Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B32—LAYERED PRODUCTS
  • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
  • B32B27/00—Layered products comprising a layer of synthetic resin
  • B32B27/32—Layered products comprising a layer of synthetic resin comprising polyolefins
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B65—CONVEYING; PACKING; STORING; HANDLING THIN OR FILAMENTARY MATERIAL
  • B65D—CONTAINERS FOR STORAGE OR TRANSPORT OF ARTICLES OR MATERIALS, e.g. BAGS, BARRELS, BOTTLES, BOXES, CANS, CARTONS, CRATES, DRUMS, JARS, TANKS, HOPPERS, FORWARDING CONTAINERS; ACCESSORIES, CLOSURES, OR FITTINGS THEREFOR; PACKAGING ELEMENTS; PACKAGES
  • B65D65/00—Wrappers or flexible covers; Packaging materials of special type or form
  • B65D65/38—Packaging materials of special type or form
  • B65D65/40—Applications of laminates for particular packaging purposes

Definitions

• the present invention relates to a non-oriented polyolefin resin film, a laminate, and a packaging material.
• Unstretched polypropylene resin films are inexpensive, and packaging materials made from them have excellent heat sealing properties, so they are widely used as heat-sealable films.
• Packaging is mainly produced by producing a laminate using polyamide resin film, polyester resin film, or polypropylene resin film as the base film and non-oriented polyolefin resin film as the sealant, and then heating and pressing (hereafter referred to as heat sealing) the non-oriented polyolefin resin film surfaces together at a temperature close to the melting point of the polyolefin resin film.
• heat sealing heating and pressing
• packaging materials are used to pack and transport a variety of foods, including fresh produce, prepared foods, and confectionery.
• the use of packaging materials not only enables food to be delivered to consumers efficiently, but also delays food spoilage, extends the expiration date, and prevents debris from getting into the food during transport and storage.
• Patent Documents 1, 2, 3, etc. There is a known technology for improving the impact resistance of non-oriented polypropylene resin films by adding polyethylene resin to polypropylene resin.
• Patent Documents 1, 2, 3, etc. all of these documents have issues with poor thermal dimensional stability and a tendency for pitch misalignment to occur during printing.
• the object of the present invention is to provide a non-stretched polyolefin resin film that has good thermal dimensional stability and stiffness while also having high heat seal strength and resistance to pinholes caused by bending.
• the inventors have discovered that by controlling the layer structure and the resin composition of each layer of a non-stretched polypropylene-based resin film, it is possible to obtain a non-stretched polyolefin-based resin film that is excellent in heat shrinkage rate and impact resistance, and also in bag-making processability such as heat sealing property and printing processability, and have thus completed the present invention. That is, the present invention has the following aspects.
• a non-stretched polyolefin-based resin film comprising a first layer made of a resin composition containing a polypropylene-based resin, a second layer made of a resin composition containing a polypropylene-based resin, and a heat-seal layer made of a resin composition containing a polypropylene-based resin, wherein the resin compositions containing polypropylene-based resin constituting the first layer and the second layer each contain 50% by weight or more of at least one polymer selected from a polypropylene homopolymer and a propylene- ⁇ -olefin copolymer ( ⁇ -olefin has 2 or 4 to 20 carbon atoms), and the resin composition containing polypropylene-based resin constituting the heat-seal layer contains 50% by weight or more of a propylene- ⁇ -olefin copolymer ( ⁇ -olefin has 2 or 4 to 20 carbon atoms), and the non-stretched polyolefin-based resin
• the resin composition containing a polypropylene-based resin constituting the first layer contains a total of 55% by weight or more (preferably 55% by weight or more and 100% by weight or less, more preferably 60% by weight or more and 97% by weight or less, and even more preferably 70% by weight or more and 90% by weight or less) of at least one type selected from polypropylene homopolymers and propylene- ⁇ -olefin copolymers ( ⁇ -olefins having 2 or 4 to 20 carbon atoms) having a copolymerization ratio of 1.0 mol% or less of ⁇ -olefins.
• the resin composition constituting the second layer further contains a polyethylene-based resin in addition to the polypropylene-based resin, and the content of the polyethylene-based resin in the resin composition constituting the second layer is 10% by weight or more and 45% by weight or less (preferably 12% by weight or more and 45% by weight or less, more preferably 15% by weight or more and 40% by weight or less).
• the resin composition containing a polypropylene-based resin constituting the heat seal layer contains a total of 65% by weight or more (preferably 70% by weight or more and 100% by weight or less, more preferably 80% by weight or more and 100% by weight or less, and even more preferably 90% by weight or more and 100% by weight or less) of a propylene- ⁇ -olefin copolymer (the ⁇ -olefin has 2 or 4 to 20 carbon atoms) having a copolymerization ratio of ⁇ -olefin exceeding 1.0 mol%.
• the resin composition containing a polypropylene-based resin for the three layers of the first layer, the second layer, and the heat seal layer contains at least one type selected from a polypropylene homopolymer and a propylene- ⁇ -olefin copolymer (the carbon number of the ⁇ -olefin is 2 or 4 to 20) having a copolymerization ratio of 1.0 mol % or less, in an amount of 50 wt % or more and 70 wt % or less (preferably 50 wt % or more and 65 wt % or less, more preferably 50 wt % or more and 62 wt % or less), in total, for the three layers.
• the content thereof in the resin composition of the heat seal layer is 70% by weight or higher (preferably 70% by weight or higher and 100% by weight or lower, more preferably 80% by weight or higher and 100% by weight or lower, and even more preferably 90% by weight or higher and 100% by weight or lower).
• a laminate comprising at least one selected from the group consisting of a biaxially oriented polyolefin resin film, a biaxially oriented polyamide resin film, and a biaxially oriented polyester resin film, and the non-oriented polyolefin resin film according to any one of [1] to [8].
• the laminate according to [9] having a heat seal strength of 18 N/15 mm or more at 160° C., 0.1 MPa, and 1 sec.
• a packaging material comprising the laminate according to [9] or [10].
• the present invention provides a non-oriented polyolefin resin film that has good thermal dimensional stability and stiffness while also exhibiting high heat seal strength and resistance to pinholes caused by bending.
• the present invention relates to a non-stretched polyolefin-based resin film comprising a first layer made of a resin composition containing a polypropylene-based resin, a second layer made of a resin composition containing a polypropylene-based resin, and a heat-seal layer made of a resin composition containing a polypropylene-based resin, wherein the polypropylene-based resin-containing resin compositions constituting the first layer and the second layer both contain 50% by weight or more of at least one polymer selected from a polypropylene homopolymer and a propylene- ⁇ -olefin copolymer ( ⁇ -olefin has 2 or 4 to 20 carbon atoms), the polypropylene-based resin-containing resin composition constituting the heat-seal layer contains 50% by weight or more of a propylene- ⁇ -olefin copolymer ( ⁇ -olefin has 2 or 4 to 20 carbon atoms), and
• the heat shrinkage rate of the unstretched polyolefin resin film in the longitudinal direction at 120° C. for 30 minutes is 1.0% or less.
• the resin composition containing the polypropylene-based resin contained in the first layer contains a total of 55% by weight or more of at least one type selected from a polypropylene homopolymer and a propylene- ⁇ -olefin copolymer (the ⁇ -olefin has 2 or 4 to 20 carbon atoms) having a copolymerization ratio of 1.0 mol% or less of ⁇ -olefin.
• the resin composition constituting the second layer further contains a polyethylene-based resin in addition to the polypropylene-based resin, and the content of the polyethylene-based resin in the resin composition constituting the second layer is 10% by weight or more and 45% by weight or less.
• the resin composition containing a polypropylene-based resin constituting the heat seal layer contains a total of 65% by weight or more of a propylene- ⁇ -olefin copolymer (the ⁇ -olefin has 2 or 4 to 20 carbon atoms) having a copolymerization ratio of ⁇ -olefin exceeding 1.0 mol%.
• the resin composition containing a polypropylene-based resin for the three layers of the first layer, the second layer, and the heat seal layer contains at least one type selected from a polypropylene homopolymer and a propylene- ⁇ -olefin copolymer (the carbon number of the ⁇ -olefin is 2 or 4 to 20) having a copolymerization ratio of 1.0 mol % or less, in an amount of 50 wt % to 70 wt %, in total, for the three layers.
• a resin composition containing three layers of polypropylene-based resin contains a predetermined amount of at least one type selected from polypropylene homopolymer and propylene- ⁇ -olefin copolymer having a copolymerization ratio of ⁇ -olefin of 1.0 mol % or less in the total of the three layers, thereby exhibiting good thermal dimensional stability (e.g., low thermal shrinkage rate) and stiffness (e.g., high Young's modulus).
• the resin composition containing the polypropylene-based resin that constitutes the heat seal layer contains a predetermined amount of a propylene- ⁇ -olefin copolymer having a copolymerization ratio of ⁇ -olefin exceeding 1.0 mol %, thereby improving the heat seal strength. Furthermore, by adjusting the content of the polyethylene resin in the resin composition constituting the second layer to a predetermined amount, it is possible to improve the pinhole resistance due to bending.
• the unstretched polyolefin-based resin film includes a first layer made of a resin composition containing a polypropylene-based resin, a second layer made of a resin composition containing a polypropylene-based resin, and a heat seal layer made of a resin composition containing a polypropylene-based resin.
• the non-stretched polyolefin resin film of the present invention comprises a first layer (laminate layer), a second layer (core layer), and a heat seal layer in this order.
• the heat seal layer and the first layer (laminate layer) are layers located on the surface side of the film, and the second layer (core layer) is located therebetween.
• the first layer (laminate layer) is a layer suitable for bonding a base film such as a biaxially oriented polyamide film, and in practice, it is preferable to laminate the first layer (laminate layer) with the base film via an adhesive resin. In addition, the first layer (laminate layer) can be printed.
• the heat seal layer is a layer suitable for producing a package by overlapping two sheets of the above-mentioned laminate so that the polyolefin-based resin film of the obtained laminate is on the inside and heat sealing them.
• the unstretched polyolefin resin film of the present invention includes the first layer, the second layer, and the heat seal layer, it may also include other layers (for example, a layer provided on the surface of the first layer (e.g., an adhesive layer), a layer provided between the first layer and the second layer, and a layer provided between the second layer and the heat seal layer).
• the unstretched polyolefin resin film of the present invention comprises a first layer, a second layer, and a heat seal layer in this order, with no other layer being present between the first layer and the second layer, and no other layer being present between the second layer and the heat seal layer.
• the lower limit of the thickness of the non-stretched polyolefin resin film is preferably 15 ⁇ m, more preferably 20 ⁇ m, and further preferably 25 ⁇ m. When the film thickness is 15 ⁇ m or more, sufficient heat seal strength is easily obtained.
• the upper limit of the film thickness is preferably 80 ⁇ m, more preferably 70 ⁇ m, even more preferably 65 ⁇ m, and even more preferably 60 ⁇ m. When the film thickness is 80 ⁇ m or less, the film is not too stiff and is easy to process, and a suitable package is easily produced.
• the lower limit of the ratio of the thickness of the first layer to the thickness of the film is preferably 15%, more preferably 18%, and even more preferably 20%. By making the ratio of the thickness of the first layer 15% or more, it is easy to obtain a laminate strength.
• the upper limit of the ratio of the thickness of the first layer is preferably 35%, more preferably 27%, and even more preferably 25%. By making the ratio of the thickness of the first layer 35% or less, it is possible to maintain a high heat seal strength.
• the lower limit of the ratio of the thickness of the second layer to the film thickness is preferably 40%, more preferably 45%, and even more preferably 50%.
• the upper limit of the ratio of the thickness of the second layer is preferably 70%, more preferably 65%, and even more preferably 60%.
• the heat seal strength can be kept high.
• the lower limit of the ratio of the thickness of the heat seal layer to the thickness of the film is preferably 15%, more preferably 18%, and even more preferably 20%. By making the ratio of the thickness of the heat seal layer 15% or more, it is easy to obtain heat seal strength.
• the upper limit of the ratio of the thickness of the heat seal layer is preferably 35%, more preferably 27%, and even more preferably 25%. By making the ratio of the thickness of the heat seal layer 35% or less, it is possible to maintain high bending pinhole resistance.
• the first layer, second layer, and heat seal layer are each explained below.
• the first layer is made of a resin composition containing a polypropylene-based resin (A), and the polypropylene-based resin (A) contains at least one type selected from a polypropylene homopolymer (A1) and a propylene- ⁇ -olefin copolymer (A2). Furthermore, the resin composition constituting the first layer may contain a polyethylene resin (B) and an optional component (C).
• polypropylene resin (A) of the polypropylene-based resins (A), the polypropylene homopolymer (A1) may be any polypropylene having a given melt flow rate (MFR) and melting point.
