KR100262348B1 - A producing method of polyester film - Google Patents

Abstract

PURPOSE: A method for preparing a polyester film which has high quality in electric character, resistance to abrasion, and prevents inorganic particles from separating or debris from generating while slitting is provided, by coextruding polyester of low molecular weight to improve resistance to slitting and polyester of high molecular weight. CONSTITUTION: The method for preparing a polyester film has characteristics such as followings: (i) a repetition unit is composed of polyethyleneterephthalate or ethylenenaphthalate, and its sheet prior to drawing has a 3 layer structure; (ii) the polyester of outside layers(A) has no inert particles or no internal deposited particles, but the polyester of inside layer(B) has inert particles or internal deposited particles by coextruding; (iii) the molecular weight of the polyester of outside layers(A) is 0.600-0.650, and that of the polyester of inside layers(B) is 0.550-0.600; and (iv) the polyester of inside layer(B) contains 0.1-1wt.% of inert particles with mean particle diameter 0.1-2.0μm.

Description

A manufacturing method of polyester film

The present invention relates to a method for producing a polyester film, and specifically limited to the molecular weight of the polyester to a certain range and at the same time coextruded polyester A, B limited in the amount and size of particles in the polyester to a predetermined thickness It has excellent running characteristics and abrasion resistance, and has a very low generation of debris or wear in the cross section during slitting as well as the occurrence of wear debris from the film during the manufacturing process or product use. It relates to a manufacturing method.

Polyester, generally represented by polyethylene terephthalate, has a stable chemical structure and high mechanical properties, and has excellent heat resistance, chemical resistance, and durability. It is widely used for various purposes such as description of magnetic recording media.

Films made from such polyesters have a film surface in contact with a processing process, for example, a roll, which is in contact with an increasing process speed, for example, a printing process for packaging use, a magnetic material application for a recording medium, calendar ring, or slitting. Wear causes problems in post-processing and product characteristics (quality). In particular, in the case of magnetic recording media, inorganic and organic particles such as calcium carbonate, silica, kaolin, and alumina are added as inert particles to improve the running and processability of the film. The problem of deterioration of the electronic properties due to the roughening of the complex and the increase in film wear with the dropping of the added inert particles and the increase in the production rate has a complex problem.

In recent years, the improvement of the electronic conversion characteristics according to the trend of high performance of the magnetic recording medium requires a film having a flatter surface, and on the contrary, the increase in the production speed of the magnetic recording tape has been shown to prevent the falling out of the driving characteristics, wear resistance and particles during high-speed driving. The situation is increasing the demand for.

Furthermore, the increase in process speed is associated with an increase in the tension of the process, which makes the film under more severe conditions, and the increase in dropping off of the particles inside the film is a cause of foreign matter or contamination during the process. This results in a drop out characteristic of the tape.

In order to solve this problem, a number of methods for improving the electronic properties, the running characteristics, and the wear resistance of the film have been conventionally proposed. However, when the electronic characteristics are improved, the driving characteristics are deteriorated and the wear resistance is poor. The effect is still insufficient.

In addition, the improvement of wear resistance of the film increases the wear and foreign matters generated during the slitting process, resulting in a drop in the tape dropout characteristics, and the occurrence of end caps such as debris and end jaws in the cross section. It may also increase appearance defects.

Accordingly, an object of the present invention is to provide a method for producing a polyester film for the development of a polyester film excellent in running and wear resistance and at the same time excellent in slitting property, to solve the conventional problems described above. have.

The present invention for achieving the above object is to be achieved by limiting the molecular weight of the polyester to a specific range and at the same time by stretching by co-extrusion of the polyester with a limited amount and size of particles in the polyester.

1 is a schematic view showing a polyester film according to the present invention.

<Description of Symbols for Major Parts of Drawings>

Referring to the present invention with reference to the accompanying drawings Figure 1 as follows.

The present invention relates to a film having a structure of at least three layers before stretching, wherein the outermost layer of polyester (A) has a higher molecular weight than that of the middle layer and has inert particles or internal precipitated particles. It is a manufacturing method.

The present invention uses a relatively low molecular weight polyester in the middle layer to arrange the lubricant added to the polyester in order to impart the running property of the film to the middle layer (polyester B) and to improve the slitting property. It is characterized by arranging a layer (polyester A) containing no inert particles or internal precipitated particles so as to prevent dropping of the lubricant and to improve abrasion resistance of the film surface.

In more detail, when the polyester sheet containing the lubricant is drawn, the lubricant particles are relatively moved in the thickness direction of the sheet, thereby forming protrusions on the surface, thereby providing the active activity. In this case, the particle-free layer constituting the outermost layers surrounds the particles to prevent the lubricant from falling off from the film. Furthermore, by arranging polyester of high molecular weight in the outermost layer, it is characterized by reducing crystallization on the film surface to improve wear resistance.

