JP4813238B2 - Oxygen barrier multilayer film and deep-drawn molded product - Google Patents

Description

The present invention, moldability into such deep drawing relates good oxygen barrier multilayer films and deep drawing molded article.

  Since the development of ethylene-vinyl alcohol copolymer (EVOH), which has excellent gas (oxygen, carbon dioxide) barrier properties, EVOH has been replaced by glass, metal, or conventional plastic materials. In the field of industrial chemicals and the like, it is a resin that is widely used as a gas barrier material for packaging materials or containers for products that dislike oxygen. The EVOH has a hygroscopic property, and if it absorbs moisture, the gas barrier property is lowered. Therefore, is EVOH covered with a hydrophobic thermoplastic resin such as polyolefin resin or polyester resin? Or, it is usually used as a multilayer structure in which EVOH is an intermediate layer and thermoplastic resin is an inner layer and an outer layer.

  EVOH is widely used for packaging materials by utilizing its gas barrier properties, but it does not completely block oxygen, but does not have the function of absorbing oxygen, so it has a slight oxygen permeation rate. Is inevitable. In addition to this permeated oxygen, oxygen that is already present inside when sealed, or especially in food containers that are used with the lid often opened and closed, the removal of oxygen that newly enters when opening and closing is mainly in the food sector. Development of packaging materials that combine a gas barrier resin such as EVOH, and an oxygen-absorbing resin (oxygen-absorbing resin) composed of an oxidizable resin and an oxidation catalyst has been actively conducted. (For example, refer to Patent Document 1).

  The oxygen-absorbing resin is composed of an oxidizable resin and an oxidation catalyst. Specifically, as the oxidizable resin, a thermoplastic resin or polyolefin resin having a carbon-carbon double bond (particularly tertiary carbon in the main chain). It is easy to be oxidized in the presence of an oxidation catalyst such as those having atoms) and develops oxygen absorption performance (oxygen scavenging function) by reacting with oxygen in the air. As the oxidation catalyst, transition metals such as cobalt and the like The organic acid salt or inorganic acid salt is generally used. In addition, as another oxygen-absorbing resin, a polyamide composition containing polyamide (PA) and a PA-reactive oxidizable polybutadiene or oxidizable polyether, and a polyamide containing an oxidation promoting metal salt catalyst in the polyamide composition A multilayer product in which a barrier resin layer such as EVOH is provided as an adjacent layer of the composition and an oxygen barrier polyamide layer made of this polyamide composition has been proposed (for example, see Patent Document 2).

  However, the oxygen-absorbing resin loses the oxygen-absorbing performance after absorbing a certain amount of oxygen, and thereafter cannot obtain the effect of absorbing oxygen. That is, the oxidizing resin does not react with oxygen or hardly reacts with oxygen after reacting with a certain amount of oxygen.

  Therefore, a multilayer structure in which an oxygen absorbing layer having an oxygen absorbing resin and a barrier layer made of a gas barrier resin are laminated, and the oxygen absorption performance is controlled for a desired period by controlling the amount or speed of oxygen reaching the oxygen absorbing layer. There is something to maintain (see, for example, Patent Document 3). In addition, by having a structure in which the oxygen absorption layer is sandwiched between the barrier layers, the oxygen reaching the oxygen absorption layer from the inside and outside of the container is blocked, and after the container is manufactured, the content is filled and sealed In some cases, the oxygen absorption performance is maintained for a long time even when stored in the air (see, for example, Patent Document 4).

However, simply increasing the thickness of the barrier layer in order to reduce the amount of oxygen reaching the oxygen absorbing layer not only increases the cost of the film, but also increases the rigidity of the multilayer film and deteriorates the formability of the package or container. In particular, there is a problem that the suitability of the film at the time of bag making and the followability of the film at the time of deep drawing are lowered.
JP 2001-39475 A JP-T-2004-527395 Japanese Patent Laid-Open No. 5-115776 Japanese Patent Laid-Open No. 2002-240813

Therefore, the object of the present invention is that the oxygen absorption performance is not deactivated in the state of the film raw material , it is easy to handle during storage, has gas barrier properties and oxygen absorption properties, and particularly high humidity due to retorting. The object is to develop an oxygen-barrier multilayer film and a deep-drawn molded article that are excellent in preservability of the contents by effectively blocking oxygen from the outside even under conditions and eliminating substantial oxygen permeation for a certain period.

