JP4983189B2 - Packaging material and manufacturing method thereof - Google Patents

Description

  The present invention relates to a packaging material and a method for producing the same, and more particularly to a packaging material having a foam layer on the surface and a method for producing the same.

As a packaging material, a material used for a cup or other packaging container and having a foam layer on the surface is known (for example, see Patent Document 1). The packaging container having the foamed layer is excellent in heat resistance and does not feel extremely hot even if the user directly holds the packaging container containing the hot liquid therein. As a packaging material having a foam layer, a heat-resistant paper container having a layer structure of low density polyethylene (LDPE; foam layer) / paper / medium density polyethylene (MDPE) is known from the surface side (for example, Patent Document 2). reference).
JP 2004-018101 A JP-A-57-110439

  In a heat-resistant paper container having a layer structure of low density polyethylene (LDPE; foam layer) / paper / medium density polyethylene (MDPE) from the surface side, the laminate is heated to evaporate water from the paper. Then, the LDPE of the surface layer is deformed to form a foam layer. At this time, since the melting point of the LDPE serving as the foam layer is lower than the melting point of the MDPE inside the paper, the MDPE is not deformed by heating, and only the surface LDPE can be foamed by the moisture of the paper.

  In order to produce a packaging material having a foam layer, in addition to such a laminate, a laminate using another material having a melting point higher than that of LDPE can be used instead of MDPE.

  However, in any of the packaging materials described above, it is necessary to form resins having different melting points on both sides of the paper, which takes time and effort for producing the packaging material, and the cost is high.

  Then, an object of this invention is to provide the packaging material which has a foaming layer which can be produced more simply, and its manufacturing method.

  In order to achieve the above object, the packaging material of the present invention comprises, from the outer surface side, a cover layer made of low density polyethylene, a base material layer made of paper, a clay coat layer containing clay, and an innermost layer made of low density polyethylene. It is at least laminated, and the cover layer is formed in a foamed shape by heating the packaging material.

  According to this, since the clay coat layer prevents moisture contained in the paper from permeating, the moisture contained in the paper goes out to the cover layer side when the packaging material is heated. Therefore, the cover layer melted by heating is formed into a foamed shape by the moisture, and a packaging material having a foamed layer is produced. In this way, a low-density polyethylene is formed on both sides of a base material layer having a clay coat layer, and a packaging material having a foam layer is produced by heating. Thus, two types having different melting points are used to form the foam layer. There is no need to use the above resins, and there is no need for temperature control due to the different melting points of the resins. Therefore, the manufacturing process of the packaging material is simplified, and the manufacturing cost can be reduced.

  The packaging material of the present invention is characterized in that an outermost layer made of medium density polyethylene having a melting point higher by 5 ° C. or more than low density polyethylene is laminated on the outer surface side of the cover layer.

  According to this, by having medium density polyethylene on the surface of the packaging material, the heating temperature can be controlled so that the low density polyethylene of the cover layer is foamed and the medium density polyethylene of the outermost layer is not foamed. Then, since the outermost layer and the innermost layer of the packaging material have smooth surface properties, the packaging material can be easily transported and the subsequent processing can be easily performed.

  The packaging material of the present invention is characterized in that the clay coat layer is formed on the base material layer.

  According to this, since the clay coat layer is formed not on the innermost layer side but on the base material layer, it is possible to further prevent the moisture of the base material layer from permeating.

  In the packaging material of the present invention, the clay coat layer includes at least one of kaolin, talc, calcium carbonate, and titanium dioxide.

  According to this, when the clay coat layer contains these materials, it is possible to further prevent the moisture of the base material layer from permeating.

  The packaging material of the present invention is characterized in that a barrier layer is provided between the clay coat layer and the innermost layer.

  According to this, by having the barrier layer, it is possible to further prevent moisture permeation and content flavor from being lowered.

