JP2010280757A - Process for producing stretched polyolefin resin film, and stretched polyolefin resin film obtained therefrom - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for producing a stretched polyolefin resin film with less fish eyes and excellent appearance.
A method for producing a stretched polyolefin resin film, characterized by stretching a polyolefin resin film having a number of fish eyes of 50 μm or more and 10 / m ² or less, and a stretched polyolefin resin film obtained therefrom.
[Selection figure] None

Description

  The present invention relates to a method for producing a stretched polyolefin resin film and a stretched polyolefin resin film obtained therefrom.

  Polyolefin resins are used in a wide range of industrial fields because they are excellent in economic efficiency, mechanical strength, transparency, moldability, hygiene, etc. For example, they are processed into single-layer or multi-layer films, and optical protective films are used. First, it is widely used as a protective film for metal plates, resin plates, automobiles, electronic materials and the like.

  Demands for the quality of the protective film are becoming stricter year by year, and in particular, there is a demand for a reduction in fish eyes that impair the appearance, and a low contamination property that does not contaminate the counterpart material to be protected. Here, the fish eye is one of the drawbacks of a resin film that comes from the presence of foreign matter or gel in the film, and its peripheral part looks like a fish's eye when viewed with the naked eye, a polarizing plate, or a microscope.

  In the case of a polyolefin resin film, it is known that the gel which is one of the causes of fish eyes includes an unmelted gel and a crosslinked gel.

  The crosslinked gel is a gel in which a polyolefin resin is three-dimensionally crosslinked and is difficult to be melted by heating and dissolving in a solvent. On the other hand, an unmelted gel is a gel that can be melted or dissolved by heating, and when melt-kneaded by an extruder and extruded from a die or the like, the ratio of retaining the state as an unmelted gel is high. Incurs a decline.

  In particular, polyolefin resins obtained by high-pressure radical polymerization using a Bessel-type reactor or a tubular-type reactor, such as ethylene-vinyl acetate copolymer and low-density polyethylene, often have the above-mentioned unmelted gel and crosslinked gel. Are known. In the high-temperature reactor, hydrogen is radically extracted from the produced polymer and branches are formed. The reason for this is that this branched polymer is exposed to high temperature separators connected to the reactor and high temperature during the pelletization process, causing unmelted gel as aggregates or cross-linking reaction to form cross-linked gel. It is.

  Therefore, as a method for solving this problem, for example, when ethylene is polymerized under specific polymerization conditions in the presence of a radical polymerization initiator, it is proposed that a radical polymerization inhibitor coexists in the reaction system (for example, , See Patent Document 1).

  In addition, a method for removing the cross-linked gel and unmelted gel contained in the resin during molding has been proposed. For example, a gear pump for transporting a high-viscosity resin melt in an extruder, and a method for producing a film by extruding a molten polyethylene-based resin by installing a sintered filter as a filtration device have been proposed (for example, see Patent Document 2). ).

  Furthermore, a film obtained by sandwiching a melted film-like polyolefin resin between a cast roll and an endless belt formed in an arc shape along the roll has been proposed (see, for example, Patent Document 3). ).

JP 2003-342307 A JP-A-8-103952 JP-A-8-25460

  However, although the method proposed in Patent Document 1 has a certain effect of reducing fish eye, its level is insufficient, and when it is used as a protective film formed on a polyethylene resin film to coexist with a radical polymerization inhibitor, There is a disadvantage of contaminating the partner.

  In addition, the methods described in Patent Documents 2 and 3 have not completely solved the problem that a crosslinked gel is formed because the polyolefin resin is exposed to a high temperature. In particular, the method described in Patent Document 2 uses a sintered filter in which polyolefin is dissolved, so that it takes a long time to be exposed to high temperature, and since the viscosity is high, high pressure is required for filtration, so that the crosslinked gel is deformed. There was a problem of passing through the filter.

  Furthermore, when a raw film having a large amount of fish eyes is stretched, defect holes are formed during stretching, and the film cannot be thinned.

  Therefore, an object of the present invention is to provide a method for producing a stretched polyolefin resin film having less fish eyes and excellent appearance.

