JP5869828B2 - Gas barrier paper and package using the same - Google Patents

Description

  In order to advance the construction of a low-carbon society in response to recent global environmental protection issues, the present invention saves materials, resources, processes, saves energy, uses biomass resources, reduces the amount of organic adhesive used, and saves laminates. This is related to gas barrier papers that meet extremely important global needs such as composting.

  In addition, the present invention has excellent gas barrier properties, particularly oxygen gas barrier properties, so that it is possible to suppress oxidative deterioration, acid rot, oxidation discoloration, generation of wrinkles and generation of peroxides in the package, and further gas barriers under high humidity. It is related with the package which can prevent the fall of property.

  Therefore, the present invention solves the problem of oxidation and moisture absorption in various fields such as foods, beverages, pharmaceuticals, electronic device parts, industrial products, various machine parts, textile products, etc. The present invention relates to packaging materials such as packaging materials, various packaging containers, bags, folding packaging, and overlaps that can increase the use ratio of renewable materials.

  The paper packaging material has excellent appearance characteristics of paper, hand feeling, high quality, expression of Japanese style, etc., and excellent bending properties (dead hold), three-dimensional characteristics due to high rigidity, bulkiness, It has antistatic properties and writing properties.

  However, since the packaging material having a paper structure does not have gas barrier properties, it is common to laminate other barrier materials in the above-mentioned applications. For example, a laminate of an aluminum foil having a thickness of 7 μm to 20 μm, a laminate of a film on which a metal or a metal oxide is deposited, or a laminate or coating of a gas barrier resin is applied. As the gas barrier resin, an ethylene / vinyl alcohol copolymer resin film, a metaxylenediamine-based polyamide resin film, a vinylidene chloride resin coated film, a polyvinyl alcohol resin coated film, or the like is used.

  However, a laminate of a metal foil or a barrier film consumes a great amount of electric energy and has a problem that there are many processing losses because vacuum deposition is performed in a batch system.

  Further, the laminate needs to be incinerated at the disposal stage from the distribution process, and is not satisfied from the viewpoint of processing problems in the incinerator.

  Furthermore, a paper-like body laminated with a thermoplastic plastic film coated with a gas barrier resin cannot be subjected to high-temperature heat treatment because the thermoplastic plastic film has a softening point and a melting point, and the crystallinity of the coating material is sufficient. However, if the vinylidene chloride resin is excluded, there is a problem that the gas barrier property is lowered under high humidity.

  For example, when a polyvinyl alcohol resin or an ethylene / vinyl alcohol copolymer resin is used, the oxygen gas permeability at a high humidity of about 80% RH or more is 10 to 30 times the oxygen gas permeability at 65% RH. Therefore, it is well known that gas barrier properties are not substantially exhibited.

  For example, Patent Document 1 describes a gas barrier paper in which a polyvinyl alcohol resin aqueous solution is applied to paper. However, since the paper described in Patent Document 1 has a bulky structure that is completely different from the surface structure of the thermoplastic film, the polyvinyl alcohol resin aqueous solution is easily absorbed, and a uniform gas barrier resin layer is not formed. There is a problem that it is difficult to obtain a high gas barrier property even under humidity.

  This is because it has not been studied to optimize the wetting characteristics of the aqueous polyvinyl alcohol resin solution, not to absorb the aqueous solution in a short time, and balance the absorbency in a long time of several tens of seconds.

  For example, if the absorption rate is too fast, the coating liquid is immediately absorbed by the paper and the coating layer becomes discontinuous before drying. On the other hand, when the absorption rate is too slow, adhesion failure or the like occurs due to dripping or poor permeability due to the repelling phenomenon, and a strong and uniform continuous coating layer is not formed.

  In order to clarify the actual situation, the film quality of the gas barrier layer must be taken up. It is obvious that the barrier characteristics can be improved by coating an excessively thick gas barrier resin in order to obtain gas barrier properties. However, excessive thickness will not only make the economy cheaper, but also cause loss of film flexibility, bending pinhole resistance, laminating strength, etc. Due to the external force and deformation, the gas barrier layer is damaged and the gas barrier property is remarkably lowered. Further, when the layer absorbs moisture under high humidity or moisture from the contents, a large amount of moisture is accumulated as an absolute amount, and the gas barrier property is lowered. Therefore, it is important that the barrier layer including the economy is as thin as possible and has a necessary gas barrier property. As a characteristic that can specifically evaluate the high quality of the film, it can be confirmed by a gas permeation coefficient indicating a characteristic characteristic of the gas barrier film. The gas permeability coefficient is expressed by equation (1).

In this equation, gas permeability is expressed by equation (2). In Patent Document 1, the characteristics are evaluated by this gas permeability.

  Therefore, the gas permeation coefficient is expressed by equation (3).

The thickness of the gas barrier layer is generally expressed as a coating amount (W) g / m ² . The relationship between the coating amount and the coating thickness can be known from equation (4).

Accordingly, the coating thickness can be calculated by dividing the coating amount by the density.
Therefore, since it is generally expressed by a simple coating amount, the transmission coefficient calculated by simply replacing the gas barrier layer thickness in the equation (3) with the coating amount is defined as a simple transmission coefficient. How to make the simple transmission coefficient low is a basic matter of the present invention which cannot be found in the prior art.

Among the examples described in Patent Document 1, in Example 6 having the highest oxygen gas permeability, the coating amount is 2 g / m ² and the oxygen gas permeability is 42 g / m ² . It is described. Then, the simple transmission coefficient is 84 cc · g · m ⁻² / m ² · 24 hr · atm. Therefore, the present invention realizes a simple transmission coefficient lower than that of the prior art, that is, a high barrier characteristic.

Patent Document 2 describes a paper product in which a lower layer-forming paint and an upper-layer-forming paint are applied to at least one surface of a paper substrate having a specific Cobb water absorption. However, since the paper substrate described in Patent Document 2 has a Cobb water absorption adjusted by adjusting the amount of the sizing agent, the Cobb water absorption can only be reduced to about 20 g / m ^2. It was.

  As a result, the coating material for forming the lower layer readily penetrates into the paper substrate, so the smoothness of the lower layer tends to deteriorate, making it difficult to apply the coating material for forming the upper layer with a uniform thickness, resulting in variations in moisture permeability. There was a problem that it was easy. Furthermore, although it is described that the water absorption of Cobb, surface roughness, undercoat and overcoat layer are provided, there is no description of specific means for achieving oxygen gas barrier properties, and no specific requirements are specified.

Patent Document 2 also exemplifies polyvinyl alcohol and acrylic polymers. However, if the polyvinyl alcohol that emphasizes gas barrier properties is not crystalline polyvinyl alcohol as in the present invention, the gas barrier properties cannot be secured. In the case of polyvinyl alcohol resin, the density is generally in the range of 1.19 to 1.31 g / cm ³ , but in the present invention, the density of the formed polyvinyl alcohol resin layer is 1.25 to 1.40 g / cm ^3. It is a preferred condition to have a high density up to cm ³ .

Furthermore, the gas barrier property as in the present invention cannot be obtained with an acrylic polymer. Furthermore, the upper layer has a curing reaction type material structure containing inorganic or metal alkoxides, and is significantly different from the present invention.
Furthermore, although there are descriptions of surface roughness and Cobb water absorption, it also includes a range in which gas barrier properties cannot be obtained as in the present invention, and only the surface roughness and Cobb water absorption are high in the present invention. It is impossible to obtain gas barrier properties.

