JP2001260285A - Method for manufacturing oxygen absorbable laminated film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for manufacturing an oxygen absorbable laminated film having high productivity using a general iron deoxidizer and a packaging material using the same and having excellent durability. SOLUTION: To manufacture the oxygen absorbable laminated film having an oxygen absorption layer D made of an oxygen absorbing resin composition in which a particulate deoxidizer containing an iron powder as a base compound is dispersed in a polyolefin resin and having an oxygen barrier layer A, an intermediate layer B, an adhesion reinforced layer C, the oxygen absorbing layer D and a sealant layer E sequentially laminated from at least an outside, The layer C, the layer D or the layer C, the layer D and the layer E are co- extrusion laminated on a surface of the layer B. In this case, a melt flow rate of the polyolefin resin used for the layer C is smaller than that of the polyolefin resin used for the layer D, and this resin of the layer C is applied.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a laminated film having oxygen absorption performance and a packaging material using the same. More specifically, a method for producing an oxygen-absorbing laminated film having an oxygen-absorbing layer composed of an oxygen-absorbing resin composition in which iron powder is dispersed in a polyolefin resin and having excellent productivity, and packaging having excellent durability using the same. About the material.

[0002]

2. Description of the Related Art Many proposals have been made for techniques for providing an oxygen absorbing function to a packaging material itself using an oxygen absorbing resin composition in which an oxygen scavenger is dispersed in a polyolefin resin. Various inorganic and organic oxygen scavengers are known, but from the viewpoints of oxygen absorption performance, thermal stability to withstand high temperatures during processing, economy and hygiene, iron powder and oxidation promotion Those consisting of agents are preferably used. This iron-based oxygen scavenger is generally in the form of particles or powder.

[0003] As a method for producing an oxygen-absorbing laminated film containing an iron-based oxygen-absorbing agent, an oxygen-absorbing resin composition constituting an oxygen-absorbing layer and a resin layer constituting another layer are simultaneously heated and heated.
A co-extrusion lamination method of melting and laminating, an extrusion lamination method of heating and melting only the oxygen-absorbing resin composition and laminating a resin film constituting another layer, and further forming a single-layer oxygen-absorbing layer film in advance A known method such as a dry lamination method in which a film forming another layer is bonded to the film using an adhesive is applied.

Regardless of which method is applied, when the oxygen absorbing layer and the oxygen barrier layer are adjacent to each other, the iron-based oxygen scavenger contained in the oxygen absorbing layer penetrates the oxygen barrier layer to cause irregularities and impair the appearance. Not only that, the oxygen barrier property may be reduced. As a countermeasure, it is conceivable to use iron powder that has been sufficiently atomized compared to the thickness of the oxygen absorption layer. However, fine iron powder is not only expensive, but also has the danger of ignition during handling. Production is difficult.

As a solution to this problem, an oxygen-absorbing laminated film in which a polyolefin resin layer is interposed between an oxygen-absorbing layer and an oxygen barrier layer is disclosed in Japanese Patent Laid-Open No. 9-234832.
Is disclosed. The resin layer is a single-layer polyolefin resin film, and is characterized in that a heated and melted oxygen-absorbing composition is directly extruded on the surface thereof. The iron-based oxygen scavenger in the oxygen absorbing layer absorbs irregularities by digging into the resin layer, and furthermore, the oxygen barrier layer side of the resin layer is kept smooth. It is effective for protection.

However, in a film-like packaging material whose thickness is generally limited to about 200 μm from the viewpoint of rigidity and handleability, it is desired that the oxygen absorbing layer be as thin as possible by providing the above-mentioned resin layer. A large amount of iron-based oxygen absorber is blended in the oxygen absorbing layer which has been thinned in order to maintain the oxygen absorbing performance equivalent to the thickness of the iron-based oxygen absorbing agent. The iron-based oxygen scavenger contained in the oxygen-absorbing layer becomes a kind of foreign matter at the time of the extrusion process, and there is a problem that the thinned oxygen-absorbing layer is liable to crack and the productivity is deteriorated. Further, when a pouch is prepared and the contents are put and stored for a long period of time, the adhesiveness between the oxygen absorbing layer and the resin layer is insufficient, and thus the pouch lacks practical durability.