  The inventors of the present invention conducted intensive studies to solve the above-mentioned problems. As a result, an inner barrier layer made of an ethylene-vinyl alcohol copolymer (EVOH) and an inner side of an oxygen-absorbing resin layer made of an oxygen-absorbing resin, and In a multilayer film in which an intermediate layer composed of an outer barrier layer is provided by coextrusion molding, the film thickness ratio of the intermediate layer is set to a specific range, and the film structure is adjusted by specifying the layer configuration of the multilayer film, and the air It is preferable to prevent oxygen in the inside from permeating the oxygen barrier multilayer structure from the outside to reach the inner contents, so that the oxygen permeation amount is substantially zero for a certain period of time. It has been found that a film having good processability can be obtained while improving the handleability in the state of the original film before forming. The present invention has been made based on such findings.

That is, the present invention is to provide an oxygen barrier multilayer films and deep drawing molded article the following constitution described.

The oxygen barrier multilayer film according to the present invention comprises an oxygen-absorbing resin layer (B) comprising a reaction product of a polyamide and an oxidizable polydiene and a transition metal salt , an ethylene-vinyl alcohol having an ethylene content of 25 to 50 mol%. The intermediate barrier layer comprising the inner barrier layer (A) and the outer barrier layer (C) made of a copolymer, and the (A) layer, (B) layer, and (C) layer are sequentially laminated; and a multilayer film having a heat seal layer laminated via an adhesive layer on the inner barrier layer of the intermediate layer (a), a, and an outer layer laminated the outside barrier layer (C) of said intermediate layer, wherein (a) layer, the sum of the thickness of the intermediate layer be composed of the layer (B) and (C) layer is the 10 to 50% of the total thickness of the multilayer film, a tensile modulus at ordinary temperature of the multilayer film (JIS K7113 ) Is 18000 (kg / cm ² ) or less .

The oxygen barrier multilayer film according to the present invention is characterized in that the total film thickness of the multilayer film is 50 to 300 μm .

The oxygen barrier multilayer film according to the present invention has a tensile strength at break (JIS K7113) at room temperature of 300 (Kg / cm ² ) or more and an elongation (JIS K7113) of 100 (%) or more. It is characterized by being .

The oxygen barrier multi-layer film according to the present invention is a coherent laminate in the order of heat seal layer / adhesive layer / inner barrier layer (A) / oxygen-absorbing resin layer (B) / outer barrier layer (C) / outer layer from the inner layer side. An oxygen barrier multilayer film formed by extrusion molding, wherein the outer layer is a polyolefin-based resin layer laminated to the outer barrier layer (C) via an adhesive layer or a polyamide-based polymer laminated without an adhesive layer It is a resin layer.

The oxygen barrier multilayer film according to the present invention is a co-extrusion laminated in the order of at least a heat seal layer / adhesive layer / inner barrier layer (A) / oxygen absorbing resin layer (B) / outer barrier layer (C) from the inner layer side. An oxygen-barrier multilayer film obtained by laminating an outer layer on a molded multilayer film, wherein the outer layer is laminated on the outer barrier layer (C) by dry lamination or wet lamination.

The deep-drawn molded product according to the present invention is formed by deep-drawing the above-described oxygen barrier multilayer film.

According to the present invention, the film can be easily handled in the raw film, and oxygen permeation into the packaging container can be substantially eliminated for a certain period of time, and the film is flexible despite having a high oxygen barrier property. And a multilayer film excellent in suitability for bag making can be obtained.

According to the present invention, the layer structure is simplified, and it is possible to suitably prevent the occurrence of defective molding such as delamination or pinholes particularly during the formation of a multilayer film such as deep drawing.