• MFR melt flow rate
• the lower limit of the melt flow rate (MFR) (measured at 230° C. under a load of 2.16 kg) of the propylene homopolymer (A1) is preferably 2.0 g/10 min, more preferably 2.5 g/10 min, and even more preferably 3.0 g/10 min. If the melt flow rate of the propylene homopolymer (A1) is less than the above range, the uniformity of the film thickness may be impaired.
• the upper limit of the melt flow rate (MFR) of the propylene homopolymer (A1) is preferably 10.0 g/10 min, more preferably 9.0 g/10 min, and even more preferably 8.0 g/10 min. If the melt flow rate of the propylene homopolymer (A1) exceeds the above range, the uniformity of the film thickness may be impaired, and problems such as stickiness of the film and poor impact strength (impact strength) of the film may occur.
• the melt flow rate is measured, for example, based on JIS K-7210-1 (measurement conditions: 230° C., load 2.16 kg).
• the melting point of the propylene homopolymer (A1) is preferably 153°C or higher, more preferably 155°C or higher, even more preferably 157°C or higher, and preferably 170°C or lower, more preferably 167°C or lower, and even more preferably 164°C or lower.
• the melting point is measured, for example, using a differential scanning calorimeter.
• propylene homopolymer (A1) examples include propylene homopolymer FLX80E4 (MFR 7.5g/10min, melting point 164°C) manufactured by Sumitomo Chemical Co., Ltd., propylene homopolymer F-300SP (MFR 3.0g/10min, melting point 160°C) manufactured by Prime Polymer Co., Ltd., propylene homopolymer PP525P (MFR 3.0g/10min, melting point 161°C, plant-derived) manufactured by SABIC, and propylene homopolymer F300SP (MFR 3.0g/10min, melting point 161°C, petroleum-derived) manufactured by Prime Polymer Co., Ltd.
• propylene homopolymer FLX80E4 MFR 7.5g/10min, melting point 164°C
• propylene homopolymer F-300SP MFR 3.0g/10min, melting point 160°C
• propylene homopolymer PP525P MFR 3.0g/10min, melting point 161°C, plant
• the propylene- ⁇ -olefin copolymer (A2) may be a random copolymer or a block copolymer, and is preferably a random copolymer.
• Examples of the ⁇ -olefin monomer having 2 or 4 to 20 carbon atoms in the propylene- ⁇ -olefin copolymer (A2) include ethylene, butene-1, pentene-1, 4-methylpentene-1, hexene-1, and octene-1. From the viewpoint of heat sealability, the propylene- ⁇ -olefin copolymer (A2) preferably contains ethylene as an ⁇ -olefin monomer.
• the copolymerized component may be at least one type, and two or more types may be used as necessary.
• a propylene-ethylene copolymer is preferred
• a propylene-ethylene-butene random copolymer in which the main monomer is propylene and a certain amount of ethylene and butene are copolymerized is preferred.
• the monomer having the highest monomer composition ratio constituting the random copolymer is described first.
• the propylene- ⁇ -olefin copolymer (A2) may be derived from petroleum or may be derived from plants.
• the lower limit of the melt flow rate (MFR) of the propylene- ⁇ -olefin copolymer (A2) is preferably 2.0 g/10 min, more preferably 3.0 g/10 min, and further preferably 4.0 g/10 min. If the melt flow rate of the propylene- ⁇ -olefin copolymer (A2) is less than the above range, the uniformity of the film thickness may be impaired.
• the upper limit of the melt flow rate of the propylene- ⁇ -olefin copolymer (A2) is preferably 8.0 g/10 min, more preferably 7.5 g/10 min, and even more preferably 7.0 g/10 min. If the melt flow rate of the propylene- ⁇ -olefin copolymer (A2) exceeds the above range, problems such as stickiness of the film and poor impact strength (impact strength) of the film may occur.
• the melting point of the propylene- ⁇ -olefin copolymer (A2) is, for example, 140 to 165°C, preferably 142 to 163°C, and more preferably 144 to 161°C.
• Propylene- ⁇ -olefin copolymer (A2) is, for example, a propylene-ethylene random copolymer Prime Polypro F-724NPC (MFR 7.0g/10min at 230°C and a load of 2.16kg, melting point 142°C) manufactured by Prime Polymer Co., Ltd., a propylene-ethylene-butene random copolymer Sumitomo Noblen FL8115A (MFR 7.0g/10min at 230°C and a load of 2.16kg, melting point 148°C) manufactured by Sumitomo Chemical Co., Ltd., and a propylene-ethylene-butene random copolymer Prime Polypro F-794NV (MFR 7.0g/10min at 230°C and a load of 2.16kg, melting point 148°C) manufactured by Prime Polymer Co., Ltd.
• Prime Polypro F-724NPC MFR 7.0g/10min at 230°C and a load of 2.16kg, melting point 142°C
• Examples include propylene-ethylene-butene random copolymer Sumitomo Noblen FL6745A manufactured by Sumitomo Chemical Co., Ltd. (MFR 6.0 g/10 min at 230°C and a load of 2.16 kg, melting point 130°C), propylene- ⁇ -olefin copolymer PP621P manufactured by SABIC (MFR 8.1 g/10 min, melting point 140°C), and propylene-ethylene random copolymer WF836DG3 manufactured by Sumitomo Chemical Co., Ltd. (MFR 7.0 g/10 min, melting point 158°C, ethylene content 0.6 mol%, petroleum-derived).
• the propylene- ⁇ -olefin copolymer (A2) preferably includes at least one selected from propylene- ⁇ -olefin copolymers (A2-1) in which the copolymerization ratio of ⁇ -olefin is 1.0 mol% or less (the ⁇ -olefin has 2 or 4 to 20 carbon atoms) and propylene- ⁇ -olefin copolymers (A2-2) in which the copolymerization ratio of ⁇ -olefin is greater than 1.0 mol% (the ⁇ -olefin has 2 or 4 to 20 carbon atoms), and more preferably includes propylene- ⁇ -olefin copolymers (A2-2) in which the copolymerization ratio of ⁇ -olefin is 1.0 mol% or less (the ⁇ -olefin has 2 or 4 to 20 carbon atoms).
• ⁇ -olefin monomer having 2 or 4 to 20 carbon atoms in the propylene- ⁇ -olefin copolymer (A2-1) having a copolymerization ratio of ⁇ -olefin of 1.0 mol % or less ethylene, butene-1, pentene-1, 4-methylpentene-1, hexene-1, octene-1, etc. can be used.
• the propylene- ⁇ -olefin copolymer (A2-1) having a copolymerization ratio of olefin of 1.0 mol % or less is preferably a propylene-ethylene copolymer, a propylene-butene copolymer, a propylene-pentene copolymer, a propylene-methylpentene copolymer, a propylene-hexene copolymer, a propylene-octene copolymer, or the like, more preferably a propylene-ethylene copolymer or a propylene-butene copolymer, and even more preferably a propylene-ethylene copolymer.
• the copolymerization ratio of ⁇ -olefin (preferably ethylene) in the propylene- ⁇ -olefin copolymer ( ⁇ -olefin has 2 or 4 to 20 carbon atoms) (A2-1) is preferably 0.9 mol% or less, more preferably 0.8 mol% or less, even more preferably 0.7 mol% or less, and preferably 0.1 mol% or more, more preferably 0.15 mol% or more, even more preferably 0.2 mol% or more.
• the melting point of a propylene- ⁇ -olefin copolymer (wherein the ⁇ -olefin has 2 or 4 to 20 carbon atoms) having a copolymerization ratio of ⁇ -olefin of 1.0 mol% or less is preferably 153°C or more, more preferably 155°C or more, even more preferably 157°C or more, and preferably 170°C or less, more preferably 167°C or less, and even more preferably 164°C or less.
• propylene- ⁇ -olefin copolymer with a copolymerization ratio of ⁇ -olefin of 1.0 mol% or less is propylene-ethylene copolymer WF836DG3 (MFR 7.0 g/10 min, melting point 158°C, ethylene content 0.6 mol%) manufactured by Sumitomo Chemical Co., Ltd.
• Examples of the ⁇ -olefin monomer having 2 or 4 to 20 carbon atoms in the propylene- ⁇ -olefin copolymer (A2-2) having a copolymerization ratio of ⁇ -olefin exceeding 1.0 mol % include the same as those mentioned above.
• the propylene- ⁇ -olefin copolymer (A2-2) having a copolymerization ratio of olefin exceeding 1.0 mol % (the number of carbon atoms of the ⁇ -olefin is 2 or 4 to 20) is preferably a propylene-ethylene-butene copolymer, a propylene-ethylene-heptene copolymer, or the like, and more preferably a propylene-ethylene-butene copolymer.
• the copolymerization ratio of the ⁇ -olefin in the propylene- ⁇ -olefin copolymer (wherein the carbon number of the ⁇ -olefin is 2 or 4 to 20) (A2-2) is preferably 1.1 mol% or more in total, more preferably 1.5 mol% or more, even more preferably 2.0 mol% or more, even more preferably 3.0 mol% or more, and is preferably 9.0 mol% or less, more preferably 8.0 mol% or less, even more preferably 7.0 mol% or less, and even more preferably 6.0 mol% or less.
• the copolymerization ratio of ethylene in the propylene- ⁇ -olefin copolymer (wherein the ⁇ -olefin has 2 or 4 to 20 carbon atoms) (A2-2) is preferably 0.2 mol% or more, more preferably 0.4 mol% or more, even more preferably 0.6 mol% or more, even more preferably 0.8 mol% or more, and is preferably 2.0 mol% or less, more preferably 1.8 mol% or less, even more preferably 1.6 mol% or less, even more preferably 1.4 mol% or less.
• the copolymerization ratio of butene in the propylene- ⁇ -olefin copolymer (wherein the carbon number of the ⁇ -olefin is 2 or 4 to 20) (A2-2) is preferably 0.9 mol% or more, more preferably 1.2 mol% or more, even more preferably 1.5 mol% or more, even more preferably 1.8 mol% or more, and is preferably 7.0 mol% or less, more preferably 6.0 mol% or less, even more preferably 5.0 mol% or less, even more preferably 4.0 mol% or less.
• the melting point of a propylene- ⁇ -olefin copolymer (A2-2) in which the copolymerization ratio of ⁇ -olefin is more than 1.0 mol% (the carbon number of ⁇ -olefin is 2 or 4 to 20) is preferably lower than the melting point of a propylene- ⁇ -olefin copolymer (A2-1) in which the copolymerization ratio of ⁇ -olefin is 1.0 mol% or less, more preferably 135°C or more, even more preferably 137°C or more, even more preferably 140°C or more, preferably less than 153°C, more preferably 151°C or less, even more preferably 150°C or less.
• the polypropylene-based resin (A) contained in the first layer preferably contains a propylene homopolymer (A1) or a propylene- ⁇ -olefin copolymer (A2-1) having a copolymerization ratio of ⁇ -olefin of 1.0 mol % or less (the ⁇ -olefin has 2 or 4 to 20 carbon atoms).
• the polypropylene-based resin (A) contained in the first layer contains a propylene homopolymer (A1) or a propylene- ⁇ -olefin copolymer (A2-1) having a copolymerization ratio of ⁇ -olefin of 1.0 mol % or less (the ⁇ -olefin has 2 or 4 to 20 carbon atoms), it may contain a propylene- ⁇ -olefin copolymer (A2-2) having a copolymerization ratio of ⁇ -olefin of more than 1.0 mol % (the ⁇ -olefin has 2 or 4 to 20 carbon atoms).
• the resin composition containing the polypropylene-based resin (A) constituting the first layer contains 50% by weight or more of at least one polymer selected from a polypropylene homopolymer (A1) and a propylene- ⁇ -olefin copolymer (A2) (the ⁇ -olefin has 2 or 4 to 20 carbon atoms).
• the content of at least one selected from polypropylene homopolymer and propylene- ⁇ -olefin copolymer is 50% by weight or more, preferably 55% by weight or more, more preferably 60% by weight or more, even more preferably 70% by weight or more, and most preferably 75% by weight or more.
• the upper limit is 100% by weight, preferably 97% by weight or less, more preferably 90% by weight or less, even more preferably 85% by weight or less, and even more preferably 80% by weight or less.
• the content of propylene- ⁇ -olefin copolymer ( ⁇ -olefin has 2 or 4 to 20 carbon atoms) (A2-1) in which the copolymerization ratio of olefin is 1.0 mol% or less in the resin composition constituting the first layer is preferably 50% by weight or more, more preferably 55% by weight or more, even more preferably 60% by weight or more, even more preferably 70% by weight or more, particularly preferably 75% by weight or more, and preferably 100% by weight or less, more preferably 97% by weight or less, even more preferably 90% by weight or less, even more preferably 85% by weight or less, particularly preferably 80% by weight or less.