For example, although the average surface roughness Ra is described as 50 μm or less, when the coating amount is much thinner than 50 μm as in the present invention, the roughness height clearly exceeds the coating thickness, and is determined according to the present invention. This is far from the smoothness with which a continuous film of a barrier layer can be formed. In other words, it means that the barrier film cannot be formed continuously and uniformly, so that it can be understood that the product relates to a different standard product.
In the present invention, the smoothness is generally represented by a value of Beck smoothness. This is because paper is a three-dimensional three-dimensional surface, and it is difficult to accurately measure with a general stylus roughness meter. The surface roughness Ra is not acceptable up to 50 μm, and it is impossible to control the absorption amount, absorption speed, wetting characteristics, etc. of the coating solution with such a rough surface.

JP 2001-254292 A JP 2001-303483 A

  In view of the above-described problems of the prior art, the problem to be solved by the present invention is a gas barrier having a high gas barrier property with a low gas permeation coefficient indicating an intrinsic characteristic per unit barrier layer thickness and a small humidity dependency of the gas barrier property. It is to provide a paper-like body and a package using the same.

  That is, the said subject can be achieved by the following solution means.

Smooth at least one side of the base paper or processed paper with at least one water-dispersible or water-soluble resin so that the solid content of the resin after drying is 0.5 to 20 g / m ^2. If the degree of the ink is 200,000 seconds or more and 100 mg of water droplets are dropped and left for 5 seconds and then the paper body is set to a vertical angle, the water drops move or drop, and after 60 seconds of standing, the inclination angle is 25 degrees. On the precoat layer of a paper-like body having surface characteristics that do not fall below, cobb water absorption of 0.03 to 15 g / m ² , and water droplet contact angle of 5 to 60 degrees. , which crystalline polyvinyl alcohol-based resin is provided a gas barrier resin layer containing more than 75 wt% by the coating method, the oxygen gas permeability ^{23 ℃, 20cc / m 2 ·} 24hr at 65% RH A gas barrier sheet-like body, characterized in that atm or less.

Further, it is preferable simple transmission coefficient indicating the unique quality of the gas barrier layer is 23 ° C., or less ^{80cc · g · m -2 / m} 2 · 24hr · atm below RH 85%.
[Definition of simple transmission coefficient]
The product of the gas permeability of the gas barrier paper and the resin solid content after drying or heat treatment of the gas barrier resin layer is defined as a simple permeability coefficient.

  The crystalline polyvinyl alcohol-based resin preferably contains 80 to 100 mol% of polyvinyl alcohol segments having a saponification degree of 80 to 99.99 mol% and a polymerization degree of 200 to 3,000.

Further, the oxygen gas permeability of the gas barrier paper is preferably 100 cc / m ² · 24 hr · atm or less at 23 ° C. and 85% RH, and further, the gas barrier resin layer is crystallized at a high temperature to thereby generate oxygen gas. The value of the change in transmittance / change in humidity is 3.0 or less, and the simple transmission coefficient is 80 cc · g · m ⁻² / m ² · 24 hr · atm or less at 23 ° C. and 85% RH or less. Is preferred.

  Furthermore, it is preferably obtained by a production method in which heat treatment is performed at a temperature not lower than the crystallization temperature of the gas barrier resin and not higher than a temperature at which the strength retention with respect to the initial strength of the paper-like body is 60% or higher.

In these cases, a moisture-proof layer having a water vapor permeability of 25 g / m ² · 24 hr or less or a water absorption of 0.5 to 25 g / m ² so as to be in contact with any layer of the gas barrier paper. It is more desirable to provide a layer having a property.

  Further, in the present invention, a packaging body in which another oxygen barrier layer, a printing layer, or a coating layer or film having heat sealability is provided on at least one side of the gas barrier paper-like body shown in any of the above-described embodiments. Is also provided.

  The gas barrier paper of the present invention and the package using the same can achieve the following effects.

Realization of high gas barrier property The surface of the paper-like body is smooth, and the paper-like body has a uniform wettability characteristic of the coating solution containing the gas barrier resin and a surface characteristic in which the coating solution is not immediately absorbed. Can be realized.

Improvement of bending pinhole resistance Bending pinhole resistance can be improved by providing a flexible resin layer on the surface of the paper-like body and imparting flexibility to the gas barrier resin within a range not impairing the gas barrier property.

Improvement of humidity dependence of gas barrier properties Non-chlorine-based gas barrier resins have a drawback in that the gas barrier properties deteriorate at high humidity. Therefore, this defect can be improved by crystallizing the gas barrier resin layer at a high temperature by utilizing the fact that the base material is a paper-like body having no melting point.

It is the schematic which shows the structure of the gas barrier paper-like body of this invention. It is the schematic which shows the structure of the package using the gas barrier paper-like body of this invention. It is the schematic which shows the structure of the package using the gas barrier paper-like body of this invention. It is the schematic which shows the structure of the package using the gas barrier paper-like body of this invention.

Embodiments of the present invention will be described below.
In the present invention, at least one surface of a base paper or processed paper is pre-coated with at least one water-dispersible or water-soluble resin so that the resin solid content after drying is 0.5 to 20 g / m ² , When the Beck smoothness is 200,000 seconds or more, after dropping 100 mg of water droplets, after standing for 5 seconds, and when the paper body is set to a vertical angle, the water droplets move or drop, and after leaving for 60 seconds, tilt A paper-like body having surface characteristics that do not fall at an angle of 25 degrees or less, cobb water absorption of 0.03 to 15 g / m ² , and water droplet contact angle of 5 to 60 degrees. on the precoat layer, which crystalline polyvinyl alcohol-based resin is provided a gas barrier resin layer containing more than 75 wt% by the coating method, the oxygen gas permeability 23 ℃, 20cc / m ² at 65% RH A gas barrier sheet-like body is 24 hr or · atm or less, a simple transmission coefficient indicating the unique quality of the gas barrier layer using the same, and gas barrier sheet-like member is not more than ^{80cc · g · m -2 / m} 2 · 24hr · atm It is a package.

Definition of paper-like body The paper-like body of the present invention is a paper-like body obtained by making paper using wood pulp as a raw material and having a highly functional surface. Moreover, the paper-like body made from the fiber or nanofiber which used the hemicellulose extracted from the timber and the grain cell as a raw material may be sufficient, and the paper-like body which made the nanofiber of 3-100 nm size in high density especially is preferable.

Smoothness of paper-like body It is an essential requirement that the surface of the paper-like body of the present invention has a Beck smoothness of 200,000 seconds or more. If the Beck smoothness is less than 200,000 seconds, a continuous gas barrier resin layer cannot be obtained, resulting in poor gas barrier properties.

Solution absorption properties of paper-like material It is important that the gas barrier resin solution to be coated is not immediately absorbed by the paper-like material. In the present invention, after 5 seconds have passed since 100 mg of water droplets were dropped on the paper body, it is essential that the water droplets move or drop when the paper body is held vertically. Further, when the paper body is tilted after 60 seconds from the time when the water droplet is dropped, it is essential that the water droplet does not fall at an angle of 25 degrees or less. Furthermore, it is an essential requirement that the Cobb water absorption is 0.03 to 15 g / m ² .

Wetting characteristics of the paper-like body In order for the coating solution to wet uniformly, it is an essential requirement that the water droplet contact angle is 5 to 60 degrees or less.

