A polyethylene resin composition for a stretched substrate film, a stretched substrate film made therefrom, and a laminate and packaging material containing the same.

Abstract

To provide a polyethylene resin composition for a stretched base material which is excellent in impact strength, and is suitable as a stretched base material.SOLUTION: A polyethylene resin composition for a stretched base material film satisfies all of the following physical properties (a-1) to (a-4). (a-1): density of 0.880 g-0.935 g / cm3, (a-2): melt flow rate (MFR) at a temperature of 190°C and a load of 2.16 kg of 0.1-7 g / 10 min, (a-3): maximum take-up speed (MDS) at 190°C and MFR at a temperature of 190°C and a load of 2.16 kg satisfying all the (i) to (iii): (i) 0<MDS≤220, (ii) MDS≥40MFR (only in the case of 0.1≤MFR≤2.5) and (iii) MDS≥100 (only in the case of 2.5<MFR≤7.0), and (a-4): (Mw / Mn) of 1.5-10.0.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a polyethylene resin composition for oriented substrate films, an oriented substrate film obtained by stretching a film made of the composition, a laminate containing the oriented substrate film, and a packaging material made of the laminate. [Background technology]

[0002] Conventionally, one of the basic structures of packaging materials is a structure in which a heat seal layer and a base layer are bonded together with an adhesive. Of these, a film made of a polyethylene resin composition, which has moderate flexibility, transparency, and excellent heat sealability, is widely used for the heat seal layer. On the other hand, a stretched film made of a polyester resin composition or a polyamide resin composition is used for the base layer in terms of rigidity, impact resistance, and heat resistance (see Patent Document 1).

[0003] In recent years, along with the growing demand for the creation of a recycling-oriented society, there has been a demand for packaging materials with high recyclability. However, as described above, conventional packaging bodies are made of different types of resin materials, and because it is difficult to separate the resin materials, they are not currently recycled.

[0004] One way to achieve high recyclability is to create a packaging material made entirely of the same resin material (mono-material packaging material).Since polyethylene resin compositions are widely used as raw materials for packaging materials, packaging materials in which both the heat seal layer and the base layer are made of a film made of a polyethylene resin composition are expected to be highly recyclable packaging materials that will help realize a recycling-oriented society.

[0005] However, when a film made of a polyethylene resin composition is used as a substrate layer, if a film obtained by inflation or T-die molding is used as is, not only will the impact strength of the packaging material be insufficient, but the film will stretch when printed due to its insufficient rigidity, resulting in misalignment of the image. To compensate for this, a film obtained by molding a polyethylene resin composition by inflation or T-die molding and then stretching the resulting film is used. As polyethylene resin compositions for stretched films, for example, a resin composition blending LLDPE and HDPE (see Patent Document 2) and an LLDPE containing a specific crystalline component (see Patent Document 3) have been proposed. However, both of these polyethylene resin compositions are intended for use in shrink films, not as substrates, and therefore there has been a demand for the development of a polyethylene resin composition intended for use as a stretched substrate. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Laid-Open No. 2009-202519 [Patent Document 2] Japanese Patent Application Laid-Open No. 2005-89693 [Patent Document 3] Japanese Patent Application Laid-Open No. 2004-238543 Summary of the Invention [Problem to be solved by the invention]

[0007] An object of the present invention is to provide a polyethylene resin composition for stretched substrates which has excellent impact strength and is suitable as a stretched substrate, and to provide a resin laminate and a packaging material which use the same. [Means for solving the problem]

[0008] As a result of intensive research to solve the above problems, the inventors of the present invention formed a film by inflation molding using a polyethylene resin composition satisfying specific conditions, and stretched the obtained film using a hot roll stretching machine. As a result, it was found that the film exhibited characteristics capable of solving the above problems, and based on these findings, the inventors completed the present invention.

[0009] That is, according to the present invention [1], there is provided a polyethylene resin composition for a stretched base film used as a base material of a resin laminate, which satisfies all of the following physical properties (a-1) to (a-4). (a-1) The density is 0.880 g to 0.935 g / cm ,

[0010] ,

[0011] , , , is (a-2) The melt flow rate (MFR) at a temperature of 190 °C and a load of 2.16 kg is 0.1 to 7 g / 10 min. (a-3) The maximum draw speed (= Max Draw Speed, MDS) at 190 °C and the melt flow rate (MFR) at a temperature of at a temperature of 190 °C and a load of 2.16 kg satisfy all of the following formulas (i) to (iii). (i) 0 < MDS ≤ 220 (ii) MDS ≥ 40MFR (only when 0.1 ≤ MFR ≤ 2.5) (iii) MDS ≥ 100 (only when 2.5 < MFR ≤ 7.0) (a-4) The molecular weight distribution [ratio of weight average molecular weight (Mw) to number average molecular weight (Mn) (Mw / Mn)] by gel permeation chromatography (GPC) is 1.5 to 10.0.

