JP2000212448A - Oxygen-absorbing resin composition and multilayer packaging material using same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an oxygen-absorbing resin composition, which has adequate capability of absorbing oxygen in an atmosphere of low humidity and exhibits a reduced degree of generation of a gas other than oxygen when absorbing oxygen without causing the change in quality of a content, the lowering of flavor and the like, and also a multilayer packaging material using the resin composition. SOLUTION: The oxygen-absorbing resin composition comprises a thermoplastic resin having a water absorption of 1% or below, a reducing iron power having an average particle size of 10 to 50 μm, a specific surface area of 0.5 m2/g or over, and an apparent density of 2.2. g/cm3 or below, and sodium iodide. The reducing iron power should preferably be one that contains not less than 50% or over, based on the total particles, of flat particles having a degree of compaction of 20% or over and an aspect ratio of 0.75 or below.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an oxygen-absorbing resin composition and a multilayer packaging material using the resin composition.

[0002]

2. Description of the Related Art In order to preserve foods, cosmetics, etc., there is a problem of deterioration of quality such as deterioration and flavor caused by oxygen. Has been done more. As such oxygen absorbents, those using a reduction metal oxidation reaction and adding a metal halide as an oxidation reaction accelerator are widely used. However, since the oxidation reaction of the reducing metal requires the presence of water, a package using this type of oxygen absorber is not suitable for foods that deteriorate or lose flavor due to moisture,
Sufficient oxygen absorption could not be performed during storage of contents such as cosmetics that require a low humidity atmosphere. Further, when a gas other than oxygen, such as hydrogen, is generated by the oxidation reaction of the reducing metal, the quality of the product may be deteriorated, such as expansion of the package due to the generated gas.

[0003]

Accordingly, the present invention provides
An oxygen-absorbing resin composition that has sufficient oxygen absorption capacity even in a low-humidity atmosphere, generates little gas other than oxygen when absorbing oxygen, and does not cause deterioration of the contents or a decrease in flavor; and An object is to provide a multilayer packaging material using a resin composition.

[0004]

In order to solve the above-mentioned problems, the present invention has the following configuration. 1. A thermoplastic resin having a water absorption of 1% or less, a reducing iron powder having an average particle size of 10 to 50 μm, a specific surface area of 0.5 m ² / g or more, and an apparent density of 2.2 g / cm ³ or less, and iodine. An oxygen-absorbing resin composition containing sodium chloride. 2. The oxygen-absorbing resin according to claim 1, wherein the reducing iron powder contains flat particles having a compression degree of 20% or more and an aspect ratio of 0.75 or less, 50% or more of all the particles. Composition. 3. The reducing iron powder has a copper content of 150 ppm or less,
3. The oxygen-absorbing resin composition according to 1 or 2, wherein the content of sulfur is 500 ppm or less. 4. The oxygen-absorbing ability according to any one of claims 1 to 3, which contains 1 to 100 parts by weight of reducing iron powder per 100 parts by weight of the resin and 0.001 to 30 parts by weight of sodium iodide. Resin composition. 5.1. A multilayer packaging material including an oxygen-absorbing resin layer constituted by the oxygen-absorbing resin composition according to any one of items 1 to 4. 6. 6. The multilayer packaging material according to 5, having a gas barrier layer outside the oxygen-absorbing resin layer, and an inner resin layer separating the oxygen-absorbing resin layer from the contents of the packaging material inside.

[0005]

DETAILED DESCRIPTION OF THE INVENTION In the present invention, a reducing iron powder having a certain average particle size, a specific surface area and an apparent density and a sodium iodide (N
An oxygen-absorbing resin composition is constituted by blending the oxygen absorbent consisting of aI). As the reducing iron powder, for example, a reduced iron powder, an electrolytic iron powder, a spray iron powder, or a crushed cast iron is used. In the present invention, the reducing iron powder has an average particle size of 1
By using a material having a specific surface area of 0.5 m ² / g or more and an apparent density of 2.2 g / cm ³ or less, oxygen can be effectively absorbed even in a low humidity atmosphere. A resin composition can be obtained.

