JP6988068B2 - Paper barrier laminates and paper barrier containers - Google Patents

Description

The present invention relates to a paper barrier laminate suitable for packaging foods, toiletry products, pharmaceuticals, etc., and a paper barrier container formed by using the paper barrier laminate.

Many foods, toiletry products, pharmaceuticals, etc. are required to have an oxygen barrier property in the packaging container in order to prevent the contents from being oxidized and deteriorated by oxygen in the air. In addition, when the contents containing volatile chemicals such as fragrances and medicinal ingredients are stored in the packaging container, the volatile chemicals in the contents permeate the packaging container and diffuse to the outside during the transportation and storage process. Therefore, the material of the packaging container is required to have a property of suppressing the permeation of volatile chemicals so that the contents do not deteriorate or deteriorate.
In addition, "odor transfer", in which external odors permeate the packaging container and attach to the contents during transportation and storage, is also a problem. From these viewpoints, the material of the packaging container is required to have a gas barrier property that suppresses the permeation of oxygen, odor, odor and the like.

Until now, many containers made of plastic or the like have been used as packaging containers. However, most of plastics are finite resources derived from petroleum, and they have high combustion heat even when they are disposed of, and problems such as environmental hormones have been pointed out. With the recent environmental protection-type thinking and the enforcement of the Containers and Packaging Recycling Law, it is necessary to switch from plastic materials to materials derived from renewable natural resources such as paper.

Conventionally, as a gas barrier material that suppresses the permeation of gas such as oxygen and odor, a resin film such as an aluminum foil or a polyvinylidene chloride resin, a film coated with these resins, a ceramic vapor-deposited film, or the like has been used. There is. A laminate in which such a gas barrier material is laminated on a base material is used as a packaging material (see, for example, Patent Document 1).

Since the above-mentioned aluminum foil has excellent gas barrier properties, it is often used as a gas barrier material. However, when the packaging material contains a metal such as aluminum foil, there is a problem that metal detection cannot be performed in the inspection of the product (particularly the contents). Further, there is a problem that the microwave oven cannot be used when the contents are to be heated. Furthermore, when disposing of used packaging containers, it is desirable to separate and collect them by material for recycling, but it is especially common in ordinary households to separate the aluminum foil from the packaging materials that make up the packaging container. It is impossible and it is difficult to separate and collect and reuse aluminum. When packaging materials containing aluminum foil are incinerated, the amount of incinerator residue increases, which may damage the incinerator.

On the other hand, gas barrier materials made of resin films and ceramic vapor-deposited films can solve the above-mentioned problems of metal detection and microwave oven use, but there is concern about the depletion of petroleum-derived resources, so conversion to renewable resources is desired. ing.

Paper is an example of a material derived from renewable natural resources. Since paper has a porous structure and high gas permeability, it cannot be used alone as a gas barrier material. Therefore, it is being studied to use a laminate (paper barrier laminate) in which a barrier layer having a gas barrier property is laminated on a paper substrate as a packaging material.
As a method of laminating a barrier layer on a paper base material, for example, a method of attaching a film containing a barrier layer to a paper base material has been studied. However, in such a method, a barrier layer containing a synthetic resin derived from petroleum is laminated on paper, which is a material derived from renewable natural resources, so that the thickness of the resin layer becomes thicker than that of the paper base material, and petroleum resources are used. It is not possible to break away from.

Therefore, a method of forming a barrier layer by coating a paper substrate with a resin composition having a gas barrier property has been studied (see, for example, Patent Document 2). With this method, it is possible to form a thin barrier layer, and it is possible to make a configuration that makes use of the strength of renewable paper.

In recent years, as another method for forming a barrier layer, polyvinyl alcohol, cellulose nanofibers, which are fine fibers of cellulose, etc., are used from the viewpoint of easy formation of a barrier layer on a paper substrate and safety. A method of forming a barrier layer by applying an aqueous coating liquid containing a material that can be melted or dispersed in water as a barrier material on a paper substrate has been considered (see, for example, Patent Documents 3 and 4). .. This method can also impart high gas barrier properties to the paper substrate. In particular, since cellulose is a biodegradable biomass-derived material, it is possible to make a structure that further utilizes the strengths of paper.