[0010] Further, according to the present invention [2], there is provided a polyethylene resin composition for a stretched base film, wherein the film obtained by inflation molding or T-die molding of the polyethylene resin composition for a stretched base film of the first invention is stretched 5 times in the MD direction, and the film impact value when penetrated and broken with a 1 / 2-inch hemispherical metal ball is 12 J / mm or more. <0000​According to the present invention [3], there is also provided a stretched substrate film obtained by further stretching a film obtained by inflation molding or T-die molding using the polyethylene resin composition for stretched substrate films in the first or second invention.

[0012] According to the present invention [4], there is also provided a stretched substrate film obtained by stretching a film obtained by inflation molding or T-die molding using the polyethylene resin composition for stretched substrate films according to the first or second invention by 7 times or more in MD.

[0013] According to the present invention [5], there is also provided a stretched substrate film obtained by stretching a film obtained by inflation molding or T-die molding using the polyethylene resin composition for stretched substrate films according to the first or second invention, in both MD and TD by at least 2 times its original size. Furthermore, according to the present invention [6], there is provided a resin laminate comprising a layer made of the stretched substrate film according to any one of the third to fifth inventions, and according to the present invention [7], there is provided a resin laminate according to the sixth invention, which comprises as a substrate a layer made of the stretched substrate film according to any one of the third to fifth inventions and comprises as a sealant layer a polyethylene-based resin sealant layer, and according to the present invention [8], there is provided a resin laminate according to the sixth or seventh invention, which is characterized in that all layers constituting the resin laminate are monomaterial resin laminates made of polyethylene-based resins, and according to the present invention [9], there is provided a packaging material composed of the resin laminate according to any one of the sixth to eighth inventions. [Effects of the Invention]

[0014] The polyethylene resin composition of the present invention has excellent stretchability and can provide a stretched substrate film with little variation in thickness due to stretching. Stretching increases rigidity, making it possible to print on the surface of the stretched substrate film. Furthermore, the small thickness variation results in a good film appearance, allowing inks and adhesives to be applied uniformly, providing high-quality packaging materials. Furthermore, by using the composition in combination with a polyethylene sealant film as a substrate for a packaging material, highly recyclable packaging materials can be provided, particularly mono-material laminates and packaging materials composed of a single material. [Brief explanation of the drawings]

[0015] [Figure 1] FIG. 1 is a graph showing the relationship between MDS and MFR of a polyethylene resin composition of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0016] The present invention relates to a polyethylene resin composition for a stretched substrate film, a stretched substrate film made from the same, a laminate having a layer of the same, and a packaging material made from the same. The present invention will be described in detail below for each item. The stretched substrate film of the present invention means a film obtained by stretching a film obtained by inflation molding or T-die molding a polyethylene resin composition that satisfies the requirements of the present invention, and is used as a substrate for a resin laminate.

[0017] 1. Polyethylene resin composition The polyethylene resin composition in the present invention is a resin composition used as a raw material for the stretched substrate film, and means either a polyethylene resin alone or a polyethylene resin mixture, to which necessary additives may be added. Polymerization catalyst and polymerization method for polyethylene resin composition The polyethylene resin for constituting the polyethylene resin composition is produced using either ethylene derived from petroleum feedstocks or ethylene derived from biomass feedstocks, or both, as raw materials, using a conventionally known catalyst such as a polymerization catalyst, such as a Ziegler-Natta catalyst, a Phillips catalyst, or a metallocene catalyst. A Ziegler-Natta catalyst or a metallocene catalyst is preferred. Generally, these catalysts are complexes composed of organometallic compounds supported on a carrier such as silica or a magnesium compound. The polymerization method may be a solution method, a slurry method, a gas-phase method, or a high-pressure method, but the slurry, gas-phase, or high-pressure methods are preferred. The slurry method is a polymerization method in which a hydrocarbon compound such as hexane or isobutane is used as a solvent, and the resulting polyethylene exists in the solvent as a slurry. Depending on the shape of the reaction vessel, it can be broadly divided into two methods: the autoclave method and the loop-pipe method. The gas-phase method is a polymerization method in which ethylene, an α-olefin as a comonomer, and hydrogen as a chain transfer agent are fed in gaseous form from the bottom of a vertical reaction vessel, and a polymerization catalyst is then added. The high-pressure method is a process in which a gaseous mixture of ethylene and comonomer is pressurized using a compressor, and polymerization is carried out under high-temperature, high-pressure conditions. (From Polyethylene Technology Reader, edited by Matsuura Kazuo and Mikami Hisataka)