  In order to adjust the wetting characteristics of the surface of the paper-like body, pre-coating treatment, corona discharge treatment, plasma discharge treatment, flame treatment, ultraviolet treatment, and the like can be performed. Among these, the method of adjusting the surface wettability by precoat treatment is preferable.

Precoat layer As preferred examples of the resin forming the precoat layer, a crystalline water-soluble resin, a water-soluble resin having a carboxyl group and / or a hydroxyl group, polyethyleneimine, an organic titanium-based adhesive, a water-based polyester copolymer, terminal or side Polyethylene oxide having a functional group in the chain, a functional group-added graft copolymer, ethylene / ethyl acrylate, ethylene / acrylate and the like are used. A precoat refers to a coating that can achieve the limited surface properties necessary to obtain advanced barrier properties in the present invention.

  Further, by using a latex resin having a glass transition temperature of 20 ° C. or lower, preferably 10 ° C. or lower, the bending resistance against pinholes can be improved, and the deterioration of gas barrier properties due to bending can be prevented. In particular, when a diene latex resin having an increased degree of polymerization and / or branching is used, a precoat layer having excellent bending resistance can be obtained by a bridging action. Furthermore, if a small amount of a surfactant, a silicone-based or non-silicone-based polymer defoaming agent, a surfactant-type defoaming agent with increased hydrophobicity, an alkyl alcohol, etc. are used in combination, the dispersion state of the latex resin is reduced. It becomes good.

  Moreover, a very uniform precoat layer can be formed by making the latex resin into fine particles.

The precoat layer has a resin solid content of preferably 0.5 to 20 g / m ^2, more preferably 1.5 to 10 g / m ² . When the resin solid content is less than 0.5 g / m ² , the gas barrier property becomes unstable due to a slight change in the surface smoothness of the paper-like body, and the bending pinhole resistance also deteriorates. On the other hand, when it exceeds 20 g / m ² , the flexibility of the paper-like body is lost, and the folding property is impaired in the process of deforming the laminated paper-like body from a flat state to a bag-like body in an automatic packaging machine, When molding into a shape, a large force is required, and for this reason, the frictional force during bag making becomes large, and the bag-making property becomes unstable. Furthermore, since the paper-like material folded at the time of bag making is heat-sealed at a high temperature to make a bag, the folded portion returns to the original state before reaching the low temperature region where the adhesive force is generated. Therefore, it cannot be used in high-speed automatic packaging.

Gas barrier resin The crystalline polyvinyl alcohol-based resin used as the gas barrier resin is preferably a mixture or copolymer containing 75% by weight or more of a resin having a polyvinyl alcohol segment of 80 mol% or more. If the polyvinyl alcohol segment is less than 80 mol%, it is difficult to obtain gas barrier properties, and if it is less than 75 wt%, it is difficult to obtain high gas barrier properties.

  The crystalline polyvinyl alcohol resin may be a copolymer of an acrylic acid and an ethylenically unsaturated monomer containing an acetal group in a polyvinyl alcohol polymer.

  Even when the content of the polyvinyl alcohol resin is 75% by weight or more, it is difficult to obtain a high gas barrier property when a water-soluble polyvinyl alcohol resin that dissolves in water at room temperature is used.

  In order to obtain a high gas barrier property, it is preferable to use a crystalline polyvinyl alcohol resin that does not dissolve in water at a temperature of at least less than 55 ° C. Further, the polyvinyl alcohol segment has a polymerization degree of 200 to 3,000, and a saponification degree. It is preferably 80 to 99.99 mol%. However, the polyvinyl alcohol resin in which the crystal portion and the amorphous portion are controlled to independently adjust the low crystallinity and the high hydrogen bonding force can be dissolved in water at a wide range of temperatures, and thus is not limited thereto. It is also effective to use the resin together with an emulsion obtained by emulsion polymerization with an acrylic monomer.

As vinyl esters constituting the crystalline polyvinyl alcohol resin, vinyl acetate, vinyl propionate, vinyl pivalate, vinyl valelate, vinyl caprate, vinyl benzoate, etc. may be used alone or in combination of two or more. Also good.
In addition, the bending pinhole resistance and fatigue characteristics can be improved by adding a small amount of another monomer as a copolymerization component within a range not impairing the water solubility of the polyvinyl alcohol resin. Other monomers that can be used are α-olefins such as ethylene, propylene, 1-butene, isobutene, 4-methyl-pentene, 1-hexene, 1-octene, itaconic acid, methacrylic acid, acrylic acid as unsaturated carboxylic acid , Vinyl silane compounds such as salts such as maleic anhydride, partial or complete esters thereof, nitriles thereof, amides thereof, or anhydrides thereof.

Furthermore, as vinyl monomers copolymerizable with vinyl esters, acrylamide monomers such as acrylamide, N-methylacrylamide, N-ethylacrylamide, N, N-dimethylacrylamide, methacrylamide monomers, vinyl ether monomers Body, allyl alcohol, vinyltrimethoxysilane, N-vinyl-2-pyrrolidone, isopropenyl alcohol, 7-octen-1-ol, allyl acetate, isopropenyl acetate and the like.
Furthermore, in the copolymer of acrylic acid and an ethylenically unsaturated monomer containing an acetal group in a polyvinyl alcohol polymer, a copolymer having a polyvinyl alcohol polymer component of 75% or more can be mentioned.

  Crystalline polyvinyl alcohol resin, diene latex such as styrene / butadiene copolymer, carboxylic acid-containing latex such as methyl methacrylate and carboxylated styrene, core-shell surface carboxyl modified latex, control of crystallinity and non-crystallinity By mixing an emulsion polymer of an acrylic monomer by grafting of the special polyvinyl alcohol and the like, it is possible to improve the bending pinhole resistance and fatigue resistance which are easily lowered by high-temperature heat treatment. In addition, bending pinhole resistance and fatigue resistance characteristics can be further improved by mixing glycerin, diglycerin derivatives, polyethylene glycol, and the like within a range not inhibiting the gas barrier property.

In order to obtain a low simple permeability coefficient, which is a feature of the present invention, in addition to the gas barrier layer having a high crystallinity as described above, crystalline polyvinyl alcohol is difficult to dissolve, and mixing with a solvent and coating processing are required. Bubbles are generated by the agitation of air and entrainment of air by contact with air.
For this reason, if there are many fine bubbles in the barrier layer, the density is lowered, and in order to form a gas passage, the minimum permeation coefficient which shows the inherent characteristic of the film quality must be lowered to form a gas passage.
Therefore, it is important to use an antifoaming agent, such as a small amount of a surfactant, a silicon-based, non-silicone polymer-type antifoaming agent, a surfactant-type antifoaming agent with increased hydrophobicity, an alkyl alcohol, It is important to use an ether type activator obtained by adding ethylene oxide or propylene oxide to a higher alcohol, or an antifoaming agent considering the balance between hydrophilicity and hydrophobicity, such as ester, ether ester, ester ether type. It is also effective to mix an emulsion obtained by emulsifying higher alcohol or ester having excellent degassing properties in water.
Furthermore, in the present invention, the heat treatment is performed at a high temperature equal to or lower than the decomposition temperature of the polyvinyl alcohol, thereby degassing the internal microbubbles and forming a densified gas barrier layer. As a result, a low simple transmission coefficient can be realized.
In addition, a weathering agent, an antiblocking agent, an antioxidant, a lubricant, an antistatic agent, a leveling agent, an antifungal agent and the like may be added to the gas barrier resin layer as necessary.

