JPH08197686A - Laminated sheet - Google Patents

Abstract

PURPOSE: To obtain an inexpensive packing material not generating the deterioration of the quality of a substance generating gas during storage such as fermented food or the like in a packed state and allowing generated gas to vent easily. CONSTITUTION: A laminated sheet is constituted by laminating a layer which consists of 100 pts.wt. of an ethylene/α-olefin copolymer with density of 0.86-0.90g/cm<3> and mol.wt. distribution Mw/Mn of 3 or less, for example, an ethylene/butene-1 copolymer, 10-80 pts.wt. of at least one kind of a thermoplastic elastomer selected from a group consisting of a styrenic elastomer, a polyester elastomer and a polyurethane elastomer and 80-400 pts.wt. per 100 pts. of both of them of an inorg. filler and a stretchable nonwoven fabric.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a laminated sheet, and more particularly to a laminated sheet suitable as a packaging material for fermentable foods.

[0002]

2. Description of the Related Art Conventionally, packaging of fermented foods such as miso and natto and coffee beans which generate a large amount of gas during storage has a problem that the packaging container expands due to the gas. Therefore, as a method of packaging such a substance, it is known to use a container in which a microporous breathable film is used as a lid material or the like. In that case, the gas generated inside the container is preferably discharged to the outside of the container more easily than the gas permeable film.

[0003]

However, in the case of such a container, while the generated gas is discharged to the outside, at the same time, air (oxygen) outside the container also passes through the breathable film to the inside of the container. Come in. As a result, in the case of long-term storage or the like, the quality of the packaged substance is deteriorated, causing a problem that, for example, the color of the food or the taste of the food changes. From the above, as a packaging material for a substance that generates gas during storage of fermented foods, etc., it is possible to develop an inexpensive packaging material that does not cause deterioration or deterioration of the quality of the fermented foods, etc. Was wanted.

[0004]

Means for Solving the Problems The inventors of the present invention have conducted extensive research to solve the above problems. As a result, a laminated sheet obtained by laminating a layer made of a specific resin composition and a stretchable non-woven fabric can be stretched with a slight stress and at the same time breathable to the sheet, and when the stress is attenuated, this breathability is reduced. As a result, they have come to present the present invention.

That is, according to the present invention, (a) the density is 0.86 to 0.90 g / cm ³ , Mw / M
ethylene-α- having a molecular weight distribution represented by n of 3 or less
Olefin copolymer 100 parts by weight (b) At least one thermoplastic elastomer 10-8 selected from the group consisting of styrene elastomer, polyester elastomer and polyurethane elastomer.
0 parts by weight and (c) a laminated sheet in which a layer composed of 80 to 400 parts by weight of an inorganic filler and a stretchable nonwoven fabric are laminated with respect to 100 parts by weight of the total amount of (a) and (b). .

The ethylene-α-olefin copolymer (a) in the present invention means a density of 0.86 to 0.90 g / cm ³ according to ASTM D-1505, and a weight average molecular weight (determined by gel permeation chromatography). It is an ethylene-α olefin copolymer having a molecular weight distribution (Mw / Mn) represented by the ratio of Mw) and number average molecular weight (Mn) of 3 or less. If the density is less than 0.86 g / cm ³ , the resulting sheet will have poor heat resistance and strength. ^{On the other hand} , if it exceeds 0.90 g / cm ³ , sufficient elasticity cannot be obtained even if the thermoplastic elastomer described below is added, and strain remains in the sheet even if the pressure is attenuated after being stretched by pressurization. Will not be sufficiently reduced. The preferred density is 0.87 to 0.89 g / cm ³ . Further, an ethylene-α-olefin copolymer having a molecular weight distribution (Mw / Mn) of more than 3 has a low density, and even if it is stretched at a low stress, the obtained sheet has poor air permeability and recovery after stretching. It becomes poor in nature.

The melt flow intex of the ethylene-α-olefin copolymer used in the present invention at 190 ° C. is 0.5 to 30 g / 10 min because of the ease of generating air permeability when stretched under pressure. Range is preferred, 1-2
It is more preferably 0 g / 10 minutes.

