JPS59133246A - Orientated polyester film - Google Patents

Abstract

PURPOSE:The titled film excellent in slip property and abrasion resistance and low in scratching and chalking, prepared by adding specified BaSO4 and specified CaCO3 to a polyester containing ethylene terephthalate as the main repeating units. CONSTITUTION:A mixture is prepared by mixing a polyester at least 80mol% of the main repeating units of which comprise ethylene terephthalate with (A) 0.01-1.0wt% BaSO4 particles having an average particle diameter of 0.01- 1.5mum and a volume shape factor of the equation: f=nu/D<3> [wherein f is volume shape factor, nu is particle volume (mum<3>), and D is maximum projected area diameter of a particle (mum)], falling in the range of 0.08-0.25, and (B) 0.005- 0.1wt% CaCO3 particles having an average particle diameter of 0.5-5.0mum and a volume shape factor (greater than that of component A) of 0.08-0.40. The above mixture is molded into a film and stretched biaxially.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an oriented polyester film with excellent slip properties and abrasion resistance. In general, polyesters such as polyethylene terephthalate are used for S In addition to textiles and molded products, it is widely used in a wide variety of applications, including magnetic tape, photography, capacitors, packaging, and other films. When these films are used, their slipperiness and abrasion resistance are major factors that determine the workability of the film in the film forming process and the processing process for each application, as well as the quality of the product. In particular, when a magnetic layer is applied to the surface of a polyester film and used as a magnetic tape, the friction and abrasion between the coating roll and the film surface during application of the magnetic layer is extremely severe, and wrinkles and scratches are likely to occur on the film surface. Furthermore, even after the film coated with the magnetic layer is slit and processed into audio, video, or computer tapes, there are many guide parts, playback heads, etc. when pulling out from a reel or cassette, winding it up, or performing other operations. Significant friction and abrasion occurs between the layers, causing scratches and distortion, as well as the precipitation of white powdery substances due to abrasion of the surface of the polyester film.1
This is often a major cause of missing magnetic recording signals, that is, dropouts. Generally, to improve the slipperiness and abrasion resistance of a film, a method is adopted in which the surface of the film is made uneven to reduce the contact area with guide rolls, etc. A method of precipitating inert particles from the residue, a method of adding inert inorganic particles, etc. are used. Generally, the larger the particle size of these raw polymer particles, the greater the effect of improving slipperiness, but for precision applications such as magnetic tape, especially video, it is important that the particles are large. Since the irregularities on the surface of the film must be as fine as possible because they themselves can cause defects such as dropouts, there are currently demands to satisfy contradictory characteristics at the same time. The inventors of the present invention have developed the present invention as a result of intensive studies, particularly in view of the fact that the density of magnetic recording has been further promoted in recent years, and improvements in the slipperiness and abrasion resistance of base films for tapes are increasingly required. has been reached.

That is, in the present invention, polyester whose main repeating unit is ethylene terephthalate has an average particle size of 0.01.
0.01 to 1.0% by weight of barium sulfate particles having a volume shape factor of 0.08 to 0.25 and a mean particle diameter of 0.5 to 5.0 μm and a volume shape factor of 0.08 to 0.25 This is an oriented polyester film containing 0.005 to 0.1 it% of calcium carbonate particles having a large volume shape coefficient of o, oa to 0.40.

[However, 1 volume shape factor 1 is expressed by the following equation.

f = ν/D where ν is the particle volume (μ'') and D is the maximum diameter of the particle in the projected plane (Cμm).] The oriented polyester film of the present invention has good slip properties and abrasion resistance, Significantly less scratches and white powder generation.

Features of the oriented polyester film in the present invention are ・2
The point is that particles having specific particle diameters and volumetric shape coefficients of specific component particles of different types are used in combination, one by one. That is, the results were found only when a specific amount of barium sulfate particles having a specific particle size and volumetric shape coefficient and a specific amount of calcium carbonate particles having a specific particle size and volumetric shape coefficient coexisted in the film. be.

