Biaxially stretched polyolefin film
Patent Information
- Authority / Receiving Office
- WO · WO
- Patent Type
- Applications
- Current Assignee / Owner
- FUTAMURA CHEM CO LTD
- Filing Date
- 2025-11-04
- Publication Date
- 2026-06-04
Smart Images
Figure JPOXMLDOC01-APPB-T000001 
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Abstract
Description
Biaxially stretched polyolefin film
[0001] The present invention relates to a biaxially stretched polyolefin film.
[0002] Generally, for the surface base 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. Additives such as antistatic agents are blended into the biaxially stretched polyolefin film for production to provide 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 process 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 molding. The smoke derived from the ester leads to deterioration of the working environment, and when it cools and solidifies, it adheres to and solidifies on production equipment, films, etc., resulting in contamination of the equipment and poor quality. Furthermore, cases have been reported where, in the exhaust duct before exhaust gas treatment, for example, in a curved part, the smoking component adheres and accumulates together with dust, 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 forming processing temperature (see, for example, Patent Document 1, etc.). Also, proposals have been made to suppress smoking due to vaporization of the antistatic agent by using a low addition amount of the antistatic agent to biaxially stretched polyethylene films and stretching at a low temperature (see, for example, Patent Document 2, etc.)
[0004] Japanese Patent Application Laid-Open No. 2021-066470, Japanese Patent Application Laid-Open No. 2023-145311
[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 components and compositions aimed at suppressing 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.
[0008] The present invention relates to the following [1] to [5]. [1] A biaxially oriented polyolefin film comprising: (A) a glycerin fatty acid ester comprising 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). [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, comprising the steps 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 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 sequentially biaxially stretching the unstretched sheet by stretching it in the longitudinal (MD) direction and then in the transverse (TD) direction, wherein 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 the monoester, diester, and triester is 100% by mass). [4] A laminated film comprising a plurality of films including the biaxially oriented polyolefin film described in [1]. [5] A packaging body comprising the laminated film described in [4].
[0009] The biaxially oriented polyolefin film of the present invention is a film that exhibits excellent antistatic effects and suppresses smoke generation during film formation. 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.
[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 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 oriented polyolefin film of the present invention contains (A) a glycerin fatty acid ester, described later, and (B) one or more selected from the group consisting of aliphatic diethanolamine, fatty acid esters of polyoxyethylene aliphatic amines, fatty acid diethanolamide, and fatty acid monoesters of fatty acid diethanolamide. The above 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 esters are esters of fatty acids having 12 to 24 carbon atoms and glycerin. Depending on the degree of esterification, the esters of the above fatty acids and glycerin, which is a trihydric alcohol, can take the forms of glycerin fatty acid monoesters, glycerin fatty acid diesters, and glycerin fatty acid triesters. In the present invention, by including specific amounts of the diesters and triesters and setting the monoester content lower than that of the diesters and triesters, it is possible to suppress smoke generation due to the decomposition and vaporization of esters during the molding and processing of stretched films.
[0014] The glycerin fatty acid ester according to the present invention 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 (total of monoester, diester, and triester: 100% by mass). By keeping the proportion 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 oriented polyolefin film, and smoke generation during the transverse stretching process of the polyolefin film containing it can be suppressed. In a preferred embodiment, the glycerin fatty acid ester preferably contains 0 to 15% by mass of glycerin fatty acid monoester, more preferably 5 to 14% by mass, and even more preferably 8 to 13% by mass. The glycerin fatty acid diester preferably contains 30 to 60% by mass, more preferably 40 to 60% by mass, and even more preferably 45 to 55% by mass. The glycerin fatty acid triester is preferably included in an amount of 30 to 60% by mass, more preferably in an amount of 30 to 50% by mass, and even more preferably in an amount of 33 to 45% by mass. If the proportion of monoester in the glycerin fatty acid ester exceeds 15% by mass, there is a risk of increased fume generation. If the proportion of triester is less than 30% by mass, there is a risk of increased fume generation, and if it exceeds 60% by mass, there is a risk of contamination of the manufacturing 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 fatty acid is less than 12, there is a risk that the compatibility with polyolefin resin will decrease, making it difficult 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, and there is a risk that the antistatic performance will be inadequate. Note that one type of fatty acid may be used, or two or more types may be used in combination. For example, the glycerol fatty acid diester may be an ester compound of glycerol and two different fatty acids, and the glycerol fatty acid triester may be an ester compound of glycerol 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 of component (A) described above applies to both the single-layer and laminated forms of the biaxially oriented polyolefin film described later (for example, a form 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 diethanolamine, fatty acid esters of polyoxyethylene aliphatic amine, fatty acid diethanolamide, and fatty acid monoesters of fatty acid diethanolamide] The biaxially oriented polyolefin film according to the present invention contains, in addition to the (A) glycerin fatty acid ester, 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 as component (B).
