JP2018062072A - Laminated film with rigidity and impact resistance - Google Patents

Abstract

PROBLEM TO BE SOLVED: To solve such a problem that, in a packaging material, tearing property indicating opening property, and rigidity required for toughness of a crystalline polymer such as polyethylene can be improved by using a resin having a high density, however, performances about impact resistance and heat-sealing property are decreased, resulting in a trade-off relation.SOLUTION: The present invention provides a laminated film having layers made of polyethylene showing a difference in at least the density, in which a layer having a smaller average density is regarded as a sealing layer (12) and a layer having a larger average density is regarded as a base layer (11), the structural material of the layers comprises at least one copolymer of α-olefin and ethylene and at least one low-density polyethylene produced by a high-pressure process, the difference in the average density ranges from 0.006 g/cmto 0.033 g/cm; and a molecular weight distribution (Mw/Mn) of the copolymer of α-olefin and ethylene included in the base layer is 7.0 or more.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a laminated film having rigidity and impact resistance.

  As a sealant film used for packaging materials such as foods, heat sealability such as polyethylene and polypropylene is generally good, and adhesiveness with other laminated base materials is good, and an inexpensive film is used. Physical properties required for packaging materials include filling properties at the time of filling contents, absence of damage to the bag when external force is applied to the packaging material, appropriate physical properties related to opening properties when opening the packaging material, In addition, good productivity at the time of manufacture is required.

  The aforementioned physical properties have been studied for a long time, and for crystalline polymers such as polyethylene, the tearability that shows openability and the rigidity that gives a soft feeling to the packaging material have high crystallinity using high-density resin. It can be improved by raising it. On the other hand, in this method, there is a so-called trade-off relationship that the performance deteriorates with respect to impact resistance and heat sealability.

  For example, for compatibility of the physical properties described above, as in Patent Document 1, a low-density polyethylene resin is used on the seal layer side to impart impact resistance and heat sealability, and rigidity and tearability are imparted. In addition, a method is used in which high-density polyethylene is laminated on the laminate layer side to achieve both physical properties in a trade-off relationship.

Japanese Patent No. 4779822

  Patent Document 1 discloses a resin having a high density polyethylene on the laminate layer side and a molecular weight distribution (Mw / Mn) in the range of 2.0 to 3.5. However, since the resin has a uniform molecular weight distribution, rigidity can be imparted but tearability is not sufficient.

  In addition, since the resin has a narrow molecular weight distribution, when the processing speed during production is increased, the screw load due to the increase in shear viscosity may increase when the shear rate in the extruder increases. In addition, since the molecular weight distribution is uniform, the melt tension is lowered, and the productivity may be reduced, such as a decrease in film forming width and fluttering of the molten film during high-speed take-up.

In order to solve the above problems, one of the representative laminated films of the present invention is:
A laminated film in which at least a seal layer and a base layer are laminated,
(A) The base layer and the sealing layer each include at least one copolymer of α-olefin and ethylene, and low density polyethylene,
Average density of (b) the base layer is higher than the average density of the seal layer, the difference is in the range of ^{0.006g / cm 3 ~0.033g / cm 3} ,
(C) The molecular weight distribution (Mw / Mn) of the copolymer of α-olefin and ethylene contained in the base layer is 7.0 or more.

One of the other laminated films of the present invention is
(A) The tensile elastic modulus according to JIS K7161 is in the range of 300 MPa to 450 MPa,
(B) The range obtained by dividing the 50% fracture weight by the dirt impact method of JIS K7124-1 by the film thickness is 3.7 g / μm or more,
(C) The range obtained by dividing the tearing force in the film flow direction by the Elmendorf tearing method according to JIS K7128-2 by the film thickness is 10 mN / μm to 100 mN / μm,
(D) It is characterized in that the seal strength is 10 N / 15 mm or more when the seal layers are sealed at a seal temperature of 140 ° C. with a seal pressure of 0.2 MPa, a seal time of 1 second, a seal width of 10 mm.

Furthermore, one of the other laminated films of the present invention is
(A) the density of the copolymer resin of the base layer of α- olefin and ethylene, a 0.926g / ^{cm 3} ~0.938g / ^cm 3 in the method according to JIS K7112,
(B) the density of the copolymer resin of the sealing layer α- olefin and ethylene, characterized in that in the method according to JIS K7112 in the range of ^{0.903g / cm 3 ~0.924g / cm 3} .

Furthermore, one of the other laminated films of the present invention is
The weight ratio of the α-olefin, the ethylene copolymer and the low density polyethylene contained in the base layer and the seal layer is in the range of 98: 2 to 70:30.