In addition, in order to achieve the object of the present invention in order to improve the slitting properties of the polyester (B) layer in the middle of the relatively low molecular weight polyester and at the same time is not particularly limited, but 0.1 _to 2 ㎛ inert particles having a particle diameter _It contains _~ 1% by weight, and the outermost polyester (A) layer is characterized in that it does not contain inert particles or internal precipitated particles.

If particles are contained in the outermost layer, it is not effective to prevent the lubricant from falling off. If the lubricant is less than 0.1% in the middle layer, the surface roughness of the film is less affected and the necessary running property cannot be obtained. In this case, coarse particles are generated due to coagulation between the lubricants, and they are adversely affected. If the lubricant particle size of the middle layer is 0.1 μm or less, the surface roughness is insufficient. If the particle size is 2 μm or more, the electronic properties are poor. Done.

In general, when the molecular weight of the film is low, the degree of crystallization is increased during heat treatment for dimensional stability of the film, which is effective in improving slitting, but the wear resistance is decreased. Sea debris or high edge is generated, resulting in poor appearance.

Therefore, in order to simultaneously improve the slitting property and abrasion resistance of the film, the molecular weight of the polyester constituting each layer was adjusted to the following range.

The polyester (A) constituting the outermost layer has a molecular weight IV of 0.600 _to 0.650 to improve wear resistance, and the polyester (B) constituting the middle layer has a IV of 0.550 _to 0.600 to improve slitting. Arranged as.

In another aspect, the present invention is biaxially stretched, the sum of the thickness of the film layer 1 _~ 50㎛ and more preferably from 10 _~ 30㎛ after the end is preferred.

The method for producing polyesters A and B is not particularly limited and conventional polymerization methods of polyester are applied as it is, but inert particles or organic particles insoluble in polyester are appropriately added to the polyester B layer.

For example, insoluble inert particles used in polyester include inorganic particles such as calcium carbonate, dolomite, glass spare, fiberglass, talc, kaolin, mica, silica, barium sulfate, aluminum silicate, alumina, or one aliphatic unsaturation in the molecule. Known organic compounds such as copolymers of monovinyl compounds having a bond with compounds having two or more aliphatic unsaturated bonds as a crosslinking agent, and thermosetting phenol resins, thermosetting epoxy resins, thermosetting urea resins, benzoguanamine resins and fine powders of fluorine resins There is no particular limitation on the type of particles, but it is effective to increase the efficiency when 0.1 _to 1% by weight of inert particles having a particle diameter of 0.1 _to 2㎛. In addition, it is more effective to use a mixture of two or more kinds of the particles.

The method for producing a polyester sheet having a structure of three or more layers is not particularly limited and may be a conventionally known coextrusion method.

For example, a continuous sheet can be produced by supplying molten polyester to a multi-manifold die or pipeblock die to fix the plate-like molten polyester to a rotating cooling drum. The sheet thus produced is continuously subjected to longitudinal stretching, which may be used in one or multiple stages of stretching. The process conditions may be changed between longitudinal stretching and lateral stretching without departing from the surface roughness of the present invention.

The polyester film obtained by the present invention has excellent wear resistance and no falling off particles, and at the same time has good slitting property, which is suitable for magnetic recording media, and may be used for packaging and electrical applications.

Hereinafter, although this invention is demonstrated in detail based on an Example, this invention is not limited to these Examples. In Examples and Comparative Examples of the present invention, various performance evaluation of the produced polyester film was performed by the following method.

1) Average particle diameter

After dispersing the inorganic particles in ethylene glycol, the volume average particle diameter (mu m) was measured using a centrifugal sedimentation particle size analyzer (SA-CPII) manufactured by Shimadzu Corporation (Japan).

2) Floor thickness

Cut the cross section of the film with a microtome and observe it with an electron microscope

3) wear resistance

Using the runability tester (TBT-300H) of the Yokohama Systems Research Institute (Japan), the film was slit to a width of 1/2 inch, and then frictionally driven to the tape guide pin at a running speed of 3.3 cm / sec. Abrasion resistance is evaluated by visually or photographing the white powder on the surface.

Class A: When the guide pin has no powder at all.

Class B: 100% of the guide pin has 1/5 of the guide pin area.

C class: 100% of the guide pin is half of the guide pin area.

Class D: When a minute occurs on the entire guide pin.

