Biaxially oriented polyolefin film

Abstract

To provide a biaxially oriented polyolefin film having antistatic properties. [Solution] A biaxially stretched polyolefin film containing (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 members selected from the group consisting of aliphatic diethanolamines, fatty acid esters of polyoxyethylene fatty amines, fatty acid diethanolamides, and fatty acid monoesters of fatty acid diethanolamides, wherein the (A) glycerin fatty acid ester contains 0 to 15 mass% of glycerin fatty acid monoesters, 30 to 60 mass% of glycerin fatty acid diesters, and 30 to 60 mass% of glycerin fatty acid triesters (with the proviso that the total amount of the monoesters, diesters, and triesters is 100 mass%).

Description

[Technical Field]

[0001] The present invention relates to a biaxially oriented polyolefin film. [Background technology]

[0002] Generally, biaxially oriented polyolefin films such as biaxially oriented polypropylene films are mainly used as the surface substrate films of laminates used for packaging, from the viewpoints of rigidity, heat resistance, dimensional stability, low cost, etc. Biaxially oriented polyolefin films are produced by blending additives such as antistatic agents to provide suitability for processing steps such as printing and lamination.

[0003] Glycerin fatty acid esters are widely used antistatic agents. However, when exposed to high temperatures of around 200°C during the stretching process in polyolefin film production, some of these glycerin fatty acid esters decompose and become liberated. The heat generated during the stretching and molding processes can cause smoke (the release of flying debris). The smoke from these esters not only worsens the working environment, but also adheres to and solidifies on the manufacturing equipment and film upon cooling and solidification, resulting in equipment contamination and quality defects. Furthermore, there have been reported cases in which the smoke-generating components adhered to and accumulated with dust and other particles in exhaust ducts before exhaust gas treatment, for example, at curved sections, and ignited due to heat accumulation, posing a risk of fire. For this reason, in the case of stretched polyolefin films, efforts have been made to suppress the smoke generated by low molecular weight substances by suppressing the molding processing temperature (see, for example, Patent Document 1, etc.). In addition, there has been a proposal to add a small amount of antistatic agent to a biaxially oriented polyethylene film and stretch it at a low temperature to suppress smoke caused by vaporization of the antistatic agent (see, for example, Patent Document 2, etc.). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent Publication No. 2021-066470 [Patent Document 2] Japanese Patent Application Publication No. 2023-145311 Summary of the Invention [Problem to be solved by the invention]

[0005] Biaxially oriented polyolefin films are typically produced using a sequential biaxial orientation process. Melted resin is extruded through a T-die in an extruder, formed into a sheet, stretched longitudinally in a longitudinal stretching machine, and then introduced into a transverse stretching machine called a tenter. The sheet is then stretched transversely, followed by heat setting and cooling. While smoke from antistatic agents is limited at the T-die exit and during the longitudinal stretching process, as the film becomes thinner during the transverse stretching process, these agents rapidly separate and emit smoke within the transverse stretching machine, contaminating the tenter stretching zone and heat setting zone. The smoke-emitting components can accumulate and ignite, particularly in the tenter exhaust duct, creating a fire risk. Furthermore, in the cooling zone after transverse stretching and heat setting, as well as in the intermediate zone upstream of the cooling zone, the smoke-emitting components not only adhere to and condense on machinery and nozzles, contaminating the equipment, but also form dewdrops that fall onto the top surface of the biaxially stretched film, resulting in poor film quality. As mentioned above, measures and investigations have been carried out on ingredients and compositions that aim to suppress the separation and scattering of antistatic agents and the generation of smoke, but in some cases the desired antistatic properties cannot be obtained, and even with these measures, the separation and scattering of antistatic agents and the generation of smoke still occur.

[0006] Furthermore, with the increase in film production speed and molding temperature, the amount of air flowing from one zone to another tends to increase, accompanying the film traveling through the manufacturing equipment and circulating air. To prevent the above-mentioned smoke-generating components from being mixed into subsequent processes as an accompanying flow, improvements have been considered from the equipment side, such as blowing and recovering counter air, but when film production speed and molding temperature are increased in an effort to improve film productivity, it is not easy to prevent the mixing of smoke-generating components.