As a result of intensive studies to solve the above-mentioned problems, the present inventors have applied a polyolefin resin film with less fish eye, for example, a filtered polyolefin solution on a substrate, and then heated to evaporate the solvent. By stretching the polyolefin resin film (raw film) peeled from the film, it was found that a stretched polyolefin resin film with less fish eyes and excellent appearance was obtained, and the present invention was completed. That is, this invention is the manufacturing method of the extending | stretching polyolefin resin film which extends | stretches the polyolefin resin film whose number of fish eyes of 50 micrometers or more is 10 pieces / m < ² > or less, and the extending | stretching polyolefin resin film obtained from it.

  Hereinafter, the present invention will be described in detail.

In the method for producing a stretched polyolefin resin film of the present invention, a polyolefin resin film having a number of fish eyes of 50 μm or more and 10 / m ² or less is stretched.

As a method for producing a polyolefin resin film having a number of fish eyes of 50 μm or more and 10 / m ² or less, for example, after applying a filtered polyolefin solution on a substrate, the solvent is evaporated by heating to remove the solvent from the substrate. The exfoliated polyolefin resin film (raw film) is stretched.

  The polyolefin solution used in the method for producing a polyolefin resin film is obtained by dissolving a polyolefin resin in a solvent.

  The polyolefin resin used in the method for producing a polyolefin resin film is not particularly limited, and examples thereof include polyethylene, ethylene copolymers, polypropylene, polypropylene copolymers, and chlorinated products of these polyolefin resins. . More specifically, examples of the polyethylene include high density polyethylene, medium density polyethylene, low density polyethylene, linear low density polyethylene, and ultra low density polyethylene. Examples of the ethylene copolymer include an ethylene-α-olefin copolymer, an ethylene-vinyl ester copolymer, an ethylene-acrylic acid copolymer, an ethylene-methacrylic acid copolymer, and an ethylene-acrylic acid ester copolymer. And ethylene-methacrylic acid ester copolymer. Specifically, ethylene-1-butene copolymer, ethylene-1-hexene copolymer, ethylene-1-octene copolymer, ethylene-4 -Methylpentene-1 resin, ethylene-vinyl acetate copolymer, saponified ethylene-vinyl acetate copolymer, ethylene-vinyl alcohol resin, ethylene-propylene copolymer, ethylene-ethyl acrylate copolymer, ethylene- Examples thereof include an ethyl methacrylate copolymer. Examples of the polypropylene-based copolymer include a polypropylene block copolymer and a polypropylene random copolymer. These polyolefin resins can be used alone or in combination.

  Among them, since the polyolefin resin film obtained is flexible, the polyolefin resin used in the method for producing a polyolefin resin film is a group consisting of polyethylene, an ethylene-vinyl acetate copolymer, and a saponified product of an ethylene-vinyl acetate copolymer. It is preferably at least one polyolefin resin selected from the group consisting of:

  There is no particular limitation on the polymerization method for synthesizing these polyolefin resins, and generally known methods can be used, for example, high pressure radical polymerization method, medium-low pressure polymerization method, solution polymerization method, slurry polymerization method, etc. Can be mentioned.

  Moreover, there is no restriction | limiting in particular in the catalyst used for superposition | polymerization, For example, a peroxide type catalyst, a Ziegler-Natta catalyst, a metallocene catalyst etc. are mentioned.

  When synthesizing the polyolefin resin, various additives can be added as long as the effects of the present invention are not impaired. Examples of additives include antioxidants, dyes, organic pigments, inorganic pigments, inorganic reinforcing agents, plasticizers, processing aids such as acrylic processing aids, ultraviolet absorbers, light stabilizers, foaming agents, lubricants, and waxes. , Crystal nucleating agent, plasticizer, mold release agent, hydrolysis inhibitor, antiblocking agent, antistatic agent, radical scavenger, antifogging agent, antifungal agent, rustproofing agent, ion trapping agent, flame retardant, flame retardant An auxiliary agent, an inorganic filler, an organic filler, etc. can be mentioned.

  The molecular weight of the polyolefin resin used in the production method of the polyolefin resin film is not limited as long as the polyolefin resin dissolves in the solvent, but the film strength is maintained and the fluidity of the polymer solution is maintained to form a thin film. Therefore, the weight average molecular weight in terms of linear polyethylene is preferably 10,000 to 1,000,000, more preferably 20,000 to 700,000, and particularly preferably 25,000 to 300,000.

