JPH1044232A - Biaxially oriented ethylene-vinyl alcohol copolymer film and its preparation - Google Patents

Abstract

PROBLEM TO BE SOLVED: To stabilize production and to improve toughness, oil resistance, anti- static properties, gas shielding properties and transparency by using an ethylene- vinyl alcohol copolymer with a specified compsn. and selecting a specified manufacturing condition. SOLUTION: An ethylene-vinyl alcohol copolymer with ethylene unit of 25-45mol%, crystalline particle size obtd. by using Shehler's equation from a half-value width of a (101) diffraction peak measured by X-ray diffraction method of 30-60Å and a degree of face orientation obtd. from 10×(180-half value width)/180 of at least 85%, is used. Namely, after an undrawn film consisting of the ethylene-vinyl alcohol copolymer like this absorbs 2-10wt.% water, it is preheated at 70-90 deg.C and then, after it is simultaneously biaxially oriented 2.5-5.0-folds in the longitudinal and transverse direction and so as to make facial orienting ratio of 8-15-folds at a temp. being 5-10 deg.C higher than the temp. of preheating, heat treatment under relaxation of at most 15% in the width direction of the film is performed at 150-170 deg.C.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a tensile strength, water resistance,
Biaxially oriented ethylene-vinyl alcohol copolymer (EV) with improved physical properties such as moisture resistance and gas barrier properties
OH) Film.

[0002]

2. Description of the Related Art EVOH films are excellent in oil resistance, antistatic properties, gas barrier properties and transparency, and are widely used in packaging applications. However, EVOH has a very high crystallization speed, and crystallization progresses while the melt-extruded unstretched film is cooled and solidified, so that necking of the film easily occurs in the next stretching step, and the stretched film is stabilized. There was a problem that it was difficult to produce. In order to prevent the occurrence of such necking, it has been proposed to adjust the water absorption rate and the temperature conditions.
No. 53-43199), the toughness of the resulting film is reduced, and the film may be restricted depending on the use. Therefore, in the packaging industry and the like, it has long been expected that an EVOH film having an excellent toughness on an industrial scale will be put on the market.

[0003]

An object of the present invention is to provide an EVO which can be stably produced, has excellent toughness, and has excellent oil resistance, antistatic properties, gas barrier properties and transparency.
H film.

[0004]

Means for Solving the Problems The inventors of the present invention have conducted intensive studies in view of such a situation, and as a result, have found that EVOH having a specific composition
By using EVOH to select specific manufacturing conditions,
The inventors have found that the crystallite size and the degree of plane orientation of the film can be controlled, and that excellent toughness can be obtained, and have reached the present invention.

That is, the gist of the present invention is as follows. (1) A crystal particle size consisting of an ethylene-vinyl alcohol copolymer having an ethylene unit of 25 to 45 mol% and determined from the half width of the (101) diffraction peak measured by the X-ray diffraction method using the Scherrer equation. (ACS) 30-60Å, 10
0 x (180-half width) / 180 degree of plane orientation calculated from 180
% Or more, a biaxially oriented ethylene-vinyl alcohol copolymer film. (2) An unstretched film composed of an ethylene-vinyl alcohol copolymer having an ethylene unit of 25 to 45 mol% is made to absorb 2 to 10% by weight of water, and then preheated at a temperature of 70 to 90 ° C. 5-10 ° C higher temperature, vertically and horizontally
Simultaneously biaxially stretched to 2.5 to 5.0 times and the plane stretching ratio to 8 to 15 times, and then at 150 to 170 ° C in the film width direction.
The method for producing a biaxially oriented ethylene-vinyl alcohol copolymer film according to the above (1), wherein a relaxation heat treatment of 15% or less is performed.

[0006]

DETAILED DESCRIPTION OF THE INVENTION EVO used in the present invention
H is obtained by saponifying an ethylene-vinyl acetate copolymer having 25 to 45 mol% of ethylene units, and has a saponification degree of 95%.
Molar% or more. 25 mol% of ethylene units
If it is less than 1, the film has high hygroscopicity and poor dimensional stability. In addition, the flow start temperature becomes high, the retention stability in the melting step becomes poor, and the film forming property is lowered. On the other hand, when the amount of the ethylene unit exceeds 45 mol%, the mechanical properties of the film are reduced, and the gas barrier property is reduced, so that it is difficult to achieve the object of the present invention. If the saponification degree is less than 95 mol%, the water resistance, heat resistance, gas barrier properties, and dimensional stability of the film decrease.

[0007] The EVOH used in the present invention includes:
As long as the properties are not impaired, other copolymer components may be contained, and an antioxidant, a plasticizer, an antistatic agent, a lubricant, a colorant, a filler, and the like can be added.

[0008] The EVOH film of the present invention has a crystallite size (ACS) of 30 to 60 as measured by X-ray diffraction.
面, the degree of plane orientation determined by 100 × (180−half width) / 180 is 85% or more. ACS is a numerical value obtained from the half width of the (101) diffraction peak using Scherrer's equation. If the ACS is less than 30 °, the toughness of the film is insufficient, and the strength and elongation characteristics of the film are reduced, which is a practical problem. If the ACS exceeds 60 °, the film becomes brittle. On the other hand, when the degree of plane orientation is less than 85%, the strength and elongation of the film are reduced, and the balance between vertical and horizontal properties is deteriorated.

