JP2001031145A - Single-side absorbing type free-oxygen absorbing multilayer material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a free-oxygen absorbing film or sheet with good surface conditions wherein a high free-oxygen absorbing rate is kept while reducing an amount of iron powder. SOLUTION: The free-oxygen absorbing multilayer material comprises a free-oxygen absorbing layer (A layer) made of an open cell resin including blended porous adjuvant comprising a free-oxygen absorbing constituent and an inorganic filler which is difficult to solve in water, a shield layer (B layer) made of the open cell resin including the inorganic filler which is difficult to solve in water on one of surfaces of the A layer and a heat-sealing layer (C layer) made of an oxygen-permeable resin with an oxygen permeability of 1×10-11 to 6×10-9 [cm3/cm2.sec.Pa] wherein the layers are placed in this sequence, and a barrier layer (D layer) is placed on the other surface of the A layer. In addition, an amount of the free-oxygen absorbing constituent in the A layer is 10 to 60 wt.%, and an amount of the porous adjuvant in the A layer is 1 to 20 wt.%.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a film and a sheet having a deoxidizing function. More specifically, food,
The present invention relates to a single-sided absorption deoxidized multilayer body used to constitute a container and a package having a purpose of preventing oxidation of various products such as pharmaceuticals and metal products which are easily deteriorated by the influence of oxygen.

[0002]

2. Description of the Related Art Food, pharmaceuticals, and metal products
For the purpose of preventing the oxidation of various products which are easily deteriorated under the influence of oxygen, a deoxidizer for removing oxygen has been conventionally used. A form which was initially developed as an oxygen scavenger and is still widely used is one in which a granular or powdered oxygen scavenger is packed in a small bag. On the other hand, a film or sheet is considered as a safe oxygen absorber that is easier to handle, has a wider application range, and has no problems such as accidental eating.

[0003] In order to form a film or sheet, it is convenient to use a thermoplastic resin as a matrix component to form a composite with a granular or powdery deoxygenation component and fix the deoxygenation component. However, if the monolayer film or sheet of the composite is used as it is, there is a risk that the content of the oxygen-desorbed component may be contaminated by the oxygen-absorbing component due to the contact between the oxygen-absorbing body and the content, particularly the contact with the liquid. As a countermeasure, it is sufficient to cover this single-layer oxygen-absorbing layer with another shielding layer or a shielding package, but in order to take advantage of the characteristics of the film or sheet, the oxygen-absorbing layer must be covered with another shielding layer. It is ideal that the cover is made to adhere to the cover. However, the oxygen-absorbing film or sheet having a layer configuration covered with such a nonporous layer has no problem of elution of the oxygen-absorbing component, but has a problem that the oxygen-absorbing performance is extremely low.

On the other hand, as shown in Japanese Patent Application Laid-Open Nos. 9-234811 and 10-264279, a multilayer structure in which a deoxidized layer is made porous when stretched and its upper surface is protected by a nonporous layer. If so, an oxygen-absorbing film or sheet having a high oxygen permeation rate and no elution of the oxygen scavenger can be produced.

[0005] When producing such a deoxidized film or sheet, it is common to utilize a deoxidized component as a porogen of the deoxidized layer. It is preferable that the addition ratio of the deoxidizing component in the deoxidizing layer be as large as possible within a range where a film or a sheet can be formed.
Japanese Patent Publication No. 264279 specifies a preferable range of 60 to 85% by weight when iron powder is used as the oxygen scavenger. However, the oxygen scavenging component used for such a film or sheet application does not necessarily stay in the oxygen scavenging layer but also advances to another layer, and in some cases, projects from the film or sheet surface. To prevent this, it is effective to use a deoxidizing component having a small particle size, but there is a limit to the particle size that can be used, and it is considerably more expensive than a deoxidizing component used in a commercially available deoxidizing agent. Therefore, to prevent protrusion, it can be dealt with by reducing the filling amount of iron powder, but if the filling amount is reduced, the deoxygenation layer will not become porous,
There is a problem that it takes a long time to deoxygenate.

