JP2001220449A - High molecular weight polyolefin film having highly transparent portion and method for producing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prepare a high mol.wt. polyolefin film which has excellent mechanical strengths and a good balance between physical properties in the mechanical direction and physical properties in its orthogonal direction, in which highly transparent portions having excellent transparency are disposed, and which permits the free formation of patterns by the difference of transparency, and to provide a method for producing the film. SOLUTION: This high mol.wt. polyolefin film is characterized by having an intrinsic viscosity [η] of >=4 dl/g, a difference of >=10% between the haze value of a highly transparent portion and the haze value of an opaque portion, and partially formed transparent portions. The method for producing the high mol.wt. polyolefin film is characterized by heat-setting the pre-treated film of a high mol.wt. polyolefin having an intrinsic viscosity [η] of >=4 dl/g and obtained substantially without using a solvent and a plasticizer, thus obtaining the film having a thermal shrinkage rate of <10%, and then partially compressing and thermally treating the film under a pressure of <=0.1 MPa in a treatment range of the melting point of the film -30 deg.C to a lower temperature than the decomposition temperature of the film.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a high molecular weight polyolefin film having a partially formed highly transparent portion,
And its manufacturing method. More specifically, the intrinsic viscosity [η] is 4 dl / g or more, and the difference in haze between the highly transparent portion and the other portion (hereinafter, referred to as an opaque portion) is 10%.
The present invention relates to a high molecular weight polyolefin film and a method for producing the same.

[0002]

2. Description of the Related Art Compared with general-purpose polyolefins, high molecular weight polyolefins are superior in impact resistance, abrasion resistance, chemical resistance, tensile strength and the like, and their use as engineering plastics is expanding. However, since high molecular weight polyolefins have extremely high melt viscosity and poor fluidity compared to general-purpose polyolefins, it is very difficult to mold them by extrusion or injection molding such as conventional T-die molding and blown film molding. Was formed by compression molding, and some rods were extruded at an extremely low speed.

[0003] As a result of intensive studies by the present applicant on films using high molecular weight polyolefins having poor moldability, the following findings have been obtained. In JP-B-6-55433, the intrinsic viscosity [η] is 5d.
1 / g or more of ultra-high molecular weight polyethylene, having a tensile strength at break in the longitudinal direction of 800 kg / cm ² or more, a tensile strength in the transverse direction of 700 kg / cm ² or more, and a thickness of 10 to 1
000 μm is disclosed.

In Japanese Patent Application Laid-Open No. Hei 2-30514, an ultrahigh molecular weight polyethylene having an intrinsic viscosity [η] of 5 dl / g or more, a thickness of 0.5 to 500 μm, and a tensile strength at break of 700 kg / cm ² or more Is disclosed. further,
Japanese Patent Publication No. 4-16330 discloses a method for producing a biaxially stretched film by mixing a high-molecular-weight polyolefin with a large amount of a plasticizer and extruding the mixture.

However, these high-molecular-weight polyolefin films or high-molecular-weight polyolefin films obtained by the molding method have excellent mechanical properties, but have a drawback that they are inferior in transparency to general-purpose polyolefin films. In the method using a large amount of plasticizer,
Depending on the application, it is necessary to extract a plasticizer from the obtained polyolefin film, which not only complicates the process, but also forms voids in the portion where the plasticizer was present, which was a cause of deterioration in transparency. .

On the other hand, a high-strength transparent film using a high molecular weight polyolefin is described in the following literature. JP-A-60-255415 discloses a polyethylene resin film comprising a polyethylene having a viscosity average molecular weight of 400,000 or more and exhibiting a tensile strength of 25 kg / mm ² or more in any direction. It is described as a transparent film.

Japanese Patent Application Laid-Open No. 61-84225 discloses that a high-molecular-weight linear polyethylene is used as a base material, and has a weight average molecular weight of at least 400,000 and a tensile strength of at least 1 G.
Pa, a thickness of up to 25 μm, and an opacity of up to 15% are described. Further, JP-A-60-22812
No. 2 discloses polyethylene having a weight average molecular weight of 5 × 10 ⁵ or more, a thickness of 3 μm or less, and a tensile modulus of 200 or less.
An ultrathin polyethylene film having a breaking strength of 0 kg / cm ² or more, a breaking strength of 500 kg / cm ² or more, and a haze of 10% or less is described.