Hereinafter, the present invention will be described in detail. The thermoplastic resin constituting the (A) layer and the (C) layer has an oxygen barrier property, and a resin having a lower oxygen permeability than the (B) layer after the oxygen absorption performance is deactivated. Preferably, a resin having an oxygen permeability at 30 ° C. to 60% RH of 10 (cc · 20 μm / m ² · day · atm) or less, preferably 1.0 (cc · 20 μm / m ² · day · atm) or less is suitable. Used for. Further, the thermoplastic resin constituting the layers (A) and (C) has a melting point of 180 ° C. or higher, preferably 185 ° C. or higher, more preferably 190 ° C. or higher. As the thermoplastic resin, an ethylene-vinyl alcohol copolymer (EVOH) having an ethylene content of 25 to 50 mol% obtained by saponifying an ethylene-vinyl acetate copolymer to a saponification degree of 90% or more is suitably used. The ethylene content of the ethylene-vinyl alcohol copolymer can be appropriately selected from the above ranges, and if the oxygen barrier property is given priority, the one having a low ethylene content is preferable. From such a viewpoint, it is preferable to select one having an ethylene content of 32 to 40 mol%.

  The thermoplastic resin constituting the layer (B) is preferably composed of a reaction product of polyamide and polyamide-reactive oxidizable polydiene or oxidizable polyether and a transition metal salt. The oxidizable polydiene or polyether is reacted with a polyamide, and the polydiene or polyether is preferably acid-modified, contains an epoxy group or an anhydrous functional group, and includes a carboxyl group or amino end group of the polyamide, and further It reacts with the amide group in the polyamide skeleton.

  The polyamide may be a polymer having an amide bond, and includes a polymer having an amide bond obtained by a reaction between a carboxylic acid and an isocyanate, in addition to a polymer obtained by a dehydration condensation reaction between a carboxylic acid and an amine. Specifically, polycaproamide (nylon-6), polyundecanamide (nylon-11), polylaurolactam (nylon-12), polyhexamethylene adipamide (nylon-6,6), polyhexamethylene Aliphatic polyamide homopolymers such as bacamide (nylon-6,10); caprolactam / laurolactam copolymer (nylon-6 / 12), caprolactam / aminoundecanoic acid copolymer (nylon-6 / 11), caprolactam / Ω-aminononanoic acid copolymer (nylon-6 / 9), caprolactam / hexamethylene adipamide copolymer (nylon-6 / 6,6), caprolactam / hexamethylene adipamide / hexamethylene sebamide Aliphatic polyamide copolymers such as polymers (nylon-6 / 6, 6/6, 10); Xylylene adipamide (MX- nylon) can be used hexamethylene terephthalamide / hexamethylene isophthalamide copolymer (Nylon-6T / 6I) aromatic polyamide or a mixture of these, and the like.

  In particular, from the viewpoint of film processability, polyamide 6 having a relatively high elongation or a blend of polyamide 6 and another polyamide such as amorphous polyamide is suitable. Here, the amorphous polyamide is one having a calorie of crystal fusion measured by a differential scanning calorimeter (DSC) of 1 cal / g or less, and polymer crystallization hardly occurs or the crystallization rate is very high. A small group of polyamide resins. Examples of the oxidizable polydiene include epoxy-functionalized polybutadiene, epoxy-functionalized polyisoprene, maleic anhydride graft or copolymerized polybutadiene, maleic anhydride graft or copolymerized polyisoprene.

  Examples of the oxidizable polyether include amine, epoxy or anhydrous functional polypropylene oxide, polybutylene oxide, and polystyrene oxide. Furthermore, a transition metal salt is added to the thermoplastic resin constituting the layer (B) as an oxidation catalyst in a range of 5000 ppm or less in terms of metal atomic weight. Transition metal salts are inorganic salts, organic salts, or complex salts of transition metals such as cobalt, iron, nickel, and copper, titanium, chromium, manganese, ruthenium, and especially organic acid salts such as carboxylates and sulfonates. Specific examples thereof include acetate, stearate, propionate, hexanoate, octanoate, neodecanoate, stearate and the like.

  As the thermoplastic resin constituting the layer (B) of the present invention, other known oxygen-absorbing resins can be used. Thermoplastic resins having a carbon-carbon double bond, polyolefin resins (especially in the main chain) Oxygen absorption performance (oxygen scavenging function) by reacting with oxygen in the air that is easily oxidized in the presence of an oxidation catalyst such as those having a tertiary carbon atom) or metaxylylene adipamide (MX-nylon) or a mixture thereof. ) Can be suitably used. Furthermore, various known additives, colorants, heat and weathering agents, antistatic agents, adhesives, and ethylene-vinyl alcohol copolymers, polyamide resins, polyester resins as base resins, as long as the properties are not impaired. Other thermoplastic resins such as polyolefin resins may be added as necessary.