• the total content of the polypropylene homopolymer (A1) and the propylene- ⁇ -olefin copolymer (the ⁇ -olefin has 2 or 4 to 20 carbon atoms) (A2-1) in which the copolymerization ratio of ⁇ -olefin is 1.0 mol% or less is preferably 50% by weight or more, more preferably 55% by weight or more, even more preferably 60% by weight or more, particularly preferably 70% by weight or more, and most preferably 75% by weight or more, based on the resin composition containing the polypropylene resin constituting the first layer, from the viewpoint of thermal dimensional stability.
• the upper limit is 100% by weight, preferably 97% by weight or less, more preferably 90% by weight or less, even more preferably 85% by weight or less, and even more preferably 80% by weight or less.
• the propylene homopolymer (A1) or the propylene- ⁇ -olefin copolymer (A2) may be used alone or in combination of two or more kinds.
• the propylene homopolymer (A1) and the propylene- ⁇ -olefin copolymer (A2) may be derived from petroleum or may contain a plant-derived component. If the plant-derived component is contained, the effect of reducing the environmental load is further increased.
• Polyethylene resin (B) The resin composition constituting the first layer preferably contains a polyethylene-based resin (B) in addition to the polypropylene-based resin (A).
• the inclusion of the polyethylene resin (B) can improve pinhole resistance by bending. The effect is dramatically improved by including a polyethylene resin in the first layer as well, compared with the case where a polyethylene resin (preferably a linear low-density polyethylene resin) is included only in the second layer.
• the lower limit of the MFR (measured at 190°C and 2.16 kg) of the polyethylene resin (B) is, for example, 0.8 g/10 min, and preferably 1.5 g/10 min.
• the upper limit is, for example, 5.0 g/10 min, and preferably 4.5 g/10 min.
• the lower limit of the density of the polyethylene resin (B) is, for example, 910 kg/m 3 , preferably 912 kg/m 3 , and more preferably 915 kg/m 3. By setting the lower limit of the density of the polyethylene resin (B) to 910 kg/m 3 or more, good blocking resistance can be obtained.
• the upper limit of the density of the polyethylene resin (B) is, for example, 935 kg/m 3 , preferably 930 kg/cm 3 , and more preferably 925 kg/m 3. By setting the density of the polyethylene resin (B) to 935 kg/m 3 or less, good bag rupture resistance can be obtained.
• the density is measured, for example, by the D method of JIS K 7112:1999.
• the melting point of the polyethylene resin (B) is preferably lower than the melting point of the polypropylene resin (A), and is more preferably 115°C or higher, even more preferably 120°C or higher, even more preferably 122°C or higher, more preferably 135°C or lower, even more preferably 130°C or lower, and even more preferably 128°C or lower.
• the polyethylene resin (B) preferably contains at least one selected from a polyethylene homopolymer (B1) and a polyethylene- ⁇ -olefin copolymer (wherein the ⁇ -olefin has a carbon number of 3 to 12) (B2), and more preferably contains a polyethylene- ⁇ -olefin copolymer (wherein the ⁇ -olefin has a carbon number of 3 to 12) (B2).
• the ⁇ -olefin of the polyethylene- ⁇ -olefin copolymer may be any ⁇ -olefin derived from a fossil fuel, so long as it is generally called an ⁇ -olefin, and is preferably an ⁇ -olefin having 3 to 12 carbon atoms, such as propylene, butene-1, hexene-1, octene-1,4-methyl-1-pentene, etc.
• copolymers of ethylene and ⁇ -olefin examples include ethylene-hexene-1 copolymer, ethylene-butene-1 copolymer, ethylene-octene-1 copolymer, etc., and from the viewpoint of flex pinhole resistance, ethylene-hexene copolymer is preferred.
• the polyethylene resin (B) is preferably a linear low-density polyethylene resin, for example, an ethylene-hexene copolymer (plant-derived linear low-density polyethylene) SLH218 (MFR 2.3 g/10 min, density 916 kg/m 3 , melting point 126° C.) manufactured by Braskem, or an ethylene-hexene copolymer (petroleum-derived linear low-density polyethylene) FV201 (MFR 2.3 g/10 min, density 916 kg/m 3 ) manufactured by Sumitomo Chemical Co., Ltd.
• a linear low-density polyethylene resin for example, an ethylene-hexene copolymer (plant-derived linear low-density polyethylene) SLH218 (MFR 2.3 g/10 min, density 916 kg/m 3 , melting point 126° C.) manufactured by Braskem, or an ethylene-hexene copolymer (petroleum-derived linear low-
• the polyethylene resin (B) is preferably a plant-derived polyethylene resin from the viewpoint of reducing the environmental load.
• the plant-derived polyethylene resin can be produced by, for example, a high-pressure process, a solution process, a gas-phase process, or the like, using ethanol derived from sugarcane, corn, or the like as a raw material.
• An example of the plant-derived polyethylene resin is a copolymer of plant-derived ethylene and at least one ⁇ -olefin having 3 or more carbon atoms.
• the polyethylene resin (B) used in the first layer may be a mixture of two or more types of polyethylene resins, or may be a mixture of petroleum-derived polyethylene resins, but it is preferable that at least one type of polyethylene resin is plant-derived. If the polyethylene resin is plant-derived, the remaining impurities act as starting points for crystal nuclei, and the effect of reducing the heat shrinkage rate is increased.
• the content of the polyethylene resin (B) in the resin composition constituting the first layer is preferably 30% by weight or less, more preferably 27% by weight or less, and even more preferably 25% by weight or less, in terms of thermal dimensional stability.
• the content of the polyethylene resin (B) in the resin composition constituting the first layer is preferably 1% by weight or more, more preferably 3% by weight or more, even more preferably 5% by weight or more, even more preferably 15% by weight or more, and particularly preferably 20% by weight or more, in terms of bending pinhole resistance.
• the lower limit of the plant-derived carbon content in the plant-derived polyethylene resin is preferably 50% by weight, more preferably 80% by weight. When the content is 50% by weight or more, the carbon dioxide reduction effect is good.
• the upper limit of the content is preferably 100% by weight.
• the content of the polypropylene resin (A) and the polyethylene resin (B) in the resin composition constituting the first layer is preferably 91% by weight or more, more preferably 93% by weight or more, even more preferably 95% by weight or more, even more preferably 97% by weight or more, particularly preferably 99% by weight or more, and most preferably 100% by weight.
• the resin composition constituting the first layer may contain an optional component (C).
• Optional components (C) include antiblocking agents, lubricants, heat stabilizers, and the like.
• the resin composition containing the polyolefin resin constituting the first layer may contain an antiblocking agent.
• the antiblocking agent to be added is not particularly limited, but examples of the antiblocking agent that can be added include inorganic particles such as spherical silica, amorphous silica, zeolite, talc, mica, alumina, hydrotalcite, and aluminum borate, and organic particles such as polymethyl methacrylate and ultra-high molecular weight polyethylene.
• the content of the antiblocking agent in the resin composition containing the polypropylene-based resin constituting the first layer is preferably 3000 ppm or less, more preferably 2500 ppm or less, even more preferably 1000 ppm or less, particularly preferably 500 ppm or less, preferably 1 ppm or more, more preferably 10 ppm or more, and even more preferably 100 ppm or more, relative to the polyolefin-based resin of the layer to which the antiblocking agent is added.
• the resin composition containing the polyolefin resin constituting the first layer may contain an organic lubricant.
• the lubricating property and anti-blocking effect of the laminated film are improved, and the handling property of the film is improved. The reason for this is that the organic lubricant bleeds out and is present on the film surface, thereby exerting a lubricating effect and a mold releasing effect.
• the organic lubricant preferably has a melting point above room temperature. Examples of the organic lubricant include fatty acid amides and fatty acid esters.
• fatty acid amides such as oleic acid amide, erucic acid amide, behenic acid amide, ethylene bisoleic acid amide, hexamethylene bisoleic acid amide, ethylene bisoleic acid amide, etc.
• fatty acid esters such as glycerin fatty acid ester monoglyceride, sorbitan fatty acid ester, polyglycerin fatty acid ester, etc.
• the content of the organic lubricant is preferably 1500 ppm or less, more preferably 1000 ppm or less, and more preferably 10 ppm or more, and more preferably 50 ppm or more, relative to the polyolefin resin.
• the resin composition containing the polyolefin resin constituting the first layer may contain a heat stabilizer, which can suppress the generation of gels and the like that occur when the resin deteriorates due to heat or oxidation during melt extrusion.
• a heat stabilizer which can suppress the generation of gels and the like that occur when the resin deteriorates due to heat or oxidation during melt extrusion.
• heat stabilizers and antioxidants can be used. Specific examples include BASF's hindered phenol-based antioxidant (Irganox 1010), BASF's phosphite treatment stabilizer (Irgafos 168), and Sumitomo Chemical's phenol-phosphorus-based antioxidant (Sumilizer GP).
• Heat stabilizers may be used alone or in combination of two or more.
• the content of the heat stabilizer in the resin composition containing the polyolefin resin is preferably 1600 ppm or more, more preferably 1800 ppm or more, even more preferably 2000 ppm or more, and even more preferably 2500 ppm or more, in total, relative to the first layer. If it is less than the above, defects such as gels are likely to occur.
• the content is preferably 5000 ppm or less, more preferably 4000 ppm or less, and even more preferably 3500 ppm or less, in total, relative to the first layer. If it exceeds the above, the end surface of the film roll may turn red, impairing the appearance.
• the resin composition containing the polyolefin resin constituting the first layer may contain an appropriate amount of an antistatic agent, an antifogging agent, a neutralizing agent, a nucleating agent, a colorant, other additives, inorganic fillers, etc. in any layer as necessary, within the scope of the purpose of the present invention.
• neutralizing agents include calcium stearate.
• the second layer is made of a resin composition containing a polypropylene-based resin (A).
• the polypropylene-based resin (A) contains at least one type selected from a polypropylene homopolymer (A1) and a propylene- ⁇ -olefin copolymer (A2), and preferably contains at least one type selected from a polypropylene homopolymer (A1) and a propylene- ⁇ -olefin copolymer (A2-1) having a copolymerization ratio of ⁇ -olefin of 1 mol % or less.
• the resin composition constituting the second layer contains a polyethylene resin (B) and may contain an optional component (C).
• Polypropylene resin (A) of the polypropylene-based resins (A), the polypropylene homopolymer (A1) may be any one having a predetermined melt flow rate (MFR) and melting point.
• MFR melt flow rate
• the lower limit of the melt flow rate (MFR) (measured at 230° C. under a load of 2.16 kg) of the propylene homopolymer (A1) is preferably 2.0 g/10 min, more preferably 2.5 g/10 min, and even more preferably 3.0 g/10 min. If the melt flow rate of the propylene homopolymer (A1) is less than the above range, the uniformity of the film thickness may be impaired.
• the upper limit of the melt flow rate (MFR) of the propylene homopolymer (A1) is preferably 10.0 g/10 min, more preferably 9.0 g/10 min, and even more preferably 8.0 g/10 min. If the melt flow rate of the propylene homopolymer (A1) exceeds the above range, the uniformity of the film thickness may be impaired, and problems such as stickiness of the film and poor impact strength (impact strength) of the film may occur.
• the melt flow rate is measured based on JIS K-7210-1 (measurement conditions: 230° C., load 2.16 kg).
• the melting point of the propylene homopolymer (A1) is preferably 153°C or higher, more preferably 155°C or higher, even more preferably 157°C or higher, and preferably 170°C or lower, more preferably 167°C or lower, and even more preferably 164°C or lower.
• propylene homopolymer (A1) examples include propylene homopolymer FLX80E4 (MFR 7.5g/10min, melting point 164°C) manufactured by Sumitomo Chemical Co., Ltd., propylene homopolymer F-300SP (MFR 3.0g/10min, melting point 160°C) manufactured by Prime Polymer Co., Ltd., propylene homopolymer PP525P (MFR 3.0g/10min, melting point 161°C, plant-derived) manufactured by SABIC, and propylene homopolymer F300SP (MFR 3.0g/10min, melting point 161°C, petroleum-derived) manufactured by Prime Polymer Co., Ltd.
• propylene homopolymer FLX80E4 MFR 7.5g/10min, melting point 164°C
• propylene homopolymer F-300SP MFR 3.0g/10min, melting point 160°C
• propylene homopolymer PP525P MFR 3.0g/10min, melting point 161°C, plant
• the propylene- ⁇ -olefin copolymer (A2) may be a random copolymer or a block copolymer, and is preferably a random copolymer.
• Examples of the ⁇ -olefin monomer having 2 or 4 to 20 carbon atoms in the propylene- ⁇ -olefin copolymer (A2) include ethylene, butene-1, pentene-1, 4-methylpentene-1, hexene-1, and octene-1. From the viewpoint of heat sealability, the propylene- ⁇ -olefin copolymer (A2) preferably contains ethylene as an ⁇ -olefin monomer.
• the copolymerized component may be at least one type, and two or more types may be used as necessary.
