JPH04198328A - Polyethylene-2,6-naphthalate film - Google Patents

Abstract

PURPOSE:To obtain the subject film having a specific plane orientation degree, containing specific amounts of aluminum oxide particles, etc., and calcium carbonate particles, etc., having excellent slittability and abrasion resistance and useful as a base film for magnetic recording medium. CONSTITUTION:A polyester produced by reacting naphthalene-2,6-dicarboxylic acid, etc., as main acid components with ethylene glycol as main glycol component is used as a raw material for the objective film. The film having a plane orientation degree of 0.255-0.28 is produced by compounding the polyester with (A) 0.02-1.0wt.% of silicon oxide and aluminum oxide particles having an average particle size of 0.03-0.2mum and consisting of agglomerate of primary particles having an average particle size of 0.005-0.08mum and (B) 0.005-0.3wt.% of crosslinked polymer particles or calcium carbonate particles having an average particle size of 0.2-0.8mum.

Description

Detailed Description of the Invention [Industrial Field of Application] The present invention provides a polyethylene-2,6-naphthalate film that has excellent slitting properties, abrasion resistance, and slipperiness and is particularly suitable as a base film for magnetic recording media. Regarding.

[Prior Art and Problems to be Solved by the Invention] At present, polyethylene terephthalate films are widely used as industrial films, especially as heath films for magnetic recording media. However, in recent years, there has been a demand for smaller sizes, longer recording times, and higher recording densities, and polyethylene-2,6-naphthalate films have been attracting attention as a potential solution to these demands.

However, according to the knowledge of the present inventors, such films have poor slit properties compared to polyethylene terephthalate films (and the electromagnetic properties often deteriorate due to swelling and powder falling off at the edges during slitting). It has been proposed to incorporate various particles to improve slipperiness and abrasion resistance, but this has not necessarily reached a practical level.

(Means for Solving the Problems) In view of the above problems, the present inventors conducted intensive studies and found that the degree of plane orientation of the film was kept within a certain range, and at the same time two specific types of particles were blended. consisting of polyethylene-2
, 6-naphthalate film can achieve this purpose, and have completed the present invention.

That is, the gist of the present invention is that the degree of plane orientation is 0.255 to 0.
．． 280 polyethylene-2,6-naphthalate film, the film having (i) an average particle size of 0.280;
0.005 to 0.08 μm, and one or more particles selected from silicon oxide and aluminum oxide having an average particle size of 0.03 to 0.2 μm. 0% by weight, and (ii) 0.005 to 0.3% by weight of one or more particles selected from crosslinked polymers and calcium carbonate with an average particle size of 0.2 to 0.8 μm. Characteristic polyethylene-2,6-
Exists in naphthalate film.

The present invention will be explained in more detail below.

In the present invention, polyethylene-2,6-naphthalate is obtained by performing an esterification reaction or transesterification reaction using naphthalene-2,6-dicarboxylic acid or its alkyl ester as the main acid component and ethylene glycol as the main glycol component. It refers to polyester obtained by performing a polycondensation reaction, but a part of it may be replaced with other components. For example, part of the acid component may be replaced with naphthalene-2,7-dicarboxylic acid, terephthalic acid, isophthalic acid, fucuric acid, adipic acid, sebacic acid, P-hydroxybenzoic acid or a lower alkyl ester thereof; , some of the glycol components are trimethylene glycol, tetramethylene glycol, hexamethylene glycol, neopentyl glycol, 1.4-
It may be substituted with cyclohexane dimetatool or the like. In any case, polyethylene-2,6-naphthalate as used in the present invention refers to polyester in which 80 mol% or more, preferably 90 mol% or more, of ethylene-2,6-naphthalate units.

In addition, the polyethylene-2,6-naphthalate film of the present invention refers to a biaxially oriented film using such polyester as a starting material, and the following known method is adopted as a manufacturing method. It is possible.

