JP5751031B2 - Packaging material and paper container comprising the same - Google Patents

Description

  The present invention relates to a packaging material having a non-adsorptive sealant layer and a paper substrate layer in which the amount of organic compounds contained in contents such as pharmaceuticals, cosmetics and foods is reduced, and a paper container comprising the same. More specifically, since the adsorption amount of the organic compound in the contents is reduced, the packaging material having a sealant layer excellent in maintaining the quality of the contents and excellent in heat sealability, and paper comprising the same A container, in particular a liquid paper container.

In general, a paper container is made of a packaging material having a paper base layer and a sealant layer. As these sealant layers, a thermoplastic resin is used, and in particular, a high-pressure low-density polyethylene resin (LDPE, density 0.910 to 0.925 g / cm ³ ) and the like are excellent in terms of laminate processability and heat sealability. It is used.

  Although LDPE can achieve high adhesion strength by heat sealing, it is known that it can easily adsorb organic compound components. Therefore, the paper container having the sealant layer made of LDPE as the innermost layer, that is, the layer in contact with the contents, easily adsorbs the organic compound component contained in the contents and easily changes or deteriorates the contents.

On the other hand, in some cases, a medium density polyethylene resin (MDPE, density 0.926 to 0.940 g / cm ³ ) is used as the sealant layer. However, MDPE has a drawback that a stable sealing temperature range cannot be obtained because the heat sealing temperature during box making (molding of paper containers) must be set higher than LDPE in order to obtain sufficient adhesion strength. . Further, when heat-sealing at such a high temperature, MDPE is oxidized and an oxidized odor is generated. Therefore, in a paper container having a sealant layer made of MDPE as the innermost layer, the oxidized odor of the resin is easily transferred to the contents. Has drawbacks.

  In some cases, a polyester resin is used as the sealant layer (Patent Document 1). However, since the polyester-based resin has poor heat-sealability and is likely to cause a sealing failure at the time of box making, a paper container having a sealant layer made of such a resin has drawbacks such as leakage of contents.

JP-A-5-162737

  The present invention solves the above-mentioned problems and makes it difficult to adsorb organic compound components, that is, a packaging material having a sealant layer excellent in non-adsorbability and excellent in heat sealability, and a paper container comprising the same In particular, an object is to provide a liquid paper container.

As a result of various studies, the inventor has at least a paper base material layer, an intermediate layer, and a packaging material having a sealant layer laminated adjacently on the intermediate layer. PE), and the sealant layer is laminated via the intermediate layer by a sandwich lamination method or a coextrusion coating method, and the sealant layer is a linear low-layer adjacent to the intermediate layer. A packaging material characterized by a layer in which a density polyethylene resin (LLDPE, density 0.900-0.940 g / cm ³ ) layer and a cyclic polyolefin-based resin layer are provided in this order, and a paper container comprising the same, In particular, it has been found that a liquid paper container achieves the above object.

The present invention is characterized by the following points.
1. A packaging material used for a liquid paper container having at least a paper base layer, an intermediate layer, and a sealant layer laminated adjacently on the intermediate layer, the intermediate layer being a layer made of polyethylene resin The sealant layer is laminated through the intermediate layer by a sandwich lamination method or a coextrusion coating method, and the sealant layer has a linear low density polyethylene resin layer adjacent to the intermediate layer and a cyclic shape. The above packaging material, which is a layer in which a polyolefin-based resin layer is provided in this order.
2. 2. The packaging material according to 1 above, wherein the sealant layer is a layer composed of two layers, a linear low density polyethylene resin layer and a cyclic polyolefin resin layer.
3. The sealant layer is a layer composed of three layers in which a first linear low density polyethylene resin layer, a cyclic polyolefin resin layer, and a second linear low density polyethylene resin layer are provided in this order. The packaging material according to 1 above.
4). The sealant layer includes a first linear low density polyethylene resin layer, a cyclic polyolefin resin layer, a second linear low density polyethylene resin layer, and an inorganic filler-containing linear low density polyethylene resin layer. 2. The packaging material according to 1 above, wherein the packaging material is a four-layered layer, and the first linear low-density polyethylene resin layer is adjacent to the intermediate layer.
5. 5. The packaging material according to any one of 1 to 4 above, wherein a barrier layer is provided between the paper base material layer and the intermediate layer.
6). The barrier layer is made of an aluminum foil, an aluminum vapor deposition film, a silicon oxide vapor deposition film, an alumina vapor deposition film, an ethylene-vinyl alcohol copolymer film, a polyamide resin film, a polyvinylidene chloride resin film, and a polyacrylonitrile resin film. 6. The packaging material according to 5 above, which is a layer composed of at least one selected from the above.
7). 7. A liquid paper container formed by boxing the packaging material according to any one of 1 to 6 so that a sealant layer is an innermost layer.

  The packaging material of the present invention has an intermediate layer made of PE, an LLDPE layer forming a sealant layer, and a cyclic polyolefin resin layer adjacent to each other.