Furthermore, one of the other laminated films of the present invention is
The total thickness of the base layer and the seal layer is in the range of 40 μm to 200 μm,
The thickness of the seal layer is 5 μm to 30 μm, and the ratio of the thickness of the seal layer to the total thickness is 30% or less.

In other words, a low-density polyethylene layer with high flexibility and a high-density polyethylene layer to provide rigidity are laminated as a prescription for achieving trade-off physical properties, and resins having different branching properties are added to the composition. By including two or more kinds, it is possible to improve impact resistance and tearability. As a result, the viscosity characteristics of the resin are improved, and the productivity can be improved.

Laminated film with rigidity and impact resistance

  The present invention will be described in detail below. The basic structure of the laminated film in the present invention is a laminated film comprising a base layer 11 and a seal layer 12 and formed by an extruder.

  The laminated film in the present invention is formed by an extruder capable of heating up to 340 ° C. For this reason, various thermoplastic resins can be used as the main material of the base layer 11, but moderate flexibility and workability are required for use as a general packaging sealant film. Therefore, low density polyethylene (LDPE) based on olefin, linear low density polyethylene (LLDPE) copolymerized with α-olefin and ethylene, medium density polyethylene (MDPE), high density polyethylene (HDPE) and homopolymer. Polymers, random copolymers, polypropylene and cycloolefin polymers with block random copolymers, cycloolefin copolymers obtained by copolymerizing cycloolefin and olefin, and ethylene vinyl acetate copolymers and olefin side chains obtained by copolymerizing the above olefins with vinyl acetate Obtained by modification of ethylene-methyl acrylate copolymer (EMA), ethylene-ethyl acrylate copolymer (EEA), ethylene-butyl acrylate copolymer (EBA), ethylene-methacryl It has suitable to select appropriately used alone and more of such copolymer (EMAA).

  In particular, for the base layer 11, the required properties of the sealant film for packaging materials, filling suitability at the time of filling the contents, no damage to the bag when an external force is applied to the packaging material, and when opening the packaging material It is necessary to satisfy openability. Specifically, it must have an appropriate melting point and heat of fusion in order to be processed into a bag shape when used as a suitable laminate with a sealant film alone or a film such as polyethylene terephthalate or polyamide such as 6 nylon or 66 nylon. It becomes. From the above requirements, low density polyethylene (LDPE), linear low density polyethylene (LLDPE) copolymerized with α-olefin and ethylene, medium density polyethylene (MDPE), low density polyethylene (LDPE) and α-olefin It is preferable that both linear low density polyethylene (LLDPE) copolymerized with ethylene.

The base layer 11 has a role of imparting rigidity to the sealant film, and it is necessary to select a material having appropriate rigidity and flexibility. In general, it is known that the rigidity increases as the ratio of the crystal part of polyethylene increases. In order to increase the crystallization ratio, it is important that the number of branches is small. Moreover, it is thought that crystallization is easy to advance, so that molecular weight is small. However, when the molecular weight is small and the number of branches is small, the impact resistance is likely to be lowered. Therefore, it is necessary to select a resin within the optimum range.
From this, the α-olefin and ethylene copolymer used in the base layer have a molecular weight distribution (Mw / Mn) in the range of 7.0 to 12.0, and the density is 0.000 according to the JISK-7112 method. It is necessary to select 926 g / cm ^{3 to} 0.938 g / cm ³ .
Similarly, the molecular weight distribution with respect to low-density polyethylene (Mw / Mn) of 4.0 to 10.0, in the density selected from the range of 0.918g / ^{cm 3} ~0.925g / ^cm 3 in JISK7112 method There is a need to.

  Next, in the seal layer 12, low density polyethylene (LDPE), linear low density polyethylene (LLDPE), medium density polyethylene (MDPE), high density polyethylene (HDPE), which are materials that can be used in the base layer 11, and Polypropylene and cycloolefin polymers with homopolymers, random copolymers, block random copolymers, cycloolefin copolymers copolymerized with cycloolefin and olefin, and ethylene vinyl acetate copolymer or olefin side obtained by copolymerizing the above olefin with vinyl acetate Obtained by modifying the chain, ethylene-methyl acrylate copolymer (EMA), ethylene-ethyl acrylate copolymer (EEA), ethylene-butyl acrylate copolymer (EBA), ethylene-methacrylic acid copolymer (EMAA) can be selected appropriately used alone and more of the like.

  As with the base layer 11, the sealing layer 12 also has the required properties of a sealant film for packaging materials, such as filling ability when filling the contents, no damage to the bag when an external force is applied to the packaging material, It is necessary to satisfy the openability when opening. Specifically, it must have an appropriate melting point and heat of fusion in order to be processed into a bag shape when used as a suitable laminate with a sealant film alone or a film such as polyethylene terephthalate or polyamide such as 6 nylon or 66 nylon. It becomes. From the above requirements, low density polyethylene (LDPE), linear low density polyethylene (LLDPE) copolymerized with α-olefin and ethylene, medium density polyethylene (MDPE), low density polyethylene, α-olefin and ethylene It is preferable that both the copolymerized linear low density polyethylene are contained.