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

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

[0009] The biaxially stretched polyolefin film of the present invention is a film that exhibits an excellent antistatic effect and is also a film that suppresses smoke generation during stretching film formation. Furthermore, the biaxially oriented polyolefin film of the present invention can provide a biaxially oriented polyolefin film that not only significantly reduces smoke generation in the transverse stretching machine (tenter) during film production and reduces the risk of fire, but also reduces machine contamination and serious quality defects in film products. DETAILED DESCRIPTION OF THE INVENTION

[0010] As mentioned above, when providing biaxially oriented polyolefin films, it is desirable not only to ensure that the additives used exhibit their inherent performance, but also to minimize contamination of the manufacturing equipment and film products during film production due to additive-derived components, and to minimize degradation of film quality. In particular, with antistatic agents containing glycerin fatty acid esters, the esters can separate and disperse when heated during film formation, potentially causing smoke and even fire. Therefore, measures must be taken to prevent this. However, with the recent increase in film production speeds and higher molding temperatures, the amount of smoke-producing components circulating in the manufacturing equipment and diffusing within the equipment is also on the rise.

[0011] The biaxially oriented polyolefin film of the present invention has excellent antistatic properties, and the blended antistatic agent has low smoke-emission properties, which reduces smoke generation during film production (stretching), thereby preventing contamination of the production equipment and film, and ultimately improving film yield. Furthermore, suppressing smoke generation during film production improves the working environment during film production, thereby reducing environmental and personal burdens. Furthermore, while cleaning and maintenance of film production (stretching) equipment to remove smoke-generating components and other substances is labor-intensive and costly, the implementation of the present invention has the significant advantage of reducing the frequency of such cleaning and maintenance. These environmental and personal burdens and maintenance costs are also 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 stretched polyolefin film of the present invention contains (A) a glycerin fatty acid ester, which will be described later, and (B) at least one member selected from the group consisting of aliphatic diethanolamine, fatty acid ester of polyoxyethylene fatty amine, fatty acid diethanolamide, and fatty acid monoester of fatty acid diethanolamide. The components (A) and (B) are components that impart antistatic properties to the polyolefin resin, and can also function as components that improve the compatibility of each component with the polyolefin resin.

[0013] [(A) Glycerin fatty acid esters containing esters of fatty acids having 12 to 24 carbon atoms and glycerin] (A) Glycerin fatty acid ester is an ester of a fatty acid having 12 to 24 carbon atoms and glycerin. The esters of the above fatty acids and the trihydric alcohol glycerin may take the form of glycerin fatty acid monoesters, glycerin fatty acid diesters, and glycerin fatty acid triesters depending on the degree of esterification. In the present invention, the diesters and triesters are contained in specific amounts, and the content of monoesters is lower than that of the diesters and triesters, thereby making it possible to suppress smoke generation due to decomposition and vaporization of esters, particularly during the forming and processing of stretched films.

[0014] The glycerin fatty acid ester according to the present invention is characterized by containing 0 to 15 mass% of glycerin fatty acid monoester, 30 to 60 mass% of glycerin fatty acid diester, and 30 to 60 mass% of glycerin fatty acid triester (total of monoester, diester, and triester is 100 mass%). By setting the proportion of each ester of the glycerin fatty acid ester used in the present invention within the above numerical range, it is possible to obtain a biaxially stretched polyolefin film. This provides sufficient antistatic properties and also suppresses the generation of smoke during the transverse stretching process of a polyolefin film containing this compound. In a preferred embodiment, the glycerin fatty acid ester contains 0 to 15% by mass of glycerin fatty acid monoester, preferably 5 to 14% by mass, and even more preferably 8 to 13% by mass. The glycerin fatty acid diester is contained preferably at 30 to 60% by mass, more preferably at 40 to 60% by mass, and even more preferably at 45 to 55% by mass. The glycerin fatty acid triester is contained preferably at 30 to 60% by mass, more preferably at 30 to 50% by mass, and even more preferably at 33 to 45% by mass. If the proportion of monoesters in the glycerin fatty acid ester exceeds 15% by mass, there is a risk of increased smoke generation. If the proportion of triesters is less than 30% by mass, there is a risk of increased smoke generation. If it exceeds 60% by mass, there is a risk of contamination of the manufacturing equipment by free fatty acids. There is a risk that this may occur.

