JP3081976B2 - Oxygen absorbing multilayer sheet - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an oxygen-absorbing multilayer sheet. More specifically, the present invention relates to an oxygen-absorbing sheet which is easy to handle and whose oxygen-absorbing ability is controlled, and which is further excellent in preventing elution and contamination of an oxygen absorbent.

[0002]

2. Description of the Related Art Oxygen absorbents are used in various fields for the purpose of removing oxygen when oxygen is not preferred in preserving various products including foods.

[0003] A commonly used method of packaging a powdery oxygen absorbent with a material having air permeability has a problem that if the material is not completely sealed, the powder leaks to the outside. As the absorbent, for example, iron powder as disclosed in JP-A-62-234544 is preferably used as the oxygen absorbent in order to absorb oxygen from the air-permeable material side. In particular, fine powders have a surface that is easy to absorb oxygen in the air, and especially iron-based oxygen absorbents are difficult to handle because they are even pyrophoric.

An ordinary powder oxygen absorber is disclosed in Japanese Patent Publication No. 62-5 / 1987.
As disclosed in Japanese Patent No. 4704, a method of packaging an oxygen absorbent with a material having an appropriate air permeability is known. The commonly used method of packaging the powdered oxygen absorbent with a material having air permeability has a problem that if the material is not completely sealed, the powder leaks to the outside.

[0005] Further, the oxygen absorbent hardens in the reaction section in order to absorb oxygen from the air-permeable material surface. For this reason, there is a problem that an absorption reaction to the inside of the oxygen absorbent cannot be expected, and as a result, oxygen absorption characteristics in proportion to the filling amount of the oxygen absorbent cannot be exhibited, so that the oxygen absorption rate cannot be controlled.

A method for packaging an oxygen absorbent is disclosed in
JP-A-116436 proposes a method of continuously attaching an oxygen absorbent to a sheet coated with an adhesive to form a surface coating. However, it is impossible to accurately and quickly fill a small amount of an oxygen absorbent. Extremely difficult and expensive automatic filling and packaging machines are required.

Further, as an oxygen-absorbing sheet which is easy to handle and whose oxygen-absorbing ability is controlled, Japanese Patent Application Laid-Open No. H2-222984 discloses a method of filling a resin with an oxygen absorbent to make it porous.
As shown in Japanese Patent Publication No. 0, an oxygen absorbent is exposed on a porous surface, and particularly when a liquid (water, aqueous solution, etc.) comes into contact, the oxygen absorbent elutes (including desorption). there is a possibility.

[0008]

As described above, in the prior art, when the powdered oxygen absorbent is packaged, it leaks from the packaging material, the oxygen absorbing ability cannot be sufficiently controlled by the hardening of the powder, However, there is a problem that a difficult process of high-speed filling and packaging of the oxygen absorbent is required, and that the elution and contamination of the oxygen absorbent in the use in contact with a liquid cannot be suppressed. The term “elution contamination” as used herein refers to the fact that a liquid (water, aqueous solution, or the like) or a substance containing a liquid (solid, paste, etc.) comes into contact with the oxygen absorbent, and the main component of the oxygen absorbent is iron. It means that components (including components generated by the reaction) are eluted and desorbed, and that an electrolyte as a sub-component is eluted and contaminates a liquid or a substance containing a liquid.

An object of the present invention is to provide easy handling, no leakage of the oxygen absorbent to the outside, arbitrarily control of the oxygen absorption capacity, no need for a step of filling and packaging, and excellent elution contamination prevention. This is a method for providing an oxygen absorbing sheet.

[0010]

DISCLOSURE OF THE INVENTION In view of the above problems, the present inventors have developed an oxygen-absorbing sheet which is easy to handle, does not leak the oxygen absorbent to the outside, can arbitrarily control the oxygen-absorbing capacity, and does not elute with a liquid. I have been studying about As a result, a sheet obtained by mixing and melt-molding a thermoplastic resin and an oxygen absorbent is stretched under specific conditions, and the porous layer is disposed on the oxygen absorbing sheet layer obtained by the stretching process. The inventors have found that the problem can be solved, and have completed the present invention.