4) Slitting Debris Evaluation

Using the tape runability tester (TBT-300H) of the Yokohama System Research Institute (Japan), the film was slit to a width of 1/2 inch, and then the razor was brought into contact with the film surface while traveling at a traveling speed of 50 m / min. Evaluate the degree of debris occurrence. Observe the amount of white powder deposited on the surface of the razor and SEM to evaluate the inactivation of the particles.

Grade A: Almost no white powder at the end of the razor and no dropping of inert particles.

Class B: Almost no white powder at the end of the razor and some inert particle dropping.

Grade C: A lot of white powder is generated at the end of the razor and some inert particles are dropped.

Grade D: A lot of white powder was generated at the end of the razor and a lot of inert particles were dropped.

5) High Edge Evaluation

The height of the slitting end jaws was measured using a contact surface roughness meter (SURFCORDER SE-30D) from Kosaka Institute (Japan). Measurement conditions Touch needle diameter = 0.5㎛, after measuring 7 points, 5 points except the maximum and minimum values were averaged.

Example 1.

100 parts of dimethyl terephthalate, 70 parts of ethylene glycol, and 0.05 parts of saliva calcium acetate were placed in a reactor and subjected to a transesterification reaction. After 4 hours, the transesterification was substantially completed, and then 0.06 parts of trimethyl phosphate and 0.04 parts of antimony trioxide were added to carry out polymerization for 5 hours by a conventional method to obtain Polyester A of IV 0.620. On the other hand, in the preparation of the polyester, 0.4 wt% of calcium carbonate particles having an average particle diameter of 0.6 μm was added after 4 hours of transesterification, followed by polymerization to obtain polyester B of IV 0.570.

Next, after drying each polyester, the feed polyester A was made into the outer layer and the polyester B was made into the middle layer, and the amorphous sheet which has a 3-layered structure of 290 ^o was supplied to the die in which the pipe block was installed. Subsequently, the film was stretched 3.7 times in the longitudinal direction and 4.0 times in the transverse direction at 90 ^° C., followed by 210 ^° C. heat treatment to prepare a biaxially oriented polyester film having a thickness of 14 μm.

The results of these experiments are summarized in Table 1.

Examples _2-6 and Comparative Examples _1-5

Outer Layer IV Middle layer: Polyester B Layer thickness ratio A / B / A (㎛) Wear Resistance (Grade) SlittingDebris (rating) High Edge (㎛) Ⅳ Kinds Particle size (㎛) input(%) Example 1 0.620 0.570 Calcium carbonate 0.6 0.4 1/12/1 B A 0.07 Example 2 0.640 0.590 Calcium carbonate 0.8 0.4 1/12/1 A B 0.14 Example 3 0.630 0.590 Calcium carbonate 1.0 0.4 2/10/2 A B 0.11 Example 4 0.620 0.580 Calcium carbonate 0.8 0.3 1/12/1 B A 0.10 Example 5 0.610 0.570 Silica 0.8 0.5 1/12/1 B A 0.07 Example 6 0.640 0.590 Silica 0.8 0.4 2/10/2 A B 0.12 Comparative Example 1 0.570 0.540 Calcium carbonate 0.8 0.4 1/12/1 C A 0.05 Comparative Example 2 0.560 0.620 Calcium carbonate 1.0 0.4 1/12/1 C D 0.18 Comparative Example 3 0.630 0.650 Calcium carbonate 0.8 0.3 2/10/2 B D 0.20 Comparative Example 4 0.650 0.610 Silica 0.8 0.5 1/12/1 A D 0.16 Comparative Example 5 0.600 0.600 Silica 0.8 0.4 2/10/2 B C 0.15

Among the conditions of Example 1, the molecular weight of the polyester (A, B) and the average particle diameter of the inorganic particles added to the polyester (B), the addition amount was changed to prepare a film having a characteristic difference, respectively. Table 1 shows the results of evaluation of the characteristics of the films.

As described above, the manufacturing method according to the present invention has the effect of preventing the wear resistance and falling of the inorganic particles and at the same time obtain a good slitting property when the particle size, the protrusion height of the inorganic particles fall within the claims of the present invention. There is.

Claims (3)

(Correction) The repeating unit is composed of ethylene terphthalate or ethylene naphthalate, and the sheet before stretching is a multilayer film having a structure of at least three layers. In the method for producing a coextruded polyester film in which particles do not exist and inert particles or internal precipitated particles are present in the middle polyester (B), the polyesters (A) of the outermost layers have a molecular weight IV of 0.600. It is -0.650, The said middle layer polyester (B) is the manufacturing method of the polyester film, whose molecular weight IV is 0.550-0.600. The method for producing a polyester film according to claim 1, wherein 0.1 _to 1% by weight of inert particles having an average particle diameter of 0.1 _to 2.0 mu m is contained in the polyester (B) in the middle layer. (delete)