JP2008080543A - Multilayer coextrusion film, laminated film and packaging material using the coextrusion film - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a multilayer coextrusion film which can be used for paper and a paper container with the surface of a polyethylene based container or paper coated with a polyethylene resin and a lid material or a top material of a polyethylene wrapping material such as sterilization paper, has heat seal strength to be easily openable by hand, and is excellent in peeling appearance. <P>SOLUTION: The multilayer coextrusion film comprises laminating a sealing resin layer (A) containing low density polyethylene (a1) and a polybutene-1 resin (a2), a resin layer (B) containing linear low density polyethylene (b1) and a polybutene-1 resin (b2), and a resin layer (C) made of medium density polyethylene (c1) in the order of (A)/(B)/(C). The melting point of the linear low density polyethylene (b1) is lower than that of the low density polyethylene (a1), and the thickness ratio of the combined thickness of the sealing resin layer (A) and the resin layer (B) to the thickness of the entire multilayer coextrusion film is 40-70%. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention is a packaging material for packaging foods, medicines, medical instruments, industrial parts, miscellaneous goods, magazines, and the like. Specifically, a polyethylene container or a paper or paper container whose surface is coated with a polyethylene resin, sterilized paper, polyethylene It is a coextruded multilayer film used as a cover material or a top material of a packaging material made of a single fiber made of a polyethylene resin, a microporous film obtained by mixing fibers made of polyethylene resin and other materials such as paper pulp, or a nonwoven fabric. In addition, the present invention relates to a coextruded multilayer film having heat seal strength that can be easily opened by hand, and a laminate film and a packaging material using the film.

  Conventionally, a polyethylene container or a paper container whose paper surface is coated with a polyethylene resin, sterilized paper, a fiber made of polyethylene resin alone, or a fiber made of polyethylene resin and other materials such as paper pulp A film having polyethylene as a main component has been used as a lid or top material of a packaging material made of a mixed microporous film, nonwoven fabric or the like. In addition, in the case of paper containers whose surfaces for dairy products whose sealing strength is regulated by law are covered with polyethylene resin, a lid material using hot melt resin is used, and sterilized paper has sufficient heat. A film coated with a heat seal material that provides seal strength has been used. Thus, conventionally, it was necessary to select a film suitable for the application and product group and use it as a lid material or a top material.

  However, depending on the application and product group, if the film used as the lid or top material is different, there is a problem that it is necessary to prepare many types of films. It was strongly desired to unify and unify the film used for the film.

  In recent years, from the viewpoint of waste disposal, the adoption of paper containers coated with polyethylene resin has become active mainly in containers for dairy products, jelly, desserts, instant noodles and the like. As a cover material for this paper container, hot melt resin is often used for its sealant, but it is difficult to open due to its strong opening strength, and the polyethylene resin on the inner surface of the paper container and the hot melt resin of the cover material at the time of opening. There was a problem that the breakage occurred between the paper and the polyethylene resin without causing breakage between the paper and the paper.

  As a solution to the above problem, an easy-open composite film in which a seal layer made of low-density polyethylene and polybutene-1 and a base material layer made of polyethylene-based resin are laminated has been proposed (see, for example, Patent Document 1). .) However, this composite film has good openability, but has a problem that the peeled appearance is poor due to phenomena such as stringing and film stiffness at the time of opening.

Furthermore, an easy-open composite film in which a sealing layer made of low-density polyethylene, polybutene-1 and ethylene-α olefin copolymer rubber and a base material layer made of polyethylene resin is laminated is proposed as an improvement in the peel appearance. (For example, see Patent Document 2). However, this composite film contains an ethylene-α-olefin copolymer rubber in the seal layer, so that the problem of transparency decreases, slippage deterioration due to the rubber component, and slip agent and anti-blocking to improve blocking between films. There was a problem that it was necessary to add a large amount of an agent.
Japanese Patent Laid-Open No. 10-337829 Japanese Patent Laid-Open No. 11-58642

  The subject of the present invention is a polyethylene container, a paper or paper container whose paper surface is coated with a polyethylene resin, sterilized paper, a fiber made of polyethylene resin alone, or a fiber made of polyethylene resin and paper pulp. A wide variety of polyethylene-based packaging materials (those having a heat-seal surface containing a polyethylene-based resin) or a top material composed of a microporous film, a nonwoven fabric, etc. mixed with the above materials can be used without problems. Another object of the present invention is to provide a coextruded multilayer film having heat-sealing strength that can be easily opened by hand and having excellent peel appearance, and a laminate film and a packaging material using the film.

As a result of intensive studies, the present inventors have found that a sealing resin layer (A) containing a low density polyethylene (a1) and a polybutene-1-based resin (a2) at a certain ratio, a linear low density polyethylene (b1) and The resin layer (B) containing the polybutene-1 resin (b2) at a constant ratio and the resin layer (C) made of medium density polyethylene (c1) are in the order of (A) / (B) / (C). A coextruded multilayer film having three resin layers laminated together, wherein the linear low density polyethylene (b1) has a melting point lower than the melting point of the low density polyethylene (a1), and the entire coextruded multilayer film A co-extruded multilayer film in which the ratio of the total thickness of the sealing resin layer (A) and the resin layer (B) to the thickness is 40 to 70%, or the resin layer (C) is a polyethylene resin. Resin layer (C ) And a resin layer (C2) made of medium density polyethylene (c1), and a co-extruded multilayer film having four resin layers is a polyethylene-based packaging material (having a heat seal surface containing a polyethylene-based resin). When it was used as a sealant film of a cover material or a top material, it was found that it was excellent in easy-openability and peeled appearance, and the present invention was completed.

