JP2017222033A - Paper barrier laminate and mold container - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a paper barrier laminate that can prevent a defect from occurring in a resin layer.SOLUTION: A paper barrier laminate has a paper substrate 1, a barrier layer 2 formed to be put on one face 1a of the paper substrate 1, and a resin layer 3 formed to be put on the barrier layer 2, the resin layer 3 being a low-density polyethylene with a melt mass flow rate of 3.0-8.0 g/10 min., and the resin layer 3 formed on the barrier layer 2 having a thickness of 25 μm or more.SELECTED DRAWING: Figure 1

Description

  The present invention protects the contents from external gases such as oxygen and odor, further suppresses the deterioration and alteration of the odor and efficacy of the contents, and prevents leakage to the outside, The present invention relates to a paper barrier laminate and a molded container suitable for toiletry products and pharmaceutical packaging.

  Many foods, pharmaceuticals, and the like are required to have an oxygen barrier property in containers and packaging in order to prevent the contents from being oxidized and deteriorated by oxygen in the air. In addition, when contents containing volatile drugs such as fragrances and medicinal ingredients are stored in a packaging container, the volatile drugs in the contents permeate the packaging container and diffuse to the outside during the transportation and storage process. In order to prevent the contents from deteriorating or deteriorating, the packaging material for the contents needs to be configured to suppress the permeation of volatile chemicals. In addition, “smell transfer” in which an external odor permeates through the packaging container and gets into the contents during transportation and storage is also a problem. As described above, the packaging material is required to have a gas barrier property that does not transmit gas such as oxygen and odor.

  Until now, many molded containers made of plastic have been used as packaging containers. However, plastics are mostly finite resources derived from petroleum, and the heat of combustion is high even when discarded, and problems with environmental hormones have been pointed out. With recent environmental conservation 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 gases such as oxygen and odor, resin films such as aluminum foil, polyvinylidene chloride resin, films coated with these resins, ceramic vapor deposition films, and the like have been used. Yes. And the laminated body which laminated | stacked such a gas barrier material on the base material is used as a packaging material (for example, refer patent document 1).

  The above-mentioned aluminum foil is frequently used as a gas barrier material because of its excellent gas barrier properties. However, when the packaging material contains a metal such as an aluminum foil, there is a problem that the metal detection cannot be performed in the inspection of the product (particularly the contents). In addition, 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. However, separating and separating the aluminum foil from the packaging material that forms the packaging container is particularly important in general households. It is impossible, and it is difficult to collect and reuse aluminum separately. If the packaging material containing aluminum foil is incinerated, the incineration residue increases and the incinerator may be damaged.

  On the other hand, gas barrier materials consisting 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 it is desirable to switch to renewable resources. ing.

Paper is an example of a material derived from renewable natural resources. Since paper has a high porous gas permeability, it cannot be used alone as a gas barrier material. Then, using the laminated body (paper barrier laminated body) which laminated | stacked the barrier layer which has gas barrier property on the paper base material is examined as a packaging material.
As a technique for laminating a barrier layer on a paper base material, for example, a technique of attaching a film including a barrier layer to a paper base material has been studied. However, in such a method, a barrier layer made of metal or petroleum-derived synthetic resin or the like is laminated on paper, which is a renewable natural resource-derived material, so that the thickness of the resin layer becomes thicker than the paper substrate, The escape from oil resources cannot be solved.

  Then, the method of forming a barrier layer by providing the resin composition which has gas-barrier property on a paper base material by coating is examined (for example, refer patent document 2). In this method, it is possible to form a thin barrier layer, and it is possible to have a configuration that takes advantage of the strength of naturally derived paper.

  In recent years, as another method for forming a barrier layer by coating, an aqueous coating solution containing cellulose nanofibers, which are fine fibers of cellulose, is applied onto a paper substrate in consideration of safety to the environment and work surface. Thus, a method of forming a barrier layer has been considered (see, for example, Patent Document 3). This method can also impart high gas barrier properties to the paper substrate. Further, since cellulose is a biodegradable biomass-derived material, it can be configured to further utilize the strength of naturally derived paper.