• a propylene-ethylene copolymer is preferred
• a propylene-ethylene-butene random copolymer in which the main monomer is propylene and a certain amount of ethylene and butene are copolymerized is preferred.
• the monomer having the highest monomer composition ratio constituting the random copolymer is described first.
• the propylene- ⁇ -olefin copolymer (A2) may be derived from petroleum or may be derived from plants.
• the lower limit of the melt flow rate (MFR) of the propylene- ⁇ -olefin copolymer (A2) is preferably 2.0 g/10 min, more preferably 3.0 g/10 min, and further preferably 4.0 g/10 min. If the melt flow rate of the propylene- ⁇ -olefin copolymer (A2) is less than the above range, the uniformity of the film thickness may be impaired.
• the upper limit of the melt flow rate of the propylene- ⁇ -olefin copolymer (A2) is preferably 8.0 g/10 min, more preferably 7.5 g/10 min, and even more preferably 7.0 g/10 min. If the melt flow rate of the propylene- ⁇ -olefin copolymer (A2) exceeds the above range, problems such as stickiness of the film and poor impact strength (impact strength) of the film may occur.
• the melting point of the propylene- ⁇ -olefin copolymer (A2) is, for example, 140 to 165°C, preferably 142 to 163°C, and more preferably 144 to 161°C.
• Propylene- ⁇ -olefin copolymer (A2) is, for example, a propylene-ethylene random copolymer Prime Polypro F-724NPC (MFR 7.0 g/10 min at 230°C and a load of 2.16 kg, melting point 142°C) manufactured by Prime Polymer Co., Ltd., a propylene-ethylene-butene random copolymer Sumitomo Noblen FL8115A (MFR 7.0 g/10 min at 230°C and a load of 2.16 kg, melting point 148°C) manufactured by Sumitomo Chemical Co., Ltd., and a propylene-ethylene-butene random copolymer Prime Polypro F-794NV (MFR 7.0 g/10 min at 230°C and a load of 2.16 kg, melting point 148°C) manufactured by Prime Polymer Co., Ltd.
• Prime Polypro F-724NPC MFR 7.0 g/10 min at 230°C and a load of 2.16 kg, melting point 142
• Examples include propylene-ethylene-butene random copolymer Sumitomo Noblen FL6745A manufactured by Sumitomo Chemical Co., Ltd. (MFR 6.0 g/10 min at 230°C and a load of 2.16 kg, melting point 130°C), propylene- ⁇ -olefin copolymer PP621P manufactured by SABIC (MFR 8.1 g/10 min, melting point 140°C), and propylene-ethylene random copolymer WF836DG3 manufactured by Sumitomo Chemical Co., Ltd. (MFR 7.0 g/10 min, melting point 158°C, ethylene content 0.6 mol%, petroleum-derived).
• the propylene- ⁇ -olefin copolymer (A2) preferably includes at least one selected from propylene- ⁇ -olefin copolymers (A2-1) in which the copolymerization ratio of ⁇ -olefin is 1.0 mol% or less (the ⁇ -olefin has 2 or 4 to 20 carbon atoms) and propylene- ⁇ -olefin copolymers (A2-2) in which the copolymerization ratio of ⁇ -olefin is greater than 1.0 mol% (the ⁇ -olefin has 2 or 4 to 20 carbon atoms), and more preferably includes propylene- ⁇ -olefin copolymers (A2-2) in which the copolymerization ratio of ⁇ -olefin is 1.0 mol% or less (the ⁇ -olefin has 2 or 4 to 20 carbon atoms).
• ⁇ -olefin monomer having 2 or 4 to 20 carbon atoms in the propylene- ⁇ -olefin copolymer (A2-1) having a copolymerization ratio of ⁇ -olefin of 1.0 mol % or less ethylene, butene-1, pentene-1, 4-methylpentene-1, hexene-1, octene-1, etc. can be used.
• the propylene- ⁇ -olefin copolymer (A2-1) having a copolymerization ratio of olefin of 1.0 mol % or less is preferably a propylene-ethylene copolymer, a propylene-butene copolymer, a propylene-pentene copolymer, a propylene-methylpentene copolymer, a propylene-hexene copolymer, a propylene-octene copolymer, or the like, more preferably a propylene-ethylene copolymer or a propylene-butene copolymer, and even more preferably a propylene-ethylene copolymer.
• the copolymerization ratio of ⁇ -olefin (preferably ethylene) in the propylene- ⁇ -olefin copolymer ( ⁇ -olefin has 2 or 4 to 20 carbon atoms) (A2-1) is preferably 0.9 mol% or less, more preferably 0.8 mol% or less, even more preferably 0.7 mol% or less, and preferably 0.1 mol% or more, more preferably 0.15 mol% or more, even more preferably 0.2 mol% or more.
• the lower limit of the melting point of a propylene- ⁇ -olefin copolymer (wherein the ⁇ -olefin has 2 or 4 to 20 carbon atoms) having a copolymerization ratio of ⁇ -olefin of 1.0 mol% or less is preferably 153°C or more, more preferably 155°C or more, even more preferably 157°C or more, preferably 170°C or less, more preferably 167°C or less, and even more preferably 164°C or less.
• propylene- ⁇ -olefin copolymer with a copolymerization ratio of ⁇ -olefin of 1.0 mol% or less is propylene-ethylene copolymer WF836DG3 (MFR 7.0 g/10 min, melting point 158°C, ethylene content 0.6 mol%) manufactured by Sumitomo Chemical Co., Ltd.
• the polypropylene-based resin (A) contained in the second layer preferably contains a propylene homopolymer (A1) or a propylene- ⁇ -olefin copolymer (A2-1) in which the copolymerization ratio of ⁇ -olefin is 1.0 mol% or less (the number of carbon atoms of the ⁇ -olefin is 2 or 4 to 20).
• the resin composition containing the polypropylene-based resin (A) constituting the second layer contains 50% by weight or more of at least one polymer selected from a polypropylene homopolymer (A1) and a propylene- ⁇ -olefin copolymer (A2) (the ⁇ -olefin has 2 or 4 to 20 carbon atoms).
• the content of at least one selected from polypropylene homopolymer and propylene- ⁇ -olefin copolymer is 50% by weight or more, preferably 55% by weight or more, more preferably 60% by weight or more, even more preferably 70% by weight or more, still more preferably 75% by weight or more, and most preferably 80% by weight or more.
• the upper limit is 90% by weight or less, preferably 88% by weight or less, and even more preferably 85% by weight or less.
• the content of propylene- ⁇ -olefin copolymer ( ⁇ -olefin has 2 or 4 to 20 carbon atoms) (A2-1) in the resin composition constituting the second layer, in which the copolymerization ratio of olefin is 1.0 mol% or less, is preferably 50% by weight or more, more preferably 55% by weight or more, even more preferably 60% by weight or more, even more preferably 70% by weight or more, particularly preferably 75% by weight or more, and is preferably 90% by weight or less, more preferably 88% by weight or less, and even more preferably 85% by weight or less.
• the content of the propylene- ⁇ -olefin copolymer (A2-2) having a copolymerization ratio of olefin exceeding 1.0 mol% (the ⁇ -olefin has 2 or 4 to 20 carbon atoms) in the resin composition constituting the second layer is preferably 0 wt% or more, more preferably 1 wt% or more, even more preferably 5 wt% or more, still more preferably 10 wt% or more, and is preferably 30 wt% or less, more preferably 28 wt% or less, even more preferably 25 wt% or less, and still more preferably 22 wt% or less.
• the polypropylene resin (A) contained in the second layer preferably does not contain a propylene- ⁇ -olefin copolymer (A2-2) having a copolymerization ratio of ⁇ -olefin exceeding 1.0 mol % ( ⁇ -olefin having 2 or 4 to 20 carbon atoms).
• the resin composition containing the polypropylene-based resin constituting the second layer preferably contains a total of 55% by weight or more of at least one selected from polypropylene homopolymer and propylene- ⁇ -olefin copolymer (the number of carbon atoms of ⁇ -olefin is 2 or 4 to 20) in which the copolymerization ratio of ⁇ -olefin is 1.0 mol% or less.
• the content is, for example, 90% by weight or less, preferably 85% by weight or less, 80% by weight or less, or 70% by weight or less.
• the propylene homopolymer (A1) or the propylene- ⁇ -olefin copolymer (A2) may be used alone or in combination of two or more kinds.
• the propylene homopolymer (A1) and the propylene- ⁇ -olefin copolymer (A2) may be derived from petroleum or may contain a plant-derived component. If the plant-derived component is contained, the effect of reducing the environmental load is further enhanced.
• Polyethylene resin (B) The resin composition constituting the second layer contains a polyethylene resin (B).
• the inclusion of the polyethylene resin (B) can improve pinhole resistance by bending. The effect is dramatically improved by including a polyethylene resin in the first layer as well, compared with the case where a polyethylene resin (preferably a linear low-density polyethylene resin) is included only in the second layer.
• the lower limit of the MFR (measured at 190°C and 2.18 kg) of the polyethylene resin (B) is, for example, 0.8 g/10 min, and preferably 1.5 g/10 min.
• the upper limit is, for example, 5.0 g/10 min, and preferably 4.5 g/10 min.
• the lower limit of the density of the polyethylene resin (B) is, for example, 910 kg/m 3 , preferably 912 kg/m 3 , and more preferably 915 kg/m 3. By setting the lower limit of the density of the polyethylene resin (B) to 910 kg/m 3 or more, good blocking resistance can be obtained.
• the upper limit is, for example, 935 kg/m 3 , preferably 930 kg/cm 3 , and more preferably 925 kg/m 3. By setting the density of the polyethylene resin (B) to 935 kg/m 3 or less, good bag rupture resistance can be obtained.
• the melting point of the polyethylene resin (B) is preferably lower than the melting point of the polypropylene resin (A), and is more preferably 115°C or higher, even more preferably 120°C or higher, even more preferably 122°C or higher, more preferably 135°C or lower, even more preferably 130°C or lower, and even more preferably 128°C or lower.
• the polyethylene resin (B) preferably contains at least one selected from a polyethylene homopolymer (B1) and a polyethylene- ⁇ -olefin copolymer (wherein the ⁇ -olefin has a carbon number of 3 to 12) (B2), and more preferably contains a polyethylene- ⁇ -olefin copolymer (wherein the ⁇ -olefin has a carbon number of 3 to 12) (B2).
• the ⁇ -olefin of the polyethylene- ⁇ -olefin copolymer may be any ⁇ -olefin derived from a fossil fuel, so long as it is generally called an ⁇ -olefin, and is preferably an ⁇ -olefin having 3 to 12 carbon atoms, such as propylene, butene-1, hexene-1, octene-1,4-methyl-1-pentene, etc.
• copolymers of ethylene and ⁇ -olefin examples include ethylene-hexene-1 copolymer, ethylene-butene-1 copolymer, ethylene-octene-1 copolymer, etc., and from the viewpoint of flex pinhole resistance, ethylene-hexene copolymer is preferred.
• the polyethylene resin (B) is preferably a linear low-density polyethylene resin, for example, ethylene-hexene copolymer (plant-derived linear low-density polyethylene) SLH218 (MFR 2.3 g/10 min, density 916 kg/ m3 , melting point 126°C) manufactured by Braskem, and ethylene-hexene copolymer (petroleum-derived linear low-density polyethylene) FV201 (MFR 2.3 g/10 min, density 916 kg/ m3 ) manufactured by Sumitomo Chemical Co., Ltd.
• ethylene-hexene copolymer plant-derived linear low-density polyethylene
• SLH218 MFR 2.3 g/10 min, density 916 kg/ m3 , melting point 126°C
• FV201 ethylene-hexene copolymer (petroleum-derived linear low-density polyethylene) FV201 (MFR 2.3 g/10 min, density 9
• the polyethylene resin (B) is preferably a plant-derived polyethylene resin.
• the plant-derived polyethylene resin can be produced by, for example, a high-pressure process, a solution process, a gas-phase process, or the like, using ethanol derived from sugarcane, corn, or the like.
• Examples of the plant-derived polyethylene resin include a copolymer of plant-derived ethylene and at least one ⁇ -olefin having 3 or more carbon atoms.
• the polyethylene resin (B) used in the second layer may be a mixture of two or more polyethylene resins, or may be a petroleum-derived polyethylene resin, but it is preferable that at least one of the polyethylene resins is plant-derived. If the polyethylene resin is plant-derived, the remaining impurities act as the starting point for crystal nuclei, and the effect of reducing the heat shrinkage rate is increased.
• the content of the polyethylene resin (B) in the resin composition constituting the second layer is 10% by weight or more, preferably 12% by weight or more, and more preferably 15% by weight or more, in terms of pinhole resistance due to bending.
• the content of the polyethylene resin (B) in the resin composition constituting the second layer is 45% by weight or less, preferably 30% by weight or less, more preferably 25% by weight or less, and most preferably 20% by weight or less, in terms of thermal dimensional stability.