  That is, the first form of the present invention is a seal resin layer (A) containing 70 to 90% by mass of low density polyethylene (a1) and 30 to 10% by mass of polybutene-1 resin (a2), linear low A resin layer (B) containing 80 to 95% by mass of density polyethylene (b1) and 20 to 5% by mass of polybutene-1 resin (b2), and a resin layer (C) comprising medium density polyethylene (c1), (A) / (B) / (C) is a co-extruded multilayer film laminated in the order, the melting point of the linear low density polyethylene (b1) is lower than the melting point of the low density polyethylene (a1), And the ratio of the total thickness of the said sealing resin layer (A) and the said resin layer (B) with respect to the thickness of the said whole coextruded multilayer film is 40 to 70%, The coextruded multilayer film characterized by the above-mentioned It is.

  Moreover, the second form of the present invention is a sealing resin layer (A) containing 70 to 90% by mass of low density polyethylene (a1) and 30 to 10% by mass of polybutene-1 resin (a2), linear low Density polyethylene (b1) 80 to 95% by mass and polybutene-1 resin (b2) 20 to 5% by mass of resin layer (B), resin layer (C1) mainly composed of polyethylene resin, and medium A resin layer (C2) made of density polyethylene (c1) is a coextruded multilayer film laminated in the order of (A) / (B) / (C1) / (C2), wherein the linear low density polyethylene The total thickness of the sealing resin layer (A) and the resin layer (B) with respect to the thickness of the entire coextruded multilayer film, the melting point of (b1) being lower than the melting point of the low density polyethylene (a1). The ratio is 40-70% A coextruded multilayer film characterized and.

  Furthermore, the present invention provides a laminate film and a packaging material using the coextruded multilayer film of the above two types.

  The coextruded multilayer film of the present invention is a polyethylene container, a paper or paper container whose paper surface is coated with a polyethylene resin, sterilized paper, a fiber made of polyethylene resin alone, or a fiber and paper pulp made of polyethylene resin. Use as a sealant film for lids or top materials of a wide variety of polyethylene-based packaging materials (having a heat-seal surface containing a polyethylene-based resin) composed of microporous films, non-woven fabrics, etc. mixed with other materials It has a heat seal strength that can be easily opened by hand and has an excellent peel appearance, so it is useful for polyethylene-based packaging materials for packaging food, medicine, medical equipment, industrial parts, sundries, magazines, etc. . In addition, the coextruded multilayer film of the present invention is excellent in peeling appearance even if no rubber component is blended in the sealing resin layer, so that the slipperiness of the film caused by blending of the rubber component and blocking between films are improved. In addition, it is not necessary to add a large amount of additives such as slip agents and antiblocking agents, and such additives may be added without addition or with a minimum amount. Accordingly, low molecular weight rubber components, additives, and the like do not bleed from the film surface over time, and thus are very suitable for packaging materials for foods and medical devices that hate bleeding such as additives.

  The co-extruded multilayer film of the present invention is obtained by laminating three layers of a sealing resin layer (A), a resin layer (B) and a resin layer (C) in the order of (A) / (B) / (C), or a seal The resin layer (A), the resin layer (B), the resin layer (C1), and the resin layer (C2) are laminated in the order of (A) / (B) / (C1) / (C2).

  The low density polyethylene (a1) used for the sealing resin layer (A) may be a branched low density polyethylene obtained by a high pressure radical polymerization method. A branched low density polyethylene obtained by homopolymerizing ethylene by a high pressure radical polymerization method is used. preferable.

The density of the low density polyethylene (a1) is preferably ^{0.900~0.935g / cm 3, 0.915~0.930g / cm} 3 is more preferable. The melting point is preferably from 100 to 125 ° C, more preferably from 105 to 115 ° C. When the density and the melting point are in this range, the film has an appropriate rigidity, excellent mechanical strength such as pinhole resistance, and improves film film formability and extrusion suitability.

  Further, the melt flow rate of the low-density polyethylene (measured at 190 ° C. and 21.18 N in accordance with JIS K7210; hereinafter referred to as “MFR”) is preferably 1 to 50 g / 10 minutes, preferably 3 to 45 g. / 10 min is more preferable, and 5 to 40 g / 10 min is further preferable. If MFR is within this range, it is preferable because extrusion moldability is improved.

  Examples of the polybutene-1 resin (a2) used for the sealing resin layer (A) include a homopolymer of butene-1 monomer and an ethylene-polybutene-1 copolymer mainly containing butene-1 monomer. Or a propylene-polybutene-1 copolymer etc. are mentioned. As content of the butene-1 monomer in polybutene-1 type-resin (a2), 60-100 mol% is preferable and 70-100 mol% is more preferable. The melting point of the polybutene-1 resin (a2) is preferably 80 to 135 ° C, more preferably 105 to 130 ° C, and still more preferably 110 to 125 ° C. If melting | fusing point is this range, blocking of films can be prevented and it is excellent in low temperature heat-sealing property.

The density of the polybutene-1 resin (a2) is preferably from ^{0.89~0.93g / cm 3, 0.90~0.92g / cm} 3 is more preferable. If the density is within this range, it has appropriate rigidity, little blocking, excellent mechanical strength such as pinhole resistance, and film film formability and extrusion suitability are improved. Moreover, 0.1-50 g / 10min is preferable and, as for MFR (190 degreeC, 21.18N) of the said polybutene-1 type-resin (a2), 1-45 g / 10min is more preferable. When the MFR is within this range, the extrusion moldability of the film is improved.

