JPS6360732A - Polyethylene-2,6-naphthalate film - Google Patents

Abstract

PURPOSE:To obtain a polyethlene-2,6-naphthalate film excellent in smoothness, easily-sliding property and thickness evenness, by including inert fine particles in the film and specifying the film properties within a specified range. CONSTITUTION:A polyethylene-2,6-naphthalate film containing 0.01-10wt% inert fine particles whose average particle diameter is 0.1-10mu has characteristics described as follows. The 1/2 crystallization time is 6.0min or less and the degree of plane orientation DELTAP and the average reflective index-n satisfy the equations 1 and 2 respectively. Moreover, the numbers of unevenness units per 1mm<2> of the film surface area A, where the unevenness is constituted of a projection and a cavity having the projection as its nucleus whose longer diameter is at least 0.2mum or more, satisfy the equation 3 and the longitudinal and the transverse thickness unevenness are both 8% or less. Polyethylene-2,6- naphthalate means polymers constituted of an ethylene-2,6-naphthalate unit and it includes ethylene-2,6-naphthalate polymers modified with small amt., preferably 5% or less of a third component. A film excellent in thickness uniformity and easily-sliding property can be thereby obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a polyethylene-co-6-naphthalate film that has excellent thickness unevenness and flatness and smoothness. More specifically, the present invention relates to a polyethylene 1-1,6-naphthalate film that is particularly excellent as a base film for magnetic recording media.

[Prior art and problems to be solved by the invention] As is well known, polyethylene terephthalate film is currently mainly used as an industrial film, especially as a base film for magnetic recording media.However, in recent years polyethylene terephthalate film There are applications where film has insufficient strength and heat resistance, and new materials are required.Several materials have been proposed as candidates for Wm, but among them, Polyethylene Coco 6-naphthalate film is attracting attention because of its quality.Polyethylene Coco 6-naphthalate film has superior heat resistance compared to polyethylene terephthalate, is easy to achieve high strength, and is coarse. Due to the limited availability of polyethylene terephthalate, it is being considered for use in a variety of applications as a substitute for polyethylene terephthalate, with particular attention being focused on its use in high-quality, high-density magnetic recording media.

By the way, the most important issue in developing these applications is to impart flatness and slipperiness to the film. As is well known (
Various methods have been studied for making polyethylene terephthalate films flat and smooth. One method is to find the optimum conditions by changing the type, particle size, particle amount, particle size distribution, etc. of the inert particles contained in the film. This method is.

It has been found that the knowledge obtained with the polyethylene terephthalate film can be directly applied to the polyethylene-naphthalate film as well. On the other hand, another method is to reduce the in-plane orientation of the film to form protrusions having depressions with the protrusions formed by nine particles as cores, thereby achieving flattening and smoothing.

We investigated the application of this method to polyethylene-2,6-naphthalate film.

Simply lowering the in-plane orientation of the film is not enough.

Even when the same inert particles having the same particle size, the same amount of particles, and the same particle distribution are used, flattening and smoothing can be achieved, but the unevenness of the thickness becomes extremely worse.

It has been found that the film cannot withstand use as a high-grade film, particularly as a base film for magnetic recording media.

The object of the present invention is to discover the physical properties that a polyethylene, 2,6-naphthalate film should have, which is excellent in flatness and smoothness as well as thickness unevenness.

[Means for solving intervening vertices]

The present inventors have achieved the above object (as a result of intensive studies, we have developed a polyethylene coco, 6-naphthalade film containing inert fine particles and with the physical properties of the film defined within a certain range), which has a thickness unevenness. The present invention was achieved by discovering that good and flat smoothing can be achieved.

That is, the gist of the present invention is to prepare a polyethylene-cot 6-naphthalate film in which inert fine particles with an average particle diameter of o and i to 10μ are o, oi to 10t mill 10t, and the film has a temperature of /7/ at 200°C. The co-crystallization time is 6.0 minutes or less, the degree of plane orientation ΔP and the average refractive index n satisfy the following formulas (1) and (2), and the length of the protrusion and the major axis of the protrusion as a core are at least 0. - Concave or concave/concave units of 7v
A flat and slippery film characterized in that the number A (1 to 1) per film surface area satisfies the following formula [3] and the vertical and horizontal thickness unevenness of the film is 3% or less.