  The manufacturing method of the packaging material of the present invention that solves the above-mentioned problems comprises at least laminating a cover layer made of polyethylene, a base material layer made of paper, a clay coat layer containing clay, and an innermost layer made of polyethylene from the outer surface side. A method for producing a packaging material comprising: heating the packaging material within a range of 100 to 200 ° C. in a state where the cover layer, the base material layer, the clay coat layer, and the innermost layer are laminated. The cover layer is formed in a foam shape.

  According to this, since the clay coat layer prevents the moisture contained in the paper from permeating, the moisture contained in the paper goes out to the cover layer side when the packaging material is heated within the above temperature range. Therefore, the cover layer melted by heating is formed into a foamed shape by the moisture, and a packaging material having a foamed layer is produced. In this way, a low-density polyethylene is formed on both sides of a base material layer having a clay coat layer, and a packaging material having a foam layer is produced by heating. Thus, two types having different melting points are used to form the foam layer. There is no need to use the above resins, and there is no need for temperature control due to the different melting points of the resins. Therefore, the manufacturing process of the packaging material is simplified, and the manufacturing cost can be reduced.

  In the method for manufacturing a packaging material according to the present invention, an outermost layer made of medium density polyethylene is laminated on the outer surface side of the cover layer, and then the packaging material is heated.

  According to this, by having medium density polyethylene on the surface of the packaging material, the heating temperature can be controlled so that the low density polyethylene of the cover layer is foamed and the medium density polyethylene of the outermost layer is not foamed. Then, since the outermost layer and the innermost layer of the packaging material have smooth surface properties, the packaging material can be easily transported and the subsequent processing can be easily performed.

  In the method for producing a packaging material according to the present invention, the clay coat layer is formed on the base material layer.

  According to this, since the clay coat layer is formed not on the innermost layer side but on the base material layer, it is possible to further prevent the moisture of the base material layer from permeating.

In the method for producing a packaging material of the present invention, the amount of the clay coat layer applied is 5 to 40 g / m ² .

  According to this, the clay coat layer can sufficiently prevent the permeation of moisture, and the manufacturing process of the packaging material and the process of producing the packaging container from the packaging material can be performed without reducing the production efficiency due to the thickness. .

  According to the packaging material and the method for producing the same of the present invention, when the packaging material having the foam layer is provided, the production process of the packaging material is simplified, and the production cost can be reduced.

  Hereinafter, embodiments for carrying out the packaging material and the method for producing the same according to the present invention will be described with reference to the drawings. FIG.1 and FIG.2 is explanatory drawing which shows an example of the laminated constitution of the packaging material of this invention.

  As shown in FIG. 1 (A), the packaging material 10A of the present invention comprises, from the outer surface side, a cover layer 11A made of low density polyethylene, a base material layer 12 made of paper, a clay coat layer 13 containing clay, and low density polyethylene. The innermost layer 14 made of is laminated at least. Then, as shown in FIG. 1B, the packaging material 10 becomes a layer 11 in which the cover layer 11A is formed in a foamed shape by heating the packaging material 10A shown in FIG. Is. As shown in FIG. 2, the packaging material 10 of the present invention may have an outermost layer 15 made of medium density polyethylene laminated on the outer surface side of the cover layer 11. Below, each layer which comprises the packaging material 10 is demonstrated.

The cover layer 11 is made of low-density polyethylene, protects the outside of the base material layer 12, and is heated and bonded to the innermost layer 14 described later at the end portion of the packaging material 10. Specifically, as the low density polyethylene (LDPE), a high pressure ethylene homopolymer is preferably used. Further, linear low density polyethylene (LLDPE) which is a copolymer of ethylene and an α-olefin other than ethylene such as propylene, butene, pentene, hexene, octene, 4-methylpentene-1 is also preferably used. The density of the low density polyethylene is not particularly limited as long as it is generally referred to as low density polyethylene, but is about 0.91 to 0.925 g / cm ³ , and its melt index M.D. I. Although it is not specifically limited, Usually, it is about 1-20. Further, the melting point of the low density polyethylene is not particularly limited as long as it is within the melting point range of a normal low density polyethylene, but is about 100 to 110 ° C.