About the sealing layer 12, it has a role which provides the softness | flexibility of a sealant film, especially heat-sealing property, and it is necessary to select the material which has a softness | flexibility. Generally, it is known that the flexibility increases as the ratio of the crystal part of polyethylene decreases. In order to decrease the crystallization ratio, crystallization is inhibited as the number of branches increases and the molecular weight increases. From this, the α-olefin and ethylene copolymer used in the seal layer have a molecular weight distribution (Mw / Mn) in the range of 2.0 to 4.0, and the density is 0.000 according to the JISK-7112 method. It is necessary to select a material that is 903 g / cm ^{3 to} 0.924 g / cm ³ .
Further, regarding the low density polyethylene, the molecular weight distribution (Mw / Mn) is 4.0 to 10.0 similarly to the polyethylene used for the base layer 11, and the density is 0.918 g / cm ^{3 to} 0 by the JISK7112 method. It is necessary to select from a range of 925 g / cm ³ .

As described above, the base layer and the seal layer need to be provided with different physical properties, and in particular, the seal layer 12 needs to have a function of heat sealability, which is a characteristic of the sealant film. In the sealing step, melt-compression is performed using a heated seal bar, and sealing is performed by applying heat and pressure to the laminated film.
For the melting of polyethylene, the flow of the amorphous part, the melting, deformation, and fixing processes of the crystal part are important, but it is considered that these processes have a large relationship with the polyethylene density of the sealed part. In the present invention, α-olefin / ethylene copolymer and low-density polyethylene are mixed and used, and the requirements for laminated film are specified by defining the density index for each layer as a whole. doing.
First, it is necessary to calculate the average density in the base layer 11 and the seal layer 12. For this purpose, in the density D calculated by the method described in JISK7112, the polyethylene of the constituent elements contained in each layer is used. The mixing weight ratio is x, and the average density is calculated by the following formula 1. However, n is 2 or more.

Since the base layer has higher rigidity than the seal layer, the average density is set higher than the average density of the seal layer. When the difference in average density between the base layer and the seal layer is less than 0.006 g / cm ³ , the average density of the base layer is insufficient, making it difficult to achieve both sealing performance and rigidity. If it is greater than 033 g / cm ^3, the residual stress strain that remains when the melted polyethylene is cooled and solidified is likely to remain after molding the sealant film, and the residual stress strain is released after molding, warping the sealant film, etc. Will occur. Therefore, it is preferable that the difference of the average density of the base layer 11 and the seal layer 12 is in the range of 0.006 g / cm ³ of 0.033 g / cm ^3.

  Both the base layer 11 and the sealing layer 12 of the present invention use a mixture of at least one kind of α-olefin / ethylene copolymer and low density polyethylene. Generally, it is known that a copolymer of α-olefin and ethylene has a narrow molecular weight distribution and a relatively large number of single molecular weight components among polyethylene resins. When the molecular weight distribution is narrowed, molecules with a certain length of molecular weight are present in the film, so that the uniformity of the film increases and impact resistance increases, but the tearability, which is a required characteristic of packaging materials, decreases. . For this reason, in order to disturb the arrangement of uniform molecules to some extent, it is possible to improve tearability by mixing low density polyethylene having a relatively wide molecular weight distribution and having long chain branches.

  About molecular weight distribution in this invention, it determines using the high temperature GPC method among the methods generally used in the measurement of polyolefin. Polyethylene to be evaluated for o-dichlorobenzene is dissolved at a concentration of 1.0 g / l at 145 ° C., then measured using a differential refractometer under measurement conditions with a flow rate of 1.0 ml / min, and a polystyrene equivalent molecular weight distribution is used. The molecular weight distribution of polyethylene is converted and calculated.

It is known that the molecular weight of polyethylene affects the processability such as shear viscosity and elongational viscosity during melt film formation, and the arrangement and crystallinity of the polymer when cooled and solidified from the molten state. In the case of polyethylene having a small molecular weight, the shear viscosity and the extension viscosity, which are resistance to flow during melting, are generally small, and there is an advantage that the apparatus load can be reduced in a melting process such as an extruder. In the cooling and solidification process, since the molecular weight is small, the molecules easily move to take the lowest energy, and the crystallization of the film easily proceeds, so that the film has high rigidity. On the other hand, since the molecular weight is small, entanglement between other molecules is reduced, and impact resistance is likely to be reduced.
On the other hand, polyethylene with a large molecular weight has a disadvantage that the molecular load increases and the force required during flow increases, which increases the load on the apparatus in the melting process such as an extruder due to an increase in shear viscosity and elongational viscosity. is there. Furthermore, in the cooling and solidification process, the movement of molecules is inhibited, so that the crystallization of the film is inhibited. However, since the molecular weight is large, the entanglement with other molecules increases, which has the advantage of improving impact resistance. For the reasons described above, in general, it is important to adjust and use the molecular weight distribution, which is the ratio of the molecular weight, in order to obtain the required physical properties of polyethylene.

