JPH09207194A - Die for extrusion molding of thermoplastic resin and molding of polyester film using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To mold a polyester film free from a die line by subjecting only the lip on an anti-taking-over side among a pair of die lips to R processing or corner cut processing. SOLUTION: A die and die lips are formed so as to have a structure such that an R processing part 3 of 0.1-5.0mm, pref., 0.5-2mm or corner cut processing part is provided to the leading end of the die lip only on an anti-gaking-over side 32 among the die lips. R processing is an abridgment of round processing and the leading end of each die lip usually finished at a right angle is rounded to be formed into a circular arc shape. By this constitution, an extruded resin film is pulled rearwardly along the lip 32 on the anti-taking-over side to go away from the lip 31 on a taking-over side and, therefore, deteriorated matter becomes hard to adhere and the adhesion and growth of discharges are suppressed and no die line is generated.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thermoplastic resin extrusion molding die and a polyester film molding method using the same.

[0002]

2. Description of the Related Art Conventionally, as a method for preventing the occurrence of die lines, for example, Japanese Patent Laid-Open No. 3-231826 discloses a method in which a step is formed on a die lip and a flow path is inclined. Further, Japanese Patent Application Laid-Open No. 60-48321 discloses a technology of R-processing a lip edge with a polyester circular die, and Japanese Patent Application Laid-Open No. 6-335949 discloses a method of processing both corners of the tip of the die lip.

[0003]

When a thermoplastic polyester is extruded into a sheet shape and formed into a film by flattened stretching, streak-like defects called die lines may occur on the surface of the formed article. This die line causes a convex streak on the surface of the extruded film when the extruded film comes into contact with foreign matters, polymer deterioration products and the like attached to the tip of the die lip.

Particularly in the case of polyester, since it has a property of producing a deteriorated product by thermal decomposition, the deteriorated product adheres and grows in a bead shape at the tip of the die lip while the extrusion molding is continued, and a die line is generated. Easy to cause. The deteriorated material that adheres in a ball shape is called the eye tar.

Polyester films are widely used for applications such as magnetic tapes, plate making, X-ray photography, etc., but films with die lines do not become products and cause a large loss. Further, the eye blemishes once generated are sometimes taken off by the film and disappear, but usually the number and size increase, and die lines tend to occur frequently over time. For this reason, once a die line occurs, production must be stopped and the eye dies must be removed by a method called shigoki in which the die lip is rubbed with a spatula such as metal or bamboo. Therefore, the die line not only reduces the product quality,
Once it occurs, it will greatly reduce productivity, so a solution for it is desired.

The method of forming a step on the die lip and inclining the flow path, which is described in Japanese Patent Laid-Open No. 3-231826, is insufficient in its effect. It has a drawback that it is difficult to remove and the eye die cannot be removed sufficiently. When the flow path is tilted, it is even more difficult for the squeak to occur. There is also a drawback that the resin sticks to the lip when a new resin flows out to start the production. Further, the technique of R-processing a lip edge with a polyester circular die described in JP-A-60-48321 cannot be applied because the film forming method is different from the flat method. Further, in the method of corner processing both sides of the die lip tip described in the above-mentioned JP-A-6-335949,
At least in the shape described in the specification, it is almost the same as sharp edge processing, and although it may be effective for heat resistant polymers such as polyimide, in polyester, the dents of the deteriorated product accumulate at the corners on the take-up side. It seems that the die line is generated in the same way as when using the lip with the right angle processing.

As is clear from the above, it is an object of the present invention to provide an extrusion molding die that does not cause stripe defects called die lines on the surface when a thermoplastic polyester is extruded. . It also provides a method for molding a polyester film having no die line by using the die.

[0008]

A thermoplastic resin extrusion molding die according to the present invention is a die used for extrusion molding flat stretching film formation of a thermoplastic resin, and is a side of a pair of die lips opposite to the take-back side. It is characterized in that only the lip is rounded with a tip of 0.1 or more and 5.0 mm or less or with a corner cut of 0.1 or more and 5.0 mm or less.

Further, the method for molding a polyester film according to the present invention is a method in which thermoplastic polyester is melt-extruded and molded, and then the polyester film is molded by flat biaxial stretching. Use an extrusion die characterized in that only the lip is rounded with a tip of 0.1 or more and 5.0 mm or less or a corner cut of 0.1 or more and 5.0 mm or less, and the die is 5 degrees or more in the anti-drawing direction. Each is characterized by being tilted by 20 degrees or less.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described in detail below.
The die line referred to in the present invention is, as shown in a schematic view in FIG. 4, the die line 2 is a defect which becomes a convex streak in the same direction as the extrusion direction indicated by the arrow on the surface of the molded product (polyester film 1) and has a thickness of 0 for 100 μm film.
It often has a height of about 1 to 1 μm. The one with a high height is observed with the naked eye, while the one with a low height is observed in a strip shape when sandwiched between two polarizing plates.