  The content ratio of the low density polyethylene resin (a1) and the polybutene-1 resin (a2) in the seal resin layer (A) is (a1) :( a2) = 70: 30 to 70 on a mass basis. Although 90:10, (a1) :( a2) = 75: 25 to 90:10 is more preferable. If the content ratio of each resin is within this range, transparency is improved and an appropriate heat seal strength is obtained.

  As the linear low density polyethylene (b1) used for the resin layer (B), an ethylene monomer as a main component and a butene-1 or hexene as a comonomer are obtained by a low pressure radical polymerization method using a single site catalyst. 1, α-olefins such as octene-1, 4-methylpentene and the like are copolymerized. As comonomer content in linear low density polyethylene (b1), 0.5-10 mol% is preferable and 1-7 mol% is more preferable. In addition, when hexene-1 and octene-1 are used as a comonomer, since transparency, impact resistance, etc. improve, it is preferable.

  Examples of the single-site catalyst include known single-site catalysts such as metallocene catalyst systems such as combinations of metallocene compounds of Group IV or V transition metals and organoaluminum compounds and / or ionic compounds. In addition, the single-site catalyst has a uniform active site, so the molecular weight distribution of the resulting resin is sharper than a multi-site catalyst with a non-uniform active site. This is preferable because a resin having physical properties excellent in stability of sealing strength and anti-blocking property can be obtained.

The density of the linear low density polyethylene (b1) is preferably ^{0.900~0.935g / cm 3, 0.905~0.920g / cm} 3 is more preferable. If the density is within this range, it has appropriate rigidity, excellent mechanical strength such as pinhole resistance, and film film formability and extrusion suitability are improved. Moreover, 95-120 degreeC is preferable for melting | fusing point, and 100-115 degreeC is more preferable. If melting | fusing point is this range, kneading | mixing precision with processing stability and polybutene-1 type-resin will improve. Moreover, 2-20 g / 10min is preferable and, as for MFR (190 degreeC, 21.18N) of the said linear low density polyethylene (b1), 3-10 g / 10min is more preferable. When the MFR is within this range, the extrusion moldability of the film is improved.

  Furthermore, the melting point of the linear low density polyethylene (b1) needs to be lower than the melting point of the low density polyethylene (a1). The larger the difference between the melting points of the two, the more preferable, specifically 5 ° C or higher is preferable, 10 ° C or higher is more preferable, and 15 ° C or higher is more preferable. In addition, the difference between the melting points of the linear low density polyethylene (b1) and the melting point of the low density polyethylene (a1) is about 30 ° C. at the maximum. By providing this normal difference in melting point, when heat-sealing the coextruded multilayer film of the present invention and a packaging material such as a polyethylene resin-coated paper container or sterilized paper, the heat-sealing surface of the packaging material and the sealing resin layer Since the resin layer (B) has already melted sufficiently at the temperature at which (A) is heat-sealed, even if the heat-sealing surface of the packaging material has irregularities, a reliable heat-sealing is possible following that. Stable heat sealing is possible even with a small amount of heat. Therefore, the co-extruded multilayer film of the present invention is suitable for cases where there are irregularities such as overlapping portions of flange portions of polyethylene resin-coated paper containers and locally thick portions of sterilized paper, even when the packaging speed is high. It becomes possible to apply.

  The polybutene-1 resin (b2) used for the resin layer (B) can be the same as the polybutene-1 resin (a2) used for the seal resin layer (A), but the polybutene-1 resin can be used. As long as it is a resin, it may not be the same as the polybutene-1 resin (a2) used in the sealing resin layer (A).

  The content ratio of the linear low density polyethylene (b1) in the resin layer (B) and the polybutene-1 resin (b2) is (b1) :( b2) = 80: 20 to mass basis. Although it is 95: 5, (b1) :( b2) = 75: 25 to 90:10 is more preferable. If the content ratio of each resin is within this range, transparency is improved and an appropriate heat seal strength is obtained.

When the coextruded multilayer film of the present invention has a three-layer structure, the medium density polyethylene (c1) used for the resin layer (C) is a polyethylene that has a short branch and is obtained by the low-pressure radical polymerization method. Density is preferably 0.920~0.945g / cm ³ of the medium density polyethylene (c1), 0.925~0.940g / cm ³ is more preferable. Further, a medium-density polyethylene (c1) obtained by melt blending or dry blending high-density polyethylene and low-density polyethylene having a density within this range may be used. Furthermore, the melting point of the medium density polyethylene (c1) is preferably 110 to 135 ° C, more preferably 115 to 130 ° C. If the melting point and density are within this range, it has a suitable rigidity, suppresses the flow-out when the resin melts during heat sealing, has excellent mechanical strength such as film seal pinhole resistance, film film formability, extrusion Suitability and suitability for secondary processing during lamination are improved.

  Further, the MFR (190 ° C., 21.18N) of the medium density polyethylene (c1) is preferably 0.1 to 30 g / 10 minutes, more preferably 0.3 to 25.0 g / 10 minutes, and 0.8 to 20 More preferably, 0.0 g / 10 min. When the MFR is within this range, the extrusion moldability is improved.