That is, the present invention relates to a thermoplastic resin
70% by weight, iron powder-based oxygen absorbent 30 to 85 in which powder having a primary particle diameter of 0.01 to 20 μm is aggregated to 5 to 200 μm
Weight% of the thermoplastic resin composition having a thickness of 30 μm to 5 μm.
After processing the sheet to at least 1.5 mm
An oxygen absorbing sheet stretched at a magnification of up to 8.0 times, characterized in that a resin composition comprising a filler and a resin component is disposed as a porous layer on one or both sides of the oxygen absorbing sheet. It is an oxygen-absorbing multilayer sheet.

An oxygen absorbent is uniformly dispersed in a thermoplastic resin by melt-kneading, and the resulting film or sheet is stretched under specific conditions to form a large number of small voids (microvoids) in the thermoplastic resin film or sheet. In the generated and porous oxygen-absorbing sheet, the oxygen-absorbing agent uniformly dispersed in the film or sheet is in contact with the atmosphere through microvoids, so that oxygen in the atmosphere can be effectively absorbed. However, in such an oxygen-absorbing sheet, the microvoids are large in order to efficiently contact the oxygen absorbent with the atmosphere, so that the liquid material permeates into the voids. The oxygen-absorbing multilayer sheet of the present invention is provided with a porous layer in which a liquid material is impermeable on one or both sides of an oxygen-absorbing sheet layer containing an oxygen absorbent, thereby dissolving the oxygen absorbent by permeation of the liquid material. This is to obtain an oxygen-absorbing multilayer sheet which is prevented.

Examples of the thermoplastic resin used in the oxygen-absorbing sheet layer in the present invention include α-olefin homopolymers such as branched low-density polyethylene, high-density polyethylene, polypropylene, and polybutene obtained by a high-pressure method, and ethylene and carbon. At least one type of α-
Organic carboxylic acid derivatives having an ethylenically unsaturated bond such as copolymers with olefins, copolymers with propylene and ethylene and / or butene-1, ethylene and vinyl acetate and / or acrylates and methacrylates Or a mixture of two or more selected from copolymers with the same.

In particular, copolymers of ethylene with at least one α-olefin having 4 to 12 carbon atoms, random and block copolymers of ethylene and / or butene-1 with propylene, vinyl acetate and / or (meth) A metal salt of a copolymer of an acrylic ester and ethylene, or a copolymer of ethylene and acrylic acid is preferred. further,
A copolymer of ethylene and an α-olefin having 4 to 12 carbon atoms, having a density of 0.870 to 0.915 g / c.
An ethylene-α-olefin copolymer having a weight-average molecular chain length of 1,000 to 9000 angstroms and a content of 18 to 45% by weight of the extractable component of xylene at m ³ and 25 ° C. is preferred. Also, a thermoplastic resin containing at least 20% by weight or more of the ethylene-α-olefin copolymer can be preferably used. The ethylene-α-olefin copolymer can be produced by a known technique such as JP-A-59-230011.

The primary particle size of the oxygen absorbent used as a powder in the thermoplastic resin composition for an oxygen absorbing sheet of the present invention is 0.01 to 20 μm. Primary particle size is 0.01
If it is less than 20 μm, it is difficult to aggregate.
When the ratio exceeds, the effect of aggregation is insufficient. Further, when the particle size of the oxygen absorbent as an aggregate is less than 5 μm, the draw ratio in the case of making the material porous is reduced, and when it exceeds 200 μm, the thinning processability is deteriorated and the effect of aggregation is also reduced. Not preferred.

In the iron powder or the iron powder and the electrolyte used as the oxygen absorbent used in the present invention, the iron powder may contain an iron oxide or iron carbide as an auxiliary component. Is usually about 0.1 to 20% by weight. The particle size of the iron powder is usually preferably about 0.1 to 200 μm, more preferably 20 to 150 μm. The electrolyte promotes the oxygen absorption rate of the iron powder, and is, for example, a halide, a carbonate, a sulfate, or a hydroxide. Preferred among these types are halides, more preferably CaCl ₂ , NaCl, MgCl _{2 and the} like. The electrolyte may be used after being coated on the particles of the iron powder, or may be used as a simple blend with the iron powder. Also,
The addition amount of the electrolyte is preferably 0.1 to 10% by weight.

