JP2969932B2 - Polyethylene-2,6-naphthalate film - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention is excellent in slitting property, abrasion resistance and slipperiness,
Particularly, the present invention relates to a polyethylene-2,6-naphthalate film suitable as a base film for a magnetic recording medium.

[Problems to be solved by conventional technology and invention]

At present, polyethylene terephthalate films are widely used as industrial films, especially as base films for magnetic recording media. However, in recent years, there has been a demand for smaller size, longer time, and higher recording density, and polyethylene-2,6-naphthalate film has been receiving attention as a solution to this.

However, according to the knowledge of the present inventors, such a film has a poor slitting property as compared with a polyethylene terephthalate film, and the electromagnetic characteristics often deteriorate due to swelling or powder dropping of the end portion at the time of slitting. Although it has been proposed to mix various particles in order to improve the slipperiness and abrasion resistance of the film, it has not yet reached a practical level.

[Means for solving the problem]

In view of such a problem, the inventors of the present invention have conducted intensive studies and as a result, have found that a polyethylene-polyethylene film obtained by keeping the degree of plane orientation of a film within a specific range and simultaneously mixing two specific particles of a specific type.
The inventors have found that a 2,6-naphthalate film can achieve such an object, 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.
Is a polyethylene-2,6-naphthalate film, wherein the film is (i) 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 to 0.2 μm 0.02 to 1.0% by weight of one or more particles selected from silicon oxide and aluminum oxide, and (ii) one or more particles selected from a crosslinked polymer having an average particle size of 0.2 to 0.8 μm and calcium carbonate. A polyethylene-2,6-naphthalate film characterized by comprising 0.005 to 0.3% by weight.

 Hereinafter, the present invention will be described in more detail.

The polyethylene-2,6-naphthalate in the present invention refers to naphthalene-2,6-dicarboxylic acid or an alkyl ester thereof as a main acid component, and after performing an esterification reaction or a transesterification reaction with ethylene glycol as a main glycol component, It refers to a polyester obtained by performing a polycondensation reaction, but a part thereof may be replaced with another component. For example, a part of the acid component may be replaced with naphthalene-2,7-dicarboxylic acid, terephthalic acid, isophthalic acid, phthalic acid, adipic acid, sebacic acid, p-hydroxybenzoic acid or a lower alkyl ester thereof, or A part of the glycol component may be replaced with trimethylene glycol, tetramethylene glycol, hexamethylene glycol, neopentyl glycol, 1,4-cyclohexanedimethanol, or the like. In any case, the polyethylene-2,6-naphthalate referred to in the present invention refers to a polyester in which at least 80 mol%, preferably at least 90 mol%, 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 a polyester as a starting material, and the following known method is used for producing the film. I can do it.

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

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 slit property, the stretching conditions are selected so as to obtain a film having a limited degree of plane orientation. The plane orientation degree is an index indicating how parallel the naphthalene rings are arranged on the film surface. If this value is less than 0.255, the slit properties are insufficient and the electromagnetic properties are not improved. On the other hand, if this value exceeds 0.280, although the slit is at a satisfactory level, it is not preferable because the presence of fine notches easily causes tearing. A preferred range of the degree of plane orientation is 0.258 to 0.275, and a more preferred range is 0.262 to 0.275.

In the present invention, it is preferable that the average refractive index of the film is in the range of 1.666 to 1.676, preferably 1.668 to 1.674, while satisfying the above-mentioned degree of plane orientation. When the average refractive index is smaller than this range, the heat shrinkage increases, and
If the average refractive index is larger than this range, the wear resistance will deteriorate.

In the present invention, there is one of the characteristics in such a manner that the degree of plane orientation of the film is set to a specific range higher than usual, but in this case, the molecular chains are strongly oriented and at the same time high strength is achieved. It is often convenient, 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 strong stretching stress, and the particles are easily detached from the film surface. However, if the present inventors use aggregated particles obtained by appropriately aggregating fine primary particles, even in a film having such a degree of plane orientation, without deteriorating abrasion resistance, impart a suitable sliding property. It was found that it could be done. The reason for this is not clear, but in the case of agglomerated particles, it is unlikely that the particles fall off because the stretching stress is moderately dispersed, and it also gives relatively gentle projections, unlike the case of single particles. It is believed to provide favorable friction and wear properties.