An oxygen absorbent having an average particle size of reducing iron powder of 50 μm or less has excellent dispersibility in a thermoplastic resin and also has excellent oxygen absorption performance. However, a powder having an average particle diameter of 10 μm or more is preferable because a powder having a very small particle size or powder becomes poor in a manufacturing process such as mixing and filling. Further, when the oxygen absorbent is prepared by using a reducing iron powder having a specific surface area of less than 0.5 m ² / g, the oxygen absorption rate decreases, and when the oxygen absorbent is mixed with the resin composition, it is not sufficient. Cannot exhibit oxygen absorption performance. The apparent density of the reducing iron powder was 2.2 g /
When it exceeds cm ³ , the oxygen absorption rate of the oxygen absorbent decreases, and the flexibility, lightness, strength, and the like of the resin composition containing the same decrease. As the reducing iron powder,
It is preferable to use those having a degree of compression of at least 20% and an aspect ratio of at most 0.75 at least 50% of all particles. When an oxygen absorbent is prepared using a reducing iron powder having an aspect ratio of 0.75 or less and a reducing iron powder having a compressibility of less than 50% or less than 20%, the oxygen content within the preferred range of the present invention is obtained. There is a tendency that the oxygen absorbing performance is inferior to the absorbent.

In the present invention, the particle size of the reducing iron powder is measured using a Shimadzu laser diffraction type particle size distribution analyzer SALD1100, ethanol as a particle dispersion medium,
% Particle size is determined as an average particle size by a laser diffraction scattering method. The specific surface area is measured using a BET one-point method, for example, using a Shimadzu flowsorb type as a measuring device. The apparent density is measured according to JIS K 6721, and a cylindrical receiver having a capacity of 5 cm ³ is used as the receiver, and the distance between the outlet stopper of the funnel and the receiver is 38 mm.
Pour the measurement sample into the funnel and immediately stop the outflow when the sample that has flowed out becomes full and starts overflowing. The powder is scraped flat and the powder adhering to the outside of the receiver is gently removed.

[0008] The compression degree is measured as follows. In the same manner as when measuring the apparent density, put the powder in the receiver to the full top end. Next, the receiver containing the powder is raised horizontally by 3 cm and then dropped. This operation is performed 30 times, and the powder is further poured into the space at the upper end of the receiver formed by compressing the powder. Drop the powder 30 times in the same manner to compress the powder and pour more powder into the space at the top of the receiver. This 3
The operation of dropping 0 times and pouring the powder into the created space is repeated a total of 6 times. Finally, the upper end is scraped flat and weighed to obtain a hardened apparent density. The compression degree is calculated by the following equation using the apparent density (c) and the apparent density (d). Compressibility = (cd) / c × 100 Aspect ratio is obtained by taking a photograph by enlarging iron powder particles 250 times and passing through the length (a) of the longest axis of the particles and the midpoint of this long axis. Then, the length (b) of the orthogonal axis is measured, and is obtained by the following equation. Aspect ratio = b / a

The reducing iron powder of the present invention has a copper content of 150 ppm or less based on iron and a sulfur content of 500 ppm or less.
It is preferable to use those of less than ppm. In the case where the oxygen absorbent is prepared using the reducing iron powder having a small amount of impurities other than iron as described above, when this is mixed with the resin composition,
Sufficient oxygen absorption can be performed without lowering the flavor of the object to be preserved. The iron and copper element contents are measured by an atomic absorption method. The solution used in the analysis was prepared by dissolving 0.5 g of the reducing iron powder to be measured in 50 ml of 12N hydrochloric acid, filtering the insoluble portion, and further removing the insoluble portion with 50 ml of 6N hydrochloric acid.
The mixture is heated and dissolved with 1 and the insoluble portion is filtered again. The filtrate is combined with the hydrochloric acid solution to obtain a solution. The sulfur element content is J
It is measured according to the method specified in IS G1215.