[0015] Examples of the 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. Of the fatty acids having 12 to 24 carbon atoms, fatty acids having 14 to 18 carbon atoms can be preferably used, and saturated fatty acids can be preferably used. If the number of carbon atoms in the fatty acid is less than 12, the compatibility with the polyolefin resin may decrease, the antistatic performance may not be maintained for a long period of time, and the transparency may be poor due to excessive bleeding. On the other hand, if the number of carbon atoms is more than 24, the amount of bleeding to the resin surface may be too small, and the antistatic performance may be insufficient. The above fatty acids may be used alone or in combination of two or more. For example, the glycerin fatty acid diester may be an ester compound of glycerin and two different fatty acids, and the glycerin fatty acid triester may be an ester compound of glycerin and two or more different fatty acids.

[0016] In the biaxially stretched 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 blending amount of the glycerin fatty acid ester of the component (A) is applicable whether the biaxially oriented polyolefin film is a single layer or a laminated film (for example, a film having surface layers on both sides of a base layer containing the component (A)) as described below.

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

[0018] <Aliphatic diethanolamine> Examples of aliphatic diethanolamines include lauryldiethanolamine, myristyldiethanolamine, palmityldiethanolamine, stearyldiethanolamine, and oleyldiethanolamine, and particularly preferred are stearyldiethanolamine and oleyldiethanolamine. These may be used alone or in combination of two or more.

[0019] <Fatty acid ester of polyoxyethylene fatty amine> Examples of fatty acid esters of polyoxyethylene aliphatic amines include monoesters and diesters obtained by reacting polyoxyethylene alkylamines or polyoxyethylene alkenylamines with saturated or unsaturated fatty acids. The fatty acids include saturated or unsaturated fatty acids having 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, preferred are stearyl diethanolamine monostearate and oleyl diethanolamine monolaurate. These may be used alone 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, tridecylic acid diethanolamide, pentadecylic acid diethanolamide, palmitic acid diethanolamide, heptadecylic acid diethanolamide, stearic acid diethanolamide, oleic acid diethanolamide, nonadecanoic acid diethanolamide, and arachic acid diethanolamide. Among these, stearic acid diethanolamide and oleic acid diethanolamide are preferred from the viewpoint of antistatic properties. The fatty acid diethanolamides can be used singly or in combination of two or more.

[0021] <Fatty acid monoester of fatty acid diethanolamide> Examples of fatty acid monoesters of fatty acid diethanolamides include fatty acid monoesters of the amide compounds listed above in the section <Fatty Acid Diethanolamides>. The fatty acids include saturated or unsaturated fatty acids having 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 stretched polyolefin film according to the present invention, the component (B) can be blended in an amount of 0.10 to 1.50 mass %, preferably 0.30 to 1.00 mass %, based on the total mass of the film. The blending amount of the above-mentioned component (B) is applicable whether the biaxially oriented polyolefin film is a single layer film as described below or a laminated film (for example, a film having surface layers on both sides of a base layer containing the component (B)).

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

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

[0025] [Other ingredients] In addition to the components (A) and (B), the biaxially stretched polyolefin film of the present invention may contain various additives typically used in polyolefin resin compositions, such as antioxidants, weathering agents, ultraviolet absorbers, stabilizers, slip agents, tackifiers, and antiblocking agents, provided that the additives do not impair the object of the present invention.