  In the molecular weight distribution evaluation method in the present invention, the determination is generally made by using Mw / Mn, which is the ratio of the weight average molecular weight Mw and the number average molecular weight Mn, as an index. For the reasons described above, it is preferable that the molecular weight is appropriately selected as large or small. When the copolymer of α-olefin and ethylene contained in the base layer has a Mw / Mn smaller than 6, the molecular weight distribution is narrow and the impact resistance is good, but the rigidity and tearability are not sufficient. For this reason, Mw / Mn needs to be 6 or more, more preferably Mw / Mn is 7 or more.

  As for the α-olefin and ethylene copolymer used for the base layer 11 and the seal layer 12, the α-olefin includes propylene, butene-1, pentene-1, hexene-1, heptene-1, octene-1, Nonene-1, decene-1, dodecene-1, 4-methyl-pentene-1, 4-methyl-hexene-1 and the like can be used, and polymerization methods such as gas phase method, solution method, and slurry method can be used. In any of the methods, the polymerization catalyst can be used without particular limitation, such as a Ziegler-Natta catalyst or a metallocene catalyst. From the availability of materials, butene-1, hexene-1, 4-methyl-pentene-1 can be suitably used for α-olefins.

  About the low density polyethylene used for the base layer 11 and the sealing layer 12, it is possible to use the low density polyethylene produced using the autoclave method and the tubular method which are high pressure methods, and there is no restriction | limiting in particular. Can be used.

  The effect of mixing low-density polyethylene with long-chain branches is that the ethylene in the long-chain branches is mixed with the uniform molecular weight distribution resin, so that the elongation-strain effect is caused by the ethylene in the long-chain branches being sufficiently entangled with each other. There is an effect such as an increase in elongation viscosity due to long chain branching, and a reduction in the motor load of the extruder due to a reduction in shear viscosity due to an increase in free volume when the resin melts due to the presence of long chain branching. Leads to improvement.

  The effect of mixing low-density polyethylene with long chain branching into α-olefin and ethylene copolymer is described above, but impact resistance decreases among the physical properties of α-olefin and ethylene copolymer when the mixing amount is increased. To do. When the merit for physical properties and the merit for productivity are compared, it is preferable to use a mixing ratio of α-olefin, ethylene copolymer and low density polyethylene in a range of 70:30 to 98: 2 by weight. . For the base layer 11 and the seal layer 12, the mixing ratio of the low density polyethylene to the α-olefin and the ethylene copolymer may be the same or different, but the thickness ratio accuracy during molding deteriorates. Are preferably mixed at the same ratio.

  The film and sheet obtained from the laminate of the base layer 11 and the seal layer 12 are not particularly limited as long as they are of a thickness used in general packaging materials, but are preferably used in the range of 40 μm to 200 μm. .

  Regarding the lamination ratio of the base layer 11 and the seal layer 12, when the seal layer thickness is insufficient, the heat sealability is not sufficient, and when it is too thick, the rigidity is lowered and the practicality is lowered. For this reason, the minimum thickness of the 12 sealing layers is in the range of 7.5 μm to 30 μm, and is preferably used at 30% or less of the total thickness.

  The sealant film in the present invention is used by appropriately laminating a sealant film alone or a film of polyamide such as polyethylene terephthalate, 6 nylon or 66 nylon. It is important that the performance required in that case is in a range of a certain value or more in all physical properties such as rigidity, tear strength, impact resistance, and heat sealability. Details of each physical property item are described below.

(About rigidity)
The rigidity of the sealant film needs to be an index value greater than or equal to a predetermined value from the viewpoint of the self-supporting property of the container and the ease of taking out the contents when a single film or a laminated film is used, and the higher the rigidity, the better. The tensile modulus in the evaluation method of JISK7127 can be used as an index of rigidity. The higher the tensile modulus, the better the self-sustainability and the ease of taking out the contents, but the impact resistance decreases as a trade-off relationship. End up. For this reason, it is necessary to keep in a range where the balance between the tensile modulus (rigidity) and the impact resistance can be taken.
Specifically, when a material having a tensile modulus of elasticity of less than 300 MPa is used as a sealant for a refilling standing pouch, it cannot withstand the weight of the contents, and the standing pouch often bends and imparts independence. It becomes difficult to do. In this case, it is necessary to increase the thickness of the sealant film, but increasing the film thickness is not economical. When the tensile elastic modulus is larger than 450 MPa, the self-supporting property is excellent, but the impact resistance is lowered.
From the above requirements, the index value of the tensile modulus in the direction parallel to the film flow direction is preferably in the range of 300 MPa to 450 MPa.