The content of the oxygen absorbent in the thermoplastic resin composition used in the oxygen absorbing sheet of the present invention is 30 to 8
5% by weight. When the content of the oxygen absorbent is less than 30% by weight, the generation of microvoids is small, so that the number of microvoids communicating with the atmosphere is also reduced, and as a result, the ability to absorb oxygen in the atmosphere is extremely low and cannot be put to practical use. On the other hand, 8
If it exceeds 5% by weight, the resulting oxygen-absorbing sheet becomes extremely brittle and cannot be put to practical use.

The thickness of the thermoplastic resin composition sheet comprising the thermoplastic resin and the oxygen absorbent before stretching varies depending on the purpose of use, but is usually 10 μm to 5 mm. If the thickness is less than 10 μm, an oxygen absorbing sheet having a very large area must be used in order to obtain a desired oxygen absorbing capacity. On the other hand, if it exceeds 5 mm, it may be difficult to make the sheet have a uniform stretching temperature in stretching after sheet processing, and uniform stretching may not be possible, or the stretching stress may be so large that it may be impossible with a normal apparatus.

Regarding the stretching ratio of the obtained sheet,
If it is less than 1.5 times, the generation of microvoids is so small that the uniformly dispersed oxygen absorbent cannot come into sufficient contact with the atmosphere, so that practically sufficient oxygen absorption capacity cannot be obtained. Also,
If it exceeds 8.0 times, the obtained oxygen-absorbing sheet is not practically used because the film strength such as tearing is remarkably reduced and the sheet is broken by a slight external force.

In the present invention, the porous layer disposed on one or both sides of the oxygen absorbing sheet layer comprises 100 parts by weight of a resin component and 20 to 400 parts by weight of a filler. The mixing ratio of the resin component and the filler is a ratio necessary for stretching the porous layer to make it porous and aerated. When the porous layer is provided on both sides of the oxygen-absorbing sheet layer, the porous layer does not necessarily have to be the same, and may have a layer configuration according to the application. In addition, as a configuration of the multilayer sheet, a thermoplastic resin layer can be appropriately laminated as needed in addition to the porous layer and the oxygen absorbing sheet layer.

Examples of the resin component used in the porous layer include α-olefin homopolymers such as low-density polyethylene, high-density polyethylene, polypropylene, and polybutene, and copolymers of ethylene with at least one α-olefin having 3 to 18 carbon atoms. Polymers, copolymers of propylene with ethylene and / or butene-1, copolymers of ethylene with organic carboxylic acid derivatives having an ethylenically unsaturated bond such as vinyl acetate and / or (meth) acrylates, etc. And these are used alone or in combination.

Examples of the filler include carbonates such as calcium carbonate, magnesium carbonate and barium carbonate, sulfates such as barium sulfate, magnesium sulfate and calcium sulfate, phosphates such as magnesium phosphate and calcium phosphate, and hydroxides. Hydroxides such as magnesium and aluminum hydroxide, alumina, silica, magnesium oxide,
Oxides such as calcium oxide, zinc oxide and titanium oxide,
Chlorides such as zinc chloride, iron chloride and sodium chloride, aluminum powder, inorganic fillers such as zeolite, shirasu, clay, diatomaceous earth, talc, carbon black and volcanic ash, and cellulosic powders such as wood powder and pulp powder, nylon powder,
Polycarbonate powder, polypropylene powder, poly-4
-Synthetic resin-based powders such as -methylpentene-1 powder, crosslinked polystyrene powder, crosslinked polymethyl (meth) acrylic acid powder, and organic fillers such as starch can be used, and these are used alone or in combination.

As a method for disposing the porous layer, a method of preparing an oxygen-absorbent-containing sheet and bonding it through heat bonding or an adhesive layer, or a method such as coextrusion or lamination before stretching is used. And stretching at the same time. In the case of the former method, it is necessary to perform the heat bonding at a temperature at which the pores of the oxygen absorbent layer are not blocked by heat shrinkage and heat melting.In the case of the latter method, the urethane-based It is necessary to use a material having high oxygen permeability as described above.

The porous layer has a thickness of 10,000 at 23 ° C.
It preferably has an oxygen permeability of at least cc / m ² · day. If the oxygen permeability is 10,000 cc / m ² · day or less, the oxygen absorption rate becomes slow, and depending on the application, sufficient performance may not be exhibited.

