JPH1160762A - Sheetlike oxygen scavenger - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a sheetlike oxygen scavenger capable of shortening a time required for deoxidation by increasing a start-up oxygen absorbing rate, applicable to a use of preservation of foods, etc., in a wider range than a conventional oxygen scavenger. SOLUTION: This sheetlike oxygen scavenger is obtained by making a resin composition comprising 30-85 wt.% of an oxygen absorbing composition composed of iron powder having 0.7-7 wt.% of oxygen content and 200-2,000 m<2> /kg specific surface area and subjected to surface partial oxidation and an electrolyte and 15-70 wt.% of a polyolefin into a sheetlike shape and drawing the sheet in at least one direction at 1.5-9 times draw ratio.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sheet-shaped oxygen absorber having improved oxygen absorption performance by partially oxidizing iron powder as a main ingredient.

[0002]

BACKGROUND OF THE INVENTION Oxygen absorbers are widely used for preserving oxygen-sensitive articles such as foods. The most commonly used form of oxygen absorber is the so-called pouch type, in which a powdery or granular oxygen absorber is filled in a gas-permeable pouch, but in recent years, the pouch type has been improved to eliminate concerns about accidental eating and powder leakage. As a new form, a sheet-type oxygen absorber has been developed. Various studies have been made on the development of sheet-type oxygen absorbers. In particular, for example, JP-A-2-229840 is known as a sheet-type oxygen absorber containing iron powder as a main component.

[0003]

However, the conventional sheet-type oxygen absorber does not always have a sufficient oxygen absorption rate at the initial stage of oxygen absorption, and has a low oxygen absorption rate at the start of storage of articles. However, there are problems such as that the field of application to foods is limited, and that the applied foods and the like deteriorate until the deoxygenated state is reached. An object of the present invention is to solve the above problems and to provide a sheet-shaped oxygen absorber containing iron powder as a main component and having improved oxygen absorption performance.

[0004]

Means for Solving the Problems As a result of intensive studies to solve the above-mentioned problems, the present inventors have found that the surface of iron powder is partially oxidized in advance to increase the specific surface area of the iron powder and the electrolyte. The present inventors have found that a sheet-shaped oxygen absorber having a high oxygen absorption rate can be obtained from the start of use by using the composition, and have completed the present invention.

According to the present invention, the oxygen content is 0.7 to 7% by weight.
And a resin composition comprising 30-85% by weight of an oxygen-absorbing composition comprising an electrolyte and an iron powder whose surface is partially oxidized and having a specific surface area of 200-2000 m ² / kg, and 15-70% by weight of a polyolefin. The present invention relates to a sheet-shaped oxygen absorber that is formed into a sheet shape and then stretched at least in a uniaxial direction at a draw ratio of 1.5 to 9 times.

The sheet oxygen absorber of the present invention is prepared by uniformly dispersing a granular oxygen absorbing composition in a polyolefin by melt-kneading, forming the resulting resin composition into a sheet shape, and stretching the resulting resin composition to make it microporous. Since the oxygen-absorbing composition mainly composed of iron powder whose performance has been improved is in contact with the atmosphere through microvoids, high oxygen-removing performance is exhibited.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION In the present invention, the main oxygen-absorbing composition comprises iron powder and an electrolyte, and the iron powder as a main agent utilizes a reaction of absorbing oxygen in the presence of water and an electrolyte. In the present invention, auxiliary agents such as a deodorant and a fluidity improver can be added, if necessary, in addition to the iron powder and the electrolyte, which are the main oxygen absorbing compositions. In addition, a carbon dioxide absorbing agent or a generating agent or an alcohol generating agent can be added to impart a carbon dioxide absorbing or generating function or an alcohol generating function.

In the present invention, reduced iron powder, electrolytic iron powder, sprayed iron powder, crushed iron powder and the like are used as the raw material iron powder before partial oxidation. Sprayed iron powder is preferably used. The purity of the iron powder is not particularly limited as long as the object of the present invention is achieved,
In order to obtain a high oxygen absorption capacity, the purity of the iron powder is preferably high. The iron powder before partial oxidation has an oxygen content of 0.5
Those and a specific surface area not more than% by weight is 150 meters ² / kg or less. Also, the particle size of the raw iron powder is preferably 10 mesh or less, more preferably 50 mesh or less.