[0008] The use of the methods described in these publications makes it possible to obtain films having relatively excellent transparency, but requires high-magnification biaxial stretching in order to obtain transparency. Has the drawback that it is not possible to obtain a thick film. Also, sheets and films before stretching must be formed using a large amount of solvents and plasticizers, and the solvents and plasticizers used must be extracted after stretching, which not only complicates the process. In addition, voids are formed in portions where the solvent and the plasticizer are present, which causes deterioration of transparency. Attempts have been made to press these voids to collapse them under pressure, but have not yet achieved good transparency despite the very thin films. This is presumably because it is difficult to completely eliminate the voids existing in the film by compressing them.

In Japanese Patent Publication No. 3-73452,
A method for producing an ultra-high molecular weight polyethylene film, wherein an ultra-high molecular weight polyethylene sheet having an intrinsic viscosity of 5.0 dl / g or more is subjected to tension while being roll-rolled at a temperature of a melting point or more and a melting point of less than + 15 ° C. Is disclosed. This method is excellent in that a relatively transparent film can be obtained without using a solvent or a plasticizer. However, in order to perform rolling, a direction perpendicular to the machine axis direction (MD) of the film and the machine axis direction is required. (TD) The film properties of the film were poor in balance, and the width of the sheet before rolling was relatively narrow, so that it was difficult to produce a wide film.

In addition, it is necessary to arrange a highly transparent portion in a film without using a solvent or a plasticizer and without deteriorating the excellent properties of a high-molecular-weight polyolefin, and to create a free pattern. Until it was difficult.

[0011]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a device having excellent mechanical strength such as tensile strength and the like.
D) and the physical property balance in the orthogonal direction (TD) thereof are good, and a portion having a transparency (highly transparent portion) which has not been obtained conventionally can be arranged in the film, and a free pattern can be formed due to a difference in transparency. An object of the present invention is to provide a high-molecular-weight polyolefin film and a method for producing the high-molecular-weight polyolefin film having a wide and wide thickness range by a simple process without using a solvent or a plasticizer.

[0012]

Means for Solving the Problems The inventors of the present invention have conducted intensive studies to solve the above-mentioned problems of the prior art, and as a result, using a film before treatment with a specific high-molecular-weight polyolefin, under a specific condition, the compression heating was carried out. The present invention has been found that a high-molecular weight polyolefin film having excellent mechanical strength can be obtained without substantial use of a solvent or a plasticizer, if the treatment is performed, a highly transparent portion having excellent transparency is partially formed. It was completed.

That is, the high molecular weight polyolefin film according to the present invention has the following physical properties and is characterized by having a partially formed highly transparent portion. (A) The intrinsic viscosity [η] is 4 dl / g or more, and (b) The difference in haze between the highly transparent part and the opaque part is 10% or more.

In a preferred embodiment of the high molecular weight polyolefin film according to the present invention, the haze (H
[%]) Has a relationship with the thickness (t [μm]) according to the following equation. H ≦ 15 + (t / 3) (when t <135 μm) H ≦ 60 (when t ≧ 135 μm)

[0015] In a preferred embodiment of the high molecular weight polyolefin film according to the present invention, the tensile strength in the machine axis direction (MD) and the cross direction (TD) thereof is 50 MPa or more.

In the present invention, the high molecular weight polyolefin is preferably a high molecular weight polyethylene.

According to the present invention, the intrinsic viscosity [η] is 4
dl / g or more high molecular weight polyolefin, and a high molecular weight polyolefin pre-treated film obtained without substantially using a solvent or a plasticizer is heat-set at a fixed end or a free end to at least one direction. After the heat shrinkage was adjusted to less than 10%, the melting point of the film-3
Provided is a method for producing a high molecular weight polyolefin film having the following physical properties, in which the film is partially compressed and heated under a pressure of 0.1 MPa or more in a processing temperature range of 0 ° C. or higher and lower than the decomposition temperature of the film. You. (A) The intrinsic viscosity [η] is 4 dl / g or more, and (b) The difference in haze between the highly transparent part and the opaque part is 10% or more.

In the method for producing a high molecular weight polyolefin film of the present invention, it is preferable that the film before the high molecular weight polyolefin treatment is a uniaxially stretched film, a biaxially stretched film or an inflation film.

In the method for producing a high molecular weight polyolefin film of the present invention, it is preferable that the film before the high molecular weight polyolefin treatment is a film having a high orientation melting point.

In the present invention, the high molecular weight polyolefin is preferably a high molecular weight polyethylene.