  However, when the thermoplastic resin constituting the layer (B) is other than the oxygen-absorbing resin composition mainly composed of polyamide, interlayer adhesion between the inner barrier layer (A) and the outer barrier layer (C). Since the strength is inferior, the oxygen-absorbing resin constituting the (B) layer or the ethylene-vinyl alcohol copolymer constituting the (A) layer and the (C) layer is within a range of 5 to 35 wt%, such as a modified polyolefin. It is necessary to add a known adhesive resin.

  Further, a polyolefin resin is preferably used as the thermoplastic resin constituting the heat seal layer. As the polyolefin resin, known resins such as low density polyethylene, linear low density polyethylene, ultra low density polyethylene, linear ultra low density polyethylene, high density polyethylene, polypropylene, ethylene-propylene copolymer, and mixtures thereof are appropriately used. Can be used. Furthermore, as the adhesive resin constituting the adhesive layer, an olefin-based copolymer having a carboxyl group and an epoxy-based, polyurethane-based or polyester-based curability are preferably used. Among them, an ethylene-acrylic acid copolymer, Ethylene-methacrylic acid copolymer, maleic anhydride-modified polyethylene and the like are suitable for adhesion to a heat seal layer made of a polyolefin resin.

In addition, the following layer structure is particularly suitable as the oxygen barrier multilayer film in the present invention.
6 layer structure: Heat seal layer / adhesive layer / inner barrier layer / oxygen absorbing resin layer / outer barrier layer / outer layer from inner layer side 7 layer structure: heat seal layer / adhesive layer / inner barrier layer / oxygen absorption from inner layer side Resin layer / outer barrier layer / adhesive layer / outer layer It should be noted that a repro layer made of recycled resin can be appropriately disposed in the above layer structure. It is important not only to reduce the manufacturing cost but also to effectively use resources to pulverize the scrap material generated during molding and processing as scrap resin and use it as recycled resin.

  The multilayer packaging body and multilayer container comprising the multilayer film according to the present invention can prevent the contents from being oxidized or deteriorated by oxygen in the air, and can prolong the shelf life. Seasonings such as sauces, ketchup, dressing, edible oil, miso, ham and sausage, tea, raw noodles, pickles, processed fishery products, retort foods and beverages, cosmetics, fragrances, industrial chemicals and the like.

  Next, the present invention will be described in more detail by way of examples. The multilayer film of each Example was produced and the multilayer package was formed. Furthermore, the performance of this multilayer film and multilayer package was evaluated by the following measurement methods and standards.

(1) Tensile modulus, tensile strength at break, elongation The produced oxygen barrier multilayer film was measured at a tensile speed of 50 mm / min according to JIS K7113 (type 2).
(2) Oxygen permeation amount A multilayer package is made from an oxygen barrier multilayer film, and the oxygen permeation amount measurement device (Ox-Tran 10/50, manufactured by MOCON) is used in a high humidity environment of 23 ° C.-90% RH. It was measured. Furthermore, the oxygen barrier property under the boil sterilization condition (95 ° C. × 30 min) and the high humidity condition was evaluated over time by filling a special solution in which the content changes from white to blue when oxygen enters the package.

[Example 1]
As shown in FIG. 1, using the resins described below, heat seal layer 1 / adhesive layer 2 / inner barrier layer (A) / oxygen absorbing resin layer (B) / outer barrier layer (C) / adhesive layer from the inside A multilayer film having a 7-layer structure composed of 3 / outer layer 4 was produced by coextrusion molding. The thickness of each layer was 40: 5: 10: 20: 10: 5: 10 (μm) from the inside, and the total film thickness was 100 μm.
Heat seal layer: linear low density polyethylene (LL)
Adhesive layer: Modified polyolefin resin (Ad) (trade name: Modic L522, manufactured by Mitsubishi Chemical Corporation)
Inner barrier layer and outer barrier layer: ethylene-vinyl alcohol copolymer (EVOH) having an ethylene content of 38 mol% and a saponification degree of 99% (trade name: Soarnol ET3803, manufactured by Nippon Synthetic Chemical Co., Ltd.)
Oxygen absorbing resin layer: thermoplastic resin (OS) containing a reaction product of maleic anhydride-modified polybutadiene and polyamide and a cobalt organic acid salt
-Outer layer: linear low density polyethylene (LL)