Japanese Unexamined Patent Publication No. 2004-299203 Japanese Patent No. 4365826 Japanese Unexamined Patent Publication No. 2016-064871 Japanese Unexamined Patent Publication No. 2015-024539

However, in the case of the barrier layer formed by the water-based coating liquid, the hydrophilicity of the barrier layer is high, so that the gas barrier property is liable to deteriorate due to humidity, moisture of the contents, and the like.

When the paper barrier laminate is used as a paper container, a resin layer such as polyethylene is laminated on the barrier layer as a sealant layer for bonding at the time of container assembly, but the adhesion between the barrier layer and the resin layer is poor. There is a problem of scarcity. This is because the barrier layer is hydrophilic and the resin layer is hydrophobic, so that the surface free energy difference between the two is large, and the energy becomes unstable when the two come into contact with each other.

Based on the above circumstances, it is an object of the present invention to provide a paper barrier laminate and a paper barrier container in which deterioration of gas barrier properties due to humidity and moisture is suppressed and high adhesion between a barrier layer and a resin layer are compatible. ..

A first aspect of the present invention is a paper substrate, a barrier layer formed on one surface of the paper substrate and containing a barrier material that can be melted or dispersed in a medium containing water as a main component, and the barrier. A bonding reinforcing layer formed on the layer and a resin layer formed on the bonding reinforcing layer are provided, the barrier material is cellulose nanofibers obtained by micronizing natural cellulose, and the bonding reinforcing layer is polyethylene. It is a paper barrier laminate made of an imine-based anchor coating agent or a polybutadiene-based anchor coating agent.

The barrier layer may contain a component contained in the joint reinforcing layer.
The component may be a hydrophobic material.

The cellulose nanofibers may have a carboxy group of 0.1 mmol / g or more and 3.5 mmol / g or less per cellulose mass.
The average fiber diameter of the cellulose nanofibers may be 2 nm or more and 1000 nm or less.

The thickness of the barrier layer may be 100 nm or more and 2000 nm or less.

The second aspect of the present invention is a paper barrier container formed by using the paper barrier laminate of the present invention.

According to the paper barrier laminate and the paper barrier container of the present invention, it is possible to suppress deterioration of the gas barrier property due to humidity and moisture and to achieve both high adhesion between the barrier layer and the resin layer.

It is sectional drawing which shows typically the paper barrier laminated body which concerns on one Embodiment of this invention. It is a perspective view which shows typically an example of the paper barrier container which concerns on one Embodiment of this invention.

An embodiment of the present invention will be described with reference to FIGS. 1 and 2.
FIG. 1 is a cross-sectional view schematically showing the paper barrier laminate 1 of the present embodiment. The paper barrier laminate 1 was formed on the paper base material 10, the barrier layer 20 formed on the paper base material 10, the bonding reinforcing layer 30 formed on the barrier layer 20, and the bonding reinforcing layer 30. It includes a resin layer 40.

The paper used as the material of the paper base material 10 is not particularly limited, and can be appropriately selected depending on the use of the paper barrier laminate 1. For example, ordinary high-quality paper, various coated papers, backing papers, impregnated papers, cardboards and art papers, coated papers, kraft papers, coated balls, ivory papers, card papers, cup base papers and the like can be exemplified.

The barrier layer 20 of the present embodiment is formed on one surface 10a of the paper base material 10. The barrier layer 20 may be formed on both sides of the paper substrate 10 (one surface 10a and the other surface 10b).
The barrier layer 20 contains a barrier material that can be dissolved or dispersed in a medium containing water as a main component, and is configured to exhibit gas barrier properties as a layer. Examples of the barrier material contained in the barrier layer 20 include cellulose nanofibers (CNF), polyvinyl alcohol resin, ethylene-vinyl alcohol copolymer resin, aqueous polyurethane resin, polyacrylic acid resin, polyuronic acid resin, and carboxymethyl cellulose (CMC). Examples include resins and starches. Of these, CNF and polyvinyl alcohol resins are preferable from the viewpoint of high gas barrier properties and coatability. The barrier material contained in the barrier layer 20 may be one kind or a mixture of two or more kinds.

The above-mentioned CNF is a fine fiber of cellulose obtained by refining natural cellulose. The average diameter (average fiber diameter) of a general cellulose fiber is 2 nm or more and 10 μm or less. The average fiber length of general cellulose fibers ranges from several hundred nm to several μm.
As a method for measuring the average diameter of cellulose fibers, shape observation is performed using a device such as an atomic force microscope (AFM) or a scanning electron microscope (SEM), and the fiber diameter of an arbitrary number of samples is measured. There are a method of taking an average and a method of measuring from the result of particle size measurement of a coating liquid containing cellulose fibers using a device such as a particle size distribution meter, but the average fiber diameter in the present invention is measured by any method. May be good.