In the present invention, the polyester constituting the oriented polyester film is a polyester in which 80 mol% or more of the main repeating units are ethylene terephthalate,
Other components include dicarboxylic acids, glycols, oxycarboxylic acids, etc. that can be copolymerized with this product.
It may be copolymerized in less than mol%. In the present invention, the average particle size of the barium sulfate particles, which is the first component of the inert inorganic particles to be added, is 0.01 to 1.5 μm.
10.1 to 1.2 μm is more preferable, and 0.2 to 1.0 μm is particularly preferable. Also, the amount added is
It is necessary to set it as 0.01-1.0 weight% with respect to this polyester, and 0.1-0.6 weight% is more preferable. Second
The average particle size of the component calcium carbonate particles is 0.5 to 5.
．． The particle size is required to be in the range of 0 μm, more preferably 0.5 to 1.5 μm, and needs to be larger than the average particle size of the barium sulfate particles that are the first component. The amount added should be 0.005 to 0.1% by weight based on the polyester, and more preferably 0.03 to 0.1% by weight.

If the barium sulfate particles, which are the first component, and the calcium carbonate particles, which are the second component, each deviate from their appropriate ranges, the objective of the present invention is to prevent scratches by imparting good slipperiness and abrasion resistance. This results in either no effect being achieved, or inability to prevent the contamination of coarse particles, which causes dropout due to the particles themselves.

The relationship between the amounts of barium sulfate particles and calcium carbonate particles added may be within a range that satisfies the conditions specified above in 1. However, the amount of barium sulfate particles added, which are small in size, is large in size. More preferable results can be obtained if the amount is greater than the amount of calcium carbonate particles added.

The average particle diameter referred to herein refers to the diameter at the cumulative 50% point of the equioblate particle size distribution calculated based on the Stokes formula.

Next, the reason why the particle composition of the present invention is preferable will be described.

Many proposals have been made for adding inert particles to polyester in order to improve the slipperiness and abrasion resistance of polyester films for magnetic tape bases. The requirements have not yet been fully met. Therefore, the present inventors conducted a detailed study on the relationship between the characteristic values of various types of particles (particle size, shape, and hardness), the amount added, and the film characteristic values to improve slipperiness and abrasion resistance. Preferably, the particles are spherical or cubic and have little anisotropy, and the average particle size is small in the range of 0.01 to 1.5 μm, in the range of 0.5 to 5.0 μm, and in the range of 0.11 μm. It has been found that the most preferable state is the coexistence of two types of particles having larger particle diameters than the above particles.

Calcium carbonate, which has a volumetric shape coefficient o, oa~0.40 in terms of shape, hardness, etc., is suitable for these conditions.
In particular, it has been found that heavy calcium carbonate particles containing mainly calcite crystals are most preferable.

However, because this heavy calcium carbonate is produced by mechanically crushing limestone, the lower limit of its average particle size is 0.5 μm, which corresponds to the larger particle size of the two required particles. The problem is that you can only get things.

Next, barium sulfate particles having a volume shape coefficient of 0.08 to 0.25 are exemplified as particles suitable for the purpose in terms of shape 1 hardness and the like. Barium sulfate particles can have a small particle size of about 0.01 to 1.5 μm by appropriate classification treatment or grade selection.

For the reasons mentioned above, barium sulfate has good sliding properties and wear resistance, and as a large particle component, the volume shape coefficient is 0.08 to 0.
Most preferably, 40% calcium carbonate is used in combination as in the particle composition of the present invention.

In the present invention, the inert particles may be added to the polyester in either a slurry or powder form at any stage in the polyester production process, but they can be used to prevent particle scattering, uniformity, etc. From this point of view, it is desirable to disperse it in the form of a slurry in ethylene glycol, which is a type of polyester component, and add it in a predetermined amount. Furthermore, when dispersing in a slurry form, it is important to take care to reproduce the original primary particle size of the inert particles as much as possible and to avoid the presence of coarse agglomerated particles.

In particular, the presence of coarse particles of 10 μm or more causes dropouts when used as a magnetic tape, so it is necessary to remove them by appropriate means such as classification or separation.

