JP3077573B2 - Paper container - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a paper container capable of containing liquids such as milk and juice.

[0002]

2. Description of the Related Art Conventionally, as a liquid paper container, a heat seal layer made of a polyolefin polymerized by a multi-site catalyst, for example, low-density polyethylene, is used as an inner layer, and a paper, print layer, protective layer, etc. are formed as outer layers. A material composed of laminated materials is often used. However, low-density polyethylene polymerized using a multi-site catalyst is not good in transparency and mechanical strength of the film, has a resinous odor, and also has an improved low-temperature sealability. There was room.

[0003] In view of the above, in recent years, polyolefins polymerized using a multi-site catalyst have been replaced with polyolefins polymerized using a single-site catalyst, for example, a single-site catalyst as described in JP-A-7-148895. Attempts have been made to substitute ethylene-α-olefin copolymers that have been used for polymerization. When a polyolefin polymerized using a single-site catalyst is used, its mechanical strength is improved and the smell of resin odor is eliminated as compared with a case where a polyolefin polymerized using a multi-site catalyst is used. Further, since the low-temperature sealing property and the hot tack property are improved, the productivity is improved. However, in the heat sealing process of the paper container, particularly in the top and bottom sealing processes of the paper container, there is often a time lag from the heating to the pressure bonding, and in such a case, the resin filling or bonding of the heat-sealed portion is difficult. There was a problem that defects occurred.

[0004]

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, has good low-temperature sealability and mechanical strength, has little transfer of resinous odor to contents, and has a high heat resistance. It is an object of the present invention to provide an improved paper container that exhibits good sealing properties in a sealing step and does not cause poor resin filling.

[0005]

SUMMARY OF THE INVENTION The present invention comprises a paper layer and a blend of linear low density polyethylene polymerized using a single site catalyst and low density polyethylene polymerized using a multisite catalyst. A paper container having an inner layer.

[0006]

BEST MODE FOR CARRYING OUT THE INVENTION In order to improve the heat-sealing property of a paper container using linear low-density polyethylene polymerized using a single-site catalyst and to improve resin filling failure,
Diligent research was conducted.

[0007] Linear low-density polyethylene polymerized using a single-site catalyst has a narrow composition distribution and molecular weight distribution, a thin crystal lamella, and a large number of tie molecules. For this reason, it is possible to lower the melting point by reducing the density, and a film using this is excellent in low-temperature sealability. Also, the hot tack and mechanical properties of the film are better than other low density polyethylenes.

[0008] The linear low-density polyethylene polymerized using the single-site catalyst has almost no raw material odor peculiar to resin as compared with other low-density polyethylenes, and is used as the innermost layer of a package. However, there is little odor transfer in the contents.

However, when a paper container is formed by using only a linear low-density polyethylene polymerized using the single-site catalyst as a heat seal layer, a resin filling defect at a bottom portion occurs. Poor resin embedding, for example, when forming the bottom portion of a paper container, by folding the sealing pieces and bonding them together, a step occurs between the sealing pieces, and the molten resin does not sufficiently flow between the steps. To happen. In addition, poor adhesion often occurs when the top portion of the paper container is folded and sealed. This means that, even once bonded, by the time the molten resin solidifies,
Due to the repulsion of the paper, a peeling force is applied to the bonded portion, which is generated. It is considered that the resin embedding failure at the bottom portion and the adhesion failure at the top portion are caused by the melt flow rate, melt tension, and melt viscosity of the resin.

[0010] The melt flow rate of linear low-density polyethylene polymerized using a single-site catalyst is higher than that of low-density polyethylene polymerized using a multi-site catalyst. The low density polyethylene polymerized using is larger. This is because, when the gap is filled with the low-density polyethylene melted by heating and pressing, when a strong peeling force is applied to the gap, the single-site catalyst is lower than the low-density polyethylene polymerized using the multi-site catalyst. Means that the straight-chain low-density polyethylene polymerized by using is easier to escape.

At low shear rates, the apparent melt viscosity of linear low-density polyethylene polymerized using a single-site catalyst is smaller, and at high shear rates, the apparent melt viscosity is lower than that of a single-site catalyst. Chain low density polyethylene is larger. This indicates that when the shear rate applied to the molten resin is high, the linear low-density polyethylene polymerized using the single-site catalyst is difficult to flow, so that the resin filling is poor.