The average fiber diameter of CNF used as the barrier material of the barrier layer 20 is preferably 2 nm or more and 1000 nm or less, for example. In this case, the barrier layer 20 can be formed as a dense film having sufficiently small voids. That is, the barrier layer 20 having excellent gas barrier properties can be formed.

The gas barrier property is exhibited by the barrier layer 20 blocking the permeation of gas (gas). In order to develop the gas barrier property, it is important that the barrier layer 20 is sufficiently dense so that the gas molecules to be shielded cannot permeate, and that a plurality of voids do not communicate with each other. CNF has high rigidity, and fibers are firmly bonded to each other due to the hydrogen bond effect of a large number of hydroxyl groups and carboxy groups present in the molecule, so that a dense film can be formed. In addition, CNF has high crystallinity and small molecular movement, so it is considered that CNF tends to exhibit high gas barrier properties.

As the CNF used for the barrier layer 20, a CNF having a carboxy group introduced into the cellulose molecule can be preferably used. As a method for introducing a carboxy group into a cellulose molecule, a known method can be appropriately used, and for example, a TEMPO (2,2,6,6-tetramethyl-1-pipedinyloxyradical) catalyst can be used. There is a method of oxidizing using an oxidizing agent such as sodium hypochlorite and a bromide such as sodium bromide while adjusting the pH.
According to the above method, the hydroxyl group at the C6 position of the glucose unit on the surface of the cellulose microfibrils is selectively carboxylated. In the TEMPO-oxidized cellulose obtained by this method, the electrostatic repulsion between the fibers increases and it becomes easy to disperse. Therefore, a dispersion liquid of cellulose nanofibers can be obtained by performing a slight defibration treatment in water. The TEMPO-oxidized cellulose can be made into nanofibers while maintaining the high crystallinity of the raw material cellulose, and is suitable as a barrier material.

The amount of carboxy group introduced into the cellulose molecule is preferably in the range of 0.1 mmol / g or more and 3.5 mmol / g or less, and 1.0 mmol / g or more and 1.8 mmol, based on the mass of cellulose. It is more preferably in the range of / g or less. The amount of carboxy group can be measured by the conductivity titration method of cellulose.
If the carboxy group is less than 0.1 mmol / g, the dispersibility may be lowered and the barrier layer 20 may not sufficiently exhibit the gas barrier property. Further, when the carboxy group is 3.5 mmol / g or more, the crystallinity of cellulose is lowered, and the oxygen barrier property and the water resistance under high humidity may be lowered.
That is, when the amount of carboxy groups is in the range of 0.1 mmol / g or more and 3.5 mmol / g or less, the dispersion stability is increased due to the electrostatic repulsion effect of the carboxy groups, and the barrier layer 20 is uniformly spread on the paper substrate 10. It becomes easy to form. As a result, the uniformly formed barrier layer tends to sufficiently exhibit gas barrier properties, and oxygen barrier properties under high humidity and deterioration of water resistance are suitably suppressed, which is preferable.

As described above, since the barrier layer 20 contains a barrier material that can be melted or dispersed in a medium containing water as a main component, the barrier layer 20 can be easily formed on the paper substrate 10. Specifically, a water-based coating liquid in which a barrier material is melted or dispersed in a medium containing water as a main component is prepared, and this water-based coating liquid is simply applied onto a paper substrate 10 and dried to obtain a barrier layer 20. Is formed on the paper substrate 10. That is, the surface of the paper base material 10 can be easily modified to easily impart gas barrier properties to the paper base material 10.

As a method for applying the water-based coating liquid, various known methods can be used. Specifically, a gravure coater, a dip coater, a reverse coater, a wire bar coater, a die coater and the like can be used. By using the wet film forming method, a coating film of the water-based coating liquid can be uniformly formed on the surface of the paper substrate 10. Water is preferable as the medium, but a solvent such as alcohol can be appropriately added in order to improve the drying efficiency and the coatability.

