Multilayer Film

Abstract

To provide a multilayer film, a food packaging film, an industrial release film and a liquid crystal protective film having excellent releasability, printability and heat sealability.SOLUTION: A multilayer film is composed of at least two layers including a release layer (A) containing a polyolefin resin such as a polypropylene resin and a silylated polyolefin resin such as a silylated polypropylene resin, and a base material layer (B), where a percentage content of the silylated polypropylene resin contained in the release layer (A) is 1-50 mass%, and a thermoplastic resin having flexural elastic modulus of 400-2,000 MPa is contained in the base material layer (B).SELECTED DRAWING: None

Description

[Technical field]

[0001] The present invention relates to a multilayer film having releasability that can be suitably used as a food packaging film, an industrial release film, and a liquid crystal protective film. [Background technology]

[0002] Polyolefin resins such as polyethylene resins and polypropylene resins have excellent moldability, mechanical strength, transparency, chemical resistance, etc., and are used in various fields. In particular, polypropylene resins are widely used in applications requiring heat resistance and rigidity.

[0003] In recent years, food packaging films that reduce food waste and leave less content behind are in demand. On the other hand, such films are also required to be suitable for printing, so multi-layer films are used as films that satisfy both of these properties. Low molecular weight release agents such as silicone oil and fatty acid amides are used in the release layers of multi-layer films, but there is an issue that the low molecular weight components bleed over time and migrate into food. Meanwhile, industrial release films such as protective films and tape base materials also face issues such as migration of low molecular weight components to the substrate due to bleeding over time and deterioration of performance.

[0004] In response to such problems, Patent Document 1 discloses a silylated polypropylene resin obtained by reacting a terminally unsaturated polypropylene resin with a siloxane copolymer having a specific structure through hydrosilylation, and discloses that by adding a small amount of this resin to a polypropylene resin, it is possible to improve the water / oil repellency and mold releasability while maintaining the inherent heat sealability of the polypropylene resin.

[0005] Furthermore, Patent Document 2 discloses a single-layer or multi-layer packaging material containing a silylated polyolefin resin, and describes that polypropylene resin may be used for the releasable layer (layer having releasability) and base layer that constitute the multilayer film.

[0006] Furthermore, Patent Document 3 discloses a molded article and a multilayer film made of a silylated polyolefin resin and a thermoplastic resin, and describes that the molded article can easily remove algae. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] JP 2017-179344 A [Patent Document 2] JP 2014-177541 A [Patent Document 3] JP 2019-127582 A Summary of the Invention [Problem to be solved by the invention]

[0008] However, Patent Document 1 does not disclose the effect of the multilayer film using the silylated polypropylene resin, and there are many unclear points. Furthermore, Patent Document 2 does not describe or suggest anything about the layer structure or type of polypropylene resin that can exhibit higher performance. Furthermore, Patent Document 3 discloses only a blend of a silylated polyethylene resin and a low-density polyethylene resin as the release layer that constitutes the multilayer film. Since low-density polyethylene has low rigidity, there is a concern that it may have poor releasability.

[0009] The present invention has been made to solve the above problems. That is, an object of the present invention is to provide a multilayer film, a food packaging film, an industrial release film, and a liquid crystal protective film that have excellent releasability, printability, and heat sealability. [Means for solving the problem]

[0010] As a result of intensive research to solve the above problems, the present inventors have found that the release properties are significantly improved by including a thermoplastic resin having a specific elastic modulus in the base layer, and that a multi-layer structure can achieve both printability and heat sealability, leading to the completion of the present invention. That is, the present invention has the following features.

[0011] [1] A multilayer film consisting of at least two layers including a release layer (A) containing a polyolefin resin and a silylated polyolefin resin, and a base layer (B), wherein the base layer (B) contains a thermoplastic resin having a flexural modulus of 400 to 2000 MPa. [2] The multilayer film according to [1], wherein the silylated polyolefin resin contained in the release layer (A) is a silylated polypropylene resin. [3] The multilayer film according to [1] or [2], wherein the content of the silylated polyolefin resin in the release layer (A) is 1 to 50 mass %.