  In general, it is known that a cyclic polyolefin-based resin has a high intermolecular force during melt film formation and causes aggregation between polymers. As a result, it is difficult to obtain a uniform film surface by agglomerating the resin throughout the film to form a knob-like gel mass. This tendency becomes more prominent during film formation by the inflation method, and the cyclic polyolefin resin film obtained by the method generates innumerable gel lumps on the entire surface.

  However, according to the present invention, by forming the cyclic polyolefin resin layer adjacent to the LLDPE layer and forming the film together, uneven aggregation of the molecules of the cyclic polyolefin resin is suppressed. Therefore, the sealant layer of the packaging material of the present invention is easy to form a film, and can form a beautiful layer that is homogeneous and has good transparency. In addition, the generation of gel lumps can be suppressed during high-speed film formation by the inflation method.

  In such a packaging material of the present invention, the cyclic polyolefin resin layer has a dense surface structure with a close intermolecular distance based on the high intermolecular force of the cyclic polyolefin resin, and the LLDPE layer has The film exhibits high interlayer adhesion with the cyclic polyolefin resin layer, and imparts good film forming stability to the cyclic polyolefin resin layer. The packaging material of the present invention having such a structure hardly adsorbs the components in the contents, that is, has excellent non-adsorption properties.

  In addition, the sealant layer that forms the packaging material of the present invention exhibits good heat-sealability, can be heat-sealed in a wide range of sealing temperatures, and exhibits sufficient sealing strength during box making even when heat-sealing at low temperatures. To do. Therefore, processing is easy and there is little generation | occurrence | production of resin oxidation odor etc.

  Further, in the packaging material of the present invention, the sealant layer is sandwich-laminated with a paper base layer or a barrier layer via an intermediate layer (adhesive layer) made of PE, or on the paper base layer or barrier layer. Are laminated by coextrusion coating. Therefore, the packaging material of the present invention can be produced easily and at low cost while maintaining excellent non-adsorbability and heat sealability, and there is no concern about residual solvent.

  In addition, the intermediate layer made of PE not only functions as an adhesive layer, but also melts by heat sealing at the time of box making and contributes to stable sealing by filling the gap generated in the stepped portion of the paper container. Allows filling of liquid.

  Therefore, the packaging material of the present invention is suitable for forming a paper container, particularly a liquid paper container that is required to maintain the quality of contents.

It is a schematic sectional drawing which shows the example about the layer structure of the packaging material of this invention. It is a schematic sectional drawing which shows the example about the layer structure of the packaging material of this invention. It is a schematic sectional drawing which shows the example about the layer structure of the packaging material of this invention.

The above-described present invention will be described in more detail below.
<I> Layer Configuration of Laminate Forming Packaging Material of the Present Invention FIGS. 1 to 3 are schematic sectional views showing an example of the layer configuration of the packaging material of the present invention.

1-3, the packaging material of this invention is based on the structure which laminated | stacked the paper base material layer 1 and the sealant layer 3 via the intermediate | middle layer 2 which consists of PE. Here, the sealant layer 3 includes an LLDPE layer (a, a ₁ , a ₂ ), a cyclic polyolefin resin layer (b), and an inorganic filler-containing LLDPE layer (c) as the case may be.

  As an aspect of the packaging material of the present invention, as shown in FIG. 1, the sealant layer 3 is a layer composed of two layers, an LLDPE layer (a) and a cyclic polyolefin-based resin layer (b).

As another aspect of the packaging material of the present invention, as shown in FIG. 2, the sealant layer 3 includes a first LLDPE layer (a ₁ ), a cyclic polyolefin-based resin layer (b), and a second LLDPE layer (a ₂ ) is a three-layered layer provided in this order.

As still another embodiment of the packaging material of the present invention, as shown in FIG. 3, the sealant layer 3 includes a first LLDPE layer (a ₁ ), a cyclic polyolefin resin layer (b), and a second LLDPE layer ( a ₂ ), and an inorganic filler-containing LLDPE layer (c), which is a four-layered layer provided in this order.

  The packaging material of the present invention may have a barrier layer made of any gas barrier film between the paper base layer 1 and the intermediate layer 2 as necessary. In this case, the barrier layer and the sealant layer 3 are laminated via the intermediate layer 2. The barrier layer and the paper substrate layer 1 can be laminated by any method such as sandwich lamination or dry lamination.

  The packaging material of the present invention may also have a layer made of any polyethylene resin (PE) on the surface opposite to the sealant layer as a surface protective layer that becomes the outermost layer of the paper container. The surface protective layer can be laminated on the surface of the packaging material by extrusion coating a molten PE resin or by laminating a PE film by any method.

  Hereinafter, the resin names used in the present invention are those commonly used in the industry. In the present invention, the density was measured according to JIS K7112.

