JPH05271488A - Gas-barrier composition and foamed gas-barrier sheet made by using it - Google Patents

Abstract

PURPOSE:To obtain a resin composition which gives a layered film excellent in gas-barrier properties by incorporating a specified amount of a polyamide resin having a specified melt viscosity into a polyethylene mixture containing two specified polyethylenes. CONSTITUTION:20-60wt.% low-density polyethylene (including linear low-density polyethylene and ultra-low-density polyethylene) having a melt flow index (MI for short hereinafter) of 0.5 to 3 is mixed with 80-40wt.% high-density polyethylene having an MI of 0.5 to 3 to produce a polyethylene mixture. 100wt.% of this mixture is mixed with a polyamide resin (e.g. nylon 6) having a melt viscosity, measured at 240 deg.C under a shear rate of 100 per sec, of 1,000 to 10,000 P in an amount of 2-15phr to produce a gasbarrier resin composition. A film formed by melting this composition has a layered structure wherein a layer of the high-viscosity polyethylene resin mixture is surrounded on the outside by a layer of the low-viscosity polyamide resin.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a bubble sheet widely used as a cushioning packaging material, a heat insulating material and the like.

[0002]

2. Description of the Related Art An air bubble sheet made of a synthetic resin film is widely used as a cushioning material, a packaging material and a heat insulating material because of its soft cushioning property, airtightness, heat insulating property and the like. This bubble sheet is generally made of polyethylene resin as a raw material in view of workability and price. However, polyethylene resin is inferior in gas barrier property to polyamide resin, ethylene / vinyl alcohol copolymer resin, etc.
There is a drawback in that the air in the bubbles is lost due to aging or external pressure, and the buffering property is reduced. Therefore, particularly for applications requiring gas barrier properties, it is necessary to use a resin having a better gas barrier property than polyethylene as a material.
However, polyamide resins, polyvinyl alcohol resins, ethylene / vinyl alcohol copolymer resins, and the like, which have excellent gas barrier properties, have the disadvantage that they have large hygroscopicity, and that when they absorb moisture, their gas barrier properties are greatly reduced. Therefore, the air bubble sheet made of these gas barrier resin films alone has a reduced gas barrier function due to moisture absorption, the air in the air bubble chamber escapes to the atmosphere, the amount of enclosed air in the air bubble chamber decreases, and the air bubble sheet loses its buffering property. It has the drawback of being exposed.

In order to improve such drawbacks, the conventional general air bubble sheet is a single-layer film made of a polyethylene resin which is excellent in moisture resistance but inferior in gas barrier property, whereas it is a gas barrier property. In order to improve the moisture resistance, for example, in Japanese Utility Model Laid-Open No. 1-99615, a three-layer film having a surface layer of a polyolefin resin, a lower layer of a gas barrier resin, and an adhesive resin between both layers is used to form a bubble sheet. A method of making is disclosed. Further, in JP-A 1-271233, in order to reduce the amount of expensive gas barrier resin used and thin the barrier film, both surface layers are polyolefin resin, the intermediate layer is gas barrier resin, and both surface layers and intermediate layer. An attempt to make a bubble sheet using a five-layer film having an adhesive resin layer between and is also presented. Further, in JP-A-62-246934, an attempt has been made to prepare a gas barrier film by melt-mixing a polyolefin resin and a gas barrier resin.

However, in the above-mentioned five-layer film, both surface layers are made of moisture resistant polyolefin resin and the intermediate layer is made of gas barrier nylon. However, since the polyolefin resin and nylon resin have no adhesiveness to each other, ethylene / Use of an adhesive resin such as a copolymer resin of maleic anhydride or ethylene / fumaric acid is essential. Three extruders are required to extrude such three kinds of resins. Further, in order to obtain the above-mentioned laminated film consisting of five layers from three kinds of molten resins, not only a complicated and expensive laminating apparatus for distributing and laminating into five layers is required, but also three kinds of resins having different melt viscosities are required. It is difficult to obtain a film having a more uniform five-layer structure, and there is a problem that a high level of driving skill is required. Further, in an attempt to obtain a moisture-resistant gas barrier film by melt-mixing a polyolefin resin and a gas barrier resin, in many cases, the polyolefin film particles and the gas barrier resin are contained in the produced film. Since and exist in a non-uniform dispersed state, there is a problem that the gas barrier property cannot be expected and the gas barrier property is inferior as expected from the usage ratio of the gas barrier resin. However, as a solution to this problem, a special compatibilizer is interposed between the polyolefin resin and the gas barrier resin to form a gas barrier resin layer in the polyolefin resin particles to improve the gas barrier property of the film. Although there is an attempt of JP-A-1-275137, there are problems that the extrusion conditions are limited and the compatibilizer is expensive.

