Biaxially oriented polyolefin film

Abstract

To provide a biaxially oriented polyolefin film having antistatic properties. [Solution] A biaxially oriented polyolefin film comprising (A) a glycerin fatty acid ester consisting of an ester of a fatty acid having 12 to 24 carbon atoms and glycerin, and (B) one or more selected from the group consisting of aliphatic diethanolamine, fatty acid esters of polyoxyethylene aliphatic amine, fatty acid diethanolamide, and fatty acid monoester of fatty acid diethanolamide, wherein the (A) glycerin fatty acid ester comprises 0 to 15% by mass of glycerin fatty acid monoester, 30 to 60% by mass of glycerin fatty acid diester, and 30 to 60% by mass of glycerin fatty acid triester (provided that the total amount of the monoester, diester, and triester is 100% by mass).

Description

Technical Field

[0001] The present invention relates to a biaxially stretched polyolefin film.

Background Art

[0002] Generally, for the surface base material film of a laminate used for packaging, biaxially stretched polyolefin films such as biaxially stretched polypropylene films are mainly used from the viewpoints of rigidity, heat resistance, dimensional stability, and low cost. Biaxially stretched polyolefin films are manufactured by blending additives such as antistatic agents in order to have suitability in processing steps such as printing and lamination.

[0003] Among antistatic agents, widely used ones include glycerin fatty acid esters. However, when exposed to a high temperature of about 200°C in the stretching step during the production of polyolefin films, a part of the glycerin fatty acid ester decomposes and dissociates, and may generate smoke (generation of flying substances) due to the heat during stretching and forming. The smoke derived from the ester leads to deterioration of the working environment, and when cooled and solidified, it adheres and solidifies to the manufacturing apparatus, film, etc., leading to contamination of the apparatus and poor quality. Furthermore, there have been reported cases where the smoking component adheres and accumulates together with dust, etc. in the exhaust duct before exhaust gas treatment, for example, in a curved part, etc., and is heat-stored and catches fire, posing a risk of causing a fire. Therefore, in polyolefin-based stretched films, measures have been taken to suppress smoking caused by low molecular weight substances by suppressing the molding processing temperature (see, for example, Patent Document 1, etc.). In addition, proposals have been made to suppress smoking due to vaporization of an antistatic agent by using a low addition amount of the antistatic agent for biaxially stretched polyethylene films and stretching at a low temperature (see, for example, Patent Document 2, etc.).

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

[0005] Biaxially oriented polyolefin films are generally obtained by a sequential biaxial stretching method, in which molten resin is extruded from a T-die in an extruder, formed into a sheet, stretched longitudinally in a longitudinal stretcher, then guided to a transverse stretcher called a tenter, stretched transversely, and then heat-set and cooled. In this process, smoke emission from antistatic agent components is limited at the T-die exit and during the longitudinal stretching process, but as the film thins during the transverse stretching process, these components suddenly separate and emit smoke within the transverse stretcher, contaminating the tenter stretching zone and heat-set zone. In particular, it has been found that the accumulation of smoke-emitting components in the tenter exhaust duct creates a risk of fire due to ignition or combustion. Furthermore, in the cooling zone after transverse stretching and heat-set, and in the intermediate zone located upstream of the cooling zone, the emitted smoke components not only adhere to and condense on machinery and nozzles, contaminating the equipment, but also fall as dewdrops onto the upper surface of the biaxially stretched film, causing poor film quality. As described above, although measures and studies have been taken regarding the components and composition to suppress the separation, scattering, and smoke emission of antistatic agents, the desired antistatic properties are not always achieved, and problems such as the separation, scattering, and smoke emission of antistatic agents still persist despite these measures.

[0006] Furthermore, with the acceleration of film production and the increase in molding temperatures, the airflow rate from one zone to another tends to increase, accompanying the film and circulating air within the manufacturing equipment. While improvements from the equipment side, such as blowing and recovering counter-air, are being considered to prevent the aforementioned smoke components from being mixed into subsequent processes as accompanying airflow, it is not easy to prevent the inclusion of smoke components when increasing film production speed and molding temperature to improve film productivity.

