JPH0691735A - Manufacture of vinylidene fluoride resin film which is superior in transparency - Google Patents

Abstract

PURPOSE:To provide a vinylidene fluoride resin film which is superior in transparency by specifying the copolymerization composition of a vinylidene fluoride resin to be used and a distance between a die-lip of an extruder and a cooling- casting roll. CONSTITUTION:As a vinylidene fluoride resin, a copolymer resin which contains 92-75wt.% of a vinylidene fluoride unit and 8-25wt.% of a hexafluoropropylene unit is used. The conditions for extrusion molding using an extruder 1 are, e.g. that the heating-kneading in a cylinder of the extruder 1 is performed at 170-230 deg.C, and normally, the resin temperature in a T die 2 is set in a range of 200-260 deg.C. Then, a distance between a die-lip 2' of the T die 2 and a cooling- casting roll 4 is set to be not more than 20mm. By this method a vinylidene fluoride resin film which is superior in transparency, thickness precision and productivity can be obtained.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a method for producing a vinylidene fluoride resin film having excellent transparency by extrusion molding.

[0002]

2. Description of the Related Art As a method for producing a highly transparent vinylidene fluoride resin film, vinylidene fluoride resin is kneaded in an extruder, and the melt-extruded resin film is adhered to a mirror-like cooling casting roll. Let 60 ℃
A method of quenching to the following temperature is known. In this method, when the film take-up speed is 2 m / min or less, the extruded film completely adheres to the cooling casting roll to obtain a film having excellent transparency. If it exceeds, the adhesion between the film and the roll becomes non-uniform, the transparency becomes non-uniform between the adhered portion and the non-adhered portion, and a smooth film cannot be obtained. In order to solve this problem, if the roll temperature is in the range of 80 to 120 ° C., the extruded molten resin film can be evenly adhered to the roll, but the cooling of the film does not become a rapid cooling but becomes a slow cooling. However, only a film with insufficient transparency can be obtained.

There is also known a method of passing a molten resin film of vinylidene fluoride resin extruded from an extruder through a thin air layer and onto a cooling casting roll whose surface temperature is 60 ° C. or less. In this method, it is good when the thickness accuracy of the width direction of the resin film is high, but if the thickness accuracy is reduced, the thickness of the air layer of the thin film formed between the resin film and the roll becomes non-uniform, A phenomenon in which the resin film and the roll are in close contact with each other is seen partially, and the transparency becomes uneven between that part and the other part,
In addition, it is difficult to obtain a smooth film.

Furthermore, the die lip clearance of the extruder is
A method is also known in which the vinylidene fluoride resin is melt-extruded with the distance between the die lip and the cooling casting roll set to 0.5 to 0.1 mm and 20 mm or less.
In this method, it is necessary to use an expensive die with good processing accuracy in order to obtain a uniform film with good thin and thin accuracy, and in order to reduce the lip clearance, the extrusion amount is reduced and the productivity is reduced. There is a problem of decrease. Moreover, although a film having a considerable transparency can be obtained, a film having a higher transparency is demanded.

As the vinylidene fluoride resin, a blend of a vinylidene fluoride homopolymer and a methacrylic acid ester polymer is used, which is kneaded in an extruder to cool the extruded molten resin film. A method of passing over a casting roll is also known. In this method, a methacrylic acid ester-based polymer (for example, methyl methacrylate resin) itself is non-crystalline and highly transparent, and this is blended with a vinylidene fluoride homopolymer at an appropriate ratio. As a result, a fairly transparent film is obtained. However, on the other hand, it has a drawback that brittleness, particularly brittleness over time, develops. Therefore, in order to avoid this drawback, blending of a methacrylic acid ester polymer (eg, methyl methacrylate resin) with an acrylate ester polymer (eg, butyl acrylate) as a rubber-like component has been carried out. ,
Such a blend of rubber-like components brings about a decrease in transparency, and thus further improvement is desired.

[0006]

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a method for effectively solving the above-mentioned various problems and effectively producing a vinylidene fluoride resin film having excellent transparency. .

[0007]

According to the present invention, a vinylidene fluoride resin film is melt-extruded by using an extruder and the extruded resin film is passed over a cooling casting roll. In the method for producing, a copolymer resin containing 92 to 75% by weight of vinylidene fluoride units and 8 to 25% by weight of hexafluoropropylene units is used as the vinylidene fluoride-based resin, and Provided is a method for producing a vinylidene fluoride resin film having excellent transparency, which is characterized in that a distance between a die lip and a cooling casting roll is 20 mm or less.