Ethylene-α of (a) used in the present invention
The α-olefin of the olefin copolymer has 4 to 10 carbon atoms in order to have the above-mentioned density and molecular weight distribution.
.Alpha.-olefins are preferred. Examples of the α-olefin having 4 to 10 carbon atoms include butene-1, 4-methylpentene-1 and the like. Further, the content of the α-olefin is 2 to 40 mol% in order to make the laminated sheet of the present invention have good flexibility and stretchability,
Further, it is preferably 5 to 20 mol%. Also,
The melting point is preferably 60 to 100 ° C. further,
The crystallinity by X-ray is 5 for good porosity.
It is preferably in the range of -25%.

Next, in the present invention, it is necessary to mix a specific elastomer with the above-mentioned ethylene-α-olefin copolymer in order to obtain a layer excellent in stretchability and breathability during stretching.

The thermoplastic elastomer that can be used is selected from styrene elastomers, polyester elastomers and polyurethane elastomers, and more preferably styrene elastomers.

The styrene-based elastomer has a polystyrene block as a hard segment and polybutadiene, polyisoprene, polyethylene-polybutylene, polyethylene-polypropylene, etc. as a soft segment. Specifically, a styrene-butadiene block copolymer and styrene are used. -Isoprene block copolymer, styrene-ethylene-propylene block copolymer, styrene-
An ethylene butene copolymer etc. can be mentioned.

Of these, the styrene-butadiene block copolymer and the styrene-isoprene block copolymer are the styrene-butadiene block copolymer and the butadiene unit or isoprene remaining in the styrene-isoprene block copolymer, respectively. Hydrogen is added to the unsaturated bond derived from the unit. In the present invention, these hydrogenated styrene elastomers can be preferably used in order to improve moldability, stretchability and the like. The degree of hydrogenation is preferably such that 99% or more of the number of unsaturated bonds remaining in the copolymer is hydrogenated.

The styrene-based elastomer preferably has a high content of the soft segment from the viewpoint of moldability and stretchability. Usually, the styrene content is 10 to 20.
It is preferably in the range of% by weight.

Further, the styrene-based elastomer preferably has good fluidity because of good moldability. For example, the melt flow index at 190 ° C. (load 2160 g) is in the range of 0.1 to 20 g / 10 minutes. Those are preferable.

Examples of the polyester elastomer include a block copolymer having a crystalline polyester in the hard segment and a polyether or an aliphatic polyester in the soft segment. These are also preferably selected from those having many soft segment components and having flexibility.

Further, the polyurethane elastomer is a thermoplastic elastomer composed of a soft segment composed of polyol and diisocyanate and a hard segment composed of glycol and diisocyanate.

The mixing ratio of these thermoplastic elastomers is 10 to 80 parts by weight, preferably 10 to 50 parts by weight, based on 100 parts by weight of the above-mentioned ethylene-α-olefin copolymer.

When the mixing ratio is less than 10 parts by weight, there is no difference from the stretchability of the ethylene-α-olefin copolymer alone, and the strain remains in the sheet even after stretching by pressure, and the pressure is attenuated. Even the breathability will not decrease. On the other hand, if the amount exceeds 80 parts by weight, breathability does not occur even if the sheet is stretched by pressure, which is not preferable.

The inorganic filler used in the present invention generally has a particle size of 0.1 to 5 used for resins or rubbers.
Those having a thickness of 0 μm, preferably 0.5 to 10 μm can be used without particular limitation. Specific examples of the inorganic filler include, for example, Al, Si, Pb, Zn, Fe, Cu, Ni, Pd,
Metals such as Co, Mn, Cr, Mo, W, Ti, Zr;
Metal oxides such as alumina, silica, antimony trioxide, zinc oxide, magnesium oxide, calcium oxide, iron oxide, copper oxide, silver oxide, titanium oxide; metal hydroxides such as magnesium hydroxide, calcium hydroxide, aluminum hydroxide Substances; metal carbonates such as calcium carbonate, magnesium carbonate, barium carbonate, sodium carbonate; metal sulfates such as sodium sulfate, calcium sulfate, barium sulfate, aluminum sulfate, iron sulfate; metal carbides such as silicon carbide; silicon nitride, nitriding Metal nitrides such as boron; metal sulfides such as zinc sulfide, mercury sulfide, copper sulfide, silver sulfide, iron sulfide, and selenium sulfide. Of these, calcium carbonate, barium sulfate, silicon oxide, titanium oxide and the like are preferably used in consideration of hygiene.