In the present invention, the above-mentioned raw iron powder is partially oxidized to obtain a partially oxidized iron powder having an oxygen content of 0.7 to 7% by weight and a specific surface area of 200 to 2000 m ² / kg. And When the oxygen content does not reach 0.7% by weight and the specific surface area is 200 m ² / kg or less due to insufficient partial oxidation, the degree of partial oxidation of the iron powder surface is insufficient.
The oxidation reaction when used as a sheet-shaped oxygen absorber is not activated, and the oxygen absorption rate at the time of rising does not increase. Further, when the partial oxidation promotes partial oxidation and the oxygen content exceeds 7% by weight and the specific surface area becomes 2000 m ² / kg or more, it becomes difficult to uniformly disperse it in polyolefin, which hinders the production of a sheet-type oxygen absorber. Occurs. Further, if the oxides and hydroxides increase due to excessive partial oxidation of the iron powder surface, when kneading the resin and the oxygen absorbing composition, odor may be generated due to oxidation or decomposition of the resin, In order to obtain a sheet-like oxygen absorber that does not substantially generate odor, it is preferable that the oxygen content of the partially oxidized iron powder is 3% by weight or less. The iron powder whose surface is partially oxidized used in the present invention has an oxygen content of 0.7 to 7% by weight and a specific surface area of 200 to 2000 m.
² / kg, and in order to improve the oxygen absorption rate without generating odor, the oxygen content should be 0.7 to 3% by weight and the specific surface area should be 200 to 1500 m ² / kg. preferable. Even if the oxygen content is 0.7 to 7% by weight, for example, if the specific surface area is less than 200 m ² / kg, improvement in the oxygen absorption rate cannot be expected.

The partial oxidation of the iron powder is performed by reacting the iron powder with oxygen in the air in the presence of an electrolyte. For example,
The following method is appropriately selected, and partial oxidation of the iron powder can be performed by utilizing the manufacturing process of the oxygen scavenger. (1) Iron powder and powder or granular electrolyte (0.1% for iron powder)
(1 to 10% by weight) in an atmosphere having a humidity of 60% or more at room temperature or under heating for a predetermined period of time. (2) In the method of (1), a mixture of iron powder and powdery or granular electrolyte is sealed in a container together with a predetermined amount of air, and the oxygen concentration in the atmosphere becomes 0.1% or less in the presence of water. Mix until stirring. (3) Spraying and impregnating an aqueous electrolyte solution (concentration of 1 to 70% by dissolving 0.1 to 4% by weight of an electrolyte with respect to the iron powder in water to a concentration of 1 to 70%) while stirring the iron powder in the air The mixture is stirred and mixed at room temperature or under heating for a predetermined time. (4) In the method of (3), a mixture of the iron powder and the aqueous electrolyte solution is sealed in a container together with a predetermined amount of air, and the mixture is stirred and mixed until the oxygen concentration in the atmosphere becomes 0.1% or less. (5) While stirring the iron powder under vacuum or a nitrogen atmosphere, an aqueous electrolyte solution (a solution in which 0.1 to 4% by weight of an electrolyte is dissolved in water with respect to the iron powder to a concentration of 1 to 70%) is added. Spraying,
After impregnating and drying, the iron powder is stirred and mixed for a predetermined time at room temperature or under heating in an atmosphere having a humidity of 60% or more. (6) In the method of (5), iron powder impregnated with an aqueous electrolyte solution and dried is sealed in a container together with a predetermined amount of air, and the oxygen concentration in the atmosphere is 0.1% in the presence of water. Stir and mix until below.

In each of the above methods (1) to (6),
The degree of partial oxidation is adjusted by appropriately setting conditions such as the electrolytic mass, water content, humidity, and reaction time of the main agent with respect to the iron powder so that the oxygen content in the iron powder is in the range of 0.7 to 7% by weight. Is adjusted. The stirring may be a method in which the mixture is allowed to stand and sometimes stirred, but in order to uniformly oxidize the surface of the iron powder, it is preferable to oxidize while constantly stirring and mixing.

The iron powder partially oxidized by each of the above methods (1) to (6) may contain moisture. Although it is possible to use it as it is, it is preferable to make it dry due to handling problems. In order to make the partially oxidized iron powder dry, in the last step of each of the above methods,
Methods such as heating to the atmosphere, suction and deaeration at room temperature or under heating, or maintaining a heated state by using oxidizing heat can be employed.

Examples of the electrolyte used in the present invention include metal halides, carbonates, sulfates, and hydroxides, and metal halides are preferably used. Among the metal halides, sodium chloride, potassium chloride, calcium chloride and magnesium chloride are more preferred.