[0007] The present invention provides a biaxially oriented polyolefin film having antistatic properties, which significantly reduces smoke generation during the film manufacturing process, thereby reducing not only the risk of fire but also contamination of machinery and serious quality defects in the film product. [Means for solving the problem]

[0008] The present invention relates to the following [1] to [5]. [1] (A) Glycerin fatty acid esters consisting of esters of fatty acids with 12 to 24 carbon atoms and glycerol, (B) One or more selected from the group consisting of aliphatic diethanolamines, fatty acid esters of polyoxyethylene aliphatic amines, fatty acid diethanolamides, and fatty acid monoesters of fatty acid diethanolamides. A biaxially oriented polyolefin film containing the following: The (A) glycerin fatty acid ester is characterized by containing 0 to 15% by mass of glycerin fatty acid monoester, 30 to 60% by mass of glycerin fatty acid diester, and 30 to 60% by mass of glycerin fatty acid triester (provided that the total amount of the monoester, diester, and triester is 100% by mass), and is a biaxially oriented polyolefin film. [2] The biaxially oriented polyolefin film according to [1], comprising 0.05 to 0.40% by mass of component (A) based on the total mass of the biaxially oriented polyolefin film. [3] A method for producing a biaxially oriented polyolefin film, A process to obtain an unstretched sheet by T-die method from a raw material mixture comprising (A0) a glycerin fatty acid ester mixture containing an ester of a fatty acid having 12 to 24 carbon atoms and glycerin, (B) one or more selected from the group consisting of aliphatic diethanolamine, fatty acid esters of polyoxyethylene aliphatic amine, fatty acid diethanolamide, and fatty acid monoesters of fatty acid diethanolamide, and (C) a polyolefin resin, and The process includes a step of sequentially biaxial stretching the unstretched sheet, which is stretched in the longitudinal (MD) direction and then in the transverse (TD) direction. The (A0) glycerin fatty acid ester mixture contains 0 to 15% by mass of glycerin fatty acid monoester, 30 to 60% by mass of glycerin fatty acid diester, and 30 to 60% by mass of glycerin fatty acid triester (provided that the total amount of monoester, diester, and triester is 100% by mass). Manufacturing method. [4] A laminated film comprising a plurality of films, including the biaxially oriented polyolefin film described in [1]. [5] [4] A packaging body made of the laminated film described above. [Effects of the Invention]

[0009] The biaxially oriented polyolefin film of the present invention is a film that exhibits excellent antistatic effects and also suppresses smoke generation during the formation of the stretched film. Furthermore, the biaxially oriented polyolefin film of the present invention not only significantly reduces smoke generation in the transverse stretching machine (tenter) during film manufacturing, thereby reducing the risk of fire, but also enables the reduction of machine contamination and serious quality defects in the film product. [Modes for carrying out the invention]

[0010] As mentioned above, when providing biaxially oriented polyolefin films, it is desirable not only for the additives to perform to their full potential, but also to minimize contamination of manufacturing equipment and film products by components derived from these additives during film production, as well as to minimize any deterioration in film quality. In particular, with antistatic agents containing glycerin fatty acid esters, heating during film molding can cause the esters to separate and scatter, potentially leading to smoke, ignition, and even fire, so measures to address these issues are required. However, with the recent increase in film production speed and molding temperatures, the amount of smoke-generating components that diffuse into the manufacturing equipment along with the circulating air is also tending to increase.

[0011] The biaxially oriented polyolefin film according to the present invention has excellent antistatic properties, and because the incorporated antistatic agent is low-smoke, the amount of smoke generated during film manufacturing (stretching) can be reduced, thereby preventing contamination of manufacturing equipment and film, and ultimately leading to an improvement in film yield. Furthermore, suppressing smoke generation during film manufacturing leads to an improvement in the working environment during film formation, thus reducing environmental and human burden. In addition, since cleaning and maintenance of smoke components and other substances adhering to film manufacturing (stretching) equipment is labor-intensive and costly, implementing the present invention has the significant advantage of reducing the frequency of such cleaning and maintenance. These reductions in environmental and human burden and maintenance costs are reflected in the price of the biaxially oriented polyolefin film itself. The present invention will be described in detail below.

