substantially completed in about 9 hours after the start of the reaction. Next, the reaction solution was transferred to a polymerization vessel, and 50,079 parts of triethyl phosphate and 0.0 parts of orthophosphoric acid were added. After adding 4 parts of ethylene glycol solution mixed with 4 parts of ethylene glycol, and further adding 0.0 parts of magnesium acetate tetrahydrate in the case of Comparative Example 3, 0.0 parts of magnesium acetate tetrahydrate were added. A polycondensation reaction was carried out. That is, after adding antimony trioxide, the temperature of the reaction system is -
While the temperature was gradually raised from j j 'C to rj C, the pressure was gradually reduced from normal pressure, and finally 3. , HIl
And so. After a period of time, return the system to normal pressure and remove the polyester.

I got [A]. The intrinsic viscosity of the obtained polyester is O,tS
S frame, internal particle observation shows average particle size o, b~o3μ
It is a very uniform particle of m, the particle cap is about θ, t
s wt%. (Production of masterbatch containing poly(ethylene chloride)) 1 part of polyester(a)tin and 0 parts of average molecular weight,
330 parts of polyester (ethylene glycol) was homogeneously triblended and melt-kneaded in an extruder at ??C to obtain a masterbatch (b). (Manufacture of polyester film) The thus obtained polyester (i.e. ) and masterbatch (b) were blended so that the amounts of poly(ethylene glycol) shown in Table 1 were obtained, and after blending them uniformly, they were melt-extruded at 90°C using an extruder and subjected to an electrostatic cooling method. An amorphous sheet was obtained at a cooling drum circumferential speed of -07Fl/mlr.Then, it was stretched 3.4 times in the machine direction, q and o times in the transverse direction,
Further, heat treatment was performed at IO° C. for 3 seconds to finally obtain a biaxially oriented polyester film having a film thickness/J μm. Table 1 shows the properties of the obtained film and the electromagnetic conversion properties when used as a videotape. The specific resistance of the sampled amorphous sheet during the film-forming process when melted at 2g k'G was
0"Ω・Me, comparative example-Gaza, 0×10・Ω・Me,
Comparative Example 3 had a value of λ, OX / 0"Ω.Furthermore, the circumferential speed of the cooling drum was gradually increased from 10 m/- while changing the extrusion rate so that the final film thickness was /-μm. When looking at the speed at which confined bubbles begin to enter, that is, the limit speed for application of the electrostatic cooling method, it was found that Comparative Example 1 was J 9 r.
rL/Ryu 1c, while the comparative example is J j 1rL/I
nn, Comparative Example 3 was j j 7Fl/m. Example 1 The poly(ethylene glycol)-containing masterbatch shown in Comparative Examples 1 to J was combined with the following poly(tetramethylene glycol) component (A) and poly(butylene terephthalate) and/or poly(butylene isophthalate) component CB. A film was obtained in the same manner as in Comparative Example 1, except that the blended masterbatch was changed to the following. (Production of blended masterbatch of component (A) and component (B)) Transesterification of go part of dimethyl terephthasheet, aO part of dimethyl iso-7-thalerate, l, 56 parts of Hiro-butanediol, and 0.06 part of titanium tetrabutoxide. The mixture was charged into a reaction vessel and heated from 10° C. to 170° C. to gradually distill out methanol, and it took 1.3 hours after the start of the reaction to substantially complete the transesterification reaction. After transferring the anti-iN to a polymerization reactor, 0.04 parts of titanium tetrabutoxide was added, and 1 part of poly(tetramethylene glycol) with an average molecular weight of l*ooo was added.
After adding 1.7 parts, a polycondensation reaction was carried out in a conventional manner. That is, poly