[0007]

SUMMARY OF THE INVENTION Under the background of the prior art described in the preceding paragraph, an object of the present invention is to provide a method for producing an oxygen-absorbing laminated film having high productivity using a general-purpose iron-based oxygen scavenger, and a method for producing the same. An object of the present invention is to provide a packaging material having excellent durability.

[0008]

Means for Solving the Problems As a result of intensive studies to solve the above problems, the present inventors have found that an adhesion strengthening layer and an iron-based layer are provided on an intermediate layer provided between an oxygen barrier layer and an oxygen absorbing layer. By coextruding and laminating an oxygen absorbing layer containing a deoxidizer, the productivity of the oxygen absorbing laminated film is increased, and the obtained packaging material is found to have excellent durability, and the present invention It was completed. That is, in the present invention, at least from the outside, when producing an oxygen-absorbing laminated film composed of an oxygen barrier layer A / intermediate layer B / adhesion reinforcing layer C / iron-based oxygen absorbing agent-containing oxygen absorbing layer D / sealant layer E,
On the surface of the intermediate layer B, the adhesion reinforcing layer C, the iron-based oxygen absorbing agent-containing oxygen absorbing layer D or the adhesive reinforcing layer C, the iron-based oxygen absorbing agent-containing oxygen absorbing layer
D. A method for producing an oxygen-absorbing laminated film, comprising laminating a sealant layer E by coextrusion.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail.

In the method for producing an oxygen-absorbing laminated film of the present invention, the adhesion-enhancing layer C and the oxygen-absorbing layer D containing an iron-based oxygen scavenger (hereinafter sometimes referred to as oxygen-absorbing layer D) are provided on the intermediate layer B. They are co-extruded and laminated, and the adhesion reinforcing layer C is disposed between the intermediate layer B and the oxygen absorbing layer D. This will be described in more detail.

The oxygen-absorbing layer D is formed from an oxygen-absorbing resin composition in which a particulate oxygen-absorbing agent mainly composed of iron powder (hereinafter sometimes referred to as an oxygen-absorbing agent) is dispersed in a polyolefin resin, as described later. Is done. When the oxygen absorbing layer D is formed, the oxygen scavenger becomes a kind of foreign matter, and based on this, a film crack occurs, which causes deterioration of film forming property. In particular, in the case of a film-like packaging material in which the thickness of the laminate is limited to approximately 200 μm or less, it is required to make the oxygen-absorbing layer thinner in terms of rigidity and handleability, so that further film formation becomes more difficult. The thickness of the oxygen absorbing layer D is appropriately selected in the range of 10 to 80 μm in consideration of required oxygen absorbing performance.

In the present invention, it has been found that the cohesion extruding of the adhesion reinforcing layer C and the oxygen absorbing layer D improves the film forming property. At this time, it is preferable that the melt flow rate (hereinafter, may be abbreviated as MFR) of the polyolefin resin used for the adhesion reinforcing layer C is smaller than the MFR of the polyolefin resin used for the oxygen absorption layer D.

The MFR is measured in accordance with JIS K7210, and is represented by a gram amount (g / 10 minutes) of resin flowing out at a predetermined temperature and a predetermined pressure for 10 minutes. The smaller the MFR, the higher the degree of polymerization and the higher the viscosity when melted by heating. In the present invention, the MFR of the polyolefin resin used for the adhesion-enhancing layer C is selected to be smaller than the MFR of the polyolefin resin used for the oxygen-absorbing layer D, and both layers are co-extruded to remove the MFR of the oxygen-absorbing layer D. This has the effect of preventing film cracking caused by the oxygen agent. When the MFR of the polyolefin resin used for the adhesion reinforcing layer C is the same as or larger than the MFR of the polyolefin resin used for the oxygen absorbing layer D, such an effect is not recognized.