<II> Paper base material layer As the paper base material constituting the paper base material layer of the present invention, various formability, flex resistance, rigidity, waist, strength, etc. are selected according to the application of the paper container to be applied. Arbitrary paper can be used, for example, the main strength material, strong size bleached or unbleached paper, or pure white roll paper, kraft paper, paperboard, processed paper, milk base paper, etc. Paper can be used. The paper base material layer may be obtained by laminating a plurality of layers of these papers. The paper base material layer has a basis weight of 80 to 600 g / m ² , preferably a basis weight of 100 to 450 g / m ² , and a thickness of 110 to 860 μm, preferably 140 to 640 μm. If it is thinner than this, the strength as a container is insufficient, and if it is thicker than this, the rigidity becomes too high, and the processing may be difficult. Note that, for example, letters, figures, symbols, and other desired patterns can be arbitrarily formed on the paper base by a normal printing method.

<III> Intermediate Layer In the present invention, the intermediate layer is made of polyethylene resin (PE). This intermediate layer is located between the paper base material layer or the barrier layer and the sealant layer and adheres to them, and is melted by heat sealing at the time of box making to further increase the adhesive strength between the layers. The gap generated in the step portion is filled to improve the sealing performance of the container.

As the PE for forming the intermediate layer of the present invention, any polyethylene can be used, but it exhibits a melt viscosity (fluidity) suitable for filling the voids, and has film forming suitability and processing suitability. A high-pressure low-density polyethylene resin (LDPE) having a density of 0.910 to 0.925 g / cm ³ and a melt flow rate (MFR) of 1 to 10 g / 10 min (190 ° C.) can be particularly preferably used.

  The thickness of the intermediate layer is 10 to 50 μm, preferably 15 to 40 μm. If it is thinner than this, sufficient adhesive strength cannot be obtained, and the sealing performance of the paper container may be impaired. On the contrary, if it is thicker than this, the low-temperature sealing property is inferior, which is not preferable.

<IV> Sealant Layer The sealant layer of the present invention has an LLDPE layer and a cyclic polyolefin resin layer. In the packaging material of the present invention, the LLDPE layer is located on the surface (bonding surface) of the sealant layer and is adjacent to the intermediate layer.

i) Structure of Sealant Layer In one embodiment of the present invention, the sealant layer is a layer composed of only two layers of an LLDPE layer and a cyclic polyolefin resin layer. In the sealant layer having this configuration, the cyclic polyolefin-based resin layer becomes the outermost layer of the packaging material of the present invention, that is, the innermost layer of the paper container, and therefore can exhibit excellent non-adsorbability.

  In this configuration, the total thickness of the sealant layer and the thickness of each layer can be appropriately set according to the application of the paper container to be applied. From the viewpoint of film formation, non-adsorption property, and product cost, for example, the total thickness is 20 to 80 μm, more preferably 30 to 60 μm. If it is thicker than this, the rigidity of the paper container becomes high, causing molding defects. If it is thinner, sufficient adhesive strength cannot be obtained, and the sealing performance of the paper container may be impaired. The ratio of the layer thickness of the LLDPE layer to the cyclic polyolefin resin layer is suitably in the range of LLDPE layer: cyclic polyolefin resin layer = 1: 1 to 10: 1. If the layer thickness of the LLDPE layer is too thin, sufficient adhesive strength cannot be obtained, and the sealing performance of the paper container may be impaired. Further, as the layer thickness of the cyclic polyolefin resin layer is thicker, the non-adsorption property is increased, but if it is too thick, sufficient adhesive strength cannot be obtained, and the sealing property of the paper container may be impaired. Absent.

  In another aspect of the present invention, the sealant layer is a layer composed of three layers in which a first LLDPE layer, a cyclic polyolefin resin layer, and a second LLDPE layer are provided in this order. The sealant layer having this configuration has excellent laminate strength and content resistance, and can exhibit high seal strength while maintaining good non-adsorption properties.

  In this configuration, the total thickness of the sealant layer and the thickness of each layer can be appropriately set according to the application of the paper container to be applied. From the viewpoint of film formation, non-adsorption property, and product cost, for example, the total thickness is 20 to 80 μm, more preferably 30 to 60 μm. If it is thicker than this, the rigidity of the paper container becomes high, causing molding defects. If it is thinner, sufficient adhesive strength cannot be obtained, and the sealing performance of the paper container may be impaired. The ratio of each layer thickness is as follows: first LLDPE layer (layer on the side in contact with the adhesive layer for dry lamination): cyclic polyolefin-based resin layer: second LLDPE layer (layer that becomes the innermost layer) = 1: 1: A range of 1-10: 1: 10 is suitable. If the thickness of the first LLDPE layer is too thin, sufficient adhesive strength cannot be obtained, and the sealing performance of the paper container may be impaired. Further, as the layer thickness of the cyclic polyolefin resin layer is thicker, the non-adsorption property is increased, but if it is too thick, sufficient adhesive strength cannot be obtained, and the sealing property of the paper container may be impaired. Absent. Similarly, if the layer thickness of the second LLDPE layer is too thin, sufficient adhesive strength cannot be obtained, and the sealing performance of the paper container may be impaired.