  On the other hand, when the coextruded multilayer film of the present invention has a four-layer structure, the resin layer (C) is a two-layered resin layer (C1) and resin layer (C2). In this case, the resin layer (C1) is mainly composed of a polyethylene resin. Examples of the polyethylene resin include low density polyethylene, linear low density polyethylene, medium density polyethylene, high density polyethylene, and ethylene. -Alpha-olefin copolymer etc. are mentioned. Examples of resins other than these polyethylene resins include polybutene-1 resins, polypropylene resins, cyclic polyolefin resins, polyamide resins, and ethylene vinyl alcohol copolymers (EVOH). In addition, the polyethylene resin and other resins may be used alone or in combination of two or more. In addition, 50-100 mass% is preferable, as for the content rate of the polyethylene-type resin in the said resin layer (C1), 75-100 mass% is more preferable, and 85-100 mass% is further more preferable. Furthermore, as the resin for the resin layer (C1), the end of the film generated by trimming the film end when the coextruded multilayer film of the present invention is produced can be recovered and reused.

  The medium density polyethylene (c1) used for the resin layer (C2) is the same as the medium density polyethylene (c1) used for the resin layer (C).

  The melting point of each of the above resins can be measured using a differential scanning calorimeter (DSC). As the differential scanning calorimeter device used for the melting point measurement, for example, “DSC200” manufactured by Seiko Denshi Kogyo Co., Ltd. can be used.

  In the coextruded multilayer film of the present invention, the ratio of the total thickness of the sealing resin layer (A) and the resin layer (B) to the thickness of the entire film is 40 to 70%. When this ratio is less than 40%, when the coextruded multilayer film of the present invention is used as a cover material for a paper container coated with polyethylene resin, the step of the overlapping portion of the flange portion may be filled when heat-sealing. In addition, it becomes difficult, and when the lid is opened, paper peeling occurs that causes separation between the polyethylene resin coated on the paper container and the paper. Also, when heat-sealing with sterilized paper, there is a problem that the thickness of the sterilized paper itself is uneven, which causes problems such as unstable heat seal strength. When opening after heat-sealing, it can be opened from the heat-sealed part. Therefore, there is a problem that the sterilized paper is torn at a thin portion or paper dust is generated due to peeling in the sterilized paper. In particular, when used for packaging for medical instruments used in aseptic operating rooms or the like, there is a problem that the generation of paper dust due to peeling of paper becomes a source of contamination. On the other hand, if the ratio exceeds 70%, the rigidity of the film becomes extremely low, and the slipperiness of the film decreases, so that the processability at the time of film formation and secondary processing such as lamination is reduced. There is.

  In the sealing resin layer (A), resin layer (B), (C), (C1), or (C2) of the coextruded multilayer film of the present invention, an antifogging agent, an antistatic agent, Components such as a heat stabilizer, a nucleating agent, an antioxidant, a lubricant, an antiblocking agent, a release agent, an ultraviolet absorber, and a colorant can be added within a range that does not impair the object of the present invention. In particular, the surface friction coefficient of the sealing resin layer (A), the resin layer (C), and the resin layer (C2) is set to 1.5 in order to provide processing suitability during film forming and packaging suitability when used in a filling machine. In the following, since it is preferable to make it 1.2 or less, it is preferable to appropriately add a lubricant or an antiblocking agent to these resin layers.

  Although it does not specifically limit as a manufacturing method of the coextruded multilayer film of this invention, For example, it can manufacture by the following method.

[Method for producing co-extruded multilayer film having a three-layer structure]
Low density polyethylene (a1) and butene-1 resin (a2) used for the sealing resin layer (A), and linear low density polyethylene (b1) and butene-1 resin (b2) used for the resin layer (B) And the medium density polyethylene (c1) used for the resin layer (C) are heated and melted by different extruders, and are melted in a molten state by a method such as a co-extrusion multilayer die method or a feed block method (A) / (B ) / (C), and a co-extruded multilayer film having a three-layer structure can be produced by a co-extrusion method in which a film is formed by inflation, T-die / chill roll method, or the like. This coextrusion method is preferable because the thickness ratio of each layer can be adjusted relatively freely, and a multilayer film excellent in hygiene and cost performance can be obtained.

[Method for producing co-extruded multilayer film having four layers]
Low density polyethylene (a1) and butene-1 resin (a2) used for the sealing resin layer (A), and linear low density polyethylene (b1) and butene-1 resin (b2) used for the resin layer (B) And a resin mainly composed of a polyethylene-based resin used for the resin layer (C1) and medium density polyethylene (c1) are heated and melted in different extruders, respectively, such as a coextrusion multilayer die method or a feed block method. After laminating in the order of (A) / (B) / (C1) / (C2) in the molten state by the method, it is formed into a film by inflation, T-die / chill roll method, etc. in the same manner as the three-layer coextruded multilayer film. A co-extruded multilayer film having a four-layer structure can be produced by the co-extrusion method.

  The coextruded multilayer film of the present invention can be used as a sealant film for a laminate film. When the coextruded multilayer film of the present invention is used as a sealant film for a laminate film, the seal resin layer (A) is a seal layer, and the resin layer (C) or the resin layer (C2) is a laminate layer on the adhesive surface with the substrate. It becomes.

  As a manufacturing method of the said laminate film, the method of laminating | stacking a base material through adhesive resin or an adhesive agent on the resin layer (C) or resin layer (C2) of the coextruded multilayer film of this invention is mentioned. Examples of the adhesion method when laminating the substrate include dry lamination, wet lamination, non-solvent lamination, extrusion lamination, and the like. Examples of the adhesive used in the dry lamination include a polyether-polyurethane adhesive and a polyester-polyurethane adhesive.

  The substrate used for the laminate film is not particularly limited as long as it does not impair the sealing properties and packaging suitability. For example, biaxially stretched polyester (PET), biaxially stretched polypropylene (OPP), and ethylene vinyl alcohol are used. Coextruded biaxially oriented polypropylene with polymer (EVOH) as the central layer, biaxially oriented ethylene vinyl alcohol copolymer (EVOH), coextruded biaxially oriented polypropylene coated with polyvinylidene chloride (PVDC), biaxially oriented nylon And aluminum foil.