  Although the formation method of the cover layer 11 is not specifically limited, For example, it forms by carrying out extrusion coating to one side of the base material layer 12. FIG. The cover layer 11 is a layer that becomes the surface of the paper container, but a print layer can be further provided on the surface, and in order to improve the adhesion of the printing ink used for the print layer, the surface is subjected to, for example, corona treatment. It is preferable to perform a surface treatment. As will be described later, the outermost layer 15 can be further provided on the surface. The thickness of the cover layer 11 is not particularly limited, but is usually about 10 to 60 μm before being formed into a foam shape, and about 20 to 600 μm after being formed into a foam shape.

  The cover layer 11 is formed on the base material layer 12 as described above (see FIG. 1A) and then formed into a foamed shape by heating (see FIG. 1B). The heating temperature at this time is not particularly limited as long as it is not lower than the melting point of the low-density polyethylene as the material and the packaging material 10 is not altered, but is usually 100 to 200 ° C., preferably 110 to 160. ° C. In addition, when the outermost layer 15 made of medium density polyethylene, which will be described later, is formed on the cover layer 11 (see FIG. 2), particularly when the melting point is not less than the melting point of the low density polyethylene and not more than the melting point of the medium density polyethylene Although it is not limited, it is 120-180 degreeC normally, Preferably, it is 130-170 degreeC. The heating time of the cover layer 11 is not particularly limited, but is usually about 10 seconds to 5 minutes. The heating method of the cover layer 11 is not particularly limited, and can be heated by a conventionally known method used when forming a conventional foamed layer. For example, hot air, infrared rays, far infrared rays, microwaves, high frequencies, etc. Heating.

The base material layer 12 is made of paper, and since this paper becomes a basic material constituting the paper container, a material having formability, bending resistance, rigidity, waist, strength and the like can be used. As paper, for example, it is a main strength material, and uses various types of paper base materials such as high-size bleached or unbleached paper base, or pure white roll paper, kraft paper, paperboard, processed paper, milk base paper, etc. can do. The base material layer 12 may be a laminate of a plurality of these papers. The paper has a basis weight of about 80 to 600 g / m ² , preferably about 100 to 450 g / m ² and has a thickness of about 110 to 860 μm, preferably about 140 to 640 μm. . Note that, for example, letters, figures, symbols, and other desired patterns can be arbitrarily formed on the paper base by a normal printing method.

  The clay coat layer 13 is obtained by applying a coating liquid containing clay to the base material layer 12 and laying clay particles on one surface of the base material layer 12. The clay is not particularly limited as long as it is generally called clay, but kaolin, talc, bentonite, smectite, vermiculite, mica, chlorite, kibushi clay, gyrome clay, halloysite, mica, etc. are used. It is done. Of these, kaolin and talc are preferably used as the clay. Kaolin has excellent concealability and water absorption, and talc has low hardness (Mohs hardness 1) and excellent heat resistance. Improvement in dimensional stability can be expected.

  The clay coat layer 13 preferably contains calcium carbonate, titanium dioxide, amorphous silica, expandable barium sulfate, satin white and the like as a pigment in addition to clay. By using calcium carbonate or titanium dioxide as a pigment, the smoothness of the surface of the clay coat layer 13 can be increased, and the concealability can be increased. Furthermore, calcium carbonate is preferably used because it is inexpensive.

  The coating liquid for coating the clay coat layer 13 contains the above clay, a binder, and, if necessary, other pigments and additives in a solvent. As the solvent, water, alcohol or the like is usually used. The binder is usually a latex binder (eg, styrene butadiene latex, acrylic latex vinyl acetate latex), water soluble binder (eg starch (modified starch, oxidized starch, hydroxyethyl etherified starch, phosphate ester). Modified starch), polyvinyl alcohol, casein and the like. Examples of additives that can be used include pigment dispersants, antifoaming agents, antifoaming agents, viscosity modifiers, lubricants, water resistance agents, water retention agents, coloring materials, and printability improvers.