[0012] [4] The multilayer film according to any one of [1] to [3], wherein the polyolefin resin contained in the release layer (A) is a polypropylene resin. [5] The multilayer film according to any one of [1] to [4], wherein the polyolefin resin contained in the release layer (A) is a propylene-ethylene copolymer. [6] The multilayer film according to any one of [1] to [5], wherein the thermoplastic resin contained in the base layer (B) is a polypropylene resin.

[0013] [7] The multilayer film according to any one of [1] to [6], which has a thickness of 10 to 500 μm. [8] A food packaging film comprising the multilayer film according to any one of [1] to [7]. [9] An industrial release film comprising the multilayer film according to any one of [1] to [7].

[10] A liquid crystal protective film comprising the multilayer film according to any one of [1] to [7]. Effect of the Invention

[0014] Because the multilayer film, food packaging film, industrial release film, and liquid crystal protective film of the present invention have the above-mentioned configuration, they have the release properties, stain resistance, oil repellency, and low friction properties specific to silicone resins while maintaining the transparency, water repellency, rigidity, strength, printability, and heat sealability inherent to polyolefin resins. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0015] The present invention will be described in detail below. However, the following description is an example of an embodiment of the present invention, and the present invention is not limited to the contents of the following description as long as it does not go beyond the gist of the present invention. The present invention can be modified and implemented as desired without departing from the gist of the present invention.

[0016] The multilayer film of the present invention comprises at least two layers including a release layer (A) and a substrate layer (B).

[0017] <Release layer (A)> The release layer (A) of the present invention contains a polyolefin resin and a silylated polyolefin resin. By containing a polyolefin resin in the release layer (A), the multilayer film of the present invention has excellent heat sealability. In addition, by containing a silylated polyolefin resin in the release layer (A), the multilayer film of the present invention has excellent releasability.

[0018] Examples of the polyolefin resin contained in the release layer (A) include polypropylene resin, high-density polyethylene resin, low-density polyethylene resin, linear low-density polyethylene resin, ethylene-vinyl alcohol copolymer, ethylene-vinyl acetate copolymer, ethylene-alkyl acrylate copolymer, ethylene-methyl (meth)acrylate copolymer, and ethylene-α-olefin copolymer. Among these, polypropylene resin is preferred from the viewpoints of high rigidity and ability to impart mold releasability.

[0019] Examples of polypropylene resins include propylene homopolymers, propylene-ethylene copolymers, propylene-α-olefin copolymers, and acid-modified versions of these. Examples of α-olefins that can be copolymerized with propylene include butene-1, hexene-1, and octene-1. These may be random copolymers, block copolymers, or mixtures. Among these, a propylene-ethylene copolymer, generally called random PP, is preferred because it can impart excellent heat sealability to the release layer (A). The polymerization catalyst for the polypropylene resin may be either a Ziegler-Natta catalyst or a metallocene catalyst.

[0020] The silylated polyolefin resin contained in the release layer (A) is a polymer obtained by reacting a polyolefin resin having an unsaturated bond at one end and / or both ends with a siloxane copolymer. Examples of the silylated polyolefin resin include a silylated polypropylene resin that can be produced by hydrosilylation using a platinum catalyst according to the method described in JP 2017-179344 A; and a silylated polyethylene resin that can be produced by the method described in JP 2014-177541 A. Among these, silylated polypropylene resins are preferred because they have an excellent balance of releasability, heat resistance, transparency, and the like.

[0021] From the viewpoint of reactivity, the unsaturated ends of the polyolefin resin having an unsaturated bond at one end and / or both ends are preferably a vinyl group, a vinylene group or a vinylidene group, more preferably a vinyl group or a vinylidene group, and even more preferably a vinylidene group.

[0022] The weight average molecular weight of the polyolefin resin having an unsaturated bond at one end and / or both ends is preferably 5,000 to 100,000 g / mol, more preferably 10,000 to 80,000 g / mol, still more preferably 15,000 to 70,000 g / mol, particularly preferably 20,000 to 60,000 g / mol, and most preferably 30,000 to 50,000 g / mol. When the weight average molecular weight of the polyolefin resin having an unsaturated bond is within the above range, the silylated polypropylene resin has excellent moldability while maintaining sufficient reactivity.