The electrolyte may be used in the form of a powder or granules, which may be mixed with the iron powder. However, the electrolyte is dispersed on the surface of the iron powder using an aqueous solution of the electrolyte, and then the coated iron powder (water) is removed. It is preferably used as coated iron powder). The electrolyte is usually 0.1 to 10% by weight based on the iron powder.
Is used in the range, but the amount can be reduced by coating. The electrolytic mass in the case of coating is preferably 0.1 to 4% by weight based on the iron powder. When the electrolytic mass is less than the above range, the oxygen absorption rate becomes slow.On the other hand, when the electrolytic mass is more than the above range, moisture is absorbed and moisture covers the iron powder surface, and the oxygen absorption reaction may be stopped. Therefore, it is not preferable in any case.

The method of coating the electrolyte is not particularly limited, and any method may be used before, after, or simultaneously with the partial oxidation of the iron powder. In addition, the iron powder is dried in the last step of the partial oxidation of the iron powder and the coating of the electrolyte by the above-described method, because the handleability becomes poor when the coated iron powder contains moisture as in the partially oxidized iron powder. Is preferred.

The polyolefin used in the present invention includes ethylene, propylene, butene, methylpentene,
A homopolymer or copolymer such as α-olefin may be mentioned, but a resin having a structure with as few branches as possible is suitable from the viewpoint of stability when melt-kneaded with the oxygen absorbing composition, and a high-density polyethylene or linear low- High density polyethylene is particularly preferably used.

In the present invention, the content of the oxygen absorbing composition in the resin composition must be 30 to 85% by weight. When the content of the oxygen absorbing composition is less than 30% by weight, the oxygen absorbing ability of the sheet oxygen absorber becomes small,
If it exceeds 85% by weight, it becomes difficult to form a sheet. The resin composition is melt-kneaded using an extruder or the like,
It is produced by uniformly dispersing the oxygen absorbing composition in the polyolefin. In addition, the resin may decompose during melting and kneading, and odor may be generated.However, odor generation may be caused by the addition of a moisture absorbent or antioxidant, sealing with an inert gas, or mild operating conditions. Can be prevented.

In the present invention, the resin composition is formed into a sheet having a thickness of, for example, 10 μm to 5 mm by a known molding method such as inflation processing, calendering processing, T-die processing and the like, and this is stretched 1.5 to 9 times. Stretch at magnification.
Stretching is performed, for example, uniaxially or biaxially under a temperature setting of room temperature to 70 ° C. When the stretching ratio is smaller than the above range, sufficient microvoids are not generated due to insufficient stretching, and when it is larger than the above range, the strength of the sheet is reduced.

In the present invention, a sheet-like deodorant layer can be laminated for deodorization. As the sheet-like deodorant layer, for example, a material in which the deodorant itself is fiberized and mixed with other fibers, a material in which paper or nonwoven fabric carries the deodorant, and the like are used. The deodorant is not particularly limited, but activated carbon is preferably used because of its excellent deodorizing effect. The sheet-like deodorant layer is, for example, laminated with a sheet-like oxygen absorber via a molten resin. As the lamination method, extrusion lamination or heat lamination is preferable.

[0020]

【Example】

<Example 1> 50 kg of iron powder having an oxygen content of 0.0% by weight, a specific surface area of 70 m ² / kg, and a particle size of 100 mesh or less in the atmosphere.
While stirring, 2 kg of a 50% calcium chloride aqueous solution is sprinkled and impregnated, and then heated to about 100 ° C. for 30 minutes and then cooled, and the partial iron oxide powder (oxygen absorbing composition) coated with calcium chloride is dried. I got it. The partial iron oxide powder had a water content of 0.2% by weight, an oxygen content analyzed by an infrared absorption method of 1.2% by weight, and B.I. E. FIG. T. The specific surface area analyzed by the method was 500 m ² / kg. Also, SEM
As a result, it was confirmed that the surface of the iron powder was oxidized. 35 kg of the oxygen-absorbing composition and 15 kg of high-density polyethylene (density 0.96 g / cm ³ ) are melt-kneaded in a nitrogen atmosphere, formed into a sheet, and further uniaxially stretched at a stretch ratio of 7 times to a thickness of 0.1 mm. A 6 mm sheet oxygen absorber was prepared. 0.4 g of the sheet oxygen absorber (dimension 2
(0 mm × 40 mm) was packed in a small bag (dimensions: 40 mm × 60 mm) made of a breathable nonwoven fabric (trade name: Tyvek, manufactured by DuPont) to obtain an oxygen absorber package. This was put in a bag made of KON / PE (vinylidene chloride-coated stretched nylon / polyethylene) together with the scotch cake (water activity: 0.9), and sealed by heat sealing so that the air in the bag became 100 ml. Next, the sealed bag of the oxygen scavenger package is kept at a temperature of 25 ° C., and the oxygen concentration in the bag is analyzed over time by a zirconia oximeter, whereby the oxygen concentration in the bag is reduced to zero. .Time to reach 1% or less (hereinafter, referred to as
Deoxygenation time) was measured. Three days later, the sealed bag was opened, and a sensory test for odor in the bag was performed. The results are shown in Table 1 and FIG.