• the lower limit of the plant-derived carbon content in the plant-derived polyethylene resin is preferably 50% by weight, more preferably 80% by weight. When the content is 50% by weight or more, the carbon dioxide reduction effect is good.
• the upper limit of the content is preferably 100% by weight.
• the content of the polypropylene resin (A) and the polyethylene resin (B) in the resin composition constituting the second layer is preferably 91% by weight or more, more preferably 93% by weight or more, even more preferably 95% by weight or more, even more preferably 97% by weight or more, particularly preferably 99% by weight or more, and most preferably 100% by weight.
• the resin composition constituting the second layer may contain an optional component (C).
• Optional components (C) include antiblocking agents, lubricants, heat stabilizers, and the like.
• the resin composition containing the polyolefin resin constituting the second layer may contain an antiblocking agent.
• the antiblocking agent to be added is not particularly limited, but examples of the antiblocking agent that can be added include inorganic particles such as spherical silica, amorphous silica, zeolite, talc, mica, alumina, hydrotalcite, and aluminum borate, and organic particles such as polymethyl methacrylate and ultra-high molecular weight polyethylene.
• the content of the antiblocking agent contained in the resin composition containing the polypropylene resin constituting the second layer is preferably 3000 ppm or less, more preferably 2500 ppm or less, even more preferably 1000 ppm or less, particularly preferably 500 ppm or less, preferably 1 ppm or more, more preferably 10 ppm or more, and even more preferably 100 ppm or more, relative to the polyolefin resin of the layer to which it is added.
• the content of the antiblocking agent is 3000 ppm or less, transparency is good.
• the resin composition containing the polyolefin resin constituting the second layer may contain an organic lubricant.
• the lubricating property and anti-blocking effect of the laminated film are improved, and the handling property of the film is improved. The reason for this is that the organic lubricant bleeds out and is present on the film surface, thereby exerting a lubricating effect and a mold releasing effect.
• the organic lubricant preferably has a melting point above room temperature. Examples of the organic lubricant include fatty acid amides and fatty acid esters.
• fatty acid amides such as oleic acid amide, erucic acid amide, behenic acid amide, ethylene bisoleic acid amide, hexamethylene bisoleic acid amide, ethylene bisoleic acid amide, etc.
• fatty acid esters such as glycerin fatty acid ester monoglyceride, sorbitan fatty acid ester, polyglycerin fatty acid ester, etc.
• the content of the organic lubricant is preferably 1500 ppm or less, more preferably 1000 ppm or less, more preferably 10 ppm or more, and more preferably 50 ppm or more, based on the polyolefin resin. By making it 1500 ppm or less, blocking is unlikely to occur even if it is stored in a place exposed to high temperatures such as a warehouse in summer. In addition, it is preferably 200 ppm or more, more preferably 250 ppm or more. By making it 200 ppm or more, good slip properties can be obtained.
• the polyolefin-based resin composition constituting the second layer may contain a heat stabilizer, which can suppress the generation of gels and the like that occur when the resin deteriorates due to heat or oxidation during melt extrusion.
• a heat stabilizer which can suppress the generation of gels and the like that occur when the resin deteriorates due to heat or oxidation during melt extrusion.
• heat stabilizers and antioxidants can be used. Specific examples include BASF's hindered phenol-based antioxidant (Irganox 1010), BASF's phosphite treatment stabilizer (Irgafos 168), and Sumitomo Chemical's phenol-phosphorus-based antioxidant (Sumilizer GP).
• Heat stabilizers may be used alone or in combination of two or more.
• the content of the heat stabilizer in the resin composition containing the polyolefin resin is preferably 1600 ppm or more, more preferably 1800 ppm or more, and even more preferably 2000 ppm or more, in total, relative to the second layer. If it is less than the above, defects such as gels are likely to occur. Moreover, the content is preferably 5000 ppm or less, more preferably 4000 ppm or less, and even more preferably 3500 ppm or less, in total, relative to the second layer. If it exceeds the above, the end surface of the film roll may turn red, impairing the appearance.
• the resin composition containing the polyolefin resin constituting the second layer may contain an appropriate amount of an antistatic agent, an antifogging agent, a neutralizing agent, a nucleating agent, a colorant, other additives, inorganic fillers, etc. in any layer as necessary, within the scope of not impairing the object of the present invention.
• neutralizing agents include calcium stearate, etc.
• the resin can be reused without compromising heat seal strength, reducing the environmental impact.
• the heat seal layer is made of a resin composition containing a polypropylene-based resin, and the polypropylene-based resin (A) contains a polypropylene homopolymer (A1) and a propylene- ⁇ -olefin copolymer (A2). Furthermore, if the heat seal layer contains a polyethylene-based resin such as linear low-density polyethylene, the heat seal strength may decrease due to poor compatibility with each other. Therefore, it is preferable that the heat seal layer does not contain a polyethylene-based resin (B). Furthermore, the resin composition constituting the heat seal layer may contain an optional component (C).
• MFR melt flow rate
• the slipperiness can be improved.
• the propylene homopolymer to be used is not particularly limited, but isotactic polypropylene is preferable from the viewpoint of blocking resistance.
• the propylene homopolymer may be derived from petroleum or may be derived from plants.
• the lower limit of the melt flow rate (MFR) (measured at 230° C. under a load of 2.16 kg) of the propylene homopolymer (A1) is preferably 2.0 g/10 min, more preferably 2.5 g/10 min, and even more preferably 3.0 g/10 min. If the melt flow rate of the propylene homopolymer (A1) is less than the above range, the uniformity of the film thickness may be impaired.
• the upper limit of the melt flow rate (MFR) of the propylene homopolymer (A1) is preferably 10.0 g/10 min, more preferably 9.0 g/10 min, and even more preferably 8.0 g/10 min.
• melt flow rate of the propylene homopolymer (A1) exceeds the above range, the uniformity of the film thickness may be impaired, and problems such as stickiness of the film and poor impact strength (impact strength) of the film may occur.
• the melt flow rate is measured, for example, based on JIS K-7210-1 (measurement conditions: 230° C., load 2.16 kg).
• propylene homopolymer (A1) examples include propylene homopolymer FLX80E4 (MFR 7.5 g/10 min, melting point 164°C) manufactured by Sumitomo Chemical Co., Ltd. and propylene homopolymer F-300SP (MFR 3.0 g/10 min, melting point 160°C) manufactured by Prime Polymer Co., Ltd.
• the propylene- ⁇ -olefin copolymer (A2) may be a random copolymer or a block copolymer, and is preferably a random copolymer.
• Examples of the ⁇ -olefin monomer having 2 or 4 to 20 carbon atoms in the propylene- ⁇ -olefin copolymer (A2) include ethylene, butene-1, pentene-1, 4-methylpentene-1, hexene-1, and octene-1. From the viewpoint of heat sealability, the propylene- ⁇ -olefin copolymer (A2) preferably contains ethylene as an ⁇ -olefin monomer.
• the copolymerized component may be at least one type, and two or more types may be used as necessary.
• a propylene-ethylene copolymer is preferred
• a propylene-ethylene-butene random copolymer in which the main monomer is propylene and a certain amount of ethylene and butene are copolymerized is preferred.
• the monomer having the highest monomer composition ratio constituting the random copolymer is described first.
• the propylene- ⁇ -olefin copolymer (A2) may be derived from petroleum or may be derived from plants.
• the lower limit of the melt flow rate (MFR) of the propylene- ⁇ -olefin copolymer (A2) is preferably 2.0 g/10 min, more preferably 3.0 g/10 min, and further preferably 4.0 g/10 min. If the melt flow rate of the propylene- ⁇ -olefin copolymer (A2) is less than the above range, the uniformity of the film thickness may be impaired.
• the upper limit of the melt flow rate of the propylene- ⁇ -olefin copolymer (A2) is preferably 8.0 g/10 min, more preferably 7.5 g/10 min, and even more preferably 7.0 g/10 min. If the melt flow rate of the propylene- ⁇ -olefin copolymer (A2) exceeds the above range, problems such as stickiness of the film and poor impact strength (impact strength) of the film may occur.
• the melting point of the propylene- ⁇ -olefin copolymer (A2) contained in the heat seal layer is preferably lower than the melting point of the propylene- ⁇ -olefin copolymer (A2) contained in the first and second layers, and is more preferably 120 to 165°C, even more preferably 125 to 163°C, and even more preferably 130 to 160°C.
• Propylene- ⁇ -olefin copolymer (A2) is, for example, a propylene-ethylene random copolymer Prime Polypro F-724NPC (MFR 7.0 g/10 min at 230°C and a load of 2.16 kg, melting point 142°C) manufactured by Prime Polymer Co., Ltd., a propylene-ethylene-butene random copolymer Sumitomo Noblen FL8115A (MFR 7.0 g/10 min at 230°C and a load of 2.16 kg, melting point 148°C) manufactured by Sumitomo Chemical Co., Ltd., and a propylene-ethylene-butene random copolymer Sumitomo Noblen FL8115A (MFR 7.0 g/10 min at 230°C and a load of 2.16 kg, melting point 148°C) manufactured by Prime Polymer Co., Ltd.
• Prime Polypro F-724NPC MFR 7.0 g/10 min at 230°C and a load of 2.16 kg,
• Examples include the copolymer Prime Polypro F-794NV (MFR 5.7 g/10 min at 230°C and a load of 2.16 kg, melting point 134°C), propylene-ethylene-butene random copolymer Sumitomo Noblen FL6745A manufactured by Sumitomo Chemical Co., Ltd. (MFR 6.0 g/10 min at 230°C and a load of 2.16 kg, melting point 130°C, ethylene content 4.0 mol%, butene content 3.6 mol%), and propylene- ⁇ -olefin copolymer PP621P manufactured by SABIC (MFR 8.1 g/min, melting point 140°C).
• the propylene- ⁇ -olefin copolymer (A2) preferably includes at least one selected from propylene- ⁇ -olefin copolymers (A2-1) in which the copolymerization ratio of ⁇ -olefin is 1.0 mol% or less (the number of carbon atoms of ⁇ -olefin is 2 or 4 to 20) and propylene- ⁇ -olefin copolymers (A2-2) in which the copolymerization ratio of ⁇ -olefin is greater than 1.0 mol%, and more preferably includes propylene- ⁇ -olefin copolymers (A2-2) in which the copolymerization ratio of ⁇ -olefin is greater than 1.0 mol% (the number of carbon atoms of ⁇ -olefin is 2 or 4 to 20).
• Examples of the propylene- ⁇ -olefin copolymer (A2-1) having an ⁇ -olefin copolymerization ratio of 1 mol % or less include those described for the first and second layers.
• the ⁇ -olefin monomer having 2 or 4 to 20 carbon atoms in the propylene- ⁇ -olefin copolymer (A2-2) constituting the heat seal layer in which the copolymerization ratio of the ⁇ -olefin exceeds 1.0 mol % ethylene, butene-1, pentene-1, 4-methylpentene-1, hexene-1, octene-1, etc. can be used.
• the propylene- ⁇ -olefin copolymer (A2-2) having a copolymerization ratio of the ⁇ -olefin exceeding 1.0 mol% preferably contains ethylene from the viewpoint of heat sealability.
• the copolymerized component may be at least one type, and two or more types may be used as necessary.
• a propylene-ethylene copolymer is preferred
• a propylene-ethylene-butene random copolymer in which the main monomer is propylene and a certain amount of ethylene and butene are copolymerized is preferred.
• the propylene- ⁇ -olefin copolymer (A2-2) having a copolymerization ratio of olefin exceeding 1.0 mol % (the number of carbon atoms of the ⁇ -olefin is 2 or 4 to 20) is preferably a propylene-ethylene-butene copolymer, a propylene-ethylene-heptene copolymer, or the like, and more preferably a propylene-ethylene-butene copolymer.
• the monomer having the largest monomer composition ratio constituting the random copolymer is described first.
• the propylene- ⁇ -olefin random copolymer may be derived from petroleum or may be derived from plants.
• the melting point of the propylene- ⁇ -olefin copolymer (A2-2) having a copolymerization ratio of the ⁇ -olefin contained in the heat seal layer exceeding 1.0 mol% is preferably lower than the melting point of the propylene- ⁇ -olefin copolymer (A2-2) having a copolymerization ratio of the ⁇ -olefin contained in the first and second layers exceeding 1.0 mol% (the carbon number of the ⁇ -olefin is 2 or 4 to 20) in terms of heat sealability, more preferably 120°C or higher, even more preferably 123°C or higher, even more preferably 125°C or higher, more preferably 145°C or lower, even more preferably 140°C or lower, and even more preferably 135°C or lower.
• the propylene- ⁇ -olefin copolymer used may be a mixture of two or more polypropylenes, and at least one of them is preferably a plant-derived polypropylene.