Next, the adhesion reinforcing layer C is composed of the intermediate layer B and the oxygen absorbing layer.
Explain that it is arranged between D. As described above, in order to prevent film cracking, the adhesion-enhancing layer C
The same effect can be obtained by arranging. However, when the adhesion reinforcing layer C is disposed between the oxygen absorbing layer D and the sealant layer E, there is a problem that the oxygen absorbing rate is reduced.
In other words, the oxygen-absorbing laminated film of the present invention incorporates oxygen and moisture necessary for the oxidation reaction of iron powder into the oxygen-absorbing layer D from the heat seal layer E side in contact with the contents, so that the adhesion reinforcing layer C By disposing between the two layers, extra time is required until oxygen and moisture reach the oxygen absorbing layer D, and as a result, the oxygen absorbing rate becomes slow, which is not preferable.

Further, the adhesion reinforcing layer C is disposed between the intermediate layer B and the oxygen absorbing layer D so that the intermediate layer B and the oxygen absorbing layer
It also has the effect of enhancing the adhesive strength of D. In other words, when the oxygen absorbing layer D is directly adjacent to the intermediate layer B, the adhesion between the two layers is increased by the volume expansion due to the oxidation of the iron powder in the oxygen scavenger that has penetrated the intermediate layer B and the incorporation of moisture by the oxidation promoter. Due to the decrease, delamination may occur, which causes a problem in durability of the packaging material. On the other hand, by providing the adhesion strengthening layer C, the polyolefin resin necessary for bonding the two layers is sufficiently supplied between the intermediate layer B and the oxygen absorbing layer D, so that there is no practical problem with the packaging material. Durability is obtained. From the above, it is preferable that the adhesion reinforcing layer C is disposed on the intermediate layer B and the oxygen absorbing layer D. Further, the thickness of the adhesion reinforcing layer C is 3
１５15 μm is preferable. When the adhesive strength lower layer C is thinner than this, the effect of improving the adhesive strength is low, and when the thickness is larger than 15 μm, not only the adhesive strength is not further improved but also the thickness of the entire film increases. Therefore, the handling property is deteriorated, which is not preferable.

Further, the intermediate layer B of the present invention does not necessarily have to be a single layer, and may be another resin layer as long as the surface of the intermediate layer B on which the adhesion reinforcing layer C is laminated is a polyolefin resin. For example, a laminate of nylon and a polyolefin resin is exemplified. The thickness of the intermediate layer B is determined by the maximum particle size of the oxygen absorber used as described later,
Is appropriately selected in consideration of the thickness of the oxygen absorbing layer D and the thickness of the oxygen absorbing layer D, but is preferably in the range of usually 10 to 50 μm. Also,
The intermediate layer B is preferably in the form of a film in advance. If the intermediate layer B and the oxygen absorbing layer D are co-extruded, the oxygen scavenger may pass through the intermediate layer B and reach the oxygen barrier layer A, which is not preferable.

In the present invention, the surface of the intermediate layer B on which the adhesion reinforcing layer C is laminated, the adhesion reinforcing layer C, the oxygen absorbing layer D, and the sealant layer E are preferably a polyolefin resin capable of being thermally bonded to an adjacent layer. . For example, polyethylene,
Polypropylene, ethylene-propylene copolymer, various ethylene-α-olefin copolymers, polybutene, polymethylpentene, acid-modified polyolefin, and the like are preferable, and a mixture may be used.

The procedure for laminating the oxygen-absorbing laminated film of the present invention is not particularly limited, except that the adhesion-enhancing layer C composed of a polyolefin resin and the oxygen-absorbing layer D are co-extruded on the intermediate layer B. The oxygen barrier layer A may be laminated on the other surface in advance. The sealant layer E is preferably thermally bonded to the oxygen absorbing layer D in a film state or a molten state, and a filler such as titanium oxide may be added.
On the other hand, after forming the intermediate layer B, the adhesion reinforcing layer C, and the oxygen absorbing layer D, the sealant layer D can be laminated by a dry lamination method using an adhesive, but the number of steps is increased, and oxygen and It is not preferable because there is no adhesive that can transmit moisture well.

