JPS61278559A - Polyester film - Google Patents

Abstract

PURPOSE:To provide the titled film having excellent wear resistance, transpar ency and easy slipperiness and suitable for use in the fields of magnetic tape, metallized film and photographic film, by molding a polyester contg. an inorg. fiber into a film and biaxially orienting the film. CONSTITUTION:An inorg. fiber having an average fiber diameter (d) of 0.5mu or below, an average fiber length (l) of 5mu or below and a ratio of l/d of 3-10, obtd. by carrying out the adjusting of size and the removal of coarse particles in a refining process, selected from among potassium titanate, calcium carbonate and high silica zeolite, is added as a glycol slurry in a ratio satisfying the formula [wherein W is inorg. fiber content in wt%; d and l (mu) are as defined above]. The glycol slurry and dimethyl phthalate, etc. are subjected to a transesterification or esterification reaction. The resulting polyester such as polyethylene terephthalate is molded into a film, which is then biaxially oriented.

Description

[Detailed Description of the Invention] The present invention relates to a polyester film, and more specifically, it contains uniformly dispersed non-I fibers and has excellent abrasion resistance, slipperiness and transparency. This invention relates to an excellent biaxially oriented polyester film.

Polyester in general, and polyethylene terephthalate in particular, has excellent mechanical and chemical properties and is widely used in films, fibers, and the like.

However, when producing films or fibers that take full advantage of their transparency and brightness, process defects often occur during the molding and processing steps. The cause is often due to high *i* coefficients.

Conventionally, many methods have been proposed to reduce the coefficient of friction of polyester, including the presence of fine particles in polyester, but the affinity between the fine particles and polyester is insufficient, and the transparency of films, Il fibers, etc. The abrasion properties were not all satisfactory. To explain this method further, conventional methods for improving the surface properties of polyester include: ■ A method in which part or all of the catalyst used during polyester synthesis is precipitated in the reaction process (internal particle precipitation method) ■ Calcium carbonate, oxidation Many methods have been proposed in which fine particles such as silicon are added during or after polymerization (external particle addition method).

However, in the internal particle precipitation method (2), since the particles are metal salts of the polyester component, the affinity with polyester is good to some extent, but on the other hand, the method generates particles during the reaction, so the amount of particles is 2 particles. It is difficult to control the diameter and prevent the generation of coarse particles.

On the other hand, in method (2), if the particle size, amount added, etc. are appropriately selected, and fine particles from which coarse particles have been removed by classification etc. are added, excellent slipperiness can be obtained.

However, since the affinity between the inorganic particles and the organic component polyester is not sufficient, peeling occurs at the interface between the particles and the polyester during stretching, etc., and voids are generated.

If these voids exist in the polyester film, particles are likely to separate from the polyester film due to damage to the polyester film due to wear between the polyester films or between the polyester film and other base materials.
For example, it causes white powder and dropouts in magnetic tape films. Furthermore, the presence of large voids around the particles impairs the transparency of the polyester film. Therefore, the lack of affinity between inorganic particles and polyester is a problem that must be solved in terms of wear resistance and transparency.

To improve the affinity between inorganic particles and polyester, surface treatment using a coupling reaction between inorganic particles and silane compounds or titanate compounds, for example, has been proposed, but the treatment process is complex and the effects are not expected. There were various problems such as not being able to cut the edges.

On the other hand, the winding properties of polyester film 1 dimensional stability;
As a method to improve the strength of the waist, etc., 0.1% by weight or more, especially 0.5 to 0.1% by weight, of single fibers of metal titanate having a diameter of 2μ or less, a length of 50μ or less, and a length/diameter of 5 or more is used. A method of dispersing in 1% by weight polyester has been proposed (Japanese Unexamined Patent Application Publication No. 1989-1996).
9-71036>. When the present inventor manufactured a polyester film using the single fibers used in the specific example of the above-mentioned publication, it became clear that there was a problem in terms of voids.