That is, polyester is usually extruded into a sheet from an extruder at 280 to 320°C, rapidly cooled to 90°C or less to form a substantially amorphous sheet, and then biaxially stretched or simultaneously biaxially stretched in length and width. In this case, the film may be stretched to an area magnification of 10 times or more, preferably 13 times or more, and more preferably 15 times or more so that the naphthalene rings are arranged more parallel to the film surface.

In this case, each stretching may be performed in multiple stages, or so-called re-stretching may be employed.

In any case, in the present invention, in order to improve the slitting properties, stretching conditions are selected from these to obtain a film having a certain limited degree of plane orientation. The degree of plane orientation is an index showing how parallel the naphthalene rings are arranged to the film plane, and this value is 0.255.
If it is less than that, the slitting properties will be insufficient and the NMi gas properties will not be improved.

If this value exceeds 0.280, although the slits are at a satisfactory level, the presence of minute notches will easily cause tearing, which is not preferable.

The preferable range of the degree of plane orientation is 0.258 to 0.275,
A more preferable range is 0.262 to 0.275.

In addition, in the film of the present invention, the average refractive index of the film is 1.666 to 1676 while satisfying the above degree of plane orientation.
, preferably in the range of 1.668 to 1.674. If the average refractive index is smaller than this range, the thermal shrinkage rate will increase, and if the average refractive index is larger than this range, the abrasion resistance will deteriorate.

One of the characteristics of the present invention is that the degree of plane orientation of the film is set within a certain range higher than usual, but in this case, the molecular chains are strongly oriented and at the same time high strength is achieved. This is advantageous in many cases, but on the other hand, the affinity between the film and the particles becomes poor. This is because voids are generated around the particles due to the strong stretching stress, making it easier for the particles to detach from the film surface. However, if the present inventors use agglomerated particles obtained by appropriately aggregating fine primary particles, even if the film has such a degree of plane orientation, it will be possible to impart appropriate slipperiness without impairing wear resistance. I found out that it is possible. The reason for this is not certain, but
In the case of agglomerated particles, the stretching stress is appropriately dispersed, making it difficult for the particles to fall off, and since the particles form relatively gentle protrusions, they provide favorable friction and wear characteristics that are different from those of single particles. Conceivable.

Specifically, it is an aggregate of primary particles having an average particle size of 0.005 to 0.08 μm, and the average particle size is 0.03 μm.
One or more particles selected from silicon oxide and aluminum oxide having a size of ~0.2 μm are used.

These particles (hereinafter referred to as "first group particles") can be obtained, for example, by a so-called pyrolysis method, and particles whose secondary particle size is within a desired range can also be obtained. These often form aggregates larger than 1 μm. Aggregates of appropriate particle size used in the present invention are, for example,
It can be easily obtained by crushing such coarse aggregates.

For the pulverization process, for example, a rondo mill, a ball mill, a vibrating rod mill, a vibrating ball mill, a pan mill, a roller mill, an impact mill, an agitation mill, a fluid energy mill, etc. can be used.

In addition, if necessary, ultrasonic dispersion treatment may be applied, but
If it is too strong, it will be dispersed to -order particles or a state close to it, so care must be taken. Of course, in the present invention, treatments such as classification and filtration may be used in combination.

If the average particle size of the aggregates is less than 0.03 μm, the slipperiness will not be significantly improved, and if this value exceeds 0.2 μm, coarse projections will often be present and the hardness of the particles will decrease. Perhaps because it is expensive, the wear and tear on the film slitting blade becomes significant.

In addition, in this invention, the average particle diameter of the primary particle which comprises such an aggregate is 0.005-0.08 micrometer. When this value is less than 0.005 μm, the aggregates often have very strong bonds, and even stretching stress hardly breaks the bonds, making it difficult to obtain the effects specific to the present invention. Moreover, if this value exceeds 0.08 μm, the aggregate particles will separate and fall off, deteriorating the electromagnetic properties.