The oxygen barrier layer A used in the present invention is not particularly limited, and may be a metal foil or a metal-deposited film of aluminum or the like, a silica or alumina-deposited polyethylene terephthalate film, an ethylene-vinyl alcohol copolymer, a poly (meth) acrylic. An acid-baked polyethylene terephthalate film is exemplified. Further, a substrate such as polyethylene terephthalate may be laminated outside the oxygen barrier layer.

In the present invention, an oxygen scavenger containing iron powder as a main component is used. There is no particular limitation on the purity and type of iron powder. In addition to iron powder such as reduced iron powder and spray iron powder, cast iron, steel scrap,
A crushed piece of grinding iron waste is used. The iron powder is pulverized and mixed with an additive such as an oxidation accelerator to become an oxygen scavenger. Specific examples of the oxidation promoter include alkali metal chlorides such as sodium chloride and alkaline earth metal oxides such as calcium chloride and magnesium chloride. These may be used alone or in combination. The addition amount of the oxidation promoter is preferably 1 to 30% by weight based on the iron powder. Furthermore, silica, silicates such as diatomaceous earth, alumina,
Clay minerals such as carbon black, kaolin, talc, mica and bentonite; sulfates such as calcium sulfate and barium sulfate; carbonates such as calcium carbonate and magnesium carbonate; and phosphorus such as sodium and potassium pyrophosphate. An inorganic powder such as an acid salt may be appropriately added. The maximum particle size of the particulate oxygen absorber may exceed the thickness of the oxygen absorbing layer D, and may be less than the sum of (intermediate layer B + adhesion reinforcing layer C + oxygen absorbing layer D). Therefore, it is not necessary to particularly use fine iron powder which is expensive and may cause ignition during handling, and iron powder having an average particle diameter of 5 to 50 μm is preferably used.

The oxygen scavenger is dispersed in a heat-melted polyolefin resin such as polyethylene, polypropylene or various ethylene-α-olefin copolymers using a twin-screw extruder or the like. Layer D
It is preferable to use it for forming. The amount of oxygen scavenger added
In consideration of the required oxygen absorption performance, it is appropriately selected in the range of 2 to 100% by weight based on the polyolefin resin. It is preferable that the resin composition is pelletized from the viewpoint of handling in the next packaging material forming step.

The packaging material using the method for producing an oxygen-absorbing laminated film of the present invention may be a three-sided or four-sided sealed flat bag,
It can take a variety of bag-like forms, such as standing pouches, sticks, gusset bags, and the like.

[0023]

EXAMPLES The present invention will be described and exemplified below with reference to examples, but the contents of the present invention are not limited to the examples.

[0024]

Example 1 Iron powder (average particle size: 10 μm, maximum particle size: 80 μm)
m) To 100 kg, add 10 kg of anhydrous calcium chloride (average particle size of 50 μm, maximum particle size of 100 μm) and 1 kg of barium sulfate (average particle size of 0.3 μm, maximum particle size of 3 μm). After performing the pulverization and coating on the surface of the iron powder using a substituted vibration ball mill, a particulate oxygen scavenger of 60 μm or less was obtained by sieving.

Next, the obtained particulate oxygen absorber was mixed with polypropylene (MFR) using a twin-screw extruder equipped with a vent by a side feed method so that the iron powder content became 20% by weight.
40), and the resulting strands were pelletized with a pelletizer to obtain an oxygen-absorbing resin composition (1).

Polyethylene terephthalate [PET] (12 μm) supplied from the first feeding section laminated with a urethane adhesive by a normal dry lamination method
/ Oxygen barrier layer A Aluminum foil [Al] (7μm) /
Middle layer B Unstretched polypropylene [CPP] (30 µm)
, And between titanium oxide-containing white unstretched polypropylene [CPPw] (30 μm) supplied from the second feeding section,
Polypropylene (10 μm, MFR35) using a die
An oxygen-absorbing laminated film was obtained by co-extruding an adhesion-enhancing layer C composed of and an oxygen-absorbing layer D composed of the oxygen-absorbing resin composition (1). The composition is PET (12μm) / oxygen barrier layer A
Al foil (7 μm) / intermediate layer B CPP (30 μm) / adhesion strengthening layer C (10 μm) / oxygen absorption layer D (30 μm) / sealant layer E CPPw (30 μm).