[0021]

BEST MODE FOR CARRYING OUT THE INVENTION The high molecular weight polyolefin film having high transparency according to the present invention will be described in detail below with respect to the forming raw material, the film before processing, heat setting, compression heat treatment, and the characteristics of the obtained high molecular weight polyolefin film. Will be described.

Raw Materials for Forming The high molecular weight polyolefin used in the present invention is a mixture of two or more ethylene, propylene and α-olefins having 4 to 8 carbon atoms, for example, by slurry polymerization using a Ziegler catalyst. Obtained by polymerization. Preferred copolymers are copolymers of ethylene and a small amount of propylene, or α-olefins having 4 to 8 carbon atoms alone or in combination of two or more. In the case of an ethylene copolymer, the content of the comonomer is preferably 5 mol% or less. Particularly preferred among these are ethylene homopolymers.

The intrinsic viscosity [η] of the high-molecular-weight polyolefin used in the film forming before treatment according to the present invention is not particularly limited as long as it does not hinder film forming.
The intrinsic viscosity [η] is preferably 4 dl / g or more, more preferably 4 to 25 dl / g. In particular, for the purpose of obtaining a high-strength film, the intrinsic viscosity [η] is 5 to 20 dl / g.
Is preferred, and particularly preferably 7 to 20 dl / g. If the intrinsic viscosity [η] exceeds 20 dl / g, it may be difficult to continuously produce a wide film or sheet due to deterioration of melt moldability.

Film before treatment In the present invention, the film before treatment refers to a film to be subjected to a heat setting and a compression heating treatment described later. For forming the film before treatment, known methods such as extrusion molding such as blown film molding and T-die molding, and uniaxial stretching and biaxial stretching after extrusion molding can be used. In the present invention, a solvent or a plasticizer is not substantially used in the formation of the film before the treatment with the high-molecular-weight polyolefin.

The fact that no solvent or plasticizer is used substantially means that
It means that the high-molecular-weight polyolefin as a forming raw material does not contain a large amount of a solvent or a plasticizer during film forming.
Therefore, various additives usually used in addition to polyolefins, such as heat stabilizers, weather stabilizers, lubricants, nucleating agents, anti-blocking agents, slip agents, pigments, dyes, and fillers, impair the purpose of the present invention. Although it may be blended in a range that does not exist, the upper limit is preferably 10% by weight or less in total, more preferably 5% by weight or less, and further preferably 3% by weight or less.
% By weight or less. Further, it is preferable that the film is not brought into contact with a solvent or a plasticizer at the time of or after the film is formed in the sense that usable film applications are not limited.

Examples of the film before high-molecular-weight polyolefin treatment include a uniaxially stretched film (stretched in the machine axis direction (MD) or its orthogonal direction (TD)) and a biaxially stretched film (MD
And stretching to TD), or a blown film.

The reason can be presumed as follows. In the extruded high molecular weight polyolefin film, the fusion interface of the polyolefin raw material powder, which is not visually observed, may remain, causing light scattering and deteriorating the transparency of the film. Thereby, the influence of this interface can be removed, and good transparency of the highly transparent portion can be obtained.

Among the above-mentioned films before high molecular weight polyolefin treatment, a biaxially stretched film and an inflation film are preferable from the viewpoint of a balance between MD and TD of physical properties such as tensile strength and elongation of the film after compression and heat treatment. Particularly, an inflation film is preferable. For the molding of high molecular weight polyolefin treated film,
This will be specifically described below by taking a method of forming a blown film as an example.

Among the high molecular weight polyolefins, those having an intrinsic viscosity [η] of less than 5 dl / g can be formed by a usual blown film forming method.
For details on the usual method of forming blown film, see Polyethylene and Polypropylene described in Chapter 4 of Chapter 4 of "Plastic Extrusion Molding and Its Application" (by Keiji Sawada, published by Seibundo Shinkosha (1966)). General methods such as those described in

In the case of the T-die molding method, it is desirable to further stretch the film after the film is formed. Preferred stretching ratio is
2 to 25 times, more preferably 3 times for MD and TD
~ 15 times. The area magnification is preferably 4 to 625 times. In contrast, in the blown film molding method,
Since the orientation is performed during molding, the process is simple. The draft ratio and expansion ratio at the time of molding are not particularly limited, but a higher draft ratio and higher expansion ratio are preferable.

Among the high-molecular-weight polyolefins having an intrinsic viscosity [η] of 5 dl / g or more and 25 dl / g or less, a film before processing can be formed by, for example, the following blown film forming method.