[0006]

Means for Solving the Problems The present inventors have found that the above problems can be solved by adding a small amount of a filler different from the oxygen scavenger as a porosification aid to this oxygen scavenging layer, and completed the present invention. did. That is, the one-side absorption type oxygen-absorbing film or sheet of the present invention comprises a resin layer (layer A) containing the oxygen-absorbing composition and a resin layer (layer B) containing a poorly water-soluble inorganic filler on one side. And a barrier layer (D layer) on the other side of the A layer, and an additive is added to the A layer as a porosification aid. . The multilayer body of the present invention is obtained by stretching at least the A layer and the B layer in a uniaxial direction 2 to 20 times.
It is manufactured by making the A layer and the B layer continuous porous.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION In the present invention, a resin having an appropriate oxygen permeability coefficient is selected as a resin constituting an oxygen-permeable heat seal layer (C layer). When the required performance is low, there is no particular limitation, but in order to meet a wider required range, the oxygen permeability coefficient is 1 × 10 ^-13 [cm ³ · cm / cm ² · sec · Pa].
More preferably, 1 × 10 ^-12 [cm ³ · cm / cm ² · sec.
Pa] or more.

[0008] The resin constituting the heat seal layer may be not only a polymer polymerized from a single monomer species, but also a mixture of various copolymers and resins. Non-polar or low-polarity polymers are preferred. Further, as long as the oxygen permeability of the entire heat seal layer satisfies the above range, the heat seal layer itself may be composed of a plurality of layers. The heat seal layer is preferably non-porous because heat seal strength can be kept high. In addition, for the heat seal layer, it is preferable to use the same resin as the matrix component of the adjacent layer, and when different resins are used, they are compatible to the extent that they can be thermally fused. Thermoplastic resins are preferred.

Specific examples of resins include homopolymers and copolymers of olefins such as ethylene, propylene, 1-butene and 4-methyl-1-pentene, ethylene-vinyl acetate copolymer, polybutadiene, Polyisoprene, styrene-butadiene copolymer and its hydrogenated product,
There are various silicone resins, and the like, and modified products, grafts, and mixtures thereof may also be used. And
The maximum value of the thickness of the heat seal layer is determined by the required performance of the object to be deoxidized represented by the oxygen permeability and the oxygen permeability coefficient of the resin. However, if it can be manufactured stably so that pinholes do not occur, and if it is certain that pinholes and tears will not occur even in contact with the contents in normal use, it is as thin as possible than the maximum value In general, the thickness is preferably about 5 to 50 [μm].

Various compositions are known as a deoxidizing component used for the deoxidizing layer (layer A). Among them, metal powders such as iron powder, aluminum powder and silicon powder, and inorganic powders such as ferrous salt are preferable. Preference is given to salts, ascorbic acid and its salts, alcohols such as catechol and glycerin, or phenols. If these deoxygenating components are solid, they can be used as a porogen, and if they are liquid, they can be used as a porogen by supporting them on a suitable granular substance. The particle size of the oxygen scavenger is not particularly limited as long as the maximum particle size is less than the thickness of the oxygen scavenging layer described later, but it does not damage the oxidation rate and other layers (penetration). (There is no such thing), it is desirable to be finer, and the maximum particle size is 200
[Μm] or less, more preferably 100 [μm] or less. The amount of the oxygen-absorbing composition in the layer A is 10 to 60 wt.
%, More preferably 30 to 55 wt%.

[0011] As a porosification aid added to the deoxygenation layer,
There is no particular limitation as long as it is an inorganic filler that is hardly soluble (including insoluble) in water. In particular, it is preferable to use an inorganic filler having a new Mohs hardness of 5 or more, and more preferably a new Mohs hardness of 7 or more, because the efficiency of porous formation is high. Such examples include silica, alumina, diatomaceous earth, titania, and the like. From the viewpoint of hardness, handling, and price, crushed silica, α-
Most preferably, alumina is used. There is no particular limitation on the particle size of the filler as long as it is equal to or less than the thickness of the deoxidized layer. The poorly water-soluble inorganic filler added to the A layer has an average particle size of 1 to 10 μm and a maximum particle size of 10 to 50.
μm particles are more preferred.