In view of the above-mentioned circumstances, the inventors of the present invention have conducted intensive studies to develop a film with excellent abrasion resistance, slipperiness, and transparency by incorporating fine inorganic substances into a polymer, and have developed a film with a specific shape. It has been discovered that a polyester film containing inorganic fibers having the following properties has improved peeling at the interface between the inorganic fibers and the polyester, and has good properties, and has arrived at the present invention.

An object of the present invention is to provide a biaxially oriented polyester film having excellent abrasion resistance, slipperiness, and transparency.

According to the invention, the average fiber diameter (d)
is 0.5μ or less, the average fiber length (dan) is 5μ or less, and u
It is made of polyester containing inorganic fibers with /d of 3 to 10 in a proportion that satisfies the following formula, and has a film average surface roughness (
This is achieved by a biaxially oriented polyester film characterized by an Ra) of 0.005 to 0.05μ.

As is clear from the above, the main singularity of the present invention is that
The purpose is to incorporate inorganic Il fibers having a specific shape into polyester under specific conditions. This makes the polyester film resistant to abrasion.

It has excellent properties of slipperiness and transparency.

The polyester used in the present invention may be any material as long as it can form a biaxially oriented film, such as polyethylene terephthalate, polytetramethylene terephthalate, polyethylene-p-oxybenzoate,
Examples include poly-1,4-cyclohexylene dimethylene terephthalate and polyethylene-2,6-naphthalene dicarboxylate. Of course, these polyesters may be homopolyesters or copolyesters, and examples of copolymerization components include diol components such as diethylene glycol, neopentyl glycol, and polyalkylene glycol, adipic acid, sebacic acid,
Phthalic acid, isophthalic acid.

2. Dicarboxylic acid components such as 6-naphthalene dicarboxylic acid and 5-sodium sulfoinphthalic acid; polyfunctional carboxylic acid components such as trimellitic acid and pyromellitic acid in an amount that maintains the polymer substantially linear, etc. can be mentioned.

The inorganic fibers contained in the polyester in the present invention are made of inorganic material, but the material is not particularly limited as long as the fiber diameter, fiber length, etc. satisfy specific conditions. However, due to ease of availability and dispersibility in polyester, potassium titanate, calcium carbonate, etc.
titanium dioxide.

Mordenite (e.g. high silica zeolite).

Attapulgite, helosite, iron oxide (ferrite)
etc. are preferred.

The ms fiber-free shape has an average fiber diameter (d) of 0.5 μ or less, an average fiber length [1) of 5 μ or less, and l/d of 3 to 10. If the particles have an fi/d of less than 3, such as spherical or lumpy particles, the resulting polyester film is likely to have voids and lack sufficient abrasion resistance and transparency.

Moreover, when l/d exceeds 10, the abrasion resistance of the film is insufficient. Further, if the average fiber diameter exceeds 0.5μ, the unevenness of the film surface becomes too large, and electromagnetic conversion characteristics deteriorate in applications such as magnetic tapes.

Furthermore, if the average fiber length exceeds 5μ, it becomes difficult to orient the film in the plane direction during stretching, making it easy to break before the desired stretching ratio is reached, and the unevenness of the film surface becomes too large, resulting in poor electromagnetic conversion characteristics. becomes worse.

In the present invention, it is preferable that the size of the inorganic m-fibers be adjusted and coarse particles removed using a purification process before the inorganic m-fibers are incorporated into the polyester. As industrial means for the purification process, examples of crushing means include jet mills, ball mills, etc., and classification means include wet or dry centrifugal separation.

Examples include filter filtration. These methods are 2
It goes without saying that more than one species may be used in combination for stepwise purification.

The mwaau-free content in the polyester film satisfies the conditions of the following formula (1), and the average surface roughness (Ra) of the film is 0.005 to 0.05μ, preferably 0.08 to 0.02μ. It is necessary to do so.