JP 2004-299203 A Japanese Patent No. 4365826 Japanese Patent Laying-Open No. 2015-024539

However, when the barrier layer is formed by coating, the barrier layer becomes a thin layer of several μm or less, and therefore, the gas barrier property is easily deteriorated by an external factor. For example, in the case of a barrier layer formed with a water-based coating liquid, the gas barrier property tends to deteriorate due to the water content of the contents because of its high hydrophilicity.
In order to prevent deterioration of the gas barrier properties of the barrier layer, for example, it is conceivable to form a water-resistant resin layer on the barrier layer. However, by simply forming a resin layer on the barrier layer, when forming a laminate (paper barrier laminate) in which a paper base material, a barrier layer and a resin layer are laminated in order into a molding container, heat and stress are applied. May cause defects such as cracks and pinholes in the resin layer. In this case, moisture passes through the defects in the resin layer and reaches the barrier layer, thereby deteriorating the gas barrier property.

  The present invention has been made in view of the above-described circumstances, and an object of the present invention is to provide a paper barrier laminate and a molded container capable of suppressing the occurrence of defects in a resin layer during molding.

  A first aspect of the present invention comprises a paper base material, a barrier layer formed to overlap with at least one surface of the paper base material, and a resin layer formed to overlap with at least the barrier layer, The resin layer is low density polyethylene having a melt mass flow rate of 3.0 to 8.0 g / 10 min, and the thickness of the resin layer formed on the barrier layer is 25 μm or more. It is a paper barrier laminate.

  The barrier layer may include a barrier material that has gas barrier properties and can be melted or dispersed in a medium containing water as a main component.

  The barrier layer may include cellulose nanofibers obtained by refining natural cellulose.

  The cellulose nanofiber may have a carboxyl 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 nanofiber may be 2 nm or more and 1000 nm or less.

  The barrier layer may have a thickness of 100 nm to 2000 nm.

  The second aspect of the present invention is a molded container comprising the paper barrier laminate according to the first aspect of the present invention.

  According to the present invention, since the melt mass flow rate (MFR) of the low density polyethylene forming the resin layer is 3.0 to 8.0 g / 10 minutes, the stress generated when the paper barrier laminate is molded into a molding container. It is possible to suppress the occurrence of defects such as cracks and pinholes in the resin layer due to heat and heat. Therefore, deterioration of the gas barrier property of the barrier layer can be suitably suppressed.

It is sectional drawing which shows typically a paper barrier laminated body in one Embodiment of this invention. It is a perspective view showing typically an example of a forming container concerning one embodiment of the present invention.

Hereinafter, details of the present invention will be described based on embodiments.
As shown in FIG. 1, a paper barrier laminate 100 according to the present embodiment is formed by overlapping a paper base material 1, a barrier layer 2 formed over the paper base material 1, and a barrier layer 2. The resin layer 3 is provided.

  The paper substrate 1 is not particularly limited and can be appropriately selected depending on the application. Examples of the paper base 1 include normal high-quality paper, various coated papers, backing paper, impregnated paper, cardboard and art paper, coated paper, craft paper, coated ball, ivory paper, card paper, and cup base paper. It is done.

The barrier layer 2 may be formed on, for example, both surfaces (one surface 1a and the other surface 1b) of the paper base material 1, but in this embodiment, it is formed only on one surface 1a of the paper base material 1. .
The barrier layer 2 has gas barrier properties. The barrier layer 2 of the present embodiment includes a barrier material that can be dissolved or dispersed in a medium containing water as a main component. Examples of the barrier material include cellulose nanofiber, polyvinyl alcohol resin, ethylene-vinyl alcohol copolymer resin, aqueous polyurethane resin, polyacrylic acid resin, polyuronic acid resin, carboxymethyl cellulose (CMC) resin, starch and the like. Among these, considering the high gas barrier property and coating property, the barrier material is more preferably cellulose nanofiber or polyvinyl alcohol resin. The barrier material may be one selected from the above-described resins, or may be a mixture of two or more selected from the above-described resins.

  Further, in order to improve the gas barrier property, the barrier layer 2 includes an additive such as inorganic particles, an amino group that reacts with the binder resin, an epoxy group, a hydroxyl group, a carbodiimide group, a polyethyleneimine, in addition to the above-described barrier material. Further, a crosslinking agent having a functional group such as isocyanate may be contained. The barrier layer 2 may be blended with additives such as pigments, dyes, and dispersants at a level that does not impair the effects of the present invention, depending on the required characteristics.

The cellulose nanofibers described above are cellulose fine fibers (hereinafter referred to as “cellulose fibers”) obtained by refining natural cellulose. The average diameter (average fiber diameter) of the cellulose fibers is 2 nm or more and 10 μm or less. The average fiber length of the cellulose fibers is in the range of several hundred nm to several μm.
The method for measuring the average diameter of cellulose fibers is to observe the shape using an apparatus such as an atomic force microscope (AFM) or a scanning electron microscope (SEM), and measure the fiber diameter of any number of samples. 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 an apparatus such as a particle size distribution meter.