The mixing ratio of these inorganic fillers to the above-mentioned resin component is 100 parts by weight of the total amount of the resin components so that the sheet can be quickly expanded and pressurized when the sheet is pressed. On the other hand, it is necessary to select in the range of 80 to 400 parts by weight.

When the amount is less than 80 parts by weight, even if the sheet is stretched by pressure, the sheet has few pores and does not become air-permeable. On the contrary, when it exceeds 400 parts by weight, it becomes difficult to form a sheet or film. .

In addition to the inorganic filler, a pigment, a stabilizer,
A small amount of a surfactant, a plasticizer, and other additives can be added as needed.

The laminated sheet of the present invention has a layer comprising the above-mentioned (a) ethylene-α-olefin copolymer, (b) thermoplastic elastomer and (c) inorganic filler. In such a layer, when stress is applied to the sheet and the sheet is stretched, the interface between the resin component of (a) and (b) and the inorganic filler contained therein is peeled to be porous, and air permeability is imparted. In this layer, when the pressure is attenuated and the sheet shrinks to its original size, the interface-peeled holes are closed due to the soft thermoplastic elastomer component. As a result, in the laminated sheet of the present invention, such stress attenuation reduces the air permeability to a small value.

For mixing the resin components (a) and (b) and the inorganic filler in the present invention, a conventional means is adopted. Generally, after mixing with a blender or the like, a melt mixer such as an extruder or a Banbury mixer is used. It is preferable that the mixture is mixed with the above, pelletized if necessary, and subjected to molding. The method of molding into a sheet or film layer is not particularly limited, but in general, a T-die molding method and an inflation molding method are preferable, and particularly in the T-die molding method, an extrusion lamination method with a non-woven fabric described later can be adopted, which is also preferable. In the present invention, the thickness of the layer composed of the resin components (a) and (b) and the inorganic filler is not particularly limited, but is preferably in the range of 5 to 50 μm in consideration of elasticity.

In the present invention, the layer comprising the above resin component and the inorganic filler is laminated on the stretchable nonwoven fabric. Here, the stretchable non-woven fabric is necessary not only for improving the strength of the sheet but also for satisfying the stretchability of the sheet, especially the shrinking force of the stretched sheet. As the stretchable nonwoven fabric, a known stretchable nonwoven fabric is used without particular limitation. Generally,
It is preferable to use a thermoplastic elastomer such as a polyurethane elastomer, a polyester elastomer, or a styrene elastomer as a raw material.

It is preferable that these non-woven fabrics have a low elongation and a small permanent set, and have a breaking elongation of 200 to 6
It is preferably 00%. Further, it is preferable that the tensile strength at 50% elongation is 50 to 500 g / 25 mm and the recovery rate after 50% elongation is 80 to 100%. The unit weight of these non-woven fabrics is usually preferably in the range of 10 to 50 g / m ² . Specific examples of the non-woven fabric preferably used in the present invention include polyurethane-based non-woven fabric "Espensione" (trade name, manufactured by Kanebo Co., Ltd.) and styrene-based elastomer non-woven fabric "Microflex (trade name, Kuraray Co., Ltd.). Manufactured) ”and the like.

In the present invention, as the method for laminating the non-woven fabric, a general laminating technique is usually used. The above-mentioned T-
In addition to die extrusion lamination, dry lamination using an adhesive, wet lamination, and thermal lamination can be performed.

The thickness of the laminated sheet of the present invention obtained as described above is not particularly limited, but is generally 30.
˜300 μm is preferred.