Vinylidene Fluoride Resin In the present invention, it is important to use, as the vinylidene fluoride resin, a copolymer resin containing vinylidene fluoride units and hexafluoropropylene units. It is possible to obtain a film having excellent transparency without impairing the excellent properties of the resin. In the copolymer resin, the vinylidene fluoride unit is 92-75.
%, Preferably 88-80% by weight, and hexafluoropropylene units should be included in a proportion of 8-25% by weight, preferably 12-20% by weight. For example, when the content of the hexafluoropropylene unit is 8% by weight or less, the vinylidene fluoride homopolymer has strong properties, and thus tends to be crystallized, resulting in insufficient transparency of the obtained film. When the content of hexafluoropropylene unit is 25% by weight or more, the obtained film is transparent, but the properties of the vinylidene fluoride homopolymer are impaired, chemical resistance, especially ketones and esters. It loses its resistance to such substances and the important properties of the vinylidene fluoride resin are impaired. Incidentally, the above-mentioned copolymer resin, as long as the content of vinylidene fluoride units and hexafluoropropylene units satisfy the above range, other units, such as chlorotrifluoroethylene units, tetrafluoroethylene unit,
You may have a vinyl fluoride unit etc.

Production of Film In FIG. 1, which briefly shows an example of the production method of the present invention, a molten resin film 3 extruded through a T-die 2 is obtained by heating and kneading a vinylidene fluoride resin in an extruder 1.
Is a cooling casting roll 4 placed close to the T-die 2.
And is wound by the winding roll 5.

In the present invention, the distance between the die lip 2'of the T die 2 and the cooling casting roll 4 is 20 mm.
The following settings are also extremely important. That is, when this distance is larger than 20 mm, the neck-in of the molten resin film 3 becomes large, and the transparency of the resin film deteriorates. Further, it is preferable to set the die lip clearance of the extruder to 2.0 mm or less, particularly 1.5 mm or less. If it is larger than 2.0 mm, it may be difficult to control the extrusion rate, the thickness accuracy of the produced film may be deteriorated, and the transparency may be deteriorated.

In the present invention, the conditions for extrusion molding using the extruder 1 are those known per se, for example, heat kneading in a cylinder of the extruder 1 is carried out at 170 to 230 ° C. , Resin temperature in T-die 2 is 200-260 ℃
It is set to the range of. The thickness of the molten resin film 3 is preferably adjusted to 50 μm or less, more preferably 10 to 30 μm or less. If the thickness exceeds 50 μm, the molten resin film 3 may not be rapidly cooled, and the transparency of the finally obtained film may be insufficient. The thickness of the molten resin film 3 can be easily adjusted by changing the draft rate by changing the extrusion speed and the take-up speed. Generally, this take-up speed is 0.5 to 40 m / min,
A range of 5 to 20 m / min is particularly suitable.

In the present invention, the temperature of the cooling casting roll 4 is preferably set in the range of 10 to 140 ° C, particularly 20 to 130 ° C. When this temperature exceeds 140 ° C, the vinylidene fluoride-based molten resin is rapidly crystallized and the transparency is rapidly lost. If the temperature is lower than 10 ° C., the degree of rapid cooling becomes too large and the heat shrinkage becomes large, which may cause wrinkles in the film on the roll.

In the present invention, if necessary, the air nozzle 6 is provided and air is blown from the back surface of the molten resin film 3, so that the molten resin film 3 can be cooled efficiently. In order to maximize this effect, it is preferable that the position where the air is blown is near the beginning of cooling of the film, the air nozzle 6 is brought close to the casting roll 4, and the distance between the roll 4 and the air nozzle 6 is increased. Is preferably set to 30 mm or less, particularly 20 mm or less. The air pressure does not have to be particularly high, and if the air pressure is too high, the film may shake. Air amount to be discharged from the general air nozzle 6 for this purpose, per film width 1 m 0.1 to 10 m ³ / min, it is desirable in particular in the range of from .6 to 2.4 m ³ / min. That is, when it is less than 0.1 m ³ / min, the effect of the air nozzle is not effectively expressed, and 10 m ³
When it is higher than / minute, the wind speed is too high, so that it is difficult to obtain a uniform wind pressure, and the film tends to shake. Further, the opening slit gap of the air nozzle 6 is preferably in the range of 0.5 to 10 mm, particularly 1.0 to 2.0 mm. Further, depending on the width of the resin film 3, the air nozzle 6 is equal to the film width, A slightly wider one is preferable.