For photographic use such as plate making and X-ray photography, a silver halide emulsion is coated on a polyester film 1 to obtain a product. However, if there is a defect such as a die line 2, uneven coating of the emulsion occurs, so that the naked eye is required. It should not be a die line that cannot be observed. Therefore, as soon as a die line occurs, the production must be interrupted and the eye crocodile must be removed by squeezing.

The effect of preventing die line generation can be evaluated by the number of continuous production days until the die line is generated.

The thermoplastic resins referred to in the present invention are polyolefins such as polyethylene and polypropylene, polyamides such as nylon 6, nylon 66, nylon 610 and nylon 132, melt extrusion molding of polystyrene, polycarbonate, polyvinyl chloride and the like. This refers to the resin used, but it can be preferably applied to thermoplastic polyesters in which the die line tends to be emphasized by biaxial stretching.

The thermoplastic polyester is an aromatic dicarboxylic acid such as terephthalic acid, isophthalic acid or naphthalene-2,6-dicarboxylic acid, or an ester thereof,
Polyester obtained by polycondensation with glycols such as ethylene glycol, diethylene glycol, tetramethylene glycol and neopentyl glycol. Polyester can be formed by directly polycondensing an aromatic dicarboxylic acid and a glycol, or can be subjected to a transcondensation after transesterification of an aromatic dicarboxylic acid dialkyl ester and a glycol, or can be polycondensed with an aromatic dicarboxylic acid diester. And the like. Typical examples of such polymers include polyethylene terephthalate, polybutylene terephthalate, polyester-2,6-naphthalate and the like, or copolymers thereof. Moreover, what copolymerized the 3rd component may be sufficient. Furthermore, pigments such as titanium oxide, barium sulfate, silica and calcium carbonate, coloring dyes, optical brighteners, ultraviolet absorbers, antistatic agents, lubricants and the like can be added.

Extrusion molding flat stretching film formation means that a molten polymer is extruded from a die having parallel slits, formed into a sheet, and then rolled, a stenter, or the like.
It is a method of forming a film by sequentially or simultaneously stretching in the longitudinal and transverse biaxial directions. In the case of polyester, generally, a roll is provided with a peripheral speed difference and stretched 2.0 to 6.0 times in the longitudinal direction, and stretched 2.0 to 6.0 times in the transverse direction by a stenter, and then stretched. The method of heat fixing is adopted. In magnetic tape applications and the like, a method of transverse stretching and then longitudinal stretching again is used to obtain strength in the longitudinal direction. The present invention is not applicable to the method of depositing the eye varnish in a film-forming method that is not a flat method, such as a tubular method, because the method of attaching the resin is different.

As shown in FIGS. 1 and 2, the die and die lip of the present invention have a rounded portion having a tip of 0.1 or more and 5.0 mm or less, preferably 0.5 or more and 2 mm or less only on the non-drawing side 32. 33 or a corner cut processing portion 34 is provided. The anti-take-away side 32 refers to the lip opposite to the take-out direction when the molten polymer is extruded and drawn into a sheet as shown in FIG. In the present invention, the non-take-back side 32
Only the lip is provided with a rounded portion or a corner cut portion 34 having a tip of 0.1 or more and 5.0 mm or less, preferably 0.5 or more and 2 mm or less.

The R processing is an abbreviation for round processing, and as shown in FIG. 1, the tip of a die lip which is normally finished at a right angle is rounded into an arc shape. In the present invention, the effect of die line prevention is exhibited when the radius of the arc is 0.1 or more and 5.0 mm or less, preferably 0.5 or more and 2 mm or less. As will be shown in later examples, when R0.1 mm or less, the effect is insufficient and R5
If the thickness is greater than or equal to mm, the extruded resin film may adhere to the lip surface on the non-take-back side. The optimum value of R varies depending on the viscosity of the applied resin, the amount of extrusion, the take-up speed, etc., but in the range of viscosity generally used for film formation, R 0.5 mm or more and 2.0 mm or less seems to be most preferable. Is. In addition, as shown in FIG. 3, the corner of the die lip is dropped by corner cutting, and the length of one side to be cut is 0.1 to 5.0 mm, preferably 0.5 mm.
The effect of preventing die line is exhibited when the distance is 2.0 mm or less. This is also shown in the other examples, but if it is 0.1 mm or less, the effect is insufficient, and if it is 5 mm or more, there is a problem that the extruded resin film adheres to the lower surface of the anti-take-up side lip. Here, it is not always necessary to scrape off an isosceles triangle, and it can be easily conceived that the shape of the triangle can be changed and devised according to the characteristics of the resin.