Formation of Gas Barrier Resin Layer As a method for coating the gas barrier resin solution, kiss roll coat, gravure roll coat, reverse roll coat, Mayer bar coat, bar coat, fountain coat, multilayer coextrusion coat, etc. are used. In particular, in the fountain coat, high-speed and uniform defoaming can be performed by using the fountain coat and the smoothing bar in combination.

  In order to remove the solvent of the entire coating layer uniformly and completely and to prevent generation of bubbles due to boiling of the solvent during drying, it is preferable to perform multi-stage drying with a temperature difference.

In order to reduce the amount of residual solvent, the gas barrier resin layer is preferably 15 g / m ² or less in terms of resin solid content, and more preferably in the range of 2 to 10 g / m ² from the viewpoint of cost performance.

If the resin solid content exceeds 15 g / m ² , bending pinhole resistance and fatigue properties are deteriorated, and crazing is likely to occur in the gas barrier resin layer, resulting in deterioration of gas barrier properties. Moreover, the variation in gas barrier properties increases due to the deterioration of the dry state, the increase in residual solvent, and the generation of bubbles when the solvent evaporates. Furthermore, when the thickness of the gas barrier resin layer is increased, the humidity dependency of the gas barrier property is increased. On the other hand, if it is less than 0.5 g / m ² , high gas barrier properties cannot be obtained.

  In order to obtain a gas barrier resin layer with little humidity dependency, it is preferable to promote defoaming and crystallization by performing high temperature heat treatment using infrared drying and / or electromagnetic wave drying in combination with high temperature hot air drying.

  By high-temperature heat treatment, the crystalline polyvinyl alcohol-based resin layer becomes a highly crystallized state, and a gas barrier paper body having a small humidity dependency, that is, a change amount of oxygen gas permeability / a change amount of humidity of 3 or less is obtained. . If this value exceeds 3, it becomes a gas barrier paper that reacts sensitively to humidity, and the superiority over existing gas barrier materials is lost.

  However, it is not necessary to simply perform a heat treatment at a high temperature, and it is important to prevent thermal degradation of the gas barrier resin and to prevent a decrease in physical strength due to thermal degradation of the paper. Specifically, the heat treatment is preferably performed at a temperature not lower than the crystallization temperature of the gas barrier resin and not higher than a temperature at which the strength retention of the gas barrier paper after the heat treatment with respect to the initial strength of the paper is 60% or higher. Further, the heat treatment time can be appropriately selected within the range of several seconds to several tens of seconds.

Further suppression of humidity dependency A layer having a moisture-proof property is provided so that the water vapor permeability is 25 g / m ² · 24 hr or less, preferably 10 g / m ² · 24 hr or less so as to be in contact with any layer of the gas barrier paper. Then, since the intrusion of moisture from the outside air can be prevented more reliably, the humidity dependency of the gas barrier property can be further reduced.

Further, if a layer having a hygroscopicity of 0.5 to 25 g / m ² is provided on at least the outside air side of the gas barrier paper, the moisture entering from the outer surface is absorbed, and the gas barrier paper is absorbed into the gas barrier paper. Since the moisture transfer can be prevented, the gas barrier property can be prevented from being lowered. Furthermore, if layers having hygroscopicity are provided on both surfaces of the gas barrier paper body, not only the entry of moisture from the outside air can be prevented, but also the deterioration of the gas barrier property due to the moisture inside the package using the gas barrier paper body can be prevented. . Specifically, the humidity dependency of the gas barrier property can be extremely reduced by laminating a moisture absorbing film.

The hygroscopic layer is not a passive barrier with controlled permeation resistance as in a conventional moisture-proof film, but an active barrier that can remove outside moisture and / or moisture inside the package as described above. Therefore, due to the difference in mechanism, it cannot be expressed only by the numerical value of water vapor permeability. However, if measured by the same method, the water vapor permeability of the hygroscopic layer is preferably 5 g / m ² · 24 hr or less, preferably 3 g / m More preferably, m ² · 24 hr or less.

  With the hygroscopic layer, the humidity of the gas barrier paper can be kept at 65% RH or less, preferably 50% RH or less even when the outside air is 80% RH. This action can prevent the gas barrier property from being lowered even under high humidity.

  By providing the hygroscopic layer on both sides of the gas barrier paper, it can be applied to packages such as highly water-active foods, pharmaceuticals, and cosmetics that have a relatively large amount of water evaporating from the package.

  As a method of forming a moisture-proof or hygroscopic layer, a method of laminating a film having the function, a method of coating with a coating material having the function, a method of impregnating a resin solution having the function, and providing the function For example, a method of extrusion laminating the obtained resin is used.

In the method of laminating a film, a film formed by forming a resin mixed with a moisture-proofing agent or a moisture-absorbing agent, or a film coated with a moisture-proofing material or a moisture-absorbing agent can be used.
Examples of the moisture-proofing agent or moisture-absorbing agent include silica gel, molecular sieve, bentonite, various phosphates and anhydrides, various hydrate-forming salts, etc., but in the present invention, these materials are superior to these materials. Of these, magnesium chloride, magnesium oxide, magnesium sulfate, calcium oxide and the like are preferable. Further, the combined use of magnesium chloride and magnesium oxide can increase the amount of moisture absorbed by the interaction.

  In addition, since the actual processing process is performed in a natural environment, moisture absorption sensitivity adjustment is necessary to absorb moisture during the processing process, transportation, and inventory period. In particular, before mixing the hygroscopic agent with the thermoplastic resin, the original hygroscopic ability is lost because of direct contact with the natural environment. It is preferable to coat the surface with. Further, the hygroscopic material cannot be practically obtained simply by mixing it with a plastic material to form a film.

  Such inorganic materials require a large amount of mixing in order to absorb moisture contained in the package and water vapor entering the film from the outside air, and as a result, the laminate characteristics and heat sealability of the film are impaired. is there. In the present invention, these problems can be practically solved by forming a multilayer structure including the absorbing layer.

  Further, in the thermoplastic material to be mixed, a polyolefin resin is particularly preferable, and more preferably polyethylene, linear polyethylene, ethylene vinyl acetate copolymer, two or more kinds for improving the moisture absorption rate, the amount of moisture absorption and the maintenance level of the humidity level. It is selected from an ethylene-α-olefin copolymer consisting of components and a mixture of at least two selected from these resins.

  A typical configuration example of a paper-like body having a moisture-proof or hygroscopic layer is as follows. Here, the moisture-proof layer is M, the hygroscopic layer is K, the gas barrier paper is B, the heat seal layer is S, and the layer formed by stacking the moisture-proof layer and the heat seal layer is MS. A layer in which a hygroscopic layer and a heat seal layer are laminated is expressed as KS. MS is obtained by laminating a moisture-proof layer and a heat seal layer, and KS is obtained by laminating a hygroscopic layer and a heat seal layer by coextrusion, tandem extrusion lamination, or the like.

  Typical configuration examples include M / B / S, B / M / S, M / B / M / S, B / MS, M / B / MS, B / M / MS, S -M / B / MS, M / B / M / MS, K / B / S, B / K / S, K / B / K / S, B / KS, K / B / K -S, B / K / KS, SK / B / KS, K / B / K / KS, M / B / K / S, M / B / KS, M / K / B / S, M / K / B / M / S, M / K / B / KS, and the like. Furthermore, using one of these as a barrier block, a general type biaxially oriented polypropylene film, a highly moisture-proof type biaxially oriented polypropylene film, a film laminated with an aluminum foil, a metal oxide or aluminum vapor deposited film, A film coated with vinylidene or vinylidene chloride copolymer may be laminated.