That is, a high molecular weight polyolefin is melted by a screw extruder, and then the mandrel rotates with or independently of the screw. L / D (L: length of a tube die composed of a mandrel and an outer die) , D: The clearance between the mandrel and the outer die, that is, the thickness of the die lip), is extruded from a tube die having a diameter of 5 or more, and then a gas is blown into the inside of the molten tubular film to be expanded to an expansion ratio of 1.1 to 20. It is obtained by an inflation film forming method of cooling to a film.

Here, a preferred draft ratio is 5 or more, more preferably 8 or more. Further, a preferable expansion ratio is 5 or more, and more preferably 8 or more. An embodiment relating to the blown film forming apparatus is described in detail in Japanese Patent Publication No. 6-55433 filed by the present applicant. Further, it can be molded by a method as described in JP-A-9-183156.

The intrinsic viscosity [η] of the high molecular weight polyolefin forming the unprocessed film obtained as described above is
4 dl / g or more, preferably 5 dl / g or more, more preferably 6 dl / g or more, still more preferably 7 dl / g.
/ G or more, and its upper limit is determined by the intrinsic viscosity [η] of the forming raw material, and is usually 25 dl / g or less, preferably 20 dl / g or less. Intrinsic viscosity [η] is 4dl
If it is less than / g, the melt fluidity becomes too large at a temperature equal to or higher than the melting point, so that compression heat treatment may be difficult, which is not preferable. Further, it is difficult to obtain excellent physical properties of the high molecular weight polyolefin, which is not preferable.

The crystallinity of a high molecular weight polyolefin forming a film before processing (differential scanning calorimeter (DSC))
From the heat of crystal fusion) is preferably 40
% Or more, more preferably 50% or more, further preferably 60% or more, and particularly preferably 60 to 70%.

Further, in order to obtain excellent transparency, it is preferable that the high molecular weight polyolefin forming the film before treatment has a high orientation melting point. In order to have a high orientation melting point, at the time of forming a film before processing, stretching is performed at a high magnification, or an inflation film is formed at a high draft ratio and a high expansion ratio.

It is considered that oriented polyolefin crystals in a state where molecular chains are elongated exist in the polyolefin film having a high orientation melting point and form a network-like matrix structure. This can be estimated from the fact that a high tensile strength can be observed in a polyolefin film having a high orientation melting point. The presence of this network-like matrix structure makes it possible to form a highly transparent portion which is hardly affected by the fusion interface of the polyolefin raw material powder even after the compression heat treatment.

Here, the highly oriented melting point in the present invention is:
When the melting point is measured at a fixed end by a differential scanning calorimeter (DSC) at a heating rate of 10 ° C./min in accordance with ASTM D3417, the peak on the high temperature side when the peak appears as two or more separated peaks ( When three or more peaks appear, it means the highest peak temperature). On the other hand, the peak temperature on the low temperature side (the peak of the lowest temperature when three or more peaks appear) is simply referred to as the melting point (Tm ₁ ).

The thickness of the high-molecular-weight polyolefin-treated film of the present invention is not particularly limited, but is generally 5 to 200 μm when the film is a narrowly defined film, and is more than 200 μm and 1 mm or less when the film is a sheet. is there. Within this thickness range, the difference between the haze values of the transparent portion and the opaque portion is a preferred range.

Heat setting It is preferable that the film subjected to the compression heating treatment described below has a small heat shrinkage during the treatment. This is to prevent the film from being torn due to a force caused by a difference in heat shrinkage at the boundary between the compressed portion and the non-compressed portion in the compression heat treatment. Therefore, it is preferable to heat-set the film before the treatment before the compression heat treatment in order to reduce the heat shrinkage.

The heat set is performed at the fixed end or the free end.
Heat treatment is performed at a temperature lower than the melting point of the unprocessed film (if the film has a high orientation melting point). Here, the fixed end refers to a state where the film is fixed in one direction, preferably two directions perpendicular to each other, and the free end refers to a state where the film is not fixed in any direction. Among these, it is preferable to heat-set at a fixed end in that high strength is obtained.

The heat setting condition is that the heat shrinkage is 10%.
The necessary temperature and processing time are selected within the above range so as to be less than the above. Usually, the higher the temperature, the shorter the processing time,
If the temperature is low, the processing time is lengthened. In the present invention, the heat shrinkage rate was determined by leaving a 10 cm × 10 cm sample cut out of a heat-set film in an air oven at 115 ° C. for 10 minutes to cool to room temperature,
And the average value of the respective shrinkage rates determined from the measured lengths of TD and TD.