• the lower limit of the melt flow rate (MFR) (measured at 230°C and 2.18 kg) of the propylene- ⁇ -olefin copolymer (A2-2) having a copolymerization ratio of ⁇ -olefin exceeding 1.0 mol% is preferably 2.0 g/10 min, more preferably 3.0 g/10 min, and even more preferably 4.0 g/10 min. If it is less than the above, the uniformity of the film thickness may be impaired.
• the upper limit of the melt flow rate of the propylene- ⁇ -olefin copolymer (A2-2) having a copolymerization ratio of ⁇ -olefin exceeding 1.0 mol % is preferably 10.0 g/10 min, more preferably 9.0 g/10 min, and even more preferably 8.0 g/10 min. If the upper limit is exceeded, problems such as stickiness of the film and poor impact strength (impact strength) of the film may occur.
• propylene- ⁇ -olefin copolymers (A2-2) having a copolymerization ratio of ⁇ -olefin exceeding 1.0 mol% examples include propylene-ethylene random copolymers (Prime Polypro F-724NPC manufactured by Prime Polymer Co., Ltd., MFR 7.0 g/10 min at 230° C. and a load of 2.16 kg, melting point 142° C.), propylene-ethylene-butene random copolymers (Prime Polypro F-794NV manufactured by Prime Polymer Co., Ltd., MFR 5.7 g/10 min at 230° C.
• the ⁇ -olefin copolymerization ratio of the propylene- ⁇ -olefin copolymer (A2-2) contained in the heat seal layer is preferably higher than the ⁇ -olefin copolymerization ratio of the propylene- ⁇ -olefin copolymer (A2) contained in the first and second layers, from the viewpoints of lowering the heat seal initiation temperature and heat seal strength.
• the copolymerization ratio of the olefin in the propylene- ⁇ -olefin copolymer (wherein the ⁇ -olefin has 2 or 4 to 20 carbon atoms) (A2-2) is, in total, preferably 1.5 mol% or more, more preferably 2.0 mol% or more, even more preferably 4.0 mol% or more, even more preferably 6.0 mol% or more, and is preferably 15.0 mol% or less, more preferably 10.0 mol% or less, even more preferably 9.0 mol% or less, and even more preferably 8.0 mol% or less, from the viewpoint of heat seal strength.
• the copolymerization ratio of ethylene in the propylene- ⁇ -olefin copolymer ( ⁇ -olefin has 2 or 4 to 20 carbon atoms) (A2-2) is preferably 0.8 mol% or more, more preferably 1.2 mol% or more, even more preferably 1.5 mol% or more, even more preferably 1.8 mol% or more, from the viewpoint of heat seal strength, and is preferably 7.0 mol% or less, more preferably 6.5 mol% or less, even more preferably 6.0 mol% or less, even more preferably 5.5 mol% or less.
• the copolymerization ratio of butene in the propylene- ⁇ -olefin copolymer ( ⁇ -olefin has 2 or 4 to 20 carbon atoms) (A2-2) is preferably 0.7 mol% or more, more preferably 1.1 mol% or more, even more preferably 1.4 mol% or more, even more preferably 1.7 mol% or more, from the viewpoint of heat seal strength, and is preferably 6.5 mol% or less, more preferably 6.0 mol% or less, even more preferably 5.0 mol% or less, even more preferably 4.0 mol% or less.
• the polypropylene-based resin (A) contained in the heat seal layer contains a propylene- ⁇ -olefin copolymer (A2-2) in which the copolymerization ratio of ⁇ -olefin is greater than 1.0 mol% (the ⁇ -olefin has 2 or 4 to 20 carbon atoms), it may contain a propylene homopolymer (A1) or a propylene- ⁇ -olefin copolymer (A2-1) in which the copolymerization ratio of ⁇ -olefin is 1.0 mol% or less (the ⁇ -olefin has 2 or 4 to 20 carbon atoms).
• the resin composition containing the polypropylene resin that constitutes the heat seal layer contains 50% by weight or more of propylene- ⁇ -olefin copolymer ( ⁇ -olefin has 2 or 4 to 20 carbon atoms) (A2).
• the resin composition containing a polypropylene-based resin that constitutes the heat seal layer contains a total of 65% by weight or more of a propylene- ⁇ -olefin copolymer (the ⁇ -olefin has 2 or 4 to 20 carbon atoms) having a copolymerization ratio of ⁇ -olefin exceeding 1.0 mol%.
• the content of propylene- ⁇ -olefin copolymer (the ⁇ -olefin has 2 or 4 to 20 carbon atoms) having a copolymerization ratio of ⁇ -olefin exceeding 1.0 mol% is, for example, 65% by weight or more, preferably 70% by weight or more, more preferably 80% by weight or more, even more preferably 90% by weight or more, even more preferably 95% by weight or more, and particularly preferably 97% by weight or more.
• the upper limit is 100% by weight.
• the content of propylene homopolymer (A) in the resin composition constituting the heat seal layer is preferably 10% by weight or less, more preferably 5% by weight or less, even more preferably 3% by weight or less, and particularly preferably 0% by weight.
• the melting point of the propylene- ⁇ -olefin copolymer (wherein the ⁇ -olefin has 2 or 4 to 20 carbon atoms) contained in the polypropylene resin of the heat seal layer is 145°C or lower, and it is preferable that the content of the propylene- ⁇ -olefin copolymer is 70% by weight or higher in the resin composition constituting the heat seal layer.
• the resin composition constituting the heat seal layer may contain an optional component (C).
• Optional components (C) include antiblocking agents, lubricants, heat stabilizers, and the like.
• the resin composition containing the polyolefin resin constituting the heat seal layer may contain an antiblocking agent. Although one type of antiblocking agent may be used, the use of two or more types of inorganic particles having different particle sizes and shapes can form complex protrusions even on the unevenness of the film surface, thereby obtaining a higher level of antiblocking effect.
• the antiblocking agent to be added is not particularly limited, but examples of the antiblocking agent that can be added include inorganic particles such as spherical silica, amorphous silica, zeolite, talc, mica, alumina, hydrotalcite, and aluminum borate, and organic particles such as polymethyl methacrylate and ultra-high molecular weight polyethylene.
• the content of the antiblocking agent contained in the resin composition containing the polypropylene resin constituting the heat seal layer is preferably 5000 ppm or less, more preferably 3500 ppm or less, and even more preferably 2000 ppm or less, based on the polyolefin resin of the layer to which it is added.
• the antiblocking agent By making it 5000 ppm or less, it is possible to reduce the falling off of the antiblocking agent.
• it is preferably 500 ppm or more, and more preferably 1000 ppm or more. By making it 500 ppm or more, it is possible to obtain good antiblocking properties.
• the resin composition containing the polyolefin resin constituting the heat seal layer may contain an organic lubricant.
• the lubricating property and anti-blocking effect of the laminated film are improved, and the handling property of the film is improved. The reason for this is that the organic lubricant bleeds out and is present on the film surface, thereby exerting a lubricating effect and a mold releasing effect.
• the organic lubricant preferably has a melting point above room temperature. Examples of the organic lubricant include fatty acid amides and fatty acid esters.
• fatty acid amides such as oleic acid amide, erucic acid amide, behenic acid amide, ethylene bisoleic acid amide, hexamethylene bisoleic acid amide, ethylene bisoleic acid amide, etc.
• fatty acid esters such as glycerin fatty acid ester monoglyceride, sorbitan fatty acid ester, polyglycerin fatty acid ester, etc.
• the content of the organic lubricant is preferably 1500 ppm or less, more preferably 1000 ppm or less, more preferably 10 ppm or more, and more preferably 50 ppm or more, based on the polyolefin resin. By making it 1500 ppm or less, blocking is unlikely to occur even if it is stored in a place exposed to high temperatures such as a warehouse in summer. In addition, it is preferably 200 ppm or more, more preferably 250 ppm or more. By making it 200 ppm or more, good slip properties can be obtained.
• the resin composition containing the polyolefin resin constituting the heat seal layer may contain a heat stabilizer, which can suppress the generation of gels and the like that occur when the resin deteriorates due to heat or oxidation during melt extrusion.
• a heat stabilizer which can suppress the generation of gels and the like that occur when the resin deteriorates due to heat or oxidation during melt extrusion.
• Commercially available heat stabilizers and antioxidants can be used.
• BASF's hindered phenol-based antioxidant Irganox 1010
• BASF's phosphite treatment stabilizer Irgafos 168
• Sumitomo Chemical's phenol-phosphorus-based antioxidant Sumitomo Chemical's phenol-phosphorus-based antioxidant (Sumilizer GP)
• the heat stabilizer may be used alone or in combination of two or more kinds.
• the content of the heat stabilizer in the resin composition containing the polyolefin resin is preferably 1600 ppm or more, more preferably 1800 ppm or more, and even more preferably 2000 ppm or more, in total, relative to the heat seal layer. If it is less than the above, defects such as gels are likely to occur. In addition, the content is preferably 5000 ppm or less, more preferably 4000 ppm or less, and even more preferably 3500 ppm or less, in total, relative to the heat seal layer. If it exceeds the above, the end surface of the film roll may turn red, impairing the appearance.
• the resin composition containing the polyolefin resin that constitutes the heat seal layer of the present invention may contain an appropriate amount of an antistatic agent, an antifogging agent, a neutralizing agent, a nucleating agent, a colorant, other additives, inorganic fillers, etc. in any layer as necessary, within the scope that does not impair the object of the present invention.
• An example of a neutralizing agent is calcium stearate.
• the absolute value of the difference in the content of the polyethylene resin in the resin composition containing the polypropylene resin constituting the heat seal layer and the second layer is not particularly limited, but is preferably 1% by weight or more and 25% by weight or less.
• the absolute value of the difference in the concentration of the polyethylene resin in the heat seal layer and the second layer is more preferably 18% by weight or less, even more preferably 15% by weight or less, and particularly preferably 10% by weight or less.
• the absolute value of the difference in the content of the polyethylene resin in the resin composition containing the polypropylene resin constituting the second layer and the first layer is preferably 1% by weight or more and 25% by weight or less.
• the absolute value of the difference in the content of the polyethylene resin in the second layer and the first layer is more preferably 18% by weight or less, even more preferably 15% by weight or less, and particularly preferably 10% by weight or less.
• the surface of the laminate layer of the non-oriented polyolefin resin film is activated by a known method such as corona treatment. This not only improves the lamination strength with the base film, but also improves printability.
• the content of polyethylene resin in the polypropylene resin composition constituting the second layer is preferably greater than the content of polyethylene resin in the polypropylene resin composition constituting the heat seal layer
• the content of polyethylene resin in the polypropylene resin composition constituting the first layer is preferably greater than the content of polyethylene resin in the polypropylene resin composition constituting the second layer.
• the resin composition containing the polypropylene-based resin of the three layers of the first layer, the second layer, and the heat seal layer contains at least one type selected from polypropylene homopolymer and propylene- ⁇ -olefin copolymer (the number of carbon atoms of ⁇ -olefin is 2 or 4 to 20) having a copolymerization ratio of 1.0 mol% or less in the total of the three layers, from the viewpoint of thermal stability and stiffness, in an amount of 50% by weight to 70% by weight, preferably 50% by weight to 65% by weight, and more preferably 50% by weight to 62% by weight.
• the resin composition containing the three layers of polypropylene-based resin, the first layer, the second layer, and the heat seal layer contains, in the three layers in total, preferably 16% by weight or more and 35% by weight or less, more preferably 18% by weight or more and 33% by weight or less, and even more preferably 20% by weight or more and 31% by weight or less, of a propylene- ⁇ -olefin copolymer ( ⁇ -olefin has 2 or 4 to 20 carbon atoms) having a copolymerization ratio of ⁇ -olefin of more than 1.0 mol%, from the viewpoint of high impact strength and high sheet seal initiation temperature.
• the resin composition containing the polypropylene-based resin of the three layers of the first layer, the second layer, and the heat seal layer contains a polyethylene-based resin in a total amount of preferably 10% by weight to 30% by weight, more preferably 11% by weight to 28% by weight, and even more preferably 13% by weight to 26% by weight.
• a polyolefin-based resin laminate film having a seal layer, a second layer, and a first layer in that order can be obtained by melt-extruding the polypropylene-based resin compositions constituting each layer using separate extruders, co-extruding the molten resin from a die to form three layers: seal layer/second layer/first layer, and cooling the molten resin sheet with a cooling roll to form an unstretched sheet.
• Methods for preventing segregation include the following 1) to 5). 1) A method of feeding the raw materials into the extruder before segregation occurs, i.e., a method of mixing the raw materials in small amounts and feeding them into the extruder each time. 2) A method for preventing differences in the speed at which materials slide down the inner wall of the hopper, i.e., a method for making the shape of the hopper closer to cylindrical.
• the lower limit of the content of the polyethylene resin constituting the master batch is preferably 40% by weight, more preferably 55% by weight. If it is less than the above, the polyethylene resin cannot be efficiently added to the film, which may result in high costs.
