JPH01232020A - Oriented polyethylene-2,6-naphthalate film - Google Patents

Abstract

PURPOSE:To prevent particles from falling off because of broken voids by carrying out surface treatment of an irregular shaped polyethylene-2,6- naphthalate film by means of a crystallization accelerator and then orienting the same. CONSTITUTION:A non-oriented film is formed by applying the melt extrusion method to a base polymer with constitution units of ethylene-2,6-naphthalate substantially. Said non-oriented film is quenched to become substantially irregu lar (amorphous). The surface of the polyethylene-2,6-naphthalate non-oriented film thus prepared is surface treated by means of a crystallization accelerator such as methylene chloride or the like. After that, the same is heated and ori ented in the vertical direction and then lateral direction, and a film is manufac tured by heat fixing. An extremely clean film without any broken voids at all is manutactured by said process. The film thus manufactured is used for a recording flexible disc, a magnetic recording tape and an electrical insulating material film.

Description

Detailed Description of the Invention <Industrial Application Field> Crystallization accelerator on the surface of a substantially amorphous polyethylene-2,6-naphthalene dicarboxylate (hereinafter abbreviated as polyethylene-2,6-naphthalate) film. After surface treatment with
- Concerning naphthalate films. The present invention relates to improvements in magnetic recording media and electrically insulating films using oriented polyethylene-2,6-naphthalate films.

<Prior art and its problems> Due to its excellent physical and chemical properties, polyethylene-2,6-naphthalate film can be used as a dielectric film for capacitors, a film for speaker diaphragms, 11 air tapes, and photographic supports. Used as a film for bodies, etc.

The slipperiness of these films depends on the workability of the film manufacturing process and the processing process for each application,
Furthermore, it is a major factor that determines the quality of the product.

Generally, to improve the slipperiness and abrasion resistance of a film, a method is adopted in which the surface of the film is given extremely fine irregularities to reduce the contact area between the film surfaces and with guide rolls, etc. Broadly speaking, the methods used include a method in which inert fine particles are precipitated from a polymeric catalyst residue used as a film raw material, a method in which inert inorganic or organic fine particles are added to a film raw material, and a method in which these are used in combination.

The larger the size of the fine particles in these raw polymers is, the greater the effect of improving slipperiness is, but magnetic tape 1. Particularly in precision fields such as video applications, the large particles themselves can cause defects such as magnetic recording dropouts, so the irregularities on the film surface must be as fine as possible, and the smoothness In terms of surface roughness, there are currently demands to satisfy contradictory properties at the same time.

Furthermore, in the method of adding inert inorganic fine particles, relatively large protrusions may be formed on the film surface due to agglomeration of the particles, which causes dropouts when used as a magnetic recording medium.

In either method, the slipperiness and abrasion resistance (scratching resistance) of the film are improved by the action of fine particles;
Another problem arises when inert particles are present in the polymer and when they are stretched or oriented, voids are formed around the particles. When voids form near the surface of the film, a portion of the void ruptures, exposing particles, and tiny fragments of the voids adhere to the surface of the film. Further, when slitting or punching into a flexible disk, chips and the like are generated from the cut end.

"Garbage" such as minute chips that adhere to the surface in this way
often lowers the yield during the production of magnetic recording media and lowers the performance of the media itself.

Various methods have been proposed to suppress the formation of such voids. For example, methods for suppressing molecular orientation of polymers around particles to prevent particles from falling off the film surface, use of lubricants made of organic substances that have good affinity with polyester, and improvement of affinity by surface treatment of such lubricants. etc.

However, drop-off of particles due to void breakage has not been completely solved, and this remains an issue to be solved in high-density magnetic recording base films.

When polyethylene-2,6-naphthalate is used as an electrically insulating film, this material is extremely useful because it has excellent heat deterioration resistance and contains few oligomers. However, compared to polyethylene terephthalate film, there is a problem in that delamination is more likely to occur. That is, if the film is bent at a steep angle or if the cut end has a minute notch, delamination is likely to occur if impact force is applied to the film. If such an interlayer separation exists, the dielectric breakdown voltage will decrease, causing a problem.

When the delamination part of the film is closely observed, added inorganic particles and the like can be seen in the part where delamination starts. It is thought that these inorganic particles contribute to the occurrence and growth of delamination.

<Object of the Invention> As a result of intensive studies to eliminate the drawbacks of the prior art as described above, the present inventors have developed a substantially amorphous polyethylene-2.
, 6-naphthalate film is subjected to surface treatment with a crystallization accelerator, and then the polyethylene-2,6-naphthalate film is stretched and oriented in the -axis or biaxial direction. did.