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

  The gas barrier property is manifested by the barrier layer 2 blocking gas (gas) permeation. In order to develop gas barrier properties, it is important that the barrier layer 2 is sufficiently dense to prevent gas molecules to be shielded from passing therethrough and has no continuous voids. Cellulose nanofibers have high rigidity, and the fibers are strongly bonded to each other by the hydrogen bonding effect of hydroxyl groups and carboxy groups present in the molecule, so that a dense film can be formed. Cellulose nanofibers are considered to exhibit good gas barrier properties because of high glass transition temperature (Tg) and crystallinity and small movement of molecules.

Especially as a cellulose nanofiber used for the barrier layer 2, the cellulose nanofiber which introduce | transduced the carboxy group into the cellulose molecule can be used conveniently. As a method for introducing a carboxy group into a cellulose molecule, any of known methods can be used as appropriate. For example, a TEMPO (2,2,6,6-tetramethyl-1-pipedinyloxy radical) catalyst And oxidizing with an oxidizing agent such as sodium hypochlorite and a bromide such as sodium bromide while adjusting the pH.
According to this method, the hydroxyl group at the C6 position of the glucose unit on the surface of the cellulose microfibril is selectively carboxylated. In TEMPO-oxidized cellulose obtained by this method, the electrostatic repulsion between fibers is increased and the dispersion becomes easy to disperse. Therefore, a dispersion of cellulose nanofibers can be obtained by performing a slight fibrillation treatment in water. 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 groups introduced into the cellulose molecule is preferably in the range of 0.1 mmol / g to 3.5 mmol / g, and in the range of 1.0 mmol / g to 1.8 mmol / g per cellulose mass. More preferably. The amount of carboxy group can be measured by the conductivity titration method of cellulose.
The reason why the amount of the carboxy group is within the above range is that when the carboxy group is less than 0.1 mmol / g, the dispersibility is lowered and the barrier layer 2 cannot sufficiently exhibit the gas barrier property. Moreover, when the carboxy group is 3.5 mmol / g or more, the crystallinity of cellulose is lowered, and the oxygen barrier property and water resistance under high humidity are lowered.
That is, when the amount of the carboxy group is in the range of 0.1 mmol / g or more and 3.5 mmol / g or less, the dispersion stability is increased by the electrostatic repulsion effect of the carboxy group, and the barrier layer 2 is uniformly formed on the paper substrate 1. Can be formed. As a result, the barrier layer 2 can sufficiently exhibit gas barrier properties. Moreover, the oxygen barrier property in high humidity and the fall of water resistance can be suppressed suitably.

As described above, the barrier layer 2 of the present embodiment includes a barrier material that can be melted or dispersed in a medium containing water as a main component. For this reason, the barrier layer 2 can be easily formed on the paper substrate 1. Specifically, an aqueous coating liquid in which a barrier material is melted or dispersed in a medium is prepared, and the aqueous coating liquid is applied onto the paper substrate 1 and dried, whereby the barrier layer 2 is formed on the paper substrate 1. Can be formed. That is, it is possible to easily modify the surface of the paper substrate 1 and easily impart gas barrier properties to the paper substrate 1.
As a method for applying the aqueous coating liquid, a known method can be used. Specifically, a gravure coater, a dip coater, a reverse coater, a wire bar coater, a die coater, or the like can be used. By using the wet film formation method, a coating film of the aqueous coating liquid can be uniformly formed on the surface of the paper substrate 1. As the solvent for the coating liquid, water is preferable, but a solvent such as alcohol can be added to improve the drying efficiency and the coating property.

The thickness of the barrier layer 2 is preferably 100 nm or more and 2000 nm or less.
When the thickness of the barrier layer 2 is less than 100 nm, the surface of the paper substrate 1 cannot be sufficiently covered, and there is a high possibility that pinholes are generated in the barrier layer and sufficient gas barrier properties cannot be obtained. Moreover, when the thickness of the barrier layer 2 is larger than 2000 nm, the material cost of the barrier layer 2 increases, and the drying load at the time of coating drying increases, resulting in a decrease in production efficiency. Thereby, productivity will fall and cost will increase.