[0005]

[Problems to be Solved by the Invention]

In order to obtain an air bubble sheet having a good gas barrier property, there is no disadvantage that a complicated manufacturing apparatus having a large number of extruders is required, and the gas barrier resin is finely and unevenly dispersed. Then, the disadvantage that the gas barrier property is inferior is solved, and an air bubble sheet having a good gas barrier property is provided by using an ordinary air bubble sheet manufacturing apparatus.

The present inventor has studied based on such findings,
As a result of earnest research, the present invention has been completed.

[0008]

[Means for Solving the Problems]

FIG. 1 is a perspective view of a gas barrier air bubble sheet of the present invention, in which 1 is a bubble sheet, 2 is a cap film, 3 is a back film, and 4 is a bubble chamber.

FIG. 2 is an explanatory view exemplifying an air bubble sheet molding apparatus of the T die method, and 2 and 3 are the same as FIG. Further, 5 is an extruder, 6 is a T die, 7 is a cooling roll,
8 is a heating roll, 9 is a forming roll, 10 is a pressure roll,
11 is a peeling roll.

As the gas barrier composition, mixed polyethylene and polyamide resin are melt-mixed by the extruder 5 shown in FIG. Mixed polyethylene and polyamide resins have different viscosities. In a multi-layer flow in which resins having different viscosities coexist, a layered structure is formed in which the resin layer having low viscosity covers the outside of the resin layer having high viscosity while the flow proceeds. Therefore, a polyamide resin layer having a layered structure is formed outside the mixed polyethylene layer.

For forming the general bubble sheet 1, low density polyethylene (including linear low density polyethylene and ultra low density polyethylene) is used instead of mixed polyethylene.
Only is preferred. However, since the gas barrier foam sheet 1 of the present invention is intended, since the gas barrier property is insufficient with low-density polyethylene alone, a mixed polyethylene with a high-density polyethylene having a higher gas barrier property than the low-density polyethylene is preferable. preferable. However, if high-density polyethylene is used alone, the processability for forming a bubble sheet will be poor, so that low-density polyethylene is 20-60w.
It is preferable to use a mixed polyethylene of t% and high density polyethylene of 40 to 80 wt%.

As the gas barrier resin, a polyamide resin having a viscosity largely different from that of the mixed polyolefin is used. Examples of the polyamide resin include nylon 6 and nylon 1 produced by ring-opening polymerization reaction of lactam.
2. Nylon 11 produced by polycondensation reaction of aminocarboxylic acid, polyamides such as nylon 6-6, nylon 6-10, nylon 6-12 produced by polycondensation reaction of dibasic acid and diamine, and the like. 2/6 or more organic acids selected from nylon 6 / 6-6, nylon 6 / 6-10, nylon 6 / 6-12, m-xylenediamine and adipic acid, isophthalic acid, terephthalic acid Aromatic polyamides such as PMAIT nylon, PMAI nylon, PMAT nylon, and PMIT nylon that are copolycondensates with

As the mixed polyethylene, as described above, 20-60 wt% of low-density polyethylene having MI in the range of 0.3-3.0 and high density of MI in the range of 0.3-3.0. A mixture of 40-80 wt% polyethylene is used. More preferably, the LDPE having an MI in the range of 1.0 to 2.0 is 30 to 50 wt% and the MI is 0.5 to 1.
Mixed polyethylene of 50-70 wt% HDPE in the range of 5 is used.

Polyamide resin, which is a gas barrier resin, is added to 2 to 100 wt% of the mixed polyethylene.
The one added in the range of 15 PHR is used.

As a conventional bubble sheet forming apparatus,
There are T-die method and inflation method. The T-die method is disclosed, for example, in JP-A-60-5923, and the inflation method is disclosed, for example, in JP-B-40-16875. The bubble sheet 1 of the present invention can be molded using these conventional bubble sheet molding apparatuses. A bubble die forming apparatus of the T-die method is illustrated in FIG.