[Example 2]
As shown in FIG. 2, heat sealing layer 1 / adhesive layer 2 / inner barrier layer (A) / oxygen-absorbing resin layer (B) / outer barrier layer (C) / outer layer 4 from the inside using the resins described below. A multilayer film having a 6-layer structure was prepared by coextrusion molding. The thickness of each layer was 50: 5: 10: 20: 10: 15 (μm) and the total film thickness was 110 μm from the inside.
Heat seal layer: linear low density polyethylene (LL)
Adhesive layer: Modified polyolefin resin (Ad) (trade name: Modic L522, manufactured by Mitsubishi Chemical Corporation)
Inner barrier layer and outer barrier layer: ethylene-vinyl alcohol copolymer (EVOH) having an ethylene content of 38 mol% and a saponification degree of 99% (trade name: Soarnol ET3803, manufactured by Nippon Synthetic Chemical Co., Ltd.)
Oxygen absorbing resin layer: thermoplastic resin (OS) containing a reaction product of maleic anhydride-modified polybutadiene and polyamide and a cobalt organic acid salt
-Outer layer: Polyamide 6 (CNy) (trade name: CM1061, manufactured by Toray Industries, Inc.)

[Example 3]
As shown in FIG. 2, using the resins described below, the heat seal layer 1 / adhesive layer 2 / inner barrier layer (A) / oxygen absorbing resin layer (B) / outer barrier layer (C) are formed from the inside. A multilayer film having a layer structure was produced by coextrusion molding. Further, the outer layer 4 was laminated on the outer barrier layer (C) by dry lamination to obtain a six-layer oxygen barrier multilayer film. The thickness of each layer was 50: 5: 10: 20: 10: 15 (μm) from the inside, and the total film thickness was 115 μm (including 5 μm of the dry laminate adhesive layer).
Heat seal layer: linear low density polyethylene (LL)
Adhesive layer: Modified polyolefin resin (Ad) (trade name: Modic L522, manufactured by Mitsubishi Chemical Corporation)
Inner barrier layer and outer barrier layer: ethylene-vinyl alcohol copolymer (EVOH) having an ethylene content of 38 mol% and a saponification degree of 99% (trade name: Soarnol ET3803, manufactured by Nippon Synthetic Chemical Co., Ltd.)
Oxygen absorbing resin layer: thermoplastic resin (OS) containing a reaction product of maleic anhydride-modified polybutadiene and polyamide and a cobalt organic acid salt
-Outer layer: composed of a biaxially stretched film made of polyamide 6 (ONy)

[Comparative Example 1]
Using the resin described below, a multilayer film having a six-layer structure consisting of a heat seal layer / adhesive layer / inner barrier layer (A) / oxygen-absorbing resin layer (B) / outer barrier layer (C) / outer layer is used from the inside. It was produced by extrusion molding. The thickness of each layer was 25: 5: 10: 25: 10: 10 (μm) from the inside, and the total film thickness was 85 μm (see FIG. 2).
Heat seal layer: linear low density polyethylene (LL)
Adhesive layer: Modified polyolefin resin (Ad) (trade name: Modic L522, manufactured by Mitsubishi Chemical Corporation)
Inner barrier layer and outer barrier layer: ethylene-vinyl alcohol copolymer (EVOH) having an ethylene content of 38 mol% and a saponification degree of 99% (trade name: Soarnol ET3803, manufactured by Nippon Synthetic Chemical Co., Ltd.)
・ Oxygen-absorbing resin layer: thermoplastic resin (MXD6) containing polymetaxylylene adipamide and cobalt organic acid salt (trade name: MX nylon 6007, manufactured by Mitsubishi Gas Chemical Co., Ltd.)
-Outer layer: Polyamide 6 (CNy) (trade name: CM1061, manufactured by Toray Industries, Inc.)

  Using the oxygen-barrier multilayer film produced from Example 1 above, the packaging bag was produced by overlaying and sealing three-sided so that the heat seal layer side would be inside. The packaging bag has a layer structure of LL / Ad / EVOH / OS / EVOH / Ad / LL from the inside. This packaging bag is filled with a special solution that changes its color from white to blue when oxygen enters the bag, and is subjected to 30 ° C-80% (high temperature and high humidity conditions) environment after boil sterilization (95 ° C x 30 min) The oxygen barrier properties were evaluated over time. As a result, it was confirmed that there was no discoloration (no oxygen permeation) of the contents for one week or more. Further, delamination did not occur.