Further, in order to make the thickness of the barrier layer 2 larger than 2000 nm, it is necessary to increase the amount of the coating liquid applied to the paper substrate 1 when forming the barrier layer 2. When the amount of the coating liquid increases, the amount of the coating liquid soaked into the paper base material 1 increases and the paper base material 1 swells excessively. Thereby, the shrinkage | contraction of the paper base material 1 after drying becomes large, and an unevenness | corrugation will appear in the surface of the paper base material 1. FIG. The irregularities on the surface of the paper substrate 1 not only deteriorate the appearance, but may also adversely affect the process after the barrier layer 2 is formed (for example, the process of forming the resin layer 3).
That is, by setting the thickness of the barrier layer 2 in the range of 100 nm or more and 2000 nm or less, sufficient gas barrier properties can be exhibited, and an increase in cost can be suitably suppressed. Moreover, in the state after forming the barrier layer 2, it can suppress suitably that an unevenness | corrugation appears on the surface of the paper base material 1. FIG.

  For example, the resin layer 3 may be formed so as to overlap only on the barrier layer 2, but in the present embodiment, the resin layer 3 is also formed so as to overlap with the other surface 1b of the paper substrate 1 on which the barrier layer 2 is not formed. . The resin layer 3 may be formed on the entire surface of the barrier layer 2 or the entire other surface 1b of the paper substrate 1, for example, a part of the surface of the barrier layer 2, the other surface of the paper substrate 1. It may be formed in a part of 1b. When a molded container (for example, the cup-shaped container 200 illustrated in FIG. 2) is manufactured using the paper barrier laminate 100, the entire surface of the barrier layer 2 or the other surface 1b of the paper substrate 1 is formed by an extrusion lamination method. It is good to be formed in the whole.

  By forming the resin layer 3, liquid resistance to a liquid having high antifouling property and permeability can be imparted. The material of the resin layer 3 may be a heat sealable resin, for example. In this case, the shape can be maintained during molding, sealing can be imparted, and leakage of contents can be prevented.

The material of the resin layer 3 is not particularly limited, and known materials such as polyolefin-based, epoxy-based, urethane-based, isocyanate-based, polyester-based, plant-derived materials (bioplastics) can be used.
Examples of heat-sealable resins include low density polyethylene resins (LDPE), medium density polyethylene resins (MDPE), high density polyethylene resins (HDPE), linear low density polyethylene (LLDPE) and other polyethylene resins, polypropylene resins, A polypropylene resin such as a propylene-ethylene random copolymer or a propylene-ethylene block copolymer can be selected, but a low density polyethylene resin (LDPE) is preferable in consideration of workability, processability, cost, and the like.

The resin layer 3 of the present embodiment is LDPE having a melt mass flow rate (MFR) of 3.0 to 8.0 g / 10 minutes.
If the MFR is greater than 8.0 g / 10 min, the resin layer 3 may be roughened or foamed by heat generated when the paper barrier laminate 100 is molded into a molding container or the like, thereby causing pinholes. Is likely to occur. Further, when the MFR is smaller than 3.0 g / 10 min, the moldability of the paper barrier laminate 100 is lowered, and the resin layer 3 is pulled when the paper barrier laminate 100 is molded, so that the resin layer 3 It will be easy to crack.
That is, when the MFR of the LDPE forming the resin layer 3 is 3.0 to 8.0 g / 10 minutes, the resin layer 3 is cracked or pinholed due to stress or heat generated when the paper barrier laminate 100 is formed. The occurrence of such defects can be suppressed.

The density of the resin layer 3 is preferably 910 to 930 kg / m ³ , for example.
When the density of the resin layer 3 is less than 910 g / m ³ , the adhesiveness of the resin layer 3 is increased, so that the paper barrier laminate 100 is in a state of being blocked (overlaid by winding the paper barrier laminate 100 or the like). Phenomenon that stick to each other) is likely to occur. If blocking occurs, the resin layer 3 may be damaged when the paper barrier laminates 100 are peeled off, which is not preferable.

Further, when the density of the resin layer 3 is larger than 930 g / m ³ , the thickness of the paper barrier laminate 100 is likely to be uneven, and the state after the paper barrier laminate 100 is molded under the same processing conditions (for example, Variations in the state of molded products such as molded containers) become large. A large variation in the state after molding is not preferable because the yield of the molded product is reduced.
That is, when the density of the resin layer 3 is 910 to 930 kg / m ³ , the occurrence of blocking can be suppressed and defects in the resin layer 3 can be preferably suppressed, and the thickness of the paper barrier laminate 100 can be uneven. The yield of molded products can be improved by suppressing the occurrence of

  The method for producing LDPE forming the resin layer 3 is not particularly limited, and for example, a method of polymerizing an ethylene monomer by a high pressure polymerization method may be used. Also, the polymerization conditions such as temperature, pressure, polymerization time and the like are not particularly limited and can be appropriately selected.