  Next, examples of the gas barrier paper according to the present invention and a package using the same will be described, but the present invention is not limited thereto. Various characteristics were evaluated by the following methods.

(1) Beck smoothness According to JIS-P-8119, it has a circular hole through which air can leak in the center of a standard surface made of glass with a planar finished effective area of 10 cm ^2. A pressure of cm ² was applied and the time taken for 10 ml of air to pass was measured.

(2) Dropability of water drops 100 mg of water is gently dropped on the surface of a sample fixed on a flat glass plate, and after standing for 5 seconds, the state in which the water droplets drop when the glass plate is tilted vertically is evaluated. did.

(3) Inclined dropability 100 mg of water is gently dropped on the surface of a sample fixed on a flat glass plate, and after standing for 60 seconds, the angle at which the water droplet falls when the glass plate is gradually inclined is measured. did.

(4) Cobb water absorption The amount of water absorbed by the paper per unit area was measured in contact with water for 60 seconds according to the Cobb method defined in JIS-P-8140.

(5) Water droplet contact angle A certain amount of distilled water is brought into contact with the sample surface from the tip of the syringe, and the water droplets formed on the sample are measured with an image processing type measuring instrument manufactured by Kyowa Interface Science Co., Ltd. The contact angle was determined by the formula.
Contact angle = 2 tan ⁻¹ (h / r)
Here, h represents the height of the water droplet, and r represents the radius of the water droplet.

(6) Oxygen gas permeability It measured by OXTRAN of MOCON according to JIS-K-7126. The temperature and humidity conditions, except for a part, were 23 ° C. × 65% RH and 23 ° C. × 85% RH as standard.

(7) Moisture permeability It measured according to B conditions (40 degreeC * 90% RH) of JIS-Z-0208. Calcium chloride was used as a hygroscopic agent, the sample was attached to a test cup in a sealed state, the constant temperature and humidity chamber was maintained under the above test conditions, and the moisture permeability was measured according to the JIS method.

(8) Bending Pinhole Resistance Using a gelboflex tester manufactured by Tester Sangyo Co., Ltd., bending pinhole resistance was evaluated by the following method. An 8 inch x 11 inch gas barrier paper is formed into a cylindrical shape with a diameter of about 3.5 inches, and one end of the cylindrical paper is fixed to the fixed head side of the gelboflex tester and the other end is fixed to the movable head side. The initial gripping interval was 7 inches. At the beginning of the stroke, a twist of 400 degrees was given at 3.5 inches, and then bending fatigue was completed 5 times at a speed of 40 times / min. The number of pinholes generated in the paper was counted. The measurement was performed in an environment of 23 ° C. and 65% RH. A value obtained by averaging three measurement values was defined as bending pinhole resistance.

(9) Strength retention The tensile strength of the paper-like body measured according to JIS-K-7162 and the gas barrier paper-like body after crystallization treatment was measured using five samples and averaged, Tensile strength ÷ tensile strength of paper-like body × 100 (%) was determined and used as strength retention.

[Experiment 1]
Surface of processed paper 42SB (M) -1 (Nippon Paper Papillia Co., Ltd.) (basis weight 40 g / m ² , Beck smoothness 37,000 seconds, Cobb water absorption 20.3 g / m ² ) In addition, 5% by weight of acrylic acid emulsion A104 manufactured by Toa Gosei Co., Ltd. and 5% by weight of carboxyl group-modified styrene / butadiene copolymer latex Nipol LX407K manufactured by Nippon Zeon Co., Ltd. were mixed with isopropyl alcohol 5 A mixed solution dissolved in a solvent having a composition ratio of wt% and water 85 wt% was precoated. As a result of the pre-coating, a paper-like body whose properties immediately before coating of the barrier layer were modified as shown in Table 1 was obtained.

Crystalline polyvinyl alcohol resin (Exeval AQ4104 manufactured by Kuraray Co., Ltd.) was dissolved in a solvent composed of 90% by weight of water, 7% by weight of isopropyl alcohol and 3% by weight of an acrylic emulsion so as to be 13% by weight. The coating solution is coated on the precoat layer of the paper-like body at 6 g / m ² , then dried with hot air at 100 ° C. for 3 seconds, then dried with hot air at 120 ° C. for 3 seconds, and further heated at 250 ° C. with infrared heating. A gas barrier paper was obtained by heat treatment for 2 seconds. The resin solid content of the coating layer after the heat treatment was 5.2 g / m ² .

  Table 1 shows the surface characteristics of the paper body after pre-coating and the oxygen gas permeability of the gas barrier paper body at 23 ° C. × 65% RH. From Table 1, it can be seen that the gas barrier paper material of Experimental Example 1 in which the surface properties of the paper material are excellent has excellent gas barrier properties.

  Further, the humidity dependency of oxygen gas permeability at 23 ° C. × 65% RH and 23 ° C. × 85% RH, that is, the value of change in oxygen gas permeability / change in humidity is 2.6. The strength retention of the gas barrier paper was 85%. Furthermore, the simple transmission coefficient showing the inherent barrier quality per unit thickness of the gas barrier layer realized a remarkable effect.

[Experiment 2]
A gas barrier paper was obtained in the same manner as in Experimental Example 1 except that MTOH manufactured by Nippon Paper Industries Co., Ltd. was used and the surface was not precoated. The paper used in Experimental Example 2 has poor smoothness and high Cobb water absorption, so that the coating solution is absorbed in a very short time and a uniform barrier film is not formed, resulting in poor oxygen gas barrier properties. (Table 1).

[Experiment 3]
On the other hand, in Experimental Example 3, a gas barrier paper was obtained in the same manner as in Experimental Example 2 except that glassine paper manufactured by Nippon Paper Industries Co., Ltd. was used and the solid content of the dried gas barrier resin was 1.6 g / m ^2. It was.
In the glassine paper of Experimental Example 3, as the water droplet contact angle indicates, the coating solution does not get wet and repels. Therefore, micro repelling and bubbles are caught in the coating, and the barrier film is not formed as a continuous film. The simple transmission coefficient indicating the degree of barrier quality was about 280, far below 8.32 in Experimental Example 1 (Table 1).

[Experimental Examples 4 to 6]
The resin solid content after drying of the gas barrier resin in Experimental Example 1 is 1.5 g / m ² (Experimental Example 4), 2.5 g / m ² (Experimental Example 5), 4.0 g / m ² (Experimental Example 6). ) And changed. The other conditions were the same as in Experimental Example 1. Table 2 shows the oxygen gas permeability of the obtained gas-barrier paper.
From Table 2, when the coating amount is 1.5 g / m ² , the simple transmission coefficient is also within the scope of the present invention, but depending on the application, there are many cases where a coating amount higher than this is required, preferably 2 g / m ² or more. Can be used stably.

[Experimental Example 7]
In a solvent comprising 93% by weight of water, 5% by weight of isopropyl alcohol, and 2% by weight of an ethylene oxide adduct of ether type propyl alcohol, polyvinyl alcohol / acrylic emulsion (OKS-602 manufactured by Nippon Synthetic Chemical Industry Co., Ltd.) and styrene / A coating solution in which butadiene copolymer is dissolved to 90 wt% and 10 wt% is applied to one side of the processed paper used in Experimental Example 1 so that the resin solid content after drying is 3 g / m ^2. It was coated and dried at 150 ° C. to provide a precoat layer. Table 3 shows the surface properties of the paper.