Specific Solution> The base polymer constituting the film of the present invention may be one in which the structural unit is substantially composed of ethylene-2,6-naphthalate, and polyethylene-2,6-naphthalate Not only a small amount (for example, 10 mol% or less,
Also included are ethylene-2,6-naphthalate-modified polymers modified with a third component (preferably 5 mol % or less).

Polyethylene-2,6-naphthalate is generally synthesized by combining naphthalene-2,6-dicarboxylic acid or its functional derivative and ethylene glycol or its functional derivative under appropriate reaction conditions in the presence of a catalyst. be done. Examples of modified polymers include those in which one or more suitable third component modifiers are added to the polyethylene-2,6-naphthalate before the polymerization is completed to form a copolymer or mixed polyester.

Suitable third components include compounds having divalent ester-forming functional groups, such as oxalic acid, adipic acid, phthalic acid, isophthalic acid, and terephthalic acid.

Dicarboxylic acids or lower alkyl esters thereof such as naphthalene-2,7-dicarboxylic acid and diphenyl ether dicarboxylic acid; oxycarboxylic acids or lower alkyl esters thereof such as 20-benzoic acid and p-oxyethoxybenzoic acid; or propylene glycol, trimethylene Examples include compounds such as dihydric alcohols such as glycol, tetramethylene glycol, hexamethylene glycol, and neopentyl glycol. In addition, polyethylene-2,
6-Natalate or its modified polymer may be one in which the terminal hydroxyl group and/or carboxyl group is blocked with a monofunctional compound such as benzoic acid or methoxypolyalkylene glycol; A small amount of glycerin.

It may be modified with a tri- to tetrafunctional ester-forming compound such as pentaerythritol within the range that a substantially linear copolymer can be obtained.

The base polymer of the present invention may contain solid additives such as fine particles of silica, talc, and clay to improve slipperiness when formed into a film. Note that in applications where delamination is a problem, such as electrical insulation applications, it is better not to include inorganic additives.

The base polymer used in the present invention has an intrinsic viscosity of 0.40 or more when measured in an orthochlorophenol solution at 35°C. In particular, those having an intrinsic viscosity of 0.50 to 0.70 are preferable because they have excellent physical properties and stretching operations.

The present invention is carried out using unstretched films formed from polymers such as those described above. In order to form an unstretched film from the polymer, for example, a melt extrusion method may be employed.

An unstretched film formed by melt extrusion is rapidly cooled and becomes substantially amorphous. The surface of the thus obtained unstretched polyethylene-2,6-naphthalate film is treated with a crystallization accelerator.

Various organic solvents can be used as the compound with a crystallization promoting effect used in the present invention, but chlorine-containing organic compounds such as dichloromethane, methylene chloride, chloroform, trichloroethylene, tetrachloroethane, and monofukulobenzene are prominent. It is preferable because it produces an effect. Particularly preferred are methylene chloride and chloroform.

Further, in order to control the effect of promoting crystallization, the above-mentioned substances can be used in combination with a solvent such as an alcohol or a ketone. The degree of surface treatment with these crystallization promoters can be changed by selecting treatment conditions through preliminary experiments with conditions such as the mixing ratio of treatment agents, contact time with the film surface, and temperature.

The uniaxially or biaxially stretched polyethylene-2,6-naphthalate film of the present invention has fine protrusions on its surface. The large number of protrusions originate from the large number of microcrystalline particles formed on the film surface. Microcrystalline particles are formed by treatment with a crystallization promoter.

<Effects of the Invention> According to the present invention, the following novel effects can be obtained.

(1) The surface properties of the oriented film can be efficiently controlled simply by coating the surface of the film with an organic compound that promotes crystallization, which has great industrial advantages.

(a) When the method of the present invention is applied to polyester to which no lubricant such as fine particles of an inorganic compound is added, an extremely clean film with no voids or tears can be obtained.

Furthermore, when the film of the present invention is slit, the generation of chips due to falling off of the lubricant is relatively small compared to the film to which the lubricant has been added. Furthermore, delamination, which occurs when a relatively thick film is bent at a steep angle, is less likely to occur.

(3) Even when it is necessary to add a lubricant, by applying the present invention, the amount of lubricant added can be reduced, making it possible to produce a film with fewer large protrusions caused by agglomeration of lubricant particles. Also, voids can be reduced. These increase the light transmittance of the film and improve its transparency.

(4) When the crystallization accelerator is applied to only one side of the film, an oriented film with different surface roughness on the front and back sides can be produced.

[Example] The present invention will be further explained below with reference to Examples.

Note that various physical property values and characteristics in the present invention were measured and defined as follows.

(1) Surface roughness of film (Ra > JIS B
Measured according to 0601. Using a stylus type surface roughness meter (SLIRFCOM3B) manufactured by Tokyo Seimitsu Co., Ltd. v/J,
Chart (
A film surface roughness curve) was drawn. From the film surface roughness curve, take the measurement length part in the direction of its center line, take the center line of this cut out part as the X axis, take the vertical magnification direction as the Y axis, and define the roughness curve as Y= When expressed as f(x), the value (Ra: μm) given by the following equation is defined as the surface roughness of the film.