[0029]

EFFECTS OF THE INVENTION The laminated sheet obtained by the present invention is extremely flexible and highly stretchable, and has the property of elongating with low stress and returning to its original shape when the stress is removed. Then, at the time of extension, in the layer composed of the resin component and the inorganic filler of (a) and (b), the interface between the resin component and the inorganic filler is peeled off to form a communication hole from the front surface to the back surface, and the air permeability is improved. To have. This layer is then further relieved of stress and when the sheet contracts, its breathability is reduced to a small value by the action of the thermoplastic elastomer component.

Such properties are suitable as a packaging material for fermented foods. That is, when the fermented food is packaged in a container using the laminated sheet of the present invention as a lid material, when the pressure in the container is increased by the gas from the fermented food, the laminated sheet is stretched so that the gas is permeable. Become. Further, when the generation of gas becomes weak and the internal pressure becomes small, the laminated sheet shrinks and the gas permeability becomes small. As a result, the inflow of air (oxygen) into the container is prevented, and the chromaticity and deterioration of the fermented food are prevented.

Further, the laminated sheet of the present invention is required not only to be a packaging material for fermented foods but also to have a change in air permeability due to a change in pressure, such as a packaging material for other articles that generate gas during storage. It is widely used in industrial fields as a pressure-responsive material.

[0032]

The present invention will be described in more detail with reference to the following examples and comparative examples, but the present invention is not limited to these examples. The components used in the following Examples and Comparative Examples are shown in Tables 1 to 4. Here, each physical property of the elastic nonwoven fabric is a value measured by the following method.

(1) Breaking strength; measured in accordance with JIS P8113.

(2) 50% elongation strength: Tensile strength (g / 25 mm) at 50% elongation was measured.

(3) Recovery rate after 50% elongation: L was the length when 50% was extended and returned to the original, and L ₀ was the original length, and evaluation was made by the following formula.

[0036]

[Equation 1]

[0037]

[Table 1]

[0038]

[Table 2]

[0039]

[Table 3]

[0040]

[Table 4]

Examples 1 to 9 and Comparative Examples 1 to 8 The resin components and inorganic fillers shown in Tables 1 and 2 were mixed in a composition ratio shown in Table 5 with a super mixer, and then pelletized with a twin-screw extruder. .

This mixture was mixed with a T-shaped screw having a screw diameter of 30 mm.
The stretchable nonwoven fabric shown in Table 4 was laminated with a die extruder to obtain a laminated sheet. This laminated sheet had a basis weight of 50 g / m ² (however, Example 8 was 45 g / m ² ) and had a thickness of 150 μm.

Then, the change of the air permeability when the pressure of the obtained laminated sheet was changed was measured by the test apparatus of FIG. That is, in the test apparatus of FIG. 1, 0.02 kg / cm ² pressure (gauge pressure) in the container ^{1, 0.07kg / cm 2, 0} .
15kg / cm ² and 0.20kg / cm ² , respectively, when the pressure is raised stepwise at intervals of 10 minutes, permeating through the laminated sheet 2 at each pressure stage and permeating into the ventilation chamber 3 at 0 atmospheric pressure. The amount of air was measured.

After the above measurement, the laminated sheet was taken out from the test apparatus shown in FIG. 1 and its air permeability was examined according to JIS P8117. Then, the laminated sheet was mounted on the test apparatus shown in FIG. 1 again and similarly subjected to the air permeability test under pressure. The above results are shown in Table 5.

[0045]

[Table 5]

[Brief description of drawings]

FIG. 1 is a schematic diagram of a test device used in an example of the present invention for examining a change in air permeability of a laminated sheet when a pressure is changed.

[Explanation of symbols]

 1 container 2 laminated sheet 3 ventilation chamber 4 flow meter 5 pressure gauge 6 pressure control valve

Claims (1)

[Claims] 1. (a) Density of 0.86 to 0.90 g / cm
³ , 100 parts by weight of ethylene-α-olefin copolymer having a molecular weight distribution represented by Mw / Mn of 3 or less (b) at least one selected from the group consisting of styrene elastomer, polyester elastomer, and polyurethane elastomer Thermoplastic elastomer 10-8
0 parts by weight and (c) A laminated sheet in which a stretchable nonwoven fabric is laminated with a layer composed of 80 to 400 parts by weight of an inorganic filler per 100 parts by weight of the total amount of (a) and (b).