On the paper precoat layer, 95% by weight of crystalline polyvinyl alcohol copolymer resin (Exeval HR-3010 manufactured by Kuraray Co., Ltd.) and water-soluble polyvinyl acetate (manufactured by Nippon Synthetic Chemical Industry Co., Ltd.) A mixture of 5% by weight was mixed with 15% by weight of a mixture of 91% by weight of water, 5% by weight of polyglycerol and 4% by weight of isopropyl alcohol, and after coating, drying was performed at 150 ° C. for 5 seconds, and then 265 ° C. For 4 seconds. The resin solid content after the heat treatment was 5 g / m ² . The strength retention with respect to the initial strength of the paper as the support was 88%.

  Table 3 shows the surface characteristics of the paper-like body, the oxygen gas permeability of the gas-barrier paper-like body, and the bent pinhole resistance. From Table 3, the gas barrier paper-like material of Experimental Example 7 has improved surface properties of the paper-like material by pre-coating treatment, so it has excellent gas barrier properties and bending pinhole resistance, and the gas barrier properties are reduced even under high humidity. I understand that I do not.

[Experimental Example 8]
A gas barrier paper was obtained in the same manner as in Experimental Example 7 except that the precoat treatment was not performed.

  Table 3 shows the surface characteristics of the paper-like body, the oxygen gas permeability and the pinhole resistance of the gas barrier paper-like body. From Table 3, it can be seen that the gas barrier paper-like material of Experimental Example 8 in which the surface properties of the paper-like material are inferior has poor gas barrier properties, simple transmission coefficient and bent pinhole resistance.

[Experimental Example 9]
In a solvent of 90% by weight of water and 10% by weight of methanol, 95% by weight of the crystalline polyvinyl alcohol polymer used in Experimental Example 1 and 5% by weight of ethylene vinyl acetate copolymer emulsion (Sumitomo Chemical Co., Ltd. Sumikaflex) the mixture of the coating solution was dissolved at a 12% by weight, a paper-like material a (Nippon paper Papiria Co. NM art, basis weight 80 g / ^{m 2,} cups water absorption 0.005 g / ^{m 2,} water droplets and Contact angle 95 degrees) and paper B (commercially available copy paper, basis weight 80 g / m ² , cup water absorption 35 g / m ² , water droplet contact angle approximately 0 degrees), 5 g of resin solid content after drying / M ^2, and dried at 180 ° C. for 5 seconds. In the paper-like body A, the coating solution was repelled without getting wet uniformly, and in the paper-like body B, the coating solution was immediately absorbed. As a result, the oxygen gas permeability of the obtained gas barrier paper was 2,000 cc / m ² · 24 hr · atm or more, and no gas barrier property was obtained.

[Experimental Example 10]
Crystalline polyvinyl alcohol (Gosenol NK-05R manufactured by Nippon Chemical Synthetic Co., Ltd.) was dissolved in 15% by weight of water and isopropyl alcohol in a mixed solvent of 90% by weight and 10% by weight, respectively. The obtained mixed solution was coated on a paper-like body having the surface characteristics of Experimental Example 1 so that the resin solid content after drying was 6 g / m ² , and then dried at 180 ° C. for 5 seconds. The obtained gas barrier paper had an oxygen permeability of 2,000 cc / m ² · 24 hr · atm or more.

[Experimental Example 11]
On the opposite side of the gas barrier resin layer surface of the gas barrier paper material of Experimental Example 7, a biaxially stretched polypropylene film having a moisture absorption of 5 g / m ² and a thickness of 25 μm (technoworld company prototype, OPP in Table 4) And) were dry laminated. The oxygen gas permeability was measured by changing the relative humidity of the surface of the biaxially stretched polypropylene film of the obtained gas barrier paper.
The biaxially stretched polypropylene film used in Experimental Example 7 is composed of isotactic polypropylene having both surface layers of 10 μm, and an intermediate layer of 25 wt.% Of a mixed moisture absorbent composed of 40 wt% magnesium chloride and 60 wt% magnesium oxide. % Is a film made of isotactic polypropylene.

  Further, a 60 μm thick linear low density polyethylene film (LIX L6102 manufactured by Toyobo Co., Ltd., described as PE in Table 4) was dry-laminated on the gas barrier resin layer surface of the gas barrier paper.

  Table 4 shows oxygen gas permeability and bent pinhole resistance of the gas barrier paper. From Table 4, the gas barrier paper-like material of Experimental Example 11 has excellent bending resistance, and since the value of oxygen gas permeability change / humidity change is 3 or less, the humidity dependence of the gas barrier property is also small. I understand.

[Experimental example 12]
In Experimental Example 12, the respective films were laminated in the same manner as in Experimental Example 11 except that the gas barrier paper-like material of Experimental Example 8 was used. Table 4 shows oxygen gas permeability and bent pinhole resistance of the gas barrier paper. From Table 4, the gas barrier paper-like material of Experimental Example 12 has poor flex resistance, and the oxygen gas permeability change amount / humidity change value far exceeds 3, so that the humidity dependency of the gas barrier property is also large. I understand that.

[Experimental Example 13]
In a solvent comprising 90% by weight of water and 10% by weight of isopropyl alcohol, 90% by weight of the crystalline polyvinyl alcohol resin used in Experimental Example 1, an acetal group-containing ethylene / acrylic acid copolymer (manufactured by NOF Corporation) 7 A coating solution prepared by dissolving a mixture of 5% by weight and 3% by weight of polyethylene glycol so as to be 6% by weight has a resin solid content of 6 g / m ² on one side of the processed paper used in Experimental Example 1. And then dried at 150 ° C. for 6 seconds to provide a precoat layer. The obtained surface characteristics are Beck smoothness of 980,000 seconds, water drop dropping property, slope falling property is 65 degrees, Cobb water absorption is 8 g / m ² , water drop contact angle is 18 degrees, and surface characteristics are After the modification, subsequently, a solvent comprising 85% by weight of water and 15% by weight of isopropyl alcohol, 90% by weight of crystalline polyvinyl alcohol (Poval R-1130 manufactured by Kuraray Co., Ltd.), an acrylate emulsion (Showa Denko) Polysol Co., Ltd. (8% by weight), a betaine surfactant (1% by weight of Kawaken Fine Chemical Co., Ltd. Softazolin LMEB) and 1% by weight of polyethyleneimine were dissolved to 15% by weight. the coating solution was, on the precoat layer of paper-like material, was coated as a resin solid content after the heat treatment is 7 g / m ^2, 5 at 160 ° C. It was between dry. Subsequently, a heat treatment was performed at 230 ° C. for 10 seconds in the first stage and at 265 ° C. for 5 seconds in the second stage to obtain a gas barrier paper.

  Table 5 shows the oxygen gas permeability of the gas barrier paper. From Table 5, it can be seen that the gas barrier paper-like material of Experimental Example 13 using a paper-like material having excellent surface characteristics has a small humidity dependency of the gas barrier property.

[Experimental Example 14]
A gas barrier paper was obtained using the same gas barrier resin as in Example 13 except that the base paper used in Experimental Example 2 was used.

  Table 5 shows the oxygen gas permeability of the gas barrier paper. From Table 5, it can be seen that the gas barrier paper-like material of Experimental Example 14 using a paper-like material having inferior surface characteristics has a large humidity dependency of gas barrier properties, a large simple permeability coefficient, and poor gas barrier properties.