  The blending ratio of the coating liquid for the clay coat layer 13 is not particularly limited, but is preferably about clay: pigment: binder = 1-20%: 50-90%: 10-30%.

  The coating method of the clay coat layer 13 is not particularly limited, and a conventionally known coating method is used, but a coating method such as air knife coating, blade coating, short dwell coating, or cast coating is used.

Although the coating amount and thickness of the clay coat layer 13 are not particularly limited, the basis weight after drying is usually 5 to 40 g / m ² , and preferably 10 to 40 g / m ² . If the basis weight after drying is less than 5 g / m ² , the function for forming the outermost layer 11 in a foamed form may be inferior. If the basis weight after drying exceeds 40 g / m ² , the packaging material 10 May become too thick, resulting in poor manufacturing suitability.

  As the base material layer 12 and the clay coating layer 13, a material in which the clay coating layer 13 has already been formed on the base material layer 12 can be used. In this case, other layers may be provided at appropriate positions. .

  The clay coat layer is usually provided in order to improve the printability of paper. This is because printing quality is improved when printing is performed on paper on which the clay coat layer is formed. However, in the present invention, the clay coat layer 13 is formed on the inner side of the base material layer 12, that is, on the surface of the packaging material 10 on which the printing layer is not provided, and moisture generated from the paper of the base material layer 12 is transmitted. This prevents the moisture from coming out to the cover layer 11 side.

  The innermost layer 14 is provided on the side of the base material layer 12 having the clay coat layer 13. The innermost layer 14 is made of low-density polyethylene, and is a layer for heat-sealing the innermost layers 14 with each other or the innermost layer 14 and the cover layer 11 or the outermost layer 15 when forming the container. It becomes a layer in contact with things. As the material of the innermost layer 14, the same material as the low density polyethylene of the cover layer 11 can be used. As described above, since the innermost layer 14 is in contact with the contents of the container, when the contents are milk or the like, low-density polyethylene without additives (non-added low-density polyethylene) is used. The method for forming the innermost layer 14 is not particularly limited, but usually, extrusion coating, lamination of a film prepared in advance, dry lamination, or the like is used. The thickness of the innermost layer 14 is not particularly limited, but is usually about 10 to 100 μm.

The outermost layer 15 is arbitrarily provided on the outer side of the base material layer 12 having the cover layer 11. The outermost layer 15 is made of medium density polyethylene and is a layer to be bonded to the innermost layer 14 when forming the container, and is a layer on the outer surface of the paper container. The outermost layer 15 is provided on the surface of the packaging material 10, and in order to keep the surface smooth even when the cover layer 11 is foamed, the subsequent process of moving the packaging material 10 and the container enclosing the contents are moved. It is easy to move the packaging container in the process of performing. The medium density polyethylene is in a range generally referred to as medium density polyethylene, and a material having a melting point higher by 5 ° C. or more than the low density polyethylene used for the cover layer 11 and the innermost layer 14 is used. This medium density polyethylene is preferred to have a melting point difference of 10 ° C. or more from low density polyethylene because the temperature range in which the cover layer 11A can be foamed becomes wide. The upper limit of the melting point difference between the medium density polyethylene and the low density polyethylene is not particularly limited, but is usually about 30 ° C. When the content of the container formed from the packaging material 10 is milk or the like, it is preferable to use medium density polyethylene (additive medium density polyethylene) without additives. The density of the medium density polyethylene is not particularly limited as long as it is generally referred to as medium density polyethylene, but is about 0.926 to 0.940 g / cm ³ , and its melt index M.D. I. Although it is not specifically limited, Usually, it is about 1-20. Further, the melting point of medium density polyethylene is in the melting point range of ordinary medium density polyethylene, and is not particularly limited as long as it has the above-described difference from low density polyethylene, but is about 110 to 130 ° C.

  The method of forming the outermost layer 15 is not particularly limited, but usually, extrusion coating, co-extrusion coating together with the cover layer 11, lamination of a previously prepared film, dry lamination, or the like is used. The thickness of the outermost layer 15 is not particularly limited, but is usually about 10 to 50 μm.