[0018] <Aliphatic Diethanolamines> 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> 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. Examples of the above 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, oleyl diethanolamine monostearate, etc. Among the preferred options are stearyldiethanolamine monostearate and oleyldiethanolamine monolaurate. These may be used individually or in combination of two or more.
[0020] <Fatty Acid Diethanolamides> 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, stearic acid diethanolamide, oleic acid diethanolamide, nonadecanoic acid diethanolamide, and arachidic 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 Monoesters of Fatty Acid Diethanolamides> Fatty acid monoesters of fatty acid diethanolamides include the fatty acid monoesters of the amide compounds listed above in <Fatty Acid Diethanolamides>. Examples of the above 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 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) blended is applicable to both the single-layer and laminated forms of the biaxially oriented polyolefin film described later (for example, a form 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 component constituting the biaxially oriented polyolefin film according to the present invention is not particularly limited and includes, for example, homopolymers of α-olefins such as ethylene, propylene, 1-butene, 1-pentene, 1-hexene, and 4-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 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 appropriate starting materials such as petroleum-derived, biomass-derived, material-recycled, and chemical-recycled materials.
[0025] [Other Components] 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 the 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 on a layer comprising the 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 in the form of a laminated film of 3 to 5 layers. As an example, but not limited to these, there is an embodiment comprising two surface layers and a base layer mainly composed of polyolefin resin (an embodiment in which the surface layer is provided on both sides of the base layer), and the embodiments include: (a1) an embodiment in which the components (A) and (B) are added to at least one layer other than the surface layer (for example, the base layer); (a2) an embodiment in which an intermediate layer is provided between the surface layer and the base layer in the embodiment of (a1); (a3) an embodiment in which the components (A) and (B) are added to the intermediate layer in the embodiment of (a2); or (b1) an embodiment in which the components (A) and (B) are added to at least one of the surface layers and the base layer; (b2) an embodiment in which an intermediate layer is provided between the surface layer and the base layer in the embodiment of (b1); (b3) an embodiment in which the components (A) and (B) are added to the intermediate layer in the embodiment of (b2). 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 fatty acid ester mixture containing esters of fatty acids with 12 to 24 carbon atoms and glycerin] The (A) glycerin fatty acid ester contained in the biaxially oriented polyolefin film according to the present invention consists of esters of the above fatty acids and glycerin (consisting only of esters that satisfy the above monoester, diester, and triester ratios). However, as will be described later, when manufacturing the biaxially oriented polyolefin film, the reaction product obtained by esterifying the above fatty acids and glycerin can be blended into the (C) polyolefin resin as is, that is, in the form of a mixture including unreacted material. In other words, in the manufacture of the biaxially oriented polyolefin film, the (A) glycerin fatty acid ester can be blended 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, which includes the (A0). Of course, the biaxially oriented polyolefin film may also be manufactured using a component (A0) consisting only of glycerin fatty acid ester, which is one embodiment thereof. (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 Manufacturing 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, uniscrew extruder, and multiscrew extruder. Components (A0) and (B), and other components may be added separately to the (C) polyolefin resin, or they may be mixed beforehand and then added to the polyolefin resin from the viewpoint of obtaining an antistatic effect early. Furthermore, if the amount of component (A0) and component (B) (and other components) added is insufficient relative to the amount of polyolefin resin (C), there is a risk that these components 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 this is kneaded with polyolefin resin (C) that does not contain components (A0) and (B) to obtain the 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. As an example of the T-die method, the polyolefin resin composition is supplied to 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, the material is melt-kneaded and extruded, and cooled with a cooling roll controlled to 10 to 90°C to obtain an unstretched sheet with a thickness of 300 to 2000 μm. Co-extrusion or multilayering by lamination with other films is also possible 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 production method that includes the steps 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 sequentially biaxially stretching the unstretched sheet by stretching it in the longitudinal (MD) direction and then in the transverse (TD) direction. This production method can also be the subject of the present invention. Based on the total mass of the raw material mixture, the (A0) component can be blended in a proportion of 0.05 to 0.40% by mass, preferably 0.10 to 0.35% by mass, and the (B) component can be blended in a proportion of 0.10 to 1.50% by mass, preferably 0.30 to 1.00% by mass. Furthermore, the mass ratio of the (A0) component to the (B) component 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 is generally about 10 to 100 μm thick. Surface treatment may also be applied to improve the printability, lamination, coating suitability, etc. of the film. 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 preferred in terms of 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 Films and 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 packaging. A laminated film consisting of multiple films including this biaxially oriented polyolefin film is also subject to the present invention, and packaging made from the laminated film is also subject to the present invention. The laminated film can be a laminated film obtained by a solvent-type dry lamination method using a solvent to dilute the adhesive, or a laminated film processed 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.