(About tearability)
The tearability of the sealant film needs to be an index value of a predetermined value or more from the viewpoint of easy opening of the container when a single film or a laminated film is used. For the tearability, a value obtained by dividing the tear strength in the direction parallel to the film flow direction by the sealant film alone in the tearability described in JISK7128-2 is used.
Specifically, when tearability is less than 10 mN / μm, it becomes possible to impart easy-openability, but it is easy to tear when external force is applied, and when it is greater than 100 mN / μm, a packaging form Since it is difficult to open at the time of use, the tearability index value is preferably in the range of 10 mN / μm to 100 mN / μm.

(About impact resistance)
The impact resistance of the sealant film needs to be a predetermined index value or more from the viewpoint of content protection suitability when used as a single film or a laminated film. In impact resistance, a numerical value obtained by dividing the numerical value obtained in the impact resistance evaluation described in the JISK7124-1A method by the thickness is used.
Specifically, when the numerical value of impact resistance is smaller than 3.7 g / μm, when used as a sealant for a refilling standing pouch, when the standing pouch falls, it may not withstand the impact and may break the bag. For this reason, it is preferable that the index value of impact resistance is 3.7 g / μm or more.

(About heat sealability)
The heat sealability of the sealant film needs to be an index value of a predetermined value or more from the viewpoint of the difficulty of damaging the container when the film is filled with contents. The heat seal strength of a single sealant film after heat sealing with a seal bar at 140 ° C. for 1 second by the method described in JISZ0238 is used as an index.
Specifically, when the seal strength at the time of heat sealing at 140 ° C. is smaller than 10 N / 15 mm, it is fused in a heat fusion process such as a bag making process when the sealant film according to the present invention is used as a packaging material. Therefore, it is necessary to increase the temperature and pressure, and productivity is lowered. For this reason, it is preferable that the index value of heat seal strength is 10 N / 15 mm or more.

  To the base layer 11 and the seal layer 12, materials generally used for the film can be appropriately added in order to improve the suitability for forming the film and the sheet and the suitability for using the film and the sheet. For example, an anti-blocking agent such as a filler, a lubricant for improving slipperiness, an antioxidant for imparting processing stability, and the like can be appropriately added.

  Examples of anti-blocking agents such as fillers include acrylic particles, styrene particles, styrene acrylic particles and cross-linked products thereof, polyurethane particles, polyester particles, silicon particles, fluorine particles, copolymers thereof, and pyrophyllite. , Clay compounds particles such as talc, smectite, vermiculite, mica, chlorite, kaolin mineral, sepiolite, silica, titanium oxide, alumina, silica alumina, zirconia, zinc oxide, strontium oxide, aluminum hydroxide, strontium carbonate, strontium chloride, Strontium sulfate, strontium nitrate, strontium hydroxide, glass particles, and the like can be used as appropriate.

  As a lubricant for improving slipperiness, for example, sucrose fatty acid ester, glycerin fatty acid ester, synthetic resin system is a hydrocarbon system such as liquid paraffin, paraffin wax, synthetic polyethylene wax, fatty acid system such as stearic acid, stearyl alcohol, Fatty acid amides such as stearic acid amide, oleic acid amide, erucic acid amide, and alkylene fatty acid amides such as methylene bis stearic acid amide and ethylene bis stearic acid amide can be suitably used.

  In order to improve the handling property at the time of forming as a film and a sheet, the handling property may be improved by imparting a concavo-convex shape to the film surface other than the additives described above.

  The method for producing the film of the present invention is not particularly limited, and a known method can be used. For example, a melt kneading method using a general mixer such as a single screw extruder, a twin screw extruder, or a multi-screw extruder, a method of heating and removing the solvent after each component is dissolved or dispersed and mixed, etc. Can be used. In consideration of workability, it is preferable to use a single screw extruder or a twin screw extruder. When a single screw extruder is used, it can be used without particular limitation, such as a full flight screw, a screw having a mixing element, a barrier flight screw, and a fluided screw. The biaxial kneader is not particularly limited to the same direction rotating twin screw extruder, the different direction rotating twin screw extruder, and the screw shape is not limited to the full flight screw or kneading disc type.