In the thermoplastic resin composition containing an oxygen absorbent and the resin composition for a porous layer for obtaining the oxygen-absorbing multilayer sheet of the present invention, antioxidation is provided as long as the effects of the present invention are not substantially impaired. Agents, dispersants, antistatic agents, deodorants and the like can be incorporated.

The method for producing the oxygen-absorbing multilayer sheet of the present invention is, for example, as follows. First, a thermoplastic resin and an oxygen absorbent, and if necessary, a dispersant or a stabilizer, etc., are mixed or kneaded by a usual method using a roll-type or Banbury-type kneader or a single-screw, twin-screw extruder or the like. To obtain composition A. Further, the composition B is obtained by kneading the thermoplastic resin and the filler, and if necessary, the dispersant, the stabilizer and the like in the same manner. Next, a multilayer sheet is manufactured from the compositions A and B by a normal molding method such as multi-layer T-die processing, or a method such as forming the composition A into a sheet and then melt-laminating the B, and stretching the obtained sheet. However, the stretching is uniaxial or biaxial. In the case of uniaxial stretching, roll stretching is usually preferable, but tubular stretching may be performed.
In addition, stretching can be performed in one step or two or more steps, and in the case of biaxial stretching, simultaneous biaxial stretching is also possible, or sequential biaxial stretching in which the film is stretched in the transverse direction after stretching in the longitudinal direction is also possible. is there.

[0027]

The oxygen-absorbing multilayer sheet of the present invention has excellent oxygen-absorbing ability and controllability of the oxygen-absorbing rate, and is particularly suitable for liquids (water, aqueous solutions, etc.) or liquid-containing substances (solids, pastes, etc.). Since it is excellent in preventing the dissolution and contamination of the oxygen absorbent when it comes into contact with, it can be widely used particularly for packaging materials such as high-hydrated foods, for example, trays, lid materials, crown liners, mounts and the like.

[0028]

The present invention will be described in detail below with reference to examples, but the present invention is not limited to these examples. The measuring methods of the physical properties shown in Examples and Comparative Examples are as follows.

Oxygen absorption rate: The oxygen absorption rate is 170
The oxygen-absorbing multilayer sheet was present in a closed container at a ratio of 3.7 g with respect to cc, and the oxygen absorption amount after 24 hours was measured. The closed container is a graduated glass cylindrical container placed on an oily surface, and has a structure in which the reduced capacity is occupied by water when oxygen is absorbed.

Elution contamination prevention: The oxygen-absorbing multilayer sheet of 5 cm × 5 cm was immersed in water at 23 ° C. for 24 hours, and the elution state of the oxygen absorbent was visually observed and evaluated according to the following criteria. ：: No discoloration of water or discoloration of the sheet surface is observed. X: Discoloration of water or discoloration of the sheet surface is observed.

Weight average molecular chain length: The weight average molecular chain length of the CXS component was measured using a gel permeation chromatography (GPC) 811 manufactured by Toyo Soda Co., Ltd.
Two Ds were attached, and the measurement was carried out at 130 ° C. based on polystyrene.

Density: Density of resin is JIS K6760-
It was measured at 23 ° C. by a density gradient tube method according to 1981.

Example 1 As a thermoplastic resin composition (hereinafter, referred to as composition A) for an oxygen-absorbing agent-containing layer, linear low-density polyethylene (manufactured by Sumitomo Chemical Co., Ltd., Exelen VL200, weight average molecular chain length) The CXS component of 3700 Å
25% by weight of an ethylene-butene-1 copolymer containing 1% by weight and having a density of 0.900 g / cm ³ , iron powder having a primary particle diameter of 7 μm and an aggregate particle diameter of 106 μm as an oxygen absorbent (calcium chloride as an electrolyte) In a composition comprising 75% by weight of pure iron as an iron component and 5% by weight of iron oxide), and zinc stearate as a dispersant per 100 parts by weight of the composition. 1.0 parts by weight, and preliminarily mixed with a tumbler mixer MT50 type manufactured by Morita Seiki Co., Ltd., and the obtained mixture was mixed with a BR type Banbury manufactured by Kobe Steel Ltd. for 120 to 120 parts by weight.
The composition A was obtained by kneading at 150 ° C. for 5 minutes. This composition A was T-die molded at a processing temperature of 170 ° C. using a 30 mmφ extruder manufactured by Tanabe Plastics Co., Ltd. to obtain a sheet having a thickness of 1 mm.