The EVOH film of the present invention is manufactured by the following method. That is, the EVOH is heated to a temperature of 200
It is melt-extruded into a sheet by the T-die method at 240 ° C., and is brought into contact with a casting roll having a surface temperature adjusted to 10 ° C. or less to obtain an unstretched film. Then, the unstretched film is immersed in water to absorb 2% by weight of water. After the above, the temperature 70-90
C., and then stretched in the longitudinal and transverse directions at a temperature 5 to 10 ° C. higher than the temperature of the pre-heating at 2.5 to 5.0, respectively.
After the simultaneous biaxial stretching by the flat method so that the draw ratio becomes 8 to 15 times, the film is subjected to a relaxation heat treatment at 150 to 170 ° C. in the film width direction of 15% or less.

In the present invention, before stretching the unstretched film of EVOH, it is necessary to immerse the film in water so that the water absorption is not less than 2% by weight. It becomes difficult to obtain an EVOH film of 85% or more. Also, if the stretching temperature and the heat treatment temperature are lower than the above temperature range, the ACS is less than 30 ° and the toughness of the film is insufficient, and if the stretching temperature and the heat treatment temperature are higher than the above temperature range, the ACS exceeds 60 ° The film becomes brittle.

[0011]

Next, the present invention will be described more specifically with reference to examples. In addition, the measurement of various physical properties was performed by the following methods.

(1) Tensile strength and elongation Tensilon UTM-1 manufactured by Toyo Baldwin Co., Ltd.
100mm length, 10mm width sample film at 20 ℃, humidity 65% R
In H, the measurement was performed at a tensile speed of 200 mm / min. (2) Heat shrinkage rate In the longitudinal direction (MD) and width direction (TD) of the film,
Each strip sample with a marked line was treated in an oven at 160 ° C for 5 minutes, and the dimension between marked lines after the treatment was measured at 20 ° C and 65% RH equilibrium. It was expressed by. (3) ACS, degree of plane orientation ACS is as follows from the half width of the (101) diffraction peak measured by X-ray diffraction at 35 KV, 20 mA output using MXB-3 FE-Kα manufactured by Mac Science. It was determined using Scherrer's equation. ACS = Kλ / βcos θ where K = 0.9 (shape factor), λ = 1.518 (X-ray wavelength), β is a half width, and θ is a diffraction angle. The degree of plane orientation was determined by the formula of 100 × (180−half width) / 180.

Example 1 EVOH having an ethylene content of 32 mol% and a saponification degree of 99% or more was melt-formed at a temperature of 230 ° C., contacted with a casting roll having a surface temperature of 5 ° C., rapidly cooled, and unstretched to a thickness of 150 μm. A film was obtained. This unstretched film is placed in warm water at 50 ° C for 4 hours.
After immersion for 7 minutes (water absorption 7% by weight), preheating was performed at a temperature of 70 ° C., and then, using a tenter-type simultaneous biaxial stretching apparatus, at a temperature of 75 ° C., a magnification of 3.0 times MD, 3.0 times TD, and a speed of 30 m / min.
After stretching under the conditions described above, a 5% relaxation treatment was performed in the width direction at a heat treatment temperature of 160 ° C. to obtain an EVOH film. Table 1 shows various physical properties of the obtained EVOH film.

Examples 2 to 4 and Comparative Examples 1 to 4 EVOH films were obtained in the same manner as in Example 1 except that the stretching temperature, the stretching ratio and the heat treatment temperature were changed. In Comparative Example 4, the unstretched film was stretched without immersion in water to obtain a film. Table 1 shows various physical properties of the obtained EVOH film.

[0015]

[Table 1]

[0016]

According to the present invention, it is possible to stably produce an EVOH film having excellent properties such as toughness, dimensional stability, water resistance, moisture permeability and gas barrier properties.
The industrial application value as a packaging film is extremely large.

Claims (2)

[Claims] (1) an ethylene unit having an ethylene unit content of 25 to 45 mol%;
It is composed of a vinyl alcohol copolymer, and is obtained from the half width of the (101) diffraction peak measured by the X-ray diffraction method.
Crystal grain size (ACS) obtained using the equation
A biaxially oriented ethylene-vinyl alcohol copolymer film characterized by having a degree of plane orientation of 85% or more determined by 60 °, 100 × (180−half width) / 180. 2. An ethylene unit comprising 25 to 45 mol% of ethylene units.
Unstretched film made of vinyl alcohol copolymer
After pre-heating at a temperature of 70 to 90 ° C after absorbing 10% by weight of water,
Next, the film is simultaneously biaxially stretched at a temperature 5 to 10 ° C. higher than the preheating temperature in the longitudinal and transverse directions to 2.5 to 5.0 times and the plane stretching ratio to 8 to 15 times, and then at 150 to 170 ° C. The method for producing a biaxially oriented ethylene-vinyl alcohol copolymer film according to claim 1, wherein a relaxation heat treatment of 15% or less is performed in the width direction.