The resin obtained by adding a polyamide resin to mixed polyethylene is used to form the gas barrier air bubble sheet 1 of the present invention shown in FIG. 1 by using the air bubble sheet molding apparatus.
The bubble sheet 1 shown in FIG. 1 is a two-layer product including a cap film 2, a back film 3 and two films.
It may be a three-layered product consisting of three films in which smooth films are attached to both surfaces of the cap film 2.

On the gas barrier air bubble sheet 1, another air bubble sheet 1, a foamed sheet, a corrugated paper, a shrink film, etc. may be laminated.

A function may be added to the gas barrier air bubble sheet 1 by kneading or applying a drug. For example, the antistatic agent-containing bubble sheet 1, the volatile anticorrosive agent-containing bubble sheet 1, the freshness-retaining agent-containing bubble sheet 1, and the like. It may be the bubble sheet 1 in which a film containing an insect repellent, an antibacterial agent, an antifungal agent, an antistatic agent, or the like is laminated.

Hereinafter, according to Examples (and Comparative Examples),
The present invention will be described.

[0021]

Example 1 55 low density polyethylene with MI = 1.0
45 wt% high density polyethylene with MI = 0.9
100 wt% of mixed polyethylene obtained by mixing t%
On the other hand, using the molding device illustrated in FIG. 2 as a raw material, a mixture of nylon 6 and 6 PHR was used as the foam sheet 1.
Formed. For cap film 2 and back film 3
The temperature of each T-die 7 for use is 250 ° C., the surface temperature of the forming roll 9 is 70 ° C., and the extruded cap film 2 and the back film 3 are heat-fused to be integrated to form the bubble sheet 1.
Formed.

[0022]

Example 2 A bubble sheet 1 of Example 2 was obtained in the same manner as in Example 1 except that the added nylon 6 was 8 PHR.

[0023]

Example 3 A bubble sheet 1 of Example 3 was obtained in the same manner as in Example 1 except that the added nylon 6 was 10 PHR.

[0024]

[Comparative Example 1] 55 of low density polyethylene having MI = 1.0
45 wt% high density polyethylene with MI = 0.9
Only 100 wt% of mixed polyethylene of t%, and no gas barrier resin was added. Otherwise in the same manner as in Example 1, a bubble sheet 1 of Comparative Example 1 was obtained.

The measurement of the barrier performance of each foam sheet 1 of Examples 1 to 3 and Comparative Example 1 was carried out by the compression creep test method. That is, the air bubble sheet 1 is cut into 150 mm square, 45 pieces of the cut air bubble sheet 1 are superposed, and a load of 2 kg is applied thereon, and the temperature is 23 ° C. and the humidity is 65%.
It was left for 14 days under the condition of RH. After 14 days had elapsed, the reduction rate of the height of the 45 air bubble sheets 1 was measured and displayed as "%". The measurement results are summarized in Table 1 below, together with Examples 4 to 6 and Comparative Examples 2 to 4 below.

[0026]

Example 4 A low density polyethylene having MI = 1.0 was used as 35
65w of wt% and high density polyethylene with MI = 0.9
Using a mixture in which 3 PHR of nylon 6/66 was added to 100 wt% of mixed polyethylene of t%, the temperature of each T die 7 was 250 ° C. and the surface temperature of the forming roll 9 was 70 ° C. as in Example 1. The extruded cap film 2 and back film 3 were heat-fused and integrated to form a bubble sheet 1.

[0027]

Example 5 A bubble sheet 1 of Example 5 was obtained in the same manner as in Example 4 except that the added nylon 6/66 was 5 PHR.

[0028]

Example 6 A foam sheet 1 of Example 6 was obtained in the same manner as in Example 4 except that the added nylon 6/66 was 7 PHR.

[0029]

[Comparative Example 2] A low-density polyethylene having MI = 1.0 was used as 35
65w of wt% and high density polyethylene with MI = 0.9
Only 100 wt% of mixed polyethylene of t%, and no gas barrier resin was added. Except for this, the air bubble sheet 1 of Comparative Example 2 was obtained in the same manner as in Example 4.

[0030]

[Comparative Example 3] A bubble sheet 1 of Comparative Example 3 was prepared in the same manner as in Example 4, except that only low-density polyethylene (without mixing high-density polyethylene) was used as the mixed polyethylene, and 8 PHR of nylon 6/66 was added. Obtained.

[0031]

[Comparative Example 4] As a conventional air bubble sheet 1 having excellent gas barrier properties, a film made of nylon 6 resin was used on both sides with a film made of low density polyethylene resin having MI = 1.0 via adhesive films. A cellular sheet 1 was obtained in the same manner as in Example 1 with the laminated 5-layer product.