[0018] High-pressure method for polymerizing polyethylene resin High-pressure processes can be broadly divided into autoclave and tubular processes. Both are the same up until the point where ethylene and comonomer are pressurized using a compressor, but the autoclave process is a batch-type process in which polyethylene is polymerized in a reaction vessel. Compared to the tubular process, it is easier to uniformize reaction conditions, resulting in uniform polyethylene and a wide process window, but because it is a batch process, it is characterized by high production costs and a slow production rate. On the other hand, the tubular process is a continuous process in which polyethylene is polymerized in a long tube. Compared to the autoclave process, it is continuous, which means it is superior in terms of production costs and production rate, but it is difficult to uniformize reaction conditions in a long tube, and it is characterized by variations in physical properties and a narrow process window. Furthermore, because the high-pressure method uses substances that easily generate radicals, such as oxygen or peroxides, as polymerization initiators, the polymerization is radical polymerization, and the polyethylene produced is generally LDPE, which has a high degree of branching. However, with improvements in polymerization technology, in addition to radical polymerization using oxygen or peroxides, high-pressure methods using Ziegler-Natta catalysts or metallocene catalysts have also become possible. This polymerization method is called the high-pressure ion method. The polyethylene produced using this method is LLDPE, which has both linear and branched chains. The polyethylene resin composition for stretched substrates obtained by the preferred high-pressure polymerization method is not particularly limited, but a polyethylene resin composition polymerized by a high-pressure ion method is preferred.

[0019] Comonomer composition of polyethylene resin composition The polyethylene resin composition according to the present invention is an ethylene homopolymer or a copolymer of ethylene and one or more α-olefins selected from α-olefins having 3 to 18 carbon atoms. The α-olefins having 3 to 18 carbon atoms are preferably those having 3 to 12 carbon atoms, and specific examples thereof include propylene, 1-butene, 1-hexene, 1-octene, and 4-methyl-1-pentene. The total content of these α-olefins is preferably selected within a range of usually 30 mol% or less, and preferably 20 mol% or less. Within this range, films and the like will have good flexibility and heat resistance. Here, the content of α-olefin is a value measured by 13C-NMR under the following conditions. Equipment: JEOL-GSX270 manufactured by JEOL Concentration: 300mg / 2mL Solvent: orthodichlorobenzene

[0020] ·density The polyethylene resin composition for a stretched film of the present invention has a density of 0.880 to 0.935 g / cm 3 The preferred density is 0.880 to 0.932 g / cm 3 , more preferably 0.880 to 0.930 g / cm 3Here, the density is a value measured in accordance with JIS K6922-1 and 2. Density is 0.935g / cm 3 If the density exceeds 0.880 g / cm, the impact strength of the stretched film for substrate will be reduced, which is not preferable. 3 If it is less than this, the formability of the film itself will deteriorate, which is not preferable.

[0021] Melt flow rate The polyethylene resin composition of the present invention must have an MFR in the range of 0.1 to 7 g / 10 min. The preferred MFR is 0.1 to 6 g / 10 min, more preferably 0.1 to 5 g / 10 min. An MFR of less than 0.1 g / 10 min is likely to result in the formation of gels, while an MFR of more than 10 g / 10 min is undesirable because it prevents the formation of stretched films for substrates with high mechanical strength. That is, an MFR in the range of 0.1 to 7 g / 10 min is preferred because it prevents the formation of gels and provides stretched films for substrates with high mechanical strength. The MFR is the extrusion rate measured in accordance with JIS K6922-2, in which a molten polymer is extruded through a die (length: 8 mm, outer diameter: 9.5 mm, inner diameter: 2.095 mm) at 190°C and a load of 2.16 kg.

[0022] Maximum Discharge Speed ​​(MDS) It is essential that the polyethylene resin composition of the present invention has a maximum draw speed (MDS) (m / min) at 190°C and a melt flow rate (MFR) (g / 10 min) at a temperature of 190°C and a load of 2.16 kg that satisfy all of the following formulas (i) to (iii): The maximum take-up speed (MDS) of a resin composition is one of the commonly used measurement methods for indicating the melt tension of a resin, and can be measured, for example, by the following method. Using a Capirograph manufactured by Toyo Seiki Seisakusho, a resin heated and stabilized in a furnace at 190 °C is extruded from an orifice with an inner diameter of 2.095 mm and a length of 8 mm at a piston speed of 1 cm / min, and the extruded molten resin is pulled at a speed of 4 m / min. Then, the take-up speed is increased at a rate of 1.67 m / sec, and the take-up speed at the time of strand breakage is defined as the maximum take-up speed (MDS) (m / min). (i) 0 < MDS ≤ 220 (ii) MDS ≥ 40MFR (only when 0.1 ≤ MFR ≤ 2.5) (iii) MDS ≥ 100 (only when 2.5 < MFR ≤ 7.0) If this is not satisfied, in the range of 0.1 ≤ MFR ≤ 2.5, there are many entanglement points of molecular chains, and it is not preferable because it is difficult to eliminate the entanglement points during stretching and a large force is applied and it breaks. On the other hand, in the range of 2.5 < MFR ≤ 7.0, the molecular chains are short and the number of entanglement points is small, so it is not preferable because the molecular chains slip through during stretching and break. The polyethylene resin composition satisfying formulas (i) to (iii) has an appropriate molecular chain length and entanglement points, and is preferable because a stretched base film with a high draw ratio can be obtained. The lower limit value of MDS is not particularly limited, but it is preferably greater than 0, preferably 40 m / min or more while satisfying formulas (i) to (iii), more preferably 50 m / min or more while satisfying formulas (i) to (iii), and even more preferably 60 m / min while satisfying formulas (i) to (iii).