• the upper limit of the content of the polyethylene resin is preferably 85% by weight, more preferably 75% by weight. If it is less than the above, the segregation prevention effect is unlikely to be reduced. In particular, the segregation prevention effect is very large in polyethylene resins containing plant-derived carbon, particularly linear low-density polyethylene resins.
• a heat stabilizer When producing the master batch, a heat stabilizer can be added. By adding a heat stabilizer, it is possible to suppress the generation of deterioration products and the like that occur when forming a film.
• a heat stabilizer that can be used, commercially available heat stabilizers and antioxidants can be used.
• BASF's hindered phenol-based antioxidant Irganox 1010
• BASF's phosphite treatment stabilizer Irgafos 168
• Sumitomo Chemical Co., Ltd.'s phenol phosphorus-based antioxidant (Sumilizer GP) Sumitomo Chemical Co., Ltd.'s phenol phosphorus-based antioxidant (Sumilizer GP), etc.
• the heat stabilizer may be used alone or in combination of two or more kinds.
• the lower limit of the content of the heat stabilizer contained in the master batch is preferably 2000 ppm, more preferably 2500 ppm, and even more preferably 3000 ppm. If it is less than the above, defects may easily occur.
• the upper limit of the content of the heat stabilizer contained in the master batch is preferably 5000 ppm, more preferably 4000 ppm. If it exceeds the above, the end surface of the produced film roll may turn red, which may impair the appearance of the product.
• the amount of the antioxidant in the present invention is not limited, but is preferably in the range of 500 ppm to 5000 ppm relative to the resin composition containing the polypropylene resin of the three layers of the first layer, second layer, and heat seal layer. 1000 ppm to 4000 ppm is more preferable, and 1500 ppm to 3000 ppm is even more preferable. If it is less than 500 ppm, the effect of using the antioxidant in combination as described below decreases, which is not preferable. Conversely, if it exceeds 5000 ppm, the effect of using the antioxidant in combination as described below becomes saturated, and the antioxidant migrates to the film surface, causing film whitening and contamination of the cooling roll in the film formation process, which is not preferable.
• the method for preparing the master batch is not particularly limited, and known methods can be used. For example, a method of heating and melting the mixture using a kneader, a Banbury mixer, a roll, or other kneading machine, a method of heating and melting the mixture using a single-screw or twin-screw extruder, etc. can be used.
• the raw materials of the polypropylene resin composition for the heat seal layer, second layer, and first layer are mixed, melt-mixed and extruded in separate extruders, and the laminated sheet of the molten seal layer, second layer, and first layer is cast from a T-die onto a cooling roll to obtain a non-oriented sheet.
• the lower limit of the cooling roll temperature is preferably 15°C, more preferably 20°C. If it is less than the above, condensation may occur on the cooling roll, resulting in insufficient adhesion.
• the upper limit of the cooling roll is preferably 60°C, more preferably 50°C. If it exceeds the above, transparency may deteriorate.
• the surface of the first layer of the non-stretched polyolefin resin film of the present invention is preferably activated by corona treatment or the like. This improves the laminate strength with the base film.
• the lower limit of the power density of the corona treatment is preferably 15 W ⁇ min/ m2 , more preferably 17 W ⁇ min/ m2 . If it is less than 15 W ⁇ min/ m2 , the laminate strength and printability may decrease.
• the upper limit is preferably 30 W ⁇ min/ m2 , more preferably 25 W ⁇ min/ m2 . If it is more than 30 W ⁇ min/ m2 , strike-through may occur, causing roll blocking.
• the biomass degree indicates the ratio of carbon atoms derived from plants to the total carbon atoms in the film. The greater the ratio of carbon atoms derived from plants, the greater the carbon dioxide reduction effect based on the idea of carbon neutrality.
• the lower limit of the biomass degree of the non-stretched polyolefin resin film of the present invention may be 0%, but is preferably 10% or more, and more preferably 12% or more. If it is 10% or more, the carbon dioxide reduction effect is large.
• the upper limit of the biomass degree is preferably 70% or less, more preferably 40% or less, and even more preferably 30% or less. If it exceeds 70%, the heat seal strength decreases due to the influence of the linear low-density polyethylene derived from plants.
• the biomass degree is measured, for example, based on ASTM D6866.
• the lower limit of the thermal shrinkage rate in the longitudinal direction of the non-stretched polyolefin resin film of the present invention is preferably 0.2%, more preferably 0.3%, and even more preferably 0.5%. If it is 0.2% or more, the heat resistance is sufficient.
• the upper limit of the thermal shrinkage rate in the longitudinal direction of the non-stretched polyolefin resin film is 1.0%, preferably 0.9%, and more preferably 0.8%. If it is 1.0% or less, pitch deviation during printing is unlikely to occur.
• the lower limit of the heat shrinkage rate in the width direction of the non-stretched polyolefin resin film of the present invention is preferably 0.0%, more preferably 0.1%, and even more preferably 0.2%.
• the film is less likely to elongate when heated.
• the upper limit of the heat shrinkage rate in the width direction is 1.0%, preferably 0.8%, and more preferably 0.6%. If it is 1.0% or less, pitch deviation during printing is less likely to occur.
• the heat shrinkage rate is measured based on JIS Z1712, and is determined from the ratio of the longitudinal and transverse shrinkages before and after cutting an unstretched polyolefin resin film to a predetermined size and subjecting it to conditions of 120° C. and 30 minutes.
• the lower limit of the haze of the non-stretched polyolefin resin film of the present invention is preferably 1.0%, more preferably 2.0%, further preferably 2.5%, and particularly preferably 3.0%. If the haze is 1.0% or more, the unevenness of the film surface is not extremely small, so that blocking of the inner surface of the package is unlikely to occur.
• the upper limit of the haze is preferably 20.0%, more preferably 15.0%, even more preferably 10.0%, and even more preferably 8.0%. When it is 20.0% or less, visibility of the package is easily obtained.
• Linear low-density polyethylene has high crystallinity and is prone to increase in haze, but if it is added within the above preferred range, the increase in haze can be suppressed.
• the haze is measured, for example, based on JIS K7136.
• the upper limit of the static friction coefficient of the non-stretched polyolefin resin film of the present invention is preferably 0.70, more preferably 0.50, and even more preferably 0.40. If it is 0.70 or less, when filling a package with food or when opening the package, the opposite surfaces tend to slide easily against each other, and the opening is easy.
• the static friction coefficient is measured based on JIS K7125.
• the lower limit of the static friction coefficient of the film itself is preferably 0.10, more preferably 0.15, and even more preferably 0.20. If the coefficient is 0.10 or more, the film roll is less likely to become unwound during transportation.
• the lower limit of the Young's modulus (longitudinal direction) of the non-stretched polyolefin resin film of the present invention is 400 MPa, preferably 500 MPa, more preferably 600 MPa, and even more preferably 700 MPa. If it is less than 400 MPa, the film may be too weak and difficult to process.
• the upper limit of the Young's modulus (longitudinal direction) is preferably 1000 MPa, more preferably 900 MPa, and even more preferably 800 MPa. Films exceeding 1000 MPa are brittle, and may have poor pinhole resistance.
• the lower limit of the Young's modulus (width direction) of the non-stretched polyolefin resin film of the present invention is 450 MPa, preferably 500 MPa, and more preferably 600 MPa. If it is less than 450 MPa, the film may be too weak and difficult to process.
• the upper limit of the Young's modulus (width direction) is preferably 1000 MPa, more preferably 800 MPa, and even more preferably 750 MPa. A film exceeding 1000 MPa is brittle, and may have poor bending pinhole resistance.
• the Young's modulus increases, but if the amount added increases, the characteristics of linear low density polyethylene become more pronounced, and the Young's modulus decreases.
• the Young's modulus is measured, for example, based on JIS K7127.
• the lower limit of the impact strength of the non-stretched polyolefin resin film of the present invention is preferably 0.20 J, more preferably 0.25 J, and even more preferably 0.30 J. By making it 0.20 J or more, the drop-breakage resistance of the package can be improved. An impact strength of 1.00 J is sufficient. The impact strength is largely dependent on the thickness and the molecular orientation of the film. In addition, the impact strength and the drop-breakage resistance are not necessarily correlated.
• the lower limit of the accelerated blocking strength of the non-stretched polyolefin resin film of the present invention is preferably 20 mN/70 mm, more preferably 30 mN/70 mm, and even more preferably 36 mN/70 mm. If it is 20 mN/70 mm or more, the film is likely to have a firm feel.
• the upper limit of the accelerated blocking strength is preferably 100 mN/70 mm, more preferably 80 mN/70 mm, even more preferably 70 mN/70 mm, and particularly preferably 60 mN/70 mm. If it is 100 mN/70 mm or less, blocking is unlikely to occur on the inner surface of the package. If linear low density polyethylene is added to the second layer and the first layer, the deterioration of the accelerated blocking strength can be suppressed.
• the lower limit of the puncture strength of the unstretched polyolefin resin film of the present invention is preferably 1.0 N, more preferably 1.2 N, even more preferably 1.5 N, and particularly preferably 1.7 N. If it is 1.0 N or more, the laminate has good pinhole resistance. A puncture strength of 3.0 N is sufficient. The puncture strength is largely dependent on the orientation of the film, and does not change much just by changing the resin.
• the lower limit of the heat seal initiation temperature of the unstretched polyolefin resin film of the present invention is preferably 120°C, more preferably 130°C. When it is 120°C or higher, it has a high firmness and is easy to handle.
• the upper limit of the heat seal initiation temperature is preferably 150°C, more preferably 145°C, and even more preferably 140°C. When it is 150°C or lower, it is possible to produce a package at high speed, which is economically advantageous.
• the heat seal initiation temperature is greatly affected by the melting point of the seal layer. Therefore, if linear low density polyethylene is added to the second layer and the first layer, the change in the heat seal temperature is suppressed.
• the heat seal initiation temperature is measured, for example, based on JIS Z 1713 (2009).
• the lower limit of the plane orientation coefficient of the non-stretched polyolefin resin film of the present invention is preferably 0.0000, more preferably 0.0001. It is difficult to produce a film with a plane orientation coefficient below the above limit.
• the upper limit of the plane orientation of the film is preferably 0.0010, more preferably 0.0008, and even more preferably 0.0006. If it is more than the above limit, the film may be stretched non-uniformly, and the thickness uniformity may be deteriorated.
• the plane orientation coefficient is measured, for example, based on JIS K0062:1999.
• the lower limit of the wet tension of the corona-treated surface of the non-stretched polyolefin resin film of the present invention is preferably 30 mN/m, more preferably 35 mN/m. If it is 30 mN/m or more, the laminate strength is unlikely to decrease.
• the upper limit of the wet tension is preferably 55 mN/m, more preferably 50 mN/m. If it is 55 mN/m or less, blocking between films is unlikely to occur when the polyolefin resin film is wound on a roll.
• the wet tension is measured, for example, based on JIS K6768.
• the lower limit of the load capacity of the ring crush strength of the non-stretched polyolefin resin film of the present invention is preferably 0.7 N, more preferably 1.0 N, and even more preferably 1.1 N. If it is 0.9 N or less, the stiffness is low and the handling property during processing is deteriorated.
• the ring crush strength is measured, for example, based on JIS P 8126.
• the laminate using the non-stretched polyolefin resin film of the present invention is a laminate using the non-stretched polyolefin resin film as a sealant and at least one film selected from the group consisting of polyamide resin film, polyester resin film, and polypropylene resin film as a base film.
• these base films may be coated or vapor-deposited for the purpose of imparting adhesiveness or barrier properties, or may be further laminated with aluminum foil.
• the base film is preferably selected from biaxially oriented films such as biaxially oriented polyolefin resin film, biaxially oriented polyamide resin film, and biaxially oriented polyester resin film.
• biaxially oriented PET polyethylene terephthalate film/aluminum foil/sealant
• biaxially oriented PET polyethylene terephthalate film/biaxially oriented nylon film/sealant
• biaxially oriented nylon film/sealant biaxially oriented nylon film/sealant
• biaxially oriented polypropylene film/sealant biaxially oriented polyethylene terephthalate (PET) film/biaxially oriented nylon film/aluminum foil/sealant.
• PET polyethylene terephthalate
• the lamination method a known method such as a dry lamination method or an extrusion lamination method can be used, and any lamination method may be used.
• the properties of the laminate will now be described.
• Heat seal strength The lower limit of the heat seal strength of the laminate of the present invention at 160°C, 0.1 MPa, 1 sec is, for example, 18 N/15 mm, preferably 19 N/15 mm, more preferably 20 N/15 mm. If it is 18 N/15 mm or more, bag break resistance is easily obtained. If the heat seal strength is 60 N/15 mm, it is very excellent, and if it is 35 N/15 mm, it is sufficient.