[0023] The polyolefin resin having an unsaturated bond at one end and / or both ends may be produced by a known technique, or a commercially available product may be used. Commercially available products include Viscol 330-P (weight average molecular weight: 40,000 g / mol), 330-PSK (weight average molecular weight: 40,000 g / mol), 440-P (weight average molecular weight: 30,000 g / mol), 550-P (weight average molecular weight: 15,000 g / mol), and 660-P (weight average molecular weight: 8,000 g / mol), all of which are manufactured by Sanyo Chemical Industries, Ltd.

[0024] The content of the silylated polyolefin resin in the release layer (A) is preferably 1 mass % or more, more preferably 2 mass % or more, even more preferably 3 mass % or more, particularly preferably 4 mass % or more, and most preferably 5 mass % or more. When the content of the silylated polyolefin resin in the release layer (A) is 1% by mass or more, the multilayer film of the present invention has excellent releasability.

[0025] On the other hand, the content of the silylated polyolefin resin in the release layer (A) is preferably 50% by mass or less, more preferably 45% by mass or less, even more preferably 40% by mass or less, particularly preferably 35% by mass or less, and most preferably 30% by mass or less. When the content of the silylated polyolefin resin in the release layer (A) is 50% by mass or less, the multilayer film of the present invention can maintain its strength as a polyolefin resin film.

[0026] The release layer (A) may contain other resin components as long as the effects of the present invention are not impaired. Examples of the other resin components include polyvinyl chloride, polystyrene, polyvinylidene chloride, polyvinyl alcohol, ethylene-vinyl alcohol copolymers, polymethylpentene, polyphenylene ether, polyethylene terephthalate, polybutylene terephthalate, polyacetal, aliphatic polyamides, polymethyl methacrylate, polycarbonate, ABS, polyphenylene sulfide, aromatic polyamides, polyarylates, polyetherimides, polyphenylsulfones, polyetherimide sulfones, polyetherketones, polyetheretherketones, polyetherketone ketones, polyetheretherketone ketones, polyetheretherketone ketones, polyamideimides, polysulfones, polyethersulfones, liquid crystal polymers, and copolymers thereof, and mixtures thereof.

[0027] When the release layer (A) contains other resin components, the content thereof is preferably 50% by mass or less, more preferably 40% by mass or less, even more preferably 30% by mass or less, particularly preferably 20% by mass or less, and most preferably 10% by mass or less. As long as the content of other resin components contained in the release layer (A) is within the above range, the inherent effects of the multilayer film of the present invention can be appropriately imparted with properties such as heat resistance, rigidity, releasability, low abrasion, light blocking properties, weather resistance, transparency, and gas barrier properties.

[0028] <Base material layer (B)> The base layer (B) of the present invention contains a thermoplastic resin having a flexural modulus of 400 to 2000 MPa. The lower limit of the flexural modulus is preferably 450 MPa or more, more preferably 500 MPa or more, further preferably 550 MPa or more, and particularly preferably 600 MPa or more. When the flexural modulus is 400 MPa or more, sufficient rigidity can be imparted to the multilayer film of the present invention, and the releasability is sufficient.

[0029] On the other hand, the upper limit of the flexural modulus is preferably 1900 MPa or less, more preferably 1800 MPa or less, further preferably 1700 MPa or less, and particularly preferably 1600 MPa or less. If the flexural modulus is 2000 MPa or less, the film will be flexible and easy to handle.

[0030] Examples of the thermoplastic resin contained in the base layer (B) include polyolefin resins such as polyethylene resin, polypropylene resin, and ethylene-vinyl alcohol copolymer; polyvinyl chloride, polystyrene, polyvinylidene chloride, polyvinyl alcohol, polymethylpentene, polyphenylene ether, polyethylene terephthalate, polybutylene terephthalate, polyacetal, aliphatic polyamide, polymethyl methacrylate, polycarbonate, ABS, polyphenylene sulfide, aromatic polyamide, polyarylate, polyetherimide, polyphenylsulfone, polyetherimide sulfone, polyether ketone, polyether ether ketone, polyether ketone ketone, polyether ether ketone ketone, polyether ether ketone ketone, polyamide imide, polysulfone, polyether sulfone, liquid crystal polymer, and copolymers thereof, and mixtures thereof. Among these, polyolefin resins such as polyethylene and polypropylene are preferred because they have excellent rigidity and printability, and have good adhesion to the polyolefin resin and silylated polyolefin resin that constitute the release layer (A), and therefore a multilayer film can be obtained without the need for an adhesive layer.