The filler used in the concealing layer (B layer) can be considered in the same manner as the porosity-enhancing agent for the deoxidizing layer. In this case, the concealing layer is provided between the heat seal layer and the deoxidizing layer. Therefore, it is preferable that the particle size of the filler be as small as possible so as not to penetrate the heat seal layer.

As the resin used for the deoxidizing layer and the concealing layer, since both layers are continuously made porous later, the oxygen permeability of the resin itself does not matter, and deoxidizing components such as iron powder and poorly water-soluble There is no particular limitation as long as the inorganic filler can be easily mixed and dispersed. Rather, it should be selected in consideration of good compatibility with the heat seal layer, ease of stretching, the operating temperature range of the deoxidized multilayer film and sheet, and the like. Follow the example. The resins used for the A layer, the B layer, and the C layer may be different, but are preferably the same type of resin.

Materials constituting the barrier layer (D layer) having low oxygen permeability include polyesters such as polyethylene terephthalate, polyamides such as nylon 6, nylon MXD6, and chlorine-containing resins such as polyvinyl chloride and polyvinylidene chloride. And low-oxygen-permeability resins such as ethylene-vinyl alcohol copolymers, and their coated products; metal foils or metal-deposited resins such as aluminum; and inorganic compound-deposited resins such as silicon oxide. . The barrier layer is bonded, fused or vapor-deposited after other layers are stretched in advance. When a resin having low oxygen permeability is used as the barrier layer, it may be laminated in advance to form a multilayer and then stretched.

When one layer is bonded or fused to another layer, an adhesive layer or a fusion layer can be added between the layers as necessary. In this case, the same resin as the resin used for the matrix component of the deoxygenation layer or a resin compatible with the resin is used. In particular, a buffer layer made of the same resin as the resin used for the matrix component of the oxygen-absorbing layer or a resin compatible with the resin is laminated in advance on the outside of the oxygen-absorbing layer, and after stretching including the layer, the other layer is formed. Is more preferably bonded or fused. This can prevent the continuous holes from being blocked and smooth the surface.

As the material constituting each layer, other than the above-mentioned materials, a high deoxidation rate of the deoxidized film and sheet and prevention of elution of the deoxygenated component can be maintained. Various substances can be added. Examples of the additive include pigments and dyes for coloring or hiding, stabilizing components for preventing oxidation and decomposition, antistatic components, moisture absorbing components, deodorizing components, plasticizing components, flame retarding components, and the like. Is mentioned. Similarly, a printing layer, an easy-opening layer, an easy-peeling layer, and the like can be added as long as the performance of the oxygen-absorbing film and sheet is not adversely affected.

In the lamination of each layer constituting the present invention,
Conventional techniques such as co-extrusion, extrusion coating, and extrusion lamination can be used, and any of these can provide a multilayer structure consistent with the present invention.

The resin layer containing the deoxidizing composition and the porosity aid composed of the poorly water-soluble inorganic filler and the resin layer containing the poorly water-soluble inorganic filler are stretched to obtain the deoxidized composition and the poorly water-soluble inorganic filler. A void is formed around the inorganic filler, which becomes a continuous porous resin layer. In the present invention, the resin layer that is continuously porous means a resin layer having a large number of voids, and having continuous voids such that the voids communicate with each other to penetrate the resin layer. In the stretching, any of uniaxial stretching, biaxial simultaneous stretching, and biaxial sequential stretching may be used, as is generally known. At this time, the stretching temperature is set to the heating temperature because the deoxygenation layer and the layer containing the poorly water-soluble inorganic filler need to be continuously porous so as to give high oxygen permeability, and at the same time the heat seal layer needs to be thinned without breaking. It is preferable that the stretching ratio is 2 to 20 times or lower, around the melting temperature of the resin of the sealing layer.