  The resin layer 3 can be usually formed on the barrier layer 2 or the paper substrate 1 by a method for producing a packaging material. For example, a wet lamination method, a dry lamination method, a solventless lamination method, a thermal lamination method, It can be formed by a method such as an extrusion lamination method. Among these methods, the extrusion lamination method is preferable in that the method for forming the resin layer 3 is easy and the cost is low. The extrusion lamination method may be any of single laminate, tandem laminate, coextrusion laminate, and sandwich laminate.

  When the resin layer 3 is formed on the barrier layer 2, a known surface treatment such as corona treatment, ozone treatment, plasma treatment, glow discharge treatment, or oxidation treatment using chemicals is performed in advance to improve adhesion. It may be applied to the barrier layer 2. In order to improve adhesion, for example, a primer coat layer, an anchor coat layer, an adhesive layer, or the like may be arbitrarily formed between the barrier layer 2 or the paper substrate 1 and the resin layer 3.

  The thickness of the resin layer 3 formed on the barrier layer 2 is, for example, preferably 25 μm or more, and more preferably 40 μm or more. As the thickness of the resin layer 3 is increased, it becomes easier to ensure adhesion during molding, and defects such as pinholes are less likely to occur in the resin layer, so that gas barrier properties can be easily maintained. However, if the thickness of the resin layer 3 exceeds 80 μm, restrictions on the apparatus become large, and it becomes difficult to form the resin layer 3, and disadvantages such as an increase in cost are likely to occur.

  In addition to the paper base 1, the barrier layer 2, and the resin layer 3, a print layer, an antistatic layer, and the like may be laminated on the paper barrier laminate 100 of the present embodiment as necessary.

The paper barrier laminate 100 of this embodiment can be used for various molded containers formed into a cup shape, a bottle shape, a box shape, or the like.
In order to produce the cup-shaped container 200 of FIG. 2 which is an example of a molded container, first, the body material 201 formed by punching from the paper barrier laminate 100 by a punching die and the paper barrier laminate 100 in the same manner. The created bottom member 202 is molded into a cup shape by a cup molding machine.
Next, the cap-shaped container 200 is obtained by sealing and sealing the separately produced lid member 203 so as to be peelable.
Here, all of the body member 201, the bottom member 202, and the lid member 203 do not have to be the paper barrier laminate 100 of this embodiment, and different sheet materials may be used as necessary.
In the molded container of the present embodiment, the barrier layer 2 may be disposed on the inner surface side than the paper substrate 1 or may be disposed on the outer surface side.

  According to the paper barrier laminate 100 of the present embodiment, the occurrence of defects such as cracks and pinholes in the resin layer 3 due to stress and heat generated when the paper barrier laminate 100 is molded into a molding container or the like is suppressed. it can. For this reason, even if it is in the state after shape | molding the paper barrier laminated body 100 in a shaping | molding container etc., it can prevent external factors, such as a water | moisture content, reaching the barrier layer 2, and can maintain gas barrier property. That is, a molded container having excellent gas barrier properties can be provided.

  EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples. However, the present invention is not limited to these examples.

[Preparation of aqueous coating solution 1]
30 g of softwood kraft pulp was immersed in 600 g of water and dispersed with a mixer.
0.3 g of TEMPO and 3 g of NaBr previously dissolved in 200 g of water were added to the pulp slurry after dispersion, and the whole was further diluted with water to 1400 mL.
The inside of the system was kept at 20 ° C., and a sodium hypochlorite aqueous solution was measured and dropped so as to be 10 mmol with respect to 1 g of cellulose.

The pH started to decrease from the start of dropping, but a 0.5N sodium hydroxide aqueous solution was dropped at any time to keep the pH of the system at 10.
After 4 hours, when the amount of 0.5N sodium hydroxide aqueous solution dropped to 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 lower the pH to 2. The oxidized pulp was filtered and washed repeatedly with 0.01N hydrochloric acid or water to obtain oxidized pulp.
Conductivity titration of oxidized pulp with 0.1N aqueous sodium hydroxide using an automatic titrator (Toa DKK, AUT-701) revealed that the amount of carboxy groups was 1.6 mmol / g.
The obtained oxidized pulp was diluted with water and adjusted to pH 9 using a 0.5N aqueous sodium hydroxide solution to obtain a 1% oxidized pulp suspension. This suspension was subjected to a dispersion treatment with a high-speed stirrer for 2 hours to obtain a dispersion containing fine cellulose fibers as an aqueous coating solution 1.