The thickness of the barrier layer 20 is preferably 100 nm or more and 2000 nm or less. If the thickness of the barrier layer is less than 100 nm, the surface of the paper base material 10 cannot be sufficiently covered, and there is a high possibility that pinholes will occur in the barrier layer and sufficient gas barrier properties cannot be obtained. Further, when the thickness of the barrier layer is larger than 2000 nm, the material cost of the barrier layer increases, the drying load during coating drying increases, and the manufacturing efficiency decreases. This reduces productivity and increases total manufacturing costs.

Further, in order to make the thickness of the barrier layer 20 larger than 2000 nm, it is necessary to increase the amount of the coating liquid applied to the paper substrate 10 when forming the barrier layer 20. When the amount of the coating liquid increases, the amount of the coating liquid soaked into the paper base material 10 increases, and the paper base material 10 may swell excessively. As a result, the shrinkage of the paper base material 10 after drying becomes large, and the surface of the paper base material 10 becomes uneven. The unevenness on the surface of the paper base material 10 not only causes a poor appearance, but may also adversely affect the process after forming the barrier layer 20 (for example, the process of forming the bonding reinforcing layer 30).
That is, by setting the thickness of the barrier layer 20 in the range of 100 nm or more and 2000 nm or less, sufficient gas barrier properties can be exhibited and an increase in manufacturing cost can be suitably suppressed. Further, it is possible to suitably suppress the occurrence of irregularities on the surface of the paper base material 10 after the barrier layer 20 is formed.

The resin layer 40 is formed on the barrier layer 20 with the joint reinforcing layer 30 sandwiched between them. In the present embodiment, it is also formed on the other surface 10b of the paper substrate 10, but this is not essential and may be provided only on the one surface 10a side.
When the resin layers 40 are provided on both sides of the paper barrier laminate 1 in the thickness direction as in the present embodiment, the paper barrier laminate 1 is used to suitably manufacture a paper container such as a paper cup as described later. can do.

The resin layer 40 can impart liquid resistance to a liquid having high stain resistance and permeability to the paper barrier laminate 1, and can improve shape retention during molding or the like. Further, when the resin layer 40 is formed of a heat-sealable resin, the airtightness of the manufactured paper container can be improved and leakage of the contents can be prevented.

The specific material of the resin layer 40 is not particularly limited, and various known resin materials such as polyolefin-based, epoxy-based, urethane-based, isocyanate-based, polyester-based, and plant-derived materials (bioplastics) can be used.
Examples of the heat-sealable resin include polyethylene-based resins such as low-density polyethylene resin (LDPE), medium-density polyethylene resin (MDPE), high-density polyethylene resin (HDPE), and linear low-density polyethylene (LLDPE), and polypropylene resins. It can be selected from polypropylene-based resins such as propylene-ethylene random copolymer and propylene-ethylene block copolymer, but LDPE is preferable in consideration of workability, processability, cost and the like.

The resin layer 40 can be formed on the joint reinforcing layer 30 or the paper base material 10 by the same method as in the case of manufacturing a general packaging material. As the method, for example, a wet lamination method, a dry lamination method, a solventless lamination method, a thermal lamination method, an extrusion lamination method and the like can be exemplified. Of these methods, the extrusion lamination method is preferable in that it is easy and low in cost. The extrusion lamination method may be any of single laminating, tandem laminating, coextruding laminating, and sandwich laminating.

The method of forming the resin layer 40 using LDPE is not particularly limited, and for example, a method of polymerizing an ethylene monomer by a high-pressure polymerization method may be used. Further, the polymerization conditions such as temperature, pressure and polymerization time are not particularly limited and can be appropriately set.

The bonding reinforcing layer 30 is formed on the barrier layer 20, and the bonding strength between the resin layer 40 and the barrier layer 20 formed on the barrier layer 20 is higher than that in the case where the resin layer is directly formed on the barrier layer 20. It is high.
The structure of the joint reinforcing layer 30 differs depending on the method of forming the resin layer 40. For example, when the resin layer 40 is formed by the extrusion lamination method, known known anchor coating agents for extrusion lamination such as organic titanium-based, urethane-based, polyethyleneimine-based, and polybutadiene-based can be appropriately selected and used. When the resin layer 40 is formed by the dry lamination method, a known dry lamination adhesive such as polyester or polyether can be appropriately selected and used as the material of the bonding reinforcing layer 30.