Compression Heat Treatment The compression heat treatment in the present invention is performed by subjecting the high molecular weight polyolefin film obtained as described above to a specific treatment temperature using a known compression device such as a press molding machine or a pair of rolls. It is performed under pressure conditions. The compression heat treatment is performed under the conditions selected for the temperature, pressure, and processing time so that the haze value of the highly transparent portion of the film after the treatment can be reduced as much as possible, preferably within the ranges described below.

The temperature range for the compression heat treatment depends on the treatment time and pressure, but is usually from the temperature of the melting point of the high molecular weight polyolefin film to be treated to -30 ° C. to less than the decomposition temperature of the film. Especially when high strength is required,
Preferably, from the temperature of the melting point of the film (Tm ₁ ) -30 ° C. to the highly oriented melting point of the film + 5 ° C., more preferably from the temperature of the melting point of the film (Tm ₁ ) -20 ° C. to the highly oriented melting point of the film + 5 ° C, more preferably the temperature range from the temperature of the film melting point (Tm ₁ ) -20 ° C to the highly oriented melting point of the film. If the processing temperature is in such a range, it is possible to impart sufficient transparency to the highly transparent portion,
There is no danger that the haze will be worsened due to the disappearance of the network matrix.

If the high molecular weight polyolefin film is a highly oriented film, if it is heated above its melting point, heat shrinkage usually occurs, making it difficult to perform a heat treatment operation. However, in the present invention, since the high molecular weight polyolefin film is heated under pressure, the compression heating treatment can be performed without causing heat shrinkage even at a temperature higher than the melting point.

The melting point of the high molecular weight polyolefin is determined by measuring the melting point with a differential scanning calorimeter (DSC), and the decomposition temperature is determined from the temperature at which the weight change starts by thermogravimetry (TG).

The pressure of the compression heat treatment is a pressure applied by a press plate or a roll to a film at the time of compression through an uneven plate or a mold film for forming a highly transparent portion.
a or more is preferable. Although the upper limit is not particularly limited, a sufficient effect can be obtained if the upper limit is approximately 20 MPa. If the pressure is too low beyond the above range, the transparency of the film may become uneven, which is not preferable. When heating at a temperature lower than the melting point of the film before high molecular weight polyolefin treatment, the pressure is usually 10
It is preferably at least MPa.

The time of the compression heat treatment is usually 10 minutes or less,
The time is preferably adjusted to 5 minutes or less, more preferably 1 minute or less, depending on the pressure and temperature. The atmosphere of the compression heat treatment may be in an inert gas such as nitrogen or air, but is usually performed in air. In this case, the processing temperature is preferably lower than the decomposition temperature measured in an air atmosphere of the high molecular weight polyolefin film before the processing.

In order to form a highly transparent portion in the high molecular weight polyolefin film of the present invention, an uneven plate or a mold film is placed on a heat-set unprocessed film, and pressure is applied thereto to perform a compression heat treatment. By using an uneven plate or a mold film, the convex part of the uneven plate becomes a compressed part, the concave part becomes an uncompressed part, the film part of the mold film becomes a compressed part, and the die-cut part becomes an uncompressed part. The part is processed to selectively become a highly transparent part, and the uncompressed part becomes an opaque part. According to such a method, a picture drawn by a difference in transparency can be freely created by selecting an uneven plate or a mold film. FIGS. 1 to 3 show pattern examples of the uneven plate and the mold film. The hatched part in the figure is a part to be a compression part.

The compression heat treatment in the present invention is not intended to reduce the film thickness or to achieve high orientation and high strength, and is therefore essentially different from the rolling treatment. The film thickness does not change significantly before and after the compression heat treatment, and even if it becomes thinner, the difference is less than 20%, preferably less than 10%, usually less than 5% of the thickness of the film before treatment. is there. In the compression heat treatment of the present invention, it is desirable that the film thickness does not significantly change before and after the treatment. Therefore, a film having a wider width can be processed as compared with a rolling process or the like.

Further, it is preferable that the heat shrinkage of the film before and after the compression heat treatment is small from the viewpoint of suppressing the deformation of the picture. The acceptable limit of film shrinkage is usually less than 30%, preferably less than 20%, more preferably less than 10%, and even more preferably less than 5%.

High-Molecular-Weight Polyolefin Film The high-molecular-weight polyolefin film having a partially formed highly transparent portion according to the present invention and obtained as described above has the following physical properties.