[Tetramethylene glycol] After adding,
The temperature of the reaction system was gradually raised from 210°C to 30°C, while the pressure inside the system was reduced from normal pressure, and finally
It was set as HI. After 3 hours, the pressure in the system was returned to normal, and a masterbatch (c) containing component (A) and component (E) was obtained. The intrinsic viscosity of the obtained polymer is Oo! Il de atatsu nine. One part of the thus obtained component (A) and component CB) blended masterbatch (2) and part of the polyester (1) obtained in Comparative Example 1 were uniformly tri-blended and subjected to an extruder. -g of amorphous sheet sampled during film processing
The specific resistance when melting at 5°C was i, 1xto''Ω・a. Also, the limit speed for application of the electrostatic cooling method was 17M, which was a much higher production speed than the comparative example, 23771/Rime. On the other hand, as shown in Table 1, it was confirmed that the film properties of this example were excellent in all aspects of abrasion resistance, protrusion deformation resistance, and number of coarse protrusions. Example 1 component (A) component (B) blended masterbatch (
c) In the production, the molecular weight of poly(tetramethylene glycol) in Example 3 was 67 parts, and in the case of Example 3, the molecular weight of poly(tetramethylene glycol) was
The ingredients used in manufacturing polyester film (
A) Component CB) Combination A film was formed and evaluated in the same manner as in Example except that the blending amount of the master patch (c) was changed to 1 part. The results of film properties etc. are shown in Table/. In either case, the limit speed for applying the 1# electric current application method is J9?7
1/In1l was used, and the same results as in Example 1 were obtained regarding the physical properties of the film. Example Hiroshi (Manufacture of polyester) 700 parts of dimethyl tere-7 tallate, 70 parts of ethylene glycol, and 0.0 parts of calcium acetate were charged into a transesterification can, heated from 130°C to 230°C, and methanol was accumulated successively. After a certain period of time, the transesterification reaction was substantially completed.Then, the reaction solution was transferred to a polymerization reactor, and the transesterification solution was mixed with phosphoric acid O, Oa and an average particle size of 0.49 μm.
After adding an ethylene glycol solution in which 0.3 part of calcium carbonate had been mixed and dispersed and 0.0 qS part of antimony trioxide, a polycondensation reaction was carried out in a conventional manner (as described in Comparative Example 1). The intrinsic viscosity of the obtained polyester (d) is 0
．． It was 6-23. (Manufacture of polyester film) 97 parts of polyester (d) thus obtained and Example J
Component (A) Component CB) Master Patch (C) obtained in
Three parts were uniformly dry blended to obtain a film in the same manner as in Examples 1 to 3. The resulting film had excellent abrasion resistance and anti-protrusion deformation properties, although the number of coarse protrusions was slightly increased. In addition, the specific resistance of the amorphous sheet when melted at txl
OgΩ・The limit speed for application of electrostatic cooling method is Da 11rL
Productivity was extremely improved compared to /IMt and Example/-J and Comparative Example. Comparative Example Comparative Example 1 Polyester (a) qt, part and average molecular weight -,000 poly(tetramethylene glycol 91.2
A film was obtained in the same manner as in Example 3. The properties of the obtained film are fi
As shown in /, the abrasion resistance and protrusion deformation resistance were poor, making it unsuitable as a base film for magnetic recording media. That is, it was found that blending only component (A) was ineffective in improving wear resistance. Comparative Example j Example/Component (A) Component (B) Master Patch (
-9 When producing poly(tetramethylene glycol)
Component (B) obtained in the same manner except that component (A) was not added.
) ゛ only masterbatchco, double part and polyester of Comparative Example 1 (a) 97. Tri-blend part A uniformly,
A film was obtained in the same manner as in Example 1. Like the comparative example, the obtained film had poor abrasion resistance, and it was found that blending only component (B) had no effect.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram showing a running system of a wear evaluation machine for planning wear resistance, and in the figure, CI) represents a fixed pin and (11) a tension pickup. Applicant Diafoil Co., Ltd. Agent Patent attorney Hase - 1 other figure, 1

Claims (1)

[Scope of Claims] (1) Poly(tetramethylene glycol) component (A) and poly(butylene terephthalate) and/or poly(butylene isophthalate) component ( A biaxially oriented polyester film for magnetic recording media, characterized in that it is blended with B). 0.005≦A≦5 (I) 0.005≦B≦10 (II) 1/9≦A/B≦9/1 (III) A: Poly( (2) The component (A) and component (B) are represented by the following formula (IV) ~
The polyester film according to claim (1), which satisfies (VI) at the same time. 0.05≦A≦2……(IV) 0.05≦B≦5……(V) 1/9≦A/B≦9/1……(VI)