[0012] [Biaxially oriented polyolefin film] The biaxially oriented polyolefin film of the present invention contains (A) a glycerin fatty acid ester, as described later, and (B) one or more selected from the group consisting of aliphatic diethanolamine, fatty acid esters of polyoxyethylene aliphatic amine, fatty acid diethanolamide, and fatty acid monoesters of fatty acid diethanolamide. The above components (A) and (B) are components that impart antistatic properties to polyolefin resins, and can also function as components that improve the compatibility of each component with polyolefin resins.

[0013] [(A) Glycerin fatty acid esters containing esters of fatty acids with 12 to 24 carbon atoms and glycerol] (A) Glycerin fatty acid esters are esters of fatty acids with 12 to 24 carbon atoms and glycerin. The ester of the above fatty acid and glycerin, which is a trivalent alcohol, takes the form of glycerin fatty acid monoester, glycerin fatty acid diester, and glycerin fatty acid triester depending on the degree of esterification. In the present invention, by containing a specific amount of the above diester and triester and making the content of the monoester lower than these diesters and triesters, it is possible to particularly suppress the smoke generation due to the decomposition and vaporization of the ester during the molding and processing of the stretched film.

[0014] In the glycerin fatty acid ester according to the present invention, the glycerin fatty acid monoester is contained at 0 to 15% by mass, the glycerin fatty acid diester is contained at 30 to 60% by mass, and the glycerin fatty acid triester is contained at 30 to 60% by mass (total 100% by mass of the monoester, diester, and triester). By setting the ratio of each ester of the glycerin fatty acid ester used in the present invention within the above numerical range, sufficient antistatic properties can be imparted to the biaxially stretched polyolefin film, and the smoke generation in the transverse stretching process of the polyolefin film containing this can be suppressed. In a preferred embodiment, the glycerin fatty acid ester preferably contains the glycerin fatty acid monoester at from 0 to 15% by mass, more preferably at from 5 to 14% by mass, and even more preferably at from 8 to 13% by mass. For the glycerin fatty acid diester, it is preferably contained at from 30 to 60% by mass, more preferably at from 40 to 60% by mass, and even more preferably at from 45 to 55% by mass. For the glycerin fatty acid triester, it is preferably contained at from 30 to 60% by mass, more preferably at from 30 to 50% by mass, and even more preferably at from 33 to 45% by mass. If the proportion of the monoester in the above glycerin fatty acid ester exceeds 15% by mass, there is a risk that the smoke generation property will increase. If the proportion of the triester is less than 30% by mass, there is a risk that the smoke generation property will increase, and if it exceeds 60% by mass, there is a risk of contamination of the production equipment by free fatty acids.

[0015] Examples of fatty acids having 12 to 24 carbon atoms include saturated fatty acids such as lauric acid, myristic acid, palmitic acid, stearic acid, arachidic acid, behenic acid, and lignoceric acid; monounsaturated fatty acids such as palmitoleic acid and oleic acid; and polyunsaturated fatty acids such as linoleic acid and linolenic acid. Among the fatty acids having 12 to 24 carbon atoms, fatty acids having 14 to 18 carbon atoms are preferably used, and saturated fatty acids are also preferably used. If the number of carbon atoms in the above fatty acid is less than 12, there is a risk that its compatibility with polyolefin resin will decrease, making it impossible to maintain long-term antistatic performance, and it may also cause poor transparency due to excessive bleeding. On the other hand, if the number of carbon atoms exceeds 24, the amount of bleeding to the resin surface will be insufficient, which may result in inadequate antistatic performance. The above fatty acids may be used individually or in combination of two or more. For example, the above glycerin fatty acid diester may be an ester compound of glycerin and two different fatty acids, and the above glycerin fatty acid triester may be an ester compound of glycerin and two or more different fatty acids.