[0014]

EXAMPLES The excellent effects of the present invention will be described in the following specific examples. Example 1 In a 40φ extruder, the cylinder temperature was 170-220.
℃, the die temperature is set to 220 ℃, extruded a copolymer resin composition of vinylidene fluoride unit 85 wt%, hexafluoropropylene unit 15 wt%, casting roll temperature 100 ℃, film take-up speed 10 m / min, die lip clearance A film of 650 mm width is extruded from the T-die under the condition of 0.8 mm and the distance between the die lip and the casting roll is 10 mm, and the extruded resin film is cooled to 20 μm.
A film with a thickness of The transparency of the obtained film is measured by a haze meter (manufactured by Nippon Denshoku Co., Ltd.) and the results are shown in Table 1 (according to JIS-K-6714).

Example 2 A film having a thickness of 20 μm was produced in the same manner as in Example 1 except that the distance between the die lip and the casting roll was 20 mm. Table 1 shows the results of the transparency measurement of the obtained film.

Example 3 A film having a thickness of 20 μm was produced in the same manner as in Example 1 except that a copolymer resin having a composition of vinylidene fluoride unit of 80% by weight and hexafluoropropylene unit of 20% by weight was used. Table 1 shows the results of the transparency measurement of the obtained film.

Example 4 A film having a thickness of 20 μm was produced in the same manner as in Example 3 except that the distance between the die lip and the casting roll was 20 mm. Table 1 shows the results of the transparency measurement of the obtained film.

Example 5 A film having a thickness of 50 μm was produced in the same manner as in Example 4 except that the film take-up speed was 4 m / min. Table 1 shows the results of the transparency measurement of the obtained film.

Example 6 Example 6 was repeated except that an air nozzle was used.
A film with a thickness of 50 μm was produced. Table 1 shows the results of the transparency measurement of the obtained film.

Comparative Example 1 The procedure of Example 1 was repeated except that a copolymer resin having a composition of vinylidene fluoride unit of 92% by weight and hexafluoropropylene unit of 8% by weight was used and an air nozzle was used.
A film with a thickness of μm was produced. Table 1 shows the results of the transparency measurement of the obtained film.

Comparative Example 2 A film having a thickness of 20 μm was produced in the same manner as in Comparative Example 1 except that the distance between the die lip and the casting roll was 20 mm. Table 1 shows the results of the transparency measurement of the obtained film.

Comparative Example 3 A film having a thickness of 20 μm was produced in the same manner as in Example 1 except that a vinylidene fluoride homopolymer was used and an air nozzle was used. Table 1 shows the results of the transparency measurement of the obtained film.

Comparative Example 4 20 μm was obtained in the same manner as in Example 1 except that a vinylidene fluoride homopolymer was blended with 25% by weight of a methyl methacrylate polymer (MMA resin) and an air nozzle was used.
A film with a thickness of The obtained film exhibited brittleness with time, and was brittle such that it was easily torn when the film was pulled after being left at room temperature for about 3 months. The results of the transparency measurement are shown in Table 1.

Comparative Example 5 Vinylidene fluoride homopolymer, methyl methacrylate polymer (MMA resin) and butyl acrylate polymer (BA)
20 μm in the same manner as in Example 1 except that 25% by weight of a 1: 1 blend with the above was blended and an air nozzle was used.
A film with a thickness of m 3 was produced. The results of the transparency measurement are shown in Table 1.

[0025]

[Table 1]

[0026]

According to the present invention, it is possible to obtain a vinylidene fluoride resin film which is excellent in transparency, thickness accuracy and productivity.

[Brief description of drawings]

FIG. 1 is an explanatory view for explaining a manufacturing method of the present invention.

 ─────────────────────────────────────────────────── --- Continuation of the front page (72) Inventor Toshige Arai 2668-22 Sunayama, Hasaki-machi, Kashima-gun, Ibaraki Prefecture Shin-Etsu Chemical Co., Ltd.

Claims (1)

[Claims] 1. A method for producing a vinylidene fluoride resin film by melt-extruding a vinylidene fluoride resin using an extruder and allowing the extruded resin film to pass through a cooling casting roll, wherein the vinylidene fluoride resin film is used. As the resin, a copolymer resin containing 92 to 75% by weight of vinylidene fluoride units and 8 to 25% by weight of hexafluoropropylene units is used, and the distance between the die lip of the extruder and the cooling casting roll is used. Is 20 mm or less, and a method for producing a vinylidene fluoride resin film having excellent transparency.