[0023] · Molecular weight distribution The polyethylene resin composition of the present invention must have a molecular weight distribution [the ratio of weight average molecular weight (Mw) to number average molecular weight (Mn) (Mw / Mn)] in the range of 1.5 to 10.0. The preferable range of the Mw / Mn ratio is 2.0 to 9.0. When Mw / Mn is 10.0 or more, stretching at a high magnification is not possible, and the obtained stretched film for the base material may become opaque, which is not preferable. By using the polyethylene resin composition having Mw / Mn in the range of 1.5 to 10.0, it is possible to obtain an optimal film for the stretched film for the base material, which is preferable.

[0024] Resin Blend In the present invention, the polyethylene resin composition may be a single one, or two or more kinds may be mixed to produce a polyethylene resin that satisfies the above requirements at the same time, and this may be used.

[0025] Additives The polyethylene resin or resin composition according to the present invention may be blended with additives generally used for resin compositions, such as antioxidants, heat stabilizers, neutralizing agents, antiblocking agents, tackifiers, antistatic agents, slip agents, nucleating agents, foaming agents, crosslinking agents, biomass resources, and biodegradation accelerators, within the scope of the present invention.

[0026] 2. Stretched film Raw material manufacturing method and manufacturing conditions A stretched film can be obtained by stretching a raw sheet. Examples of methods for producing the raw sheet include inflation molding, T-die molding, and calendar molding. In terms of production speed and ease of production, inflation molding and T-die molding are preferred. Although the conditions for producing the raw sheet are not particularly limited, the thickness of the film is preferably 20 μm to 200 μm, more preferably 30 μm to 200 μm, and even more preferably 50 μm to 200 μm.

[0027] ·Stretching method The stretched film may be a uniaxially stretched film or a biaxially stretched film, and the stretching method may be any of longitudinal uniaxial stretching, transverse uniaxial stretching, sequential biaxial stretching, and simultaneous biaxial stretching.

[0028] Longitudinal stretching ratio The stretching ratio in the machine direction (MD) of the stretched film is preferably 2 to 15 times, more preferably 5 to 10 times, and more preferably 7 times or more in the MD direction. By stretching the stretched film at a stretch ratio of 2 or more in the machine direction (MD), the strength and heat resistance of the laminate of the present invention can be improved. Furthermore, the printability of the substrate can be improved. Furthermore, the transparency of the substrate can be improved, thereby improving the visibility of an image formed on the surface of the substrate facing the heat seal layer. Meanwhile, the upper limit of the stretch ratio in the machine direction (MD) of the stretched film is not particularly limited, but is preferably 15 times or less, more preferably 10 times or less, from the viewpoint of the breaking limit of the stretched film.

[0029] ·Horizontal stretch ratio The stretching ratio in the transverse direction (TD) of the stretched film is preferably 1.5 times or more, and more preferably 2 times or more. By setting the stretching ratio in the transverse direction (TD) of the stretched film for substrate to 1.5 times or more, the strength and heat resistance of the laminate of the present invention can be improved. Furthermore, the printability of the substrate can be improved. Furthermore, since the transparency of the substrate can be improved, when an image is formed on the surface of the substrate on the heat seal layer side, the visibility of the image can be improved. On the other hand, the upper limit of the stretching ratio in the transverse direction (TD) of the stretched film is not particularly limited, but from the viewpoint of the breaking limit of the stretched film, it is preferably 10 times or less.

[0030] ·Biaxial stretching ratio When the stretched substrate film is stretched in both MD and TD, the stretching is preferably 1.5 times or more, more preferably 2 times or more, in each direction. Increasing the MD and TD stretching ratios of the stretched substrate film can improve the strength and heat resistance of the laminate of the present invention. Furthermore, the printability of the substrate can be improved. Furthermore, the transparency of the substrate can be improved, thereby improving the visibility of an image formed on the heat-sealable layer side surface of the substrate. While the upper limits of the MD and TD stretching ratios of the stretched substrate film are not particularly limited, from the viewpoint of the breaking point limit of the stretched substrate film, it is preferable that the lower limits of the MD and TD stretching ratios are 1.5 times, preferably 2 times, and that the product of the MD stretching ratio and the TD stretching ratio is 50 or less.

[0031] Impact strength The film impact value is used as an index of the impact strength of a stretched substrate film. The film impact value is a measure of the fragility of a film against impact, measured from the work (J) required for penetration when struck with a penetration part of a standard tip diameter using a tester conforming to JIS P8134 (Film Impact Tester, manufactured by Toyo Seiki Seisakusho Co., Ltd.). The higher the film impact value, the more energy is required for penetration and therefore the better the impact strength. There is no particular restriction on the lower limit of the film impact value, but the value when penetrated and broken with a diameter of 1 / 2 inch (12.7 mm) is preferably 12 J / mm or more, more preferably 13 J / mm or more, and even more preferably 14 J / mm or more.