The intrinsic viscosity [η] is 4 dl / g or more, preferably 5 dl / g or more, more preferably 6 dl / g.
/ G or more, particularly preferably 7 dl / g or more.
The upper limit of the intrinsic viscosity [η] is determined by the intrinsic viscosity [η] of the film before high molecular weight polyolefin treatment, and is usually 25.
dl / g or less, preferably 20 dl / g or less.

The film thickness is preferably from 5 to 200 μm when the film is a film in a narrow sense, and more than 200 μm and 1 mm or less when the film is a sheet.

The difference between the haze of the highly transparent part and the haze of the opaque part is 10% or more, preferably 20% or more, more preferably 30% or more, further preferably 40% or more, and most preferably 50% or more. The haze of the opaque part is usually 3
At 0% or more, it is preferable that the difference in haze value is large because the picture becomes clear. The ratio of the area of the highly transparent portion is usually 0.1
９９99.9%.

The haze (H [%]) of the highly transparent portion is preferably H ≦ 15 + (t / 3), more preferably H ≦ 10 when the thickness (t [μm]) is less than 135 μm.
+ (T / 3), more preferably H ≦ 5 + (t / 3), particularly preferably H ≦ (t / 3), and the thickness 135
Above μm, the relationship is preferably H ≦ 60, more preferably H ≦ 50, further preferably H ≦ 40, and particularly preferably H ≦ 30.

The tensile strength is preferably 50 MPa or more in MD and TD, more preferably 70 MPa in MD and TD.
MPa or more, more preferably 100 in MD and TD
MPa or more. The preferred ratio between MD tensile strength and TD tensile strength (MD / TD) is not particularly limited, but may be 0.25
-4, more preferably 0.33-3, even more preferably 0.5-2.

The tensile modulus is not particularly limited and is usually 15
0 MPa to 2 GPa, preferably 200
MPa to 2 GPa, more preferably 300 MPa to 2 G
Pa. A suitable ratio of MD tensile modulus to TD tensile modulus (MD / TD) is from 0.25 to 4, preferably from 0.3 to 4.
It is preferably in the range of 3 to 3, more preferably 0.5 to 2.

The tensile elongation is not particularly limited, and is usually in the range of 50 to 1500%. A preferable ratio of MD tensile elongation to TD tensile elongation (MD / TD) is 0.25 to 4,
Preferably it is in the range of 0.33-3, more preferably 0.5-2.

According to the present invention, in a wide range of thickness,
Not only is it possible to obtain a high-strength high-molecular-weight polyolefin film having a partially highly transparent part, but also the impact resistance and abrasion resistance obtained by being high-molecular-weight,
A film having self-lubricating properties, chemical resistance, high tensile strength and the like can be obtained.

The high-molecular-weight polyolefin film having a highly transparent portion as described above makes use of these characteristics and utilizes a viewing restriction film, a film for preventing glass scattering, a light scattering film for a light source, a sliding tape, a thrust washer, a slip sheet, Lining materials for guides, skis, snowboards, etc., lining materials for hoppers and chutes, doctor knives, liners for cassette tapes, slit sheets for cassette tapes, coating films for rolls, pipes, steel pipes, etc., food packaging films and low temperature resistance Packaging films such as storage bags, medical sterilization / sterilization materials such as blood storage bags, electrical insulating materials, condenser films, agricultural films such as agricultural houses and multi-films, electret films, and building materials such as house wraps. , Packaging tape, circuit board fill It can be suitably used as a material for a speaker, a diaphragm, an airmail envelope, clothing, a bag, a bag, and the like.

The characteristics used in the present specification are as follows:
It was measured by the method.Intrinsic viscosity [Η] Based on ASTM D4020, 13
It was measured at 5 ° C.thickness In accordance with JIS Z1702, Digital Thickness Tester
(Toyo Seiki Co., Ltd., detection ability 1 μm) using an indenter 5
mmφ, load 125g, measuring pressure 637Kg / cm ^TwoMeasured with
Specified.

Haze and total light transmittance Fully automatic haze meter (manufactured by Tokyo Denshoku Technical Center Co., Ltd., T
C-H III DPK) according to JIS K6714. When the area of the highly transparent portion or the opaque portion was small, a light shielding material such as an aluminum foil punched out of a 5 mmφ circle was applied to the film, and the haze of the minute portion was measured.