In the present invention, the oxygen absorbing reaction of reducing iron powder,
That is, NaI is used as an accelerator for the oxidation reaction. In the oxygen-absorbing resin composition of the present invention, NaI is used as a reaction accelerator.
Unlike the case where other metal halides are used, sufficient oxygen absorption can be performed in a low humidity atmosphere, and generation of gases other than oxygen such as hydrogen can be suppressed. It is possible to prevent quality deterioration such as expansion of the package due to gas generated when used as a material.

The amount of NaI added to the reducing iron powder is preferably from 0.1 to 30 parts by weight, particularly preferably from 0.5 to 10 parts by weight, per 100 parts by weight of the reducing iron powder. If the compounding amount of NaI is less than 0.1 part by weight, sufficient oxygen absorbing ability is not exhibited, and if it exceeds 30 parts by weight, NaI oozes out of the resin composition to deteriorate the contents. Both are not preferred.

In the present invention, an oxygen-absorbing resin composition is formed by blending the above-mentioned reducing iron powder and NaI into a thermoplastic resin. As the thermoplastic resin used here,
A resin having a water absorption of 1% or less may be selected. For example, polypropylene, polypropylene-ethylene copolymer,
Polybutene-1, poly-4-methylpentene-1, low-,
Polyolefins such as medium- or high-density polyethylene, ethylene-vinyl acetate copolymer (EVA), ethylene-ethyl acrylate copolymer (EEA), ion-crosslinked olefin copolymer (ionomer); polystyrene, styrene-butadiene Aromatic vinyl copolymer such as copolymer; polyacrylic resin; nitrile polymer such as acrylonitrile-styrene copolymer, acrylonitrile-styrene-butadiene copolymer; polyethylene terephthalate (PET), polytetramethylene terephthalate, etc. Polyesters; various polycarbonates; fluororesins; and polyacetals such as polyoxymethylene. Any of these can be used alone or as a blend with another resin. By using a resin composition in which the above specific reducing iron powder and NaI are mixed with the thermoplastic resin having a water absorption of 1% or less, sufficient oxygen absorption can be performed in a low humidity atmosphere. If the water absorption of the thermoplastic resin exceeds 1%, sufficient oxygen absorption capacity cannot be obtained because the resin traps the water necessary for the oxidation reaction of the reducing iron powder. The water absorption of the resin is measured according to JIS K 7209 “Method A for measuring water absorption”
Measure according to That is, a square test piece having a side of 50 mm and a thickness of 3 mm, dried at 50 ° C. for 24 hours,
Immerse in distilled water at 23 ° C. for 24 hours. The water absorption is calculated from the mass (M1) of the test piece before water absorption and the mass (M2) of the test piece after water absorption by the following equation. Water absorption (%) = (M2-M1) / M1 × 100

The amount of the reducing iron powder mixed with the thermoplastic resin is as follows:
1 to 100 parts by weight, especially 5 to 6 parts by weight per 100 parts by weight of resin
It is preferably 0 parts by weight, and the amount of NaI is preferably 0.001 to 30 parts by weight, particularly preferably 0.005 to 10 parts by weight, per 100 parts by weight of the resin. If the amount of the reducing iron powder and NaI is less than this, sufficient oxygen absorption performance cannot be obtained.
The moldability of the resin composition is deteriorated, the strength is reduced, and the weight of the resin composition is increased by the reducing iron powder having a large specific gravity, and the handleability is deteriorated. In the present invention, an oxygen absorbent is prepared by previously pulverizing and mixing the reducing iron powder and NaI with a ball mill or the like, and when this is mixed with the resin, the oxygen absorbent is uniformly dispersed in the resin. This is preferable because the oxygen absorption performance can be further enhanced.

The oxygen-absorbing resin composition of the present invention can be used alone as a packaging material, or can be used as a multilayer packaging material by laminating it with another resin or metal foil. In the case of a multilayer packaging material, with the preservation side of the packaging material inside, a gas barrier layer outside the oxygen-absorbing resin layer, and an inner resin layer inside which separates the oxygen-absorbing resin layer from the contents of the packaging material. It is preferable to provide a package material because an effective oxygen absorbing property can be imparted to the packaging material and deterioration of the object to be preserved due to the oxygen absorbent itself can be prevented.

