JP2001199433A - Paper container - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a paper container which is comfortable to feeling with odor prevented from soaking into contents of the container. SOLUTION: The innermost layer of the paper container is formed of an ethylene-α olefine copolymer polymerized by using a single site catalyst. Since the ethylene-α olefine copolymer polymerized by using the single site catalyst has a narrow molecular weight distribution and has a very small content of low molecular weight matters, soaking of odor into contents can be minimized and the paper container becomes confortable to feeling.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a paper container, and more particularly to a paper container characterized by using an ethylene-α-olefin copolymer obtained by using a single-site catalyst as the innermost layer of the paper container.

[0002]

2. Description of the Related Art In general, a liquid paper container is formed using various kinds of laminates in order to ensure the storability of contents and the strength as a container. The laminate used for this liquid paper container is polyethylene (PE) / paper / P
E, PE / paper / PE / Al / PE, PE / paper / PE / A
1 / Polyester (PET) / PE laminates are known and are still widely used at present.

Conventionally, a high-pressure (low-density) polyethylene is generally used as the innermost layer of a liquid paper container.
This is because heat sealing is easy and processing is easy.
Also, if you dislike polyethylene odor like water or sake,
Because it is better than high-pressure low-density polyethylene, an ethylene-α-olefin copolymer film obtained using a Ziegler catalyst (called a multi-site catalyst because of multiple active sites) is used as the innermost layer of the liquid paper container. Sometimes.

[0004]

However, when the high-pressure low-density polyethylene is used as the innermost layer of the liquid paper container, the low-molecular-weight material contained in the high-pressure low-density polyethylene contains the contents in the paper container. And the taste of the contents changes. Especially, the contents are sake, shochu,
In the case of whiskey, mineral water, etc., this problem is serious.

[0005] Further, due to the low molecular weight substances contained in the high-pressure low-density polyethylene, the film has poor lubricity, hinders processing, and when a lubricant is added to improve the lubricity of the film, the lubricant becomes There is a problem that the content shifts to the content and the taste of the content changes.

Further, when an ethylene-α-olefin copolymer film obtained by using a Ziegler catalyst is used as the innermost layer of a liquid paper container, this film has a high sealing temperature and has a problem in workability. If the density of the film is reduced to improve the processability, the amount of low molecular weight substances increases, and as a result, the lubricity of the film is poor, there is a problem in processing, and a lubricant is added to improve the lubricity of the film. Then, there is a problem that the lubricant transfers to the contents and the taste of the contents changes.

[0007] The present invention has been made in view of the above problems, and has as its object to provide a paper container which does not cause odor to the contents and is therefore organoleptically good.

[0008]

In order to achieve the above object, the paper container of the present invention has an innermost layer of an ethylene-α-olefin copolymer layer polymerized by using a single-site catalyst.

Further, the paper container of the present invention is preferably such that, in the above-mentioned paper container of the present invention, α-olefin is converted to propylene, 1-butene, 3-methyl-1-butene, 4-methyl-1-pentene, -Hexene, 1-octene, and one or more selected from decene.

[0010]

In the paper container of the present invention, an ethylene-α-olefin copolymer layer polymerized using a single-site catalyst is used as the innermost layer, and the ethylene-α-olefin polymerized using this single-site catalyst is used. Since the copolymer has a narrow molecular weight distribution and a very low content of low molecular weight substances, there is no odor transfer to the contents, and thus a functionally good paper container can be obtained.

Further, the ethylene-α-olefin copolymer polymerized by using a single-site catalyst has good lubricity without adding a lubricant, so that it can be easily processed and the production of a paper container becomes easy. . At the same time, there is no problem that occurs when a lubricant is added.

Furthermore, an ethylene-α-olefin copolymer polymerized using a single-site catalyst has excellent low-temperature heat sealability and good filling machine suitability, so that the production of paper containers becomes very easy.

Hereinafter, the paper container of the present invention will be described in detail. The paper container of the present invention is a single-site catalyst (SS
The ethylene-α-olefin copolymer layer polymerized using C) is used as the innermost layer of the paper container.

Here, a single-site catalyst (including a metallocene catalyst, a so-called Kaminski catalyst) is characterized in that active sites are uniform (single-site). This single-site catalyst is a catalyst comprising a metallocene-based transition metal compound and an organoaluminum compound, and may be used while being supported by an inorganic substance.