[0016] In the biaxially oriented polyolefin film according to the present invention, the glycerin fatty acid ester of component (A) can be blended in an amount of 0.05 to 0.40% by mass, preferably 0.10 to 0.35% by mass, based on the total mass of the film. The amount of glycerin fatty acid ester in component (A) described above applies to both the single-layer and laminated configurations of the biaxially oriented polyolefin film described later (for example, a configuration in which a surface layer is provided on both sides of a substrate layer containing component (A)).

[0017] [(B) One selected from the group consisting of aliphatic diethanolamines, fatty acid esters of polyoxyethylene aliphatic amines, fatty acid diethanolamides, and fatty acid monoesters of fatty acid diethanolamides] The biaxially oriented polyolefin film according to the present invention contains, in addition to the (A) glycerin fatty acid ester, one or more components selected from the group consisting of aliphatic diethanolamine, fatty acid esters of polyoxyethylene aliphatic amine, fatty acid diethanolamide, and fatty acid monoesters of fatty acid diethanolamide as component (B).

[0018] <Aliphatic diethanolamine> Examples of aliphatic diethanolamines include lauryl diethanolamine, myristyl diethanolamine, palmityl diethanolamine, stearyl diethanolamine, and oleyl diethanolamine, with stearyl diethanolamine and oleyl diethanolamine being particularly preferred. These may be used individually or in combination of two or more.

[0019] <Fatty acid esters of polyoxyethylene aliphatic amines> Examples of fatty acid esters of polyoxyethylene aliphatic amines include monoesters and diesters obtained by reacting a saturated or unsaturated fatty acid with a polyoxyethylene alkylamine or polyoxyethylene alkenylamine. Examples of the above fatty acids include saturated or unsaturated fatty acids with 8 to 22 carbon atoms, such as caprylic acid, capric acid, lauric acid, myristic acid, palmitic acid, stearic acid, isostearic acid, oleic acid, and behenic acid. More specific examples of fatty acid esters of polyoxyethylene aliphatic amines include, but are not limited to, lauryl diethanolamine monostearate, myristyl diethanolamine monooleate, palmityl diethanolamine monostearate, stearyl diethanolamine monolaurate, stearyl diethanolamine monostearate, stearyl diethanolamine monooleate, stearyl diethanolamine monobehenate, and oleyl diethanolamine monostearate. Among these, stearyl diethanolamine monostearate and oleyl diethanolamine monolaurate are particularly preferred. These may be used individually or in combination of two or more.

[0020] <Fatty acid diethanolamide> Examples of fatty acid diethanolamides include coconut fatty acid diethanolamide, lauric acid diethanolamide, myristic acid diethanolamide, tridecyl acid diethanolamide, pentadecyl acid diethanolamide, palmitic acid diethanolamide, heptadecyl acid diethanolamide, stearate diethanolamide, oleic acid diethanolamide, nonadecanoic acid diethanolamide, and arachid acid diethanolamide. Among these, stearic acid diethanolamide and oleic acid diethanolamide are preferred from the viewpoint of antistatic properties. Fatty acid diethanolamides can be used individually or in combination of two or more.

[0021] <Fatty acid monoester of fatty acid diethanolamide> Fatty acid monoesters of fatty acid diethanolamides include the fatty acid monoesters of the amide compounds listed above under <Fatty Acid Diethanolamides>. Examples of the above fatty acids include saturated or unsaturated fatty acids with 8 to 22 carbon atoms, such as caprylic acid, capric acid, lauric acid, myristic acid, palmitic acid, stearic acid, isostearic acid, oleic acid, and behenic acid.

[0022] In the biaxially oriented polyolefin film according to the present invention, component (B) can be blended in an amount of 0.10 to 1.50% by mass, preferably 0.30 to 1.00% by mass, based on the total mass of the film. The amount of component (B) described above applies to both the single-layer and laminated configurations of the biaxially oriented polyolefin film described later (for example, a configuration in which a surface layer is provided on both sides of a substrate layer containing component (B)).

[0023] Furthermore, in the biaxially oriented polyolefin film according to the present invention, the mass ratio of component (A) to component (B) can be, for example, 5:95 to 60:40, preferably 10:90 to 50:50.