[Experimental Example 15]
An isotactic polypropylene film (Pyrene OT P2161 manufactured by Toyobo Co., Ltd.) was dry-laminated on the surface opposite to the gas barrier layer surface of the gas barrier paper obtained in Experimental Example 7, and the gas barrier layer surface and the thickness of 40 μm were further laminated. An ethylene / methacrylic acid copolymer (Nucleel AN4228C, Mitsui DuPont Polychemical Co., Ltd.) is melted to a thickness of 7 μm between the linear low density polyethylene film (Nippon Polyethylene Co., Ltd. kernel). Extrusion and sand lamination were performed.

  Table 6 shows the oxygen gas permeability of the gas barrier paper at 23 ° C. × 65% RH. From Table 6, if a polypropylene film with relatively high flexibility is dry-laminated and sand lamination is performed with a highly flexible ethylene / methacrylic acid copolymer, not only a stable gas barrier property is obtained, but also bending resistance. It can be seen that the properties can be further improved.

[Experimental Example 16]
Gas barrier paper used for the trunk part 90% by weight of water and 10% by weight of isopropyl alcohol, a vinyl acetate modified polyvinyl alcohol copolymer resin (Nippon Gosei Chemical Co., Ltd. Gohsenol GL-05), The coating solution dissolved so as to be 10% by weight is made into a paperboard A (manufactured by Oji Paperboard Co., Ltd., basis weight 300 g / m ² , Beck smoothness 100 seconds), and the resin solid content after drying is 5 g. / M ² , dried at 150 ° C. for 4 seconds, Beck smoothness of 1,200,000 seconds or more, water drop dropping property, inclined dropping property of 34 °, cup water absorption of 14 g / m ^{2. The} surface was modified to a water droplet contact angle of 35 degrees.
Furthermore, 88% by weight of water, 10% by weight of isopropyl alcohol and 2% by weight of the betaine surfactant used in Experimental Example 13 were mixed with 90% by weight of the crystalline polyvinyl alcohol polymer used in Experimental Example 1. The coating solution so dissolved was coated on the precoat layer so that the resin solid content after drying was 7 g / m ² and dried to obtain a gas barrier paper. The drying conditions were 160 ° C. for 7 seconds at the first stage and 5 seconds at 240 ° C. for the second stage. The resulting gas barrier paper had an oxygen gas permeability of 0.7 cc / m ² · 24 hr · atm at 23 ° C. × 65% RH, and a simple permeability coefficient of 4.9 cc · g · m ⁻² / m ^2. -An extremely excellent gas barrier property of 24 hr.atm was obtained.

A three-layer polyethylene composite film having a thickness of 100 μm was dry-laminated using a metallocene linear low density polyethylene (kernel manufactured by Nippon Polyethylene Co., Ltd.) as a base material on the coating surface of the gas barrier paper. The film was composed of a composite film of linear low density polyethylene having a function of moisture absorption of 13 g / m ^{2 in} the intermediate layer and both outer layers having no moisture absorption, and was laminated with the corona discharge treated surface.
Furthermore, the linear low-density polyethylene film used in Experimental Example 11 having a thickness of 60 μm was dry-laminated on the inner surface side on the opposite side to obtain a gas barrier paper-like body used for the body portion.

A gas barrier paper-like body used for the bottom part and the lid part is subjected to the same processing as that applied to the paperboard A on the paperboard B (manufactured by Oji Paperboard Co., Ltd., basis weight 150 g / m ² ). 150,000 seconds or more, water drop dropability, inclined fall dropability of 25 degrees or less, cup water absorption of 15 g / m ² , water drop contact angle of 25 degrees, pre-coating and surface modification, used for the bottom and lid A gas barrier paper was obtained.

  A gas barrier paper-like body used for the body portion was formed into a cylindrical shape, and both ends were ultrasonically sealed to prepare a body portion. Next, the gas barrier paper body used for the lid is bent at both the upper and lower ends of the body part, the lid is sealed with an ultrasonic seal, and further filled with 100 g of Japanese tea, then manually filled with nitrogen gas, The gas barrier paper used for the bottom was similarly sealed by ultrasonic sealing. At this time, a humidity measuring sensor was inserted when filling the contents. Further, an adhesive rubber piece was attached from the outer surface, and the humidity and oxygen gas concentration inside the container were measured with an oxygen concentration meter. Next, measurement was performed after storage for 1 week under the environmental conditions of 23 ° C. × 65% RH and 23 ° C. × 85% RH, and comparison was made before and after storage.

  The humidity in the container after storage decreased to 1.2% RH in any environmental condition. The oxygen gas concentration was 3.2% at the initial concentration, 2.8% after storage at 23 ° C. × 65% RH, and 3.1% after storage at 23 ° C. × 85% RH. That is, almost no increase in oxygen gas concentration was observed, and the humidity dependence of gas barrier properties was satisfactory.

[Experimental Example 17]
The ratio of crystalline polyvinyl alcohol resin in a mixture of crystalline polyvinyl alcohol resin (G polymer OKS-1011 manufactured by Nippon Synthetic Chemical Industry Co., Ltd.) and water-soluble vinyl acetate resin emulsion (Polysol manufactured by Showa Denko Co., Ltd.) It adjusted to 75 weight% and 95 weight%. A coating solution in which the mixture was dissolved in a solvent consisting of 90% by weight of water, 7% by weight of isopropyl alcohol and 3% by weight of an acrylic emulsion was dissolved in 13% by weight of the paper-like material used in Experimental Example 1. The precoat layer was coated so that the resin solid content after the heat treatment was 6 g / m ² , then dried with hot air at 100 ° C. for 3 seconds, and then dried with hot air at 120 ° C. for 3 seconds. Furthermore, infrared heating was performed at 250 ° C. for 5 seconds to obtain a gas barrier paper.

[Experiment 18]
A gas barrier paper was obtained in the same manner as in Experimental Example 17, except that the ratio of the crystalline polyvinyl alcohol resin in the mixture of the crystalline polyvinyl alcohol resin and the water-soluble vinyl acetate resin was adjusted to 70% by weight.

  Table 7 shows the oxygen gas permeability of the gas barrier paper bodies of Experimental Examples 17 and 18 at 23 ° C. × 65% RH. From Table 7, it can be seen that if 75% by weight or more of the crystalline polyvinyl alcohol resin is blended in the gas barrier resin layer, the gas barrier property is excellent.

[Experimental Example 19]
In a solvent consisting of 85% by weight of water and 15% by weight of isopropyl alcohol, 65% by weight of polyvinyl alcohol resin (G polymer OKS-1011 manufactured by Nippon Synthetic Chemical Industry Co., Ltd.), water-soluble acrylic resin (manufactured by Toagosei Co., Ltd.) A coating solution in which a mixture of 20% by weight of sodium polyacrylate T-40) and 15% by weight of a water-soluble vinyl acetate resin (Sumikaflex manufactured by Sumitomo Chemical Co., Ltd.) was dissolved to 7% by weight was carried out. The surface of the processed paper used in Example 1 was coated so that the resin solid content after drying was 2 g / m ^2, and dried at 140 ° C. for 5 seconds to provide a precoat layer. The surface characteristics after the pre-coating treatment were as follows: Beck smoothness of 500,000 seconds, water drop dropping property, inclined dropping property of 38 degrees, Cobb water absorption of 5 g / m ² , and water drop contact angle of 21 degrees.