Therefore, increasing the melt tension of the linear low-density polyethylene polymerized using a single-site catalyst and improving the fluidity of the linear low-density polyethylene is effective in improving resin filling failure. .

[0013] From the above, the present inventors have proposed that, as the inner layer of a paper container, a linear low-density polyethylene polymerized using a single-site catalyst and a low-density polyethylene polymerized using a multi-site catalyst are used. It has been found that a blend is used.

By blending a linear low-density polyethylene polymerized using a single-site catalyst and a low-density polyethylene polymerized using a multi-site catalyst, the melt viscosity is reduced, but the single-site catalyst is used. The melt tension can be increased while maintaining the low-temperature sealing property, hot tack property and mechanical properties of the polymerized linear low-density polyethylene to some extent. This makes it easy for low-density polyethylene to flow even if a force is applied in the direction of peeling off the sealed part due to the repulsion of the paper after heating and pressure-bonding, and even if a step occurs in the sealed part. Since it is difficult to escape from the resin, the resin filling becomes good.

The blend ratio of the linear low-density polyethylene polymerized using the single-site catalyst to the low-density polyethylene polymerized using the multi-site catalyst is preferably 90/10 to 70/30, more preferably 80/30.
/ 20.

In the paper container of the present invention, the resin thus obtained is used as a heat seal layer. In addition, a blend of a linear low-density polyethylene polymerized using a single-site catalyst and a low-density polyethylene polymerized using a multi-site catalyst includes, for example, an antioxidant, an ultraviolet absorber, an antistatic agent, and an antiblocking agent. Agent, lubricant,
Additives such as flame retardants, inorganic and organic fillers, dyes, and pigments can be added.

Here, the single site catalyst refers to a catalyst comprising a metallocene transition metal compound and an organoaluminum compound. Examples of the metallocene transition metal compound include, for example, a transition metal element selected from Group IVB, such as titanium, zirconium, and hafnium, a cyclopentadienyl group, a substituted cyclopentadienyl group, an indenyl group, a tetrahydroindenyl group, and a substituted tetrahydroindene. A carbonyl group, a fluoronyl group, or a substituted fluorenyl group;
Or two or a group in which two of these groups are cross-linked by a covalent bond are bonded, and a hydrogen atom, oxygen atom, halogen atom, alkyl atom, alkoxy atom, aryl group, acetylacetonate Groups having a ligand such as a 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 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. can give.

The chain or cyclic aluminoxane is produced by contacting an alkylaluminum with water. Furthermore, the single-site catalyst can be supported on an inorganic substance carrier such as silica gel, zeolite, and diatomaceous earth.

Examples of the polymerization method include bulk polymerization, solution polymerization, suspension polymerization, gas phase polymerization and the like. Hereinafter, with reference to the drawings,
The present invention will be specifically described. FIG. 1 is a diagram showing one embodiment of the paper container of the present invention. FIG. 2 is a view showing a state in which a part of the paper container shown in FIG. 1 is cut out, and FIG. 3 is a partially enlarged view of a cross section 10 in FIG.

As shown in FIG. 1, the paper container 1 is a hollow rectangular cylindrical container having a roof-shaped top 3 and a flat bottom 2 and is called a Gabel-top type. This paper container 1
As shown in FIG. 3, for example, is constituted by a laminate composed of an inner layer 11, a paper layer 12, and an outer layer 13. At least the inner layer of the paper container 1 among the inner layer 11 and the outer layer 13 is composed of a linear low-density polyethylene polymerized using a single-site catalyst and a low-density polyethylene polymerized using a multi-site catalyst, for example, 80/20. It is blended in the ratio of

FIG. 4 shows another embodiment of the laminate constituting the paper container of the present invention. The laminate 20 is used for a paper container having a printed layer 18 formed on an outer surface, and includes an inner layer 17, a paper layer 12, and an outer layer 19. The inner layer 17
It consists of a blend (80/20) of a linear low density polyethylene polymerized using a single site catalyst and a low density polyethylene polymerized using a multisite catalyst.