[0024] [Resin component: (C) Polyolefin resin] The resin components constituting the biaxially oriented polyolefin film according to the present invention are not particularly limited, and include, for example, ethylene, propylene, 1-butene, 1-pentene, 1-hexene, 4- These include homopolymers of α-olefins such as methyl-1-pentene, copolymers of the α-olefins, copolymers of α-olefins with monomers other than α-olefins that can copolymerize with the α-olefins, and mixtures thereof. Examples of monomers other than α-olefins that can copolymerize with the α-olefins include vinyl acetate, maleic acid, vinyl alcohol, methacrylic acid, methyl methacrylate, and ethyl methacrylate. Specific examples of these include homopolymers of α-olefins such as low-density polyethylene, high-density polyethylene, polypropylene, and polybutene-1; copolymers of α-olefins such as ethylene-propylene copolymer, ethylene-butene-1 copolymer, propylene-butene-1 copolymer, propylene-ethylene-butene-1 copolymer, and ethylene-propylene-butene-1 copolymer; ethylene-acrylic acid copolymer, ionomers obtained by crosslinking ethylene-acrylic acid copolymer with metal ions, and ethylene-vinyl acetate copolymer. These may be used individually or in combination of two or more types. These resins are appropriately selected from resins produced from suitable starting materials such as petroleum-derived, biomass-derived, material-recycled, and chemical-recycled materials.

[0025] [Other ingredients] In addition to components (A) and (B) above, the biaxially oriented polyolefin film according to the present invention may contain various additives commonly used in polyolefin resin compositions, to the extent that they do not impair the objectives of the present invention. Examples of such additives include antioxidants, weathering agents, ultraviolet absorbers, stabilizers, slip agents, tackifiers, and antiblocking agents.

[0026] The biaxially oriented polyolefin film according to the present invention may be a single layer comprising components (A) and (B) (and optionally other components) and the polyolefin resin (C), or it may be a laminated form in which another layer is laminated to a layer comprising components (A) and (B) (and optionally other components) and the polyolefin resin (C).

[0027] When the biaxially oriented polyolefin film according to the present invention is in a laminated form, for example, it can be a laminated film of 3 to 5 layers. As an example, but not limited to these, it can be a form comprising two surface layers mainly composed of polyolefin resin and a base layer (a form in which the surface layers are provided on both sides of the base layer), (a1) an embodiment in which components (A) and (B) are added to at least one layer other than the surface layer (for example, a base layer), (a2) In the embodiment of (a1) above, an intermediate layer is provided between the surface layer and the base material layer, (a3) In the embodiment of (a2) above, the intermediate layer is provided with components (A) and (B), or, (b1) an embodiment in which components (A) and (B) are added to at least one of the surface layer and the base layer, (b2) In the embodiment of (b1) above, an intermediate layer is provided between the surface layer and the base material layer, (b3) In the embodiment of (b2) above, the components (A) and (B) are added to the intermediate layer. Examples of such behaviors can be cited. As described above, components (A) and (B) (i.e., antistatic components) are often added to at least one layer other than the surface layer. In this case, for example, they may be added only to the base layer, or to the base layer and the intermediate layer. When components (A) and (B) are also added to the surface layer, it is assumed that only a small amount of these components are added to the surface layer, so it is desirable that they be added to the base layer and the intermediate layer in addition to the surface layer.