In the case of polyethylene, the density of the polyolefin resin used in the method for producing the polyolefin resin film is preferably 900 to 965 kg / m ³ from the viewpoint that the resulting film is flexible and easy to handle. An ethylene-vinyl acetate copolymer In this case, it is preferably 923 to 970 kg / m ³ , and in the case of a saponified ethylene-vinyl acetate copolymer, it is preferably 923 to 1200 kg / m ³ .

The solvent used in the method for producing the polyolefin resin film is not particularly limited as long as it is a solvent that dissolves the polyolefin resin. For example, the halogen solvent, the boiling point is 70 to 140 ° C., and the solubility index is 13 to 20 MPa ^1/2 . Examples thereof include at least one non-halogen solvent selected from aliphatic hydrocarbon compounds, aromatic hydrocarbon compounds, ether compounds, acetal compounds, and the like. These solvents can be used in combination of two or more, and the ratio is not particularly limited.

  Examples of the halogen-based solvent include 1,1-dichloroethane, 1,2-dichloroethane, methylene chloride, chloroform, 1,1,1-trichloroethane, 1,1,2-trichloroethane, carbon tetrachloride, trichloroethylene, and perchloroethylene. Chlorinated solvents such as ethane, brominated solvents such as ethane bromide, fluorinated solvents such as monofluorobenzene, 1,4-difluorobenzene, perfluoroheptane, perfluorooctane, dichloropentafluoropropane, bromochloromethane, 1, Examples include a solvent containing bromine and fluorine such as 2-dibromo-1,1-difluoroethane.

Examples of non-halogen solvents for aliphatic hydrocarbon compounds, aromatic hydrocarbon compounds, ether compounds, and acetal compounds having a boiling point of 70 to 140 ° C. and a solubility index of 13 to 20 MPa ^1/2 include, for example, n -Heptane, 2-methylhexane, 3-methylhexane, 2,3-dimethylpentane, 2,4-dimethylpentane, n-octane, 2,2,3-trimethylpentane, isooctane, 2,2,5-trimethylhexane , 1-heptene, 1-octene, methylcyclopentane, cyclohexane, methylcyclohexane, ethylcyclohexane, cyclohexene and other aliphatic hydrocarbon compounds, benzene, toluene, m-xylene, p-xylene, ethylbenzene and other aromatic hydrocarbons Compounds, cyclopentyl methyl ether, ethylamino ether Examples include ether compounds such as ether, dioxane and dipropyl ether, and acetal compounds such as diethyl acetal.

  Among these solvents, a solvent capable of dissolving the polyolefin resin at, for example, 80 to 120 ° C. is preferable from the viewpoint of solubility of the polyolefin resin, and a solvent having a low boiling point is preferable from the viewpoint of evaporation of the solvent. From these viewpoints, 1,1,2-trichloroethane, n-heptane, methylcyclohexane, toluene and cyclopentylmethyl ether are preferable, and 1,1,2-trichloroethane and methylcyclohexane are more preferable.

  The melting temperature of the polyolefin resin is appropriately determined depending on the solvent and polyolefin to be used. If the polyolefin resin does not dissolve below the boiling point of the solvent used, it can be dissolved at a temperature above the boiling point of the solvent using a pressure vessel if necessary, but the boiling point at normal pressure of the solvent used. It is preferable from the economical aspect to dissolve in the following. Although there is no restriction | limiting in particular in dissolution temperature, 60-200 degreeC is preferable and 60-150 degreeC is more preferable.

  The dissolution time depends on the shape of the polyolefin resin used and the dissolution temperature, and is preferably 20 minutes to 8 hours, for example, and more preferably 30 minutes to 2 hours. Moreover, it is necessary to completely dissolve the polyolefin resin, and it is preferable to dissolve the polyolefin resin until a certain solution viscosity is reached.

  Moreover, there is no restriction | limiting in particular in the apparatus to melt | dissolve, For example, a vessel, a tube, a horizontal reactor, an extruder etc. can be used. The dissolution is preferably carried out with stirring.