The bonding reinforcing layer 30 not only enhances the adhesion between the barrier layer 20 and the resin layer 40, but also has the effect of suppressing the barrier deterioration of the barrier layer 20 caused by humidity and moisture. This effect is considered to be exerted by the following mechanism. That is, when the bonding reinforcing layer 30 is formed on the barrier layer 20, a part of the material of the bonding reinforcing layer 30 permeates the barrier layer 20 and then polymerizes or cures to increase the bonding strength between the barrier materials. It works like that. As a result, the barrier layer 20 has a structure containing the components contained in the joint reinforcing layer 30, and the water resistance of the barrier layer 20 is improved as compared with the case where the barrier layer is provided alone, and the structure is such that moisture is less likely to penetrate. Become.

From the viewpoint of the barrier deterioration suppressing effect described above, it is preferable that the joint reinforcing layer 30 is formed by the wet film forming method. By using the wet film forming method, the components of the bonding reinforcing layer 30 easily permeate into the barrier layer 20, which preferably contributes to the improvement of the water resistance of the barrier layer 20. As the wet film forming method, various known methods can be appropriately selected and used. For example, a method such as a gravure coater, a dip coater, a reverse coater, a wire bar coater, and a die coater can be exemplified.

When the bonding reinforcing layer 30 is formed by the wet film thickness method, the amount of the coating liquid containing the material of the bonding reinforcing layer is not particularly limited as long as it can achieve both improvement of bonding strength and suppression of barrier deterioration. The wet film thickness of the applied coating liquid is preferably ½ or more of the film thickness of the barrier layer 20, and more preferably the wet film thickness is ½ or more of the film thickness of the barrier layer 20. By doing so, the components of the bonding reinforcing layer 30 are more likely to permeate into the barrier layer 20, and the barrier property deterioration suppressing effect is suitably exhibited.

The bonding reinforcing layer 30 preferably contains a hydrophobic material in any of the above-described embodiments. When the hydrophobic material permeates the barrier layer 20, a higher barrier deterioration suppressing effect can be obtained. Most of the urethane-based anchor coating agents and dry lamination adhesives described above are hydrophobic materials.

The paper barrier laminate 1 of the present embodiment can be used as a material for various paper containers molded into a desired shape such as a cup shape, a bottle shape, or a box shape.
FIG. 2 shows a cup-shaped paper barrier container 100 formed of the paper barrier laminate 1 as an example of a paper container. The paper barrier container 100 of the present embodiment has a substantially circular bottom member 101 and a body member 102 joined to the bottom member 101 to form a side surface.

When manufacturing the paper barrier container 100, first, the sheet-shaped paper barrier laminate 1 is punched out with a punching die to form the bottom member 101 and the body material 102. Next, the bottom member 101 and the body member 102 are joined into a cup shape while being joined by a known cup molding machine. Further, when the separately prepared lid material 110 is joined to the upper opening of the body material 102 in a peelable manner and sealed, the paper barrier container 100 is completed. When the resin layer 40 in the paper barrier laminate 1 is formed of a heat-sealable resin, the bottom member 101 and the body member 102 can be easily joined by heat-sealing, so that the paper barrier container can be easily formed. can.

The lid material 110 is not essential in the paper barrier container of the present embodiment, and may not be provided if it is not necessary. Further, the lid material 110 does not necessarily have to be formed of the paper barrier laminate of the present invention, and a part or all of the lid material 110 may be formed by using another barrier sheet material. Similarly, in the paper barrier container of the present invention, if at least a part of the paper barrier laminate of the present invention is used, a part or all of the bottom member 101 and the body material 102 can be made of another barrier sheet material. It may be formed using.
Further, when forming the paper barrier container, the arrangement of the barrier layer 20 is not particularly limited. That is, the barrier layer 20 may be arranged on the inner surface side of the paper barrier container with respect to the paper base material 10, or the barrier layer 20 may be arranged on the outer surface side with respect to the paper base material 10.

The paper barrier laminate and the paper barrier container of the present embodiment will be further described with reference to Examples and Comparative Examples. However, the technical scope of the present invention is not limited to the specific contents of these examples.

First, a procedure for producing an aqueous coating liquid for forming the barrier layer 20 will be described.

