JPH06106612A - Ultrapolymeric polyethylene rough surface film and its manufacture - Google Patents

Abstract

PURPOSE:To manufacture a rough surface film of superior dymanic properties and resistance to voltage and also of superior non-permeability of gas and the like by using an ultrapolymeric film of specified viscosity average molecular weight and specifying the centerline average roughness and the centerline maximum roughness. CONSTITUTION:A film is composed of ultrapolymeric polyethylene-orinted film of viscosity average molecular weight of 300,000 or more, and its centerline average roughness value Ra measured by using the cut-off value 0.8mm is at least 1.0mum and the centerline maximum roughness value Rt measured by the same is at least 8mum. The film is prepared by extruding polymeric polyethylene in the molten state in a sheet shape out of a die section 2 of an extrusion molding machine 1 and orienting by means of first to fifth rolls 3, 4, 5, 6a and 6b. The sheet should be oriented preferably approximately two times as much as the length of an original sheet. Then the film is passed through cooling rolls 7a and 7b and a rough surface film 9 is manufactured by a take-off device 8.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ultra-high molecular weight polyethylene rough surface film and a method for producing the same, and more particularly, it has excellent abrasion resistance, impact resistance, water resistance, chemical resistance, gas impermeability and the like. In addition, the present invention relates to an ultrahigh molecular weight polyethylene rough surface film having good tensile strength and elastic modulus, and a method for producing the same.

[0002]

2. Description of the Related Art Conventionally, as a method for producing a rough surface film, for example, a method of processing the surface of the film by an embossing method, a scratch method, a sandblasting method, a chemical treatment, corona discharge or the like has been used.

However, in these methods,
The obtained rough film has drawbacks such as inferior mechanical properties such as tensile strength and elastic modulus, or reduced withstand voltage, and further, there is a problem in economical efficiency due to an increase in the number of processes. Further, as a condition of the rough surface film having a low friction coefficient and excellent in tensile strength and elastic modulus, it is necessary to have specific surface roughness and molecular orientation.

[0004]

SUMMARY OF THE INVENTION The present invention is directed to tensile strength,
The purpose of the present invention is to obtain a rough surface film made of ultra-high molecular weight polyethylene having excellent mechanical properties such as elastic modulus, withstand voltage property, and excellent properties such as gas impermeability by a relatively simple manufacturing process. It is a thing.

[0005]

In view of such circumstances, the present inventors have used an ultra high molecular weight polyethylene film which is excellent in impact resistance and water resistance but poor in processability, and the surface of the film is stretched by a stretching method. As a result of earnest studies to develop a method for roughening and improving mechanical properties such as tensile strength and elastic modulus, an ultrahigh molecular weight polyethylene having a predetermined viscosity average molecular weight was used, and the polyethylene was melted at a temperature not lower than its melting point. It was found that the object can be achieved by extruding into a sheet shape at a temperature of, and stretching the obtained sheet to a specific ratio at a predetermined temperature, and based on this finding, the present invention has been completed. .

That is, the present invention comprises an ultrahigh molecular weight polyethylene stretched film having a viscosity average molecular weight of 300,000 or more, and a center line average roughness Ra value measured using a cutoff value of 0.8 mm is at least 1.0 μm. And a centerline maximum roughness Rt value of at least 8 μm, an ultrahigh molecular weight polyethylene rough surface film,
And a powdery ultra-high molecular weight polyethylene having a viscosity average molecular weight of 300,000 or more for producing the above-mentioned ultra-high molecular weight polyethylene rough surface film is extruded at a temperature equal to or higher than its melting point to form a sheet. 5 from its melting point
The present invention provides a method for producing an ultrahigh molecular weight polyethylene rough surface film, which comprises heating to a temperature higher than or equal to 0 ° C and lower than 145 ° C, and stretching so as to be about twice the original length. Here, when the draw ratio is 1.5 times or less,
The surface of the film cannot be sufficiently roughened, and if it is 2.5 times or more, the film is broken.

The ultrahigh molecular weight polyethylene used in the present invention has a viscosity average molecular weight of 300,000 or more, and if it is extruded into a sheet and stretched under specific conditions, lattice-like irregularities are formed only on the surface of the film. The film has the property that the elastic modulus and the tensile strength increase due to the orientation.

Further, the ultrahigh molecular weight polyethylene used in the method of the present invention means not only ultrahigh molecular weight polyethylene but also low molecular weight polyethylene and high molecular weight polyethylene. From the viewpoint of processability, polyethylene containing a low molecular weight polyethylene or high molecular weight polyethylene is preferable, and ultrahigh molecular weight polyethylene obtained by multistage polymerization of ultrahigh molecular weight polyethylene and low molecular weight or high molecular weight polyethylene is particularly preferable.

FIG. 1 is a diagram showing the construction of an extrusion molding system for producing the roughened film of the present invention. Ultra high molecular weight polyethylene powder is heated and melted at a temperature above its melting point. Although the melting point of ultra-high molecular weight polyethylene is around 130 ° C., it does not show much fluidity at a temperature just above this melting point, so the preferable heating temperature is in the range of 220 to 250 ° C. Extruder 1 for molten high molecular weight polyethylene
The sheet is extruded from the die portion 2 of. The extruded sheet moves while being stretched by the first roll 3, the second roll 4, the third roll 5, the fourth roll 6a, and the fifth roll 6b. The stretching of the sheet is preferably performed at a temperature higher than the melting point by 5 ° C. or higher and lower than 145 ° C. and stretched to be about twice the length of the original sheet. Then
A rough surface film 9 is obtained by the take-up device 8 through the cooling rolls 7a and 7b. The stretching may be biaxial stretching instead of uniaxial stretching as described above.