  Furthermore, in order to improve adhesiveness with printing ink and suitability for lamination, it is preferable to perform a surface treatment on the resin layer (C) or the resin layer (C2). Examples of such surface treatment include corona treatment, plasma treatment, chromic acid treatment, flame treatment, hot air treatment, surface oxidation treatment such as ozone / ultraviolet treatment, and surface unevenness treatment such as sandblasting. Corona treatment is preferable.

  A laminate film using the above-mentioned coextruded multilayer film of the present invention as a sealant film can be used as a packaging lid or top material. In addition, as a packaging material sealed by heat-sealing the lid material or the top material, a polyethylene container or a paper container whose paper surface is coated with a polyethylene resin, a sterilized paper, a fiber made of a polyethylene resin Examples thereof include a microporous film, a nonwoven fabric, etc. obtained by mixing fibers made of polyethylene resin alone and other materials such as paper pulp. Since these packaging materials have a heat seal surface containing a polyethylene resin, the co-extruded multilayer film of the present invention can be suitably used.

  For the sterilized paper, a microporous film (for example, “Medica” manufactured by Oji Specialty Paper Co., Ltd.) in which fibers made of polyethylene resin alone, or fibers made of polyethylene resin and other materials such as paper pulp are mixed. There are fiber fabrics made of high-density polyethylene (for example, “Tyvek” manufactured by Asahi DuPont Flashspun Products Co., Ltd.), non-woven fabrics and the like.

  The packaging material of the present invention wraps the contents by heat-sealing a packaging material having a heat-sealing surface containing the above polyethylene-based resin and a laminate film using the coextruded multilayer film of the present invention as a sealant film. is there.

  The packaging material may be subjected to sterilization treatment such as electron beam, γ-ray, ethylene oxide (EOG), autoclave treatment and the like.

  Next, the present invention will be described in more detail with reference to examples and comparative examples. In addition, melting | fusing point of each resin used by the Example and the comparative example was measured with the following measuring methods.

(Measurement of melting point of each resin)
About 3 mg of each resin sample was weighed, set in a differential scanning calorimeter (“DSC200” manufactured by Seiko Denshi Kogyo Co., Ltd.), heated to 200 ° C., held at 200 ° C. for 3 minutes, and then 10 ° C. It cooled to 30 degreeC with the temperature-fall rate of / min. Subsequently, after hold | maintaining at 30 degreeC for 3 minute (s), it heated up again at 200 degreeC with the temperature increase rate of 10 degree-C / min, and obtained the DSC curve. The melting peak of the obtained DSC curve was taken as the melting point of the resin. When a plurality of melting peaks exist, the largest melting peak is taken as the melting point of the resin.

(Example 1)
As a resin for the sealing resin layer (A), low density polyethylene (“UBE polyethylene F522” manufactured by Ube Maruzen Polyethylene Co., Ltd., density: 0.925 g / cm ³ , melting point 115 ° C., MFR: 5 g / 10 min (190 ° C., 21 18N); hereinafter referred to as “LDPE”) and 80 parts by mass of polybutene-1 resin (“8240” manufactured by BASELL, density: 0.91 g / cm ³ , MFR: 2 g / 10 minutes (190 ° C., 21. 18N); hereinafter referred to as "PB") Resin composition added to 20 parts by weight of mixed resin at a ratio such that the concentration of erucic acid amide (lubricant) is 500 ppm and the concentration of natural silica (anti-blocking agent) is 3000 ppm. As a resin for the resin layer (B), linear low density density polyethylene (“UBE polyethylene manufactured by Ube Maruzen Polyethylene Co., Ltd.”) is used. 0540 ", density: 0.905 g / cm ^3, melting point 100 ℃, MFR:. 4g / 10 min (190 ° C., 21.18 N); hereinafter referred to as" LLDPE ") 85 parts by mass and PB15 parts by weight mixed resin As the resin for the resin layer (C), medium density polyethylene (“LW01” manufactured by Tosoh Corporation, density: 0.933 g / cm ³ , melting point 128 ° C., MFR: 8 g / 10 min (190 ° C., 21.18 N) Hereinafter referred to as “MDPE”).

  These resins are supplied to an extruder for sealing resin layer (A) (caliber 40 mm), an extruder for resin layer (B) (caliber 40 mm), and an extruder for resin layer (C) (caliber 50 mm), respectively. After melting at ˜230 ° C., each film is fed to a T-die / chill roll co-extruded multilayer film production apparatus (feed block and T-die temperature: 250 ° C.) having a feed block to perform co-melt extrusion, and the film layer A co-extruded multilayer film having a three-layer constitution (A) / (B) / (C) and a thickness of each layer of 10 μm / 5 μm / 15 μm (total 30 μm) was obtained.

(Example 2)
Example 1 except that a mixed resin of 90 parts by mass of LDPE and 10 parts by mass of PB was used as the resin for the sealing resin layer (A), and a mixed resin of 80 parts by mass of LLDPE and 20 parts by mass of PB was used as the resin for the resin layer (B). In the same manner as above, a coextruded multilayer film was prepared so that the thickness of each layer of the film was (A) / (B) / (C) = 10 μm / 10 μm / 10 μm (total 30 μm). Got.

(Example 3)
Example 1 except that a mixed resin of 70 parts by mass of LDPE and 30 parts by mass of PB was used as the resin for the sealing resin layer (A), and a mixed resin of 95 parts by mass of LLDPE and 5 parts by mass of PB was used as the resin for the resin layer (B). In the same manner as above, a coextruded multilayer film was prepared so that the thickness of each layer of the film was (A) / (B) / (C) = 8 μm / 4 μm / 18 μm (total 30 μm). Got.