If the value of (dx statement On the other hand, if the value of (dx, QXw) exceeds 1, the effect of imparting slipperiness and improving wear resistance will not be further exhibited, and on the contrary, the electromagnetic conversion characteristics will deteriorate, resulting in a reduction in filter life during film formation, etc. The negative effects of this will begin to occur.

The preferred content of inorganic fibers is within a range that satisfies the condition of formula (2) below.

0.006≦dX sentence×W≦0.5 ・・・・・・
・('2J [However, di and w are the same as the above definitions] Inorganic fibers can be incorporated into polyester at any time and by any method, but before the polymerization reaction of the polyester reaction, especially transesterification or esterification. A method of adding the glycol slurry before the end of the reaction is preferred.

For polyester film, use the above polyester as is,
Alternatively, it can be obtained by diluting it with another polyester (polyester that does not contain tail-free at a predetermined ratio) and forming a film. Other polyesters used for dilution include, for example, polyesters produced by conventional precipitation or addition methods or particle-free polyesters. In any case, it is necessary that the finally obtained film contains the above-mentioned inorganic fibers in the above-mentioned predetermined amount.

The film forming conditions are a known method, for example, usually after melt extrusion into a sheet at 280 to 300 ° C., cooling and solidifying to form an amorphous sheet, for example, sequentially in the vertical and horizontal directions, or vertically, horizontally, and longitudinally. A method of biaxial stretching, a method of simultaneous two-wheel stretching in the longitudinal and transverse directions, etc. can be employed.

11 - 11 The biaxially oriented polyester film of the present invention has various advantages such as almost no generation of voids (gaps) or detachment of particles from the film surface during stretching, and a sufficient slipperiness imparting effect. Because of this, it can be used for various purposes.

It can be particularly preferably used in the field of magnetic tapes, vapor deposited films, photographic films, etc., which require abrasion resistance and transparency.

This will be explained in detail by giving examples below. Note that "parts" in the examples mean parts by weight. Further, each characteristic value in the Examples was measured according to the following method.

(1) The average fiber diameter and average fiber length of 8m11 non-fibers were determined using a microscope. That is, after photographing by passing through a film containing inorganic fibers or inorganic m-fibers, the diameter and fiber length of the inorganic fibers were measured, and the number average value was calculated to determine the average fiber diameter and average 411i length.

(2) Film surface roughness (Ra) JIS 8
Measured according to 0801. A chart (film surface roughness curve) was drawn using a stylus type surface roughness meter (SURFCOM 3B) manufactured by Tokyo Seimitsu Co., Ltd. under the conditions of a needle radius of 2 μm and a load of 0.07 g. A part of measurement length L is extracted from the film surface roughness curve in the direction of its center line, the center line of this extracted part is set as the X axis, and the direction of vertical magnification is set as the Y axis.
When the roughness curve is expressed as Y-f(x) as the axis, the value (Ra: μm) given by the following equation is defined as the film surface roughness.

In the present invention, Ra
expressed.

(3) Abrasion evaluation - ■ Place the 1/2 inch wide film surface on a 5sIIφ stainless steel mesh SUS fixed bottle (surface roughness 0.58) at an angle of 15
They are brought into contact at 0° and moved back and forth at a speed of 27 FL per minute for approximately 15 cIR to create friction (at this time, the entry side tension T1 was set to 409).

After repeating this operation and measuring 20 times, the degree of scratches generated on the surface was visually determined.

At this time, it is judged in 4 stages: ◎ if there are almost no scratches, O if there are only a few scratches, ×1 if there are many scratches on the entire surface, Δ if the scratches are between the former two. do.

(4) Evaluation of abrasion resistance - ■ The abrasion resistance of the running surface of the base film was evaluated using a 5-stage mini super calender. Calendar 7 is a 5-stage calender with nylon rolls and steel rolls, processing temperature is 80°C, and linear pressure applied to the film is 200 kg/c.
tn, and the film speed was 507 FL/min. After running the running film for a total length of 2000 m, the abrasion resistance of the base film was evaluated based on the dirt that adhered to the top roller of the calendar.