  In still another aspect of the present invention, the sealant layer is a layer composed of four layers in which a first LLDPE layer, a cyclic polyolefin-based resin layer, a second LLDPE layer, and an inorganic filler-containing LLDPE layer are provided in this order. . The sealant layer having this configuration has excellent laminate strength and content resistance, and can exhibit high seal strength while maintaining good non-adsorption properties. In addition, the inorganic filler-containing LLDPE layer, which is the outermost layer of the packaging material, has good slippage on the surface of the layer, so the blank can be supplied smoothly in the frame sealer in the paper container manufacturing process, and handling is easy. is there.

In this configuration, the total thickness of the sealant layer and the thickness of each layer can be appropriately set according to the application of the paper container to be applied. From the viewpoint of film formation, non-adsorption property, and product cost, for example, the total thickness is 20 to 80 μm, more preferably 30 to 60 μm. If it is thicker than this, the rigidity of the paper container becomes high, causing molding defects. If it is thinner, sufficient adhesive strength cannot be obtained, and the sealing performance of the paper container may be impaired. The ratio of each layer thickness is in the range of first LLDPE layer: cyclic polyolefin resin layer: second LLDPE layer: inorganic filler-containing LLDPE layer = 1: 1: 1: 1 to 10: 1: 10: 1. Is appropriate. If the thickness of the first LLDPE layer is too thin, sufficient adhesive strength cannot be obtained, and the sealing performance of the paper container may be impaired. Further, as the layer thickness of the cyclic polyolefin resin layer is thicker, the non-adsorption property is increased, but if it is too thick, sufficient adhesive strength cannot be obtained, and the sealing property of the paper container may be impaired. Absent. Furthermore, if the layer thickness of the second LLDPE layer is too thin, sufficient adhesive strength cannot be obtained, and the sealing performance of the paper container may be impaired. In addition, if the layer thickness of the inorganic filler-containing LLDPE layer is too thick, the absolute amount of the inorganic filler increases, which adversely affects the sealing properties and functionality, and increases the cost. Further, if it is too thin, it is difficult to obtain the effect of the inorganic filler, and the slipperiness is inferior.

ii) Linear low density polyethylene resin (LLDPE) layer In the present invention, the LLDPE constituting the LLDPE layer in the sealant layer is a linear polyethylene having a density of 0.900 to 0.940 g / cm ³ and is a metallocene. It is a copolymer obtained by copolymerizing ethylene and an α-olefin having 3 to 20 carbon atoms at low temperature and low pressure using a single site catalyst such as a catalyst or a multisite catalyst such as a Ziegler-Natta catalyst.

  Specific examples of the α-olefin having 3 to 20 carbon atoms include propylene, 1-butene, 1-pentene, 4-methyl-1-pentene, 1-hexene, 1-octene, 1-nonene and 1-decene. , 1-dodecene and the like.

  Examples of the copolymerization method include polymerization methods of ethylene and α-olefin, such as a low pressure method, a slurry method, a solution method, and a gas phase method.

  The LLDPE of the present invention has 3 to 25 short chain branches per 1000 carbon atoms as short chain branches, but is not distinguished from LDPE in that it does not have long chain branches exceeding about 20 carbon atoms. Usually, in LLDPE, the structural unit derived from ethylene is about 99.9 to 90 mol%, and the structural unit derived from α-olefin is about 0.1 to 10 mol%. In the present invention, LLDPE prepared with a metallocene catalyst can be suitably used because of excellent structural uniformity.

  Suitable LLDPE for use in the present invention includes “Sumikasen” manufactured by Sumitomo Chemical Co., Ltd.

  Further, the main component is LLDPE as described above, and if necessary, an antioxidant, an ultraviolet absorber, a light stabilizer, an antistatic agent, an antiblocking agent, a flame retardant, a crosslinking agent, a colorant, etc. One or more of these additives may be added.

iii) Cyclic polyolefin resin layer In the present invention, the cyclic polyolefin resin constituting the cyclic polyolefin resin layer includes a ring-opening metathesis polymer (COP) obtained by polymerizing a cyclic olefin by a metathesis ring-opening polymerization reaction, Copolymers with α-olefins (chain olefins), that is, cyclic olefin copolymers (COC) are included.

  As the cyclic olefin, any cyclic hydrocarbon having an ethylenically unsaturated bond and a bicyclo ring can be used, particularly those having a bicyclo [2.2.1] hept-2-ene (norbornene) skeleton. preferable.