[0028] [(A0) Glycerin lipid containing esters of fatty acids with 12-24 carbon atoms and glycerol] [Leprosate ester mixture] The (A) glycerin fatty acid ester contained in the biaxially oriented polyolefin film according to the present invention consists of an ester of the above fatty acid and glycerin (consisting only of esters that satisfy the above monoester, diester, and triester ratio). However, as will be described later, when manufacturing the biaxially oriented polyolefin film, the reaction product obtained by esterifying the above fatty acid and glycerin can be blended directly into the (C) polyolefin resin, that is, in the form of a mixture including unreacted material. In other words, in the production of a biaxially oriented polyolefin film, the (A) glycerin fatty acid ester can be incorporated into the biaxially oriented polyolefin film as a glycerin fatty acid ester mixture containing (A0) esters of fatty acids with 12 to 24 carbon atoms and glycerin. Of course, the biaxially oriented polyolefin film may also be produced using a mixture consisting solely of glycerin fatty acid ester as component (A0). (A0) The glycerin fatty acid ester mixture is characterized by containing 0 to 15% by mass of glycerin fatty acid monoester, 30 to 60% by mass of glycerin fatty acid diester, and 30 to 60% by mass of glycerin fatty acid triester (provided that the total amount of the monoester, diester, and triester is 100% by mass).

[0029] [Method for producing biaxially oriented polyolefin film] The biaxially oriented polyolefin film according to the present invention can be manufactured by known methods. First, a polyolefin resin composition is obtained by heating and kneading the (C) polyolefin resin, components (A0) and (B), and optionally other components using a known mixer or extruder such as a Banbury mixer, Henschel mixer, tumbler mixer, single-screw extruder, or multi-screw extruder. Components (A0) and (B), and other components may be added to the (C) polyolefin resin separately, or they may be mixed beforehand and then added to the polyolefin resin from the viewpoint of obtaining an antistatic effect early. If the amount of components (A0) and (B) (and other components) added is insufficient relative to the amount of (C) polyolefin resin, there is a risk that they will not be uniformly dispersed in the resin. Therefore, a masterbatch method may be adopted in which a masterbatch containing high concentrations of components (A0) and (B) is prepared in advance and kneaded with the (C) polyolefin resin that does not contain components (A0) and (B) to obtain a predetermined content.

[0030] The obtained polyolefin resin composition is converted into an unstretched sheet by methods such as the T-die method, inflation method, or calendering method. An example of the T-die method involves supplying the polyolefin resin composition to an extruder hopper, heating the extruder to, for example, a cylinder temperature of 180-240°C and a T-die temperature of 200-250°C, melt-kneading and extruding the mixture, and then cooling it with a cooling roll controlled to 10-90°C to obtain an unstretched sheet with a thickness of 300-2000 μm. Furthermore, co-extrusion or lamination with other films can be used to impart strength or other functions to the film.

[0031] Biaxial stretching of an unstretched sheet can be performed by sequential biaxial stretching using rolls and a tenter. In the sequential biaxial stretching method, the unstretched sheet is stretched in the longitudinal direction at a roll temperature of 50 to 150°C and a stretching ratio of 1.5 to 8 times, depending on the rotational speed ratio of the drive rolls, for example, and then continuously stretched in the transverse direction at a stretching temperature of 100 to 200°C, a stretching ratio of 4 to 12 times, and a heat-fixing temperature of 100 to 200°C to obtain a biaxially oriented polyolefin film.

[0032] One preferred embodiment of the method for producing a biaxially oriented polyolefin film is a step of obtaining an unstretched sheet from a raw material mixture containing the (A0) and (B) components and the (C) polyolefin resin by a T-die method, and A manufacturing method can be described as one that includes a step of sequential biaxial stretching, in which the unstretched sheet is stretched in the longitudinal (MD) direction and then stretched in the transverse (TD) direction, and this manufacturing method is also subject to the present invention. can. Furthermore, based on the total mass of the raw material mixture, component (A0) can be blended in a proportion of 0.05 to 0.40% by mass, preferably 0.10 to 0.35% by mass, and component (B) can be blended in a proportion of 0.10 to 1.50% by mass, preferably 0.30 to 1.00% by mass. In addition, the mass ratio of component (A0) to component (B) can be, for example, 5:95 to 60:40, preferably 10:90 to 50:50.

[0033] The thickness of the biaxially oriented polyolefin film according to the present invention can be appropriately set according to the application, required performance, price, etc., and can generally be about 10 to 100 μm thick. Furthermore, surface treatment may be applied to improve the printability, lamination properties, and coating suitability of the film. Examples of surface treatment methods include corona discharge treatment, plasma treatment, and acid treatment, and any of these methods can be used. Among these, corona discharge treatment is the most preferred due to its simplicity. Printing on the film surface can be done using commonly used methods such as screen printing, flexographic printing, offset printing, and gravure printing.