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 to 0.2 μm
And at least one kind of particles selected from silicon oxide and aluminum oxide. These particles (hereinafter, referred to as “first group particles”) can be obtained, for example, by a so-called pyrolysis method, and those having a primary particle size within a desired range can be obtained. Is often 1 μm
To form aggregates. The aggregate having an appropriate particle size used in the present invention can be easily obtained, for example, by pulverizing such a coarse aggregate.

For the pulverizing treatment, for example, a rod mill, a ball mill, a vibrating rod mill, a vibrating ball mill, a pan mill, a roller mill, an impact mill, a stirring and grinding mill, a fluid energy mill and the like can be used. If necessary, an ultrasonic dispersion treatment may be performed. However, if the degree is high, the particles are dispersed to primary particles or a state close to the primary particles. Of course, in the present invention, treatments such as classification and filtration may be used in combination.

If the average particle size of the agglomerates is less than 0.03 μm, the slipperiness is not significantly improved, and if this value exceeds 0.2 μm, coarse projections often exist and the hardness of the particles is high. In addition, wear of the film slit blade becomes remarkable.

In the present invention, the average particle size of the primary particles constituting the aggregate is 0.005 to 0.08 μm. This value
When the thickness is less than 0.005 μm, the aggregate often has an extremely strong bond, and the bond is hardly broken even by a stretching stress, so that it is difficult to obtain the effects specific to the present invention. Also, this value
If it exceeds 0.08 μm, the aggregated particles will separate and fall off, deteriorating the electromagnetic characteristics.

In the present invention, the amount of the particles of the first group in the film is 0.02 to 1.0% by weight, preferably 0.04 to 1.0% by weight.
Select from the range of ~ 0.7% by weight. 0.02% by weight
If the amount is less than the above, the sliding property and abrasion resistance are hardly improved, and if the amount exceeds 1.0% by weight, the surface roughness becomes too large.

In addition, in the film of the present invention, particularly when aluminum oxide is contained, in addition to slipperiness and abrasion resistance,
Scratch resistance, that is, the degree of difficulty of scratching the film surface is also remarkably improved, which is preferable.

Furthermore, in the present invention, a certain amount of the second group of particles is present in order to improve the winding characteristics during film formation. That is, 0.005 to 0.3% by weight, preferably 0.01 to 0.2% by weight of one or more particles selected from a crosslinked polymer and calcium carbonate having an average particle diameter of 0.2 to 0.8 μm, preferably 0.3 to 0.7 μm.
Mix. In order to provide a relatively steep, constant level of protrusions on the film surface, these must be single particles, the shape of which may be spherical, massive, flat, etc., but close to monodisperse Are preferred. 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 1.
What is 05 or less may be used.

Examples of crosslinked polymer particles include, for example,
As described in Japanese Patent Publication No. 16-316, a monovinyl compound having only one aliphatic unsaturated bond in a molecule and a compound having two or more aliphatic unsaturated bonds in a molecule as a crosslinking agent are used. Examples of the polymer include, but are not limited to, a thermosetting phenol resin, a thermosetting epoxy resin, a thermosetting urea resin, and a benzoguanamine resin. These particles preferably have a group capable of reacting with the polyester. The method for producing such particles is not particularly limited. For example, those obtained by suspension polymerization may be pulverized and classified, or may be obtained by an emulsion polymerization method.
Further, it may have a multi-layer structure or may be slightly deformed during stretching. Typical examples are (1) acrylic acid, methacrylic acid and their alkyl esters,
Crosslinked polymer particles obtained by copolymerizing at least one compound selected from styrene and its alkyl derivative and at least one compound selected from (2) divinylbenzene and ethylene glycol dimethacrylate are preferably used.

Further, as the calcium carbonate particles, those obtained by a synthesis method are particularly preferable, for example, as described in JP-A-59-69425, obtained by reacting a liquid of calcium hydroxide with a carbon dioxide-containing gas. In addition to calcite-type calcium carbonate particles, vaterite-type calcium carbonate particles obtained by performing the same reaction in alcohol can be suitably used. Of course, the production method is not limited as long as the requirements of the present invention are satisfied.

The surface of these calcium carbonates may be treated to reduce solubility in polyester, improve dispersibility, improve affinity, and the like. For example, effective use of a surface treating agent as described in JP-A-59-69426 or JP-A-1-256558, particularly a high-molecular polycarboxylic acid or a sodium salt or an ammonium salt thereof, is effective. Can be.