<Example 2> A nonwoven fabric sheet having 5 g of activated carbon per 1 m ² supported on the sheet-shaped oxygen absorber obtained in Example 1 was laminated by extrusion lamination through a polyethylene film to a thickness of 1 mm. To prepare a sheet-shaped deoxidizer having a deodorant layer laminated. Except that this sheet-shaped oxygen absorber of the deodorant layer laminate was used, in the same manner as in Example 1,
An oxygen absorption test was performed. The results are shown in Table 1 and FIG.

<Comparative Example 1> ² kg of a 50% aqueous calcium chloride solution was stirred while stirring 50 kg of iron powder having an oxygen content of 0.0% by weight, a specific surface area of 70 m ² / kg and a particle size of 100 mesh or less under a vacuum of 30 mmHg. It was sprayed and impregnated, heated to about 100 ° C. for 1 hour in that state, and then cooled to obtain a calcium chloride-coated iron powder (oxygen absorbing composition) in a dry state. The water content of the iron powder was 0.1% by weight, the oxygen content analyzed by infrared absorption method was 0.6% by weight, E. FIG. T. The specific surface area analyzed by the method was 160 m ² / kg. From the surface analysis by SEM, it was confirmed that the surface of the iron powder was hardly oxidized. Using this oxygen absorbing composition,
A sheet-like oxygen absorber having a thickness of 0.6 mm was produced in the same manner as in Example 1, and then an oxygen absorber package was produced, and an oxygen absorption test was carried out. The results are shown in Table 1 and FIG.

[0023]

[Table 1] Sensory evaluation criteria of odor A: No off-flavor (odor other than scotch cake) is felt at all. ：: Almost no smell (odor other than scotch cake) is felt.

[0024]

The sheet oxygen absorber according to the present invention has a high oxygen absorption rate at the initial stage, so that the oxygen absorption time is short, and the odor is hardly generated. It can be applied to preservation of etc.

[Brief description of the drawings]

FIG. 1 is a graph summarizing the results of Examples and Comparative Examples, in which the relationship between oxygen concentration in a bag and elapsed time is plotted.

Claims (6)

[Claims] 1. An oxygen-absorbing composition comprising an electrolyte having an oxygen content of 0.7 to 7% by weight and a partially oxidized iron powder having a specific surface area of 200 to 2000 m ² / kg and an electrolyte.
A sheet-shaped oxygen absorber obtained by forming a resin composition comprising 85% by weight and 15 to 70% by weight of a polyolefin into a sheet shape and then stretching the resin composition in at least a uniaxial direction at a stretching ratio of 1.5 to 9 times. 2. The iron powder whose surface is partially oxidized has an oxygen content of 0.7 to 3% by weight and a specific surface area of 200 to 150%.
Sheet deoxidizer according to claim 1, characterized in that the 0 m ² / kg. 3. An oxygen-absorbing composition comprising an iron powder and an electrolyte.
The sheet oxygen absorber according to claim 1, wherein the oxygen absorber is coated with 1 to 4% by weight. 4. An iron powder whose surface is partially oxidized has an oxygen content of 0.5% by weight or less and a specific surface area of 150 m ² / kg.
The sheet-shaped oxygen absorber according to claim 1, wherein the following iron powder is partially oxidized. 5. The sheet-shaped oxygen absorber according to claim 1, wherein the polyolefin is high-density polyethylene or linear low-density polyethylene. 6. A sheet-shaped oxygen absorber obtained by laminating a sheet-shaped deodorant layer on the sheet-shaped oxygen absorber according to claim 1.