JPS62124136A - Polyethylene film - Google Patents

Abstract

PURPOSE:To provide a polyethylene film containing an antistatic agent and having a specific density and excellent antistaticity and transparency. CONSTITUTION:The objective film is composed of a high-density polyethylene having a density of >=0.935g/cm<3>, a surface resistivity of <=10<13>OMEGA and a half-life period of <=5sec and containing 0.05-0.7wt% antistatic agent. the film can be produced by passing a high-density polyethylene stock film having a density of >=0.935g/cm<3> through a triple hot roll mill and cooling the product. The temperature of the 2nd roll is set higher than the temperatures of the 1st and the 3rd rolls and between 105 deg.C and the melting point of the film. The temperatures of the 1st and the 3rd rolls are preferably <=90 deg.C and 120-80 deg.C, respectively, and the rolling ratio is preferably 1-3.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a high-density polyethylene film with excellent antistatic ability, and furthermore, a high-density polyethylene film with excellent antistatic ability and excellent transparency. The present invention relates to polyethylene films, and also relates to high-density polyethylene films that have excellent antistatic properties and transparency, and also have excellent film strength.

[Conventional technology]

One method of imparting antistatic ability to a synthetic resin is to knead (blend) an antistatic agent with the resin.

Even in the case of high-density polyethylene films, in order to impart antistatic properties to the film, a method has conventionally been mainly adopted in which an antistatic agent is blended with a high-density polyethylene resin.

In this case, the antistatic effect is obtained by uniformly bleeding the antistatic agent onto the film surface, but because the density of high-density polyethylene film is high, the antistatic agent is difficult to bleed onto the surface and is not sufficient. No effect was obtained.

On the other hand, as is well known, high-density polyethylene films (hereinafter sometimes referred to as HDPR films) have poor transparency compared to low-density polyethylene films, and in particular, HDPE films formed by the inflation method It has poor transparency, which prevents its use from expanding despite its excellent sealing properties, ITIF cold resistance, and rigidity.

Therefore, various proposals have been made to improve the transparency of HDPE films.

One method is to pass the molten resin through a slit die and rapidly cool it with a chill roll or water. In this method, the handle resin used has a low molecular weight in order to improve its processability. The transparency and strength of the obtained transparent film are weak.

As a method for improving film strength, there is a method using an air-cooled inflation method.

In this method, a film with excellent strength can be obtained by balancing the molecular orientation with the blow ratio, but only an opaque or translucent film can be obtained due to cooling with air.

In addition, transparency can be improved to some extent even with high molecular weight HDPR by passing the film between heated rolls having a glossy surface to improve its surface smoothness, but this is still insufficient.

Further, in order to make the HDPE film transparent, a method is known in which a translucent HDPE film is rolled between di-rolls uniaxially oriented 5 to 5 times. However, although the films obtained by these methods certainly have excellent transparency, the films obtained are significantly oriented in the stretching and rolling directions, resulting in significant directional properties in terms of film strength. However, they had the disadvantages that they were easy to tear, did not have sufficient strength, and did not have uniform heat shrinkage, causing distortion in the film.

[Problem that the invention seeks to solve]

An object of the present invention is to provide an HDPE film with excellent antistatic ability.

Another object of the present invention is to provide an HDPK film that has excellent antistatic ability and excellent transparency.

Still another object of the present invention is to provide a DPE film having excellent antistatic ability, transparency, and film strength.

Other objects and novel features of the present invention will become apparent from the entire description herein.

[Means for solving problems]

The present invention is a film made of high-density polyethylene having a density of 0.9559/ff13 or more and containing 0.05 to 0.7% by weight of an antistatic agent, the surface resistivity of which is 10%.
2 or less and a half-life of 5 seconds or less, and furthermore, in the above, a high-density polyethylene film with a haze value of less than 10% and excellent antistatic and transparency, and In the above, the HDPE film has a melt index (MI) of 1,01//1 m' or less and has further improved film strength.

The high-density polyethylene constituting the high-density polyethylene film of the present invention may be an ethylene homopolymer or a copolymer of ethylene and one or more comonomers. Examples of such copolymers include ethylene/propylene, ethylene/butene-1, and ethylene/hexene-1 copolymers.

The high-density polyethylene may be a blend with other polymers, or a composition containing additives such as antioxidants, pigments, and inorganic fillers. Examples of other polymers to be blended include low density polyethylene, polypropylene, copolymers of ethylene tovinyl acetate, and copolymers of ethylene and 7-acrylate. In such cases, high-density polyethylene of at least 7
It is preferable to contain 0 wt% or more. Further, the density of the strong high-density polyethylene is 0.955 i /crrr5 or more. That is, in the case of high-density polyethylene, it is necessary to consider the combination of antistatic effect, which is the main objective of the present invention, and sufficient performance as a film.