The compounding amount of the particles of the second group with respect to the polyester film is in the range of 0.005 to 0.3% by weight, preferably 0.006 to 0.1% by weight. If the amount is too small, the winding characteristics will not be improved, and if it is too large, the surface roughness of the film will increase and the electromagnetic characteristics will deteriorate.

In the present invention, when the second group of particles is used in an amount of about 2 to 20% by weight with respect to the first group of particles, the effect can be maximized.

In the present invention, other lubricating agents may be used together, or a coloring agent, an antistatic agent, a weathering agent, etc. may be used in combination, as long as the gist of the present invention is not impaired.

The film of the present invention, which is particularly suitable for a magnetic recording medium, can be obtained for the first time by combining a specific degree of plane orientation and two groups of particles, but the surface roughness of the film has a center line average. Roughness (Ra), usually 0.004 to 0.0
It is selected from the range of 15 μm, preferably 0.005 to 0.013 μm.

The film thickness is usually 3 to 3 for magnetic tape.
It is selected from the range of 25 μm, preferably 4 to 15 μm.

〔Example〕

Hereinafter, the present invention will be described in more detail with reference to examples, but the present invention is not limited to the following examples as long as the gist is not exceeded.

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

In the examples, “parts” and “%” mean “parts by weight” and “% by weight”, respectively.

(1) Average Particle Size and Particle Size Distribution The particles in the dry powder and slurry were measured for particle size using an electron microscope. The average particle size was calculated as the particle size (diameter) at the point of 50% by weight in terms of equivalent sphere. Although this value is a weight average particle size, a number average particle size is also determined at the same time,
It was a measure of the sharpness of the particle size distribution.

The particle size of the aggregate 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 the end face when wound up into a film roll was determined according to the following criteria.

(A) Rolls with almost no wrinkles or rugged defects on the end surface and with uniform end faces ○ (b) Rolls with few wrinkles on the roll surface but with some rugged defects and slightly irregular end faces △ ( C) Wrinkles or ridge-like defects are generated on the roll surface, or the end face is extremely irregular. × (3) Measurement of the refractive index of the film The refractive index within the film surface is measured using an Abbe refractometer manufactured by Atago Optical Co., Ltd. The maximum value nγ and 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 equations. The measurement of the refractive index was performed at 23 ° C. using a sodium D line.

(4) Film Surface Roughness The center line average roughness (Ra) was measured according to the method described in JIS B0601.

(5) Runability A film is wound around a fixed hard chrome-plated metal pin (diameter 6 mm) and brought into contact at an angle of 135 ° C. A load of 53 g is applied to one end and the film is run at a speed of 1 m / min, and the resistance at the other end is measured. Then, the coefficient of friction of the film was determined by Euler's equation and used as a measure of running performance.

(6) Abrasion resistance A film is wound around a fixed hard chrome-plated metal pin (diameter 6 mm) at an angle of 135 °, and the film is run over 1000 m at a speed of 10 m / min and a tension of 200 g, and the amount of white powder adhering to the pin Were visually divided into the following four ranks.

Rank A: Not adhered at all Rank B: Adhered in a small amount Rank C: Adhered in a small amount (more than Rank B) Rank D: Adhered in an extremely large amount (7) Slit property First, apply the following magnetic paint to a polyester film The magnetic layer was formed so that the film thickness after drying was 2 μm. That is, 200 parts of magnetic fine powder, 30 polyurethane resin
Parts, nitrocellulose 10 parts, vinyl chloride-vinyl acetate copolymer 10 parts, lecithin 5 parts, cyclohexanone 100 parts, methyl isobutyl ketone 100 parts and methyl ethyl ketone 300 parts were mixed and dispersed in a ball mill for 48 hours, and then 5 parts of a polyisocyanate compound was added. As a magnetic paint, after applying this to the polyester film, before the paint is sufficiently dried and solidified, magnetically oriented,
Then it was dried.

Next, the coated film was surface-treated with a super calender and slit to a 1/2 inch width to obtain a video tape. The slit property at this time was classified into the following three ranks by observing the cross section of the slit portion with an electron microscope.

Rank A: There is almost no swelling in the cross section and the winding appearance is good.