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

[0027] When the biaxially stretched polyolefin film according to the present invention is in a laminated form, it can be, for example, a laminated film of 3 to 5 layers. One example, but not limited to, is a form having two surface layers and a base layer mainly made of polyolefin resin (a form having surface layers on both sides of the base layer), (a1) An embodiment in which the components (A) and (B) are added to at least one layer other than the surface layer (for example, a substrate layer), (a2) In the above (a1) embodiment, an intermediate layer is provided between the surface layer and the substrate layer; (a3) In the embodiment (a2), the components (A) and (B) are added to the intermediate layer. or, (b1) An embodiment in which the components (A) and (B) are added to at least one of the surface layer and the base layer; (b2) In the above (b1) embodiment, an intermediate layer is provided between the surface layer and the base layer. (b3) In the embodiment (b2), the components (A) and (B) are added to the intermediate layer. The following embodiments can be mentioned. As described above, the components (A) and (B) (i.e., the components imparting antistatic properties) are often added to at least one layer other than the surface layer, and in this case, for example, they may be added only to the substrate layer, or to the substrate layer and the intermediate layer. When the components (A) and (B) are also added to the surface layer, it is expected that the amount of the components added to the surface layer will be small, so it is desirable to add them to the substrate layer and the intermediate layer in addition to the surface layer.

[0028] [(A0) Glycerin fat containing esters of fatty acids having 12 to 24 carbon atoms and glycerin] Fatty acid ester mixture The (A) glycerin fatty acid ester contained in the biaxially oriented polyolefin film according to the present invention is composed of an ester of the above-mentioned fatty acid and glycerin (composed only of esters satisfying the ratio of monoester, diester, and triester). However, as will be described later, when producing the biaxially oriented polyolefin film, the reaction product obtained by esterifying the above-mentioned fatty acid and glycerin can be blended as it is, i.e., in the form of a mixture including unreacted materials, into the (C) polyolefin resin. That is, in the production of a biaxially stretched polyolefin film, the (A) glycerin fatty acid ester can be blended into the biaxially stretched polyolefin film in the form of a glycerin fatty acid ester mixture (A0) containing an ester of glycerin and a fatty acid having 12 to 24 carbon atoms. Of course, a biaxially stretched polyolefin film may be produced using only the glycerin fatty acid ester as component (A0), which is one embodiment of the component (A0). (A0) The glycerin fatty acid ester mixture is characterized by containing 0 to 15 mass% of glycerin fatty acid monoester, 30 to 60 mass% of glycerin fatty acid diester, and 30 to 60 mass% of glycerin fatty acid triester (provided that the total amount of the monoester, diester, and triester is 100 mass%).

[0029] [Method of manufacturing biaxially oriented polyolefin film] The biaxially oriented polyolefin film according to the present invention can be produced by a known method. First, the polyolefin resin (C), the components (A0) and (B), and optionally other components are heated and kneaded using a known mixer or extruder, such as a Banbury mixer, Henschel mixer, tumbler mixer, single-screw extruder, or multi-screw extruder, to obtain a polyolefin resin composition. The components (A0), (B), and other components may be added separately to the polyolefin resin (C). Alternatively, to achieve an antistatic effect more quickly, they may be premixed and then added to the polyolefin resin. If the amounts of components (A0) and (B) (and other components) added relative to the amount of polyolefin resin (C) are too small, they may be difficult to disperse uniformly in the resin. Therefore, a masterbatch method may be used in which a masterbatch containing high concentrations of components (A0) and (B) is prepared in advance and then kneaded with a polyolefin resin (C) that does not contain components (A0) and (B) to achieve the desired content.

[0030] The obtained polyolefin resin composition is made into an unstretched sheet by a T-die method, an inflation method, a calendar method, or the like. In an example of the T-die method, the polyolefin resin composition is fed into an extruder hopper, the extruder is heated to, for example, a cylinder temperature of 180 to 240°C and a T-die temperature of 200 to 250°C, melt-kneaded and extruded, and cooled with a cooling roll controlled at 10 to 90°C to obtain an unstretched sheet having a thickness of 300 to 2000 μm. Note that multilayering by coextrusion or lamination with other films is also possible for the purpose of imparting strength or other functions to the film.