  A polyolefin solution obtained by dissolving a polyolefin resin in a solvent needs to be filtered in order to reduce gel that causes fish eyes. If it is not filtered, the gel remains in the polyolefin resin solution and causes pores during stretching after film formation. The filtration is preferably performed in a state where the polyolefin resin is dissolved. There is no restriction | limiting in particular in the filtration method, A well-known method can be used, For example, natural filtration, centrifugal filtration, pressure filtration, reduced pressure filtration, decantation etc. are mentioned. Examples of the filter medium include metal mesh, laminated wire mesh sintered body, metal nonwoven fabric sintered body, resin woven fabric, resin nonwoven fabric, resin membrane, filter fabric, paper, and the like. These filter media can be used singly or in combination, and filtration can be performed in multiple stages in order to increase filtration accuracy. The opening of the filter medium is preferably 100 μm or less, more preferably 50 μm or less, and particularly preferably 30 μm or less.

  There is no restriction | limiting in particular in the temperature at the time of filtering a polyolefin solution, For example, it can carry out in the state etc. in which the polyolefin resin melt | dissolved below the boiling point of the solvent to be used.

  There is no restriction | limiting in particular in the density | concentration of polyolefin solution, It can set suitably with the selected solvent, 0.1 to 50 weight% is preferable, 1 to 30 weight% is further more preferable, and 5 to 25 weight% is especially. preferable.

  The temperature of the polyolefin solution applied on the substrate is preferably 60 to 200 ° C., more preferably 60 to 150 ° C., because the appearance of the resulting polyolefin resin film is excellent.

  There is no restriction | limiting as a base material used by the manufacturing method of a polyolefin resin film, For example, polytetrafluoroethylene, 4-fluorinated ethylene-perchloroalkoxy copolymer, 4-fluorinated ethylene-6-fluoropropylene Copolymer, 2-ethylene-4-fluoroethylene copolymer, polyvinylidene fluoride, fluororesin film such as polyvinyl fluoride, polyethylene terephthalate, polyester film such as polyethylene naphthalate, polycarbonate film, polyamide film, polymethyl methacrylate Resin films such as films, polyvinyl alcohol films, saponified polyethylene resin films, etc., and various resin films whose surfaces are subjected to surface treatment by hard coating such as silicon treatment and acrylic resin. Various resin films or the like of performing a metal deposition process to the resin film. Furthermore, examples include metal foils such as aluminum, copper, and stainless steel, various films such as metal films and metal sheets, polymer coatings on these metal materials as necessary, and inorganic coatings. it can. Moreover, it can also apply | coat on a rotating metal drum as needed, and can apply | coat on an endless polymer belt and a metal belt.

  Especially, as a base material used with the manufacturing method of this invention, since it is excellent in heat resistance and durability, a polyester film is preferable and a polyethylene terephthalate film is especially preferable.

  There is no particular limitation on the method of applying the polyolefin solution on the substrate in the production method of the polyolefin resin film, for example, gravure coater method, comma coater method, die coater method, double Mayer bar coater method, doctor blade method, etc. Is done. In particular, it is preferable to use a die coater method in order to suppress an increase in the viscosity of the polyolefin solution due to rapid volatilization of the solvent.

  The thickness of the polyolefin solution on the substrate immediately after being formed by coating is preferably 3 to 500 μm, and the coating speed is preferably 0.5 to 50 m / min.

  In the method for producing a polyolefin resin film, in order to evaporate the solvent by heating, for example, a method in which the polyolefin solution layer formed on the substrate is heated from one stage to multiple stages. The temperature range is preferably 50 to 200 ° C., and in the case of drying in multiple stages, a method such as primary drying at 50 to 100 ° C. and secondary drying at a range of 100 to 200 ° C. can be exemplified. Moreover, it is also possible to perform drying in 3 steps or more as required.

  In the method for producing a polyolefin resin film, there is no particular limitation on the method for evaporating the solvent by heating. In view of good heating efficiency, a method of heating with hot air is preferable.

  In the production method of the present invention, the polyolefin resin film (raw film) peeled from the substrate is stretched.

  The film thickness of the raw film (film before stretching) in the production method of the present invention is preferably 5 to 200 μm, more preferably 10 to 150 μm, and particularly preferably 20 to 120 μm.

  In the production method of the present invention, the method for stretching the film is not particularly limited, and any known method may be used. For example, a longitudinal uniaxial stretching method by roll stretching, a lateral stretching method by tenter stretching, and simultaneous biaxial stretching. And a sequential biaxial stretching method in which transverse stretching is performed after longitudinal stretching. In order to obtain a wide film, the transverse stretching method by tenter stretching and the simultaneous biaxial stretching method are preferable. Furthermore, the simultaneous biaxial stretching method is more preferable in terms of high film thickness accuracy of the obtained film.