(Evaluation of film-forming properties) The number of cracks in the oxygen-absorbing layer D existing around a width of 780 mm x a length of 1000 m of the obtained oxygen-absorbing laminated film was determined by a defect detector (detection limit).
(Diameter 1 mm). Table 1 shows the results.

The two oxygen-absorbing laminated films thus obtained were used as side surfaces, and PET (12 μm) / Al foil (7 μm) / CPP (6
(0 μm) as a bottom surface, and a standing pouch having an inner volume of 250 ml was prepared by a bag making machine. The inner area of the oxygen-absorbing laminated film excluding the heat-sealed portion was 350 cm2. The following evaluation was performed using this pouch.

(Evaluation of Oxygen Absorption Performance) The obtained pouch was filled with 1 ml of tap water and 60 ml of air (12.5 ml as oxygen), and subjected to a retort treatment at 121 ° C. for 8 minutes. The oxygen absorption was calculated by measuring by chromatography. Table 1 shows the results.

(Evaluation of the durability of the packaging material) The obtained pouch was sealed with 200 ml of tap water, retorted at 121 ° C for 8 minutes, and further stored at 66 ° C for 10 days. After the storage period, the side surface of the pouch was cut with a cutter, and the cut surface was observed with a microscope.

(Evaluation of handleability) The obtained pouch was set on a filling machine for opening the pouch by applying a suction disk to the side of the pouch and pulling the opposing sides in opposite directions while reducing the pressure, and the opening property was examined. . Table 1 shows the results.

[0032]

Example 2 The same operation as in Example 1 was carried out except that the intermediate layer B was a laminated film of nylon (15 μm) and maleic anhydride-modified polypropylene (5 μm). Table 1 shows the results of evaluating the durability and handleability of the packaging material.

[0033]

[Comparative Example 1] MFR of polypropylene used for adhesion reinforcing layer C
Was changed as shown in Table 1, and the same operation as in Example 1 was performed. Table 1 shows the results of evaluating the film forming property, oxygen absorbing performance, durability of the packaging material, and handleability.

[0034]

Comparative Example 2 The same operation as in Example 1 was performed except that the positions of the adhesion reinforcing layer C and the oxygen absorbing layer D were different, and the film forming property, oxygen absorbing performance, durability of the packaging material, and handleability were evaluated. Table 1 shows the results. In addition, the structure of the obtained oxygen-absorbing laminated film is as follows. PET (12μm) / Oxygen barrier layer A
Al foil (7 μm) / intermediate layer B CPP (30 μm) / oxygen absorption layer D (30 μm) / adhesion strengthening layer C (10 μm) / sealant layer E CPPw (30 μm)

[0035]

Comparative Example 3 The same operation as in Example 1 was performed except that the thickness of the adhesion reinforcing layer C was changed as shown in Table 1, and the film forming property, oxygen absorption performance, durability of the packaging material, and handleability were evaluated. Table 1 shows the results of the evaluation.

[0036]

[Comparative Example 4] The same operation as in Example 1 was performed except that the adhesion reinforcing layer C was not present, and the results of evaluating the film forming property, oxygen absorbing performance, durability of the packaging material, and handleability are shown in Table 1. Show.

[0037]

[Comparative Example 5] Polyethylene terephthalate [PET] (12 µm) supplied from the first feeding section laminated with a urethane adhesive by a normal dry laminating method
/ Between aluminum foil [Al] (7 µm) and titanium oxide-containing white unstretched polypropylene [CPPw] (30 µm) supplied from the second feeding section, polypropylene (40 µm, MFR35) and oxygen were added using a T-die. An oxygen-absorbing layer D composed of the absorbent resin composition (1) was co-extruded to obtain an oxygen-absorbing laminated film. The composition is PET (12 μm) / Oxygen barrier layer A Al foil (7 μm) / PP (40 μm) / Oxygen absorption layer D (30 μm) / Sealant layer E CPPw (30 μm)
m). Table 1 shows the results of evaluating the film-forming properties, oxygen-absorbing performance, durability of the packaging material, and handleability in the same manner as in Example 1.