The materials constituting the gas barrier layer include:
All known resins can be used, and examples thereof include gas-barrier resins such as ethylene-vinyl alcohol copolymer, polyvinylidene chloride-based resin, polyvinyl alcohol, and fluorine-based resin. In addition, aluminum, or an inorganic vapor-deposited film provided with a vapor-deposited film of a metal oxide such as silica or alumina on a thermoplastic resin film, aluminum foil,
A metal thin film such as a steel foil is also used.

As the material constituting the inner resin layer, any resin having oxygen permeability can be used. For example, the same resin as the thermoplastic resin to which the above-mentioned oxygen absorbent can be blended can be used. .

When manufacturing a multilayer packaging material, an adhesive or an anchor made of an epoxy resin, a polyamide resin, a polyester resin, a urethane resin, a polyethyleneimine resin or the like is interposed between the respective layers as necessary. And an acid-modified polyolefin resin can be interposed depending on the use. In addition, the resin constituting each layer is blended with a colorant, a bulking agent, a plasticizer, a stabilizer, a lubricant, an antioxidant, an ultraviolet absorber, an antistatic agent, an antifungal agent, a compatibilizer and the like as necessary. be able to. The layer thickness of each layer is appropriately adjusted according to the shape of the package as the final form and the properties of the object to be preserved.

[0018]

(Example 1) 2 parts of NaI powder were added to 100 parts (parts by weight: the same applies hereinafter) of reducing iron powder produced from iron ore sized to 2.4 mm to 12 mm, for a total of 1.5 kg.
The resulting mixture was subjected to vibration grinding together with steel balls in a 3.0 L vibration mill for 3 hours to obtain an oxygen absorbent. 30 parts of this oxygen absorbent and 70 parts of low-density polyethylene (LDPE) having a water absorption of 0.007% and a melt index (MI) at 190 ° C. of 2.0 g / 10 min are melt-kneaded by a twin-screw extruder. To make a pellet. This oxygen absorbent blended LDPE (LO) is used as an intermediate layer, LDPE is used as an outer layer,
White L blended with 12% by weight of titanium white pigment in LDPE
Three-layer, three-layer film with DPE as inner layer (layer thickness: inner layer 30)
μm / intermediate layer 50 μm / outer layer 20 μm) by using an inner layer extruder, an intermediate layer extruder, an outer layer extruder, a feed block,
-Manufactured by a molding device consisting of a die, a cooling roll, and a film take-off device An aluminum foil (7 μm) and polyethylene terephthalate (12 μm) were laminated on the outer layer side of this film by a dry lamination method using a polyurethane-based adhesive to produce a multilayer film.

Comparative Example 1 A multilayer film was manufactured in the same manner as in Example 1 except that sodium chloride powder was used instead of NaI powder. Comparative Example 2 A multilayer film was manufactured in the same manner as in Example 1 except that calcium chloride powder was used instead of NaI powder. Comparative Example 3 A multilayer film was obtained in the same manner as in Example 1 except that potassium iodide powder was used instead of NaI powder. The reducing iron powder in the oxygen absorbent used in Example 1 and Comparative Examples 1 to 3 had an average particle diameter of 26 to 3 in all cases.
0 μm, the specific surface area was 1.8 to 2.2 m ² / g, and the apparent density was 1.7 to 1.9 g / cm ³ .

(Comparative Example 4) As a raw material of reducing iron powder,
A multilayer film was manufactured in the same manner as in Example 1, except that iron ore having a proper size was used instead of iron ore having a size of 2.4 to 12 mm. The average particle size of the reducing iron powder in this oxygen absorbent is 30 μm, and the specific surface area is 0.4 m ² /
g and apparent density were 2.45 g / cm ³ .

Comparative Example 5 The procedure of Example 1 was repeated except that a blend of LDPE and polyvinyl alcohol (PVA) [LDPE: PVA = 95: 5 (weight ratio)] was used instead of the LDPE of the LO layer. To produce a multilayer film. The water absorption of this blend was 1.5%.