  In the case of the transverse stretching method by tenter stretching, the film is preheated before stretching, and then subjected to one-stage stretching or multi-stage stretching in the machine direction (MD direction) and the transverse direction (TD direction).

  The stretching temperature is preferably in the range of “melting point−40” ° C. to “melting point + 10” ° C., more preferably, for preventing the deterioration of the film thickness accuracy of the obtained stretched film and preventing the film from tearing during stretching. Is “melting point−20” ° C. to “melting point + 5 ° C.” of the polyolefin resin, more preferably “melting point−10 ° C.” to “melting point + 3 ° C.” of the polyolefin resin.

  Here, the melting point refers to the maximum endothermic peak associated with the melting point of the crystal, which is recognized when thermal analysis is performed with a differential scanning calorimeter (DSC).

  Examples of a method for warming the film during the stretching process include a method of stretching by using a heater, hot air, or a combination of both. When heating with hot air, a punching nozzle, a plate nozzle, or the like can be used as the nozzle in order to minimize the influence of the twist on the film surface.

  The stretching ratio is not particularly limited, but in order to achieve the effect of thinning and prevent film breakage during the stretching process, the stretching area ratio (longitudinal stretching × lateral stretching) is 1.2 to 9.0 times. preferable.

  The ratio of the stretch ratio of the stretched film in the longitudinal direction (MD direction) and the transverse direction (TD direction) is not particularly limited, and may be appropriately adjusted in order to minimize film thickness unevenness.

  The stretching speed in the longitudinal direction is not particularly limited, but is preferably 0.5 to 10 m / min as the stretching entrance speed. More preferably, it is 1-6 m / min. If the stretching line speed is high, the film is torn, and if it is slow, the resin dissolves and tension is not applied to the film, making stretching difficult.

  The stretching speed in the width direction is not particularly limited, but is preferably 0.1 to 2 m / min. More preferably, it is 0.2-1.2 m / min.

  The time for the stretching treatment is not particularly limited, but is preferably from 10 seconds to 3 minutes because good stretchability with small stretching unevenness can be obtained.

  The polyolefin resin film of the present invention is not particularly limited in length and width, and is a planar molded product, and includes tapes and ribbons.

  The film thickness of the stretched polyolefin resin film after stretching obtained by the production method of the present invention is preferably 1 to 100 μm, more preferably 5 to 60 μm, and particularly preferably 10 to 40 μm.

The stretched polyolefin resin film obtained by the production method of the present invention has a fish eye of 10 pieces / m ² or less, preferably 1 piece / m ² or less, and is excellent in appearance.

  The stretched polyolefin resin film obtained by the production method of the present invention may contain various additives as long as the effects of the present invention are not impaired. Examples of additives include antioxidants, dyes, organic pigments, inorganic pigments, inorganic reinforcing agents, plasticizers, processing aids such as acrylic processing aids, ultraviolet absorbers, light stabilizers, foaming agents, lubricants, and waxes. , Crystal nucleating agent, plasticizer, mold release agent, hydrolysis inhibitor, antiblocking agent, antistatic agent, radical scavenger, antifogging agent, antifungal agent, rustproofing agent, ion trapping agent, flame retardant, flame retardant An auxiliary agent, an inorganic filler, an organic filler, etc. can be mentioned.

  According to the present invention, it is possible to provide a method for producing a stretched polyolefin resin film having few fish eyes and excellent appearance. The production method of the present invention is useful, for example, as a production method of a protective film that requires high quality. Since the stretched polyolefin resin film obtained by the production method of the present invention has few fish eyes and is excellent in appearance, it is useful, for example, as a protective film that requires high quality.

  The present invention will be described in more detail with reference to the following examples. However, these are examples for helping understanding of the present invention, and the present invention is not limited to these examples.