It is a polyethylene 1-1,6-naphthalate film with excellent film thickness unevenness.

JP≦/Mamoru 35-u, / ,? A Curved surface/curve/
・■/, &l,! 0≦n≦7.6750 Curved surface... Song■OkuA≦/! 000 ・Curves・Curved surfaces・■Polyethylene-2,6-naphthalate as used in the present invention refers to a polymer whose constitutional units are substantially composed of ethylene-6-naphthalate units.
Ethylene-2,6-naphthalate polymer functional derivatives modified with 0 mol %, preferably 3 mol % or less of a third component 1, such as naphthalene, methyl 6-dicarboxylate, etc., and ethylene glycol in the presence of a catalyst. modified by condensation under appropriate reaction conditions. In this case, the third component other than naphthalene, 6-dicarboxylic acid, and ethylene glycol is dicarboxylic acid or lower alkyl ester thereof such as adipic acid, oxalic acid, inophthalic acid, terephthalic acid, naphthalene, 7-dicarboxylic acid, and diphenyl ether dicarboxylic acid. :p-oxybenzoic acid.

Oxycarboxylic acids or lower alkyl esters thereof such as p-oxybenzoate; or propylene glycol, trimethylene glycol, tetramethylene glycol, pentamethylene glycol, hexamethylene glycol/L/.

Examples include polyalkylene glycols such as diethylene glycol and lI-cyclohexane dimetatool. Further, during the first polymerization, a matting agent, a light shielding agent, a stabilizer, an antioxidant, a polymerization regulator, a plasticizer, etc. may be added.

Furthermore, if the degree of monopolymerization of the polyethylene coco, 6-naphthalate used in the present invention is too low, the mechanical properties will deteriorate.
Its intrinsic viscosity is 0.110 or more, preferably 0.33 to O
, De's.

The film of the present invention can be suitably used for various purposes, particularly as a magnetic recording medium base film, but it can be used for any purpose.

In order to provide runnability, it is necessary to include fine inert particles to provide slipperiness. or.

The average particle size of the inert fine particles is 0.7 to 10 μm.

The amount of particles should be between 0.01 and IO weight percent.

Preferably, the particle size is in the range of 0.3 to 3μ, and the amount of particles is,
0.02 to 0.121 inches, more preferably 0, OJ to 0
．． It is selected from a range of 3% by weight. If the particle size is smaller than 0.7 μm or less than 0.0% by weight, the surface roughness of the film will be too small and will not contribute to slipperiness, which is unsuitable. On the other hand, if it is larger than 10 μm or larger than 10 wt-m %, the surface roughness of the film will be too rough, making it unsuitable.

One method for incorporating such inert fine particles into the film is to add a phosphorus compound to the metal compound dissolved in the reaction system during polyethylene naphthalate production, for example, to the metal compound that remains wet in the system after the transesterification reaction. act to precipitate fine particles. There is a so-called precipitated particle method. This method is particularly preferable because it uses fewer coarse particles, but as a simple method, another method, the so-called additive particle method, is more preferably used.

Here, the added particle method is a method in which inert fine particles are blended into the polyethylene naphthalate polymer raw material in any step from the polyethylene-6-naphthalate manufacturing process to the fA preperitoneal extrusion process. Examples of the inert fine particles include kaolin, zeolite, celite, talc, magnesium carbonate, calcium carbonate, barium carbonate, calcium sulfate, and lithium phosphate.

Calcium phosphate, magnesium phosphate, aluminum oxide, silicon r52, titanium oxide, lithium fluoride,
Calcium oxalate and Oa, Ba.

Examples include seven or more metal compounds selected from terephthalates of Z n and M n 9, and carbon black. The shape of this inert compound is spherical,
It may be either lumpy or flat (and there are no particular restrictions on its hardness, specific gravity, color, etc.).

In the present invention, the plane orientation degree JP and the average refractometer must satisfy the following formulas (1) and (2).

JP≦1. Hiro 3・n-ko, /36 ・・・・・・・・・
...■i, tt, go≦n≦/, 1.7!0
・・・・・・・・・・・・■Here, the average refractometer is the amount expressed by the following formula (a), which is generally determined by the heat-setting temperature and is known to be proportional to the density of the film. .