  The method for laminating the base layer 11 and the seal layer 12 is not particularly limited, and a known method can be used. For example, a method of laminating the base layer 11 and the seal layer 12 by applying heat above the melting point to each film or sheet and pressurizing the base layer 11 and the seal layer 12 with different extruders. A method of obtaining a film by laminating in a heated and molten state can be used. In consideration of workability, a laminating method using a co-extruder for laminating in a molten state to obtain a film is preferable. As the coextrusion method, the thermoplastic resin that becomes each layer is melted with an extruder, and then the molten resin is laminated with a feed block to obtain a laminated film from the T-die. The feed block method, and the plastic that becomes each layer with an extruder It is possible to use a multi-manifold method in which a laminated film is obtained by melting and then passing through a manifold to obtain a laminated film, or a multilayer inflation molding method.

The film cooling method of the base layer 11 and the seal layer 12 is not particularly limited. For example, in the case of the T-die method, an air cooling method such as an air chamber, a vacuum chamber, an air knife, etc., or a cooling roll is dipped into a cold water pan. It is possible to use a water cooling method such as.
When the inflation molding method is used, a method using room temperature, heated air, or the like can be appropriately selected at the blow unit.

  In the sealant film obtained by the present invention, it is not particularly limited with respect to use by laminating with a single film and another base material, and a bag making mode. Even when used as a single film or laminated, the seal layer 12 side can be used as a content contact surface, and can be used for three-sided bags, jointed bags, gusset bags, standing pouches, pouches with spouts, pouches with beaks, and the like.

  As described above, in either case of laminating with a single film and another base material, it is possible to appropriately carry out a surface modification treatment that improves the suitability of the post-process. For example, it is possible to perform a surface modification treatment on the base layer 11 side in order to improve the printing suitability when using a single film and the laminate suitability when using a laminate. For surface modification treatment, it is possible to suitably use methods such as corona discharge treatment, plasma treatment, flame treatment, etc. to express functional groups by oxidizing the film surface, or modification by wet processes such as coating of easy-adhesion layers. It is.

  Examples of the present invention will be described in detail below, but the present invention is not limited to the following examples.

For the base layer 11, as a copolymer of α-olefin and ethylene, hexene-1 is used for the α-olefin, the density is 0.931 g / cm ³ , and the molecular weight distribution (Mw / Mn) is 10.1. Using a tubular method, a material having a density of 0.924 g / cm ³ and a molecular weight distribution (Mw / Mn) of 4.2 was mixed at a weight ratio of 80:20 to obtain a raw material for the base layer 11.

As the sealing layer 12, a material having a density of 0.913 g / cm ³ and a molecular weight distribution (Mw / Mn) of 2.3, using hexene-1 as an α-olefin as a copolymer of α-olefin and ethylene, A material having a density of 0.924 g / cm ³ and a molecular weight distribution (Mw / Mn) of 4.2 using a tubular method was mixed at a weight ratio of 80:20 to obtain a raw material for the seal layer 12.

  The raw material of the base layer 11 and the raw material of the seal layer 12 are respectively put into a single screw extruder having a full flight type screw and melted at 260 ° C., and then the thickness of the base layer 11 by a T-die extruder having a feed block. Was laminated to have a thickness of 85 μm and the sealing layer 12 had a thickness of 15 μm, and the film of Example 1 was produced.

In Example 1, a material in which the density of the copolymer of α-olefin and ethylene used for the seal layer 12 is 0.918 g / cm ³ and the molecular weight distribution (Mw / Mn) is 2.3 is used. In the same manner as above, the base layer 11 was laminated so that the thickness of the base layer 11 was 85 μm, and the thickness of the seal layer 12 was 15 μm, so that the film of Example 2 was produced.

In Example 1, a material having a density of 0.903 g / cm ³ and a molecular weight distribution (Mw / Mn) of α-olefin / ethylene copolymer used for the seal layer 12 of 2.3 is used. In the same manner as described above, the base layer 11 was laminated so that the thickness of the base layer 11 was 85 μm, and the thickness of the seal layer 12 was 15 μm.

In Example 1, a material in which the density of the copolymer of α-olefin and ethylene used for the seal layer 12 is 0.924 g / cm ³ and the molecular weight distribution (Mw / Mn) is 2.3 is used. In the same manner as above, the base layer 11 was laminated so that the thickness of the base layer 11 was 85 μm, and the thickness of the seal layer 12 was 15 μm.

  In Example 1, the same material was used for the base layer 11 and the seal layer 12, and the base layer 11 was laminated so that the thickness of the base layer 11 was 90 μm, and the thickness of the seal layer 12 was 10 μm, thereby producing the film of Example 5.

  In Example 1, the same material was used for the base layer 11 and the seal layer 12, and the base layer 11 was laminated to have a thickness of 70 μm and the seal layer 12 had a thickness of 30 μm, thereby producing a film of Example 6.