<Polyolefin resin>
(1) Polyethylene LDPE; Petrocene (registered trademark) 220K (MFR = 1.0 g / 10 min, density = 930 kg / m ³ ), manufactured by Tosoh Corporation (2) Ethylene-vinyl acetate copolymer EVA; Ultrasen (registered) (Trademark) 546K (vinyl acetate content 10 wt%, MFR = 6 g / 10 min, density = 929 kg / m ³ ), manufactured by Tosoh Corporation (3) Saponified product of ethylene-vinyl acetate copolymer EVAOH; Mersen H (registered trademark) ) H-6051K (MFR = 5.5 g / 10 min, density = 970 kg / m ³ ), manufactured by Tosoh Corporation <Substrate>
PET film; Melinex (registered trademark) type S (thickness: 100 μm), manufactured by Teijin DuPont Films Co., Ltd. <Coating>
The coating was carried out using a coating machine provided with a 300 mm wide die coater capable of heating. A 5 L tank manufactured by Unicontrols Co., Ltd. and a die coater having a width of 300 mm were connected with a Teflon (registered trademark) tube. The tank was equipped with a nitrogen introduction valve for pressurization and a heating jacket, and the temperature was adjusted using HST-120CT manufactured by Mysec. The temperature of the Teflon (registered trademark) (registered trademark) tube was adjusted using a hose heater manufactured by MYSEC Co., Ltd. and HST-120CT. The die coater adjusted the temperature using a mold temperature controller TSW-75S manufactured by Nippon Mold Industry Co., Ltd. The polyolefin solution in the tank was applied onto the substrate from the die coater by pressurizing the tank with nitrogen.

<Measurement of haze>
According to JIS K7105, haze (diffuse transmittance / total light transmittance × 100 (%)) was measured using a haze meter NDH-300A (manufactured by Nippon Denshoku Co., Ltd.).

<Measurement of film thickness>
The thickness of the obtained polyolefin resin film in the width direction was measured at intervals of 10 mm, and the measured film thickness was averaged to calculate the average film thickness. The apparatus used was a high resolution linear gauge sensor HS-3412 manufactured by Ono Sokki Co., Ltd.

<Fisheye measurement>
A fluorescent lamp was irradiated from under the obtained film, and the number and size of fish eyes in the film were measured by visual observation or using a magnifying glass, and calculated as the number per 1 m ² .

<Measurement of density>
The density of the polyolefin resin film was measured by a density-squeeze tube method in accordance with JIS K7112 (1999).

Example 1
3.6 kg of LDPE pellets and 28.8 kg of 1,1,2-trichloroethane were charged into a 30 L autoclave and stirred at 110 ° C. for 2 hours under heating to dissolve LDPE to obtain a polyolefin solution. While this solution was filtered through a 500 mesh metal net, 3 L of the solution was transferred to a 5 L tank heated to 105 ° C. The tank was pressurized with nitrogen and fed to a 300 mm wide coating die heated to 105 ° C. through a Teflon (registered trademark) tube with a heating jacket kept at 105 ° C., and the polyolefin solution was transferred from the die. It was cast on the surface of a PET film as a substrate and dried at 150 ° C. The speed of the PET film was set at 2 m / min. The LDPE film was peeled from the laminate of the obtained PET film and LDPE film to obtain a polyolefin resin film (raw fabric film). The film thickness, haze, and fish eye of the obtained raw film were measured. The results are shown in Table 1.

次に原反フィルムを延伸機を用いて、延伸温度を１１５℃に設定し、横方向（ＴＤ方向）に３倍の横延伸を行った。延伸入り口速度を１ｍ／分に設定した。得られた延伸ポリオレフィン樹脂フィルムの膜厚、欠陥孔の数を測定した。その結果を表１に示す。

Next, the original film was stretched at a stretching temperature of 115 ° C. using a stretching machine, and stretched three times in the transverse direction (TD direction). The stretching entrance speed was set to 1 m / min. The film thickness of the obtained stretched polyolefin resin film and the number of defect holes were measured. The results are shown in Table 1.

  The obtained stretched polyolefin resin film was a film with few fish eyes and excellent appearance.

Example 2
A polyolefin resin film (raw film) was obtained in the same manner as in Example 1 except that the film thickness was adjusted to be thick. The film thickness, haze, and fish eye of the original film were measured. The results are shown in Table 1.

  Next, the stretching temperature of the raw film was set to 115 ° C. using a stretching machine, and simultaneous biaxial stretching was performed twice in the machine direction (MD direction) and twice in the transverse direction (TD direction). The film thickness and film thickness accuracy of the obtained stretched polyolefin resin film were measured. The results are also shown in Table 1.

  The obtained stretched polyolefin resin film was a film with few fish eyes and excellent appearance.