Ra-1/Lf, l f (x) ldx In the present invention,
The reference length was set to 0.25 m, and 8 measurements were taken, 3 of which had the largest values were removed, and Ra was expressed as the average value of 5 of the measurements.

■ Frequency of occurrence of void breakage Aluminum is vacuum-deposited uniformly on the film surface to a thickness of about 40 to 50nra or less, and under a microscope
Twenty surface photographs were taken at 0x magnification and at different positions. From this photo, the tip of the protrusion shows polyethylene-2,6-
The number of protrusions from which naphthalate was completely or partially exfoliated was counted and expressed as a value per unit area.

(3) Flexible disk dropout 5.
Drop-out/drop-in counter 5K made by Tokyo Engineering, punched into a 25-inch disc.
Track-by-track dropout was measured using 444B. The quality of dropout was compared based on the degree of decrease in output for each track.

(4) Electromagnetic conversion characteristics of magnetic coating film The video characteristics of the magnetic coating film are as follows:
H8 system VTR (manufactured by Victor Japan, product name rHR73)
This is a value obtained by measuring the reproduction output at 4 MHz using 00J). The standard tape is a commercially available γ-FezOa layer coating type 1/2 VH8 tape.

The C/N ratio is the C/N ratio when a 4 MH2 carrier signal is recorded and the level at 30 MHz of the reproduced field-of-view modulation signal is taken as the noise level.

(5) Durability of magnetic tape A cassette was placed in a home video tape recorder (helical scan), and the tape was run for 100 hours while repeatedly starting and stopping, and the running condition was examined and the output was measured.
In this running, if all of the following items are satisfied, the running performance is determined to be good, and if not, the running performance is determined to be poor.

■ The edges of the tape do not bend or become seaweed. ■ The tape does not squeal while running. ■ The tape does not tear or break. (6) Dropout magnetic coating tape (172 inch width) is now commercially available. The 5 μsec xlo dB(7) t'0 dropout was counted using a dropout counter (Shibaku VHOIBZ type), and the number of counts per minute was calculated.

Example 1 and Comparative Example 1.2 A product with an intrinsic viscosity of 0.0 that does not substantially contain a lubricant such as inert fine particles.
Polyethylene-2,6-naphthalate No. 60 was melt extruded and cooled on a casting drum to obtain an unstretched film. This unstretched film was treated with chloroform for 3 seconds from both sides.

This unstretched film was heated to 130° C. and stretched 3.6 times in the machine direction. Then 3.7 in the transverse direction at 125°C
Stretched twice. Further heat setting was carried out at 230℃ to obtain a thickness of 1
A 5 μm film was obtained (Example 1).

On the other hand, the above polyethylene-2,6-naphthalate to which 0.25% by weight of kaolin (average particle size 0.6 μm), which is an inert fine particle, was added as a lubricant, was melt-extruded and stretched on two wheels under the same conditions as above. Then, it was heat-set to obtain a film (Comparative Example 1).

In addition, a film was produced under the same conditions as in Example 1, but did not include only the chloroform treatment step in an unstretched state (Comparative Example 2).

The properties of these films are shown in Table 1. In the film of Example 1, no void breakage occurred. Comparative Example 2 also had no voids or tears, but the surface roughness was too small, and when the film was wound into a zero-roll shape, there were bump-like defects in some places, making the film unsuitable for coating with a magnetic layer. .

Table 1 These films were coated with the following magnetic paint (solid content conversion rate: 3
9/g), dried at 120°C, and dried at 80°C.

Calendar treatment under the condition of 300Kg/cm, 1
Composition of magnetic paint wound into a roll under tension of 5 to 9/cd CO-containing γ2 F2O3 100 parts by weight Vinyl chloride, vinyl acetate copolymer resin (manufactured by Union Carbide) VAG
H10 Urethane resin 17 Hardening agent
10 Butyl acetate
140 Methyl ethyl ketone
200 Next, the obtained roll-shaped coated ware was aged at 57°C for 3 days and nights (72 hours), and then a 5.25-inch disc was hit by a conventional method to form a dropout manufactured by Tokyo Engineering ■. Dropout for each track was measured using a drop-in counter 5K-4448.

In the flexible disk made from the film of Example 1, no decrease in output due to dropout was observed.

On the other hand, in the flexible disk made from the film of Comparative Example 1, many small dropouts occurred, and a decrease in output was clearly observed.

As is clear from these results, it can be seen that the flexible disk using the film of the present invention is extremely useful.