The area ratio film of the highly transparent portion was cut out into a sample of 10 cm × 10 cm square and measured. Maximum area ratio of highly transparent part is 10cm × 10c
Cut the sample so that the highly transparent part within the m-square has the maximum area and the minimum area ratio of the highly transparent part is the minimum area of the highly transparent part, and measure the area of the highly transparent part. It was determined as a ratio to the area. When the size of the film was less than 10 cm, the area ratio was measured without changing the size. (For example, if the film size is 15cm x 7
cm, the sample was cut out to 10 cm × 7 cm and measured. )

Tensile strength, tensile elastic modulus, tensile elongation Tensileon (Model RTM) manufactured by Orientec
100 type) at room temperature (23 ° C.). The measuring method was based on JIS K6781. Based on the melting point ASTM D3417, a differential scanning calorimeter (D
SC). The measurement was performed at the fixed end and the heating rate was 10
C./min., And the peak value was taken as the melting point. When the peaks were separated into two or more peaks, the lowest temperature peak on the low temperature side was taken as the melting point (Tm ₁ ), and the highest temperature peak on the high temperature side was taken as the highly oriented melting point.

Decomposition temperature By thermogravimetry (TG), the temperature at which weight change started was defined as the pyrolysis temperature. The measurement is performed under a nitrogen atmosphere at a heating rate of 20 ° C./min, and the increase or decrease in weight is 1% of the total weight.
Was reached as the decomposition temperature. The measurement was performed in the air in the same manner. (In this case, "decomposition temperature measured in an air atmosphere" is particularly described.)

[0067]

The present invention will be described in more detail with reference to the following examples, which should not be construed as limiting the scope of the invention.

(Example 1) [Preparation of film before treatment] A film before treatment with high-molecular-weight polyethylene was prepared using an inflation film production apparatus shown in FIG. The specifications of the blown film manufacturing apparatus are as follows. First screw outer diameter of extruder 50mmφ Effective screw length 1100mm Flight pitch 30mm constant Screw compression ratio 1.8 Screw die effective length 1490mm (L / D = 28) Die outlet outer die inner diameter 66mmφ Die outlet mandrel outer diameter 58mmφ Outer diameter of second screw of screw die 70mmφ Effective length of second screw 238mm Flight pitch 25mm constant Second screw compression ratio 1.0 Outer diameter of stabilizer rod 39mmφ Length of stabilizer rod 600mm Inner diameter of gas flow path 8mmφ

Intrinsic viscosity [η]: 8.9 dl / g, melting point:
About 135 ° C, decomposition temperature: 495 ° C (air atmosphere 255)
C.), the extruder, the joint (J), the die base (D1) and the die tip (D2) were set at 200 ° C. and 180 ° C. respectively in the apparatus shown in FIG. , 170 ° C, 170 ° C. Compressed air is blown from a gas passage extending inside the second screw, the mandrel and the stabilizer rod shaft to inflate the parison to about 8.5 times (expansion ratio) the inner diameter of the outer die (66 mmφ). 2 with a draft ratio of 2 1 was produced. Tables 1 and 2 show the physical properties of the film before processing.

[0070]

[Table 1]

[Table 2]

[Heat setting] The obtained film before high molecular weight polyolefin treatment was heat set using MD and TD as fixed ends. The heat setting was performed in an air oven at 135 ° C. for 30 minutes. The heat shrinkage of the film after heat setting was 5%.

[Compression Heating Treatment] The heat-set high-molecular-weight polyolefin-untreated film was subjected to compression heating treatment. The compression heating process is performed by MINI manufactured by Toyo Seiki Co., Ltd.
Using TEST PRESS-10, the following method was performed under each condition described in Table 3. On both sides of the heat-set unprocessed film, Lumirror ^TM T
60 (thickness: 25 μm) are stacked, and an uneven plate (made of metal; the shape is shown in FIG. 1) for forming a compressed portion having a predetermined shape between the release film on one side and the unprocessed film is inserted as a spacer. Was placed between a pair of stainless steel plates and set on a press plate.

At first, the film was compressed at 115 ° C. at a pressure of 20 MPa so that the film before processing did not shrink. Thereafter, the temperature is increased to a compression processing temperature of 135 ° C (heating rate: about 6 to 7 ° C / mi).
n) and kept for 5 minutes, and slowly cooled at room temperature (23 ° C.) in a compressed state. After the temperature was lowered to 115 ° C., the film was taken out and the physical properties of the film were measured. Table 3 shows the results. (Examples 2 and 3) Except for using a mold film (the material is the same as that of a release film; the shape is shown in FIGS. 2 and 3) instead of a concave and convex plate as a spacer for forming a compressed portion having a predetermined shape.
A high molecular weight polyolefin film having a highly transparent portion was obtained in the same manner as in Example 1. Table 3 shows the measurement results of the physical properties of this product.