  The packaging material 10 can form other layers as needed in addition to the layers described above. For example, a conventionally known barrier layer can be formed between the clay coat layer 13 and the innermost layer 14. As the barrier layer, a film on which an inorganic oxide is deposited, a metal foil such as aluminum, MX nylon, or the like is used. The method for forming the barrier layer is not particularly limited, but it is general that the clay coat layer 13 and the barrier layer are sandwich-laminated using an intermediate layer made of EMAA resin or polyethylene. The barrier layer and the innermost layer 14 are formed by extrusion coating, or by sandwich lamination, dry lamination or the like of a film prepared in advance. When MX nylon is used for the barrier layer, an intermediate layer may be further provided, and the intermediate layer, barrier layer, and innermost layer 14 may be coextrusion coated, or PE / adhesive layer / MX nylon / adhesive layer / PE. Sequentially laminated films may be sandwich laminated with an intermediate layer.

  The thickness of the packaging material 10A having such a layer structure before foaming the cover layer 11 is not particularly limited, but is usually about 150 μm to 700 μm. And the thickness after making the cover layer 11 of the packaging material 10 foam is not specifically limited, Usually, it is about 170 micrometers-about 1300 micrometers.

  The method for producing the packaging material 10 of the present invention is not particularly limited as long as the cover material 11 can be formed into a foamed shape by heating as described above. The clay coating layer 13 is formed by applying and drying the coating liquid 13, the cover layer 11 and the innermost layer 14 are laminated, and the cover layer 11 is formed in a foamed shape by heating. When the outermost layer 15 made of medium density polyethylene is formed on the packaging material 10, the outermost layer 15 is usually formed on the cover layer 11 and then heated to form the cover layer 11 in a foamed state.

  Production of a packaging container (paper container) using the packaging material 10 of the present invention is usually performed as follows. After forming the sheet of the packaging material 10 having the above-described layer structure, a printing layer is formed as necessary, punched, and the end face is skived and hemmed so that the contents do not come into contact with the end face. And the top part is heat-sealed by hot air heating, flame heating, etc. to make a paper container.

  The shape of the paper container may be appropriately determined according to the use and purpose, and examples thereof include a shape such as a gobel top type, a brick type, a flat top type, and a cup type. In addition, 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 contents of the paper container are not particularly limited, and drinks such as milk, juice, mineral water, green tea, black tea, oolong tea, sake, shochu, etc., cooking oil, soy sauce, mirin, vinegar, seasoning containing solids, etc. Various liquids such as non-food products such as foods, shampoos, rinses and machine oils can be used as the contents.

  The present invention will be described more specifically with reference to examples and comparative examples.

Example 1
A clay coat layer made of the following coating liquid A for clay coat layer was formed on one surface of a base material layer made of base paper for liquid containers having a basis weight of 370 g / m ² by an air knife coating method. The clay coat layer had a basis weight of 20 g / m ² .

<Clay coat layer coating liquid A>
Kaolin clay 10% by mass
Calcium carbonate 70% by mass
Styrene butadiene latex 9% by mass
Polyvinyl acetate latex 9% by mass
Sodium polyacrylate 0.4% by mass
Other 1.6% by mass
Above, solid content

A low-density polyethylene resin (density: 0.923 g / cm ³ , melting point: 110 ° C., melt index MI; 3.8) is extruded on the surface of the base material layer opposite to the surface on which the clay coat layer is formed. A coat layer having a thickness of 40 μm was formed by coating. Also, the surface of the base material layer on which the clay coat layer is formed is extrusion coated with a low-density polyethylene resin (density: 0.923 g / cm ³ , melting point: 110 ° C., melt index MI; 3.8). An innermost layer having a thickness of 20 μm was formed to obtain a packaging material.

  Next, the packaging material was heated at 160 ° C. for 90 seconds to form a cover layer in a foamed state, and the thickness of the cover layer was about 90 μm.