[0031] Examples of polyolefin resins include polypropylene resins, high-density polyethylene resins, low-density polyethylene resins, linear low-density polyethylene resins, ethylene-vinyl alcohol copolymers, ethylene-vinyl acetate copolymers, ethylene-alkyl acrylate copolymers, ethylene-methyl (meth)acrylate copolymers, and ethylene-α-olefin copolymers. Among these, polypropylene resin is preferred from the viewpoints of high rigidity and ability to impart mold releasability.

[0032] Examples of polypropylene resins include propylene homopolymers, propylene-ethylene copolymers, propylene-α-olefin copolymers, and acid-modified versions of these. Examples of α-olefins that can be copolymerized with propylene include butene-1, hexene-1, and octene-1. These may be random copolymers, block copolymers, or mixtures. Among these, propylene homopolymers, generally called homo-PP, are preferred because they can impart high rigidity to the base layer (B). The polymerization catalyst for the polypropylene resin may be either a Ziegler-Natta catalyst or a metallocene catalyst.

[0033] The base material layer (B) preferably contains 50% by mass or more of polypropylene resin, more preferably 60% by mass or more, even more preferably 70% by mass or more, particularly preferably 80% by mass or more, and most preferably 90% by mass or more of the entire base material layer (B). When the proportion of the polypropylene resin in the components constituting the base layer (B) is within the above range, the multilayer film of the present invention is excellent in releasability, printability and transparency.

[0034] The content of silylated polyolefin resin contained in the substrate layer (B) is preferably 1% by mass or less, and more preferably zero. When the content of the silylated polyolefin resin in the substrate layer (B) is 1% by mass or less, the multilayer film of the present invention has excellent printability.

[0035] The substrate layer (B) may be one layer, or may be two or more layers. When the base layer has two or more layers, the total value obtained by multiplying the flexural modulus of each layer constituting the base layer by the layer ratio of each layer may be 400 to 2000 MPa.

[0036] <Multilayer film> The multilayer film of the present invention is composed of at least two layers, with a release layer (A) and a base layer (B) disposed as the outermost layers. By including a polyolefin resin and a silylated polyolefin resin in the release layer (A), both releasability and heat sealability can be achieved. In addition, by including a thermoplastic resin having a specific flexural modulus in the base layer (B), it is possible to ensure rigidity and improve releasability. The base layer (B) may have a multi-layer structure of two or more layers.

[0037] The multilayer film may have a release layer (A) and a base layer (B) as the outermost layers, and examples of such a multilayer film include a two-layer structure (A) / (B), a three-layer structure (A) / (C) / (B) including an additional layer (C), a four-layer structure (A) / (C) / (D) / (B) including additional layers (C) and (D), a five-layer structure (A) / (C) / (D) / (C) / (B), and a five-layer structure (A) / (C) / (D) / (E) / (B) including additional layers (C), (D), and (E). The base layer (B) may have a two-layer structure such as (B1) / (B2) or a multilayer structure of more than two layers. Examples of other layers include a heat-resistant layer, a conductive layer, an antistatic layer, a protective layer, a support layer, a weather-resistant layer, a heat-shielding layer, a light-controlling layer, a coloring layer, an adhesive layer, and an easy-peel layer.

[0038] The lower limit of the thickness of the multilayer film is preferably 10 μm or more, more preferably 15 μm or more, even more preferably 20 μm or more, particularly preferably 25 μm or more, and most preferably 30 μm or more. When the thickness of the multilayer film is equal to or greater than the above lower limit, the film can be given sufficient rigidity and has excellent releasability.

[0039] On the other hand, the upper limit of the thickness of the multilayer film is preferably 500 μm or less, more preferably 450 μm or less, even more preferably 400 μm or less, particularly preferably 350 μm or less, and most preferably 300 μm or less. When the thickness of the multilayer film is equal to or less than the above upper limit, the transparency is excellent.

[0040] The multilayer film of the present invention may contain various additives such as heat stabilizers, antioxidants, ultraviolet absorbers, light stabilizers, antibacterial and antifungal agents, antistatic agents, lubricants, pigments, and dyes, as long as the effects of the present invention are not impaired.