[Preparation of aqueous coating solution 2]
A commercially available polyvinyl alcohol (PVA) (molecular weight 100,000, saponification degree 98%) 4% solids aqueous solution was prepared as an aqueous coating solution 2.

[Preparation of aqueous coating solution 3]
A 4% solid aqueous solution of commercially available polyvinyl alcohol (PVA) (molecular weight 100,000, saponification degree 98%) was mixed with the aqueous coating solution 1 so that the mass ratio of cellulose to PVA was 1: 1. Furthermore, the PVA addition cellulose fine fiber dispersion was obtained as the aqueous coating liquid 3 by stirring with a magnetic stirrer for 3 hours.

[Preparation of aqueous coating solution 4]
An aqueous coating solution 4 was produced in the same procedure as the aqueous coating solution 1 except that the stirring treatment was performed for 20 minutes with a high-speed stirrer. The aqueous coating solution 4 was inferior to the aqueous coating solution 1 and was cloudy.

[Preparation of aqueous coating solution 5]
Water was added to the softwood kraft pulp to adjust the solid content concentration to 1%, and the mixture was dispersed with a high-speed stirrer for 2 hours to prepare a dispersion containing cellulose fibers as an aqueous coating solution 5. The aqueous coating solution 5 was inferior in transparency to the aqueous coating solutions 1 and 4 and was cloudy. As with the aqueous coating solution 1, the amount of carboxy groups was measured and found to be 0.05 mmol / g.

[Preparation of aqueous coating solution 6]
The aqueous coating solution 6 was prepared in the same procedure as the aqueous coating solution 1 except that the temperature in the system was 60 ° C., the reaction time was 3 hours, and the dropwise addition amount of the 0.5N sodium hydroxide aqueous solution was 6.0 mmol / g. . As with the aqueous coating solution 1, the amount of carboxy group was measured and found to be 3.8 mmol / g.

[Evaluation of aqueous coating solutions 1 and 4-6]
Each aqueous coating liquid 1,4-6 containing cellulose nanofibers was diluted to a concentration of 0.01% and applied onto mica to observe the fiber form. The aqueous coating solutions 1, 5, and 6 were observed with an AFM, and the aqueous coating solution 4 was observed with a laser microscope. And the average of the width | variety of 10 arbitrary fibers which exist one by one was calculated | required, and this was made into the average fiber diameter.
Average fiber diameter of aqueous coating solutions 1 and 6: 4 nm
Average fiber diameter of aqueous coating solution 4: 2 μm
Average fiber diameter of aqueous coating solution 5: 1.2 μm

[Production of cup-shaped container of Example 1]
An uncoated cup base paper having a basis weight of 260 g / m ² was used as a paper base material. The aqueous coating solution 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. This formed a barrier layer on one side of the paper substrate.
Next, the surface of the exposed barrier layer was subjected to corona treatment.
Thereafter, LDPE having an MFR of 3.7 g / 10 min and a density of 925 kg / m ³ was formed on the surface of the exposed paper substrate (the other surface) and the barrier layer by extrusion lamination. The thickness of the resin layer on the barrier layer side was 40 μm, and the thickness of the resin layer on the paper substrate side was 20 μm. As a result, a paper barrier laminate was obtained.
Finally, the paper barrier laminate was punched out with a punching die to create a body and a bottom member, and the body and the bottom member were molded into three types of cup-shaped containers using a cup molding machine. Thus, a cup-shaped container (capacity: 200 mL) of Example 1 was obtained.
In the cup-shaped container of Example 1, the barrier layer was disposed on the inner surface side of the paper substrate.

[Production of cup-shaped container of Example 2]
A cup-shaped container (capacity 200 mL) of Example 2 was produced in the same procedure as the cup-shaped container of Example 1 except that the aqueous coating liquid 2 was applied to one surface of the paper substrate.
In the cup-shaped container of Example 2, the barrier layer was disposed on the inner surface side of the paper substrate.

[Production of cup-shaped container of Example 3]
A cup-shaped container (capacity 200 mL) of Example 2 was produced in the same procedure as the cup-shaped container of Example 1 except that the aqueous coating liquid 3 was applied to one surface of the paper substrate.
In the cup-shaped container of Example 3, the barrier layer was disposed on the inner surface side of the paper substrate.