Example 3
A polyolefin resin film (raw film) was obtained in the same manner as in Example 1 except that EVA was used as the polyolefin resin. The film thickness, haze, and fish eye of the obtained raw film were measured. The results are shown in Table 1.

  Next, the original film was stretched three times in the transverse direction (TD direction) under the condition of a stretching temperature of 80 ° C. using a stretching machine. The film thickness of the obtained stretched polyolefin resin film and the number of defect holes were measured. The results are also shown in Table 1.

  The obtained stretched polyolefin resin film was a film with few fish eyes and excellent appearance.

Example 4
A polyolefin resin film (raw film) was obtained in the same manner as in Example 1 except that EVAOH was used as the polyolefin resin. The film thickness, haze, and fish eye of the original film were measured. The results are shown in Table 1.

  Next, the original fabric film was stretched three times in the transverse direction (TD direction) under the condition of a stretching temperature of 85 ° C. using a stretching machine.

  The film thickness of the obtained stretched polyolefin resin film and the number of defect holes were measured. The results are also shown in Table 1. The obtained stretched polyolefin resin film was a film with few fish eyes and excellent appearance.

Comparative Example 1
Using LDPE as the polyolefin resin, a film was formed by the T-die method. The apparatus used was a lab plast mill manufactured by Toyo Seiki Seisakusho Co., Ltd. connected to a φ20 mm single-screw extruder and a 250 mm wide T-die. The temperature of the extruder and the T die was 180 ° C., and the screw rotation speed was 50 rpm. The film thickness, haze, and fish eye of the obtained raw film were measured. The results are also shown in Table 1.

  Next, the original fabric film was stretched three times in the transverse direction (TD direction) under the condition of a stretching temperature of 85 ° C. using a stretching machine.

  Many defective holes were confirmed in the obtained stretched film, and fish eyes were observed in the ridges. The results are shown in Table 1.

Comparative Example 2
A raw film was obtained in the same manner as in Comparative Example 1 except that the film thickness was adjusted to be thicker. The film thickness, haze, and fish eye of the obtained raw film were measured. The results are shown in Table 1.

  Next, the original fabric film was subjected to simultaneous biaxial stretching twice in the machine direction (MD direction) and twice in the transverse direction (TD direction) under the condition of a stretching temperature of 115 ° C. using a stretching machine.

  Many defect holes were confirmed in the obtained stretched film. The results are also shown in Table 1.

Comparative Example 3
A raw film was obtained in the same manner as in Comparative Example 1 using EVA as the polyolefin resin. The film thickness, haze, and fish eye of the obtained raw film were measured. The results are also shown in Table 1.

  Next, the original film was stretched three times in the transverse direction (TD direction) under the condition of a stretching temperature of 80 ° C. using a stretching machine.

  Many defect holes were confirmed in the obtained stretched film. The results are shown in Table 1.

Comparative Example 4
A raw film was obtained in the same manner as in Comparative Example 1 using EVAOH as the polyolefin resin. The film thickness, haze, and fish eye of the obtained raw film were measured. The results are also shown in Table 1.

  Next, the original fabric film was stretched three times in the transverse direction (TD direction) under the condition of a stretching temperature of 85 ° C. using a stretching machine.

  Many defect holes were confirmed in the obtained stretched film. The results are shown in Table 1.

  The present invention provides a method for producing a stretched polyolefin resin film having few fish eyes and excellent appearance. Since the stretched polyolefin resin film obtained by the production method of the present invention has few fish eyes and is excellent in appearance, it is useful, for example, as a protective film that requires high quality.

Claims (5)

A method for producing a stretched polyolefin resin film, comprising stretching a polyolefin resin film having a number of fish eyes of 50 μm or more and 10 pieces / m ² or less. The method for producing a stretched polyolefin resin film according to claim 1, wherein the polyolefin solution obtained by filtering the polyolefin resin film is applied on a substrate and heated to evaporate the solvent. The method for producing a stretched polyolefin resin film according to claim 1 or 2, wherein the stretched area ratio is 1.2 to 9.0 times. The stretched polyolefin resin film is at least one polyolefin resin selected from the group consisting of polyethylene, ethylene-vinyl acetate copolymer, and saponified ethylene-vinyl acetate copolymer. Item 4. A method for producing a stretched polyolefin resin film according to any one of Items 3 to 3. A stretched polyolefin resin film obtained by the method for producing a stretched polyolefin resin film according to any one of claims 1 to 4.