On the other hand, as the resin composition of the porous layer (hereinafter referred to as composition B), linear low-density polyethylene A
20 parts by weight (Excellen VL200 manufactured by Sumitomo Chemical Co., Ltd., density 0.900 g / cm ³ ), linear low density polyethylene B (Sumikasen-LF manufactured by Sumitomo Chemical Co., Ltd.)
A201 60 parts by weight of density 0.919 g / cm ³ ) and high-pressure low-density polyethylene (Sumikasen F208-0 manufactured by Sumitomo Chemical Co., Ltd., density 0.922 g / cm)
³ ) 100 parts by weight of a thermoplastic resin consisting of 20 parts by weight and calcium carbonate (Whiteton S manufactured by Shiraishi Calcium Co., Ltd.)
SB (red)) of the composition A
Was kneaded in the same manner as in the case of the production of the composition B. Composition B was added to the oxygen-absorbing sheet comprising composition A obtained above.
Was melt-laminated at 280 ° C. to 200 μm on both front and back sides to obtain a multilayer sheet.

This multilayer sheet was stretched 3.8 times in MD at 60 ° C. by a roll stretching machine of Nippon Steel Corporation to obtain an oxygen-absorbing multilayer sheet, and its oxygen absorption characteristics were measured at 5 ° C.

As a result, as shown in Table 1, an oxygen-absorbing multilayer sheet having high oxygen-absorbing ability and excellent elution-contamination prevention properties was obtained.

Example 2 The resin component used for the porous layer was linear low-density polyethylene (Sumikasen-L GA801 manufactured by Sumitomo Chemical Co., Ltd.).
80% by weight of density 0.920 g / cm ³ ) and high-pressure low-density polyethylene (Sumikasen F2 manufactured by Sumitomo Chemical Co., Ltd.)
08-0, density 0.922 g / cm ³ ) An oxygen-absorbing multilayer sheet was obtained in the same manner as in Example 1 except that the weight was 25% by weight. As a result, an oxygen-absorbing sheet having high oxygen-absorbing ability as in Example 1 and having excellent elution-contamination prevention properties was obtained.

Example 3 The same composition B as in Example 1 was used for the porous layer, and the composition B was applied under the same processing conditions as the laminate of Example 1 to a thickness of 20%.
The sheet was formed into a sheet having a thickness of 0 μm to obtain a sheet for a porous layer. For the oxygen absorbent-containing layer, the composition A of Example 1 was used,
A 1 mm-thick oxygen absorbent-containing layer sheet was obtained in the same manner as in Example 1. The oxygen absorbent-containing layer sheet and the porous layer sheet are each stretched 3.8 times at 60 ° C., and then the porous layers are adhered to both sides of the oxygen absorbent sheet with a urethane-based adhesive to form an oxygen-absorbing multilayer sheet. Was obtained, and the oxygen absorption characteristics were measured at 5 ° C. As a result, an oxygen-absorbing multilayer sheet having almost the same performance as that of Example 1 was obtained.

Example 4 An oxygen-absorbing multilayer sheet was obtained in the same manner as in Example 1, except that composition B was melt-laminated only on one side of the oxygen-absorbing sheet comprising composition A. As a result, no desorption was observed from the laminate surface, and an oxygen-absorbing multilayer sheet having almost the same oxygen-absorbing performance as that of Example 1 was obtained.

Example 5 A high-density polyethylene (manufactured by Toyo Soda Co., Ltd., manufactured by Toyo Soda Co., Ltd.) was applied to the other surface of the multilayer sheet obtained by melt laminating Composition B only on one side of the oxygen absorbing sheet comprising Composition A in Example 4. Nipolon Hard 6200, MFR = 0.92, density 0.95
7 g / cm ³ ) was melt-laminated at 200 ° C. at a resin temperature of 200 ° C. to obtain an oxygen absorbing sheet. As a result, an oxygen-absorbing multilayer sheet resistant to bending deformation was obtained.