  Moreover, the container was produced by deep drawing using the oxygen barrier property multilayer film produced from the said Example 2. FIG. The container has a layer structure composed of LL / Ad / EVOH / OS / EVOH / CNy from the inside. Subsequently, the heat-sealing layer of each other was thermally welded to the container using the oxygen barrier multilayer film produced from Example 3 as a lid, and sealed. The lid has a layer structure composed of LL / Ad / EVOH / OS / EVOH // ONy from the heat seal layer side (the notation “/” indicates lamination by co-extrusion molding, “//” indicates dry lamination adhesion) It shows that it is laminated | stacked with an agent respectively). The oxygen permeation amount of this container was measured over time using an oxygen permeation amount measuring device (Ox-Tran 10/50, manufactured by MOCON). As a result, it was confirmed that there was no oxygen permeation at room temperature for over a year.

  As described above in detail, the multilayer film having the inner barrier layer, the oxygen absorbing layer, and the outer barrier layer of the present invention has a good balance between oxygen barrier properties and oxygen absorbing performance, and in addition, the handleability and processing of the film. It has good properties and is useful as a packaging film for storing contents that dislike oxygen.

2 is a schematic cross-sectional view illustrating a layer configuration of a multilayer film in Example 1. FIG. It is a cross-sectional schematic diagram which shows the layer structure of the multilayer film in Example 2, 3 and the comparative example 1. FIG.

Explanation of symbols

1 Heat Seal Layer 2 Adhesive Layer 3 Adhesive Layer 4 Outer Layer (A) Inner Barrier Layer (B) Oxygen Absorbing Resin Layer (C) Outer Barrier Layer

Claims (6)

An oxygen-absorbing resin layer (B) comprising a reaction product of polyamide and oxidizable polydiene and a transition metal salt, and an inner barrier layer (A) comprising an ethylene-vinyl alcohol copolymer having an ethylene content of 25 to 50 mol% An intermediate layer that is directly sandwiched between the outer barrier layers (C) and is formed by sequentially laminating the (A) layer, the (B) layer, and the (C) layer ;
A heat seal layer laminated on the inner barrier layer (A) of the intermediate layer via an adhesive layer ;
An outer layer laminated on the outer barrier layer (C) of the intermediate layer,
Layer (A), from 10 to 50% of the total thickness of the layer (B) and (C) is the sum of the thickness of the intermediate layer be composed of layers said multilayer film,
An oxygen-barrier multilayer film, wherein the multilayer film has a tensile elastic modulus (JIS K7113) at normal temperature of 18000 (kg / cm ² ) or less. 2. The oxygen barrier multilayer film according to claim 1, wherein a total film thickness of the multilayer film is 50 to 300 [mu] m. Wherein with the tensile strength at break at room temperature of the multilayer film (JIS K7113) is 300 (Kg / cm ²⁾ or more,
The oxygen barrier multilayer film according to claim 1 or 2, wherein the elongation (JIS K7113) is 100 (%) or more. It is an oxygen barrier multilayer film formed by coextrusion and laminated in the order of heat seal layer / adhesive layer / inner barrier layer (A) / oxygen absorbing resin layer (B) / outer barrier layer (C) / outer layer from the inner layer side. There,
3 wherein the outer layer from claim 1, wherein is an outer barrier layer polyamide resin layer laminated without passing through the polyolefin resin layer or an adhesive layer laminated through an adhesive layer (C) The oxygen barrier multilayer film according to any one of the above. The outer layer is laminated to a multilayer film formed by coextrusion and laminated in the order of at least the heat seal layer / adhesive layer / inner barrier layer (A) / oxygen-absorbing resin layer (B) / outer barrier layer (C) from the inner layer side. An oxygen barrier multilayer film comprising:
The oxygen barrier multilayer film according to any one of claims 1 to 3, wherein the outer layer is laminated on the outer barrier layer (C) by dry lamination or wet lamination. A deep-drawn molded product obtained by deep-drawing the oxygen-barrier multilayer film according to any one of claims 1 to 5 .

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