[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] [Preparation of Biaxially Oriented Polyolefin Films] Biaxially oriented polyolefin films for Examples 1 to 4 and Comparative Examples 1 to 5 were prepared using the following procedure. Each material 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 5 times in the longitudinal (MD) direction by roll stretching, followed by tenter stretching at a preheating temperature of 175-185°C, a stretching temperature of 155-165°C, and a heat-fixing temperature of 160-170°C in the transverse (TD) direction at an 8-fold rate. 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)> A mixture of glycerin fatty acid esters (total 100% by mass) with the ester ratios shown in Table 1 was used. <Aliphatic diethanolamines, etc.> • B1: Oleyl diethanolamine • B2: Stearyl diethanolamine • B3: Stearyl diethanolamine 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 was used for the base layer, which consisted 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. 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 the raw materials used for the first and second surface layers and the raw materials used for the base layer being 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] 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] 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 generation during film forming] To evaluate the degree of smoke generation during film forming, the presence or absence of smoke due to vaporization from additives (G1-G2, A1, B1-B4) was visually confirmed at the outlet of the tenter equipment, which is the stretching section in the lateral (TD) direction. A score of "0" was given for no smoke generation observed at all, "1" for some smoke generation observed, and "2" for smoke generation that was easily visible.
[0043]
[0044] As shown in Table 2, glycerin fatty acid ester (mixture) A1 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, and Examples 1 to 4 containing B1 to B4 such as aliphatic diethanolamine have a surface resistivity value of 10 １３ (Ω / sq) or less, and a result was obtained that the smoke generation property was evaluated as 0. On the other hand, in the glycerin fatty acid ester mixture, in Comparative Examples 1 to 5 using mixture G1 or G2 in which the ratios of monoester, diester, and triester are different from the above predetermined ranges, smoke generation was observed. Particularly, in Comparative Examples 1, 3, and 4 using mixture G1 having a large monoester ratio, significant smoke generation was observed.
Claims
1. A biaxially oriented polyolefin laminated film comprising at least two surface layers and a base layer, wherein at least one layer other than the two surface layers contains: (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 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 the monoester, diester, and triester is 100% by mass), and the (A) glycerin fatty acid ester is contained in an amount of 0.05 to 0.40% by mass based on the total mass of the biaxially oriented polyolefin laminated film.
2. A method for producing a biaxially oriented polyolefin laminated film, wherein the biaxially oriented polyolefin laminated film comprises at least two surface layers and a base layer, and includes the steps of obtaining an unstretched sheet by T-die method from a raw material mixture other than the two surface layers, 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 sequentially biaxially stretching the unstretched sheet by stretching it in the longitudinal (MD) direction and then stretching it 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), and the manufacturing method is characterized in that the (A0) glycerin fatty acid ester mixture is contained in an amount of 0.05 to 0.40% by mass based on the total mass of the raw material mixture.
3. A laminated film comprising a plurality of films, including the biaxially oriented polyolefin laminated film described in claim 1.
4. A packaging body made of the laminated film described in claim 3.