Comparative Example 1 In the same manner as in Example 1, the composition B was melt-laminated on the front and back surfaces of the oxygen absorbing sheet made of the composition A at a temperature of 280 ° C. to 200 μm to obtain a multilayer sheet. The oxygen absorbing performance of the multilayer sheet not subjected to this stretching was evaluated. As a result, the sheet did not become porous and had no oxygen absorbing ability at all.

Comparative Example 2 Example 1 except that the thickness of the oxygen absorbent layer was changed to 7.0 mm.
Although processing was performed in the same manner as in Example 1 to obtain a sheet, the sheet was broken during stretching, and an oxygen-absorbing multilayer sheet could not be obtained.

Comparative Example 3 A sheet was processed in the same manner as in Example 1 except that the composition of the oxygen absorbent-containing layer was changed to 10% by weight of the thermoplastic resin and 90% by weight of the oxygen absorbent. The agent layer could not be formed into a composition and could not be formed into a sheet.

Comparative Example 4 An oxygen-absorbing sheet was obtained in the same manner as in Example 1, except that the porous layer was not provided. As a result, although the oxygen absorption performance was the same, the sheet was inferior in elution contamination prevention property and could not be used under wet conditions.

Comparative Example 5 A sheet was obtained by processing in the same manner as in Example 1 except that iron powder as an oxygen absorbent was used, which had an average particle size of 2 μm and was not agglomerated. Bad seat.

The iron powder as an oxygen absorbent was mixed with an average particle size of 106
Example 1 except that a non-aggregated one was used.
In the same manner as in the above, a sheet was obtained. As a result, since the surface area of the iron powder was smaller than that of the aggregate type, a sheet having poor oxygen absorbing ability was obtained.

[0047]

[Table 1]

[0048]

[Table 2]

──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Takanori Kume 2-10-1 Tsukahara, Takatsuki-shi, Osaka Sumitomo Chemical Industries Co., Ltd. (72) Inventor Takashi Sakakibara 2-1-1 Tsukahara, Takatsuki-shi, Osaka Sumitomo Examiner in Chemical Industry Co., Ltd. Hiroaki Hirai (56) References JP-A-2-72851 (JP, A) JP-A-2-229840 (JP, A) JP-A-2-203937 (JP, A) (58) Field surveyed (Int. Cl. ⁷ , DB name) B32B 1/00-35/00 B29C 55 / 00- 55/30

Claims (4)

(57) [Claims] 1. A thermoplastic resin composition comprising 15 to 70% by weight of a thermoplastic resin and 30 to 85% by weight of an iron powder-based oxygen absorbent in which powder having a primary particle size of 0.01 to 20 μm is aggregated to 5 to 200 μm. An oxygen-absorbing sheet obtained by processing a product into a sheet having a thickness of 10 μm to 5 mm and then stretching at least 1.5 to 8.0 times in one axial direction, wherein a filler and a resin are provided on one or both sides of the oxygen-absorbing sheet. An oxygen-absorbing multilayer sheet characterized by comprising a resin composition comprising components as a porous layer. 2. The oxygen-absorbing multilayer sheet according to claim 1, wherein the porous layer is a resin composition comprising 100 parts by weight of a resin component and 50 to 400 parts by weight of a filler. 3. The thermoplastic resin is a branched low-density polyethylene,
Linear low-density polyethylene, high-density polyethylene, a copolymer of ethylene and / or butene-1 with propylene, a copolymer of ethylene and an α-olefin having 4 to 12 carbon atoms, vinyl acetate and / or (meth) 2. The oxygen-absorbing multilayer sheet according to claim 1, wherein the oxygen-absorbing multilayer sheet is one or a mixture of two or more selected from copolymers of acrylates and ethylene. 4. A linear low-density polyethylene in which at least 20% by weight or more of the thermoplastic resin is a copolymer of ethylene and an α-olefin having 4 to 12 carbon atoms, and having a weight average molecular chain length of 1,000 to 1,000. It has 18% to 45% by weight of xylene extract at room temperature of 9000 angstroms,
Oxygen absorbing multi-layer sheet according to claim 1, characterized in that the density of 0.870~0.915g / cm ^3.