[0032] Thickness variation The standard deviation (s) of thickness is used as an index of the degree of variation in the thickness of a stretched substrate film. s is the thickness of a film measured at four points around a certain point using a thickness meter, and the average of the measurements is taken as the thickness at that point. This is performed at 12 points at 10 cm intervals along the MD of the film, and the standard deviation of the thickness at the 12 points is calculated. The smaller s is, the smaller the thickness variation is. This is preferable because ink can be applied more evenly during printing and adhesive can be applied more evenly during dry lamination. Furthermore, a small s is preferable because, when stretched in the TD by sequential biaxial stretching, stretching stress is applied uniformly, making it less likely to break and allowing for uniform stretching. The upper limit of s is not particularly limited, but it is preferably 3.00 or less, more preferably 2.75 or less, and even more preferably 2.50 or less.

[0033] The stretched film is preferably subjected to a surface treatment, which can improve adhesion between adjacent layers. The surface treatment method is not particularly limited, and examples thereof include physical treatments such as corona discharge treatment, ozone treatment, low-temperature plasma treatment using oxygen gas and / or nitrogen gas, and glow discharge treatment, as well as chemical treatments such as oxidation treatment using chemicals. Alternatively, an anchor coating layer may be formed on the surface of the substrate using a conventionally known anchor coating agent.

[0034] The stretched polyethylene film may have an image such as a letter, a pattern, a symbol, etc. formed on at least one surface thereof. In order to prevent deterioration of the image over time, it is preferable that the image be formed on the side of the stretched polyethylene film where the heat-sealable polyethylene layer is laminated. The method for forming the image is not particularly limited, and examples thereof include conventionally known printing methods such as gravure printing, offset printing, flexographic printing, etc. Among these, flexographic printing is preferred from the viewpoint of environmental load.

[0035] Vapor deposition film The stretched film may have a vapor-deposited film on at least one surface thereof, which may be a vapor-deposited film made of a metal such as aluminum, or an inorganic oxide such as aluminum oxide, silicon oxide, magnesium oxide, calcium oxide, zirconium oxide, titanium oxide, boron oxide, hafnium oxide, or barium oxide.

[0036] The thickness of the vapor-deposited film is preferably 1 nm or more and 150 nm or less, more preferably 5 nm or more and 60 nm or less, and even more preferably 10 nm or more and 40 nm or less. By making the thickness of the vapor-deposited film 1 nm or more, the oxygen barrier property and water vapor barrier property of the laminate of the present invention can be further improved, and by making the thickness of the vapor-deposited film 150 nm or less, the occurrence of cracks in the vapor-deposited film can be prevented and the recyclability of the laminate of the present invention can be improved.

[0037] When the vapor-deposited film is an aluminum vapor-deposited film, its OD value is preferably 2 or more and 3.5 or less. This makes it possible to improve the oxygen barrier property and water vapor barrier property while maintaining the productivity of the laminate of the present invention. In the present invention, the OD value can be measured in accordance with JIS-K-7361.

[0038] The vapor-deposited film can be formed using a conventionally known method, for example, physical vapor deposition methods (PVD methods) such as vacuum deposition, sputtering, and ion plating, and chemical vapor deposition methods (CVD methods) such as plasma chemical vapor deposition, thermal chemical vapor deposition, and photochemical vapor deposition.

[0039] Furthermore, for example, a composite film consisting of two or more layers of vapor-deposited films of different inorganic oxides can be formed and used by combining physical vapor deposition and chemical vapor deposition. The degree of vacuum in the vapor deposition chamber is preferably about 10-2 to 10-8 mbar before oxygen is introduced, and about 10-1 to 10-6 mbar after oxygen is introduced. The amount of oxygen introduced varies depending on the size of the vapor deposition machine. An inert gas such as argon gas, helium gas, or nitrogen gas may be used as a carrier gas for the introduced oxygen, provided that no problems occur. The film transport speed can be about 10 to 800 m / min.

[0040] The surface of the deposited film is preferably subjected to the above-mentioned surface treatment, which can improve adhesion to adjacent layers.

[0041] The laminate of the present invention can have a heat-resistant coating layer or a barrier coating layer on a substrate, and contains at least one resin material, such as polyester, polyolefin, cellulose resin, (meth)acrylic resin, urethane resin, or vinyl resin.

[0042] The proportion of the resin material contained in the coating layer to the total resin material contained in the laminate is preferably 3% by mass or less, more preferably 1% by mass or less, which allows the heat resistance of the laminate of the present invention to be improved while maintaining the recyclability.

[0043] The thickness of the coating layer is preferably 0.1 μm or more and 5 μm or less, and more preferably 0.5 μm or more and 3 μm or less, which can improve the heat resistance while maintaining the recyclability of the laminate of the present invention.