Here, as the metallocene transition metal compound, for example, a transition metal selected from the IVB group [titanium (Ti), zirconium (Zr), hafnium (H
f)] includes a cyclopentadienyl group, a substituted cyclopentadienyl group, an indenyl group, a substituted indenyl group, a tetrahydroindenyl group, a substituted tetrahydroindenyl group,
A fluoronyl group or a substituted fluorenyl group having 1 to 2 bonds, or a structure in which two of these groups are cross-linked by a covalent bond, and a hydrogen atom, an oxygen atom, a halogen atom, an alkyl group And those having a ligand such as an alkoxy group, an aryl group, an acetylacetonate group, a carbonyl group, a nitrogen molecule, an oxygen molecule, a Lewis base, a substituent containing a silicon atom, and an unsaturated hydrocarbon.

Further, as the organoaluminum compound,
Examples thereof include alkyl aluminum, and a chain or cyclic aluminoxane. Here, as the alkylaluminum, triethylaluminum, triisobutylaluminum, dimethylaluminum chloride, diethylaluminum chloride, methylaluminum dichloride, ethylaluminum dichloride, dimethylaluminum fluoride, diisobutylaluminum hydride, diethylaluminum hydride, ethylaluminum sesquichloride, etc. No.

The chain or cyclic aluminoxane is produced by bringing alkyl aluminum into contact with water. For example, it can be obtained by adding alkyl aluminum at the time of polymerization and adding water later, or by reacting water of crystallization of a complex salt or water of adsorption of an organic / inorganic compound with alkyl aluminum.

Examples of the inorganic substance supporting the single-site catalyst include silica gel, zeolite, and diatomaceous earth. Examples of the polymerization method include bulk polymerization, solution polymerization, suspension polymerization, and gas phase polymerization. These polymerizations may be a batch method or a continuous method.

The polymerization conditions are usually from 100 to 100 hours.
250 ° C., polymerization time 5 minutes to 10 hours, reaction pressure normal pressure 300 kg / cm ² . As the α-olefin which is a comonomer copolymerized with ethylene, propylene,
-Butene, 3-methyl-1-butene, 4-methyl-1-
Examples include pentene, 1-hexene, 1-octene, and decene. These α-olefins may be used alone or in combination of two or more.

The mixing ratio of the α-olefin is preferably 1 to 50 mol%. The ethylene-α-olefin copolymer includes an antioxidant, an ultraviolet absorber, an antistatic agent, an antiblocking agent, a lubricant (fatty acid amide), a flame retardant, an inorganic and organic filler, a dye, a pigment, and the like. May be appropriately added.

The physical properties of the ethylene-α-olefin copolymer polymerized using the single-site catalyst are, for example, those having a molecular weight of 5 × 10 ^{3 to} 5 × 10 ⁶ and a density of 0.89 to 0.
95 (g / cm ³ ), melt index [MI]
0.1 to 50.

The present invention is characterized in that the paper container uses an ethylene-α-olefin copolymer layer obtained by using a single-site catalyst as described above as the innermost layer of the paper container. The layer configuration other than the innermost layer of the container is not particularly limited. That is, various layer configurations other than the innermost layer can be considered.

As described above, various forms of the laminate for forming the paper container of the present invention can be considered, and examples of the laminate are shown in FIGS. The laminate shown in FIG.
E layer (outermost layer) 2 / paper substrate 1 / ethylene-α-olefin copolymer layer (innermost layer) 3 obtained using a single-site catalyst.

Here, as the outermost PE layer 2, for example, high-pressure low-density polyethylene is used. PE layer 2
Is suitably about 5 to 50 μm. Further, the surface of the PE layer 2 is preferably subjected to corona treatment in order to impart printability. The basis weight of the paper substrate 1 is 100 to 500
g / m ² is appropriate. Examples of the method of laminating the ethylene-α-olefin copolymer layer 3 obtained using a single-site catalyst include an extrusion lamination method, a T-die method, and a method of dry laminating or sand laminating a film formed by an inflation method. Is mentioned.