[Production of cup-shaped container of Example 4-5]
Using the aqueous coating solution 1, a barrier layer was formed on one surface of the paper substrate in the same manner as in Example 1.
Next, the surface of the exposed barrier layer was subjected to corona treatment.
Thereafter, LDPE having an MFR of 3.7 g / 10 min and a density of 925 kg / m ³ was formed on the surface of the exposed paper substrate (the other surface) and the barrier layer by extrusion lamination. Regarding the thickness of the resin layer on the barrier layer side, two types of 30 μm and 50 μm were prepared. The thickness of the resin layer on the paper substrate side was 20 μm. Thereby, two types of paper barrier laminates were obtained.
Finally, the body and the bottom member were formed by punching from each type of paper barrier laminate with a punching die, and two types of cup-shaped containers were formed using the cup molding machine. Thus, a cup-shaped container (capacity: 200 mL) of Example 4-5 was obtained.
In the cup-shaped container of Example 4-5, the barrier layer was disposed on the inner surface side of the paper substrate. In the cup-shaped container of Example 4, the thickness of the resin layer on the barrier layer side was 30 μm. In the cup-shaped container of Example 5, the thickness of the resin layer on the barrier layer side was 50 μm.

[Production of cup-shaped container of Comparative Example 1]
A cup-shaped container of Comparative Example 1 (capacity 200 mL) was prepared in the same procedure as the cup-shaped container of Example 1 except that the aqueous coating solution 4 was applied to one surface of the paper substrate.
In the cup-shaped container of Comparative Example 1, the barrier layer was disposed on the inner surface side of the paper substrate.

[Production of cup-shaped container of Comparative Example 2]
Using the aqueous coating solution 1, a barrier layer was formed on one surface of the paper substrate in the same manner as in Example 1.
Next, the surface of the exposed barrier layer was subjected to corona treatment.
Thereafter, LDPE having an MFR of 3.7 g / 10 min and a density of 925 kg / m ³ was formed on the surface of the exposed paper substrate (the other surface) and the barrier layer by extrusion lamination. The thickness of the resin layer on the barrier layer side was 20 μm, and the thickness of the resin layer on the paper substrate side was 20 μm. As a result, a paper barrier laminate was obtained.
Finally, a cup-shaped container (capacity 200 mL) of Comparative Example 2 was produced from the above paper barrier laminate in the same manner as in Example 1.
In the cup-shaped container of Comparative Example 2, the barrier layer was disposed on the inner surface side of the paper base material.

[Production of cup-shaped container of Comparative Example 3]
Using the aqueous coating solution 1, a barrier layer was formed on one surface of the paper substrate in the same manner as in Example 1.
Next, the surface of the exposed barrier layer was subjected to corona treatment.
Thereafter, LDPE having an MFR of 2 g / 10 min and a density of 924 kg / m ³ was formed on the surface of the exposed paper substrate (the other surface) and the barrier layer by extrusion lamination. The thickness of the resin layer on the barrier layer side was 40 μm, and the thickness of the resin layer on the paper substrate side was 20 μm. As a result, a paper barrier laminate was obtained.
Finally, a cup-shaped container (capacity: 200 mL) of Comparative Example 3 was produced from the above paper barrier laminate in the same manner as in Example 1.
In the cup-shaped container of Comparative Example 3, the barrier layer was disposed on the inner surface side of the paper substrate.

[Production of cup-shaped container of Comparative Example 4]
Using the aqueous coating solution 1, a barrier layer was formed on one surface of the paper substrate in the same manner as in Example 1.
Next, the surface of the exposed barrier layer was subjected to corona treatment.
Thereafter, LDPE having an MFR of 9.4 g / 10 min and a density of 922 kg / m ³ was formed on the surface of the exposed paper substrate (the other surface) and the barrier layer by extrusion lamination. The thickness of the resin layer on the barrier layer side was 40 μm, and the thickness of the resin layer on the paper substrate side was 20 μm. As a result, a paper barrier laminate was obtained.
Finally, a cup-shaped container (capacity: 200 mL) of Comparative Example 4 was produced from the above paper barrier laminate in the same manner as in Example 1.
In the cup-shaped container of Comparative Example 4, the barrier layer was disposed on the inner surface side of the paper substrate.

[Production of cup-shaped container of Comparative Example 5]
A cup-shaped container (capacity 200 mL) of Comparative Example 5 was prepared in the same procedure as the cup-shaped container of Example 1 except that the aqueous coating solution 5 was applied to one surface of the paper substrate.
In the cup-shaped container of Comparative Example 5, the barrier layer was disposed on the inner surface side of the paper substrate.

[Production of cup-shaped container of Comparative Example 6]
A cup-shaped container (capacity 200 mL) of Comparative Example 6 was produced in the same procedure as the cup-shaped container of Example 1 except that the aqueous coating liquid 6 was applied to one surface of the paper substrate.
In the cup-shaped container of Comparative Example 6, the barrier layer was disposed on the inner surface side of the paper substrate.

  Table 1 shows various parameters of Example 1-5 and Comparative Example 1-6 (the thickness of the resin layer, the MFR of LPDE in the resin layer, the average fiber diameter of cellulose nanofibers in the barrier layer, and the amount of carboxy groups in the barrier layer). .

[Evaluation of Example 1-5 and Comparative Example 1-6]
IPA (isopropyl alcohol) is dropped on the entire inner surface of each cup-shaped container of Example 1-5 and Comparative Example 1-6, and IPA permeates into the paper base material around the bonded portion of the body and the bottom member. Was confirmed visually. In order to correspond to the location where defects such as pinholes and cracks occur in the resin layer, the location where the penetration into the paper substrate corresponds to the location where the penetration into the paper substrate is the resin It was measured as the number of defects generated in the layer.
Then, after protecting the bonding part of the circumferential direction both ends of the cup material of each cup-shaped container with an epoxy adhesive, the oxygen permeability measuring device MOCON (trade name: OX-TRAN2 / 21, manufactured by Modern Control) Was used to measure the oxygen permeability (cc / pg / day / 0.21 atm) of each cup-shaped container.
The results are shown in Table 2.

As shown in Table 1, Comparative Example 2 in which the thickness of the resin layer on the barrier layer side is 20 μm is thin, Comparative Example 3 in which the MFR of LDPE forming the resin layer is smaller than 3.0 g / 10 min, and LDPE forming the resin layer In Comparative Example 4 having an MFR greater than 8.0 g / 10 min, it was confirmed that a defect occurred in the resin layer.
In contrast, Examples 1-5 and Comparative Examples in which the thickness of the resin layer on the barrier layer side is 25 μm or more, and the MFR of the LDPE forming the resin layer is 3.0 g / 10 min or more and 8.0 g / 10 min or less. In 1, 5 and 6, it was confirmed that no defects occurred in the resin layer.

Comparative Example 2-4 in which defects are generated in the resin layer, and the average fiber diameter of the cellulose nanofibers contained in the layer formed using the aqueous coating liquid 4 although no defects are generated in the resin layer is 2 μm. Comparative Example 1 in which the amount of carboxy groups in the layer formed using the aqueous coating solution 5 is 0.05 mmol / g Comparative Example 5 in which the amount of carboxy groups in the layer formed using the aqueous coating solution 6 is 3 In Comparative Example 6 that was .8 mmol / g, it was confirmed that the oxygen permeability was excessively large. In Comparative Examples 1, 5, and 6, it was confirmed that the layer formed using the aqueous coating solution 4-6 did not function as a barrier layer.
In contrast, Examples 1 and 3 in which no defects occurred in the resin layer, the average fiber diameter of the cellulose nanofibers contained in the barrier layer was 4 nm, and the amount of carboxy groups in the barrier layer was 1.6 mmol / g. 5 and Example 2 in which no defects occurred in the resin layer and the barrier layer contained PVA, it was confirmed that the oxygen permeability was sufficiently reduced. That is, it was confirmed that the paper barrier laminate used for the cup-shaped container of Example 1-5 can impart high gas barrier properties.

DESCRIPTION OF SYMBOLS 1 ... Paper base material 2 ... Barrier layer 3 ... Resin layer 100 ... Paper barrier laminated body 200 ... Cup-shaped container (molding container)

Claims (7)

A paper substrate;
A barrier layer formed to overlap with at least one surface of the paper substrate;
A resin layer formed at least on the barrier layer,
The resin layer is a low density polyethylene having a melt mass flow rate of 3.0 to 8.0 g / 10 minutes,
A paper barrier laminate, wherein the resin layer formed on the barrier layer has a thickness of 25 μm or more.   The paper barrier laminate according to claim 1, wherein the barrier layer has a gas barrier property and includes a barrier material that can be melted or dispersed in a medium mainly composed of water.   The paper barrier laminate according to claim 1 or 2, wherein the barrier layer contains cellulose nanofibers obtained by refining natural cellulose.   The paper barrier laminate according to claim 3, wherein the cellulose nanofiber has a carboxyl group of 0.1 mmol / g or more and 3.5 mmol / g or less per mass of cellulose.   The paper barrier laminate according to claim 3 or 4, wherein an average fiber diameter of the cellulose nanofiber 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 barrier layer has a thickness of 100 nm or more and 2000 nm or less.   A molded container comprising the paper barrier laminate according to any one of claims 1 to 6.

Images