According to the study by the present inventors, when the polyester is melt-extruded, the resin swells due to a phenomenon called the ballast effect, and the distance between the lower surface of the lip on the take-up side and the resin film becomes shorter, so that the eye resin is attached to the take-up side. It has been found that it is easy to do and die lines easily occur. As a countermeasure against this, by applying specific processing only to the anti-take side lip, the extruded resin film is pulled rearward along the anti-take side lip, and deteriorated substances adhere to it as it moves away from the take side lip. It is considered that the adhesion becomes less likely to occur, the adhesion growth of the eye crocodile is suppressed, and the die line does not occur.

In the present invention, it is important to perform the above-mentioned processing only on the lip on the non-take-back side, and the lip on the take-up side must be subjected to conventional right-angle processing. When the take-up lip is rounded or corner-cut, the resin film is pulled in the take-up direction, and contrary to the object of the present invention, the adhesion and growth of the eye varnish is fast and a die line is likely to occur. .

When extrusion molding is carried out using the die of the present invention, as shown in FIG.
Can be tilted at 0 degrees or less. As described above, since it is effective to keep the lip on the take-up side and the resin film away from each other, the effect of the present invention can be enhanced by tilting the die in the take-up direction. However, when the angle is 5 degrees or less, there is almost no difference from the vertical direction, and when the angle is 20 degrees or more, the resin film adheres to the non-take-up side lip at the start of extrusion, which is not preferable. When the die is tilted, it has a drawback that it is difficult for the die to die, but when the die of the present invention is used, the eye die is less likely to adhere, and therefore the die is almost unnecessary.

The die resin flow path surface and the lip tip to bottom surface can be plated with chromium, copper, nickel, titanium, zinc or the like. When the tip of the die lip is scratched, streaks are generated from it, so plating can improve scratch resistance. Hard chrome plating is particularly preferable. Further, surface processing instead of plating, such as carbon sputtering, may be applied.

A conventionally known method can be applied to the method for molding the polyester film. For example, polyester is melt-extruded and rapidly cooled by a casting drum or water cooling to form an amorphous sheet, then 2 to 6 times in the longitudinal direction due to a difference in roll peripheral speed, and 2 in the lateral direction by a stenter method.
~ 6 times, sequential biaxial stretching or simultaneous biaxial stretching, 160 ~
Heat setting is performed at about 250 ° C. Stretching is vertical-horizontal, horizontal-vertical,
The order of vertical-horizontal-vertical is not limited. However, the present invention is effective in the case where the flat biaxial stretching makes the die lines generated at the die lip more conspicuous and becomes more noticeable, and the film forming methods other than the flat method such as the circular method film are not applicable.

[0023]

The present invention will be described in more detail with reference to the following examples. Example 1 Polyethylene terephthalate pellets having an intrinsic viscosity of 0.65 were dried at 150 ° C. for 6 hours and then melt-extruded under the following apparatus and conditions to form a sheet having a thickness of 1.1 mm.

Apparatus: Mitsubishi Heavy Industries, Ltd. (cylinder bore: 90 mm, L / D: 20) was used as an extruder. Further, as the extrusion molding die, a coat hanger type T die and a lip end R 0.4 mm processed on the non-take-back side were used.

Conditions: The extruder has a set temperature = 290 ° C.,
The screw rotation speed was set to 50 rpm and the casting roll temperature was set to 30 ° C. The formed sheet was longitudinally and laterally biaxially stretched under the following conditions, heat-fixed, slits in both ears, and wound into a film having a thickness of 100 μm.

Longitudinal stretching: Stretching due to difference in roll peripheral speed Preheating roll temperature: 78 ° C. Infrared heater heating Film temperature during stretching: 95 ° C. Stretching ratio: 3.3 times Horizontal stretching: Stenter system stretching zone temperature: 100 ° C. Stretching ratio: 3.3 times heat setting temperature: 220 ° C. The effect of preventing die line generation was evaluated by the continuous molding time until the die line was generated. As a result of the experiment, it was possible to continue for 7 consecutive days until the occurrence of die lines was confirmed.