Example 4
As a resin for the sealing resin layer (A), it was added to a mixed resin of 80 parts by mass of LDPE and 20 parts by mass of PB in such a ratio that the concentration of erucic acid amide (lubricant) was 500 ppm and the concentration of natural silica (anti-blocking agent) was 3000 ppm. Using the resin composition, a mixed resin of 85 parts by mass of LLDPE and 15 parts by mass of PB was used as the resin for the resin layer (B). The resin layer (C) has a two-layer structure of resin layers (C1) and (C2). As the resin layer (C1), a mixed resin of 84 parts by mass of MDPE, 8 parts by mass of LDPE, 5 parts by mass of LLDPE, and 3 parts by mass of PB is used. Used, MDPE was used as the resin layer (C2).

  These resins are respectively used as an extruder for sealing resin layer (A) (diameter 40 mm), an extruder for resin layer (B) (diameter 40 mm), an extruder for resin layer (C1) (diameter 50 mm), and a resin layer (C2 ) Fed to an extruder (50 mm in diameter) and melted at 200 to 230 ° C., and then fed to a T-die / chill roll co-extrusion multilayer film production apparatus (feed block and T-die temperature: 250 ° C.) having a feed block. Supplying and co-melt extrusion, the layer structure of the film is (A) / (B) / (C1) / (C2), and the thickness of each layer is 10 μm / 5 μm / 10 μm / 5 μm (total) A co-extruded multilayer film having a thickness of 30 μm was obtained.

(Comparative Example 1)
As a resin for the sealing resin layer (A), it was added to a mixed resin of 90 parts by mass of LDPE and 10 parts by mass of PB in such a ratio that the concentration of erucic acid amide (lubricant) was 500 ppm and the concentration of natural silica (anti-blocking agent) was 3000 ppm. Using the resin composition, MDPE was used as the resin for the resin layer (C). These resins were respectively fed to an extruder for sealing resin layer (A) (caliber 40 mm) and an extruder for resin layer (C) (caliber 50 mm) and melted at 200 to 230 ° C., and then T having a feed block A co-extrusion multilayer film production apparatus (feed block and T-die temperature: 250 ° C.) of the die / chill roll method is supplied to each other to perform co-melt extrusion, and the film has a two-layer structure (A) / (C). Thus, a coextruded multilayer film in which the thickness of each layer was 10 μm / 20 μm (total 30 μm) was obtained.

(Comparative Example 2)
Example 1 except that a mixed resin of 90 parts by mass of LLDPE and 10 parts by mass of PB was used as the resin for the sealing resin layer (A), and a mixed resin of 90 parts by mass of LDPE and 10 parts by mass of PB was used as the resin for the resin layer (B). In the same manner as above, a coextruded multilayer film in which the thickness of each layer of the film was (A) / (B) / (C) = 10 μm / 5 μm / 15 μm (total 30 μm) was obtained.

(Comparative Example 3)
Example 1 except that a mixed resin of 80 parts by mass of LDPE and 20 parts by mass of PB was used as the resin for the sealing resin layer (A), and a mixed resin of 70 parts by mass of LLDPE and 30 parts by mass of PB was used as the resin for the resin layer (B). In the same manner as above, a coextruded multilayer film in which the thickness of each layer of the film was (A) / (B) / (C) = 10 μm / 5 μm / 15 μm (total 30 μm) was obtained.

(Comparative Example 4)
Example 1 A mixed resin of 80 parts by mass of LDPE and 20 parts by mass of PB was used as the resin for the sealing resin layer (A), and a mixed resin of 97 parts by mass of LLDPE and 3 parts by mass of PB was used as the resin for the resin layer (B). In the same manner as above, a coextruded multilayer film in which the thickness of each layer of the film was (A) / (B) / (C) = 10 μm / 5 μm / 15 μm (total 30 μm) was obtained.

(Comparative Example 5)
Example 1 A mixed resin of 60 parts by mass of LDPE and 40 parts by mass of PB was used as the resin for the sealing resin layer (A), and a mixed resin of 85 parts by mass of LLDPE and 15 parts by mass of PB was used as the resin for the resin layer (B). In the same manner as above, a coextruded multilayer film in which the thickness of each layer of the film was (A) / (B) / (C) = 10 μm / 5 μm / 15 μm (total 30 μm) was obtained.

(Comparative Example 6)
Example 1 except that a mixed resin of 95 parts by mass of LDPE and 5 parts by mass of PB was used as the resin for the sealing resin layer (A), and a mixed resin of 85 parts by mass of LLDPE and 15 parts by mass of PB was used as the resin for the resin layer (B). In the same manner as above, a coextruded multilayer film in which the thickness of each layer of the film was (A) / (B) / (C) = 10 μm / 5 μm / 15 μm (total 30 μm) was obtained.

(Comparative Example 7)
Example 1 except that a mixed resin of 90 parts by mass of LDPE and 10 parts by mass of PB was used as the resin for the sealing resin layer (A), and a mixed resin of 85 parts by mass of LLDPE and 15 parts by mass of PB was used as the resin for the resin layer (B). In the same manner as above, a coextruded multilayer film in which the thickness of each layer of the film was (A) / (B) / (C) = 5 μm / 5 μm / 20 μm (total 30 μm) was obtained.