[Preparation of water-based coating liquid 1]
30 g of softwood kraft pulp was immersed in 600 g of water and dispersed with a mixer.
To the dispersed pulp slurry, 0.3 g of TEMPO previously dissolved in 200 g of water and 3 g of NaBr were added, and further diluted with water to make 1400 mL in total.
The inside of the system was kept at 20 ° C., and an aqueous sodium hypochlorite solution was weighed and added dropwise so as to have 10 mmol per 1 g of cellulose.
After the start of dropping the sodium hypochlorite aqueous solution, the pH started to decrease, but the pH of the system was kept at 10 by dropping a 0.5N sodium hydroxide aqueous solution at any time.
After 4 hours, when the dropping amount of the 0.5N sodium hydroxide aqueous solution reached 2.8 mmol / g, 30 g of ethanol was added to stop the reaction.
0.5N hydrochloric acid was added to the reaction system to reduce the pH to 2. Oxidized pulp was filtered and washed repeatedly with 0.01N hydrochloric acid or water to obtain oxidized pulp.
When the conductivity titration of the oxidized pulp was performed with a 0.1N sodium hydroxide aqueous solution using an automatic titrator (DKK-TOA, AUT-701), the calculated amount of carboxy group was 1.6 mmol / g.
The obtained oxidized pulp was diluted with water and adjusted to pH 9 with a 0.5N aqueous sodium hydroxide solution to obtain a 1% suspension of oxidized pulp. By dispersing this suspension with a high-speed stirrer for 2 hours, an aqueous coating liquid 1 as a dispersion liquid containing CNF as a barrier material was obtained.

[Preparation of water-based coating liquid 2]
A commercially available 4% solid content aqueous solution of polyvinyl alcohol (PVA) (molecular weight 100,000, saponification degree 98%) was prepared and used as an aqueous coating solution 2.

[Preparation of water-based coating liquid 3]
The water-based coating liquid 2 was mixed with the above-mentioned water-based coating liquid 1 so that the mass ratio of cellulose and PVA was 1: 1. Further, by stirring with a magnetic stirrer for 3 hours, an aqueous coating liquid 3 as a PVA-added cellulose fine fiber dispersion liquid was obtained.

[Evaluation of water-based coating liquid 1]
The aqueous coating solution 1 containing CNF was diluted to a concentration of 0.01%, applied onto mica, and the fiber morphology was observed by AFM. Then, the average width of 10 arbitrary fibers existing one by one was obtained, and this was used as the average fiber diameter. The average fiber diameter of CNF in the water-based coating liquid 1 calculated by the above method was 4 nm.

Next, a procedure for producing a coating liquid for forming the joint reinforcing layer 30 will be described.

[Preparation of coating liquid 1]
Urethane-based anchor coating agent (AD-335AE manufactured by Toyo Morton Co., Ltd., solid content 40% by weight (wt%)) and ethyl acetate are mixed so as to have a mass ratio of 5/95 to obtain a coating liquid 1. rice field. The solid content of the coating liquid 1 after preparation was 2.0 wt%.

[Preparation of coating liquid 2]
A polyethyleneimine-based anchor coating agent (AD-372MW, NV7 manufactured by Toyo Morton Co., Ltd.), water, and 2-propanol were mixed so as to have a mass ratio of 15/40/45 to obtain a coating liquid 2. The solid content of the coating liquid 2 after preparation was 1.05 wt%.

[Preparation of coating liquid 3]
A 10/90 mass ratio of a polyethyleneimine-based anchor coating agent (Polyment NK-380, NV30 manufactured by Nippon Shokubai Co., Ltd.), which has a higher hydrophobicity than that used for the coating liquid 2, and 4-methyl-2-pentanone. The mixture was mixed so as to obtain a coating liquid 3. The solid content of the coating liquid 3 after preparation was 3.0 wt%.

[Preparation of coating liquid 4]

A polybutadiene anchor coating agent (Titabond T-180E, NV10 manufactured by Nippon Soda Co., Ltd.) and 2-propanol were mixed so as to have a mass ratio of 10/90 to obtain a coating liquid 4. The solid content of the coating liquid 4 after preparation was 1.0 wt%.

Subsequently, the procedure for manufacturing the paper barrier laminate and the paper barrier container in each Example and Comparative Example will be shown.