[0031] The biaxial stretching of the unstretched sheet can be carried out by successive biaxial stretching using a roll and a tenter. In the successive biaxial stretching method, the unstretched sheet is stretched in the machine direction at a roll temperature of 50 to 150°C and a stretching ratio of 1.5 to 8 times, depending on the rotation speed ratio of the drive rolls, and then continuously stretched in the transverse direction under conditions of a stretching temperature of 100 to 200°C, a stretching ratio of 4 to 12 times, and a heat setting temperature of 100 to 200°C, to obtain a biaxially stretched polyolefin film.

[0032] One preferred embodiment of the method for producing a biaxially oriented polyolefin film includes a step of obtaining an unstretched sheet from a raw material mixture containing the components (A0) and (B) and the polyolefin resin (C) by a T-die method; Examples of the production method include a step of sequentially biaxially stretching the unstretched sheet by stretching it in the machine direction (MD) and then in the transverse direction (TD), and this production method is also within the scope of the present invention. can. Based on the total mass of the raw material mixture, the component (A0) can be blended in an amount of 0.05 to 0.40 mass%, preferably 0.10 to 0.35 mass%, and the component (B) can be blended in an amount of 0.10 to 1.50 mass%, preferably 0.30 to 1.00 mass%. The mass ratio of the components (A0) to (B) can be, for example, 5:95 to 60:40, preferably 10:90 to 50:50.

[0033] The thickness of the biaxially stretched polyolefin film according to the present invention can be appropriately set depending on the application, required performance, price, etc., and can generally be set to about 10 to 100 μm. The film may be subjected to a surface treatment for the purpose of improving the printability, lamination property, coating suitability, etc. Examples of surface treatment methods include corona discharge treatment, plasma treatment, acid treatment, etc., and any of these methods can be used. Among these, corona discharge treatment is the most preferable from the viewpoint of simplicity. Printing on the film surface can be performed by 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 laminate film (laminate film) obtained 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 a polyolefin resin. From the viewpoint of a single material (monomaterial), it is preferable that the biaxially oriented polyolefin film serving as the substrate of the laminate film and the sealant film share the same main resin. The laminate film is suitably used as a packaging material for various items such as food, daily necessities, and parts, and is formed into packages and used. The present invention also covers a laminated film made up of a plurality of films including this biaxially oriented polyolefin film, and a package made up of the laminated film. The laminated film may be either a laminated film obtained by a solvent-based dry lamination method in which a solvent is used to dilute the adhesive, or a laminated film processed with a solventless adhesive. The structure of the laminated film is not particularly limited as long as it contains the biaxially oriented polyolefin film. [Example]

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

[0036] [Preparation of biaxially oriented polyolefin film] The biaxially stretched polyolefin films of Examples 1 to 4 and Comparative Examples 1 to 5 were produced according to the following procedure. The materials described below were blended in the prescribed proportions (mass%) shown in Table 2 and fed into an extrusion device. The mixture was melted and kneaded and co-extruded into a three-layer sheet using a T-die method, consisting of a first surface layer, a base layer, and a second surface layer, laminated in that order, to obtain an unstretched sheet. The unstretched sheet was then stretched in the machine direction (MD) and the transverse direction (TD) to produce a biaxially stretched film with a thickness of 20 μm. The stretching process involved sequential biaxial stretching by roll-to-roll stretching in the machine direction (MD) at a magnification of 5x, followed by tenter stretching at a magnification of 8x in the transverse direction (TD) under conditions of a preheating temperature of 175-185°C, a stretching temperature of 155-165°C, and a heat setting temperature of 160-170°C. After film formation, the first and second surface layers were subjected to corona treatment under conditions typically used for films, and the wet tension was adjusted to approximately 36 mN / m.

[0037] [Materials used] <Polyolefin resin> PP1: Homopolypropylene (Japan Polypropylene Corporation; "FL203D") PP2: Random polypropylene (Japan Polypropylene Corporation; "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 diethanolamine, etc.> B1: Oleyldiethanolamine B2: Stearyldiethanolamine B3: Stearyldiethanolamine monostearate B4: Oleyldiethanolamine monolaurate

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

[0039] According to the following procedures, the biaxially stretched polyolefin films of Examples 1 to 4 and Comparative Examples 1 to 5 were measured for wet tension (mN / m) and surface resistivity (Ω / □), and the presence or absence of smoke generation during film formation was also evaluated.