When a barrier layer having low oxygen permeability is added later, the barrier layer is bonded or fused by a usual method such as heat lamination, dry lamination, or extrusion coating to form a final multilayer structure. Can be.

The oxygen-absorbing film and sheet of the present invention are:
As a deoxidizing packaging material having one side gas-barrier and the other side capable of absorbing oxygen, it is used in various forms, for example, in a part or all of a packaging bag or a packaging container according to its characteristics. For example, top seal film for packaging containers,
Can be used for packaging bags. The content can be not only solid but also liquid or a mixture of solid and liquid.

[0021]

EXAMPLES Hereinafter, the present invention will be described in more detail with reference to Examples and Comparative Examples, but the present invention is not limited thereto. The common items in the description are as follows.

Example 1 A deoxidizing composition coated with an aqueous solution containing 2 parts by weight of calcium chloride sprayed on 100 parts by weight of iron powder having a maximum particle size of about 50 μm, and dried by heating, pulverized as a poorly water-soluble inorganic filler. Silica (CRYSTALITE VX-S2, manufactured by Tatsumori Co., Ltd., new Mohs hardness 7, average particle size 5 μm, maximum particle size 30 μm), and
After dry blending polypropylene (Nippon Polychem Co., Ltd., FW3E, melt flow rate 7.0g / 10min), kneading with a 30mm diameter twin screw extruder, extruding from a strand die, cooling, cutting with a pelletizer, A pellet was obtained. The composition of the oxygen-absorbing resin is 50% by weight of the oxygen-absorbing composition, 10% by weight of ground silica, and 40% by weight of polypropylene.

Crushed silica (CRYSTALITE VX-S2, manufactured by Tatsumori Co., Ltd., average particle size 5 μm, maximum particle size 30 μm) as a poorly water-soluble inorganic filler, and polypropylene (Mitsubishi Chemical)
Co., Ltd., FW3E, melt flow rate 7.0g / 10min), dry kneading, kneading with 30mm diameter twin screw extruder, extruding from strand die, cooling, cutting with pelletizer,
A white resin pellet was obtained. The composition of the white resin is 50% by weight of ground silica and 50% by weight of polypropylene.

As a heat seal layer, polypropylene (Nippon Polychem Co., Ltd., FW3E, melt flow rate 7.0 g / 10 mi)
n) and an ethylene-hydrogenated butadiene copolymer (JSR Co., Ltd., DYNARON 6200P) in a 1: 1 weight ratio mixture, as the concealing layer, the white resin, as the deoxidizing layer, as the deoxidizing resin and as the buffer layer. Polypropylene (Mitsubishi Chemical Corporation)
FW3E, a melt flow rate of 7.0 g / 10 min), a total of four layers were laminated by coextrusion to obtain a laminated body composed of four layers. The thickness of each layer of this laminate is 50 μm for the heat seal layer / 150 μm for the concealment layer.
μm / deoxygenation layer 150 μm / buffer layer 40 μm.

This laminate was stretched 6 times with a uniaxial stretching machine. Next, an aluminum foil was adhered to the buffer layer as a barrier layer by dry lamination to obtain a deoxidized multilayer film. The thickness of each layer of the obtained deoxidized multilayer film was 20 μm for the heat seal layer / 40 μm for the concealing layer / 50 μm for the deoxidized layer / 10 μm for the buffer layer / 10 μm for the barrier layer, and no protrusion of the iron powder was observed.

A bag made of a deoxygenated multilayer film is filled with a predetermined amount of air and an absorbent cotton soaked with water for humidification so that the air content is 1 cc per area of 1 cm ² of the deoxygenated film. Heat sealed. Gas chromatograph (Shimazu Corporation, GC-1)
4B), and the deoxidation rate was determined by the time until the oxygen concentration reached 0.1 vol% (deoxygenation time). The deoxygenation time was 20 hours.