(Comparative Example 8)
Example 1 except that a mixed resin of 90 parts by mass of LDPE and 10 parts by mass of PB was used as the resin for the sealing resin layer (A), and a mixed resin of 85 parts by mass of LLDPE and 15 parts by mass of PB was used as the resin for the resin layer (B). In the same manner as above, a coextruded multilayer film in which the thickness of each layer of the film was (A) / (B) / (C) = 10 μm / 15 μm / 5 μm (total 30 μm) was obtained.

(Production of laminate film)
A biaxially stretched polyethylene terephthalate (PET) film (thickness: 12 μm) is bonded to the surface of the resin layer (C) or (C2) of the coextruded multilayer film obtained in the above-mentioned Examples and Comparative Examples by dry lamination, A laminate film was obtained. At this time, as a dry lamination adhesive, a two-component curable adhesive (polyester adhesive “LX63F” and a curing agent “KP90”) manufactured by Dainippon Ink & Chemicals, Inc. was used.

(Evaluation of laminating suitability)
The laminate film produced above was cut into a size of 20 cm × 20 cm, the degree of curling after storage for 1 day in a constant temperature and humidity chamber at 40 ° C. and 60% humidity was confirmed, and laminating suitability was evaluated according to the following criteria. .
○: The film is curled and not completely curled.
X: The film is curled and completely curled.

(Measurement of heat seal strength in paper containers)
A round cup paper container having a flange portion having an outer diameter of 70 mm, a depth of 50 mm, and a width of 5 mm made of paper coated with polyethylene resin on the surface of the sealing resin layer (A), using the laminate film obtained above as a lid. Was sealed with a seal temperature of 140 ° C., a seal pressure of 0.2 MPa, and a seal time of 1 second. Next, the heat-sealed film was naturally cooled at 23 ° C., and then cut into a 15 mm-wide strip to obtain a test piece. This test piece was subjected to a tensile tester (A & Co., Ltd.) in a thermostatic chamber at 23 ° C. and 50% RH. 90 ° peeling was performed at a rate of 300 mm / min, and the heat seal strength was measured.

(Evaluation of heat sealability in paper containers)
From the result of the heat seal strength measured above, the heat seal property in a paper container was evaluated according to the following criteria.
○: Heat seal strength is 5 to 20 N / 15 mm.
X: Heat seal strength is less than 5 N / 15 mm or more than 20 N / 15 mm.

(Evaluation of openability in paper containers)
Using the same heat-sealed lid material made of the laminate film obtained above to the flange part of the round cup paper container prepared at the time of measuring the above heat-sealing strength, the lid material was opened by hand and opened. The opening feeling was confirmed, and the opening property in the paper container was evaluated according to the following criteria.
○: The force required for peeling off the lid is constant, and smooth peeling is easy.
X: The force required for peeling off the lid material is not constant, and the peeling is not smooth.

(Evaluation of peeling appearance in paper containers)
In the above-described evaluation of openability, the outer appearance of the flange part and the seal part of the round cup paper container after opening the lid material is visually observed, and the film residue, stringing and paper are evaluated according to the following criteria as an evaluation of peeling appearance. The peeling was evaluated.

(Evaluation of film residue and stringing in paper containers)
○: No film residue or stringing.
X: A film having at least one of film remaining and stringing.

(Evaluation of paper peeling in paper containers)
○: No paper peeling.
×: There is paper peeling.

(Evaluation of sealing performance in paper containers)
Using the same heat-sealed lid material made of the laminate film obtained above to the flange part of the round cup paper container prepared at the time of measuring the heat seal strength, a nozzle was inserted into the bottom of the container, and the air Was applied, internal pressure was applied, and the burst strength when the lid material burst was measured with a seal tester (manufactured by San Kagaku Co., Ltd.). From the obtained burst strength, sealability was evaluated according to the following criteria.
○: Burst strength is 20 KPa or more.
X: The burst strength is less than 20 KPa.

(Measurement of heat seal strength with sterilized paper)
The sealing surface of the laminate film obtained above and the sealing surface of non-coated sterilized paper (“Tyvek 1059B” manufactured by Asahi DuPont Flashspan Products Co., Ltd.) are overlapped, and the heat sealing temperature is 140 ° C. and the sealing pressure is 0.2 MPa. Then, heat sealing was performed under the condition of a sealing time of 0.7 seconds. Next, the heat-sealed film was naturally cooled at 23 ° C., and then cut into a 15 mm-wide strip to obtain a test piece. This test piece was subjected to a tensile tester (A & Co., Ltd.) in a thermostatic chamber at 23 ° C. and 50% RH. 90 ° peeling was performed at a rate of 300 mm / min, and the heat seal strength was measured.

(Evaluation of heat sealability with sterilized paper)
From the result of the heat seal strength measured above, the heat seal property in a paper container was evaluated according to the following criteria.
○: Heat seal strength is 3 to 9 N / 15 mm.
X: The heat seal strength is less than 3 N / 15 mm or more than 9 N / 15 mm.

(Evaluation of openability with sterile paper)
Using the same heat-sealed laminate film and sterilized paper obtained above when measuring the heat-sealing strength, the laminate film and sterilized paper are opened manually, and then opened when opened. The feeling was confirmed, and the openability in a paper container was evaluated according to the following criteria.
○: The force required for peeling off the lid is constant, and smooth peeling is easy.
X: The force required for peeling off the lid material is not constant, and the peeling is not smooth.

(Evaluation of peeling appearance with sterilized paper)
In the above evaluation of unsealing properties, the appearance of the sealing part of the laminated film and the sterilized paper after opening the laminated film and the sterilized paper is visually observed, and the film residue and stringing are evaluated according to the following criteria as an evaluation of the peel appearance. And paper peeling was evaluated.