Specifically, bicyclo [2.2.1] hept-2-ene and derivatives thereof, tricyclo [4.3.0.1 ^2.5 ] -3-decene and derivatives thereof, tricyclo [4.4.0.1 ^2.5] -3-undecene and derivatives thereof, tetracyclo [4.4.0.1 ^2.5 .1 ^7.10] -3-dodecene and derivatives thereof, pentacyclo ^{[6.5.1.1 3.6 .0 2.7 .0 9.13]} - 4 pentadecene and its derivatives, pentacyclo ^{[7.4.0.1 2.5 .1 9.12 .0 8.13]} -3- pentadecene and its derivatives, pentacyclo ^{[6.5.1.1 3.6 .0 2.7 .0 9.13]} - 4,10 penta decadiene and its derivatives, pentacyclo ^{[8.4.0.1 2.5 .1 9.12 .0 8.13]} -3- hexadecene and it derivatives, and the like, without limitation. The cyclic olefin may have a polar group such as an ester group, a carboxyl group, and a carboxylic anhydride group as a substituent.

  As the α-olefin copolymerized with the cyclic olefin, ethylene, an α-olefin having 3 to 20 carbon atoms can be used, and specifically, ethylene, propylene, 1-butene, 1-pentene, 3-methyl. Examples include -1-butene, 1-hexene, 4-methyl-1-pentene, and preferably ethylene.

  In the present invention, the production of the ring-opening metathesis polymer is not particularly limited as long as it is a known ring-opening metathesis polymerization reaction, and can be produced by ring-opening polymerization of the above cyclic olefin using a polymerization catalyst. .

  In the production of the cyclic olefin copolymer, 25 to 45 mol% of α-olefin and 55 to 75 mol% of cyclic olefin are randomly polymerized using a single site catalyst such as a metallocene catalyst or a multisite catalyst. Is made by

Ring-opening metathesis polymer and a cyclic olefin copolymer are preferably used in the present invention, some are commercially available, for example, Nippon Zeon Co., Ltd. of "ZEONOR ^(R)" and manufactured by Polyplastics Co., Ltd., "TOPAS ^{(R )} "And the like.

  In addition, in order to obtain the more uniform film | membrane surface in the said cyclic polyolefin resin in order to suppress the generation | occurrence | production of the gel lump by aggregation of cyclic polyolefin resin at the time of film forming, It can be added arbitrarily within a range not impairing the non-adsorption property. The olefin-based resin may be any polyethylene or polypropylene having a melt flow rate (MFR) at 190 ° C. of 5 to 40 g / 10 minutes, preferably 15 to 30 g / 10 minutes. it can. Moreover, as an addition amount, it is good to mix | blend an olefin resin with the ratio of 3-50 mass% of the whole, Preferably 5-10 mass%.

  If necessary, one or more additives such as an antioxidant, an ultraviolet absorber, a light stabilizer, an antistatic agent, an antiblocking agent, a flame retardant, a crosslinking agent, and a colorant are added. May be.

iv) Inorganic filler-containing LLDPE layer In the present invention, the inorganic filler-containing LLDPE layer is a layer made of a resin composition in which an inorganic filler is dispersed in LLDPE by a master batch type blending method.
In this resin composition, as the LLDPE that can be suitably used, the same resins as those described for the LLDPE layer can be used.

Further, suitable inorganic fillers which may be _{used, SiO 2, AL 2 O 3} , TiO 2, ZnO, Fe 2 O 3, SnO 2, CeO 2, NiO, PbO, S 2 Cl 2, ZnCl 2, FeCl 2 , CaCO ₃ , B ₂ O _{3, and the} like, and a filler having an average particle diameter of 2 to 15 μm can be used. Preferably, a silicon oxide SiO ₂ filler is used. When the average particle size of the inorganic filler is less than 2 μm, there is no effect in improving the slipperiness, and when the average particle size exceeds 15 μm, the container surface is rubbed by the inorganic filler protruding on the surface of the film forming film. And hurt. In addition, in this invention, an average particle diameter means the particle size of the particle which exists most by particle size distribution measurement. The particle size distribution can be measured by a Coulter counter method.

  In this resin composition, the inorganic filler is added in an amount of 2.0 to 5.0 wt% of the whole. When the content of the inorganic filler in the resin composition is less than 2.0 wt%, it is difficult for the filler to come out on the surface of the sealant layer, and the effect of improving slip failure is small, and when the content exceeds 5.0 wt% Since the filler becomes saturated on the surface of the sealant layer, even if more filler is added, an effect commensurate with the cost cannot be obtained. In addition, when the saturated state is reached, seal inhibition occurs, and conversely, the seal start temperature may be increased.

  If necessary, the resin composition may contain one or two additives such as an antioxidant, an ultraviolet absorber, a light stabilizer, an antistatic agent, an antiblocking agent, a flame retardant, a crosslinking agent, and a colorant. More than seeds may be added.

  Further, in order to improve the film forming stability and the fluidity of the resin at the time of sealing the paper container, LDPE may be added to the resin composition in an amount of 0 to 20 wt%. However, it is not preferable to add LDPE in excess of 20 wt% because non-adsorption is impaired.