In a solvent composed of 90% by weight of water and 10% by weight of isopropyl alcohol, a mixture composed of 98% by weight of crystalline polyvinyl alcohol resin (AZF8035 manufactured by Nippon Synthetic Chemical Industry Co., Ltd.) and 2% by weight of polyethylene glycol was 10% by weight. The coating solution thus dissolved was coated on the surface of the precoat layer so that the resin solid content after drying was 4 g / m ² and dried at 160 ° C. for 7 seconds. Subsequently, the coating solution was coated again so that the resin solid content after the heat treatment was 4 g / m ² , dried at 160 ° C., and further heat-treated at 245 ° C. for 5 seconds. Between the obtained gas barrier paper and a linear low density polyethylene film having a thickness of 50 μm (kernel manufactured by Nippon Polyethylene Co., Ltd.), the ethylene / methacrylic acid copolymer used in Experimental Example 15 has a thickness of 4 μm. The mixture was melt extruded and sand lamination was performed. Table 8 shows the oxygen gas permeability at 23 ° C. × 65% RH after the 5-fold bending test.

  From Table 8, it can be seen that the bending resistance can be further improved by sand lamination.

[Experiment 20]
Instead of the processed paper of Experimental Example 19, a xylan-based nanofiber substrate (prototype, fiber diameter 100 nm) derived from hemicellulose was used. Since the surface properties of the base material were Beck smoothness of 150,000 seconds and other properties required modification, the same precoat layer as in Experimental Example 19 was applied, dried at 170 ° C. for 8 seconds, and after drying The resin solid content was 1.1 g / m ² . The surface characteristics after pre-coating are as follows: Beck smoothness of 11,110,000 seconds, water drop dropping property, inclined dropping property of 28 °, Cobb water absorption of 0.8 g / m ² , water drop contact angle of 48 Reformed every time. Next, the same gas barrier resin as that of Experimental Example 19 was coated, except that the drying conditions and the heat treatment conditions were 180 ° C. for 5 seconds and 275 ° C. for 5 seconds, and the resin solid content after the heat treatment was 3.5 g / m ^2. Obtained a gas barrier paper in the same manner as in Experimental Example 19.

The obtained gas barrier paper had an oxygen gas permeability at 23 ° C. × 65% RH of 0.4 cc / m ² · 24 hr · atm, and oxygen gas permeation at 23 ° C. × 65% RH after bending 5 times. The degree was 0.6 cc / m ² · 24 hr · atm, and an excellent bending resistance of 2.1 cc · g · m ⁻² / m ² · 24 hr · atm was obtained even after the simple transmission coefficient was bent.

[Experiment 21]
Commercially available copy paper (reference surface roughness Ra is 57 μm, Beck smoothness is 25 seconds, water drop dropping property is, but water drop falling angle is 24 degrees, Cobb water absorption is 59 g / m ² , water drop contact angle is 89 In order to modify the surface characteristics of the resin, a polyvinyl alcohol resin (Nippon Gosei Chemical Co., Ltd. Gohsenol N-300) is pre-coated so that the resin solid content after drying is 15 g / m ² , Dry at 150 ° C. for 5 seconds.
As a result, the surface of the paper-like body has a Beck smoothness of 260,000 seconds, a drop-dropping property, a drop-drop inclination angle of 48 degrees, a Cobb water absorption of 12 g / m ² , and a drop contact angle of 28. It was a degree.
Next, the crystalline polyvinyl alcohol-based resin solution used in Experimental Example 19 was coated on the paper precoat layer so that the resin solid content after the heat treatment was 8 g / m ² . Drying was performed at 150 ° C. for 6 seconds, and then infrared heat treatment was performed at 240 ° C. for 3 seconds.

  Between the obtained gas barrier paper and the linear low-density polyethylene film used in Experimental Example 19, the ethylene / methacrylic acid copolymer used in Experimental Example 15 was melt-extruded to a thickness of 4 μm. , Sand lamination. Table 9 shows the oxygen gas barrier properties after the sand lamination.

[Experimental example 22]
On the other hand, for comparison, sand lamination similar to Experimental Example 21 was performed on the gas barrier paper obtained in the same manner as in Experimental Example 21, except that the precoat treatment was not performed. Table 9 shows the results of oxygen gas barrier properties after the sand lamination.

  It can be seen from Table 9 that the gas barrier paper of Experimental Example 21 is excellent in gas barrier properties.

  The present invention relates to a gas barrier paper-like material that can be used in a gas-saving packaging material application that requires a characteristic of paper and can be used in a saving laminate that also has gas barrier properties when the paper and the gas barrier material must each be laminated. Ideal for body use.

1: base paper or processed paper 2: precoat layer 3: gas barrier resin layer 4: plastic film (including moisture barrier layer and gas barrier film)
5: Hygroscopic layer 6: Heat seal layer

Claims (8)

At least one surface of the base paper or processed paper is pre-coated with at least one water-dispersible or water-soluble resin so that the resin solid content after drying is 0.5 to 20 g / m ² ,
Beck smoothness is 200,000 seconds or more,
After adding 100 mg of water drops,
If the paper body is left at a vertical angle after being left for 5 seconds, the water drops will move or drop,
After leaving for 60 seconds, it has a surface characteristic that does not fall when the inclination angle is 25 degrees or less,
On the precoat layer of the paper-like body having a surface property of Cobb water absorption of 0.03 to 15 g / m ² and water droplet contact angle of 5 to 60 degrees,
A gas barrier resin layer containing 75% by weight or more of a crystalline polyvinyl alcohol resin is provided by a coating method,
A gas barrier paper having an oxygen gas permeability of 20 cc / m ² · 24 hr · atm or less at 23 ° C. and 65% RH. ^2. The gas barrier paper according to claim 1, wherein a simple permeability coefficient indicating the intrinsic quality of the gas barrier resin layer is 80 cc · g · m ⁻² / m ² · 24 hr · atm or less at 23 ° C. and 85% RH or less.
[Definition of simple transmission coefficient]
The product of the gas permeability of the gas barrier paper and the resin solid content after drying or heat treatment of the gas barrier resin layer is defined as a simple permeability coefficient.   The crystalline polyvinyl alcohol-based resin contains 80 to 100 mol% of polyvinyl alcohol segments having a saponification degree of 80 to 99.99 mol% and a polymerization degree of 200 to 3,000. The gas barrier paper according to 1 or 2. The gas barrier paper according to any one of claims 1 to 3, wherein an oxygen gas permeability is 100 cc / m ² · 24 hr · atm or less at 23 ° C and 85% RH. Crystallize the gas barrier resin layer at high temperature,
The oxygen gas permeability change / humidity change value is 3.0 or less, and the oxygen gas permeability is 80 cc / m ² · 24 hr · atm or less at 23 ° C. and 85% RH. The gas barrier paper according to any one of claims 1 to 4. It is obtained by a manufacturing method in which heat treatment is performed at a temperature not lower than a crystallization temperature of a gas barrier resin constituting the gas barrier resin layer and not higher than a temperature at which a strength retention ratio with respect to an initial strength of a paper-like body is 60% or higher. The gas barrier paper according to any one of claims 1 to 5. In contact with any layer of the gas barrier paper,
7. A moisture-proof layer having a water vapor permeability of 25 g / m ² · 24 hr or less or a water-absorbing layer having a water absorption of 0.5 to 25 g / m ² is provided. The gas barrier paper according to 1.   A package comprising a gas barrier paper according to any one of claims 1 to 7 and at least one surface of which is provided with another oxygen barrier layer, a printing layer, or a coating layer or film having heat sealability.