High density polyethylene is 70 wt% or less and density is 0.9
If the film is less than 54M+/-, it cannot have the excellent properties of an HDPE film, such as stiffness and Young's modulus, barrier properties (moisture resistance), and impact strength.

In the present invention, Yo! 0-76, in order to improve the strength of the film, Mr of high density polyethylene should be 1.0.
It is best to set it to less than &/on'.

Next, the present invention will be explained in more detail while showing a preferred example of a method for producing an HDPE film having excellent antistatic effect, good transparency, and film strength according to the present invention.

The HDPE film of the present invention preferably has a cloth strength of 7j.
A raw high-density polyethylene film of i O, 9351/013 or higher can be obtained by passing it between three heating rolls under the following temperature conditions and then cooling it.

The temperature conditions of the three heating rolls are as follows: the first heating roll (hereinafter referred to as R1), the second heating roll (hereinafter referred to as R2), according to the order in which the raw film passes through the three heating rolls.
) and the third heating roll (hereinafter referred to as R3), the temperature of R2 is higher than the temperature of R7 and R3,
The temperature of R2 is preferably 105C or higher, which is below the melting point of the film.

The above-mentioned original FF film is manufactured by a film forming method of each glaze, such as an inflation method or a T-die method.

In particular, when the present invention is applied to a high-density polyethylene film manufactured by the inflation method, which has a problem with transparency, excellent results can be obtained. When producing the raw film, various antistatic agents used in the textile field, such as cationic, anionic, and nonionic yarns, are blended with high-density polyethylene.

Even if an antistatic agent is blended according to the above-mentioned formulation, an excellent antistatic effect can be obtained in the HD PE film in the present invention.

However, it is necessary to use an appropriate amount of antistatic agent, and the content in high-density polyethylene or a composition containing the polyethylene is 0.05 to 0.7 wt!
%; preferably 0.2 to 0.5 wt%.

If it is less than 0.05%, it is difficult to achieve an antistatic effect;
If the amount exceeds 7 wt%, the antistatic agent bleeds onto the film surface and becomes a white powder, making it less practical as a film.

By the above treatment method, it is possible to make the HDPK film highly transparent, which has been considered difficult in the past, to obtain a haze value of less than 10%, and to make the film transparent while maintaining the film strength.

By using three heating rolls, creating a temperature difference between these rolls, and then quenching them, a much more transparent H'D PE film can be obtained, and according to Mizutoshi, crystallization on the film surface is prevented. Not only the external haze value, which is a problem due to unevenness of parts, but also the internal haze value can be significantly reduced.

The temperature of R1 is below the melting point. The temperature of R1 is 900
If it exceeds 90C, the neck-in of the film will increase, so from this point of view, 90C or less is preferable.

In addition, the temperature of R3 is preferably 120C or lower and 80C or higher, and 1
If it exceeds 20C, good transparency cannot be obtained;
If it is less than 800, the film will adhere to the R20-ru and sufficient transparency will not be obtained.

The original film is passed through the gap between the three heated rolls, which are made of metal rolls having a hard chromium plating layer on the surface, for example, with a thickness equal to or less than the original film thickness, to obtain a transparent film having a thickness equal to or less than the original film thickness. . It is preferable that the rolling ratio is 1 to 3.

After passing through the heating roll, the film is cooled by, for example, two (Df) chill rolls.The temperature of the chill roll is 70C or lower.
It is preferable to set it to 00 or more.

If it exceeds 70tZ', it will be difficult to function as a chill roll.

If the temperature is less than 30C, it is difficult to ensure sufficient flatness of the film.

FIG. 1 shows an example of the arrangement of heating rolls and chill rolls in the present invention. In the same figure, 1 is R1 roll, 2 is R2 roll
0-ru, 3 is R30-ru, 4 and 5 are chill rolls, and 6 is a raw film.

The thickness of the raw film is not particularly limited,
Although the desired product thickness is determined by the desired product thickness, it is preferably 50 to 400μ, more preferably 50μ to 400μ.
150μ is good.

HDP of product] i: Film thickness is preferably 20 to 2
00μ, more preferably 40 to 100μ because it is easy to use as a film.

Considering the handling and use of the HD and PK films of the present invention in fields that require various types of static prevention and as materials for various devices such as capacitors, the surface resistivity of the HD and PK films is 10.
It is preferable that it is 13Ω or less, and the half-life is 5 seconds or less,
By using an appropriate amount of antistatic agent and preferably by using the above film strategy of the present invention, an HDPE film having excellent antistatic effect can be obtained.