[0041] <Manufacturing method> The multi-layer film of the present invention can be produced by a general molding method, such as extrusion molding, pressure molding, and press molding. In each molding method, the apparatus and processing conditions are not particularly limited.

[0042] The multilayer film can be obtained by stretching or not stretching the constituent materials of the film. In this case, for example, the film can be produced by melt-kneading the constituent materials, extruding the mixture, and cooling the mixture. For the melt kneading, a known kneader such as a single-screw or twin-screw extruder can be used. The melting temperature is adjusted appropriately depending on the type and mixing ratio of the resin, and the presence and type of additives, but from the viewpoint of productivity, etc., it is preferably 160° C. or higher, and more preferably 180° C. or higher. Moreover, from the viewpoint of preventing decomposition of the resin, it is preferably 300° C. or lower, more preferably 250° C. or lower, and even more preferably 220° C. or lower.

[0043] The multilayer film may be produced by any of the following methods: a coextrusion method in which the resin compositions of each layer are laminated together; an extrusion lamination method in which each layer is formed into a film and then laminated; and a thermocompression bonding method in which each layer is formed into a film and then thermocompression bonded together. From the viewpoint of productivity, however, it is preferable to use the coextrusion method. Co-extrusion methods include a multi-manifold method in which the resin compositions of each layer join at a die, and a feed block method in which the resin compositions join at a feed block. Either method may be used, but it is preferable to use the multi-manifold method, which has excellent thickness accuracy.

[0044] When the T-die method is used, the temperature of the casting roll needs to be appropriately adjusted depending on the resin that is in close contact with the casting roll, but is preferably 20° C. or higher, more preferably 30° C. or higher. When the temperature of the casting roll is equal to or higher than the lower limit, the adhesion between the film and the casting roll is good, and a film having good appearance and thickness accuracy can be obtained. On the other hand, the upper limit is preferably 100° C. or lower, and more preferably 80° C. or lower. When the temperature of the casting roll is equal to or lower than the upper limit, the film can be prevented from sticking to the casting roll, and a film with good appearance and thickness accuracy can be obtained.

[0045] In the case of inflation molding, the blow ratio is usually in the range of 1.1 to 10 times, and from the viewpoint of physical properties, the range of 1.3 to 5 times is preferable, and the range of 1.5 to 4 times is more preferable. Either an air-cooled inflation method or a water-cooled inflation method may be used, and the blowing direction may be either upward or downward. In general, the air-cooled inflation method has excellent productivity. On the other hand, the water-cooled inflation method has excellent transparency and thickness accuracy because the film can be rapidly cooled. You can select the equipment you need depending on your purpose.

[0046] In the case of calendar molding, the roll setting temperature is appropriately adjusted depending on the flow characteristics of the resin composition, roll peelability, film formation speed, etc., but is preferably 160 to 250°C, more preferably 180 to 220°C. If the roll temperature setting during calendar molding is within this range, decomposition of the resin can be suppressed while sufficient moldability can be ensured.

[0047] <Use and mode of use> The multilayer film of the present invention has excellent releasability, heat sealability and printability, and can therefore be suitably used as a food packaging film, an industrial release film and a liquid crystal protective film. EXAMPLES

[0048] The present invention will be described in more detail below using examples, but the present invention is not limited to the following examples as long as it does not exceed the gist of the invention. The values ​​of various production conditions and evaluation results in the following examples are meant as preferred upper or lower limit values ​​in the embodiment of the present invention, and the preferred range may be a range defined by a combination of the above-mentioned upper or lower limit values ​​and the values ​​of the following examples or values ​​of the examples.

[0049] [Physical Properties] <Mold releasability> Cloth adhesive tape <ls>No. 123 (manufactured by Nichiban Co., Ltd.) was cut to a size of 15 mm width x 100 mm length, attached to the release layer (A) side of the multilayer film, and held in an environment of 23°C x 50% RH for one hour. After that, a peel test was performed using a tensile tester under conditions of 23°C x 50% RH and 200 mm / min, and the peel strength was measured.