[0034] [Laminated film / packaging] The biaxially oriented polyolefin film according to the present invention can be used as a single film, or as a laminated film (laminated film) formed by laminating two or more films including the biaxially oriented polyolefin film. For example, the biaxially oriented polyolefin film according to the present invention can be laminated with a sealant film made of polyolefin resin, and from the viewpoint of a single material (monomaterial), it is preferable that the biaxially oriented polyolefin film and the sealant film that serve as the base material for the laminated film have the same main resin. The laminated film is suitably used as packaging material for various articles such as food, daily necessities, and parts, and is used after being molded into a package or the like. A laminated film consisting of multiple films including this biaxially oriented polyolefin film is also a subject of the present invention, as is a packaging body made of the laminated film. The laminated film may be obtained by a solvent-type dry lamination method using a solvent to dilute the adhesive, or by processing with a solvent-free adhesive. The structure of the laminated film is not particularly limited as long as it includes the biaxially oriented polyolefin film. [Examples]

[0035] The present invention will be described in detail with reference to the following embodiments, but the present invention is not limited to these embodiments.

[0036] [Fabrication of biaxially oriented polyolefin film] Biaxially oriented polyolefin films for Examples 1 to 4 and Comparative Examples 1 to 5 were prepared using the following procedure. Each of the materials described later was blended in the predetermined proportions (mass%) shown in Table 2 and supplied to an extruder. The mixture was melted and kneaded, and then co-extruded using the T-die method to form a three-layer sheet consisting of a first surface layer, a base layer, and a second surface layer in that order, to obtain an unstretched sheet. Subsequently, the unstretched sheet was stretched in the longitudinal (MD) and transverse (TD) directions to produce a biaxially oriented film with a film thickness of 20 μm. In the stretching process, the film was sequentially biaxially stretched by 5 times in the longitudinal (MD) direction using roll stretching, followed by 8 times in the transverse (TD) direction using tenter stretching under temperature conditions of preheating temperature 175-185°C, stretching temperature 155-165°C, and heat setting temperature 160-170°C. After film formation, the first and second surface layers were subjected to corona treatment under conditions commonly used for films to adjust the wetting tension to approximately 36 mN / m.

[0037] [Materials used] <Polyolefin resin> • PP1: Homopolypropylene (manufactured by Nippon Polypropylene Co., Ltd.; "FL203D") • PP2: Random polypropylene (manufactured by Nippon Polypropylene Co., Ltd.; "FX4EA") <Glycerin fatty acid ester (mixture)> Glycerin fatty acid esters (mixtures) having the ester ratios shown in Table 1 (total 100% by mass) were used. [Table 1] <Aliphatic diethanolamines, etc.> B1: Oleyldiethanolamine B2: Stearyldiethanolamine B3: Stearyldiethanolamine monostearate B4: Oleyl diethanolamine monolaurate

[0038] [Example 1] In the biaxially oriented polyolefin film of Example 1, 100% by mass of PP2 was used for the first and second surface layers, and a raw material mixture of 99% by mass of PP1, 0.4% by mass of A1, 0.2% by mass of B1, and 0.4% by mass of B3 was used for the base layer. The amount of raw material discharged was adjusted so that the ratio of the first surface layer:base layer:second surface layer was 1:18:1 for the thickness of each layer, and a biaxially oriented polyolefin film with a total thickness of 20 μm was obtained. [Examples 2-4, Comparative Examples 1-5] Except for using the raw materials for the first and second surface layers, and the raw materials for the base layer, as shown in Table 2, the same procedure and layer thicknesses (first surface layer, second surface layer, base layer) as in [Example 1] were used to obtain biaxially oriented polyolefin films of Examples 2-4 and Comparative Examples 1-5 with a total thickness of 20 μm.