[0032]

[Table 1]

Table 1 shows the results of the compression creep test of each foam sheet 1 of Examples 1 to 6 and Comparative Examples 1 to 4. In the table, LDPE is low-density polyethylene, HDPE is high-density polyethylene, and wt% is 1% mixed polyethylene.
It is each wt% of LDPE and HDPE set to 00 wt%. In the compression creep test, the above-mentioned bubble sheet 1
Forty-five pieces of the cut bubble sheet 1 were cut into m-square pieces, a load of 2 kg was applied thereon, and the pieces were left for 14 days under the conditions of temperature = 23 ° C. and humidity = 65% RH. After 14 days had elapsed, the reduction rate of the height of the 45 air bubble sheets 1 was measured and displayed as "%".

As the mixed polyethylene of Examples 1 to 3 and Comparative Example 1, a mixture of 55 wt% of low-density polyethylene with MI = 1.0 and 45 wt% of high-density polyethylene with MI = 0.9 was used. Nylon 6 was added to this mixed polyethylene, 0 PHR in Comparative Example 1, 6 RPH in Example 1, and 8 P in Example 2.
HR, in Example 3, 10 PHR was added. In the compression creep test, about half of the air leaked from the inside of the bubbles in Comparative Example 1, whereas the air leaked from the inside of the bubbles in Example 1 was only 10%, and the gas barrier property was dramatically improved. Example 2
Further, when the amount of nylon 6 added in Example 3 was increased, the gas barrier property was improved to 5% as in Comparative Example 4. In Examples 4 to 6 and Comparative Example 2, the proportion of high density polyethylene in the mixed polyethylene was increased (low density polyethylene 3
5 wt% and high density polyethylene 65 wt%). Comparative Example 1
When the material was changed from Comparative Example 2 to Comparative Example 2, the gas barrier property was improved from 51% to 46% in the compression creep test. Similarly, the compression creep test of 5% in Comparative Example 4 was reached in Example 3 where Nylon 6 = 10 PHR.
It was possible to reach in Example 6 in which PHR was reduced to 7 PHR. In Comparative Example 3 using only low-density polyethylene (no high-density polyethylene was mixed) as the mixed polyethylene, the compression creep test was reduced from 7% to 56% as compared with Example 2 in which high-density polyethylene was mixed. It has been shown that the gas barrier property is not improved so much by using low density polyethylene alone without mixing high density polyethylene.

[0035]

Each of the films of the bubble sheet 1 of the present invention is a layered structure film in which when a synthetic resin mixture as a raw material is melted into a film, the outside of the mixed polyethylene resin layer of high viscosity is surrounded by the polyamide resin layer of low viscosity. Therefore, the gas barrier property is effectively exhibited.

[0036]

EFFECTS OF THE INVENTION It is not necessary to form a complicated laminated film,
A bubble sheet 1 having an effective gas barrier property can be obtained by using a general bubble sheet forming apparatus without using an extra and complicated auxiliary device.

[Brief description of drawings]

FIG. 1 is a perspective view of a gas barrier air bubble sheet of the present invention.

FIG. 2 is an explanatory diagram illustrating a bubble sheet forming apparatus.

Table 1 is a table summarizing the composition of gas barrier properties and the results of the compression creep test.

[Explanation of symbols]

 1 Air bubble sheet 2 Cap film 3 Back film 4 Bubble chamber 5 Extruder 6 T die 7 Cooling roll 8 Heating roll 9 Forming roll 10 Pressure roll 11 Peeling roll

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Claims (2)

[Claims] 1. A melt flow index (hereinafter referred to as MI
20 to 60 wt% of low density polyethylene (including linear low density polyethylene and ultra low density polyethylene) in the range of 0.5 to 3.0 and MI of 0.5 to 3.0.
100 wt% of polyethylene mixed with 40-80 wt% of high density polyethylene in the range of
Melt viscosity at 0 ° C, shear rate = 100 per second is 1
A gas barrier resin composition comprising 2 to 15 PHR of a polyamide resin having a porosity of 10,000 poise or less and a poise of 1,000 poise or more. 2. A bubble sheet comprising a cap film having a large number of convex portions and a smooth back film attached to the cap film, wherein the film is the film comprising the gas barrier composition according to claim 1. A gas barrier air bubble sheet.