[0010]

The roughened film obtained by the method of the present invention has a centerline average roughness Ra value of at least 1.0 μm and a centerline maximum roughness Rt value of at least 8 μm measured using a cutoff value of 0.8 mm. Yes, it is also excellent in elastic modulus and tensile strength.

According to the method of the present invention, the cutoff value is 0.8.
The centerline average roughness Ra value measured using mm is at least 1.0 μm, and the centerline maximum roughness Rt value is at least 8 μm, and it is possible to easily obtain a roughened film. It has excellent mechanical properties such as elastic modulus, tensile strength, and low friction coefficient, as well as excellent wear resistance, water resistance, gas impermeability, and chemical resistance. Next, the present invention will be described in more detail with reference to examples.

[0012]

【Example】

Example 1 Ultra high molecular weight polyethylene powder having a viscosity average molecular weight of 300,000 (manufactured by Mitsui Petrochemical Co., Ltd., registered trademark LUBMER L)
3000P) was formed into a sheet by an extruder (L / D 32, screw diameter 65 mm) under the conditions of a cylinder temperature of 230 ° C. and a die temperature of 240 ° C., and the metal roll continuously shown in FIG. 1 while maintaining a molten state. It was stretched by a stretching machine. Stretching is performed from the die section of the extruder to the first roll,
The rotation speed of the first roll to the third roll is 5 m / min, and the first and second roll temperatures are 80 ° C.
Roll temperature 135 ° C, 4th and 5th roll speed 9m /
The uniaxial stretching process was performed under the conditions of the fourth, fifth roll temperatures of 70 ° C. for minutes.

Mechanical properties of this uniaxially stretched film,
The center line average roughness is shown in Table 1. The tensile strength, elastic modulus, and coefficient of friction were measured according to JIS K7 using a Tensilon tensile tester (UTM-500 manufactured by Orientec Co., Ltd.).
113-1980, ASTM D1894-87. Each measured value means the following. Tensile strength: The stress value at tensile rupture, which is the value obtained by dividing the load at rupture by the original cross-sectional area of the test piece. Elastic Modulus: Ratio of tensile stress to strain at the starting point of deformation. Further, the centerline average roughness Ra and the centerline maximum roughness Rt
Is a stylus method surface roughness measuring device (manufactured by Kosaka Laboratory Ltd.,
SE-3AK) was measured according to JIS B6501 with a cutoff value of 0.8 mm, and the measurement results are shown in Table 1.

Example 2 Example 1 except that the third roll temperature was 140 ° C.
Film formation was performed under the same conditions as in. The results are shown in Table 1.

Example 3 Example 1 except that the third roll temperature was 143 ° C.
Film formation was performed under the same conditions as in. The results are shown in Table 1.

Comparative Example 1 Example 1 except that the third roll temperature was set to 130 ° C.
Film formation was performed under the same conditions as in. The results are shown in Table 1.

Comparative Example 2 Example 1 except that the third roll temperature was 145 ° C.
Film formation was performed under the same conditions as in. As a result, breakage occurred in the stretching process, and the film could not be formed.

[0018]

[Table 1]

[0019]

According to the method of the present invention, a roughened film having a centerline average roughness Ra value of at least 1.0 μm and a centerline maximum roughness Rt value of at least 8 μm measured using a cutoff value of 0.8 mm. The resulting rough film has excellent mechanical properties such as elastic modulus, tensile strength, and low friction coefficient, and also has abrasion resistance, water resistance, gas impermeability, and chemical resistance. And so on.

Since this rough film can reduce the friction coefficient as compared with a glossy film, it is preferable as a friction reducing material such as a slip sheet or a slip sheet used in the running portion of a magnetic recording medium. .

[Brief description of drawings]

FIG. 1 is a cross-sectional view illustrating an example of an apparatus for carrying out the method of the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Extruder, 2 ... Die part, 3 ... 1st roll, 4 ...
Second roll, 5 ... Third roll, 6a ... Fourth roll, 6b
... fifth roll, 7a ... cooling roll, 7b ... cooling roll,
8 ... Take-up device, 9 ... Rough surface film

Claims (2)

[Claims] 1. A centerline average roughness R measured from a stretched ultra high molecular weight polyethylene film having a viscosity average molecular weight of 300,000 or more and a cutoff value of 0.8 mm.
a value is at least 1.0 μm and centerline maximum roughness R
An ultrahigh molecular weight polyethylene rough surface film having a t-value of at least 8 μm. 2. An ultra-high molecular weight polyethylene powder having a viscosity average molecular weight of 300,000 or more is extruded at a temperature above its melting point to form a sheet, at a temperature 5 ° C. higher than the melting point of the sheet and less than 145 ° C. Of an ultrahigh molecular weight polyethylene rough surface film having a centerline average roughness Ra value of at least 1.0 μm and a centerline maximum roughness Rt value of at least 8 μm measured using a cutoff value of 0.8 mm, which is characterized by stretching. Production method.