Further, in the present invention, the amount of the first group of particles to be blended into the film is selected from the range of 0.02 to 1.0% by weight, preferably 0.04 to 0.7% by weight. If the amount is less than 0.02% by weight, the slipperiness and abrasion resistance will hardly be improved, and if this amount exceeds 1.0% by weight, the surface roughness will become too large.

In addition, in the film of the present invention, it is particularly preferable that aluminum oxide is contained, since in addition to the slipperiness and abrasion resistance, the scratch resistance, that is, the degree of resistance to scratching of the film surface, is significantly improved.

Furthermore, in the present invention, a certain amount of particles of the second group is present in order to improve the winding characteristics during film formation. That is, the average particle size is 0.2 to 0.8 μm, preferably 0.3 to 0.
．． 0.005 to 0.3% by weight, preferably 0.01 to 0.2% by weight of one or more particles selected from a 7 μm crosslinked polymer and calcium carbonate are blended.

In order to provide a relatively steep and constant level of protrusions on the film surface, these must be single particles, and their shape may be spherical, lumpy, oblate, etc., but they are close to monodisperse. Preferably.

For this purpose, the ratio of the weight average particle size to the number average particle size of these particles is 1.20 or less, preferably 1.10 or less,
More preferably, it is 1.05 or less.

Examples of crosslinked polymer particles include, for example, Japanese Patent Publication No. 59-5
A combination of a monovinyl compound having only one aliphatic unsaturated bond in the molecule and a compound having two or more aliphatic unsaturated bonds in the molecule as a crosslinking agent, as described in Publication No. 216. Examples of polymers include, but are not limited to, thermosetting phenol resins, thermosetting epoxy resins, thermosetting urea resins, Henzu guanamine resins, and the like. Preferably, these particles have a group capable of reacting with polyester. In addition, there are no particular restrictions on the method for producing such particles; for example, particles obtained by suspension polymerization are pulverized,
Classification may be used, or emulsion polymerization may be used. Furthermore, it may have a multilayer structure, or it may deform to some extent during stretching. Typical examples include (1) one or more compounds selected from acrylic acid, methacrylic acid and their alkyl esters, styrene and their alkyl derivatives; and (2) one selected from divinylbenzene and ethylene glycol dimethacrylate. Crosslinked polymer particles copolymerized with more than one type of compound are preferably used.

In addition, calcium carbonate particles are preferably produced by a synthetic method, for example, particles obtained by reacting a calcium hydroxide solution with a carbon dioxide-containing gas, as described in JP-A No. 59-69425. In addition to calcite-type calcium carbonate particles, vaterite-type calcium carbonate particles obtained by carrying out a similar reaction in alcohol can be suitably used. Of course, the manufacturing method is not limited as long as it satisfies the requirements necessary for the present invention.

The surface of these calcium carbonates may be treated in order to reduce solubility, improve dispersibility, and improve affinity for polyester. For example, JP-A-59-69426
Surface treatment agents such as those described in JP-A-1-256558 or JP-A-1-256558, particularly high-molecular polycarboxylic acids or their sodium salts and ammonium salts, can be effectively used.

The blending amount of the second group of particles in the polyester film is 0.005 to 0.3% by weight, preferably 0.0% by weight.
The range is from 0.06 to 0.1% by weight. If this amount is too small, the winding properties will not be improved, and if it is too large, the film surface roughness will increase and the electromagnetic properties will deteriorate.

In addition, in the present invention, the effect can be maximized by setting the dose of the second group of particles to 2 to 20 to 0.015 of the first group of particles.

In addition, in the present invention, as long as the purpose is not impaired,
Other lubricants may be used in combination, as well as colorants, antistatic agents, weathering agents, etc.

The film of the present invention is particularly suitable for use in magnetic recording media.
Although it can only be obtained by combining a specific degree of plane orientation and two sets of particle groups, the surface roughness of the film is usually 0.004 to 0.004 in terms of centerline average roughness (Ra).
0.015 μm, preferably 0.005-0.013
It is selected from the range of μm.

In addition, the film thickness is usually 3 to 2 for magnetic tape.
5 μm, preferably selected from the range of 4 to 15 μm.