[0050] <Printability> A line was drawn on the base layer (B) of the multilayer film using the "Pentel Pen ENN50" (manufactured by Pentel Co., Ltd.), and the ink repelling property was evaluated. If the line could be written neatly, it was rated as "◯", and if the ink was repelled and it was not possible to write neatly, it was rated as "×".

[0051] <Heat seal temperature> The multilayer films were stacked with the release layer (A) sides facing each other, and heat-sealed under conditions of 10 mm width, 2 N, and 1 second while increasing the temperature from 100° C. by 10° C. each time. Thereafter, a peel test was carried out using a tensile tester under conditions of 23° C.×50% RH and 200 mm / min., and the temperature at which the interface between the films broke without peeling was recorded as the heat seal temperature.

[0052] <Production of silylated polypropylene resin> [Raw materials] Terminally unsaturated polypropylene resin (Sanyo Chemical Industries, Ltd., Viscol 330-PSK, weight average molecular weight = 40,000 g / mol, number average molecular weight = 12,000 g / mol, vinylidene terminal reactive group ratio = 0.08 mmol / g) Methylhydrosiloxane dimethylsiloxane copolymer (Nusil Technology, XL1-116, number average molecular weight = 6,610 g / mol, SiH reactive group substitution ratio = 0.9 mmol / g) Catalyst: Platinum-divinyltetramethyldisiloxane complex (Gelest, SIP6831.2)

[0053] (Production Example 1) A terminally unsaturated bond polypropylene resin (25 g, reactive group = 2.0 mmol), methylhydrosiloxane dimethylsiloxane copolymer (7.22 g, reactive group = 6.5 mmol), and 156 mL of toluene were added to a four-neck flask equipped with a mechanical stirrer, and nitrogen was bubbled for 15 minutes. The mixture was then heated to 103°C and stirred uniformly, after which platinum catalyst (4.9 μL) was added and stirred at 103°C for 5 hours.

[0054] The reaction solution was then cooled to 80°C with stirring, and isopropanol (270mL) was added until the polymer precipitated. The precipitated polymer was collected by filtration and washed with isopropanol (200mL). The resulting polymer was dried under reduced pressure at 70°C. The final yield was 29.3g. 1 H-NMR measurements confirmed that the terminal vinylidene groups had disappeared, and gel permeation chromatography measurements confirmed that the number average molecular weight had increased to 24,000 g / mol. These results, taken together, demonstrated that the hydrosilylation reaction had progressed, resulting in the bonding of silicone and polypropylene.

[0055] <Release layer (A)> [Raw materials] (a)-1: Propylene-ethylene copolymer (Novatec PP FW4B, manufactured by Japan Polypropylene Co., Ltd., bending modulus = 700 MPa) (a)-2: Silylated polypropylene (prepared in Production Example 1) (a)-3: Linear low-density polyethylene (Nippon Polyethylene Co., Ltd., Novatec C6 SF8402, flexural modulus = 340 MPa) (a)-4: Propylene homopolymer (Japan Polypropylene Corporation, Novatec PP FY6, flexural modulus = 1500 MPa)

[0056] <Base material layer (B)> [Raw materials] (b)-1: Propylene-ethylene copolymer (Novatec PP FW4B, Japan Polypropylene Corporation, flexural modulus = 700 MPa) (b)-3: Linear low-density polyethylene (Nippon Polyethylene Co., Ltd., Novatec C6 SF8402, flexural modulus = 340 MPa) (b)-4: Propylene homopolymer (Japan Polypropylene Corporation, Novatec PP FY6, flexural modulus = 1500 MPa)

[0057] <Example 1> A three-type, three-layer extrusion system with three single-screw extruders was used. The extrusion temperature was 200°C for all layers. The innermost layer was blended with (a)-1:[(a)-2]=90:10, and (b)-1 was added to the middle and outermost layers. By adjusting the extruder rotation speed and take-up speed, a multilayer film having a two-layer structure with a release layer (A) / substrate layer (B) of 10 μm / 40 μm was obtained. The obtained film was subjected to various evaluations. The results are shown in Table 1.

[0058] <Example 2> A multilayer film was obtained in the same manner as in Example 1, except that (b)-4 was used for the intermediate layer to form a film having a substantially three-type three-layer structure. The results are shown in Table 1. The base layer (B) is composed of two layers, middle layer (B1) / outermost layer (B2) = 30 / 10 μm (layer ratio = 75 / 25), and the flexural moduli of the resin components constituting each layer are 1500 MPa and 700 MPa, respectively, so the total value obtained by multiplying these values ​​is 1300 MPa.