Five = //J (na + n7 + n,)
, , , , , , , , (a) net is the refractive index s in the thickness direction of the film after uniaxial orientation heat fixation
r is the maximum refractive index of the same film within the film plane, and nz is the refractive index in the direction perpendicular to the r direction within the film plane. Five /, 61. , A; if it is less than 0, the film will have poor thermal properties and a high thermal shrinkage rate, making it unsuitable. −
Mangokuga/, 4ri! If it exceeds 0, it is unsuitable because the mechanical strength of the film decreases.

One-sided orientation degree ΔP is a degree of orientation expressed by the following formula (b), and generally indicates the degree of orientation within the plane of the film.

In other words, it indicates the degree to which the naphthalene rings of polyethylene-,2,A-naphthalate are oriented in parallel within the plane.

Δp = //2 (ny +”/ )−−・・
(b) Films in which the relationship between JP and 5 satisfies the above formula are compared to films that do not satisfy the above formula (■).

It has excellent flatness and smoothness.

A film whose plane orientation degree JP and average refraction weight satisfy the above formula (2) can be obtained by various methods. For example, 1. A film biaxially stretched using a conventional method.

It can also be obtained by heat setting for a long time at a temperature of 60° C. or higher and just below the melting point. It can also be obtained by relaxing in the width direction during heat setting after biaxial stretching. With this method, J
Even in a film in which the relationship between P and 5 satisfies the above formula (■).

Although some flattening can be achieved.

In order to strongly exhibit this effect, it is necessary to satisfy the above formula (2) by suppressing the longitudinal orientation, that is, the birefringence of the longitudinally-axially stretched film, to a low value in sequential biaxial stretching in the longitudinal and lateral directions. (In the film thus obtained, uneven units consisting of depressions with the protrusions as the core are formed around the protrusions.

Therefore, in the present invention, the number A (number of pieces 1 to 1) of the film surface area/xJ half of the uneven unit consisting of a protrusion and a depression whose major axis is at least O9-μm or more with the protrusion as the core is calculated by the following formula [3
] must be satisfied.

o < A≦/yoOOO・・・・・・・・・・・・・・・
・■ If there are zero A, there is no flat smoothing effect and it is 1soo.

If it exceeds 1, the abrasion resistance of the film deteriorates and is unsuitable. Preferably 3 or more and 5ooo or less.

More preferably 3 or more 2! ;00 or less.

However, when the film is used as an industrial material, particularly as a material for a magnetic recording medium, the basic property is that the film must have good thickness unevenness. The thickness unevenness that should be satisfied for the film after biaxial stretching and heat setting is t% at x7X for both vertical and horizontal directions.
It is preferably 3% or less. Here, R is the difference between the maximum thickness and minimum thickness at jm&, and i is the average thickness.

When the thickness unevenness was measured for films satisfying the above formulas (1), (2), and 0, there was a mixture of good thickness unevenness and poor thickness unevenness. Therefore, we investigated the factors that lead to good thickness unevenness.

It has been found that the crystallization time of the film at 200°C has a strong influence. In other words, the temperature of the film at 200℃/
/2 It is essential that the crystallization time is 6 minutes or less. Preferably it is 5 minutes or less, more preferably da minute or less.

Here, there are various methods for increasing the crystallization time of the film at 200° C., but a common recipe is to include a crystallization accelerator. As a crystallization accelerator, local aliphatic carboxylic acids or metal salts thereof (?lJ
Sodium montanate, sodium stearin)
, aromatic carboxylic acids or metal salts thereof (eg, sodium benzoate), alkylsulfonic acids, alkylbenzenesulfonic acids, ionomers, polyalkylene glycols, and other known compounds may be used.

The content in the film may be such that the co-crystallization time at 00°C falls within a predetermined range, but generally 0.01-! , 0 weight-! It is 1%. However, especially when used as a film for magnetic recording media, organic crystallization promoters such as those described above may cause coarse lumps or bleed out, resulting in a decrease in adhesion.

It is best to use purified products that have been kept to the minimum necessary level and have as many impurities removed as possible. Preferably, the method for increasing the crystallization rate at 200°C is to carry out a special combination formulation during polyethylene co-6-naphthalate polymerization and to use a non-contact crystallization nucleating agent such as kaolin or charcoal. It is preferable to use Cal etc. in combination.

As a result, we were able to discover an innovative napolyethylene 11, 6-naphthalate film, IL/mu, which was excellent in thickness unevenness, flatness, and slipperiness.The film-forming recipe will be specifically described below.

A polymer composition in which an organic crystallization accelerator is optionally contained in a polyethylene-co-6-naphthalate polymer containing a predetermined amount of inert fine particles using special phosphorus during polymerization is prepared by known means. A substantially non-oriented unstretched film of polyethylene, 6-naphthalate, which was dried and cast into a cooling drum shape after bow-melt extrusion, was first stretched in the longitudinal direction.

At that time, the film is first stretched (pre-stretching) so that the birefringence Δn is at least o, oso and at most o, oqo.

This pre-stretching may be performed in stages or in multiple stages. Stretching temperature is polyethyleneco, 6
- Stretching may be carried out at a hot water temperature of 10° C. or above the second-order transition temperature of naphthalate and in the range of 10 g to a, 0 times. It is also preferable to include a thermal relaxation step for orientation relaxation during or after the first-stage stretching. The thermal relaxation step may be carried out with a roll or by external heating, but at a temperature equal to or higher than the longitudinal stretching temperature before the thermal relaxation treatment, for 5 to 3.0 seconds, /
It is best to do this at a magnification of 0.01 times or less. The thus obtained film is further modified in the longitudinal direction to have a birefringence Δn of 0.090 or more o, i
After stretching (second stage stretching) so that the film temperature is below ao, it is laterally stretched and heat-set at a temperature of /jθ°C or more and 0°C or less to produce a biaxially oriented heat-set film. In order to keep the thickness unevenness of the film within a predetermined range, it is necessary to perform the above-mentioned longitudinal stretching in multiple stages.

The reason why the thickness unevenness was improved only when the co-crystallization time of the film at 200°C was short is because the crystallization speed increases in the above-mentioned latter stage stretching, so oriented crystallization progresses with low stretching ratio. However, it seems that the thickness unevenness has been improved.

As stated above (according to the present invention, even if the degree of plane orientation of the polyethylene-6-naphthalate film is reduced,
A film with good thickness unevenness and excellent flatness and smoothness can be obtained, and the polyethylene 1-1,6-naphthalate film can be applied to high-quality film applications, and has extremely excellent industrial value.

〔Example〕

The present invention will be explained below with reference to examples, but the present invention is not limited by the following examples unless it exceeds the gist thereof. The various physical properties of the film were measured as follows.

(1) Thickness The thickness was measured along the vertical and horizontal directions of the biaxially stretched film using a continuous film thickness measuring device (using a micrometer) manufactured by Madarasu Ritsu Denki Co., Ltd., and calculated using the following formula for a length of 3 m.

(2) Birefringence Δn The thickness of the longitudinally stretched film was measured using a polarizing microscope manufactured by Carl Zeiss, and the birefringence Δn was determined using a linear equation.

Δn=R/a R: Retardation: Film thickness (3) Refractive index The refractive index in the γ direction, β direction, and thickness direction was measured at 5° C. using an Atsabe type refractometer manufactured by Atago Co., Ltd. by the method. .

(4) Average protrusion height Ra It was performed by the method described in JIB BOAO1-/97A. The measurement was carried out using the surface roughness measuring machine model 8 manufactured by Kosaka Laboratory.
jF was used. The stylus diameter was μ, the stylus pressure was 30 cm, the cut-off value was o, og non-, and the measurement length was co, ju. Measurement was carried out at 12 points, the maximum value and minimum value were cut off, and the average value of the 10 points was shown.

(5) gdJ friction coefficient μd with metal Fixed hard chrome plated bottle (diameter 4 yx
The film is brought into contact with the winding angle /, 3° (θ), and a load of j-, 71Tz) is applied to one end of the film, and the film is run at a speed of 7m7, and the resistance force at the other end ( Tt
) to measure. The Masatsu coefficient at this time was determined using the following formula.

(6) Number A of uneven units having protrusions as cores and depressions around them.7! The surface of a film on which aluminum was deposited was measured using a Carl Zeiss differential interference microscope. Photographs were taken at a magnification of rθ, and the number A (1 to 1) of uneven units having a major axis of Oo and 2 μm or more was counted per surface area of the film, which had a total of 1 to 1.

(7) Crystallization time of film at 200°C: D80 Knee B manufactured by PerkinElmer was used.

The sample was heated to 300°C at 16°C/min.

After leaving at 300℃ for 5 minutes, heat at AII℃/min.
After rapidly lowering the temperature to 0.degree. C. and performing isothermal crystallization at 00.degree. C., the time until the crystallization peak was measured.

Comparative Example 1 100 parts of dimethyl naphthalene-6-dicarboxylate,
10 parts of ethylene glycol and 0 calcium acetate hydrate
．． 7 parts of vinegar and 0.77 parts of IJ thiium dihydrate were charged into a reactor, heated at the tip of a knife, distilled off methanol, and carried out a transesterification reaction. The transesterification was substantially completed.

Next, to this reaction product, triethyl phosphate o, Js
of antimony tridisperse as a polycondensation catalyst.
．． 0! After adding 1.0 parts, a polyester was obtained according to a conventional method. At this time, [n]=0.53. This was subjected to solid phase polymerization to obtain a polymer composition with [n]=0.63.

Next, after drying the raw material polyester, bath melt extrusion was performed to obtain an unstretched film. At that time, we adopted the silent contact method. The unstretched film was first stretched at 733°C by a factor of Δ
The film with m=0.010 was further stretched 2 times at tSO°C to obtain a longitudinally-axially stretched film with Δn=0.200. At this time, as the stretching roll, a ceramic coated roll having an upper surface roughness of /S was used. Next, the longitudinally-axially stretched film i! After stretching 9.0 times with a tenter at ro℃,
! A 10μ film was obtained by heat setting at T°C. Table 1 shows the physical properties of the film obtained.

Example/100 parts of dimethyl naphthalene-6-dicarboxylate,
Part of ethylene glyco-Al2O and 0.11 parts of calcium acetate hydrate were placed in a reactor and heated to raise the temperature, and methanol was distilled off to carry out the transesterification reaction. After the start of the reaction, the temperature was raised to 230°C over a period of about 1 hour. After achieving this and substantially completing the transesterification, lithium acetate dihydrate Q, 77
part was added. Next, 0.2 g part of trimethyl phosphate was added to this reaction product, and then 0.05 part of antimony dioxide was added as a polycondensation catalyst, and then a polyester was obtained according to a conventional method. Solid phase polymerization was carried out in the same manner as in Comparative Example 1 (
n) = o, ts.

Film formation was carried out in the same manner as in Comparative Example 1 to obtain a sample.

In Example/Example/, after addition of trimethyl phosphate, calcium carbonate of average particle size/, 2μ, 7 o o
Polymerization was carried out in the same manner as in Example except that ppm was added to obtain a single polymer composition. A film was obtained by forming a film using this polymer composition in the same manner as in Comparative Example.

Example 3 Using the same polymer composition as in Example 3, higher fatty acids were added during extrusion film formation. ;000 ppm tri-blending and extrusion, followed by stretching in the same manner as in Example C to obtain a film. These results are shown in Table 1.

〔Effect of the invention〕

According to the method of the present invention, a film excellent in both thickness unevenness and flatness and smoothness can be obtained.

Claims (2)

[Claims] (1) 0.0 inert fine particles with an average particle size of 0.1 to 10μ
A polyethylene-2,6-naphthalate film containing 1 to 10% by weight, the 1/2 crystallization time of the film at 200°C is 6.0 minutes or less, and the degree of plane orientation Δ
P and the average refractive index @n@ satisfy the following formulas [1] and [2], and the long axis of the protrusion and the protrusion as a core is at least 0.2
Film surface area of the unit of unevenness consisting of depressions of μm or more 1
A flat and slippery film characterized by the number A per mm^2 (pieces/mm^2) satisfying the following formula [3], and the thickness unevenness in both the vertical and horizontal directions of the film being 8% or less. Polyethylene-2,6-naphthalate film with excellent thickness unevenness. ΔP≦1.43@n@−2.136…………[1]1.
6650≦@n@≦1.6750……[2]0<A
≦15000…………[3] (2) A substantially unoriented unstretched film of polyethylene-2,6-naphthalate is first stretched in the longitudinal direction so that the birefringence Δn becomes 0.030 or more and 0.090 or less (pre-stretching), and then The birefringence Δn is 0.090 or more in the direction
．． 14. The polyethylene-2,6-naphthalate film according to claim 1, wherein the polyethylene-2,6-naphthalate film is stretched to a molecular weight of 140 or less (post-stage stretching) and then laterally stretched.