  In Example 1, the same material is used for the base layer 11 and the seal layer 12, and the base layer 11 is laminated so that the thickness of the base layer 11 is 42.5 μm and the thickness of the seal layer 12 is 7.5 μm, thereby producing the film of Example 7. did.

  In Example 1, the same material was used for the base layer 11 and the seal layer 12, and the base layer 11 was laminated so that the thickness of the base layer 11 was 130 μm, and the thickness of the seal layer 12 was 20 μm, and the film of Example 8 was produced.

  In Example 1, the base layer 11 and the seal layer 12 were mixed so that the weight ratio of α-olefin, ethylene copolymer and low-density polyethylene was 95: 5, the thickness of the base layer 11 was 85 μm, and the seal layer 12 The film of Example 9 was produced with a thickness of 15 μm.

  In Example 8, the base layer 11 and the seal layer 12 were mixed so that the weight ratio of α-olefin, ethylene copolymer and low-density polyethylene was 70:30, the thickness of the base layer 11 was 85 μm, and the seal layer 12 The film of Example 10 was made with a thickness of 15 μm.

Example 1 is the same as Example 1 except that the base layer 11 is made of a material in which the density of α-olefin and ethylene copolymer is 0.926 g / cm ³ and the molecular weight distribution (Mw / Mn) is 7.8. The film of Example 11 was produced.

Example 1 was the same as Example 1 except that the base layer 11 was made of a material in which the density of α-olefin and ethylene copolymer was 0.938 g / cm ³ and the molecular weight distribution (Mw / Mn) was 10.5. The film of Example 12 was produced.

In Example 12, the density of the α-olefin copolymer in the seal layer 12 was 0.903 g / cm ³ , the molecular weight distribution (Mw / Mn) was 2.3, and both the base layer 11 and the seal layer 12 were α-olefin and ethylene. Example 13 was obtained in the same manner as in Example 1 except that the weight ratio of the copolymer and low-density polyethylene was 95: 5.

  In Example 1, the thickness of the base layer 11 was changed to 95 μm, and the thickness of the seal layer 12 was changed to 5 μm, so that a film of Example 14 was produced.

  In Example 1, the thickness of the base layer 11 was changed to 60 μm, and the thickness of the seal layer 12 was changed to 40 μm, and the film of Example 15 was produced.

  The film of Example 16 was produced by changing the thickness of the base layer 11 to 35 μm and the thickness of the seal layer 12 to 5 μm in Example 1.

  In Example 1, the thickness of the base layer 11 was changed to 180 μm, and the thickness of the seal layer 12 was changed to 20 μm, so that a film of Example 17 was produced.

  In Example 1, the base layer 11 and the seal layer 12 were mixed so that the weight ratio of α-olefin, ethylene copolymer and low density polyethylene was 60:40, the thickness of the base layer 11 was 85 μm, and the seal layer 12 The film of Example 18 was produced with a thickness of 15 μm.

  In Example 1, the base layer 11 and the seal layer 12 were mixed so that the weight ratio of α-olefin, ethylene copolymer and low-density polyethylene was 99: 1, the thickness of the base layer 11 was 85 μm, and the seal layer 12 A film of Example 19 was produced with a thickness of 15 μm.

[Comparative Example 1]
In Example 1, a material in which the density of the α-olefin and ethylene copolymer of the base layer 11 is 0.924 g / cm ³ and the molecular weight distribution (Mw / Mn) is 2.3 is used. In the same manner as in Example 1, a film of Comparative Example 1 was produced.

[Comparative Example 2]
In Example 1, a material having a density of 0.926 g / cm ³ and a molecular weight distribution (Mw / Mn) of α-olefin and ethylene copolymer used for the seal layer 12 of 7.8 is used. A film of Comparative Example 2 was produced in the same manner as Example 1.

  The obtained film was subjected to tensile modulus, impact resistance test, tearability, and heat seal strength evaluation.

  In the tensile modulus test, the measurement was performed in accordance with the method described in JISK7127. The flow direction during film formation was the long side direction of the strip, and the film was cut into 15 mm width and 150 mm length. Evaluation was carried out with n = 5 using a tensile tester (model number AGS-500NX) manufactured by Shimadzu Corporation with a distance between marked lines of 50 mm and a tensile speed of 200 mm / min.

  In the impact resistance test, JISK7124-1 free fall impact test method using the Dirt method, Part 1 staircase method A method using a tester industry Co., Ltd. dirt impact tester (model number IM-302) 50% The breaking weight was measured. The measured 50% fracture weight was measured in units of μm by the method described in JISK7130, and the 50% fracture weight was divided by the measured thickness, and the 50% fracture weight per μm was calculated as an impact resistance value.