When considering the transparency of the film, the C-axis orientation function (FC) of the crystals in the film should be 0.1 or more, and the difference Δn in refractive index between the amorphous part and the crystal part in the film should be 0.1070 or less. In addition, it is preferable that the surface roughness of the film surface be 0.1 μm or less.

In other words, the transparency of a film can be divided into the transparency of the film surface and the transparency of the interior, and the transparency of the film surface (
Surface haze) can be effectively improved by smoothing the film surface, preferably by reducing the surface roughness of the film surface to 0.1μ or less, but by doing the above, internal haze can also be improved. The inventors of the present invention have found through intensive studies that the width can be reduced to a large extent.

In other words, the present inventors thoroughly investigated the factors that cause this internal haze, and found that the cause of internal haze is the orientation of crystal lattice axes (the refractive index of the a, b, and c axes of polyethylene is na = = L5 j 4゜nb == 1-519
, no=1.575) and the refractive index fluctuation resulting from the difference Δn between the refractive index of the crystal layer and the amorphous layer. The orientation of the crystal lattice axes was determined from the orientation function Fc, Δn ftLolenz-LOlenz equation, and the relationship between the transparency of the film was determined from various data. As a result, Fc and Δn are closely related to the internal transparency of the film. I discovered something.

That is, the larger Fc is (the more uniform the C-axis orientation becomes),
It was found that the smaller Δn, the better the transparency inside the film.

As a result, it was found that when Fc is 0.1 or more and Δn is 0.1070 or less, the transparency of an HDPE film with one smooth surface is significantly improved, leading to the present invention.

Here, the C-axis orientation function Fc is determined from the polarized infrared spectrum according to 5tain. (Macromolθc
uleyu 116 1968) ” ” (D730') /CD7sa + Z
) pb = (D, 2o-1) / (n, 2o + Z
) Fa + Fb + Fc = 0 DD is the infrared dichroic ratio at 750t:m and 720crn Fa, Fb, Fc are the orientation functions of the a, b, and c axes of the crystal, and the difference in refractive index between crystal and amorphous Δn f '1 Lolenz
-Lolenz variant (Glasstic VO15
1A2 P54) n is the refractive index of the film, which was measured using an Atsube refractometer.

ρ is the film density, which was determined using a density gradient tube.

Δρ is the density difference between crystal and amorphous, and the following literature value was used.

Crystal density: 1. o 1i/cm' E, R, Wal
ter: , r.

Polymer Sci 21 561 K1956
Amorphous density: 0.851/cm' A, Do, Do
olittla: J, App, Phys, 22 1
471 K195Haze measurement is ASTM D
-1005.

〔Example〕

Next, the present invention will be explained based on examples.

Note that the surface resistivity value was measured based solely on JIS K6911. In addition, the half-life is expressed as the time (in seconds) it takes after applying a voltage of 5KV to the surface of a glasstic (film) and then removing the voltage until the charged voltage shows the charged voltage on the hand just before the voltage was removed. Ta.

Example 1 Melt index 0.041/10 min, density a, q 1 of 50 g/cm5 (DPE with antistatic agent (Electro Stripper EA, Kao Corporation ~) [hereinafter referred to as A
Agent S] was blended in the amount shown in Table 1, and a 5100 μm original film was formed by the inflation method. Using this film, a polyethylene film was obtained under the temperature conditions R1 to R3 shown in Table 1. The results are shown in Table 1.

Practical Examples 2 to 5 Polyethylene films were obtained in the same manner as Practical Example 1 except that the conditions shown in Table 1 were used. The results are shown in Table 1.

Comparative Examples 1 and 2 A polyethylene film was obtained in the same manner as in Actual Winding Example 1 except that the conditions shown in Table 1 were used. The results are shown in Table 1.

However, when 1.0% of the AS agent was blended (Comparative Example 1), the AS agent bled into the blown raw film, resulting in surface whitening, so in Comparative Example 1, the subsequent steps were omitted at the raw film stage.

[Effects of the Invention] - According to the present invention, a high-density polyethylene film with excellent antistatic ability could be provided.

Furthermore, we were able to provide a day-density polyethylene film that has excellent transparency as well as antistatic ability.

Furthermore, we were able to provide a high-density polyethylene film with excellent film strength in addition to these. ”

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram showing an example of the arrangement of rolls used in the present invention. 1...R1 heating roll 2...R2 3...R5 4...chill roll 5...chill roll 6...original film

Claims (1)

[Claims] When the density is 0.935g/cm^3 or more, the antistatic agent is added to 0.935g/cm^3 or more.
A film made of high-density polyethylene containing 05 to 0.7% by weight, and whose surface resistivity is 10^1^3
A high-density polyethylene film with a half-life of 5 seconds or less at Ω or less.