[0044] 3. Resin laminate Multilayer stretched film In addition to stretched films made from polyethylene resin compositions that satisfy the requirements of the present invention, films may also be laminated with layers of films obtained by further stretching films made from at least one or more polyethylene resin compositions obtained by inflation molding or T-die molding. Usable resins include high-density polyethylene (HDPE), medium-density polyethylene (MDPE), low-density polyethylene (LDPE), linear low-density polyethylene (LLDPE), and ultra-low-density polyethylene (ULDPE). Furthermore, lamination may involve further stretching a co-extruded film obtained by co-extrusion molding, or by bonding films together using an adhesive.

[0045] It may also be a resin laminate containing a layer made of a stretched film as a substrate and a polyethylene resin sealant as a sealant layer.

[0046] The resin laminate may be a resin laminate in which all layers constituting the resin laminate are composed of polyethylene-based resins. This resin laminate can be treated as a mono-material resin laminate. The proportion of the main component in the mono-material resin laminate is not particularly limited, but is preferably 70% by weight, more preferably 80% by weight.

[0047] ·glue An adhesive can be used to laminate the resin laminate. The adhesive used contains at least one resin composition, but there are no particular limitations. Examples of adhesives that can be used include epoxy, acrylic, and urethane adhesives. The adhesive containing any of the above resin compositions is not particularly limited, and one-component, two-component, or hot melt type may be used as needed. In addition, using an adhesive with barrier properties, such as PASLIM (manufactured by DIC) or Maxive (manufactured by Mitsubishi Gas Chemical Company, Inc.), is preferable because it reduces the amount of other barrier materials used and increases the proportion of polyethylene in the resin laminate.

[0048] 4. Packaging material The laminate of the present invention can be particularly suitably used for packaging material applications. The shape of the packaging material is not particularly limited and may be a packaging bag or a stand-up pouch. In the stand-up pouch, only the body may be formed of the resin laminate, only the bottom may be formed of the resin laminate, or both the body and the bottom may be formed of the resin laminate.

[0049] ·Packaging bag The bag-shaped packaging material can be produced by folding the laminate in half, overlapping it so that the heat seal layer of the laminate is on the inside, and heat sealing the ends. Alternatively, a bag-shaped packaging material can be produced by overlapping two laminates with their heat-sealable layers facing each other, and then heat-sealing the ends of the laminate.

[0050] Stand-up pouch A stand-up pouch-shaped packaging material can be produced by heat-sealing the laminate into a cylindrical shape with the heat-seal layer facing inward to form a body, then folding the laminate into a V-shape with the heat-seal layer facing inward, sandwiching one end of the body, and heat-sealing to form a bottom.

[0051] The heat sealing method is not particularly limited, and can be performed by any known method such as bar sealing, rotary roll sealing, belt sealing, impulse sealing, high frequency sealing, or ultrasonic sealing.

[0052] The contents filled into the packaging material are not particularly limited, and may be liquid, powder, or gel. The contents may also be food or non-food. After filling the contents, the opening can be heat-sealed to form a package. [Example]

[0053] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples. The evaluations and resins used in the examples and comparative examples are as follows.

[0054] Evaluation method (1) Density Measurements were carried out in accordance with JIS K6922-1 and 2. (2) MFR Measurement was carried out in accordance with JIS K6922-2 at 190°C under a load of 2.16 kg. (3)Molecular weight distribution The molecular weights (number average molecular weight (Mn), weight average molecular weight (Mw), and Z average molecular weight (Mz)) were measured by GPC, and the molecular weight distribution (ratio of weight average molecular weight (Mw) to number average molecular weight (Mn) (Mw / Mn)) was calculated. (4) Maximum collection speed Using a Toyo Seiki Co., Ltd. Capillograph, resin that had been heated and stabilized at 190°C in a furnace was extruded through an orifice with an inner diameter of 2.095 mm and a length of 8 mm at a piston speed of 1 cm / min. The extruded molten resin was pulled at a speed of 4 m / min, and then the take-up speed was increased at a rate of 1.67 m / sec. The take-up speed at which the strand broke was defined as the maximum take-up speed (MDS). (5) Film impact value A Toyo Seiki Seisakusho film impact tester (hereafter simply referred to as the "testing machine") was used to measure the work required to penetrate and break the film per unit thickness. Specifically, the test film was stored in an atmosphere of 23°C and 50% humidity, and after conditioning, the test film was fixed to the testing machine using a 50 mm diameter holder. A 1 / 2 inch (12.7 mm) hemispherical metal object was struck at the penetration point from the inner surface of the test film, and the work required to penetrate and break the film was measured. The load was then removed, and the maximum scale (work load) was adjusted to 1.5 J. The film impact value was determined by dividing the work load by the film thickness. (6) Thickness variation The standard deviation of thickness (s) is used as an index of the degree of variation in the thickness of a stretched substrate film. s is the thickness of a film measured at four points around a certain point using a thickness meter, and the average of these measurements is taken as the thickness at that point. This is done at 12 points at 10 cm intervals along the MD of the film, and the standard deviation of the thickness at these 12 points is calculated.