  By providing the inorganic filler-containing LLDPE layer thinly on the outermost layer portion of the sealant layer, the sliding property can be improved without impairing the fluidity of the heat seal resin constituting the sealant layer. Therefore, the packaging material of this invention which has this inorganic type filler containing LLDPE layer maintains favorable heat-sealability, and shows the slip characteristic suitable for film forming and box making.

v) Method for Producing Sealant Layer In one aspect of the present invention, the sealant layer may be a layer made of a sealant film. In this case, the sealant layer is laminated with the paper base layer or the barrier layer by a sandwich lamination method through the intermediate layer.

  In the present invention, the sealant film is preferably formed by a coextrusion method using a resin and a resin composition constituting each layer. By forming a film by the coextrusion method, high interlayer adhesion and good film forming stability can be obtained, non-adsorbability and heat sealability can be further improved, and a beautiful film can be obtained. In the present invention, the sealant film is particularly preferably formed by a coextrusion inflation method. By forming a film by the coextrusion inflation method, film formation can be performed at a low temperature, trouble due to a resin odor caused by heating is reduced, and interlayer adhesion is further improved.

  In another embodiment of the present invention, the sealant layer is a layer that is laminated by coextrusion coating on the paper substrate layer or barrier layer along with the intermediate layer. By using PE that constitutes the intermediate layer and the resin that constitutes each layer in the sealant layer, these are coextruded on the substrate together to obtain high interlayer adhesion and good film formation stability. In addition, non-adsorbability and heat sealability are further improved, and a beautiful film can be obtained.

<V> Barrier Layer In the packaging material of the present invention, a barrier layer having gas barrier properties can be provided between the paper base material layer 1 and the dry laminate adhesive layer 2 as necessary. Thereby, the smell leak of the content to the exterior and the penetration | invasion of oxygen and water vapor | steam gas from the outside can be suppressed, and the quality change of a content can be prevented.
As such a barrier layer, any gas barrier film can be used depending on the application of the paper container to be applied.

  For example, as the gas barrier film, a metal foil such as an aluminum foil, or a laminated film of a metal foil and a plastic film can be used. In this case, excellent gas barrier properties can be obtained and light shielding properties can be obtained. Become. The thickness of the metal foil used suitably or the laminated film of metal foil and a plastic film is about 6-30 micrometers.

  Moreover, you may use the vapor deposition film which has a vapor deposition layer of an inorganic oxide or a metal as a gas barrier film. Here, preferable examples of the inorganic oxide include aluminum oxide, silicon oxide, and magnesium oxide. Moreover, aluminum etc. are mentioned as a metal used suitably. Moreover, as a base film which carries a vapor deposition layer, the resin film which consists of polyester, polyamide, a polypropylene, etc. can be used. The thickness of the vapor deposition film used suitably is about 9-40 micrometers. In addition, when a barrier layer consists of a vapor deposition film, it is preferable to laminate | stack so that the vapor deposition film side may contact | connect a paper base material layer from viewpoints, such as handling at the time of a process.

Furthermore, as the gas barrier film, a gas barrier film made of at least one of ethylene-vinyl alcohol copolymer, polyamide resin, polyvinylidene chloride resin, and polyacrylonitrile resin can be used. The thickness of these gas barrier films that are preferably used is about 5 to 30 μm.
Moreover, you may select and use 2 or more types for a barrier layer from said various gas-barrier films.

  In the case where the packaging material of the present invention has a barrier layer, the barrier layer and the paper base material layer 1 are sandwich laminate methods or dry laminates using a thermoplastic resin in consideration of manufacturing cost, required content resistance, etc. The film can be laminated by any method such as a dry laminating method using an adhesive. At this time, the surface of the paper substrate layer may be subjected to surface treatment such as corona treatment, flame treatment, anchor coating treatment, etc., and the surface of the barrier layer is subjected to in-line corona treatment, ozone treatment, etc. Also good. As the thermoplastic resin used for the sandwich laminate, a resin layer made of any thermoplastic resin that can be melted by heat and fused to each other can be used. For example, LDPE, MDPE, LLDPE, ionomer resin, ethylene -An acrylic acid copolymer etc. can be used.

<VI> Surface Protective Layer The packaging material of the present invention may have a layer made of any polyethylene resin (PE) on the surface opposite to the sealant layer as a surface protective layer that becomes the outermost layer during box making. .
The surface protective layer protects the outside of the paper base material layer and is bonded to the sealant layer by heating at the end portion of the packaging material. As the polyethylene, LDPE, LLDPE, MDPE, high density polyethylene (HDPE) and the like are used, and are not particularly limited. However, LDPE and LLDPE are preferable from the viewpoint of sealability and processability with the sealant layer of the packaging material of the present invention. Used.

  Although the formation method of a surface protective layer is not specifically limited, For example, it forms by carrying out extrusion coating of the molten polyethylene resin to one side of a paper base material layer. The surface protective layer is a layer that becomes the surface of the container, but a printing layer can be further provided on the surface, and in order to improve the adhesion of the printing ink used for the printing layer, the surface is a surface such as a corona treatment. Processing can also be performed. Although the thickness of a surface protective layer is not specifically limited, Usually, it is about 10-60 micrometers.