[0039] Following the procedure described below, the wetting tension (mN / m) and surface resistivity (Ω / □) of the biaxially oriented polyolefin films of Examples 1-4 and Comparative Examples 1-5 were measured, and the presence or absence of smoke generation during film formation was evaluated.

[0040] [Measurement of wetting tension] The wetting tension (mN / m) was measured in accordance with JIS K 6768 (1999). If the wetting tension is less than 36 mN / m, the film can be evaluated as having poor printability and lamination suitability.

[0041] [Measurement of surface resistivity] The surface resistivity (Ω / □) was measured in accordance with JIS K 6911 (2006). A higher surface resistivity indicates a film with inferior antistatic performance. 13 If the value is less than (Ω / □), it can be considered to have excellent antistatic properties.

[0042] [Evaluation of smoke emission during film molding] To evaluate the degree of smoke generation during film formation, the presence or absence of smoke due to vaporization from additives (G1-G2, A1, B1-B4) was visually checked at the outlet of the tenter equipment, which is the stretching section in the lateral (TD) direction. A rating of "0" was given for no smoke generation at all, "1" for some smoke generation, and "2" for smoke generation that was easily visible.

[0043] [Table 2]

[0044] As shown in Table 2, Examples 1 to 4, which include glycerin fatty acid ester (mixture) A1 containing 0-15% by mass of glycerin fatty acid monoester, 30-60% by mass of glycerin fatty acid diester, and 30-60% by mass of glycerin fatty acid triester, and B1-B4 which are aliphatic diethanolamines, etc., have a surface resistivity value of 10 13 The results showed excellent antistatic performance with a value of less than (Ω / □), while also achieving a smoke emission rating of 0. On the other hand, in Comparative Examples 1 to 5, which used mixtures G1 or G2 in which the proportions of monoesters, diesters, and triesters differed from the above-mentioned predetermined range in the glycerin fatty acid ester mixture, smoke emission was observed. In particular, smoke emission was significantly observed in Comparative Examples 1, 3, and 4, which used mixture G1 with a high proportion of monoesters.

Claims

1. (A) Glycerin fatty acid esters consisting of esters of fatty acids with 12 to 24 carbon atoms and glycerol, (B) One or more selected from the group consisting of aliphatic diethanolamines, fatty acid esters of polyoxyethylene aliphatic amines, fatty acid diethanolamides, and fatty acid monoesters of fatty acid diethanolamides. A biaxially oriented polyolefin film containing the following: The (A) glycerin fatty acid ester is characterized by containing 0 to 15% by mass of glycerin fatty acid monoester, 30 to 60% by mass of glycerin fatty acid diester, and 30 to 60% by mass of glycerin fatty acid triester (provided that the total amount of the monoester, diester, and triester is 100% by mass). Biaxially oriented polyolefin film.

2. Based on the total mass of the biaxially oriented polyolefin film, the amount of component (A) is 0.05 to 0.40% by mass. The biaxially oriented polyolefin film according to claim 1.

3. A method for producing a biaxially oriented polyolefin film, A process to obtain an unstretched sheet by T-die method from a raw material mixture comprising (A0) a glycerin fatty acid ester mixture containing an ester of a fatty acid having 12 to 24 carbon atoms and glycerin, (B) one or more selected from the group consisting of aliphatic diethanolamine, fatty acid esters of polyoxyethylene aliphatic amine, fatty acid diethanolamide, and fatty acid monoesters of fatty acid diethanolamide, and (C) a polyolefin resin, and The process includes a step of sequentially biaxial stretching the unstretched sheet, which is stretched in the longitudinal (MD) direction and then in the transverse (TD) direction. The (A0) glycerin fatty acid ester mixture is characterized by containing 0 to 15% by mass of glycerin fatty acid monoester, 30 to 60% by mass of glycerin fatty acid diester, and 30 to 60% by mass of glycerin fatty acid triester (provided that the total amount of the monoester, diester, and triester is 100% by mass). Manufacturing method.

4. A laminated film comprising a plurality of films, including the biaxially oriented polyolefin film described in claim 1.

5. A packaging body made of the laminated film described in claim 4.

Images