[0055] <Resin used and method for producing stretched film> Films were prepared using the following resins and then stretched to prepare stretched films. Note that the preheating temperature and stretching temperature during stretching were appropriately adjusted since they depend on the melting point of the resin. [Example 1] Metallocene-based linear low-density polyethylene (R1), MFR = 0.9 g / 10 min, density = 0.923 g / cm 3 Ethylene-1-hexene copolymer was prepared. This metallocene-based linear low-density polyethylene was made into a 150 μm film using an inflation molding machine at 190° C. and a blow ratio of 2.2. The obtained film was then stretched in a longitudinal stretching device at a payout rate of 1.0 m / min, a preheating temperature of 100°C, a stretching temperature of 101°C, a cooling temperature of 30°C, and a stretching ratio of 5 to obtain a stretched film. The results for each item are shown in Table 1. [Example 2] Manufactured by Japan Polyethylene Co., Ltd., product name Novatec LL, Ziegler-Natta linear low-density polyethylene (R2), grade name: UF421, MFR = 0.9 g / 10 min, density = 0.926 g / cm 3 Ethylene-1-butene copolymer was prepared. This Ziegler-Natta linear low-density polyethylene was extruded in an inflation molding machine at 190°C and a blow ratio of 2.2 to form a 150μm film. The obtained film was then stretched in a longitudinal stretching device at a payout rate of 1.0 m / min, a preheating temperature of 100°C, a stretching temperature of 110°C, a cooling temperature of 30°C, and a stretching ratio of 5 to obtain a stretched film. The results for each item are shown in Table 1. [Example 3] Japan Polyethylene Co., Ltd., product name: Harmolex, metallocene-based linear low-density polyethylene (R3), grade: NF324A, MFR = 1.0 g / 10 min, density = 0.906 g / cm 3 Ethylene-1-hexene copolymer was prepared. This metallocene-based linear low-density polyethylene was made into a 150 μm film using an inflation molding machine at 190° C. and a blow ratio of 2.2. The obtained film was then stretched in a longitudinal stretching device at a payout rate of 1.0 m / min, a preheating temperature of 70°C, a stretching temperature of 70°C, a cooling temperature of 30°C, and a stretching ratio of 5 to obtain a stretched film. The results for each item are shown in Table 1. [Example 4] Japan Polyethylene Co., Ltd., product name: Harmolex, metallocene-based linear low-density polyethylene (R4), grade: NF375B, MFR = 1.0 g / 10 min, density = 0.921 g / cm 3 Ethylene-1-hexene copolymer was prepared. This metallocene-based linear low-density polyethylene was made into a 150 μm film using an inflation molding machine at 190° C. and a blow ratio of 2.2. The obtained film was then stretched in a longitudinal stretching device at a payout rate of 1.0 m / min, a preheating temperature of 90°C, a stretching temperature of 110°C, a cooling temperature of 30°C, and a stretching ratio of 5 to obtain a stretched film. [Example 5] Japan Polyethylene Co., Ltd., product name: Harmolex, metallocene-based linear low-density polyethylene (R5), grade: NF384A, MFR = 1.7 g / 10 min, density = 0.926 g / cm 3 Ethylene-1-hexene copolymer was prepared. This metallocene-based linear low-density polyethylene was made into a 150 μm film using an inflation molding machine at 190° C. and a blow ratio of 2.2. The obtained film was then stretched in a longitudinal stretching device at a payout rate of 1.0 m / min, a preheating temperature of 90°C, a stretching temperature of 110°C, a cooling temperature of 30°C, and a stretching ratio of 5 to obtain a stretched film. [Example 6] Metallocene-based linear low-density polyethylene (R6), MFR = 1.3 g / 10 min, density = 0.935 g / cm 3 Ethylene-1-hexene copolymer was prepared. This metallocene-based linear low-density polyethylene was made into a 150 μm film using an inflation molding machine at 190° C. and a blow ratio of 2.2. The obtained film was then stretched in a longitudinal stretching device at a payout rate of 1.0 m / min, a preheating temperature of 110°C, a stretching temperature of 120°C, a cooling temperature of 30°C, and a stretching ratio of 5 to obtain a stretched film. [Comparative Example 1] Nippon Polyethylene Co., Ltd., product name: Novatec LD, low-density polyethylene (S1), grade: LF240, MFR = 0.7 / 10 min, density = 0.924 g / cm 3 We have prepared the following. This low-density polyethylene was made into a 150 μm film using an inflation molding machine at 180° C. and a blow ratio of 2.2. The obtained film was then stretched in a longitudinal stretching device at a payout rate of 1.0 m / min, a preheating temperature of 100°C, a stretching temperature of 100°C, a cooling temperature of 30°C, and a stretching ratio of 4 to obtain a stretched film. The results for each item are shown in Table 1. Comparative Example 2 Nippon Polyethylene Co., Ltd., product name: Novatec HD, high-density polyethylene (S2), grade: HF335, MFR = 0.6 g / 10 min, density = 0.949 g / cm 3 We have prepared the following. This high density polyethylene was made into a 150 μm film using an inflation molding machine at 180° C. and a blow ratio of 2.2. The obtained film was then stretched in a longitudinal stretching device at a payout rate of 1.0 m / min, a preheating temperature of 120°C, a stretching temperature of 129°C, a cooling temperature of 30°C, and a stretching ratio of 5 to obtain a stretched film. The results for each item are shown in Table 1.