The laminate shown in FIG. 2 has a PE layer (outermost layer) 2
/ Paper base 1 / Ethylene-methacrylic acid copolymer layer 4 / Aluminum foil 5 / Ethylene-methacrylic acid copolymer layer 4 / Ethylene-α-olefin copolymer layer obtained using a single-site catalyst (innermost layer) Consists of three.

Here, the PE layer 2, the paper substrate 1, and the ethylene-α-olefin copolymer layer 3 obtained using the single-site catalyst are the same as in the case of the laminate shown in FIG. The thickness of the aluminum foil 5 is suitably about 5 to 40 μm. The ethylene-methacrylic acid copolymer layer 4
Is used for bonding an aluminum foil and a paper substrate by extrusion lamination. The thickness of the ethylene-methacrylic acid copolymer layer 4 is suitably about 5 to 50 μm.

The laminate shown in FIG. 3 has a PE layer (outermost layer) 2
/ Paper base 1 / ethylene-methacrylic acid copolymer layer 4 / aluminum foil 5 / biaxially stretched polyethylene terephthalate (PE
T) Layer 6 / Ethylene-α-olefin copolymer layer (innermost layer) 3 obtained using a single-site catalyst.

Here, PE layer 2, paper substrate 1, ethylene-
The methacrylic acid copolymer layer 4, the aluminum foil 5, and the ethylene-α-olefin copolymer layer 3 obtained by using a single-site catalyst are the same as in the case of the laminate shown in FIG. The thickness of the biaxially stretched PET layer 6 is suitably about 7 to 25 μm.

In the laminate shown in FIGS. 2 and 3, instead of the aluminum foil 5 and the biaxially stretched polyethylene terephthalate layer 6, a silica-deposited film (for example, silica-deposited PET) or the like is used as a barrier film. May be used.

The paper container of the present invention formed using the laminate as shown in FIGS. 1 to 3 can be assembled into various shapes such as a goebel top type, a flat top type and a box type. In this case, after the laminated sheet is punched as shown in the development view of the paper container, in the case of the gobel-top type and the flat-top type, the body is bonded by a frame seal or a hot air seal, and the box is formed in a filling machine. I do. Further, in the case of a box type, after punching out a laminate sheet, it is often supplied in a roll form to a filling machine, sealed, and box-formed. In addition, when using the laminated body as shown in FIG. 3, the end surface of the laminated sheet is not in contact with the contents,
It is preferable to cover the end surface of the laminate sheet by tape attachment of skive hemming or the like.

The use of the paper container of the present invention is not particularly limited. For example, sake, shochu, wine, juice, beverages with milk, seasonings such as soy sauce, mirin, dressing, mentsuyu, detergents, It is suitably used as a paper container for chemical products such as oils, waxes, paints and adhesives. Further, the use of the paper container of the present invention is not limited to the use for liquid.

[0032]

EXAMPLES The present invention will be described below more specifically based on examples. (Example 1) As shown in FIG. 1, the surface of the paper substrate having a basis weight of 270 g / m ^2, high-pressure low-density polyethylene (density d:
0.927 g / cm ³ , melt index [MI]:
4) was extrusion coated to a thickness of 25 μm. Next, a single-site catalyst (Kamminski catalyst: a catalyst obtained by combining zirconocene dichloride and methylalumoxane (molar ratio 1: 800)) was injected into the polymerization reactor on the other surface of the paper base, and polymerization was performed. Ethylene-1-hexene copolymer (d: 0.920 g / cm ³ , [MI]: 4)
It was extrusion-coated at a thickness of 0 μm to form a laminate sheet for box-making. Then, a gobel top type paper container having an inner volume of 1 liter was produced using this box-forming laminate sheet.