(Evaluation of film residue and stringing with sterilized paper)
○: No film residue or stringing.
X: A film having at least one of remaining film and stringing.

(Evaluation of peeling with sterilized paper)
○: No paper peeling.
×: There is paper peeling.

  The results obtained above are shown in Tables 1 and 2.

  From the evaluation results of Examples 1 to 4 shown in Table 1, the following was found.

  It was found that when the coextruded multilayer films of Examples 1 to 4 of the present invention were used as a sealant film for a laminate film, curling after lamination was small and the laminating suitability was excellent. In addition, the laminate film using the coextruded multilayer film of the present invention has an appropriate heat seal strength when heat-sealed with a paper container or sterilized paper, has a good heat-sealing property, and can be smoothly opened. It was possible and the opening property was stable, and it was found that the sealed portion after opening was excellent in peeling appearance without film lump, stringing and paper peeling. Furthermore, it has also been found that when a laminate film using the coextruded multilayer film of the present invention is used as a lid for a paper container, it has sufficient sealing properties.

  From the evaluation results of Comparative Examples 1 to 8 shown in Table 2, the following was found.

  Comparative Example 1 is an example of a coextruded multilayer film without the resin layer (B), but both the paper container and the sterilized paper had film stiffness and stringing after opening, and the peeled appearance was impaired. Moreover, since the sealing strength with sterilized paper is too strong, there is a problem that the paper peels off. Furthermore, the sealing performance when used as a cover material for paper containers was insufficient.

  Comparative Example 2 is a coextrusion using a low density polyethylene instead of a low density polyethylene in the sealing resin layer (A) and a low density polyethylene instead of a linear low density polyethylene in the resin layer (B). Although it is an example of a multilayer film, both the paper container and the sterilized paper had film stiffness and stringing after opening, and the peeled appearance was impaired. Moreover, since the sealing strength with sterilized paper is too strong, there is a problem that the paper peels off when opened.

  Comparative Example 3 is an example of a co-extruded multilayer film in which the content ratio of the linear low-density polyethylene in the resin layer (B) is less than 80% by mass. There was a pull and the peeling appearance was impaired.

  Comparative Example 4 is an example of a coextruded multilayer film in which the content ratio of the linear low-density polyethylene in the resin layer (B) is more than 95% by mass. There was stringing and stringing, and the peel appearance was impaired. Further, when used for sterilized paper, there is a problem that the paper peels off when opened.

  Comparative Example 5 is an example of a coextruded multilayer film in which the content ratio of the low-density polyethylene in the sealing resin layer (A) is less than 70% by mass, but both the paper container and the sterilized paper have insufficient heat seal strength, There was a problem in heat sealability.

  Comparative Example 6 is an example of a co-extruded multilayer film in which the content ratio of the low density polyethylene in the sealing resin layer (A) is a ratio exceeding 90% by mass, but the heat seal strength is too high for both the paper container and the sterilized paper. There was a problem with opening. In addition, when used for sterilized paper, there is a problem that the paper peels off when opened.

  Comparative Example 7 is an example of a coextruded multilayer film in which the ratio of the total thickness of the sealing resin layer (A) and the resin layer (B) to the total film thickness is less than 40%. The sealability when used as a lid was also insufficient. Further, there is a problem that the film cannot follow the uneven thickness of the sterilized paper, the sealing strength is not stable, and the paper peels off when opened.

Comparative Example 8 is an example of a coextruded multilayer film in which the ratio of the total thickness of the sealing resin layer (A) and the resin layer (B) to the thickness of the entire film is a ratio exceeding 70%. The rigidity of the laminate was low, the curl after lamination with the base material was large, and the laminating suitability was insufficient.

Claims (5)

Seal resin layer (A) containing 70 to 90% by mass of low density polyethylene (a1) and 30 to 10% by mass of polybutene-1 resin (a2), 80 to 95% by mass of linear low density polyethylene (b1) And a resin layer (B) containing 20 to 5% by mass of the polybutene-1 resin (b2) and a resin layer (C) composed of medium density polyethylene (c1) are (A) / (B) / (C) In which the melting point of the linear low-density polyethylene (b1) is lower than the melting point of the low-density polyethylene (a1) and the total thickness of the co-extruded multilayer film is A co-extruded multilayer film, wherein the ratio of the total thickness of the sealing resin layer (A) and the resin layer (B) is 40 to 70%. Seal resin layer (A) containing 70 to 90% by mass of low density polyethylene (a1) and 30 to 10% by mass of polybutene-1 resin (a2), 80 to 95% by mass of linear low density polyethylene (b1) And a resin layer (C2) containing 20 to 5% by mass of a polybutene-1 resin (b2), a resin layer (C1) containing a polyethylene resin as a main component, and a medium density polyethylene (c1) (C2 ) Is a coextruded multilayer film laminated in the order of (A) / (B) / (C1) / (C2), wherein the linear low density polyethylene (b1) has a melting point of the low density polyethylene ( The ratio of the total thickness of the sealing resin layer (A) and the resin layer (B) to the total thickness of the coextruded multilayer film is lower than the melting point of a1) and is 40 to 70%. Characteristic coextrusion multilayer film Lum. The coextruded multilayer film according to claim 1 or 2, wherein the difference between the melting point of the low density polyethylene (a1) and the melting point of the linear low density polyethylene (b1) is 5 ° C or more. A laminate film comprising a sealant film comprising the coextruded multilayer film according to claim 1. A packaging material obtained by heat-sealing a packaging material having a heat-sealing surface containing a polyethylene resin and the laminate film according to claim 4.