For the average particle size measurement, the value at the cumulative 50% point of the equioblate sphere diameter distribution obtained by a centrifugal sedimentation type particle size distribution analyzer manufactured by Takasu Seisakusho was adopted. In addition, evaluation of film slipperiness and abrasion resistance was performed by rubbing a tape-like roll with narrow film slits against a metal guide roll and running it for a long time (at high speed). The magnitude of the tape tension and the amount of white powder generated on the surface of the guide roll were each evaluated on a five-point scale and expressed in the following rankings.

The amount of coarse particles in the film can be determined by sandwiching a small portion of the obtained film between two cover glasses, melting it, rapidly cooling it, and pressing it.The phase contrast microscope image of the obtained sample is analyzed using an image analysis processing device Luzetx 500 ( (manufactured by Nippon Regulator) and ranked according to the number of secondary agglomerated particles having a maximum length of 10 μm or more in one particle image as follows.

Grade 1: Many coarse particles Grade 2: Slightly more coarse particles Grade 3: coarse particles, normal Grade 4: No coarse particles Grade 5: No coarse particles The following is an example of roasting: L7 Fubinrou Σ Kinmei 4ro.

The mixture was uniformly dispersed in ethylene glycol, and the streaks were added to a reaction system for producing polyethylene terephthalate by a conventional method in the required amounts listed in Table 1, and the reaction was completed to contain barium sulfate particles and calcium carbonate particles. Polyethylene terephthalate was obtained. The obtained polyethylene terephthalate was then extruded at 285°C, longitudinally stretched at 90°C with a draw ratio of 3.5 times, transversely stretched at 95°C with a draw ratio of 3.6x, and heat treated at 220°C to obtain a thickness of 15 μm. A biaxially stretched polyester film was obtained.

The slipperiness, abrasion resistance, and amount of coarse particles of the various films obtained were evaluated, and it was found that all the films obtained under conditions satisfying the present invention had very desirable qualities for use in magnetic tapes. .

Examples 7 to 9 and Comparative Examples 5 to 6 The same methods as Examples 1 to 6 were used, except that the average particle diameters of precipitated barium sulfate particles and heavy calcium carbonate particles were those listed in Table 2. A biaxially stretched polyester film was obtained. When the slipperiness, abrasion resistance, and amount of O/coarse particles of the various films obtained were evaluated, it was found that all the films obtained under the conditions satisfying the present invention had very desirable qualities for use in magnetic tapes. Was.

Comparative Examples 7 to 11 As inert inorganic particles to be added, 1 average particle size is 0.5 μm
Precipitated barium sulfate particles with a volume shape factor of 0.21 were
．． 25% by weight, average particle size 1.0 μm, volume shape coefficient 0.
0.05% by weight of heavy calcium carbonate particles of No. 24 1 0.25% by weight of kaolin particles with an average particle size of 0.5 μm and a volume shape coefficient of 0.065, and 0.05% by weight of silica particles with an average diameter of 1.5 μm % and 0.50 wt % of silica particles with an average particle size of 0.04 μm were added alone, respectively.
Biaxially stretched polyester films were obtained in the same manner as in Examples 1 to 6.

When the slipperiness, abrasion resistance, and amount of coarse particles of the obtained various films were evaluated, the results shown in Table 3 were obtained, and all of them were of a quality that could not be said to be sufficient for use in magnetic tapes, and these are conditions that satisfy the present invention. It can be seen that the preferred quality for magnetic tapes cannot be obtained in other cases.

Table 2 Table 3 Patent applicant: Toyobo Co., Ltd.

Claims (1)

[Scope of Claims] The main repeating unit is polyester consisting of ethylene terephthalate, and the average particle size is 0.01 to 1.5 μm.
0.01-1.0% by weight of barium sulfate particles with a volume shape factor of 0.08-0.25 and an average particle size of 0.
．． Oriented polyester film 0 containing 0.005 to 0.1% by weight of calcium carbonate particles having a diameter of 5 to 5°0 μm, larger than the barium sulfate particles, and a volume shape coefficient of 0.08 to 0.40 [However, , the volumetric shape factor f is expressed by the following equation. f=ν/D3 where ν is the particle volume (μ, I) and D is the maximum diameter (μTn) in the projection plane of the particle0]