[0038]

[Table 1]

The above results indicate that the co-extrusion of the adhesion-enhancing layer C and the oxygen-absorbing layer D on the intermediate layer B and the MFR of the co-extruded resin
By making the specific, it is possible to easily produce an oxygen-absorbing laminated film without the occurrence of film cracking, and that the packaging material obtained from this production method has excellent durability and handleability. ing.

[0040]

As described above, the oxygen-absorbing layer D composed of the oxygen-absorbing resin composition in which the particulate oxygen absorber mainly composed of iron powder is dispersed in the polyolefin resin is provided. Layer A / Intermediate layer B / Adhesion strengthening layer C
When manufacturing an oxygen-absorbing laminated film composed of / oxygen-absorbing layer D / sealant layer E, an adhesion-enhancing layer C, an oxygen-absorbing layer D or an adhesion-enhancing layer C containing an iron-based oxygen absorber on the surface of the intermediate layer B, By co-extruding and laminating the oxygen absorber-containing oxygen absorbing layer D and the sealant layer E, and by applying a polyolefin resin having a specific melt flow rate, it becomes possible to produce an oxygen-absorbing laminated film with high productivity. The obtained oxygen-absorbing laminated film does not cause interlayer separation and has excellent durability.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of a basic laminated film of the present invention.

[Explanation of symbols]

 11) Oxygen barrier layer A 12) Intermediate layer B 13) Adhesion strengthening layer C 14) Oxygen absorbing layer D 15) Sealant layer E

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) // B29K 23:00 B29K 23:00 103: 06 103: 06 505: 12 505: 12 B29L 9:00 B29L 9:00 F term (reference) 3E086 AB01 BA04 BA15 BA35 BB05 4F100 AA05 AA05H AA07 AA07H AA21 AA21H AB02D AB10B AB33B AK03C AK03D AK07 AK07B AK07C AK07E AK42A AK48BAL03 E03 BA03 AR01 AR00A03A00 AR07C ARD JL00 JL02 JL11C JL12E 4F207 AA03 AB16 AG01 AG03 AH54 KA01 KA17 KB26 KF02 KK84 KL65

Claims (5)

[Claims] An oxygen barrier layer A / intermediate layer B / adhesion reinforcing layer C / iron-based oxygen absorbing agent-containing oxygen absorbing layer D /
In producing the oxygen-absorbing laminated film composed of the sealant layer E, the adhesion reinforcing layer C, the iron-based oxygen absorbing agent-containing oxygen absorbing layer D or the adhesive reinforcing layer C, the iron-based oxygen absorbing agent-containing oxygen absorption A method for producing an oxygen-absorbing laminated film, comprising laminating a layer D and a sealant layer E by coextrusion. 2. The oxygen-absorbing layer D containing an iron-based oxygen-absorbing agent comprises an oxygen-absorbing resin composition in which an oxygen-absorbing agent containing iron powder as a main component is dispersed in a polyolefin resin.
The production method of the oxygen-absorbing laminated film according to the above. 3. The oxygen-absorbing laminate according to claim 1, wherein the melt flow rate of the polyolefin resin used for the adhesion reinforcing layer C is lower than the melt flow rate of the polyolefin resin used for the oxygen absorbing layer D. Film production method. 4. A single-layer or laminated intermediate layer B, on which the adhesion-enhancing layer C is laminated, the adhesion-enhancing layer C, the oxygen-absorbing layer D and the sealant layer E are made of a polyolefin resin which can be thermally bonded to adjacent layers. The method for producing an oxygen-absorbing laminated film according to any one of claims 1 to 3, wherein 5. A packaging material obtained by the method for producing an oxygen-absorbing laminated film according to claim 1.