Example 2 A polyester film was molded in the same manner as in Example 1 except that the tip of the lip opposite to the take-up side of the die was 0.8 mm in corner cut. As a result of the experiment, it was possible to continue for 7 consecutive days until the occurrence of die lines was confirmed.

Example 3 A polyester film was continuously molded in the same manner as in Example 1 except that the die of Example 1 was tilted 10 degrees from the vertical direction in the anti-drawing direction. As a result of the experiment, it could be continued for 8 consecutive days until the occurrence of die lines was confirmed.

Example 4 A polyester film was continuously molded in the same manner as in Example 2 except that hard chrome plating was applied from the resin flow path surface to the lower surface of the lip on the opposite side of the die of Example 2.
As a result of the experiment, it is continuous 7 until the occurrence of die line is confirmed.
I was able to continue for a day.

Comparative Example 1 R processing of the tip of the lip on the non-take-back side of the die of Example 1 was performed.
Extrusion of the polyester film was started in the same manner as in Example 1 except that the thickness was set to 0 mm, but when the resin film came out of the die, the resin film curled and stuck to the lip on the non-take-back side, and normal casting was performed. There wasn't.

Comparative Example 2 R processing of the tip of the lip on the non-take-back side of the die of Example 1 was performed.
A polyester film was continuously molded in the same manner as in Example 1 except that the thickness was set to 05 mm. As a result of the experiment, the number of continuous days until the occurrence of die line was confirmed was 2 days.

COMPARATIVE EXAMPLE 3 A polyester film was continuously formed in the same manner as in Example 1 except that the die end of the die of Example 1 was R0.4 mm-processed and the lip edge of the non-take-up side was normally right-angled. Molding was carried out. As a result of the experiment, the number of continuous days before the occurrence of die line was confirmed was one day.

[0033]

As is clear from the experimental results of the above-mentioned Examples and Comparative Examples, according to the present invention, the effect of preventing die line generation is 7 days or more continuously, and stable molding is possible. It will be easier and beneficial for improving production efficiency, and the problems mentioned above will be solved.

[Brief description of drawings]

FIG. 1 is a schematic sectional view showing an embodiment of a die according to the present invention.

FIG. 2 is a schematic sectional view showing another embodiment of the present invention.

FIG. 3 is a schematic diagram showing the arrangement angle of the dies.

FIG. 4 is a schematic diagram of a die line.

[Explanation of symbols]

 1: Polyester film 2: Die line 30: Extrusion molding die 31: Take-up side 32: Anti-take-off side 33: R processing part 34: Corner cut part 35: Casting drum

Front Page Continuation (72) Inventor, Etsunori Chiba, Tokyo, Hino City, No. 1 Sakura-cho, Konica Co., Ltd. (72) Inventor, Kenya Katsunuma, Tokyo, Hino-shi, No. 1, Sakura-machi, Konica Co., Ltd. (72) Inventor, Mori Ryoji 1 Takamichi, Iwazuka-machi, Nakamura-ku, Nagoya, Aichi Prefecture, Nagoya Research Institute, Mitsubishi Heavy Industries, Ltd. (72) Inventor Toshiro Miki 1-high, Iwatsuka-machi, Nakamura-ku, Nagoya, Aichi Prefecture, Nagoya Research Institute, Mitsubishi Heavy Industries, Ltd. (72 ) Inventor Kaoru Takano 1 Takamichi, Iwazuka-cho, Nakamura-ku, Nagoya, Aichi Prefecture Mitsubishi Heavy Industries, Ltd. Nagoya Research Laboratory

Claims (3)

[Claims] 1. A die used for extrusion molding of a thermoplastic resin for flat film formation, wherein only a lip opposite to the take-up side of a pair of die lips has a radius of 0.1 or more and 5.0 mm or less, or a radius of less than 0.1 mm. An extrusion die having a corner cut of 1 to 5.0 mm. 2. A method in which a thermoplastic polyester is melt extruded and molded, and then a polyester film is molded by a flat biaxial stretching method. Of a pair of die lips, only the non-take-back side lip has a tip of 0.1 to 5.0 mm. A method for molding a polyester film, which comprises using an extrusion die characterized by the following R processing or corner cutting processing of 0.1 to 5.0 mm. 3. The method for molding a polyester film according to claim 2, wherein the die is tilted in a direction opposite to the pulling direction from 5 degrees to 20 degrees.