(Performance Test) Example 1 and Comparative Examples 1 to
The oxygen absorption amount and the hydrogen generation amount of the multilayer film obtained in 5 were measured as follows. Table 1 shows the results. (Measurement method) A test piece (20 × 150 m) cut out of each multilayer film was placed in a gas-impermeable cup having an internal volume of 87 ml.
m) and 2 m of a glycerin aqueous solution having the following concentration as a humidity control liquid:
was sealed with a heat-sealing lid made of a gas-impermeable aluminum foil laminated film and sealed by heating. After storing them at 22 ° C. for a certain period, the oxygen concentration and the hydrogen concentration in the container were analyzed using a gas chromatograph to determine the oxygen absorption amount and the hydrogen generation amount per unit area of the film. (Glycerin aqueous solution concentration) Humidity in the container Glycerin concentration 100% RH 0% 49% RH 80% 36% RH 87%

[0023]

[Table 1]

As is evident from Table 1, the multilayer film of Example 1 is superior to the multilayer films of Comparative Examples in oxygen absorbing ability under a low humidity atmosphere. Further, compared to Comparative Examples 1, 2, and 5, the generation of hydrogen due to the oxygen absorption reaction is small. In addition, the reason why the amount of generated hydrogen in Comparative Examples 3 and 4 is small is that these multilayer films are inferior in the oxygen absorbing ability and the oxygen absorbing reaction itself is small.

(Example 2) 30 parts of an oxygen absorbent produced in the same manner as in Example 1 were used.
70 parts of polypropylene (PP) having an MI of 0.6 g / 10 min at 0 ° C. was melt-kneaded with a twin-screw extruder to prepare pellets. 60% or more of the reducing iron powder in the oxygen absorbent has an aspect ratio of 0.25 to 0.6.
0 and the degree of compression was 39%. This oxygen-absorbing agent-containing pellet (PO) was used as a first intermediate layer, and an ethylene-vinyl alcohol copolymer (EVOH: ethylene content 3) was used.
2 mol%, a saponification degree of 99.6 mol%) as a second intermediate layer, and white PP obtained by mixing 8 wt% of titanium white pigment with PP.
Are inner and outer layers, and M at 230 ° C. is provided on both sides of the EVOH layer.
I was provided with an adhesive layer (ADH layer) made of maleic anhydride-modified PP with 1.0 g / 10 min to produce a multilayer sheet of 4 types and 6 layers. The layer thickness of each layer is PP layer (40 μm) / A
DH layer (1 μm) / EVOH layer (10 μm) / ADH layer (1 μm) / PO layer (20 μm) / PP layer (10 μm)
Met. After heating the obtained multilayer sheet to 190 ° C., a square cup having a depth of 30 mm and a capacity of 115 ml was manufactured using a vacuum forming machine such that the PO layer was inside the EVOH layer.

Comparative Example 6 As an oxygen absorbent, a particle size of 30 was used.
The reduced iron powder pulverized to a micron
A square cup was manufactured in the same manner as in Example 2 except that an aqueous solution of NaI was sprayed so that aI was 2 parts, and then an oxygen absorbent obtained by removing water was used. The reduced iron powder in the oxygen absorbent used here has few flat particles,
Those having an aspect ratio of 0.75 or more exceeded 60%. The degree of compression was 18%.

(Performance Test) The oxygen barrier performance of the square cups obtained in Example 2 and Comparative Example 6 was measured as follows. Each square cup was filled with 1 ml of water, and a gas-impermeable aluminum foil laminate lid was heat-sealed under a nitrogen atmosphere. After a retort sterilization treatment at 120 ° C. for 30 minutes, the solution was stored in an atmosphere of 30 ° C. and 80% RH for a certain period, and then the oxygen concentration in the container was measured using a gas chromatograph. Table 2 shows the results.

[0028]

[Table 2]

As is clear from Table 2, the square cup of Example 2 showed excellent oxygen barrier performance as compared with the cup of Comparative Example 6.