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

[0041] [Measurement of surface resistivity] The surface resistivity (Ω / □) was measured in accordance with JIS K 6911 (2006). The higher the surface resistivity, the worse the film's antistatic performance. 13 If the value is less than (Ω / □), it can be evaluated as having excellent antistatic properties.

[0042] [Smoke generation evaluation during film molding] The degree of smoke generation during film molding was evaluated by visually checking for the presence or absence of smoke due to vaporization from additives (G1-G2, A1, B1-B4) at the exit of the tenter equipment, which is the stretching section in the transverse (TD) direction. A score of "0" was given for no smoke generation, a score of "1" for some smoke generation, and a score of "2" for easily visible smoke generation.

[0043] [Table 2]

[0044] As shown in Table 2, Examples 1 to 4 containing glycerin fatty acid ester (mixture) A1 containing 0 to 15 mass% of glycerin fatty acid monoester, 30 to 60 mass% of glycerin fatty acid diester, and 30 to 60 mass% of glycerin fatty acid triester, and B1 to B4 which are aliphatic diethanolamines or the like, have a surface resistivity value of 10 13 The result was that the antistatic performance was excellent with less than (Ω / □), while the smoke generation was evaluated as 0. On the other hand, smoke generation was observed in Comparative Examples 1 to 5, which used Mixture G1 or G2, in which the ratio of monoesters, diesters, and triesters in the glycerin fatty acid ester mixture was different from the above-mentioned specified range. In particular, smoke generation was significantly observed in Comparative Examples 1, 3, and 4, which used Mixture G1, which had a high ratio of monoesters.

Claims

1. A biaxially oriented polyolefin laminate film comprising at least two surface layers and a substrate layer, wherein at least one layer other than the two surface layers comprises: (A) a glycerin fatty acid ester consisting of 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 diethanolamines, fatty acid esters of polyoxyethylene fatty amines, fatty acid diethanolamides, and fatty acid monoesters of fatty acid diethanolamides; and The (A) glycerin fatty acid ester contains 0 to 15% by mass of a glycerin fatty acid monoester, 30 to 60% by mass of a glycerin fatty acid diester, and 30 to 60% by mass of a glycerin fatty acid triester (provided that the total amount of the monoester, diester, and triester is 100% by mass), The biaxially stretched polyolefin laminate film contains 0.05 to 0.40 mass% of the glycerin fatty acid ester (A) based on the total mass of the biaxially stretched polyolefin laminate film. Biaxially oriented polyolefin laminated film.

2. A method for producing a biaxially oriented polyolefin laminate film, comprising: The biaxially oriented polyolefin laminate film comprises at least two surface layers and a substrate layer, a step of obtaining an unstretched sheet by a T-die method from a raw material mixture for at least one layer other than the two surface layers, the raw material mixture including raw materials for the two surface layers, (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, a fatty acid ester of polyoxyethylene fatty amine, a fatty acid diethanolamide, and a fatty acid monoester of a fatty acid diethanolamide, and (C) a polyolefin resin; and The method includes a step of sequentially biaxially stretching the unstretched sheet by stretching it in the machine direction (MD) and then stretching it in the transverse direction (TD), The (A0) glycerin fatty acid ester mixture contains 0 to 15% by mass of a glycerin fatty acid monoester, 30 to 60% by mass of a glycerin fatty acid diester, and 30 to 60% by mass of a glycerin fatty acid triester (provided that the total amount of the monoester, diester, and triester is 100% by mass), The raw material mixture contains the glycerin fatty acid ester mixture (A0) in an amount of 0.05 to 0.40% by mass based on the total mass of the raw material mixture. Manufacturing method.

3. A laminated film comprising a plurality of films each including the biaxially oriented polyolefin laminated film according to claim 1.

4. A packaging material comprising the laminated film according to claim 3.

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