  In the tearing test, the tearing force in the flow direction during film formation was measured at n = 5 using the Elmendorf tearing method described in JISK7128-2. The tear force measured at n = 5 was divided by the thickness measured in μm by the method described in JISK7130 and calculated as a unit of mN / μm.

  In the measurement of the heat seal strength, a seal pressure of 0.2 MPa, a seal time of 1 second, a seal width of 10 mm using a heat sealer manufactured by Tester Sangyo (model number TP-701-B), and a seal temperature of 140 ° C. Sealed. The sealed film was cut into 15 mm width x 80 mm, the distance between chucks was 20 mm, the tensile speed was 300 mm / min, and evaluation was performed with n = 5 using Shimadzu Corporation tensile tester (model number AGS-500NX). did.

  Table 1 shows the results of physical property evaluation performed on the films described in Examples 1 to 19 and Comparative Examples 1 and 2.

  In Examples 1 to 19 and Comparative Examples 1 and 2, the tensile modulus is 300 MPa or more, the impact resistance is 3.7 g / μm or more, the tearability is 100 mN / μm or less, and the heat sealability is 10 N / 15 mm or more. It was evaluated as a criterion.

In Examples 1 to 13, all the above criteria are satisfied. Examples 14 to 18 are practically usable, but their use is limited because of some lack of performance. For Example 14, the heat seal strength is lower than the insufficient thickness of the seal layer 12, and if the seal layer 12 is too thick as in Example 15, the heat seal property is improved, but the tensile modulus (rigidity) is It will decline. Examples 16 and 17 are evaluations related to the thickness of the entire sealant film. When the seal layer thickness is too thin, there is no problem in use, but the rigidity and impact strength are not sufficient. Although it can be used without any problem, there is a demerit due to an increase in cost. Examples 18 and 19 are evaluated when the low density polyethylene ratio in each layer is changed. However, when the low density polyethylene ratio is large, the impact resistance is insufficient, and when it is small, the tearability is insufficient. There are restrictions on applications.
In Comparative Example 1, the resin density of the base layer is low and the rigidity cannot be sufficiently ensured, and in Comparative Example 2, the density of the sealing layer 12 is too high to exhibit sufficient heat sealability.

  In addition, this invention is not limited to an above-described Example, Various modifications are included. It is also possible to replace a part of the configuration of one embodiment with the configuration of another embodiment. Further, the above-described embodiments are described for easy understanding of the present invention, and are not necessarily limited to those having all the configurations described.

11 ... Base layer 12 ... Seal layer

Claims (5)

A laminated film in which at least a seal layer and a base layer are laminated,
(A) The base layer and the sealing layer each include at least one copolymer of α-olefin and ethylene, and low density polyethylene,
Average density of (b) the base layer is higher than the average density of the seal layer, the difference is in the range of ^{0.006g / cm 3 ~0.033g / cm 3} ,
(C) The laminated film, wherein the α-olefin and ethylene copolymer contained in the base layer has a molecular weight distribution (Mw / Mn) of 7.0 or more. In the laminated film according to claim 1,
(A) The tensile elastic modulus according to JIS K7161 is in the range of 300 MPa to 450 MPa,
(B) The range obtained by dividing the 50% fracture weight by the dirt impact method of JIS K7124-1 by the film thickness is 3.7 g / μm or more,
(C) The range obtained by dividing the tearing force in the film flow direction by the Elmendorf tearing method according to JIS K7128-2 by the film thickness is 10 mN / μm to 100 mN / μm,
(D) Lamination characterized by a seal pressure of 0.2 MPa, a seal time of 1 second, a seal width of 10 mm, and a seal strength of 10 N / 15 mm or more when the seal layers are sealed at 140 ° C. the film. In the laminated film according to claim 1 or 2,
(A) the density of the copolymer resin of the base layer of α- olefin and ethylene, a 0.926g / ^{cm 3} ~0.938g / ^cm 3 in the method according to JIS K7112,
(B) laminated film density of the copolymer resin of the sealing layer α- olefin and ethylene, characterized in that it is in the range of 0.903g / ^{cm 3} ~0.924g / ^cm 3 in the method according to JIS K7112 . In the laminated film according to any one of claims 1 to 3,
A laminated film, wherein a weight ratio of α-olefin, ethylene copolymer and low density polyethylene contained in the base layer and the sealing layer is in a range of 98: 2 to 70:30. In the laminated film according to any one of claims 1 to 4,
The total thickness of the base layer and the sealing layer is in the range of 40 μm to 200 μm,
The thickness of the said sealing layer is 5 micrometers-30 micrometers, The ratio of the thickness of the said sealing layer with respect to the said total thickness is 30% or less, The laminated film characterized by the above-mentioned.

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