〔Example〕

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.

The various physical properties of the present invention were measured by the following methods.

In the examples, "part" and "%" mean "1 part by weight" and "% j by weight," respectively.

(1) Average particle size and particle size distribution The particle sizes of the particles in the dry powder and slurry were measured using an electron microscope. The average particle size was calculated as the particle size (diameter) at a point where the weight fraction of the equivalent sphere was 50%. Note that this value is the weight average particle size, but the number average particle size is also determined at the same time.
This was used as a measure of the sharpness of the particle size distribution.

In addition, the particle size of the aggregates in the film was confirmed by observing the cross section of the film with an electron microscope.

(2) Winding Characteristics The appearance of the film roll surface and end face when the film was rolled up into a film roll was evaluated according to the following criteria.

(a) Rolls with almost uniform end faces with wrinkles and lump-like defects on the surface ○ (b)
There are almost no wrinkles on the roll surface, but there are some lump-like defects, and the end face is slightly uneven. △ (C) Roll surface has wrinkles and lump-like defects, or the end face is extremely uneven. × (3) Measuring the refractive index of the film Using an Atsube 2 refractometer manufactured by Atago Optical Co., Ltd., measure the maximum refractive index in the film plane (+!nr, the refractive index n in the direction perpendicular to it).
β, and the refractive index nα in the thickness direction of the film are measured,
The degree of plane orientation and the average refractive index were calculated according to the following formula. The refractive index was measured using sodium D line at 23°C.
I went there.

Average refractive index n-□ (4) Film surface roughness The centerline average roughness (Ra) was measured according to the method described in JIS BO601.

(5) Running property Wrap the film around a fixed hard chrome-plated metal pin (diameter 6 mm) and touch it at an angle of 135°C.
The film was run at a speed of 1 m/min under a load of 100 g, and the resistance force at the other end was measured, and the coefficient of friction of the film was determined using Euler's equation, which was used as a measure of runnability.

(6) Abrasion resistance Wrapping the film around a fixed hard cronin pin (diameter 6an), contacting it at an angle of 135°, speed 10m
The film was run over 1000 m at a tension of 200 g per minute, and the amount of white powder adhering to the pins was visually classified into the following four ranks.

Rank A: No adhesion Rank C: A small amount of adhesion Rank C: A small amount of adhesion (more than rank B) Rank D = Extremely large amount of adhesion (7) Slit property First, apply the following magnetic paint to the polyester film. A magnetic layer was formed so that the film thickness after drying was 2 μm. That is, 200 parts of magnetic fine powder, 3 parts of polyurethane resin
0 parts, 10 parts of nitrocellulose, 10 parts of salt-vinyl acetate copolymer, 5 parts of lecithin, 100 parts of cyclohexanone, 100 parts of methyl isobutyl ketone, and 300 parts of methyl ethyl ketone.
After 48 hours of mixing and dispersion in a ball mill, 5 parts of a polyisocyanate compound was added to form a magnetic paint, which was applied to a polyester film. Before the paint was sufficiently dried and solidified, it was magnetically oriented and then dried.

Next, this coated film was surface-treated using a supercalender and slit into 2-inch widths to make a videotape.

The slit properties at this time were classified into the following three ranks by observing the cross section of the slit portion with an electron microscope.

Rank C: There is almost no swelling in the small amount and the roll appearance is good.

Rank C: A small amount of bulge of about 0.1 to 0.3 μm is observed, and a small amount of powdery or elongated slit debris is observed.

Rank C: There is a bulge of 0.3 μ or more on the cross section,
Slit debris can be seen quite clearly.

(8) Electromagnetic properties The obtained videotape was run on a Matsushita Electric Co., Ltd. NV-3700 video deck, and the following magnetic tape properties were evaluated by a regular user.

VTR head output: The VTR head output was measured at a measurement frequency of 4 MHz using a synchroscope, and the relative value to the reference sample was expressed in decibels (dB).