[Example 1]
The uncoated cup base paper having a basis weight of 260 g / m ² was used as the paper base material 10. A water-based coating liquid 1 was applied to one surface of the paper substrate with a bar coater so as to have a dry film thickness of 1000 nm, and dried in an oven at 120 ° C. for 5 minutes. As a result, the barrier layer 20 was formed on one surface of the paper substrate 10.
Next, the coating liquid 1 was applied to the upper surface of the barrier layer 20 using a bar coater so that the dry weight was 0.03 g / m ^2, and dried in an oven at 100 ° C. for 1 minute. As a result, the joint strengthening layer 30 was formed on the barrier layer 20. The wet film thickness of the coating liquid 1 was 1.7 μm.
Next, after corona treatment was applied to the upper surface of the bonded reinforcing layer 30, LDPE resin (Novatec LD LC520 manufactured by Japan Polyethylene Corporation) was supplied onto the bonded reinforcing layer 30 by extrusion lamination to form a resin layer 40. .. Further, after corona treatment was applied to the other surface of the paper substrate 10, the same LDPE resin was supplied onto the paper substrate 10 by extrusion lamination to form a resin layer 40 on the other surface as well. The thickness of the resin layer 40 on the barrier layer 20 side was 30 μm, and the thickness of the resin layer 40 on the opposite side of the barrier layer 20 was 20 μm. From the above, the paper barrier laminated body of Example 1 was obtained. The corona treatment is a treatment performed to improve the adhesion between layers.
Further, the paper barrier laminate of Example 1 is punched out with a punching die to produce a bottom member 101 and a body material 102, and the bottom member 101 and the body material 102 are formed by using a cup molding machine while the barrier layer 20 is on the inner surface side. The paper barrier container of Example 1 was produced by assembling and joining. The paper barrier container of Example 1 is cup-shaped and has a capacity of 200 mL.

[Example 2]
The paper barrier laminate and the paper barrier container of Example 2 were produced in the same procedure as in Example 1 except that the water-based coating liquid 2 was applied to form the barrier layer 20.

[Example 3]
The paper barrier laminate and the paper barrier container of Example 3 were produced in the same procedure as in Example 1 except that the water-based coating liquid 3 was applied to form the barrier layer 20.

[Example 4]
The paper barrier laminate and the paper barrier container of Example 4 were produced in the same procedure as in Example 1 except that the coating liquid 2 was applied to form the bonding reinforcing layer 30. The wet film thickness of the coating liquid 2 was 3.2 μm.

[Example 5]
The paper barrier laminate and the paper barrier container of Example 5 were produced in the same procedure as in Example 1 except that the coating liquid 3 was applied to form the bonding reinforcing layer 30. The wet film thickness of the coating liquid 3 was 1.3 μm.

[Example 6]
The paper barrier laminate and the paper barrier container of Example 6 were produced in the same procedure as in Example 1 except that the coating liquid 4 was applied to form the bonding reinforcing layer 30. The wet film thickness of the coating liquid 4 was 3.8 μm.

[Comparative Example 1]
The paper barrier laminate and the paper barrier container of Comparative Example 1 were produced in the same procedure as in Example 1 except that the bonding reinforcing layer was not formed on the barrier layer 20.

[Comparative Example 2]
The paper barrier laminate and the paper barrier container of Comparative Example 2 were produced in the same procedure as in Example 2 except that the joint reinforcing layer was not formed on the barrier layer 20.

[Comparative Example 3]
The paper barrier laminate and the paper barrier container of Comparative Example 3 were produced in the same procedure as in Example 3 except that the bonding reinforcing layer was not formed on the barrier layer 20.

The following evaluations were performed using the paper barrier laminates and paper barrier containers of each Example and Comparative Example.

[Evaluation of joint strength between barrier layer and resin layer]
The paper barrier laminates of each example and each comparative example were cut out into strips having a width of 15 mm and a length of 10 cm to prepare test pieces. The test pieces of each example were subjected to T-shaped peeling at a tensile speed of 300 mm / min in accordance with JIS-K-7127, and the peel strength (N / 15 mm) of the resin layer was measured. The test piece after the peel strength measurement was stained with a 1% diluted solution of o-toluidine blue. Since this liquid can dye the carboxyl group of CNF in purple and the paper in blue, it is possible to identify the layers where peeling has occurred by dyeing the peeled surface after measuring the adhesion strength.
For those in which peeling occurs in the middle portion of the paper base material in the thickness direction, the barrier layer 20 and the resin are broken because the paper base material is destroyed before the peeling occurs at the interface between the barrier layer 20 and the resin layer 40. It can be said that the bond with the layer 40 is stronger.