Thus, the packaging material of the Example laminated | stacked in order of LDPE90micrometer / paper 370g / m < ² > / clay coat layer 20g / m < ² > / LDPE20micrometer from the outer side was manufactured.

(Example 2)
Medium density polyethylene (density: 0.933 g / cm ³ , melting point) on a low density polyethylene resin (coat layer) on the surface opposite to the surface on which the clay coat layer is formed in the base material layer of Example 1 A packaging material of Example 2 was prepared in the same manner as in Example 1 except that 128 ° C. and melt index MI; 4.3) were formed.

(Comparative Example 1)
A packaging material of Comparative Example 1 was produced in the same manner as in Example 1 except that the clay coat layer of Example 1 was not formed.

(Comparative Example 2)
Instead of the clay coat layer of Example 1, 20 μm thick medium density polyethylene (density; 0.933 g / cm ³ , melting point: 128 ° C., melt index MI; 4.3) was extruded onto the substrate layer A packaging material of Comparative Example 2 was produced in the same manner as in Example 1 except that coating was performed. When this packaging material was heated at 160 ° C., it was necessary to heat for 120 seconds in order to form the cover layer in a foamed state.

(Evaluation methods)
About the packaging material of an Example and a comparative example, the extent of foaming of the cover layer and the innermost layer was evaluated. The results and the heating temperature and heating time for foaming are shown in Table 1. About the degree of foaming, the presence or absence of foaming and whether it foamed uniformly were investigated. Table 1 shows the case of uniform foaming as ◯, the case of partial foaming as Δ, and the case of non-foaming as x.

  As shown in Table 1, the packaging material of each example of the present invention can form the cover layer appropriately in a foamed state as compared with Comparative Example 1, and the innermost layer is not deformed by the clay coat layer. It was. Moreover, the packaging material of each Example of the present invention can be foamed in a shorter time than the packaging material of Comparative Example 2 when the heating temperature for forming the cover layer in the foamed state is the same. The manufacturing process was simple because MDPE was not used as compared with Comparative Example 2 while reducing the time.

It is sectional drawing which shows each example of the layer structure at the time of producing the packaging material of this invention. It is sectional drawing which shows an example of the layer structure of the other packaging material of this invention.

Explanation of symbols

10, 10A Packaging material 11 Cover layer (after foaming)
11A Cover layer (before foaming)
12 Base material layer 13 Clay coat layer 14 Innermost layer 15 Outermost layer

Claims (8)

From the outer surface side, a packaging layer formed by laminating at least a cover layer made of low-density polyethylene, a base material layer made of paper, a clay coat layer containing clay, and an innermost layer made of low-density polyethylene,
The basis weight of the clay coat layer is 10 to 40 g / m ² ,
The packaging material, wherein the cover layer is formed in a foamed shape by heating the packaging material.   The packaging material according to claim 1, wherein an outermost layer made of medium density polyethylene having a melting point higher than that of low density polyethylene by 5 ° C or more is laminated on the outer surface side of the cover layer.   The packaging material according to claim 1, wherein the clay coat layer is formed on the base material layer.   The packaging material according to any one of claims 1 to 3, wherein the clay coat layer contains at least one of kaolin, talc, calcium carbonate, and titanium dioxide.   The packaging material according to claim 1, further comprising a barrier layer between the clay coat layer and the innermost layer. From the outer surface side, a cover layer made of polyethylene, a base material layer made of paper, a clay coat layer containing clay, an innermost layer made of polyethylene, a method for producing a packaging material comprising at least lamination,
The coating amount of the clay coat layer is 10 to 40 g / m ² ,
In the state where the cover layer, the base material layer, the clay coat layer, and the innermost layer are laminated, the cover material is foamed by heating the packaging material within a range of 100 to 200 ° C. A method for producing a packaging material.   The method for producing a packaging material according to claim 6, wherein an outermost layer made of medium density polyethylene is laminated on the outer surface side of the cover layer, and then the packaging material is heated. The method for producing a packaging material according to claim 6 or 7, wherein the clay coat layer is formed on the base material layer.

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