Example 2 The composition of the oxygen-absorbing resin was changed to 50% by weight of the oxygen-absorbing composition,
Example 1 was repeated except that 5 wt% and 35 wt% of polypropylene were used. No protrusion of iron powder was observed in the obtained deoxidized multilayer film, and the deoxidation time was 16 hours.

Example 3 The composition of the oxygen-absorbing resin was as follows: 55% by weight of the oxygen-absorbing composition, α-alumina (A31, manufactured by Nippon Light Metal Co., Ltd.)
New Mohs hardness 12, average particle size 5μm, maximum particle size 20μm) 5wt
%, And 40% by weight of polypropylene, in the same manner as in Example 1. No protrusion of iron powder was observed in the obtained deoxidized multilayer film, and the deoxidation time was 26 hours.

Comparative Example 1 Example 1 was repeated except that the composition of the oxygen-absorbing resin was changed to 50% by weight of the oxygen-absorbing composition and 50% by weight of polypropylene without containing ground silica.
Same as. No protrusion of iron powder was observed in the obtained deoxidized multilayer film, the deoxidation time required 100 hours, and the deoxidation rate was low.

Comparative Example 2 The composition of the oxygen-absorbing resin was changed to 50% by weight of the oxygen-absorbing composition,
The procedure was the same as in Example 1 except that 5 wt% and 25 wt% of polypropylene were used. Extrusion could not be performed with a uniform thickness, and a practical film could not be obtained.

Comparative Example 3 The composition of the oxygen-absorbing resin was changed to 70% by weight of the oxygen-absorbing composition,
The procedure was the same as in Example 1 except that wt% and polypropylene were 25 wt%. Although the deoxidation time was 20 hours, the protrusion of iron powder was observed on the surface of the multilayer body, and the appearance was reduced.

[0032]

The oxygen-absorbing film or sheet of the present invention comprises
Even if the amount of iron powder is reduced, a high oxygen absorption rate can be maintained, reducing the amount of iron powder while maintaining the same effect as a conventional stretch-type deoxidized film or sheet, improving the surface condition and reducing costs. It can contribute to.

 ────────────────────────────────────────────────── ─── Continued on the front page (72) Inventor Noriyuki Kimura 6-1-1 Shinjuku, Katsushika-ku, Tokyo Mitsubishi Gas Chemical Co., Ltd. Tokyo Research Laboratory F-term (reference) 3E067 AB01 AB81 AB99 BB25A BB30A CA03 CA06 CA24 CA30 GA30 GB13 4F100 AA01A AA01B AA20 AK01A AK01B AK01C AK04 AK07 AK29 AL01 BA04 BA07 BA10A BA10D CA23A CA23B CB03C DC11A DJ03A DJ03B EH20 EJ38A EJ38B GB16 GB66 JB11A JB11JJD13 JD13JD13

Claims (4)

[Claims] 1. An oxygen-absorbing layer (A layer) composed of a continuous porous resin mixed with a porosity auxiliary comprising an oxygen-absorbing composition and a poorly water-soluble inorganic filler. Hiding layer (B) made of continuous porous resin containing filler
Layer), oxygen permeability is 1 × 10 ^{-11 to} 6 × 10 ^-9 [cm ³ / cm ² · sec
[Pa], a heat seal layer (C layer) made of an oxygen-permeable resin, and a barrier layer (D
And the amount of the oxygen-absorbing composition in the layer A is 10 to 60 wt%, and the amount of the pore-forming auxiliary in the layer A is 1 to 20 wt%. Deoxygenated multilayer body. 2. The multilayer body according to claim 1, wherein the poorly water-soluble inorganic filler added to the layer A is a particle having a new Mohs hardness of 5 or more. 3. The hardly water-soluble inorganic filler added to the layer A has an average particle size of 1 to 10 μm and a maximum particle size of 10 to 50 μm.
The multilayer body according to claim 1, which is a particle. 4. The multilayer body according to claim 1, wherein the A layer and the B layer are each a continuous porous resin layer uniaxially or biaxially stretched 2 to 20 times.