[Oxygen permeability (isopressure method) (cm ³ / m ²・ day ・ Pa)]
Each Example and each in an atmosphere of 30 ° C., 40% RH (relative humidity), and 30 ° C., 90% RH using an oxygen permeability measuring device MOCON (OX-TRAN2 / 21, manufactured by Modern Control). The oxygen permeability of the paper barrier laminate of the comparative example was measured.
The measured values under each atmosphere are shown, the oxygen permeability at 40% RH is "A", the oxygen permeability at 90% RH is "B", and B / A is an index of deterioration of oxygen barrier property due to a high humidity environment. And said. It was defined that when the B / A was 5 or less and the B was 50 cm ³ / m ² · day · Pa or less, the deterioration of the oxygen barrier property due to the high humidity environment was sufficiently suppressed.

[Oxygen barrier property evaluation of paper barrier container]
The paper barrier containers of each example and each comparative example are filled with 200 mL of deoxidized pure water, and then a lid material having an oxygen barrier property (polyethylene 30 μm / aluminum 9 μm / PET 38 μm) is joined by heat sealing. It was sealed and stored in a 5 ° C environment for 14 days. After storage, the lid material was opened and the dissolved oxygen concentration in pure water was immediately measured.

The results are shown in Table 1.

As shown in Table 1, in Comparative Examples 1 to 3 in which the bonding reinforcing layer was not provided between the barrier layer and the resin layer, peeling occurred at the interface between the barrier layer and the resin layer. Regarding oxygen permeability, the B / A value was 5 or more, and the barrier property was significantly deteriorated by the high humidity environment.

On the other hand, in Examples 1 to 6 in which the bonding reinforcing layer is provided between the barrier layer and the resin layer, the paper base material is destroyed without peeling at the interface between the barrier layer and the resin layer, and the bonding strength is improved. It was shown to be. Regarding oxygen permeability, the B / A value is 5 or less, and B is 50 cm ³ / m ² · day · Pa or less, and even if the barrier layer uses a water-soluble barrier material, it is highly humid. Deterioration of gas barrier property due to the environment was sufficiently suppressed. In Examples 1 to 3 and 5 in which a material having a higher hydrophobicity was contained in the joint reinforcing layer, the B / A value was smaller, and the effect of suppressing the deterioration of the barrier property due to the high humidity environment was further excellent.

In the paper barrier container of each example, the dissolved oxygen concentration after storage of the filled pure water was lower than that of the paper barrier container of the comparative example. It is considered that this is because the paper barrier laminate of the example has high water resistance, and therefore the deterioration of the barrier property is unlikely to occur even if the liquid contents are stored.

Although one embodiment and the examples of the present invention have been described above, the technical scope of the present invention is not limited to the contents of the above-described embodiments and the like, and various components thereof are used without departing from the spirit of the present invention. It is possible to make or delete changes to.

For example, when the resin layer is formed on the paper base material without the barrier layer as in the other surface 10b of the paper base material 10 in the above embodiment, the bonding reinforcing layer is formed between the paper base material and the resin layer. May be provided.

Further, in addition to the above-mentioned layers, the barrier laminate of the present invention may be provided with a printing layer, an antistatic layer, or the like to which a desired design effect, information, or the like is imparted, as necessary.

1 Paper barrier laminate 10 Paper base material 20 Barrier layer 30 Bonding reinforcement layer 40 Resin layer 100 Paper barrier container

Claims (7)

Paper substrate and
A barrier layer formed on one surface of the paper substrate and containing a barrier material that can be melted or dispersed in a medium containing water as a main component,
The joint strengthening layer formed on the barrier layer and
The resin layer formed on the joint reinforcing layer and
Equipped with
The barrier material is cellulose nanofiber obtained by refining natural cellulose.
The joint reinforcing layer is made of a polyethyleneimine-based anchor coating agent or a polybutadiene-based anchor coating agent.
Paper barrier laminate. The paper barrier laminate according to claim 1, wherein the barrier layer contains a component contained in the joint reinforcing layer. The paper barrier laminate according to claim 2, wherein the component is a hydrophobic material. The paper barrier laminate according to claim 1 , wherein the cellulose nanofibers have a carboxy group of 0.1 mmol / g or more and 3.5 mmol / g or less per cellulose mass. The paper barrier laminate according to claim 1 or 4 , wherein the average fiber diameter of the cellulose nanofibers is 2 nm or more and 1000 nm or less. The paper barrier laminate according to any one of claims 1 to 5 , wherein the thickness of the barrier layer is 100 nm or more and 2000 nm or less. A paper barrier container formed by using the paper barrier laminate according to any one of claims 1 to 6.

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