Example 2 As shown in FIG. 3, an ethylene-1-hexene copolymer (d: 0.925 g / cm ³ , [MI]: 1) polymerized using a Kaminsky catalyst was blown by an inflation method. As a result, a film having a thickness of 60 μm was obtained. Then, this film was dry-laminated on the biaxially stretched PET side of a laminated film obtained by dry laminating a 9 μm thick aluminum foil and a 12 μm thick biaxially stretched PET with a two-component curable urethane adhesive. One side of a paper base material having a basis weight of 340 g / m ² via an ethylene-methacrylic acid copolymer layer (Nucrel 1180C: manufactured by Mitsui Dupont Chemical Co.) having a thickness of 30 μm on the aluminum foil side of the obtained laminate. Was subjected to sand lamination. Further, on the other surface of the paper base material, a high-pressure low-density polyethylene (Mirason L6P: manufactured by Mitsui Petrochemical Co., Ltd.) (density d:
0.923 g / cm ³ , [MI]: 3.7) is 30 μm
And extrusion-coating to form a laminate sheet for box-making. Then, a gobel top type paper container having an inner volume of 1 liter was produced using this box-forming laminate sheet.
In order to prevent the end face of the laminated sheet for box-making from coming into contact with the contents, the end face of the laminated sheet was covered with skive hemming tape when pasting the body.

Comparative Example 1 A high-pressure low-density polyethylene (density d: 0.923 g / cm ³ , [M
I]: 3.7) was extruded and coated, and the content was the same as in Example 1 except that the ethylene-1-hexene copolymer polymerized using a single-site catalyst (Kamminsky catalyst) was not used. A 1 liter goebel top paper container was produced.

(Comparative Example 2) Instead of the ethylene-1-hexene copolymer film polymerized by using a Kaminski catalyst in Example 2, a film having a thickness of 6 by an inflation method was used.
0 μm high-pressure low-density polyethylene (density d: 0.92
5 g / cm ³ , [MI]: 2) A gobel top paper container having an internal volume of 1 liter was produced in the same manner as in Example 2 except that a film was used.

Comparative Example 3 Instead of the film polymerized using the Kaminsky catalyst in Example 2, an ethylene-4-methylpentine-1 copolymer (d =
0.920 [MI] = 2) A gobel top paper container having an internal volume of 1 liter was produced in the same manner as in Example 2 except that a film was used.

The above Examples 1 and 2 and Comparative Examples 1 and 2
In No. 3, the density d was measured in accordance with ASTM D1505, and the measurement index [MI] was measured in accordance with ASTM D1238.

(Sensory Evaluation) Examples 1 and 2 and Comparative Example 1
The mineral water was filled at 80 ° C. into the 1 liter internal volume goebel top paper container obtained in
After storage at a temperature of 1 week, sensory evaluation was performed. As a result, the mineral water in the paper containers of Examples 1 and 2 did not give off-flavor and was good, but the mineral water in the paper containers of Comparative Examples 1 and 2 gave off-odor.

[0039]

As described in detail above, the paper container of the present invention is obtained by polymerizing ethylene-α using a single-site catalyst.
The olefin copolymer is used as the innermost layer, and the ethylene-α-olefin copolymer polymerized using this single-site catalyst has a narrow molecular weight distribution and a very low content of low molecular weight substances. There is no odor transfer to the product, so that a paper container having a good sensory quality is obtained.

The ethylene-α-olefin copolymer polymerized using a single-site catalyst has good lubricity without adding a lubricant, so that it can be easily processed and a paper container can be easily manufactured. . At the same time, there is no problem that occurs when a lubricant is added.

Further, the ethylene-α-olefin copolymer polymerized by using a single-site catalyst has excellent low-temperature heat sealability and good filling machine suitability, so that the production of paper containers becomes very easy.

[Brief description of the drawings]

FIG. 1 is a partial cross-sectional view showing one example of a laminate for forming a paper container of the present invention.

FIG. 2 is a partial cross-sectional view showing another example of a laminate for forming the paper container of the present invention.

FIG. 3 is a partial cross-sectional view illustrating another example of a laminate for forming the paper container of the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Paper base material, 2 ... PE layer, 3 ... Ethylene-alpha olefin copolymer layer obtained using a single site catalyst, 4 ...
Ethylene-methacrylic acid copolymer layer, 5 ... aluminum foil, 6
... Biaxially stretched polyethylene terephthalate (PET) layer

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) B65D 5/40 B65D 5/40 B C08F 210/16 C08F 210/16 // C08F 4/642 4/642

Claims (2)

[Claims] 1. A paper container wherein an ethylene-α-olefin copolymer layer polymerized using a single-site catalyst is used as an innermost layer. 2. The α-olefin is one or more selected from propylene, 1-butene, 3-methyl-1-butene, 4-methyl-1-pentene, 1-hexene, 1-octene and decene. The paper container according to claim 1, wherein: