JP5728597B2 - Method for producing 4-methyl-1-pentene polymer film - Google Patents

Description

The present invention relates to a method for producing a 4-methyl-1-pentene polymer film. In particular, the present invention relates to a method for producing a 4-methyl-1-pentene polymer film suitable for biaxial stretching.

4-Methyl-1-pentene polymer is excellent in heat resistance, transparency, releasability, gas permeability, etc. In addition to physics and labware, microwave oven tableware, release film, release paper, sheath for manufacturing high pressure rubber hose -Widely used in industrial material fields such as mandrels and LED molds, food packaging fields such as heat-resistant wrap film and freshness-maintaining bags for fruits and vegetables.

In addition, a film of 4-methyl-1-pentene polymer has high optical isotropy (that is, a low retardation value), and is useful as a film for optical applications. The optical isotropy becomes even better when the film is stretched.

However, a film of 4-methyl-1-pentene polymer has poor stretch moldability, and stretching unevenness such as necking or stretching breakage occurs during stretching, and it is difficult to obtain a stretched film having a uniform film thickness. This is especially true when the draw ratio is high.

Therefore, a method has been proposed in which a biaxially stretched film of 4-methyl-1-pentene polymer is produced by performing simultaneous biaxial stretching at a specific temperature and then heat-fixing at the specific temperature (for example, patents). Reference 1). In this method, condition management in stretch molding is complicated.

In addition, a method has been proposed in which a 4-methyl-1-pentene polymer is blended with a resin component such as an α-olefin copolymer or a softener such as hydrocarbon oil (for example, a patent). Reference 2). This method is suitable for improving the stretch moldability, but it impairs the properties of the 4-methyl-1-pentene polymer itself and causes bleeding when a large amount of liquid component is added.

JP 58-185226 A JP 58-191734 A

In view of the above circumstances, an object of the present invention is to provide a method for producing a 4-methyl-1-pentene polymer film that can be satisfactorily stretched without impairing the properties of the 4-methyl-1-pentene polymer itself. And

The present inventors melt-extruded 4-methyl-1-pentene-based polymer from a die into a film, and then passed between a pair of rolls while applying a constant roll linear pressure to 4-methyl-1-pentene. In the method for producing a polymer film, by making the roll linear pressure a specific small value, the thickness of the film remains almost unchanged before and after passing through the roll, and the thickness is uniform and the surface is smooth. The inventors have found that the above object can be achieved while obtaining a film, and have reached the present invention.

That is, the present invention is a method for producing a 4-methyl-1-pentene polymer film for biaxial stretching, after only 4-methyl-1-pentene polymer is melt-extruded from a die into a film. In the method of producing a 4-methyl-1-pentene polymer film through a pair of rolls, the melt flow rate of the 4-methyl-1-pentene polymer (260 ° C. and 5.0 kg according to ASTM D1238) (Measured under load conditions) is 5 to 39 g / 10 minutes, and the roll linear pressure for the film-like melt extrudate passing between the rolls is 0.1 kg / cm to 90 kg / cm. .

The film obtained by the method of the present invention has a uniform film thickness and excellent biaxial stretch moldability. Therefore, the film obtained by biaxially stretching this has a uniform film thickness. Moreover, since the film obtained by extending | stretching has the outstanding optical isotropy (namely, retardation value is low), it is useful as a film for optical uses.

It is a figure which shows the cell used for evaluation of the film thickness stability of a stretched film.

The “4-methyl-1-pentene polymer” in the present invention is a copolymer of 4-methyl-1-pentene and other α-olefin in addition to a homopolymer of 4-methyl-1-pentene. Is included. These can be used individually by 1 type or in combination of 2 or more types. The α-olefin has 2 carbon atoms such as ethylene, propylene, 1-butene, 1-hexene, 1-octene, 1-decene, 1-detradecene, 1-octadecene, 1-hexadecene, 1-dodecene and 1-tetradecene. -30 olefins, which can be used alone or in admixture of two or more.

The 4-methyl-1-pentene polymer in the present invention has a melt flow rate (MFR) measured according to ASTM D1238 under the conditions of a load of 5.0 kg and a temperature of 260 ° C. It is preferably in the range of 10 minutes. More preferably, it is the range of 5-200 g / 10min. The melting point is preferably 130 to 250 ° C, more preferably 150 to 240 ° C.

The 4-methyl-1-pentene polymer can be produced by a conventionally known method, and a commercially available product can also be used. Examples of commercially available products include TPX MX002O, MX021 and RT31 manufactured by Mitsui Chemicals.

The 4-methyl-1-pentene polymer extruded and melted in the method of the present invention is a heat stabilizer, antioxidant, light stabilizer, ultraviolet absorber, lubricant, antibacterial agent as long as the object of the present invention is not impaired. Further, it may contain a deodorant, an antiblocking agent and the like.

The 4-methyl-1-pentene polymer film in the present invention is obtained by melt-extruding a 4-methyl-1-pentene polymer from a die into a film, forming a film through a pair of rolls, cooling, winding A specific roll linear pressure is applied to the film-like melt extrudate which is produced by a so-called T-die method and takes between rolls.

In the method of the present invention, by controlling the roll linear pressure to 90 kg / cm or less, preferably 20 kg / cm or less, more preferably 5 kg / cm or less, a film having a uniform film thickness and suitable for biaxial stretching can be obtained. . The roll linear pressure is preferably small, but the lower limit is 0.1 kg / cm due to practical problems. If the roll linear pressure is larger than the above value, the film may break when the obtained film is subjected to biaxial stretching. The roll linear pressure can be controlled by adjusting the pressure applied to the roll with air pressure or hydraulic pressure.

In the method of the present invention, the temperature of the roll is not particularly limited. For example, 20-100 degreeC is used suitably.

The conditions for film formation in the method of the present invention can be appropriately selected depending on the melting point and MFR of the raw materials, the thickness of the obtained film, and the like. Preferably, a melting temperature of 200 to 320 ° C and a die temperature of 200 to 320 ° C are used. . Further, the line speed may be appropriately selected, and is preferably in the range of 0.5 to 50 m / min. The draw ratio is preferably as small as possible, and the ratio of the speed at the winding portion to the speed between the pair of rolls is preferably 0.9 to 1.1. Moreover, it is preferable that a lip opening is 1 to 70 times the film thickness between a pair of rolls.

The film thus obtained has a uniform film thickness, and when subjected to biaxial stretching, a film having a uniform film thickness and a low retardation value (R0) can be obtained. In the present specification, the retardation value (R0) is a retardation in the film plane represented by the following formula, and is a value measured at a wavelength of 590 nm.
R0 = (Nx−Ny) xd
Here, Nx and Ny are refractive indexes in directions orthogonal to each other in the film plane (where Nx ≧ Ny), and d is the thickness of the film.

The thickness of the biaxially stretching film of the present invention is not particularly limited, but is preferably 10 μm or more. If it is less than 10 μm, problems such as tearing occur during stretching. More preferably, it is 100 μm or more and less than 5 mm.

The film obtained by the method of the present invention can then be subjected to normal stretching. The film obtained by the method of the present invention is particularly suitable for biaxial stretching (sequential biaxial stretching, simultaneous biaxial stretching). Even if the film obtained by the method of the present invention is biaxially stretched at a high magnification of 6 times in both the longitudinal and lateral directions, a film having a uniform film thickness can be obtained, and the stretched film thus obtained is more than the film before stretching. Since the retardation value is lowered and the optical isotropy is further improved, it is useful as a film for optical applications.

[Example]
Hereinafter, the present invention will be described with reference to the following examples and comparative examples, but the present invention is not limited thereto.

Examples 1-7 and Comparative Examples 1-3
A 4-methyl-1-pentene polymer shown in Table 1 is melt-kneaded using a T-die extruder and extruded from a die, and the roll shown in Table 1 is placed between a pair of cooling rolls at a temperature of 70 ° C. An original film having a thickness of 350 μm and a width of 50 cm was produced by passing it at a speed of 10 m / min while applying a linear pressure. The die temperature is as shown in Table 1.
In Comparative Example 2, an air knife method was used instead of using a pair of cooling rolls, and an electrostatic contact method was used in Comparative Example 3, so that both roll linear pressures were 0 kg / cm.

The obtained raw film was simultaneously biaxially stretched at a stretching temperature shown in Table 1 using a pantograph batch biaxial stretching apparatus (manufactured by Toyo Seiki Seisakusho, heavy type) (4 × 4 times, stretching speed 1 m / min). .
The following evaluation tests were performed on the obtained raw film and biaxially stretched film. The results are shown in Table 1.

Test Method (1) Film thickness stability of raw film Films were measured for a total of 12 thicknesses, 4 at 10 cm intervals in the width direction and 3 at 20 cm intervals in the flow direction. The difference between the maximum value and the minimum value of the obtained 12 thickness data was defined as R, and a value of (R / average thickness) × 100 was determined and determined according to the following criteria. The thickness was measured using a digital micrometer mumate manufactured by Sony Magnescale Co., Ltd. Hereinafter, all thickness measurements were performed with the same measuring device.
○: Less than 40 ×: 40 or more

(2) Smoothness of the raw film The film formed into a film having a full width (50 cm) × 1 m is cut into a test piece, and this is a perspective view having a grid line with 1 cm square on the surface. Placed on a possible flat plate. The ratio of the number of cells in which the test piece is in contact with the plate with respect to the number of cells (5000) of the entire test piece was determined and determined according to the following criteria. The contact was confirmed by visual inspection from the plate side. The test piece was sampled from the outermost layer of the wound film immediately after film formation and winding.
○: 30% or more ×: Less than 30%

(3) Film thickness stability of stretched film With respect to 16 squares with 9 mm square x 100 (10 x 10) squares stretched 4x4 times and numbered 1-16 shown in Fig. 1 , The value of each square after stretching (horizontal length / longitudinal length) x100 is obtained, and the case where the value is 70 to 130 and the number of squares is 12 or more is 8 to 11 In some cases, ◯, in the case of 4 to 7 pieces, Δ, and in the case of 3 pieces or less, x.

(4) Retardation value (R0)
R0 of the raw film and stretched film was measured by a parallel Nicol rotation method using a phase difference measuring device KOBRA-WR manufactured by Oji Scientific Instruments.

The samples used are as follows.
(1) TPX T3700: manufactured by Mitsui Chemicals, 4-methyl-1-pentene copolymer, MFR (ASTM D1238, load 5.0 kg, temperature 260 ° C.) 39 g / 10 minutes, melting point 160 ° C., density (ASTM D1505) 0.839 g / cm ³
(2) TPX MX002O: manufactured by Mitsui Chemicals, Copolymer of 4-methyl-1-pentene with ethylene and hexene-1, MFR (ASTM D1238, load 5.0 kg, temperature 260 ° C.) 21 g / 10 minutes, Melting point 224 ° C., density (ASTM D1505) 0.835 g / cm ³
(3) TPX RT31: manufactured by Mitsui Chemicals, Copolymer of 4-methyl-1-pentene and hexene-1, MFR (ASTM D1238, load 5.0 kg, temperature 260 ° C.) 21 g / 10 min, melting point 235 ° C, density (ASTM D1505) 0.833 g / cm ³

As is clear from Table 1, in Examples 1 to 7 using a linear pressure in a specific range, a raw film excellent in film thickness stability and smoothness is obtained, and obtained by biaxially stretching it. The film has excellent film thickness stability and a good retardation value lower than that of the original film.

On the other hand, in Comparative Example 1 using a linear pressure higher than the range of the present invention, the raw film had good film thickness stability and smoothness. However, when it was subjected to biaxial stretching, the film was broken. It was impossible to stretch.

In Comparative Examples 2 and 3 where the linear pressure is 0 kg / cm, the film thickness stability and smoothness of the raw film are poor, and the film obtained by biaxially stretching the film also has insufficient film thickness stability. there were. Moreover, the retardation value was also high.

The film obtained by the method of the present invention has a uniform film thickness, good smoothness, and excellent biaxial stretching moldability. When this film is biaxially stretched, a film having a uniform film thickness can be obtained. Moreover, the film obtained by extending | stretching has high optical isotropy (namely, retardation value is low). Therefore, it is useful as a film for optical applications in addition to conventional applications.

Claims (2)

A method for producing a 4-methyl-1-pentene polymer film for biaxial stretching, in which only a 4-methyl-1-pentene polymer is melt-extruded from a die into a film and then passed between a pair of rolls. In the method for producing a 4-methyl-1-pentene polymer film, the melt flow rate of the 4-methyl-1-pentene polymer (measured in accordance with ASTM D1238 at 260 ° C. and 5.0 kg load) Is 5 to 39 g / 10 min, and the roll linear pressure for the film-like melt extrudate passing between the rolls is 0.1 kg / cm to 90 kg / cm. A 4-methyl-1-pentene polymer film having a retardation value of 3.5 nm or less, comprising biaxially stretching the 4-methyl-1-pentene polymer film obtained by the method according to claim 1. How to manufacture.

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