[0056] [Table 1]

[0057] <Evaluation> ·Stretchability The maximum stretching ratio in Table 1 is an index for evaluating stretchability. The maximum stretching ratio is the maximum stretching ratio at which a film can be obtained without breaking when the stretching ratio of the film is increased. In Examples 1 to 6, stretching of 5 times or more was possible because the MDS and MFR satisfied the requirements of the present invention, but in Comparative Example 1, stretching was only possible up to 4 times because the relationship between MDS and MFR did not satisfy the requirements of the present invention, which indicates that the polyethylene resin composition of the present invention has excellent stretchability.

[0058] Impact strength The film impact value in Table 1 is an evaluation index for impact strength. A larger value indicates better impact strength. In Examples 1 to 6, the requirements of the present invention were satisfied, and thus stretched films having excellent impact strength with film impact values ​​of 12 J / mm or more were obtained. On the other hand, in Comparative Example 2, the density did not satisfy the requirements of the present invention, and therefore the film impact value was small and the impact strength was low, and therefore it can be said that the polyethylene resin composition of the present invention has excellent impact strength.

[0059] Thickness variation The standard deviation s of thickness in Table 1 is an index of thickness variation. The smaller this value, the smaller the thickness variation. In Examples 1 to 6, stretched substrate films with little thickness variation, where s was 3.00 or less, were obtained because they satisfied the requirements of the present invention. On the other hand, in Comparative Example 2, the requirements of the present invention were not satisfied, so the s value was 4.65, which was a large thickness variation, and the appearance of the film was poor. Therefore, it can be said that the polyethylene resin composition of the present invention is excellent in that it has little thickness variation.

Claims

1. A polyethylene resin composition for a stretched substrate film used as a substrate for a resin laminate, characterized in that the polyethylene resin in the polyethylene resin composition is an ethylene homopolymer or a copolymer of ethylene and one or more α-olefins selected from α-olefins having 3 to 18 carbon atoms, and the polyethylene resin composition for a stretched substrate film satisfies all of the following physical properties (a-1) to (a-4): (a-1) Density is 0.880 g to 0.935 g / cm ３ is (a-2) The melt flow rate (MFR) at a temperature of 190°C and a load of 2.16 kg is 0.1 to 2.5 g / 10 min. (a-3) The maximum draw speed at 190°C (= Max Draw Speed, MDS) and the melt flow rate (MFR) at a temperature of 190°C and a load of 2.16 kg satisfy all of the following formulas (i) to (iii). (i) 0<MDS≦220 (ii) MDS≧40MFR (only when 0.1≦MFR≦2.5) (a-4) The molecular weight distribution [ratio (Mw / Mn) of weight average molecular weight (Mw) to number average molecular weight (Mn)] measured by gel permeation chromatography (GPC) is 1.5 to 10.

0.

2. 2. The polyethylene resin composition for a stretched substrate film according to claim 1, wherein a film obtained by subjecting the polyethylene resin composition for a stretched substrate film according to claim 1 to inflation molding or T-die molding and stretching the film 5 times in the machine direction has a film impact value of 12 J / mm or more when the film is penetrated and broken with a ½-inch hemispherical metal ball.

3. 3. A stretched substrate film obtained by further stretching a film obtained by inflation molding or T-die molding using the polyethylene resin composition for stretched substrate films according to claim 1 or 2.

4. 3. A stretched substrate film obtained by stretching a film obtained by inflation molding or T-die molding using the polyethylene resin composition for stretched substrate films according to claim 1 or 2 in MD by 5 times or more.

5. 3. A stretched substrate film obtained by stretching a film obtained by inflation molding or T-die molding using the polyethylene resin composition for stretched substrate films according to claim 1 or 2 in both MD and TD by at least 2 times its original size.

6. A method for producing a stretched substrate film, comprising molding a film by inflation molding or T-die molding using the polyethylene resin composition for a stretched substrate film according to claim 1 or 2, and stretching the film in the machine direction by 5 times or more.

7. A method for producing a stretched substrate film, comprising molding a film by inflation molding or T-die molding using the polyethylene resin composition for a stretched substrate film according to claim 1 or 2, and stretching the film by at least two times in both MD and TD.

8. A resin laminate comprising a layer made of the stretched substrate film according to any one of claims 3 to 5.

9. 9. The resin laminate according to claim 8, comprising a layer made of the stretched substrate film according to any one of claims 3 to 5 as a substrate, and a polyethylene resin sealant layer as a sealant layer.

10. 10. The resin laminate according to claim 8, wherein the resin laminate is a mono-material resin laminate in which all layers constituting the resin laminate are made of polyethylene-based resin.

11. A packaging material comprising the resin laminate according to any one of claims 8 to 10.

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