<VII> Use of packaging material The packaging material of the present invention can be suitably used to form a paper container, particularly a paper container that is required to maintain the quality of contents.
Production of a paper container from the packaging material of the present invention is usually performed as follows. That is, after printing as necessary on the surface of the packaging material of the present invention, it is punched out, and the end face is skived and hemmed so that the contents do not come into contact with the end face. Heat seal by heating, flame heating, etc. to make a paper container.

  The shape of the paper container may be determined as appropriate according to the use and purpose, and examples thereof include a gable top type, a brick type, a flat type, and a cylindrical paper such as a rectangular container or a round shape. A can etc. are mentioned. For example, a polyethylene cap, a pull tab-type opening mechanism, and the like may be appropriately provided at the spout of the paper container.

The content of the paper container is not particularly limited, either solid or gel-like, but liquids such as liquor, juices such as fruit drinks, various beverages such as mineral water, soy sauce, sauces, soups, etc. Liquid seasonings or various liquid foods and drinks such as curry, stew, and soup, edible oils, machine oils, chemicals such as adhesives and adhesives, cosmetics, miscellaneous goods such as pharmaceuticals, other shampoos, rinses and detergents It may be a chemical product or the like.
Next, the present invention will be specifically described with reference to examples.

[Example 1]
(1) LLDPE (manufactured by Ube Maruzen Polyethylene Co., Ltd., UM0540F) was used as a base resin, and silica (average particle size: 4.9 μm) was added thereto in an amount of 10 wt% of the whole to prepare a master batch. Blending 45 wt% of the master batch, 45 wt% of LLDPE (UM0540F manufactured by Ube Maruzen Polyethylene Co., Ltd.) and 10 wt% of LDPE (LC520 manufactured by Nippon Polyethylene Co., Ltd.) to prepare a resin composition for an LLDPE layer containing an inorganic filler did.

(2) LLDPE (Ube Maruzen Polyethylene Co., Ltd., UM0540F), Cyclic Olefin Copolymer (Polyplastics Co., Ltd. TOPAS ^(R) 8007F-500; Melt Flow Rate (MFR) 1.9 g / 10 min (190 ° C. ); Density 1.02 g / cm ³ ), and the inorganic filler-containing resin composition for LLDPE layers described in (1) above, by a coextrusion inflation method, the first LLDPE layer 20 μm / cyclic olefin copolymer layer A 40 μm thick sealant film consisting of 4 layers of 5 μm / second LLDPE layer 10 μm / inorganic filler-containing LLDPE layer 5 μm was formed. The obtained sealant film had a beautiful film surface without gel lump. In the description of the laminate in the present specification, “/” indicates that the left and right layers are laminated and integrated.

(3) Using a two-component curable urethane adhesive, a 12 μm thick polyethylene terephthalate (PET) film was laminated on a 6 μm thick aluminum foil by a dry lamination method to form a gas barrier film. The amount of adhesive applied at this time was such that the thickness of the adhesive was 3 g / m ² as a dry film.

(4) On the other hand, 20 μm thick LDPE (LC520 manufactured by Nippon Polyethylene Co., Ltd.) as a surface protective layer was laminated on one surface of a paperboard having a basis weight of 340 g / m ² by an extrusion coating method. Further, the other surface of the paperboard is opposed to the aluminum foil surface of the gas barrier film produced in the above (3), and an ethylene-methacrylic acid-methacrylic acid ester copolymer (Mitsui DuPont Polychemical Co., Ltd.) having a thickness of 20 μm therebetween. N0908C (adhesive resin layer) made by extruding and laminating and laminating a laminate film consisting of surface protective layer / paper substrate layer / adhesive resin layer / barrier layer (aluminum foil / adhesive layer for dry lamination / PET film) Was made.

(5) A two-component curable urethane-based adhesive was applied to the surface of the laminate film produced in (4) on the PET film side and dried by heating to form an anchor coat layer. The amount of adhesive applied at this time was such that the thickness of the adhesive was 0.2 g / m ² as a dry film.

(6) The surface on the anchor coat layer side of the laminate film produced in (5) above is opposed to the surface on the first LLDPE layer side of the sealant film produced in (2) above, and a thickness of 20 μm is interposed therebetween. LDPE (Nippon Polyethylene Co., Ltd. LC520) (intermediate layer) was extruded and sandwich laminated, and surface protective layer / paper substrate layer / adhesive resin layer / barrier layer (aluminum foil / adhesive layer for dry lamination / PET film) A packaging material of the present invention having a layer structure of / anchor coat layer / intermediate layer / sealant layer (first LLDPE layer / cyclic polyolefin resin layer / second LLDPE layer / inorganic filler-containing LLDPE layer) was obtained.