Example 2. Comparative Example 3 Polyethylene-2,6 that does not contain lubricants such as inorganic particles
- Naphthalate (intrinsic viscosity >0.65) was melt-extruded at 305°C and rapidly cooled to obtain an unstretched film with a thickness of about 130 μm. Only one side of the unstretched film thus obtained was coated with a mixture of chloroform and ethanol ( Mixing ratio 2:
1) to treat the surface. Next, this was stretched 5.6 times in the machine direction at 125°C, and stretched 1 times in the transverse direction using a stenter.
After stretching 3.4 times at 40°C, it was heat-set at 240°C for 10 seconds. In this way, a biaxially oriented film with a thickness of 7 μm was obtained (Example 2).

On the other hand, 0.30% by weight of silica with an average particle size of 0.12 μm
A film was obtained in exactly the same manner as in Example 1, except that polyethylene-2,6-naphthalate (intrinsic viscosity 0.65) containing polyethylene-2,6-naphthalate (intrinsic viscosity 0.65) was crystallized in an unstretched film (Comparative Example 3). .

The properties of these films are shown in Table 2.

Table 2 On the other hand, acicular α-Fe OO containing 5% cobalt
α-Fe 203 obtained by thermally decomposing H was reduced with hydrogen to obtain ferromagnetic iron powder with an average needle length of 0.2 μm.

100 parts by weight of the above ferromagnetic iron powder (hereinafter simply referred to as "Part F")
The following composition was mixed and dispersed in a ball mill for 12 hours.

Polyester polyurethane 12 parts Vinyl chloride-vinyl acetate-maleic anhydride copolymer 10 parts α-alumina 5 parts Carbon black
1 part butyl acetate
70 parts methyl ethyl ketone 35
After dispersing 100 parts of cyclohexanone, 1 part of fatty acid, 1 part of oleic acid, 1 part of palmitic acid, and 1 part of fatty acid ester (amyl stearate) are further added and kneaded for another 15 to 30 minutes. Furthermore, 7 parts of a 25% ethyl acetate solution of a triisocyanate compound was added and dispersed under high-speed shearing for 1 hour to prepare a magnetic coating liquid. The obtained coating liquid was applied onto the above-mentioned film having a thickness of 7 μm so that the dry film thickness was 2.5 μm.

In Example 2, the coating was applied to the untreated side.

Next, after orientation treatment in a DC magnetic field, it was dried at 100°C. After drying, it was calendered and slit into 172 inch width and 8 JIIl width to obtain a video magnetic tape.

The evaluation results of the thus obtained magnetic tape are shown in Table 3, and the electromagnetic conversion characteristics also show that the C/N ratio is +7. There is enough Od3,
Moreover, the durability of the tape was also good.

Table 3 Example 3. Comparative Example 4 Polyethylene-2,6 containing no lubricant such as inorganic particles
- Naphthalate (intrinsic viscosity 0.62) was melt-extruded at 300°C and rapidly cooled to obtain an unstretched film with a thickness of about 1000 μm. Both surfaces of this unstretched film were treated by contacting them with chloroform. Next, this was stretched 3.6 times in the machine direction at 125°C and 3.1 times in the transverse direction at 135°C to obtain a 230
Heat-fixed at ℃ for 20 seconds. In this way, the thickness is 75 μm.
A film of (Example 3) was obtained.

On the other hand, calcium carbonate with an average particle size of 0.60 μm was added to the
A film was obtained using polyethylene-2,6-naphthalate (intrinsic viscosity 0.62) containing 25% additive in the same manner as in Example 3 except for surface treatment (Comparative Example 4).
. The obtained film was subjected to delaminate John evaluation.

Using a NEW LONG sewing machine, 100 holes were punched perpendicularly to the film surface using a sewing machine needle (diameter 2 m). Delamination was evaluated by determining the area of the cracks (including the enlarged portions) using Luzex 500 (manufactured by Nippon Regulator Co., Ltd.).

In films with good delamination, the punched holes are as small as the diameter of the needle, whereas in films with bad delamination, the punched holes are enlarged to the periphery, and delamination increases the area of the punched portion.

The punched area of the film of Example 3 was 4.5 - per needle hole, and that of Comparative Example 4 was 7.0 -. It was found that the film of the present invention in Example 3 is an excellent film that does not easily cause delamination.

Patent applicant Teijin Kaisha Ltd.

Claims (1)

[Claims] 1. Polyethylene prepared by surface-treating a substantially amorphous polyethylene-2,6-naphthalene dicarboxylate film with a crystallization promoter and then uniaxially or biaxially stretching orienting the film. 2,6-naphthalene dicarboxylate film. 2. A magnetic recording flexible disk comprising the film according to claim 1. 3. A magnetic recording tape using the film according to claim 1. 4. A film for electrically insulating material using the film according to claim 1.