Method for manufacturing inflation film

Abstract

To provide a method for manufacturing an inflation film with high haze and excellent high-speed and thin-film molding properties of the resulting inflation film.SOLUTION: In a method for manufacturing an inflation film, resin containing high pressure low density polyethylene is molded by an inflation molding machine having a die and an air ring having at least one cooling air outlet, where the die and air ring are arranged so that a distance (L) between a top of the die and a bottom of the cooling air outlet is 45 mm or less.SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to a method for manufacturing an inflation film, particularly a method for manufacturing a film suitable for an optical film or a protective film of a dry film resist.

Background Art

[0002] Inflation film forming is a method of extruding molten resin from an annular discharge port of an annular die to form a tubular bubble, and further expanding the bubble by air (inflation air) blown into the inside to form a tubular film having a desired diameter and thickness. It is widely used as a method for obtaining various resin films such as polyethylene. In a molding apparatus that performs such an inflation molding method, an external cooling device (hereinafter referred to as an "air ring") that cools the resin bubble in the expansion process from the outer peripheral surface side is disposed above the die.

[0003] The air ring is equipped with at least one or more cooling air outlets, and the opening degree and the air volume of the air can be appropriately adjusted according to the properties and temperature of the molten resin, the molding speed, and the like. In the inflation film forming of polyethylene, it is generally known that the transparency becomes better (the haze is lower) as the bubble is rapidly cooled, and the high-speed moldability and the thin film moldability deteriorate (Non-Patent Document 1).

[0004] In recent years, a protective film for a dry film resist has attracted attention as a film obtained by forming an inflation film of polyethylene. High haze is required for this film, but slow cooling of the bubble alone is not sufficient, and polyethylene having a high melt tension is often used.

[0005] However, polyethylene having a high melt tension has insufficient high-speed and thin film moldability, and a method that satisfies high haze and high-speed and thin film moldability has been demanded.

Prior Art Documents

Non-Patent Documents

[0006] [Non-Patent Document 1] Toshitaka Kanai, "Film Forming," J-Stage Publishing, 1993, pp. 752-757. [Overview of the project] [Problems that the invention aims to solve]

[0007] The present invention has been made in view of the above problems, and aims to provide a method for manufacturing an inflation film that has high haze and excellent high-speed and thin-film molding properties. [Means for solving the problem]

[0008] The inventors of the present invention diligently studied and found that the above problems could be solved by devising the arrangement of the die and air ring in the manufacturing of inflation film, thus completing the present invention.

[0009] In other words, the present invention relates to a method for manufacturing an inflation film, characterized by using an inflation molding machine equipped with a die and an air ring having one cooling air outlet, wherein the die and air ring are arranged such that the distance (L) between the top of the die and the bottom of the cooling air outlet is 45 mm or less, and molding a resin containing high-pressure low-density polyethylene. [Effects of the Invention]

[0010] According to the present invention, it is possible to provide an inflation film molding method that achieves both high haze and high-speed, thin-film molding properties, which have been difficult to achieve in the past. This not only improves the productivity of dry film resist protective films but also contributes to reducing waste. [Brief explanation of the drawing]

[0011] [Figure 1]This diagram shows the configuration of the die and air ring in the present invention. [Modes for carrying out the invention]

[0012] A method for manufacturing an inflation film, which is one aspect of the present invention, will be described in detail below.

[0013] The manufacturing method of the present invention uses an inflation molding machine. An inflation molding machine with a general configuration can be used, and one example is one equipped with an extruder, die, inflation / cooling section, clamping roll, and winding machine. Figure 1 shows the configuration of the die and air ring.

[0014] The die that makes up the molding machine is an annular mold, and it is a device that shapes and discharges the molten resin extruded from the extruder that makes up the inflation film molding machine into an annular shape.

[0015] In the inflation and cooling section, the molten resin is expanded by air introduced into the die, and then the resin bubbles in the expansion process are cooled from the outer surface by an external cooling device (air ring). In other words, this is the section where the air ring is installed.

[0016] A cooling air outlet is the part of an air ring that blows cooling air onto the outside of a cylindrical molten resin (bubble) discharged from an annular die during inflation film molding. In inflation molding, it is usually necessary to cool the molten resin bubble by blowing air onto it from all sides, so the outlet is ring-shaped.

[0017] In a molding machine, it is preferable to arrange the die and air ring such that the distance (L) between the top of the die and the bottom of the cooling air outlet is 45 mm or less, and more preferably 42 mm or less.

[0018] The number of cooling air outlets is usually one or more. When there are two or more, openings are provided in the air ring so that ring-shaped outlets are arranged in order with respect to the advancing direction of the molten resin. When there are two, the outlet closer to the die can be referred to as the lower outlet, and the outlet farther from the die can be referred to as the upper outlet.

[0019] It is preferable that there is one cooling air outlet, because it has a great effect of increasing haze and is excellent in high-speed and thin-film formability. In that case, it is preferable that the opening width (W1) is 35 mm or less because it has a high effect of increasing haze, more preferably 30 mm or less, and most preferably 25 mm or less.

[0020] Also, when there are two cooling air outlets, it is preferable that the ratio (W1 / W2) of the opening width (W1) at the lower part of the outlet to the opening width (W2) at the upper part of the outlet is 1 or less, because it has a great effect of increasing haze and is excellent in high-speed and thin-film formability, more preferably 0.7 or less, and most preferably 0.4 or less.

[0021] In the production method of the present invention, the winding speed of the film is preferably 60 m / min or more, and further preferably 65 m / min or more. Thereby, the haze of the obtained film is higher, and molding can be performed with high productivity.