Number of dropouts; Play back a videotape recording a 4.4 MHz signal, measure the number of dropouts at 15μsec -20dB for about 20 minutes using a dropout counter manufactured by Daiichi Industry ■, and calculate the number of dropouts per minute ( pcs/min).

Example 1 (Manufacture of particles) - Silicon oxide aggregates with a primary particle size of 0.03 μm were dispersed in ethylene glycol and gradually crushed with a sand grinder to obtain aggregates with an average particle size of 0.12 μm.

On the other hand, 3.2 parts of potassium persulfate and 0.004 parts of sodium lauryl sulfate were added to 1,500 parts of demineralized water, and then 60 parts of styrene, 120 parts of ethylene glycol dimethacrylate, and 20 parts of divinylbenzene were added, and the mixture was prepared by a conventional method. Emulsion polymerization was performed. The average particle size of the obtained particles was 0.40μ
m, the ratio of weight average particle size to number average particle size was 1.05.

(Manufacture of polyester) Next, 100 parts of dimethyl-2,6-naphthalate, 60 parts of ethylene glycol, and 0.08 parts of mag2 acetate.
A portion was placed in a reactor and transesterification was carried out. Next, 0.15 parts of the previously obtained silicon oxide aggregates and 0.05 parts of crosslinked polymer particles were added, and then 0.04 parts of ethyl acid phosphate and 0.04 parts of antimony trioxide were added. Polyethylene-2,6-naphthalate having an intrinsic viscosity of 0.55 was obtained by polymerization according to a conventional method. Next, solid phase polymerization was performed to increase the intrinsic viscosity to 0.60.

(Production of film) After drying the obtained polyester, it was melt extruded and an unstretched sheet was obtained using an electrostatic cooling method.

Then, in the vertical direction, 4.5 times at 130"C and 13 times in the horizontal direction.
Stretched 4.0 times at 0°C, further longitudinally stretched 1.15 times at 130"C, then transversely stretched again 1.15 times at 210"C, and heat set at 220°C to increase the thickness. A film with a thickness of 7 μm was obtained.

The results regarding the obtained film are shown in Table 1 together with the results of other Examples and Comparative Examples.

Examples 2 and 3 and Comparative Examples 1 to 3 A film was obtained in the same manner as in Example 1, except that the particles added, the degree of plane orientation of the film, and the average refractive index were changed as shown in Table 1, and then a magnetic tape was manufactured. did.

While the films of Examples have excellent running properties and abrasion resistance, as well as the electromagnetic properties of the final magnetic tape, the film of Comparative Example 1, which does not contain particles of the second group, has poor winding properties and running properties. It was inferior in strength and abrasion resistance, and the performance of the magnetic tape was also inferior. Furthermore, although Comparative Example 2 satisfied the requirements for the particle system, the degree of plane orientation was low, resulting in poor slitting performance and frequent sludge and stubble-out. Comparative Example 3 is an example in which single particles were used as particles, and the electromagnetic properties were particularly deteriorated due to the lack of affinity of silicon oxide with polyester.

/ [Effects of the Invention] The film of the present invention has improved slitting properties, abrasion resistance, and slipperiness by adjusting the degree of plane orientation and particle system within a certain range, and is particularly suitable for magnetic recording. In particular, it can be suitably used for high-density recording, for example, as a hair film for so-called metal tapes and vapor-deposited tapes, so its industrial value is high.

Claims (1)

[Claims] (1) A polyethylene-2,6-naphthalate film having a degree of plane orientation of 0.255 to 0.280, the film comprising: (i) a primary particle having an average particle size of 0.005 to 0.08 μm; 0.02 to 1.0% by weight of one or more particles selected from silicon oxide and aluminum oxide, which are aggregates of particles and have an average particle size of 0.03 to 0.2 μm, and (ii) Polyethylene-2,6 characterized by containing 0.005 to 0.3% by weight of one or more particles selected from crosslinked polymers and calcium carbonate having an average particle size of 0.2 to 0.8 μm. −
naphthalate film.