Rank B: The cross section has a swelling of about 0.1 to 0.3 μm, and a small amount of powdery or elongated slit debris is observed.

Rank C: There is a swelling of 0.3 μ or more in the cross section, and slit chips are clearly recognized.

(8) Electromagnetic properties The obtained video tape was mounted on an NV-3700 type video deck manufactured by Matsushita Electric Industrial Co., Ltd., and the following magnetic tape properties were evaluated at normal speed.

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

Number of dropouts: Play a video tape on which a signal of 4.4 MHz is recorded, and use a dropout counter manufactured by Okura Industry Co., Ltd. to reduce the number of dropouts at 15 μsec-20 dB to about 2
Measure for 0 minutes, dropout number per minute (pcs /
Minutes).

Example 1 (Production of Particles) An aggregate of silicon oxide having a primary particle size of 0.03 μm was dispersed with ethylene glycol, and was gradually crushed with a sand grinder to obtain an aggregate having an average particle size of 0.12 μm.

On the other hand, after adding 3.2 parts of potassium persulfate and 0.004 part of sodium lauryl sulfate to 1500 parts of demineralized water, 60 parts of styrene,
Ethylene glycol dimethacrylate (20 parts) and divinylbenzene (20 parts) were added, and emulsion polymerization was performed by a conventional method. The average particle size of the obtained particles was 0.40 μm, and the ratio between the weight average particle size and the number average particle size was 1.05.

(Production of Polyester) Next, 100 parts of dimethyl-2,6-naphthalate, 60 parts of ethylene glycol and 0.08 part of magnesium acetate were placed in a reactor to carry out a transesterification reaction. Next, 0.15 parts of the silicon oxide aggregate obtained earlier, and 0.05 parts of crosslinked polymer particles were added, and 0.04 parts of ethyl acid phosphate and 0.04 parts of antimony trioxide were added, followed by polymerization according to a conventional method. Polyethylene-2,6-naphthalate having an intrinsic viscosity of 0.55 was obtained. Next, solid-state polymerization was performed to increase the intrinsic viscosity to 0.60.

(Production of film) After drying the obtained polyester, melt extrusion is performed.
An unstretched sheet was obtained by using an electrostatic application cooling method.

Next, 4.5 times at 130 ° C in the vertical direction and 4.0 times at 130 ° C in the horizontal direction.
The film was stretched twice and stretched again at 130 ° C. 1.15 times. Then 2
The film was transversely stretched 1.15 times at 10 ° C. and heat-set at 220 ° C. to obtain a film having a thickness of 7 μm.

Table 1 shows the results of the obtained films together with the results of other examples and comparative examples.

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

While the film of Example has excellent running properties and abrasion resistance, and furthermore the electromagnetic properties of the finally obtained magnetic tape, the film of Comparative Example 1 in which the particles of the second group are not present has the winding properties and running properties. Inferiority and abrasion resistance, and the performance of the magnetic tape was inferior. In Comparative Example 2, the requirements for the particle system were satisfied, but the degree of plane orientation was low, so the slit property was poor and the dropout was large. Comparative Example 3 is an example in which single particles were used as the particles, and the electromagnetic characteristics were particularly deteriorated due to the lack of affinity of silicon oxide with the polyester.

[Effects of the Invention] The film of the present invention has improved degree of plane orientation, particle system, slit properties, abrasion resistance and easy slipperiness, particularly for magnetic recording, In particular, it can be suitably used as a base film for high-density recording, for example, a so-called metal tape or vapor-deposited tape, and therefore has high industrial value.

Continuation of front page (58) Field surveyed (Int. Cl. ⁶ , DB name) C08J 5/18 C08K 3/00 C08K 5/00 C08K 7/00

Claims (1)

(57) [Claims] 1. A polyethylene-2,6-naphthalate film having a degree of plane orientation of 0.255 to 0.280, wherein the film comprises: (i) an aggregate of primary particles having an average particle size of 0.005 to 0.08 μm. And 0.02 to 1.0% by weight of one or more particles selected from silicon oxide and aluminum oxide having an average particle size of 0.03 to 0.2 μm, and (ii) a crosslinked polymer having an average particle size of 0.2 to 0.8 μm. A polyethylene-2,6-naphthalate film, comprising 0.005 to 0.3% by weight of one or more particles selected from calcium carbonate and calcium carbonate.