Example 3 An oxygen absorber produced using a reducing iron powder having a copper content of 60 ppm relative to iron and a sulfur content of 210 ppm was used. A cup was manufactured.

(Reference Examples 1 and 2) As reducing iron powder, those having a copper content of 1010 ppm and a sulfur content of 3400 ppm with respect to iron (Reference Example 1), a copper content of 200 ppm with respect to iron and a sulfur content of 200 ppm Content is 540pp
A square cup was manufactured in the same manner as in Example 2 except that each of m (Reference Example 2) was used.

(Performance Test) After filling each square cup of Example 3, Reference Example 1 and Reference Example 2 with 100 ml of purified water of the Japanese Pharmacopoeia, the gas-impermeable aluminum foil laminate lid material was heat-sealed under a nitrogen atmosphere. did. A retort sterilization treatment was performed at 120 ° C. for 30 minutes, and after cooling, the lid was peeled off and tested for flavor. Flavorability was evaluated by a sensory test. 30 ° C, 80% R with lid
The oxygen concentration in the container of the square cup stored for a certain period in an atmosphere of H was measured using a gas chromatograph. Table 3 shows the results.

[0033]

[Table 3]

As is evident from Table 3, the square cup of Example 3 was excellent not only in oxygen barrier performance but also in flavor over a long period of time.

[0035]

The oxygen-absorbing resin composition of the present invention has the following effects by adopting the above constitution. 1. It has sufficient oxygen absorption capacity under low humidity atmosphere. Therefore, preservation objects such as foods and cosmetics, which are liable to be degraded by not only oxygen but also moisture, can be stored for a long period of time without lowering the flavor. 2. Generation of gases other than oxygen such as hydrogen during oxygen absorption is small. Therefore, there is no decrease in commercial value such as expansion of the package due to gas generated when used as a packaging material. 3. As reducing iron powder in the oxygen absorbent, copper for iron,
When the sulfur content is equal to or less than a certain value, it has a sufficient oxygen absorbing ability and does not cause a decrease in the flavor of the contents.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat (Reference) C08K 3:16) F term (Reference) 4F100 AA05A AA21C AA36A AB02A AB10D AB17A AB33D AK01A AK06A AK06B AK06C AK42D AK51G BA03 BA04 BA07 BA10B BA10C BA10D BA16 CA09A CA13C CB00 DE01A GB15 GB23 JB16A JD02B JD03C JD14 JD14C JD15A YY00A 4J002 AC081 BB031 BB061 BB071 BB121 BB151 BB171 BB231 BC031 BD121 BG101 BG151 CB101 DD001 001

Claims (6)

[Claims] 1. A thermoplastic resin having a water absorption of 1% or less has an average particle size of 10 to 50 μm and a specific surface area of 0.5 m ^2.
An oxygen-absorbing resin composition comprising a reducing iron powder having an apparent density of 2.2 g / cm ³ or more and sodium iodide or more. 2. The reducing iron powder is obtained by converting flat particles having a compressibility of not less than 20% and an aspect ratio of not more than 0.75 to 50% of all particles.
The oxygen-absorbing resin composition according to claim 1, wherein the composition contains the above. 3. The reducing iron powder has a copper content of 150 pp.
The oxygen-absorbing resin composition according to claim 1 or 2, wherein the content of sulfur is 500 ppm or less and the sulfur content is 500 ppm or less. 4. The method according to claim 1, further comprising 1 to 100 parts by weight of the reducing iron powder and 0.001 to 30 parts by weight of sodium iodide per 100 parts by weight of the resin. Item 10. The oxygen-absorbing resin composition according to item 8. 5. A multilayer packaging material comprising an oxygen-absorbing resin layer composed of the oxygen-absorbing resin composition according to any one of claims 1 to 4. 6. The multilayer according to claim 5, further comprising a gas barrier layer outside the oxygen absorbing resin layer, and an inner resin layer separating the oxygen absorbing resin layer from the contents of the packaging material inside the gas barrier layer. Packaging material.