[0022] In the production method of the present invention, high-pressure low-density polyethylene is molded. The high-pressure low-density polyethylene may be a single component or a composition containing other resins. Further, it may contain additives such as a plasticizer and an antioxidant.

[0023] The high-pressure low-density polyethylene is not particularly limited, and can be appropriately selected and used from commercially available ones. Such high-pressure low-density polyethylene is commercially available, for example, under the trade name Petrothene from Tosoh Corporation.

[0024] The melt tension of high-pressure low-density polyethylene measured at 190°C is preferably in the range of 80 to 140 mN, as this exhibits high haze and excellent high-speed, thin-film molding properties, and more preferably in the range of 100 to 120 mN.

[0025] Furthermore, high-pressure low-density polyethylene is preferable when its melt mass flow rate (MFR), measured according to JIS K6760, is between 0.3 and 12 g / 10 min, as this exhibits excellent inflation film moldability. More preferably, it is between 0.5 and 7 g / 10 min, and most preferably between 1 and 5 g / 10 min.

[0026] Furthermore, the density of high-pressure low-density polyethylene according to JIS K6760 is 918-930 kg / m³. 3 This is preferable because the film has high rigidity and excellent blocking resistance, and more preferably 921-925 kg / m 3 That is the case.

[0027] High-pressure low-density polyethylene may contain other polyolefins. Examples of such polyolefins include copolymers of ethylene and α-olefins having 3 to 12 carbon atoms, high-density polyethylene, propylene polymers, 1-butene copolymers, and 4-methyl-1-pentene.

[0028] Furthermore, known additives commonly used in polyethylene, such as antioxidants, UV inhibitors, dispersants, foaming agents, lubricants, pigments, and flame retardants, may be incorporated to the extent that they do not impair the objectives of the present invention.

[0029] Next, the inflation film obtained by the manufacturing method of the present invention will be described in detail.

[0030] The inflation film obtained by the manufacturing method of the present invention preferably has a haze of 5-30% because it provides excellent appearance for the protective film of the dry film resist, and more preferably 10-20%.

[0031] The film thickness is preferably 10-20 μm from the viewpoint of economy and environmental protection, and more preferably 10-17 μm.

[0032] The film obtained by the inflation film molding method of the present invention can be used in a variety of applications such as packaging, construction and civil engineering materials, and agricultural use, and is particularly suitable as a protective film such as a dry film resist. [Examples]

[0033] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples.

[0034] Example 1 The base raw material has a density of 922 kg / m³. 3 Low-density polyethylene with a melt flow rate (MFR) of 3.4 was used as the raw material, and molding was performed at a molding temperature of 165°C and a cooling temperature of room temperature using an air-cooled inflation molding machine manufactured by Placo Co., Ltd. A two-outlet air ring was used. The molding conditions for the inflation film are shown in Table 1. The haze of the obtained film was measured in accordance with JIS K7105 using a haze meter (NDH-300A) manufactured by Nippon Denshoku Industries, Ltd. Table 2 shows the haze and high-speed moldability. In the high-speed moldability section of the table, "○" indicates that stable high-speed molding was possible, and "×" indicates that the bubbles were not stable at all and film formation was not possible.

[0035] Example 2 The process was carried out in the same manner as in Example 1, except that W1 in Table 1 was set to 23 mm. The results for haze and high-speed moldability are shown in Table 2.

[0036] Example 3 The process was carried out in the same manner as in Example 1, except that W1 in Table 1 was set to 13 mm. The results for haze and high-speed moldability are shown in Table 2.

[0037] Example 4 A single air outlet was used as the air ring, and the process was carried out in the same manner as in Example 1, except that L was adjusted to 17 mm and W1 was set to 4 mm. The results for haze and high-speed moldability are shown in Table 2.

[0038] Comparative Example 1 The process was carried out in the same manner as in Example 1, except that L was 50 mm and W1 was 40 mm. The results for haze and high-speed moldability are shown in Table 2.

[0039] Comparative Example 2 The process was carried out in the same manner as in Example 1, except that L was 60 mm and W1 was 40 mm. The results for haze and high-speed moldability are shown in Table 2.

[0040] Comparative Example 3 The process was carried out in the same manner as in Example 4, except that an air ring with L = 50 mm and W1 = 40 mm was used. The results for haze and high-speed moldability are shown in Table 2.

[0041] [Table 1]

[0042] [Table 2] [Explanation of symbols]

[0043] A Air ring for forming inflation film B Inflation film molding die C Annular discharge port D Lower cooling air outlet E Upper cooling air outlet L: Distance between the top of the die and the bottom of the cooling air outlet. W1 D air vent opening W2 E vent opening

Claims

1. An inflation molding machine is used, which comprises a die and an air ring having at least one cooling air outlet, with the die and air ring positioned such that the distance (L) between the top of the die and the bottom of the cooling air outlet is 45 mm or less, and the opening degree (W1) of the cooling air outlet is 35 mm or less. The melt mass flow rate (MFR) measured according to JIS K6760 is 0.3 to 12 g / 10 min, and the density according to JIS K6760 is 918 to 930 kg / m³. ３ A method for producing an inflation film, characterized by forming an inflation film with a resin containing high-pressure low-density polyethylene having a melt tension of 80 to 140 mN measured at 190°C, at a film winding speed of 60 m / min or more, and having an inflation film thickness of 10 μm to 20 μm and a haze of 5 to 30%.

2. The method for manufacturing an inflation film according to claim 1, characterized in that the air ring is provided with two cooling air outlets, and the ratio (W1 / W2) of the opening degree of the die-side outlet (W1) to the opening degree of the other outlet (W2) is 1 or less.

3. A method for manufacturing an inflation film according to claim 1 or 2, characterized in that the film winding speed is 65 m / min or more.

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