• the lower limit of the heat seal initiation temperature of the laminate of the present invention is preferably 120° C., more preferably 130° C. If it is 120° C. or higher, the laminate has a high firmness and is easy to handle.
• the upper limit of the heat seal initiation temperature is preferably 160° C., more preferably 155° C. If it is 160° C. or lower, the appearance of the heat sealed portion of the package is not easily impaired even in the case of a laminate with a substrate having low heat resistance such as a biaxially oriented polypropylene resin film.
• the lower limit of the puncture strength of the laminate of the present invention is preferably 7N, more preferably 8N, and even more preferably 9N. If it is 7N or more, pinholes are unlikely to occur when the protrusions come into contact with the package.
• the upper limit of the puncture strength is preferably 45N, more preferably 30N, and even more preferably 15N. If it is 45N or less, the laminate does not feel too stiff and is easy to handle.
• the puncture strength is largely dependent on the orientation of the film, so it does not change much just by changing the resin.
• the flex resistance can be measured by Gelbo pinhole evaluation.
• the upper limit of the number of pinholes after bending the laminate of the present invention 1000 times at 1° C. is, for example, 8, preferably 7, more preferably 4, even more preferably 2, and particularly preferably 1. If the number is 8 or less, pinholes are unlikely to occur due to bending impact during transportation of the package.
• the present invention also includes a package made of the non-stretched polyolefin resin film or the laminate arranged to wrap around the contents, such as food, for the purpose of protecting the contents from dust, gas, etc. in the natural world.
• the package is produced by cutting out the non-stretched polyolefin resin film or the laminate, bonding the inner surfaces together with a heated heat seal bar or ultrasonic waves, etc., and forming it into a bag shape.
• a four-sided sealed bag in which two rectangular sheets are stacked with the heat seal layer side facing inward and the four sides are heat sealed, or a back-sealed packaging bag, etc. are widely used.
• the contents may be food, but may also be other products such as daily necessities, and the shape of the package may be a shape other than a rectangle, such as a standing pouch or a pillow package.
• the present invention will be described in detail below with reference to examples, but is not limited to these.
• the properties obtained in each example were measured and evaluated by the following methods.
• the flow direction of the film in the film production process was defined as the longitudinal direction (MD direction)
• the direction perpendicular to the flow direction was defined as the width direction (TD direction).
• biomass degree was calculated from the C14 (carbon atom having a mass number of 14) concentration in the film.
• Heat shrinkage rate Measured according to JIS Z1712 by the following method. The film was cut into pieces of 20 mm width and 200 mm length in both the longitudinal and transverse directions, and was heated for 30 minutes by hanging in a hot air oven at 120° C. The length after heating was measured, and the heat shrinkage rate was calculated as the ratio of the shrunken length to the original length.
• the unstretched polyolefin resin film was cut into a length of 148 mm and a width of 105 mm.
• the sealing surfaces were placed face to face and overlapped.
• the film was sandwiched between 7.0 cm square aluminum plates held at 50°C.
• MP-SCH manufactured by Toyo Seiki Seisakusho Co., Ltd.
• the aluminum plate and the sample were pressed at 50°C and 100 kN and held for 15 minutes.
• the removed sample was cut into a width of 70 mm.
• the overlapped sample was opened by 30 mm, and a metal rod with a diameter of 3 mm was inserted so as to be parallel to the width direction.
• Puncture Strength The puncture strength of the non-stretched polyolefin resin film and the laminate was measured at 23°C in accordance with "2. Testing Method for Strength, etc.” in "Standards for Foods, Additives, etc., Part 3: Apparatus and Containers and Packaging” (Ministry of Health and Welfare Notification No. 20, 1982) in the Food Sanitation Act.
• a needle with a tip diameter of 0.7 mm was pierced into the film at a piercing speed of 50 mm/min, and the strength at which the needle penetrated the film was measured.
• Heat seal initiation temperature 1 For the non-stretched polyolefin resin film, the heat seal initiation temperature was measured in accordance with JIS Z 1713 (2009). At this time, the film was cut into a rectangular test piece (for heat seal) of 50 mm x 250 mm (width direction x length direction of the film). The heat seal layer parts of two test pieces were overlapped, and a heat gradient tester (heat seal tester) manufactured by Toyo Seiki Seisakusho Co., Ltd. was used, and the heat seal pressure was 0.2 MPa and the heat seal time was 1.0 sec. In the measurement of the film alone, it was protected with a biaxially oriented polyester resin film so that the resin would not adhere to the heat seal bar.
• the heat seal was performed under the condition of increasing the temperature with a gradient of 5 ° C. After heat sealing, the test piece was cut out to a width of 15 mm. The test piece fused by heat sealing was opened at 180 °, and the unsealed part was sandwiched in a zipper and the sealed part was peeled off. Then, the temperature at the time when the heat seal strength reached 4.9 N was obtained.
• Plane Orientation Coefficient (Nx+Ny)/2 ⁇ Nz (Equation 1)
• Nx refractive index in the longitudinal direction
• Ny refractive index in the width direction
• Nz refractive index in the thickness direction
• Example 1 (Raw materials used in the first layer)
• PP-1 Propylene-ethylene random copolymer WF836DG3 (MFR 7.0 g/10 min, melting point 158° C., ethylene content 0.6 mol%, petroleum-derived), manufactured by Sumitomo Chemical Co., Ltd.
• PP-2 SABIC propylene homopolymer PP525P (MFR 3.0 g/10 min, melting point 161° C., derived from plants)
• PP-3 Propylene homopolymer F300SP (MFR 3.0 g/10 min, melting point 161°C, petroleum-derived), manufactured by Prime Polymer Co., Ltd.
• PP-4 Manufactured by Sumitomo Chemical Co., Ltd., propylene-ethylene-butene random copolymer FL8115A (MFR 7.0 g/10 min, melting point 148°C, ethylene content 1 mol%, butene content 3.6 mol%, derived from petroleum)
• LL-1 Ethylene-hexene copolymer (plant-derived linear low-density polyethylene) SLH218 (MFR 2.3 g/10 min, density 916 kg/m 3 , melting point 126° C.), manufactured by Braskem LL-2: Ethylene-hexene copolymer (petroleum-derived linear low-density polyethylene) FV201 (MFR 2.3 g/10 min, density 916 kg/m 3 ), manufactured by Sumitomo Chemical Co., Ltd.
• PP-1 Propylene-ethylene random copolymer WF836DG3 (MFR 7.0 g/10 min, melting point 158° C., ethylene content 0.6 mol%, petroleum-derived), manufactured by Sumitomo Chemical Co., Ltd.
• PP-2 SABIC propylene homopolymer PP525P (MFR 3.0 g/10 min, melting point 161° C., derived from plants)
• PP-3 Propylene homopolymer F300SP (MFR 3.0 g/10 min, melting point 161°C, petroleum-derived), manufactured by Prime Polymer Co., Ltd.
• PP-4 Manufactured by Sumitomo Chemical Co., Ltd., propylene-ethylene-butene random copolymer FL8115A (MFR 7.0 g/10 min, melting point 148°C, ethylene content 1 mol%, butene content 3.6 mol%, derived from petroleum)
• LL-1 Ethylene-hexene copolymer (plant-derived linear low-density polyethylene) SLH218 (MFR 2.3 g/10 min, density 916 kg/m 3 , melting point 126° C.), manufactured by Braskem LL-2: Ethylene-hexene copolymer (petroleum-derived linear low-density polyethylene) FV201 (MFR 2.3 g/10 min, density 916 kg/m 3 ), manufactured by Sumitomo Chemical Co., Ltd.
• Silica amorphous silica KMP130-4 (average particle size 4 ⁇ m), manufactured by Shin-Etsu Chemical Co., Ltd.
• Organic lubricant Behenic acid amide BNT-22H, manufactured by Nippon Fine Chemicals Co., Ltd.
• PP-1 Propylene-ethylene random copolymer WF836DG3 (MFR 7.0 g/10 min, melting point 158° C., ethylene content 0.6 mol%, petroleum-derived), manufactured by Sumitomo Chemical Co., Ltd.
• PP-5 Manufactured by Sumitomo Chemical Co., Ltd., propylene-ethylene-butene random copolymer FL6745A (MFR 6.0 g/10 min, ethylene content 4.0 mol%, butene content 3.6 mol%, melting point 130° C., derived from petroleum)
• Silica amorphous silica KMP130-4 (average particle size 4 ⁇ m), manufactured by Shin-Etsu Chemical Co., Ltd.
• Organic lubricant Behenic acid amide BNT-22H, manufactured by Nippon Fine Chemicals Co., Ltd.
• Non-oriented polyolefin resin film For the non-oriented polypropylene resin film of Example 1, the raw materials were prepared based on the resin composition and the ratio of each layer shown in Table 1 below. The raw materials were transported in a fixed amount by a screw feeder and weighed. For one lightweight batch, the first layer was 14 kg, the second layer was 40 kg, and the heat seal layer was 14 kg. In addition, the preparations in each layer shown in Table 1 were 100% by weight, and 360 ppm of behenic acid amide was added to the heat seal layer as an organic lubricant and 2000 ppm of silica having an average particle size of 4 ⁇ m was added to the inorganic antiblocking agent as a master batch. 270 ppm of behenic acid amide was added to the second layer as an organic lubricant and 380 ppm of silica having an average particle size of 4 ⁇ m was added to the inorganic antiblocking agent as a master batch.
• the mixed raw materials for the second layer were extruded in a three-stage single-screw extruder with a screw diameter of 90 mm, and the mixed raw materials for the heat seal layer and the first layer were extruded in the order of heat seal layer/second layer/first layer using three-stage single-screw extruders with a screw diameter of 65 mm and 45 mm, respectively.
• the preland was made into two stages with a width of 1400 mm, and the step part was curved so that the flow of the molten resin was uniform in the die.
• the die was extruded at an outlet temperature of 230° C.
• the thickness ratio of the heat seal layer/second layer/first layer was 25%/55%/20%, respectively.
• the molten resin sheet coming out of the die was cooled with a cooling roll at 35°C to obtain an unstretched polyolefin resin film having a thickness of 30 ⁇ m.
• both ends of the film on the cooling roll were fixed with an air nozzle, the entire width of the molten resin sheet was pressed against the cooling roll with an air knife, and at the same time, a vacuum chamber was operated to prevent air from being entrained between the molten resin sheet and the cooling roll.
• the air nozzles were installed in series in the film traveling direction at both ends.
• the die was surrounded by a sheet to prevent the molten resin sheet from being exposed to wind.
• the direction of the suction port of the vacuum chamber was aligned with the traveling direction of the extruded sheet.
• corona treatment The surface of the laminate layer of the film was subjected to corona treatment (power density: 20 W ⁇ min/m 2 ).
• Example 2 (Examples 2 to 8)
• the raw materials used for the second layer and the first layer were changed to the ratio shown in Table 1, and a 30 ⁇ m unstretched polyolefin resin film was obtained in the same manner as in Example 1.
• a laminate was obtained in the same manner as in Example 1. The evaluation results are shown in Table 1.
• Example 1 (Comparative Examples 1 to 7)
• the raw materials used for the heat seal layer, the second layer, and the first layer were changed to the ratios shown in Table 2, and a 30 ⁇ m unstretched polyolefin resin film was obtained in the same manner as in Example 1.
• a laminate was obtained in the same manner as in Example 1.
• Table 2 shows the evaluation results.
• the heat seal layer had a low polypropylene resin content in the propylene- ⁇ -olefin copolymer, in which the copolymerization ratio of ⁇ -olefin was 1.0 mol% or less, and so the low-temperature sealability was poor.
• the second layer did not contain polyethylene resin, and therefore had poor pinhole resistance when bent and poor low-temperature sealing properties.
• the film had a high content of polypropylene homopolymer and propylene- ⁇ -olefin copolymer in which the copolymerization ratio of ⁇ -olefin was 1.0 mol% or less, resulting in poor low-temperature sealability.
• A Content (wt%) of polyethylene resin in the resin composition containing polypropylene resin in the entire film (first layer, second layer, heat seal layer)
• B The content (wt%) of the total amount of polypropylene homopolymer and propylene- ⁇ -olefin copolymer having a copolymerization ratio of ⁇ -olefin of 1.0 mol% or less ( ⁇ -olefin has 2 or 4 to 20 carbon atoms) relative to the resin composition containing the polypropylene-based resin in the entire film (first layer, second layer, heat seal layer)
• C The content (wt%) of the total amount of polypropylene homopolymer and propylene- ⁇ -olefin copolymer ( ⁇ -olefin has 2 or 4 to 20 carbon atoms) having a copolymerization ratio of more than 1.0 mol
• the present invention makes it possible to provide an environmentally friendly, non-stretched film that has good thermal dimensional stability and stiffness while also having high heat seal strength and resistance to pinholes caused by bending, making a significant contribution to industry.

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