[0059] <Example 3> A multilayer film was obtained in the same manner as in Example 2, except that the composition of the innermost layer was [(a)-1]:[(a)-2]=80:20. The results are shown in Table 1.

[0060] <Example 4> A multilayer film was obtained in the same manner as in Example 2, except that the composition of the innermost layer was [(a)-2]:[(a)-4]=10:90. The results are shown in Table 1.

[0061] <Comparative Example 1> A multilayer film was obtained in the same manner as in Example 1, except that the composition of the innermost layer was [(a)-2]:[(a)-3]=10:90, the intermediate layer and the outermost layer were (b)-3, and the multilayer film was essentially a two-layer film with a release layer (A) / base layer (B)=10 μm / 40 μm. The results are shown in Table 1.

[0062] <Comparative Example 2> A film was obtained in the same manner as in Example 1, except that (a)-1 was used as the film material and a single-layer film (thickness: 50 μm) of (a)-1 was used. The results are shown in Table 1.

[0063] <Comparative Example 3> A film was obtained in the same manner as in Example 1, except that the film material was [(a)-1]:[(a)-2]=90:10 and a single-layer film (thickness: 50 μm) was obtained with [(a)-1]:[(a)-2]=90:10. The results are shown in Table 1.

[0064] [Table 1]

[0065] From Table 1, it was found that the films of Examples 1 to 4 corresponding to the present invention have excellent release properties because they contain a silylated polypropylene resin in the release layer (A) and further contain a polypropylene resin having an optimal elastic modulus in the base layer (B). In addition, it was found that by making the outermost layer from a polypropylene resin, they also have excellent printability. Furthermore, since the films of Examples 1 to 3 use a propylene-ethylene copolymer in the release layer (A), they also have heat sealability at low temperatures and are therefore suitable as packaging materials.

[0066] On the other hand, the film of Comparative Example 1 uses linear low-density polyethylene for the base layer (B), and since the flexural modulus of this material is low at 340 MPa, it was found that although the film had excellent printability and heat sealability, it did not have sufficient releasability. Furthermore, the film of Comparative Example 2 was essentially a single-layer film of a propylene-ethylene copolymer and did not contain a silylated polypropylene resin, and therefore had insufficient releasability. Moreover, the film of Comparative Example 3 was essentially a single-layer film of a blend of a propylene-ethylene copolymer and a silylated polypropylene resin, and although it had excellent releasability and heat sealability, its printability was insufficient.< / ls>

Claims

1. A multilayer film consisting of at least two layers including a release layer (A) containing a polyolefin resin and a silylated polyolefin resin, and a base layer (B), The silylated polyolefin resin is a polymer obtained by reacting a polyolefin resin having an unsaturated bond at one end and / or both ends with a siloxane copolymer, The weight average molecular weight of the polyolefin resin having an unsaturated bond at one end and / or both ends is 5,000 g / mol or more and 100,000 g / mol or less, The silylated polyolefin resin contained in the release layer (A) is a silylated polypropylene resin, A multilayer film, comprising a substrate layer (B) containing a thermoplastic resin having a flexural modulus of 400 to 2000 MPa.

2. The multilayer film according to claim 1, wherein the content of the silylated polyolefin resin in the release layer (A) is 1 to 50 mass %.

3. The multilayer film according to claim 1 or 2, wherein the polyolefin resin contained in the release layer (A) is a polypropylene resin.

4. The multilayer film according to any one of claims 1 to 3, wherein the polyolefin resin contained in the release layer (A) is a propylene-ethylene copolymer.

5. The multilayer film according to any one of claims 1 to 4, wherein the thermoplastic resin contained in the base layer (B) is a polypropylene resin.

6. The multilayer film according to any one of claims 1 to 5, having a thickness of 10 to 500 µm.

7. A food packaging film comprising the multilayer film according to any one of claims 1 to 6.

8. An industrial release film comprising the multilayer film according to any one of claims 1 to 6.

9. A liquid crystal protective film comprising the multilayer film according to any one of claims 1 to 6.

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