[0074]

[Table 3]

[0075]

According to the present invention, there is provided a highly transparent portion having good transparency over a wide thickness range, and excellent mechanical properties such as tensile strength can be obtained by using the mechanical axis direction (MD) and the orthogonal direction (TD). ) Is a film that is well-balanced.
Provided is a high-molecular-weight polyolefin film capable of forming a free pattern such as a geometric pattern and a picture. According to the method for producing a high molecular weight polyolefin film of the present invention, the high molecular weight polyolefin film can be obtained with a wide width and a simple process with high productivity. Further, this production method does not require any contact with a solvent or a plasticizer, and is excellent in environmental adaptability.

[Brief description of the drawings]

FIG. 1 is an example of a pattern showing the shape of a compressed portion of an uneven plate used as a spacer in the present invention.

FIG. 2 is an example of a pattern showing the shape of a compressed portion of a mold film used as a spacer in the present invention.

FIG. 3 is another example of a pattern showing the shape of a compressed portion of a mold film used as a spacer in the present invention.

FIG. 4 is a front sectional view showing an example of a molding device for producing a film before high molecular weight polyolefin treatment in the present invention.

[Explanation of symbols]

 Reference Signs List 1 extruder 2 grooved cylinder 3 first screw 10 torpedo 11 pressure gauge 20 screw die 20A second screw tip 20B screw die middle part 20C screw die outlet 21 second screw 22 outer die 23 mandrel 24 gas flow path 25 air ring 26 Stabilizing bar 27 Windproof tube 30 Parison 31 Blown film

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Yuji Takamura 2-1-1 Tango-dori, Minami-ku, Nagoya-shi, Aichi F-term (reference) in Mitsui Chemicals, Inc. 4F071 AA14 AA15 AA20 AA21 AA88 AF15Y AF30Y AF61Y AG22 AG28 AH01 AH03 AH04 AH12 BB07 BB08 BB09 BC01 4F210 AA04A AA04C AA06 AG01 QA01 QC01 QC05 QK01 4J002 BB001 BB021 BB031 BB111 BB151 BB171 GA01 GB01 GC00 GG02 GL00 GQ01

Claims (8)

[Claims] 1. A high-molecular-weight polyolefin film or sheet having the following physical properties and having a partially formed highly transparent portion (hereinafter referred to as a film); (a) intrinsic viscosity [η] is 4 dl / g (B) The difference between the haze values of the highly transparent part and the other part is 10
%that's all. 2. The high molecular weight polyolefin film according to claim 1, wherein the haze (H [%]) of the highly transparent portion has a relationship with the thickness (t [μm]) according to the following formula: H ≦ 15 + (t / 3) (when t <135 μm) H ≦ 60 (when t ≧ 135 μm) 3. The high molecular weight polyolefin film according to claim 1, wherein the tensile strength in the machine axis direction (MD) and the cross direction (TD) is 50 MPa or more. 4. The high molecular weight polyolefin film according to claim 1, wherein the high molecular weight polyolefin is a high molecular weight polyethylene. 5. A pre-treated high-molecular-weight polyolefin film comprising a high-molecular-weight polyolefin having an intrinsic viscosity [η] of 4 dl / g or more and obtained without substantially using a solvent or a plasticizer, is fixed or free-ended. After heat-setting at the end so that the heat shrinkage in at least one direction is less than 10%, in the processing temperature range of not less than the melting point of the film −30 ° C. and less than the decomposition temperature of the film.
A method for producing a high-molecular-weight polyolefin film having the following physical properties by partially compressing and heating the film under a pressure of 1 MPa or more; (a) intrinsic viscosity [η] of 4 dl / g or more; (b) highly transparent portion and The difference between the haze values of the other parts is 10
%that's all. 6. The method for producing a high molecular weight polyolefin film according to claim 5, wherein the film before the high molecular weight polyolefin treatment is a uniaxially stretched film, a biaxially stretched film or an inflation film. 7. The method for producing a high molecular weight polyolefin film according to claim 5, wherein the film before high molecular weight polyolefin treatment is a film having a high orientation melting point. 8. The method for producing a high molecular weight polyolefin film according to claim 5, wherein the high molecular weight polyolefin is a high molecular weight polyethylene.