FIG. 5 shows still another embodiment of the laminate constituting the paper container of the present invention. This laminate 30
Is used for a paper container having a barrier property, and includes an inner layer 17, a silicon oxide deposited layer 33, a polyester layer 32,
Low density polyethylene layer 34, low density polyethylene layer 3
5, a paper layer 12, and an outer layer 19 are sequentially laminated. The silicon oxide deposited layer 33 is deposited on the polyester layer 32 in advance. Inner layer 17 and silicon oxide deposited layer 33
Preferably, an anchor layer is provided between the polyester layer 32 and the low-density polyethylene layer 34 in order to improve adhesion.

The inner layer 17 is made of a blend (8) of a linear low-density polyethylene polymerized using a single-site catalyst and a low-density polyethylene polymerized using a multi-site catalyst.
0/20) and used as an inner layer of a paper container.
The anchor layer is made of, for example, a urethane resin or a resin composed of a saturated polyester / isocyanate compound, and is used to improve the adhesion between the silicon oxide-deposited polyester layer 32 and the inner layer 17 or the low-density polyethylene layer 34. The low-density polyethylene layer 34 and the low-density polyethylene layer 35 are provided for bonding between the layers and for securing the overall rigidity.

[0025]

[0026]

[0027]

[0028]

[0029]

[0030]

[0031]

[0032]

[0033]

[0034]

[0035]

The shape of the paper container of the present invention is not limited to a goebel top type paper container as shown in FIG.
FIG. 9 is a view showing another embodiment of the present invention, and FIG. 10 is a view schematically showing a cross section of FIG. As shown in FIG.
The paper container of the present invention may have a cylindrical shape. This paper container can be formed using, for example, a laminate as shown in FIG. As shown in FIG. 10, as shown in FIG. 10, a cylindrical container body 120 formed by curving a sheet made of a laminated body into a cylindrical shape, and sealing the matched both sides to each other, A shallow cup-shaped bottom member 130 provided in one of the two openings, and a take-out port 111 provided in the other opening and having a shallow cup-shaped shape and having a bottom portion removably sealed with a seal member 140. And a lid member 110 having the same. The open ends of the container body 120 each have folded pieces 121 and 122 folded inward from the ends by a predetermined length, and a gap between the folded piece 122 and the main body 120 includes a side wall of the bottom member 130. 132 is inserted and the folded piece 121 is inserted.
In the gap between the main body 120 and the side wall 112 of the lid member 110,
Are inserted and sealed by heating.

In this container, the seal member 140 is provided with the knob 1
The contents can be taken out from the take-out opening 111 by peeling off with the trigger 41. Also, this container has good low-temperature sealability and mechanical strength,
The filling of the resin was sufficient as in the case of the Gebel-top type paper container, and the transfer of the resin odor to the contents was small. As described above, the paper container of the present invention has good resin embedding and excellent impact resistance.

[0038]

According to the present invention, the low-temperature sealing property and the mechanical strength are good, the resin filling defect does not occur in the heat sealing step, and the odor of resin odor is less transferred to the contents. A quality paper container is obtained. Further, the paper container of the present invention has excellent productivity because of its excellent low-temperature sealability.

[Brief description of the drawings]

FIG. 1 is a perspective view showing one embodiment of a paper container of the present invention.

FIG. 2 is a view showing a state in which a part of the paper container shown in FIG. 2 is cut out.

FIG. 3 is a partially enlarged view of section 10 of FIG. 3;

FIG. 4 is a view showing another embodiment of the laminate constituting the paper container of the present invention.

FIG. 5 is a view showing still another embodiment of the laminate constituting the paper container of the present invention.

FIG. 6 is a diagram showing a compression direction in a compression test.

FIG. 7 is a view showing a compression direction in a compression test.

FIG. 8 is a view showing a compression direction in a compression test.

FIG. 9 is a perspective view showing another embodiment of the paper container of the present invention.

FIG. 10 is a diagram schematically showing a longitudinal section of FIG. 9;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Paper container 2 ... Bottom part 3 ... Top part 10 ... Cross section 11, 17 ... Inner layer 13, 19 ... Outer layer 12 ... Paper layer 18 ... Printing layer 20, 30 ... Laminate 32 ... Silicon oxide vapor-deposited polyester layer 34, 35 ... Low density Polyethylene layer

Claims (1)

(57) [Claims] 1. A paper container having a paper layer and an inner layer consisting essentially of a blend of linear low density polyethylene polymerized using a single site catalyst and low density polyethylene polymerized using a multisite catalyst.