4-level judgment> ◎ No stains on the nylon roll 0 Almost no stains on the nylon roll Δ Nylon roll stains × Very dirty nylon roll (5) Affinity film between inorganic fiber and polyester is etched to form a surface polymer Removed and inorganic! After exposing the IM, it was observed under a scanning electron microscope at 20,000x magnification.

Regarding affinity, voids generated around inorganic fibers (
The following judgments were made regarding the size of voids.

1st grade: No void or very small 2nd grade:
Tertiary grade with some small voids: Example 1 with large voids Potassium titanate is added to ethylene glycol (hereinafter abbreviated as EG), then dispersed with a dispersa mill, and further processed with a grind mill and centrifugal separation. and the average fiber diameter is 0
．． A potassium titanate-containing EG slurry with an average tliM length of 0.8μ was obtained.

While heating 100 parts of dimethyl terephthalate, 70 parts of EG, and 0.035 parts of manganese acetate tetrahydrate under a nitrogen atmosphere, by-product methanol was distilled off to perform a transesterification reaction.

At the stage when the transesterification reaction was substantially completed, the previously prepared EG slurry of potassium titanate was heated at a temperature of 210°C so that the potassium titanate content in the polymer was 0.2% by weight.
It was added so that Next, antimony trioxide 0.0
3 parts and 0.03 part of trimethyl phosphate were added, and the pressure was gradually reduced to carry out a polycondensation reaction in a conventional manner to obtain polyethylene terephthalate having an intrinsic viscosity (Ortsk 00 phenol solvent, 35° C.) of 0.63.

This polyethylene terephthalate was then heated to 180°C.
After drying, it was formed into a sheet using a melt extruder and solidified by cooling. Subsequently, the longitudinal stretching ratio was 4.0 times at 90°C.

Sequential biaxial stretching at a transverse stretching ratio of 3.5 times, and further at 200°C
A film with a thickness of 15 μm was obtained by heat treatment.

The properties of this film are shown in Table-1. The obtained film had good surface roughness, abrasion resistance, and affinity.

Examples 2 and 3 and Comparative Examples 1 to 6 Same as Example 1 except that the average fiber diameter, average fiber length, and content of potassium titanate in Example 1 were changed as shown in Table 1. I went and got the film. The properties of this film are shown in Table-1. Those that did not meet the conditions of the present invention had poor surface roughness and wear resistance.

Examples 4 and 5 In Example 1, potassium titanate was replaced with mordenite (
A film was obtained in the same manner as in Example 1, except that the crystal type offretite/eriotite) or calcium carbonate was used, and the conditions were changed to those listed in Table 1. The properties of this film are shown in Table-1. All films had good characteristics.

Comparative Examples-7 and 8 Example-1 except that potassium titanate in Examples-1 was changed to granular calcium carbonate or titanium dioxide
I went the same way and got the film.

The properties of this film are shown in Table-1. Both had poor abrasion resistance and 5M compatibility.

(Margin below) Procedural amendment August 79, 1985

Claims (1)

[Claims] 1. The average fiber diameter (d) is 0.5μ or less, the average fiber length (l
) is 5μ or less and l/d is 3 to 10, and is made of polyester containing inorganic fibers in a proportion that satisfies the following formula, and the film has an average surface roughness (Ra) of 0.005 to 0.05μ. Biaxially oriented polyester film. 0.005≦d×l×w≦1 where d: Average fiber diameter of inorganic fiber (μ) l: Average fiber length of inorganic fiber (μ) w: Content of inorganic fiber (% by weight) 2. The biaxially oriented polyester film according to claim 1, characterized in that it is at least one member selected from the group consisting of potassium titanate, calcium carbonate, and mordenite.