[Example 2]
Example 1 except that a sealant film having a thickness of 40 μm consisting of only two layers of an LLDPE layer of 35 μm / a cyclic olefin copolymer layer of 5 μm was used as the sealant layer, and the LLDPE layer side surface was in contact with the intermediate layer. In the same manner as above, the packaging material of the present invention was produced. In addition, the resin similar to Example 1 was used for LLDPE and a cyclic olefin copolymer. The sealant film was formed by a coextrusion inflation method. The obtained sealant film had a beautiful film surface without gel lump.

[Comparative Example 1]
A packaging material was produced in the same manner as in Example 1 except that LLDPE (manufactured by Ube Maruzen Polyethylene Co., Ltd., UM0540F) was used instead of the cyclic olefin copolymer.

[Comparative Example 2]
A packaging material was produced in the same manner as in Example 2 except that LLDPE (Ube Maruzen Polyethylene Co., Ltd., UM0540F) was used instead of the cyclic olefin copolymer.

[Adsorption test]
Using the packaging materials of Examples 1-2 and Comparative Examples 1-2, a menthol prepared by making a gable top type paper container with a side of 70 mm square and a capacity of 1 L, and having a menthol concentration of 5 μm / ml 1 l of ethanol solution was charged.
After storing for 2 weeks in an atmosphere at 50 ° C., the menthol content in the solution was measured by the GC / MS method. From the difference between the measured value and the menthol content before storage, the amount of menthol adsorbed per 1 cm ² of the inner wall of the paper container was determined. The results are shown in Table 1 below.

  In the paper container which consists of the packaging material of Examples 1-2, the adsorption amount of menthol was restrained to the low value. In contrast, the paper containers made of the packaging materials of Comparative Examples 1 and 2 adsorbed a large amount of menthol.

[Heat sealability test]
Using the packaging materials of Examples 1 and 2 and Comparative Examples 1 and 2 and printing the desired pattern and display on the surface of the surface protective layer by the offset printing method, then simultaneously punching into a predetermined shape is necessary A ruled line was provided at each location to obtain a blank sheet. Next, the barrel part was bonded together by a frame seal method to form a cylindrical sleeve, and this cylindrical sleeve was supplied to a filling machine (manufactured by DNK Co., Ltd., DR-10). The bottom part was heat-sealed with hot air from a filling machine, then the contents (mineral water) were filled, and finally the top part was heat-sealed to produce a gable-top type paper container (1.8 liter capacity). .

If the hot air temperature of the filling machine is too low, the adhesive strength becomes insufficient due to insufficient heating. On the other hand, if the temperature is too high, bubbling occurs in the seal portion due to overheating, and in either case, the contents leak or the container swells.
When heat-sealing the bottom part and top part of the packaging material amount of each example and comparative example, the hot air temperature of the filling machine was changed every 10 ° C., and the hot air temperature adhered firmly without leaking the contents Range was measured. The results are shown in Table 2 below.

  As in the comparative example, the packaging materials of Examples 1 and 2 can be heat-sealed in a wide temperature range, exhibit sufficient sealing strength even at a low temperature of 320 to 340 ° C., and have good heat-sealability. Indicated.

1: Paper base layer 2: Intermediate layer 3: Sealant layer a: Linear low density polyethylene resin layer a ₁ : First linear low density polyethylene resin layer a ₂ : Second linear low density polyethylene Resin layer b: Cyclic polyolefin resin layer c: Linear low-density polyethylene resin layer containing inorganic filler

Claims (4)

A packaging material for a liquid paper container, comprising at least a paper base layer, an intermediate layer, and a sealant layer laminated adjacently on the intermediate layer,
The intermediate layer is a layer made of polyethylene resin,
The sealant layer is laminated through the intermediate layer by a sandwich lamination method or a coextrusion coating method, and
The sealant layer is a layer composed of three layers in which a first linear low density polyethylene resin layer, a cyclic polyolefin resin layer, and a second linear low density polyethylene resin layer are provided in this order, or The first linear low density polyethylene resin layer, the cyclic polyolefin resin layer, the second linear low density polyethylene resin layer, and the inorganic filler-containing linear low density polyethylene resin layer were provided 4 in this order. a layer comprising a layer, characterized that you said first linear low density polyethylene resin layer is adjacent to the intermediate layer, the packaging material. The packaging material according to claim 1, further comprising a barrier layer between the paper base layer and the intermediate layer. The barrier layer is made of an aluminum foil, an aluminum vapor deposition film, a silicon oxide vapor deposition film, an alumina vapor deposition film, an ethylene-vinyl alcohol copolymer film, a polyamide resin film, a polyvinylidene chloride resin film, and a polyacrylonitrile resin film. The packaging material according to claim 2, wherein the packaging material is a layer composed of at least one selected from the above. A liquid paper container formed by boxing the packaging material according to any one of claims 1 to 3 so that a sealant layer is an innermost layer.

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